Flyback power supply and double-tube flyback conversion topology circuit

Abstract

This invention discloses a flyback power supply and a dual-transistor flyback converter topology circuit. The dual-transistor flyback converter topology circuit includes MOSFET Q1, MOSFET Q2, resistors R2, R3, R4, and R8, capacitor C4, TVS diode D3, and Zener diode D4. MOSFET Q2 controls MOSFET Q1 through resistor R2, capacitor C4, TVS diode D3, and Zener diode D4. This dual-transistor flyback converter topology circuit eliminates the need for an isolation transformer or isolation driver chip, thus helping to reduce the cost and size of the flyback power supply.

Description

Technical Field

[0001] This utility model relates to the field of power supply, and in particular to a flyback power supply and a two-transistor flyback converter topology circuit. Background Technology

[0002] Existing flyback power supplies use a dual-transistor flyback converter topology circuit to achieve voltage-power conversion by switching two MOSFETs together. However, since the ground of the upper MOSFET (i.e., the MOSFET connected to the primary winding of the main transformer of the flyback power supply) in the existing dual-transistor flyback converter topology circuit is floating, an additional isolation transformer or isolation driver chip is required to generate the driving power to drive the upper MOSFET, which increases the design difficulty, size and cost of the flyback power supply.

[0003] In view of the above problems, it is necessary to study a flyback power supply and a two-transistor flyback converter topology circuit. This two-transistor flyback converter topology circuit does not require isolation transformers or isolation driver chips for driving, which helps to reduce the cost and size of the flyback power supply. Utility Model Content

[0004] The purpose of this invention is to provide a flyback power supply and a dual-transistor flyback converter topology circuit. This dual-transistor flyback converter topology circuit does not require an isolation transformer or isolation driver chip for driving, which helps to reduce the cost and size of the flyback power supply.

[0005] To achieve the above objectives, the solution of this utility model is:

[0006] A dual-transistor flyback converter topology includes MOSFETs Q1 and Q2, resistors R2, R3, R4, and R8, capacitor C4, TVS diode D3, and Zener diode D4. The first terminal of resistor R2 is connected to the first terminal of the dual-transistor flyback converter topology. The second terminal of resistor R2 is connected to the first terminal of capacitor C4, the cathode of Zener diode D4, and the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the second terminal of the dual-transistor flyback converter topology. The source of MOSFET Q1, the second terminal of capacitor C4, the cathode of TVS diode D3, and the anode of Zener diode D4 are connected to the drain of MOSFET Q2. The gate of MOSFET Q2 is connected to the first terminals of resistors R3 and R4. The second terminal of resistor R3 is connected to the control terminal of the dual-transistor flyback converter topology. The source of MOSFET Q2 is connected to the second terminal of resistor R4 and the first terminal of resistor R8. The second terminal of resistor R8 and the anode of TVS diode D3 are connected to the input ground.

[0007] A flyback power supply includes a DC input circuit, a control circuit, a main transformer T1, an output rectifier circuit, an output feedback circuit, and a two-transistor flyback converter topology as described above. The DC input circuit is connected to the first terminal of the two-transistor flyback converter topology and the first terminal of the primary winding of the main transformer T1. The second terminal of the two-transistor flyback converter topology is connected to the second terminal of the secondary winding of the main transformer T1. The secondary winding of the main transformer T1 is connected to the output rectifier circuit. The output feedback circuit is connected to the output rectifier circuit and the control circuit. The control circuit is connected to the control terminal of the two-transistor flyback converter topology.

[0008] The flyback power supply also includes an RCD snubber circuit connected to the first and second ends of the primary winding of the main transformer T1.

[0009] The RCD absorption circuit includes a resistor R1, a capacitor C1, and a fast recovery diode D1. The first end of the resistor R1 and the first end of the capacitor C1 are connected to the first end of the primary winding of the main transformer T1. The second end of the resistor R1 and the second end of the capacitor C1 are connected to the cathode of the fast recovery diode D1. The anode of the fast recovery diode D1 is connected to the second end of the primary winding of the main transformer T1.

[0010] The control circuit includes a control chip U1 and a capacitor C6; pins 1, 4, and 7 of the control chip U1 are connected to the input ground, pin 2 of the control chip U1 is connected to the output terminal of the output feedback circuit, pin 5 of the control chip U1 is connected to the control terminal of the dual-transistor flyback converter topology circuit, pin 8 of the control chip U1 is connected to the input ground through capacitor C6, and pin 6 of the control chip U1 is connected to the DC input circuit.

