CN105357814A - Peak current detection circuit and method for LED constant current driving circuit - Google Patents
Peak current detection circuit and method for LED constant current driving circuit Download PDFInfo
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- CN105357814A CN105357814A CN201510515666.5A CN201510515666A CN105357814A CN 105357814 A CN105357814 A CN 105357814A CN 201510515666 A CN201510515666 A CN 201510515666A CN 105357814 A CN105357814 A CN 105357814A
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Abstract
The invention discloses a peak current detection circuit and method for an LED constant current driving circuit, and belongs to the technical fields of peak current detection circuits and methods. The peak current detection circuit comprises a peak current sampling resistance unit used for sampling an inductive current, a peak current detection unit used for performing peak value detection on the sampled inductive current, a zero-crossing detection unit used for detecting a resonant voltage of a drain of a power switch tube to output an inductive current zero-crossing signal, a constant current control unit used for performing constant current control on the output current of an LED driving power supply, a logic and driving unit used for performing logic control on the output signal of the constant current control unit for further driving the power switch tube and controlling the peak current detection unit, a power switch tube unit for performing switched output for the control chip, and a power supply unit used for generating a VDD voltage for supplying power to each unit and for peak current detection.
Description
Technical field
The present invention relates to a kind of peak current detection circuit and method, particularly relate to a kind of peak current detection circuit for constant current driver circuit for LED and method.
Background technology
In constant current driver circuit for LED, the control mode adopting former limit to feed back widely is to realize the current constant control of output current.The control mode of former limit feedback, in order to realize the current constant control of output current, except needing accurately to detect except the moment of transformer secondary output winding current zero passage, also needs the peak current accurately detecting primary winding.
In the peak current detecting primary winding, traditional solution is the electric current utilizing sampling resistor sampling primary winding, and is that sampled voltage is input to control chip by this current conversion.Compared by the reference voltage of this input voltage and control chip inside in control chip inside, the result compared is as the peak current detection signal of armature winding.
Fig. 1 is traditional constant current driver circuit for LED with primary winding peak current detection circuit, generally includes: rectifier bridge D1 ~ D4, input filter capacitor C1, starting resistance R3, power supply electric capacity C2, control chip U1, FB divider resistance R1, R2, rectifier diode D5, peak current sampling resistor R4, power switch pipe Q1, transformer T1, secondary commutation diode D6, output capacitance C3, output resistance R5 and LED load LEDs.In power switch pipe Q1 conduction period, the primary winding current of transformer T1 in time slope rises, and the voltage now on peak current sampling resistor R4 also in time slope rises and is input to control chip inside.As shown in Figure 2, compare at a reference voltage of control chip this input voltage inner and chip internal.When the reference voltage height of this input voltage than control chip inside, comparator exports a peak current detection signal and delivers in constant-current control circuit.
Traditional peak current detection circuit generally adopts and directly the method that peak current sampled voltage and a reference voltage compare is produced a peak current detection signal.This peak current detection method needs control chip to need the pins such as GND, CS, VCC, FB and GD, simultaneously control chip GND be systematically connected.In the LED drive power design of exquisite circuit cost, the design of peripheral component is more and more simplified, and the pin of control chip is also fewer and feweri.As shown in Figure 3, be the inverse-excitation type constant current driver circuit for LED of low cost of the present invention, this control chip only has DRN, VDD and GND tri-pins, and encapsulation is simple, and cost is cheap.Traditional peak current detection technology can not meet the pin requirement of this control chip, in the application of the LED constant current driving power of low cost, more and more have limitation.
Summary of the invention
For traditional deficiency with the constant current driver circuit for LED of peak current detection circuit and limitation, the invention provides a kind of peak current detection circuit for constant current driver circuit for LED.Described peak current detection circuit comprises: a peak current sampling resistor unit, for sampling to inductive current; One peak current detection unit, for carrying out peakvalue's checking to sampled inductive current, exports a peak current detection signal; One zero passage detection unit, the resonance potential for draining to power switch pipe detects the signal exporting an inductive current zero passage; One constant-current control unit, for carrying out current constant control to the output current of LED drive power; One logical AND driver element, for carrying out logic control to the output signal of constant-current control unit, and then driving power switching tube and control peak current detection unit; One power switch pipe unit, carries out switch output to control chip; One power supply unit, powers for generation of giving each unit and for the vdd voltage of peak current detection.
Further, as shown in Figure 4, invention also provides a kind of constant current driver circuit for LED, described constant current driver circuit for LED also comprises: a rectifier bridge, input filter capacitor, VDD filter capacitor, transformer, output diode, output capacitance, output resistance and LED load.
