CN203691709U - Non-isolated DC-DC constant current LED drive circuit - Google Patents
Non-isolated DC-DC constant current LED drive circuit Download PDFInfo
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- CN203691709U CN203691709U CN201420015317.8U CN201420015317U CN203691709U CN 203691709 U CN203691709 U CN 203691709U CN 201420015317 U CN201420015317 U CN 201420015317U CN 203691709 U CN203691709 U CN 203691709U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
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Abstract
The utility model discloses a non-isolated DC-DC constant current LED drive circuit. The circuit comprises a current control unit, a light modulation unit, a switch unit and a PFC chip. The PFC chip is connected to the current control unit, the light modulation unit and the switch unit. The circuit utilizes the PFC chip to replace the LED drive chip in the conventional drive circuit to achieve the DC-DC voltage reduction function. The PFC chip is used for detecting the current state of the current control unit, and the current control unit is used for reducing switch loss when current changes allows the LED to shift connection and disconnection states with the ground, so that a large oscillation pulse current is prevented from generating in the current control unit, and then the whole circuit achieves a good EMC function.
Description
Technical field
The utility model relates to LED lighting technical field, particularly a kind of non-isolation DC-DC constant current LED drive circuit.
Background technology
The application of non-isolation DC-DC constant current driver IC circuits is comparatively extensive, on the little current circuit of low pressure, uses less components and parts can realize respond well working effect especially.But in high-voltage great-current application, just there are some problems in existing non-isolation DC-DC driver IC circuits structure.
Existing non-isolation DC-DC driver IC circuits as shown in Figure 1.As can be seen from Figure 1, input voltage at power end Vbus is very high, and in the very low situation of the voltage of LED (pressure reduction between the anodal LED+ of LED and LED negative pole LED-), because the electric current of LED is determined by the sampling of resistance R a, in the resistance of resistance R a constant and load LED constant, the switching frequency of switching tube V is determined by inductance L.As long as the voltage on resistance R a reaches the magnitude of voltage (this magnitude of voltage drives chip IC inner setting by LED, and it is HV9961 that LED drives the model of chip IC) of setting, switching tube V will close; Now the inductive current in inductance L is not cut off, and is responsible for the afterflow effect of inductive current by fast diode D; The voltage on resistance R a constantly declines.When the lower voltage on resistance R a is after certain value, switching tube V conducting again, the inductive current of inductance L can flow to ground from switching tube V, now on switching tube V, can produce a very large oscillating impulse electric current, under the effect of the conducting resistance in conjunction with switching tube V inside, switching tube V can produce very large switching loss.And, along with a succession of larger On current, can have a strong impact on the EMC(Electro magnetic compatibility of whole circuit, Electro Magnetic Compatibility, the electromagnetic energy that the equipment of meaning produces neither produces and disturbs miscellaneous equipment, the ability that not disturbed by the electromagnetic energy of other equipment) function.
Thereby prior art need to improve.
Utility model content
In view of above-mentioned the deficiencies in the prior art part, the purpose of this utility model is to provide a kind of non-isolation DC-DC constant current LED drive circuit, to solve the problem that can produce oscillating impulse electric current on the switching tube of existing non-isolation DC-DC driver IC circuits, increase switching loss.
In order to achieve the above object, the utility model has been taked following technical scheme:
A kind of non-isolation DC-DC constant current LED drive circuit, it comprises:
For in the time that LED carries out break-make switching with ground, reduce the current control unit of switching loss;
For the pwm signal of input being converted to the light modulation unit of light modulation enabling signal;
Be used for the switch element of the open/close states of controlling PFC chip;
For light modulation enabling signal being changed to the operating state of dim signal control current control unit, and detect the PFC chip of the current status of current control unit;
Described PFC chip connects current control unit, light modulation unit and switch element.
Described non-isolation DC-DC constant current LED drive circuit, wherein, the model of described PFC chip is TDA4863;
Described current control unit comprises the first resistance, the second resistance, the 3rd resistance, inductance, switching tube, the first electric capacity and the first diode, the control end of described switching tube connects the GD end of PFC chip by the first resistance, the first link of switching tube connects the different name end of the positive pole of the first diode and the first winding of inductance, the second link of switching tube connects the Isense end of PFC chip, also by the 3rd grounding through resistance, the negative pole of described the first diode connects power end and LED positive pole, the Same Name of Ends of the first winding of described inductance connects LED negative pole, also connect LED positive pole by the first electric capacity, the Same Name of Ends of the second winding of inductance connects the GND end of PFC chip, the different name end of the second winding of inductance connects the ZCD end of PFC chip by the second resistance, the GND end ground connection of PFC chip.