[0011] The output rectifier circuit includes diodes D2 and D5, capacitors C2, C3, C12, and C13, and inductors L1 and L2. The anode of diode D2 is connected to the first end of the primary winding of the main transformer T1. The cathode of diode D2 is connected to the first end of capacitor C2 and the first end of inductor L1. The second end of inductor L1 and the first end of capacitor C12 are connected to the positive output terminal of the output rectifier circuit. The cathode of diode D5 is connected to the second end of the secondary winding of the main transformer T1. The anode of diode D5 is connected to the first end of capacitor C3 and the first end of inductor L2. The second end of inductor L2 and the first end of capacitor C13 are connected to the negative output terminal of the output rectifier circuit. The second ends of capacitors C2, C3, C12, and C13 are connected to the first end of the secondary winding of the main transformer T1 and the second end of the primary winding of the main transformer T1, respectively. The second ends of capacitors C2, C3, C12, and C13 are connected to the output ground.

[0012] The output feedback circuit includes resistors R7, R9, R10, and R12, capacitors C8 and C9, a voltage reference chip U2, and an optocoupler U3. The positive terminal of the output side of the optocoupler U3 is connected to the output terminal of the output feedback circuit, and the negative terminal of the output side of the optocoupler U3 is connected to the input ground. The first terminals of resistors R7 and R10, the second terminals of resistors R7 and R9 are connected to the input terminal of the output feedback circuit, which is connected to the output rectifier circuit. The second terminal of resistor R10 is connected to the negative terminal of the input side of the optocoupler U3, the first terminal of capacitor C8, the first terminal of resistor R11, and the cathode of the voltage reference chip U2. The first terminal of resistor R11 is connected to the first terminal of capacitor C9. The second terminals of resistors R9, R12, C8, and C9 are connected to the reference terminal of the voltage reference chip U2. The second terminal of resistor R12 is connected to the anode of the voltage reference chip and then to the output ground.

[0013] The flyback power supply also includes an auxiliary power supply circuit, which includes a diode D6 and a capacitor C5. The anode of the diode D6 is connected to the first end of the auxiliary winding of the main transformer T1. The cathode of the diode D6 and the first end of the capacitor C5 are connected to the output terminal of the auxiliary power supply circuit. The output terminal of the auxiliary power supply circuit is connected to pin 6 of the control chip U1. The second end of the capacitor C5 and the second end of the auxiliary winding of the main transformer T1 are connected to the input ground.

[0014] The DC input circuit includes resistor R5, resistor R6, capacitor CE1, capacitor CE2, and DC port HV-DC; the first end of resistor R5 and the positive terminal of capacitor CE1 are connected to DC port HV-DC, the second end of resistor R5 is connected to the first end of resistor R6, the positive terminals of resistor R6 and capacitor CE2 are connected to pin 6 of control chip U1, and the negative terminals of capacitor CE2 and capacitor CE1 are connected to input ground.

[0015] Pin 3 of the control chip U1 is connected to the first end of resistor R8 in the dual-transistor flyback converter topology circuit.

[0016] After adopting the above scheme, the working principle of the dual-transistor flyback converter topology circuit of this utility model is as follows:

[0017] When the PWM signal output from the control circuit to the control terminal of the dual-transistor flyback converter topology is high, MOSFET Q2 is turned on, causing the anode of Zener diode D4 to be shorted to the input ground. In this way, resistor R2 and Zener diode D4 form a current loop. Due to the presence of Zener diode D4, a driving voltage is generated at the gate of MOSFET Q1, which in turn turns on MOSFET Q1. At this time, both MOSFET Q1 and MOSFET Q2 are turned on.

[0018] When the PWM signal output from the control circuit to the control terminal of the dual-transistor flyback converter topology is low, MOSFET Q2 is turned off, causing its drain voltage to rise rapidly. (Because MOSFET Q2 is turned off, the voltage originally applied to the primary winding of the main transformer T1 will be quickly applied to the drain of MOSFET Q2.) Thus, the drain voltage of MOSFET Q2 forms a loop through the forward conduction of Zener diode D4 to TVS diode D3 and input ground. At this time, the drain-to-source voltage of MOSFET Q2 is equal to the clamping voltage of TVS diode D3. At the same time, Zener diode D4 is forward conducted, making the gate-to-source voltage of MOSFET Q1 equal, thereby turning off MOSFET Q1.

