CN102752896A - Ripple filter circuit of high-efficiency light emitting diode (LED) constant current source - Google Patents
Ripple filter circuit of high-efficiency light emitting diode (LED) constant current source Download PDFInfo
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- CN102752896A CN102752896A CN2012102141594A CN201210214159A CN102752896A CN 102752896 A CN102752896 A CN 102752896A CN 2012102141594 A CN2012102141594 A CN 2012102141594A CN 201210214159 A CN201210214159 A CN 201210214159A CN 102752896 A CN102752896 A CN 102752896A
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Abstract
The invention relates to the technical field of light emitting diode (LED) lighting, in particular to a ripple filter circuit of a high-efficiency LED constant current source. According to principles of low sampling voltage of a bipolar junction transistor (BJT) and controllable and variable internal resistance of the BJT, current is detected by a resistor R2 and an inductor L1, and a detection result is accurately adjusted by a triode amplification unit, so low-frequency ripple and switching pulse ripple in the circuit are filtered, electric energy on an electrolytic capacitor constantly flows to an LED load, and the current which is obtained by the LED load can be pure constant current which is substantially free from the ripple. The ripple filter circuit of the high-efficiency LED constant current source has the advantages that the content of the low-frequency ripple is not more than 1 percent, and the filter efficiency can be between 97 percent and 99 percent. The ripple filter circuit is simple in structure, small in quantity of circuit elements, small in size, low in cost and high in circuit reliability and working efficiency, the insertion loss of the circuit is only 1 to 3 percent, and the cost performance of a product is greatly improved.
Description
Technical field
The present invention relates to the LED lighting technical field, particularly relate to a kind of ripple filter circuit of realizing high efficiency LED constant-current source.
Background technology
The LED luminous efficiency is high, and energy consumption is low, becomes the first-selection of energy-saving lighting lamp, is the main trend that following energy-conserving product uses.For the many LED lamp strings of quantity, mostly adopt the mode of constant current power supply now, make the LED luminous efficiency increase, increase useful life.Low-frequency ripple that the civil power low-frequency ac causes but the common LED constant-current supply usually can occur and the comprehensive ripples such as high-frequency impulse interference that the switching circuit of self produced; And do not reach accurate required ripple-free lighting requirement of high standard illumination; Because LED is the voltage-type load; Small voltage on the common filter capacitor changes all can cause the variation greatly of load LED electric current, thereby causes its ripple coefficient bigger.Because large ripple current can make the brightness of lamp have the light and shade of 100 or 120 times/per second to change, though this variation human eye perceives less than, do not influence general lighting yet, in the short time human eye also imperceptible have any unusual.But, if when the light that changes in this light and shade is for a long time worked down, can influence the comfort level of human eye, be easy to generate visual fatigue, can quicken young man's myopia, or the elderly's presbyopic.In addition; The light of this big ripple is during as photo illumination; Because the scanning frequency of photography is asynchronous with the ripple frequency of light, the illumination of high ripple can cause the brightness irregularities of every width of cloth image, thereby has influenced the quality of image; Therefore the LED lamp source of ripple-free (ripple coefficient≤1%) will become the first-selection of the application scenario that light is had relatively high expectations, for example: film studio, office, school etc.
The implementation of the low ripple circuit of LED constant-current source mainly contains following several kinds at present:
The one, between civil power AC rectification output and switching circuit input, strengthen filter capacitor (with bigger electrochemical capacitor), sort circuit is simple in structure, and cost is low; Good wave filtering effect, and the operating efficiency of power supply is also higher, but its power factor (PF) is too low; Be generally 0.5-0.6PF; Do not meet the economize on electricity and the safe requirement of national grid, unsuitable large-scale popularization is used, and particularly should not in more powerful power supply, use;
The 2nd, between civil power AC rectification output and switching circuit input, add the power factor compensation circuit, this is a method commonly used at present, but the cost of this part is higher, and volume is bigger, and total work efficient of power supply reduces more;
The 3rd, the rectification output end in switching circuit back adds very big filter capacitor, and sort circuit is simple in structure, the power factor (PF) of power supply and operating efficiency can be done higherly, but; The volume of sort circuit and cost can rise significantly, such as: 20% ripple is reduced to 1%, and the volume of electric capacity and cost all will increase about 20 times simultaneously; These are in a lot; The volume of power supply does not allow so big, and cost does not allow so high yet, and its scope of application is limited naturally.
