A small power wide voltage input flyback isolation type switching power supply circuit with protection circuit

Abstract

The utility model provides a kind of low-power wide voltage input flyback isolation type switching power supply circuit with protection circuit, including three-phase / single-phase ac rectifier circuit, AC voltage input is converted into DC voltage output;DCDC control IC circuit, output PWM control signal;Isolation type high-frequency transformer circuit, through PWM control signal adjustment, DC voltage input is converted into low-voltage AC output;Output rectification filtering feedback loop circuit, low-voltage AC input is rectified as low-voltage DC output;Control protection circuit, between three-phase / single-phase ac rectifier circuit and isolation type high-frequency transformer circuit, including two series driving tubes MOSFET, adapt superhigh voltage input, protect switching power supply circuit;The utility model integrates input overcurrent, overvoltage, current overshoot protection, circuit over-temperature protection, driving tube peak voltage protection, improve circuit reliability;Adopt transformer coupling drive multiple MOSFET series topology structure, give consideration to high voltage input adaptation and low-voltage output stability.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a low-power, wide-voltage input flyback isolated switching power supply circuit with protection circuit. Background Technology

[0002] In industrial control systems, low-voltage DC is generally used as the power supply system. Furthermore, the range of power supply voltages for household or industrial use varies in different countries; for example, common single-phase voltages are 110VAC and 220VAC, while three-phase voltages are 240VAC, 380VAC, and 600VAC.

[0003] In the existing technology, the AC input range of general switching power supplies is relatively small, and they are basically single-phase AC input. Different switching power supplies with different input voltages need to be matched for different voltage applications. When multiple different switching power supplies are present in a system, they may interfere with each other, which will greatly reduce the stability of the control system. Summary of the Invention

[0004] The purpose of this invention is to provide a low-power, wide-voltage input flyback isolated switching power supply circuit with protection circuitry, solving the problems of narrow input voltage range and incompatibility between different voltage levels in existing switching power supplies.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows: A low-power, wide-voltage input flyback isolated switching power supply circuit with protection circuitry includes: Three-phase / single-phase AC rectifier circuits are used to convert AC voltage input into DC voltage output; The DC-DC control IC circuit is used to output PWM control signals; An isolated high-frequency transformer circuit, regulated by a PWM control signal, receives a DC voltage input and converts the DC voltage input into a low-voltage AC output. The output rectifier and filter feedback loop circuit receives low-voltage AC input and is used to rectify the low-voltage AC input into low-voltage DC output. The control and protection circuit, located between the three-phase / single-phase AC rectifier circuit and the isolated high-frequency transformer circuit, includes two series-connected MOSFETs to adapt to ultra-high voltage input and protect the entire switching power supply circuit.

[0006] Furthermore, it also includes an input protection circuit, which comprises a first fuse F1, a second fuse F2, a third fuse F3, a first varistor RV1, a second varistor RV2, a third varistor RV3, a first NTC resistor RT1, a second NTC resistor RT2, and a third NTC resistor RT3. One end of the first fuse F1, the second fuse F2, and the third fuse F3 are respectively connected to the first phase line L1, the second phase line L2, and the third phase line L3. The two ends of the first varistor RV1 are respectively connected to the first fuse F1 and the second fuse F2. At the other end, the two ends of the second varistor RV2 are respectively connected to the other ends of the first fuse F1 and the third fuse F3. The two ends of the third varistor RV3 are respectively connected to the other ends of the second fuse F2 and the third fuse F3. The other ends of the first fuse F1, the second fuse F2 and the third fuse F3 are respectively connected to one end of the first NTC resistor RT1, the second NTC resistor RT2 and the third NTC resistor RT3. The other ends of the first NTC resistor RT1, the second NTC resistor RT2 and the third NTC resistor RT3 are connected to a three-phase / single-phase AC rectifier circuit.

