WO2012008002A1 - Light-emitting diode drive device and light-emitting diode drive semiconductor device - Google Patents

Light-emitting diode drive device and light-emitting diode drive semiconductor device Download PDF

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Publication number
WO2012008002A1
WO2012008002A1 PCT/JP2010/006790 JP2010006790W WO2012008002A1 WO 2012008002 A1 WO2012008002 A1 WO 2012008002A1 JP 2010006790 W JP2010006790 W JP 2010006790W WO 2012008002 A1 WO2012008002 A1 WO 2012008002A1
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Prior art keywords
switching element
circuit
current
value
emitting diode
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PCT/JP2010/006790
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French (fr)
Japanese (ja)
Inventor
崇 國松
敏史 石田
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パナソニック株式会社
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Publication of WO2012008002A1 publication Critical patent/WO2012008002A1/en

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]

Definitions

  • the present invention relates to a light emitting diode driving device and a semiconductor device used for driving the light emitting diode, and more particularly to a step-down chopper type driving device.
  • a light emitting diode driving device for driving a light emitting diode (hereinafter referred to as an LED (Light Emitting Diode)) and a light emitting diode driving semiconductor device used for driving the LED have been developed and put into practical use.
  • mass production of lighting devices such as LED bulbs using white LEDs as a light source has been actively performed.
  • Various drive circuits for appropriately driving LEDs have been proposed. For example, when a plurality of LEDs are connected in series, if a specific LED becomes open, the output voltage may rise unnecessarily, increasing the load on the components, or excessively high drive circuitry. There was a risk of voltage being applied.
  • Patent Document 1 a light emitting diode driving device (illumination device) having a function of detecting such LED open and switching to a safe operation mode is disclosed.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus described in Patent Document 1.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus described in Patent Document 1.
  • the conventional light emitting diode driving device 11 is connected to an LED light source unit 18 including a plurality of LEDs 18a connected in series, and controls lighting of the plurality of LEDs 18a. As shown in FIG. 8, the conventional LED driving device 11 flows through the LED light source unit 18 and the lighting circuit unit 12 including a converter that converts the power supply voltage into a predetermined DC voltage and outputs the voltage to the LED light source unit 18. And a current detection resistor 13 for detecting a current. Further, the conventional light emitting diode driving device 11 includes a voltage detection circuit unit 19.
  • the lighting circuit unit 12 is a so-called step-up DC / DC converter, and includes an inductance element 14, a diode 15, a switching element 16, a capacitance element 20, and a drive control circuit 17.
  • the inductance element 14 is connected to the high voltage side of the DC power supply VE.
  • the diode 15 is a backflow preventing diode having an anode connected to the other end of the inductance element 14.
  • the switching element 16 is a power element such as an FET (Field Effect Transistor) connected between the other end of the inductance element 14 and the low voltage side of the DC power supply VE.
  • Capacitance element 20 is connected between the cathode of diode 15 and the low voltage side of DC power supply VE.
  • the drive control circuit 17 controls the output voltage V of the lighting circuit unit 12.
  • the drive control circuit 17 controls on and off of the switching element 16 while monitoring the output of the lighting circuit unit 12 by the voltage detection circuit unit 19 and the current detection resistor 13.
  • the drive control circuit 17 has a control function and a mode setting function.
  • the control function is a function for controlling on and off of the switching element 16.
  • the mode setting function is a function for setting the operation mode of the lighting circuit unit 12 to a normal mode or a standby mode for non-connection (no load) (or a stop mode) depending on the connection state of the LED light source unit 18.
  • the current detection resistor 13 is a resistor connected between the cathode of the LED light source unit 18 and the low voltage side of the DC power source VE.
  • the current detection resistor 13 converts the current I flowing through the LED light source unit 18 into voltage information and feeds it back to the feedback terminal FB of the drive control circuit 17.
  • the drive control circuit 17 determines that the LED light source unit 18 is connected if the current I detected by the current detection resistor 13 exceeds a predetermined threshold value.
  • the drive control circuit 17 operates in a normal mode in which the output voltage of the converter is adjusted so that the current flowing through the LED light source unit 18 becomes a predetermined set value.
  • the drive control circuit 17 determines that the LED light source unit 18 is not connected and operates in the standby mode or the stop mode.
  • the standby mode is a mode in which the output voltage is decreased to a predetermined value
  • the stop mode is a mode in which the output of the lighting circuit unit 12 is stopped.
  • the predetermined threshold value is set such that when the LED light source unit 18 is normally connected, the current flowing through the LED light source unit 18 is at least a value exceeding the threshold value.
  • the conventional light-emitting diode driving device described in Patent Document 1 requires a current detection resistor for detecting the current flowing through the LED.
  • the drive control circuit requires a terminal for inputting the current detection information detected by the current detection resistor, thereby reducing the size and space of the driving device, the size of the lighting circuit IC, and the size of the terminal. It becomes a problem when it is realized. Further, since the LED current flows through the current detection resistor, the loss of power consumption in the current detection resistor is large.
  • a step-down drive circuit is effective to efficiently supply a high voltage rectified and smoothed based on a commercial AC power supply (AC100V / 240V, etc.) to an LED light source that is lower than the input power supply voltage. It is.
  • AC100V / 240V, etc. a commercial AC power supply
  • the potential of the current detection resistor becomes a high voltage, and thus a high voltage element is required in the drive control circuit in order to input the detected information to the drive control circuit.
  • a smoothing capacitor and a dummy resistor are often connected in parallel in the immediate vicinity of the LED light source in order to reduce ripples in the current waveform flowing through the LED light source and to prevent noise. In such a case, even if the LED is open, current may flow through the smoothing capacitor and the dummy resistor, so the drive control circuit may not be able to detect normally.
  • An object of the present invention is to provide a light-emitting diode driving device and a light-emitting diode driving semiconductor device capable of normally detecting LED open.
  • a light-emitting diode driving device is a step-down chopper type light-emitting diode driving device that drives one or more light-emitting diodes.
  • An LED light source unit a choke coil connected in series to the LED light source unit, a series connection loop circuit including a diode for supplying back electromotive force generated in the choke coil to the LED light source unit, and the series connection
  • a power supply unit that is connected to a loop circuit and supplies an input voltage to the LED light source unit and the choke coil, and a switching unit that is connected to the series connection loop circuit and that controls the current flowing through the LED light source unit.
  • a driving circuit comprising: a switching element block; a control circuit block;
  • the switching element block includes a switching element that is connected in series to the series connection loop circuit and intermittently supplies an input voltage supplied by the power supply unit to the LED light source unit and the choke coil
  • the control circuit block includes a SW control circuit that controls switching of the switching element on and off, and a current value of a current that flows through the switching element when the switching element is turned off.
  • An upper limit determination circuit for determining whether the current value of the current flowing through the switching element is equal to or higher than a predetermined lower limit reference value; The current value of the current flowing through the switching element is equal to or lower than the upper limit reference value by the upper limit determination circuit.
  • the switching element is controlled by a method different from that in the first operation mode.
  • the current flowing through the switching element is used to detect the opening of the LED, a dedicated resistor and terminal are not required. That is, since a resistor for detecting the current flowing through the LED light source unit is not required, it is not necessary to consider a loss in the resistor, and high-efficiency driving is possible.
  • the current value of the current flowing through the switching element when the switching element is turned off is equal to or lower than the upper limit reference value, the current flows through the switching element due to the open of the LED (high load impedance state of the LED light source unit). It can be detected that the current has decreased. Therefore, since it is possible to determine whether the LED light source unit is open using the current flowing through the switching element, an additional terminal is not required, and the light emitting diode driving device can be reduced in size and space can be saved.
  • the value of the current flowing through the switching element is greater than or equal to the lower limit reference value
  • the value of the current flowing through the switching element is low even if the LED is normal (for example, when the input voltage is low, or when a smoothing capacitor or the like is connected in parallel with the LED, it is possible to prevent erroneous detection that the LED is open.
  • the number of times that the value of the current flowing through the switching element is less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value is measured and the measured number is compared with the determination reference value, the LED continuously The case where it is open can be detected.
  • the dedicated resistor and terminal are not required, and even when the input voltage is low and when the smoothing capacitor or the like is connected in parallel to the LED, the LED normally Open can be detected.
  • the control circuit block further includes a current detection circuit that detects a current value of a current flowing through the switching element, and the upper limit determination circuit is configured such that the current value detected by the current detection circuit is equal to the upper limit reference.
  • the lower limit determination circuit may determine whether or not the current value detected by the current detection circuit is equal to or greater than the lower limit reference value.
  • both the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) use the current value detected by the current detection circuit, the determination is easily performed. be able to. For example, by performing the upper limit determination and the lower limit determination at the same time, a circuit for temporarily holding one of the determination results is not required, so that the circuit configuration necessary for the determination can be simplified.
  • the SW control circuit switches the switching element from OFF to ON at a preset period, and the upper limit determination circuit is a period during which the switching element is ON in the period.
  • the maximum duty period that is the maximum value of the switching element is set, and the period during which the switching element is on reaches the maximum duty period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum duty detection circuit to determine.
  • the period during which the switching element is on in the cycle reaches the maximum duty period (maximum duty drive).
  • the open state of the LED can be detected by counting the number of times when the maximum duty drive is performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the maximum duty drive is performed, so that the open detection accuracy can be improved.
  • the SW control circuit turns on the switching element after a predetermined period from when the switching element is turned off, and the upper limit determination circuit turns on the switching element.
  • a maximum on-period that is a maximum value of a certain period of time is set, and when the period during which the switching element is on reaches the maximum on-period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum ON period detection circuit determined to exist.
  • the period during which the switching element is on reaches the maximum on period (maximum on-time driving).
  • the current flowing through the switching element is equal to or lower than the upper reference value. Therefore, regardless of whether or not the current flowing through the switching element reaches a preset upper limit reference value, it is possible to detect the opening of the LED by counting the number of times when the maximum on-time driving is performed. . At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
  • the control circuit block further includes a peak current detection circuit that outputs a peak current detection signal when the current value of the current flowing through the switching element reaches a preset peak value, and the SW control The circuit may turn off the switching element when the peak current detection signal is input in the first operation mode, and the upper reference value may be a value equal to or lower than the peak value.
  • the upper limit reference value can be arbitrarily set according to the current value of the LED light source unit, it is possible to improve the detection accuracy of LED open.
  • the control circuit block may further include a current adjustment circuit that dynamically changes the peak value according to a value input from the outside.
  • the current adjustment circuit may further change the upper limit reference value in accordance with the change of the peak value.
  • the open detection accuracy of the LED light source unit can be improved.
  • the power supply unit may include an AC power source that generates an AC voltage, and a rectifier circuit that generates the input voltage that is a pulsating voltage by rectifying the AC voltage.
  • the control circuit block further includes an input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage, and the SW control when the input voltage is equal to or higher than the set voltage.
  • an input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage
  • the SW control circuit causes the switching element to turn on and off in the first operation mode.
  • a start / stop circuit for stopping the switching.
  • the switching operation of the switching element (on / off switching control) is stopped. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the on-time of the switching element is extended to reach the maximum on-time or the maximum on-duty. The possibility of false detection is low.
  • the series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and the lower limit reference value is a current of a current flowing through the resistor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
  • the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
  • the series-connected loop circuit further includes a capacitor connected in parallel to the LED light source unit, and the lower limit reference value is a current flowing through the capacitor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
  • the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
  • the series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and a capacitor connected in series to the resistor and connected in parallel to the LED light source unit, and the lower limit reference value is When the at least one light emitting diode is open, it may be a value equal to or smaller than the current value of the current flowing through the resistor and the capacitor.
  • the lower limit determination circuit may reset the determination result each time the switching element is turned on.
  • the determination result by the lower limit determination circuit is reset for each switching cycle of the switching element, the possibility of erroneous detection can be reduced.
  • the lower limit determination circuit may determine whether a current value of a current flowing through the switching element is equal to or higher than the lower limit reference value during a period from when the switching element is turned on to when the switching element is turned off. .
  • the count circuit may reset the number of times when the measured number does not increase in synchronization with the timing at which the switching element is turned off.
  • the number of counts is reset when the current flowing through the switching element is continuously exceeding the upper limit reference value or the peak value is reached while the number of counts is continuously increasing. Can be lowered.
  • the count circuit may reset the measured number of times when the switching of the switching element is stopped.
  • the SW control circuit may stop the switching element from latching as the second operation mode.
  • the SW control circuit may perform a timer intermittent operation in which the switching element is driven and stopped at regular intervals as the second operation mode.
  • the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element.
  • the light emitting diode driving device may further include an abnormality processing circuit that outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit is equal to or greater than the determination reference value. Good.
  • an abnormality determination signal is output. Therefore, the supply of input voltage is stopped using this abnormality determination signal, and the peripheral device is informed that the LED light source unit is open. By transmitting or sounding an alarm, the user can be informed that the LED light source unit is abnormal.
  • a semiconductor device for driving a light emitting diode is a semiconductor device for driving a light emitting diode, and includes the switching element block and the control circuit block. And the control circuit block are formed on the same semiconductor substrate or incorporated in the same package.
  • the switching element and the control circuit can be incorporated into one package. Therefore, if the light emitting diode driving device is configured using this semiconductor device, the number of parts of the light emitting diode driving device can be greatly reduced, and the light emitting diode driving device can be easily reduced in size, weight and cost. Can be realized.
  • a dedicated resistor and terminal are not required, and even when the input voltage is low and when a smoothing capacitor or the like is connected in parallel to the LED, the open of the LED is normally detected. be able to.
  • FIG. 1 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2A is a waveform diagram showing a waveform of an input voltage and an operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2B is a waveform diagram showing the waveform of the input voltage and the operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 3 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 1 of the present invention.
  • FIG. 1 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2A is a waveform diagram showing a waveform of an input voltage and an operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 4 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 2 of the present invention.
  • FIG. 5 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 2 of the present invention.
  • FIG. 6A is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 6B is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 6C is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 4 of the present invention.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus.
  • the light-emitting diode driving apparatus is a step-down chopper type driving apparatus that drives one or more light-emitting diodes (LEDs), and the current flowing through the switching element at a predetermined timing is the upper limit reference. It is determined whether it is less than the value and greater than or equal to the lower limit reference value. Then, the LED driving apparatus according to Embodiment 1 of the present invention counts the number of times that the current flowing through the switching element is determined to be equal to or lower than the upper limit reference value and equal to or higher than the lower limit reference value, and the number of times counted When the value is equal to or greater than a predetermined criterion value, abnormality processing is performed.
  • FIG. 1 is a circuit diagram showing an example of the configuration of the light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention.
  • the light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention is a step-down chopper type driving apparatus that drives one or more LEDs.
  • the light emitting diode driving device 100 includes a power supply unit 110, a series connection loop circuit 120, a switching driving circuit 200, a capacitor 130, and a resistor 140.
  • the switching drive circuit 200 is an example of a semiconductor device according to the first embodiment of the present invention.
  • the power supply unit 110 is connected to the series connection loop circuit 120 and supplies an input voltage to the LED light source unit 121 and the choke coil 122 included in the series connection loop circuit 120. As shown in FIG. 1, the power supply unit 110 includes an AC power supply 111, a rectifier circuit 112, and a smoothing capacitor 113.
  • AC power supply 111 generates an AC voltage.
  • the AC power supply 111 is a commercial power supply.
  • the rectifier circuit 112 is connected to the AC power source 111 and generates a pulsating voltage by rectifying the AC voltage.
  • the rectifier circuit 112 is a full-wave rectifier circuit, for example, and generates a full-wave rectified voltage from an AC voltage.
  • the high potential side of the rectifier circuit 112 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the smoothing capacitor 113 generates the input voltage Vin by smoothing the full-wave rectified voltage generated by the rectifier circuit 112.
  • the high potential side of the smoothing capacitor 113 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the generated input voltage Vin is supplied to the LED light source unit 121 and the choke coil 122.
  • the waveform of the input voltage Vin is sufficiently smoothed or becomes a pulsating waveform depending on the capacitance value of the smoothing capacitor 113.
  • the case where the input voltage waveform is a pulsating voltage waveform as shown in FIG. 2A will be described as an example.
  • the series connection loop circuit 120 includes an LED light source unit 121, a choke coil 122, and a diode 123. As shown in FIG. 1, the LED light source unit 121, the choke coil 122, and the diode 123 form a loop.
  • the LED light source unit 121 includes a plurality of light emitting diodes (LEDs). The plurality of LEDs are connected in series.
  • the choke coil 122 is connected to the LED light source unit 121 in series.
  • the diode 123 is connected in parallel to the LED light source unit 121 and the choke coil 122, and supplies back electromotive force generated in the choke coil 122 to the LED light source unit 121.
  • the high potential side of the rectifier circuit 112 and the smoothing capacitor 113 is connected to the anode terminal side of the LED light source 121 and the cathode terminal side of the diode 123.
  • the common connection point between the choke coil 122 and the anode terminal of the diode 123 is connected to the high potential side terminal DRN of the switching drive circuit 200.
  • the choke coil 122 is connected to the cathode terminal side of the LED light source unit 121, but may be connected to the anode terminal side. Further, an LED light source in which a plurality of light emitting diodes are connected in series will be described as an example. However, it is sufficient that the number of light emitting diodes is one or more.
  • the plurality of light emitting diodes may be connected not only in series but also in a matrix. The same applies to the embodiments described below.
  • the switching drive circuit 200 is an example of a light emitting diode driving semiconductor device according to Embodiment 1 of the present invention, and is a semiconductor device for constant current control of the current flowing through the LED light source unit 121. As shown in FIG. 1, the switching drive circuit 200 includes a switching element block 210 and a control circuit block 220. The switching drive circuit 200 has five terminals (rectified voltage application terminal IN, high potential side terminal DRN, low potential side terminal GND, power supply terminal VCC, and external current adjustment terminal EX) connected to the outside.
  • the rectified voltage application terminal IN is connected to the high potential side of the rectifier circuit 112, and an input voltage Vin having a pulsating voltage waveform is input thereto.
  • the high potential side terminal DRN is connected to the series connection loop circuit 120 as described above.
  • the low potential side terminal GND is a ground terminal connected to the ground potential of the control circuit block 220 and serves as a reference potential (ground potential).
  • the capacitor 130 is connected between the power supply terminal VCC and the low potential side terminal GND.
  • the external current adjustment terminal EX is connected to the power supply terminal VCC via the resistor 140.
  • the switching element block 210 includes a switching element 211 and a current detection switching element 212.
  • the switching element 211 is connected in series to the series connection loop circuit 120 and intermittently supplies the input voltage Vin supplied from the power supply unit 110 to the LED light source unit 121 and the choke coil 122. Specifically, the switching element 211 is connected between the series connection loop circuit 120 and the grounded low potential side terminal GND.
  • the current detection switching element 212 is connected in parallel with the switching element 211 so that a current having a constant current ratio flows smaller than the current flowing through the switching element 211.
  • the high potential side terminal of the switching element 211 and the high potential side terminal of the current detection switching element 212 are connected in common and connected to the high potential side terminal DRN of the switching drive circuit 200.
  • the control terminal of the switching element 211 and the control terminal of the current detection switching element 212 are connected in common, and the control signal Vg is applied from the control circuit block 220.
  • the low potential side terminal of the switching element 211 is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the low potential side terminal of the current detection switching element 212 is connected to one end of a resistor 221 included in the control circuit block 220. The other end of the resistor 221 is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the switching element 211 and the current detection switching element 212 are supplied with a common control signal Vg at their commonly connected control terminals, the switching operation is performed simultaneously. That is, the switching element 211 and the current detection switching element 212 are turned on or turned off at the same timing.
  • the control circuit block 220 includes a resistor 221, a junction FET 222, a regulator circuit 223, an input voltage detection circuit 224, a start / stop circuit 225, a current adjustment circuit 226, a peak current detection circuit 227, and a SW control circuit. 228, a count circuit 229, and a current determination circuit 230.
  • the resistor 221 and the current detection switching element 212 are an example of a current detection circuit that detects a current value of a current flowing through the switching element 211.
  • the resistor 221 has one end connected to the low potential side terminal of the current detection switching element 212 and the other end connected to the low potential side terminal GND.
  • the resistor 221 is a resistor for converting a current flowing through the current detection switching element 212 into a voltage. That is, in the embodiment of the present invention, the current flowing through the switching element 211 is detected as voltage information.
  • the resistor 221 does not directly measure the current flowing through the switching element 211 but measures the current flowing through the current detection switching element 212. Since the current flowing through the switching element 212 for current detection is proportional to the current flowing through the switching element 211, the current value of the current flowing through the switching element 211 is indirectly measured by the configuration according to the embodiment of the present invention. be able to.
  • the high potential side terminal of the junction FET 222 is connected to the rectified voltage application terminal IN.
  • the low potential side terminal of the junction FET 222 is connected to the regulator circuit 223 and the input voltage detection circuit 224.
  • the regulator circuit 223 outputs the low potential side voltage of the junction FET 222 to the capacitor 130 via the power supply terminal VCC.
  • the regulator circuit 223 operates so that the voltage of the capacitor 130 (the voltage Vcc of the power supply terminal VCC) becomes constant.
  • the operation power supply voltage of the control circuit block 220 is generated using the voltage obtained by rectifying the AC voltage from the commercial power supply (AC power supply 111), the voltage during operation of the control circuit block 220 can be kept constant. it can. Therefore, on / off control (switching control) of the switching element 211 by the control circuit block 220 can be stabilized.
  • the input voltage detection circuit 224 determines whether or not the input voltage generated by the power supply unit 110 is equal to or higher than a predetermined set voltage. Specifically, the input voltage detection circuit 224 receives the low potential side voltage of the junction FET 222 and compares it with an internal reference voltage to detect whether the input power supply voltage Vin is equal to or higher than the set voltage. . Then, the input voltage detection circuit 224 outputs a detection signal whose state changes according to the detection result. Specifically, the signal level is high when the input power supply voltage Vin is equal to or higher than the set voltage, and a low level signal is output when the input power voltage Vin is lower than the set voltage.
  • the output terminal of the input voltage detection circuit 224 is connected to the input terminal of the start / stop circuit 225.
  • both the regulator circuit 223 and the input voltage detection circuit 224 are configured to be connected to the junction FET 222, but the present invention is not limited to this.
  • Various other circuits for converting the input voltage, which is a high voltage, into the power supply voltage Vcc of the switching drive circuit 200 are provided and are well known to those skilled in the art.
  • the configuration of the input voltage detection circuit 224 is not limited to this.
  • the input voltage is input from the rectified voltage application terminal IN to the switching drive circuit 200 through a voltage reduction resistor, and the divided voltage using resistance division is compared with the internal reference voltage inside the switching drive circuit 200, thereby obtaining the input voltage.
  • both the input signal to the regulator circuit 223 and the input signal to the input voltage detection circuit 224 need not be applied from the rectified voltage application terminal IN, and may be configured to have separate application terminals.
  • the start / stop circuit 225 causes the SW control circuit 228 in the first operation mode to start switching on and off of the switching element when the input voltage is equal to or higher than the set voltage. Further, the start / stop circuit 225 causes the SW control circuit 228 to stop switching of the switching element on and off when the input voltage is less than the set voltage.
  • the SW control circuit 228 and its operation mode will be described later.
  • the start / stop circuit 225 outputs either an ENABLE signal or a DISABLE signal according to the signal level from the input voltage detection circuit 224.
  • a signal (ENABLE signal or DISABLE signal) output from the start / stop circuit 225 is input to the SW control circuit 228 and the count circuit 229.
  • the ENABLE signal is a signal that enables switching control of the switching element 211 (that is, switching of the switching element 211 on and off), for example, a signal having a high signal level.
  • the DISABLE signal is a signal for stopping the switching control of the switching element 211, for example, a signal having a low signal level.
  • the current adjustment circuit 226 is connected to the external current adjustment terminal EX.
  • the current adjustment circuit 226 is connected to the peak current detection circuit 227.
  • the current adjustment circuit 226 inputs a signal corresponding to the current value applied from the external current adjustment terminal EX to the peak current detection circuit 227. That is, the current adjustment circuit 226 adjusts the reference voltage Vref according to the current value input from the external current adjustment terminal EX, and outputs a signal indicating the adjusted reference voltage Vref.
  • the peak current detection circuit 227 detects whether or not the current flowing through the switching element 211 has reached a preset peak value. When the current flowing through the switching element 211 reaches a preset peak value, the peak current detection circuit 227 outputs a peak current detection signal ILIMIT indicating that fact.
  • the peak current detection circuit 227 is a comparator having a plus input terminal, a minus input terminal, and an output terminal.
  • a connection portion between the current detection switching element 212 and the resistor 221 is connected to the positive input terminal, and a detection voltage Vsn generated in the resistor 221 by the current flowing through the current detection switching element 212 is input.
  • the reference voltage Vref adjusted by the current adjustment circuit 226 is input to the negative input terminal.
  • the output terminal is connected to the SW control circuit 228.
  • the peak current detection circuit 227 outputs a peak current detection signal ILIMIT having a high signal level when the detection voltage Vsn applied to the plus input terminal becomes equal to or higher than the reference voltage Vref.
  • the peak current detection signal ILIMIT output from the peak current detection circuit 227 is input to the SW control circuit 228. Since the reference voltage Vref is determined by the power supply voltage Vcc and the value of the resistor 140, it can be changed to an arbitrary value by changing the value of the resistor 140.
  • the current flowing through the current detection switching element 212 and the resistor 221 has a constant current ratio with respect to the current ID flowing through the switching element 211. Therefore, the peak current detection circuit 227 detects whether or not the current ID flowing through the switching element 211 has reached a predetermined peak value Ip by comparing the reference voltage Vref and the detection voltage Vsn. Can do. In addition, since the current flowing through the current detection switching element 212 and the resistor 221 is smaller than the current flowing through the switching element 211, the power loss can be reduced as compared with the case where the current flowing through the switching element 211 is directly detected by the resistor.
  • the peak current detection circuit 227 can compare the internal reference voltage Vref and the detection voltage Vsn.
  • the method for detecting the current flowing through the switching element 211 is not limited to these methods, and the detection method is not limited.
  • the current adjustment circuit 226 may dynamically change the peak value according to a value input from the outside. That is, the current adjustment circuit 226 may change the peak value by changing the reference voltage Vref according to the current value input from the external current adjustment terminal EX. Further, the current adjustment circuit 226 may change an upper limit reference value to be described later with the change of the peak value.
  • SW control circuit 228 controls on / off switching of switching element 211 in the first operation mode. Further, as will be described later, when the number of times measured by the count circuit 229 is equal to or greater than a predetermined determination reference value, the SW control circuit 228 is set to the first operation mode in the second operation mode for abnormality processing. Controls the switching element 211 in a different manner. As the determination reference value (number of times) for the number of counts, an optimum value is selected from about a dozen times depending on the oscillation frequency of the switching element 211 and the off time in the first operation mode.
  • the first operation mode is a normal operation mode and is a mode that is executed when it is determined that the LED light source unit 121 is not open. That is, the first operation mode is a mode in which switching control of the switching element 211 is performed according to a predetermined control method.
  • the second operation mode is an operation mode that is different from the first operation mode, and is an operation mode that is executed when any abnormality is detected in the series connection loop circuit 120. For example, in the second operation mode, the switching control of the switching element 211 is stopped.
  • the determination reference value is determined to such an extent that the switching element 211, the current detecting switching element 212, and other components can be prevented from being destroyed by applying an excessive voltage. Specifically, the determination reference value is determined based on the oscillation frequency of the switching element 211, the current value flowing through the switching element 211 when the LED light source unit 121 is opened, and the like.
  • the SW control circuit 228 performs switching control of the switching element 211 as an operation in the first operation mode during a period in which the ENABLE signal is input from the start / stop circuit 225.
  • the SW control circuit 228 inputs the switching control signal Vg to the switching element 211 at a preset timing, thereby turning on the switching element 211 and causing a current to flow through the switching element 211.
  • the SW control circuit 228 turns off the switching element 211 at the timing when the peak current detection signal ILIMIT output from the peak current detection circuit 227 is input. Thereby, the SW control circuit 228 performs control so that the peak current value of the current ID flowing through the switching element 211 is always the peak value Ip.
  • the SW control circuit 228 stops the operation of the switching element 211 during a period in which the DISABLE signal is input from the start / stop circuit 225.
  • the switching control method of the switching element 211 includes a PWM (Pulse Width Modulation) system that controls the on-duty of switching, a current mode PWM control system that changes the peak value of the current flowing through the switching element 211, and the like.
  • PWM Pulse Width Modulation
  • a current mode PWM control system that changes the peak value of the current flowing through the switching element 211
  • the control method is not limited.
  • the configuration based on these control systems is not shown in FIG.
  • the current determination circuit 230 is connected to a common connection portion between the current detection switching element 212 and the resistor 221 and receives the detection voltage Vsn. As shown in FIG. 1, the current determination circuit 230 includes an integration circuit 231, two comparators 232 and 233, and an AND circuit 234.
  • Integral circuit 231 receives detection voltage Vsn and outputs the maximum value of detection voltage Vsn. Note that when the switching element 211 is turned off, the output signal of the integrating circuit 231 is reset.
