CN103369769A - LED fly-back constant current driving circuit - Google Patents
LED fly-back constant current driving circuit Download PDFInfo
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- CN103369769A CN103369769A CN201210093452XA CN201210093452A CN103369769A CN 103369769 A CN103369769 A CN 103369769A CN 201210093452X A CN201210093452X A CN 201210093452XA CN 201210093452 A CN201210093452 A CN 201210093452A CN 103369769 A CN103369769 A CN 103369769A
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Abstract
An LED fly-back constant current driving circuit comprises a rectification filter circuit, a fly-back transformer, a current sampling reactive circuit, a photoelectric isolation voltage detection circuit, a PWM wave genecyclen unit and a switch tube, wherein the output terminal of the rectification filter circuit is connected with one terminal of the primary winding of the fly-back transformer; the other terminal of the primary winding of the fly-back transformer is connected with the first terminal of the switch tube; the second terminal of the switch tube is grounded through a resistor; the control terminal of the switch tube is connected with the output terminal of the PWM wave generating unit; the PWM wave generating unit outputs PWM waves having a certain duty cycle according to the current sampling reactive circuit; the input terminal of the photoelectric isolation voltage detection circuit is connected with the output terminal of a commutated and filtered secondary winding of the fly-back transformer, for detecting the voltage at the output terminal of the commutated and filtered secondary winding of the fly-back transformer; and when the detected voltage exceeds a preset value, the PWM wave generating unit reduces the output PWM duty cycle.
Description
Technical field
The present invention relates to the LED technical field, particularly relate to a kind of LED inverse-excitation type constant-current drive circuit.
Background technology
LED is as new type light source, and it has energy-saving and environmental protection, efficient characteristics, and technology is ripe and be applied to every field, and LED is widely used as lighting source.Present low-power LED occurring on the market is mostly based on the constant-current control circuit of BUCK structure, although this circuit is simple in structure, cost is low, and reliability is low, and is Non-isolation model, will burn out LED in case drive plate work is undesired.
Summary of the invention
Based on this, be necessary the LED inverse-excitation type constant-current drive circuit that provides a kind of reliability high.
A kind of LED inverse-excitation type constant-current drive circuit, comprise current rectifying and wave filtering circuit, flyback transformer, the current sampling feedback circuit, photoelectricity isolation voltage testing circuit, PWM ripple generating unit, switching tube, the output of described current rectifying and wave filtering circuit connects an end of the former limit winding of described flyback transformer, the other end of the former limit winding of described flyback transformer connects the first end of described switching tube, the second end of described switching tube passes through grounding through resistance, the control end of described switching tube connects the output of described PWM ripple generating unit, the PWM ripple that the Voltage-output that described PWM ripple generating unit feeds back according to the current sampling feedback circuit has certain duty ratio, the input of described photoelectricity isolation voltage testing circuit is connected to the output of secondary winding behind rectifying and wave-filtering of described flyback transformer, detect the voltage of the output of secondary winding behind rectifying and wave-filtering of described flyback transformer, when the voltage that detects surpassed predetermined value, described PWM ripple generating unit reduced to export the duty ratio of PWM.
Therein among embodiment, described current sampling feedback circuit comprises the first operational amplifier, the second operational amplifier, sampling resistor and the first voltage-reference, described sampling resistor is serially connected in the loop at LED load place, the end that described sampling resistor current potential is high is connected with the in-phase input end of described the first operational amplifier, the other end of described sampling resistor is connected with the inverting input of described the first operational amplifier, the output of described the first operational amplifier is connected with the inverting input of described the second operational amplifier, the in-phase input end of described the second operational amplifier is connected with the output of described the first voltage-reference, and the output of described the second operational amplifier is connected with the feedback input end of described PWM ripple generating unit.
Therein among embodiment, described current sampling feedback circuit also comprises first frequency compensating circuit and second frequency compensating circuit, described first frequency compensating circuit is connected between the inverting input and output of the first operational amplifier, and described second frequency compensating circuit is connected between the inverting input and output of the second operational amplifier.
Therein among embodiment, described first frequency compensating circuit comprises the first electric capacity and the first resistance, after being connected in parallel, described the first electric capacity and the first resistance is connected between the inverting input and output of described the first operational amplifier, described second frequency compensating circuit comprises the second electric capacity, the 3rd electric capacity and the second resistance, described the second electric capacity and the second resistance are connected in series, and described the 3rd Capacitance parallel connection is connected between the inverting input and output of described the second operational amplifier after on described the second electric capacity and the second resistance.
