Constant current constant voltage dual circuit

Abstract

The embodiment of the present application provides a constant-current constant-voltage dual-circuit, comprising: a transformer comprising a primary winding and a secondary winding coupled to each other, the primary winding being used for receiving an input voltage, and the primary winding being grounded through a switch tube; a first output circuit connected with the secondary winding and used for outputting a voltage; a second output circuit connected with the primary winding and used for outputting a current; a first feedback circuit connected with the first output circuit and used for obtaining a first feedback signal based on the output voltage; a second feedback circuit connected with the second output circuit and used for obtaining a second feedback signal based on the output current; and a controller connected with the switch tube, the first feedback circuit and the second feedback circuit, and used for driving the switch tube based on the first feedback signal or the second feedback signal. The constant-current constant-voltage dual-circuit of the embodiment of the present application can realize constant-voltage output and constant-current output through one controller, so that the circuit structure can be simplified and the cost can be reduced.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to a constant current and constant voltage dual-channel circuit. Background Technology

[0002] In existing switching power supplies, the flyback voltage uses a constant voltage mode, requiring one chip for control; the buck circuit uses a constant current mode, requiring another chip for control. Therefore, achieving constant current and constant voltage control requires two chips, resulting in a complex circuit structure and high cost. Utility Model Content

[0003] This application provides a constant current and constant voltage dual-channel circuit, which can realize constant voltage output and constant current output through a single controller, thereby simplifying the circuit structure and reducing costs.

[0004] This application provides a constant current and constant voltage dual-channel circuit, including: A transformer includes a primary winding and a secondary winding coupled to each other, wherein the primary winding is used to receive input voltage and the primary winding is grounded through a switching transistor; The first output circuit is connected to the secondary winding and is used to output voltage; The second output circuit is connected to the primary winding and is used to output current. A first feedback circuit, connected to the first output circuit, is used to obtain a first feedback signal based on the output voltage; A second feedback circuit, connected to the second output circuit, is used to obtain a second feedback signal based on the output current; The controller is connected to the switching transistor, the first feedback circuit, and the second feedback circuit, and is used to drive the switching transistor based on the first feedback signal or the second feedback signal.

[0005] In some embodiments, the first feedback circuit includes: A voltage sampling circuit is connected to the first output circuit; The comparator includes a first input terminal, a second input terminal, and an output terminal. The first input terminal is connected to the voltage sampling circuit, and the second input terminal is used to input a reference voltage. The first optocoupler includes a first input side, a second input side, a first output side, and a second output side. The first input side is connected to the first output circuit, the second input side is connected to the output terminal, the first output side is grounded, and the second output side is connected to the controller.

[0006] In some embodiments, the voltage sampling circuit includes a first resistor and a second resistor, one end of the first resistor is connected to the first output circuit, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is grounded, and the first input terminal is connected between the first resistor and the second resistor.

[0007] In some embodiments, the first feedback circuit further includes a first diode, the anode of which is connected to the controller, and the cathode of which is connected to the second output side.

[0008] In some embodiments, the second feedback circuit includes: A current sampling circuit is connected to the second output circuit; The transistor has its base connected to the current sampling circuit and its emitter used to receive the input voltage. The second optocoupler includes a third input side, a fourth input side, a third output side, and a fourth output side. The third input side is connected to the second output circuit, the fourth input side is connected to the collector of the transistor, the third output side is grounded, and the fourth output side is connected to the controller.

[0009] In some embodiments, the current sampling circuit includes a third resistor, a fourth resistor, and a fifth resistor. One end of the third resistor is connected to the second output circuit, the other end of the third resistor is connected to one end of the fourth resistor, the other end of the fourth resistor is grounded, one end of the fifth resistor is grounded, the other end of the fifth resistor is connected to the emitter of the transistor, and the base of the transistor is connected between the third resistor and the fourth resistor.

[0010] In some embodiments, the second feedback circuit further includes a second diode, the positive terminal of which is connected to the controller, and the negative terminal of which is connected to the fourth output side.

