CN101707826B - LED constant current driving circuit - Google Patents
LED constant current driving circuit Download PDFInfo
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- CN101707826B CN101707826B CN2009101060780A CN200910106078A CN101707826B CN 101707826 B CN101707826 B CN 101707826B CN 2009101060780 A CN2009101060780 A CN 2009101060780A CN 200910106078 A CN200910106078 A CN 200910106078A CN 101707826 B CN101707826 B CN 101707826B
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Abstract
The invention relates to an LED constant current driving circuit comprising LED load, a power supply, and also at least one constant current chip, a main control circuit and a switching circuit, wherein the at least one constant current chip is electrically connected with the LED load and used for conducting constant current regulation on the LED load, the main control circuit is connected with the power supply and used for conducting pulse width modulation according to input signals of the constant current chip and outputting control signals, and the switching circuit is electrically connected between the control signal outputting end of the main control circuit and the LED load. The LED constant current driving circuit has the advantages of capability of supplying adjustable constant current value, high constant current accuracy, high efficiency, high circuit reliability, simple circuit and low cost.
Description
Technical field
The present invention relates to a kind of drive circuit, more particularly, relate to a kind of LED constant-current drive circuit.
Background technology
Nowadays, LED is as light source of new generation, and range of application more and more widely.But LED needs constant drive current usually, the unstable a little flicker that will cause the light that LED sends of the electric current at its two ends.At present, low-voltage is exempted from the following dual mode of the general employing of isolated high power LED constant-current driving circuit:
One, adopts reduction voltage circuit (buck) or booster circuit (boost) or step-down and pulse width modulation controlled (PWM, Pulse Width Modulator) the LED constant-current drive circuit that boosts and combine.This mode feeds back to main control unit (MCU, Micro Controller Unit) with the signal of telecommunication of LED load output, utilizes MCU internal processes algorithm to carry out the PWM modulation then, to reach the effect of regulating electric current and constant current.Referring to Fig. 1, it is a kind of constant-current circuit of available technology adopting reduction voltage circuit, and it adopts L; C; D three devices constitute the buck circuit, and by the pulse duration of PWM control switch Q output, its Current Control principle is: the signal of telecommunication that the LED load of resistance R sense collection is exported feeds back to MCU; And then carry out PWM control buck circuit, and then regulate the output constant current.But it has following critical defect: the constant current effect is undesirable; Serious jitter phenomenon can appear in output current when multiplying power relation (or being bordering on the multiplying power relation) appears in sample frequency and PWM frequency, at this time also need in signal sample circuit, increase a RC filter.And R, the parameter selection of C need be big or small according to output current, and the PWM frequency; Parameter settings such as Rsense size, when Circuits System some adjustment occurred or changes, these parameters all need reset; This has increased very big difficulty for debugging work; Even and overcome the light jitter phenomenon, and entire circuit can not be controlled constant current accurately, and this circuit the error about 10% can occur with the constant current value of work one after as a child when just bringing into operation.
Two: adopt special-purpose LDO constant current analog chip to simulate regulation and control.But the special chip of every kind of model all has fixing input voltage range and output current scope, and it is occurring under the higher situation of short circuit and input voltage; Chip is prone to heating; Even occur being burnt phenomenon, and size of current fixes, and can't regulate the Constant Electric Current flow valuve of output.
Summary of the invention
The technical problem that the present invention will solve is, the unfavorable defective of constant current effect to the above-mentioned constant-current circuit of prior art provides the LED constant-current drive circuit that a kind of constant current accuracy is high, constant current value is adjustable, reliability is high and circuit is simple, cost is low.
The technical solution adopted for the present invention to solve the technical problems is: construct a kind of LED constant-current drive circuit; Comprise LED load and power supply, comprise that also with LED load being used for of being electrically connected at least one constant current chip of constant flow regulation, being used for of linking to each other with said power supply being carried out in the LED load carries out the governor circuit of pulse-width modulation and output control signal and be connected electrically in the control signal output ends of said governor circuit and the switching circuit between the LED load according to the input signal of constant current chip.
In LED constant-current drive circuit of the present invention, said governor circuit comprises main control unit MCU and the voltage-reference that is used for providing reference voltage to MCU that links to each other with said MCU, and the input of said each constant current chip links to each other with the signal sampling end of MCU.
In LED constant-current drive circuit of the present invention, said constant current chip is connected with said LED load.
In LED constant-current drive circuit of the present invention; The input of said constant current chip links to each other with the negative electrode of said LED load; The signal of telecommunication so that LED is flowed out feeds back to MCU, and the power end of said constant current chip links to each other with the output of said switching circuit and the anode of LED load simultaneously.
In LED constant-current drive circuit of the present invention, said switching circuit comprises switching tube, and said switching tube is FET or thyristor or relay.
