阅读说明：本技术 一种电源的调光控制电路和电源 (Dimming control circuit of power supply and power supply ) 是由 王宗友 江军 郭怀峰 邹超洋 于 2019-08-13 设计创作，主要内容包括：本发明涉及一种电源的调光控制电路和电源,包括：主控电路、与主控电路连接的驱动电路和补偿电路、与驱动电路和主控电路连接的电流采样电路；驱动电路用于接收主控电路输出的控制信号,并根据控制信号产生驱动信号驱动电源进行调光；电流采样电路用于在驱动电路导通时,采集电源的调光电流并产生电流采样信号；补偿电路用于在驱动电路导通时,根据控制信号产生补偿信号至主控电路；主控电路根据补偿信号和电流采样信号控制电源的输出电流。该电源的调光控制电路在调光小于20％负载时,电源IC不会进入打隔离模式,有效解决Buck拓扑结构中LED灯出现灯闪的问题,以及开关机和空载时MOS管来不及关断,造成BUCK电感瞬间饱和等问题,提升产品的性能及应用。(the invention relates to a dimming control circuit of a power supply and the power supply, comprising: the current sampling circuit is connected with the driving circuit and the main control circuit; the driving circuit is used for receiving the control signal output by the main control circuit and generating a driving signal according to the control signal to drive the power supply to adjust the light; the current sampling circuit is used for collecting dimming current of the power supply and generating a current sampling signal when the driving circuit is switched on; the compensation circuit is used for generating a compensation signal to the main control circuit according to the control signal when the driving circuit is conducted; the main control circuit controls the output current of the power supply according to the compensation signal and the current sampling signal. When the dimming control circuit of the power supply is dimming and is less than 20% of load, the power supply IC can not enter into a disconnecting mode, the problem that the LED lamp flashes in the Buck topological structure is effectively solved, and the problems that the BUCK inductor is instantly saturated and the like due to the fact that the MOS tube is not turned off when the power supply is turned on or off and is in no-load are solved, and the performance and the application of the product are improved.)

1. a dimming control circuit for a power supply, comprising: the circuit comprises a main control circuit, a driving circuit and a compensating circuit which are connected with the main control circuit, and a current sampling circuit which is connected with the driving circuit and the main control circuit;

The driving circuit is used for receiving the control signal output by the main control circuit and generating a driving signal according to the control signal to drive the power supply to adjust the light;

the current sampling circuit is used for collecting dimming current of a power supply and generating a current sampling signal when the driving circuit is switched on;

The compensation circuit is used for generating a compensation signal to the main control circuit according to the control signal when the driving circuit is conducted;

And the main control circuit controls the output current of the power supply according to the compensation signal and the current sampling signal.

2. The dimming control circuit of claim 1, wherein the driving circuit comprises: a buffer circuit and a driving tube;

the input end of the buffer circuit is connected with the control signal output end of the main control circuit, the output end of the buffer circuit is connected with the control end of the driving tube, the output end of the driving tube outputs the driving signal, and the pull-down end of the driving tube is connected with the current sampling circuit;

The buffer circuit is used for receiving the control signal, buffering the control signal and outputting the driving signal to the driving tube so as to drive the driving tube to be switched on or switched off.

3. The dimming control circuit of claim 2, wherein the buffer circuit comprises: a twenty-sixth resistor, a twenty-seventh resistor and a buffer diode; the driving tube comprises an MOS tube;

A first end of the twenty-sixth resistor and an anode of the buffer diode are connected with a grid electrode of the MOS tube, a second end of the twenty-sixth resistor is connected with a first end of the twenty-seventh resistor, and a second end of the twenty-seventh resistor is connected with a control signal output end of the main control circuit; the source electrode of the MOS tube is connected with the current sampling circuit, and the drain electrode of the MOS tube outputs the driving signal;

The second end of the twenty-seventh resistor is the input end of the buffer circuit, and the first end of the twenty-sixth resistor is the output end of the buffer circuit.

4. The dimming control circuit of claim 1, wherein the current sampling circuit comprises: the current acquisition circuit and the detection circuit;

The first end of the current acquisition circuit is connected with the driving circuit, and the second end of the current acquisition circuit is grounded; the first end of the detection circuit is connected with the first end of the current acquisition circuit, and the second end of the detection circuit is connected with the sampling signal detection end of the main control circuit;

The current acquisition circuit is used for acquiring dimming current of a power supply and generating the current sampling signal when the driving circuit is switched on;

The detection circuit is used for detecting the current sampling signal generated by the current acquisition circuit and sending the current sampling signal to the sampling signal detection end of the main control circuit.