Further, as shown in Figure 6, invention also provides a kind of constant current driver circuit for LED, described constant current driver circuit for LED also comprises: a rectifier bridge, input filter capacitor, VDD filter capacitor, power inductance, fly-wheel diode, output capacitance, output resistance and LED load.
Further, an input of described peak current detection unit connects the output of described peak current sampling resistor unit, and the output of peak current detection unit connects first input of described constant-current control unit; Another input of described constant-current control unit connects the output of described zero passage detection unit, and the output of constant-current control unit connects the input of described logical AND driver element; An output of described logical AND driver element connects the gate input of described power switch pipe unit and second input of described peak current detection unit respectively, and two other output of logical AND driver element connects the 3rd and the 4th input of described peak current detection unit respectively; The source electrode output of described power switch pipe unit connects the output of described peak current sampling resistor unit, and the drain output of power switch pipe unit connects the input of described power supply unit and the input of described zero passage detection unit respectively; The output of described power supply connects the input of VDD filter capacitor.
Further, described peak current detection unit comprises: a switch control logic unit, the first switch, second switch, 3rd switch, the 4th switch, the 5th switch, sampling holding capacitor, operation amplifier and comparator unit, the first reverser unit and the second reverser unit; Three inputs of described switch control logic unit connect three outputs of described logical AND driver element respectively, and five outputs of switch control logic unit control the closed of described first switch, second switch, the 3rd switch, the 4th switch and the 5th switch respectively and disconnect; One end of described first switch connects the output of chip ground and described peak current sampling resistor unit, and the other end connects the positive input terminal of described operation amplifier and comparator unit; The peak current detection reference voltage of one end connection control chip internal of described second switch, the other end connects the positive input terminal of described operation amplifier and comparator unit; One end of described 3rd switch connects the output of described operation amplifier and comparator unit, and the other end connects the negative input end of described operation amplifier and comparator unit and one end of described sampling holding capacitor; The other end of described sampling holding capacitor connects the output VDD power supply of described power supply; One end of described 4th switch connects the output of described operation amplifier and comparator unit, and the other end connects the input of described first inverter module and one end of described 5th switch; The other end of described 5th switch connects chip ground; The input of described second reverser unit connects the output of described first inverter module, and the output of the second reverser unit is connected to first input of described constant-current control unit.
The invention provides a kind of peak current detection method for constant current driver circuit for LED, apply the above-mentioned peak current detection circuit for constant current driver circuit for LED, be specially: described power switch pipe blocking interval, described operation amplifier and comparator unit are operated in operational amplifier state, described peak current detection reference voltage is sampled the negative input end of described operational amplifier and is kept by sampling holding capacitor; In described power switch pipe conduction period, described operation amplifier and comparator unit are operated in comparator state, the positive input chip termination ground of described comparator; Now described vdd voltage relative to chip along with the rising of peak current sampled voltage slope decline, because the voltage at holding capacitor two ends of sampling remains unchanged, when peak current sampled voltage rises to described peak current detection reference voltage threshold value, described vdd voltage have dropped described peak current detection reference voltage threshold size relative to chip, now the negative input end voltage drop of described comparator is to zero, comparator overturns and exports peak current detection signal, thus achieves the peak current detection of described constant current driver circuit for LED.
The invention provides the application of the above-mentioned peak current detection circuit for constant current driver circuit for LED, the described peak current detection circuit for constant current driver circuit for LED be applied to step-down, boosting, buck, flyback multiple topology LED constant current driving power source system in.
The present invention has following advantage and effect relative to prior art:
Compared with traditional peak current detection technology for constant current driver circuit for LED, peak current detection circuit for constant current driver circuit for LED of the present invention, carried out the variable quantity of indirect detection peak current sampled voltage by differential mode detection vdd voltage relative to the variable quantity on chip ground, thus achieve the peak current detection to constant current driver circuit for LED.This peak current detection technology only needs control chip to have three packaging pins, makes the encapsulation of control chip become simple, has also simplified the design of peripheral component simultaneously, has saved the cost of LED drive power.Exquisite circuit cost LED drive power design in, of the present invention can be more and more obvious for the peak current detection circuit of constant current driver circuit for LED and the advantage of method.
Accompanying drawing explanation
Can be further understood by following detailed Description Of The Invention and institute's accompanying drawings about the advantages and spirit of the present invention.