[0007] Furthermore, the three-phase / single-phase AC rectifier circuit includes a first rectifier diode SD1, a second rectifier diode SD2, a third rectifier diode SD3, a fourth rectifier diode SD4, a fifth rectifier diode SD5, a sixth rectifier diode SD6, a common-mode inductor LF1, a first filter capacitor E1, a second filter capacitor E2, a third filter capacitor E3, a first voltage balancing resistor R1, a second voltage balancing resistor R2, and a third voltage balancing resistor R3; The first rectifier diode SD1, the second rectifier diode SD2, the third rectifier diode SD3, the fourth rectifier diode SD4, the fifth rectifier diode SD5, and the sixth rectifier diode SD6 are connected in series and parallel to form a full-wave rectifier circuit to realize the conversion of AC voltage to DC voltage. One end of the common-mode inductor LF1 is connected to the DC voltage output after full-wave rectification to filter out common-mode signals, and the other end is connected to the filter capacitor circuit. The first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 are aluminum electrolytic capacitors, which are connected in series to form a high-voltage filter circuit. The first voltage balancing resistor R1, the second voltage balancing resistor R2, and the third voltage balancing resistor R3 are connected in parallel across the first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 to balance the capacitor voltage.

[0008] Furthermore, the DC-DC control IC circuit includes a PWM control IC U1, which includes a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a ninth capacitor C9, a thirteenth resistor R13, a fourteenth resistor R14, and a fourth NTC resistor RT4. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, and the ninth capacitor C9 are MLCC filter capacitors. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, and the ninth capacitor C9 are respectively connected to pins 6, 7, 3, and 2 of the PWM control IC U1. The thirteenth resistor R13 adjusts the switching frequency of the PWM control IC U1. The fourth NTC resistor RT4 is used for temperature detection, and the fourteenth resistor R14 is used for PWM output protection.

[0009] Furthermore, the isolated high-frequency transformer circuit includes a high-frequency transformer T1, a third diode D3, a twelfth resistor R12, and a first electrolytic capacitor E4. The high-frequency transformer T1 has four windings. Pins 3 and 8 of the high-frequency transformer T1 are secondary output windings, pins 4, 7, 2, and 9 of the high-frequency transformer T1 are primary power windings, and pins 1 and 10 of the high-frequency transformer T1 are primary auxiliary windings. One end of the third diode D3 is connected to the auxiliary winding, and the other end of the third diode D3 is connected to the twelfth resistor R12. One end of the first electrolytic capacitor E4 is connected to the twelfth resistor R12, and the other end of the first electrolytic capacitor E4 is connected to the primary auxiliary winding. The third diode D3, the twelfth resistor R12, and the first electrolytic capacitor E4 constitute the power input of the PWM control IC U1.

[0010] Further, the control and protection circuit includes a first capacitor C1, a second capacitor C2, a sixth capacitor C6, a first diode D1, a second diode D2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fifteenth resistor R15, a first driving transistor M1, a second driving transistor M2, a first Zener diode ZD1, a second Zener diode ZD2, a third Zener diode ZD3, a fourth Zener diode ZD4, a first driving transistor Q1, a second driving transistor Q2, and a driving transformer T2. The sixth resistor R6, the seventh resistor R7, the ninth resistor R9, the tenth resistor R10, the first capacitor C1, the second capacitor C2, the first diode D1, and the second diode D2 are connected in series and parallel to form an RCD absorption circuit. The first Zener diode ZD1, the second... Zener diodes ZD2, ZD3, and ZD4 are connected in series to form a gate protection circuit. The first driving transistor M1 and the second driving transistor M2 are respectively connected to the primary power winding of the high-frequency transformer T1. The first driving transistor Q1 and the second driving transistor Q2 form a complementary push-pull circuit. The bases of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fourteenth resistor R14, and the emitters of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fifteenth resistor R15. The fifteenth resistor R15 and the sixth capacitor C6 are connected in series to the driving transformer T2. The driving transformer T2 converts one PWM signal into two signals to control the first driving transistor M1 and the second driving transistor M2 respectively. The fourth NTC resistor RT4 detects the circuit temperature. When an abnormality occurs, the feedback causes the PWM control IC U1 to start the low-power protection mode.