5. The dimming control circuit of claim 4, wherein the current sampling circuit further comprises: and the filter circuit is used for filtering the current sampling signal.

6. The dimming control circuit of claim 5, wherein the current acquisition circuit comprises: a sampling resistor, the detection circuit comprising: a sense resistor, the filter circuit comprising: a filter capacitor;

The first end of the sampling resistor is used as the first end of the current acquisition circuit and is connected with the driving circuit, and the second end of the sampling resistor is used as the second end of the current acquisition circuit and is grounded;

a first end of the detection resistor is used as a first end of the detection circuit and connected with a first end of the sampling resistor, and a second end of the detection resistor is used as a second end of the detection circuit and connected with a sampling signal detection end of the main control circuit;

the first end of the filter capacitor is connected with the second end of the detection resistor, and the second end of the filter capacitor is connected with the second end of the sampling resistor and is connected to the ground.

7. The dimming control circuit of claim 1, wherein the compensation circuit comprises: the isolation circuit and the control signal sampling circuit;

The first end of the isolation circuit is connected with the control signal output end of the main control circuit, the second end of the isolation circuit is connected with the first end of the control signal sampling circuit, the second end of the control signal sampling circuit is grounded, and the third end of the control signal sampling circuit is connected with the sampling signal detection end of the main control circuit.

8. the dimming control circuit of claim 7, wherein the compensation circuit further comprises: a backflow prevention circuit;

The first end of the backflow prevention circuit is connected with the third end of the control signal sampling circuit, and the second end of the backflow prevention circuit is connected with the sampling signal detection end of the main control circuit.

9. the dimming control circuit of claim 8, wherein the isolation circuit comprises: an isolation diode; the control signal sampling circuit includes: a coupling capacitor, a thirty-fifth resistor and a forty-fourth resistor; the backflow prevention circuit comprises: a back-flow prevention diode;

the anode of the isolation diode is connected with the control signal output end of the main control circuit, the cathode of the isolation diode is connected with the first end of the coupling capacitor and the second end of the forty-th resistor, and the first end of the forty-th resistor and the first end of the thirty-fifth resistor are connected and connected to the ground;

The second end of the coupling capacitor is connected with the second end of the thirty-fifth resistor and the anode of the backflow prevention diode, and the cathode of the backflow prevention diode is connected with the control signal output end of the main control circuit;

The anode of the isolation diode is the first end of the isolation circuit, and the cathode of the isolation diode is the second end of the isolation circuit;

A connection end of a second end of the forty-th resistor and a first end of the coupling capacitor is a first end of the control signal sampling circuit, a connection end of the first end of the forty-th resistor and a first end of the thirty-fifth resistor is a second end of the control signal sampling circuit, and a second end of the coupling capacitor is a third end of the control signal sampling circuit;

The anode of the anti-backflow diode is the first end of the anti-backflow circuit, and the cathode of the anti-backflow diode is the second end of the anti-backflow circuit.

10. a power supply characterized by a dimming control circuit comprising a power supply according to any one of claims 1 to 9.

Technical Field

the invention relates to the technical field of LED driving, in particular to a dimming control circuit of a power supply and the power supply.

Background

with the rapid development of LED illumination, the original isolated LED power supply can not meet the application requirements of the market, a non-isolated power supply with high cost performance is favored, and the LED illumination has the outstanding advantages of energy conservation, high light efficiency and the like, so that the LED illumination is widely applied to various illumination places. Meanwhile, the requirement of people on light is higher and higher, and the phenomenon of lamp flashing cannot occur in any condition of dimming.

The BUCK topology constant current samples the maximum value of Vcs (namely Vcspk-Idspk Rcs) through a chip CS pin, and the value is sent to the negative phase input end of an error amplifier inside the IC, and the IC controls the LED current through an internal integrated quasi-full period detection technology.

the existing buck line constant current technology has the following defects:

Firstly, the topological constant current of Buck is the CS foot sampling detection control through the chip, and the voltage that the CS foot was adopted is lower when adjusting luminance and being less than 20% load, and IC gets into easily and beats the mode of separating, and LED can appear little lamp and dodge this moment.

