Slightness-removing turn-off circuit for non-isolated LED power supply

Abstract

The invention provides a non-isolated LED power supply minuteness-removing turn-off circuit, which comprises a second power supply processing module, a minuteness-removing turn-off module and an LED lamp module, and is characterized in that the second power supply processing module is used for converting a high-voltage direct-current power supply into an LED lamp module working power supply; the micro-brightness removal turn-off module is arranged between the output end of the second power supply processing module and the LED lamp module and comprises a direct-current impedance conversion unit, an alternating-current impedance conversion unit and a switching tube, and the switching tube is arranged on a direct-current loop; and the control unit of the second power supply processing module reduces the DC voltage and the non-isolated AC induced voltage to be below the set voltage through the switching signal and the DC impedance conversion unit and the combined action of the switching signal and the AC impedance conversion unit, thereby realizing the minuteness-removing turn-off of the LED lamp module. According to the invention, contactless switch control can be realized, circuit loss is reduced, and working noise is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power supply circuit, in particular to a non-isolated LED power supply micro-bright off circuit. BACKGROUND

[0002] The non-isolated LED power supply has a physical contact relationship between the output end and the input end (L, N line) during shutdown. After the power supply is controlled by the shutdown signal, the circuit stops working. However, since the input end is an alternating voltage, a relatively high alternating induced voltage exists between the (L, N line) and the ground. This induced voltage generates a weak current through the LED lamp module beads and the aluminum base of the lamp beads (the aluminum base of the lamp beads is grounded through the shell), which generates a weak brightness of the LED lamp module beads, affecting the comfort and experience of the environment.

[0003] The current technology is to shut down the positive and negative poles of the lamp beads by a relay switch, so that the positive and negative poles of the LED have no physical contact with the AC L and N lines, and the impedance is infinite, thereby solving the problem of weak brightness of the LED lamp module beads. However, since the relay needs a certain current to supply power to work, the circuit power consumption is increased, which is not conducive to the energy efficiency of the product. The relay is a mechanical switch, which not only has a sound, but also cannot be made small in size, thereby being not conducive to the miniaturization and thinning of the product. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a non-isolated LED power supply micro-bright off circuit.

[0005] The present application is a non-isolated LED power supply micro-bright off circuit, which comprises a second power supply processing module, a micro-bright off module and an LED lamp module. The second power supply processing module is used to convert a high-voltage direct-current power supply into an LED lamp module working power supply. The micro-bright off module is arranged between the output end of the second power supply processing module and the LED lamp module. The micro-bright off module comprises a direct-current impedance conversion unit, an alternating-current impedance conversion unit and a switch tube. The switch tube is arranged on a direct-current loop. The control unit of the second power supply processing module reduces the direct-current voltage and the non-isolated alternating-current induced voltage below a set voltage through a switch signal and the direct-current impedance conversion unit, and cooperates with the alternating-current impedance conversion unit, thereby realizing the micro-bright off of the LED lamp module.

[0006] Further, the dim-out module further comprises an energy storage unit, an isolation unit, a logic control unit, the output end of the second power processing module is connected with the input end of the energy storage unit, the isolation unit and the DC impedance conversion unit respectively, the control end of the DC impedance conversion unit is connected with the switch signal of the LED lamp module, the output end is connected with the power ground, the control end of the logic control unit is connected with the switch signal of the LED lamp module, the output end is connected with the control end of the switch tube, one end of the AC impedance conversion unit is connected with the positive and negative poles of the LED lamp module, the other end is connected with the ground.

[0007] Further, the AC impedance conversion unit comprises a capacitor CY4 and a capacitor CY3, one end of the capacitor CY4 is connected with the first input pin of the LED lamp module, the other end is connected with the ground, one end of the capacitor CY3 is connected with the second input pin of the LED lamp module, the other end is connected with the ground.

[0008] Further, the logic control unit comprises a triode Q7, a triode Q8 and a triode Q9, wherein the base of the triode Q8 is connected with the switch signal of the LED lamp module through the resistor R36, the emitter is connected with the ground, the collector is connected with the base of the triode Q9, and then is connected with the driving power source through the resistor R28, the emitter of the triode Q9 is connected with the ground, the collector is connected with the base of the triode Q7 through the resistor R27, the emitter of the triode Q7 is connected with the driving power source, the collector is connected with the control end of the switch tube through the resistor R20, and the control end of the switch tube is also connected with the ground through the resistor R21.

