Switching power supply capable of adjusting high voltage and outputting low ripples

Abstract

The invention discloses an adjustable high-voltage output low-ripple switching power supply which comprises an input filter circuit, a VCC power supply circuit, a PWM controller, a main power circuit, a high-frequency transformer, a linear voltage regulation circuit, an output rectification filter, an output voltage regulation circuit and an output auxiliary source reference circuit. The method for realizing low-ripple high-voltage adjustable output and controlling the voltage and current slew rate of an external N-channel MOSFET switch comprises the steps of independently setting the voltage slew rate and the current slew rate, setting the voltage slew rate through an external capacitor and setting the current slew rate through an external resistor. The high-voltage adjustable output is realized, the output ripple is reduced, the voltage regulation rate is improved, the EMI (Electro-Magnetic Interference) performance is optimized, the high-frequency harmonic power is reduced, the efficiency loss is reduced, and the problem that the traditional switching power supply cannot realize high-voltage, adjustable and low-ripple output at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of electronic technology, and in particular to an adjustable high-voltage output low-ripple switching power supply. Background Technology

[0002] Most switching power supplies on the market are buck switching power supplies, which cannot achieve voltage boost and high voltage adjustable low ripple output. Simple boost power supplies cannot achieve adjustable output voltage, and have poor voltage regulation, large ripple, and basically no electromagnetic compatibility (EMI) design, thus generating waveforms full of high-frequency harmonics, which then propagate through the rest of the system. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies, such as the inability to achieve high-voltage adjustable low-ripple output, the inability of simple boost power supplies to achieve adjustable output voltage, poor voltage regulation, large ripple, and the lack of electromagnetic compatibility (EMI) design, resulting in waveforms full of high-frequency harmonics that then propagate through the rest of the system. Therefore, this invention proposes an adjustable high-voltage output low-ripple switching power supply.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An adjustable high-voltage output low-ripple switching power supply includes: an input filter circuit, a VCC power supply circuit, a PWM controller, a main power circuit, a high-frequency transformer, a linear voltage regulation circuit, an output rectification and filtering circuit, an output voltage regulation circuit, and an output auxiliary power source reference circuit. By controlling the voltage slew rate and current slew rate of an external N-channel MOSFET, low-ripple high-voltage adjustable output is achieved.

[0006] The control of the voltage and current slew rates of the external N-channel MOSFET switch includes independently setting the voltage slew rate and current slew rate, setting the voltage slew rate through an external capacitor, and setting the current slew rate through an external resistor.

[0007] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the PWM controller is composed of a PWM chip U2, resistors R21, R22, R23, R24, capacitors C9, C19, C20, and C21.

[0008] The resistor R21 is connected to pin 4 of the PWM chip U2 at one end and grounded at the other end; the resistor R22 is connected to pin 8 of the PWM chip U2 at one end and grounded at the other end; the resistor R23 is connected to pin 16 of the PWM chip U2 at one end and grounded at the other end; the resistor R24 ​​is connected to pin 15 of the PWM chip U2 at one end and grounded at the other end; the capacitor C9 is connected to pins 3, 14, and 17 of the PWM chip U2 at one end and grounded at the other end; the capacitor C19 is connected to pin 7 of the PWM chip U2 at one end and grounded at the other end; the capacitor C20 is connected to pin 10 of the PWM chip U2 at one end and grounded at the other end; and the capacitor C21 is connected to pin 13 of the PWM chip U2 at one end and grounded at the other end.

[0009] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the main power circuit includes an integrated MOSFET U1, resistors R9, R10, R11, and R12, and capacitors C10, C11, C12, and C13.

[0010] One end of resistor R9 is connected to pin 4 of MOSFET U1 and resistor R11. The other end of resistor R11 is connected to pin 3 of U1. One end of resistor R10 is connected to pin 2 of MOSFET U1 and one end of resistor R12. The other end of resistor R12 is connected to pin 1 of MOSFET U1. Pins 5 and 6 of MOSFET U1 are connected to capacitor C11. The other end of capacitor C11 is connected to capacitor C10. The other end of capacitor C10 is connected to GND. Pins 7 and 8 of MOSFET U1 are connected to capacitor C13. The other end of capacitor C13 is connected to capacitor C12. The other end of capacitor C12 is connected to GND.

