Flyback converter for high-voltage direct current input and control method thereof

Abstract

The invention belongs to a flyback converter circuit structure, and provides a flyback converter for high-voltage direct current input and a control method thereof in order to solve the technical problems that under the condition of high-voltage direct current input at present, system reliability and efficiency are easily reduced, and switching element selection is affected. Comprising a primary high-voltage direct-current input power loop, a secondary power supply output loop and an auxiliary winding power supply loop, the auxiliary winding power supply loop comprises a primary winding and a secondary winding which form a transformer, and the primary high-voltage direct-current input power loop comprises a plurality of input sub-loops. Each input sub-loop comprises a voltage-sharing loop, an N-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), an RC (Resistance-Capacitance) cascade loop and a Schottky diode; and the secondary power output loop comprises an output diode. The primary high-voltage direct-current input power loop adopts a multi-N-channel MOSFET cascading mode, the voltage stress of the system can be effectively shared, system faults are reduced, and therefore reliable operation of the flyback converter under high-voltage direct-current input is ensured.

Description

Technical Field

[0001] The present application relates to a flyback converter circuit structure, and more particularly to a flyback converter for high voltage DC input and a control method thereof. Background Art

[0002] With the continuous advancement of power electronics technology, the stability and efficiency of auxiliary power supplies have become crucial. This is especially true in large-scale energy storage devices and medium-, high-, and high-capacity power electronic converter systems, where high-voltage DC power is often converted to low-voltage DC power for use by various system modules. In most cases, to meet this low-voltage DC requirement, an external switching power supply is typically used to convert the input AC power to low-voltage DC.

[0003] In auxiliary power supply designs, flyback converters are often used to provide stable power to the secondary circuits of converter modules, particularly in medium- to high-voltage, large-capacity power electronic converter systems. Typically, the flyback converter uses the DC bus voltage within the cabinet to provide input to the auxiliary power supply, which in turn provides stable power output to the secondary circuits of each converter module. However, in the case of high-voltage DC input, the main switch of a single-switch flyback converter must withstand voltage stress close to twice the input voltage, which can easily lead to reduced system reliability and efficiency, and can also affect the selection of switching components. Summary of the Invention

[0004] The present application addresses the current technical issues that high voltage DC input easily leads to reduced system reliability and efficiency and affects the selection of switching elements. It provides a flyback converter for high voltage DC input and a control method thereof.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions: In a first aspect, the present application proposes a flyback converter for high voltage DC input, comprising: a primary high voltage DC input power circuit, a secondary power output circuit, and an auxiliary winding power supply circuit; The auxiliary winding power supply circuit includes multiple coil windings on the primary side and at least one coil winding on the secondary side, which respectively constitute the primary winding and secondary winding of the transformer; The primary high-voltage DC input power loop includes multiple input sub-loops, each input sub-loop includes a voltage equalizing loop, an N-channel MOSFET, an RC cascade loop and a Schottky diode; the drain of the N-channel MOSFET is connected to the anode of the Schottky diode, the RC cascade loop, and one end of the voltage equalizing loop in sequence, the source of the N-channel MOSFET is connected to the other end of the voltage equalizing loop, and the gate of the N-channel MOSFET is used to receive a control signal for controlling the N-channel MOSFET to be turned on or off; the two ends of the first primary winding are respectively connected to the drain of the first N-channel MOSFET and one end of the voltage equalizing circuit, the two ends of the other primary windings are respectively connected to the source of the previous N-channel MOSFET and the drain of the next N-channel MOSFET, and the source of the last N-channel MOSFET is grounded; one end of the first voltage equalizing circuit is connected to the positive electrode of the high-voltage DC input, and the other end of the last voltage equalizing circuit is connected to the negative electrode of the high-voltage DC input; The secondary power output loop includes an output diode, the anode of the output diode is connected to one end of the secondary winding, and the cathode of the output diode and the other end of the secondary winding are connected to two ends of the load respectively.