[0009] Further, the DC impedance conversion unit comprises a triode Q11 and a triode Q12, wherein the anode of the triode Q12 is connected with the switch signal of the LED lamp module through the resistor R59, the emitter is connected with the power ground, the collector is connected with the base of the triode Q11 through one or more than one resistor in series, the collector of the triode Q11 is connected with the power ground through a resistor network, and the emitter is connected with the output end of the second power processing module.

[0010] Further, the second power processing module comprises a voltage stabilizing chip U1, an isolation driving transformer T3, a switch tube Q1 and a transformer T2, wherein the input end of the voltage stabilizing chip is connected with the high-voltage DC power source, the output end is connected with the primary side of the isolation driving transformer T3, the secondary side of the isolation driving transformer T3 is connected with the control end of the switch tube Q1, the output end of the switch tube Q1 is connected with the secondary side first pin of the transformer T2, the secondary side second pin of the transformer T2 is connected with the input end of the dim-out module, the primary side first pin of the transformer T2 is connected with the FB feedback pin of the voltage stabilizing chip U1, and the primary side second pin of the transformer T2 is connected with the power ground.

[0011] Further, the first power processing module is used for converting alternating current into direct current, and outputting the converted direct current to the direct current calibration module; and the direct current calibration module is used for converting unstable high-voltage direct current into stable high-voltage direct current, and then outputting the second power processing module.

[0012] Further, the direct current calibration module adopts a voltage stabilizing circuit or a power factor correction circuit.

[0013] Further, the power factor correction circuit comprises a diode D1 connected in series at an output end of the first power processing module, a negative electrode of the diode D1 outputs the high-voltage direct current source to the second power processing module in the rear stage, and the power factor correction circuit further comprises a PFC control chip U3, a transformer T1, a switching tube Q4 and a triode Q5, wherein a first pin of a secondary side of the transformer T1 is connected to a positive electrode of the diode D1, a second pin of the secondary side of the transformer T1 is connected to a negative electrode of the diode D1 in series with the diode D2, an output end of the PFC control chip U3 is connected to a positive electrode of a diode D7 and a base of the triode Q5 through a resistor R11, a negative electrode of the diode D7 is connected to an emitter of the triode Q5 and a gate of the switching tube Q4, a collector of the triode Q5 is connected to a power supply ground, a source of the switching tube Q4 is connected to the power supply ground through a resistor R13, a drain of the switching tube Q4 is connected to a positive electrode of the diode D2, a pin 5 of the PFC control chip U3 is connected to a first pin of a primary side of the transformer T1 through a resistor R6, a second pin of the primary side of the transformer T1 is connected to the power supply ground, and a pin 4 of the PFC control chip U3 is connected to the resistor R13 and the source of the switching tube Q4 through a single group R15.

[0014] Compared with the prior art, the present application has the following beneficial effects: after the switching tube is turned off, the two connecting lines of the LED lamp module are turned off, and then the micro-brightness-off module of the present application is used to make the LED lamp module bead have a small ground-induced voltage, that is, the LED lamp module bead has only a very low voltage to the base, so that the LED lamp module bead will not have weak brightness.

[0015] The switching tube is used to replace the existing relay, and the switching tube has low power consumption and can be integrated on the existing power supply circuit, so that the volume of the product is not increased, and the product is small and thin; the switching tube is used to replace the existing relay, and the switching tube realizes non-contact switch control, reduces circuit loss and noise, and can quickly extinguish the light without turning off the AC line, so that the problem that the LED lamp module bead has weak brightness after the light is turned off in the prior art is solved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to make the technical scheme of the present application clearer, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0017] Figure 1 Structure diagram of the present application; Figure 2 Circuit principle diagram of an embodiment of the second power processing module and the micro-bright-off module of the present application; Figure 3 Circuit principle diagram of an embodiment of the first power processing module and the direct current calibration module of the present application. DETAILED DESCRIPTION

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description of the application herein is for describing particular embodiments only and is not intended to be limiting of the application; the description and claims of the application as well as the above drawings description will be understood to include all equivalents of the described structures as would be understood by one of ordinary skill in the art. The use of the terms "including", "containing", "having" and "with" are used herein to mean "comprising" unless otherwise noted. The terms "first", "second", and the like, as used herein do not have any specific meaning unless otherwise noted.