  • the comparator 232 is an example of an upper limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or lower than a predetermined upper limit reference value when the switching element 211 is turned off. In the present embodiment, the comparator 232 determines whether or not the current value detected by the resistor 221 is equal to or lower than the upper limit reference value.
  • the upper reference value is a value equal to or less than the peak value Ip.
  • the upper limit reference voltage IDH is input to the plus input terminal, and the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the minus input terminal.
  • the upper limit reference voltage IDH is set to a value smaller than a voltage corresponding to the peak value Ip (specifically, the reference voltage Vref).
  • the comparator 232 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is smaller than the upper limit reference voltage IDH.
  • the comparator 233 is an example of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value. In the present embodiment, the comparator 233 determines whether or not the current value detected by the resistor 221 is greater than or equal to the lower limit reference value.
  • the comparator 233 the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal.
  • the comparator 233 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is higher than the lower limit reference voltage IDL.
  • both the comparators 232 and 233 perform determination at the timing when the switching element 211 is turned off. Since the current flowing through the switching element 211 is maximized immediately before the switching element 211 is turned off, the comparators 232 and 233 use the maximum value of the current flowing through the switching element 211 (actually, the corresponding detection voltage Vsn). Make a decision.
  • the AND circuit 234 has two input terminals and an output terminal, calculates a logical product of signals input to the input terminal, and outputs the calculation result from the output terminal. Specifically, the output signals of the comparators 232 and 233 are input to the two input terminals, respectively, and the logical product of the output signals of the comparators 232 and 233 is output to the count circuit 229.
  • the values of the upper limit reference voltage IDH and the lower limit reference voltage IDL are arbitrary values set in advance so that Vref> IDH> IDL is satisfied.
  • the value of the upper limit reference voltage IDH may be adjusted according to the value of the reference voltage Vref adjusted by the current adjustment circuit 226.
  • the current determination circuit 230 outputs a high-level signal to the count circuit 229 when the maximum value of the detection voltage Vsn has a relationship of not less than IDL and not more than IDH.
  • the count circuit 229 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be equal to or lower than the upper limit reference value by the upper limit determination circuit and is determined to be equal to or higher than the lower limit reference value by the lower limit determination circuit. .
  • the count circuit 229 is a circuit that counts the number of high-level signals output from the current determination circuit 230.
  • the count circuit 229 outputs an open signal to the SW control circuit 228 when the count number reaches a predetermined determination number (determination reference value).
  • the count circuit 229 receives an output signal (ENABLE signal or DISABLE signal) from the start / stop circuit 225.
  • an output signal ENABLE signal or DISABLE signal
  • the count number of the count circuit 229 is reset.
  • 2A and 2B are waveform diagrams showing an example of an input voltage waveform and an operation period of the light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention.
  • FIG. 2A is a diagram showing the relationship between the input voltage waveform and the detection voltage Vinuv of the input voltage detection circuit 224.
  • the period of the input voltage Vin> the detection voltage Vinuv is a period in which the switching drive circuit 200 and the control circuit block 220 can operate.
  • the switching element 211 stops operating.
  • FIG. 2B is a diagram showing a waveform when the input voltage gradually increases when the input voltage is a pulsating waveform.
  • the switching drive circuit 200 and the control circuit block 220 are not operating, so the switching element 211 is also not operating.
  • the control circuit block 220 can operate in the period T2 in which the input voltage Vin is higher than the detection voltage Vinuv and lower than the output voltage VF_LED. Therefore, the SW control circuit 228 inputs the switching control signal Vg to the switching element 211, and the switching element 211 starts a switching operation, but no current flows through the switching element 211.
  • a waveform of a current flowing through the switching element 211 during normal operation is indicated by IDS1 in FIG.
  • the current waveform IDS1 is a simple increase current waveform having a slope (Vin ⁇ VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin ⁇ VF_LED) between the two terminals of the LED light source 121. It becomes.
  • the SW control circuit 228 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211, thereby causing the peak of the current flowing through the switching element 211.
  • the value is always controlled to be constant at Ip.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220 (that is, the detection voltage Vsn detected by the resistor 221), the upper limit reference voltage IDH, and the lower limit reference voltage IDL is expressed as “the maximum value of Vsn> IDH. Since “> IDL”, the current determination circuit 230 does not output a high level signal to the count circuit 229.
  • the internal control circuit block 220 and the switching element 211 start on and off control (switching operation).
  • the period T2 no current flows through the switching element 211 as described above.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> IDL> Vsn maximum value”.
  • the circuit 230 does not output a high level signal to the count circuit 229.
  • the open failure of the light-emitting diode can be classified into two types, a case where it is completely electrically insulated and a half-open state where a resistance component remains.
  • the input voltage Vin is not applied to the choke coil 122 and the switching element 211. For this reason, there is no possibility that a high voltage is applied to the choke coil 122 and the switching element 211 even if the LED light source 121 is opened.
  • the current that flows through the switching element 211 when the LED light source unit 121 is in a semi-open state is shown in IDS2 of FIG.
  • the impedance is higher than that in the normal state, and the current increase rate is reduced.
  • the switching element 211 is turned off according to the control method of the SW control circuit 228 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> maximum value of Vsn> IDL”.
  • a high level signal is output to the count circuit 229.
  • the count circuit 229 determines that the LED light source 121 that is a load is open when the number of counts is equal to or greater than a predetermined determination reference value, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped as the second operation mode for abnormality processing.
  • the light emitting diode driving apparatus 100 configured as described above does not require a dedicated resistor for detecting the current flowing through the LED light source unit 121, and is a current flowing through the switching element 211.
  • the open determination of the LED light source part 121 is possible.
  • the switching drive circuit 200 does not require an additional terminal, and the light emitting diode drive device 100 can be reduced in size and space.
  • the light-emitting-diode drive device 100 includes the count circuit 229, and determines a state where the LED light source unit 121 may be open a plurality of times. For example, as described above, when the input voltage is low, such as when the power is turned on, there is a case where it is determined that the LED light source unit 121 is open even if the LED light source unit 121 is not open. In this case, it is determined that the input voltage is not open (that is, normal) as the input voltage increases.
  • the determination is performed a plurality of times, even if it is determined that the circuit is open a predetermined number of times or less, it is not open. judge. Therefore, according to the light emitting diode drive device 100 according to Embodiment 1 of the present invention, erroneous detection can be prevented by setting the determination reference value to an appropriate value.
  • the light emitting diode driving apparatus 100 includes the current adjustment circuit 226, and can adjust the peak value Ip flowing through the switching element 211 to an appropriate value from the outside. Therefore, the LED open detection accuracy can be improved by arbitrarily setting the upper limit reference voltage IDH and the lower limit reference voltage IDL.
  • the light-emitting diode driving apparatus 100 includes the input voltage detection circuit 224, and stops the on / off control (switching operation) of the switching element 211 when the input voltage decreases. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the ON time of the switching element 211 is extended to reach the maximum ON time or the maximum ON duty period. The possibility of false detection of open is low.
  • the switching operation of the switching element 211 is stopped by the input voltage detection circuit 224.
  • the count is reset. That is, the count circuit 229 resets the measured number of times when the switching (switching operation) of the switching element 211 is stopped. For this reason, when the switching operation of the switching element 211 is restarted by the input voltage detection circuit 224 next, the number of counts is not held, so the possibility of erroneous detection is reduced.
  • the switching element block 210 and the control circuit block 220 are integrated on the same substrate, or the switching drive circuit 200 is configured as a semiconductor device incorporated in the same package, whereby a light emitting diode drive device (illumination device) is formed. ) Can be significantly reduced.
  • the present configuration is not limited to the light emitting diode driving device according to the first embodiment of the present invention, and can also be applied to light emitting diode driving devices according to other embodiments described below.
  • the full-wave rectifier circuit is used as the rectifier circuit 112 that rectifies the AC voltage, it is obvious that the same effect can be obtained even if the half-wave rectifier circuit is used. Furthermore, the effect of the present invention can be enjoyed even when a DC power supply is used instead of the AC power supply 111. The same applies to the embodiments described below.
  • the light emitting diode driving device determines whether or not the current flowing through the switching element is equal to or lower than the upper limit reference value by determining whether or not the maximum duty driving is performed.
  • the maximum duty drive is a control method in which the switching element is driven at a constant period, and when the period during which the switching element is on reaches a preset maximum period (maximum duty), the switching element is turned off. That is.
  • the current flowing through the switching element reaches the peak value and the switching element is turned off by the maximum duty drive before the switching element is turned off.
  • the current flowing through the switching element is not more than the upper reference value.
  • FIG. 4 is a circuit diagram showing an example of the light emitting diode driving apparatus 300 according to Embodiment 2 of the present invention. 4, constituent elements corresponding to those shown in FIG. 1 are given the same reference numerals as those in FIG. 1, and descriptions thereof are omitted.
  • the light emitting diode driving device 300 according to the second embodiment of the present invention is different from the first embodiment in the configuration of the control circuit block 420 of the switching driving circuit 400. Further, the connection relationship of the resistor 140 is different. Other configurations are the same as those in the first embodiment.
  • the SW control circuit 228 switches the switching element 211 from off to on in a preset cycle in the first operation mode (normal operation mode). Further, when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input, the switching element 211 is turned off.
  • the control circuit block 420 includes a count circuit 429, a comparator 433, a flip-flop circuit 435, and a clock generator 436 as shown in FIG. 4 instead of the count circuit 229 and the current determination circuit 230.
  • the resistor 140 is connected to the high potential side of the rectifier circuit 112 and the smoothing capacitor 113.
  • the reference voltage Vref set by the current adjustment circuit 226 changes according to the waveform of the input voltage.
  • the clock generator 436 is an example of a maximum duty detection circuit, and sets a maximum duty period (also described as maximum on-duty).
  • the maximum duty period is a maximum value of a period during which the switching element 211 is on in a cycle in which the switching element 211 is switched from on to off.
  • the clock generator 436 has a current value of the current flowing through the switching element 211 equal to or lower than the above upper limit reference value (IDH). It is determined that
  • the clock generator 436 includes an oscillator and outputs a CLOCK signal that determines the turn-on timing of each cycle of the switching element 211 and a MAXDUTY signal that determines the maximum on-duty.
  • the CLOCK signal is input to the SW control circuit 228, the SW control circuit 228 outputs the control signal Vg to the switching element 211, thereby turning on the switching element 211.
  • the peak current detection circuit 227 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, that is, when the detection voltage Vsn input to the peak current detection circuit 227 reaches the reference voltage Vref, the peak current detection circuit 227 is The peak current detection signal ILIMIT is output to the SW control circuit 228. As a result, the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211. By this control, control is performed so that the peak value of the current flowing through the switching element 211 is always constant at Ip.
  • the clock generator 436 when the clock generator 436 outputs the MAXDUTY signal to the SW control circuit 228 before the peak current detection circuit 227 outputs the peak current detection signal ILIMIT to the SW control circuit 228, the SW control circuit 228 causes the switching element 211 to be switched. A control signal Vg for turning off is output. Although not shown in FIG. 4, actually, when the SW control circuit 228 outputs the control signal Vg for turning off the switching element 211 by the peak current detection signal ILIMIT, the clock generator 436 does not output the MAXDUTY signal.
  • the comparator 433 is a part of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value.
  • the detection voltage Vsn is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal.
  • the comparator 433 outputs a high level signal to the flip-flop circuit 435 when the detection voltage Vsn is greater than the lower limit reference voltage IDL.
  • the comparator 433 determines whether the current value of the current flowing through the switching element 211 is greater than or equal to the lower limit reference value between the time when the switching element 211 is turned on and the time when the switching element 211 is turned off. Then, the determination result is held by the flip-flop circuit 435.
  • the flip-flop circuit 435 is a part of the lower limit determination circuit, and holds the determination result by the comparator 433. Each time the switching element 211 is turned on, the determination result is reset.
  • the flip-flop circuit 435 is, for example, an RS flip-flop circuit having a set terminal, a reset terminal, and an output terminal.
  • the output signal of the comparator 433 is input to the set terminal, and the CLOCK signal is input from the clock generator 436 to the reset terminal.
  • the output terminal is connected to the count circuit 429, and outputs an output signal to the count circuit 429 until a signal is input to the reset terminal after a signal is input to the set terminal.
  • the output signal is reset every time the CLOCK signal is output from the clock generator 436. That is, at the timing when the switching element 211 is turned on, the output of the flip-flop circuit 435 is reset once and then set by the output signal from the comparator 433.
  • the count circuit 429 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value.
  • the current value of the current flowing through the switching element 211 is compared with the upper reference value by detecting the time until the peak value is reached instead of directly comparing the current values. .
  • the count circuit 429 includes a peak current detection signal ILIMIT from the peak current detection circuit 227, a MAXDUTY signal from the clock generator 436, and a start / stop circuit 225.
  • Output signal (ENABLE signal or DISABLE signal).
  • the count circuit 429 increases the number of counts by one when the output signal from the flip-flop circuit 435 and the MAXDUTY signal from the clock generator 436 are input.
  • count circuit 429 outputs an open signal to SW control circuit 228.
  • the count circuit 429 resets the number of counts.
  • Embodiment 2 of the present invention configured as described above, the operation when the LED light source unit 121 is normal will be described.
  • the waveform of the current flowing through the switching element 211 during normal operation and the signal waveform of the control circuit block 420 are shown in IDS1 of FIG.
  • the current waveform IDS1 at this time is a simple increase current having a slope (Vin ⁇ VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin ⁇ VF_LED) between both terminals of the LED light source 121. It becomes a waveform.
  • the control circuit block 420 and the switching element 211 in the internal control circuit block 420 and the switching element 211 start on and off control, but in the period in which no current flows through the switching element 211,
  • the relationship between the detection voltage Vsn inside 420 and the lower limit reference voltage IDL is IDL> Vsn. For this reason, the count circuit 429 does not increase the number of counts.
  • the number of counts is reset by the peak current detection signal ILIMIT from the peak current detection circuit 227.
  • the on-period of the switching element 211 reaches the maximum on-duty defined by the clock generator 436 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip.
  • the clock generator 436 outputs a MAXDUTY signal
  • the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433.
  • the output signal is output to the count circuit 429.
  • the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the flip-flop circuit 435 When the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. . Even if the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn ⁇ IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit, the count circuit 429 can increase the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the light emitting diode driving apparatus 300 performs maximum duty driving when the value of the current flowing through the switching element 211 does not reach the peak value. That is, when the period during which the switching element 211 is on reaches a preset maximum duty period, the switching element 211 is turned off.
  • the current mode PWM control method for changing the peak value of the current flowing through the switching element 211 is described as an example of the control method for the switching element 211.
  • the present invention is not limited to this. Absent. Even in the case of the PWM method for controlling the switching on-duty, it is possible to perform the same control as in the second embodiment by defining the maximum on-duty of the switching element 211.
  • the same control as that of the second embodiment is performed also in the off-time fixed control method in which the off-time of the switching element 211 is fixed at a preset value or the PFM control method in which the oscillation frequency is changed.
  • Can do For example, first, a maximum time during which the switching element 211 can be turned on for each pulse, that is, a maximum ON period is defined.
  • the output signal from the flip-flop circuit 435 and a signal (not shown in FIG. 4) indicating that the maximum on-period has elapsed are applied to the count circuit 429, the number of counts is increased by one. Thus, the same effect can be obtained.
  • the light emitting diode driving apparatus determines whether or not the current flowing in the switching element 211 is equal to or lower than the upper reference value by determining whether or not the driving is the maximum on-time driving. Determine whether or not.
  • the maximum on-time driving is to turn off the switching element 211 when the period during which the switching element 211 is on reaches a preset maximum period (maximum on period). That is, in the light emitting diode driving device according to the modification of the second embodiment of the present invention, the current flowing through the switching element 211 reaches the peak value and is turned off by the maximum on-time driving before the switching element 211 is turned off. By detecting this, it is detected that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value.
  • the SW control circuit 228 turns on the switching element 211 after a predetermined period after the switching element 211 is turned off by the fixed off time control method. . As described above, the SW control circuit 228 turns off the switching element 211 when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input. .
  • the clock generator 436 is an example of a maximum on-period detection circuit, and sets a maximum on-period that is the maximum value of the period during which the switching element 211 is on. Then, when the period during which the switching element 211 is on reaches the maximum on-period (that is, when the maximum on-time driving is performed), it is determined that the current value of the current flowing through the switching element 211 is equal to or less than the upper limit reference value. Is done.
  • the number of times when the maximum on-time driving is performed is counted, thereby detecting LED open. It can be performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
  • the CLOCK signal for turning on the switching element 211 from the clock generator 436 is applied to the reset terminal of the flip-flop circuit 435, and detection is performed every switching cycle of the switching element 211. Less likely.
  • the count circuit 429 resets the number of times when the measured number does not increase in synchronization with the timing at which the switching element 211 is turned off. Thereby, the possibility of erroneous detection can be reduced.
  • the light emitting diode driving device is characterized in that a resistor, a capacitor, or a resistor and a capacitor connected in series with each other are connected in parallel to the LED light source unit.
  • the third embodiment is different from the first and second embodiments in the configuration of the series connection loop circuit 120. More specifically, an additional component is connected in parallel with the LED light source unit 121.
  • FIG. 6A to 6C are circuit diagrams showing an example of the configuration of the series connection loop circuit according to the third embodiment of the present invention.
  • the switching drive circuit light emitting diode drive semiconductor device
  • the power supply unit for driving these series-connected loop circuits are the circuit shown in FIG. 1 and the implementation shown in FIG. Either of the circuits shown in Embodiment 2 can be used.
  • 6A includes a LED light source unit 121, a choke coil 122, a diode 123, and a resistor 524.
  • the open failure of the light emitting diode can be classified into two types, that is, a case where it is completely electrically insulated (fully open state) and a semi-open state where a resistance component remains.
  • the resistance load is determined by the resistor 524 in the fully open state, and the residual high resistance and the resistor 524 are in the half open state. And combined resistance load.
  • a case where the LED light source unit 121 is in a completely open state will be described as an example.
  • the impedance becomes higher than that in the normal state, and the current increase rate becomes lower.
  • the maximum value of the current ID flowing through the switching element 211 does not reach the peak value Ip, and the ON period of the switching element 211 is determined by the clock generator 436.
  • the clock generator 436 outputs a MAXDUTY signal.
  • the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211.
  • the value of the lower limit reference voltage IDL is set in advance to be “a current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the resistor 524 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the lower limit reference voltage IDL may be a fixed value set inside in advance, or may be configured to be freely adjustable by the user from the outside. Further, the user sets the value of the resistor 524 according to the set IDL value and the number of connected light emitting diodes connected to the LED light source unit 121, that is, according to the value of VF_LED, “current value corresponding to IDL ⁇ VF_LED. / R524 "is adjusted. Thereby, in the period T2 of FIG. 2B, it is not erroneously determined that the LED light source unit 121 is open.
  • the current flowing through the switching element 211 and the signal waveform of the control circuit block 420 are similar to those of the IDS 3 in FIG. Also in this case, in the period T2 described with reference to FIG. 2B, the value of the lower limit reference voltage IDL and the maximum value of the current flowing through the resistor 524 are “current value corresponding to IDL> IRP524 (that is, the maximum value of the current)”. Therefore, the number of counts of the count circuit 429 does not increase.
  • the flip-flop circuit 435 when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433. The output signal is output to the count circuit 429. Even when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn ⁇ IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit 429, the count circuit 429 can increase the number of counts by one.
  • the series connection loop circuit 520b shown in FIG. 6B includes an LED light source unit 121, a choke coil 122, a diode 123, and a smoothing capacitor 525. As shown in FIG. 6B, a smoothing capacitor 525 is connected in parallel with the LED light source unit 121.
  • the value of the lower limit reference voltage IDL is “IC525> IDL beforehand. It is set so that it corresponds to the “current value”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty. When the number of counts is equal to or greater than a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the open state of the LED light source 121 can be accurately detected by the same operation as in FIG. 6A.
  • the series connection loop circuit 520c shown in FIG. 6C includes an LED light source unit 121, a choke coil 122, a diode 123, a resistor 524, and a smoothing capacitor 525. As shown in FIG. 6C, a smoothing capacitor 525 and a resistor 524 connected in series are connected to the LED light source unit 121 in parallel.
  • the LED light source 121 when the LED light source 121 is opened, a current flows through the smoothing capacitor 525 and the resistor 524. Further, the value of the flowing current is limited by the resistance value R524 of the resistor 524. Therefore, as in the period T2 described with reference to FIG. 2B, the maximum value of the current that flows during the period in which the input voltage Vin is lower than the output voltage VF_LED is determined by the IRP 524.
  • IR524 VF_LED / R524 is determined, and the value of the lower limit reference voltage IDL is set in advance so that “current value corresponding to IDL> IRP524”. For this reason, the current corresponding to the lower limit reference voltage IDL does not flow through the switching element 211 during the period T2.
  • the value of the lower limit reference voltage IDL is set in advance such that “current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or less than the current value of the current flowing through the resistor 524 and the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the user can connect the set IDL value and the LED light source by connecting a resistor 524 in series with the smoothing capacitor 525.
  • a resistor 524 in series with the smoothing capacitor 525.
  • erroneous detection of the LED light source unit 121 can be easily prevented. That is, by adjusting the value of the resistor 524 in accordance with the value of VF_LED so as to be in the range of “current value corresponding to IDL ⁇ VF_LED / R524”, the LED light source unit 121 is erroneously set in the period T2 of FIG. 2B. It is possible to easily adjust so that it is not determined to be open.
  • the open state of the LED light source unit 121 can be accurately detected by the same operation as in FIG. 6A.
  • Embodiment 3 of the present invention configured as described above, a current flows through the components connected in parallel even when the LED light source 121 is opened, but the comparator is an example of a lower limit determination circuit. Since it is detectable by 433, the detection accuracy of LED open improves.
  • the light emitting diode driving device includes an abnormality processing circuit that outputs an abnormality determination signal when the number of counts is equal to or greater than a predetermined determination reference value.
  • FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus 600 according to Embodiment 4 of the present invention.
  • the fourth embodiment includes a new abnormality processing circuit 650, a power supply unit 610 instead of the power supply unit 110, and a switching drive circuit 700 instead of the switching drive circuit 400. The point to prepare is different.
  • the switching drive circuit 700 newly has an external connection terminal OP, and outputs the open signal output from the count circuit 429 to the abnormality processing circuit 650 via the external connection terminal OP.
  • the abnormality processing circuit 650 outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit 429 is greater than or equal to the determination reference value. Specifically, the abnormality processing circuit 650 outputs an abnormality determination signal to the switch 614 included in the power supply unit 610 when an open signal is input via the external connection terminal OP.
  • the power supply unit 610 newly includes a switch 614.
  • the switch 614 is connected in series between the rectifier circuit 112 and the series connection loop circuit 120, and determines whether or not to apply the input voltage Vin to the LED light source unit 121 and the choke coil 122. Specifically, when an abnormality determination signal is input from the abnormality processing circuit 650, the switch 614 is turned off and stops supplying the input voltage Vin.
  • the count circuit 429 determines that the LED light source 121 that is a load is open when the number of counts exceeds a predetermined determination reference value, and outputs an open signal to the SW control circuit 228. Further, the open signal is also output to the abnormality processing circuit 650 via the external connection terminal OP.
  • the abnormality processing circuit 650 When the open signal is input, the abnormality processing circuit 650 outputs an abnormality determination signal to turn off the switch 614 so that the input voltage Vin is not supplied to the LED light source unit 121 side. As a result, it is possible to prevent an excessive voltage from being applied to peripheral components and switching elements.
  • the SW control circuit 228 may turn off the switching element 211 and hold the state where the switching operation is stopped.
  • the switching element 211 is stopped, and the input voltage is not applied, so that safety can be further improved.
  • the open signal output from the external connection terminal OP terminal may be configured to transmit a signal to another drive device different from the light emitting diode drive device. That is, the abnormality processing circuit 650 may output an abnormality determination signal to an external device in order to notify the user that the LED light source unit 121 is abnormal.
  • an open signal may be transmitted to another device to indicate that an abnormality has occurred to a third party.
  • the abnormality processing circuit 650 can display on the display unit that the LED light source unit 121 is open by outputting an abnormality determination signal to an external display unit.
  • the abnormality processing circuit 650 can notify the user that the LED light source unit 121 is open by an alarm sound or the like by outputting an abnormality determination signal to an external sound output unit.
  • the light emitting diode driving device 600 configured as described above outputs an abnormality determination signal when detecting the open of the LED. For this reason, the supply of input voltage is stopped using this output signal, the peripheral device is notified that the LED light source is open, an alarm is sounded, and the user is notified of an abnormality in the LED light source unit. it can.
  • the light emitting diode driving device and the light emitting diode driving semiconductor device according to the present invention have been described based on the embodiments, but the present invention is not limited to these embodiments. Unless it deviates from the meaning of this invention, the form which carried out the various deformation
  • the SW control circuit 228 may perform a timer intermittent operation that repeats driving and stopping of the switching element 211 at regular intervals as the second operation mode for abnormality processing. According to this, when the opening of the LED is detected, the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element 211.
  • comparison with the lower limit reference value may not be performed. That is, when the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value by the upper limit determination circuit is greater than or equal to a predetermined determination reference value, the count circuit 229 or 429 outputs the open signal. It may be output. Then, the SW control circuit 228 executes the second operation mode for abnormality processing when it is continuously detected a plurality of times that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value. Thereby, it can be detected that the LED light source unit 121 is open.
  • the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) may be performed simultaneously.
  • a circuit (specifically, the flip-flop circuit 435) for temporarily holding any determination result is not required, and thus a circuit configuration necessary for the determination is provided. It can be simplified.
  • the light-emitting diode driving device and the semiconductor device for driving a light-emitting diode according to the present invention can be used for all devices and devices using light-emitting diodes, and are useful as, for example, LED bulbs or LED lighting devices.

Abstract

Provided is a step-down chopper type LED drive device (100) is equipped with: an LED light source unit (121); a power source unit (110) to supply an input voltage; and a switching drive circuit (200) to keep the current flowing to the LED light source unit (121) constant. The switching drive circuit (200) has: a switching element (211) that intermittently supplies an input voltage to the LED light source unit (121); an SW control circuit (228) that controls the on and off switching of the switching element (211); comparators (232, 233) that determine whether the current value of the current flowing to the switching element (211) is below an upper reference value and above a lower reference value; and a count circuit (229) that measures the number of times the current value is below the upper reference value and above the lower reference value. The SW control circuit (228) executes an error processing mode when the measured number of times the current value is above an acceptable criterion value.

Description

発光ダイオード駆動装置及び発光ダイオード駆動用半導体装置Light emitting diode driving device and light emitting diode driving semiconductor device
　本発明は、発光ダイオード駆動装置、及び、発光ダイオードの駆動に用いられる半導体装置に関し、特に、降圧チョッパ型の駆動装置に関する。 The present invention relates to a light emitting diode driving device and a semiconductor device used for driving the light emitting diode, and more particularly to a step-down chopper type driving device.
　近年、発光ダイオード（以下、ＬＥＤ（Ｌｉｇｈｔ　Ｅｍｉｔｔｉｎｇ　Ｄｉｏｄｅ）と記載）を駆動する発光ダイオード駆動装置、及び、ＬＥＤの駆動に用いられる発光ダイオード駆動用半導体装置が開発され、実用化されている。特に、白色ＬＥＤを光源としたＬＥＤ電球などの照明装置の量産化が盛んに行われている。また、ＬＥＤを適切に駆動する駆動回路が種々提案されている。例えば、複数のＬＥＤが直列に接続されている場合に、特定のＬＥＤがオープンになった場合には不必要に出力電圧が上昇し、部品への負荷が増大する恐れや、駆動回路に過大な電圧が印加される恐れがあった。 In recent years, a light emitting diode driving device for driving a light emitting diode (hereinafter referred to as an LED (Light Emitting Diode)) and a light emitting diode driving semiconductor device used for driving the LED have been developed and put into practical use. In particular, mass production of lighting devices such as LED bulbs using white LEDs as a light source has been actively performed. Various drive circuits for appropriately driving LEDs have been proposed. For example, when a plurality of LEDs are connected in series, if a specific LED becomes open, the output voltage may rise unnecessarily, increasing the load on the components, or excessively high drive circuitry. There was a risk of voltage being applied.
　そこで、このようなＬＥＤのオープンを検出して安全な動作モードに切り替える機能を有する発光ダイオード駆動装置（照明装置）が開示されている（特許文献１）。 Therefore, a light emitting diode driving device (illumination device) having a function of detecting such LED open and switching to a safe operation mode is disclosed (Patent Document 1).
　図８を用いて、特許文献１に記載された従来の発光ダイオード駆動装置について説明する。図８は、特許文献１に記載された従来の発光ダイオード駆動装置の構成を示す回路図である。 Referring to FIG. 8, a conventional light emitting diode driving device described in Patent Document 1 will be described. FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus described in Patent Document 1. In FIG.