[0011] Further, the output rectification and filtering feedback loop circuit includes a seventh capacitor C7, an eighth capacitor C8, a fourth diode D4, a differential-mode inductor L1, a second electrolytic capacitor E5, a third electrolytic capacitor E6, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, an isolation optocoupler OP1, and a voltage regulator U2. The fourth diode D4 and the second electrolytic capacitor E5 form a half-wave rectification and filtering circuit. The sixteenth resistor R16 and the seventh capacitor C7 form an RC absorption circuit. One end of the seventeenth resistor R17 is connected to the anode of the isolation optocoupler OP1. The cathode of P1 is connected in sequence to the eighth capacitor C8 and the voltage regulator U2. One end of the eighteenth resistor R18 is connected between the seventeenth resistor R17 and the isolation optocoupler OP1. One end of the twenty-first resistor R21 is connected between the eighth capacitor C8 and the voltage regulator U2. The cathode of the voltage regulator U2 is connected to the cathode of the isolation optocoupler OP1. The twentieth resistor R20 is connected to the voltage regulator U2. The differential mode inductor L1 is connected in sequence to the seventeenth resistor R17, the nineteenth resistor R19 and the third electrolytic capacitor E6. The other end of the nineteenth resistor R19 is connected to the twenty-first resistor R21 and the twentieth resistor R20. The collector output of the isolation optocoupler OP1 is connected to the feedback pin of the PWM control IC U1 to form an output feedback system.

[0012] The switching power supply circuit of this utility model is sequentially connected to an input protection circuit, a three-phase / single-phase AC rectifier circuit, an isolation high-frequency transformer circuit, an output rectifier filter feedback loop circuit, a DC-DC control IC circuit, and a control protection circuit, which work together to achieve signal control and safety protection.

[0013] After the power is turned on, the fuse, varistor, and NTC resistor in the input protection circuit of this utility model first activate the protection function to filter abnormal signals. The AC input is converted into DC high voltage by a three-phase / single-phase AC rectifier circuit. After being filtered by a common-mode inductor and stored in a capacitor, it is sent to the primary power winding of the isolated high-frequency transformer. The PWM control IC outputs a PWM signal, which is enhanced by a complementary push-pull circuit and then converted into two signals by the drive transformer to control the conduction and cutoff of drive transistors M1 and M2, thereby realizing the energy transfer of the high-frequency transformer.

[0014] The low-voltage AC signal output from the secondary output winding of this invention is rectified and filtered by the output rectification and filtering feedback loop circuit to output a stable low-voltage DC power. When the output voltage fluctuates, the feedback loop transmits the signal to the PWM control IC through the isolation optocoupler to adjust the PWM signal duty cycle in real time and maintain the output voltage stability.

[0015] During circuit operation, the NTC resistor continuously monitors the temperature. When the temperature is abnormal, the PWM control IC immediately activates the protection mode. The RCD absorption circuit and gate protection circuit continuously protect the drive transistor to prevent peak voltage from damaging the components and ensure the long-term stable operation of the entire circuit.

[0016] This utility model has a wide input voltage range, which can meet the power supply requirements of 85VAC~650VAC or 120VDC~1000VDC, and is compatible with various voltage specifications in different countries and regions, so as to achieve universal use. This utility model integrates input terminal overcurrent, overvoltage, and current overshoot protection, circuit overtemperature protection, and drive tube spike voltage protection, thereby improving circuit reliability. This invention employs a transformer-coupled topology to drive multiple MOSFETs in series, balancing high-voltage input compatibility with low-voltage output stability. This invention uses a negative feedback regulation system to precisely control the output voltage, resulting in high stability. It is suitable for industrial control and various household appliances. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of the present invention.