[0011] In some embodiments, the controller includes a feedback port and a drive port. The feedback port is connected to the first feedback circuit and the second feedback circuit, and the drive port is connected to the switching transistor. The drive port is used to output a drive signal to drive the switching transistor, and the controller is used to control the duty cycle of the drive signal according to the signal from the feedback port.

[0012] In some embodiments, the switching transistor is a MOSFET, the gate of the MOSFET is connected to the driving port, the drain of the MOSFET is connected to the primary winding, and the source of the MOSFET is grounded.

[0013] In some embodiments, the first output circuit includes a third diode and a first capacitor. The positive terminal of the third diode is connected to one end of the secondary winding, the negative terminal of the third diode is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the other end of the secondary winding and grounded. The third diode and the first capacitor are used for output voltage. The second output circuit includes a fourth diode and a second capacitor. The positive terminal of the fourth diode is connected to the primary winding, and the negative terminal of the fourth diode is connected to one end of the second capacitor. The other end of the second capacitor is used to receive the input voltage, and the fourth diode and the second capacitor are used to output current.

[0014] The constant current and constant voltage dual-path circuit of this application embodiment has a first feedback circuit connected to the first output circuit and the controller, and a second feedback circuit connected to the second output circuit and the controller. By driving the switching transistor through the controller, both constant voltage output of the first output circuit and constant current output of the second output circuit can be realized. Constant voltage output and constant current output can be realized through a single controller, thus simplifying the circuit structure and reducing costs. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the constant current and constant voltage dual-channel circuit according to an embodiment of this application.

[0017] Figure 2 This is a circuit example diagram of a constant current and constant voltage dual-channel circuit according to an embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] This application provides a constant current and constant voltage dual-channel circuit. The constant current and constant voltage dual-channel circuit has two outputs, one of which can output a constant voltage, i.e., a constant voltage output; the other can output a constant current, i.e., a constant current output.

[0020] refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a constant current and constant voltage dual-channel circuit 100 according to an embodiment of this application. The constant current and constant voltage dual-channel circuit 100 includes a transformer T, a first output circuit 10, a second output circuit 20, a first feedback circuit 30, a second feedback circuit 40, and a controller 50.

[0021] The transformer T consists of a primary winding Na and a secondary winding Ns, which are coupled together. The primary winding Na is connected to the power supply to receive the input voltage HV. The primary winding Na is grounded through a switching transistor Q1. The switching transistor Q1 controls whether the primary winding Na receives or receives energy. For example, when the switching transistor Q1 is on, the primary winding Na receives energy; when the switching transistor Q1 is off, the primary winding Na stops receiving energy.

[0022] The first output circuit 10 is connected to the secondary winding Ns to obtain the first output Vo1. The first output Vo1 is used to output voltage. In this embodiment, the first output Vo1 can output a constant voltage. The first output Vo1 also has a corresponding ground side Vo1_GND, which is grounded. In practical applications, the secondary winding Ns can be connected to the ground side Vo1_GND through the first output circuit 10 to achieve grounding. The first output circuit 10 outputs voltage through the secondary winding Ns. Due to the transformer T isolating the input and output, it can be understood as an isolated circuit structure.

[0023] The second output circuit 20 is connected to the primary winding Na to obtain the second output Vo2. The second output Vo2 is used to output current. In this embodiment, the second output Vo2 can output a constant current. The second output Vo2 also has a corresponding ground side Vo2_GND, which is grounded. In practical applications, the second output circuit 20 can also be connected to a power supply to receive the input voltage HV. The second output circuit 20 outputs current through the primary winding Ns, and there is no isolation between the input and output; therefore, it can be understood as a non-isolated circuit structure.

[0024] The first feedback circuit 30 is connected to the first output circuit 10 and is used to obtain a first feedback signal based on the output voltage of the first output circuit 10. In practical applications, the first feedback signal can be a voltage signal.

[0025] The second feedback circuit 40 is connected to the second output circuit 20 and is used to obtain a second feedback signal based on the output current of the second output circuit 20. In practical applications, the second feedback signal can be a voltage signal.