　従来の発光ダイオード駆動装置１１は、直列に接続された複数のＬＥＤ１８ａを含むＬＥＤ光源部１８に接続され、複数のＬＥＤ１８ａの点灯を制御する。図８に示すように、従来の発光ダイオード駆動装置１１は、電源電圧を所定の直流電圧に変換してＬＥＤ光源部１８に出力するコンバータを備えた点灯回路部１２と、ＬＥＤ光源部１８に流れる電流を検出する電流検出用抵抗１３とを有する。さらに、従来の発光ダイオード駆動装置１１は、電圧検出回路部１９を備える。 The conventional light emitting diode driving device 11 is connected to an LED light source unit 18 including a plurality of LEDs 18a connected in series, and controls lighting of the plurality of LEDs 18a. As shown in FIG. 8, the conventional LED driving device 11 flows through the LED light source unit 18 and the lighting circuit unit 12 including a converter that converts the power supply voltage into a predetermined DC voltage and outputs the voltage to the LED light source unit 18. And a current detection resistor 13 for detecting a current. Further, the conventional light emitting diode driving device 11 includes a voltage detection circuit unit 19.
　点灯回路部１２は、いわゆる昇圧型のＤＣ／ＤＣコンバータであり、インダクタンス素子１４と、ダイオード１５と、スイッチング素子１６と、キャパシタンス素子２０と、駆動制御回路１７とを備える。 The lighting circuit unit 12 is a so-called step-up DC / DC converter, and includes an inductance element 14, a diode 15, a switching element 16, a capacitance element 20, and a drive control circuit 17.
　インダクタンス素子１４は、直流電源ＶＥの高電圧側に一端が接続される。ダイオード１５は、アノードがインダクタンス素子１４の他端に接続される逆流防止用のダイオードである。スイッチング素子１６は、インダクタンス素子１４の他端と直流電源ＶＥの低電圧側との間に接続される、ＦＥＴ（Ｆｉｅｌｄ　Ｅｆｆｅｃｔ　Ｔｒａｎｓｉｓｔｏｒ）等のパワー素子である。キャパシタンス素子２０は、ダイオード１５のカソードと直流電源ＶＥの低電圧側との間に接続される。駆動制御回路１７は、点灯回路部１２の出力電圧Ｖを制御する。 One end of the inductance element 14 is connected to the high voltage side of the DC power supply VE. The diode 15 is a backflow preventing diode having an anode connected to the other end of the inductance element 14. The switching element 16 is a power element such as an FET (Field Effect Transistor) connected between the other end of the inductance element 14 and the low voltage side of the DC power supply VE. Capacitance element 20 is connected between the cathode of diode 15 and the low voltage side of DC power supply VE. The drive control circuit 17 controls the output voltage V of the lighting circuit unit 12.
　駆動制御回路１７は、電圧検出回路部１９及び電流検出用抵抗１３により、点灯回路部１２の出力を監視しながら、スイッチング素子１６のオン及びオフの制御を行う。具体的には、駆動制御回路１７は、制御機能とモード設定機能とを備えている。制御機能は、スイッチング素子１６のオン及びオフの制御を行う機能である。モード設定機能は、ＬＥＤ光源部１８の接続状態によって、点灯回路部１２の動作モードを通常モード又は非接続時（無負荷時）用の待機モード（若しくは、停止モード）に設定する機能である。 The drive control circuit 17 controls on and off of the switching element 16 while monitoring the output of the lighting circuit unit 12 by the voltage detection circuit unit 19 and the current detection resistor 13. Specifically, the drive control circuit 17 has a control function and a mode setting function. The control function is a function for controlling on and off of the switching element 16. The mode setting function is a function for setting the operation mode of the lighting circuit unit 12 to a normal mode or a standby mode for non-connection (no load) (or a stop mode) depending on the connection state of the LED light source unit 18.
　電流検出用抵抗１３は、ＬＥＤ光源部１８のカソードと直流電源ＶＥの低電圧側との間に接続される抵抗である。電流検出用抵抗１３は、ＬＥＤ光源部１８に流れる電流Ｉを電圧情報に変換し、駆動制御回路１７のフィードバック端子ＦＢにフィードバックする。 The current detection resistor 13 is a resistor connected between the cathode of the LED light source unit 18 and the low voltage side of the DC power source VE. The current detection resistor 13 converts the current I flowing through the LED light source unit 18 into voltage information and feeds it back to the feedback terminal FB of the drive control circuit 17.
　駆動制御回路１７は、電流検出用抵抗１３によって検出された電流Ｉが所定の閾値を越えていれば、ＬＥＤ光源部１８が接続されていると判断する。そして、駆動制御回路１７は、ＬＥＤ光源部１８に流れる電流が、予め定められた設定値となるようにコンバータの出力電圧を調整する通常モードで動作する。 The drive control circuit 17 determines that the LED light source unit 18 is connected if the current I detected by the current detection resistor 13 exceeds a predetermined threshold value. The drive control circuit 17 operates in a normal mode in which the output voltage of the converter is adjusted so that the current flowing through the LED light source unit 18 becomes a predetermined set value.
　また、駆動制御回路１７は、電流検出用抵抗１３によって検出された電流が上記閾値以下であれば、ＬＥＤ光源部１８が接続されていないと判断して、待機モード又は停止モードで動作する。待機モードは、上記出力電圧を所定値まで減少させるモードであり、停止モードは、点灯回路部１２の出力を停止するモードである。なお、上記所定の閾値は、ＬＥＤ光源部１８が正常に接続されている際に、ＬＥＤ光源部１８に流れる電流が少なくとも上記閾値を越える値であるように設定される。 Further, if the current detected by the current detection resistor 13 is equal to or less than the threshold value, the drive control circuit 17 determines that the LED light source unit 18 is not connected and operates in the standby mode or the stop mode. The standby mode is a mode in which the output voltage is decreased to a predetermined value, and the stop mode is a mode in which the output of the lighting circuit unit 12 is stopped. The predetermined threshold value is set such that when the LED light source unit 18 is normally connected, the current flowing through the LED light source unit 18 is at least a value exceeding the threshold value.
特許第４１６９００８号公報Japanese Patent No. 4169008
　しかしながら、上記従来技術では、次のような課題がある。 However, the above prior art has the following problems.
　まず、特許文献１に記載の従来の発光ダイオード駆動装置では、ＬＥＤに流れる電流を検出するための電流検出用抵抗が必要である。また、駆動制御回路には、電流検出用抵抗によって検出された電流検出情報を入力するための端子が必要となり、駆動装置の小型化、省スペース化、点灯回路ＩＣの小型化、小端子化を実現する際の課題となる。また、電流検出用抵抗にＬＥＤ電流が流れるので、電流検出用抵抗での消費電力のロスが大きい。 First, the conventional light-emitting diode driving device described in Patent Document 1 requires a current detection resistor for detecting the current flowing through the LED. In addition, the drive control circuit requires a terminal for inputting the current detection information detected by the current detection resistor, thereby reducing the size and space of the driving device, the size of the lighting circuit IC, and the size of the terminal. It becomes a problem when it is realized. Further, since the LED current flows through the current detection resistor, the loss of power consumption in the current detection resistor is large.
　また、商用交流電源（ＡＣ１００Ｖ／２４０Ｖなど）を元に整流平滑した高電圧を電源電圧とし、入力電源電圧に対して低電圧であるＬＥＤ光源に効率よく供給するためには降圧型駆動回路が有効である。降圧型駆動回路で使用する場合は、電流検出用抵抗の電位は高電圧になるので、検出した情報を駆動制御回路に入力するためには、駆動制御回路に高耐圧素子が必要になる。 In addition, a step-down drive circuit is effective to efficiently supply a high voltage rectified and smoothed based on a commercial AC power supply (AC100V / 240V, etc.) to an LED light source that is lower than the input power supply voltage. It is. When used in a step-down drive circuit, the potential of the current detection resistor becomes a high voltage, and thus a high voltage element is required in the drive control circuit in order to input the detected information to the drive control circuit.
　また、力率改善などのために商用交流電源を整流後に平滑しないで使用する入力脈流電圧駆動の場合、入力電圧が出力電圧よりも低くなる期間が発生する。この期間は、ＬＥＤ光源に電流が流れないため、ＬＥＤがオープンになったと誤検出する場合がある。 Also, in the case of input pulsating voltage driving that uses a commercial AC power supply without rectification after rectification for power factor improvement or the like, a period in which the input voltage is lower than the output voltage occurs. During this period, since no current flows through the LED light source, it may be erroneously detected that the LED is open.
　また、ＬＥＤ光源に流れる電流波形のリップル低減やノイズ対策などのためにＬＥＤ光源の直近に平滑用コンデンサ及びダミー抵抗を並列接続することが多い。このような場合、ＬＥＤがオープンになっても、平滑用コンデンサ及びダミー抵抗を介して電流が流れるため、駆動制御回路は正常に検出できない場合がある。 Also, a smoothing capacitor and a dummy resistor are often connected in parallel in the immediate vicinity of the LED light source in order to reduce ripples in the current waveform flowing through the LED light source and to prevent noise. In such a case, even if the LED is open, current may flow through the smoothing capacitor and the dummy resistor, so the drive control circuit may not be able to detect normally.
　そこで、本発明は、上記従来の問題点に鑑み、専用の抵抗及び端子を必要とせず、入力電圧が低い場合、及び、ＬＥＤに平滑用コンデンサなどが並列接続されている場合であっても、正常にＬＥＤのオープンを検出することができる発光ダイオード駆動装置及び発光ダイオード駆動用の半導体装置を提供することを目的とする。 Therefore, in view of the above-described conventional problems, the present invention does not require a dedicated resistor and terminal, and when the input voltage is low, and when a smoothing capacitor or the like is connected in parallel to the LED, An object of the present invention is to provide a light-emitting diode driving device and a light-emitting diode driving semiconductor device capable of normally detecting LED open.
　上記目的を達成するために、本発明の一態様に係る発光ダイオード駆動装置は、１個以上の発光ダイオードを駆動する降圧チョッパ型の発光ダイオード駆動装置であって、前記１個以上の発光ダイオードを有するＬＥＤ光源部、前記ＬＥＤ光源部に直列に接続されたチョークコイル、及び、前記チョークコイルに生じる逆起電力を前記ＬＥＤ光源部に供給するためのダイオードを有する直列接続ループ回路と、前記直列接続ループ回路に接続され、前記ＬＥＤ光源部及び前記チョークコイルに入力電圧を供給するための電源部と、前記直列接続ループ回路に接続され、前記ＬＥＤ光源部に流れる電流を定電流制御するためのスイッチング駆動回路とを備え、前記スイッチング駆動回路は、スイッチング素子ブロックと、制御回路ブロックとを含み、前記スイッチング素子ブロックは、前記直列接続ループ回路に直列に接続され、前記電源部によって供給される入力電圧を断続的に前記ＬＥＤ光源部及び前記チョークコイルへ供給するスイッチング素子を有し、前記制御回路ブロックは、第１動作モードにおいて、前記スイッチング素子のオン及びオフの切り替えを制御するＳＷ制御回路と、前記スイッチング素子がターンオフする際に、前記スイッチング素子に流れる電流の電流値が予め定められた上限基準値以下であるか否かを判定する上限判定回路と、前記スイッチング素子に流れる電流の電流値が予め定められた下限基準値以上であるか否かを判定する下限判定回路と、前記スイッチング素子に流れる電流の電流値が、前記上限判定回路によって前記上限基準値以下であると判定され、かつ、前記下限判定回路によって前記下限基準値以上であると判定された回数を計測するカウント回路とを有し、前記ＳＷ制御回路は、前記カウント回路によって計測された回数が予め定められた判定基準値以上である場合に、異常処理用の第２動作モードにおいて、前記第１動作モードとは異なる方式で前記スイッチング素子の制御を行う。 In order to achieve the above object, a light-emitting diode driving device according to an aspect of the present invention is a step-down chopper type light-emitting diode driving device that drives one or more light-emitting diodes. An LED light source unit, a choke coil connected in series to the LED light source unit, a series connection loop circuit including a diode for supplying back electromotive force generated in the choke coil to the LED light source unit, and the series connection A power supply unit that is connected to a loop circuit and supplies an input voltage to the LED light source unit and the choke coil, and a switching unit that is connected to the series connection loop circuit and that controls the current flowing through the LED light source unit. A driving circuit, the switching driving circuit comprising: a switching element block; a control circuit block; The switching element block includes a switching element that is connected in series to the series connection loop circuit and intermittently supplies an input voltage supplied by the power supply unit to the LED light source unit and the choke coil, In the first operation mode, the control circuit block includes a SW control circuit that controls switching of the switching element on and off, and a current value of a current that flows through the switching element when the switching element is turned off. An upper limit determination circuit for determining whether the current value of the current flowing through the switching element is equal to or higher than a predetermined lower limit reference value; The current value of the current flowing through the switching element is equal to or lower than the upper limit reference value by the upper limit determination circuit. And a count circuit that counts the number of times determined by the lower limit determination circuit to be equal to or greater than the lower limit reference value, and the SW control circuit has a predetermined number of times measured by the count circuit. In the second operation mode for abnormality processing, the switching element is controlled by a method different from that in the first operation mode.
　本態様によれば、ＬＥＤのオープンを検出するのにスイッチング素子に流れる電流を利用するので、専用の抵抗及び端子を必要としない。つまり、ＬＥＤ光源部に流れる電流を検出するための抵抗を必要としないため、抵抗でのロスを考慮する必要がなく、高効率での駆動が可能である。また、スイッチング素子がオフする際のスイッチング素子に流れる電流の電流値が上限基準値以下であるか否かを判定するので、ＬＥＤのオープン（ＬＥＤ光源部の高負荷インピーダンス状態）によってスイッチング素子に流れる電流が小さくなったことを検出することができる。したがって、スイッチング素子に流れる電流を用いて、ＬＥＤ光源部のオープン判定が可能なため、追加の端子が不要であり、発光ダイオード駆動装置の小型化、及び、省スペース化を実現することができる。 According to this aspect, since the current flowing through the switching element is used to detect the opening of the LED, a dedicated resistor and terminal are not required. That is, since a resistor for detecting the current flowing through the LED light source unit is not required, it is not necessary to consider a loss in the resistor, and high-efficiency driving is possible. In addition, since it is determined whether or not the current value of the current flowing through the switching element when the switching element is turned off is equal to or lower than the upper limit reference value, the current flows through the switching element due to the open of the LED (high load impedance state of the LED light source unit). It can be detected that the current has decreased. Therefore, since it is possible to determine whether the LED light source unit is open using the current flowing through the switching element, an additional terminal is not required, and the light emitting diode driving device can be reduced in size and space can be saved.
　さらに、本態様によれば、スイッチング素子に流れる電流の電流値が下限基準値以上であるか否かを判定することで、ＬＥＤが正常であってもスイッチング素子に流れる電流値が低くなる場合（例えば、入力電圧が低い場合、又は、ＬＥＤに並列に平滑用コンデンサなどが接続されている場合）を、ＬＥＤがオープンであると誤検出することを防止することができる。さらに、スイッチング素子に流れる電流値が上限基準値以下であり、かつ、下限基準値以上であると判定した回数を計測し、計測した回数と判定基準値とを比較するので、継続してＬＥＤがオープンである場合を検出することができる。したがって、例えば、入力電圧が出力電圧よりも低くなり、ＬＥＤ光源部に電流が流れない期間が発生しても、予め設定された下限基準値以上の電流がスイッチング素子に流れていない期間は、カウント回路の計測を行わないため、誤検出を防止することができる。 Furthermore, according to this aspect, when the value of the current flowing through the switching element is greater than or equal to the lower limit reference value, the value of the current flowing through the switching element is low even if the LED is normal ( For example, when the input voltage is low, or when a smoothing capacitor or the like is connected in parallel with the LED, it is possible to prevent erroneous detection that the LED is open. Furthermore, since the number of times that the value of the current flowing through the switching element is less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value is measured and the measured number is compared with the determination reference value, the LED continuously The case where it is open can be detected. Therefore, for example, even if a period in which the input voltage is lower than the output voltage and no current flows in the LED light source unit occurs, a period in which no current exceeding the preset lower limit reference value flows in the switching element is counted. Since the circuit is not measured, erroneous detection can be prevented.
　このように、本態様によれば、専用の抵抗及び端子を必要とせず、入力電圧が低い場合、及び、ＬＥＤに平滑用コンデンサなどが並列接続されている場合であっても、正常にＬＥＤのオープンを検出することができる。 As described above, according to this aspect, the dedicated resistor and terminal are not required, and even when the input voltage is low and when the smoothing capacitor or the like is connected in parallel to the LED, the LED normally Open can be detected.
　また、前記制御回路ブロックは、さらに、前記スイッチング素子に流れる電流の電流値を検出する電流検出回路を有し、前記上限判定回路は、前記電流検出回路によって検出された電流値が、前記上限基準値以下であるか否かを判定し、前記下限判定回路は、前記電流検出回路によって検出された電流値が、前記下限基準値以上であるか否かを判定してもよい。 The control circuit block further includes a current detection circuit that detects a current value of a current flowing through the switching element, and the upper limit determination circuit is configured such that the current value detected by the current detection circuit is equal to the upper limit reference. The lower limit determination circuit may determine whether or not the current value detected by the current detection circuit is equal to or greater than the lower limit reference value.
　本態様によれば、上限基準値との比較（上限判定）及び下限基準値との比較（下限判定）の双方とも、電流検出回路によって検出された電流値を利用するので、判定を容易に行うことができる。例えば、上限判定及び下限判定を同時に行うことで、いずれかの判定結果を一時的に保持するための回路を必要としないので、判定に必要な回路構成を簡略化することができる。 According to this aspect, since both the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) use the current value detected by the current detection circuit, the determination is easily performed. be able to. For example, by performing the upper limit determination and the lower limit determination at the same time, a circuit for temporarily holding one of the determination results is not required, so that the circuit configuration necessary for the determination can be simplified.
　また、前記ＳＷ制御回路は、前記第１動作モードにおいて、前記スイッチング素子を予め設定された周期でオフからオンに切り替え、前記上限判定回路は、前記周期内における前記スイッチング素子がオンしている期間の最大値である最大デューティ期間を設定し、前記スイッチング素子がオンしている期間が前記最大デューティ期間に達した場合に、前記スイッチング素子に流れる電流の電流値が前記上限基準値以下であると判定する最大デューティ検出回路を有してもよい。 In the first operation mode, the SW control circuit switches the switching element from OFF to ON at a preset period, and the upper limit determination circuit is a period during which the switching element is ON in the period. When the maximum duty period that is the maximum value of the switching element is set, and the period during which the switching element is on reaches the maximum duty period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum duty detection circuit to determine.
　本態様によれば、周期内におけるスイッチング素子がオンしている期間の最大値である最大デューティ期間が設定されるので、スイッチング素子がオンしている期間が最大デューティ期間に達すること（最大デューティ駆動）が、スイッチング素子に流れる電流が上限基準値以下であることを意味する。したがって、スイッチング素子に流れる電流が、予め設定された上限基準値に達するかどうかに係わりなく、最大デューティ駆動となった場合の回数をカウントすることで、ＬＥＤのオープンの検出を行うことができる。このとき、上限基準値との比較のために電流の検出を行わなくてよく、最大デューティ駆動であるか否かを判定するだけでよいので、オープンの検出精度を向上することができる。 According to this aspect, since the maximum duty period, which is the maximum value of the period during which the switching element is on in the cycle, is set, the period during which the switching element is on reaches the maximum duty period (maximum duty drive). ) Means that the current flowing through the switching element is equal to or lower than the upper limit reference value. Therefore, regardless of whether or not the current flowing through the switching element reaches a preset upper limit reference value, the open state of the LED can be detected by counting the number of times when the maximum duty drive is performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the maximum duty drive is performed, so that the open detection accuracy can be improved.
　また、前記ＳＷ制御回路は、前記第１動作モードにおいて、前記スイッチング素子がターンオフされてから予め設定された期間後に、前記スイッチング素子をターンオンし、前記上限判定回路は、前記スイッチング素子がオンしている期間の最大値である最大オン期間を設定し、前記スイッチング素子がオンしている期間が前記最大オン期間に達した場合に、前記スイッチング素子に流れる電流の電流値が前記上限基準値以下であると判定する最大オン期間検出回路を有してもよい。 In the first operation mode, the SW control circuit turns on the switching element after a predetermined period from when the switching element is turned off, and the upper limit determination circuit turns on the switching element. A maximum on-period that is a maximum value of a certain period of time is set, and when the period during which the switching element is on reaches the maximum on-period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum ON period detection circuit determined to exist.
　本態様によれば、スイッチング素子がオンしている期間の最大値である最大オン期間が設定されるので、スイッチング素子がオンしている期間が最大オン期間に達すること（最大オン時間駆動）が、スイッチング素子に流れる電流が上限基準値以下であることを意味する。したがって、スイッチング素子に流れる電流が、予め設定された上限基準値に達するかどうかに係わりなく、最大オン時間駆動となった場合の回数をカウントすることで、ＬＥＤのオープンの検出を行うことができる。このとき、上限基準値との比較のために電流の検出を行わなくてよく、最大オン時間駆動であるか否かを判定するだけでよいので、オープンの検出精度を向上することができる。 According to this aspect, since the maximum on period that is the maximum value of the period during which the switching element is on is set, the period during which the switching element is on reaches the maximum on period (maximum on-time driving). This means that the current flowing through the switching element is equal to or lower than the upper reference value. Therefore, regardless of whether or not the current flowing through the switching element reaches a preset upper limit reference value, it is possible to detect the opening of the LED by counting the number of times when the maximum on-time driving is performed. . At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
　また、前記制御回路ブロックは、さらに、前記スイッチング素子に流れる電流の電流値が予め設定されたピーク値になった場合に、ピーク電流検出信号を出力するピーク電流検出回路を有し、前記ＳＷ制御回路は、前記第１動作モードにおいて、前記ピーク電流検出信号が入力された場合に、前記スイッチング素子をターンオフさせ、前記上限基準値は、前記ピーク値以下の値であってもよい。 The control circuit block further includes a peak current detection circuit that outputs a peak current detection signal when the current value of the current flowing through the switching element reaches a preset peak value, and the SW control The circuit may turn off the switching element when the peak current detection signal is input in the first operation mode, and the upper reference value may be a value equal to or lower than the peak value.
　本態様によれば、ＬＥＤ光源部の電流値に応じて上限基準値を任意に設定できるため、ＬＥＤのオープンの検出精度を向上することができる。 According to this aspect, since the upper limit reference value can be arbitrarily set according to the current value of the LED light source unit, it is possible to improve the detection accuracy of LED open.
　また、前記制御回路ブロックは、さらに、外部から入力される値に応じて、前記ピーク値を動的に変更する電流調整回路を有してもよい。 The control circuit block may further include a current adjustment circuit that dynamically changes the peak value according to a value input from the outside.
　本態様によれば、ＬＥＤ光源部に流れる電流を調整することが可能である。また、ＬＥＤ光源部のオープンの判定が可能である。 According to this aspect, it is possible to adjust the current flowing through the LED light source unit. In addition, it is possible to determine whether the LED light source unit is open.
　また、前記電流調整回路は、さらに、前記ピーク値の変更に伴って、前記上限基準値を変更してもよい。 Further, the current adjustment circuit may further change the upper limit reference value in accordance with the change of the peak value.
　本態様によれば、ピーク値の変更とともに上限基準値を変更することができるので、ＬＥＤ光源部のオープンの検出精度を向上することができる。 According to this aspect, since the upper limit reference value can be changed together with the change of the peak value, the open detection accuracy of the LED light source unit can be improved.
　また、前記電源部は、交流電圧を生成する交流電源と、前記交流電圧を整流することで、脈流電圧である前記入力電圧を生成する整流回路とを有してもよい。 Further, the power supply unit may include an AC power source that generates an AC voltage, and a rectifier circuit that generates the input voltage that is a pulsating voltage by rectifying the AC voltage.
　本態様によれば、入力電圧が出力電圧よりも低くなりＬＥＤ光源部に電流が流れない期間が発生しても、予め設定された下限基準値以上の電流がスイッチング素子に流れていない期間はカウント回路の計測を行わないため、誤検出することはない。 According to this aspect, even if a period in which the input voltage is lower than the output voltage and no current flows in the LED light source unit occurs, a period in which no current exceeding the preset lower limit reference value flows in the switching element is counted. Since the circuit is not measured, there is no false detection.
　また、前記制御回路ブロックは、さらに、前記入力電圧が予め定められた設定電圧以上であるか否かを判定する入力電圧検出回路と、前記入力電圧が前記設定電圧以上である場合、前記ＳＷ制御回路に前記第１動作モードにおける前記スイッチング素子のオン及びオフの切り替えを起動させ、前記入力電圧が前記設定電圧未満の場合、前記ＳＷ制御回路に前記第１動作モードにおける前記スイッチング素子のオン及びオフの切り替えを停止させる起動／停止回路とを有してもよい。 The control circuit block further includes an input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage, and the SW control when the input voltage is equal to or higher than the set voltage. When the circuit activates switching of the switching element in the first operation mode and the input voltage is less than the set voltage, the SW control circuit causes the switching element to turn on and off in the first operation mode. And a start / stop circuit for stopping the switching.
　本態様によれば、入力電圧が低下した際に、スイッチング素子のスイッチング動作（オン及びオフの切り替え制御）が停止される。このため、入力電圧値と出力電圧値とが近接して、スイッチング素子のオン時間が延びて最大オン時間又は最大オンデューティに達する前に、スイッチング動作を停止することが可能であり、ＬＥＤオープンを誤検出する可能性が低い。 According to this aspect, when the input voltage decreases, the switching operation of the switching element (on / off switching control) is stopped. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the on-time of the switching element is extended to reach the maximum on-time or the maximum on-duty. The possibility of false detection is low.
　また、前記直列接続ループ回路は、さらに、前記ＬＥＤ光源部に並列接続された抵抗を有し、前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記抵抗に流れる電流の電流値以下の値であってもよい。 The series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and the lower limit reference value is a current of a current flowing through the resistor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
　本態様によれば、ＬＥＤ光源部がオープンになっても、並列接続された抵抗に電流が流れるが、下限判定回路によって、ＬＥＤ光源部がオープンであるために電流が流れていることを検出することができる。したがって、ＬＥＤのオープンの検出精度を向上することができる。 According to this aspect, even if the LED light source unit is open, a current flows through the resistor connected in parallel, but the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
　また、前記直列接続ループ回路は、さらに、前記ＬＥＤ光源部に並列接続されたコンデンサを有し、前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記コンデンサに流れる電流の電流値以下の値であってもよい。 The series-connected loop circuit further includes a capacitor connected in parallel to the LED light source unit, and the lower limit reference value is a current flowing through the capacitor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
　本態様によれば、ＬＥＤ光源部がオープンになっても、並列接続されたコンデンサに電流が流れるが、下限判定回路によって、ＬＥＤ光源部がオープンであるために電流が流れていることを検出することができる。したがって、ＬＥＤのオープンの検出精度を向上することができる。 According to this aspect, even when the LED light source unit is opened, a current flows through the capacitors connected in parallel, but the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
　また、前記直列接続ループ回路は、さらに、前記ＬＥＤ光源部に並列接続された抵抗と、前記抵抗に直列接続され、前記ＬＥＤ光源部に並列接続されたコンデンサとを有し、前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記抵抗及び前記コンデンサに流れる電流の電流値以下の値であってもよい。 The series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and a capacitor connected in series to the resistor and connected in parallel to the LED light source unit, and the lower limit reference value is When the at least one light emitting diode is open, it may be a value equal to or smaller than the current value of the current flowing through the resistor and the capacitor.
　本態様によれば、ＬＥＤ光源がオープンになっても、並列接続された部品（抵抗及びコンデンサ）に電流が流れるが、下限判定回路によって、ＬＥＤ光源部がオープンであるために電流が流れていることを検出することができる。したがって、ＬＥＤのオープンの検出精度を向上することができる。 According to this aspect, even if the LED light source is open, current flows through the components (resistors and capacitors) connected in parallel, but the current flows because the LED light source unit is open by the lower limit determination circuit. Can be detected. Therefore, the detection accuracy of LED open can be improved.
　また、前記下限判定回路は、前記スイッチング素子がターンオンされる度に、判定結果をリセットしてもよい。 The lower limit determination circuit may reset the determination result each time the switching element is turned on.
　本態様によれば、下限判定回路による判定結果を、スイッチング素子のスイッチングサイクル毎にリセットするので、誤検出の可能性を低くすることができる。 According to this aspect, since the determination result by the lower limit determination circuit is reset for each switching cycle of the switching element, the possibility of erroneous detection can be reduced.
　また、前記下限判定回路は、前記スイッチング素子がターンオンしてからターンオフするまでの期間に、前記スイッチング素子に流れる電流の電流値が、前記下限基準値以上であるか否かを判定してもよい。 The lower limit determination circuit may determine whether a current value of a current flowing through the switching element is equal to or higher than the lower limit reference value during a period from when the switching element is turned on to when the switching element is turned off. .
　これにより、下限判定のタイミングを比較的自由に変更できるので、誤検出の可能性をより低くすることができる。 This makes it possible to change the timing of the lower limit determination relatively freely, thereby further reducing the possibility of erroneous detection.
　また、前記カウント回路は、計測した回数が、前記スイッチング素子がターンオフするタイミングと同期して増加しない場合、当該回数をリセットしてもよい。 Further, the count circuit may reset the number of times when the measured number does not increase in synchronization with the timing at which the switching element is turned off.