[0018] Figure label: F1~3 First~Third Fuse, RV1~3 First~Third Varistors RT1~4 First~Fourth NTC Resistors SD1~6 First~Sixth Rectifier Diodes LF1 common mode inductor, E1~3 First~Third Filter Capacitors E4 is the first electrolytic capacitor, E5 is the second electrolytic capacitor, and E6 is the third electrolytic capacitor. R1~3 are the first to third voltage balancing resistors. R6~21, the sixth to twenty-first resistors, C1~9, the first to ninth capacitors, U1 PWM control IC, U2 voltage regulator, OP1 isolation optocoupler ZD1~4 First~Fourth Zener Diodes D1~4, the first to fourth diodes, M1 first drive transistor, M2 second drive transistor Q1 is the first driver transistor, Q2 is the second driver transistor. T1 is a high-frequency transformer, and T2 is a drive transformer. Detailed Implementation

[0019] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0020] This embodiment discloses a low-power, wide-voltage input flyback isolated switching power supply circuit with protection circuitry, including: Three-phase / single-phase AC rectifier circuits are used to convert AC voltage input into DC voltage output; like Figure 1 As shown, the three-phase / single-phase AC rectifier circuit includes a first rectifier diode SD1, a second rectifier diode SD2, a third rectifier diode SD3, a fourth rectifier diode SD4, a fifth rectifier diode SD5, a sixth rectifier diode SD6, a common-mode inductor LF1, a first filter capacitor E1, a second filter capacitor E2, a third filter capacitor E3, a first voltage balancing resistor R1, a second voltage balancing resistor R2, and a third voltage balancing resistor R3.

[0021] The first rectifier diode SD1, the second rectifier diode SD2, the third rectifier diode SD3, the fourth rectifier diode SD4, the fifth rectifier diode SD5, and the sixth rectifier diode SD6 are connected in series and parallel to form a full-wave rectifier circuit, which realizes the conversion from AC voltage input to DC voltage output.

[0022] One end of the common-mode inductor LF1 is connected to the DC voltage output after full-wave rectification to filter out common-mode signals, and the other end is connected to the filter capacitor circuit.

[0023] The first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 are aluminum electrolytic capacitors, which are connected in series to form a high-voltage filter circuit to effectively reduce DC ripple. The first voltage balancing resistor R1, the second voltage balancing resistor R2, and the third voltage balancing resistor R3 are connected in parallel across the first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 to balance the capacitor voltage. Since the input voltage range is wide, the voltage withstand of a single filter capacitor is insufficient, and the voltage of the filter capacitor is prone to fluctuation when the load changes. By connecting the voltage balancing resistor in parallel across each capacitor, the voltage of the three filter capacitors can be kept consistent, avoiding capacitor failure and providing stable energy to the subsequent circuit.

[0024] The DC-DC control IC circuit is used to output PWM control signals; like Figure 1As shown, the DC-DC control IC circuit includes a highly integrated current-mode PWM control IC U1, designed for an offline flyback switching power supply. The PWM control IC U1 includes a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a ninth capacitor C9, a thirteenth resistor R13, a fourteenth resistor R14, and a fourth NTC resistor RT4. The third capacitor C3, fourth capacitor C4, fifth capacitor C5, and ninth capacitor C9 are MLCC filter capacitors. These capacitors are connected to pins 6, 7, 3, and 2 of the PWM control IC U1, respectively. The thirteenth resistor R13 adjusts the switching frequency of the PWM control IC U1, ensuring stable operation under the designed conditions. The fourth NTC resistor RT4 is used to monitor the operating temperature of the control loop in real time, and the fourteenth resistor R14 is used to protect the PWM output signal.