Fig. 1 is traditional inverse-excitation type constant current driver circuit for LED with peak current detection circuit;
Fig. 2 is traditional peak current detection comparator circuit;
Fig. 3 is the inverse-excitation type constant current driver circuit for LED with peak current detection circuit of the present invention;
Fig. 4 is the first enforcement figure with the constant current driver circuit for LED of peak current detection circuit of the present invention;
Fig. 5 is the key node oscillogram with the first embodiment of the constant current driver circuit for LED of peak current detection circuit of the present invention;
Fig. 6 is the second enforcement figure with the constant current driver circuit for LED of peak current detection circuit of the present invention;
Fig. 7 is a concrete enforcement figure of peak current detection circuit of the present invention.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
The control chip pin that the invention solves traditional peak current detection technology for constant current driver circuit for LED is more, the problems such as driving power cost is higher, provide peak current detection circuit and the method for the constant current driver circuit for LED solving this problem.Carried out the variable quantity of indirect detection peak current sampled voltage by differential mode detection vdd voltage relative to the variable quantity on chip ground, thus achieve the object of the peak current detection to constant current driver circuit for LED.
First embodiment
As shown in Figure 4, be the first embodiment of the peak current detection circuit for constant current driver circuit for LED of the present invention.Peak current detection circuit 409 for constant current driver circuit for LED comprises: peak current sampling resistor unit 403, peak current detection unit 410, zero passage detection unit 411, constant-current control unit 412, logical AND driver element 413, power supply unit 414, power switch pipe unit 415.
The described peak current detection circuit for constant current driver circuit for LED also comprises rectifier bridge 400, input filter capacitor 401, transformer 404, secondary commutation diode 405, output capacitance 406, output resistance 407, LED load 408.
At described power switch pipe unit 415 blocking interval, the output voltage VDD of described power supply unit 414 is a constant direct voltage relative to the voltage on chip ground, equal relative to voltage systematically with VDD.Now, on described peak current sampling resistor unit 403, voltage is zero, and chip ground is equal with current potential systematically.In described power switch pipe unit 415 conduction period, the voltage in described peak current sampling resistor electricity unit 403 in time slope rises, then described chip ground also in time slope rises relative to voltage systematically.Due to the voltages keep constant on described VDD filter capacitor unit 402, then the output voltage VDD of described power supply unit 414 declines on slope in time relative to the voltage on chip ground.When described VDD reaches the peak current detection reference voltage threshold value set by chip internal relative to the slippage of the voltage on chip ground, described peak current detection unit 410 exports the peak current detection signal of a high level, deliver in described constant-current control unit 412, achieve peak current detection.
Fig. 5 is the key node oscillogram with the first embodiment of the constant current driver circuit for LED of peak current detection circuit of the present invention.As we can see from the figure, at power switch pipe blocking interval, the electric current of primary winding is zero, VDD is a constant voltage relative to the voltage on chip ground; In power switch pipe conduction period, the electric current of primary winding in time slope rises, and VDD declines with same slope relative to the voltage on chip ground simultaneously.When the electric current of primary winding rises to peak current, the voltage drop peak current detection threshold quantity on VDD opposite chip ground, now power switch pipe starts again to turn off.Simultaneously as we can see from the figure, detecting VDD by differential mode can the peak current value of indirect detection primary winding relative to the voltage variety on chip ground.
Second embodiment
As shown in Figure 6, be the second embodiment of the peak current detection circuit for constant current driver circuit for LED of the present invention.Peak current detection circuit 609 for constant current driver circuit for LED comprises: peak current sampling resistor unit 603, peak current detection unit 610, zero passage detection unit 611, constant-current control unit 612, logical AND driver element 613, power supply unit 614, power switch pipe unit 615.
The described peak current detection circuit for constant current driver circuit for LED also comprises rectifier bridge 600, input filter capacitor 601, VDD filter capacitor unit 602, power inductance 604, fly-wheel diode 605, output capacitance 606, output resistance 607, LED load 608.
Specifically, the peak current detection circuit design of the present embodiment is identical with the first embodiment, and the operation principle of its peak current detection is also identical with process, does not repeat them here.Difference is, the constant current driver circuit for LED of the present embodiment is buck drive circuit, instead of the inverse-excitation type drive circuit of described first embodiment; Accordingly, the present embodiment have employed power inductance 604, instead of transformer is as energy-storage travelling wave tube, eliminates secondary winding, and this saves the cost of system further and reduces the volume of LED drive power.