Therein among embodiment, described PWM ripple generation unit is the UCC2803 chip.
Therein among embodiment, described photoelectricity isolation voltage testing circuit comprises photoelectrical coupler, second voltage a reference source, described second voltage a reference source links to each other with the input cathode of described photoelectrical coupler, the input anode of photoelectrical coupler connects the output of secondary winding behind rectifying and wave-filtering of flyback transformer, and the output of the secondary winding of described flyback transformer behind rectifying and wave-filtering connects the positive pole of LED load.
Therein among embodiment, also comprise soft starting circuit, soft starting circuit comprises the 3rd resistance, diode, the 4th electric capacity, the PNP triode, the VREF pin of described chip UCC2803 connects the negative electrode of described diode, the negative electrode of described diode D1 connects an end of described the 3rd resistance, the other end of described the 3rd resistance connects the anode of described diode, one end of described the 4th electric capacity of the anodic bonding of described diode and the base stage of PNP triode, the other end of described the 4th electric capacity connects power supply ground after connecting the collector electrode of described PNP triode, and the emitter of described PNP triode Q2 connects the COMP pin of described chip UCC2803.
Above-mentioned LED inverse-excitation type constant-current drive circuit, when described LED inverse-excitation type constant-current drive circuit is unloaded, when namely not accessing LED load or LED load cut-off, the value that described current sampling feedback circuit feeds back to PWM ripple generating unit is zero, impel PWM ripple generating unit constantly to increase the duty ratio of output PWM, thereby the voltage of secondary winding on the output behind the rectifying and wave-filtering of flyback transformer is constantly increased, at the secondary winding of flyback transformer after the output behind the rectifying and wave-filtering has connected photoelectricity isolation voltage testing circuit, detect the voltage of secondary winding on the output behind the rectifying and wave-filtering of flyback transformer, if the voltage that detects surpasses predetermined value, then make PWM ripple generating unit reduce to export the duty ratio of PWM, make output voltage remain on predetermined value, improved the reliability of LED inverse-excitation type constant-current drive circuit.
Description of drawings
Fig. 1 is the schematic block diagram of the LED inverse-excitation type constant-current drive circuit of a kind of embodiment;
Fig. 2 is the circuit diagram of the LED inverse-excitation type constant-current drive circuit of a kind of embodiment;
Fig. 3 is the circuit diagram of the LED inverse-excitation type constant-current drive circuit of another kind of embodiment.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is described in more detail.Should be appreciated that specific embodiment described herein only in order to explain the present invention, is not intended to limit the present invention.
Switching tube Q1 among Fig. 2, Fig. 3 is the switching tube 600 among Fig. 1.
As shown in Figure 1, the LED inverse-excitation type constant-current drive circuit that present embodiment provides comprises current rectifying and wave filtering circuit 100, flyback transformer 200, current sampling feedback circuit 300, photoelectricity isolation voltage testing circuit 400, PWM ripple generating unit 500 and switching tube 600.The output of current rectifying and wave filtering circuit 100 connects an end of the former limit winding of flyback transformer 200, the first end of the other end connecting valve pipe 600 of the former limit winding of flyback transformer 200, the second end of switching tube 600 passes through grounding through resistance, the control end of switching tube 600 connects the output that is used for output PWM waveform of PWM ripple generating unit 500, the PWM ripple that the Voltage-output that PWM ripple generating unit 500 feeds back according to current sampling feedback circuit 300 has certain duty ratio, the input of photoelectricity isolation voltage testing circuit 400 is connected to the output of secondary winding behind rectifying and wave-filtering of flyback transformer 200, voltage for detection of the output of secondary winding behind rectifying and wave-filtering of flyback transformer 200, when the voltage that detects surpasses predetermined value, PWM ripple generating unit 500 reduces to export the duty ratio of PWM, to reduce the voltage of flyback transformer 200 secondary windings output.
See also Fig. 2, current rectifying and wave filtering circuit 100 comprises full-bridge rectification bridge heap BR1 and filter capacitor C1, the input of full-bridge rectification heap BR1 connects alternating current, the output head anode of full-bridge rectification heap BR1 connects the positive pole of filter capacitor C1, and the negative pole of output end of full-bridge rectification bridge heap BR1 connects the negative pole of filter capacitor C1.
The output head anode of full-bridge rectification heap BR1 also connects an end of the former limit winding of flyback transformer 200, the first end of the other end connecting valve pipe Q1 of the former limit winding of flyback transformer 200, the second end of switching tube Q1 is by grounding through resistance, and the control end of switching tube Q1 connects the output that is used for output PWM waveform of PWM ripple generating unit 500.
