TWI434601B - Feedback control circuit and led driving circuit - Google Patents

Description

Feedback control circuit and LED driving circuit

The invention relates to a feedback control circuit and a light-emitting diode driving circuit, in particular to a feedback control circuit and a light-emitting diode driving circuit which can improve the dimming accuracy of the light-emitting diode.

In recent years, due to the long service life of the LED, high luminous efficiency, and stable and fast brightness, it is regarded as the main source of illumination and illumination for the next generation. Light-emitting diodes can be used in a wide range of lighting applications, including indoor lighting, outdoor lighting, advertising signs, and the like. As the light-emitting diodes replace the current illumination source one by one, how to obtain the light-emitting diode of the stable light source and provide appropriate protection, so that the light-emitting diode can exert its characteristics and improve the safety of use has become an important issue today. .

Please refer to the first figure, which is a circuit diagram of a conventional LED driving circuit. The LED driving circuit includes a feedback control circuit 100, a conversion circuit 130, and a light emitting diode module 140. The conversion circuit 130 is coupled to an input voltage source VIN, and the feedback control circuit 100 generates a control signal Sc1 to control the conversion circuit 130 to transfer the amount of power from the input voltage source VIN to an output terminal. The output end of the conversion circuit 130 is coupled to the LED module 140 to apply an output voltage VOUT to the LED module 140 to cause the LED module 140 to emit light through an output current IOUT. The output current IOUT simultaneously flows through a current detecting resistor Ri to generate a current feedback signal IFB1.

The feedback control circuit 100 includes a pulse width control unit 110 and a feedback unit 120. The feedback unit 120 includes an amplifying unit 122 and a compensation unit 124. The amplifying unit 122 receives the current feedback signal IFB1 and a reference signal Vr, and generates an output signal according to the error compensation signal 124 to obtain a pulse width control signal Vea1. The pulse width control unit 110 includes a pulse width modulation unit 112 and a driving unit 114. The pulse width modulation unit 112 receives the pulse width control signal Vea1 and a triangular wave signal to generate a pulse width modulation signal S1 to the driving unit 114, and the driving unit 114 generates the control signal Sc1 according to the pulse width modulation signal S1. .

In general, the feedback control circuit 100 stabilizes the output current IOUT to a predetermined output current Io, at which time the output voltage VOUT is also stabilized at a predetermined output voltage Vo. However, the amplifying unit 122 compares the current feedback signal IFB1 and the reference signal Vr, and adjusts the error of the two signal signals by the compensation unit 124 to adjust the level of the pulse width control signal. Such a feedback control process causes the output current IOUT and the output voltage VOUT to be near the predetermined output current Io and the predetermined output voltage Vo.

Please refer to the second figure, which is the signal waveform diagram of the light-emitting diode driving circuit shown in the first figure during the dimming process. The driving unit 114 receives a dimming signal DIM and determines whether to output the control signal Sc1 according to the dimming signal DIM. During the time interval T1-T4, the dimming signal represents the on state, at which time the driving unit 114 outputs the control signal Sc1; in the time interval of the time point T4-T1, the dimming signal represents the off state, at which time the driving unit 114 stops. The control signal Sc1 is output. In the time interval of the time point T4-T1, the driving unit 114 stops outputting the control signal Sc1, so that the conversion circuit 130 stops transmitting power to the LED module 140, and causes the output voltage VOUT to drop to the light-emitting diode at the time point T5. The threshold voltage Vf of the body module 140, and the output current Iout also drops to zero. This causes the current feedback signal IFB1 to maintain a positive error with the reference signal Vr, and raises the level of the pulse width control signal Vea1 even to the maximum level. In the ideal state, there is no power consumption in the time interval of the time point T4-T1, so that the output voltage VOUT is maintained equal to the threshold voltage Vf. However, in reality, the LED driving circuit may have a leakage current, which may cause the output voltage VOUT to decrease, so that the output voltage VOUT continues to fall below the threshold voltage Vf during the time interval T5-T1. At the time point T1, when the driving unit 114 re-outputs the control signal Sc1, since the level of the pulse width control signal Vea1 is at the maximum value, the duty cycle (Duty Cycle) of the control signal Sc1 is also at the maximum value.