Summary of the invention
Deficiency to prior art; The invention provides a kind of ripple filter circuit of high efficiency LED constant-current source; Problems such as purpose is to solve in the prior art that the low ripple circuit element quantity of LED constant current is many, volume big, complex structure, poor stability, efficient are low provide a kind of improved circuit that is used to eliminate LED constant-current supply ripple, minimizing circuit element quantity; Reduced volume, reduce cost, reduce the wastage, improve circuit reliability, operating efficiency and filter effect.
For achieving the above object; The present invention realizes through following technical scheme: the ripple filter circuit of high efficiency LED constant-current source; Described ripple filter circuit is to be connected between constant current switch transformer rectification output end and the LED load; Described ripple filter circuit is made up of capacitor C 1, resistance R 1, capacitor C 2, resistance R 2, triode amplifying unit, diode D1 and inductance L 1; Wherein capacitor C 1 is connected in parallel on constant current switch transformer rectification output end, and is parallelly connected with capacitor C 1 again after resistance R 1 and capacitor C 2 series connection, and an end of resistance R 2 is connected on the total end of junction of resistance R 1 and capacitor C 2; The constant current control end of another termination triode amplifying unit of resistance R 2; The input of triode amplifying unit is connected in the total end of the junction of capacitor C 1 and resistance R 1, and the output of triode amplifying unit is connected with an end of inductance L 1, an end of another termination LED load of inductance L 1; The other end of LED load is connected in the total end of the junction of capacitor C 1 and capacitor C 2, and diode D1 is parallelly connected with the triode amplifying unit.
Described capacitor C 1 tentatively is filtered into direct current output comparatively stably with the output rectified current of constant current switch power supply; Said capacitor C 2 obtains standard and level and smooth voltage through resistance R 1 from capacitor C 1; Said resistance R 2 detects with 1 pair of output current of inductance L, and wherein the DC internal resistance of resistance R 2 and inductance L 1 detects the low-frequency current in the output current, and the induction reactance of said inductance L 1 detects the switching pulse in the output current; Output current after process resistance R 2 detects with inductance L 1 is through the amplification adjustment of triode amplifying unit, and filters low ripple and switching pulse ripple are adjusted in the internal resistance of promptly managing through BJT automatically, and output current is smoothed to the almost direct current output of ripple-free; Described resistance R 1, resistance R 2 and diode D1 also are used for the triode amplifying unit is carried out charge and discharge protecting, prevent that amplifying unit from damaging because of overvoltage or overcurrent.
Further; The second amplifying circuit that described triode amplifying unit is made up of NPN type triode Q1 and positive-negative-positive triode Q2, the end of the base stage connecting resistance R2 of triode Q1, the base stage of the collector connecting transistor Q2 of triode Q1; The emitter of triode Q1 connects the collector electrode of triode Q2; The emitter of triode Q2 connects the negative electrode of diode D1, and the collector electrode of triode Q2 connects the anode of diode D1, the collector electrode of a termination triode Q2 of inductance L 1; The other end of inductance L 1 is the filtered positive source output of ripple; This cathode output end connects the positive pole of LED load, and the cathode output end of this power supply connects the negative pole of capacitor C 1, capacitor C 2 and LED load respectively, and the cathode output end of this power supply all leads directly to before and after ripple filtering.
Further, the second amplifying circuit that described triode amplifying unit is made up of positive-negative-positive triode Q1 and NPN type triode Q2, the end of the base stage connecting resistance R2 of triode Q1; The base stage of the collector connecting transistor Q2 of triode Q1; The emitter of triode Q1 connects the collector electrode of triode Q2, and the emitter of triode Q2 connects the anode of diode D1, and the collector electrode of triode Q2 connects diode D1 negative electrode; The collector electrode of one termination triode Q2 of inductance L 1; The other end of inductance L 1 is the filtered power cathode output of ripple, and this cathode output end connects the negative pole of LED load, and the cathode output end of this power supply connects the positive pole of capacitor C 1, capacitor C 2 and LED load respectively.
