CN204291527U - LED drive circuit and constant-current driver - Google Patents
LED drive circuit and constant-current driver Download PDFInfo
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- CN204291527U CN204291527U CN201420866633.6U CN201420866633U CN204291527U CN 204291527 U CN204291527 U CN 204291527U CN 201420866633 U CN201420866633 U CN 201420866633U CN 204291527 U CN204291527 U CN 204291527U
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Abstract
The utility model provides a kind of LED drive circuit and constant-current driver, and this driver comprises: power switch, and input receives input voltage, and output connects sampling resistor incoming end; Error amplifier, compares to produce error signal with the first reference voltage preset by sampled voltage; Peak current comparator, the second reference voltage comparing conducting voltage and preset, its output produces cut-off signals in response to this conducting voltage reaches this second reference voltage, and conducting voltage corresponds to the On current of power switch conduction period; Turn-off time control circuit, determines the turn-off time according to error signal, produces open signal in response to timing reaches the turn-off time; Logic and driver circuitry, opens power switch in response to opening signal, the switch-off power switch in response to cut-off signals.The utility model, when output current is very little, still can uses less inductance to realize current constant control, be conducive to the miniaturization realizing LED drive circuit.
Description
Technical field
The utility model relates to switch power technology, particularly relates to a kind of LED drive circuit and constant-current driver.
Background technology
With reference to figure 1, the LED drive circuit of the buck configuration of traditional source drive mainly comprises constant-current driver 100, resistance R1, sustained diode 1, output load capacitance C1, input capacitance C2, inductance L 1, first power switch M1 and sampling resistor Rcs, wherein, constant-current driver 100 comprises zero cross detection circuit 101, logic and driver circuitry 102, comparator circuit 103, rest-set flip-flop circuit 104 and the second power switch M2.When the first power switch M1 conducting, second power switch M2 also conducting time, input current flows through output load capacitance C1 and output, inductance L 1, second power switch M2, the first power switch M1, sampling resistor Rcs, and the electric current in inductance L 1 increases, inductance L 1 stored energy.Now, flow through output load capacitance C1 identical with the electric current flowing through sampling resistor Rcs with the electric current of output, the ON time of the first power switch M1 and the second power switch M2 is controlled by peak value Current-Limiting Comparator circuit 103, when the electric current flowing through sampling resistor Rcs reaches set point Vr1/Rcs, peak value Current-Limiting Comparator circuit 103 overturns, and produces the drive singal GT of shutoff first power switch M1 and the second power switch M2 through rest-set flip-flop circuit 104, logic and driver circuitry 102.Wherein, Vr1 is the magnitude of voltage of the reference voltage Vr1 that peak value Current-Limiting Comparator circuit 103 receives, and Rcs is the resistance value of sampling resistor Rcs.
First power switch M1 and the second power switch M2 close and have no progeny, and the electric current in inductance L 1 is through sustained diode 1 afterflow, and the electric current in inductance L 1 reduces, and inductance L 1 releases energy output load capacitance C1 and output.When the electric current in inductance L 1 reduces to zero, zero cross detection circuit 101 detects the zero passage of inductance L 1 electric current, produce zero passage detection signal ZCD to rest-set flip-flop circuit 104, produce the drive singal GT opening the first power switch M1, the second power switch M2 through logic and driver circuitry 102.
First power switch M1 and the second power switch M2 repeats switch motion above, and circuit continuous firing, is in critical current mode conducting state all the time.
Composition graphs 1 and Fig. 2, under critical current mode conduction mode, export the half that average current is the peak current of inductance L 1 substantially.And the peak current of inductance L 1 is fixed as Vr1/Rcs, so just can controls to output to the current constant on load LED, thus reach constant current object.
The output current control of circuit realiration shown in Fig. 1, circuit is simple, and cost is cheap.Owing to exporting the half that average current is inductance L 1 current peak substantially, when output current is very little, peak current is also very little.Be unlikely to too little to control ON time, the inductance value of General Requirements inductance L 1 is enough large, otherwise circuit cannot normally work, and at this moment the volume of inductance L 1 will become very large, causes cost to raise, is also unfavorable for the miniaturization of whole LED drive circuit.
Utility model content
Problem to be solved in the utility model is to provide a kind of LED drive circuit and constant-current driver, when output current is very little, less inductance still can be used to realize current constant control, be conducive to the miniaturization realizing LED drive circuit.