[0006] Furthermore, it also includes a control loop; the primary winding of the transformer also includes a first auxiliary winding; The control loop includes a control resistor R 10. Resistors R 4. Resistors R 5. Diode D 6. Power control chip, resistor R 8. Capacitor C 4. Resistors R 7. Resistors R 9. Capacitor C 5. Capacitor C 6. Capacitor C 7 and resistor R 6; One end of the first auxiliary winding is grounded, and the other end is connected to a resistor R One end of 10, diode D 6 and resistor R 4 parallel resistors R The other end of 10 is connected to the diode D 6 anode; The ZCD pin of the power control chip is connected to a resistor R One end of 5 and the diode D 6 cathode, resistor R The other end of 5 is grounded; the FB pin of the power control chip is connected to the voltage feedback circuit; the CS pin of the power control chip is used to monitor the current peak of the primary high-voltage DC input power loop for overcurrent protection; the GND pin of the power control chip is grounded; the CT pin of the power control chip is connected to the capacitorC One end of 4, capacitor C The other end of 4 is grounded; the FAULT pin of the power control chip is connected to a resistor R One end of 9, resistor R The other end of 9 is connected to the resistor R 7. The cathode of diode D10 and the VCC pin of the power control chip; resistor R One end of 8 is connected to the capacitor C 4, and the other end is connected to the high voltage DC input; the VCC pin of the power control chip is connected to the capacitor in turn C 5 and ground; the DRV pin of the power control chip serves as the MOS drive output pin of the power control chip, connected to the gate of the N-channel MOSFET, and is used to receive the control signal that controls the N-channel MOSFET to turn on or off; the capacitor C 6. One end of the resistor is connected to the VCC pin of the power control chip and the other end is grounded. R 6 and capacitor C 7 After parallel connection, one end is connected to the resistor R 9 and resistor R 7, and the other end is grounded.

[0007] Furthermore, it also includes a voltage stabilizing circuit; One end of the voltage stabilizing circuit is connected to one end of the first auxiliary winding, and the other end is connected to the VCC pin of the power control chip and the capacitor C Between 6.

[0008] Furthermore, the voltage stabilizing circuit includes an electrolytic capacitor C 10. Diode D 9. Diode D 7. Transistor Q 4. Schottky diode D 8. Resistors R 16. Resistors R 17. Diode D 7 and capacitor C 9; The electrolytic capacitor C 10's positive terminal and diode D The cathode of 9 is connected to the VCC pin of the power control chip; the diode D 9's anode is connected to the transistor Q 4 emitter, Schottky diode D 8 anode and electrolytic capacitor C The negative poles of 10 are grounded; Schottky diodes D 8 cathode, triode Q 4 base and resistor R One end of 16 is connected to the resistor R The other end of 16, transistorQ 4 collector, resistor R One end of 17 and the diode D 7's cathode is connected; resistor R The other end of 17 and the capacitor C One end of 9 is connected to the diode D 7 anode, capacitor C The other end of 9 is connected to the other end of the first auxiliary winding.

[0009] Furthermore, the voltage feedback circuit includes an isolation optocoupler U1, a resistor R 13. Resistors R 14. Resistors R 15. Capacitor C 8. TL431 voltage regulator, resistor R 11 and resistor R 12; The collector of the isolation optocoupler U1 is connected to the FB pin of the power control chip, the emitter is grounded, and the anode is connected to the resistor R One end of 13; the cathode of the isolation optocoupler U1, the cathode of the voltage regulator TL431, and the resistor R One end of 14 and the resistor R One end of 15 is connected to the resistor R The other end of 15 and the capacitor C One end of 8 is connected to the capacitor C The other end of 8, the reference electrode of the voltage regulator TL431, the resistor R One end of 11 and the resistor R One end of 12 is connected to the resistor R The other end of 13, the resistor R The other end of 14 and the resistor R The other end of 11 is connected to one end of the load; the anode of the voltage regulator TL431 and the resistor R The other end of 12 is connected to the other end of the load.

[0010] Furthermore, the voltage balancing circuit includes a resistor and an electrolytic capacitor connected in parallel.