Then, after the time point T2, the output current IOUT is higher than the predetermined output current Io, so that the amplifying unit 122 starts to pull down the level of the pulse width control signal Vea1. However, due to the error compensation relationship of the compensation unit 124, the pulse width control signal Vea1 cannot be directly lowered to an error stable value Vea1o (this value is the level of the corresponding pulse width control signal Vea1 when the output current IOUT stabilizes the predetermined output current Io). This causes the duty cycle of the control signal Sc1 at this time to be too large, so that the output current IOUT continues to rise until the pulse width control signal Vea1 is lower than the error stable value Vea1o. Thereafter, the output current IOUT is again lower than the predetermined output current Io, so that the pulse width control signal Vea1 rises again and exceeds the error stable value Vea1o. The above process will continue until time point T3, and the output current IOUT, the output voltage VOUT, and the pulse width control signal Vea1 respectively converge to the corresponding predetermined output current Io, the predetermined output voltage Vo, and the error stable value Vea1o.

Therefore, when the dimming signal is turned off, the leakage current of the LED driving circuit causes the output voltage VOUT to fall below the threshold voltage Vf, so that when the dimming signal is turned on, the LED is driven. It takes a long time for the circuit to stabilize, which affects the accuracy of dimming.

In view of the prior art, the LED driving circuit may have the problem of inaccurate dimming during the dimming process. The present invention is used to control the switching circuit to maintain a minimum power conversion when the dimming signal represents off, to maintain the output voltage. Near the threshold voltage of the LED module. The present invention can further maintain the output voltage and the control signal for controlling the conversion circuit to convert the power to be near the value of the stable operation, so that the operation of the next cycle can be directly and stably operated.

To achieve the above object, the present invention provides a feedback control circuit for controlling a conversion circuit to convert power of a power source to drive a light emitting diode module. The feedback control circuit includes a feedback unit and a pulse width control unit. The feedback unit receives a feedback signal representing a state of the LED module to generate a pulse width control signal; the pulse width control unit generates at least one control signal according to the pulse width control signal to control the conversion circuit. Power conversion. The pulse width control unit includes a dimming control unit and a driving unit. The dimming control unit generates a pulse signal generated by the control unit according to a dimming signal and a dimming a dimming control signal; the driving unit generates at least one control signal according to the pulse width control signal and the dimming control signal. The dimming signal is switched between a first state and a second state. When the dimming signal is in the first state, the feedback control circuit controls the conversion circuit to drive the LED module to stably emit light; the dimming signal is In the second state, the feedback control circuit controls the conversion circuit to maintain the conversion circuit for power conversion such that an output voltage generated by the conversion circuit is maintained near a threshold voltage of the LED module.

The invention also provides a light emitting diode driving circuit for driving a light emitting diode module, the light emitting diode module has a plurality of light emitting diode strings and the light emitting diode strings are connected in parallel with each other. The LED driving circuit comprises a current balancing module, an extreme voltage detecting circuit, a converting circuit and a feedback control circuit. The current balancing module has a plurality of current balancing ends correspondingly coupled to the plurality of LED strings for balancing the currents of the plurality of LED strings. The extreme voltage detecting circuit is coupled to the plurality of current balancing terminals, and generates a feedback signal according to the potentials of the plurality of current balancing terminals. The conversion circuit is coupled to the LED module for converting the power of an input voltage into an output voltage to drive the LED module. The feedback control circuit is configured to control the conversion circuit to perform voltage conversion, and the feedback control circuit receives a dimming signal and operates in a first state or a second state according to the dimming signal. Wherein, when the feedback control circuit operates in the first state, the average value of the power conversion of the conversion circuit is greater than the average value of the power conversion of the conversion circuit when the feedback control circuit operates in the second state and both are greater than zero.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Referring to the third figure, there is shown a circuit diagram of a light emitting diode driving circuit according to a first preferred embodiment of the present invention. The LED driving circuit includes a feedback control circuit 200 and a conversion circuit 230 for driving an LED module 240. The feedback control circuit 200 receives a current feedback signal IFB2 to perform feedback control accordingly to generate a control signal Sc2 to control the conversion circuit 230. The input end of the conversion circuit 230 is coupled to an input voltage source VIN, and the output end is coupled to the LED module 240 to regulate the power of the input voltage source VIN according to the control signal Sc2, and is converted into an appropriate output voltage VOUT. The LED module 240 is driven to stabilize an output current IOUT flowing through the LED module 240 to a predetermined output current value. The output current IOUT also flows through a current detecting resistor Ri to generate a current feedback signal IFB2 representing the magnitude of the output current IOUT.

