CN-224233540-U - Active flyback circuit without auxiliary winding and switching power supply

CN224233540UCN 224233540 UCN224233540 UCN 224233540UCN-224233540-U

Abstract

The application discloses an active flyback circuit without an auxiliary winding and a switching power supply, wherein the active flyback circuit comprises a rectifying and filtering circuit, a transformer, an output circuit, a clamping circuit, a switching circuit and a control circuit, wherein the rectifying and filtering circuit is used for rectifying and filtering an input voltage, the transformer comprises a primary winding and a secondary winding, the first end of the primary winding is connected with the output end of the rectifying and filtering circuit, the output circuit is connected with the secondary winding, the clamping circuit is connected with the second end of the primary winding, the switching circuit is connected with the second end of the primary winding, the first end of the control circuit is connected with the control end of the switching circuit, the second end of the control circuit is connected with the control end of the clamping circuit, the power end of the control circuit is respectively connected with the output end of the rectifying and filtering circuit and the clamping circuit, the control circuit is used for controlling the conduction of the clamping circuit, the current between the first end and the second end of the primary winding is reduced, and the clamping circuit is used for supplying power to the control circuit. Through the mode, efficiency is improved, and components are reduced.

Inventors

WU YONGHUI
XU LIXING
XU ZEKAI

Assignees

安克创新科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20250528

Claims (10)

1. An active flyback circuit without an auxiliary winding, comprising: The rectification filter circuit is used for rectifying and filtering the input voltage; The transformer comprises a primary winding and a secondary winding, and a first end of the primary winding is connected with the output end of the rectifying and filtering circuit; an output circuit connected with the secondary winding; the clamping circuit is connected with the second end of the primary winding; a switching circuit connected to a second end of the primary winding; the first end of the control circuit is connected with the control end of the switch circuit, the second end of the control circuit is connected with the control end of the clamping circuit, and the power end of the control circuit is respectively connected with the output end of the rectifying and filtering circuit and the clamping circuit; The control circuit is used for controlling the clamp circuit to be conducted and controlling the switch circuit to be disconnected, current between the first end and the second end of the primary winding is reduced, and the clamp circuit is used for supplying power to the control circuit.
2. The active flyback circuit of claim 1 wherein the clamping circuit comprises a first switching tube, a first capacitor, a first inductor and a voltage regulator tube, wherein a first end of the first switching tube is connected with a second end of the primary winding, a second end of the first switching tube is grounded through the first capacitor, a control end of the first switching tube is connected with a second end of the control circuit, one end of the first inductor is connected with the second end of the first switching tube, the other end of the first inductor is connected with a power end of the control circuit and a negative electrode of the voltage regulator tube respectively, and an anode of the voltage regulator tube is grounded.
3. The active flyback circuit of claim 2 wherein the control circuit is configured to control the first switching tube to conduct, the first capacitor is connected to the second end of the primary winding through the first switching tube, the first capacitor is charged, and the first capacitor is configured to supply power to the control circuit through the first inductor and the voltage regulator after the charging is completed.
4. The active flyback circuit of claim 2 wherein the switching circuit comprises a second switching tube and a first resistor, the first end of the second switching tube being connected to the second end of the primary winding, the second end of the second switching tube being grounded through the first resistor, the third end of the control circuit being connected between the second end of the second switching tube and the first resistor.
5. The active flyback circuit of claim 4 wherein the control circuit is configured to control the second switching tube to open, the parasitic capacitance of the second switching tube being charged, the parasitic capacitance of the second switching tube powering the control circuit through the first inductor and the regulator.
6. The active flyback circuit of claim 4 wherein the control circuit is configured to control the second switching tube to conduct and the first switching tube to open and the transformer operates normally.
7. The active flyback circuit of any of claims 1-6 further comprising a second resistor and a third resistor, wherein a power supply terminal of the control circuit is connected to an output terminal of the rectifying and filtering circuit through the second resistor and the third resistor.
8. The active flyback circuit of claim 7 wherein the rectifying and filtering circuit comprises a first diode, a second diode, a third diode, a fourth diode, a second capacitor, a second inductor, and a third capacitor, the cathode of the first diode being connected to the anode of the second diode, the cathode of the second diode being connected to the cathode of the third diode, the anode of the third diode being connected to the cathode of the fourth diode, the anode of the fourth diode being connected to the anode of the first diode, the junction of the first diode and the second diode being connected to the junction of the third diode and the fourth diode receiving the input voltage, one end of the second inductor being connected between the cathode of the second diode and the cathode of the third diode, the other end of the second inductor being connected to one end of the second capacitor, the first end of the primary winding and the cathode of the second resistor being connected to the other end of the second diode, the other end of the second inductor being connected to the anode of the third diode, the other end of the second inductor being connected to the other end of the second capacitor and the anode of the fourth diode.
9. The active flyback circuit of claim 7 wherein the output circuit comprises a fifth diode, a fourth capacitor and a fourth resistor, the anode of the fifth diode being connected to the first end of the secondary winding, the cathode of the fifth diode being connected to one end of the fourth capacitor and one end of the fourth resistor, respectively, and the other end of the fourth resistor being connected to the fourth capacitor and the second end of the secondary winding, respectively.
10. A switching power supply comprising an active flyback circuit according to any of claims 1-9.

