CN103124460A - LED driving circuit - Google Patents
LED driving circuit Download PDFInfo
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- CN103124460A CN103124460A CN 201310007773 CN201310007773A CN103124460A CN 103124460 A CN103124460 A CN 103124460A CN 201310007773 CN201310007773 CN 201310007773 CN 201310007773 A CN201310007773 A CN 201310007773A CN 103124460 A CN103124460 A CN 103124460A
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Abstract
The invention provides an LED driving circuit which comprises a DC-DC conversion circuit, a voltage division circuit, a driving module and a controller. The DC-DC conversion circuit is used for receiving a power voltage and converting the power voltage into an LED lamp voltage by the aid of a PWM (pulse width modulation) signal; the voltage division circuit is used for outputting a voltage detection signal reflecting the LED lamp voltage; the driving module is used for outputting a PWM switching control signal and a duty ratio adjusting control signal, and the controller comprises a PWM module and is used for receiving the voltage detection signal, the PWM switching control signal and the duty ratio adjusting control signal so as to output the PWM signal. Compared with the prior art, the LED driving circuit has the advantages that a ripple upper limit threshold value and a ripple lower limit threshold value of the LED lamp voltage are taken as reference voltages and are associated with the maximum duty ratio and the minimum duty ratio of the PWM signal, the PWM signal is directly outputted according to the duty ratio adjusting control signal, on or off of the PWM signal is more rapidly adjusted when the output voltage is changed without waiting for passing of the signal through an integral closed-loop control circuit, and accordingly, response speed is higher.
Description
Technical field
The present invention relates to a kind of drive circuit, relate in particular to a kind of LED(Light Emitting Diode, light-emitting diode) drive circuit.
Background technology
Current, demand for energy savings is more and more stronger all over the world, LED (Light Emitting Diode, light-emitting diode) because it has many advantages such as long service life, volume is little, power consumption is low, working temperature is low, is subject to liking and use of industry day by day.Correspondingly, LED drive circuit is the luminous circuit of driving LED.In general, when promoting LED, its final purpose is all that the electric current that will control the LED that flows through reaches or presses close to as much as possible default current values, and makes it stable and not affected by the factors such as supply voltage, temperature, forward bias voltage drop difference, and is too short or damaged service time to prevent LED.
In the prior art; LED driver often judges by the feedback voltage after dividing potential drop whether its output voltage arrives specified LED modulating voltage; and design this feedback voltage as overvoltage protection (OVP; Over Voltage Protect) and the key foundation of under-voltage protection (UVP, Under Voltage Protect).After voltage stabilization, then make the LED current constant and do brightness adjustment control (dimming control) by LED driver.Thus, control under framework at this, must feed back to the DC-DC change-over circuit by LED driver and carry out voltage control, certainly will cause the low frequency signal that light modulation is used to see through feedback circuit and interfere with the DC-DC change-over circuit.In addition, when LED load momentary variation, this framework also easily causes variation and response speed slower, causes unnecessary loss.
In view of this, how designing a kind of LED drive circuit, to address the aforementioned drawbacks or not enough, effectively reduce the ripple of DC-DC change-over circuit output voltage, improve the response speed of system, is a problem needing to be resolved hurrily of person skilled in the industry.
Summary of the invention
For the existing defects of LED drive circuit of the prior art, the invention provides a kind of LED drive circuit of novelty.
According to one aspect of the present invention, a kind of drive circuit is provided, comprising:
One DC-DC change-over circuit in order to receiving a supply voltage, and is converted to a LED modulating voltage by a pulse-width modulation (Pulse Width Modulation, PWM) signal with described supply voltage;
One bleeder circuit is arranged at the output of described DC-DC change-over circuit, in order to a voltage detection signal of the described LED modulating voltage of output reflection;
One drives module, in order to export a PWM switch controlling signal and a duty cycle adjustment control signal; And
One controller comprises a PWM module, and described PWM module receives described voltage detection signal, described PWM switch controlling signal and described duty cycle adjustment control signal, thereby exports described pwm signal to described DC-DC change-over circuit.
Preferably, described bleeder circuit comprises one first resistance and one second resistance that is connected in series, and an end of described the first resistance is electrically connected to the output of described DC-DC change-over circuit, and an end of described the second resistance is electrically connected to an earth terminal.
Preferably, when described LED modulating voltage is between the lower threshold of its ripple and upper limit threshold, the described pwm signal of described PWM module output one fixed duty cycle.
Preferably, when the LED modulating voltage during lower than the lower threshold of its ripple, by described duty cycle adjustment control signal, the duty ratio of described pwm signal is increased to maximum.
Preferably, when the LED modulating voltage during higher than the upper limit threshold of its ripple, by described duty cycle adjustment control signal, the duty ratio of described pwm signal is decreased to minimum value.
Preferably, described LED modulating voltage also comprises an overvoltage threshold and a under-voltage threshold value, and described overvoltage threshold is higher than the upper limit threshold of described ripple, and described under-voltage threshold value is lower than the lower threshold of described ripple.
In an embodiment therein, during higher than described overvoltage threshold, stop export described pwm signal by described PWM switch controlling signal when described LED modulating voltage.
In an embodiment therein, during lower than described under-voltage threshold value, stop export described pwm signal by described PWM switch controlling signal when described LED modulating voltage.
Preferably, described PWM module comprises: an error amplifier, and its first input end is in order to receive described voltage detection signal, and its second input is electrically connected to a reference voltage, and its output is in order to export an error voltage signal; One PWM modulator is electrically connected to described error amplifier, in order to receiving described error voltage signal and a carrier signal, and exports a benchmark pwm signal; And a PWM controller, in order to receiving described benchmark pwm signal, described PWM switch controlling signal and described duty cycle adjustment control signal, thereby export described pwm signal to described DC-DC change-over circuit.
Preferably, described carrier signal is a sawtooth signal.
Adopt LED drive circuit of the present invention, see through bleeder circuit and export a voltage detection signal of reflection LED modulating voltage, and utilize the driving module to export PWM switch controlling signal and duty cycle adjustment control signal, then the PWM module by controller receives above-mentioned voltage detection signal, PWM switch controlling signal and duty cycle adjustment control signal, thereby output pwm signal is to the DC-DC change-over circuit.than prior art, the present invention by the upper limit threshold of the ripple of LED modulating voltage and lower threshold as reference voltage, carry out correlation comparison with maximum duty cycle and the minimum duty cycle of pwm signal, and come direct output pwm signal according to the duty cycle adjustment control signal, can adjust more quickly pwm signal when output voltage is changed opens or closes, and need not again to adjust after the close loop control circuit of waiting signal through integral body, therefore response speed is faster, and corresponding output pwm signal frequency is not changed, and then reduced the design specification of output capacitance, save cost and dwindle and take up room.
Description of drawings
The reader will become apparent various aspects of the present invention after the reference accompanying drawing has been read the specific embodiment of the present invention.Wherein,
Fig. 1 illustrates the structural representation of a kind of LED drive circuit of the prior art;
Fig. 2 illustrates in the LED drive circuit of Fig. 1, the control sequential schematic diagram of the pwm signal of the LED modulating voltage of DC-DC change-over circuit output and controller output;
Fig. 3 illustrates the structural representation according to the LED drive circuit of one embodiment of the present invention;
Fig. 4 illustrates in the LED drive circuit of Fig. 3, the waveform schematic diagram of the pwm signal of the overvoltage threshold of LED modulating voltage, ripple upper limit threshold, ripple lower threshold, under-voltage threshold value, LED lamp current and controller output; And
Fig. 5 illustrates the structure composition frame chart of a specific embodiment of the PWM module in the LED drive circuit of Fig. 3.
Embodiment
For technology contents that the application is disclosed is more detailed and complete, can be with reference to accompanying drawing and following various specific embodiments of the present invention, in accompanying drawing, identical mark represents same or analogous assembly.Yet those of ordinary skill in the art should be appreciated that the embodiment that hereinafter provides limits the scope that the present invention is contained.In addition, accompanying drawing only is used for schematically being illustrated, and does not draw according to its life size.