[0019] As described above, the dual-transistor flyback converter topology of this invention controls the on / off state of MOSFET Q1 by controlling the switching on and off state of MOSFET Q2, eliminating the need for an isolation transformer or isolation driver chip, thus helping to reduce the cost and size of the flyback power supply. Furthermore, through the clamping effect of the TVS diode D3, this invention ensures that the voltage across MOSFETs Q1 and Q2 during turn-off is less than the output voltage of the DC input voltage, allowing the use of MOSFETs with lower voltage ratings for Q1 and Q2, further contributing to cost reduction. Attached Figure Description

[0020] Figure 1 This is the circuit diagram of the flyback power supply of this utility model. Detailed Implementation

[0021] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.

[0022] like Figure 1 As shown, this utility model discloses a flyback power supply, which includes a DC input circuit, a control circuit, a main transformer T1, an output rectifier circuit, an output feedback circuit, and a two-transistor flyback converter topology circuit. The DC input circuit is connected to the first terminal of the two-transistor flyback converter topology circuit and the first terminal of the primary winding of the main transformer T1. The second terminal of the two-transistor flyback converter topology circuit is connected to the second terminal of the secondary winding of the main transformer T1. The secondary winding of the main transformer T1 is connected to the output rectifier circuit. The output feedback circuit is connected to the output rectifier circuit and the control circuit. The control circuit is connected to the control terminal of the two-transistor flyback converter topology circuit.

[0023] In an embodiment of this utility model, the dual-transistor flyback converter topology includes a MOSFET Q1, a MOSFET Q2, resistors R2, R3, R4, and R8, a capacitor C4, a TVS diode D3, and a Zener diode D4. The first terminal of resistor R2 is connected to the first terminal of the dual-transistor flyback converter topology. The second terminal of resistor R2 is connected to the first terminal of capacitor C4, the cathode of Zener diode D4, and the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the second terminal of the dual-transistor flyback converter topology. The source of MOSFET Q1, the second terminal of capacitor C4, the cathode of TVS diode D3, and the anode of Zener diode D4 are connected to the drain of MOSFET Q2. The gate of MOSFET Q2 is connected to the first terminals of resistors R3 and R4. The second terminal of resistor R3 is connected to the control terminal of the dual-transistor flyback converter topology. The source of MOSFET Q2 is connected to the second terminal of resistor R4 and the first terminal of resistor R8. The second terminal of resistor R8 and the anode of TVS diode D3 are connected to the input ground. The working principle of the dual-transistor flyback converter topology is as follows:

[0024] When the PWM signal output from the control circuit to the control terminal of the dual-transistor flyback converter topology is high, MOSFET Q2 is turned on, causing the anode of Zener diode D4 to be shorted to the input ground. This creates a current loop between resistor R2 and Zener diode D4. Furthermore, the presence of Zener diode D4 generates a driving voltage at the gate of MOSFET Q1, causing MOSFET Q1 to turn on. At this time, both MOSFETs Q1 and Q2 are turned on. The DC input circuit then applies a voltage to the primary winding of the main transformer T1, causing the current in the primary winding of the main transformer T1 to rise slowly, allowing the main transformer T1 to store energy.

[0025] When the PWM signal output from the control circuit to the control terminal of the dual-transistor flyback converter topology is low, MOSFET Q2 turns off, causing its drain voltage to rise rapidly. (Because MOSFET Q2 is turned off, the voltage originally applied to the primary winding of the main transformer T1 will quickly be applied to the drain of MOSFET Q2.) Thus, the drain voltage of MOSFET Q2 forms a loop through the forward conduction of Zener diode D4 to TVS diode D3 and input ground. At this time, the drain-to-source voltage of MOSFET Q2 is equal to the clamping voltage of TVS diode D3. Simultaneously, Zener diode D4 is forward-conducting, making the gate-to-source voltage of MOSFET Q1 equal, thereby turning off MOSFET Q1. In this way, both MOSFETs Q1 are turned off, the main transformer T1 releases energy, and the output rectifier circuit performs rectification.