For solving the problems of the technologies described above, the utility model provides a kind of constant-current driver of LED drive circuit, comprising:
Power switch, its input connects voltage input end to receive input voltage, and its output connects sampling resistor incoming end;
Error amplifier, is connected to described sampling resistor incoming end directly or indirectly to receive sampled voltage, is compared to produce error signal by this sampled voltage with the first reference voltage preset, and this sampled voltage corresponds to the output current of described LED drive circuit;
Peak current comparator, its first input end receives conducting voltage, its second input receives the second reference voltage preset, its output produces cut-off signals in response to this conducting voltage reaches this second reference voltage, and described conducting voltage corresponds to the On current that described power switch conduction period flows through this power switch;
Turn-off time control circuit, receives described error signal, determines the turn-off time according to this error signal, reaches the described turn-off time in response to timing, produces and opens signal;
Logic and driver circuitry, opens signal in response to described and open described power switch, turning off described power switch in response to described cut-off signals.
According to an embodiment of the present utility model, described power switch comprises:
First power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its gate configuration is for connect described voltage input end via the first resistance;
Second power tube, its drain electrode connects the source electrode of described first power tube, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
According to an embodiment of the present utility model, described power switch comprises:
3rd power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its grid connects the output of described logic and driver circuitry;
Built-in sampling resistor, its first end connects the source electrode of described 3rd power tube, and its second end connects described sampling resistor incoming end;
4th power tube, its drain electrode connects described voltage input end, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
In order to solve the problem, the utility model additionally provides a kind of LED drive circuit, and comprise constant-current driver and output current sample circuit, described constant-current driver comprises:
Power switch, its input connects voltage input end to receive input voltage, and its output connects sampling resistor incoming end;
Error amplifier, is connected to described sampling resistor incoming end directly or indirectly to receive sampled voltage, is compared to produce error signal by this sampled voltage with the first reference voltage preset, and this sampled voltage corresponds to the output current of described LED drive circuit;
Peak current comparator, its first input end receives conducting voltage, its second input receives the second reference voltage preset, its output produces cut-off signals in response to this conducting voltage reaches this second reference voltage, and described conducting voltage corresponds to the On current that described power switch conduction period flows through this power switch;
Turn-off time control circuit, receives described error signal, determines the turn-off time according to this error signal, reaches the described turn-off time in response to timing, produces and opens signal;
Logic and driver circuitry, opens signal in response to described and open described power switch, turning off described power switch in response to described cut-off signals;
The first end of described output current sample circuit connects described sampling resistor incoming end, second end of described output current sample circuit is connected with the output of described LED drive circuit directly or indirectly, and described output current sample circuit comprises sampling resistor in parallel and filter capacitor.
According to an embodiment of the present utility model, described power switch comprises:
First power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its gate configuration is for connect described voltage input end via the first resistance;
Second power tube, its drain electrode connects the source electrode of described first power tube, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
According to an embodiment of the present utility model, described power switch comprises:
3rd power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its grid connects the output of described logic and driver circuitry;
Built-in sampling resistor, its first end connects the source electrode of described 3rd power tube, and its second end connects described sampling resistor incoming end;
4th power tube, its drain electrode connects described voltage input end, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
According to an embodiment of the present utility model, described LED drive circuit also comprises:
Inductance, its first end connects the second end of described output current sample circuit, and its second end connects the output of described LED drive circuit;
Output capacitance, its first end connects the output of described LED drive circuit, and its second end connects the reference ground of described LED drive circuit, and described output capacitance is configured in parallel with load;
Fly-wheel diode, its negative pole connects the first end of described output current sample circuit, and its positive pole connects the reference ground of LED drive circuit.
According to an embodiment of the present utility model, the first end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage transfers to described error amplifier via positive and negative level shifting circuit.
According to an embodiment of the present utility model, the second end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage directly transfers to described error amplifier.
According to an embodiment of the present utility model, described LED drive circuit also comprises:
Inductance, its first end connects the first end of described output current sample circuit, and its second end connects the reference ground of described LED drive circuit;
Output capacitance, its first end connects the second end of output current sample circuit and the output of described LED drive circuit, and described output capacitance is configured in parallel with load;
Fly-wheel diode, its positive pole connects the second end of described inductance, and its negative pole connects the second end of output capacitance.