Fig. 7 is a concrete enforcement figure of peak current detection unit in the present invention.Described peak current detection unit is by switch control logic unit 700, first switch 701, second switch 702,3rd switch 705,4th switch the 706, five switch 707, sampling holding capacitor 703, operation amplifier and comparator unit 704, first reverser unit 708 and the second reverser unit 709 form.The peak current of described peak current detection unit to described constant current driver circuit for LED detects.When described power switch pipe turns off, described second switch 702 is closed after the minimum turn-off time of described power switch pipe, described first switch 701 disconnects simultaneously, and now described peak current detection reference voltage is added in the positive input terminal of described operation amplifier and comparator unit 704.Accordingly, described 3rd switch 705 and described 5th switch 707 close, and described 4th switch 706 disconnects; Now, described operation amplifier and comparator unit 704 are operated in operational amplifier state.Therefore, the negative input end voltage of described operation amplifier and comparator unit 704 equals its positive input terminal voltage, and carries out sampling maintenance by described sampling holding capacitor 703 to described negative input end voltage; Meanwhile, described second reverser unit 709 exports a low level signal.When described power switch pipe conducting, described second switch 702 disconnects, and described first switch 701 closes, and now the positive input terminal of described operation amplifier and comparator unit 704 is connected to chip ground.Accordingly, described 3rd switch 705 disconnects, and described 4th switch 706 closes; Now, described operation amplifier and comparator unit 704 are operated in comparator state.After the minimum ON time of described power switch pipe, described 5th switch 707 disconnects.In described power switch pipe conduction period, the voltage on described peak current sampling resistor unit in time slope rises, and therefore the output voltage VDD of described power supply unit declines with corresponding slope relative to chip.Because the voltage at described sampling holding capacitor 703 two ends remains unchanged, then the negative input end voltage of described operation amplifier and comparator unit 704 also declines with corresponding slope relative to chip ground.When described operation amplifier and comparator unit 704 negative input end voltage relative to chip drop to zero time, the voltage rise on described peak current sampling resistor unit is to peak current detection reference voltage threshold value; Now, the output of described operation amplifier and comparator unit 704 is overturn by low level is high level; Accordingly, described second inverter module 709 exports the peak current detection signal of a high level.Now, described power switch pipe turns off again, then described operation amplifier and comparator unit 704 are operated in operational amplifier state again.So repeatedly, the detection of the peak current to constant current driver circuit for LED is achieved.
Described in this specification is only preferably embodiment of the present invention, for illustration of technical scheme of the present invention, but not limitation of the present invention, all those skilled in the art according to design of the present invention by logical analysis, reasoning, or a limited experiment to invention has been some adjustment and changing and the technical scheme that obtains, such as the technology of peak current detection circuit of the present invention is applied in boosting, in the LED drive power of the topology such as buck.Be still main idea place of the present invention, all should be within the scope of the present invention.
Claims (7)
1. for a peak current detection circuit for constant current driver circuit for LED, it is characterized in that, described peak current detection circuit comprises:
One peak current sampling resistor unit, for sampling to inductive current;
One peak current detection unit, for carrying out peakvalue's checking to sampled inductive current, exports a peak current detection signal;
One zero passage detection unit, the resonance potential for draining to power switch pipe detects the signal exporting an inductive current zero passage;
One constant-current control unit, for carrying out current constant control to the output current of LED drive power;
One logical AND driver element, for carrying out logic control to the output signal of constant-current control unit, and then driving power switching tube and control peak current detection unit;
One power switch pipe unit, carries out switch output to control chip;
One power supply unit, powers for generation of giving each unit and for the vdd voltage of peak current detection.
2., as claimed in claim 1 for the peak current detection circuit of constant current driver circuit for LED, it is characterized in that, described constant current driver circuit for LED also comprises: a rectifier bridge, input filter capacitor, VDD filter capacitor, transformer, output diode, output capacitance, output resistance and LED load.
3., as claimed in claim 1 for the peak current detection circuit of constant current driver circuit for LED, it is characterized in that, described constant current driver circuit for LED also comprises: a rectifier bridge, input filter capacitor, VDD filter capacitor, power inductance, fly-wheel diode, output capacitance, output resistance and LED load.
