CN202385336U - LED current control circuit - Google Patents
LED current control circuit Download PDFInfo
- Publication number
- CN202385336U CN202385336U CN 201120469497 CN201120469497U CN202385336U CN 202385336 U CN202385336 U CN 202385336U CN 201120469497 CN201120469497 CN 201120469497 CN 201120469497 U CN201120469497 U CN 201120469497U CN 202385336 U CN202385336 U CN 202385336U
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- control chip
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- control circuit
- auxiliary winding
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Abstract
The utility model relates to an LED current control circuit, comprising a boost circuit and a U1 control chip. The control circuit is equipped with an auxiliary winding, one end of the auxiliary winding is connected with the FB pin of the U1 control chip and the other end is grounded, and the auxiliary winding is coupled and connected with the inductor L1 of the boost circuit. The LED current control circuit uses the auxiliary winding to substitute the conventional sampling resistor to compute the switch turn-off time, so that the current control circuit efficiency is improved, the cost is reduced, and the stability and the security are improved.
Description
Technical field
The utility model relates to the switch power technology field, refers in particular to a kind of LED current control circuit.
Background technology
Because LED light-emitting diode conduction voltage drop is variant and change with temperature,, generally require the LED operating current constant for the luminosity that makes LED keeps constant and colour temperature is consistent.For the led drive circuit of booster type, adopt the operating current of a sampling resistor sampling LED usually, compare with a reference signal, and realize the LED current constant with a feedback control loop.Yet sampling resistor has increased power consumption, and the inefficacy of sampling resistor causes circuit overloads to be burnt easily, and feedback control loop causes the instability of system easily.Publication number CN201830140U; Open day on May 11st, 2011; Name is called in the Chinese utility model patent of " a kind of BOOST drive circuit, drive unit and LED liquid crystal module " and discloses a kind of BOOST drive circuit, drive unit and LED liquid crystal module; Replace the low-voltage driving high-voltage MOS pipe with two more ripe common metal-oxide-semiconductors of technology, elder generation drives high-voltage MOS pipe with the signal after boosting after with a metal-oxide-semiconductor signal of importing being risen to high pressure from low pressure again.Compared with prior art, this utility model has reached same effect with the lower Costco Wholesale of littler technical risk.But this utility model does not still solve sampling resistor exists the problem of bringing power consumption to increase.
The utility model content
The purpose of the utility model is the problem that the sampling resistor that overcomes the Boost booster circuit of LED in the prior art increases power consumption, provides the auxiliary winding of a kind of usefulness to replace sampling resistor, improves the power of circuit and the LED current control circuit of fail safe.
The purpose of the utility model is to be achieved through following technical proposals:
A kind of LED current control circuit comprises Boost booster circuit, U1 control chip, and control circuit is provided with auxiliary winding, and the FB pin of U1 control chip connects an end of auxiliary winding, the other end ground connection of auxiliary winding; The inductance L 1 of auxiliary winding and Boost booster circuit is of coupled connections.The voltage of the FB pin that auxiliary winding connects surpasses the rising edge and the trailing edge compute switch turn-off time Tons and the switch periods T that are lower than 0.1V of 0.1V, and the time of Tons just in time is the time of switching current from peak I pk to 0.Need not resistance sampling LED operating current, also need not export feedback control loop, realize the constant of LED operating current.
As a kind of preferred version, the Boost circuit also comprises triode Q1, diode D1, light-emitting diode group, filter capacitor C1; The Vin pin of U1 control chip connects input voltage vin; The Vin pin of U1 control chip also is connected with inductance L 1; The L1 other end is connected to the anode of diode D1, and the negative electrode of D1 is connected with an end of light-emitting diode group, the other end ground connection of light-emitting diode group; The negative electrode of D1 also is connected with filter capacitor C1, C1 other end ground connection; The OUT pin that the L1 other end also connects the D utmost point, the U1 control chip of Q1 connects the G utmost point of Q1, the emitter of Q1 connects resistance R 1, and the CS pin of U1 control chip is connected on the point that the S utmost point is connected with R1; The GND pin ground connection of U1 control chip.Its circuit working principle is following: during switch Q1 conducting, input voltage gives inductance L 1 charging, and electric current rises.When electric current rose to chip internal set point Ipk, switch turn-offed.Electric current is to diode D1 and output afterflow then, and inductance L 1 electric current descends simultaneously, drops to 0 up to electric current.Subsequently, chip at inner setting constantly, conducting Q1 once more, next switch periods begins.Control chip U1 is through detecting the boost switching current; Ipk is constant for the control switch current peak; While control chip U1 control switch duty ratio; The ON time Tons and the switch periods time T proportions constant that keep output diode D1, then the mean value
of the interior LED output current of switch periods is constant.
As a kind of preferred version, switching device Q1 is the switch MOS pipe.The switch MOS pipe provides electric current in the undesired signal source basically, and input impedance is high.
As a kind of preferred version, the U1 control chip is provided with the clocking capability module, and the clocking capability module connects the FB pin.The time of clocking capability module records Tons and cycle T.
As a kind of preferred version, the U1 control chip is provided with inner constant voltage control module, and inner constant voltage control module connects the FB pin.Its operation principle is when detecting FB greater than 0.4V, and in next switch periods, chip can reduce duty cycle of switching, reduces input current, thereby reduces output voltage.
The beneficial effect of the utility model is, through replacing the existing sampling resistor compute switch turn-off time with auxiliary winding, improved the efficient of current control circuit, and cost reduces, and stable fail safe is improved.
Description of drawings
Fig. 1 is a kind of circuit diagram of the utility model;
Fig. 2 is a kind of circuit diagram of prior art;
Fig. 3 is the current waveform of switching current through diode D1.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is further described.