[0011] Furthermore, the secondary power output circuit also includes an electrolytic capacitor; The electrolytic capacitor is connected in parallel with the load.

[0012] Furthermore, the withstand voltage of the N-channel MOSFET The calculation method includes:

[0013] in, is the maximum DC input voltage of the primary high-voltage DC input power circuit, is the reflected voltage of the secondary power supply output loop, is the voltage margin set.

[0014] Furthermore, the reflected voltage of the secondary power supply output circuit The calculation method includes:

[0015] in, is the transformer turns ratio, is the output voltage of the secondary power output circuit, It is the conduction voltage of the output diode of the secondary power supply output circuit.

[0016] In a second aspect, the present application proposes a control method for the flyback converter for high voltage DC input, comprising: By controlling the on-time of the N-channel MOSFETs in multiple input sub-loops, the output voltage stability of the secondary power supply output loop can meet the preset requirements.

[0017] Compared with the prior art, this application has the following beneficial effects: The present application proposes a flyback converter for high-voltage DC input, comprising a primary high-voltage DC input power circuit, a secondary power output circuit, and an auxiliary winding power supply circuit. The auxiliary winding power supply circuit comprises a primary winding and a secondary winding of a transformer. The primary high-voltage DC input power circuit comprises multiple input sub-circuits, each of which comprises a voltage-equalizing circuit, an N-channel MOSFET, an RC cascade circuit, and a Schottky diode. The secondary power output circuit comprises an output diode. The primary high-voltage DC input power circuit of the present application employs a cascade of multiple N-channel MOSFETs, which can effectively distribute the voltage stress of the system and reduce the occurrence of system failures, thereby ensuring the reliable operation of the flyback converter under high-voltage DC input. The present application exhibits particularly outstanding unique advantages in the design of auxiliary power supplies for large-scale energy storage equipment and medium-voltage, high-capacity power electronic converter systems. Combined with distributed power supply technology, the present application can effectively improve the voltage stress problem of the switch tube under high-voltage DC input conditions while improving system efficiency, further improving the reliability and stability of the system.

[0018] This application also proposes a control method for a flyback converter for high-voltage DC input. By controlling the conduction time of N-channel MOSFETs in multiple input sub-circuits, the output voltage stability of the secondary power supply output circuit meets the preset requirements. The time for system energy storage and release can be adjusted to ultimately achieve a stable output voltage. It also has all the advantages of the above-mentioned flyback converter for high-voltage DC input. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A circuit diagram of an embodiment of a flyback converter for high voltage DC input according to the present application; Figure 2 Schematic diagram of the waveforms of the drain-source voltage Vds and the drain current Id of the N-channel MOSFET during the operation of the flyback converter in an embodiment of the present application; Figure 3 Schematic diagram of a control circuit in an embodiment of the present application; Figure 4 is a circuit diagram of a voltage feedback circuit in an embodiment of the present application; Figure 5 for Figure 3 Circuit diagram of the medium voltage regulator circuit. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0024] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the product of the invention is usually placed when in use. This is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0025] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0026] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in this application based on specific circumstances.

[0027] With the rapid development of power electronics technology, the stability and efficiency of auxiliary power supplies have become key factors affecting system performance. This is particularly true for large-scale energy storage devices and medium-, high-voltage, and large-capacity power electronics converter systems. Converting high-voltage DC power to low-voltage DC power to meet the power needs of various system modules is a critical technical task. Traditionally, obtaining low-voltage DC power has often involved converting AC power to the required low-voltage DC form using an external switching power supply.

[0028] Flyback converters play a crucial role in auxiliary power supply design, particularly for supplying stable power to the secondary circuits of converter modules in medium- to high-voltage, large-capacity power electronic converter systems. Typically, the DC bus voltage within the cabinet serves as the auxiliary power input, outputting stable power to each converter module. This design not only simplifies the connection architecture of the secondary circuits within and outside the system, reducing the complexity of line insulation and electromagnetic interference management, but also overcomes the strict timing constraints of power-up and power-down between the power supply and control power supply in traditional power electronic devices. In some application scenarios, it can even replace power supply devices such as UPS (Uninterruptible Power Supply) within the cabinet, effectively streamlining system configuration.

