CN202679727U - Constant current driver of light emitting diode - Google Patents

Abstract

The utility model relates to a constant current driver of a light emitting diode, comprising a rectification circuit, a switch circuit and a feedback circuit. The rectification circuit is connected with an AC source, and the rectification circuit outputs a DC source; the switch circuit is connected with the DC source of the rectification circuit, the DC source is switched by the switch circuit in a pulse-width modulation (PMW) mode, and the switch circuit possesses an output terminal to connect a load; and the feedback circuit is connected between the output terminal of the switch circuit and the switch circuit, the work period of the switch circuit is controlled according to the magnitude of the output current of the output terminal, and the current output to the load can be controlled to keep constant.

Description

The constant-flow driver of light-emitting diode

Technical field

The utility model is a kind of driver, and particularly a kind of load provides constant current supply to drive luminous electronic driver to multi-path parallel LEDs.

Background technology

Light-emitting diode (Light Emitting Diode, LED) has the characteristics such as long service life, low power consuming, and it becomes many consumption electronic products of today or the main flow that light fixture provides light source already.

Make LED luminous; must produce forward current by this element by driver; in general; LED is that bunchiness is that a module is as the load of driver; during actual application, this driver also will promote the load (LED module) of multi-channel parallel usually, therefore; when the design driven circuit, must consider to allow the LED of each load end produce consistent luminosity, and this task can be reached by stiff or constant current supply.

The drive circuit that stiff generally is provided is the minimum solution of cost, and it is the current-limiting resistance of front end series connection in the LED load, adds stiff in the two ends of circuit again.Yet this method has its shortcoming, the electric current that current-limiting resistance can restricted passage, and the non-linear V-I curve of the LED of load end also allows the non-constant of current stabilization ability of this method; In addition, as long as the forward voltage of applied voltage or LED has any change, the electric current by LED all can change.Suppose when specified forward voltage is 3.6 V, have 20 mA electric currents by LED, if temperature or process reform become 3 V (still in normal 3 V to 4 V tolerances) by this voltage, then forward current will drop to 14 mA; In other words, forward voltage is as long as change 11%, and 30% significant change will appear in forward current, and the extreme change of this electric current directly affects the LED luminosity, and its degree is that many application apparatuss institute is unacceptable.

As for traditional constant current supply driver, its circuit structure design is complicated, the element that forms is various, make each driver show the quality that identical operating characteristic just must strictly be screened these electronic components, not only the yield of driver is difficult to promote, and manufacturing cost is high, is unfavorable for again the reduction of volume, and still has the space of many improvement; In addition, particularly when driving the LED load of multi-channel parallel, if remove for some reason or disconnect the load of wherein arbitrary parallel connection, then the electric current supplied of this driver will directly be distributed in other remaining loads, probably will cause overcurrent and directly impact the life-span that LED uses.

The utility model content

In order to solve the problems of the technologies described above, the utility model provides a kind of constant-flow driver of light-emitting diode, comprising:

One is connected in the rectification circuit in an AC power and output DC source;

One is connected in the DC power supply of this rectification circuit and switches the switching circuit of this DC power supply in the mode of pulse width modulation, and it has one and feedbacks control end in order to the output and that connects load; And

One is connected between the back coupling control end of the output of this switching circuit and this switching circuit and makes output current be controlled constant feedback circuit according to the output current size of this output with work period of control switch circuit.

As optimal technical scheme, this switching circuit comprises one to be subjected to the control of PWM controller and to change electronic switch, a high frequency transformer and the PWM controller of its switching frequency and work period, the primary side of this high frequency transformer is connected in the dc power output end of this rectification circuit, the switch terminals of this electronic switch then is serially connected with between the primary side and ground connection of this high frequency transformer, and the control end of this electronic switch then is connected in this PWM controller.

As optimal technical scheme, this electronic switch is a metal oxide semiconductcor field effect electric crystal, bipolarity junction electric crystal or isolation gate bipolar transistor.

As optimal technical scheme, described feedback circuit comprises a transfer resistance, a comparator and an optical coupler, wherein be connected in series this transfer resistance in this switching circuit and the formed loop of load, the two ends of this transfer resistance are connected to respectively the input of comparator, the output of comparator is connected in the input of optical coupler, and the output of optical coupler is connected to the back coupling control end of switching circuit, give switching circuit with the reset signal, when the voltage abnormal on the transfer resistance, comparator is namely controlled optical coupler and is carried out switching motion.