Further, described triode amplifying unit is the multiple tube amplifying circuit that is made up of complementary triode Q1 of polarity and triode Q2.
Further, the amplifying circuit formed by single triode of described triode amplifying unit.
Further, the three-stage amplifier formed by three triodes of described triode amplifying unit.
The present invention is that the internal resistance through triode (BJT) is controlled variable principle; Detect through resistance R 2 and 1 pair of electric current of inductance L; Its testing result is accurately adjusted through the triode amplifying unit; Thereby low-frequency ripple in the filtering circuit and switching pulse ripple make that the electric energy on the electrochemical capacitor flows to the LED load consistently, thereby realize that the resulting electric current of LED load is the almost pure constant current of ripple-free.
The invention has the beneficial effects as follows:
(1) circuit of the present invention can make low-frequency ripple in the LED constant-current source reach≤1%, its filtration efficiency can reach 97-99%, filtration efficiency is high;
(2) circuit structure of the present invention is simple, and circuit element is few, and volume is little, cost is low, the insertion loss of circuit 1-3% only, and circuit reliability and high efficiency make cost performance of product improve greatly.
Description of drawings
Fig. 1 is the circuit theory diagrams of the first embodiment of the present invention.
Fig. 2 is the circuit theory diagrams of the second embodiment of the present invention.
Embodiment
Combine accompanying drawing and embodiment that the present invention is further specified at present.
Embodiment 1; With reference to shown in Figure 1, the ripple filter circuit of a kind of high efficiency LED constant-current source of the present invention, described ripple filter circuit are to be connected between constant current switch transformer rectification output end and the LED load; Described ripple filter circuit is made up of capacitor C 1, resistance R 1, capacitor C 2, resistance R 2, triode amplifying unit, diode D1 and inductance L 1; Described triode amplifying unit is the secondary circuit that NPN type triode Q1 and positive-negative-positive triode Q2 form, and wherein capacitor C 1 is connected in parallel on constant current switch transformer rectification output end, and resistance R 1 is parallelly connected with capacitor C 1 again after connecting with capacitor C 2; One end of resistance R 2 is connected on the total end of junction of resistance R 1 and capacitor C 2; The base stage of another termination triode Q1 of resistance R 2, the base stage of the collector connecting transistor Q2 of triode Q1, the emitter of triode Q1 connects the collector electrode of triode Q2; The emitter of triode Q2 connects the negative electrode of diode D1; The collector electrode of triode Q2 connects diode D1 anode, and the collector electrode of a termination triode Q2 of inductance L 1, the other end of inductance L 1 are the filtered positive source output of ripple; This cathode output end connects the positive pole of LED load, and the cathode output end of this power supply connects the negative pole of capacitor C 1, capacitor C 2 and LED load respectively.
Constant current filtering operation principle is: the dc pulse signal before the filtering inserts from V1V0, and filtered pure direct current connects the LED load from V2V0 output, and capacitor C 1 tentatively is filtered into direct current output comparatively stably with the output rectified current of constant current switch power supply; Said capacitor C 2 obtains standard and level and smooth voltage through resistance R 1 from capacitor C 1; In said resistance R 2 and the inductance L 1 output current is detected, wherein the DC internal resistance of resistance R 2 and inductance L 1 detects the low-frequency current in the output current, and the induction reactance of said inductance L 1 detects the switching pulse in the output current; Through the secondary amplification adjustment of the output current after resistance R 2 and inductance L 1 detection through triode Q1 and triode Q2; Promptly adjust automatically through the internal resistance of BJT triode, filters low ripple and switching pulse ripple are smoothed to the almost direct current output of ripple-free with output current; Thereby realize the electric current that flows through the LED load is carried out accurately level and smooth adjustment; This adjustment does not change the size of the average current of power supply, only needs except that the low-and high-frequency ripple, thereby makes LED obtain the almost continuous current of ripple-free.Simultaneously resistance R 1, resistance R 2 and diode D1 also form charge-discharge protection circuit, guarantee that triode Q1, triode Q2 at any time can not damage because of overcurrent or superpressure.