[0011] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the input filter circuit includes capacitor C7 and capacitor C14, wherein capacitor C7 and capacitor C14 are connected in parallel and their two ends are respectively connected to +VIN and -VIN.

[0012] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, wherein: the VCC power supply circuit includes a Zener diode D3, a transistor Q1, a capacitor C5, a resistor R7, and a resistor R8, wherein;

[0013] One end of resistors R7 and R8 is connected to the input +VIN, and the other end of resistor R8 is connected to the cathode of Zener diode D3, capacitor C5 and the base of Q1. Capacitor C5 is connected in parallel with Zener diode D3.

[0014] The other end of the resistor R7 is connected to the collector of the transistor Q1, and the emitter of the transistor Q1 is connected to pin 17 of the PWM chip U2 to supply power to the PWM controller.

[0015] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the high-frequency transformer has a total of 10 pins, of which 7 pins are used, wherein 1, 2, and 3 are primary side pins, 6 and 8 are secondary output main circuit pins, and 9 and 10 are secondary auxiliary reference pins.

[0016] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the output rectification and filtering is composed of diode D1, diode D2, resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, capacitor C1, capacitor C2, capacitor C3, and capacitor C4.

[0017] The output terminal of resistor R1 is connected to VO, and the other end of resistor R1 is connected to the anode of diode D1 and capacitor C3. The cathode of diode D1 is connected to the anode of diode D2.

[0018] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the linear voltage regulation circuit is composed of transistor Q2, transistor Q3, resistor R16, resistor R17, capacitor C6, and capacitor C16.

[0019] The emitter of transistor Q3 is connected to +VIN and one end of capacitor C6, while the other end of capacitor C6 is grounded.

[0020] The emitter of the transistor Q2 is connected to the resistor R17, and the other end of the resistor R17 is grounded.

[0021] The base of transistor Q3 is connected to the collector of transistor Q2, the base of transistor Q2 is connected to resistor R16, and the other end of resistor R16 is connected to capacitor C16.

[0022] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the output voltage regulation circuit is composed of operational amplifier U3, resistor R18, resistor R19, resistor R20, capacitor C15, capacitor C17, and capacitor C18.

[0023] One end of resistor R18 is connected to capacitor C15 and the other end is connected to pin 4 of operational amplifier U3. One end of capacitor C17 is connected to pin 5 of operational amplifier U3 and the other end is grounded. Resistor R19 is connected in parallel with capacitor C18. One end of resistor R19 is connected to pin 3 of operational amplifier U3 and the other end is connected to pin 2 of operational amplifier U3. Pin 2 of operational amplifier U3 is grounded.

[0024] As a preferred embodiment of the adjustable high-voltage output low-ripple switching power supply of the present invention, the output auxiliary source reference circuit is composed of diode D4, diode D5, diode D6, diode D7, capacitor C8, capacitor C30, resistor R13, resistor R14, resistor R15, and resistor R30.

[0025] The cathodes of diodes D4 and D6, capacitor C8, and resistor R13 are connected. The other end of capacitor C8 is grounded. The anode of diode D4 is connected to the cathode of diode D5. The anode of diode D5 is connected to the anode of diode D7. The anode of diode D6 is connected to the cathode of diode D7. The other end of resistor R13 is connected to resistor R14. Resistors R15, R30, and capacitor C30 are connected in parallel, with one end connected to resistor R14 and the other end grounded.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] By independently controlling the voltage and current slew rate of the external N-channel MOSFET, high-voltage adjustable output is achieved, significantly reducing output ripple and improving voltage regulation. At the same time, EMI performance is optimized, high-frequency harmonic power is reduced, and efficiency loss is minimized, solving the problem that traditional switching power supplies cannot simultaneously achieve high voltage, adjustable, and low ripple output. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an adjustable high-voltage output low-ripple switching power supply proposed in this invention.

[0029] Figure 2 This is a block diagram illustrating the principle of an adjustable high-voltage output low-ripple switching power supply proposed in this invention.

[0030] Figure 3 This is a schematic diagram of the internal chip of an adjustable high-voltage output low-ripple switching power supply proposed in this invention.

[0031] Figure 4 This is the input filter circuit diagram;

[0032] Figure 5 Circuit diagram for supplying power to VCC;

[0033] Figure 6 This is a circuit diagram of a PWM controller.

[0034] Figure 7 Main power circuit diagram;

[0035] Figure 8 This is a circuit diagram of a high-frequency transformer.