In LED constant-current drive circuit of the present invention, said switching tube is a FET.
In LED constant-current drive circuit of the present invention, said MCU is HT46R47.
In LED constant-current drive circuit of the present invention, the 7th pin of said MCU connects the negative electrode of LED load, and its 5th pin connects the 3rd pin of voltage-reference through resistance R 5, and its 8th pin connects the 1st pin of voltage-reference, and its 10th pin connects the grid of FET.
In LED constant-current drive circuit of the present invention, said voltage-reference is the TL431 chip.
In LED constant-current drive circuit of the present invention, said constant current chip is QX7135.
A kind of LED constant-current drive circuit of embodiment of the present invention has following beneficial effect: it gives MCU through the constant current chip with the electrical signal collection of LED load, is carried out the break-make of pulse-width modulation and control switch circuit according to the signal of telecommunication by the program of MCU; And constant current chip and governor circuit can be regulated the constant current value in the LED load; Make the present invention can provide the high constant current of precision and constant current value simply adjustable, in addition, the constant current chip is sent into the signal of telecommunication of LED load that governor circuit can carry out short circuit, opens circuit, and overcurrent protection; Improved the reliability of circuit; And entire circuit is simple, and cost is low.
Description of drawings
To combine accompanying drawing and embodiment that the present invention is described further below, in the accompanying drawing:
Fig. 1 is the circuit theory diagrams that available technology adopting step-down mode is carried out constant current control;
Fig. 2 is a schematic block circuit diagram of the present invention;
Fig. 3 is the circuit theory diagrams that the present invention adopts a preferred embodiment of a constant current chip;
Fig. 4 is the circuit diagram that the present invention adopts a preferred embodiment of a constant current chip;
Fig. 5 is the circuit theory diagrams that the present invention adopts an embodiment of a plurality of constant current chips.
Embodiment
The present invention utilizes the constant current chip that the output signal of telecommunication of load is sampled MCU, through MCU control constant current chip, carries out constant current accurately control and circuit protection again.
Referring to Fig. 2, it has shown out theory diagram of the present invention.LED constant-current drive circuit provided by the invention comprises: power supply 1, governor circuit 2, switching circuit 3, LED load 4, and constant current chip 5.Constant current chip 5 is connected with LED load 4, and the input of constant current chip 5 links to each other with the negative electrode of LED load 4.Governor circuit 2 links to each other with power supply 1, and governor circuit 2 comprises MCU and the voltage-reference that is used for providing reference voltage to MCU that links to each other with said MCU, and the signal sampling end of MCU links to each other with the negative electrode of LED load, thereby samples the signal of telecommunication that flows out from the LED load.The reference voltage that MCU provides this signal of telecommunication and reference voltage source again compares with the output control signal entire circuit is handled, and for example changes the width ratio of the high-low level of the MCU output signal of telecommunication, the break-make of output Signal-controlled switch.Switching circuit 3 is connected between the control signal output ends and LED load 4 of governor circuit 2, and switching circuit 3 is according to the disconnection and closed state of the output signal change switch of MCU.Switching circuit 3 can be FET or thyristor or relay, or other can realize the components and parts of the conversion of conducting and disconnection.Because the response speed that is preferably switch here is comparatively fast with protective circuit, so preferably, switch is a FET in the switching circuit 3.
Fig. 4 is the circuit diagram that the present invention adopts a preferred embodiment of a constant current chip 5.In Fig. 6, governor circuit 2 comprise MCU, link to each other with MCU with voltage-reference that fixing 2.5V voltage is provided, and resistance R 1, R2, R5, capacitor C 1, C2, C3, switch S 1.MCU can adopt the single-chip microcomputer of two above A/D mouths of 8 bit strips, for example atiny18 single-chip microcomputer of HT46R47, AVR etc.Single-chip microcomputer needs the signal of telecommunication of a voltage-reference relatively to collect from the LED load, and preferably, voltage-reference adopts TL431.The pin 3 of voltage-reference links to each other with the pin 5 of MCU through current-limiting resistance R5, and its pin 1 connects the pin 8 of MCU.Pin 9 ground connection of MCU; Its pin 11 is through filter capacitor C2 ground connection, and its pin 12 is through while connecting resistance R1 between filter capacitor C1 ground connection, pin 12 and the capacitor C 2, and its pin 13 is through current-limiting resistance R2 ground connection; Its pin 10 links to each other with the grid of FET in the switching circuit with the output control signal through resistance R 4; Its signal sampling end, promptly pin 7 connects the negative electrode of LED load, is connected between the pin 2 and ground of MCU after filter capacitor C3 and switch S 1 are parallelly connected.In the present embodiment, the preferred P-channel field-effect transistor (PEFT) pipe of switch, for example Irml6401 in the switching circuit.The constant current chip can adopt for example QX7135 series, and this circuit adopts sb42351a, and the normal value of its constant current is 335mA.The signal of telecommunication that the signal input pin 1 of constant current chip flows out the LED load feeds back to the signal sampling end of MCU in the control circuit; The said signal of telecommunication is preferably voltage signal; In governor circuit, voltage signal is realized control more easily than current signal, and the better effects if of control.The control circuit root compares the voltage of voltage signal that collects and voltage-reference, and then can judge entire circuit whether problem is arranged, and then protects, and the physical circuit protection philosophy will be described below.In governor circuit; Because the control signal output ends of MCU links to each other with switching circuit; Close the PWM function of the PD0 mouth of MCU, make it be made as common I/O mouth, can change level to realize the effect of pulse-width modulation through the MCU plug-in; The conducting and the disconnection of switch in the output of MCU and then the control switch circuit, thereby can control the different constant current value of output.In the present embodiment, can select corresponding different programs with the different constant current value of control output through switch S 1.