Described non-isolation DC-DC constant current LED drive circuit, wherein, described switching tube is NMOS pipe, described the first diode is fast diode.
Described non-isolation DC-DC constant current LED drive circuit, wherein, described light modulation unit comprises the 4th resistance, the 5th resistance, the 6th resistance, the second electric capacity and the second diode, the Vsense that the negative pole of described the second diode connects PFC chip holds, also passes through the 6th grounding through resistance, the positive pole of the second diode connects brightness adjustment control end by the 5th resistance, and the second electric capacity and the 4th resistance are connected in parallel between the negative pole of the second diode and the VAout of PFC chip end.
Described non-isolation DC-DC constant current LED drive circuit, wherein, described switch element comprises the 7th resistance and the 3rd electric capacity, and the MULT that one end of described the 7th resistance connects PFC chip holds, also passes through the 3rd capacity earth, the other end connecting valve control end of the 7th resistance.
Described non-isolation DC-DC constant current LED drive circuit, wherein, also comprise the 4th electric capacity and the 5th electric capacity, described the 4th electric capacity is connected between power end and ground, one end of described the 5th electric capacity connects Vcc end and the operating voltage end of PFC chip, and the other end of the 5th electric capacity connects the GND end of PFC chip.
Compared to prior art, a kind of non-isolation DC-DC constant current LED drive circuit that the utility model provides, replace LED in existing drive circuit to drive chip to realize DC-DC buck functionality with PFC chip, detected the current status of current control unit by PFC chip, in the time that curent change causes LED and ground to carry out break-make switching, reduce switching loss by current control unit, avoid producing a very large oscillating impulse electric current in current control unit, make whole circuit there is good EMC function.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of existing non-isolation DC-DC constant current driver IC circuits.
Fig. 2 is the circuit diagram of the utility model non-isolation DC-DC constant current LED drive circuit preferred embodiment.
Embodiment
The utility model provides a kind of non-isolation DC-DC constant current LED drive circuit, replaces LED in existing drive circuit to drive chip to realize DC-DC buck functionality with PFC chip, avoids producing very large oscillating impulse electric current at switching tube, reduces switching loss.For making the purpose of this utility model, technical scheme and effect clearer, clear and definite, referring to the accompanying drawing embodiment that develops simultaneously, the utility model is further described.Should be appreciated that specific embodiment described herein is only in order to explain the utility model, and be not used in restriction the utility model.
Refer to Fig. 2, non-isolation DC-DC constant current LED drive circuit that the utility model provides comprises current control unit 100, light modulation unit 200, switch element 300 and PFC chip U1, and described PFC chip U1 connects current control unit 100, light modulation unit 200 and switch element 300.Described switch element 300 is controlled the open/close states (work or do not work) of PFC chip U1.The model of described PFC chip is TDA4863, due to circuit structure and the pin setting of PFC chip U1 self, directly the pwm signal of the outside input of reception & disposal, need to be converted to the pwm signal of input after light modulation enabling signal by light modulation unit 200, could be by PFC chip identification.Described PFC chip U1 is by the operating state of light modulation enabling signal conversion dim signal control current control unit, according to being connected between dim signal control LED and ground or disconnecting.In the time of normal work, because can making LED and ground, the curent change of current control unit 100 inside carries out break-make switching, need to be detected by PFC chip U1 the current status of current control unit, in the time that curent change causes LED and ground to carry out break-make switching, reduce switching loss by current control unit.
Wherein, described current control unit 100 comprises the first resistance R 1, the second resistance R 2, the 3rd resistance R 3, inductance, switching tube V1, the first capacitor C 1 and the first diode D1, and described switching tube V1 is NMOS pipe, and described the first diode D1 is fast diode.The control end (being the grid of NMOS pipe) of described switching tube V1 connects the GD end of PFC chip U1 by the first resistance R 1, the first link (being the drain electrode of NMOS pipe) of switching tube V1 connects the different name end of the positive pole of the first diode D1 and the first winding L A of inductance, the second link (being the source electrode of NMOS pipe) of switching tube V1 connects the Isense end of PFC chip, also by the 3rd resistance R 3 ground connection, the negative pole of described the first diode D1 connects power end Vbus and the anodal LED+ of LED, the Same Name of Ends of the first winding L A of described inductance connects LED negative pole LED-, also connect the anodal LED+ of LED by the first capacitor C 1, the Same Name of Ends of the second winding L B of inductance connects the GND end of PFC chip, the different name end of the second winding L B of inductance connects the ZCD end of PFC chip by the second resistance R 2, the GND end ground connection of PFC chip.
