TWI642326B - Feedback circuit - Google Patents

Abstract

Different from the feedback unit used by the prior art, the fixed voltage output or the constant current output of the LED power supply can be maintained only unilaterally, and the present invention proposes to help maintain the constant current, constant voltage and constant power of the LED power supply. The output of a new type of feedback circuit, the main components of which include: a sampling unit, a feedback unit, a signal conversion unit, and a signal adjustment unit. In the operation of the feedback circuit, the current error amplifier in the feedback unit outputs a current error signal according to a current sampling signal and a dimming signal outputted by the signal conversion unit, thereby informing the PWM (pulse width modulation) , Pulse Width Modulation) The control unit maintains the constant current output of the LED power supply. At the same time, according to a voltage sampling signal and a calibration signal output by the reference signal adjusting unit, the voltage error amplifier in the feedback unit cooperates with the PWM control unit to make the output voltage of the LED power supply follow the output constant current. And adaptively adjust, in this way to maintain the constant power output of the LED power supply.

Description

Feedback circuit

The present invention relates to the technical field of electronic circuits, and more particularly to a feedback circuit for use in a power converter and a power supply.

With the development and advancement of electronic technology, a wide variety of electronic devices and products are widely used in people's daily lives, and traditionally use a linear power supply to provide a stable voltage / Current is supplied to the electronic device. However, the conventional linear power supply has the disadvantages of being bulky and having a low power conversion efficiency. Therefore, the switch mode power supply technology (Switch Mode Power) is disclosed in the U.S. Patent No. 4,253,137 by Neti R. Supply, SMPS).

Switched power supply technology is also used in LED power supplies (or LED drivers). Please refer to FIG. 1 , which is a circuit block diagram of a conventional LED power supply. As shown in FIG. 1 , a conventional LED power supply 1 ′ includes: an electromagnetic interference filtering unit 10 ′ coupled to a voltage source V _S ′, a rectifying unit 11 ′, and a PFC unit 12 ′ (power factor correcting unit). a power switch unit 13', a transformer unit 14', an output filter rectification unit 15', a feedback unit 16', a PWM (Pulse Width Modulation) control unit 17', and a dimming The unit 19'; wherein the feedback unit 16' is generally constituted by an error amplifier unit 161' and an optocoupler feedback device 162'. Also, as is well known to those skilled in the art of power electronic circuitry, the error amplifier unit 161' typically includes a voltage error amplifier 1611' and a current error amplifier 1612'.

It must be specifically noted that the voltage error amplifier 1611' and the current error amplifier 1612' are transmitted through a voltage sampling according to the feedback control technique of the LED driving circuit taught by US Patent Publication No. US2013/0127356 (A1). The unit V _SU ' and a current sampling unit C _SU ' respectively obtain a voltage sampling signal and a current sampling signal from the output end. Further, the optocoupler 162' outputs an error signal to the PWM control unit 17', so that the PWM control unit 17' can correspondingly output a pulse width modulation signal to control the switch of the power switch unit 13'. This achieves the effect of stabilizing the output signal of the LED power supply 1'.

An electronic engineer familiar with the development and design of the LED driving circuit can know, according to FIG. 1, that the current error amplifier 1612' outputs a current error signal to the PWM control according to the dimming control signal and the current sampling signal sent by the dimming unit 19'. The unit 17'; likewise, the voltage error amplifier 1611' correspondingly outputs a voltage error signal to the PWM control unit 17' according to the voltage sampling signal. Also, it is worth noting that only the error signal for instructing the PWM control unit 17' to lower the output voltage/current of the LED power supply 1' is output through the OR logic gate 1613'.

Obviously, the conventional technology mainly uses the error amplifier unit 161' composed of the voltage error amplifier 1611', the current error amplifier 1612' and the OR logic gate 1613' to input the dimming control signal according to the dimming unit 19'. The PWM control unit 17' is actuated to maintain a stable output of the output voltage/current of the LED power supply 1'. However, because the feedback unit 16' and the PWM control unit 17' can only individually reduce the output voltage or current, even the conventional LED power supply 1' can regulate the current of the LED lamp 2'. Voltage-driven, the feedback control technology used by the technology does not allow the LED power supply 1' to maintain a constant power output.