Operation principle of the present invention combines Fig. 3 and Fig. 4 to be elaborated:
The normal value of constant current of supposing the constant current chip is I, utilizes the width ratio of MCU output high-low level, directly the service time Ton of control switch pipe Q and turn-off time Toff, and then output current is that adjustable constant-flow is exported Iout=I * [Ton/ (Ton+Toff)]; Therefore LED can obtain the adjustable constant-flow value adapting to illumination or the decoration demand of people to different brightness, and constant current accuracy is high.
In Fig. 3, because constant current chip IC 1 is a power consumption formula analog chip,, then possibly cause heating in case its work pressure drop is too high, even situation about being damaged.MCU of the present invention samples to pressure drop signal from the input input of IC1; Carry out programmed algorithm in MCU inside; Get the repeatedly mean value of sampling,, be higher than Vlg in case MCU detects the pressure drop signal sample mean at MCU inner setting one pressure drop limiting value Vlg; Then export control signal with cut-off switch Q1 to cut off circuit, the time that perhaps shortens Ton is with the effective pressure drop of balance.
Constant-current circuit reliability of the present invention is high, can carry out short circuit, open circuit, reaches overcurrent protection, and the principle when the supposition switch is the P-channel field-effect transistor (PEFT) pipe is following:
When LED opens circuit; MCU is 0 at the voltage signal that the input of constant current chip 5 samples; Can set FET disconnection in the MCU output high level control switch circuit 3 this moment; Thereby cut off circuit with protective circuit,, can also draw malfunction indicator lamp from MCU and carry out the fault prompting as malfunction indicator lamp is arranged in the fruit product.
When the LED short circuit, MCU is supply voltage Vin at the voltage signal that the input of constant current chip 5 samples, if this moment shut-off circuit not; With causing burning of constant current chip 5, even damage MCU, so the short-circuit protection of LED is very important; It judges that with open circuit fault principle is identical; It is higher unusually at first to sample the input voltage signal that the input of constant current chip 5 sends by MCU, and MCU output control signal is cut off circuit with control switch circuit 3, and then improves the reliability of circuit.
When the LED overcurrent, collect the input voltage signal Vout output abnormality that the input of constant current chip 5 sends by MCU, MCU can adjust the time of Ton, to reduce effective pressure drop Vreal=Vout * [Ton/ (Ton+Toff)].
Because LED is normally by low-voltage driving, and the minor variations of voltage all can cause the very large variation of LED two ends electric current, so power supply of the present invention 1 adopts low tension; Preferably; The present invention adopts low-voltage direct, baby battery for example, therefore; Circuit of the present invention can so also can be simplified circuit in order to avoid isolate.
Referring to Fig. 5, the circuit theory diagrams of its embodiment of a plurality of constant current chips for the present invention adopts.When the current value of circuit needs surpasses the maximum constant current value of single constant current chip 5; Can carry out mode like Fig. 5; With connecting with the LED load after a plurality of constant current chip 5 parallel connections to enlarge electric current, control principle is identical with above-mentioned single constant current chip, repeats no more at this again.
The above is merely the preferred embodiments of the present invention, not in order to restriction the present invention, all any modifications of in spirit of the present invention and principle, being done, is equal to and replaces or improvement etc., all should be included in protection scope of the present invention.
Claims (7)
1. LED constant-current drive circuit; Comprise LED load and power supply; It is characterized in that, also comprise with said LED load being used for of being electrically connected to said LED load carry out at least one constant current chip of constant flow regulation, the input signal according to said constant current chip of being used for that links to each other with said power supply carries out pulse-width modulation and exports the governor circuit of control signal and be connected electrically in the control signal output ends of said governor circuit and the switching circuit between the said LED load;
Said governor circuit comprises main control unit MCU and the voltage-reference that is used for providing reference voltage to said MCU that links to each other with said MCU, and the input of each said constant current chip links to each other with the signal sampling end of said MCU; The reference voltage that voltage signal that said MCU will collect from said LED load and said voltage-reference provide compares the said control signal with output control switch conducting and disconnection.