According to an embodiment of the present utility model, the first end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage directly transfers to described error amplifier.
According to an embodiment of the present utility model, described LED drive circuit also comprises: building-out capacitor, and its first end connects the output of described error amplifier, and its second end is connected to the reference ground of described constant-current driver.
Compared with prior art, the utility model has the following advantages:
The LED drive circuit Direct Sampling output current of the utility model embodiment, exporting sample circuit adopts sampling resistor in parallel and filter capacitor to obtain average output current, the turn-off time of power switch is controlled through error amplifier, peak current comparator Direct Sampling flows through the electric current of power switch, the cut-off signals that the ON time of power switch is exported by peak current comparator is determined, this LED drive circuit is without the need to detecting inductive current zero passage, only need set inductance peak current and export average current, just accurately can control output current.This LED drive circuit is particularly useful for the less application scenarios of output current, when output current is very little, less inductance still can be used to realize current constant control, be conducive to the miniaturization of LED drive circuit.
Accompanying drawing explanation
Fig. 1 is the electrical block diagram of a kind of LED drive circuit in prior art;
Fig. 2 is the working signal oscillogram of LED drive circuit shown in Fig. 1;
Fig. 3 is the electrical block diagram of the LED drive circuit according to the utility model first embodiment;
Fig. 4 is the electrical block diagram of a kind of turn-off time control circuit in the LED drive circuit according to the utility model first embodiment;
Fig. 5 is according to the electrical block diagram of the LED drive circuit of the utility model second embodiment;
Fig. 6 is the electrical block diagram of the LED drive circuit according to the utility model the 3rd embodiment;
Fig. 7 is the electrical block diagram of the LED drive circuit according to the utility model the 4th embodiment.
Embodiment
Below in conjunction with specific embodiments and the drawings, the utility model is described in further detail, but should not limit protection range of the present utility model with this.
First embodiment
With reference to figure 3, Fig. 3 shows the LED drive circuit of the first embodiment, this LED drive circuit is buck configuration, mainly comprises: constant-current driver 200, resistance R1, input capacitance C2, building-out capacitor C3, output current sample circuit 210, inductance L 1, electric capacity C1 and sustained diode 1.
Wherein, constant-current driver 200 can comprise: power switch, error amplifier 203, peak current comparator 202, turn-off time control circuit 201, logic and driver circuitry 204 and positive and negative level shifting circuit 205.
The input of power switch connects voltage input end to receive input voltage vin, and the output of power switch connects sampling resistor incoming end, and the control end of power switch is connected to the output of logic and driver circuitry 204.In a first embodiment, this power switch comprises: the first power tube M1, its drain electrode connects voltage input end to receive input voltage vin, and its source electrode connects the first input end of peak value current comparator 202, and its gate configuration is for be connected to voltage input end via resistance R1; Second power tube M2, the source electrode of its drain electrode connection first power tube M1, its source electrode connects sampling resistor incoming end, and its grid connects the output of logic and driver circuitry 204.
Error amplifier 203 is connected to sampling resistor incoming end to receive sampled voltage Vcs via positive and negative level shifting circuit 205, is compared to obtain error signal Vc by this sampled voltage Vcs with the first reference voltage Vr1 preset.
The first input end of peak current comparator 202 receives conducting voltage, its second input receives the second reference voltage Vr2 preset, reach the second reference voltage Vr2 in response to this conducting voltage, the signal upset of the output of this peak current comparator 202 is to produce cut-off signals Reset.This conducting voltage corresponds to the On current that power switch conduction period flows through this power switch, more specifically, in a first embodiment, source-drain voltage Vd2 when this conducting voltage is the second power tube M2 conducting, also be, during the second power tube M2 conducting, the pressure drop that the electric current flowing through the second power tube M2 produces in the conducting resistance of the second power tube M2.
Turn-off time control circuit 201 receives error signal Vc, determines the turn-off time according to this error signal Vc, reaches this turn-off time in response to timing, produces and opens signal Set.Turn-off time control circuit 201 can comprise timing circuit.
Logic and driver circuitry 204 produces drive singal GT according to opening signal Set and cut-off signals Reset, and this drive singal GT is in order to control the turn-on and turn-off of the second power tube M2.In response to opening signal Set, this logic and driver circuitry 204 controls the second power tube M2 conducting; In response to cut-off signals Reset, this logic and driver circuitry 204 controls the second power tube M2 and turns off.In other words, when reaching the turn-off time determined, open the first power tube M1 and the second power tube M2; When reaching the inductance peak current of setting, turn off the first power tube M1 and the second power tube M2.