[0025] An isolated high-frequency transformer circuit, regulated by a PWM control signal, receives a DC voltage input and converts the DC voltage input into a low-voltage AC output. like Figure 1 As shown, the isolated high-frequency transformer circuit includes a high-frequency transformer T1, a third diode D3, a twelfth resistor R12, and a first electrolytic capacitor E4. The high-frequency transformer T1 has four windings: the secondary output winding outputs low-voltage AC, the primary power winding transmits electrical energy, and the primary auxiliary winding supplies power to the PWM control IC U1.

[0026] Pins 3 and 8 of the high-frequency transformer T1 are the secondary output windings, pins 4, 7, 2, and 9 of the high-frequency transformer T1 are the primary power windings, and pins 1 and 10 of the high-frequency transformer T1 are the primary auxiliary windings. One end of the third diode D3 is connected to the auxiliary winding, and the other end of the third diode D3 is connected to the twelfth resistor R12. One end of the first electrolytic capacitor E4 is connected to the twelfth resistor R12, and the other end of the first electrolytic capacitor E4 is connected to the primary auxiliary winding. The third diode D3, the twelfth resistor R12, and the first electrolytic capacitor E4 form the independent power input circuit of the PWM control IC U1, ensuring the stable operation of the PWM control IC U1.

[0027] The output rectifier and filter feedback loop circuit receives low-voltage AC input and is used to rectify the low-voltage AC input into low-voltage DC output. like Figure 1As shown, the output rectifier filter feedback loop circuit includes a seventh capacitor C7, an eighth capacitor C8, a fourth diode D4, a differential mode inductor L1, a second electrolytic capacitor E5, a third electrolytic capacitor E6, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, an isolation optocoupler OP1, and a voltage regulator U2. The fourth diode D4 and the second electrolytic capacitor E5 form a half-wave rectifier filter circuit. The sixteenth resistor R16 and the seventh capacitor C7 form an RC absorption circuit to protect the fourth diode D4 from voltage surges.

[0028] One end of the seventeenth resistor R17 is connected to the anode of the isolation optocoupler OP1. The cathode of the isolation optocoupler OP1 is connected in sequence to the eighth capacitor C8 and the voltage regulator U2. One end of the eighteenth resistor R18 is connected between the seventeenth resistor R17 and the isolation optocoupler OP1. One end of the twenty-first resistor R21 is connected between the eighth capacitor C8 and the voltage regulator U2. The cathode of the voltage regulator U2 is connected to the cathode of the isolation optocoupler OP1. The twentieth resistor R20 is connected to the voltage regulator U2. The differential mode inductor L1 is connected in sequence to the seventeenth resistor R17, the nineteenth resistor R19 and the third electrolytic capacitor E6. The differential mode inductor L1 and the third electrolytic capacitor E6 filter out differential mode interference in the DC signal and output a stable low-voltage DC power. The other end of the nineteenth resistor R19 is connected to the twenty-first resistor R21 and the twentieth resistor R20. The collector output of the isolation optocoupler OP1 is connected to the feedback pin of the PWM control IC U1 to form an output feedback system.

[0029] When the output voltage VDD increases, the isolation optocoupler OP1 is turned on. After the PWM control IC U1 detects the overvoltage signal, it reduces the duty cycle of the PWM signal, which shortens the turn-on time of the first drive transistor M1 and the second drive transistor M2. The output energy of the high-frequency transformer T1 is reduced, causing the output voltage to fall back to a stable value, thus forming a negative feedback regulation mechanism.

[0030] The control and protection circuit, located between the three-phase / single-phase AC rectifier circuit and the isolation high-frequency transformer circuit, includes two series-connected drive MOSFETs to adapt to ultra-high voltage input and protect the entire switching power supply circuit. like Figure 1As shown, the control and protection circuit includes a first capacitor C1, a second capacitor C2, a sixth capacitor C6, a first diode D1, a second diode D2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fifteenth resistor R15, a first driving transistor M1, a second driving transistor M2, a first Zener diode ZD1, a second Zener diode ZD2, a third Zener diode ZD3, a fourth Zener diode ZD4, a first driving transistor Q1, a second driving transistor Q2, and a driving transformer T2. The sixth resistor R6, the seventh resistor R7, the ninth resistor R9, the tenth resistor R10, the first capacitor C1, the second capacitor C2, the first diode D1, and the second diode D2 are connected in series and parallel to form an RCD absorption circuit, which eliminates the voltage spikes caused by the leakage inductance of the high-frequency transformer T1 and protects the first driving transistor M1 and the second driving transistor M2.