　本態様によれば、カウント回数が連続的に増加中にスイッチング素子に流れる電流が上限基準値以上である場合、又は、ピーク値に達した場合はカウント回数がリセットされるので、誤検出の可能性を低くすることができる。 According to this aspect, the number of counts is reset when the current flowing through the switching element is continuously exceeding the upper limit reference value or the peak value is reached while the number of counts is continuously increasing. Can be lowered.
　また、前記カウント回路は、前記スイッチング素子のオン及びオフの切り替えが停止された場合に、計測した回数をリセットしてもよい。 In addition, the count circuit may reset the measured number of times when the switching of the switching element is stopped.
　本態様によれば、例えば、入力電圧が脈流電圧の場合で徐々に電圧が低下する際に誤ってカウント回数を計測しても、スイッチング素子のオン・オフ制御が停止されると、カウント回数がリセットされる。このため、次にスイッチング素子のオン・オフ制御が再開されたときに、カウント回数が保持されていないので、誤検出の可能性を低くすることができる。 According to this aspect, for example, when the on-off control of the switching element is stopped even if the count number is erroneously measured when the input voltage is a pulsating voltage and the voltage gradually decreases, the count number Is reset. For this reason, when the on / off control of the switching element is restarted next time, the number of counts is not held, so that the possibility of erroneous detection can be reduced.
　また、前記ＳＷ制御回路は、前記第２動作モードとして、前記スイッチング素子をラッチ停止させてもよい。 The SW control circuit may stop the switching element from latching as the second operation mode.
　本態様によれば、ＬＥＤのオープンを検出した際に、周辺部品又はスイッチング素子に過大な電圧が印加されることを防止できる。 According to this aspect, when an open state of the LED is detected, it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element.
　また、前記ＳＷ制御回路は、前記第２動作モードとして、一定の間隔で前記スイッチング素子の駆動と停止とを繰り返すタイマー間欠動作を行ってもよい。 The SW control circuit may perform a timer intermittent operation in which the switching element is driven and stopped at regular intervals as the second operation mode.
　本態様によれば、ＬＥＤのオープンを検出した際に、スイッチング動作によるエネルギー出力を低下させる動作となるため、周辺部品又はスイッチング素子に過大な電圧が印加されることを防止できる。 According to this aspect, when the open state of the LED is detected, the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element.
　また、前記発光ダイオード駆動装置は、さらに、前記カウント回路によって計測された回数が前記判定基準値以上である場合に、異常であることを示す異常判定信号を出力する異常処理回路を有してもよい。 The light emitting diode driving device may further include an abnormality processing circuit that outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit is equal to or greater than the determination reference value. Good.
　本態様によれば、ＬＥＤオープンを検出した際に、異常判定信号を出力するため、この異常判定信号を利用して入力電圧の供給を停止し、ＬＥＤ光源部がオープンであることを周辺装置に伝達し、又は、アラームを鳴らすことでＬＥＤ光源部が異常であることを使用者に知らせることができる。 According to this aspect, when an LED open is detected, an abnormality determination signal is output. Therefore, the supply of input voltage is stopped using this abnormality determination signal, and the peripheral device is informed that the LED light source unit is open. By transmitting or sounding an alarm, the user can be informed that the LED light source unit is abnormal.
　また、本発明の一態様に係る発光ダイオード駆動用の半導体装置は、発光ダイオードを駆動するための半導体装置であって、上記の前記スイッチング素子ブロックと前記制御回路ブロックとを備え、前記スイッチング素子ブロックと前記制御回路ブロックとは、同一の半導体基板上に形成されている、又は、同一のパッケージに組み込まれている。 A semiconductor device for driving a light emitting diode according to one aspect of the present invention is a semiconductor device for driving a light emitting diode, and includes the switching element block and the control circuit block. And the control circuit block are formed on the same semiconductor substrate or incorporated in the same package.
　本態様によれば、スイッチング素子と制御回路とを１つのパッケージに組み込むことが可能となる。したがって、この半導体装置を用いて発光ダイオード駆動装置を構成すれば、発光ダイオード駆動装置の部品点数を大幅に削減することができ、発光ダイオード駆動装置の小型化及び軽量化さらには低コスト化を容易に実現することができる。 According to this aspect, the switching element and the control circuit can be incorporated into one package. Therefore, if the light emitting diode driving device is configured using this semiconductor device, the number of parts of the light emitting diode driving device can be greatly reduced, and the light emitting diode driving device can be easily reduced in size, weight and cost. Can be realized.
　本発明によれば、専用の抵抗及び端子を必要とせず、入力電圧が低い場合、及び、ＬＥＤに平滑用コンデンサなどが並列接続されている場合であっても、正常にＬＥＤのオープンを検出することができる。 According to the present invention, a dedicated resistor and terminal are not required, and even when the input voltage is low and when a smoothing capacitor or the like is connected in parallel to the LED, the open of the LED is normally detected. be able to.
図１は、本発明の実施の形態１に係る発光ダイオード駆動装置の一例を示す回路図である。FIG. 1 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention. 図２Ａは、本発明の実施の形態１に係る入力電圧の波形と発光ダイオード駆動装置の動作期間とを示す波形図である。FIG. 2A is a waveform diagram showing a waveform of an input voltage and an operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention. 図２Ｂは、本発明の実施の形態１に係る入力電圧の波形と発光ダイオード駆動装置の動作期間とを示す波形図である。FIG. 2B is a waveform diagram showing the waveform of the input voltage and the operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention. 図３は、本発明の実施の形態１に係るスイッチング素子に流れる電流の波形の一例を示す波形図である。FIG. 3 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 1 of the present invention. 図４は、本発明の実施の形態２に係る発光ダイオード駆動装置の一例を示す回路図である。FIG. 4 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 2 of the present invention. 図５は、本発明の実施の形態２に係るスイッチング素子に流れる電流の波形の一例を示す波形図である。FIG. 5 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 2 of the present invention. 図６Ａは、本発明の実施の形態３に係る直列接続ループ回路の一例を示す回路図である。FIG. 6A is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention. 図６Ｂは、本発明の実施の形態３に係る直列接続ループ回路の一例を示す回路図である。FIG. 6B is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention. 図６Ｃは、本発明の実施の形態３に係る直列接続ループ回路の一例を示す回路図である。FIG. 6C is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention. 図７は、本発明の実施の形態４に係る発光ダイオード駆動装置の一例を示す回路図である。FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 4 of the present invention. 図８は、従来の発光ダイオード駆動装置の構成を示す回路図である。FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus.
　以下、本発明の実施の形態について、図面を参照しながら説明する。なお、各図面において同一の構成要素には同じ符号を付し、重複する説明を省略する。以下の実施の形態は、本発明を具体化した一例を示すものであって、本発明は、例えば、構成要素の配置等が下記のものに特定されるものではない。本発明は、請求の範囲において様々な変更を加えることができる。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component in each drawing, and the overlapping description is abbreviate | omitted. The following embodiment shows an example in which the present invention is embodied, and the present invention is not limited to the following, for example, the arrangement of components and the like. The present invention can be modified in various ways within the scope of the claims.
　（実施の形態１）
　本発明の実施の形態１に係る発光ダイオード駆動装置は、１個以上の発光ダイオード（ＬＥＤ）を駆動する降圧チョッパ型の駆動装置であって、所定のタイミングで、スイッチング素子に流れる電流が上限基準値以下であり、かつ、下限基準値以上であるか否かを判定する。そして、本発明の実施の形態１に係る発光ダイオード駆動装置は、スイッチング素子に流れる電流が上限基準値以下であり、かつ、下限基準値以上であると判定された回数をカウントし、カウントした回数が予め定められた判定基準値以上である場合に、異常処理を行うことを特徴とする。 (Embodiment 1)
The light-emitting diode driving apparatus according to Embodiment 1 of the present invention is a step-down chopper type driving apparatus that drives one or more light-emitting diodes (LEDs), and the current flowing through the switching element at a predetermined timing is the upper limit reference. It is determined whether it is less than the value and greater than or equal to the lower limit reference value. Then, the LED driving apparatus according to Embodiment 1 of the present invention counts the number of times that the current flowing through the switching element is determined to be equal to or lower than the upper limit reference value and equal to or higher than the lower limit reference value, and the number of times counted When the value is equal to or greater than a predetermined criterion value, abnormality processing is performed.
　図１は、本発明の実施の形態１に係る発光ダイオード駆動装置１００の構成の一例を示す回路図である。本発明の実施の形態１に係る発光ダイオード駆動装置１００は、１個以上のＬＥＤを駆動する降圧チョッパ型の駆動装置である。 FIG. 1 is a circuit diagram showing an example of the configuration of the light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention. The light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention is a step-down chopper type driving apparatus that drives one or more LEDs.
　図１に示すように、発光ダイオード駆動装置１００は、電源部１１０と、直列接続ループ回路１２０と、スイッチング駆動回路２００と、コンデンサ１３０と、抵抗１４０とを備える。なお、スイッチング駆動回路２００は、本発明の実施の形態１に係る半導体装置の一例である。 As shown in FIG. 1, the light emitting diode driving device 100 includes a power supply unit 110, a series connection loop circuit 120, a switching driving circuit 200, a capacitor 130, and a resistor 140. The switching drive circuit 200 is an example of a semiconductor device according to the first embodiment of the present invention.
　電源部１１０は、直列接続ループ回路１２０に接続され、直列接続ループ回路１２０に含まれるＬＥＤ光源部１２１及びチョークコイル１２２に入力電圧を供給する。図１に示すように、電源部１１０は、交流電源１１１と、整流回路１１２と、平滑用コンデンサ１１３とを備える。 The power supply unit 110 is connected to the series connection loop circuit 120 and supplies an input voltage to the LED light source unit 121 and the choke coil 122 included in the series connection loop circuit 120. As shown in FIG. 1, the power supply unit 110 includes an AC power supply 111, a rectifier circuit 112, and a smoothing capacitor 113.
　交流電源１１１は、交流電圧を生成する。例えば、交流電源１１１は、商用電源である。 AC power supply 111 generates an AC voltage. For example, the AC power supply 111 is a commercial power supply.
　整流回路１１２は、交流電源１１１に接続され、交流電圧を整流することで脈流電圧を生成する。整流回路１１２は、例えば、全波整流回路であって、交流電圧から全波整流電圧を生成する。整流回路１１２の高電位側は、直列接続ループ回路１２０に接続され、低電位側は、スイッチング駆動回路２００の低電位側端子ＧＮＤに接続される。 The rectifier circuit 112 is connected to the AC power source 111 and generates a pulsating voltage by rectifying the AC voltage. The rectifier circuit 112 is a full-wave rectifier circuit, for example, and generates a full-wave rectified voltage from an AC voltage. The high potential side of the rectifier circuit 112 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200.
　平滑用コンデンサ１１３は、整流回路１１２によって生成された全波整流電圧を平滑することで、入力電圧Ｖｉｎを生成する。平滑用コンデンサ１１３の高電位側は、直列接続ループ回路１２０に接続され、低電位側は、スイッチング駆動回路２００の低電位側端子ＧＮＤに接続される。生成された入力電圧Ｖｉｎは、ＬＥＤ光源部１２１及びチョークコイル１２２に供給される。 The smoothing capacitor 113 generates the input voltage Vin by smoothing the full-wave rectified voltage generated by the rectifier circuit 112. The high potential side of the smoothing capacitor 113 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200. The generated input voltage Vin is supplied to the LED light source unit 121 and the choke coil 122.
　なお、入力電圧Ｖｉｎの波形は、平滑用コンデンサ１１３の容量値に依存して、十分に平滑され、又は、脈流波形になる。本発明の実施の形態１では、入力電圧波形は、図２Ａのように脈流電圧波形である場合を例に説明を行う。 Note that the waveform of the input voltage Vin is sufficiently smoothed or becomes a pulsating waveform depending on the capacitance value of the smoothing capacitor 113. In Embodiment 1 of the present invention, the case where the input voltage waveform is a pulsating voltage waveform as shown in FIG. 2A will be described as an example.
　直列接続ループ回路１２０は、ＬＥＤ光源部１２１と、チョークコイル１２２と、ダイオード１２３とを備える。図１に示すように、ＬＥＤ光源部１２１と、チョークコイル１２２と、ダイオード１２３とで、ループが構成されている。 The series connection loop circuit 120 includes an LED light source unit 121, a choke coil 122, and a diode 123. As shown in FIG. 1, the LED light source unit 121, the choke coil 122, and the diode 123 form a loop.
　ＬＥＤ光源部１２１は、複数個の発光ダイオード（ＬＥＤ）を備える。複数個のＬＥＤは、直列に接続されている。チョークコイル１２２は、ＬＥＤ光源部１２１に直列に接続される。ダイオード１２３は、ＬＥＤ光源部１２１とチョークコイル１２２とに並列に接続され、チョークコイル１２２に生じる逆起電力をＬＥＤ光源部１２１に供給する。 The LED light source unit 121 includes a plurality of light emitting diodes (LEDs). The plurality of LEDs are connected in series. The choke coil 122 is connected to the LED light source unit 121 in series. The diode 123 is connected in parallel to the LED light source unit 121 and the choke coil 122, and supplies back electromotive force generated in the choke coil 122 to the LED light source unit 121.
　整流回路１１２及び平滑用コンデンサ１１３の高電位側は、ＬＥＤ光源部１２１のアノード端子側とダイオード１２３のカソード端子側とに接続される。また、チョークコイル１２２とダイオード１２３のアノード端子との共通接続点は、スイッチング駆動回路２００の高電位側端子ＤＲＮに接続される。 The high potential side of the rectifier circuit 112 and the smoothing capacitor 113 is connected to the anode terminal side of the LED light source 121 and the cathode terminal side of the diode 123. The common connection point between the choke coil 122 and the anode terminal of the diode 123 is connected to the high potential side terminal DRN of the switching drive circuit 200.
　なお、本発明の実施の形態１では、チョークコイル１２２は、ＬＥＤ光源部１２１のカソード端子側に接続されているが、アノード端子側に接続してもよい。また、複数個の発光ダイオードを直列接続したＬＥＤ光源を例に説明するが、発光ダイオードは、１個以上であればよい。 In the first embodiment of the present invention, the choke coil 122 is connected to the cathode terminal side of the LED light source unit 121, but may be connected to the anode terminal side. Further, an LED light source in which a plurality of light emitting diodes are connected in series will be described as an example. However, it is sufficient that the number of light emitting diodes is one or more.
　また、複数個の発光ダイオードを備える場合であっても、複数個の発光ダイオードは、直列接続に限らず、マトリクス状に接続してもよい。これらは、以降に説明する実施の形態においても同様である。 Further, even when a plurality of light emitting diodes are provided, the plurality of light emitting diodes may be connected not only in series but also in a matrix. The same applies to the embodiments described below.
　スイッチング駆動回路２００は、本発明の実施の形態１に係る発光ダイオード駆動用の半導体装置の一例であり、ＬＥＤ光源部１２１に流れる電流を定電流制御するための半導体装置である。図１に示すように、スイッチング駆動回路２００は、スイッチング素子ブロック２１０と制御回路ブロック２２０とを含む。また、スイッチング駆動回路２００は、外部に接続する５つの端子（整流電圧印加端子ＩＮ、高電位側端子ＤＲＮ、低電位側端子ＧＮＤ、電源端子ＶＣＣ及び外部電流調整端子ＥＸ）を有する。 The switching drive circuit 200 is an example of a light emitting diode driving semiconductor device according to Embodiment 1 of the present invention, and is a semiconductor device for constant current control of the current flowing through the LED light source unit 121. As shown in FIG. 1, the switching drive circuit 200 includes a switching element block 210 and a control circuit block 220. The switching drive circuit 200 has five terminals (rectified voltage application terminal IN, high potential side terminal DRN, low potential side terminal GND, power supply terminal VCC, and external current adjustment terminal EX) connected to the outside.
　整流電圧印加端子ＩＮは、整流回路１１２の高電位側に接続され、脈流電圧波形の入力電圧Ｖｉｎが入力される。高電位側端子ＤＲＮは、上述したように直列接続ループ回路１２０に接続される。低電位側端子ＧＮＤは、制御回路ブロック２２０のグランド電位に接続された接地端子であり、基準電位（グランド電位）となる。また、電源端子ＶＣＣと低電位側端子ＧＮＤとの間にコンデンサ１３０が接続される。外部電流調整端子ＥＸは、抵抗１４０を介して電源端子ＶＣＣに接続される。 The rectified voltage application terminal IN is connected to the high potential side of the rectifier circuit 112, and an input voltage Vin having a pulsating voltage waveform is input thereto. The high potential side terminal DRN is connected to the series connection loop circuit 120 as described above. The low potential side terminal GND is a ground terminal connected to the ground potential of the control circuit block 220 and serves as a reference potential (ground potential). Further, the capacitor 130 is connected between the power supply terminal VCC and the low potential side terminal GND. The external current adjustment terminal EX is connected to the power supply terminal VCC via the resistor 140.
　スイッチング素子ブロック２１０は、スイッチング素子２１１と、電流検出用スイッチング素子２１２とを備える。 The switching element block 210 includes a switching element 211 and a current detection switching element 212.
　スイッチング素子２１１は、直列接続ループ回路１２０に直列に接続され、電源部１１０によって供給される入力電圧Ｖｉｎを断続的にＬＥＤ光源部１２１及びチョークコイル１２２へ供給する。具体的には、スイッチング素子２１１は、直列接続ループ回路１２０と、接地されている低電位側端子ＧＮＤとの間に接続されている。 The switching element 211 is connected in series to the series connection loop circuit 120 and intermittently supplies the input voltage Vin supplied from the power supply unit 110 to the LED light source unit 121 and the choke coil 122. Specifically, the switching element 211 is connected between the series connection loop circuit 120 and the grounded low potential side terminal GND.
　電流検出用スイッチング素子２１２は、スイッチング素子２１１に流れる電流よりも小さく、かつ、一定の電流比の電流が流れるように、スイッチング素子２１１と並列に接続される。 The current detection switching element 212 is connected in parallel with the switching element 211 so that a current having a constant current ratio flows smaller than the current flowing through the switching element 211.
　スイッチング素子２１１の高電位側端子と、電流検出用スイッチング素子２１２の高電位側端子とは、共通接続されて、スイッチング駆動回路２００の高電位側端子ＤＲＮに接続される。スイッチング素子２１１の制御端子と、電流検出用スイッチング素子２１２の制御端子とは、共通接続され、制御回路ブロック２２０から制御信号Ｖｇが印加される。 The high potential side terminal of the switching element 211 and the high potential side terminal of the current detection switching element 212 are connected in common and connected to the high potential side terminal DRN of the switching drive circuit 200. The control terminal of the switching element 211 and the control terminal of the current detection switching element 212 are connected in common, and the control signal Vg is applied from the control circuit block 220.
　また、スイッチング素子２１１の低電位側端子は、スイッチング駆動回路２００の低電位側端子ＧＮＤに接続される。電流検出用スイッチング素子２１２の低電位側端子は、制御回路ブロック２２０が備える抵抗２２１の一端に接続される。抵抗２２１の他端は、スイッチング駆動回路２００の低電位側端子ＧＮＤに接続される。 Further, the low potential side terminal of the switching element 211 is connected to the low potential side terminal GND of the switching drive circuit 200. The low potential side terminal of the current detection switching element 212 is connected to one end of a resistor 221 included in the control circuit block 220. The other end of the resistor 221 is connected to the low potential side terminal GND of the switching drive circuit 200.
　なお、スイッチング素子２１１と電流検出用スイッチング素子２１２とは、共通接続された制御端子に共通の制御信号Ｖｇが入力されるので、スイッチング動作は同時に行われる。すなわち、スイッチング素子２１１と電流検出用スイッチング素子２１２とは、同じタイミングでターンオン又はターンオフする。 Note that, since the switching element 211 and the current detection switching element 212 are supplied with a common control signal Vg at their commonly connected control terminals, the switching operation is performed simultaneously. That is, the switching element 211 and the current detection switching element 212 are turned on or turned off at the same timing.
　制御回路ブロック２２０は、抵抗２２１と、接合型ＦＥＴ２２２と、レギュレータ回路２２３と、入力電圧検出回路２２４と、起動／停止回路２２５と、電流調整回路２２６と、ピーク電流検出回路２２７と、ＳＷ制御回路２２８と、カウント回路２２９と、電流判定回路２３０とを備える。 The control circuit block 220 includes a resistor 221, a junction FET 222, a regulator circuit 223, an input voltage detection circuit 224, a start / stop circuit 225, a current adjustment circuit 226, a peak current detection circuit 227, and a SW control circuit. 228, a count circuit 229, and a current determination circuit 230.
　抵抗２２１と電流検出用スイッチング素子２１２は、スイッチング素子２１１に流れる電流の電流値を検出する電流検出回路の一例である。抵抗２２１は、上述したように、一端が電流検出用スイッチング素子２１２の低電位側端子に接続され、他端が、低電位側端子ＧＮＤに接続される。抵抗２２１は、電流検出用スイッチング素子２１２を流れる電流を電圧に変換するための抵抗である。つまり、本発明の実施の形態では、スイッチング素子２１１に流れる電流を電圧情報として検出する。 The resistor 221 and the current detection switching element 212 are an example of a current detection circuit that detects a current value of a current flowing through the switching element 211. As described above, the resistor 221 has one end connected to the low potential side terminal of the current detection switching element 212 and the other end connected to the low potential side terminal GND. The resistor 221 is a resistor for converting a current flowing through the current detection switching element 212 into a voltage. That is, in the embodiment of the present invention, the current flowing through the switching element 211 is detected as voltage information.
　なお、本発明の実施の形態では、抵抗２２１は、スイッチング素子２１１に流れる電流を直接測定するのではなく、電流検出用スイッチング素子２１２に流れる電流を測定する。電流検出用スイッチング素子２１２に流れる電流は、スイッチング素子２１１に流れる電流と比例関係にあるので、本発明の実施の形態に係る構成により、スイッチング素子２１１に流れる電流の電流値を間接的に測定することができる。 In the embodiment of the present invention, the resistor 221 does not directly measure the current flowing through the switching element 211 but measures the current flowing through the current detection switching element 212. Since the current flowing through the switching element 212 for current detection is proportional to the current flowing through the switching element 211, the current value of the current flowing through the switching element 211 is indirectly measured by the configuration according to the embodiment of the present invention. be able to.
　接合型ＦＥＴ２２２の高電位側端子は、整流電圧印加端子ＩＮに接続される。接合型ＦＥＴ２２２の低電位側端子は、レギュレータ回路２２３と入力電圧検出回路２２４とに接続される。 The high potential side terminal of the junction FET 222 is connected to the rectified voltage application terminal IN. The low potential side terminal of the junction FET 222 is connected to the regulator circuit 223 and the input voltage detection circuit 224.
　レギュレータ回路２２３は、接合型ＦＥＴ２２２の低電位側電圧を、電源端子ＶＣＣを介してコンデンサ１３０へ出力する。そして、レギュレータ回路２２３は、コンデンサ１３０の電圧（電源端子ＶＣＣの電圧Ｖｃｃ）が一定となるように動作する。 The regulator circuit 223 outputs the low potential side voltage of the junction FET 222 to the capacitor 130 via the power supply terminal VCC. The regulator circuit 223 operates so that the voltage of the capacitor 130 (the voltage Vcc of the power supply terminal VCC) becomes constant.
　これにより、商用電源（交流電源１１１）からの交流電圧を整流した電圧を用いて制御回路ブロック２２０の動作電源電圧を生成する場合に、制御回路ブロック２２０の動作中の電圧を一定に保つことができる。したがって、制御回路ブロック２２０によるスイッチング素子２１１のオン及びオフの制御（スイッチング制御）を安定化できる。 Thus, when the operation power supply voltage of the control circuit block 220 is generated using the voltage obtained by rectifying the AC voltage from the commercial power supply (AC power supply 111), the voltage during operation of the control circuit block 220 can be kept constant. it can. Therefore, on / off control (switching control) of the switching element 211 by the control circuit block 220 can be stabilized.
　入力電圧検出回路２２４は、電源部１１０によって生成された入力電圧が、予め定められた設定電圧以上であるか否かを判定する。具体的には、入力電圧検出回路２２４には、接合型ＦＥＴ２２２の低電位側電圧が入力され、内部の基準電圧と比較することで入力電源電圧Ｖｉｎが設定電圧以上であるか否かを検出する。そして、入力電圧検出回路２２４は、検出結果に応じて状態が変化する検出信号を出力する。具体的には、入力電源電圧Ｖｉｎが設定電圧以上の場合に信号レベルがハイレベルとなり、設定電圧を下回る場合にロウレベルとなる信号を出力する。なお、入力電圧検出回路２２４の出力端子は、起動／停止回路２２５の入力端子に接続される。 The input voltage detection circuit 224 determines whether or not the input voltage generated by the power supply unit 110 is equal to or higher than a predetermined set voltage. Specifically, the input voltage detection circuit 224 receives the low potential side voltage of the junction FET 222 and compares it with an internal reference voltage to detect whether the input power supply voltage Vin is equal to or higher than the set voltage. . Then, the input voltage detection circuit 224 outputs a detection signal whose state changes according to the detection result. Specifically, the signal level is high when the input power supply voltage Vin is equal to or higher than the set voltage, and a low level signal is output when the input power voltage Vin is lower than the set voltage. The output terminal of the input voltage detection circuit 224 is connected to the input terminal of the start / stop circuit 225.
　ここで、レギュレータ回路２２３と入力電圧検出回路２２４とはともに、接合型ＦＥＴ２２２に接続される構成としたが、これに限るものではない。高電圧である入力電圧をスイッチング駆動回路２００の電源電圧Ｖｃｃに変換する回路は、この他にも様々な回路が提供されており、当業者には周知である。 Here, both the regulator circuit 223 and the input voltage detection circuit 224 are configured to be connected to the junction FET 222, but the present invention is not limited to this. Various other circuits for converting the input voltage, which is a high voltage, into the power supply voltage Vcc of the switching drive circuit 200 are provided and are well known to those skilled in the art.
　また、入力電圧検出回路２２４の構成もこれに限るものではない。整流電圧印加端子ＩＮから電圧低減用の抵抗を介してスイッチング駆動回路２００に入力し、スイッチング駆動回路２００内部で、さらに抵抗分割を用いた分圧を内部の基準電圧と比較することで、入力電圧のレベルを検出する方法などがある。さらに、レギュレータ回路２２３への入力信号と入力電圧検出回路２２４への入力信号とはともに、整流電圧印加端子ＩＮから印加する必要もなく、別々に印加端子を設けた構成としてもよい。 Further, the configuration of the input voltage detection circuit 224 is not limited to this. The input voltage is input from the rectified voltage application terminal IN to the switching drive circuit 200 through a voltage reduction resistor, and the divided voltage using resistance division is compared with the internal reference voltage inside the switching drive circuit 200, thereby obtaining the input voltage. There is a method of detecting the level of the. Further, both the input signal to the regulator circuit 223 and the input signal to the input voltage detection circuit 224 need not be applied from the rectified voltage application terminal IN, and may be configured to have separate application terminals.
　起動／停止回路２２５は、入力電圧が設定電圧以上である場合、第１動作モードにおけるＳＷ制御回路２２８にスイッチング素子のオン及びオフの切り替えを起動させる。また、起動／停止回路２２５は、入力電圧が設定電圧未満である場合、ＳＷ制御回路２２８にスイッチング素子のオン及びオフの切り替えを停止させる。なお、ＳＷ制御回路２２８、及び、その動作モードについては、後で説明する。 The start / stop circuit 225 causes the SW control circuit 228 in the first operation mode to start switching on and off of the switching element when the input voltage is equal to or higher than the set voltage. Further, the start / stop circuit 225 causes the SW control circuit 228 to stop switching of the switching element on and off when the input voltage is less than the set voltage. The SW control circuit 228 and its operation mode will be described later.
　具体的には、起動／停止回路２２５は、入力電圧検出回路２２４からの信号レベルに応じて、ＥＮＡＢＬＥ信号及びＤＩＳＡＢＬＥ信号のいずれかを出力する。起動／停止回路２２５から出力される信号（ＥＮＡＢＬＥ信号又はＤＩＳＡＢＬＥ信号）は、ＳＷ制御回路２２８及びカウント回路２２９に入力される。 Specifically, the start / stop circuit 225 outputs either an ENABLE signal or a DISABLE signal according to the signal level from the input voltage detection circuit 224. A signal (ENABLE signal or DISABLE signal) output from the start / stop circuit 225 is input to the SW control circuit 228 and the count circuit 229.
　ＥＮＡＢＬＥ信号は、スイッチング素子２１１のスイッチング制御（すなわち、スイッチング素子２１１のオン及びオフの切り替え）を可能にする信号であって、例えば、信号レベルがハイレベルの信号である。ＤＩＳＡＢＬＥ信号は、スイッチング素子２１１のスイッチング制御を停止させる信号であって、例えば、信号レベルがロウレベルの信号である。 The ENABLE signal is a signal that enables switching control of the switching element 211 (that is, switching of the switching element 211 on and off), for example, a signal having a high signal level. The DISABLE signal is a signal for stopping the switching control of the switching element 211, for example, a signal having a low signal level.