Current sampling feedback circuit 300 comprises the first operational amplifier U1, the second operational amplifier U2, sampling resistor R1 and the first voltage-reference, sampling resistor R1 is serially connected in the loop at LED load place, the end that sampling resistor R1 current potential is high is connected with the in-phase input end of the first operational amplifier U1, the other end of sampling resistor is connected with the inverting input of the first operational amplifier U1, the output of the first operational amplifier U1 is connected with the inverting input of the second operational amplifier U2, the in-phase input end of the second operational amplifier U2 is connected with the output of the first voltage-reference, and the output of the second operational amplifier U2 is connected with the feedback input end of PWM ripple generating unit 200.
The inverting input of the second operational amplifier U2 is connected with the output of the first voltage-reference, and the output of the second operational amplifier U2 is connected with the feedback input end of PWM ripple generating unit 500.
In a preferred embodiment, current sampling feedback circuit 300 also comprises first frequency compensating circuit 301 and second frequency compensating circuit 302, first frequency compensating circuit 301 is connected between the in-phase input end and output of the first operational amplifier U1, and second frequency compensating circuit 302 is connected between the in-phase input end and output of the second operational amplifier U2.
In the present embodiment, first frequency compensating circuit 301 comprises after the first capacitor C 2 and the first resistance R 2, the first capacitor C 2 and the first resistance R 2 are connected in parallel and being connected between the inverting input and output of the first operational amplifier U1.
Second frequency compensating circuit 302 comprises the second capacitor C 3, the 3rd capacitor C 4 and the second resistance R 3, the second capacitor C 3 and the second resistance R 3 are connected in series, and the 3rd capacitor C 4 is connected between the inverting input and output of the second operational amplifier U2 after being connected in parallel on the second capacitor C 3 and the second resistance R 3.
Photoelectricity isolation voltage testing circuit 400 comprises photoelectrical coupler U3, second voltage a reference source, second voltage a reference source links to each other with the input negative pole of photoelectrical coupler U3, and the input anode of photoelectrical coupler U3 connects the output of secondary winding behind rectifying and wave-filtering of flyback transformer 200.
In the present embodiment, PWM ripple generating unit 500 is the UCC2803 chip, and the output head anode of photoelectrical coupler U3 connects the COMP pin, and the negative pole of output end of photoelectrical coupler U3 connects the FB pin.Photoelectricity isolation voltage testing circuit 400 detects the voltage of the output of secondary winding behind rectifying and wave-filtering of flyback transformer 200, when the voltage that detects during greater than the voltage of second voltage a reference source, the photophore of photoelectrical coupler U3 is luminous, make the phototriode conducting of photoelectrical coupler U3, the COMP pin input of UCC2803 chip is less than the voltage of VREF, the predeterminated voltage of this voltage and UCC2803 inside relatively after, control PWM ripple generating unit 500 reduces to export the duty ratio of PWM.
After LED inverse-excitation type constant-current drive circuit band carries startup, the current sampling of 300 pairs of LED loads of current sampling feedback circuit, and amplify the feedback input end of exporting to PWM generating unit 500.If the electric current that samples increases, then PWM generating unit 200 reduces to export the duty ratio of PWM; If the electric current that samples reduces, then PWM generating unit 200 increases the duty ratio of output PWM, makes the current constant of LED load.If when LED load cut-off or zero load, photoelectricity isolation voltage testing circuit 400 detects the voltage of the output of secondary winding behind rectifying and wave-filtering of flyback transformer 200, when the voltage that detects during greater than second voltage a reference source, control PWM ripple generating unit 500 reduces to export the duty ratio of PWM.When the LED load worked, photoelectricity isolation voltage testing circuit 400 was not worked.
In the present embodiment, LED inverse-excitation type constant-current drive circuit also comprises soft starting circuit, soft starting circuit comprises the 3rd resistance R 4, diode D1, the 4th capacitor C 5, PNP triode Q2, the VREF pin of chip UCC2803 connects the negative electrode of diode D1, the negative electrode of diode D1 connects an end of the 3rd resistance R 4, the other end of the 3rd resistance R 4 connects the anode of diode D1, one end of anodic bonding the 4th capacitor C 5 of diode D1 and the base stage of PNP triode Q2, connect power supply ground behind the collector electrode of the other end connection PNP triode Q2 of the 4th capacitor C 5, the emitter of PNP triode Q2 connects the COMP pin of chip UCC2803.