[0031] The first Zener diode ZD1, the second Zener diode ZD2, the third Zener diode ZD3, and the fourth Zener diode ZD4 are connected in series to form a gate protection circuit to prevent the gates of the first driving transistor M1 and the second driving transistor M2 from being broken down due to excessive voltage. The first driving transistor M1 and the second driving transistor M2 adopt a series topology to adapt to the wide voltage input requirements. The first driving transistor M1 and the second driving transistor M2 are respectively connected to the primary power winding of the high-frequency transformer T1.

[0032] The first driving transistor Q1 and the second driving transistor Q2 form a complementary push-pull circuit to enhance the driving capability of the PWM signal. The bases of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fourteenth resistor R14, and the emitters of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fifteenth resistor R15. The fifteenth resistor R15 and the sixth capacitor C6 are connected in series and then connected to the driving transformer T2. The driving transformer T2 converts one PWM signal into two signals to control the first driving transistor M1 and the second driving transistor M2 respectively, controlling the conduction and turn-off of the first driving transistor M1 and the second driving transistor M2.

[0033] The fourth NTC resistor RT4 detects the circuit temperature. When an abnormality occurs, it triggers the PWM control IC U1 to start the low-power protection mode through feedback. When the fourth NTC resistor RT4 detects an abnormal increase in circuit temperature, it triggers the PWM control IC U1 to start the low-power protection mode or stop working through the feedback signal to avoid circuit damage.

[0034] Input protection circuit, such as Figure 1 As shown, it includes a first fuse F1, a second fuse F2, a third fuse F3, a first varistor RV1, a second varistor RV2, a third varistor RV3, a first NTC resistor RT1, a second NTC resistor RT2, and a third NTC resistor RT3.

[0035] When applied to a three-phase AC rectifier circuit, one end of the first fuse F1, the second fuse F2, and the third fuse F3 is connected to the first phase line L1, the second phase line L2, and the third phase line L3, respectively. When applied to a single-phase AC rectifier circuit, the first phase line L1 serves as the phase line L of the single-phase power, the second phase line L2 serves as the neutral line N of the single-phase power, and the third phase line L3 is a normally closed contact NC.

[0036] The two ends of the first varistor RV1 are respectively connected to the other ends of the first fuse F1 and the second fuse F2. The two ends of the second varistor RV2 are respectively connected to the other ends of the first fuse F1 and the third fuse F3. The two ends of the third varistor RV3 are respectively connected to the other ends of the second fuse F2 and the third fuse F3. The first varistor RV1, the second varistor RV2 and the third varistor RV3 are used to absorb high-frequency pulses in the input voltage to prevent the subsequent circuit from being damaged by the impact.

[0037] The other ends of the first fuse F1, the second fuse F2, and the third fuse F3 are respectively connected to one end of the first NTC resistor RT1, the second NTC resistor RT2, and the third NTC resistor RT3. The other ends of the first NTC resistor RT1, the second NTC resistor RT2, and the third NTC resistor RT3 are connected to a three-phase / single-phase AC rectifier circuit. The first NTC resistor RT1, the second NTC resistor RT2, and the third NTC resistor RT3 can prevent current overshoot during power-on.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A low-power, wide-voltage input flyback isolated switching power supply circuit with protection circuitry, characterized in that, include: Three-phase / single-phase AC rectifier circuits are used to convert AC voltage input into DC voltage output; The DC-DC control IC circuit is used to output PWM control signals; An isolated high-frequency transformer circuit, regulated by a PWM control signal, receives a DC voltage input and converts the DC voltage input into a low-voltage AC output. The output rectifier and filter feedback loop circuit receives low-voltage AC input and is used to rectify the low-voltage AC input into low-voltage DC output. The control and protection circuit, located between the three-phase / single-phase AC rectifier circuit and the isolated high-frequency transformer circuit, includes two series-connected MOSFETs to adapt to ultra-high voltage input and protect the entire switching power supply circuit.