In view of the prior art, the feedback unit 16' can only maintain the constant voltage output or the constant current output of the LED power supply 1' alone, and the LED power supply 1' cannot maintain the constant power output. The inventor of the present invention The invention was vigorously studied, and finally a feedback circuit of the present invention was developed.

Unlike the feedback unit used in the prior art, which can only maintain the constant voltage output or the constant current output of the LED power supply, the main object of the present invention is to provide a feedback circuit, which is particularly useful for maintaining the LED power supply. The constant current, constant voltage and constant power output of the supplier include a sampling unit, a feedback unit, a signal conversion unit, and a signal adjustment unit. In the operation of the feedback circuit, the current error amplifier in the feedback unit outputs a current error signal according to the current sampling signal and a dimming signal outputted by the signal conversion unit to notify the PWM (pulse width modulation, Pulse) Width Modulation) control unit maintains LED power supply Current output. At the same time, according to the voltage sampling signal and the adjustment signal output by the reference signal adjusting unit, the voltage error amplifier and the PWM control unit in the feedback unit cooperate with each other, so that the output constant voltage of the LED power supply adapts with the output constant current. Ground adjustment, in this way to maintain the constant power output of the LED power supply.

In order to achieve the above-mentioned primary object of the present invention, the inventor of the present invention provides an embodiment of the feedback circuit, which is disposed in an LED power supply, wherein the LED power supply includes at least: a rectifying unit, a power switching unit, a transformer unit, an output filter rectifying unit, and a PWM control unit; and the feedback circuit includes: a sampling unit coupled to a power output end of the LED power supply, A voltage sampling signal and a current sampling signal are obtained from the power output end; a feedback unit is coupled to the sampling unit, and includes a current error amplifier and a voltage error amplifier; a signal conversion unit is coupled to An external dimming circuit and the current error amplifier are configured to convert a dimming control signal outputted by the dimming circuit into a dimming signal, and output the dimming signal to the current error amplifier; a signal adjusting unit The signal conversion unit and the voltage error amplifier are coupled to the reference signal according to the dimming signal output by the signal conversion unit Performing a signal adjustment process, and outputting an adjustment signal to the voltage error amplifier; wherein, according to the current sampling signal and the dimming signal, the current error amplifier outputs a current error signal to the PWM control unit, so that the PWM control The unit correspondingly outputs a first pulse width modulation signal to control the switch of the power switch unit, wherein the output of the LED power supply is fixed to an external LED lamp; The voltage error amplifier outputs a voltage error signal to the PWM control unit according to the voltage sampling signal and the adjustment signal, so that the PWM control unit correspondingly outputs a second pulse width modulation signal to control the power switching unit. The switch is configured to adaptively adjust the output constant voltage of the LED power supply to output a constant current to maintain a constant power output of the LED power supply.

In addition, in order to achieve the above-mentioned primary object of the present invention, the inventor of the present invention provides another embodiment of the feedback circuit, which is disposed in an LED power supply, wherein the LED power supply includes at least: a rectification a unit, a power switch unit, a transformer unit, an output filter rectification unit, and a PWM control unit; and the feedback circuit includes: a sampling unit coupled to a power output of the LED power supply a voltage sampling signal and a current sampling signal are obtained from the power output end; a feedback unit is coupled to the sampling unit, and includes a current error amplifier and a voltage error amplifier; a signal conversion unit And coupled to the external dimming circuit and the current error amplifier for converting a dimming control signal outputted by the dimming circuit into a dimming signal, and outputting the dimming signal to the current error amplifier; The current sampling signal and the dimming signal, the current error amplifier outputs a current error signal to the PWM control unit, so that the PWM control Output unit corresponds to a first PWM signal to control the switching unit of the power switch, whereby the output of the way so that the power supply of the LED to an external constant current LED lamp; The voltage error amplifier outputs a voltage error signal to the PWM control unit according to the voltage sampling signal, a reference signal, and the adjustment signal, so that the PWM control unit outputs a second pulse width modulation signal correspondingly. The switch of the power switch unit is controlled in such a manner that the output constant voltage of the LED power supply is adaptively adjusted with the output constant current to maintain the constant power output of the LED power supply.