[0019] Reference to "an embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in some embodiments" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all directed to the same embodiments, or are they necessarily alternatives to each other.

[0020] For those skilled in the art to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely in conjunction with the drawings.

[0021] As shown in Figure 1 The present application is used for a non-isolated LED power micro-bright-off circuit, which comprises a second power processing module and a micro-bright-off module. The second power processing module is used for converting a high-voltage direct current power into an LED lamp module working power. The micro-bright-off module is arranged between the output end of the second power processing module and the LED lamp module, and comprises a switch tube. The switch tube is arranged on a direct current loop, and is used for realizing micro-bright-off through the switch tube.

[0022] Preferably, the example further comprises a first power processing module for converting alternating current into direct current, and outputting the converted direct current to a direct current calibration module, and the direct current calibration module is used for converting unstable high-voltage direct current into stable high-voltage direct current, and then outputting the second power processing module.

[0023] The direct current calibration module of the example can adopt a linear voltage stabilizing circuit, a power factor correction circuit, or the like.

[0024] As shown in Figure 2 As an embodiment of the application, the C part is the second power processing module of the application, which is mainly a DC-DC constant current control circuit controlled by a DC-DC voltage stabilizing chip U1. The second power processing module of the example comprises the voltage stabilizing chip U1, an isolated driving transformer T3, a switch tube Q1, and a transformer T2. The input end of the voltage stabilizing chip is connected to a high-voltage direct current power supply, and the output end is connected to the primary side of the isolated driving transformer T3. The secondary side of the isolated driving transformer T3 is connected to the control end of the switch tube Q1. The output end of the switch tube Q1 is connected to the secondary side first pin of the transformer T2. The secondary side second pin of the transformer T2 is connected to the input end of the micro-brightness off module. The primary side first pin of the transformer T2 is connected to the FB feedback pin of the voltage stabilizing chip U1. The primary side second pin of the transformer T2 is connected to the power supply ground. The conduction time of the switch tube Q1 controlled by the voltage stabilizing chip U1 can obtain the required current of the LED lamp module.

[0025] The ASUVCC power supply of the example is connected to the input power supply. When the entire circuit is connected to the power supply, the ASUVCC power supply of the example is input to the power supply end of the voltage stabilizing chip U1 through two large resistors R51 and R8 for voltage division, so as to start the voltage stabilizing chip U1. After starting, the switch tube Q1 is disconnected, and the working voltage is provided by the VCC power supply, so as to avoid the loss of the circuit power caused by the large resistor, and to ensure that the voltage stabilizing chip U1 can start to work at the first moment of connecting the power supply. The feedback pin 5 of the voltage stabilizing chip U1 is connected to the transformer T2, so as to obtain the output voltage of the transformer T2 in real time. In addition, the pin 6 of the voltage stabilizing chip U1 of the example is a detection pin, which detects the working current through the parallel detection resistors R19, R18, and R19A. When the super-high set current value is reached, the voltage stabilizing chip U1 controls the switch tube Q1 to be disconnected through the output pins 8 and 9, so as to stop supplying power to the LED lamp module in the rear stage, and to realize the overcurrent and overvoltage protection.

[0026] Part D is the dimming-off module of the present application, which further comprises an energy storage unit, an isolation unit, a switching unit, a logic control unit, a DC impedance conversion unit and an AC impedance conversion unit. The output end of the second power processing module is connected with the input end of the energy storage unit, the isolation unit and the DC impedance conversion unit respectively. The control end of the DC impedance conversion unit is connected with the switching signal of the LED lamp module, and the output end is connected with the power supply ground. The control end of the logic control unit is connected with the switching signal of the LED lamp module, and the output end is connected with the control end of the switching tube. One end of the AC impedance conversion unit is connected with the positive and negative poles of the LED lamp module, and the other end is connected with the ground. The control unit of the second power processing module works together with the switching signal, the DC impedance conversion unit and the AC impedance conversion unit to reduce the DC voltage and the non-isolated AC induced voltage to below the set voltage, thereby realizing the dimming-off of the LED lamp module.