Secondly, the minimum dimming is set to be more than 20% of load, so that the IC is not in an isolation mode, the minimum dimming does not meet the requirements of customers, and the performance of the product is reduced.

disclosure of Invention

The present invention provides a dimming control circuit of a power supply and a power supply, which address the above-mentioned drawbacks of the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: a dimming control circuit of a power supply is provided, including: the circuit comprises a main control circuit, a driving circuit and a compensating circuit which are connected with the main control circuit, and a current sampling circuit which is connected with the driving circuit and the main control circuit;

the driving circuit is used for receiving the control signal output by the main control circuit and generating a driving signal according to the control signal to drive the power supply to adjust the light;

the current sampling circuit is used for collecting dimming current of a power supply and generating a current sampling signal when the driving circuit is switched on;

the compensation circuit is used for generating a compensation signal to the main control circuit according to the control signal when the driving circuit is conducted;

And the main control circuit controls the output current of the power supply according to the compensation signal and the current sampling signal.

In one embodiment, the driving circuit includes: a buffer circuit and a driving tube;

the input end of the buffer circuit is connected with the control signal output end of the main control circuit, the output end of the buffer circuit is connected with the control end of the driving tube, the output end of the driving tube outputs the driving signal, and the pull-down end of the driving tube is connected with the current sampling circuit;

the buffer circuit is used for receiving the control signal, buffering the control signal and outputting the driving signal to the driving tube so as to drive the driving tube to be switched on or switched off.

in one embodiment, the buffer circuit includes: a twenty-sixth resistor, a twenty-seventh resistor and a buffer diode; the driving tube comprises an MOS tube;

A first end of the twenty-sixth resistor and an anode of the buffer diode are connected with a grid electrode of the MOS tube, a second end of the twenty-sixth resistor is connected with a first end of the twenty-seventh resistor, and a second end of the twenty-seventh resistor is connected with a control signal output end of the main control circuit; the source electrode of the MOS tube is connected with the current sampling circuit, and the drain electrode of the MOS tube outputs the driving signal;

The second end of the twenty-seventh resistor is the input end of the buffer circuit, and the first end of the twenty-sixth resistor is the output end of the buffer circuit.

in one embodiment, the current sampling circuit includes: the current acquisition circuit and the detection circuit;

the first end of the current acquisition circuit is connected with the driving circuit, and the second end of the current acquisition circuit is grounded; the first end of the detection circuit is connected with the first end of the current acquisition circuit, and the second end of the detection circuit is connected with the sampling signal detection end of the main control circuit;

The current acquisition circuit is used for acquiring dimming current of a power supply and generating the current sampling signal when the driving circuit is switched on;

The detection circuit is used for detecting the current sampling signal generated by the current acquisition circuit and sending the current sampling signal to the sampling signal detection end of the main control circuit.

in one embodiment, the current sampling circuit further comprises: and the filter circuit is used for filtering the current sampling signal.

In one embodiment, the current acquisition circuit comprises: a sampling resistor, the detection circuit comprising: a sense resistor, the filter circuit comprising: a filter capacitor;

the first end of the sampling resistor is used as the first end of the current acquisition circuit and is connected with the driving circuit, and the second end of the sampling resistor is used as the second end of the current acquisition circuit and is grounded;

a first end of the detection resistor is used as a first end of the detection circuit and connected with a first end of the sampling resistor, and a second end of the detection resistor is used as a second end of the detection circuit and connected with a sampling signal detection end of the main control circuit;

The first end of the filter capacitor is connected with the second end of the detection resistor, and the second end of the filter capacitor is connected with the second end of the sampling resistor and is connected to the ground.

in one embodiment, the compensation circuit includes: the isolation circuit and the control signal sampling circuit;

The first end of the isolation circuit is connected with the control signal output end of the main control circuit, the second end of the isolation circuit is connected with the first end of the control signal sampling circuit, the second end of the control signal sampling circuit is grounded, and the third end of the control signal sampling circuit is connected with the sampling signal detection end of the main control circuit.