<present invention>

2‧‧‧LED power supply

3‧‧‧LED lamps

20‧‧‧Electromagnetic interference filtering unit

21‧‧‧Rectifier unit

22‧‧‧Power factor correction unit

23‧‧‧Power switch unit

24‧‧‧Transformer unit

25‧‧‧Output filter rectifier unit

27‧‧‧PWM Control Unit

1‧‧‧Return circuit

10‧‧‧Sampling unit

11‧‧‧Responsible unit

12‧‧‧Signal conversion unit

13‧‧‧Signal adjustment unit

101‧‧‧Output current sampling unit

102‧‧‧Output voltage sampling unit

Rsen‧‧‧current detecting resistor

Rsam‧‧‧ signal sampling resistor

GND‧‧‧ ground

Rv1‧‧‧First voltage divider resistor

Rv2‧‧‧Second voltage divider resistor

111‧‧‧ Current Error Amplifier

112‧‧‧Voltage error amplifier

113‧‧‧Optocoupler

4‧‧‧ dimming circuit

Rx1‧‧‧first signal conversion resistor

Rx2‧‧‧second signal conversion resistor

17‧‧‧Nonlinear dimming unit

15‧‧‧Signal isolation unit

1112‧‧‧First Input Buffer Unit

1113‧‧‧First error amplifier

151‧‧‧First voltage follower

131‧‧‧Differential Amplifier Unit

132‧‧‧Voltage comparator unit

133‧‧‧Stabilizer

152‧‧‧Second voltage follower

V _REF1 ‧‧‧First reference voltage

OP‧‧‧Operational Amplifier

R514‧‧‧First resistance

R515‧‧‧second resistance

Di‧‧‧ diode

R511‧‧‧ third resistor

V _REF2 ‧‧‧second reference voltage

1121‧‧‧Second input buffer unit

1122‧‧‧Second error amplifier

A‧‧‧ curve

B‧‧‧ Curve

C‧‧‧ Curve

D‧‧‧ Curve

130‧‧‧ Error Detector

OP’‧‧‧Operational Amplifier

Rv3‧‧‧ third voltage divider resistor

Rv4‧‧‧ fourth voltage divider resistor

D1‧‧‧First Diode

D2‧‧‧ second diode

Eop‧‧‧Error Amplifier

V _REF ‧‧‧ reference signal

<知知>

1'‧‧‧LED power supply

2’‧‧‧LED lamps

V _S '‧‧‧voltage source

10'‧‧‧Electromagnetic interference filtering unit

11'‧‧‧Rectifier unit

12’‧‧‧PFC unit

13’‧‧‧Power Switch Unit

14’‧‧‧Transformer unit

15'‧‧‧Output filter rectifier unit

16’‧‧‧Responsible unit

17’‧‧‧PWM Control Unit

161'‧‧‧Error Amplifier Unit

162'‧‧‧Optical coupling backhaul

1611'‧‧‧Voltage Error Amplifier

1612'‧‧‧ Current Error Amplifier

V _SU '‧‧‧Voltage Sampling Unit

C _SU '‧‧‧current sampling unit

19'‧‧‧ dimming circuit

1613’‧‧‧OR logic gate

1 is a circuit block diagram showing a conventional LED power supply; FIG. 2 is a circuit block diagram showing an LED power supply including a feedback circuit of the present invention; and FIG. 3 is a circuit showing the feedback circuit of the present invention. FIG. 4 is a circuit diagram showing an output current with respect to an output voltage; FIG. 5 is a circuit diagram showing a second embodiment of a feedback circuit of the present invention; A circuit block diagram of an LED power supply incorporating the feedback circuit of the present invention.

In order to more clearly describe a feedback circuit of the present invention, a preferred embodiment of the present invention will be described in detail below with reference to the drawings.

First embodiment

Please also refer to FIG. 2, which is a circuit block diagram of an LED power supply including a feedback circuit of the present invention. As shown in FIG. 2, the current LED power supply device 2 generally includes an electromagnetic interference filtering unit 20, a rectifying unit 21, a power factor correcting unit 22, a power switching unit 23, and a transformer unit. 24. An output filter rectifying unit 25 and a PWM control unit 27.