Embodiment 2; With reference to shown in Figure 2, the ripple filter circuit of a kind of high efficiency LED constant-current source of the present invention, described ripple filter circuit are to be connected between constant current switch transformer rectification output end and the LED load; Described ripple filter circuit is made up of capacitor C 1, resistance R 1, capacitor C 2, resistance R 2, triode amplifying unit, diode D1 and inductance L 1; Described triode amplifying unit is the secondary circuit that positive-negative-positive triode Q1 and NPN type triode Q2 form, and wherein capacitor C 1 is connected in parallel on constant current switch transformer rectification output end, and resistance R 1 is parallelly connected with capacitor C 1 again after connecting with capacitor C 2; One end of resistance R 2 is connected on the total end of junction of resistance R 1 and capacitor C 2; The base stage of another termination triode Q1 of resistance R 2, the base stage of the collector connecting transistor Q2 of triode Q1, the emitter of triode Q1 connects the collector electrode of triode Q2; The emitter of triode Q2 connects the anode of diode D1; The collector electrode of triode Q2 connects diode D1 negative electrode, and the collector electrode of a termination triode Q2 of inductance L 1, the other end of inductance L 1 are the filtered power cathode output of ripple; This cathode output end connects the negative pole of LED load, and the cathode output end of this power supply connects the positive pole of capacitor C 1, capacitor C 2 and LED load respectively.
To sum up, the ripple filter circuit of high efficiency LED constant-current source of the present invention is when triode Q1 is the NPN type; Q2 then is a positive-negative-positive, and when triode Q1 is a positive-negative-positive, Q2 then is the NPN type; Be that Q1Q2 composition polarity is the multiple tube of complementary type, the advantage of this combination is: its sampling voltage has only about 0.7V.The sampling voltage of the multiple tube of same polarity is (three same polarities then is about 2.1V) about 1.4V, and in addition, the sampling voltage of metal-oxide-semiconductor is up to 2-4V.Because the total losses of filter circuit become certain proportional relationship with sampling voltage, promptly sampling voltage is high more, and the filtering loss is just big more; So the sampling voltage that reduces between V4 and V2 just can reduce the filtering loss effectively, thereby the insertion loss of entire circuit is reduced greatly, multiple tube can make the filter capacity of power supply improve by all means more than 100 times than single; So the capacity of capacitor C 2 can reduce greatly, the volume of filter circuit and cost also further dwindle like this; Simultaneously; The electric current of resistance R 1 also dwindles more than 100 times, and the pressure drop of resistance R 1 can significantly reduce, and this has also further dwindled total filtering loss.
Although specifically show and introduced the present invention in conjunction with preferred embodiment; But the those skilled in the art should be understood that; In the spirit and scope of the present invention that do not break away from appended claims and limited; Can make various variations to the present invention in form with on the details, be protection scope of the present invention.
Claims (6)
1. the ripple filter circuit of high efficiency LED constant-current source; It is characterized in that described ripple filter circuit is to be connected between constant current switch transformer rectification output end and the LED load, described ripple filter circuit is made up of capacitor C 1, resistance R 1, capacitor C 2, resistance R 2, triode amplifying unit Q1Q2, diode D1 and inductance L 1; Wherein capacitor C 1 is connected in parallel on constant current switch transformer rectification output end; Parallelly connected with capacitor C 1 again after resistance R 1 and capacitor C 2 series connection, an end of resistance R 2 is connected on the total end of junction of resistance R 1 and capacitor C 2, the constant current control end of another termination triode amplifying unit of resistance R 2; The input of triode amplifying unit is connected in the total end of the junction of capacitor C 1 and resistance R 1; The output of triode amplifying unit is connected with an end of inductance L 1, and an end of another termination LED load of inductance L 1, the other end of LED load are connected in the total end of the junction of capacitor C 1 and capacitor C 2; Diode D1 is parallelly connected with the triode amplifying unit
Described capacitor C 1 tentatively is filtered into direct current output comparatively stably with the output rectified current of constant current switch power supply; Said capacitor C 2 obtains standard and level and smooth voltage through resistance R 1 from capacitor C 1; Said resistance R 2 detects with 1 pair of output current of inductance L, and wherein the DC internal resistance of resistance R 2 and inductance L 1 detects the low-frequency current in the output current, and the induction reactance of said inductance L 1 detects the switching pulse in the output current; Through the amplification adjustment of the output current after resistance R 2 and inductance L 1 detection through the triode amplifying unit, filters low ripple and switching pulse ripple are smoothed to the almost direct current output of ripple-free with output current; Described resistance R 1, resistance R 2 and diode D1 also are used for the triode amplifying unit is carried out charge and discharge protecting.