[0026] As described above, the dual-transistor flyback converter topology of this invention controls the on / off state of MOSFET Q1 by controlling the switching on and off state of MOSFET Q2, eliminating the need for an isolation transformer or isolation driver chip, thus helping to reduce the cost and size of the flyback power supply. Furthermore, through the clamping effect of the TVS diode D3, this invention ensures that the voltage across MOSFETs Q1 and Q2 during turn-off is less than the output voltage of the DC input voltage, allowing the use of MOSFETs with lower voltage ratings for Q1 and Q2, further contributing to cost reduction.

[0027] In an embodiment of this utility model, the control circuit includes a control chip U1 and a capacitor C6. The control chip U1 can be an NCP1380D. Pins 1, 4, and 7 of the control chip U1 are connected to the input ground. Pin 2 of the control chip U1 is connected to the output terminal of the output feedback circuit. Pin 5 of the control chip U1 is connected to the control terminal of the dual-transistor flyback converter topology circuit. Pin 8 of the control chip U1 is connected to the input ground through capacitor C6. Pin 6 of the control chip U1 is connected to the DC input circuit. Pin 3 of the control chip U1 provides a PWM signal to the control terminal of the dual-transistor flyback converter topology circuit. The DC input circuit supplies power to the control chip U1. The output feedback circuit feeds back the output voltage of the output rectifier circuit to pin 2 of the control chip U1, so that the control chip U1 adjusts the duty cycle of the PWM signal provided to the control terminal of the dual-transistor flyback converter topology circuit accordingly, thereby stabilizing the output voltage of the output rectifier circuit.

[0028] In an embodiment of this utility model, pin 3 of the control chip U1 can be connected to the first end of the resistor R8 of the dual-transistor flyback converter topology circuit; when the voltage at the first end of the resistor R8 exceeds a set threshold, the control chip U1 stops providing PWM signals to the control terminal of the dual-transistor flyback converter topology circuit, thereby shutting down the dual-transistor flyback converter topology circuit to achieve overcurrent protection.

[0029] In an embodiment of this utility model, the control circuit further includes capacitors C7 and C11. Pin 2 of the control chip U1 is grounded through capacitor C7, and pin 3 of the control chip U1 is grounded through capacitor C11. Capacitors C7 and C11 have the function of stabilizing the loop control.

[0030] In an embodiment of this invention, the DC input circuit includes resistors R5 and R6, capacitors CE1 and CE2, and a DC port HV-DC. The first terminal of resistor R5 and the positive terminal of capacitor CE1 are connected to the DC port HV-DC. The second terminal of resistor R5 is connected to the first terminal of resistor R6. Resistor R6 and the positive terminal of capacitor CE2 are connected to pin 6 of control chip U1. The negative terminals of capacitor CE2 and CE1 are connected to input ground. When the DC port HV-DC is connected to a DC power supply, resistors R5 and R6 charge capacitor CE2. When the voltage of capacitor CE2 exceeds the startup voltage of control chip U1, control chip U1 operates, causing pin 5 of control chip U1 to output a PWM signal to the dual-transistor flyback converter topology circuit.

[0031] In an embodiment of this utility model, the output rectifier circuit includes diode D2, diode D5, capacitors C2, C3, C12, and C13, inductor L1, and inductor L2. The anode of diode D2 is connected to the first terminal of the primary winding of the main transformer T1. The cathode of diode D2 is connected to the first terminal of capacitor C2 and the first terminal of inductor L1. The second terminal of inductor L1 and the first terminal of capacitor C12 are connected to the positive output terminal of the output rectifier circuit. The cathode of diode D5 is connected to the second terminal of the secondary winding of the main transformer T1. The diode D5's anode is connected to the first terminal of capacitor C3 and the first terminal of inductor L2. The second terminal of inductor L2 and the first terminal of capacitor C13 are connected to the negative output terminal of the output rectifier circuit. The second terminals of capacitors C2, C3, C12, and C13 are connected to the first terminal of the second winding of the main transformer T1 and the second terminal of the first winding of the main transformer T1. The second terminals of capacitors C2, C3, C12, and C13 are connected to the output ground.