[0026] The controller 50 is connected to the switching transistor Q1, the first feedback circuit 30, and the second feedback circuit 40. The controller 50 drives the switching transistor Q1 based on the first or second feedback signal to regulate the input energy of the primary winding Na, thereby keeping the output voltage of the first output circuit 10 constant, or keeping the output current of the second output circuit 20 constant. Thus, the constant voltage and constant current output of the constant current / constant voltage dual-path circuit 100 can be achieved.

[0027] The constant current and constant voltage dual-path circuit 100 of this application embodiment has a first feedback circuit 30 connected to the first output circuit 10 and the controller 50, and a second feedback circuit 40 connected to the second output circuit 20 and the controller 50. By driving the switching transistor Q1 through the controller 50, both constant voltage output of the first output circuit 10 and constant current output of the second output circuit 20 can be achieved. Constant voltage output and constant current output can be achieved through a single controller, thus simplifying the circuit structure and reducing costs.

[0028] In some embodiments, reference Figure 2 , Figure 2 This is a circuit example diagram of a constant current and constant voltage dual-channel circuit 100 according to an embodiment of this application. The first feedback circuit 30 includes a voltage sampling circuit, a comparator U2, and a first optocoupler.

[0029] The voltage sampling circuit is connected to the first output circuit 10 and is used to obtain a first feedback signal based on the output voltage of the first output circuit 10. In some embodiments, the voltage sampling circuit includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the first output circuit 10, the other end of the first resistor R1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is grounded.

[0030] Comparator U2 includes a first input terminal 21, a second input terminal 22, and an output terminal 23. The first input terminal 21 is connected to a voltage sampling circuit, for example, connected between a first resistor R1 and a second resistor R2. The second input terminal is used to input a reference voltage Vref. In one example, the reference voltage Vref can be 2.5V. The output terminal 23 is connected to a first optocoupler. In practical applications, comparator U2 may also include a power supply terminal 24 and a ground terminal 25. The power supply terminal 24 is used to input the power supply voltage VCC2, and the ground terminal 25 is grounded.

[0031] The first optocoupler includes a first input side 31, a second input side 32, a first output side 33, and a second output side 34. In practical applications, the first optocoupler includes a light-emitting diode (LED) U3A and a phototransistor U3B, which are coupled to each other to achieve the transmission and conversion of optical signals into electrical signals. The first input side 31 and the second input side 32 are located at the two ends of the LED U3A, and the first output side 33 and the second output side 34 are located at the two ends of the phototransistor U3B.

[0032] In this circuit, the first input side 31 is the positive terminal of the LED U3A, and is connected to the first output circuit 10. The second input side 32 is the negative terminal of the LED U3A, and is connected to the output terminal 23 of the comparator U2. The first output side 33 can be the emitter of the phototransistor U3B, and is grounded. The second output side 34 can be the collector of the phototransistor U3B, and is connected to the controller U1. It should be noted that... Figure 2 The controller U1 in the middle is Figure 1 The controller 50 in the middle.

[0033] In some embodiments, the first feedback circuit 30 further includes a first diode D1. The anode of the first diode D1 is connected to the controller U1, and the cathode of the first diode D1 is connected to the second output side 34 of the first optocoupler. The second output side 34 of the first optocoupler is connected to the controller U1 through the first diode D1.

[0034] In some embodiments, a resistor R6 is also connected between the first input side 31 of the first optocoupler and the first output circuit 10. The resistor R6 can limit the current and prevent excessive current from damaging the first optocoupler.

[0035] Continue to refer to Figure 2 In some embodiments, the second feedback circuit 40 includes a current sampling circuit, a transistor Q2, and a second optocoupler.

[0036] The current sampling circuit is connected to the second output circuit 20 and is used to obtain a second feedback signal based on the output current of the second output circuit 20. In some embodiments, the current sampling circuit includes a third resistor R3, a fourth resistor R4, and a fifth resistor R5. One end of the third resistor R3 is connected to the second output circuit, and the other end of the third resistor R3 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 being grounded. One end of the fifth resistor R5 is grounded, and the other end of the fifth resistor R5 is connected to the emitter of the transistor Q2.