As previously mentioned, in LED drive circuit, the electric current of each LED in flow through single led or LED lamp string has determined luminosity, and the size of electric current has also determined forward voltage drop.According to the voltage-to-current curve characteristic of LED as can be known, when the voltage that is added in LED two ends slightly has fluctuation, all can cause the acute variation of electric current, be easy to cause electric current excessive this moment, and LED is caused expendable damage.Therefore, only control the LED modulating voltage and be not enough to stabilized illumination brightness, must carry out constant current and control.At this moment, the currents match between different light-emitting diodes just becomes very crucial problem.
In general, existing LED circuit connects and roughly comprises following four kinds: the first adopts parallel connection LED, and constant driving voltage and the load current control of open loop approach are provided.This method of attachment is determined load current with the resistance that is serially connected in the LED load, although input voltage can very random variation, load regulation is very poor, and the currents match effect is also relatively poor; It two is to adopt parallel connection LED, constant driving voltage is provided and controls with the load current of closed loop feedback.This method of attachment is determined load current with feedback resistance, and the LED branch road that is serially connected with feedback resistance can obtain accurate Current Control, but other each branch current must rely on output voltage adjustment, thereby the currents match degree is not good yet; It three is the current-modes that adopt parallel connection LED, and this pattern is fit to parallel connection LED to be used, and its currents match characteristic is better, and single led damage can not affect other normal operation, but the LED quantity that this mode was suitable for is comparatively limited; It four is to adopt connection in series-parallel LED and with the Current Control of closed loop feedback.That is this connected mode first is connected in series a plurality of LED and consists of a LED lamp string, forms a series-parallel LED network thereby then different LED lamp connection in series-parallel is connected.In this connected mode, the LED of series connection has splendid currents match, from the angle of statistics and probability, LED lamp string and main LED lamp string in parallel have currents match preferably, and this is to be better than the matching degree of single led forward voltage drop due to the matching degree of the LED forward voltage drop sum of a plurality of serial connections.
In addition, LED light regulating technology (dimming control) mainly comprises three types: PWM light modulation, simulation light modulation and digital dimming.Take the PWM light modulation as example, it is based on the human eye characteristic responsive not to brightness flicker, and dark when bright when making the LED load, if bright dark frequency surpasses 100Hz, what human eye was seen is exactly mean flow rate, rather than the flicker of LED.By adjusting bright and dark time scale, reach the purpose of adjusting brightness.The peculiar advantage of PWM light modulation is that the electric current color can not be offset, because when adjusting brightness, the electric current of the LED that flows through can not change.
The LED drive circuit that the present invention pays close attention to had both adopted connection in series-parallel LED and with the Current Control of closed loop feedback, had adopted again the PWM brightness adjustment control.Fig. 1 illustrates the structural representation of a kind of LED drive circuit of the prior art.
With reference to Fig. 1, this LED drive circuit comprises that a DC-DC change-over circuit 10, drives module 20 and a controller 30.Wherein, DC-DC change-over circuit 10 is in order to receiving a supply voltage Vin, and according to a pulse-width modulation that comes self-controller 30 (Pulse Width Modulation, PWM) signal, supply voltage Vin is converted to a LED modulating voltage VLED.Drive module 20 and be electrically connected to one or more LED lamp strings and controller 30.The LED modulating voltage VLED of DC-DC change-over circuit 10 outputs obtains a voltage detection signal FB1 and is admitted to controller 30 after processing via bleeder circuit.After voltage stabilization, then make the LED current constant and carry out brightness adjustment control by driving module 20.
Thus, control under framework at this, LED drive circuit must provide feedback signal FB2 to DC-DC change-over circuit 10 by driving module 20, in order to the LED modulating voltage is carried out voltage control, this will certainly cause the low frequency signal that light modulation is used also to see through controller 30 and interfere with DC-DC change-over circuit 10.In addition, when LED load momentary variation, the skew of LED modulating voltage and the slower situation of response speed easily appear in this framework, cause unnecessary circuit loss.
Fig. 2 illustrates in the LED drive circuit of Fig. 1, the control sequential schematic diagram of the pwm signal of the LED modulating voltage of DC-DC change-over circuit output and controller output.