The feedback control circuit 200 includes a feedback unit 220 and a pulse width control unit 210. The feedback unit 220 includes an amplification unit 222, a compensation unit 224, and a feedback switch 226. The non-inverting input terminal of the amplifying unit 222 receives a first reference signal Vr1, and the inverting input terminal receives the current feedback signal IFB2 to generate an error signal accordingly. The compensation unit 224 generates a pulse width control signal Vea2 according to the error signal. The compensation unit 224 generally includes a capacitor and a resistor, and adjusts the relationship between the voltage gain of the compensation unit 224 and the frequency according to the circuit of the actual application, so that the feedback control of the feedback control circuit 200 has a better transient response. The feedback switch 226 is coupled between the amplifying unit 222 and the compensation unit 224 for transmitting the error signal to the compensation unit 224 according to a dimming signal DIM. When the state of the dimming signal DIM is a first state representing "ON", the feedback switch 226 is turned on, and the error signal generated by the amplifying unit 222 is transmitted to the compensation unit 224 through the feedback switch 226; and when the dimming signal DIM When the state is a second state representing "OFF", the feedback switch 226 is turned off, and the error signal generated by the amplifying unit 222 is stopped from being transmitted to the compensation unit 224.

The pulse width control unit 210 generates a control signal Sc2 according to the pulse width control signal Vea2 to thereby control the conversion circuit 230 to perform voltage conversion. The pulse width control unit 210 includes a pulse width modulation unit 212, a dimming control unit 216, and a driving unit 214. The pulse width modulation unit 212 can be a comparator, and the non-inverting input terminal receives the pulse width control signal Vea2 and the inverting input terminal receives a triangular wave signal to generate a pulse width modulation signal S2 to the driving unit 214. The dimming control unit 216 includes a dipole signal 218 that receives a dimming signal DIM and a dimming off control unit 217 to generate a dimming control signal P2. The period signal generated by the dimming off control unit 217 can be a fixed pulse width signal. Then, the driving unit 214 receives the pulse width modulation signal S2 and the dimming control signal P2 at the same time. When the dimming signal DIM is in a first state, the driving unit 214 generates the control signal Sc2 according to the pulse width modulation signal S2; When the signal DIM is in the second state, the driving unit 214 generates the control signal Sc2 according to the dimming control signal P2 generated by the dimming control unit 216. When the dimming signal SIM is in the first state, the feedback control circuit 200 controls the conversion circuit 230 to drive the LED module 240 to stably emit light; when the dimming signal DIM is in the second state, the feedback control circuit 200 controls the conversion. The circuit 230 performs power conversion by maintaining the conversion circuit 230 such that an output voltage VOUT generated by the conversion circuit 230 is maintained near a threshold voltage of the LED module 240.