[0036] Figure 9 This is the output rectifier and filter circuit diagram;

[0037] Figure 10 The circuit diagram for the auxiliary power source is shown below.

[0038] Figure 11 This is a diagram of a linear voltage regulator circuit.

[0039] Figure 12 This is a circuit diagram for output voltage regulation. Detailed Implementation

[0040] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] Please see Figures 1-2 As shown, the purpose of this embodiment is to provide an adjustable high-voltage output low-ripple switching power supply, including an input filter circuit, a VCC power supply circuit, a PWM controller, a main power circuit, a high-frequency transformer, a linear voltage regulation circuit, an output rectification and filtering circuit, an output voltage regulation circuit, and an output auxiliary power source reference circuit. By controlling the voltage slew rate and current slew rate of an external N-channel MOSFET, low-ripple high-voltage adjustable output is achieved.

[0043] Controlling the voltage and current slew rates of an external N-channel MOSFET switch includes independently setting the voltage and current slew rates, setting the voltage slew rate through an external capacitor, setting the current slew rate through an external resistor, adjusting the voltage across the transformer by using an input linear regulator, and optimizing the harmonic content and efficiency of the switching waveform by setting the current and voltage slew rates.

[0044] The specific circuit structure is as follows:

[0045] like Figure 4 As shown, the input filter circuit includes capacitor C7 and capacitor C14, which are connected in parallel and their two ends are connected to +VIN and -VIN respectively.

[0046] like Figure 5 As shown, the VCC power supply circuit includes a Zener diode D3, a transistor Q1, a capacitor C5, resistors R7 and R8, wherein;

[0047] One end of resistors R7 and R8 is connected to the input +VIN, and the other end of resistor R8 is connected to the cathode of Zener diode D3, capacitor C5 and the base of Q1. Capacitor C5 is connected in parallel with Zener diode D3.

[0048] The other end of resistor R7 is connected to the collector of transistor Q1, and the emitter of transistor Q1 is connected to pin 17 of PWM chip U2 to power the PWM controller.

[0049] like Figure 6 As shown, the PWM controller consists of PWM chip U2, resistors R21, R22, R23, R24, capacitors C9, C19, C20, and C21.

[0050] One end of resistor R21 is connected to pin 4 of PWM chip U2, and the other end is grounded. One end of resistor R22 is connected to pin 8 of PWM chip U2, and the other end is grounded. One end of resistor R23 is connected to pin 16 of PWM chip U2, and the other end is grounded. One end of resistor R24 ​​is connected to pin 15 of PWM chip U2, and the other end is grounded. One end of capacitor C9 is connected to pins 3, 14, and 17 of PWM chip U2, and the other end is grounded. One end of capacitor C19 is connected to pin 7 of PWM chip U2, and the other end is grounded. One end of capacitor C20 is connected to pin 10 of PWM chip U2, and the other end is grounded. One end of capacitor C21 is connected to pin 13 of PWM chip U2, and the other end is grounded.

[0051] like Figure 7 As shown, the main power circuit includes an integrated MOSFET U1, resistors R9, R10, R11, and R12, and capacitors C10, C11, C12, and C13, wherein;

[0052] One end of resistor R9 is connected to pin 4 of MOSFET U1 and resistor R11. The other end of resistor R11 is connected to pin 3 of U1. One end of R10 is connected to pin 2 of MOSFET U1 and one end of resistor R12. The other end of resistor R12 is connected to pin 1 of MOSFET U1. Pins 5 and 6 of MOSFET U1 are connected to capacitor C11. The other end of capacitor C11 is connected to capacitor C10. The other end of capacitor C10 is connected to GND. Pins 7 and 8 of MOSFET U1 are connected to capacitor C13. The other end of capacitor C13 is connected to capacitor C12. The other end of capacitor C12 is connected to GND.

[0053] like Figure 8 As shown, the high-frequency transformer has a total of 10 pins, of which 7 are used. Pins 1, 2, and 3 are primary side pins, pins 6 and 8 are secondary output main circuit pins, and pins 9 and 10 are secondary auxiliary reference pins.

[0054] like Figure 9As shown, the output rectifier filter consists of diode D1, diode D2, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, C3, and C4, where;

[0055] The output terminal of resistor R1 is connected to VO, and the other end of resistor R1 is connected to the anode of diode D1 and capacitor C3. The cathode of diode D1 is connected to the anode of diode D2.