[0027] The AC impedance conversion unit of the present application comprises a capacitor CY4 and a capacitor CY3. One end of the capacitor CY4 is connected with the first input pin of the LED lamp module, and the other end is connected with the ground. One end of the capacitor CY3 is connected with the second input pin of the LED lamp module, and the other end is connected with the ground.

[0028] Preferably, the dimming-off module of the present application further comprises an LED lamp module interface J1 and a common mode inductor L1 arranged at the input end of the LED lamp module interface J1. One end of the capacitor CY4 is connected with the first input pin of the common mode inductor L1, and the other end is connected with the ground. One end of the capacitor CY3 is connected with the second input pin of the common mode inductor L1, and the other end is connected with the ground.

[0029] The logic control unit comprises a triode Q7, a triode Q8 and a triode Q9. The base of the triode Q8 is connected with the switching signal of the LED lamp module through a resistor R36, the emitter is connected with the ground, and the collector is connected with the base of the triode Q9, which is connected with the driving power supply through a resistor R28. The emitter of the triode Q9 is connected with the ground, and the collector is connected with the base of the triode Q7 through a resistor R27. The emitter of the triode Q7 is connected with the driving power supply, and the collector is connected with the control end of the switching tube through a resistor R20. The control end of the switching tube is also connected with the ground through a resistor R21.

[0030] The DC impedance conversion unit comprises a triode Q11 and a triode Q12. The anode of the triode Q12 is connected with the switching signal of the LED lamp module through a resistor R59, the emitter is connected with the power supply ground, and the collector is connected with the base of the triode Q11 through one or more resistors in series. The collector of the triode Q11 is connected with the power supply ground through a resistor network, and the emitter is connected with the output end of the second power processing module.

[0031] The working principle of the present application is as follows: Part C and part D of the example is controlled by the ON / OFF switch signal of the voltage stabilizing chip U1, when the ON / OFF high level shutdown signal arrives, the voltage stabilizing chip U1 stops working, the triode Q1 is closed, at the same time, the triode Q8 is turned on, the triode Q9 is turned off, the triode Q7 is turned off, the triode Q6 is turned off, the triode Q12 is turned on, and the triode Q11 is turned on.

[0032] Direct current loop processing: Because the switch tube Q1 is closed, the triode Q11 of the direct current impedance conversion unit is turned on, the resistance R57 is directly connected to the polarity capacitor EC3, and the voltage on the polarity capacitor EC3 can be quickly discharged, so that the LED lamp module is not turned on as long as the direct current voltage is lower than the working voltage of the LED lamp module, and the LED lamp module will not produce afterglow after shutdown, and will be immediately extinguished.

[0033] Alternating current loop processing: Because the CY3 and CY4 in the alternating current impedance conversion unit are junction capacitors, after the alternating current passes through the junction capacitors, the alternating current voltage is already low after being attenuated by the capacitor capacity, but because the LED lamp module shell is connected to the ground, the present application is a non-isolated unit, and there is an alternating current induced voltage between the zero line and the live line of the alternating current and the ground, and the LED lamp module is generally composed of multiple lamp beads, and if the voltage of a single lamp bead is greater than 3V, there is still a possibility that individual lamp beads are lit, because the parasitic capacitor (LED CAP) between the positive and negative electrodes of the LED lamp module and the shell is very small, and is not enough to attenuate the alternating voltage between the two ends, therefore, the present application adds two large capacitors CY3 and CY4 to form an alternating current impedance conversion unit, and the alternating voltage between the positive and negative electrodes of the LED lamp module and the shell is reduced again, and as long as the alternating voltage is low enough, the LED lamp module beads will not be lit.

[0034] In summary, the present application solves the problem that the LED lamp module beads produce weak brightness after the light is turned off from the direct current loop and the alternating current loop, and solves the problem through the synergistic effect of each circuit unit.

[0035] As shown in Figure 3 Part A is a first power supply processing module, and part B is a direct current calibration module, in part A, the alternating current passes through the fuse F1 overcurrent protection, then passes through the capacitor CX1 and the common mode inductor L2 filtering, enters the rectifier BD1 rectification, and obtains the unstable direct current BD+.