2. LED constant-current drive circuit according to claim 1 is characterized in that, said constant current chip is connected with said LED load.
3. LED constant-current drive circuit according to claim 1; It is characterized in that; The input of said constant current chip links to each other with the negative electrode of said LED load; The signal of telecommunication so that said LED load is flowed out feeds back to said MCU, and the power end of said constant current chip links to each other with the output of said switching circuit and the anode of LED load simultaneously.
4. LED constant-current drive circuit according to claim 1 is characterized in that said switching circuit comprises switching tube, and said switching tube is FET or thyristor or relay.
5. LED constant-current drive circuit according to claim 4 is characterized in that, said MCU is HT46R47; (7) pin of said MCU connects the negative electrode of said LED load; Its (5) pin connects (3) pin of said voltage-reference through resistance R 5; Its (8) pin connects (1) pin of said voltage-reference, and its (10) pin connects the grid of said FET.
6. LED constant-current drive circuit according to claim 1 is characterized in that, said voltage-reference is the TL431 chip.
7. LED constant-current drive circuit according to claim 1 is characterized in that, said constant current chip is QX7135.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101060780A CN101707826B (en) | 2009-03-19 | 2009-03-19 | LED constant current driving circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101060780A CN101707826B (en) | 2009-03-19 | 2009-03-19 | LED constant current driving circuit |
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| CN101707826A CN101707826A (en) | 2010-05-12 |
| CN101707826B true CN101707826B (en) | 2012-12-19 |
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| CN2009101060780A Expired - Fee Related CN101707826B (en) | 2009-03-19 | 2009-03-19 | LED constant current driving circuit |
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Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101815388B (en) * | 2010-05-31 | 2014-01-08 | 海洋王照明科技股份有限公司 | Led lamp control circuit and led lamp |
| CN102695319B (en) * | 2011-03-23 | 2014-12-17 | 海洋王照明科技股份有限公司 | LED stepless light regulating circuit |
| CN102695320B (en) * | 2011-03-24 | 2015-11-11 | 海洋王照明科技股份有限公司 | Constant-current drive circuit |
| CN102711307B (en) * | 2011-03-28 | 2015-03-11 | 海洋王照明科技股份有限公司 | Dimmable light-emitting diode (LED) drive circuit and lamp |
| CN102291875B (en) * | 2011-05-05 | 2013-09-04 | 佛山冠今光电科技有限公司 | DSP (digital signal processor)/digital signal processor-based high-side driving LED (light-emitting diode) constant-current source circuit |
| CN103517498A (en) * | 2012-06-26 | 2014-01-15 | 海洋王照明科技股份有限公司 | Intelligent temperature-controlled light-modulation control circuit of LED electric torch |
| CN103619097A (en) * | 2013-11-21 | 2014-03-05 | 江门市三泰照明制品有限公司 | Wirelessly-controlled LED lamp |
| CN103648216B (en) * | 2013-12-06 | 2015-12-09 | 武汉精立电子技术有限公司 | A kind of Intelligent constant flow drives the method for great power LED |
| CN104780681B (en) * | 2015-04-10 | 2018-03-13 | 常州市赛尔交通器材有限公司 | Headlamp lighting reponse system for rail vehicle |
| CN106304556A (en) * | 2016-08-25 | 2017-01-04 | 上海传英信息技术有限公司 | Current control circuit and current control method |
| CN106328072A (en) * | 2016-10-27 | 2017-01-11 | 刘勇 | Backlight intensity circuit and display device thereof |
| CN113473675B (en) * | 2021-06-03 | 2022-10-18 | 荣耀终端有限公司 | Light source circuit and terminal |
| CN114420057A (en) * | 2021-12-28 | 2022-04-29 | 荣耀终端有限公司 | Backlight power supply, display device and electronic equipment |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101227778A (en) * | 2008-02-19 | 2008-07-23 | 东南大学 | Self-excited oscillation type high power LED constant-current driving circuit |
| CN101370335A (en) * | 2008-09-27 | 2009-02-18 | 易际平 | Driving circuit for LED illumination |
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2009
- 2009-03-19 CN CN2009101060780A patent/CN101707826B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101227778A (en) * | 2008-02-19 | 2008-07-23 | 东南大学 | Self-excited oscillation type high power LED constant-current driving circuit |
| CN101370335A (en) * | 2008-09-27 | 2009-02-18 | 易际平 | Driving circuit for LED illumination |
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Granted publication date: 20121219 Termination date: 20190319 |