[0037] The base of transistor Q2 is connected to the current sampling circuit, for example, the base of transistor Q2 is connected between the third resistor R3 and the fourth resistor R4. The emitter of transistor Q2 is connected to the power supply to receive the input voltage HV. The collector of transistor Q2 is connected to the second optocoupler.

[0038] The second optocoupler includes a third input side 41, a fourth input side 42, a third output side 43, and a fourth output side 44. In practical applications, the second optocoupler includes a light-emitting diode (LED) U4A and a phototransistor U4B, which are coupled to each other to achieve the transmission and conversion of optical signals into electrical signals. The third input side 41 and the fourth input side 42 are located at the two ends of the LED U4A, and the third output side 43 and the fourth output side 44 are located at the two ends of the phototransistor U4B.

[0039] The third input side 41 is the positive terminal of LED U4A and is connected to the second output circuit 20. The fourth input side 42 is the negative terminal of LED U4A and is connected to the collector of transistor Q2. The third output side 43 can be the emitter of phototransistor U4B and is grounded. The fourth output side 44 can be the collector of phototransistor U4B and is connected to controller U1.

[0040] In some embodiments, the second feedback circuit 40 further includes a second diode D2. The positive terminal of the second diode D2 is connected to the controller U1, and the negative terminal of the second diode D2 is connected to the fourth output side 44 of the second optocoupler. The fourth output side 44 of the second optocoupler is connected to the controller U1 through the second diode D2.

[0041] In some embodiments, a resistor R7 is also connected between the third input side 41 of the second optocoupler and the second output circuit 20. The resistor R7 can limit the current and prevent excessive current from damaging the second optocoupler.

[0042] Continue to refer to Figure 2 In some embodiments, the controller U1 includes a feedback port FB and a drive port G. The feedback port FB is connected to a first feedback circuit 30 and a second feedback circuit 40. For example, the feedback port FB is connected to the second output side 34 of the first optocoupler via a first diode D1, and to the fourth output side 44 of the second optocoupler via a second diode D2. The drive port G is connected to the switching transistor Q1. For example, the drive port G can be connected to the switching transistor Q1 via a resistor R8. The drive port G is used to output a drive signal to drive the switching transistor Q1.

[0043] The feedback port FB is used to receive the first feedback signal from the first feedback circuit 30 and the second feedback signal from the second feedback circuit 40 to obtain the corresponding signal, namely, the corresponding voltage signal. The controller U1 is used to control the duty cycle of the drive signal according to the signal from the feedback port FB to adjust the input energy of the primary winding Na, thereby keeping the output voltage of the first output circuit 10 constant or keeping the output current of the second output circuit 20 constant.

[0044] In practical applications, controller U1 may also include a power supply port VDD, a ground port GND, and a chip select port CS. The power supply port VDD is used to input the power supply voltage VCC1. The ground port GND is grounded. The chip select port CS is connected to the switching transistor Q1.

[0045] In some embodiments, the switching transistor Q1 is a MOSFET. The gate of the MOSFET is connected to the drive port G of the controller U1, for example, through a resistor R8. The drain of the MOSFET is connected to the primary winding Na. The source of the MOSFET is grounded. In some embodiments, a resistor R9 can also be connected between the source of the MOSFET and ground. Resistor R9 limits the current and prevents excessive current from damaging the switching transistor Q1.

[0046] Continue to refer to Figure 2 In some embodiments, the first output circuit 10 includes a third diode D3 and a first capacitor C1. The anode of the third diode D3 is connected to one end of the secondary winding Ns, and the cathode of the third diode D3 is connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the other end of the secondary winding Ns and grounded. The voltage output between the third diode D3 and the first capacitor C1 is used to obtain the first output Vo1. It is understood that the first resistor R1 and resistor R6 can both be connected between the third diode D3 and the first capacitor C1.