As optimal technical scheme, this comparator is comprised of operational amplifier.

As optimal technical scheme, output parallel multiplex load when this switching circuit, each road load all is serially connected with a transfer resistance, and the resistance of each transfer resistance is all equal, when the load that arbitrary road is arranged is removed or disconnects, then the voltage on the transfer resistance of other road load connection is greater than preset value (being abnormal), comparator is namely controlled optical coupler and is carried out switching motion, change immediately feedback signal and adjust the work period of PWM controller, to change the ON time of electronic switch, and then the adjustment output current, make each road load be all the constant current supply.

The constant-flow driver of light-emitting diode of the present utility model is to utilize simple design of electronic circuits, and the constant current supply of finishing the multi-channel parallel load drives, and it is not only stable high, cheap for manufacturing cost, is more conducive to the application of miniaturization; The more important thing is, even if remove or when disconnecting the LED load on arbitrary road in the multi-channel parallel, what link tester was crossed feedback signal relatively reaches detecting, initiatively constant current control is carried out in other loads, makes the useful life that can not produce overcurrent and affect LED.

Description of drawings

Fig. 1 is circuit block diagram of the present utility model.

Fig. 2 is detailed circuit diagram of the present utility model.

[main element symbol description]

1 ... rectification circuit;

2 ... switching circuit;

21 ... the output of switching circuit;

22 ... the back coupling control end of switching circuit;

3 ... feedback circuit;

4 ... load;

Q1 ... electronic switch;

U1 ... the PWM controller;

TR1 ... high frequency transformer;

L1, L2 ... .LX ... choke;

RT1, RT2 ... RTX ... transfer resistance;

U2 ... comparator;

PC1 ... optical coupler.

Embodiment

The utility model is described in further detail below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the utility model and being implemented, but illustrated embodiment is not as to restriction of the present utility model.

Head sees also Fig. 1, and it is circuit block diagram of the present utility model.The constant-flow driver of light-emitting diode of the present utility model (LED) makes its stabilized illumination in order to drive light-emitting diode, it comprises a rectification circuit 1, a switching circuit 2 and a feedback circuit 3, this rectification circuit 1 is connected in an AC power, and the output DC source; This switching circuit 2 is connected in the DC power supply that this rectification circuit 1 is exported, and switches this DC power supply in the mode of pulse width modulation (PWM), and it has an output 21 and a back coupling control end 22, and this output 21 is in order to connect a LED load 4; This feedback circuit 3 is connected between the back coupling control end 22 of the output 21 of this switching circuit 2 and this switching circuit 2, according to the output current size of this output 21 work period with control switch circuit 2, makes the output current can be constant by control.

Please consult simultaneously Fig. 2, it is detailed circuit diagram of the present utility model.Driver of the present utility model is converted to DC power supply to drive lumination of light emitting diode with AC power, and be provided with feedback circuit take the control output current as constant, wherein rectification circuit 1 is mainly a bridge rectifier, rectification circuit 1 shown in the figure is by the sub-BD1 of bridge rectifier, capacitor C X1, the elements such as C1 and resistance R 1 form, and certainly also can be the rectifier of other forms.

Rectification circuit 1 is changed DC power supply with AC power, its DC power supply of exporting is delivered to switching circuit 2, this switching circuit 2 is that a high frequency suitching type direct current is to DC power supply circuit (DC-to-DC Converter), mainly by a high frequency transformer TR1, one electronic switch Q1 and a PWM (pulse width modulation) controller U1 form, the primary side of this high frequency transformer TR1 is connected in the dc power output end of rectification circuit 1, the switch terminals of electronic switch Q1 then be serially connected with the primary side of high frequency transformer TR1 and ground connection between, therebetween or can be connected in series again a resistance R 2, the control end of electronic switch Q1 then is connected in PWM controller U1, makes electronic switch Q1 can be subjected to the control of PWM controller and changes its switching frequency and work period (duty cycle).Electronic switch Q1 can be metal oxide semiconductcor field effect electric crystal (MOSFET), bipolarity junction electric crystal (BJT) or isolation gate bipolar transistor (IGBT) etc., but also not as limit.The back coupling control end 22 of PWM controller U1 can be accepted the feedback signal input, to change the work period of electronic switch Q1.