The first end of output current sample circuit 210 connects the sampling resistor incoming end of constant-current driver 200, and its second end is connected to the output end vo ut of LED drive circuit via inductance L 1.This output current sample circuit 210 comprises sampling resistor Rcs in parallel and filter capacitor C4.In first embodiment, the first end of output current sample circuit 210 is connected to the reference ground GND2 of constant-current driver 200, sampled voltage Vcs is output from the second end of output current sample circuit 210, for the reference ground GND2 of constant-current driver 200, sampled voltage Vcs is negative level, therefore, adopting power conversion circuit 205 that the sampled voltage Vcs of negative level is converted to positive level in the first embodiment, is also-Vcs.
The first end of output capacitance C1 connects the output end vo ut of LED drive circuit, and second end of output capacitance C1 connects the reference ground GND1 of LED drive circuit (being also the reference ground of input voltage vin), and output capacitance C1 is configured in parallel with load.
The negative pole of sustained diode 1 connects the first end of output current sample circuit 210, and the positive pole of sustained diode 1 connects the reference ground GND1 of LED drive circuit.
Show a kind of particular circuit configurations of turn-off time control circuit with reference to figure 4, Fig. 4, can comprise: comparator 401, current source 402, switching tube 403 and electric capacity 404.Wherein, the first end of current source 402 connects power supply, and the first end of electric capacity 404 connects the second end of current source 402, the second end ground connection of electric capacity 404.The control end of switching tube 403 receives drive singal GT, and the first end of switching tube 403 connects the first end of electric capacity 404, and the second end of switching tube 403 connects the second end of electric capacity 404.The first input end of the first input end 401 of comparator receives error signal Vc, and the second input connects the second end of electric capacity 404, and output is used for output and opens signal Set.
When drive singal GT controls power switch shutoff, switching tube 403 also turns off under the control of drive singal GT, current source 402 pairs of electric capacity 404 charge, when the voltage charging to electric capacity 404 two ends reaches error signal Vc, the output level upset of comparator 401, thus signal Set is opened in generation, opens signal Set and makes drive singal open power switch.When drive singal GT control power switch is opened, switching tube 403 is also open-minded under the control of drive singal GT, and electric capacity 404 is discharged, until charge when power switch turns off next time, and so forth again.It will be appreciated by those skilled in the art that the control circuit of turn-off time shown in Fig. 4 is only example, it can also adopt the timing circuit of other appropriate configuration to realize.
Still with reference in the circuit shown in figure 3, Fig. 3, sampling resistor Rcs and inductance L 1 are connected, and therefore by the electric current of sampling resistor Rcs Direct Sampling inductance L 1, can obtain sampled voltage Vcs.Because sampling resistor Rcs directly connects with inductance L 1, also connect with output end vo ut, therefore the output current Iout of this LED drive circuit is embodied in the sampled voltage Vcs on sampling resistor Rcs completely.
And then, first power tube M1 and the second power tube M2 is connected with sampling resistor Rcs by sampling resistor incoming end again, therefore, by the sampling to conducting voltage corresponding to the On current of the first power tube M1 and the second power tube M2, the Direct Sampling to output current Iout can be realized, again by the comparison of peak current comparator 202, the control to output current Iout can be realized.
Wherein, error amplifier 203 can be trsanscondutance amplifier, it has the characteristic that output current Igm is directly proportional to input difference voltage Vr1-(-Vcs), also namely: Igm=Gm* (Vr1+Vcs), wherein, Vcs is negative level relative to the reference ground GND2 of constant-current driver 200, and Gm is the mutual conductance of error amplifier 203, and Gm is a steady state value normally.The output of error amplifier 203 is connected to the reference ground GND2 of constant-current driver 200 via building-out capacitor C3.
Building-out capacitor C3 is used for realizing loop compensation, and carry out integration to the error signal Vc that error amplifier 203 exports, the mean value finally realizing two inputs of error amplifier 203 is equal.After loop stability, the error signal Vc on building-out capacitor C3 stablizes, and the switch periods of this LED drive circuit is determined.Building-out capacitor C3 can also adopt the forms such as the connection in series-parallel of resistance capacitance to replace, to regulate stability and the dynamic characteristic of LED circuit.