Next, please refer to the fourth figure, which is the signal waveform diagram of the dimming process of the LED driving circuit shown in the third figure. Please also refer to the third figure. At time t1, the dimming signal DIM is changed from the low level of the second state to the high level of the first state. At this time, the output voltage VOUT rises from the vicinity of the threshold voltage Vf, and the output current IOUT rises from the zero level. At this time, the feedback switch 226 is turned on. Therefore, the duty cycle of the control signal Sc2 is controlled by feedback from a predetermined duty cycle. At the time point t2, the output current IOUT reaches the predetermined output current Io, at which time the pulse width control signal Vea2 reaches a peak value. The pulse width control signal Vea2 starts to rise from a predetermined duty cycle, and the predetermined duty cycle is equal to or lower than an error stable value Vea2o (this value is the corresponding pulse width control signal when the output current IOUT is stabilized to the predetermined output current Io). The level of Vea2 does not start from the maximum value of the pulse width control signal Vea2 as in the prior art, so the peak does not easily reach the maximum value of the pulse width control signal Vea2.

Therefore, the output voltage VOUT, the output current IOUT, and the pulse width control signal Vea2 are stabilized faster than the prior art. At time t3, the dimming signal DIM is changed from the high level of the first state to the low level of the second state. The output voltage VOUT and the output current IOUT start to drop until the output current IOUT is zero. At this time, the duty cycle of the control signal Sc2 is a pulse signal for providing a very small power to the output of the conversion circuit 230 to compensate for power leakage such as leakage current on the circuit, so that the output voltage VOUT can be maintained at the threshold voltage. Near Vf. Therefore, when the pulse signal is generated, the output voltage VOUT rises so that the output voltage VOUT is near the threshold voltage Vf.

The conversion circuit in the LED driving circuit of the present invention can utilize a conversion circuit having a DC voltage output function, such as a DC-to-DC rise/down circuit, a flyback conversion circuit, a forward conversion circuit, and the like. The following is a description of the forward conversion circuit.

Referring to FIG. 5, it is a circuit diagram of a light emitting diode driving circuit according to a second preferred embodiment of the present invention. Compared with the first preferred embodiment shown in FIG. 3, the LED driver circuit in the embodiment additionally adds a driving switch 350 coupled to the LED module 340 to be based on the dimming signal DIM. Controlling whether the conversion circuit supplies power to the LED module 340. The LED driving circuit includes a feedback control circuit 300 and a conversion circuit 330 for driving a LED module 340. The conversion circuit 330 is coupled to an AC input power source VAC through a bridge rectifier BD to perform a power conversion of the AC input power source VAC according to a control signal Sc3 to drive the LED module 340 to emit light. In the present embodiment, the conversion circuit 330 is a forward conversion circuit including a transformer T, a transistor switch SW, rectifying diodes D1, D2, an inductor L, and an output capacitor C. One end of the primary side of the transformer T is coupled to the AC input power source VAC, the other end is coupled to one end of the transistor switch SW, and the other end of the transistor switch SW is grounded through a current detecting resistor to generate a current feedback signal IFB3. The output capacitor C is coupled to the secondary side of the transformer T through the rectifying diodes D1, D2 and the inductor L. A voltage detection circuit 332 is coupled to the capacitor C to generate a voltage feedback signal VFB3 representative of the magnitude of the output voltage VOUT. In order to ensure stable illumination of the LED module 340, the LED module 340 is coupled to a current source Is such that the output current IOUT is stabilized at a predetermined output current value.

The feedback control circuit 300 includes a feedback unit 320 and a pulse width control unit 310. The feedback unit 320 includes a comparator 322 and a signal superposition unit 324. The signal superimposing unit 324 receives the current feedback signal IFB3 and the voltage feedback signal VFB3 to generate a feedback signal FB3. The inverting input of the comparator 322 receives a second reference signal Vr2, and the non-inverting input receives the feedback signal FB3 to generate the pulse width control signal Vea3 accordingly. The pulse width control unit 310 includes an SR flip-flop 312, a dimming control unit 316, and a driving unit 314. The set terminal S of the SR flip-flop 312 receives a clock signal PU, and the reset terminal R receives the pulse width control signal Vea3. When the SR flip-flop 312 receives the clock signal PU at the set terminal S, a pulse width modulation signal S3 is generated from the output terminal Q to the driving circuit 314.