　電流調整回路２２６は、外部電流調整端子ＥＸに接続される。電流調整回路２２６は、ピーク電流検出回路２２７に接続される。電流調整回路２２６は、外部電流調整端子ＥＸから印加された電流値に応じた信号をピーク電流検出回路２２７に入力する。すなわち、電流調整回路２２６は、外部電流調整端子ＥＸから入力される電流値に応じて基準電圧Ｖｒｅｆを調整し、調整した基準電圧Ｖｒｅｆを示す信号を出力する。 The current adjustment circuit 226 is connected to the external current adjustment terminal EX. The current adjustment circuit 226 is connected to the peak current detection circuit 227. The current adjustment circuit 226 inputs a signal corresponding to the current value applied from the external current adjustment terminal EX to the peak current detection circuit 227. That is, the current adjustment circuit 226 adjusts the reference voltage Vref according to the current value input from the external current adjustment terminal EX, and outputs a signal indicating the adjusted reference voltage Vref.
　ピーク電流検出回路２２７は、スイッチング素子２１１に流れる電流が予め設定されたピーク値に達したか否かを検出する。スイッチング素子２１１に流れる電流が予め設定されたピーク値に達した場合、ピーク電流検出回路２２７は、その旨を示すピーク電流検出信号ＩＬＩＭＩＴを出力する。 The peak current detection circuit 227 detects whether or not the current flowing through the switching element 211 has reached a preset peak value. When the current flowing through the switching element 211 reaches a preset peak value, the peak current detection circuit 227 outputs a peak current detection signal ILIMIT indicating that fact.
　例えば、ピーク電流検出回路２２７は、プラス入力端子と、マイナス入力端子と、出力端子とを有するコンパレータである。プラス入力端子には、電流検出用スイッチング素子２１２と抵抗２２１との接続部が接続され、電流検出用スイッチング素子２１２に流れる電流によって抵抗２２１に発生する検出電圧Ｖｓｎが入力される。マイナス入力端子には、電流調整回路２２６で調整された基準電圧Ｖｒｅｆが入力される。出力端子は、ＳＷ制御回路２２８に接続される。 For example, the peak current detection circuit 227 is a comparator having a plus input terminal, a minus input terminal, and an output terminal. A connection portion between the current detection switching element 212 and the resistor 221 is connected to the positive input terminal, and a detection voltage Vsn generated in the resistor 221 by the current flowing through the current detection switching element 212 is input. The reference voltage Vref adjusted by the current adjustment circuit 226 is input to the negative input terminal. The output terminal is connected to the SW control circuit 228.
　ピーク電流検出回路２２７は、プラス入力端子に印加された検出電圧Ｖｓｎが基準電圧Ｖｒｅｆ以上になると、信号レベルがハイレベルのピーク電流検出信号ＩＬＩＭＩＴを出力する。ピーク電流検出回路２２７から出力されるピーク電流検出信号ＩＬＩＭＩＴは、ＳＷ制御回路２２８に入力される。基準電圧Ｖｒｅｆは、電源電圧Ｖｃｃと抵抗１４０の値によって決定されるため、抵抗１４０の値を変更することで任意の値に変更することが可能である。 The peak current detection circuit 227 outputs a peak current detection signal ILIMIT having a high signal level when the detection voltage Vsn applied to the plus input terminal becomes equal to or higher than the reference voltage Vref. The peak current detection signal ILIMIT output from the peak current detection circuit 227 is input to the SW control circuit 228. Since the reference voltage Vref is determined by the power supply voltage Vcc and the value of the resistor 140, it can be changed to an arbitrary value by changing the value of the resistor 140.
　電流検出用スイッチング素子２１２及び抵抗２２１に流れる電流は、スイッチング素子２１１に流れる電流ＩＤに対して一定の電流比の電流である。このため、ピーク電流検出回路２２７は、基準電圧Ｖｒｅｆと検出電圧Ｖｓｎとを比較することでスイッチング素子２１１に流れる電流ＩＤが予め設定された所定のピーク値Ｉｐに達したか否かを検出することができる。また、電流検出用スイッチング素子２１２及び抵抗２２１に流れる電流は、スイッチング素子２１１に流れる電流よりも小さいので、スイッチング素子２１１に流れる電流を抵抗により直接検知するよりも電力損失を低減することができる。 The current flowing through the current detection switching element 212 and the resistor 221 has a constant current ratio with respect to the current ID flowing through the switching element 211. Therefore, the peak current detection circuit 227 detects whether or not the current ID flowing through the switching element 211 has reached a predetermined peak value Ip by comparing the reference voltage Vref and the detection voltage Vsn. Can do. In addition, since the current flowing through the current detection switching element 212 and the resistor 221 is smaller than the current flowing through the switching element 211, the power loss can be reduced as compared with the case where the current flowing through the switching element 211 is directly detected by the resistor.
　また、スイッチング素子２１１に流れる電流ＩＤを検出する方法として、スイッチング素子２１１のドレイン端子電圧を検出する方法もある。スイッチング素子２１１がオンしている際に発生するオン電圧を検出電圧Ｖｓｎとすることで、ピーク電流検出回路２２７は、内部の基準電圧Ｖｒｅｆと検出電圧Ｖｓｎとを比較することが可能である。なお、スイッチング素子２１１に流れる電流を検出する方法は、これらの方法に限定されるものではなく、その検出方法は問わない。 Also, as a method of detecting the current ID flowing through the switching element 211, there is a method of detecting the drain terminal voltage of the switching element 211. By making the ON voltage generated when the switching element 211 is ON as the detection voltage Vsn, the peak current detection circuit 227 can compare the internal reference voltage Vref and the detection voltage Vsn. The method for detecting the current flowing through the switching element 211 is not limited to these methods, and the detection method is not limited.
　なお、電流調整回路２２６は、外部から入力される値に応じて、ピーク値を動的に変更してもよい。つまり、電流調整回路２２６は、外部電流調整端子ＥＸから入力される電流値に応じて基準電圧Ｖｒｅｆを変更することで、ピーク値を変更してもよい。また、電流調整回路２２６は、ピーク値の変更に伴って、後述する上限基準値を変更してもよい。 Note that the current adjustment circuit 226 may dynamically change the peak value according to a value input from the outside. That is, the current adjustment circuit 226 may change the peak value by changing the reference voltage Vref according to the current value input from the external current adjustment terminal EX. Further, the current adjustment circuit 226 may change an upper limit reference value to be described later with the change of the peak value.
　ＳＷ制御回路２２８は、第１動作モードにおいて、スイッチング素子２１１のオン及びオフの切り替えを制御する。また、ＳＷ制御回路２２８は、後述するように、カウント回路２２９によって計測された回数が予め定められた判定基準値以上である場合に、異常処理用の第２動作モードにおいて、第１動作モードとは異なる方式でスイッチング素子２１１の制御を行う。カウント回数の判定基準値（回数）は、第１動作モード時のスイッチング素子２１１の発振周波数及びオフ時間などに依存して十数回程度から最適値が選択される。 SW control circuit 228 controls on / off switching of switching element 211 in the first operation mode. Further, as will be described later, when the number of times measured by the count circuit 229 is equal to or greater than a predetermined determination reference value, the SW control circuit 228 is set to the first operation mode in the second operation mode for abnormality processing. Controls the switching element 211 in a different manner. As the determination reference value (number of times) for the number of counts, an optimum value is selected from about a dozen times depending on the oscillation frequency of the switching element 211 and the off time in the first operation mode.
　なお、第１動作モードは、通常動作モードであって、ＬＥＤ光源部１２１がオープンではないと判定された場合に実行されるモードである。すなわち、第１動作モードは、予め定められた制御方式に従って、スイッチング素子２１１のスイッチング制御を行うモードである。 Note that the first operation mode is a normal operation mode and is a mode that is executed when it is determined that the LED light source unit 121 is not open. That is, the first operation mode is a mode in which switching control of the switching element 211 is performed according to a predetermined control method.
　また、第２動作モードは、第１動作モードとは異なる動作モードであって、直列接続ループ回路１２０に何らかの異常が検出された場合に実行する動作モードである。例えば、第２動作モードでは、スイッチング素子２１１のスイッチング制御を停止する。 The second operation mode is an operation mode that is different from the first operation mode, and is an operation mode that is executed when any abnormality is detected in the series connection loop circuit 120. For example, in the second operation mode, the switching control of the switching element 211 is stopped.
　なお、判定基準値は、スイッチング素子２１１、電流検出用スイッチング素子２１２及びその他の構成要素が、過大な電圧が印加されることにより破壊されてしまうのを防止できる程度に決定される。具体的には、判定基準値は、スイッチング素子２１１の発振周波数、ＬＥＤ光源部１２１がオープンになった場合にスイッチング素子２１１に流れる電流値などに基づいて決定される。 The determination reference value is determined to such an extent that the switching element 211, the current detecting switching element 212, and other components can be prevented from being destroyed by applying an excessive voltage. Specifically, the determination reference value is determined based on the oscillation frequency of the switching element 211, the current value flowing through the switching element 211 when the LED light source unit 121 is opened, and the like.
　具体的には、ＳＷ制御回路２２８は、起動／停止回路２２５からＥＮＡＢＬＥ信号が入力される期間は、第１動作モードにおける動作として、スイッチング素子２１１のスイッチング制御を行う。ＳＷ制御回路２２８は、予め設定されたタイミングでスイッチング素子２１１にスイッチング制御信号Ｖｇを入力することで、スイッチング素子２１１をターンオンし、スイッチング素子２１１に電流を流す。また、ＳＷ制御回路２２８は、ピーク電流検出回路２２７から出力されるピーク電流検出信号ＩＬＩＭＩＴが入力されたタイミングで、スイッチング素子２１１をターンオフさせる。これにより、ＳＷ制御回路２２８は、スイッチング素子２１１に流れる電流ＩＤのピーク電流値が常にピーク値Ｉｐになるように制御する。 Specifically, the SW control circuit 228 performs switching control of the switching element 211 as an operation in the first operation mode during a period in which the ENABLE signal is input from the start / stop circuit 225. The SW control circuit 228 inputs the switching control signal Vg to the switching element 211 at a preset timing, thereby turning on the switching element 211 and causing a current to flow through the switching element 211. In addition, the SW control circuit 228 turns off the switching element 211 at the timing when the peak current detection signal ILIMIT output from the peak current detection circuit 227 is input. Thereby, the SW control circuit 228 performs control so that the peak current value of the current ID flowing through the switching element 211 is always the peak value Ip.
　また、ＳＷ制御回路２２８は、起動／停止回路２２５からＤＩＳＡＢＬＥ信号が入力される期間は、スイッチング素子２１１の動作を停止させる。 Also, the SW control circuit 228 stops the operation of the switching element 211 during a period in which the DISABLE signal is input from the start / stop circuit 225.
　なお、スイッチング素子２１１のスイッチング制御方法は、スイッチングのオンデューティを制御するＰＷＭ（Ｐｕｌｓｅ　Ｗｉｄｔｈ　Ｍｏｄｕｌａｔｉｏｎ）方式、スイッチング素子２１１に流れる電流のピーク値を変化させる電流モードＰＷＭ制御方式などがある。また、スイッチング素子２１１のオフ時間を予め設定された値で固定にするオフ時間固定制御方式、発振周波数を変化させるＰＦＭ（Ｐｕｌｓｅ　Ｆｒｅｑｕｅｎｃｙ　Ｍｏｄｕｌａｔｉｏｎ）制御方式などもあり、その制御方法は問わない。ただし、上述の制御方式に必要な回路は当業者には周知であるので、これらの制御方式による構成については図１には図示しない。 Note that the switching control method of the switching element 211 includes a PWM (Pulse Width Modulation) system that controls the on-duty of switching, a current mode PWM control system that changes the peak value of the current flowing through the switching element 211, and the like. There are also an off-time fixed control method for fixing the off-time of the switching element 211 at a preset value, a PFM (Pulse Frequency Modulation) control method for changing the oscillation frequency, and the control method is not limited. However, since the circuit necessary for the above-described control system is well known to those skilled in the art, the configuration based on these control systems is not shown in FIG.
　電流判定回路２３０は、電流検出用スイッチング素子２１２と抵抗２２１との共通接続部に接続され、検出電圧Ｖｓｎが入力される。図１に示すように、電流判定回路２３０は、積分回路２３１と、２つのコンパレータ２３２及び２３３と、ＡＮＤ回路２３４とを備える。 The current determination circuit 230 is connected to a common connection portion between the current detection switching element 212 and the resistor 221 and receives the detection voltage Vsn. As shown in FIG. 1, the current determination circuit 230 includes an integration circuit 231, two comparators 232 and 233, and an AND circuit 234.
　積分回路２３１には、検出電圧Ｖｓｎが入力され、検出電圧Ｖｓｎの最大値を出力する。なお、スイッチング素子２１１がターンオフされると、積分回路２３１の出力信号は、リセットされる。 Integral circuit 231 receives detection voltage Vsn and outputs the maximum value of detection voltage Vsn. Note that when the switching element 211 is turned off, the output signal of the integrating circuit 231 is reset.
　コンパレータ２３２は、スイッチング素子２１１がオフする際に、スイッチング素子２１１に流れる電流の電流値が予め定められた上限基準値以下であるか否かを判定する上限判定回路の一例である。本実施の形態では、コンパレータ２３２は、抵抗２２１によって検出された電流値が上限基準値以下であるか否かを判定する。上限基準値は、ピーク値Ｉｐ以下の値である。 The comparator 232 is an example of an upper limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or lower than a predetermined upper limit reference value when the switching element 211 is turned off. In the present embodiment, the comparator 232 determines whether or not the current value detected by the resistor 221 is equal to or lower than the upper limit reference value. The upper reference value is a value equal to or less than the peak value Ip.
　具体的には、コンパレータ２３２は、プラス入力端子に上限基準電圧ＩＤＨが入力され、マイナス入力端子に、抵抗２２１によって検出された電流値に対応する検出電圧Ｖｓｎの最大値が入力される。なお、上限基準電圧ＩＤＨは、ピーク値Ｉｐに相当する電圧（具体的には、基準電圧Ｖｒｅｆ）より小さな値に設定されている。コンパレータ２３２は、検出電圧Ｖｓｎの最大値が上限基準電圧ＩＤＨより小さい場合に、ハイレベルとなる信号をＡＮＤ回路２３４に出力する。 Specifically, in the comparator 232, the upper limit reference voltage IDH is input to the plus input terminal, and the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the minus input terminal. The upper limit reference voltage IDH is set to a value smaller than a voltage corresponding to the peak value Ip (specifically, the reference voltage Vref). The comparator 232 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is smaller than the upper limit reference voltage IDH.
　コンパレータ２３３は、スイッチング素子２１１に流れる電流の電流値が予め定められた下限基準値以上であるか否かを判定する下限判定回路の一例である。本実施の形態では、コンパレータ２３３は、抵抗２２１によって検出された電流値が下限基準値以上であるか否かを判定する。 The comparator 233 is an example of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value. In the present embodiment, the comparator 233 determines whether or not the current value detected by the resistor 221 is greater than or equal to the lower limit reference value.
　具体的には、コンパレータ２３３は、プラス入力端子に、抵抗２２１によって検出された電流値に対応する検出電圧Ｖｓｎの最大値が入力され、マイナス入力端子に下限基準電圧ＩＤＬが入力される。コンパレータ２３３は、検出電圧Ｖｓｎの最大値が下限基準電圧ＩＤＬより大きい場合に、ハイレベルとなる信号をＡＮＤ回路２３４に出力する。 Specifically, in the comparator 233, the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal. The comparator 233 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is higher than the lower limit reference voltage IDL.
　なお、本実施の形態では、コンパレータ２３２及び２３３ともに、スイッチング素子２１１がターンオフするタイミングで判定を行う。スイッチング素子２１１がターンオフする直前が、スイッチング素子２１１に流れる電流が最大となるので、コンパレータ２３２及び２３３は、スイッチング素子２１１に流れる電流の最大値（実際には、対応する検出電圧Ｖｓｎ）を用いて判定を行う。 In this embodiment, both the comparators 232 and 233 perform determination at the timing when the switching element 211 is turned off. Since the current flowing through the switching element 211 is maximized immediately before the switching element 211 is turned off, the comparators 232 and 233 use the maximum value of the current flowing through the switching element 211 (actually, the corresponding detection voltage Vsn). Make a decision.
　ＡＮＤ回路２３４は、２つの入力端子と出力端子とを有し、入力端子に入力される信号の論理積を演算し、演算結果を出力端子から出力する。具体的には、２つの入力端子には、コンパレータ２３２及び２３３の出力信号がそれぞれ入力され、コンパレータ２３２及び２３３の出力信号の論理積が、カウント回路２２９に出力される。 The AND circuit 234 has two input terminals and an output terminal, calculates a logical product of signals input to the input terminal, and outputs the calculation result from the output terminal. Specifically, the output signals of the comparators 232 and 233 are input to the two input terminals, respectively, and the logical product of the output signals of the comparators 232 and 233 is output to the count circuit 229.
　上限基準電圧ＩＤＨ及び下限基準電圧ＩＤＬの値は、Ｖｒｅｆ＞ＩＤＨ＞ＩＤＬが成り立つように、予め設定された任意の値である。また、図１では図示しないが、電流調整回路２２６によって調整された基準電圧Ｖｒｅｆの値に応じて、上限基準電圧ＩＤＨの値が調整される構成としてもよい。これにより、電流判定回路２３０は、検出電圧Ｖｓｎの最大値がＩＤＬ以上かつＩＤＨ以下の関係にあるとき、ハイレベルの信号をカウント回路２２９に出力する。 The values of the upper limit reference voltage IDH and the lower limit reference voltage IDL are arbitrary values set in advance so that Vref> IDH> IDL is satisfied. Although not shown in FIG. 1, the value of the upper limit reference voltage IDH may be adjusted according to the value of the reference voltage Vref adjusted by the current adjustment circuit 226. Thereby, the current determination circuit 230 outputs a high-level signal to the count circuit 229 when the maximum value of the detection voltage Vsn has a relationship of not less than IDL and not more than IDH.
　カウント回路２２９は、スイッチング素子２１１に流れる電流の電流値が、上限判定回路によって上限基準値以下であると判定され、かつ、下限判定回路によって下限基準値以上であると判定された回数を計測する。具体的には、カウント回路２２９は、電流判定回路２３０から出力されるハイレベル信号の回数をカウントする回路である。カウント回路２２９は、カウント回数が予め設定された判定回数（判定基準値）に達すると、ｏｐｅｎ信号をＳＷ制御回路２２８へ出力する。 The count circuit 229 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be equal to or lower than the upper limit reference value by the upper limit determination circuit and is determined to be equal to or higher than the lower limit reference value by the lower limit determination circuit. . Specifically, the count circuit 229 is a circuit that counts the number of high-level signals output from the current determination circuit 230. The count circuit 229 outputs an open signal to the SW control circuit 228 when the count number reaches a predetermined determination number (determination reference value).
　また、カウント回路２２９には、起動／停止回路２２５からの出力信号（ＥＮＡＢＬＥ信号又はＤＩＳＡＢＬＥ信号）が入力される。起動／停止回路２２５からＤＩＳＡＢＬＥ信号が入力されるとき、カウント回路２２９のカウント回数は、リセットされる。 Also, the count circuit 229 receives an output signal (ENABLE signal or DISABLE signal) from the start / stop circuit 225. When the DISABLE signal is input from the start / stop circuit 225, the count number of the count circuit 229 is reset.
　以上のように構成された本発明の実施の形態１に係る発光ダイオード駆動装置１００について、入力電源電圧Ｖｉｎと制御回路ブロック２２０とスイッチング素子２１１との動作開始タイミングの関係について説明する。図２Ａ及び図２Ｂは、本発明の実施の形態１に係る入力電圧波形と発光ダイオード駆動装置１００の動作期間との一例を示す波形図である。 Regarding the light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention configured as described above, the relationship among the input power supply voltage Vin, the operation start timings of the control circuit block 220 and the switching element 211 will be described. 2A and 2B are waveform diagrams showing an example of an input voltage waveform and an operation period of the light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention.
　図２Ａは、入力電圧波形と入力電圧検出回路２２４の検出電圧Ｖｉｎｕｖとの関係を表す図である。入力電圧波形が脈流波形の場合、入力電圧Ｖｉｎ＞検出電圧Ｖｉｎｕｖの期間は、スイッチング駆動回路２００及び制御回路ブロック２２０が動作可能な期間となる。入力電圧Ｖｉｎ＜検出電圧Ｖｉｎｕｖの期間は、スイッチング素子２１１は、動作を停止する。 FIG. 2A is a diagram showing the relationship between the input voltage waveform and the detection voltage Vinuv of the input voltage detection circuit 224. When the input voltage waveform is a pulsating waveform, the period of the input voltage Vin> the detection voltage Vinuv is a period in which the switching drive circuit 200 and the control circuit block 220 can operate. During the period of the input voltage Vin <the detection voltage Vinuv, the switching element 211 stops operating.
　図２Ｂは、入力電圧が脈流波形の場合において、入力電圧が徐々に増加するときの波形を示す図である。入力電圧Ｖｉｎが検出電圧Ｖｉｎｕｖよりの低い期間Ｔ１は、スイッチング駆動回路２００及び制御回路ブロック２２０は、動作を停止しているので、スイッチング素子２１１も動作を停止している。 FIG. 2B is a diagram showing a waveform when the input voltage gradually increases when the input voltage is a pulsating waveform. During the period T1 when the input voltage Vin is lower than the detection voltage Vinuv, the switching drive circuit 200 and the control circuit block 220 are not operating, so the switching element 211 is also not operating.
　ＬＥＤ光源部１２１の順方向電圧の合計電圧（すなわち、ＬＥＤ光源部１２１の出力電圧）を出力電圧ＶＦ＿ＬＥＤと表すと、電源入力電圧Ｖｉｎが出力電圧ＶＦ＿ＬＥＤよりも低い期間は、ＬＥＤ光源部１２１に電流は流れない。この結果、入力電圧Ｖｉｎが検出電圧Ｖｉｎｕｖよりも高く、出力電圧ＶＦ＿ＬＥＤよりも低い期間Ｔ２においては、制御回路ブロック２２０は動作が可能である。したがって、ＳＷ制御回路２２８は、スイッチング素子２１１にスイッチング制御信号Ｖｇを入力し、スイッチング素子２１１は、スイッチング動作を開始するが、スイッチング素子２１１に電流は流れない。 When the total forward voltage of the LED light source unit 121 (that is, the output voltage of the LED light source unit 121) is expressed as an output voltage VF_LED, a current is supplied to the LED light source unit 121 during a period when the power input voltage Vin is lower than the output voltage VF_LED. Does not flow. As a result, the control circuit block 220 can operate in the period T2 in which the input voltage Vin is higher than the detection voltage Vinuv and lower than the output voltage VF_LED. Therefore, the SW control circuit 228 inputs the switching control signal Vg to the switching element 211, and the switching element 211 starts a switching operation, but no current flows through the switching element 211.
　そして、入力電圧Ｖｉｎが出力電圧ＶＦ＿ＬＥＤ以上になると、ＬＥＤ光源部１２１に電流が流れるため、スイッチング素子２１１にも電流が流れる。入力電圧Ｖｉｎが徐々に低下する際にも、同様の現象が発生する。出力電圧ＶＦ＿ＬＥＤが検出電圧Ｖｉｎｕｖよりも低い場合は、入力電圧Ｖｉｎが検出電圧Ｖｉｎｕｖよりも高くなり、スイッチング駆動回路２００及び制御回路ブロック２２０が動作可能となると、ＬＥＤ光源部１２１及びスイッチング素子２１１に電流が流れる。 Then, when the input voltage Vin becomes equal to or higher than the output voltage VF_LED, a current flows through the LED light source unit 121, so that a current also flows through the switching element 211. A similar phenomenon occurs when the input voltage Vin gradually decreases. When the output voltage VF_LED is lower than the detection voltage Vinuv, when the input voltage Vin becomes higher than the detection voltage Vinuv and the switching drive circuit 200 and the control circuit block 220 are operable, the LED light source unit 121 and the switching element 211 are supplied with current. Flows.
　以下では、まず、ＬＥＤ光源部１２１が正常な場合の動作について説明する。 Hereinafter, the operation when the LED light source unit 121 is normal will be described first.
　正常な動作時にスイッチング素子２１１に流れる電流波形を、図３のＩＤＳ１に示す。この場合、電流波形ＩＤＳ１は、チョークコイル１２２のインダクタンス値ＬとＬＥＤ光源部１２１の両端子電圧差（Ｖｉｎ－ＶＦ＿ＬＥＤ）から決定される傾き（Ｖｉｎ－ＶＦ＿ＬＥＤ）／Ｌをもった単純増加の電流波形となる。 A waveform of a current flowing through the switching element 211 during normal operation is indicated by IDS1 in FIG. In this case, the current waveform IDS1 is a simple increase current waveform having a slope (Vin−VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin−VF_LED) between the two terminals of the LED light source 121. It becomes.
　そして、スイッチング素子２１１に流れる電流ＩＤが予め設定されたピーク値Ｉｐに達すると、ＳＷ制御回路２２８は、スイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力することによって、スイッチング素子２１１に流れる電流のピーク値が常にＩｐで一定になるように制御する。この際、制御回路ブロック２２０内部の検出電圧Ｖｓｎ（すなわち、抵抗２２１によって検出された検出電圧Ｖｓｎ）の最大値と上限基準電圧ＩＤＨと下限基準電圧ＩＤＬとの関係は、「Ｖｓｎの最大値＞ＩＤＨ＞ＩＤＬ」となるため、電流判定回路２３０は、カウント回路２２９にハイレベル信号を出力しない。 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211, thereby causing the peak of the current flowing through the switching element 211. The value is always controlled to be constant at Ip. At this time, the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220 (that is, the detection voltage Vsn detected by the resistor 221), the upper limit reference voltage IDH, and the lower limit reference voltage IDL is expressed as “the maximum value of Vsn> IDH. Since “> IDL”, the current determination circuit 230 does not output a high level signal to the count circuit 229.
　また、図２Ｂで説明した期間Ｔ２のように内部の制御回路ブロック２２０及びスイッチング素子２１１は、オン及びオフの制御（スイッチング動作）を開始している。しかしながら、期間Ｔ２では、上述したように、スイッチング素子２１１に電流が流れない。このため、期間Ｔ２では、制御回路ブロック２２０内部の検出電圧Ｖｓｎの最大値と上限基準電圧ＩＤＨと下限基準電圧ＩＤＬとの関係は、「ＩＤＨ＞ＩＤＬ＞Ｖｓｎの最大値」となるため、電流判定回路２３０は、ハイレベルの信号をカウント回路２２９に出力することはない。 Also, as in the period T2 described with reference to FIG. 2B, the internal control circuit block 220 and the switching element 211 start on and off control (switching operation). However, in the period T2, no current flows through the switching element 211 as described above. For this reason, in the period T2, the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> IDL> Vsn maximum value”. The circuit 230 does not output a high level signal to the count circuit 229.
　次に、ＬＥＤ光源部１２１を構成する発光ダイオード素子のいくつかが破壊され、オープン不良になった場合について説明する。発光ダイオードのオープン不良は、完全に電気的に絶縁される場合と、抵抗成分が残った半オープン状態との２種類に分類できる。図１のように、負荷がＬＥＤ光源部１２１だけで構成される場合に発光ダイオードが電気的に絶縁されると、入力電圧Ｖｉｎがチョークコイル１２２及びスイッチング素子２１１に印加されない。このため、ＬＥＤ光源部１２１がオープンになってもチョークコイル１２２及びスイッチング素子２１１に高電圧が印加される恐れはない。 Next, a case where some of the light-emitting diode elements constituting the LED light source unit 121 are destroyed and become open defects will be described. The open failure of the light-emitting diode can be classified into two types, a case where it is completely electrically insulated and a half-open state where a resistance component remains. As shown in FIG. 1, when the load is configured only by the LED light source unit 121 and the light emitting diode is electrically insulated, the input voltage Vin is not applied to the choke coil 122 and the switching element 211. For this reason, there is no possibility that a high voltage is applied to the choke coil 122 and the switching element 211 even if the LED light source 121 is opened.
　一方、ＬＥＤ光源部１２１が半オープン状態になった場合にスイッチング素子２１１に流れる電流を、図３のＩＤＳ２に示す。この場合、ＬＥＤ光源部１２１は、抵抗成分だけが残るため、正常時よりもインピーダンスが高くなり、電流増加率が低くなる。そして、スイッチング素子２１１に流れる電流ＩＤの最大値がピーク値Ｉｐに達することなく、ＳＷ制御回路２２８の制御方式に従って、スイッチング素子２１１はターンオフする。 On the other hand, the current that flows through the switching element 211 when the LED light source unit 121 is in a semi-open state is shown in IDS2 of FIG. In this case, since only the resistance component remains in the LED light source unit 121, the impedance is higher than that in the normal state, and the current increase rate is reduced. Then, the switching element 211 is turned off according to the control method of the SW control circuit 228 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip.