In conjunction with Fig. 1 and Fig. 2, control sequential according to this, the output voltage V out(of DC-DC change-over circuit 10 also can be described as the LED modulating voltage) variation and the pwm signal that comes self-controller 30 that receives of the switching tube of inside circuit closely related.Might as well set the overvoltage protection threshold value of output voltage V out corresponding to voltage V1, and the under-voltage protection threshold value of output voltage V out is corresponding to voltage V2.
When output voltage V out was between V1 and V2, circuit was in normal operating conditions, and pwm pulse is opened, and as gate drive signal V
GSBe continuously applied to this switching tube.During lower than V2, circuit is in the under-voltage protection state as output voltage V out, and pwm pulse is closed, and the grid of switching tube does not provide any driving signal.During higher than V1, circuit is in the overvoltage protection state as output voltage V out, and pwm pulse is also closed, and the grid of switching tube does not also provide any driving signal.Thus, this LED drive circuit is only controlled the open and close of pwm signal according to overvoltage threshold V1 and under-voltage threshold value V2, in case when the LED load is undergone mutation, must can adjust through after whole single close loop control circuit by waiting signal, thereby response speed is comparatively slow.
Fig. 3 illustrates the structural representation according to the LED drive circuit of one embodiment of the present invention.With reference to Fig. 3, LED drive circuit of the present invention comprises that a DC-DC change-over circuit 40, drives module 50, a controller 60 and a bleeder circuit 70.
DC-DC change-over circuit 40 is in order to receiving a supply voltage, and by a pulse-width signal, this supply voltage is converted to a LED modulating voltage.At this, this pulse-modulated signal comes from the PWM module 62 of controller 60.Bleeder circuit 70 is arranged at the output of DC-DC change-over circuit 40, in order to a voltage detection signal of output reflection LED modulating voltage.In one embodiment, bleeder circuit 70 comprises one first resistance R 1 and one second resistance R 2 that is connected in series.One end of the first resistance R 1 is electrically connected to the output of DC-DC change-over circuit 10.The other end of the first resistance R 1 is connected with an end of the second resistance R 2.The other end of the second resistance R 2 is electrically connected to an earth terminal.
Fig. 4 illustrates in the LED drive circuit of Fig. 3, the waveform schematic diagram of the pwm signal of the overvoltage threshold of LED modulating voltage, ripple upper limit threshold, ripple lower threshold, under-voltage threshold value, LED lamp current and controller output.
With reference to Fig. 4, V1 represents the overvoltage threshold of LED modulating voltage, and V2 represents the under-voltage threshold value of LED modulating voltage, and V3 represents the ripple upper limit threshold of LED modulating voltage, and V4 represents the ripple lower threshold of LED modulating voltage, and ILED represents the LED lamp current.As can be seen from the figure, overvoltage threshold V1 is higher than the upper limit threshold V3 of ripple, and under-voltage threshold value V2 is lower than the lower threshold V4 of ripple.When modulating voltage VLED is between ripple upper limit threshold V3 and ripple lower threshold V4, the pwm signal of PWM module output fixed duty cycle.
As modulating voltage VLED during lower than ripple lower threshold V4, the PWM module increases to maximum by the duty cycle adjustment control signal with the duty ratio of pwm signal.In other words, adjacent two pulses in pwm signal are almost overlapping, and pulsewidth is corresponding to high potential.As modulating voltage VLED during higher than its ripple upper limit threshold V3, the PWM module is decreased to minimum value by the duty cycle adjustment control signal with the duty ratio of pwm signal.That is adjacent two pulses in pwm signal are also almost overlapping, and only the pulsewidth of this moment is corresponding to electronegative potential.
Fig. 5 illustrates the structure composition frame chart of a specific embodiment of the PWM module in the LED drive circuit of Fig. 3.
With reference to Fig. 5, in this embodiment, PWM module 60 comprises an error amplifier 621, a PWM modulator 623 and a PWM controller 625.