The PWM ripple generating unit 500 PWM ripple that 300 outputs have certain duty ratio according to the current sampling feedback circuit.
In a preferred embodiment, see also Fig. 3, current rectifying and wave filtering circuit 100 also comprises transformer L1, the second filter capacitor C6 and the 3rd filter capacitor C7, two outputs of transformer L1 connect respectively two inputs of full-bridge rectification bridge heap BR1, between two inputs of full-bridge rectification bridge heap BR1, also connect the second filter capacitor C6, the input of transformer L1 connects alternating current, also connects the 3rd filter capacitor C7 between two inputs of transformer L1.Can obtain the direct voltage that we want by transformer L1 and full-bridge rectification bridge heap BR1.
Above-mentioned LED inverse-excitation type constant-current drive circuit, when described LED inverse-excitation type constant-current drive circuit is unloaded, when namely not accessing LED load or LED load cut-off, the value that the current sampling feedback circuit feeds back to PWM ripple generating unit is zero, impel PWM ripple generating unit constantly to increase the duty ratio of output PWM, thereby the voltage of secondary winding on the output behind the rectifying and wave-filtering of flyback transformer is constantly increased, at the secondary winding of flyback transformer after the output behind the rectifying and wave-filtering has connected photoelectricity isolation voltage testing circuit, detect the voltage of secondary winding on the output behind the rectifying and wave-filtering of flyback transformer, if the voltage that detects surpasses predetermined value, then make PWM ripple generating unit reduce to export the duty ratio of PWM, make output voltage remain on predetermined value, improved the reliability of LED inverse-excitation type constant-current drive circuit.
The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.
Claims (7)
1. LED inverse-excitation type constant-current drive circuit, it is characterized in that, comprise current rectifying and wave filtering circuit, flyback transformer, the current sampling feedback circuit, photoelectricity isolation voltage testing circuit, PWM ripple generating unit, switching tube, the output of described current rectifying and wave filtering circuit connects an end of the former limit winding of described flyback transformer, the other end of the former limit winding of described flyback transformer connects the first end of described switching tube, the second end of described switching tube passes through grounding through resistance, the control end of described switching tube connects the output of described PWM ripple generating unit, the PWM ripple that the Voltage-output that described PWM ripple generating unit feeds back according to the current sampling feedback circuit has certain duty ratio, the input of described photoelectricity isolation voltage testing circuit is connected to the output of secondary winding behind rectifying and wave-filtering of described flyback transformer, detect the voltage of the output of secondary winding behind rectifying and wave-filtering of described flyback transformer, when the voltage that detects surpassed predetermined value, described PWM ripple generating unit reduced to export the duty ratio of PWM.
2. LED inverse-excitation type constant-current drive circuit according to claim 1, it is characterized in that, described current sampling feedback circuit comprises the first operational amplifier, the second operational amplifier, sampling resistor and the first voltage-reference, described sampling resistor is serially connected in the loop at LED load place, the end that described sampling resistor current potential is high is connected with the in-phase input end of described the first operational amplifier, the other end of described sampling resistor is connected with the inverting input of described the first operational amplifier, the output of described the first operational amplifier is connected with the inverting input of described the second operational amplifier, the in-phase input end of described the second operational amplifier is connected with the output of described the first voltage-reference, and the output of described the second operational amplifier is connected with the feedback input end of described PWM ripple generating unit.
3. LED inverse-excitation type constant-current drive circuit according to claim 2, it is characterized in that, described current sampling feedback circuit also comprises first frequency compensating circuit and second frequency compensating circuit, described first frequency compensating circuit is connected between the inverting input and output of the first operational amplifier, and described second frequency compensating circuit is connected between the inverting input and output of the second operational amplifier.
4. LED inverse-excitation type constant-current drive circuit according to claim 3, it is characterized in that, described first frequency compensating circuit comprises the first electric capacity and the first resistance, after being connected in parallel, described the first electric capacity and the first resistance is connected between the inverting input and output of described the first operational amplifier, described second frequency compensating circuit comprises the second electric capacity, the 3rd electric capacity and the second resistance, described the second electric capacity and the second resistance are connected in series, and described the 3rd Capacitance parallel connection is connected between the inverting input and output of described the second operational amplifier after on described the second electric capacity and the second resistance.
5. according to LED inverse-excitation type constant-current drive circuit claimed in claim 1, it is characterized in that, described PWM ripple generating unit is the UCC2803 chip.