　この際、制御回路ブロック２２０内部の検出電圧Ｖｓｎの最大値と上限基準電圧ＩＤＨと下限基準電圧ＩＤＬとの関係は、「ＩＤＨ＞Ｖｓｎの最大値＞ＩＤＬ」となるため、電流判定回路２３０は、カウント回路２２９にハイレベル信号を出力する。そして、カウント回路２２９は、カウント回数が所定の判定基準値以上になると、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、異常処理用の第２動作モードとして、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。 At this time, the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> maximum value of Vsn> IDL”. A high level signal is output to the count circuit 229. The count circuit 229 determines that the LED light source 121 that is a load is open when the number of counts is equal to or greater than a predetermined determination reference value, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped as the second operation mode for abnormality processing.
　以上のように構成された本発明の実施の形態１に係る発光ダイオード駆動装置１００は、ＬＥＤ光源部１２１に流れる電流を検出するための専用の抵抗を必要せず、スイッチング素子２１１に流れる電流でＬＥＤ光源部１２１のオープン判定が可能である。このため、スイッチング駆動回路２００には、追加の端子が不要であり、発光ダイオード駆動装置１００の小型化及び省スペース化が可能となる。 The light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention configured as described above does not require a dedicated resistor for detecting the current flowing through the LED light source unit 121, and is a current flowing through the switching element 211. The open determination of the LED light source part 121 is possible. For this reason, the switching drive circuit 200 does not require an additional terminal, and the light emitting diode drive device 100 can be reduced in size and space.
　さらに、電源起動時又は入力電圧が脈流電圧である場合などの、入力電圧が出力電圧よりも低い期間において、ＬＥＤ光源部１２１に電流が流れない期間が発生しても、スイッチング素子２１１に予め設定された下限基準値以上の電流が流れていない期間は、カウント回路２２９による計測を行わない。このため、本発明の実施の形態１に係る発光ダイオード駆動装置１００によれば、誤検出を防止することができる。 Further, even when a period in which no current flows through the LED light source unit 121 during a period when the input voltage is lower than the output voltage, such as when the power is turned on or when the input voltage is a pulsating voltage, Measurement by the count circuit 229 is not performed during a period in which no current exceeding the set lower limit reference value flows. For this reason, according to the light emitting diode drive device 100 according to Embodiment 1 of the present invention, erroneous detection can be prevented.
　なお、本発明の実施の形態１に係る発光ダイオード駆動装置１００は、カウント回路２２９を備えることで、ＬＥＤ光源部１２１がオープンとなっている可能性のある状態を複数回判定している。例えば、上述したように、電源起動時などの入力電圧が低い場合には、ＬＥＤ光源部１２１がオープンでない場合であっても、オープンであると判定される場合が存在する。この場合、入力電圧の増加とともに、オープンでない（すなわち、正常である）と判定されることになる。 In addition, the light-emitting-diode drive device 100 according to Embodiment 1 of the present invention includes the count circuit 229, and determines a state where the LED light source unit 121 may be open a plurality of times. For example, as described above, when the input voltage is low, such as when the power is turned on, there is a case where it is determined that the LED light source unit 121 is open even if the LED light source unit 121 is not open. In this case, it is determined that the input voltage is not open (that is, normal) as the input voltage increases.
　本発明の実施の形態１に係る発光ダイオード駆動装置１００では、複数回の判定を行うので、所定の判定基準値以下の回数だけオープンであると判定された場合であっても、オープンではないと判定する。したがって、本発明の実施の形態１に係る発光ダイオード駆動装置１００によれば、判定基準値を適切な値に設定することで、誤検出を防止することができる。 In the light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention, since the determination is performed a plurality of times, even if it is determined that the circuit is open a predetermined number of times or less, it is not open. judge. Therefore, according to the light emitting diode drive device 100 according to Embodiment 1 of the present invention, erroneous detection can be prevented by setting the determination reference value to an appropriate value.
　また、本発明の実施の形態１に係る発光ダイオード駆動装置１００は、電流調整回路２２６を備え、スイッチング素子２１１に流れるピーク値Ｉｐを外部から適切な値に調整することが可能である。したがって、上限基準電圧ＩＤＨ及び下限基準電圧ＩＤＬを任意に設定することで、ＬＥＤオープン検出精度を向上させることができる。 The light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention includes the current adjustment circuit 226, and can adjust the peak value Ip flowing through the switching element 211 to an appropriate value from the outside. Therefore, the LED open detection accuracy can be improved by arbitrarily setting the upper limit reference voltage IDH and the lower limit reference voltage IDL.
　また、本発明の実施の形態１に係る発光ダイオード駆動装置１００は、入力電圧検出回路２２４を備え、入力電圧が低下した際にスイッチング素子２１１のオン及びオフの制御（スイッチング動作）を停止する。このため、入力電圧値と出力電圧値とが近接してスイッチング素子２１１のオン時間が延びて、最大オン時間又は最大オンデューティ期間に達する前に、スイッチング動作を停止することが可能であり、ＬＥＤオープンを誤検出する可能性が低い。 The light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention includes the input voltage detection circuit 224, and stops the on / off control (switching operation) of the switching element 211 when the input voltage decreases. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the ON time of the switching element 211 is extended to reach the maximum ON time or the maximum ON duty period. The possibility of false detection of open is low.
　さらに、入力電圧が脈流電圧の場合であって、徐々に電圧が低下する際に、誤ってカウント回数を計測した場合であっても、入力電圧検出回路２２４によってスイッチング素子２１１のスイッチング動作が停止されるとカウント回数がリセットされる。すなわち、カウント回路２２９は、スイッチング素子２１１のオン及びオフの切り替え（スイッチング動作）が停止された場合に、計測した回数をリセットする。このため、次に、入力電圧検出回路２２４によってスイッチング素子２１１のスイッチング動作が再開されたときに、カウント回数が保持されていないので、誤検出の可能性が低くなる。 Further, even when the input voltage is a pulsating voltage and the number of counts is erroneously measured when the voltage gradually decreases, the switching operation of the switching element 211 is stopped by the input voltage detection circuit 224. The count is reset. That is, the count circuit 229 resets the measured number of times when the switching (switching operation) of the switching element 211 is stopped. For this reason, when the switching operation of the switching element 211 is restarted by the input voltage detection circuit 224 next, the number of counts is not held, so the possibility of erroneous detection is reduced.
　また、スイッチング素子ブロック２１０と制御回路ブロック２２０とが同一基板上に集積化され、又は、同一のパッケージに組み込まれた半導体装置としてスイッチング駆動回路２００を構成することにより、発光ダイオード駆動装置（照明装置）の部品点数を大幅に削減することができる。また、本構成は、本発明の実施の形態１に係る発光ダイオード駆動装置に限定される構成ではなく、以降に説明する他の実施の形態に係る発光ダイオード駆動装置にも適用することができる。 In addition, the switching element block 210 and the control circuit block 220 are integrated on the same substrate, or the switching drive circuit 200 is configured as a semiconductor device incorporated in the same package, whereby a light emitting diode drive device (illumination device) is formed. ) Can be significantly reduced. In addition, the present configuration is not limited to the light emitting diode driving device according to the first embodiment of the present invention, and can also be applied to light emitting diode driving devices according to other embodiments described below.
　また、交流電圧を整流する整流回路１１２として全波整流回路を使用したが、半波整流回路を使用しても同様の効果が得られるのは明白である。さらに、交流電源１１１の代わりに、直流電源を使用した場合においても本発明の効果を享受できる。これらは、以降に説明する実施の形態においても同様である。 Further, although the full-wave rectifier circuit is used as the rectifier circuit 112 that rectifies the AC voltage, it is obvious that the same effect can be obtained even if the half-wave rectifier circuit is used. Furthermore, the effect of the present invention can be enjoyed even when a DC power supply is used instead of the AC power supply 111. The same applies to the embodiments described below.
　（実施の形態２）
　続いて、本発明の実施の形態２に係る発光ダイオード駆動装置及び発光ダイオード駆動用の半導体装置について説明する。本発明の実施の形態２に係る発光ダイオード駆動装置は、最大デューティ駆動であるか否かを判定することで、スイッチング素子に流れる電流が上限基準値以下であるか否かを判定することを特徴とする。最大デューティ駆動とは、スイッチング素子を一定周期で駆動させる制御方法において、スイッチング素子がオンしている期間が、予め設定された最大の期間（最大デューティ）に達した場合に、スイッチング素子をターンオフすることである。すなわち、本発明の実施の形態２に係る発光ダイオード駆動装置では、スイッチング素子に流れる電流がピーク値に達して、スイッチング素子がターンオフされる前に、最大デューティ駆動によりターンオフされることを検出することで、スイッチング素子に流れる電流が上限基準値以下であることを検出する。 (Embodiment 2)
Subsequently, a light emitting diode driving device and a light emitting diode driving semiconductor device according to the second embodiment of the present invention will be described. The light emitting diode driving device according to Embodiment 2 of the present invention determines whether or not the current flowing through the switching element is equal to or lower than the upper limit reference value by determining whether or not the maximum duty driving is performed. And The maximum duty drive is a control method in which the switching element is driven at a constant period, and when the period during which the switching element is on reaches a preset maximum period (maximum duty), the switching element is turned off. That is. That is, in the light emitting diode driving device according to Embodiment 2 of the present invention, it is detected that the current flowing through the switching element reaches the peak value and the switching element is turned off by the maximum duty drive before the switching element is turned off. Thus, it is detected that the current flowing through the switching element is not more than the upper reference value.
　図４は、本発明の実施の形態２に係る発光ダイオード駆動装置３００の一例を示す回路図である。図４において、図１に示す構成要素に相当する構成要素には、図１と同じ符号を付し、それらについての説明は省略する。 FIG. 4 is a circuit diagram showing an example of the light emitting diode driving apparatus 300 according to Embodiment 2 of the present invention. 4, constituent elements corresponding to those shown in FIG. 1 are given the same reference numerals as those in FIG. 1, and descriptions thereof are omitted.
　本発明の実施の形態２に係る発光ダイオード駆動装置３００は、実施の形態１と比較すると、スイッチング駆動回路４００の制御回路ブロック４２０の構成が異なる。また、抵抗１４０の接続関係が異なる。それ以外の構成については実施の形態１と同様である。 The light emitting diode driving device 300 according to the second embodiment of the present invention is different from the first embodiment in the configuration of the control circuit block 420 of the switching driving circuit 400. Further, the connection relationship of the resistor 140 is different. Other configurations are the same as those in the first embodiment.
　実施の形態２では、スイッチング素子２１１の制御方式として、スイッチング素子２１１に流れる電流ピークを変化させる電流モードＰＷＭ制御方式を例に説明する。具体的には、本発明の実施の形態２では、ＳＷ制御回路２２８は、第１動作モード（通常動作モード）において、スイッチング素子２１１を予め設定された周期でオフからオンに切り替える。また、スイッチング素子２１１に流れる電流がピーク値Ｉｐに達した場合に、すなわち、ピーク電流検出信号ＩＬＩＭＩＴが入力された場合に、スイッチング素子２１１をターンオフにする。 In the second embodiment, as a control method for the switching element 211, a current mode PWM control method for changing a current peak flowing through the switching element 211 will be described as an example. Specifically, in Embodiment 2 of the present invention, the SW control circuit 228 switches the switching element 211 from off to on in a preset cycle in the first operation mode (normal operation mode). Further, when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input, the switching element 211 is turned off.
　制御回路ブロック４２０は、カウント回路２２９と、電流判定回路２３０との代わりに、図４に示すように、カウント回路４２９と、コンパレータ４３３と、フリップフロップ回路４３５と、クロック発生器４３６とを備える。 The control circuit block 420 includes a count circuit 429, a comparator 433, a flip-flop circuit 435, and a clock generator 436 as shown in FIG. 4 instead of the count circuit 229 and the current determination circuit 230.
　抵抗１４０は、整流回路１１２及び平滑用コンデンサ１１３の高電位側に接続されている。この結果、入力電圧波形が図２Ａのように脈流電圧波形である場合、抵抗１４０の抵抗値Ｒ１４０と入力電圧Ｖｉｎとの値に応じて外部電流調整端子ＥＸに印加される電流ＩＥＸは、「ＩＥＸ＝Ｖｉｎ／Ｒ１４０」の式から算出される。この結果、電流調整回路２２６が設定する基準電圧Ｖｒｅｆは、入力電圧の波形に応じて変化する。 The resistor 140 is connected to the high potential side of the rectifier circuit 112 and the smoothing capacitor 113. As a result, when the input voltage waveform is a pulsating voltage waveform as shown in FIG. 2A, the current IEX applied to the external current adjustment terminal EX in accordance with the resistance value R140 of the resistor 140 and the input voltage Vin is “ It is calculated from the equation “IEX = Vin / R140”. As a result, the reference voltage Vref set by the current adjustment circuit 226 changes according to the waveform of the input voltage.
　クロック発生器４３６は、最大デューティ検出回路の一例であって、最大デューティ期間（最大オンデューティとも記載）を設定する。最大デューティ期間は、スイッチング素子２１１をオンからオフに切り替える周期内における、スイッチング素子２１１がオンしている期間の最大値である。後述するように、スイッチング素子２１１がオンしている期間が最大デューティ期間に達した場合に、クロック発生器４３６は、スイッチング素子２１１に流れる電流の電流値が、上記の上限基準値（ＩＤＨ）以下であると判定する。 The clock generator 436 is an example of a maximum duty detection circuit, and sets a maximum duty period (also described as maximum on-duty). The maximum duty period is a maximum value of a period during which the switching element 211 is on in a cycle in which the switching element 211 is switched from on to off. As will be described later, when the period during which the switching element 211 is on reaches the maximum duty period, the clock generator 436 has a current value of the current flowing through the switching element 211 equal to or lower than the above upper limit reference value (IDH). It is determined that
　例えば、クロック発生器４３６は、発振器などで構成され、スイッチング素子２１１の毎周期のターンオンのタイミングを決定するＣＬＯＣＫ信号と、最大オンデューティを決定するＭＡＸＤＵＴＹ信号とを出力する。ＣＬＯＣＫ信号がＳＷ制御回路２２８に入力されると、ＳＷ制御回路２２８は、スイッチング素子２１１に制御信号Ｖｇを出力することで、スイッチング素子２１１をターンオンさせる。 For example, the clock generator 436 includes an oscillator and outputs a CLOCK signal that determines the turn-on timing of each cycle of the switching element 211 and a MAXDUTY signal that determines the maximum on-duty. When the CLOCK signal is input to the SW control circuit 228, the SW control circuit 228 outputs the control signal Vg to the switching element 211, thereby turning on the switching element 211.
　そして、スイッチング素子２１１に流れる電流ＩＤが、予め設定されたピーク値Ｉｐに達すると、すなわち、ピーク電流検出回路２２７に入力される検出電圧Ｖｓｎが基準電圧Ｖｒｅｆに達すると、ピーク電流検出回路２２７は、ピーク電流検出信号ＩＬＩＭＩＴをＳＷ制御回路２２８に出力する。これによって、ＳＷ制御回路２２８は、スイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力する。本制御によって、スイッチング素子２１１に流れる電流のピーク値が、常にＩｐで一定になるように制御する。 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, that is, when the detection voltage Vsn input to the peak current detection circuit 227 reaches the reference voltage Vref, the peak current detection circuit 227 is The peak current detection signal ILIMIT is output to the SW control circuit 228. As a result, the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211. By this control, control is performed so that the peak value of the current flowing through the switching element 211 is always constant at Ip.
　また、ピーク電流検出回路２２７がＳＷ制御回路２２８にピーク電流検出信号ＩＬＩＭＩＴを出力する前に、クロック発生器４３６がＳＷ制御回路２２８にＭＡＸＤＵＴＹ信号を出力すると、ＳＷ制御回路２２８は、スイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力する。なお、図４に図示しないが、実際には、ＳＷ制御回路２２８がピーク電流検出信号ＩＬＩＭＩＴによってスイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力すると、クロック発生器４３６は、ＭＡＸＤＵＴＹ信号を出力しない。 Further, when the clock generator 436 outputs the MAXDUTY signal to the SW control circuit 228 before the peak current detection circuit 227 outputs the peak current detection signal ILIMIT to the SW control circuit 228, the SW control circuit 228 causes the switching element 211 to be switched. A control signal Vg for turning off is output. Although not shown in FIG. 4, actually, when the SW control circuit 228 outputs the control signal Vg for turning off the switching element 211 by the peak current detection signal ILIMIT, the clock generator 436 does not output the MAXDUTY signal.
　コンパレータ４３３は、スイッチング素子２１１に流れる電流の電流値が予め定められた下限基準値以上であるか否かを判定する下限判定回路の一部である。コンパレータ４３３は、プラス入力端子に検出電圧Ｖｓｎが入力され、マイナス入力端子に下限基準電圧ＩＤＬが入力される。コンパレータ４３３は、検出電圧Ｖｓｎが下限基準電圧ＩＤＬより大きい場合に、ハイレベルとなる信号をフリップフロップ回路４３５に出力する。 The comparator 433 is a part of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value. In the comparator 433, the detection voltage Vsn is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal. The comparator 433 outputs a high level signal to the flip-flop circuit 435 when the detection voltage Vsn is greater than the lower limit reference voltage IDL.
　本実施の形態では、コンパレータ４３３は、スイッチング素子２１１がターンオンしてからターンオフするまでの間に、スイッチング素子２１１に流れる電流の電流値が、下限基準値以上であるか否かを判定する。そして、判定結果は、フリップフロップ回路４３５によって保持される。 In this embodiment, the comparator 433 determines whether the current value of the current flowing through the switching element 211 is greater than or equal to the lower limit reference value between the time when the switching element 211 is turned on and the time when the switching element 211 is turned off. Then, the determination result is held by the flip-flop circuit 435.
　フリップフロップ回路４３５は、下限判定回路の一部であり、コンパレータ４３３による判定結果を保持する。なお、スイッチング素子２１１がターンオンされる度に、判定結果はリセットされる。 The flip-flop circuit 435 is a part of the lower limit determination circuit, and holds the determination result by the comparator 433. Each time the switching element 211 is turned on, the determination result is reset.
　フリップフロップ回路４３５は、例えば、セット端子と、リセット端子と、出力端子とを有するＲＳフリップフロップ回路である。セット端子にコンパレータ４３３の出力信号が入力され、リセット端子にクロック発生器４３６からＣＬＯＣＫ信号が入力される。出力端子は、カウント回路４２９に接続され、セット端子に信号が入力されてからリセット端子に信号が入力されるまで、出力信号をカウント回路４２９に出力する。 The flip-flop circuit 435 is, for example, an RS flip-flop circuit having a set terminal, a reset terminal, and an output terminal. The output signal of the comparator 433 is input to the set terminal, and the CLOCK signal is input from the clock generator 436 to the reset terminal. The output terminal is connected to the count circuit 429, and outputs an output signal to the count circuit 429 until a signal is input to the reset terminal after a signal is input to the set terminal.
　フリップフロップ回路４３５では、クロック発生器４３６からＣＬＯＣＫ信号が出力される毎に、出力信号がリセットされる。すなわち、スイッチング素子２１１がターンオンするタイミングで、フリップフロップ回路４３５の出力は一度リセットされ、その後コンパレータ４３３からの出力信号によってセットされる。 In the flip-flop circuit 435, the output signal is reset every time the CLOCK signal is output from the clock generator 436. That is, at the timing when the switching element 211 is turned on, the output of the flip-flop circuit 435 is reset once and then set by the output signal from the comparator 433.
　すなわち、フリップフロップ回路４３５は、検出電圧Ｖｓｎが下限基準電圧ＩＤＬより大きい場合に、すなわち、スイッチング素子２１１に流れる電流の電流値が下限基準値より大きい場合に、ＣＬＯＣＫ信号が入力されるまでの期間、ハイレベルとなる信号をカウント回路４２９に出力する。 That is, the period until the CLOCK signal is input when the detection voltage Vsn is greater than the lower limit reference voltage IDL, that is, when the current value of the current flowing through the switching element 211 is greater than the lower limit reference value. , A signal that becomes a high level is output to the count circuit 429.
　カウント回路４２９は、スイッチング素子２１１に流れる電流の電流値が上限基準値以下であり、かつ、下限基準値以上であると判定された回数を計測する。本発明の実施の形態２では、電流値を直接比較するのではなく、ピーク値に達するまでの時間を検出することで、スイッチング素子２１１に流れる電流の電流値と上限基準値との比較を行う。 The count circuit 429 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value. In the second embodiment of the present invention, the current value of the current flowing through the switching element 211 is compared with the upper reference value by detecting the time until the peak value is reached instead of directly comparing the current values. .
　具体的には、カウント回路４２９には、フリップフロップ回路４３５の出力信号の他に、ピーク電流検出回路２２７からピーク電流検出信号ＩＬＩＭＩＴと、クロック発生器４３６からＭＡＸＤＵＴＹ信号と、起動／停止回路２２５からの出力信号（ＥＮＡＢＬＥ信号又はＤＩＳＡＢＬＥ信号）とが入力される。カウント回路４２９は、フリップフロップ回路４３５からの出力信号と、クロック発生器４３６からのＭＡＸＤＵＴＹ信号とが入力されたときにカウント回数を１つ増加させる。そして、カウント回数が予め設定された判定基準値に達すると、カウント回路４２９は、ｏｐｅｎ信号をＳＷ制御回路２２８へ出力する。また、起動／停止回路２２５からＤＩＳＡＢＬＥ信号が入力されるか、又は、ピーク電流検出回路２２７からピーク電流検出信号ＩＬＩＭＩＴが入力されると、カウント回路４２９は、カウント回数をリセットする。 Specifically, in addition to the output signal of the flip-flop circuit 435, the count circuit 429 includes a peak current detection signal ILIMIT from the peak current detection circuit 227, a MAXDUTY signal from the clock generator 436, and a start / stop circuit 225. Output signal (ENABLE signal or DISABLE signal). The count circuit 429 increases the number of counts by one when the output signal from the flip-flop circuit 435 and the MAXDUTY signal from the clock generator 436 are input. When the number of counts reaches a preset determination reference value, count circuit 429 outputs an open signal to SW control circuit 228. When the DISABLE signal is input from the start / stop circuit 225 or the peak current detection signal ILIMIT is input from the peak current detection circuit 227, the count circuit 429 resets the number of counts.
　以上のように構成された本発明の実施の形態２に係る発光ダイオード駆動装置３００について、ＬＥＤ光源部１２１が正常な場合の動作について説明する。正常な動作時にスイッチング素子２１１に流れる電流波形及び制御回路ブロック４２０の信号波形を、図５のＩＤＳ１に示す。 Regarding the light emitting diode driving apparatus 300 according to Embodiment 2 of the present invention configured as described above, the operation when the LED light source unit 121 is normal will be described. The waveform of the current flowing through the switching element 211 during normal operation and the signal waveform of the control circuit block 420 are shown in IDS1 of FIG.
　クロック発生器４３６からＣＬＯＣＫ信号が出力されると、ＳＷ制御回路２２８から出力される制御信号Ｖｇは、ハイレベルとなり、スイッチング素子２１１がターンオンして電流が流れ始める。このときの電流波形ＩＤＳ１は、チョークコイル１２２のインダクタンス値Ｌと、ＬＥＤ光源部１２１の両端子電圧差（Ｖｉｎ－ＶＦ＿ＬＥＤ）から決定される傾き（Ｖｉｎ－ＶＦ＿ＬＥＤ）／Ｌをもった単純増加の電流波形となる。 When the CLOCK signal is output from the clock generator 436, the control signal Vg output from the SW control circuit 228 becomes a high level, the switching element 211 is turned on, and a current starts to flow. The current waveform IDS1 at this time is a simple increase current having a slope (Vin−VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin−VF_LED) between both terminals of the LED light source 121. It becomes a waveform.
　そして、スイッチング素子２１１に流れる電流ＩＤが予め設定されたピーク値Ｉｐに達すると、ＳＷ制御回路２２８からの制御信号Ｖｇはロウレベルとなり、スイッチング素子２１１をターンオフさせる。本制御によってスイッチング素子２１１に流れる電流のピーク値が常にＩｐで一定になるように制御する。 Then, when the current ID flowing through the switching element 211 reaches a preset peak value Ip, the control signal Vg from the SW control circuit 228 becomes low level, and the switching element 211 is turned off. By this control, control is performed so that the peak value of the current flowing through the switching element 211 is always constant at Ip.
　この際、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、Ｖｓｎ＞ＩＤＬであるので、フリップフロップ回路４３５から出力信号がカウント回路４２９に入力される。また、スイッチング素子２１１のオン期間はクロック発生器４３６が規定する最大オンデューティ以内であるので、ＭＡＸＤＵＴＹ信号は出力されない（図５では、ＭＡＸＤＵＴＹ信号を点線で示す）。よって、カウント回路４２９は、カウント回数を増加しない。 At this time, since the relationship between the detection voltage Vsn inside the control circuit block 420 and the lower limit reference voltage IDL is Vsn> IDL, an output signal is input from the flip-flop circuit 435 to the count circuit 429. Further, since the ON period of the switching element 211 is within the maximum on-duty defined by the clock generator 436, the MAXDUTY signal is not output (in FIG. 5, the MAXDUTY signal is indicated by a dotted line). Therefore, the count circuit 429 does not increase the number of counts.
　また、図２Ｂで説明した期間Ｔ２のように、内部の制御回路ブロック４２０及びスイッチング素子２１１は、オン及びオフの制御を開始しているがスイッチング素子２１１に電流が流れない期間では、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、ＩＤＬ＞Ｖｓｎとなる。このため、カウント回路４２９は、カウント回数を増加しない。 Further, as in the period T2 described with reference to FIG. 2B, the control circuit block 420 and the switching element 211 in the internal control circuit block 420 and the switching element 211 start on and off control, but in the period in which no current flows through the switching element 211, The relationship between the detection voltage Vsn inside 420 and the lower limit reference voltage IDL is IDL> Vsn. For this reason, the count circuit 429 does not increase the number of counts.
　また、ピーク電流検出回路２２７からのピーク電流検出信号ＩＬＩＭＩＴによって、カウント回数はリセットされる。 Further, the number of counts is reset by the peak current detection signal ILIMIT from the peak current detection circuit 227.
　次に、ＬＥＤ光源部１２１を構成する発光ダイオード素子のいくつかが破壊され、オープン不良になり、スイッチング素子２１１がオンしている期間に微小電流が流れる場合について説明する。この場合のスイッチング素子２１１に流れる電流及び制御回路ブロック４２０の信号波形を、図５のＩＤＳ２に示す。 Next, a case will be described in which some of the light-emitting diode elements constituting the LED light source unit 121 are destroyed, resulting in an open failure, and a minute current flows while the switching element 211 is on. The current flowing through the switching element 211 and the signal waveform of the control circuit block 420 in this case are shown in IDS2 of FIG.
　この場合、ＬＥＤ光源部１２１は抵抗成分だけが残るため、正常時よりもインピーダンスが高くなり、電流増加率が低くなる。このため、スイッチング素子２１１に流れる電流ＩＤの最大値がピーク値Ｉｐに達することなく、スイッチング素子２１１のオン期間がクロック発生器４３６で規定される最大オンデューティに達する。このとき、クロック発生器４３６は、ＭＡＸＤＵＴＹ信号を出力し、ＳＷ制御回路２２８は、スイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力する。 In this case, since only the resistance component remains in the LED light source unit 121, the impedance becomes higher than that in the normal state, and the current increase rate becomes lower. Therefore, the on-period of the switching element 211 reaches the maximum on-duty defined by the clock generator 436 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip. At this time, the clock generator 436 outputs a MAXDUTY signal, and the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211.
　この際、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、予めＶｓｎ＞ＩＤＬとなるように設定されているため、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。また、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路４２９に出力される。このため、カウント回路４２９は、カウント回数を１つ増加させる。 At this time, since the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL, the flip-flop circuit 435 is set by the output signal from the comparator 433. The output signal is output to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
　カウント回路４２９は、ピーク電流検出回路２２７がピーク電流検出信号ＩＬＩＭＩＴを出力すると、カウント回数をリセットする。カウント回数は、スイッチング素子２１１のオン期間が毎回最大オンデューティであるときにのみ増加する。 The count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
　そして、カウント回数が所定の判定基準値以上となると、カウント回路４２９は、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。すなわち、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１をラッチ停止させる。 When the number of counts exceeds a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
　次に、ＬＥＤ光源部１２１を構成する発光ダイオード素子のいくつかが破壊されオープン不良になり、スイッチング素子２１１がオンしている期間中のある期間だけにスパイク電流が流れる場合について説明する。この場合のスイッチング素子２１１に流れる電流及び制御回路ブロック４２０の信号波形を、図５のＩＤＳ３に示す。 Next, a case will be described in which some of the light emitting diode elements constituting the LED light source unit 121 are destroyed and become open defective, and a spike current flows only during a certain period during the period when the switching element 211 is on. The current flowing through the switching element 211 and the signal waveform of the control circuit block 420 in this case are shown in IDS 3 of FIG.
　スイッチング素子２１１に流れるスパイク電流によって検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係がＶｓｎ＞ＩＤＬとなると、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。スイッチング素子２１１のオン期間中に検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係がＶｓｎ＜ＩＤＬになっても、フリップフロップ回路４３５の出力信号に変化はない。このため、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路に出力されると、カウント回路４２９は、カウント回数を１つ増加させることが可能となる。 When the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. . Even if the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn <IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit, the count circuit 429 can increase the number of counts by one.