[0047] In some embodiments, the second output circuit 20 includes a fourth diode D4 and a second capacitor C2. The anode of the fourth diode D4 is connected to the primary winding Na; for example, the anode of the fourth diode D4 can be connected between the primary winding Na and the switching transistor Q1. The cathode of the fourth diode D4 is connected to one end of the second capacitor C2. The other end of the second capacitor C2 is connected to the power supply to receive the input voltage HV. The connection between the fourth diode D4 and the second capacitor C2 is used for output current, i.e., to obtain the second output Vo2. It is understood that the third resistor R3 and resistor R7 can both be connected between the fourth diode D4 and the second capacitor C2.

[0048] The constant current and constant voltage dual-channel circuit 100 of this application embodiment works as follows: For the first output Vo1, when the output voltage increases, for example, when it exceeds the set value, the voltage at the first input terminal 21 of comparator U2 will increase synchronously, the voltage at the output terminal 23 will decrease, the voltage of LED U3A will increase, the current of LED U3A will also increase, the current of phototransistor U3B will also increase, causing the voltage at the feedback port FB of controller U1 to decrease, the duty cycle of the U1 control drive signal to decrease, the input energy of the primary winding Na to decrease, and thus the voltage of the secondary winding Ns to decrease, thereby causing the voltage of the first output Vo1 to decrease and tend to stabilize.

[0049] Conversely, when the output voltage of the first output Vo1 decreases, the voltage at the first input terminal 21 of comparator U2 decreases synchronously, the voltage at the output terminal 23 increases, the voltage of LED U3A decreases, the current of LED U3A decreases, the current of phototransistor U3B decreases, causing the voltage at the feedback port FB of controller U1 to increase, the duty cycle of the U1 control drive signal to increase, the input energy of the primary winding Na increases, and thus the voltage of the secondary winding Ns increases, thereby causing the voltage of the first output Vo1 to increase and tend to stabilize.

[0050] This allows the output voltage of the first output, Vo1, to remain stable, achieving constant voltage output.

[0051] For the second output Vo2, after Vo2 is connected to a load, resistor R5 will detect the magnitude of the load current. The larger the current, the higher the voltage of resistor R4, which means the higher the base voltage of transistor Q2, the larger the base current, the larger the collector current, the larger the current of LED U4A, and the larger the current of phototransistor U4B. This causes the voltage of the feedback port FB of controller U1 to decrease, the duty cycle of the U1 control drive signal to decrease, the input energy of primary winding Na to decrease, and the voltage of secondary winding Ns to decrease. This causes the voltage of the second output Vo2 to decrease, the voltage of the second capacitor C2 to decrease, and finally the load current of the second output Vo2 to decrease and stabilize, balancing at the set value.

[0052] Conversely, after Vo2 is connected to a load, if the load current decreases, the voltage across resistor R4 decreases, which in turn decreases the base voltage of transistor Q2. This reduces the base current, which in turn reduces the collector current, causing the current in LED U4A and phototransistor U4B to decrease. This leads to an increase in the voltage at the feedback port FB of controller U1, increasing the duty cycle of the U1 control drive signal. This increases the input energy of the primary winding Na, which in turn increases the voltage in the secondary winding Ns. Consequently, the voltage of the second output Vo2 increases, and the voltage of the second capacitor C2 also increases. Ultimately, this increases the load current of the second output Vo2, which then tends to stabilize and balance at the set value.

[0053] This allows the output current of the second output, Vo2, to remain constant, achieving constant current output.

[0054] Therefore, the constant current and constant voltage dual-path circuit 100 of this application embodiment can achieve both constant voltage output of the first output circuit 10 and constant current output of the second output circuit 20 by driving the switching transistor Q1 through the controller 50. Constant voltage output and constant current output can be achieved through a single controller, thus simplifying the circuit structure and reducing costs.