The feedback circuit 1 of the present invention is disposed in the LED power supply 2 for coordinating the PWM control unit 27 to stabilize the output voltage, current and power of the LED power supply 2 by means of feedback control. . Briefly, the feedback circuit 1 of the present invention helps the LED power supply 2 to output a constant current and/or a constant voltage to an external LED lamp 3 at a constant power. As shown in FIG. 2, the feedback circuit 1 of the present invention includes: a sampling unit 10, a feedback unit 11, a signal conversion unit 12, and a signal adjustment unit 13. Referring to FIG. 3 at the same time, a circuit architecture diagram of a first embodiment of the feedback circuit of the present invention is shown. As shown in FIG. 2 and FIG. 3, the sampling unit 10 includes an output current sampling unit 101 and an output voltage sampling unit 102. The output current sampling unit 101 is composed of a current detecting resistor Rsen and a signal sampling resistor Rsam; and one end of the current detecting resistor Rsen is coupled to the power output end, and the signal sampling resistor Rsam is The two ends are respectively coupled to the other end of the current detecting resistor Rsen and a ground GND.

On the other hand, the output voltage sampling unit 102 is composed of a first voltage dividing resistor Rv1 and a second voltage dividing resistor Rv2, wherein one end of the first voltage dividing resistor Rv1 is coupled to the power output end, and The two ends of the second voltage dividing resistor Rv2 are respectively coupled to the other end of the first voltage dividing resistor Rv1 and the ground terminal GND. With the conventional feedback circuit In the same manner, the present invention is coupled to the sampling unit 10 by a feedback unit 11 composed of a current error amplifier 111, a voltage error amplifier 112 and an optical coupler 113. However, unlike the conventional feedback circuit, the present invention is coupled to the external dimming circuit 4 by the signal conversion unit 12 for converting a dimming control signal outputted by the dimming circuit 4 into a The dimming signal is output, and the dimming signal is output to the current error amplifier 111 and the signal adjusting unit 13. Briefly, in the design of the present invention, the current error amplifier 111 is not directly coupled to the external dimming circuit 4. So, according to the current sampling signal and a reference signal, the current error amplifier 111 outputs a current error signal to the PWM control unit 27 through the optical coupler 113, so that the PWM control unit 27 correspondingly outputs a first pulse width. The modulation signal is controlled to control the switch of the power switch unit 23 to maintain a constant current output of the LED power supply 2. It must be specially stated that the reference signal referred to herein is the dimming signal.

As shown in FIG. 2 and FIG. 3, the signal adjustment unit 13 is coupled to the signal conversion unit 12 and the voltage error amplifier 112 for performing a reference signal according to the dimming signal output by the signal conversion unit 12. A signal adjustment process is performed, and then an adjustment signal is output to the voltage error amplifier 112. Finally, according to the voltage sampling signal and the adjustment signal, the voltage error amplifier 112 outputs a voltage error signal to the PWM control unit 27 through the optical coupler 113, so that the PWM control unit 27 correspondingly outputs a second pulse width adjustment. The variable signal is used to control the switch of the power switch unit 23; thus, the output constant voltage of the LED power supply 2 can be adaptively adjusted according to the output constant current, thereby maintaining the setting of the LED power supply 2 Power output. It should be noted that the dimming control signal outputted by the dimming circuit 4 is converted into a signal conversion unit 12 into The dimming signal can ensure that the signal adjusting unit 13 and the current error amplifier 111 receive the same dimming signal, thereby avoiding signal distortion or signal transmission error.

As can be seen from FIG. 3, the signal conversion unit 12 is composed of a first signal conversion resistor Rx1 and a second signal conversion resistor Rx2. The one end of the first signal conversion resistor Rx1 is coupled to the external dimming circuit 4, and the two ends of the second signal conversion resistor Rx2 are respectively coupled to the other end of the first signal conversion resistor Rx1. Ground GND. It should be noted that in the design of the present invention, a non-linear dimming unit 17 is selectively coupled to both ends of the first signal conversion resistor Rx1, such as a dip switch or a variable resistor. By the addition of the nonlinear dimming unit 17, the user can use the nonlinear dimming unit 17 to complete a non-linear dimming of the LED lamp 3. Therefore, it must be additionally noted that the external dimming circuit 4 may be a variable resistance dimmer, a DC dimmer (1-10 VDC), a pulse width modulation signal dimmer, and a a digital dimmer of a demodulation interface (DALI DIM) or a touch dimmer (TOUCH DIM); wherein the dimmers are all outputted by outputting a dimming control signal to the signal conversion unit. A linear dimming of the LED luminaire 3 having the feedback circuit 1 of the present invention.