In more detail, the first input end of error amplifier 621 is in order to receiver voltage detection signal V
FB, its second input is electrically connected to a reference voltage V
REF, its output is in order to export representative voltage detection signal V
FBWith reference voltage V
REFAn error voltage signal V of difference
EPWM modulator 623 is electrically connected to error amplifier 621, in order to receive error voltage signal V
EWith a carrier signal V
M, and export a benchmark pwm signal.PWM controller 625 is in order to receiving benchmark pwm signal, PWM switch controlling signal and duty cycle adjustment control signal, thereby exports this pwm signal to the DC-DC change-over circuit, wherein, and V
GThe potential voltage of expression pwm signal.
In one embodiment, carrier signal V
MIt is a sawtooth signal.
In addition, during higher than overvoltage threshold, the PWM module stops output pwm signal by the PWM switch controlling signal when the LED modulating voltage.During lower than under-voltage threshold value, the PWM module stops output pwm signal by the PWM switch controlling signal when the LED modulating voltage.
Adopt LED drive circuit of the present invention, see through bleeder circuit and export a voltage detection signal of reflection LED modulating voltage, and utilize the driving module to export PWM switch controlling signal and duty cycle adjustment control signal, then the PWM module by controller receives above-mentioned voltage detection signal, PWM switch controlling signal and duty cycle adjustment control signal, thereby output pwm signal is to the DC-DC change-over circuit.than prior art, the present invention by the upper limit threshold of the ripple of LED modulating voltage and lower threshold as reference voltage, carry out correlation comparison with maximum duty cycle and the minimum duty cycle of pwm signal, and come direct output pwm signal according to the duty cycle adjustment control signal, can adjust more quickly pwm signal when output voltage is changed opens or closes, and need not again to adjust after the close loop control circuit of waiting signal through integral body, therefore response speed is faster, and corresponding output pwm signal frequency is not changed, and then reduced the design specification of output capacitance, save cost and dwindle and take up room.
Above, describe the specific embodiment of the present invention with reference to the accompanying drawings.But those skilled in the art can understand, in the situation that without departing from the spirit and scope of the present invention, can also do various changes and replacement to the specific embodiment of the present invention.These changes and replacement all drop in claims limited range of the present invention.
Claims (10)
1. LED(Light Emitting Diode, light-emitting diode) drive circuit, it is characterized in that, described LED drive circuit comprises:
One DC-DC change-over circuit in order to receiving a supply voltage, and is converted to a LED modulating voltage by a pulse-width modulation (Pulse Width Modulation, PWM) signal with described supply voltage;
One bleeder circuit is arranged at the output of described DC-DC change-over circuit, in order to a voltage detection signal of the described LED modulating voltage of output reflection;
One drives module, in order to export a PWM switch controlling signal and a duty cycle adjustment control signal; And
One controller comprises a PWM module, and described PWM module receives described voltage detection signal, described PWM switch controlling signal and described duty cycle adjustment control signal, thereby exports described pwm signal to described DC-DC change-over circuit.
2. LED drive circuit according to claim 1, it is characterized in that, described bleeder circuit comprises one first resistance and one second resistance that is connected in series, one end of described the first resistance is electrically connected to the output of described DC-DC change-over circuit, and an end of described the second resistance is electrically connected to an earth terminal.
3. LED drive circuit according to claim 1, is characterized in that, when described LED modulating voltage is between the lower threshold of its ripple and upper limit threshold, and the described pwm signal of described PWM module output one fixed duty cycle.
4. LED drive circuit according to claim 1, is characterized in that, when described LED modulating voltage during lower than the lower threshold of its ripple, by described duty cycle adjustment control signal, the duty ratio of described pwm signal increased to maximum.
5. LED drive circuit according to claim 1, is characterized in that, when described LED modulating voltage during higher than the upper limit threshold of its ripple, by described duty cycle adjustment control signal, the duty ratio of described pwm signal is decreased to minimum value.
6. LED drive circuit according to claim 1, is characterized in that, described LED modulating voltage also comprises an overvoltage threshold and a under-voltage threshold value, and described overvoltage threshold is higher than the upper limit threshold of described ripple, and described under-voltage threshold value is lower than the lower threshold of described ripple.
7. LED drive circuit according to claim 6, is characterized in that, during higher than described overvoltage threshold, stops export described pwm signal by described PWM switch controlling signal when described LED modulating voltage.