In the present embodiment, utilize the zero current detection pin (being ZCD end) of PFC chip, on the basis of existing inductance (being the first winding L A in the present embodiment), increase by the second winding L B and come the conducting of delay switch pipe, make again after electric current on the second winding L A is discharged switching tube conducting, can avoid producing oscillating impulse electric current; Specific works principle is as follows: in the time that whole circuit is normally worked, in the time that the voltage in the 3rd resistance R 3 reaches the magnitude of voltage of setting, switching tube V1 will close.The magnitude of voltage of described setting is determined by the model of PFC chip.Now the electric current on the first winding L A of inductance is responsible for afterflow by the first diode D1, and the voltage in the 3rd resistance R 3 is constantly declined.When the lower voltage in the 3rd resistance R 3 is to after certain value (as 0.3V), switching tube V1 does not now have conducting (switching tube of existing drive circuit at this moment can conducting).The present embodiment need to be waited until and be less than the value of setting by the induced current on the second winding L B of inductance (this value is determined by the model of PFC chip, in the present embodiment, be TDA4863) after, switching tube V1 is conducting again, and now the electric current on the first winding L A of inductance can become large gradually by zero.Therefore, on switching tube V1, just can not produce a very large oscillating impulse electric current, so both can reduce significantly the switching loss that switching tube V1 produces, and make whole circuit there is good EMC function.
Because adopting PFC chip, the utility model replace the LED in existing drive circuit to drive chip, the pwm signal of brightness adjustment control end PWM input can not directly be inputted (because the not relevant pin of this PFC chip) in PFC chip, therefore needs light modulation unit 200 to change.Described light modulation unit 200 comprises the 4th resistance R 4, the 5th resistance R 5, the 6th resistance R 6, the second capacitor C 2 and the second diode D2, the Vsense that the negative pole of described the second diode D2 connects PFC chip U1 holds, also passes through the 6th resistance R 6 ground connection, the positive pole of the second diode D2 connects brightness adjustment control end PWM by the 5th resistance R 5, and the second capacitor C 2 and the 4th resistance R 4 are connected in parallel between the negative pole of the second diode D2 and the VAout of PFC chip end.PFC chip U1 will light modulation enabling signal after conversion dim signal from its GD end output, control switch pipe V1 conducting or close, thus the break-make realizing between LED and ground is switched.
Because internal circuit setting and the pin of PFC chip are set, control when PFC chip opens and closes and need switch element 300 by after the switch controlling signal conversion of switch control end ON/OFF input, could be by PFC chip identification.In the present embodiment, described switch element 300 comprises the 7th resistance R 7 and the 3rd capacitor C 3, and the MULT that one end of described the 7th resistance R 7 connects PFC chip holds, also passes through the 3rd capacitor C 3 ground connection, the other end connecting valve control end ON/OFF of the 7th resistance R 7.
In order to stablize the power supply of LED and the power supply of PFC chip, described non-isolation DC-DC constant current LED drive circuit also comprises the 4th capacitor C 4 and the 5th capacitor C 5, described the 4th capacitor C 4 is connected between power end Vbus and ground, one end of described the 5th capacitor C 5 connects Vcc end and the operating voltage end Vcc of PFC chip, and the other end of the 5th capacitor C 5 connects the GND end of PFC chip.
In sum, a kind of non-isolation DC-DC constant current LED drive circuit that the utility model provides, the second winding L B by inductance carrys out control switch pipe turn on delay, electric current before switching tube conducting on the first winding of inductance discharges, and the electric current after switching tube conducting from the first winding becomes large gradually by zero; Switching tube conducting can avoid like this in prior art that inductive current does not discharge time, causes a very large oscillating impulse electric current producing on switching tube, reduces significantly the switching loss that switching tube produces, and makes whole circuit have good EMC function.