In particular, in order to prevent the dimming signal from being directly input to the current error amplifier 111 and the signal adjusting unit 13, the present invention further couples a signal isolation unit 15 to the signal conversion unit 12 and the current error. Between the amplifier 111 and the signal adjusting unit 13. Moreover, as shown in FIG. 3, the current error amplifier 111 is coupled to a first input of the first voltage follower 151 of the signal isolation unit 15. The buffer unit 1112 and a first error amplifier 1113 are composed. The negative input terminal of the first error amplifier 1113 is coupled to the other end of the signal sampling resistor Rsam, and the positive input terminal and the output terminal are coupled to the first input buffer unit 1112 and the optical coupler 113 respectively. .

Please refer to Figure 3 again. The signal adjustment unit 13 is composed of a differential amplifier unit 131, a voltage comparator unit 132 and a voltage stabilization unit 133. The negative input terminal of the differential amplifier unit 131 is coupled to the signal isolation unit 15 A second voltage follower 152 receives the dimming signal, and a positive input terminal is coupled to a first reference voltage V _REF1 . On the other hand, the voltage comparator unit 132 is composed of an operational amplifier OP, a first resistor R514, a second resistor R515, a diode Di, and a third resistor R511. As shown in FIG. 3, the positive input terminal of the operational amplifier OP is coupled to a second reference voltage V _REF2 , and the negative input terminal thereof is transmitted through a partial voltage formed by the first resistor R 514 and the second resistor R 515 . The resistor unit is coupled to the signal isolation unit 15 . Furthermore, the output terminal of the operational amplifier OP is coupled to the positive input terminal of the differential amplifier unit 131 through the diode Di and the third resistor R511 which are connected in series with each other. Moreover, the voltage stabilizing unit 133 is coupled to the output end of the differential amplifier unit 131.

On the other hand, the voltage error amplifier 112 is composed of a second input buffer unit 1121 and a second error amplifier 1122. The second input buffer unit 1121 is coupled to the signal adjustment unit 13 to receive the adjustment signal. The positive input terminal of the second error amplifier 1122 is coupled to the output terminal of the differential amplifier unit 131 through the voltage stabilizing unit 133, and the negative input terminal and the output terminal are respectively coupled to the output terminal. The voltage sampling unit 102 and the optical coupler 113. It should be noted that the voltage comparator unit 132 and the voltage stabilizing unit 133 are provided to stably adjust the output of the signal to eliminate the phenomenon of signal drift.

Thus, the above description has completely and clearly illustrated the detailed construction of a feedback circuit of the present invention. Continuing, the feasibility of the feedback circuit of the present invention will be confirmed by the presentation of analog data. Please refer to Figure 4 for a graph showing the output current versus output voltage. Among them, the information about the curve A to the curve D in FIG. 4 is organized in the following table (1).

It should be particularly noted that the curve C is the actual simulation result of maintaining the constant power output of the LED power supply 2 by the feedback circuit 1 of the present invention; in contrast, the curve D is to maintain the LED power supply by using the feedback circuit 1 of the present invention. The ideal result of the constant power output of the supply 2. Therefore, the circuit simulation data of FIG. 4 confirms that the feedback circuit 1 of the present invention does contribute to maintaining the constant current, constant voltage, and constant power output of the LED power supply 2.