　カウント回路４２９は、ピーク電流検出回路２２７がピーク電流検出信号ＩＬＩＭＩＴを出力すると、カウント回数をリセットする。カウント回数は、スイッチング素子２１１のオン期間が毎回最大オンデューティであるときにのみ増加する。 The count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
　そして、カウント回数が所定の判定基準値以上となると、カウント回路４２９は、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。すなわち、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１をラッチ停止させる。 When the number of counts exceeds a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
　このように構成された本発明の実施の形態２に係る発光ダイオード駆動装置３００は、スイッチング素子２１１に流れる電流値がピーク値に達しない場合は、最大デューティ駆動となる。すなわち、スイッチング素子２１１がオンである期間が、予め設定された最大デューティ期間に達した場合に、スイッチング素子２１１は、ターンオフされる。 The light emitting diode driving apparatus 300 according to the second embodiment of the present invention configured as described above performs maximum duty driving when the value of the current flowing through the switching element 211 does not reach the peak value. That is, when the period during which the switching element 211 is on reaches a preset maximum duty period, the switching element 211 is turned off.
　よって、スイッチング素子２１１に流れる電流が予め設定された上限基準値以下であることを検出するために、直接電流値の比較を行う必要はない。代わりに、予め設定された上限基準値に達するかどうかに係わりなく、最大デューティ駆動となった回数をカウントすることで、ＬＥＤ光源部１２１がオープンであるか否かを判定するので、ＬＥＤのオープン検出精度を向上することができる。 Therefore, it is not necessary to directly compare the current values in order to detect that the current flowing through the switching element 211 is equal to or less than a preset upper reference value. Instead, whether or not the LED light source unit 121 is open is determined by counting the number of times that the maximum duty drive is performed, regardless of whether or not the preset upper limit reference value is reached. Detection accuracy can be improved.
　なお、本発明の実施の形態２では、スイッチング素子２１１の制御方式として、スイッチング素子２１１に流れる電流のピーク値を変化させる電流モードＰＷＭ制御方式を例に説明したが、これに限定されるものではない。スイッチングのオンデューティを制御するＰＷＭ方式の場合でも、スイッチング素子２１１の最大オンデューティを規定することによって、実施の形態２と同様の制御を行うことが可能である。 In the second embodiment of the present invention, the current mode PWM control method for changing the peak value of the current flowing through the switching element 211 is described as an example of the control method for the switching element 211. However, the present invention is not limited to this. Absent. Even in the case of the PWM method for controlling the switching on-duty, it is possible to perform the same control as in the second embodiment by defining the maximum on-duty of the switching element 211.
　また、スイッチング素子２１１のオフ時間を予め設定された値で固定にするオフ時間固定制御方式、又は、発振周波数を変化させるＰＦＭ制御方式においても、上記の実施の形態２と同様の制御を行うことができる。例えば、まず、スイッチング素子２１１がパルス毎にオンできる最大時間、すなわち、最大オン期間を規定する。そして、フリップフロップ回路４３５からの出力信号と最大オン期間が経過したことを示す信号（図４には図示しない）とがともに、カウント回路４２９に印加されたときにカウント回数を１つ増加させることで、同様の効果を得ることができる。 The same control as that of the second embodiment is performed also in the off-time fixed control method in which the off-time of the switching element 211 is fixed at a preset value or the PFM control method in which the oscillation frequency is changed. Can do. For example, first, a maximum time during which the switching element 211 can be turned on for each pulse, that is, a maximum ON period is defined. When the output signal from the flip-flop circuit 435 and a signal (not shown in FIG. 4) indicating that the maximum on-period has elapsed are applied to the count circuit 429, the number of counts is increased by one. Thus, the same effect can be obtained.
　言い換えると、本発明の実施の形態２の変形例に係る発光ダイオード駆動装置は、最大オン時間駆動であるか否かを判定することで、スイッチング素子２１１に流れる電流が上限基準値以下であるか否かを判定する。最大オン時間駆動とは、スイッチング素子２１１がオンしている期間が、予め設定された最大の期間（最大オン期間）に達した場合に、スイッチング素子２１１をターンオフすることである。すなわち、本発明の実施の形態２の変形例に係る発光ダイオード駆動装置では、スイッチング素子２１１に流れる電流がピーク値に達して、スイッチング素子２１１がターンオフされる前に、最大オン時間駆動によりターンオフされることを検出することで、スイッチング素子２１１に流れる電流が上限基準値以下であることを検出する。 In other words, the light emitting diode driving apparatus according to the modification of the second embodiment of the present invention determines whether or not the current flowing in the switching element 211 is equal to or lower than the upper reference value by determining whether or not the driving is the maximum on-time driving. Determine whether or not. The maximum on-time driving is to turn off the switching element 211 when the period during which the switching element 211 is on reaches a preset maximum period (maximum on period). That is, in the light emitting diode driving device according to the modification of the second embodiment of the present invention, the current flowing through the switching element 211 reaches the peak value and is turned off by the maximum on-time driving before the switching element 211 is turned off. By detecting this, it is detected that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value.
　具体的には、ＳＷ制御回路２２８は、第１動作モード（通常動作モード）において、オフ時間固定制御方式により、スイッチング素子２１１がターンオフされてから予め設定された期間後に、スイッチング素子２１１をターンオンする。また、上述したように、ＳＷ制御回路２２８は、スイッチング素子２１１に流れる電流がピーク値Ｉｐに達した場合に、すなわち、ピーク電流検出信号ＩＬＩＭＩＴが入力された場合に、スイッチング素子２１１をターンオフにする。 Specifically, in the first operation mode (normal operation mode), the SW control circuit 228 turns on the switching element 211 after a predetermined period after the switching element 211 is turned off by the fixed off time control method. . As described above, the SW control circuit 228 turns off the switching element 211 when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input. .
　クロック発生器４３６は、最大オン期間検出回路の一例であり、スイッチング素子２１１がオンしている期間の最大値である最大オン期間を設定する。そして、スイッチング素子２１１がオンしている期間が最大オン期間に達した場合（すなわち、最大オン時間駆動である場合）に、スイッチング素子２１１に流れる電流の電流値が上限基準値以下であると判定される。 The clock generator 436 is an example of a maximum on-period detection circuit, and sets a maximum on-period that is the maximum value of the period during which the switching element 211 is on. Then, when the period during which the switching element 211 is on reaches the maximum on-period (that is, when the maximum on-time driving is performed), it is determined that the current value of the current flowing through the switching element 211 is equal to or less than the upper limit reference value. Is done.
　本構成によれば、スイッチング素子２１１に流れる電流が、予め設定された上限基準値に達するかどうかに係わりなく、最大オン時間駆動となった場合の回数をカウントすることで、ＬＥＤのオープンの検出を行うことができる。このとき、上限基準値との比較のために電流の検出を行わなくてよく、最大オン時間駆動であるか否かを判定するだけでよいので、オープンの検出精度を向上することができる。 According to this configuration, regardless of whether or not the current flowing through the switching element 211 reaches the preset upper limit reference value, the number of times when the maximum on-time driving is performed is counted, thereby detecting LED open. It can be performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
　また、本実施の形態では、クロック発生器４３６からスイッチング素子２１１をターンオンさせるＣＬＯＣＫ信号が、フリップフロップ回路４３５のリセット端子に印加され、スイッチング素子２１１のスイッチングサイクル毎に検出を行うので、誤検出の可能性が低い。 In this embodiment, the CLOCK signal for turning on the switching element 211 from the clock generator 436 is applied to the reset terminal of the flip-flop circuit 435, and detection is performed every switching cycle of the switching element 211. Less likely.
　また、本実施の形態では、カウント回数が連続的に増加中に、スイッチング素子２１１に流れる電流が上限基準値以上である場合、又は、ピーク値に達した場合は、カウント回数がリセットされる。言い換えると、本実施の形態では、カウント回路４２９は、計測した回数が、スイッチング素子２１１がターンオフするタイミングと同期して増加しない場合、当該回数をリセットする。これにより、誤検出の可能性を低くすることができる。 In this embodiment, when the number of counts is continuously increasing, if the current flowing through the switching element 211 is greater than or equal to the upper limit reference value or reaches a peak value, the number of counts is reset. In other words, in this embodiment, the count circuit 429 resets the number of times when the measured number does not increase in synchronization with the timing at which the switching element 211 is turned off. Thereby, the possibility of erroneous detection can be reduced.
　（実施の形態３）
　続いて、本発明の実施の形態３に係る発光ダイオード駆動装置について説明する。本発明の実施の形態３に係る発光ダイオード駆動装置は、ＬＥＤ光源部に並列に、抵抗、コンデンサ、又は、互いに直列接続された抵抗及びコンデンサが接続されていることを特徴とする。 (Embodiment 3)
Subsequently, a light-emitting diode driving apparatus according to Embodiment 3 of the present invention will be described. The light emitting diode driving device according to Embodiment 3 of the present invention is characterized in that a resistor, a capacitor, or a resistor and a capacitor connected in series with each other are connected in parallel to the LED light source unit.
　実施の形態３は、実施の形態１及び２と比較して直列接続ループ回路１２０の構成が異なる。より具体的には、ＬＥＤ光源部１２１と並列に追加の部品が接続されている。 The third embodiment is different from the first and second embodiments in the configuration of the series connection loop circuit 120. More specifically, an additional component is connected in parallel with the LED light source unit 121.
　図６Ａ～図６Ｃは、本発明の実施の形態３に係る直列接続ループ回路の構成の一例を示す回路図である。なお、これらの直列接続ループ回路を駆動するためのスイッチング駆動回路（発光ダイオード駆動用の半導体装置）及び電源部は、図１で示す実施の形態１に示す回路、及び、図４に示す実施の形態２で示す回路のどちらでも対応は可能である。 6A to 6C are circuit diagrams showing an example of the configuration of the series connection loop circuit according to the third embodiment of the present invention. Note that the switching drive circuit (light emitting diode drive semiconductor device) and the power supply unit for driving these series-connected loop circuits are the circuit shown in FIG. 1 and the implementation shown in FIG. Either of the circuits shown in Embodiment 2 can be used.
　ここでは、具体的な回路の動作説明のため、図４に示すスイッチング駆動回路４００を使用した場合の例で説明する。 Here, in order to explain specific circuit operations, an example in which the switching drive circuit 400 shown in FIG. 4 is used will be described.
　図６Ａに示す直列接続ループ回路５２０ａは、ＬＥＤ光源部１２１と、チョークコイル１２２と、ダイオード１２３と、抵抗５２４とを備える。図６Ａに示すように、ＬＥＤ光源部１２１と並列に抵抗５２４が接続されている。 6A includes a LED light source unit 121, a choke coil 122, a diode 123, and a resistor 524. The series connection loop circuit 520a illustrated in FIG. As shown in FIG. 6A, a resistor 524 is connected in parallel with the LED light source unit 121.
　ＬＥＤ光源部１２１が正常な場合の動作は、実施の形態２の動作と同様であるので詳細な説明は割愛する。 Since the operation when the LED light source unit 121 is normal is the same as the operation of the second embodiment, a detailed description thereof is omitted.
　また、図２Ｂで説明した期間Ｔ２のように、入力電圧Ｖｉｎが出力電圧ＶＦ＿ＬＥＤよりも低い期間には、ＬＥＤ光源部１２１には電流が流れない。しかし、抵抗５２４には微小な電流が流れる。この期間に抵抗５２４に流れる電流は、抵抗５２４の抵抗値をＲ５２４、流れる電流の最大値をＩＲＰ５２４とすると、ＩＲＰ５２４＝ＶＦ＿ＬＥＤ／Ｒ５２４と表すことができる。この際、下限基準電圧ＩＤＬの値は、予め、「ＩＤＬに相当する電流値＞ＩＲＰ５２４」となるように設定しておくことで、期間Ｔ２にスイッチング素子２１１に下限基準電圧ＩＤＬに相当する電流より大きな電流が流れることはない。 Further, as in the period T2 described with reference to FIG. 2B, no current flows through the LED light source unit 121 in a period in which the input voltage Vin is lower than the output voltage VF_LED. However, a minute current flows through the resistor 524. The current flowing through the resistor 524 during this period can be expressed as IRP524 = VF_LED / R524, where R524 is the resistance value of the resistor 524 and IRP524 is the maximum value of the flowing current. At this time, the value of the lower limit reference voltage IDL is set in advance such that “current value corresponding to IDL> IRP524”, so that the switching element 211 has a current corresponding to the lower limit reference voltage IDL in the period T2. A large current never flows.
　次に、ＬＥＤ光源部１２１を構成する発光ダイオード素子のいくつかが破壊されてオープン不良になった場合について説明する。発光ダイオードのオープン不良は、完全に電気的に絶縁される場合（完全オープン状態）と、抵抗成分が残った半オープン状態との２種類に分類できる。図６Ａに示す例では、ＬＥＤ光源部１２１と並列に抵抗５２４が接続されているため、完全オープン状態では、抵抗５２４で決定される抵抗負荷となり、半オープン状態では、残留の高抵抗と抵抗５２４との合成抵抗負荷となる。ここでは、ＬＥＤ光源部１２１が完全オープン状態になった場合を例に説明する。 Next, a case where some of the light emitting diode elements constituting the LED light source unit 121 are destroyed and become open defects will be described. The open failure of the light emitting diode can be classified into two types, that is, a case where it is completely electrically insulated (fully open state) and a semi-open state where a resistance component remains. In the example shown in FIG. 6A, since the resistor 524 is connected in parallel with the LED light source unit 121, the resistance load is determined by the resistor 524 in the fully open state, and the residual high resistance and the resistor 524 are in the half open state. And combined resistance load. Here, a case where the LED light source unit 121 is in a completely open state will be described as an example.
　この場合、ＬＥＤ光源部１２１は、抵抗成分だけが残るため、正常時よりもインピーダンスが高くなり電流増加率が低くなる。その結果、図５のＩＤＳ２の波形に示すように、スイッチング素子２１１に流れる電流ＩＤの最大値がピーク値Ｉｐに達することなく、スイッチング素子２１１のオン期間がクロック発生器４３６で規定される最大オンデューティに達すると、クロック発生器４３６は、ＭＡＸＤＵＴＹ信号を出力する。そして、ＳＷ制御回路２２８は、スイッチング素子２１１をターンオフさせる制御信号Ｖｇを出力する。 In this case, since only the resistance component remains in the LED light source unit 121, the impedance becomes higher than that in the normal state, and the current increase rate becomes lower. As a result, as shown in the waveform of IDS2 in FIG. 5, the maximum value of the current ID flowing through the switching element 211 does not reach the peak value Ip, and the ON period of the switching element 211 is determined by the clock generator 436. When the duty is reached, the clock generator 436 outputs a MAXDUTY signal. Then, the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211.
　この際、図２Ｂで説明した期間Ｔ３において、抵抗５２４に流れる電流ＩＲ５２４の値は、電源入力電圧Ｖｉｎと抵抗値Ｒ５２４とによって、ＩＲ５２４＝Ｖｉｎ／Ｒ５２４で決定される値となる。下限基準電圧ＩＤＬの値は、予め「ＩＲ５２４＞ＩＤＬに相当する電流値」となるように設定されている。すなわち、下限基準値は、ＬＥＤ光源部１２１に含まれる少なくとも１つの発光ダイオードがオープンである場合に、抵抗５２４に流れる電流の電流値以下の値に設定しておく。また、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、予めＶｓｎ＞ＩＤＬとなるように設定されている。 At this time, in the period T3 described with reference to FIG. 2B, the value of the current IR524 flowing through the resistor 524 becomes a value determined by IR524 = Vin / R524 depending on the power supply input voltage Vin and the resistance value R524. The value of the lower limit reference voltage IDL is set in advance to be “a current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the resistor 524 when at least one light emitting diode included in the LED light source unit 121 is open. The relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
　この結果、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。また、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路４２９に出力される。このため、カウント回路４２９は、カウント回数を１つ増加させる。 As a result, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
　カウント回路４２９は、ピーク電流検出回路２２７がピーク電流検出信号ＩＬＩＭＩＴを出力すると、カウント回数をリセットする。カウント回数は、スイッチング素子２１１のオン期間が最大オンデューティであるときにのみ増加する。 The count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
　そして、カウント回数が所定の判定基準値以上となると、カウント回路４２９は、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。すなわち、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１をラッチ停止させる。 When the number of counts exceeds a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
　下限基準電圧ＩＤＬは、予め内部で設定された固定の値でもよいし、外部からユーザーによって自由に調整が可能な構成にしてもよい。また、ユーザーは、設定されたＩＤＬの値とＬＥＤ光源部１２１に接続する発光ダイオードの接続数に応じて、すなわち、ＶＦ＿ＬＥＤの値に応じて抵抗５２４の値を「ＩＤＬに相当する電流値＜ＶＦ＿ＬＥＤ／Ｒ５２４」の範囲になるように調整する。これにより、図２Ｂの期間Ｔ２において、誤ってＬＥＤ光源部１２１がオープンであると判定されることはない。 The lower limit reference voltage IDL may be a fixed value set inside in advance, or may be configured to be freely adjustable by the user from the outside. Further, the user sets the value of the resistor 524 according to the set IDL value and the number of connected light emitting diodes connected to the LED light source unit 121, that is, according to the value of VF_LED, “current value corresponding to IDL <VF_LED. / R524 "is adjusted. Thereby, in the period T2 of FIG. 2B, it is not erroneously determined that the LED light source unit 121 is open.
　次に、スイッチング素子２１１がオンしている期間中のある期間だけにスパイク電流が流れる場合について説明する。この場合のスイッチング素子２１１に流れる電流及び制御回路ブロック４２０の信号波形は、図５のＩＤＳ３と同様な波形となる。この場合も、図２Ｂで説明した期間Ｔ２では、下限基準電圧ＩＤＬの値と抵抗５２４に流れる電流の最大値は、「ＩＤＬに相当する電流値＞ＩＲＰ５２４（すなわち、電流の最大値）」であるため、カウント回路４２９のカウント回数が増加することはない。 Next, a case where a spike current flows only during a certain period during the period when the switching element 211 is on will be described. In this case, the current flowing through the switching element 211 and the signal waveform of the control circuit block 420 are similar to those of the IDS 3 in FIG. Also in this case, in the period T2 described with reference to FIG. 2B, the value of the lower limit reference voltage IDL and the maximum value of the current flowing through the resistor 524 are “current value corresponding to IDL> IRP524 (that is, the maximum value of the current)”. Therefore, the number of counts of the count circuit 429 does not increase.
　さらに、図２Ｂで説明した期間Ｔ３において、スイッチング素子２１１に流れるスパイク電流によって検出電圧Ｖｓｎと下限基準電圧ＩＤＬの関係がＶｓｎ＞ＩＤＬとなると、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。スイッチング素子２１１のオン期間中に検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係がＶｓｎ＜ＩＤＬになってもフリップフロップ回路４３５の出力信号に変化はない。このため、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路４２９に出力されると、カウント回路４２９は、カウント回数を１つ増加させることが可能となる。 2B, when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433. The output signal is output to the count circuit 429. Even when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn <IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit 429, the count circuit 429 can increase the number of counts by one.
　次に、図６Ｂに示す直列接続ループ回路５２０ｂは、ＬＥＤ光源部１２１と、チョークコイル１２２と、ダイオード１２３と、平滑用コンデンサ５２５とを備える。図６Ｂに示すように、ＬＥＤ光源部１２１と並列に平滑用コンデンサ５２５が接続されている。 Next, the series connection loop circuit 520b shown in FIG. 6B includes an LED light source unit 121, a choke coil 122, a diode 123, and a smoothing capacitor 525. As shown in FIG. 6B, a smoothing capacitor 525 is connected in parallel with the LED light source unit 121.
　この場合、図２Ｂで説明した期間Ｔ２のように、入力電圧Ｖｉｎが出力電圧ＶＦ＿ＬＥＤよりも低い期間にはＬＥＤ光源部１２１には電流が流れない。しかし、平滑用コンデンサ５２５には微小な電流が流れる。この場合も期間Ｔ２において、平滑用コンデンサ５２５に流れる最大電流値をＩＣＰ５２５とすると、下限基準電圧ＩＤＬの値は予め、「ＩＤＬに相当する電流値＞ＩＣＰ５２５」となるように設定することによって、期間Ｔ２にスイッチング素子２１１に下限基準電圧ＩＤＬに相当する電流が流れることはない。 In this case, no current flows through the LED light source unit 121 during the period in which the input voltage Vin is lower than the output voltage VF_LED as in the period T2 described in FIG. 2B. However, a minute current flows through the smoothing capacitor 525. Also in this case, when the maximum current value flowing through the smoothing capacitor 525 is ICP525 in the period T2, the value of the lower limit reference voltage IDL is set in advance so that “current value corresponding to IDL> ICP525”. The current corresponding to the lower limit reference voltage IDL does not flow through the switching element 211 at T2.
　また、ＬＥＤ光源部１２１がオープンになった際には、図２Ｂで説明した期間Ｔ３において、平滑用コンデンサ５２５に流れる電流をＩＣ５２５とすると、下限基準電圧ＩＤＬの値は、予め「ＩＣ５２５＞ＩＤＬに相当する電流値」となるように設定する。すなわち、下限基準値は、ＬＥＤ光源部１２１に含まれる少なくとも１つの発光ダイオードがオープンである場合に、平滑用コンデンサ５２５に流れる電流の電流値以下の値に設定しておく。また、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、予めＶｓｎ＞ＩＤＬとなるように設定されている。 Further, when the LED light source unit 121 is opened, assuming that the current flowing through the smoothing capacitor 525 is IC 525 in the period T3 described with reference to FIG. 2B, the value of the lower limit reference voltage IDL is “IC525> IDL beforehand. It is set so that it corresponds to the “current value”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open. The relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
　この結果、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。また、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路４２９に出力される。このため、カウント回路４２９は、カウント回数を１つ増加させる。 As a result, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
　カウント回路４２９は、ピーク電流検出回路２２７がピーク電流検出信号ＩＬＩＭＩＴを出力すると、カウント回数をリセットする。カウント回数は、スイッチング素子２１１のオン期間が最大オンデューティであるときにのみ増加する。そして、カウント回数が所定の判定基準値以上となると、カウント回路４２９は、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。すなわち、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１をラッチ停止させる。 The count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty. When the number of counts is equal to or greater than a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
　スイッチング素子２１１がオンしている期間中のある期間だけにスパイク電流が流れる場合についても、図６Ａの場合と同様の動作によって正確にＬＥＤ光源部１２１のオープンを検出することができる。 Also in the case where the spike current flows only during a certain period during which the switching element 211 is on, the open state of the LED light source 121 can be accurately detected by the same operation as in FIG. 6A.
　次に、図６Ｃに示す直列接続ループ回路５２０ｃは、ＬＥＤ光源部１２１と、チョークコイル１２２と、ダイオード１２３と、抵抗５２４と、平滑用コンデンサ５２５とを備える。図６Ｃに示すように、直列接続された平滑用コンデンサ５２５と抵抗５２４とが、ＬＥＤ光源部１２１に並列に接続されている。 Next, the series connection loop circuit 520c shown in FIG. 6C includes an LED light source unit 121, a choke coil 122, a diode 123, a resistor 524, and a smoothing capacitor 525. As shown in FIG. 6C, a smoothing capacitor 525 and a resistor 524 connected in series are connected to the LED light source unit 121 in parallel.
　この場合、ＬＥＤ光源部１２１がオープンになると、平滑用コンデンサ５２５と抵抗５２４とに電流が流れる。また、流れる電流値は、抵抗５２４の抵抗値Ｒ５２４によって制限される。このため、図２Ｂで説明した期間Ｔ２のように、入力電圧Ｖｉｎが出力電圧ＶＦ＿ＬＥＤよりも低い期間に流れる電流の最大値は、ＩＲＰ５２４で決定される。 In this case, when the LED light source 121 is opened, a current flows through the smoothing capacitor 525 and the resistor 524. Further, the value of the flowing current is limited by the resistance value R524 of the resistor 524. Therefore, as in the period T2 described with reference to FIG. 2B, the maximum value of the current that flows during the period in which the input voltage Vin is lower than the output voltage VF_LED is determined by the IRP 524.
　よって、図６Ａの場合と同様に、ＩＲ５２４＝ＶＦ＿ＬＥＤ／Ｒ５２４で決定され、下限基準電圧ＩＤＬの値は予め、「ＩＤＬに相当する電流値＞ＩＲＰ５２４」となるように設定されている。このため、期間Ｔ２にスイッチング素子２１１に下限基準電圧ＩＤＬに相当する電流が流れることはない。 Therefore, as in the case of FIG. 6A, IR524 = VF_LED / R524 is determined, and the value of the lower limit reference voltage IDL is set in advance so that “current value corresponding to IDL> IRP524”. For this reason, the current corresponding to the lower limit reference voltage IDL does not flow through the switching element 211 during the period T2.
　また、ＬＥＤ光源部１２１がオープンになった場合は、図２Ｂで説明した期間Ｔ３において、抵抗５２４に流れる電流ＩＲ５２４の値は、入力電圧Ｖｉｎと抵抗値Ｒ５２４とによって、ＩＲ５２４＝Ｖｉｎ／Ｒ５２４で決定される値となる。下限基準電圧ＩＤＬの値は、予め「ＩＲ５２４に相当する電流値＞ＩＤＬ」となるように設定されている。すなわち、下限基準値は、ＬＥＤ光源部１２１に含まれる少なくとも１つの発光ダイオードがオープンである場合に、抵抗５２４及び平滑用コンデンサ５２５に流れる電流の電流値以下の値に設定しておく。また、制御回路ブロック４２０内部の検出電圧Ｖｓｎと下限基準電圧ＩＤＬとの関係は、予めＶｓｎ＞ＩＤＬとなるように設定されている。 When the LED light source unit 121 is opened, the value of the current IR524 flowing through the resistor 524 is determined by IR524 = Vin / R524 based on the input voltage Vin and the resistance value R524 in the period T3 described with reference to FIG. 2B. It becomes the value to be. The value of the lower limit reference voltage IDL is set in advance such that “current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or less than the current value of the current flowing through the resistor 524 and the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open. The relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
　この結果、コンパレータ４３３からの出力信号によってフリップフロップ回路４３５はセットされ、出力信号をカウント回路４２９に出力する。また、クロック発生器４３６からＭＡＸＤＵＴＹ信号がカウント回路４２９に出力される。このため、カウント回路４２９は、カウント回数を１つ増加させる。 As a result, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
　カウント回路４２９は、ピーク電流検出回路２２７がピーク電流検出信号ＩＬＩＭＩＴを出力すると、カウント回数をリセットする。カウント回数は、スイッチング素子２１１のオン期間が最大オンデューティであるときにのみ増加する。 The count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
　そして、カウント回数が所定の判定基準値以上となると、カウント回路４２９は、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持する。すなわち、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１をラッチ停止させる。 When the number of counts exceeds a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
　ＬＥＤ光源部１２１に流れる電流波形を平滑するために平滑用コンデンサ５２５を接続する場合は、平滑用コンデンサ５２５と直列に抵抗５２４を接続することによって、ユーザーは設定されたＩＤＬの値と、ＬＥＤ光源部１２１に接続する発光ダイオードの接続数とに応じて、ＬＥＤ光源部１２１の誤検出を容易に防止することができる。すなわち、ＶＦ＿ＬＥＤの値に応じて抵抗５２４の値を「ＩＤＬに相当する電流値＜ＶＦ＿ＬＥＤ／Ｒ５２４」の範囲になるように調整することで、図２Ｂの期間Ｔ２において、誤ってＬＥＤ光源部１２１がオープンであると判定されないように、容易に調整することが可能である。 When the smoothing capacitor 525 is connected to smooth the waveform of the current flowing through the LED light source unit 121, the user can connect the set IDL value and the LED light source by connecting a resistor 524 in series with the smoothing capacitor 525. Depending on the number of light emitting diodes connected to the unit 121, erroneous detection of the LED light source unit 121 can be easily prevented. That is, by adjusting the value of the resistor 524 in accordance with the value of VF_LED so as to be in the range of “current value corresponding to IDL <VF_LED / R524”, the LED light source unit 121 is erroneously set in the period T2 of FIG. 2B. It is possible to easily adjust so that it is not determined to be open.
　また、スイッチング素子２１１がオンしている期間中のある期間だけにスパイク電流が流れる場合についても、図６Ａの場合と同様の動作によって正確にＬＥＤ光源部１２１のオープンを検出することができる。 Also, even when a spike current flows only during a certain period during which the switching element 211 is on, the open state of the LED light source unit 121 can be accurately detected by the same operation as in FIG. 6A.
　このように構成された本発明の実施の形態３に係る発光ダイオード駆動装置は、ＬＥＤ光源部１２１がオープンになっても並列接続された部品に電流が流れるが、下限判定回路の一例であるコンパレータ４３３によって検出可能であるため、ＬＥＤオープンの検出精度が向上する。 In the light emitting diode driving apparatus according to Embodiment 3 of the present invention configured as described above, a current flows through the components connected in parallel even when the LED light source 121 is opened, but the comparator is an example of a lower limit determination circuit. Since it is detectable by 433, the detection accuracy of LED open improves.