Turn-off time control circuit 201 receives the error signal Vc on building-out capacitor C3, determines the turn-off time according to error signal Vc, when reaching this turn-off time, exporting and opening signal Set in order to open the first power switch pipe M1 and the second power switch pipe M2.When output current Iout is bigger than normal, the absolute value of sampled voltage Vcs is bigger than normal, through error amplifier 203 and building-out capacitor C3, makes the turn-off time become large; When output current Iout is less than normal, control procedure is contrary.
Peak current comparator 202 samples the source-drain voltage Vd2 of the second power tube M2 to limit inductive current peak.As the first power tube M1 and the second power tube M2 conducting, the ER effect flowing through inductance L 1 is large, the source-drain voltage Vd2 of the second power tube M2 becomes large, when reaching reference voltage Vr2, the output signal upset of peak current comparator 202, producing the cut-off signals Reset for turning off the first power tube M1 and the second power tube M2, turning off the first power tube M1 and the second power tube M2 through logic and driver circuitry 204.
In the application scenarios of routine, the sampled voltage that peak current comparator 202 receives can directly be produced by sampling resistor Rcs, and when sampled voltage Vcs reaches reference voltage Vr1, the first power tube M1 and the second power tube M2 turns off.And in the application scenarios that output current is very little, if the inductance value of inductance L 1 is also very little, so under minimum ON time, if there is no filter capacitor C4, the voltage drop of electric current on sampling resistor Rcs of inductance L 1 will be very large, may exceed the working range of positive and negative level shifting circuit 205 and error amplifier 203.And in the present embodiment, output current sample circuit 210 comprises sampling resistor Rcs in parallel and filter capacitor C4, therefore sampled voltage Vcs is the average voltage on sampling resistor Rcs, like this when the inductance value of inductance L 1 is less, sampled voltage Vcs also can not be excessive, thus make this LED drive circuit go for the very little application scenarios of output current.
Second embodiment
With reference to figure 5, LED drive circuit shown in Fig. 5 and Fig. 3 are substantially identical, the main distinction is, second end of current sampling circuit 210 is connected to the reference ground GND2 of constant-current driver 200, sampled voltage Vcs is output from the first end of current sampling circuit 210, make sampled voltage Vcs be positive voltage relative to the reference ground GND2 of constant-current driver 200, do not need to carry out dipole inversion by positive and negative level shifting circuit again.
But, in the LED drive circuit shown in Fig. 5, because the output current Iout flowing through output end vo ut flows through the electric current of sampling resistor Rcs and flows to reference the ground electric current sum of GND2 of constant-current driver 200, therefore make the accuracy of Current Control lower slightly relative to Fig. 3.
3rd embodiment
Substantially identical with Fig. 3 with reference to the LED drive circuit shown in figure 6, Fig. 6, the main distinction is, the structure of the power switch in constant-current driver 200 is different.
In the third embodiment, this power switch comprises the 3rd power tube M3, the 4th power tube M4 in parallel and built-in sampling resistor Rcs2.Wherein, the drain electrode of the 3rd power tube M3 connects voltage input end to receive input voltage vin, its source electrode connects the first input end of peak value current comparator 202, and its grid connects the output of logic and driver circuitry 204, controls turn-on and turn-off by logic and driver circuitry 204; The first end of built-in sampling resistor Rcs2 connects the source electrode of the 3rd power tube M3, and its second end connects sampling resistor incoming end; The drain electrode of the 4th power tube M4 connects voltage input end to receive input voltage vin, and its source electrode connects sampling resistor incoming end, and its grid connects the output of logic and driver circuitry 204, controls turn-on and turn-off by logic and driver circuitry 204.Wherein, the source electrode of the 3rd power tube M3 and the first end of built-in sampling resistor Rcs2 compare to peak current comparator 202 in order to export conducting voltage VCS2.
Because the 3rd power tube M3, built-in sampling resistor Rcs2 connect with current sampling circuit 210, inductance L 1 and output end vo ut, therefore, conducting voltage VCS2 also embodies the peak current of inductance L 1.
Wherein, because the 3rd power tube M3 and the 4th power tube M4 has certain current ratio, the introducing of the 3rd power tube M3 can reduce the loss that sample rate current brings.And when not considering power loss, the 4th power tube M4 also can be saved.