Description

Active flyback circuit without auxiliary winding and switching power supply Technical Field The application relates to the technical field of switching power supplies, in particular to an active flyback circuit without an auxiliary winding and a switching power supply. Background The flyback circuit is a common alternating current-direct current (AC-DC) conversion circuit, has wide application in various low-power switch power supply designs due to the advantages of simple structure, mature technology and the like, and is the most common AC-DC conversion scheme in a plurality of low-power electronic equipment power supply adapters. The transformer in the existing flyback circuit generally needs to use three windings, wherein one group is an auxiliary winding, and the auxiliary winding is mainly used for supplying power to the control circuit of the flyback circuit. Although the design can meet the basic power supply requirement, the number of components is increased due to the additional auxiliary winding, and the circuit cost is increased. In addition, the RCD circuit formed by a resistor, a capacitor and a diode in the existing flyback circuit absorbs peak current generated by leakage inductance of the transformer. The RCD circuit consumes energy flowing into the RCD circuit on the resistor, which not only reduces the overall efficiency of the flyback circuit, but also generates excess heat. Disclosure of utility model The application mainly provides an active flyback circuit without an auxiliary winding and a switching power supply, which solve the problems of high number of components, high circuit cost, low power density of the circuit and low overall efficiency of the flyback circuit caused by the additional auxiliary winding. The application provides an active flyback circuit without an auxiliary winding, which comprises the following components: The rectification filter circuit is used for rectifying and filtering the input voltage; The transformer comprises a primary winding and a secondary winding, and a first end of the primary winding is connected with the output end of the rectifying and filtering circuit; an output circuit connected with the secondary winding; the clamping circuit is connected with the second end of the primary winding; a switching circuit connected to a second end of the primary winding; the first end of the control circuit is connected with the control end of the switch circuit, the second end of the control circuit is connected with the control end of the clamping circuit, and the power end of the control circuit is respectively connected with the output end of the rectifying and filtering circuit and the clamping circuit; The control circuit is used for controlling the clamp circuit to be conducted and controlling the switch circuit to be disconnected, current between the first end and the second end of the primary winding is reduced, and the clamp circuit is used for supplying power to the control circuit. The clamping circuit comprises a first switching tube, a first capacitor, a first inductor and a voltage stabilizing tube, wherein a first end of the first switching tube is connected with a second end of the primary winding, a second end of the first switching tube is grounded through the first capacitor, a control end of the first switching tube is connected with a second end of the control circuit, one end of the first inductor is connected with the second end of the first switching tube, and the other end of the first inductor is connected with a power end of the control circuit and a negative electrode of the voltage stabilizing tube respectively, and an anode of the voltage stabilizing tube is grounded. The control circuit is used for controlling the first switching tube to be conducted, the first capacitor is connected with the second end of the primary winding through the first switching tube, the first capacitor is charged, and the first capacitor supplies power to the control circuit through the first inductor and the voltage stabilizing tube after charging is completed. The switching circuit comprises a second switching tube and a first resistor, wherein the first end of the second switching tube is connected with the second end of the primary winding, the second end of the second switching tube is grounded through the first resistor, and the third end of the control circuit is connected between the second end of the second switching tube and the first resistor. The control circuit is used for controlling the second switching tube to be disconnected, the parasitic capacitance of the second switching tube charges, and the parasitic capacitance of the second switching tube supplies power to the control circuit through the first inductor and the voltage stabilizing tube. The control circuit is used for controlling the second switching tube to be conducted and the first switching tube to be disconnected, and the transformer works normally. The active flyback circ