　（実施の形態４）
　続いて、本発明の実施の形態４に係る発光ダイオード駆動装置について説明する。本発明の実施の形態４に係る発光ダイオード駆動装置は、カウント回数が所定の判定基準値以上である場合に、異常判定信号を出力する異常処理回路を備えることを特徴とする。 (Embodiment 4)
Subsequently, a light-emitting diode driving apparatus according to Embodiment 4 of the present invention will be described. The light emitting diode driving device according to Embodiment 4 of the present invention includes an abnormality processing circuit that outputs an abnormality determination signal when the number of counts is equal to or greater than a predetermined determination reference value.
　図７は、本発明の実施の形態４に係る発光ダイオード駆動装置６００の一例を示す回路図である。実施の形態４は、実施の形態２と比較して、新たに異常処理回路６５０を備える点と、電源部１１０の代わりに電源部６１０を備え、スイッチング駆動回路４００の代わりにスイッチング駆動回路７００を備える点が異なっている。 FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus 600 according to Embodiment 4 of the present invention. Compared with the second embodiment, the fourth embodiment includes a new abnormality processing circuit 650, a power supply unit 610 instead of the power supply unit 110, and a switching drive circuit 700 instead of the switching drive circuit 400. The point to prepare is different.
　スイッチング駆動回路７００は、新たに、外部接続端子ＯＰを有し、カウント回路４２９から出力されたｏｐｅｎ信号を、外部接続端子ＯＰを介して異常処理回路６５０に出力する。 The switching drive circuit 700 newly has an external connection terminal OP, and outputs the open signal output from the count circuit 429 to the abnormality processing circuit 650 via the external connection terminal OP.
　異常処理回路６５０は、カウント回路４２９によって計測された回数が判定基準値以上である場合に、異常であることを示す異常判定信号を出力する。具体的には、異常処理回路６５０は、外部接続端子ＯＰを介してｏｐｅｎ信号が入力された場合に、異常判定信号を、電源部６１０が備えるスイッチ６１４に出力する。 The abnormality processing circuit 650 outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit 429 is greater than or equal to the determination reference value. Specifically, the abnormality processing circuit 650 outputs an abnormality determination signal to the switch 614 included in the power supply unit 610 when an open signal is input via the external connection terminal OP.
　電源部６１０は、新たにスイッチ６１４を備える。スイッチ６１４は、整流回路１１２と直列接続ループ回路１２０との間に直列に接続され、入力電圧ＶｉｎをＬＥＤ光源部１２１及びチョークコイル１２２に印加するか否かを決定する。具体的には、スイッチ６１４は、異常処理回路６５０から異常判定信号が入力された場合に、ターンオフされ、入力電圧Ｖｉｎの供給を停止する。 The power supply unit 610 newly includes a switch 614. The switch 614 is connected in series between the rectifier circuit 112 and the series connection loop circuit 120, and determines whether or not to apply the input voltage Vin to the LED light source unit 121 and the choke coil 122. Specifically, when an abnormality determination signal is input from the abnormality processing circuit 650, the switch 614 is turned off and stops supplying the input voltage Vin.
　実施の形態４における動作の説明を、図７を用いて、実施の形態２と異なる点について説明する。図７において、カウント回路４２９は、カウント回数が所定の判定基準値以上となると、負荷であるＬＥＤ光源部１２１がオープンであると判断して、ｏｐｅｎ信号をＳＷ制御回路２２８に出力する。さらに、ｏｐｅｎ信号は、外部接続端子ＯＰを介して、異常処理回路６５０にも出力される。 The operation of the fourth embodiment will be described with reference to FIG. 7 for differences from the second embodiment. In FIG. 7, the count circuit 429 determines that the LED light source 121 that is a load is open when the number of counts exceeds a predetermined determination reference value, and outputs an open signal to the SW control circuit 228. Further, the open signal is also output to the abnormality processing circuit 650 via the external connection terminal OP.
　異常処理回路６５０は、ｏｐｅｎ信号が入力されると、異常判定信号を出力することで、スイッチ６１４をターンオフして、入力電圧ＶｉｎがＬＥＤ光源部１２１側に供給されないようにする。この結果、周辺部品やスイッチング素子に過大な電圧が印加されることを防止できる。 When the open signal is input, the abnormality processing circuit 650 outputs an abnormality determination signal to turn off the switch 614 so that the input voltage Vin is not supplied to the LED light source unit 121 side. As a result, it is possible to prevent an excessive voltage from being applied to peripheral components and switching elements.
　また、ＳＷ制御回路２２８は、ｏｐｅｎ信号が入力されると、スイッチング素子２１１をターンオフさせ、かつ、スイッチング動作を停止した状態を保持してもよい。負荷がオープンであると検出すると、スイッチング素子２１１を停止させ、さらに入力電圧が印加されないようにすることで、安全性をより高めることが可能となる。 Further, when the open signal is input, the SW control circuit 228 may turn off the switching element 211 and hold the state where the switching operation is stopped. When it is detected that the load is open, the switching element 211 is stopped, and the input voltage is not applied, so that safety can be further improved.
　また、外部接続端子ＯＰ端子から出力されるｏｐｅｎ信号は、発光ダイオード駆動装置とは異なる別の駆動装置に信号を伝達する構成としてもよい。つまり、異常処理回路６５０は、ＬＥＤ光源部１２１が異常であることをユーザーに知らせるために、異常判定信号を外部の装置に出力してもよい。 Further, the open signal output from the external connection terminal OP terminal may be configured to transmit a signal to another drive device different from the light emitting diode drive device. That is, the abnormality processing circuit 650 may output an abnormality determination signal to an external device in order to notify the user that the LED light source unit 121 is abnormal.
　例えば、ｏｐｅｎ信号を別の装置に伝達して異常が発生していることを第三者に表示する構成としてもよい。具体的には、異常処理回路６５０は、外部の表示部に異常判定信号を出力することで、ＬＥＤ光源部１２１がオープンであることを表示部に表示させることができる。あるいは、異常処理回路６５０は、外部の出音部に異常判定信号を出力することで、アラーム音などによって、ユーザーにＬＥＤ光源部１２１がオープンであることを知らせることもできる。 For example, an open signal may be transmitted to another device to indicate that an abnormality has occurred to a third party. Specifically, the abnormality processing circuit 650 can display on the display unit that the LED light source unit 121 is open by outputting an abnormality determination signal to an external display unit. Alternatively, the abnormality processing circuit 650 can notify the user that the LED light source unit 121 is open by an alarm sound or the like by outputting an abnormality determination signal to an external sound output unit.
　このように構成された本発明の実施の形態４に係る発光ダイオード駆動装置６００は、ＬＥＤのオープンを検出した際に、異常判定信号を出力する。このため、この出力信号を利用して入力電圧の供給を停止したり、ＬＥＤ光源がオープンであることを周辺装置に伝達したり、アラームを鳴らし、ＬＥＤ光源部の異常を使用者に知らせることができる。 The light emitting diode driving device 600 according to the fourth embodiment of the present invention configured as described above outputs an abnormality determination signal when detecting the open of the LED. For this reason, the supply of input voltage is stopped using this output signal, the peripheral device is notified that the LED light source is open, an alarm is sounded, and the user is notified of an abnormality in the LED light source unit. it can.
　以上、本発明に係る発光ダイオード駆動装置及び発光ダイオード駆動用の半導体装置について、実施の形態に基づいて説明したが、本発明は、これらの実施の形態に限定されるものではない。本発明の趣旨を逸脱しない限り、当業者が思いつく各種変形を当該実施の形態に施したものや、異なる実施の形態における構成要素を組み合わせて構築される形態も、本発明の範囲内に含まれる。 The light emitting diode driving device and the light emitting diode driving semiconductor device according to the present invention have been described based on the embodiments, but the present invention is not limited to these embodiments. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to the said embodiment, and the form constructed | assembled combining the component in a different embodiment is also contained in the scope of the present invention. .
　例えば、ＳＷ制御回路２２８は、異常処理用の第２動作モードとして、スイッチング素子２１１の駆動と停止とを一定の間隔で繰り返すタイマー間欠動作を行ってもよい。これによれば、ＬＥＤのオープンを検出した際に、スイッチング動作によるエネルギー出力を低下させる動作となるため、周辺部品又はスイッチング素子２１１に過大な電圧が印加されることを防止できる。 For example, the SW control circuit 228 may perform a timer intermittent operation that repeats driving and stopping of the switching element 211 at regular intervals as the second operation mode for abnormality processing. According to this, when the opening of the LED is detected, the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element 211.
　また、下限基準値との比較（下限判定）を行わなくてもよい。すなわち、上限判定回路によってスイッチング素子２１１に流れる電流の電流値が上限基準値以下であると判定された回数が、所定の判定基準値以上である場合に、カウント回路２２９又は４２９は、ｏｐｅｎ信号を出力してもよい。そして、ＳＷ制御回路２２８は、スイッチング素子２１１に流れる電流が上限基準値以下であることが、継続して複数回検出された場合に、異常処理用の第２動作モードを実行する。これにより、ＬＥＤ光源部１２１がオープンであることを検出することができる。 Also, comparison with the lower limit reference value (lower limit determination) may not be performed. That is, when the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value by the upper limit determination circuit is greater than or equal to a predetermined determination reference value, the count circuit 229 or 429 outputs the open signal. It may be output. Then, the SW control circuit 228 executes the second operation mode for abnormality processing when it is continuously detected a plurality of times that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value. Thereby, it can be detected that the LED light source unit 121 is open.
　また、上限基準値との比較（上限判定）及び下限基準値との比較（下限判定）を同時に行ってもよい。上限判定と下限判定とを同時に行うことで、いずれかの判定結果を一時的に保持するための回路（具体的には、フリップフロップ回路４３５）を必要としないので、判定に必要な回路構成を簡略化することができる。 Also, the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) may be performed simultaneously. By performing the upper limit determination and the lower limit determination at the same time, a circuit (specifically, the flip-flop circuit 435) for temporarily holding any determination result is not required, and thus a circuit configuration necessary for the determination is provided. It can be simplified.
　本発明に係る発光ダイオード駆動装置及び発光ダイオード駆動用の半導体装置は、発光ダイオードを使用した装置及び機器全般に利用可能であり、例えば、ＬＥＤ電球、又は、ＬＥＤ照明機器として有用である。 The light-emitting diode driving device and the semiconductor device for driving a light-emitting diode according to the present invention can be used for all devices and devices using light-emitting diodes, and are useful as, for example, LED bulbs or LED lighting devices.
１１、１００、３００、６００　発光ダイオード駆動装置
１２　点灯回路部
１３　電流検出用抵抗
１４　インダクタンス素子
１５、１２３　ダイオード
１７　駆動制御回路
１６、２１１　スイッチング素子
１８、１２１　ＬＥＤ光源部
１８ａ　ＬＥＤ
１９　電圧検出回路部
２０　キャパシタンス素子
１１０、６１０　電源部
１１１　交流電源
１１２　整流回路
１１３、５２５　平滑用コンデンサ
１２０、５２０ａ、５２０ｂ、５２０ｃ　直列接続ループ回路
１２２　チョークコイル
１３０　コンデンサ
１４０、２２１、５２４　抵抗
２００、４００、７００　スイッチング駆動回路
２１０　スイッチング素子ブロック
２１２　電流検出用スイッチング素子
２２０、４２０　制御回路ブロック
２２２　接合型ＦＥＴ
２２３　レギュレータ回路
２２４　入力電圧検出回路
２２５　起動／停止回路
２２６　電流調整回路
２２７　ピーク電流検出回路
２２８　ＳＷ制御回路
２２９、４２９　カウント回路
２３０　電流判定回路
２３１　積分回路
２３２、２３３、４３３　コンパレータ
２３４　ＡＮＤ回路
４３５　フリップフロップ回路
４３６　クロック発生器
６１４　スイッチ
６５０　異常処理回路
  DESCRIPTION OF SYMBOLS 11, 100, 300, 600 Light emitting diode drive device 12 Lighting circuit part 13 Current detection resistance 14 Inductance element 15, 123 Diode 17 Drive control circuit 16, 211 Switching element 18, 121 LED light source part 18a LED
19 Voltage detection circuit unit 20 Capacitance element 110, 610 Power supply unit 111 AC power supply 112 Rectifier circuit 113, 525 Smoothing capacitor 120, 520a, 520b, 520c Series connection loop circuit 122 Choke coil 130 Capacitors 140, 221 and 524 Resistance 200, 400 , 700 Switching drive circuit 210 Switching element block 212 Current detection switching element 220, 420 Control circuit block 222 Junction FET
223 Regulator circuit 224 Input voltage detection circuit 225 Start / stop circuit 226 Current adjustment circuit 227 Peak current detection circuit 228 SW control circuit 229, 429 Count circuit 230 Current determination circuit 231 Integration circuit 232, 233, 433 Comparator 234 AND circuit 435 Flip-flop Circuit 436 Clock generator 614 Switch 650 Abnormal processing circuit

Claims (20)

  1. 　１個以上の発光ダイオードを駆動する降圧チョッパ型の発光ダイオード駆動装置であって、
    　前記１個以上の発光ダイオードを有するＬＥＤ光源部、前記ＬＥＤ光源部に直列に接続されたチョークコイル、及び、前記チョークコイルに生じる逆起電力を前記ＬＥＤ光源部に供給するためのダイオードを有する直列接続ループ回路と、
    　前記直列接続ループ回路に接続され、前記ＬＥＤ光源部及び前記チョークコイルに入力電圧を供給するための電源部と、
    　前記直列接続ループ回路に接続され、前記ＬＥＤ光源部に流れる電流を定電流制御するためのスイッチング駆動回路とを備え、
    　前記スイッチング駆動回路は、
    　スイッチング素子ブロックと、制御回路ブロックとを含み、
    　前記スイッチング素子ブロックは、
    　前記直列接続ループ回路に直列に接続され、前記電源部によって供給される入力電圧を断続的に前記ＬＥＤ光源部及び前記チョークコイルへ供給するスイッチング素子を有し、
    　前記制御回路ブロックは、
    　第１動作モードにおいて、前記スイッチング素子のオン及びオフの切り替えを制御するＳＷ制御回路と、
    　前記スイッチング素子がターンオフする際に、前記スイッチング素子に流れる電流の電流値が予め定められた上限基準値以下であるか否かを判定する上限判定回路と、
    　前記スイッチング素子に流れる電流の電流値が予め定められた下限基準値以上であるか否かを判定する下限判定回路と、
    　前記スイッチング素子に流れる電流の電流値が、前記上限判定回路によって前記上限基準値以下であると判定され、かつ、前記下限判定回路によって前記下限基準値以上であると判定された回数を計測するカウント回路とを有し、
    　前記ＳＷ制御回路は、
    　前記カウント回路によって計測された回数が予め定められた判定基準値以上である場合に、異常処理用の第２動作モードにおいて、前記第１動作モードとは異なる方式で前記スイッチング素子の制御を行う
    　発光ダイオード駆動装置。     A step-down chopper type light emitting diode driving device for driving one or more light emitting diodes,
    An LED light source unit having the one or more light emitting diodes, a choke coil connected in series to the LED light source unit, and a series having a diode for supplying back electromotive force generated in the choke coil to the LED light source unit A connection loop circuit;
    A power supply unit connected to the series connection loop circuit for supplying an input voltage to the LED light source unit and the choke coil;
    A switching drive circuit connected to the series connection loop circuit, for controlling a current flowing through the LED light source unit at a constant current;
    The switching drive circuit is
    Including a switching element block and a control circuit block;
    The switching element block is
    A switching element connected in series to the series connection loop circuit and intermittently supplying an input voltage supplied by the power supply unit to the LED light source unit and the choke coil;
    The control circuit block is
    A SW control circuit for controlling switching of the switching element between on and off in the first operation mode;
    An upper limit determination circuit for determining whether a current value of a current flowing through the switching element is equal to or lower than a predetermined upper limit reference value when the switching element is turned off;
    A lower limit determination circuit for determining whether or not a current value of a current flowing through the switching element is equal to or higher than a predetermined lower limit reference value;
    A count for measuring the number of times that the current value of the current flowing through the switching element is determined to be less than or equal to the upper limit reference value by the upper limit determination circuit and determined to be greater than or equal to the lower limit reference value by the lower limit determination circuit. Circuit and
    The SW control circuit
    When the number of times measured by the count circuit is equal to or greater than a predetermined determination reference value, the switching element is controlled in a different manner from the first operation mode in the second operation mode for abnormality processing. Diode drive device.
  2. 　前記制御回路ブロックは、さらに、前記スイッチング素子に流れる電流の電流値を検出する電流検出回路を有し、
    　前記上限判定回路は、前記電流検出回路によって検出された電流値が、前記上限基準値以下であるか否かを判定し、
    　前記下限判定回路は、前記電流検出回路によって検出された電流値が、前記下限基準値以上であるか否かを判定する
    　請求項１記載の発光ダイオード駆動装置。     The control circuit block further includes a current detection circuit that detects a current value of a current flowing through the switching element,
    The upper limit determination circuit determines whether or not the current value detected by the current detection circuit is equal to or lower than the upper limit reference value;
    The light emitting diode driving device according to claim 1, wherein the lower limit determination circuit determines whether or not a current value detected by the current detection circuit is equal to or greater than the lower limit reference value.
  3. 　前記ＳＷ制御回路は、前記第１動作モードにおいて、前記スイッチング素子を予め設定された周期でオフからオンに切り替え、
    　前記上限判定回路は、
    　前記周期内における前記スイッチング素子がオンしている期間の最大値である最大デューティ期間を設定し、前記スイッチング素子がオンしている期間が前記最大デューティ期間に達した場合に、前記スイッチング素子に流れる電流の電流値が前記上限基準値以下であると判定する最大デューティ検出回路を有する
    　請求項１記載の発光ダイオード駆動装置。     The SW control circuit switches the switching element from off to on at a preset period in the first operation mode,
    The upper limit determination circuit includes:
    A maximum duty period that is the maximum value of the period during which the switching element is on within the period is set, and the switching element flows when the period during which the switching element is on reaches the maximum duty period The light emitting diode drive device according to claim 1, further comprising a maximum duty detection circuit that determines that a current value of a current is equal to or less than the upper reference value.
  4. 　前記ＳＷ制御回路は、前記第１動作モードにおいて、前記スイッチング素子がターンオフされてから予め設定された期間後に、前記スイッチング素子をターンオンし、
    　前記上限判定回路は、
    　前記スイッチング素子がオンしている期間の最大値である最大オン期間を設定し、前記スイッチング素子がオンしている期間が前記最大オン期間に達した場合に、前記スイッチング素子に流れる電流の電流値が前記上限基準値以下であると判定する最大オン期間検出回路を有する
    　請求項１記載の発光ダイオード駆動装置。     The SW control circuit turns on the switching element after a preset period after the switching element is turned off in the first operation mode,
    The upper limit determination circuit includes:
    A maximum on period that is a maximum value of a period during which the switching element is on is set, and a current value of a current that flows through the switching element when the period during which the switching element is on reaches the maximum on period The light emitting diode drive device according to claim 1, further comprising: a maximum on-period detection circuit that determines that is less than or equal to the upper reference value.
  5. 　前記制御回路ブロックは、さらに、前記スイッチング素子に流れる電流の電流値が予め設定されたピーク値になった場合に、ピーク電流検出信号を出力するピーク電流検出回路を有し、
    　前記ＳＷ制御回路は、前記第１動作モードにおいて、前記ピーク電流検出信号が入力された場合に、前記スイッチング素子をターンオフさせ、
    　前記上限基準値は、前記ピーク値以下の値である
    　請求項２～４のいずれか１項に記載の発光ダイオード駆動装置。     The control circuit block further includes a peak current detection circuit that outputs a peak current detection signal when the current value of the current flowing through the switching element reaches a preset peak value,
    The SW control circuit turns off the switching element when the peak current detection signal is input in the first operation mode,
    The light emitting diode driving device according to any one of claims 2 to 4, wherein the upper limit reference value is a value equal to or less than the peak value.
  6. 　前記制御回路ブロックは、さらに、外部から入力される値に応じて、前記ピーク値を動的に変更する電流調整回路を有する
    　請求項５記載の発光ダイオード駆動装置。     The light emitting diode driving device according to claim 5, wherein the control circuit block further includes a current adjustment circuit that dynamically changes the peak value according to a value input from the outside.
  7. 　前記電流調整回路は、さらに、前記ピーク値の変更に伴って、前記上限基準値を変更する
    　請求項６記載の発光ダイオード駆動装置。     The light emitting diode driving device according to claim 6, wherein the current adjustment circuit further changes the upper limit reference value in accordance with the change of the peak value.
  8. 　前記電源部は、
    　交流電圧を生成する交流電源と、
    　前記交流電圧を整流することで、脈流電圧である前記入力電圧を生成する整流回路とを有する
    　請求項１～７のいずれか１項に記載の発光ダイオード駆動装置。     The power supply unit is
    An AC power source for generating AC voltage;
    The light-emitting diode driving device according to any one of claims 1 to 7, further comprising a rectifier circuit that rectifies the AC voltage to generate the input voltage that is a pulsating voltage.
  9. 　前記制御回路ブロックは、さらに、
    　前記入力電圧が予め定められた設定電圧以上であるか否かを判定する入力電圧検出回路と、
    　前記入力電圧が前記設定電圧以上である場合、前記ＳＷ制御回路に前記第１動作モードにおける前記スイッチング素子のオン及びオフの切り替えを起動させ、前記入力電圧が前記設定電圧未満の場合、前記ＳＷ制御回路に前記第１動作モードにおける前記スイッチング素子のオン及びオフの切り替えを停止させる起動／停止回路とを有する
    　請求項８記載の発光ダイオード駆動装置。     The control circuit block further includes:
    An input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage;
    When the input voltage is greater than or equal to the set voltage, the SW control circuit is activated to switch on and off the switching element in the first operation mode, and when the input voltage is less than the set voltage, the SW control The light emitting diode driving device according to claim 8, further comprising: a start / stop circuit that stops switching the on / off of the switching element in the first operation mode in the circuit.
  10. 　前記直列接続ループ回路は、さらに、前記ＬＥＤ光源部に並列接続された抵抗を有し、
    　前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記抵抗に流れる電流の電流値以下の値である
    　請求項１～９のいずれか１項に記載の発光ダイオード駆動装置。     The series connection loop circuit further includes a resistor connected in parallel to the LED light source unit,
    The light emitting diode driving apparatus according to any one of claims 1 to 9, wherein the lower limit reference value is a value equal to or smaller than a current value of a current flowing through the resistor when at least one of the light emitting diodes is open.
  11. 　前記直列接続ループ回路は、さらに、前記ＬＥＤ光源部に並列接続されたコンデンサを有し、
    　前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記コンデンサに流れる電流の電流値以下の値である
    　請求項１～９のいずれか１項に記載の発光ダイオード駆動装置。     The series connection loop circuit further includes a capacitor connected in parallel to the LED light source unit,
    The light emitting diode driving device according to any one of claims 1 to 9, wherein the lower limit reference value is a value equal to or smaller than a current value of a current flowing through the capacitor when at least one of the light emitting diodes is open.
  12. 　前記直列接続ループ回路は、さらに、
    　前記ＬＥＤ光源部に並列接続された抵抗と、
    　前記抵抗に直列接続され、前記ＬＥＤ光源部に並列接続されたコンデンサとを有し、
    　前記下限基準値は、少なくとも１つの前記発光ダイオードがオープンである場合に前記抵抗及び前記コンデンサに流れる電流の電流値以下の値である
    　請求項１～９のいずれか１項に記載の発光ダイオード駆動装置。     The series connection loop circuit further includes:
    A resistor connected in parallel to the LED light source unit;
    A capacitor connected in series to the resistor and connected in parallel to the LED light source unit;
    The light emitting diode drive according to any one of claims 1 to 9, wherein the lower limit reference value is a value equal to or smaller than a current value of a current flowing through the resistor and the capacitor when at least one of the light emitting diodes is open. apparatus.
  13. 　前記下限判定回路は、前記スイッチング素子がターンオンされる度に、判定結果をリセットする
    　請求項１～１２のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode driving apparatus according to any one of claims 1 to 12, wherein the lower limit determination circuit resets a determination result every time the switching element is turned on.
  14. 　前記下限判定回路は、前記スイッチング素子がターンオンしてからターンオフするまでの期間に、前記スイッチング素子に流れる電流の電流値が、前記下限基準値以上であるか否かを判定する
    　請求項１～１３のいずれか１項に記載の発光ダイオード駆動装置。     The lower limit determination circuit determines whether a current value of a current flowing through the switching element is equal to or higher than the lower limit reference value during a period from when the switching element is turned on to when the switching element is turned off. The light-emitting diode driving device according to any one of the above.
  15. 　前記カウント回路は、計測した回数が、前記スイッチング素子がターンオフするタイミングと同期して増加しない場合、当該回数をリセットする
    　請求項１～１４のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode driving device according to any one of claims 1 to 14, wherein the count circuit resets the number of times of measurement when the number of times of measurement does not increase in synchronization with a timing at which the switching element is turned off.
  16. 　前記カウント回路は、前記スイッチング素子のオン及びオフの切り替えが停止された場合に、計測した回数をリセットする
    　請求項１～１５のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode driving device according to any one of claims 1 to 15, wherein the count circuit resets the measured number of times when switching of the switching element between on and off is stopped.
  17. 　前記ＳＷ制御回路は、前記第２動作モードとして、前記スイッチング素子をラッチ停止させる
    　請求項１～１６のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode driving device according to any one of claims 1 to 16, wherein the SW control circuit latches and stops the switching element as the second operation mode.
  18. 　前記ＳＷ制御回路は、前記第２動作モードとして、一定の間隔で前記スイッチング素子の駆動と停止とを繰り返すタイマー間欠動作を行う
    　請求項１～１６のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode drive device according to any one of claims 1 to 16, wherein the SW control circuit performs a timer intermittent operation in which the switching element is driven and stopped at regular intervals as the second operation mode.
  19. 　前記発光ダイオード駆動装置は、さらに、前記カウント回路によって計測された回数が前記判定基準値以上である場合に、異常であることを示す異常判定信号を出力する異常処理回路を有する
    　請求項１～１６のいずれか１項に記載の発光ダイオード駆動装置。     The light emitting diode driving device further includes an abnormality processing circuit that outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit is equal to or greater than the determination reference value. The light-emitting diode driving device according to any one of the above.
  20. 　発光ダイオードを駆動するための半導体装置であって、
    　請求項１～１９のいずれか１項に記載の前記スイッチング素子ブロックと前記制御回路ブロックとを備え、
    　前記スイッチング素子ブロックと前記制御回路ブロックとは、同一の半導体基板上に形成されている、又は、同一のパッケージに組み込まれている
    　半導体装置。
          A semiconductor device for driving a light emitting diode,
    The switching element block according to any one of claims 1 to 19 and the control circuit block,
    The switching element block and the control circuit block are formed on the same semiconductor substrate or incorporated in the same package.
PCT/JP2010/006790 2010-07-16 2010-11-19 Light-emitting diode drive device and light-emitting diode drive semiconductor device WO2012008002A1 (en)

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Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6146970B2 (en) * 2012-08-09 2017-06-14 三菱電機株式会社 Light source lighting device and lighting fixture
JP5988207B2 (en) * 2012-09-07 2016-09-07 パナソニックＩｐマネジメント株式会社 Solid-state light-emitting element driving device, lighting device, and lighting fixture
EP2709426A3 (en) * 2012-09-14 2017-04-19 Panasonic Intellectual Property Management Co., Ltd. Solid-state light-emitting element drive device, lighting system and lighting fixture
TWI524811B (en) 2013-08-14 2016-03-01 Richtek Technology Corp Light emitting diode system and voltage conversion device
JP6295816B2 (en) * 2014-05-14 2018-03-20 三菱電機株式会社 lighting equipment
JP6422056B2 (en) * 2015-01-06 2018-11-14 パナソニックＩｐマネジメント株式会社 Lighting device and lighting apparatus using the same
JP6587054B2 (en) 2015-06-19 2019-10-09 パナソニックＩｐマネジメント株式会社 Lighting device and lighting apparatus
JP6803560B2 (en) * 2016-12-22 2020-12-23 パナソニックＩｐマネジメント株式会社 Lighting device and lighting equipment
JP2019054582A (en) * 2017-09-13 2019-04-04 パナソニックＩｐマネジメント株式会社 Control circuit, semiconductor light source driving device, and electronic apparatus
JP7148469B2 (en) * 2019-09-12 2022-10-05 株式会社東芝 Semiconductor circuits and semiconductor systems

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007059635A (en) * 2005-08-25 2007-03-08 Matsushita Electric Ind Co Ltd Light emitting diode driving device and semiconductor device for driving light emitting diode
JP2008235530A (en) * 2007-03-20 2008-10-02 Matsushita Electric Ind Co Ltd Light emitting diode driving device and illuminator using the same
JP2009117121A (en) * 2007-11-05 2009-05-28 Denso Corp Led drive circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007059635A (en) * 2005-08-25 2007-03-08 Matsushita Electric Ind Co Ltd Light emitting diode driving device and semiconductor device for driving light emitting diode
JP2008235530A (en) * 2007-03-20 2008-10-02 Matsushita Electric Ind Co Ltd Light emitting diode driving device and illuminator using the same
JP2009117121A (en) * 2007-11-05 2009-05-28 Denso Corp Led drive circuit

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