4th embodiment
Show the LED drive circuit of the 4th embodiment with reference to figure 7, Fig. 7, this LED drive circuit is buck configuration.Compared with the circuit shown in Fig. 3, the connected mode of output current sample circuit 210, inductance L 1, output capacitance C1 and sustained diode 1 is slightly different, be omitted the positive and negative level shifting circuit in constant-current driver 200, other circuit structure is identical.
Furthermore, the first end of inductance L 1 connects the first end of output current sample circuit 210, and the second end of inductance L 1 connects the reference ground GND1 of LED drive circuit; The first end of output capacitance C1 connects the second end of output current sample circuit 210 and the output end vo ut of LED drive circuit; The positive pole of sustained diode 1 connects the second end of inductance L 1, and its negative pole connects second end of output capacitance C1.
The above is only preferred embodiment of the present utility model, not does any pro forma restriction to the utility model.Therefore, every content not departing from technical solutions of the utility model, just according to technical spirit of the present utility model to any simple amendment made for any of the above embodiments, equivalent conversion, all still belong in the protection range of technical solutions of the utility model.
Claims (12)
1. a constant-current driver for LED drive circuit, is characterized in that, comprising:
Power switch, its input connects voltage input end to receive input voltage, and its output connects sampling resistor incoming end;
Error amplifier, is connected to described sampling resistor incoming end directly or indirectly to receive sampled voltage, is compared to produce error signal by this sampled voltage with the first reference voltage preset, and this sampled voltage corresponds to the output current of described LED drive circuit;
Peak current comparator, its first input end receives conducting voltage, its second input receives the second reference voltage preset, its output produces cut-off signals in response to this conducting voltage reaches this second reference voltage, and described conducting voltage corresponds to the On current that described power switch conduction period flows through this power switch;
Turn-off time control circuit, receives described error signal, determines the turn-off time according to this error signal, reaches the described turn-off time in response to timing, produces and opens signal;
Logic and driver circuitry, opens signal in response to described and open described power switch, turning off described power switch in response to described cut-off signals.
2. constant-current driver according to claim 1, is characterized in that, described power switch comprises:
First power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its gate configuration is for connect described voltage input end via the first resistance;
Second power tube, its drain electrode connects the source electrode of described first power tube, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
3. constant-current driver according to claim 1, is characterized in that, described power switch comprises:
3rd power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its grid connects the output of described logic and driver circuitry;
Built-in sampling resistor, its first end connects the source electrode of described 3rd power tube, and its second end connects described sampling resistor incoming end;
4th power tube, its drain electrode connects described voltage input end, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
4. a LED drive circuit, is characterized in that, comprise constant-current driver and output current sample circuit, described constant-current driver comprises:
Power switch, its input connects voltage input end to receive input voltage, and its output connects sampling resistor incoming end;
Error amplifier, is connected to described sampling resistor incoming end directly or indirectly to receive sampled voltage, is compared to produce error signal by this sampled voltage with the first reference voltage preset, and this sampled voltage corresponds to the output current of described LED drive circuit;
Peak current comparator, its first input end receives conducting voltage, its second input receives the second reference voltage preset, its output produces cut-off signals in response to this conducting voltage reaches this second reference voltage, and described conducting voltage corresponds to the On current that described power switch conduction period flows through this power switch;
Turn-off time control circuit, receives described error signal, determines the turn-off time according to this error signal, reaches the described turn-off time in response to timing, produces and opens signal;
Logic and driver circuitry, opens signal in response to described and open described power switch, turning off described power switch in response to described cut-off signals;
The first end of described output current sample circuit connects described sampling resistor incoming end, second end of described output current sample circuit is connected with the output of described LED drive circuit directly or indirectly, and described output current sample circuit comprises sampling resistor in parallel and filter capacitor.
5. LED drive circuit according to claim 4, is characterized in that, described power switch comprises:
First power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its gate configuration is for connect described voltage input end via the first resistance;
Second power tube, its drain electrode connects the source electrode of described first power tube, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
6. LED drive circuit according to claim 4, is characterized in that, described power switch comprises:
3rd power tube, its drain electrode connects described voltage input end, and its source electrode connects the first input end of described peak current comparator to transmit described conducting voltage, and its grid connects the output of described logic and driver circuitry;
Built-in sampling resistor, its first end connects the source electrode of described 3rd power tube, and its second end connects described sampling resistor incoming end;
4th power tube, its drain electrode connects described voltage input end, and its source electrode connects described sampling resistor incoming end, and its grid connects the output of described logic and driver circuitry.