2. The switching power supply circuit according to claim 1, characterized in that, It also includes an input protection circuit, which comprises a first fuse F1, a second fuse F2, a third fuse F3, a first varistor RV1, a second varistor RV2, a third varistor RV3, a first NTC resistor RT1, a second NTC resistor RT2, and a third NTC resistor RT3. One end of the first fuse F1, the second fuse F2, and the third fuse F3 are respectively connected to the first phase line L1, the second phase line L2, and the third phase line L3. The two ends of the first varistor RV1 are respectively connected to the other ends of the first fuse F1 and the second fuse F2. The two ends of the second varistor RV2 are respectively connected to the other ends of the first fuse F1 and the third fuse F3. The two ends of the third varistor RV3 are respectively connected to the other ends of the second fuse F2 and the third fuse F3. The other ends of the first fuse F1, the second fuse F2 and the third fuse F3 are respectively connected to one end of the first NTC resistor RT1, the second NTC resistor RT2 and the third NTC resistor RT3. The other ends of the first NTC resistor RT1, the second NTC resistor RT2 and the third NTC resistor RT3 are connected to a three-phase / single-phase AC rectifier circuit.

3. The switching power supply circuit according to claim 2, characterized in that, The three-phase / single-phase AC rectifier circuit includes a first rectifier diode SD1, a second rectifier diode SD2, a third rectifier diode SD3, a fourth rectifier diode SD4, a fifth rectifier diode SD5, a sixth rectifier diode SD6, a common-mode inductor LF1, a first filter capacitor E1, a second filter capacitor E2, a third filter capacitor E3, a first voltage balancing resistor R1, a second voltage balancing resistor R2, and a third voltage balancing resistor R3; The first rectifier diode SD1, the second rectifier diode SD2, the third rectifier diode SD3, the fourth rectifier diode SD4, the fifth rectifier diode SD5, and the sixth rectifier diode SD6 are connected in series and parallel to form a full-wave rectifier circuit to realize the conversion of AC voltage to DC voltage. One end of the common-mode inductor LF1 is connected to the DC voltage output after full-wave rectification to filter out common-mode signals, and the other end is connected to the filter capacitor circuit. The first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 are aluminum electrolytic capacitors, which are connected in series to form a high-voltage filter circuit. The first voltage balancing resistor R1, the second voltage balancing resistor R2, and the third voltage balancing resistor R3 are connected in parallel across the first filter capacitor E1, the second filter capacitor E2, and the third filter capacitor E3 to balance the capacitor voltage.

4. The switching power supply circuit according to claim 3, characterized in that, The DC-DC control IC circuit includes a PWM control IC U1. The PWM control IC U1 includes a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a ninth capacitor C9, a thirteenth resistor R13, a fourteenth resistor R14, and a fourth NTC resistor RT4. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, and the ninth capacitor C9 are MLCC filter capacitors. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, and the ninth capacitor C9 are connected to pins 6, 7, 3, and 2 of the PWM control IC U1, respectively. The thirteenth resistor R13 adjusts the switching frequency of the PWM control IC U1. The fourth NTC resistor RT4 is used for temperature detection, and the fourteenth resistor R14 is used for PWM output protection.