The dimming control unit 316 includes a dimming off control unit 317, an OR gate 318, and a dimmer 319. The dimmer 319 receives the DC dimming signal DC and a triangular wave to generate the dimming signal DIM. The dimming off control unit 317 is a comparator, the inverting input terminal receives a voltage feedback signal VFB3, and the non-inverting input terminal receives a third reference voltage Vr3, so that the voltage feedback signal VFB3 is lower than the third reference voltage Vr3. When the dimming off control unit 317 generates a pulse signal. The OR gate 318 receives the pulse signal generated by the dimming signal DIM and the dimming off control unit 317 to generate a dimming control signal P3 accordingly. Compared with the first preferred embodiment, the pulse signal generated by the dimming off control unit 317 is an unfixed period, but the same effect can be achieved.

Then, the driving unit 314 simultaneously receives the pulse width modulation signal S3 and the dimming control signal P3. When the dimming signal DIM is in a first state representing "ON", at this time, the driving unit 314 generates the signal according to the pulse width modulation signal S3. The control signal Sc2; when the dimming signal DIM is in a second state representing "OFF", the driving unit 314 generates the control signal Sc3 according to the dimming control signal P3. Thus, when the dimming signal DIM is in the second state, the driving switch 350 is turned off so that the power stored in the capacitor C is not lowered by the LED module 340; and the conversion circuit 330 can still provide a very small power to the capacitor C. To compensate for power loss caused by leakage current.

In this embodiment, the conversion circuit 330 is a forward conversion circuit, and the actual application may also be a reverse conversion conversion circuit, a half bridge conversion circuit or a full bridge conversion circuit, etc., and the control circuit 300 needs to correspond to the conversion circuit. Different one or more control signals are generated to properly control the operation of the conversion circuit. This is well known to the art and will not be described here.

Next, please refer to the seventh figure, which is a signal waveform diagram of the dimming process according to the LED driving circuit shown in FIG. Please also refer to the fifth figure. At time t1, the dimming signal DIM is changed from the low level of the second state to the high level of the first state, and the driving switch 350 is turned on. The output voltage VOUT starts to rise from a predetermined value, and the output current IOUT rises rapidly from the zero level. The SR flip-flop 312 is triggered by the pulse signal PU to generate a high level signal, so the control signal Sc3 is also at a high level. The current feedback signal IFB3 rises from the zero level, so that the level of the signal superimposing unit 324 also continues to rise, and the pulse width control signal Vea3 is at a low level. At time t2, the level of the signal superimposing unit 324 reaches a second reference voltage Vr2, so that the pulse width control signal Vea3 is turned to a high level, and the SR flip-flop is reset to output a low level signal, so that the control signal Sc3 Also turned to low level. In the next cycle, the pulse signal PU triggers the step of the SR flip-flop 312 to generate the high-level signal and repeats the time interval of the time point t1-t2, so that the output voltage VOUT and the output current IOUT are stabilized at a predetermined output voltage Vo and The output current Io is predetermined. At time t3, the dimming signal DIM is changed from the high level of the first state to the low level of the second state. At this time, the drive switch 350 is turned on and off, the output voltage VOUT is still maintained near the predetermined output voltage Vo, and the output current IOUT is immediately reduced to zero. During the time interval t3-t1, when the output voltage VOUT falls to a predetermined value, and the voltage feedback signal VFB3 is lower than a third test voltage, the dimming control signal P3 is turned to a high level to output the control signal Sc3. . Thus, the output voltage VOUT rises again above this predetermined value. That is, the output voltage VOUT will be maintained near this predetermined value to compensate for the power consumption of the circuit leakage current. Therefore, when the dimming signal DIM is again changed from the low level of the second state to the high level of the first state, the output voltage VOUT starts to rise from the predetermined value, and the steady state can be reached more quickly, and the accuracy of the dimming is improved.