In one embodiment, the compensation circuit further comprises: a backflow prevention circuit;

The first end of the backflow prevention circuit is connected with the third end of the control signal sampling circuit, and the second end of the backflow prevention circuit is connected with the sampling signal detection end of the main control circuit.

in one embodiment, the isolation circuit includes: an isolation diode; the control signal sampling circuit includes: a coupling capacitor, a thirty-fifth resistor and a forty-fourth resistor; the backflow prevention circuit comprises: a back-flow prevention diode;

the anode of the isolation diode is connected with the control signal output end of the main control circuit, the cathode of the isolation diode is connected with the first end of the coupling capacitor and the second end of the forty-th resistor, and the first end of the forty-th resistor and the first end of the thirty-fifth resistor are connected and connected to the ground;

The second end of the coupling capacitor is connected with the second end of the thirty-fifth resistor and the anode of the backflow prevention diode, and the cathode of the backflow prevention diode is connected with the control signal output end of the main control circuit;

The anode of the isolation diode is the first end of the isolation circuit, and the cathode of the isolation diode is the second end of the isolation circuit;

A connection end of a second end of the forty-th resistor and a first end of the coupling capacitor is a first end of the control signal sampling circuit, a connection end of the first end of the forty-th resistor and a first end of the thirty-fifth resistor is a second end of the control signal sampling circuit, and a second end of the coupling capacitor is a third end of the control signal sampling circuit;

The anode of the anti-backflow diode is the first end of the anti-backflow circuit, and the cathode of the anti-backflow diode is the second end of the anti-backflow circuit.

the invention also provides a power supply, which comprises the dimming control circuit of the power supply.

The dimming control circuit of the power supply has the following beneficial effects: the method comprises the following steps: the current sampling circuit is connected with the driving circuit and the main control circuit; the driving circuit is used for receiving the control signal output by the main control circuit and generating a driving signal according to the control signal to drive the power supply to adjust the light; the current sampling circuit is used for collecting dimming current of the power supply and generating a current sampling signal when the driving circuit is switched on; the compensation circuit is used for generating a compensation signal to the main control circuit according to the control signal when the driving circuit is conducted; the main control circuit controls the output current of the power supply according to the compensation signal and the current sampling signal. When the dimming control circuit of the power supply is dimming and is less than 20% of load, the power supply IC can not enter into a disconnecting mode, the problem that the LED lamp flashes in the Buck topological structure is effectively solved, and the problems that the BUCK inductor is instantly saturated and the like due to the fact that the MOS tube is not turned off when the power supply is turned on or off and is in no-load are solved, and the performance and the application of the product are improved.

drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

Fig. 1 is a schematic block diagram of a dimming control circuit of a power supply according to an embodiment of the present invention;

Fig. 2 is a schematic circuit diagram of a dimming control circuit of a power supply according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to solve the problem that when the dimming power supply of the conventional Buck topological structure is used for dimming less than 20% of load, the IC of the dimming power supply enters a blocking mode to cause the LED lamp of the load to flash, the invention provides a dimming control circuit of the power supply, wherein the dimming control circuit samples and compensates the output control signal to the current detection end of the dimming power supply IC, so that the current detection end still has higher voltage when the dimming is below 20% of load, the IC of the dimming power supply is prevented from entering the blocking mode, and the flash phenomenon of the lamp is avoided.

Specifically, referring to fig. 1, a schematic block diagram of a dimming control circuit of a power supply according to an embodiment of the present invention is provided.

as shown in fig. 1, the dimming control circuit of the power supply includes: the circuit comprises a main control circuit 14, a driving circuit 11 and a compensation circuit 13 which are connected with the main control circuit 14, and a current sampling circuit 12 which is connected with the driving circuit 11 and the main control circuit 14.

The driving circuit 11 is configured to receive a control signal output by the main control circuit 14, and generate a driving signal according to the control signal to drive the power supply to perform dimming; the current sampling circuit 12 is used for collecting dimming current of a power supply and generating a current sampling signal when the driving circuit 11 is switched on; the compensation circuit 13 is used for generating a compensation signal to the main control circuit 14 according to the control signal when the driving circuit 11 is turned on; the main control circuit 14 controls the output current of the power supply according to the compensation signal and the current sampling signal.