[0036] The application adopts a power factor correction circuit to convert unstable direct current into stable direct current voltage output. The power factor correction circuit in this example includes a diode D1 connected in series at the output end of a first power supply processing module, the negative electrode of the diode D1 outputs a high voltage direct current source to a second power supply processing module in the next stage. The power factor correction circuit further includes a PFC control chip U3, a transformer T1, a switching tube Q4 and a triode Q5. The first pin of the secondary side of the transformer T1 is connected to the positive electrode of the diode D1, the second pin is connected to the negative electrode of the diode D1 after connecting the diode D2 in series. The output end of the PFC control chip U3 is connected to the positive electrode of the diode D7 and the base of the triode Q5 through the resistor R11 respectively. The negative electrode of the diode D7 is connected to the emitter of the triode Q5 and the gate of the switching tube Q4 respectively. The collector of the triode Q5 is connected to the power supply ground. The source of the switching tube Q4 is connected to the power supply ground through the resistor R13. The drain of the switching tube Q4 is connected to the positive electrode of the diode D2. The pin 5 of the PFC control chip U3 is connected to the first pin of the primary side of the transformer T1 through the resistor R6. The second pin of the primary side of the transformer T1 is connected to the power supply ground. The pin 4 of the PFC control chip U3 is connected to the resistor R13 and the source of the switching tube Q4 through the single group R15.

[0037] The unstable direct current BD+ is converted by the PFC control chip U3 and the transformer T1, and the required direct current voltage of about 400V is obtained on the polarity capacitor EC2. The second branch formed by the transformer T1 in this example can raise the voltage to the required voltage, and the control of the PFC control chip U3 on the transformer T1 and the switching tube Q4 can realize stable voltage supply. The triode Q5 can quickly turn off the switching tube Q4 when the circuit is overcurrent and overvoltage, thereby improving the safety of the circuit.

[0038] As can be seen from the above, compared with the prior art, the application has the following beneficial effects: after the switching tube turns off the two connecting lines of the positive and negative electrodes of the LED lamp module bead, the LED lamp module bead is connected to the ground through the micro-brightness turn-off module of the application, so that the voltage between the positive and negative electrodes of the LED lamp module bead and the base is very low, and the LED lamp module bead will not have weak brightness.

[0039] The switching tube of the application replaces the existing relay, has low power consumption, can be integrated on the existing power supply circuit, does not increase the size of the product, and is beneficial to the miniaturization and thinning of the product. The switching tube replaces the existing relay to realize non-contact switch control, reduce circuit loss and noise, and can quickly extinguish the light without turning off the AC line, thereby solving the problem that the LED lamp module bead will have weak brightness after the light is turned off in the prior art.

[0040] The above described embodiments are the preferred embodiments of the present application, and are not intended to limit the specific implementation of the present application. The scope of the present application includes, but is not limited to, the above described embodiments. Any equivalent changes made in accordance with the present application are within the scope of the present application.

Claims

1. A circuit for shutting off low brightness in a non-isolated LED power supply, characterized in that: The application relates to a LED lamp module, which comprises a second power processing module, a micro-light-off module and an LED lamp module, the second power processing module is used for converting a high-voltage direct-current power supply into an operating power supply of the LED lamp module, the micro-light-off module is arranged between an output end of the second power processing module and the LED lamp module, the micro-light-off module comprises a direct-current impedance conversion unit, an alternating-current impedance conversion unit and a switch tube, the switch tube is arranged on a direct-current loop, a control unit of the second power processing module lowers a direct-current voltage and a non-isolated alternating-current induced voltage below a set voltage through a switch signal and the direct-current impedance conversion unit and in cooperation with the alternating-current impedance conversion unit, and the micro-light-off of the LED lamp module is realized.

2. The non-isolated LED power supply dim-to-off circuit of claim 1, wherein: The micro-light-off module further comprises an energy storage unit, an isolation unit and a logic control unit, an output end of the second power processing module is connected with input ends of the energy storage unit, the isolation unit and the direct-current impedance conversion unit respectively, a control end of the direct-current impedance conversion unit is connected with a switch signal of the LED lamp module, and an output end is connected with a power supply ground, a control end of the logic control unit is connected with the switch signal of the LED lamp module, and an output end is connected with a control end of the switch tube, one end of the alternating-current impedance conversion unit is connected with positive and negative poles of the LED lamp module, and the other end is connected with the ground.