[0056] like Figure 10 As shown, the output auxiliary source reference circuit consists of diodes D4, D5, D6, and D7, capacitors C8 and C30, and resistors R13, R14, R15, and R30.

[0057] The cathodes of diode D4 and D6, capacitor C8, and resistor R13 are connected together. The other end of capacitor C8 is grounded. The anode of diode D4 is connected to the cathode of diode D5. The anode of diode D5 is connected to the anode of diode D7. The anode of diode D6 is connected to the cathode of diode D7. The other end of resistor R13 is connected to resistor R14. Resistors R15, R30, and capacitor C30 are connected in parallel, with one end connected to resistor R14 and the other end grounded.

[0058] like Figure 11 As shown, the linear voltage regulation circuit consists of transistor Q2, transistor Q3, resistor R16, resistor R17, capacitor C6, and capacitor C16.

[0059] The emitter of transistor Q3 is connected to +VIN and one end of capacitor C6, while the other end of capacitor C6 is grounded.

[0060] The emitter of transistor Q2 is connected to resistor R17, and the other end of resistor R17 is grounded.

[0061] The base of transistor Q3 is connected to the collector of transistor Q2. The base of transistor Q2 is connected to resistor R16. The other end of resistor R16 is connected to capacitor C16.

[0062] like Figure 12 As shown, the output voltage regulation circuit consists of operational amplifier U3, resistors R18, R19, and R20, and capacitors C15, C17, and C18.

[0063] One end of resistor R18 is connected to capacitor C15, and the other end is connected to pin 4 of op-amp U3. One end of capacitor C17 is connected to pin 5 of op-amp U3, and the other end is grounded. Resistor R19 is connected in parallel with capacitor C18. One end of resistor R19 is connected to pin 3 of op-amp U3, and the other end is connected to pin 2 of op-amp U3. Pin 2 of op-amp U3 is grounded.

[0064] Additionally, the U2 (LT1683IG) chip reduces conducted and radiated electromagnetic interference (EMI). By controlling the voltage and current slew rate of an external N-channel MOSFET switch, the LT1683IG can reduce high-frequency harmonic power by up to 40 dB with minimal efficiency loss. This chip includes a gate driver and all necessary oscillator, control, and protection circuitry. An independent error amplifier circuit allows for adjustment of both positive and negative voltages. The oscillator can be synchronized with an external clock for more accurate placement of switching harmonics. The internal schematic is shown below. Figure 3 As shown.

[0065] In summary, the working process of this solution is as follows:

[0066] When the +VIN voltage is greater than 3.7V, U2 starts working. GATE A and GATE B are turned on alternately in clock cycles. GCL sets the upper limit voltage of the gate driver. The charging current of the gate driver can generate a current pulse of hundreds of milliamps, enhancing the driver's driving capability. CAP A and CAP B are feedback nodes for external voltage conversion capacitors. A small capacitor is connected from this pin to the drain of the respective MOSFET. The voltage slew rate is inversely proportional to this capacitor. The Rcsl resistor sets the current slew rate of the externally driven MOSFET. The transition time of the MOSFET current between the on and off states determines how to reduce harmonics related to di / dt. The Rvsl resistor sets the voltage slew rate of the externally driven MOSFET. The transition time of the MOSFET drain voltage between the on and off states determines how to reduce harmonics from this power supply. The output voltage and current slew rate are controlled through two feedback loops: one loop controls the MOSFET drain dv / dt, and the other loop controls di / dt. The voltage slew rate uses an external capacitor between CAP A or CAP B and the corresponding MOSFET drain. These integrating capacitors close the voltage feedback loop. The external resistor Rvsl sets the current for the integrator.

[0067] Cycle-by-cycle current protection: The switching cycle begins with an oscillator discharge pulse that resets the RS flip-flop and turns on one of the external MOSFET drivers. The switching current is monitored across an external sense resistor, and the resulting voltage is amplified and compared with the output of an error amplifier. Once the output of the current sense amplifier exceeds the voltage on the VC pin, the driver shuts down. This pulse-by-pulse current limiting is achieved.