2. the ripple filter circuit of high efficiency LED constant-current source according to claim 1; It is characterized in that the second amplifying circuit that described triode amplifying unit is made up of NPN type triode Q1 and positive-negative-positive triode Q2, the end of the base stage connecting resistance R2 of triode Q1; The base stage of the collector connecting transistor Q2 of triode Q1; The emitter of triode Q1 connects the collector electrode of triode Q2, and the emitter of triode Q2 connects the negative electrode of diode D1, and the collector electrode of triode Q2 connects the anode of diode D1; The collector electrode of one termination triode Q2 of inductance L 1; The other end of inductance L 1 is the filtered positive source output of ripple, and this cathode output end connects the positive pole of LED load, and the cathode output end of this power supply connects the negative pole of capacitor C 1, capacitor C 2 and LED load respectively.
3. the ripple filter circuit of high efficiency LED constant-current source according to claim 1; It is characterized in that the second amplifying circuit that described triode amplifying unit is made up of positive-negative-positive triode Q1 and NPN type triode Q2, the end of the base stage connecting resistance R2 of triode Q1; The base stage of the collector connecting transistor Q2 of triode Q1; The emitter of triode Q1 connects the collector electrode of triode Q2, and the emitter of triode Q2 connects the anode of diode D1, and the collector electrode of triode Q2 connects diode D1 negative electrode; The collector electrode of one termination triode Q2 of inductance L 1; The other end of inductance L 1 is the filtered power cathode output of ripple, and this cathode output end connects the negative pole of LED load, and the cathode output end of this power supply connects the positive pole of capacitor C 1, capacitor C 2 and LED load respectively.
4. the ripple filter circuit of high efficiency LED constant-current source according to claim 1 is characterized in that, described triode amplifying unit is the multiple tube amplifying circuit that is made up of the triode Q1 of polarity complementation and triode Q2.
5. the ripple filter circuit of high efficiency LED constant-current source according to claim 1 is characterized in that, the amplifying circuit that described triode amplifying unit is made up of single triode.
6. the ripple filter circuit of high efficiency LED constant-current source according to claim 1 is characterized in that, the three-stage amplifier that described triode amplifying unit is made up of three triodes.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2012102141594A CN102752896A (en) | 2012-06-27 | 2012-06-27 | Ripple filter circuit of high-efficiency light emitting diode (LED) constant current source |
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| CN2012102141594A CN102752896A (en) | 2012-06-27 | 2012-06-27 | Ripple filter circuit of high-efficiency light emitting diode (LED) constant current source |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103281838A (en) * | 2013-06-05 | 2013-09-04 | 矽力杰半导体技术(杭州)有限公司 | Circuit and method for eliminating LED stroboflash and LED drive circuit |
| CN103298218A (en) * | 2013-06-27 | 2013-09-11 | 苏州智浦芯联电子科技有限公司 | Circuit used for reducing LED ripple current |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103281838A (en) * | 2013-06-05 | 2013-09-04 | 矽力杰半导体技术(杭州)有限公司 | Circuit and method for eliminating LED stroboflash and LED drive circuit |
| CN103281838B (en) * | 2013-06-05 | 2015-11-25 | 矽力杰半导体技术(杭州)有限公司 | A kind of circuit, method and LED drive circuit eliminating LED stroboscopic |
| CN103298218A (en) * | 2013-06-27 | 2013-09-11 | 苏州智浦芯联电子科技有限公司 | Circuit used for reducing LED ripple current |
| CN103298218B (en) * | 2013-06-27 | 2015-04-22 | 苏州智浦芯联电子科技有限公司 | Circuit used for reducing LED ripple current |
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Application publication date: 20121024 |