[0029] For large-scale energy storage devices, flyback converters are a highly competitive energy conversion solution due to their significant advantages, including high efficiency, low cost, simple structure, and electrical isolation. However, when operating under high-voltage DC input conditions, the main switch of a single-switch flyback converter must withstand voltage stress of nearly twice the input voltage. This condition not only reduces system reliability and efficiency but also imposes stringent requirements on the selection of switching components, limiting its application in certain scenarios.

[0030] Based on the above situation, the present application proposes a flyback converter for high voltage DC input and a control method thereof, which will be described in detail below with reference to embodiments and drawings.

[0031] As a basic embodiment of the flyback converter for high voltage DC input of the present application, it may include: a primary high voltage DC input power circuit, a secondary power output circuit and an auxiliary winding power supply circuit.

[0032] The auxiliary winding power supply circuit includes multiple coil windings on the primary side and at least one coil winding on the secondary side, forming the primary and secondary windings of the transformer, respectively. Based on the transformer principle, the auxiliary winding power supply circuit achieves electrical isolation between the high-voltage and low-voltage sides through electromagnetic coupling between the multiple coil windings on the primary side and the secondary side. This not only effectively blocks the transmission of electrical interference from the high-voltage side to the secondary side, but also provides a stable energy transfer channel for the secondary power output circuit, ensuring the stability and purity of the secondary output voltage and meeting the load's stringent power quality requirements.

[0033] The primary high-voltage DC input power circuit includes multiple input sub-circuits, each of which includes a voltage-equalizing circuit, an N-channel MOSFET, an RC cascade circuit, and a Schottky diode; the drain of the N-channel MOSFET is connected to the anode of the Schottky diode, the RC cascade circuit, and one end of the voltage-equalizing circuit in sequence, the source of the N-channel MOSFET is connected to the other end of the voltage-equalizing circuit, and the gate of the N-channel MOSFET is used to receive a control signal that controls the N-channel MOSFET to be turned on or off; the two ends of the first primary winding are respectively connected to the drain of the first N-channel MOSFET and one end of the voltage-equalizing circuit, the two ends of the other primary windings are respectively connected to the source of the previous N-channel MOSFET and the drain of the next N-channel MOSFET, and the source of the last N-channel MOSFET is grounded; one end of the first voltage-equalizing circuit is connected to the positive electrode of the high-voltage DC input, and the other end of the last voltage-equalizing circuit is connected to the negative electrode of the high-voltage DC input.

[0034] It should be noted that in this application, multiple input sub-circuits are connected in parallel and then in series to the high-voltage DC input. This topology distributes the total voltage to each input sub-circuit. The N-channel MOSFET in each input sub-circuit serves as the core switching device, achieving high-frequency switching under the drive of the gate control signal, and precisely regulating energy transmission. The voltage-equalizing circuit ensures that the voltages borne by each N-channel MOSFET are balanced. In high-voltage input scenarios, it avoids premature device failure due to uneven voltage, greatly improving the stability and life of the system, while reducing the excessive requirements for the withstand voltage level of the N-channel MOSFET and optimizing costs. The buffer circuit composed of an RC cascade circuit (resistor-capacitor cascade circuit) can effectively absorb the voltage spike generated when the N-channel MOSFET is turned off, preventing the device from breaking down due to overvoltage. The Schottky diode reduces conduction losses due to its low forward voltage drop characteristics, and cooperates with the high-frequency switching action of the N-channel MOSFET to improve the overall energy conversion efficiency.