[0055] In the description of this application, it should be understood that terms such as “first” and “second” are used only to distinguish similar objects and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0056] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0057] The constant current and constant voltage dual-channel circuit provided in the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A constant current and constant voltage dual-channel circuit, characterized in that, include: A transformer includes a primary winding and a secondary winding coupled to each other, wherein the primary winding is used to receive input voltage and the primary winding is grounded through a switching transistor; The first output circuit is connected to the secondary winding and is used to output voltage; The second output circuit is connected to the primary winding and is used to output current. A first feedback circuit, connected to the first output circuit, is used to obtain a first feedback signal based on the output voltage; A second feedback circuit, connected to the second output circuit, is used to obtain a second feedback signal based on the output current; The controller is connected to the switching transistor, the first feedback circuit, and the second feedback circuit, and is used to drive the switching transistor based on the first feedback signal or the second feedback signal.

2. The constant current and constant voltage dual-channel circuit according to claim 1, characterized in that, The first feedback circuit includes: A voltage sampling circuit is connected to the first output circuit; The comparator includes a first input terminal, a second input terminal, and an output terminal. The first input terminal is connected to the voltage sampling circuit, and the second input terminal is used to input a reference voltage. The first optocoupler includes a first input side, a second input side, a first output side, and a second output side. The first input side is connected to the first output circuit, the second input side is connected to the output terminal, the first output side is grounded, and the second output side is connected to the controller.

3. The constant current and constant voltage dual-channel circuit according to claim 2, characterized in that, The voltage sampling circuit includes a first resistor and a second resistor. One end of the first resistor is connected to the first output circuit, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is grounded, and the first input terminal is connected between the first resistor and the second resistor.

4. The constant current and constant voltage dual-channel circuit according to claim 2, characterized in that, The first feedback circuit further includes a first diode, the positive terminal of which is connected to the controller, and the negative terminal of which is connected to the second output side.

5. The constant current and constant voltage dual-channel circuit according to claim 1, characterized in that, The second feedback circuit includes: A current sampling circuit is connected to the second output circuit; The transistor has its base connected to the current sampling circuit and its emitter used to receive the input voltage. The second optocoupler includes a third input side, a fourth input side, a third output side, and a fourth output side. The third input side is connected to the second output circuit, the fourth input side is connected to the collector of the transistor, the third output side is grounded, and the fourth output side is connected to the controller.

6. The constant current and constant voltage dual-channel circuit according to claim 5, characterized in that, The current sampling circuit includes a third resistor, a fourth resistor, and a fifth resistor. One end of the third resistor is connected to the second output circuit, and the other end of the third resistor is connected to one end of the fourth resistor. The other end of the fourth resistor is grounded, and one end of the fifth resistor is grounded. The other end of the fifth resistor is connected to the emitter of the transistor, and the base of the transistor is connected between the third resistor and the fourth resistor.

7. The constant current and constant voltage dual-channel circuit according to claim 5, characterized in that, The second feedback circuit also includes a second diode, the positive terminal of which is connected to the controller, and the negative terminal of which is connected to the fourth output side.

8. The constant current and constant voltage dual-channel circuit according to any one of claims 1 to 7, characterized in that, The controller includes a feedback port and a drive port. The feedback port is connected to the first feedback circuit and the second feedback circuit. The drive port is connected to the switching transistor. The drive port is used to output a drive signal to drive the switching transistor. The controller is used to control the duty cycle of the drive signal according to the signal from the feedback port.

9. The constant current and constant voltage dual-channel circuit according to claim 8, characterized in that, The switching transistor is a MOSFET, the gate of the MOSFET is connected to the drive port, the drain of the MOSFET is connected to the primary winding, and the source of the MOSFET is grounded.

10. The constant current and constant voltage dual-channel circuit according to any one of claims 1 to 7, characterized in that: The first output circuit includes a third diode and a first capacitor. The positive terminal of the third diode is connected to one end of the secondary winding, and the negative terminal of the third diode is connected to one end of the first capacitor. The other end of the first capacitor is connected to the other end of the secondary winding and grounded. The third diode and the first capacitor are used for output voltage. The second output circuit includes a fourth diode and a second capacitor. The positive terminal of the fourth diode is connected to the primary winding, and the negative terminal of the fourth diode is connected to one end of the second capacitor. The other end of the second capacitor is used to receive the input voltage, and the fourth diode and the second capacitor are used to output current.

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