5. The switching power supply circuit according to claim 4, characterized in that, The isolated high-frequency transformer circuit includes a high-frequency transformer T1, a third diode D3, a twelfth resistor R12, and a first electrolytic capacitor E4. The high-frequency transformer T1 has four windings. Pins 3 and 8 of the high-frequency transformer T1 are secondary output windings, pins 4, 7, 2, and 9 of the high-frequency transformer T1 are primary power windings, and pins 1 and 10 of the high-frequency transformer T1 are primary auxiliary windings. One end of the third diode D3 is connected to the auxiliary winding, and the other end of the third diode D3 is connected to the twelfth resistor R12. One end of the first electrolytic capacitor E4 is connected to the twelfth resistor R12, and the other end of the first electrolytic capacitor E4 is connected to the primary auxiliary winding. The third diode D3, the twelfth resistor R12, and the first electrolytic capacitor E4 constitute the power input of the PWM control IC U1.

6. The switching power supply circuit according to claim 5, characterized in that, The control and protection circuit includes a first capacitor C1, a second capacitor C2, a sixth capacitor C6, a first diode D1, a second diode D2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fifteenth resistor R15, a first driving transistor M1, a second driving transistor M2, a first Zener diode ZD1, a second Zener diode ZD2, a third Zener diode ZD3, a fourth Zener diode ZD4, a first driving transistor Q1, a second driving transistor Q2, and a driving transformer T2. The sixth resistor R6, the seventh resistor R7, the ninth resistor R9, the tenth resistor R10, the first capacitor C1, the second capacitor C2, the first diode D1, and the second diode D2 are connected in series and parallel to form an RCD absorption circuit. The first Zener diode ZD1, the second Zener diode... Diode ZD2, third Zener diode ZD3, and fourth Zener diode ZD4 are connected in series to form a gate protection circuit. The first driving transistor M1 and the second driving transistor M2 are respectively connected to the primary power winding of the high-frequency transformer T1. The first driving transistor Q1 and the second driving transistor Q2 form a complementary push-pull circuit. The bases of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fourteenth resistor R14, and the emitters of the first driving transistor Q1 and the second driving transistor Q2 are connected to the fifteenth resistor R15. The fifteenth resistor R15 and the sixth capacitor C6 are connected in series to the driving transformer T2. The driving transformer T2 converts one PWM signal into two signals to control the first driving transistor M1 and the second driving transistor M2 respectively. The fourth NTC resistor RT4 detects the circuit temperature. When an abnormality occurs, the feedback causes the PWM control IC U1 to start the low-power protection mode.

7. The switching power supply circuit according to claim 6, characterized in that, The output rectification and filtering feedback loop circuit includes a seventh capacitor C7, an eighth capacitor C8, a fourth diode D4, a differential-mode inductor L1, a second electrolytic capacitor E5, a third electrolytic capacitor E6, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, an isolation optocoupler OP1, and a voltage regulator U2. The fourth diode D4 and the second electrolytic capacitor E5 form a half-wave rectification and filtering circuit. The sixteenth resistor R16 and the seventh capacitor C7 form an RC absorption circuit. One end of the seventeenth resistor R17 is connected to the anode of the isolation optocoupler OP1. The cathode is connected in sequence to the eighth capacitor C8 and the voltage regulator U2. One end of the eighteenth resistor R18 is connected between the seventeenth resistor R17 and the isolation optocoupler OP1. One end of the twenty-first resistor R21 is connected between the eighth capacitor C8 and the voltage regulator U2. The cathode of the voltage regulator U2 is connected to the cathode of the isolation optocoupler OP1. The twentieth resistor R20 is connected to the voltage regulator U2. The differential mode inductor L1 is connected in sequence to the seventeenth resistor R17, the nineteenth resistor R19 and the third electrolytic capacitor E6. The other end of the nineteenth resistor R19 is connected to the twenty-first resistor R21 and the twentieth resistor R20. The collector output of the isolation optocoupler OP1 is connected to the feedback pin of the PWM control IC U1 to form an output feedback system.

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