7. the LED drive circuit according to any one of claim 4 to 6, is characterized in that, also comprises:
Inductance, its first end connects the second end of described output current sample circuit, and its second end connects the output of described LED drive circuit;
Output capacitance, its first end connects the output of described LED drive circuit, and its second end connects the reference ground of described LED drive circuit, and described output capacitance is configured in parallel with load;
Fly-wheel diode, its negative pole connects the first end of described output current sample circuit, and its positive pole connects the reference ground of LED drive circuit.
8. LED drive circuit according to claim 7, is characterized in that, the first end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage transfers to described error amplifier via positive and negative level shifting circuit.
9. LED drive circuit according to claim 7, is characterized in that, the second end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage directly transfers to described error amplifier.
10. the LED drive circuit according to any one of claim 4 to 6, is characterized in that, also comprises:
Inductance, its first end connects the first end of described output current sample circuit, and its second end connects the reference ground of described LED drive circuit;
Output capacitance, its first end connects the second end of output current sample circuit and the output of described LED drive circuit, and described output capacitance is configured in parallel with load;
Fly-wheel diode, its positive pole connects the second end of described inductance, and its negative pole connects the second end of output capacitance.
11. LED drive circuits according to claim 10, is characterized in that, the first end of described output current sample circuit connects the reference ground of described constant-current driver, and described sampled voltage directly transfers to described error amplifier.
12. LED drive circuits according to any one of claim 4 to 6, is characterized in that, also comprise:
Building-out capacitor, its first end connects the output of described error amplifier, and its second end is connected to the reference ground of described constant-current driver.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420866633.6U CN204291527U (en) | 2014-12-30 | 2014-12-30 | LED drive circuit and constant-current driver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420866633.6U CN204291527U (en) | 2014-12-30 | 2014-12-30 | LED drive circuit and constant-current driver |
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| CN204291527U true CN204291527U (en) | 2015-04-22 |
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| CN201420866633.6U Expired - Fee Related CN204291527U (en) | 2014-12-30 | 2014-12-30 | LED drive circuit and constant-current driver |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104486891A (en) * | 2014-12-30 | 2015-04-01 | 杭州士兰微电子股份有限公司 | Led drive circuit and constant current driver |
| CN107911899A (en) * | 2017-11-23 | 2018-04-13 | 杰华特微电子（杭州）有限公司 | A kind of Switching Power Supply and LED drive circuit |
| CN108390560A (en) * | 2018-05-08 | 2018-08-10 | 杰华特微电子（杭州）有限公司 | The control circuit and control method of reduction voltage circuit |
| CN116054595A (en) * | 2023-04-03 | 2023-05-02 | 无锡硅动力微电子股份有限公司 | Flyback converter control method and flyback converter |
-
2014
- 2014-12-30 CN CN201420866633.6U patent/CN204291527U/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104486891A (en) * | 2014-12-30 | 2015-04-01 | 杭州士兰微电子股份有限公司 | Led drive circuit and constant current driver |
| CN107911899A (en) * | 2017-11-23 | 2018-04-13 | 杰华特微电子（杭州）有限公司 | A kind of Switching Power Supply and LED drive circuit |
| CN107911899B (en) * | 2017-11-23 | 2024-04-23 | 杰华特微电子股份有限公司 | Switching power supply and LED drive circuit |
| CN108390560A (en) * | 2018-05-08 | 2018-08-10 | 杰华特微电子（杭州）有限公司 | The control circuit and control method of reduction voltage circuit |
| CN108390560B (en) * | 2018-05-08 | 2024-04-19 | 杰华特微电子股份有限公司 | Control circuit and control method of step-down circuit |
| CN116054595A (en) * | 2023-04-03 | 2023-05-02 | 无锡硅动力微电子股份有限公司 | Flyback converter control method and flyback converter |
| CN116054595B (en) * | 2023-04-03 | 2023-06-30 | 无锡硅动力微电子股份有限公司 | Flyback converter control method and flyback converter |
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Legal Events
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| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20150422 Termination date: 20191230 |