The DC power supply that the output 21 of switching circuit 2 is exported is connected to load 4, and is connected in parallel to feedback circuit 3, and this load 4 is the LED module, and can be one or more parallel connection, and person shown in the figure is the kenel for multi-channel parallel.Preferably, can between the output 21 of each road load 4 and switching circuit 2, be connected in series a choke L1, L2 ... .. LX is so that drive current is more stable.

In switching circuit 2 and each road load 4 formed loop, be connected in series respectively a transfer resistance RT1, RT2 ... RTX, the resistance of this transfer resistance is all equal, this transfer resistance RT1, RT2 ... ..RTX two ends are connected to respectively the input of a comparator U2 who is comprised of operational amplifier, because this transfer resistance RT1, RT2 ... ..RTX be the setting of connecting with load, it can be voltage signal with the current conversion of flowing through, and the transfer resistance RT1 that flows through, RT2 ... ..RTX the output current of load 4 namely equals to flow through, therefore comparator U2 can obtain the size of load current and be compared, the output of this comparator U2 connects the input (being LED side) of an optical coupler PC1, and the output of optical coupler PC1 namely is connected to the back coupling control end 22 of PWM controller U1, gives PWM controller U1 with the reset signal.Because the transfer resistance RT1 on each road, RT2 ... ..RTX resistance is all equal, suppose to have the LED load on arbitrary road to be removed for some reason or when disconnecting, the transfer resistance RT1 that connects of other road load then, RT2 ... ..RTX the voltage of going up is greater than preset value (being abnormal), comparator U2 namely controls optical coupler PC1 and carries out switching motion, change immediately feedback signal and adjust the work period of PWM controller U1, to change the ON time of electronic switch Q1, and then the adjustment output current, reach the purpose that the load of every road is all the constant current supply; And the voltage on the load circuit electric current that this is disconnected Wei Ling ﹐ and the transfer resistance that it is connected in series must not disturb or harmful effect for Ling Dian Ya ﹐ can not produce for the normal operation of comparator U2.

The above embodiment is the preferred embodiment that proves absolutely that the utility model is lifted, and protection range of the present utility model is not limited to this.Being equal to that those skilled in the art do on the utility model basis substitutes or conversion, all within protection range of the present utility model.Protection range of the present utility model is as the criterion with claims.

Claims (6)

1. the constant-flow driver of a light-emitting diode is characterized in that, comprising:

One is connected in the rectification circuit in an AC power and output DC source;

One is connected in the DC power supply of this rectification circuit and switches the switching circuit of this DC power supply in the mode of pulse width modulation, and it has one and feedbacks control end in order to the output and that connects load; And

One is connected between the back coupling control end of the output of this switching circuit and this switching circuit and makes output current be controlled constant feedback circuit according to the output current size of this output with work period of control switch circuit.

2. the constant-flow driver of light-emitting diode as claimed in claim 1, it is characterized in that, this switching circuit comprises one to be subjected to the control of PWM controller and to change electronic switch, a high frequency transformer and the PWM controller of its switching frequency and work period, the primary side of this high frequency transformer is connected in the dc power output end of this rectification circuit, the switch terminals of this electronic switch then is serially connected with between the primary side and ground connection of this high frequency transformer, and the control end of this electronic switch then is connected in this PWM controller.

3. the constant-flow driver of light-emitting diode as claimed in claim 2 is characterized in that, this electronic switch is a metal oxide semiconductcor field effect electric crystal, bipolarity junction electric crystal or isolation gate bipolar transistor.

4. the constant-flow driver of light-emitting diode as claimed in claim 1 or 2, it is characterized in that, described feedback circuit comprises a transfer resistance, a comparator and an optical coupler, wherein be connected in series this transfer resistance in this switching circuit and the formed loop of load, the two ends of this transfer resistance are connected to respectively the input of comparator, the output of comparator is connected in the input of optical coupler, and the output of optical coupler is connected to the back coupling control end of switching circuit.

5. the constant-flow driver of light-emitting diode as claimed in claim 4 is characterized in that, this comparator is comprised of operational amplifier.

6. the constant-flow driver of light-emitting diode as claimed in claim 4 is characterized in that, the output parallel multiplex load of this switching circuit, each road load all are serially connected with the transfer resistance that a resistance equates.

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