[0032] In an embodiment of this utility model, the output feedback circuit includes resistors R7, R9, R10, and R12, capacitors C8 and C9, a voltage reference chip U2, and an optocoupler U3. The positive terminal of the output side of the optocoupler U3 is connected to the output terminal of the output feedback circuit, and the negative terminal of the output side of the optocoupler U3 is connected to the input ground. The first terminal of the positive terminal of the input side of the optocoupler U3 is connected to the first terminal of resistor R7 and the first terminal of resistor R10. The second terminal of resistor R7 and the first terminal of resistor R9 are connected to the input terminal of the output feedback circuit. The input terminal of the output feedback circuit is connected to the output rectifier circuit. The second terminal of resistor R10 is connected to the negative terminal of the input side of the optocoupler U3, the first terminal of capacitor C8, the first terminal of resistor R11, and the cathode of the voltage reference chip U2. The first terminal of resistor R11 is connected to the first terminal of capacitor C9. The second terminals of resistor R9, resistor R12, capacitor C8, and capacitor C9 are connected to the reference terminal of the voltage reference chip U2. The second terminal of resistor R12 is connected to the anode of the voltage reference chip and then to the output ground. When the voltage supplied by the output rectifier circuit to the input terminal of the output feedback circuit exceeds the set value, the voltage reference chip U2 controls the optocoupler U3 to conduct, so that the output feedback circuit outputs a low-level signal to the control chip U1, and the control chip U1 adjusts the duty cycle of the output PWM signal.

[0033] In embodiments of this invention, the flyback power supply may further include an auxiliary power supply circuit. The auxiliary power supply circuit includes a diode D6 and a capacitor C5. The anode of diode D6 is connected to the first end of the auxiliary winding of the main transformer T1. The cathode of diode D6 and the first end of capacitor C5 are connected to the output terminal of the auxiliary power supply circuit. The output terminal of the auxiliary power supply circuit is connected to pin 6 of the control chip U1. The second end of capacitor C5 and the second end of the auxiliary winding of the main transformer T1 are connected to the input ground. This invention provides a stable power supply to the control chip U1 through the auxiliary power supply circuit.

[0034] In an embodiment of this invention, the flyback power supply further includes an RCD snubber circuit connected to the first and second terminals of the primary winding of the main transformer T1. The RCD snubber circuit demagnetizes the main transformer T1, protecting the MOSFETs Q1 and Q2 of the dual-transistor flyback converter topology. The RCD snubber circuit includes a resistor R1, a capacitor C1, and a fast recovery diode D1. The first terminals of resistor R1 and capacitor C1 are connected to the first terminal of the primary winding of the main transformer T1. The second terminals of resistor R1 and capacitor C1 are connected to the cathode of the fast recovery diode D1. The anode of the fast recovery diode D1 is connected to the second terminal of the primary winding of the main transformer T1.

[0035] The above embodiments and figures are not intended to limit the product form and style of this utility model. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of this utility model.

Claims

1. A two-transistor flyback converter topology circuit, characterized in that: This includes MOSFET Q1, MOSFET Q2, resistors R2, R3, R4, R8, capacitor C4, TVS diode D3, and Zener diode D4; The first terminal of resistor R2 is connected to the first terminal of the dual-transistor flyback converter topology. The second terminal of resistor R2 is connected to the first terminal of capacitor C4, the cathode of Zener diode D4, and the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the second terminal of the dual-transistor flyback converter topology. The source of MOSFET Q1, the second terminal of capacitor C4, the cathode of TVS diode D3, and the anode of Zener diode D4 are connected to the drain of MOSFET Q2. The gate of MOSFET Q2 is connected to the first terminals of resistor R3 and R4. The second terminal of resistor R3 is connected to the control terminal of the dual-transistor flyback converter topology. The source of MOSFET Q2 is connected to the second terminal of resistor R4 and the first terminal of resistor R8. The second terminal of resistor R8 and the anode of TVS diode D3 are connected to the input ground.

2. A flyback power supply, characterized in that: It includes a DC input circuit, a control circuit, a main transformer T1, an output rectifier circuit, an output feedback circuit, and a two-transistor flyback converter topology as described in claim 1; the DC input circuit is connected to the first connection terminal of the two-transistor flyback converter topology and the first terminal of the primary winding of the main transformer T1, the second connection terminal of the two-transistor flyback converter topology is connected to the second terminal of the secondary winding of the main transformer T1, the secondary winding of the main transformer T1 is connected to the output rectifier circuit, the output feedback circuit is connected to the output rectifier circuit and the control circuit, and the control circuit is connected to the control terminal of the two-transistor flyback converter topology.