[0068] After power-on, U2 is powered by a voltage regulator. U2 gradually emits two alternating pulses. At this time, there is no power output and the output reference is zero volts. After the external control voltage is high, the operational amplifier outputs a high level to control the output of the power linear regulator at +VIN. At this time, the primary side of the high-frequency transformer generates voltage. After the output voltage stabilizes through the initial turns ratio set by the high-frequency transformer, the external control voltage becomes the non-inverting input of the operational amplifier. The feedback winding output of the secondary side of the high-frequency transformer becomes the inverting input of the operational amplifier to form feedback. The operational amplifier compares and adjusts the output of the linear regulator to adjust the voltage on the primary side of the high-frequency transformer. The primary voltage controls the output voltage through the high-frequency transformer.

[0069] The input DC voltage (+VIN and -VIN) is filtered by parallel capacitors C7 and C14 to suppress high-frequency noise and ripple on the input side, providing a clean DC power supply for subsequent circuits. The input voltage is divided by resistors R7 and R8, and after being regulated by Zener diode D3, it provides the base voltage for transistor Q1. The emitter of Q1 outputs a stable VCC voltage, which powers the PWM controller (U2). The PWM chip U2 uses external resistors (R21–R24) and capacitors (C9, C19–C21) to set parameters such as operating frequency, soft-start, and time, generating a PWM signal to drive the main power MOSFET. The integrated MOSFET U1 switches under the control of the PWM signal, converting the DC input into a high-frequency AC signal. Resistors (R9–R12) and capacitors (C10–C13) are used to adjust switching characteristics, suppress ringing, and absorb voltage spikes. The primary side (pins 1–3) receives high-frequency signals. The AC signal is magnetically coupled to generate a high-voltage AC output on the secondary side (pins 6 and 8). The auxiliary winding (pins 9 and 10) provides feedback and reference voltage. The high-voltage AC voltage on the secondary side is rectified by diodes D1 and D2, and then filtered by a filter network composed of resistors R1–R6 and capacitors C1–C4 to smooth the output voltage and reduce ripple. A stable auxiliary reference voltage is generated by diodes D4–D7, capacitors C8 and C30, and resistors R13–R15 and R30 to provide a reference for the feedback and regulation circuit. Transistors Q2 and Q3 form a linear voltage regulator structure. The static operating point of the output voltage is adjusted by resistors R16 and R17 and capacitors C6 and C16 to further suppress ripple. Operational amplifier U3, together with external resistors (R18–R20) and capacitors (C15, C17, C18), receives the feedback signal and compares it with the reference voltage to adjust the output duty cycle of the PWM controller, thereby achieving precise adjustment of the output voltage.

[0070] It is worth noting that the entire device is controlled by a controller. Since the controller is a common device and belongs to the mature technology, its electrical connection relationship and specific circuit structure will not be described in detail here.

[0071] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A switching power supply with adjustable high-voltage output and low ripple, comprising: The circuit comprises an input filter circuit, a VCC power supply circuit, a PWM controller, a main power circuit, a high-frequency transformer, a linear voltage regulation circuit, an output rectification and filtering circuit, an output voltage regulation circuit, and an output auxiliary power reference circuit. By controlling the voltage slew rate and current slew rate of an external N-channel MOSFET, it achieves low-ripple, high-voltage adjustable output. Its key feature is: The control of the voltage and current slew rates of the external N-channel MOSFET switch includes independently setting the voltage slew rate and current slew rate, setting the voltage slew rate through an external capacitor, and setting the current slew rate through an external resistor.

2. The adjustable high-voltage output low-ripple switching power supply according to claim 1, characterized in that: The PWM controller consists of a PWM chip U2, resistors R21, R22, R23, and R24, and capacitors C9, C19, C20, and C21. The resistor R21 is connected to pin 4 of the PWM chip U2 at one end and grounded at the other end; the resistor R22 is connected to pin 8 of the PWM chip U2 at one end and grounded at the other end; the resistor R23 is connected to pin 16 of the PWM chip U2 at one end and grounded at the other end; the resistor R24 ​​is connected to pin 15 of the PWM chip U2 at one end and grounded at the other end; the capacitor C9 is connected to pins 3, 14, and 17 of the PWM chip U2 at one end and grounded at the other end; the capacitor C19 is connected to pin 7 of the PWM chip U2 at one end and grounded at the other end; the capacitor C20 is connected to pin 10 of the PWM chip U2 at one end and grounded at the other end; and the capacitor C21 is connected to pin 13 of the PWM chip U2 at one end and grounded at the other end.