8. LED drive circuit according to claim 6, is characterized in that, during lower than described under-voltage threshold value, stops export described pwm signal by described PWM switch controlling signal when described LED modulating voltage.
9. LED drive circuit according to claim 1, is characterized in that, described PWM module comprises:
One error amplifier, its first input end is in order to receive described voltage detection signal, and its second input is electrically connected to a reference voltage, and its output is in order to export an error voltage signal;
One PWM modulator is electrically connected to described error amplifier, in order to receiving described error voltage signal and a carrier signal, and exports a benchmark pwm signal; And
One PWM controller in order to receiving described benchmark pwm signal, described PWM switch controlling signal and described duty cycle adjustment control signal, thereby is exported described pwm signal to described DC-DC change-over circuit.
10. LED drive circuit according to claim 9, is characterized in that, described carrier signal is a sawtooth signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201310007773 CN103124460A (en) | 2013-01-09 | 2013-01-09 | LED driving circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201310007773 CN103124460A (en) | 2013-01-09 | 2013-01-09 | LED driving circuit |
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| CN103124460A true CN103124460A (en) | 2013-05-29 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106900118A (en) * | 2013-09-29 | 2017-06-27 | 赛尔富电子有限公司 | A kind of under-voltage protecting circuit for LED lamp |
| CN109388330A (en) * | 2017-08-07 | 2019-02-26 | 富士电机株式会社 | Power-converting device |
| CN109688659A (en) * | 2018-12-21 | 2019-04-26 | 太仓电威光电有限公司 | LED drive power mould group and the integral LED car light for applying it |
| CN110460377A (en) * | 2019-07-25 | 2019-11-15 | 浙江大学 | A kind of device carrying out LED light communication using driving circuit switching harmonics |
| WO2020107171A1 (en) * | 2018-11-26 | 2020-06-04 | 上海晶丰明源半导体股份有限公司 | Control circuit, driving system, chip, control method and driving method |
| CN111903193A (en) * | 2018-03-28 | 2020-11-06 | 株式会社小糸制作所 | Lighting circuit and vehicle lamp |
-
2013
- 2013-01-09 CN CN 201310007773 patent/CN103124460A/en active Pending
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106900118A (en) * | 2013-09-29 | 2017-06-27 | 赛尔富电子有限公司 | A kind of under-voltage protecting circuit for LED lamp |
| CN109388330A (en) * | 2017-08-07 | 2019-02-26 | 富士电机株式会社 | Power-converting device |
| CN109388330B (en) * | 2017-08-07 | 2023-11-03 | 富士电机株式会社 | power conversion device |
| CN111903193A (en) * | 2018-03-28 | 2020-11-06 | 株式会社小糸制作所 | Lighting circuit and vehicle lamp |
| US11382194B2 (en) | 2018-03-28 | 2022-07-05 | Koito Manufacturing Co., Ltd. | Lighting circuit |
| CN111903193B (en) * | 2018-03-28 | 2024-02-06 | 株式会社小糸制作所 | Lighting circuit and vehicle lamp |
| WO2020107171A1 (en) * | 2018-11-26 | 2020-06-04 | 上海晶丰明源半导体股份有限公司 | Control circuit, driving system, chip, control method and driving method |
| CN113228828A (en) * | 2018-11-26 | 2021-08-06 | 上海晶丰明源半导体股份有限公司 | Control circuit, driving system, chip, control method and driving method |
| US11737180B2 (en) | 2018-11-26 | 2023-08-22 | Shanghai Bright Power Semiconductor Co., Ltd. | Control circuit, chip and control method |
| CN109688659A (en) * | 2018-12-21 | 2019-04-26 | 太仓电威光电有限公司 | LED drive power mould group and the integral LED car light for applying it |
| CN109688659B (en) * | 2018-12-21 | 2024-04-30 | 太仓电威光电有限公司 | LED driving power supply module and integrated LED car lamp applying same |
| CN110460377A (en) * | 2019-07-25 | 2019-11-15 | 浙江大学 | A kind of device carrying out LED light communication using driving circuit switching harmonics |
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Application publication date: 20130529 |