3. The flyback power supply as described in claim 2, characterized in that: It also includes an RCD snubber circuit connected to the first and second ends of the primary winding of the main transformer T1.

4. The flyback power supply as described in claim 3, characterized in that: The RCD absorption circuit includes a resistor R1, a capacitor C1, and a fast recovery diode D1. The first end of the resistor R1 and the first end of the capacitor C1 are connected to the first end of the primary winding of the main transformer T1. The second end of the resistor R1 and the second end of the capacitor C1 are connected to the cathode of the fast recovery diode D1. The anode of the fast recovery diode D1 is connected to the second end of the primary winding of the main transformer T1.

5. The flyback power supply as described in claim 2, characterized in that: The control circuit includes a control chip U1 and a capacitor C6; pins 1, 4, and 7 of the control chip U1 are connected to the input ground, pin 2 of the control chip U1 is connected to the output terminal of the output feedback circuit, pin 5 of the control chip U1 is connected to the control terminal of the dual-transistor flyback converter topology circuit, pin 8 of the control chip U1 is connected to the input ground through capacitor C6, and pin 6 of the control chip U1 is connected to the DC input circuit.

6. The flyback power supply as described in claim 5, characterized in that: The output rectifier circuit includes diodes D2 and D5, capacitors C2, C3, C12, and C13, and inductors L1 and L2. The anode of diode D2 is connected to the first end of the primary winding of the main transformer T1. The cathode of diode D2 is connected to the first end of capacitor C2 and the first end of inductor L1. The second end of inductor L1 and the first end of capacitor C12 are connected to the positive output terminal of the output rectifier circuit. The cathode of diode D5 is connected to the second end of the secondary winding of the main transformer T1. The anode of diode D5 is connected to the first end of capacitor C3 and the first end of inductor L2. The second end of inductor L2 and the first end of capacitor C13 are connected to the negative output terminal of the output rectifier circuit. The second ends of capacitors C2, C3, C12, and C13 are connected to the first end of the secondary winding of the main transformer T1 and the second end of the primary winding of the main transformer T1, respectively. The second ends of capacitors C2, C3, C12, and C13 are connected to the output ground.

7. The flyback power supply as described in claim 5, characterized in that: The output feedback circuit includes resistors R7, R9, R10, and R12, capacitors C8 and C9, a voltage reference chip U2, and an optocoupler U3. The positive terminal of the output side of the optocoupler U3 is connected to the output terminal of the output feedback circuit, and the negative terminal of the output side of the optocoupler U3 is connected to the input ground. The first terminals of resistors R7 and R10, the second terminals of resistors R7 and R9 are connected to the input terminal of the output feedback circuit, which is connected to the output rectifier circuit. The second terminal of resistor R10 is connected to the negative terminal of the input side of the optocoupler U3, the first terminal of capacitor C8, the first terminal of resistor R11, and the cathode of the voltage reference chip U2. The first terminal of resistor R11 is connected to the first terminal of capacitor C9. The second terminals of resistors R9, R12, C8, and C9 are connected to the reference terminal of the voltage reference chip U2. The second terminal of resistor R12 is connected to the anode of the voltage reference chip and then to the output ground.

8. The flyback power supply as described in claim 5, characterized in that: It also includes an auxiliary power supply circuit, which includes a diode D6 and a capacitor C5. The anode of the diode D6 is connected to the first end of the auxiliary winding of the main transformer T1. The cathode of the diode D6 and the first end of the capacitor C5 are connected to the output terminal of the auxiliary power supply circuit. The output terminal of the auxiliary power supply circuit is connected to pin 6 of the control chip U1. The second end of the capacitor C5 and the second end of the auxiliary winding of the main transformer T1 are connected to the input ground.

9. The flyback power supply as described in claim 5, characterized in that: The DC input circuit includes resistor R5, resistor R6, capacitor CE1, capacitor CE2, and DC port HV-DC; the first end of resistor R5 and the positive terminal of capacitor CE1 are connected to DC port HV-DC, the second end of resistor R5 is connected to the first end of resistor R6, the positive terminals of resistor R6 and capacitor CE2 are connected to pin 6 of control chip U1, and the negative terminals of capacitor CE2 and capacitor CE1 are connected to input ground.

10. The flyback power supply as described in claim 5, characterized in that: Pin 3 of the control chip U1 is connected to the first end of resistor R8 in the dual-transistor flyback converter topology circuit.

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