Be understandable that; for those of ordinary skills; can be equal to replacement or change according to the technical solution of the utility model and utility model design thereof, and all these changes or replacement all should belong to the protection range of the appended claim of the utility model.
Claims (6)
1. non-isolation DC-DC constant current LED drive circuit, is characterized in that, comprising:
For in the time that LED carries out break-make switching with ground, reduce the current control unit of switching loss;
For the pwm signal of input being converted to the light modulation unit of light modulation enabling signal;
Be used for the switch element of the open/close states of controlling PFC chip;
For light modulation enabling signal being changed to the operating state of dim signal control current control unit, and detect the PFC chip of the current status of current control unit;
Described PFC chip connects current control unit, light modulation unit and switch element.
2. non-isolation DC-DC constant current LED drive circuit according to claim 1, is characterized in that, the model of described PFC chip is TDA4863;
Described current control unit comprises the first resistance, the second resistance, the 3rd resistance, inductance, switching tube, the first electric capacity and the first diode, the control end of described switching tube connects the GD end of PFC chip by the first resistance, the first link of switching tube connects the different name end of the positive pole of the first diode and the first winding of inductance, the second link of switching tube connects the Isense end of PFC chip, also by the 3rd grounding through resistance, the negative pole of described the first diode connects power end and LED positive pole, the Same Name of Ends of the first winding of described inductance connects LED negative pole, also connect LED positive pole by the first electric capacity, the Same Name of Ends of the second winding of inductance connects the GND end of PFC chip, the different name end of the second winding of inductance connects the ZCD end of PFC chip by the second resistance, the GND end ground connection of PFC chip.
3. non-isolation DC-DC constant current LED drive circuit according to claim 2, is characterized in that, described switching tube is NMOS pipe, and described the first diode is fast diode.
4. non-isolation DC-DC constant current LED drive circuit according to claim 2, it is characterized in that, described light modulation unit comprises the 4th resistance, the 5th resistance, the 6th resistance, the second electric capacity and the second diode, the Vsense that the negative pole of described the second diode connects PFC chip holds, also passes through the 6th grounding through resistance, the positive pole of the second diode connects brightness adjustment control end by the 5th resistance, and the second electric capacity and the 4th resistance are connected in parallel between the negative pole of the second diode and the VAout of PFC chip end.
5. non-isolation DC-DC constant current LED drive circuit according to claim 4, it is characterized in that, described switch element comprises the 7th resistance and the 3rd electric capacity, the MULT that one end of described the 7th resistance connects PFC chip holds, also passes through the 3rd capacity earth, the other end connecting valve control end of the 7th resistance.
6. non-isolation DC-DC constant current LED drive circuit according to claim 3, it is characterized in that, also comprise the 4th electric capacity and the 5th electric capacity, described the 4th electric capacity is connected between power end and ground, one end of described the 5th electric capacity connects Vcc end and the operating voltage end of PFC chip, and the other end of the 5th electric capacity connects the GND end of PFC chip.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420015317.8U CN203691709U (en) | 2014-01-10 | 2014-01-10 | Non-isolated DC-DC constant current LED drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420015317.8U CN203691709U (en) | 2014-01-10 | 2014-01-10 | Non-isolated DC-DC constant current LED drive circuit |
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| Publication Number | Publication Date |
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| CN203691709U true CN203691709U (en) | 2014-07-02 |
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| CN201420015317.8U Expired - Fee Related CN203691709U (en) | 2014-01-10 | 2014-01-10 | Non-isolated DC-DC constant current LED drive circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016041277A1 (en) * | 2014-09-19 | 2016-03-24 | 深圳Tcl新技术有限公司 | Led backlight boost drive circuit and liquid crystal display device |
| CN110650566A (en) * | 2019-09-12 | 2020-01-03 | 广州市哈雅光电设备有限公司 | High-power LED drive circuit |
-
2014
- 2014-01-10 CN CN201420015317.8U patent/CN203691709U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016041277A1 (en) * | 2014-09-19 | 2016-03-24 | 深圳Tcl新技术有限公司 | Led backlight boost drive circuit and liquid crystal display device |
| CN110650566A (en) * | 2019-09-12 | 2020-01-03 | 广州市哈雅光电设备有限公司 | High-power LED drive circuit |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20140702 Termination date: 20220110 |
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| CF01 | Termination of patent right due to non-payment of annual fee |