Specifically, the main control circuit 14 outputs a control signal, which is used for dimming. Optionally, the control signal is a PWM control signal. Further, after the main control circuit 14 outputs the control signal, the driving circuit 11 receives the PWM control signal and buffers the PWM control signal, and then outputs a corresponding PWM driving signal for dimming the load. Meanwhile, in the process of dimming by the PWM driving signal output by the driving circuit 11, the current sampling circuit 12 samples the dimming current and transmits the sampling signal to the sampling signal detection end of the main control circuit 14; meanwhile, after the PWM control signal outputted by the main control circuit 14 is further sampled by the compensation circuit 13, a corresponding compensation signal is generated, and the generated compensation signal is compensated to the sampling signal detection end of the main control circuit 14, so that the purpose of compensating the voltage at the sampling signal detection end of the main control circuit 14 can be achieved, and when the dimming is adjusted to be below 20% of the load, the sampling signal detection end of the main control circuit 14 still has a higher voltage, thereby preventing the IC in the main control circuit 14 from entering a cut-off mode, and eliminating the phenomenon of lamp flash.

further, in the embodiment of the present invention, the driving circuit 11 includes: a buffer circuit and a driving tube.

The input end of the buffer circuit is connected with the control signal output end of the main control circuit 14, the output end of the buffer circuit is connected with the control end of the driving tube, the output end of the driving tube outputs a driving signal, and the pull-down end of the driving tube is connected with the current sampling circuit 12. The buffer circuit is used for receiving the control signal, buffering the control signal and outputting a driving signal to the driving tube so as to drive the driving tube to be switched on or switched off. Optionally, the driving tube in the embodiment of the present invention may be implemented by using an MOS tube.

Further, in the embodiment of the present invention, the current sampling circuit 12 includes: current acquisition circuit and detection circuitry.

the first end of the current acquisition circuit is connected with the driving circuit 11, and the second end of the current acquisition circuit is grounded; the first end of the detection circuit is connected with the first end of the current acquisition circuit, and the second end of the detection circuit is connected with the sampling signal detection end of the main control circuit 14. The current acquisition circuit is used for acquiring dimming current of a power supply and generating a current sampling signal when the driving circuit 11 is switched on; the detection circuit is used for detecting the current sampling signal generated by the current acquisition circuit and sending the current sampling signal to the sampling signal detection end of the main control circuit 14. In the embodiment of the invention, the current acquisition circuit can be realized by resistors, wherein the required number and resistance value of the resistors can be determined according to the actual condition of circuit design.

further, in this embodiment of the present invention, the current sampling circuit 12 further includes: and the filter circuit is used for filtering the current sampling signal. Through setting up filter circuit, can filter the noise in the current sampling signal that the current acquisition circuit produced to obtain stable current sampling signal.

further, in the embodiment of the present invention, the compensation circuit 13 includes: an isolation circuit and a control signal sampling circuit.

The first end of the isolation circuit is connected with the control signal output end of the main control circuit 14, the second end of the isolation circuit is connected with the first end of the control signal sampling circuit, the second end of the control signal sampling circuit is grounded, and the third end of the control signal sampling circuit is connected with the sampling signal detection end of the main control circuit 14. Alternatively, the isolation circuit may be implemented by a diode.

Further, in this embodiment of the present invention, the compensation circuit 13 further includes: a backflow prevention circuit; the first end of the backflow prevention circuit is connected with the third end of the control signal sampling circuit, and the second end of the backflow prevention circuit is connected with the sampling signal detection end of the main control circuit 14. Alternatively, the back-flow prevention circuit may be implemented by a diode.

in one embodiment, as shown in fig. 2, the buffer circuit includes: a twenty-sixth resistor R26, a twenty-seventh resistor R27 and a buffer diode D01; the driving tube comprises a MOS tube Q2; wherein C13 in fig. 2 is the internal resistance of the MOS transistor Q2. The master control circuit 14 includes: master control chip U2.

a first end of a twenty-sixth resistor R26 and an anode of a buffer diode D01 are connected with a grid electrode of the MOS transistor Q2, a second end of the twenty-sixth resistor R26 is connected with a first end of a twenty-seventh resistor R27, and a second end of the twenty-seventh resistor R27 is connected with a control signal output end (pin 8 of U2) of the main control circuit 14; the source of the MOS transistor Q2 is connected to the current sampling circuit 12, and the drain of the MOS transistor Q2 outputs a drive signal. The second end of the twenty-seventh resistor R27 is the input end of the buffer circuit, and the first end of the twenty-sixth resistor R26 is the output end of the buffer circuit.