A kind of LED current control circuit of the utility model, its circuit diagram is as shown in Figure 1, comprises U1 control chip, boost booster circuit, and the Boost circuit also comprises switch MOS pipe Q1, diode D1, light-emitting diode group, filter capacitor C1.The Vin pin of U1 control chip connects input voltage vin; The Vin pin of U1 control chip also is connected with inductance L 1; The L1 other end is connected to the anode of diode D1, and the negative electrode of D1 is connected with an end of light-emitting diode group, the other end ground connection of light-emitting diode group; The negative electrode of D1 also is connected with filter capacitor C1, C1 other end ground connection; The L1 other end also connects the D utmost point of Q1, the OUT pin of U1 control chip connects the S utmost point of the CS pin connection Q1 of the G utmost point of Q1, U1 control chip; The CS pin also is connected with an end of resistance R 1, the other end ground connection of resistance R 1; The GND pin ground connection of U1 control chip.Fig. 1 compares with the prior art circuits sketch map, and the utility model has been removed the sampling resistor that connects light-emitting diode group among Fig. 1, the direct ground connection of light-emitting diode group, and the FB pin of U1 control chip connects an end of auxiliary winding, the other end ground connection of auxiliary winding; The inductance L 1 of auxiliary winding and Boost booster circuit is of coupled connections.The operation principle of current control circuit is following: during switch Q1 conducting, input voltage gives inductance L 1 charging, and electric current rises.When electric current rose to chip internal set point Ipk, switch turn-offed.Electric current is to diode D1 and output afterflow then, and inductance L 1 electric current descends simultaneously, drops to 0 up to electric current.Subsequently, chip at inner setting constantly, conducting Q1 once more, next switch periods begins.According to Fig. 3 current waveform figure, wherein Tons is the ON time of diode D1, and T is a switch periods, and Toffs is the time of T-Tons.The rising edge that the voltage of the FB pin that the time of Tons is connected by auxiliary winding surpasses 0.1V calculates with the trailing edge that is lower than 0.1V.The mean value
of the LED output current in switch periods; Control chip U1 is through detecting the boost switching current; Ipk is constant for the control switch current peak; While control chip U1 control switch duty ratio; The ON time Tons of T output diode D1 and switch periods time T proportions constant are so Io is constant.
The above only is the preferred embodiment of the utility model, is not the utility model is done any pro forma restriction.Though the utility model discloses as above with preferred embodiment, yet be not in order to limit the utility model.Any those of ordinary skill in the art; Do not breaking away under the utility model technical scheme scope situation; All the method for above-mentioned announcement capable of using and technology contents are made many possible changes and modification to the utility model technical scheme, or are revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from the utility model technical scheme, all still belongs in the scope of the utility model technical scheme protection any simple modification, equivalent variations and modification that above embodiment did according to the technical spirit of the utility model.
Although this paper has used terms such as Boost circuit, feedback control circuit morely, do not get rid of the possibility of using other term.Using these terms only is in order to describe and explain the essence of the utility model more easily; It all is contrary with the utility model spirit being construed to any additional restriction to them.
Claims (5)
1. a LED current control circuit comprises Boost booster circuit, U1 control chip, it is characterized in that described control circuit is provided with auxiliary winding, and the FB pin of U1 control chip connects an end of auxiliary winding, the other end ground connection of auxiliary winding; The inductance L 1 of auxiliary winding and Boost booster circuit is of coupled connections.
2. a kind of LED current control circuit according to claim 1 is characterized in that the Boost circuit also comprises switching device Q1, diode D1, light-emitting diode group, filter capacitor C1; The Vin pin of U1 control chip connects input voltage vin; The Vin pin of U1 control chip also is connected with inductance L 1; The L1 other end is connected to the anode of diode D1, and the negative electrode of D1 is connected with an end of light-emitting diode group, the other end ground connection of light-emitting diode group; The negative electrode of D1 also is connected with filter capacitor C1, C1 other end ground connection; The OUT pin that the L1 other end also connects the D utmost point, the U1 control chip of Q1 connects the G utmost point of Q1, the S utmost point of Q1 connects resistance R 1, and the CS pin of U1 control chip is connected on the point that the S utmost point is connected with R1; The GND pin ground connection of U1 control chip.
3. a kind of LED current control circuit according to claim 2 is characterized in that described switching device Q1 is the switch MOS pipe.
4. a kind of LED current control circuit according to claim 1 is characterized in that described U1 control chip is provided with the clocking capability module, and the clocking capability module connects the FB pin.
5. according to claim 1 or 4 described a kind of LED current control circuits, it is characterized in that described U1 control chip is provided with inner constant voltage control module, inner constant voltage control module connects the FB pin.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201120469497 CN202385336U (en) | 2011-11-23 | 2011-11-23 | LED current control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201120469497 CN202385336U (en) | 2011-11-23 | 2011-11-23 | LED current control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202385336U true CN202385336U (en) | 2012-08-15 |
Family
ID=46633801
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201120469497 Expired - Fee Related CN202385336U (en) | 2011-11-23 | 2011-11-23 | LED current control circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN202385336U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102882373A (en) * | 2012-08-22 | 2013-01-16 | 深圳桑达国际电子器件有限公司 | Power electronic converter and direct-current step up circuit thereof |
-
2011
- 2011-11-23 CN CN 201120469497 patent/CN202385336U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102882373A (en) * | 2012-08-22 | 2013-01-16 | 深圳桑达国际电子器件有限公司 | Power electronic converter and direct-current step up circuit thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 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: 20120815 Termination date: 20171123 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |