Constant voltage and constant current and light switching control power supply circuit based on IC and switching power supply

Abstract

The utility model relates to switching power supply technical field, propose a kind of power circuit and switching power supply based on IC realizes constant voltage constant current and light change control, secondary circuit output end connects constant voltage constant current circuit and light change control circuit, and constant voltage constant current and light change detection control circuit are constructed based on two separate voltage comparison devices.Constant voltage constant current circuit is composed of photoelectric coupler, comparator U2, voltage detection circuit and series current detection circuit, and voltage and current detection circuit are respectively connected into the control pin of U2;U4A is connected to the feedback pin FB of controller U1.Light change circuit is provided with overvoltage protection circuit, including vice side voltage division resistance network and filter capacitor C7, and voltage division output is connected to the detection pin DEM of U1.No MCU is used to realize the simplified circuit structure of output voltage constant, current limit and charging completion state detection indication, to reduce system cost, improve reliability and ease of use.

Description

Technical Field

[0001] This utility model relates to the technical field of switching power supplies, specifically to a power supply circuit and switching power supply based on IC to achieve constant voltage and constant current and lamp control. Background Technology

[0002] The statements in this section are merely background information related to this utility model and do not necessarily constitute prior art.

[0003] In various chargers, adapters, and switching power supplies, constant voltage and constant current control circuits, along with indicator light detection circuits, are core functional modules in power supply design to ensure stable voltage and current output to the load and automatic switching of charging states. Constant voltage ensures stable output voltage, constant current limits the maximum output current, and indicator light detection indicates the charging completion status. These functions are crucial for improving product performance and user experience.

[0004] Existing switching power supplies or charging control circuits typically use microcontrollers (MCUs) as the core control unit to achieve output voltage regulation, constant current limiting, and identification and indication of charging status (such as indicator lights). MCUs have advantages such as flexible programming, high control precision, and high functional integration, and are therefore widely used in mid-to-high-end power supply systems. However, in scenarios with higher requirements for cost, size, power consumption, and reliability (such as power banks, small chargers, and simplified adapters), MCU solutions are gradually revealing the following problems: First, the circuit structure is complex. MCU control solutions usually require supporting peripheral circuits such as reference voltage sources, operational amplifiers, MOS drivers, ADC sampling, and timing control circuits, resulting in a complex overall design, large board area, and difficulty in miniaturization. Second, power consumption is a significant issue. Even with low-power MCUs, the system still needs to maintain continuous power supply, making standby power consumption and overall energy efficiency inferior to pure analog control solutions, making it difficult to meet energy-saving requirements. Third, system reliability depends on program execution. Abnormal MCU operation, such as crashes, logic freezes, or electromagnetic interference affecting program execution, may lead to charging control logic failure, posing potential safety hazards. Utility Model Content

[0005] To address the aforementioned problems, this invention proposes a power supply circuit and switching power supply based on an IC to achieve constant voltage and current control and lamp switching control. The constant voltage and current control and lamp switching detection control circuit, constructed based on two discrete voltage comparators, achieves a simplified circuit structure that provides constant output voltage, current limiting, and charging completion status indication without the need for an MCU, thereby reducing system cost and improving reliability and ease of use.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: One or more embodiments provide a power supply circuit based on IC to implement constant voltage and constant current and lamp control, including a primary power supply circuit, a switching circuit, a transformer T1, and a secondary power supply circuit; the output terminal of the secondary power supply circuit is connected to the constant voltage and constant current circuit and the lamp control circuit. The constant voltage and constant current circuit includes an optocoupler and a voltage comparator U2 connected in sequence, a voltage detection circuit, and an output current detection circuit connected in series in the output circuit of the power supply secondary circuit. The voltage detection circuit and the output current detection circuit are respectively connected to the two control pins of the voltage comparator U2. The primary phase U4B of the optocoupler is connected in series at the power supply output terminal V. + The output terminal V of the voltage comparator U2 OUT Between them, the secondary side U4A of the optocoupler is connected to the feedback pin FB of the controller U1 of the switching circuit; The switching circuit is equipped with an overvoltage protection circuit, including a voltage divider resistor network connected to the secondary voltage output terminal of transformer T1 and a filter capacitor C7. The voltage output terminal of the voltage divider resistor network is connected to the detection pin DEM of controller U1.

[0007] One or more embodiments provide a switching power supply that employs the aforementioned IC-based power supply circuit for constant voltage and constant current control and lamp switching.

[0008] Compared with the prior art, the beneficial effects of this utility model are as follows: This implementation constructs a complete constant voltage and constant current control link using a voltage comparator combined with an optocoupler. The structure is compact and the response is fast. Simultaneously, an overvoltage protection module is added to the switching circuit, achieving a dual detection and control mechanism for the output voltage, forming a synergistic voltage control system where the front-end switching circuit and the back-end output work together. This architecture not only improves the stability of the output voltage and current but also enhances the overall safety and reliability of the system. Compared to traditional power control systems using MCU solutions, this solution eliminates the need for complex digital control logic and program support, effectively reducing system design complexity and cost, and avoiding safety risks caused by MCU instability. Furthermore, the use of an optocoupler for isolated feedback greatly improves the system's anti-interference capability and signal transmission stability, making it suitable for applications requiring small size, low power consumption, and high reliability, such as mobile chargers, simplified adapters, and low-power LED power supplies.

[0009] The advantages and additional advantages of this utility model will be described in detail in the following specific embodiments. Attached Figure Description

[0010] The accompanying drawings, which form part of this specification, are used to provide a further understanding of this utility model. The illustrative embodiments of this utility model and their descriptions are used to explain this utility model and do not constitute a limitation thereof.

[0011] Figure 1 This is a circuit diagram of the power supply circuit based on IC to achieve constant voltage and constant current and lamp control according to Embodiment 1 of this utility model; Figure 2 This is a circuit diagram of the power supply secondary circuit of Embodiment 1 of this utility model; Figure 3 This is a circuit diagram of the primary power supply circuit of Embodiment 1 of this utility model; Figure 4 This is a circuit diagram of the switching circuit of Embodiment 1 of this utility model. Detailed Implementation

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0013] It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0014] It should be noted that the terminology used herein is for descriptive purposes only and is not intended to limit the exemplary embodiments according to this invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. It should be noted that, without conflict, the various embodiments and features within those embodiments can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0015] Example 1 In one or more of the technical solutions disclosed in the embodiments, such as Figures 1 to 4 As shown, the power supply circuit based on IC to implement constant voltage and constant current and lamp control includes a primary power supply circuit, a switching circuit, a transformer T1, and a secondary power supply circuit; the output terminal of the secondary power supply circuit is connected to the constant voltage and constant current circuit and the lamp control circuit. The constant voltage and constant current circuit includes an optocoupler and a voltage comparator U2 connected in sequence, a voltage detection circuit and an output current detection circuit connected in series in the output circuit of the power supply secondary circuit. The voltage detection circuit and the output current detection circuit are respectively connected to the two control pins of the voltage comparator U2. The primary winding U4B of the optocoupler is connected in series at the power output terminal V. + The output terminal V of the voltage comparator U2 OUTBetween them, the secondary side U4A of the optocoupler is connected to the feedback pin FB of the controller U1 of the switching circuit; The switching circuit is equipped with an overvoltage protection circuit, including a voltage divider resistor network connected to the secondary voltage output terminal of transformer T1 and a filter capacitor C7. The voltage output terminal of the voltage divider resistor network is connected to the detection pin DEM of controller U1.

[0016] The power supply circuit uses transformer T1 to transfer energy between the primary and secondary power supplies, and outputs voltage and current signals on the secondary side. The constant voltage and constant current control circuit employs an analog IC control scheme. It detects the output voltage through a voltage detection circuit and monitors the output current in real time through an output current detection circuit. These two circuits are connected to the two control pins of voltage comparator U2 to determine whether the output meets the set constant voltage or constant current conditions. When the voltage or current deviates from the set value, voltage comparator U2 outputs a corresponding adjustment signal, which is isolated by optocoupler U4B and fed back to the feedback pin FB of switch controller U1, thereby dynamically adjusting the PWM duty cycle to stabilize the output. Simultaneously, the overvoltage protection circuit senses the secondary voltage through a voltage divider resistor network. Filter capacitor C7 is used to eliminate spike signals and stabilize the voltage detection result. When an overvoltage condition is detected, the protection mechanism of U1 is triggered through the DEM pin to shut down or limit the output, ensuring circuit safety. The indicator light control circuit works in conjunction with voltage comparator U2 to output control signals based on the voltage status, driving the status indicator light to provide a visual indication of charging completion or fault status.

[0017] This implementation constructs a complete constant voltage and constant current control link using a voltage comparator combined with an optocoupler. The structure is compact and the response is fast. Simultaneously, an overvoltage protection module is added to the switching circuit, achieving a dual detection and control mechanism for the output voltage, forming a synergistic voltage control system where the front-end switching circuit and the back-end output work together. This architecture not only improves the stability of the output voltage and current but also enhances the overall safety and reliability of the system. Compared to traditional power control systems using MCU solutions, this solution eliminates the need for complex digital control logic and program support, effectively reducing system design complexity and cost, and avoiding safety risks caused by MCU instability. Furthermore, the use of an optocoupler for isolated feedback greatly improves the system's anti-interference capability and signal transmission stability, making it suitable for applications requiring small size, low power consumption, and high reliability, such as mobile chargers, simplified adapters, and low-power LED power supplies.

[0018] Furthermore, a capacitor C6 is connected in parallel across the two ends of the secondary U4A of the optocoupler; In some embodiments, constant voltage control in the constant voltage and constant current circuit is achieved through a voltage detection circuit, which is connected to the power output terminal V. +The voltage detection circuit includes resistors R25, R27, R22, R23, and R28 connected in sequence; resistors R25 and R27 are connected in parallel to form a first parallel circuit, and resistors R22, R23, and R28 are connected in parallel to form a second parallel circuit. The connection point of the first parallel circuit and the second parallel circuit is connected to the pin Vctrl of the voltage comparator U2. Constant voltage control achieves constant voltage output through the comparison reference at pin 3 of voltage comparator U2. The formula for calculating constant voltage output is as follows: Vo=Vref*[1+(R25∥R27 / R22∥R23∥R28)]; Wherein, Vref is achieved by adjusting the ratio of R25∥R27 / R22∥R23∥R28 while keeping the reference voltage constant; The output voltage V+ is applied to PIN3 Vctrl through a voltage divider circuit with R25∥R27 connected in series. When the voltage rises and exceeds the Vref value, the voltage comparator U2 outputs a high level, the optocoupler U4B current decreases, the controller U1 receives a feedback stop pulse from the optocoupler U4A, and the MOSFET Q1 in the switching circuit is turned off, resulting in no energy transfer. + The voltage does not rise; on the contrary, when the output voltage decreases, the output time of MOSFET Q1 increases, the energy increases, and the output voltage is prevented from decreasing. The above process realizes the purpose of constant voltage by controlling the duty cycle of the MOSFET switch through the voltage comparator U2 to control the optocoupler.

[0019] Specifically, in this embodiment, the voltage comparator U2 is model AP4320AK; In this embodiment, the constant current control in the constant voltage and constant current circuit is achieved through an output current detection circuit connected in series at the power supply output terminal. The output current detection circuit includes resistors RS1, RS2, and R20, and capacitor C14. Resistor R20 and capacitor C14 are connected in parallel and then connected in parallel with resistors RS1 and RS2 respectively. The connection point of this parallel connection is connected to pin 4 of the voltage comparator U2, i.e., the current control pin Ictrl. The connection point of resistor R20 and capacitor C14 is connected to pin 1 of the voltage comparator U2, i.e., the Vsense pin. The connection point of resistor R20 and capacitor C14 is connected to the output terminal V of the voltage comparator U2 through capacitor C10 and resistor R26. OUT ; Such as circuits Figure 2 Constant current control is achieved through the comparison reference at pin 4 of voltage comparator U2 to achieve constant current output. The formula for calculating constant current is: Ic = Victr / RS1∥RS2; Where Victr is the reference voltage of IC U2, and the constant current can be achieved by adjusting the magnitude of RS1∥RS2.

[0020] When the output current flows through RS1|RS2, a voltage drop Vs is generated across RS1|RS2. This Vs voltage is compared with the voltage Victr at pin 4 of IC U2 for control. When the output current increases and exceeds the set current value, the voltage across RS1|RS2 increases (VRs > Victr). At this point, pin 5 of U2 outputs a high level (Vout). Through the adjustment of the optocoupler, the turn-on time of MOSFET Q1 decreases, and the output current also decreases. Conversely, when the output current decreases, the turn-on time of MOSFET Q1 increases, causing the output current to increase, thus achieving constant current output.

[0021] In the above implementation, constant current and constant voltage control of the power supply output is achieved by setting a voltage comparator U2. Compared with the traditional design method that requires separate configuration of constant voltage loop and constant current loop, this solution uses a single device to undertake dual control tasks, which not only simplifies the circuit structure and saves the number of devices and PCB space, but also improves the system integration and reliability.

[0022] In some embodiments, the overvoltage protection circuit in the switching circuit includes a voltage divider resistor network and a filter capacitor C7 connected to the secondary voltage output terminal of transformer T1; the voltage divider resistor network, including resistors R6, R7A, and R7B, is connected to the voltage output terminal of the auxiliary winding PIN1-2 of the transformer; resistors R7A, R7B, and capacitor C7 are connected in parallel to form a third parallel circuit; one end of resistor R6 is connected to the voltage output terminal of the auxiliary winding PIN1-2 of transformer T1, and the other end is grounded after being connected to the third parallel circuit; the connection point of resistor R6 and the third parallel circuit is connected to the detection pin DEM of the controller U1 of the switching circuit. Specifically, the model of the controller U1 in the switching circuit is OB2710; During operation, when the output voltage V+ rises abnormally, the induced voltage generated by the transformer auxiliary winding PIN1-2 also increases. After voltage division, the voltage applied to the DEM pin of controller U1 exceeds the internally set overvoltage threshold. Controller U1 immediately activates the overvoltage protection function, and the internal control logic enters a lock-up protection state, shutting off the output drive signal of the GATE pin, causing the MOSFET Q1 to turn off, thereby preventing further energy transfer to the secondary side and achieving overvoltage cut-off protection. In the lock-up protection state, the power supply output voltage is zero, and the system remains stopped until the fault is cleared and power is restored; only then will controller U1 re-enter normal operating mode.

[0023] A further technical solution further comprises a light switching control circuit, which includes a voltage dividing resistor, an indicator light, a current change detection circuit and a voltage comparison device U3 connected in sequence; the voltage dividing resistor is connected to the positive electrode V at the output end of the power supply secondary circuit + , the current change detection circuit detects a voltage through the resistor RS3 connected in series in the current change detection circuit, and the voltage comparison device U3 controls the on and off of the indicator light according to the voltage change; An achievable circuit structure is as Figure 2 shown, the voltage dividing resistors of the light switching control circuit include a resistor R33 and a resistor R30 connected in series; the indicator lights include two indicator lights LED1 and LED2 connected in parallel; one end of the indicator lights LED1 and LED2 after being connected in parallel is connected to the output pin V of the voltage comparison device U3 OUT ; the resistor RS3 of the current change detection circuit is connected to the Vsense pin of the voltage comparison device U3 through the resistor R29; the Vsense pin of the voltage comparison device U3 and the output pin V OUT are connected in series with a resistor R31 and a capacitor C15; The conduction path of the indicator lights LED1 and LED2 is: V+→R33→R30→LED1∥LED2→U3→GND2(V-), the on and off of the indicator lights LED1 and LED2 are realized by the voltage comparison device U3; Specifically, the model of the voltage comparison device U3 may be AP4320AK; The output current of the power supply circuit passes through the loop where the resistor RS1 is connected in series with RS3, and generates a voltage Vs2=I*(RS1+RS3) on the resistor RS1 and the resistor RS3. When the output current increases and the voltage Vs2 is greater than the reference voltage Vsense (fixed value) of the voltage comparison device U3, that is, Vrs<Vsense, the PIN5 pin of the voltage comparison device U3 outputs a low level, the path V+→R33→R30→LED1∥LED2→U3→GND2(V-) is conducted, and LED1 and LED2 are lit. Conversely, when the output current decreases and Vrs<Vsense, the PIN5 pin of the voltage comparison device U3 outputs a high level, the path V+→R33→R30→LED1∥LED2→U3→GND2(V-) is not conducted, and LED1 and LED2 are turned off.

[0024] According to the formula Vrs=I*(RS1+RS3), by adjusting the values of the resistors RS1 and RS3, the current values for turning the light on and off can be adjusted, so as to achieve the purpose of detecting the current magnitude.

[0025] In some embodiments, the power supply primary circuit includes an AC input terminal circuit, a rectifier filter circuit, and a primary RCD absorption circuit; The AC input circuit includes a fuse F1, a first filter inductor LF1, and a thermistor NTC1. The rectifier and filter circuit includes a bridge rectifier circuit BD1 and an LC filter circuit. The LC filter circuit includes an inductor L1, a capacitor EC1, and a capacitor EC2 connected in series and parallel. The primary RCD snubber circuit is set at both ends of the primary winding of transformer T1. The primary RCD snubber circuit includes parallel circuit one, parallel circuit two and diode D1 connected in series. Parallel circuit one includes capacitor C2, resistor R1A and resistor R1B connected in parallel. Parallel circuit two includes resistor R2A and resistor R2B connected in parallel. The AC input voltage of the AC input circuit enters the first filter inductor LF1 after passing through fuse F1 and thermistor NTC1 to filter external interference signals. Fuse F1 provides current protection; when an abnormally large current flows through fuse F1, fuse F1 disconnects the circuit to protect the charger. Thermistor NTC1 is a resistor with a negative temperature coefficient, and its resistance value is relatively large when the power is turned on, which can suppress the large current at the moment of power-on.

[0026] After passing through the above circuit, the AC voltage enters the bridge rectifier circuit BD1, which converts the AC voltage into DC voltage. At this time, the DC voltage is not smooth and fluctuates greatly. Through capacitors EC1 and EC2, the unsmooth and pulsating DC voltage is transformed into a smoother DC voltage to provide the DC power required by the subsequent circuits.

[0027] In some embodiments, the power supply secondary circuit includes an output rectifier filter circuit and a secondary RC snubber circuit. The output rectifier and filter circuit includes diode D6 and a filter circuit; the filter circuit includes capacitors EC4, EC5 and C8 connected in parallel. The secondary RC snubber circuit includes resistors R23B and R23A connected in parallel, and capacitor C12. In the circuit described above, the voltage becomes a DC voltage with a relatively large ripple component after passing through D6. After being smoothed by capacitors EC4 and EC5, a DC voltage with a relatively small ripple is obtained that meets the requirements. Resistors R23B and R23A and capacitor C12 form a spike absorption circuit to absorb excessively high spike voltages and protect the circuit from abnormal operation.

[0028] In some embodiments, the switching circuit, such as Figure 4 As shown, it includes a controller U1, a switching transistor drive circuit, and a MOSFET Q1. The gate of the MOSFET Q1 is connected to the control signal output terminal GATE pin of the controller U1 through the switching transistor drive circuit, and the drive circuit drives the operation of the MOSFET Q2. Optionally, the switching transistor drive circuit includes resistors R9 and R8 connected in series, and a fast recovery diode D5 connected in parallel across resistor R9. The switching transistor drive circuit provides a drive voltage to turn on the MOSFET Q1. The drain of MOSFET Q1 is connected to the high end of the primary winding of the transformer (i.e., pin 3 of T1), and the source is connected to the power supply reference ground AGND through two parallel resistors R13A and R13B; the source is connected to the CS pin of controller U1 through resistor R11, and the CS pin of controller U1 is grounded through capacitor C5. In this embodiment, resistors R13A, R13B, R11, and capacitor C5 form a current detection loop to limit overcurrent in the circuit.

[0029] When the controller U1 sends a high-level signal, the gate of MOSFET Q1 is charged through the drive resistors R8 and R9. When the gate of MOSFET Q1 receives a high-level switch drive signal, there is a voltage drop between the drain and source of MOSFET Q2 and it conducts, thus forming a switch power-on circuit.

[0030] In use, the rectified and filtered DC voltage is connected to the switching transistor Q1 through the transformer winding PIN3-4, and then to ground through the current-limiting resistors R13A and R13B, forming a switching circuit. The switching transistor Q1 is controlled by the controller U1 to switch and convert the rectified DC voltage into a high-frequency voltage, thus completing the conversion from DC voltage to AC high-frequency voltage. By changing the turns ratio of the transformer T1, the required output voltage can be obtained, which is output through the transformer output pins PIN7-8.

[0031] A further technical solution includes a switching circuit comprising a first power supply circuit and a second power supply circuit. The power supply terminals of the first power supply circuit and the second power supply circuit are respectively connected to the VDD pin of the controller. The first power supply circuit is connected to the input terminal of the bridge rectifier circuit BD1 to provide power when the controller U1 is started. The second power supply circuit is connected to the voltage output terminal of the auxiliary winding PIN1-2 of the transformer T1 to provide power during the operation of the controller U1. The first power supply circuit provides a stable power supply during the operation of controller U1. Its input is connected to the auxiliary winding PIN1-2 of transformer T1, and its output, after rectification and filtering, is connected to the VDD pin of controller U1. Specifically, the first power supply circuit includes diode D2, resistors R5 and R4, filter capacitor C3, energy storage capacitor EC3, and filter capacitor C4. Resistor R4 and filter capacitor C3 are connected in series and then in parallel with diode D2. The output of the parallel connection is connected to one end of resistor R5; the other end of resistor R5 is connected to the VDD pin of controller U1 and grounded through the parallel energy storage capacitor EC3 and filter capacitor C4. The output of the auxiliary winding of transformer T1 is rectified by D2 and then charged by the energy storage capacitor EC3 and the filter capacitors C3 and C4 through the current limiting resistor R5 and the resistor R4, thereby providing a stable DC voltage for the controller U1.

[0032] The second power supply circuit is used to provide startup power during the startup phase of controller U1. Its input is connected to the input of bridge rectifier circuit BD1 and then to the VDD pin of controller U1.

[0033] Specifically, the second power supply circuit includes diodes D3 and D4 connected to the input terminals of the bridge rectifier circuit BD1, and resistors R3 and R7 connected in series. The AC power supply current is limited by R3 and R7, and after rectification by D3 and D4, it provides the initial startup voltage for the controller U1. Once transformer T1 starts operating and provides auxiliary voltage, the first power supply circuit will replace the second power supply circuit, providing a continuous and stable operating power supply.

[0034] The energy storage capacitor EC3 and filter capacitor C4 in the first power supply circuit ensure voltage stability during system operation and suppress power supply noise and interference; the current limiting design in the second power supply circuit reduces the impact of current surges during startup on the controller U1 and the power grid, and improves the electromagnetic compatibility and reliability of the system.

[0035] Example 2 Based on Embodiment 1, this embodiment provides a switching power supply that uses the IC-based power supply circuit described in Embodiment 1 to achieve constant voltage and constant current and lamp control.

[0036] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

[0037] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. A power supply circuit based on IC to implement constant voltage and constant current and lamp switching control, characterized in that: It includes the primary circuit of the power supply, the switching circuit, the transformer T1, and the secondary circuit of the power supply; the output of the secondary circuit of the power supply is connected to the constant voltage and constant current circuit and the lamp control circuit. The constant voltage and constant current circuit includes an optocoupler and a voltage comparator U2 connected in sequence, a voltage detection circuit, and an output current detection circuit connected in series in the output circuit of the power supply secondary circuit. The voltage detection circuit and the output current detection circuit are respectively connected to the two control pins of the voltage comparator U2; the primary phase U4B of the optocoupler is connected in series at the power supply output terminal V. + The output terminal V of the voltage comparator U2 OUT Between them, the secondary side U4A of the optocoupler is connected to the feedback pin FB of the controller U1 of the switching circuit; The switching circuit is equipped with an overvoltage protection circuit, including a voltage divider resistor network connected to the secondary voltage output terminal of transformer T1 and a filter capacitor C7. The voltage output terminal of the voltage divider resistor network is connected to the detection pin DEM of controller U1.

2. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The voltage detection circuit in the constant voltage and constant current circuit includes resistors R25, R27, R22, R23, and R28 connected in sequence. Resistors R25 and R27 are connected in parallel to form a first parallel circuit, and resistors R22, R23, and R28 are connected in parallel to form a second parallel circuit. The connection point of the first parallel circuit and the second parallel circuit is connected to the pin Vctrl of the voltage comparator U2.

3. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The output current detection circuit in the constant voltage and constant current circuit includes resistors RS1, RS2, R20, and capacitor C14. Resistor R20 and capacitor C14 are connected in parallel, and then connected in parallel with resistors RS1 and RS2 respectively. The connection point of this parallel connection is connected to pin 4 of voltage comparator U2. The connection point of resistor R20 and capacitor C14 is connected to pin 1 of voltage comparator U2. The connection point of resistor R20 and capacitor C14 is connected to the output terminal V of voltage comparator U2 through capacitor C10 and resistor R26. OUT .

4. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The overvoltage protection circuit in the switching circuit is connected to the voltage output terminal of the auxiliary winding PIN1-2 of the transformer. The voltage divider resistor network includes resistors R6, R7A, and R7B. Resistors R7A, R7B, and capacitor C7 are connected in parallel to form a third parallel circuit. One end of resistor R6 is connected to the voltage output terminal of the auxiliary winding PIN1-2 of transformer T1, and the other end is grounded after being connected to the third parallel circuit. The connection point of resistor R6 and the third parallel circuit is connected to the DEM pin of the controller U1 of the switching circuit.

5. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The indicator light control circuit includes a voltage divider resistor, an indicator light, a current change detection circuit, and a voltage comparator U3 connected in sequence; the voltage divider resistor is connected to the positive terminal V of the output of the power supply secondary circuit. + The current change detection circuit detects the voltage through a resistor connected in series in the current change detection circuit. The voltage comparator U3 controls the on / off switch of the indicator light according to the voltage change.

6. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 5, characterized in that: The voltage divider resistors in the light control circuit include resistors R33 and R30 connected in series; the indicator lights include two indicator lights, LED1 and LED2, connected in parallel; one end of the parallel connection of LED1 and LED2 is connected to the output pin V of the voltage comparator U3. OUT ; The resistor RS3 in the current change detection circuit is connected to the Vsense pin of the voltage comparator U3 through resistor R29; the Vsense pin of the voltage comparator U3 is connected to the output pin V. OUT A resistor R31 and a capacitor C15 are connected in series.

7. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The primary circuit of the power supply includes the AC input circuit, the rectifier and filter circuit, and the primary RCD snubber circuit; The primary RCD snubber circuit is located at both ends of the primary winding of transformer T1. The primary RCD snubber circuit includes parallel circuit one, parallel circuit two and diode D1 connected in series. Parallel circuit one includes capacitor C2, resistor R1A and resistor R1B connected in parallel. Parallel circuit two includes resistor R2A and resistor R2B connected in parallel.

8. The power supply circuit for constant voltage and constant current control and lamp switching based on IC as described in claim 1, characterized in that: The power supply secondary circuit includes an output rectifier and filter circuit as well as a secondary RC snubber circuit. The output rectifier and filter circuit includes diode D6 and a filter circuit; the filter circuit includes resistors EC4 and EC5 connected in parallel and capacitor C8. The secondary RC snubber circuit includes resistors R23B and R23A connected in parallel, and capacitor C12.

9. A switching power supply, characterized in that: The power supply circuit based on IC to achieve constant voltage and constant current and lamp control is adopted as described in any one of claims 1-8.

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