4. as claimed in claim 1 for the peak current detection circuit of constant current driver circuit for LED, it is characterized in that, an input of described peak current detection unit connects the output of described peak current sampling resistor unit, and the output of peak current detection unit connects first input of described constant-current control unit; Another input of described constant-current control unit connects the output of described zero passage detection unit, and the output of constant-current control unit connects the input of described logical AND driver element; An output of described logical AND driver element connects the gate input of described power switch pipe unit and second input of described peak current detection unit respectively, and two other output of logical AND driver element connects the 3rd and the 4th input of described peak current detection unit respectively; The source electrode output of described power switch pipe unit connects the output of described peak current sampling resistor unit, and the drain output of power switch pipe unit connects the input of described power supply unit and the input of described zero passage detection unit respectively; The output of described power supply connects the input of VDD filter capacitor.
5. as claimed in claim 1 for the peak current detection circuit of constant current driver circuit for LED, it is characterized in that, described peak current detection unit comprises: a switch control logic unit, the first switch, second switch, 3rd switch, 4th switch, the 5th switch, sampling holding capacitor, operation amplifier and comparator unit, the first reverser unit and the second reverser unit; Three inputs of described switch control logic unit connect three outputs of described logical AND driver element respectively, and five outputs of switch control logic unit control the closed of described first switch, second switch, the 3rd switch, the 4th switch and the 5th switch respectively and disconnect; One end of described first switch connects the output of chip ground and described peak current sampling resistor unit, and the other end connects the positive input terminal of described operation amplifier and comparator unit; The peak current detection reference voltage of one end connection control chip internal of described second switch, the other end connects the positive input terminal of described operation amplifier and comparator unit; One end of described 3rd switch connects the output of described operation amplifier and comparator unit, and the other end connects the negative input end of described operation amplifier and comparator unit and one end of described sampling holding capacitor; The other end of described sampling holding capacitor connects the output VDD power supply of described power supply; One end of described 4th switch connects the output of described operation amplifier and comparator unit, and the other end connects the input of described first inverter module and one end of described 5th switch; The other end of described 5th switch connects chip ground; The input of described second reverser unit connects the output of described first inverter module, and the output of the second reverser unit is connected to first input of described constant-current control unit.
6. the peak current detection method for constant current driver circuit for LED, it is characterized in that, application rights requires the peak current detection circuit for constant current driver circuit for LED described in 1 ~ 5 any one, be specially: described power switch pipe blocking interval, described operation amplifier and comparator unit are operated in operational amplifier state, described peak current detection reference voltage is sampled the negative input end of described operational amplifier and is kept by sampling holding capacitor; In described power switch pipe conduction period, described operation amplifier and comparator unit are operated in comparator state, the positive input chip termination ground of described comparator; Now described vdd voltage relative to chip along with the rising of peak current sampled voltage slope decline, because the voltage at holding capacitor two ends of sampling remains unchanged, when peak current sampled voltage rises to described peak current detection reference voltage threshold value, described vdd voltage have dropped described peak current detection reference voltage threshold size relative to chip, now the negative input end voltage drop of described comparator is to zero, comparator overturns and exports peak current detection signal, thus achieves the peak current detection of described constant current driver circuit for LED.
7. the application of the peak current detection circuit for constant current driver circuit for LED described in any one of claim 1-5, it is characterized in that, the described peak current detection circuit for constant current driver circuit for LED be applied to step-down, boosting, buck, flyback multiple topology LED constant current driving power source system in.
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| CN201510515666.5A CN105357814B (en) | 2015-08-20 | 2015-08-20 | A kind of peak current detection circuit and method for constant current driver circuit for LED |
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| CN201510515666.5A CN105357814B (en) | 2015-08-20 | 2015-08-20 | A kind of peak current detection circuit and method for constant current driver circuit for LED |
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| CN106714367A (en) * | 2016-11-16 | 2017-05-24 | 深圳市必易微电子有限公司 | Constant current circuit and constant current controller thereof |
| CN107277966A (en) * | 2017-07-13 | 2017-10-20 | 深圳市梓晶微科技有限公司 | One kind is used for high power factor LED drive power switching frequency limiting circuit |
| CN107660013A (en) * | 2016-07-26 | 2018-02-02 | 上海莱托思电子科技有限公司 | A kind of LED both ends constant-current driven chip and constant current driving method |
| CN115219770A (en) * | 2022-09-20 | 2022-10-21 | 昆山硕通电子有限公司 | Voltage detection device, voltage sampling circuit and isolation power supply |
| CN115951116A (en) * | 2023-03-15 | 2023-04-11 | 常州同惠电子股份有限公司 | Peak current detection system and test method |
| CN116466122B (en) * | 2023-04-18 | 2024-04-19 | 海光信息技术(成都)有限公司 | Current detection circuit, method, chip, electronic component and electronic device |
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