6 is a circuit diagram of a light emitting diode driving circuit according to a third preferred embodiment of the present invention. The LED driving circuit includes a feedback control circuit 400 and a conversion circuit 430 for driving a LED module 440. The feedback control circuit 400 receives a feedback signal FB4 for performing feedback control to generate a control signal Sc4 to control the conversion circuit 430. The input end of the conversion circuit 430 is coupled to an input voltage source VIN, and the output end is coupled to the LED module 440. Compared with the embodiment shown in FIG. 3, the LED module 440 of the embodiment has a plurality of LED strings and the LED strings are connected in parallel with each other. In addition, in order to ensure that any of the light emitting diodes in the LED module 440 flows through substantially the same current, the LED driving circuit can add a current balancing unit 460 having a plurality of current balancing terminals D1 to Dn. Corresponding to the plurality of LED strings in the LED module 440, to balance the currents of the plurality of LED strings, so that the current of each string of LEDs is stabilized at a predetermined output current value. The plurality of driving switches 450 are coupled between the LED module 440 and the current balancing unit 460. Since the driving voltage required for each string of the LED strings to flow through the predetermined output current value is not the same, the voltage levels of the plurality of current balancing terminals D1 to Dn are different. In order to enable the current balancing terminals D1 DD to Dn of the current balancing unit 460 to operate normally, the current flowing through can be controlled to a predetermined output current value, and the levels of the current balancing terminals D1 DD Dn must be maintained at a minimum operable voltage value. To this end, the present invention can add an extreme voltage detecting circuit 470, coupled to a plurality of current balancing terminals D1 - Dn, and generate a feedback signal FB4 according to the lowest potential between the current balancing terminals D1 - Dn. The extreme voltage detecting circuit 470 can include a plurality of diodes, wherein the negative ends are respectively coupled to the plurality of current balancing terminals D1 DDn, and the positive terminals thereof are connected to each other and coupled to a driving power source VCC through a resistor. In this way, except for the diode corresponding to the current balance terminal having the lowest potential, the diodes can be turned on in principle, and the other diodes cannot be turned on in principle due to insufficient voltage across the voltage, so that the potential of the feedback signal FB4 is the lowest potential of the current balance terminal. Forward bias of the upper diode. Then, the circuit operation mode of the feedback control 400 is substantially the same as the circuit shown in the third figure of the present invention, and details are not described herein.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

Prior art:

100. . . Feedback control circuit

110. . . Pulse width control unit

112. . . Pulse width modulation unit

114. . . Drive circuit

120. . . Feedback unit

122. . . Amplification unit

124. . . Compensation unit

130. . . Conversion circuit

140. . . Light-emitting diode module

DIM. . . Dimming signal

VIN. . . Input voltage

VOUT. . . The output voltage

Ri. . . Current detecting resistor

Sc1. . . Control signal

IFB1. . . Current feedback signal

Vr. . . Reference signal

S1. . . Pulse width modulation signal

Vea1. . . Pulse width control signal

Vea1o. . . Error stability value

Vf. . . Threshold voltage

T1~T5. . . Time point

Vo. . . Predetermined output voltage

Io. . . Predetermined output current

this invention:

200, 300, 400. . . Feedback control circuit

210, 310. . . Pulse width control unit

212, 312. . . Pulse width modulation unit

214, 314. . . Drive circuit

216, 316. . . Dimming control unit

217, 317. . . Dimming off control unit

218, 318. . . Gate

319. . . Light modulator

220, 320. . . Feedback unit

222. . . Amplification unit

324. . . Signal superimposition unit

224. . . Compensation unit

226. . . Feedback switch

230, 330, 430. . . Conversion circuit

332. . . Voltage detection circuit

240, 340, 440. . . Light-emitting diode module

350, 450. . . Drive switch

460. . . Current balancing unit

470. . . Extreme voltage detection circuit

DIM. . . Dimming signal

VIN. . . Input voltage

VOUT. . . The output voltage

VCC. . . Drive power

Ri. . . Current detecting resistor

Is. . . Battery

Sc2, Sc3, Sc4. . . Control signal

FB3, FB4. . . Feedback signal

IFB2, IFB3. . . Current feedback signal

VFB3. . . Voltage feedback signal

Vr1. . . First reference signal

Vr2. . . Second reference signal

Vr3. . . Third reference signal

S2, S3. . . Pulse width modulation signal

Vea2, Vea3. . . Pulse width control signal

Vea2o. . . Error stability value

Vf. . . Threshold voltage

Vf’. . . Critical reference voltage

T1~t4. . . Time point

D1~Dn. . . Current balance

Vo. . . Predetermined output voltage

Vo’. . . Predetermined output reference voltage

Io. . . Predetermined output current

Io’. . . Predetermined output reference current

P2, P3. . . Dimming control signal

BD. . . Bridge rectifier

VAC. . . AC input power

T. . . transformer

SW. . . Transistor switch

D‧‧‧Rectifying diode

C‧‧‧ output capacitor

DC‧‧‧DC signal

S‧‧‧Setting end

R‧‧‧Reset

Q‧‧‧output

IOUT‧‧‧Output current

PU‧‧‧ clock signal

The first figure is a schematic circuit diagram of a conventional LED driving circuit.

The second figure is a signal waveform diagram of the dimming process according to the LED driving circuit shown in the first figure.

The third figure is a circuit diagram of a light-emitting diode driving circuit according to a first preferred embodiment of the present invention.

The fourth figure is a signal waveform diagram of the dimming process according to a first preferred embodiment of the present invention.

Figure 5 is a circuit diagram of a light-emitting diode driving circuit according to a second preferred embodiment of the present invention.

Figure 6 is a circuit diagram of a light-emitting diode driving circuit according to a third preferred embodiment of the present invention.

Figure 7 is a waveform diagram of a signal during a dimming process in accordance with a second preferred embodiment of the present invention.

200. . . Feedback control circuit

210. . . Pulse width control unit

212. . . Pulse width modulation unit

214. . . Drive unit

216. . . Dimming control unit

217. . . Dimming off control unit

218. . . Gate

220. . . Feedback unit

222. . . Amplification unit

224. . . Compensation unit

226. . . Feedback switch

230. . . Conversion circuit

240. . . Light-emitting diode module

DIM. . . Dimming signal

VIN. . . Input voltage

VOUT. . . The output voltage

Ri. . . Current detecting resistor

Sc2. . . Control signal

IFB2. . . Current feedback signal

Vr1. . . First reference signal

S2. . . Pulse width modulation signal

Vea2. . . Error amplification signal

P2. . . Dimming control signal

IOUT. . . Output current

Claims (9)