Second embodiment

Continuing to refer to FIG. 5, there is shown a circuit architecture diagram of a second embodiment of a feedback circuit of the present invention. Meanwhile, please refer to FIG. 6, which is a circuit block diagram showing an LED power supply including the feedback circuit of the present invention. 5 and FIG. 3, it can be seen that the second embodiment of the feedback circuit 1 also includes: a sampling unit 10, a feedback unit 11, and a second embodiment. The signal conversion unit 12 and the signal adjustment unit 13 are provided. It should be noted that, as shown in FIG. 3, the signal adjusting unit 13 of the first embodiment is composed of a differential amplifier unit 131, a voltage comparator unit 132 and a voltage stabilizing unit 133; however, as shown in FIG. In the second embodiment, an error detector 130 is mainly used as the signal adjusting unit 13.

In the second embodiment, the signal adjusting unit 13 is composed of an operational amplifier OP', a third voltage dividing resistor Rv3, a fourth voltage dividing resistor Rv4, a first diode D1, and a second diode. The body D2 is configured to receive the dimming signal. The positive input terminal of the operational amplifier OP' is coupled to the signal conversion unit 12 to receive the dimming signal. Further, one end of the third voltage dividing resistor Rv3 is coupled to the negative input terminal of the operational amplifier OP', and one end of the fourth voltage dividing resistor Rv4 is coupled to the other end of the third voltage dividing resistor Rv3. On the other hand, the first diode D1 is coupled to the output of the operational amplifier OP' with its positive input terminal, and is driven by its negative input. The input end is coupled to the other end of the fourth voltage dividing resistor Rv4. In addition, the second diode D2 is coupled to the output terminal of the operational amplifier OP' with its positive input terminal and coupled to the voltage error amplifier 112 with its negative input terminal.

As is well known to those skilled in the art of electronic circuit design, the operational amplifier OP', the third voltage dividing resistor Rv3 and the fourth voltage dividing resistor Rv4 constitute the main structure of the error detector 130. Moreover, in the second embodiment, the first diode D1 and the second diode D2 are further added to the main structure of the error detector 130, so that the signal adjustment unit 13 can be stably The adjustment signal is output to avoid the phenomenon that the signal is shifted by the adjustment signal. On the other hand, in the second embodiment of the circuit 1, the main structure of the voltage error amplifier 112 is a set of error amplifiers Eop; and the positive input terminal of the error amplifier Eop is coupled to a reference signal VREF, and its negative input terminal The signal is coupled to the signal conditioning unit 13 and coupled to the optical coupler 113.

Thus, the above has completely and clearly explained the circuit architecture of all embodiments of the feedback circuit of the present invention. From the above, we can know that the present invention has the following advantages:

(1) Unlike the feedback unit 16' (shown in FIG. 1) used by the prior art, which can only maintain the constant voltage output or the constant current output of the LED power supply 1' singly, the present invention proposes to contribute A new feedback circuit 1 for maintaining the constant current, constant voltage and constant power output of the LED power supply 2, the main components of which include: a sampling unit 10, a feedback unit 11, a signal conversion unit 12, and a signal adjustment Unit 13. In the operation of the feedback circuit 1, the current error amplifier 111 in the feedback unit 11 outputs a current error signal according to the current sampling signal and a dimming signal outputted by the signal conversion unit 12, The PWM control unit 27 is notified to maintain the constant current output of the LED power supply 2. At the same time, according to the reference signal output by the voltage sampling signal and the signal adjusting unit 13, the voltage error amplifier 112 in the feedback unit 11 cooperates with the PWM control unit 27, so that the output voltage of the LED power supply 2 is outputted with the output voltage. The current is adaptively adjusted in such a manner that the constant power output of the LED power supply 2 is maintained.

(2) In addition, it should be particularly noted that the circuit simulation data completed by the inventor of the present invention shows that the feedback circuit 1 of the present invention does contribute to maintaining the constant current of the LED power supply 2 in the operation of the practical circuit. Voltage and constant power output.

It is to be understood that the foregoing detailed description of the embodiments of the present invention is not intended to Both should be included in the scope of the patent in this case.

