Switching power supply control circuit with controlled single-path output
Through the cooperation of the low-level shutdown of the FB pin of the PWM circuit and the EN signal feedback circuit of the control circuit, the problems of high noise, high cost and poor reliability of the traditional single-channel output switching power supply control circuit are solved, and output control with low power consumption, low cost and high reliability are achieved.
Patent Information
- Application Number
- CN202422498095.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2025-08-26
- Estimated Expiration
- 2034-10-16
AI Technical Summary
Traditional single-channel output switching power supply control circuits have problems such as high noise, high cost, large volume and poor reliability. Especially in relays and P-MOS solutions, it is difficult to achieve low power consumption and low cost output control.
The low-level shutdown feature of the PWM circuit is adopted, and combined with the control circuit EN signal feedback circuit, the output controllability is achieved through the coordination of the photocoupling switch and transistor, reducing power consumption and saving material costs.
It realizes low-power and low-cost output control, reduces noise, improves circuit reliability and PCB wiring space utilization.
Smart Images
Figure CN223273998U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of power supply control circuits, and in particular to a single-channel output controlled switching power supply control circuit. Background Art
[0002] Traditional single-output switching power supplies require a relay in series at the output end to control the on / off of the output controlled by the control circuit. When the control circuit is at a high level, the relay coil is powered to close the relay, and the output is used to power the subsequent equipment. Alternatively, a P-MOS is connected in series to replace the relay. Neither of these two methods can achieve low power consumption and low cost by shutting down the PWM IC. First, the relay solution produces noise when the relay is turned on and off. Relays are expensive and bulky. When overcurrent or short circuit occurs in the downstream electrical equipment, the relay contacts will heat up and stick together and fail. The P-MOS solution is also expensive, and slightly higher power devices require a heat sink. Summary of the Invention
[0003] The purpose of the embodiments of the present application is to provide a single-output controlled switching power supply control circuit, which can solve the above-mentioned technical problems.
[0004] An embodiment of the present application provides a single-output controlled switching power supply control circuit, including an input terminal, a PWM circuit, a control circuit, a voltage conversion circuit, an output terminal, a control circuit EN signal feedback circuit, and a VCC power supply circuit. The input end of the input terminal is connected to an external battery assembly, the output end of the input terminal is connected to the input end of the PWM circuit, the output end of the PWM circuit is connected to the input end of the voltage conversion circuit and the input end of the control circuit, the output end of the voltage conversion circuit is connected to the output terminal, the input end of the control circuit EN signal feedback circuit is connected to the output end of the voltage circuit through the VCC power supply circuit, the output end of the control circuit EN signal feedback circuit is electrically connected to the control circuit, and the output end of the VCC power supply circuit is electrically connected to the PWM circuit.
[0005] Preferably, the PWM circuit includes a variable resistor MOV1, a conjugate inductor LF1, a capacitor CX1, a resistor R1, a resistor R2, a conjugate inductor LF2, a diode D1, a diode D2, a rectifier bridge, a capacitor CC1, a capacitor CC2, a resistor R7, and a capacitor EC1, one end of the variable resistor MOV1 is connected to the input terminal and the third port of the conjugate inductor LF1, the other end of the variable resistor MOV1 is connected to the input terminal and the first port of the conjugate inductor LF1, the fourth interface of the conjugate inductor LF1 is connected to one end of the capacitor CX1, one end of the resistor R1, and the third interface of the conjugate inductor LF2, the second interface of the conjugate inductor LF1 is connected to the other end of the capacitor CX1, one end of the resistor R2, and the first interface of the conjugate inductor LF2, the resistor R 1 is connected to the other end of the resistor R2, the second interface of the conjugate inductor LF2 is connected to the input end of the diode D2 and the third interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 is connected to the second interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 and the second interface of the rectifier bridge are both connected to the control circuit through the diode D1, the first interface of the rectifier bridge is connected to one end of the capacitor CC1, the fourth interface of the rectifier bridge is connected to the other end of the capacitor CC1 and the other end of the capacitor CC2, one end of the resistor R7 is connected to the first interface of the rectifier bridge, the other end of the resistor R7 is connected to the other end of the capacitor CC2, the capacitor EC1 is connected to one end of the resistor R7 and the transformer circuit, and the other end of the capacitor EC1 is grounded.
[0006] Preferably, the voltage conversion circuit includes a voltage stabilizing and current limiting circuit, a transformer, a diode D5, a diode D6, a resistor R35, a resistor R36, a resistor R33, a resistor R34, a resistor R37, a capacitor CC5, a capacitor C6, a capacitor EC3, a capacitor EC4, and a conjugate inductor LF3. The input end of the voltage stabilizing and current limiting circuit is connected to the PWM circuit, and the output end of the voltage stabilizing and current limiting circuit is connected to the primary coil of the transformer. One end of the secondary coil of the transformer is respectively connected to the input end of the diode D5, the input end of the diode D6, one end of the resistor R33, one end of the resistor R34, one end of the resistor R35, one end of the resistor R36, and one end of the capacitor C6. The output end of the diode D5, The output end of the diode D6 is connected to one end of the capacitor CC5, one end of the capacitor EC3, one end of the capacitor EC4, and the third interface of the conjugate inductor LF3. The other end of the resistor R33, the other end of the resistor R34, the other end of the resistor R35, and the other end of the resistor R36 are connected to the other end of the capacitor CC5. The other end of the capacitor C6 is connected to one end of the resistor R37, and the other end of the resistor R37 is connected to one end of CC5. The other end of the capacitor EC3, the other end of the capacitor EC4, and the first interface of the conjugate inductor LF3 are all grounded. The second interface of the conjugate inductor LF3 and the fourth interface of the conjugate inductor LF3 are connected to the output terminal.
[0007] Preferably, the control circuit EN signal feedback circuit includes a terminal CON3, a resistor R44, a resistor R45, a resistor R46, a capacitor C7, a photoelectric coupling switch, a resistor R31, a resistor R28, a resistor R9, a resistor R26, a capacitor C2, and a transistor Q3. The third interface and the fourth interface of the terminal CON3 are connected to the control circuit, the first interface and the second interface of the terminal CON3 are both grounded, the fourth interface of the terminal CON3 is connected to one end of the resistor R46, the other end of the resistor R46 is connected to one end of the resistor R44, one end of the capacitor C7, and one end of the input end of the photoelectric coupling switch, the other end of the resistor R44, the The other end of the capacitor C7 and the other end of the input end of the photoelectric coupling switch are both grounded through the capacitor R45. One end of the output end of the photoelectric coupling switch is connected to the control circuit through the resistor R31 and the resistor R26. The other end of the output end of the photoelectric coupling switch is grounded. One end of the resistor R27 is connected to one end of the resistor R31. The other end of the resistor R27 is connected to one end of the resistor R28, one end of the capacitor C2, and the B pole of the transistor Q3. The other end of the capacitor C2, the other end of the resistor R28, and the E pole of the transistor Q3 are all grounded. The C pole of the transistor Q3 is connected to the control circuit through the resistor R9.
[0008] Preferably, a fuse F1 and a thermistor NTC1 are provided between the input terminal and the PWM circuit.
[0009] Preferably, the output voltage of the output terminal is DC +24V.
[0010] Preferably, the VCC power supply circuit includes a resistor R20, a capacitor C1, a capacitor EC2, a diode D3, a resistor R15, a resistor R14, a transistor Q1, a transistor Q2, a capacitor CC4, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a diode D4, a capacitor C4, a resistor R21, a resistor R22, a resistor R23, and a resistor R25.
[0011] Preferably, the transformer includes an auxiliary winding, and the auxiliary winding is electrically connected to the capacitor EC2.
[0012] Beneficial effects of the utility model:
[0013] The utility model provides a single-channel output controlled switching power supply control circuit, comprising an input terminal, a PWM circuit, a control circuit, a voltage conversion circuit, an output terminal, a control circuit EN signal feedback circuit, and a VCC power supply circuit. The input terminal is connected to an external battery assembly, the output terminal is connected to the input terminal of the PWM circuit, the output terminal of the PWM circuit is connected to the input terminal of the voltage conversion circuit and the input terminal of the control circuit, the output terminal of the voltage conversion circuit is connected to the output terminal, the input terminal of the control circuit EN signal feedback circuit is connected to the output terminal of the voltage circuit via the VCC power supply circuit, the output terminal of the control circuit EN signal feedback circuit is electrically connected to the control circuit, and the output terminal of the VCC power supply circuit is electrically connected to the PWM circuit. The utility model utilizes the characteristic that a low level of the FB pin of the PWM circuit shuts off the PWM output, thereby achieving low power consumption, low cost, and no noise. The circuit pulls the FB pin of the PWM circuit to a low level so that the IC cannot normally drive to achieve output control. This circuit can save material cost, reduce power consumption, reduce PCB wiring space, and has good reliability. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.
[0015] Figure 1It is a framework diagram of the utility model;
[0016] Figure 2 This is a circuit diagram of the utility model. DETAILED DESCRIPTION
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.
[0018] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.
[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.
[0020] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended only to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0021] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.
[0022] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.
[0023] like Figure 1-2 As shown, a single-channel output controlled switching power supply control circuit includes an input terminal, a PWM circuit, a control circuit, a voltage conversion circuit, an output terminal, a control circuit EN signal feedback circuit, and a VCC power supply circuit. The input terminal is connected to an external battery assembly, the output terminal is connected to the input terminal of the PWM circuit, the output terminal of the PWM circuit is connected to the input terminal of the voltage conversion circuit and the input terminal of the control circuit, the output terminal of the voltage conversion circuit is connected to the output terminal, the input terminal of the control circuit EN signal feedback circuit is connected to the output terminal of the voltage circuit via the VCC power supply circuit, the output terminal of the control circuit EN signal feedback circuit is electrically connected to the control circuit, and the output terminal of the VCC power supply circuit is electrically connected to the PWM circuit. The utility model utilizes the characteristic that the FB pin of the PWM circuit shuts down the PWM output when it is at a low level, thereby achieving low power consumption, low cost, and no noise. This circuit pulls the FB pin of the PWM circuit to a low level so that the IC cannot normally drive to achieve output control. This circuit can save material cost, reduce power consumption, reduce PCB wiring space, and has good reliability.
[0024] like Figure 2As shown, in this embodiment, the PWM circuit includes a variable resistor MOV1, a conjugate inductor LF1, a capacitor CX1, a resistor R1, a resistor R2, a conjugate inductor LF2, a diode D1, a diode D2, a rectifier bridge, a capacitor CC1, a capacitor CC2, a resistor R7, and a capacitor EC1. One end of the variable resistor MOV1 is connected to the input terminal and the third port of the conjugate inductor LF1, the other end of the variable resistor MOV1 is connected to the input terminal and the first port of the conjugate inductor LF1, the fourth interface of the conjugate inductor LF1 is connected to one end of the capacitor CX1, one end of the resistor R1, and the third interface of the conjugate inductor LF2, the second interface of the conjugate inductor LF1 is connected to the other end of the capacitor CX1, one end of the resistor R2, and the first interface of the conjugate inductor LF2, and the The other end of the resistor R1 is connected to the other end of the resistor R2, the second interface of the conjugate inductor LF2 is connected to the input end of the diode D2 and the third interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 is connected to the second interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 and the second interface of the rectifier bridge are both connected to the control circuit through the diode D1, the first interface of the rectifier bridge is connected to one end of the capacitor CC1, the fourth interface of the rectifier bridge is connected to the other end of the capacitor CC1 and the other end of the capacitor CC2, one end of the resistor R7 is connected to the first interface of the rectifier bridge, the other end of the resistor R7 is connected to the other end of the capacitor CC2, the capacitor EC1 is connected to one end of the resistor R7 and the transformer circuit, and the other end of the capacitor EC1 is grounded.
[0025] like Figure 2As shown, in this embodiment, the voltage conversion circuit includes a voltage stabilizing and current limiting circuit, a transformer, a diode D5, a diode D6, a resistor R35, a resistor R36, a resistor R33, a resistor R34, a resistor R37, a capacitor CC5, a capacitor C6, a capacitor EC3, a capacitor EC4, and a conjugate inductor LF3. The input end of the voltage stabilizing and current limiting circuit is connected to the PWM circuit, and the output end of the voltage stabilizing and current limiting circuit is connected to the primary coil of the transformer. One end of the secondary coil of the transformer is respectively connected to the input end of the diode D5, the input end of the diode D6, one end of the resistor R33, one end of the resistor R34, one end of the resistor R35, one end of the resistor R36, and one end of the capacitor C6. The output end of the diode D5 is connected to the input end of the diode D5. The output end of the diode D6 is connected to one end of the capacitor CC5, one end of the capacitor EC3, one end of the capacitor EC4, and the third interface of the conjugate inductor LF3, the other end of the resistor R33, the other end of the resistor R34, the other end of the resistor R35, and the other end of the resistor R36 are connected to the other end of the capacitor CC5, the other end of the capacitor C6 is connected to one end of the resistor R37, and the other end of the resistor R37 is connected to one end of CC5, the other end of the capacitor EC3, the other end of the capacitor EC4, and the first interface of the conjugate inductor LF3 are all grounded, and the second interface of the conjugate inductor LF3 and the fourth interface of the conjugate inductor LF3 are connected to the output terminal.
[0026] like Figure 2As shown, in this embodiment, the control circuit EN signal feedback circuit includes a terminal CON3, a resistor R44, a resistor R45, a resistor R46, a capacitor C7, a photoelectric coupling switch, a resistor R31, a resistor R28, a resistor R9, a resistor R26, a capacitor C2, and a transistor Q3. The third interface and the fourth interface of the terminal CON3 are connected to the control circuit, the first interface and the second interface of the terminal CON3 are both grounded, the fourth interface of the terminal CON3 is connected to one end of the resistor R46, the other end of the resistor R46 is connected to one end of the resistor R44, one end of the capacitor C7, and one end of the input end of the photoelectric coupling switch, the other end of the resistor R44, The other end of the capacitor C7 and the other end of the input end of the photoelectric coupling switch are both grounded through the capacitor R45. One end of the output end of the photoelectric coupling switch is connected to the control circuit through the resistor R31 and the resistor R26. The other end of the output end of the photoelectric coupling switch is grounded. One end of the resistor R27 is connected to one end of the resistor R31. The other end of the resistor R27 is connected to one end of the resistor R28, one end of the capacitor C2, and the B pole of the transistor Q3. The other end of the capacitor C2, the other end of the resistor R28, and the E pole of the transistor Q3 are all grounded. The C pole of the transistor Q3 is connected to the control circuit through the resistor R9.
[0027] like Figure 2 As shown, in this embodiment, a fuse F1 and a thermistor NTC1 are provided between the input terminal and the PWM circuit.
[0028] like Figure 2 As shown, in this embodiment, the output voltage of the output terminal is DC +24V.
[0029] like Figure 2 As shown, in this embodiment, the VCC power supply circuit includes a resistor R20, a capacitor C1, a capacitor EC2, a diode D3, a resistor R15, a resistor R14, a transistor Q1, a transistor Q2, a capacitor CC4, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a diode D4, a capacitor C4, a resistor R21, a resistor R22, a resistor R23, and a resistor R25.
[0030] like Figure 2 As shown, in this embodiment, the transformer includes an auxiliary winding, and the auxiliary winding is electrically connected to the capacitor EC2.
[0031] This circuit has only a single 24V output voltage, which is turned on or off by the terminal product control circuit:
[0032] Open circuit: When the EN pin of terminal CON3 receives a high-level signal from the control circuit, the photoelectric coupling switch is divided by resistors R44 and R45, and then the photoelectric coupling switch emits light. OC2B is turned on to pull down the upper end level of resistor R31, so that the base level of transistor Q3 also becomes low, and transistor Q3 is not turned on. The FB pin voltage of the control circuit remains normal, and the control circuit can turn on PWM to the gate of Q1, and 24V can be output normally.
[0033] Shutdown loop: When the control circuit sends a low-level signal to the EN pin of terminal CON3, the optocoupler switch does not work, and OC2B does not receive the signal to cut off. The control circuit provides the operating voltage through the high-voltage start pin of HV, and the gate of the transistor Q1 turns on the PWM signal. At this time, the auxiliary winding of the transformer charges the capacitor EC2. The VCC voltage is divided by resistors R26, R27, and R28 to provide voltage to the base of the transistor Q3. After the transistor Q3 is turned on, the level of the FB pin of the control circuit is pulled to the ground through resistor R9. At this time, the control circuit cannot detect the FB feedback signal, and the PWM signal is turned off to achieve 24V shutdown. When the VCC voltage on the capacitor EC2 is consumed and Q3 is turned off, it will enter the next cycle, and the 24V will always remain in the off state.
[0034] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.
Claims
1. A single-output controlled switching power supply control circuit, characterized in that: It includes an input terminal, a PWM circuit, a control circuit, a voltage conversion circuit, an output terminal, a control circuit EN signal feedback circuit, and a VCC power supply circuit. The input end of the input terminal is connected to an external battery assembly, the output end of the input terminal is connected to the input end of the PWM circuit, the output end of the PWM circuit is connected to the input end of the voltage conversion circuit and the input end of the control circuit, the output end of the voltage conversion circuit is connected to the output terminal, the input end of the control circuit EN signal feedback circuit is connected to the output end of the voltage conversion circuit through the VCC power supply circuit, the output end of the control circuit EN signal feedback circuit is electrically connected to the control circuit, and the output end of the VCC power supply circuit is electrically connected to the PWM circuit.
2. The single-output controlled switching power supply control circuit according to claim 1, characterized in that: The PWM circuit includes a variable resistor MOV1, a conjugate inductor LF1, a capacitor CX1, a resistor R1, a resistor R2, a conjugate inductor LF2, a diode D1, a diode D2, a rectifier bridge, a capacitor CC1, a capacitor CC2, a resistor R7, and a capacitor EC1. One end of the variable resistor MOV1 is connected to the input terminal and the third port of the conjugate inductor LF1. The other end of the variable resistor MOV1 is connected to the input terminal and the first port of the conjugate inductor LF1. The fourth interface of the conjugate inductor LF1 is connected to one end of the capacitor CX1, one end of the resistor R1, and the third interface of the conjugate inductor LF2. The second interface of the conjugate inductor LF1 is connected to the other end of the capacitor CX1, one end of the resistor R2, and the first interface of the conjugate inductor LF2. The other end is connected to the other end of the resistor R2, the second interface of the conjugate inductor LF2 is connected to the input end of the diode D2 and the third interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 is connected to the second interface of the rectifier bridge, the fourth interface of the conjugate inductor LF2 and the second interface of the rectifier bridge are both connected to the control circuit through the diode D1, the first interface of the rectifier bridge is connected to one end of the capacitor CC1, the fourth interface of the rectifier bridge is connected to the other end of the capacitor CC1 and the other end of the capacitor CC2, one end of the resistor R7 is connected to the first interface of the rectifier bridge, the other end of the resistor R7 is connected to the other end of the capacitor CC2, the capacitor EC1 is connected to one end of the resistor R7 and the transformer circuit, and the other end of the capacitor EC1 is grounded.
3. The single-output controlled switching power supply control circuit according to claim 1, characterized in that: The voltage conversion circuit includes a voltage stabilizing and current limiting circuit, a transformer, a diode D5, a diode D6, a resistor R35, a resistor R36, a resistor R33, a resistor R34, a resistor R37, a capacitor CC5, a capacitor C6, a capacitor EC3, a capacitor EC4, and a conjugate inductor LF3. The input end of the voltage stabilizing and current limiting circuit is connected to the PWM circuit, and the output end of the voltage stabilizing and current limiting circuit is connected to the primary coil of the transformer. One end of the secondary coil of the transformer is respectively connected to the input end of the diode D5, the input end of the diode D6, one end of the resistor R33, one end of the resistor R34, one end of the resistor R35, one end of the resistor R36, and one end of the capacitor C6. The output end of the diode D5, the diode D6, the resistor R33, the resistor R34, the resistor R35, the resistor R36, and the capacitor C6. The output end of the diode D6 is connected to one end of the capacitor CC5, one end of the capacitor EC3, one end of the capacitor EC4, and the third interface of the conjugate inductor LF3. The other end of the resistor R33, the other end of the resistor R34, the other end of the resistor R35, and the other end of the resistor R36 are connected to the other end of the capacitor CC5. The other end of the capacitor C6 is connected to one end of the resistor R37, and the other end of the resistor R37 is connected to one end of CC5. The other end of the capacitor EC3, the other end of the capacitor EC4, and the first interface of the conjugate inductor LF3 are all grounded. The second interface of the conjugate inductor LF3 and the fourth interface of the conjugate inductor LF3 are connected to the output terminal.
4. The single-output controlled switching power supply control circuit according to claim 1, characterized in that: The control circuit EN signal feedback circuit includes a terminal CON3, a resistor R44, a resistor R45, a resistor R46, a capacitor C7, a photoelectric coupling switch, a resistor R31, a resistor R28, a resistor R9, a resistor R26, a capacitor C2, and a transistor Q3. The third interface and the fourth interface of the terminal CON3 are connected to the control circuit, the first interface and the second interface of the terminal CON3 are both grounded, the fourth interface of the terminal CON3 is connected to one end of the resistor R46, the other end of the resistor R46 is connected to one end of the resistor R44, one end of the capacitor C7, and one end of the input end of the photoelectric coupling switch, the other end of the resistor R44, the capacitor C7, and the input end of the photoelectric coupling switch. The other end of C7 and the other end of the input end of the photoelectric coupling switch are both grounded through the capacitor R45. One end of the output end of the photoelectric coupling switch is connected to the control circuit through the resistor R31 and the resistor R26. The other end of the output end of the photoelectric coupling switch is grounded. One end of the resistor R27 is connected to one end of the resistor R31. The other end of the resistor R27 is connected to one end of the resistor R28, one end of the capacitor C2, and the B pole of the transistor Q3. The other end of the capacitor C2, the other end of the resistor R28, and the E pole of the transistor Q3 are all grounded. The C pole of the transistor Q3 is connected to the control circuit through the resistor R9.
5. The single-output controlled switching power supply control circuit according to claim 1, characterized in that: A fuse F1 and a thermistor NTC1 are provided between the input terminal and the PWM circuit.
6. The single-output controlled switching power supply control circuit according to claim 1, characterized in that: The output voltage of the output terminal is DC +24V.
7. The single-output controlled switching power supply control circuit according to claim 3, characterized in that: The VCC power supply circuit includes a resistor R20, a capacitor C1, a capacitor EC2, a diode D3, a resistor R15, a resistor R14, a transistor Q1, a transistor Q2, a capacitor CC4, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a diode D4, a capacitor C4, a resistor R21, a resistor R22, a resistor R23, and a resistor R25.
8. The single-output controlled switching power supply control circuit according to claim 7, characterized in that: The transformer includes an auxiliary winding, and the auxiliary winding is electrically connected to the capacitor EC2.