A feedback control circuit for controlling a conversion circuit to convert power of a power source to drive a light emitting diode module, the feedback control circuit comprising: a feedback unit for receiving the light emitting diode module a feedback signal, wherein the feedback unit includes a comparator, and an inverting input of the comparator receives a second reference signal, and a non-inverting input receives the feedback signal to generate a pulse width control signal; and a pulse width control unit, comprising: a flip flop receiving the pulse width control signal, and controlling the signal according to the pulse width to generate at least one control signal to control the conversion circuit for power conversion, wherein the pulse width The control unit includes: a dimming control unit that generates a dimming control signal according to a dimming signal and a dimming signal generated by the dimming control unit; and a driving unit that controls the signal according to the pulse width and the adjustment The light control signal is configured to generate the at least one control signal; wherein the dimming signal is switched between a first state and a second state, the dimming signal is at the In the state, the feedback control circuit controls the conversion circuit to drive the LED module to stably emit light; when the dimming signal is in the second state, the feedback control circuit controls the conversion circuit to maintain the conversion circuit The power conversion is such that an output voltage generated by the conversion circuit is maintained near a threshold voltage of the LED module. The feedback control circuit of claim 1, wherein the feedback unit comprises an amplifier and a compensation unit, and one of the non-inverting input terminals receives a first reference signal and an inverting input terminal The feedback signal and an output terminal are coupled to the compensation unit, so that the compensation unit generates the pulse width control signal. The feedback control circuit of claim 2, wherein the feedback unit can include a switch coupled between the amplifier and the compensation unit, the switch switching the amplifier and the compensation according to the dimming signal Unit coupling and decoupling. The feedback control circuit of claim 3, wherein the feedback signal is a current feedback signal representing a current flowing through the LED module or applied to the LED module. One of the group output voltages is a voltage feedback signal. The feedback control circuit of any one of the first, second, and fourth aspects of the invention, wherein the dimming-off control unit includes a signal generator for generating the pulse signal at a fixed frequency, and The pulse signal has a fixed pulse width. The feedback control circuit of any one of the first, second, and fourth aspects of the invention, wherein the dimming off control unit is a comparator, and one of the comparators receives the inverting input The feedback signal, a non-inverting input terminal receives a third reference signal, and generates the pulse signal when the level of the feedback signal is lower than the level of the third reference signal. A light-emitting diode driving circuit for driving a light-emitting diode module, the light-emitting diode module having a plurality of light-emitting diode strings and the light-emitting diode strings being connected in parallel with each other, the light-emitting diode driving The circuit includes: a current balancing module having a plurality of current balancing ends coupled to the plurality of LED strings for balancing currents of the plurality of LED strings; and an extreme voltage detecting circuit coupled The plurality of current balancing terminals generate a feedback signal according to the potentials of the plurality of current balancing terminals; a conversion circuit coupled to the LED module for converting an input voltage power into an output voltage to drive a light-emitting diode module; a feedback control circuit for controlling the voltage conversion of the conversion circuit, the feedback control circuit receiving a dimming signal, and operating in a first state or a first according to the dimming signal And a plurality of driving switches correspondingly coupled to the plurality of LED strings for stopping the conversion circuit when the feedback control circuit operates in the second state Supplying power to the LED module; wherein, when the feedback control circuit operates in the first state, an average value of the conversion power of the conversion circuit is greater than when the feedback control circuit operates in the second state The average of the converted powers, and the average of the converted powers is greater than zero. A light-emitting diode driving circuit for driving a light-emitting diode module, the light-emitting diode module having a plurality of light-emitting diode strings and the light-emitting diode strings being connected in parallel with each other, the light-emitting diode driving The circuit includes: a current balancing module having a plurality of current balancing ends coupled to the plurality of LED strings for balancing currents of the plurality of LED strings; and an extreme voltage detecting circuit coupled The plurality of current balancing terminals generate a feedback signal according to the potentials of the plurality of current balancing terminals; a conversion circuit coupled to the LED module for converting an input voltage power into an output voltage to drive The LED module and a feedback control circuit for controlling the voltage conversion of the conversion circuit, the feedback control circuit receiving a dimming signal, and operating in a first state or a according to the dimming signal a second state, wherein the feedback control circuit includes a signal generator for generating the pulse signal at a fixed frequency, and the pulse signal has a fixed pulse width; wherein the feedback control The average value of the converted power of the conversion circuit when the circuit is operated in the first state is greater than the average value of the converted power of the conversion circuit when the feedback control circuit operates in the second state, and the average values of the converted powers are greater than zero. A light-emitting diode driving circuit for driving a light-emitting diode module, the light-emitting diode module having a plurality of light-emitting diode strings and the light-emitting diode strings being connected in parallel with each other, the light-emitting diode driving The circuit includes: a current balancing module having a plurality of current balancing ends correspondingly coupled to the plurality of LED strings for balancing currents of the plurality of LED strings; An extreme voltage detecting circuit is coupled to the plurality of current balancing terminals, and generates a feedback signal according to the potentials of the plurality of current balancing terminals; a conversion circuit coupled to the LED module for inputting Converting the voltage power into an output voltage to drive the LED module; and a feedback control circuit for controlling the conversion circuit to perform voltage conversion, the feedback control circuit receiving a dimming signal and according to the dimming The signal operation is in a first state or a second state, wherein the feedback control circuit includes a comparator, and one of the comparators receives the feedback signal, and the non-inverting input receives a third reference. a signal, and the pulse signal is generated when the level of the feedback signal is lower than the level of the third reference signal; wherein the feedback control circuit operates the first state to average the converted power of the conversion circuit And greater than an average value of the converted power of the conversion circuit when the feedback control circuit operates in the second state, and the average values of the converted powers are greater than zero.