Claims (18)

A feedback circuit is disposed in an LED power supply, wherein the LED power supply comprises at least: a rectifying unit, a power switching unit, a transformer unit, an output filter rectifying unit, and a PWM (pulse width) a modulating unit of the pulse Width Modulation; and the feedback circuit includes: a sampling unit coupled to a power output of the LED power supply for obtaining a voltage sampling signal from the power output And a current sampling signal; a feedback unit coupled to the sampling unit and including a current error amplifier and a voltage error amplifier; a signal conversion unit coupled to the external dimming circuit and the current error amplifier The dimming control signal outputted by the dimming circuit is converted into a dimming signal, and the dimming signal is outputted to the current error amplifier; a signal adjusting unit is coupled to the signal converting unit and the voltage An error amplifier for performing a signal adjustment process on a reference signal according to the dimming signal output by the signal conversion unit, and outputting a tone Signaling to the voltage error amplifier; wherein, according to the current sampling signal and the dimming signal, the current error amplifier outputs a current error signal to the PWM control unit, so that the PWM control unit correspondingly outputs a first pulse width modulation a signal signal to control a switch of the power switch unit, wherein the LED power supply outputs a constant current to an external LED lamp; wherein the voltage error amplifier outputs a voltage error according to the voltage sampling signal and the adjustment signal Signaling to the PWM control unit, so that the PWM control unit correspondingly outputs a second pulse width modulation signal to control the opening of the power switch unit Off, in this way, the output constant voltage of the LED power supply is adaptively adjusted according to the output constant current to maintain the constant power output of the LED power supply. The feedback circuit of claim 1, wherein the sampling unit comprises: an output current sampling unit, comprising: a current detecting resistor, one end of which is coupled to the power output end; and a The signal sampling resistor has one end coupled to the other end of the current detecting resistor and the other end coupled to a ground end; and an output voltage sampling unit including: a first voltage dividing resistor, one end thereof The first voltage-dividing resistor is coupled to the other end of the first voltage-dividing resistor, and the other end of the first voltage-dividing resistor is coupled to the ground end. The feedback circuit of claim 2, wherein the feedback unit further comprises: an optical coupler coupled to the current error amplifier, the voltage error amplifier and the PWM control unit for The current error signal outputted by the current error amplifier and the voltage error signal output by the voltage error amplifier are transmitted to the PWM control unit; and a signal isolation unit coupled to the signal conversion unit and the current error amplifier and the Between the signal adjustment units, the dimming signal is prevented from being directly input to the current error amplifier and the signal adjustment unit. The feedback circuit of claim 1, wherein the signal conversion unit comprises: a first signal conversion resistor, one end of which is coupled to the dimming circuit; and a second signal conversion resistor, one end of which The other end of the second signal conversion resistor is coupled to a ground end. The feedback circuit of claim 3, wherein the current error amplifier comprises: a first input buffer unit coupled to the signal isolation unit; and a first error amplifier having a negative input end The other end of the signal sampling resistor is coupled to the first input buffer unit, and the output end of the signal is coupled to the optical coupler. The feedback circuit of claim 4, wherein a non-linear dimming unit is selectively coupled to both ends of the first signal conversion resistor, and the non-linear dimming unit can be any of the following : Dip switch or variable resistor. The feedback circuit of claim 5, wherein the signal adjustment unit comprises: a differential amplifier unit, the negative input end of which is coupled to the signal isolation unit to receive the dimming signal, and The positive input terminal is coupled to a first reference voltage; a voltage stabilizing unit is coupled to the output end of the differential amplifier unit; a voltage comparator unit having a positive input terminal coupled to a second reference voltage, and a negative input terminal coupled to the signal isolation unit via a voltage dividing resistor unit; and an output terminal of the voltage comparator unit The system is coupled to the positive input terminal of the differential amplifier unit. The feedback circuit of claim 6, wherein the dimming circuit completes a linear dimming of the LED lamp by outputting the dimming control signal to the signal conversion unit; and A nonlinear dimming of the LED luminaire can be accomplished using the non-linear dimming unit. The feedback circuit of claim 7, wherein the voltage error amplifier comprises: a second input buffer unit coupled to the signal adjustment unit to receive the adjustment signal; and a second error amplifier The positive input terminal is coupled to the output end of the differential amplifier unit through the voltage stabilizing unit, the negative input end is coupled to the output voltage