6. LED inverse-excitation type constant-current drive circuit according to claim 5, it is characterized in that, described photoelectricity isolation voltage testing circuit comprises photoelectrical coupler, second voltage a reference source, described second voltage a reference source links to each other with the input cathode of described photoelectrical coupler, the input anode of photoelectrical coupler connects the output of secondary winding behind rectifying and wave-filtering of flyback transformer, and the output of the secondary winding of described flyback transformer behind rectifying and wave-filtering connects the positive pole of LED load.
7. LED inverse-excitation type constant-current drive circuit according to claim 5, it is characterized in that, also comprise soft starting circuit, soft starting circuit comprises the 3rd resistance, diode, the 4th electric capacity, the PNP triode, the VREF pin of described chip UCC2803 connects the negative electrode of described diode, the negative electrode of described diode D1 connects an end of described the 3rd resistance, the other end of described the 3rd resistance connects the anode of described diode, one end of described the 4th electric capacity of the anodic bonding of described diode and the base stage of PNP triode, the other end of described the 4th electric capacity connects power supply ground after connecting the collector electrode of described PNP triode, and the emitter of described PNP triode Q2 connects the COMP pin of described chip UCC2803.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210093452.XA CN103369769B (en) | 2012-03-31 | 2012-03-31 | LED fly-back constant-current drive circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210093452.XA CN103369769B (en) | 2012-03-31 | 2012-03-31 | LED fly-back constant-current drive circuit |
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| CN103369769A true CN103369769A (en) | 2013-10-23 |
| CN103369769B CN103369769B (en) | 2016-09-07 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104039039A (en) * | 2014-05-23 | 2014-09-10 | 中国科学院广州能源研究所 | Two-way output constant current LED (Light-Emitting Diode) driving circuit |
| CN104659755A (en) * | 2013-11-21 | 2015-05-27 | 海洋王（东莞）照明科技有限公司 | LED constant current driving protection circuit and lamp |
| CN106466507A (en) * | 2016-10-13 | 2017-03-01 | 上海健康医学院 | A kind of isolated programmed electrical stimulation device |
| CN107318197A (en) * | 2017-08-17 | 2017-11-03 | 无锡市益明光电有限公司 | A kind of LED multi-path current balance circuit |
| CN112968425A (en) * | 2021-04-30 | 2021-06-15 | 重庆斯微奇电子技术有限公司 | Secondary short-circuit protection circuit of switching power supply |
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| KR100201302B1 (en) * | 1996-04-19 | 1999-06-15 | 이장헌 | Strange lamp automatic detection apparatus |
| CN201204722Y (en) * | 2007-12-28 | 2009-03-04 | 王元成 | Automatic light-adjusting LED illumination driver |
| CN101677214A (en) * | 2008-09-17 | 2010-03-24 | 比亚迪股份有限公司 | Switching mode power source |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100201302B1 (en) * | 1996-04-19 | 1999-06-15 | 이장헌 | Strange lamp automatic detection apparatus |
| CN201204722Y (en) * | 2007-12-28 | 2009-03-04 | 王元成 | Automatic light-adjusting LED illumination driver |
| CN101677214A (en) * | 2008-09-17 | 2010-03-24 | 比亚迪股份有限公司 | Switching mode power source |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104659755A (en) * | 2013-11-21 | 2015-05-27 | 海洋王（东莞）照明科技有限公司 | LED constant current driving protection circuit and lamp |
| CN104039039A (en) * | 2014-05-23 | 2014-09-10 | 中国科学院广州能源研究所 | Two-way output constant current LED (Light-Emitting Diode) driving circuit |
| CN104039039B (en) * | 2014-05-23 | 2017-01-04 | 中国科学院广州能源研究所 | A kind of constant current LED drive circuit exporting two-way |
| CN106466507A (en) * | 2016-10-13 | 2017-03-01 | 上海健康医学院 | A kind of isolated programmed electrical stimulation device |
| CN106466507B (en) * | 2016-10-13 | 2023-09-08 | 上海健康医学院 | Isolated program-controlled electric stimulator |
| CN107318197A (en) * | 2017-08-17 | 2017-11-03 | 无锡市益明光电有限公司 | A kind of LED multi-path current balance circuit |
| CN112968425A (en) * | 2021-04-30 | 2021-06-15 | 重庆斯微奇电子技术有限公司 | Secondary short-circuit protection circuit of switching power supply |
| CN112968425B (en) * | 2021-04-30 | 2023-02-21 | 重庆斯微奇电子技术有限公司 | Secondary short-circuit protection circuit of switching power supply |
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| CN103369769B (en) | 2016-09-07 |
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