3. The non-isolated LED power supply dim-to-off circuit of claim 2, wherein: The alternating-current impedance conversion unit comprises a capacitor CY4 and a capacitor CY3, one end of the capacitor CY4 is connected with a first input pin of the LED lamp module, and the other end is connected with the ground, one end of the capacitor CY3 is connected with a second input pin of the LED lamp module, and the other end is connected with the ground.

4. The non-isolated LED power supply dim-to-off circuit of claim 2, wherein: The logic control unit comprises a triode Q7, a triode Q8 and a triode Q9, wherein a base of the triode Q8 is connected with the switch signal of the LED lamp module through a resistor R36, an emitter is connected with the ground, and an anode is connected with a base of the triode Q9 and then connected with a driving power supply through a resistor R28, an emitter of the triode Q9 is connected with the ground, an anode is connected with a base of the triode Q7 through a resistor R27, an emitter of the triode Q7 is connected with the driving power supply, and an anode is connected with the control end of the switch tube through a resistor R20, and the control end of the switch tube is also connected with the ground through a resistor R21.

5. The non-isolated LED power supply dim-to-off circuit of claim 2, wherein: The direct-current impedance conversion unit comprises a triode Q11 and a triode Q12, wherein a cathode of the triode Q12 is connected with the switch signal of the LED lamp module through a resistor R59, an emitter is connected with a power supply ground, and an anode is connected with a base of the triode Q11 through more than one resistor in series, an anode of the triode Q11 is connected with the power supply ground through a resistor network, and an emitter is connected with an output end of the second power processing module.

6. The non-isolated LED power supply dim-to-off circuit of claim 1, wherein: The second power processing module comprises a voltage stabilizing chip U1, an isolation driving transformer T3, a switch tube Q1 and a transformer T2, wherein the input end of the voltage stabilizing chip is connected with a high-voltage direct current power supply, the output end is connected with the primary side of the isolation driving transformer T3, the secondary side of the isolation driving transformer T3 is connected with the control end of the switch tube Q1, the output end of the switch tube Q1 is connected with the secondary side first pin of the transformer T2, the secondary side second pin of the transformer T2 is connected with the input end of the micro-brightness off module, the primary side first pin of the transformer T2 is connected with the FB feedback pin of the voltage stabilizing chip U1, and the primary side second pin of the transformer T2 is connected with a power supply ground.

7. The dimming off circuit for a non-isolated LED power supply of any one of claims 1-6, wherein: The first power processing module is used for converting alternating current into direct current, and outputting the converted direct current to the direct current calibration module, and the direct current calibration module is used for converting unstable high-voltage direct current into stable high-voltage direct current power supply, and then outputting the second power processing module.

8. The non-isolated LED power supply dim-to-off circuit of claim 7, wherein: The direct current calibration module adopts a voltage stabilizing circuit or a power factor correction circuit.

9. The non-isolated LED power supply dim-to-off circuit of claim 8, wherein: The power factor correction circuit comprises a diode D1 connected in series at the output end of the first power processing module, the negative electrode of the diode D1 outputs a high-voltage direct current source to the second power processing module in the rear stage, and the power factor correction circuit further comprises a PFC control chip U3, a transformer T1, a switch tube Q4 and a triode Q5, wherein the secondary side first pin of the transformer T1 is connected with the positive electrode of the diode D1, the secondary side second pin is connected with the negative electrode of the diode D1 after being connected with the diode D2 in series, the output end of the PFC control chip U3 is connected with the positive electrode of a diode D7 and the base of the triode Q5 through resistors R11, the negative electrode of the diode D7 is connected with the emitter of the triode Q5 and the gate of the switch tube Q4, the collector of the triode Q5 is connected with a power supply ground, the source of the switch tube Q4 is connected with the power supply ground through a resistor R13, the drain of the switch tube Q4 is connected with the positive electrode of the diode D2, the pin 5 of the PFC control chip U3 is connected with the primary side first pin of the transformer T1 through a resistor R6, the primary side second pin of the transformer T1 is connected with a power supply ground, and the pin 4 of the PFC control chip U3 is connected with the resistor R13 and the source of the switch tube Q4 through a single group R15.

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