[0035] The secondary power supply output circuit includes an output diode. The anode of the output diode is connected to one end of the secondary winding, and the cathode and the other end of the secondary winding are connected to the two ends of the load. In this circuit, the output diode performs a rectifying function, converting the AC voltage induced by the secondary winding into a DC output. This connection ensures a stable DC voltage across the load. Furthermore, the unidirectional conductivity of the output diode ensures a unidirectional flow of power, preventing backflow that could affect system operation. In practical applications, by properly selecting the output diode parameters, output performance can be further optimized, output ripple can be reduced, and power supply quality can be improved.

[0036] The flyback converter of the present application successfully solves the problem of excessive voltage stress on the main switch tube under high-voltage DC input through the coordinated design of three major circuits. Compared with traditional solutions, it has significant advantages in reliability, efficiency and cost.

[0037] like Figure 1 As shown in FIG, an embodiment of the flyback converter for high voltage DC input of the present application is shown. The auxiliary winding power supply circuit includes three coil windings on the primary side and two coil windings on the secondary side, which respectively constitute the primary winding and secondary winding of the transformer. The three coil windings in the primary winding are Figure 1 1 and 2, 3 and 4, 5 and 6, the two coil windings in the secondary winding are Figure 1 9 and 10, 11 and 12 in.

[0038] The primary high-voltage DC input power circuit consists of three input sub-circuits, each of which includes a voltage-sharing circuit, an N-channel MOSFET ( Q 1 to Q 3) RC cascade circuit and Schottky diode ( D 1 to D3). The voltage equalization circuit includes parallel resistors ( R in1 to R in3 ) and electrolytic capacitors ( C in1 to C in3 ). The RC cascade circuit includes parallel capacitors ( C 1 to C 3) and resistor ( R 1 to R 3). Through the resistor R in1 , electrolytic capacitors C in1 ,resistance R in2 , electrolytic capacitors C in2 ,resistance R in3 and electrolytic capacitors C in3 For high voltage DC input (high voltage DC input voltage is Figure 1 in V dc ) to perform voltage equalization to ensure that the voltages borne by the N-channel MOSFETs are close. The gates of the three N-channel MOSFETs are used to receive control signals that control the N-channel MOSFETs to turn on or off, corresponding to Figure 1 in DRV1 to DRV3 The secondary power supply output circuit includes the output diode ( D 4 and D 5), the anode of the output diode is connected to one end of the secondary winding, and the cathode of the output diode and the other end of the secondary winding are connected to the two ends of the load respectively. In this embodiment, the load is R o1 and R o2 , the secondary power output circuit also includes electrolytic capacitors ( C o1 and C o2 ), the electrolytic capacitor is connected in parallel with the load. Figure 1 in V o1 and V o2 is the output voltage of the secondary power supply output circuit corresponding to the two loads, AGND 1 and AGND 2 are the analog grounds corresponding to the two loads. Figure 1 The coil windings 11 and 12 are the second auxiliary windings, which have the same structure as those corresponding to 9 and 10.

[0039] This application adopts the mode of voltage balancing control of multiple N-channel MOSFETs, and takes one of the input sub-circuits as an example to illustrate. During operation, the drain-source voltage of the N-channel MOSFET V ds The operating current waveforms of the primary high-voltage DC input power circuit and the secondary power output circuit are as follows: Figure 2 As shown, Figure 2 middle, I p is the primary high voltage DC input power loop current, I s is the working current of the secondary power supply output circuit, V peak It is a spike voltage. At the moment when the N-channel MOSFET is turned off, due to the presence of parasitic inductance (such as transformer leakage inductance, line inductance, etc.) and parasitic capacitance (such as output capacitance of N-channel MOSFET, distributed capacitance between transformer windings, etc.) in the circuit, a voltage spike will be generated. This spike voltage will be superimposed on V dc and Above, the drain-source voltage acting on the N-channel MOSFET is formed V ds The maximum voltage on the input circuit. In each input sub-circuit, the withstand voltage of the N-channel MOSFET is The calculation method is:

[0040] in, is the maximum DC input voltage of the primary high-voltage DC input power circuit, is the reflected voltage of the secondary power supply output loop, The voltage margin is set to ensure that the system can operate stably under changing environments.