3. The adjustable high-voltage output low-ripple switching power supply according to claim 2, characterized in that: The main power circuit includes an integrated MOSFET U1, resistors R9, R10, R11, and R12, and capacitors C10, C11, C12, and C13, wherein; One end of resistor R9 is connected to pin 4 of MOSFET U1 and resistor R11. The other end of resistor R11 is connected to pin 3 of U1. One end of resistor R10 is connected to pin 2 of MOSFET U1 and one end of resistor R12. The other end of resistor R12 is connected to pin 1 of MOSFET U1. Pins 5 and 6 of MOSFET U1 are connected to capacitor C11. The other end of capacitor C11 is connected to capacitor C10. The other end of capacitor C10 is connected to GND. Pins 7 and 8 of MOSFET U1 are connected to capacitor C13. The other end of capacitor C13 is connected to capacitor C12. The other end of capacitor C12 is connected to GND.

4. The adjustable high-voltage output low-ripple switching power supply according to claim 3, characterized in that: The input filter circuit includes capacitor C7 and capacitor C14, which are connected in parallel and their two ends are connected to +VIN and -VIN respectively.

5. The adjustable high-voltage output low-ripple switching power supply according to claim 4, characterized in that: The VCC power supply circuit includes a Zener diode D3, a transistor Q1, a capacitor C5, resistors R7 and R8, wherein; One end of resistors R7 and R8 is connected to the input +VIN, and the other end of resistor R8 is connected to the cathode of Zener diode D3, capacitor C5 and the base of Q1. Capacitor C5 is connected in parallel with Zener diode D3. The other end of the resistor R7 is connected to the collector of the transistor Q1, and the emitter of the transistor Q1 is connected to pin 17 of the PWM chip U2 to supply power to the PWM controller.

6. The adjustable high-voltage output low-ripple switching power supply according to claim 5, characterized in that: The high-frequency transformer has a total of 10 pins, of which 7 are used. Pins 1, 2, and 3 are primary side pins, pins 6 and 8 are secondary output main circuit pins, and pins 9 and 10 are secondary auxiliary reference pins.

7. The adjustable high-voltage output low-ripple switching power supply according to claim 6, characterized in that: The output rectifier filter consists of diode D1, diode D2, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, C3, and C4, wherein; The output terminal of resistor R1 is connected to VO, and the other end of resistor R1 is connected to the anode of diode D1 and capacitor C3. The cathode of diode D1 is connected to the anode of diode D2.

8. The adjustable high-voltage output low-ripple switching power supply according to claim 7, characterized in that: The linear voltage regulation circuit consists of transistor Q2, transistor Q3, resistor R16, resistor R17, capacitor C6, and capacitor C16. The emitter of transistor Q3 is connected to +VIN and one end of capacitor C6, while the other end of capacitor C6 is grounded. The emitter of the transistor Q2 is connected to the resistor R17, and the other end of the resistor R17 is grounded. The base of transistor Q3 is connected to the collector of transistor Q2, the base of transistor Q2 is connected to resistor R16, and the other end of resistor R16 is connected to capacitor C16.

9. The adjustable high-voltage output low-ripple switching power supply according to claim 8, characterized in that: The output voltage regulation circuit consists of operational amplifier U3, resistors R18, R19, and R20, and capacitors C15, C17, and C18. One end of resistor R18 is connected to capacitor C15 and the other end is connected to pin 4 of operational amplifier U3. One end of capacitor C17 is connected to pin 5 of operational amplifier U3 and the other end is grounded. Resistor R19 is connected in parallel with capacitor C18. One end of resistor R19 is connected to pin 3 of operational amplifier U3 and the other end is connected to pin 2 of operational amplifier U3. Pin 2 of operational amplifier U3 is grounded.

10. The adjustable high-voltage output low-ripple switching power supply according to claim 9, characterized in that: The output auxiliary source reference circuit consists of diodes D4, D5, D6, and D7, capacitors C8 and C30, and resistors R13, R14, R15, and R30. The cathodes of diodes D4 and D6, capacitor C8, and resistor R13 are connected. The other end of capacitor C8 is grounded. The anode of diode D4 is connected to the cathode of diode D5. The anode of diode D5 is connected to the anode of diode D7. The anode of diode D6 is connected to the cathode of diode D7. The other end of resistor R13 is connected to resistor R14. Resistors R15, R30, and capacitor C30 are connected in parallel, with one end connected to resistor R14 and the other end grounded.

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