In this embodiment, the current collection circuit includes: sampling resistance R5, the detection circuit includes: detect resistance R75, the filter circuit includes: a filter capacitor C19.

the first end of the sampling resistor R5 is connected to the driving circuit 11 (i.e., the source of the MOS transistor Q2 in fig. 2) as the first end of the current collection circuit, and the second end of the sampling resistor R5 is grounded as the second end of the current collection circuit.

a first end of the detection resistor R75 serving as a first end of the detection circuit is connected with a first end of the sampling resistor R5, and a second end of the detection resistor R75 serving as a second end of the detection circuit is connected with a sampling signal detection end (pin 5 of U2) of the main control circuit 14; the first end of the filter capacitor C19 is connected with the second end of the detection resistor R75, and the second end of the filter capacitor C19 is connected with the second end of the sampling resistor R5 and is connected with the ground.

In this embodiment, the isolation circuit includes: an isolation diode D8; the control signal sampling circuit includes: a coupling capacitor C15, a thirty-fifth resistor R35 and a forty-fourth resistor R40; prevent flowing backward the circuit includes: the backflow prevention diode D12.

An anode of the isolation diode D8 is connected to the control signal output terminal of the main control circuit 14, a cathode of the isolation diode D8 is connected to the first terminal of the coupling capacitor C15 and the second terminal of the forty-th resistor R40, and the first terminal of the forty-th resistor R40 and the first terminal of the thirty-fifth resistor R35 are connected to ground.

the second end of the coupling capacitor C15 is connected to the second end of the thirty-fifth resistor R35 and the anode of the anti-backflow diode D12, and the cathode of the anti-backflow diode D12 is connected to the control signal output terminal of the main control circuit 14.

The anode of the isolation diode D8 is the first end of the isolation circuit, and the cathode of the isolation diode D8 is the second end of the isolation circuit. The connection end of the second end of the forty-th resistor R40 and the first end of the coupling capacitor C15 is the first end of the control signal sampling circuit, the connection end of the first end of the forty-th resistor R40 and the first end of the thirty-fifth resistor R35 is the second end of the control signal sampling circuit, and the second end of the coupling capacitor C15 is the third end of the control signal sampling circuit; the anode of the backflow prevention diode D12 is the first end of the backflow prevention circuit, and the cathode of the backflow prevention diode D12 is the second end of the backflow prevention circuit.

as shown in fig. 2, the pin 8 of the main control chip U2 outputs a PWM control signal, the PWM control signal passes through the twenty-sixth resistor R26, the twenty-seventh resistor R27 and the buffer diode D01, and then outputs a PWM driving signal to the MOS transistor Q2, and the PWM driving signal controls the on/off of the MOS transistor Q2, so as to achieve the purpose of dimming. Meanwhile, the sampling resistor R5 in the current sampling circuit 12 samples the dimming current and generates a current sampling signal (peak voltage) at the first end of the sampling resistor R5, which is detected by the detection resistor R75 and transmitted to the sampling signal detection end (Cs pin) of the main control chip U2; meanwhile, after the PWM control signal output by the pin 8 of the main control chip U2 is sampled by the compensation circuit 13, the PWM control signal is compensated to the sampling signal detection terminal of the main control chip U2 through the isolation diode D8 and the coupling capacitor C15, so that when the dimming is adjusted to be below 20% of the load, the sampling signal detection terminal of the main control chip U2 still has a higher voltage, thereby preventing the main control chip U2 from entering the isolation mode and eliminating the phenomenon of lamp flash.

Further, as shown in fig. 2, when the PWM control signal is at a high level, the isolation diode D3 is turned on, the PWM control signal is divided into two paths after passing through the coupling capacitor C15, one path passes through the backflow prevention diode D12 to the sampling signal detection end of the main control chip U2, and the other path passes through the thirty-fifth resistor R35 to ground. Wherein, through setting up anti-flowing backwards diode D12, can prevent that the voltage on the sampling signal detection end of main control chip U2 from flowing backwards, the normal work of interference sampling signal detection end. When the PWM control signal is low, the coupling capacitor C15 needs to be discharged, and the ground is discharged through the fortieth resistor R40, so as to prepare for PWM high-level charging in a next period.

the invention also provides a power supply which comprises the dimming control circuit of the power supply disclosed by the embodiment of the invention. Alternatively, the power supply may be a driving power supply, such as an LED driving power supply, wherein the LED driving power supply is a power supply that can be used for dimming.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.