[0041] Reflected voltage of the secondary power supply output loop The calculation method is:

[0042] in, is the transformer turns ratio, is the output voltage of the secondary power output circuit, It is the conduction voltage of the output diode of the secondary power supply output circuit.

[0043] When the N-channel MOSFET ( Q 1. Q 2. Q3) When the diode is turned on, the high voltage DC flows through the primary winding of the transformer and the N-channel MOSFET, storing energy in the magnetic core of the transformer. At this time, the voltage polarity of the winding on the secondary side of the transformer is opposite, and the diode on the secondary side is D 4 and diode D 5 Reverse bias, the secondary power supply output circuit is not conductive.

[0044] When the N-channel MOSFET ( Q 1. Q 2. Q 3) When shutting down, the high voltage DC input of the primary high voltage DC input power circuit ( V dc ) is interrupted, and the energy stored in the transformer is transmitted through the secondary winding. At this time, the diode D 4 and diode D 5Forward conduction, energy is released from the magnetic core and passes through the diode D 4 and diode D 5 After rectification, supply the load R o1 and load R o2 The voltage in the primary high voltage DC input power circuit is reversed, and the energy in the circuit is supplied by the resistor. R 1. Capacitor C 1. Schottky diode D 1. Resistors R 2. Capacitor C 2. Schottky diode D 2. Resistance R 3. Capacitor C 3. Schottky diode D The RCD (Resistor-Capacitor-Diode) network composed of 3 absorbs the DRV 1. DRV 2. DRV 3, that is, the conduction time of N-channel MOSFET ( Q 1. Q 2. Q 3) The on-time adjusts the time for the system to store and release energy, and ultimately achieves a stable output voltage.

[0045] like Figure 3 FIG2 is a circuit diagram of a control loop. In this embodiment, a control loop is also included, and the primary winding of the transformer also includes a first auxiliary winding.

[0046] The control circuit includes the control resistor R 10. Resistors R 4. Resistors R 5. Diode D6. Power control chip, resistor R 8. Capacitor C 4. Resistors R 7. Resistors R 9. Capacitor C 5. Capacitor C 6. Capacitor C 7 and resistor R 6. One end of the first auxiliary winding is grounded and the other end is connected to a resistor R One end of 10, diode D 6 and resistor R 4 parallel resistors R The other end of 10 is connected to the diode D 6 anode.