sampling unit, and the output end thereof is coupled to the optical coupler . A feedback circuit is disposed in an LED power supply, wherein the LED power supply comprises at least: a rectifying unit, a power switching unit, a transformer unit, an output filtering rectifying unit, and a PWM control unit; And, the feedback circuit system includes: a sampling unit is coupled to a power output end of the LED power supply for obtaining a voltage sampling signal and a current sampling signal from the power output end; a feedback unit coupled to the sampling unit And comprising a current error amplifier and a voltage error amplifier; a signal conversion unit is coupled to the external dimming circuit and the current error amplifier for converting a dimming control signal output by the dimming circuit into a tone a signal signal, and outputting the dimming signal to the current error amplifier; a signal adjustment unit coupled to the signal conversion unit and the voltage error amplifier for performing the dimming signal output by the signal conversion unit Signal adjustment processing, and outputting an adjustment signal to the voltage error amplifier; wherein, according to the current sampling signal and the dimming signal, the current error amplifier outputs a current error signal to the PWM control unit, so that the PWM control unit corresponds Grounding a first pulse width modulation signal to control the switch of the power switch unit, thereby making the LED power supply And outputting a constant current to an external LED lamp; wherein, according to the voltage sampling signal, a reference signal, and the adjustment signal, the voltage error amplifier outputs a voltage error signal to the PWM control unit, so that the PWM control unit outputs correspondingly a second pulse width modulation signal to control the switch of the power switch unit, wherein the output voltage of the LED power supply is adaptively adjusted according to the output constant current to maintain the LED power supply Power output. The feedback circuit of claim 10, wherein the sampling unit comprises: An output current sampling unit includes: a current detecting resistor, one end of which is coupled to the power output end; and a signal sampling resistor, one end of which is coupled to the other end of the current detecting resistor, and the other One end is coupled to a ground end; and an output voltage sampling unit includes: a first voltage dividing resistor, one end of which is coupled to the power output end; and a second voltage dividing resistor, one end of which is coupled To the other end of the first voltage dividing resistor, and the other end thereof is coupled to the ground end. The feedback circuit of claim 11, wherein the feedback unit further comprises: an optical coupler coupled to the current error amplifier, the voltage error amplifier and the PWM control unit for The current error signal outputted by the current error amplifier and the voltage error signal output by the voltage error amplifier are transmitted to the PWM control unit; and a signal isolation unit is coupled between the signal conversion unit and the current error amplifier To prevent the dimming signal from being directly input to the current error amplifier. The feedback circuit of claim 10, wherein the signal conversion unit comprises: a first signal conversion resistor, one end of which is coupled to the dimming circuit; A second signal conversion resistor has one end coupled to the other end of the first signal conversion resistor, and the other end of the second signal conversion resistor coupled to a ground end. The feedback circuit of claim 12, wherein the current error amplifier comprises: a first input buffer unit coupled to the signal isolation unit; and a first error amplifier having a negative input end The other end of the signal sampling resistor is coupled to the first input buffer unit, and the output end of the signal is coupled to the optical coupler. The feedback circuit of claim 13, wherein a non-linear dimming unit is selectively coupled to both ends of the first signal conversion resistor, and the non-linear dimming unit can be any of the following : Dip switch or variable resistor. The feedback circuit of claim 11, wherein the signal adjustment unit comprises: an operational amplifier, the positive input end of which is coupled to the signal conversion unit to receive the dimming signal; a voltage dividing resistor, one end of which is coupled to the negative input end of the operational amplifier; a fourth voltage dividing resistor, one end of which is coupled to the other end of the third voltage dividing resistor; a first diode is The positive input terminal is coupled to the output end of the operational amplifier, and the negative input terminal is coupled to the other end of the fourth voltage dividing resistor; A second diode is coupled to the output of the operational amplifier with its positive input terminal and coupled to the voltage error amplifier with its negative input terminal. The feedback circuit of claim 12, wherein the voltage error amplifier comprises: an error amplifier having a positive input coupled to the reference signal and a negative input coupled to the signal adjustment unit And its output is coupled to the optical coupler. The feedback circuit of claim 15, wherein the dimming circuit completes a linear dimming of the LED lamp by outputting the dimming control signal to the signal conversion unit; A non-linear dimming of the LED luminaire can be accomplished by using the nonlinear dimming unit.