[0047] In this embodiment, the ZCD pin, FB pin, CS pin, GND pin, CT pin, FAULT pin, VCC pin and DRV pin of the power control chip are mainly used. It should be noted that in the power control chip, the ZCD pin is mainly used for zero current detection input to detect whether the inductor current on the primary side of the transformer drops to zero. The FB pin is mainly used for feedback input to receive the sampling signal of the output voltage. The CS pin is mainly used for current detection input to monitor the switch tube current or the primary side current of the transformer. The GND pin is mainly used as a ground terminal to provide a circuit reference potential. The CT pin is mainly used to set the current sampling time or perform compensation. The FAULT pin is mainly used for fault output to indicate the working status of the power control chip. The VCC pin is mainly used for power input to provide the operating voltage for the power control chip. The DRV pin is mainly used for drive output to provide the switch tube gate drive signal. Specifically in this embodiment: Connect a resistor to the ZCD pin of the power control chip R One end of 5 and the diode D 6 cathode, resistor R The other end of 5 is grounded. The ZCD pin is connected to the ground via the first auxiliary winding ( Figure 1 7 and 8) with resistors R 4. Resistors R 5. Resistors R 10 and diode D 6 The transmitted signal is used for current zero-crossing detection, and the diode D 6 is used to detect the zero crossing point faster when shutting down. The FB pin of the power control chip is connected to the voltage feedback circuit. The FB pin converts the voltage output of the secondary power output circuit ( V o1 and V o2) is transmitted to the FB pin through the isolation optocoupler U1, facilitating the power control chip to control the high-voltage DC circuit. The CS pin of the power control chip is used to monitor the current peak of the primary high-voltage DC input power circuit to provide overcurrent protection for the system. The GND pin of the power control chip is grounded and connected to pin 8 of the first auxiliary winding. The CT pin of the power control chip is connected to the capacitor C One end of 4, capacitor C The other end of 4 is grounded, CT pin, by setting the capacitor C 4 capacitance value, adjust the system working cycle. Connect the resistor to the FAULT pin of the power control chip R One end of 9, resistor R The other end of 9 is connected to the resistor R 7. The cathode of diode D10 and the VCC pin of the power control chip, resistor R One end of 8 is connected to the capacitor C 4, and the other end is connected to the high voltage DC input. The FAULT pin is the overvoltage protection pin of the power control chip, which passes the input high voltage DC through the resistor R 6 and resistor R 7-voltage divider, capacitor C 7 After filtering R 9 flows into the chip, completing the overvoltage protection of the system, shutting down in the case of low voltage, and waiting for the set input voltage to be reached before completing the system startup. The VCC pin of the power control chip is connected to the capacitor in turn. C 5 and ground. The VCC pin is the power supply pin of the power control chip, which is mainly supplied by the high-voltage DC input through the resistor used for soft start. R 8 Start and pass Figure 5 The voltage stabilization circuit shown realizes the power supply to the power control chip from the first auxiliary winding. The DRV pin of the power control chip serves as the MOS drive output pin of the power control chip, connected to the gate of the N-channel MOSFET, and is used to receive the control signal that controls the N-channel MOSFET to be turned on or off. Through the feedback input of the power control chip, the N-channel MOSFET is controlled to achieve stable output of the system. C 6. One end of the resistor is connected to the VCC pin of the power control chip and the other end is grounded. R 6 and capacitor C 7 After parallel connection, one end is connected to the resistor R 9 and resistor R 7, and the other end is grounded.

[0048] like Figure 5 As shown, Figure 3 Circuit diagram of the voltage stabilization circuit. The voltage stabilization circuit includes electrolytic capacitors C 10. Diode D 9. DiodeD 7. Transistor Q 4. Schottky diode D 8. Resistors R 16. Resistors R 17. Diode D 7 and capacitor C 9. Electrolytic capacitor C 10's positive terminal and diode D The cathode of 9 is connected to the VCC pin of the power control chip; the diode D 9's anode is connected to the transistor Q 4 emitter, Schottky diode D 8 anode and electrolytic capacitor C The negative poles of 10 are grounded; Schottky diodes D 8 cathode, triode Q 4 base and resistor R One end of 16 is connected to the resistor R The other end of 16, transistor Q 4 collector, resistor R One end of 17 and the diode D 7's cathode is connected; resistor R The other end of 17 and the capacitor C One end of 9 is connected to the diode D 7 anode, capacitor C The other end of 9 is connected to the other end of the first auxiliary winding.

[0049] In the system through Figure 3 Resistors for soft start R 8 After startup, the system enters the flyback control mode, the first auxiliary winding generates voltage through the magnetic core, and the diode D 7 After rectification, the current is transmitted to the next stage resistor. R 17 and capacitor C 9 is a diode D 7 absorption circuit. When the voltage output by the first auxiliary winding exceeds the bias voltage of the diode D7, the signal is transmitted to the subsequent circuit and the current flows through the resistor R 16. When the transistor Q When the base-emitter voltage of 4 is greater than the conduction voltage, the transistor Q 4 is turned on, and the current flows to the subsequent circuit and finally to the VCC pin of the power control chip. C 10 plays a role in voltage stabilization, Schottky diode D 8 Maintain transistor Q The base voltage of 4 does not exceed the working voltage of the VCC pin of the power control chip, and the diode D 9 to protect the transistor Q 4. Prevent breakdown.

[0050] like Figure 4 The voltage feedback circuit includes an isolation optocoupler U1, a resistor R 13. Resistors R 14. Resistors R 15. Capacitor C 8. TL431 voltage regulator, resistor R 11 and resistor R 12. The collector of the isolation optocoupler U1 is connected to the FB pin of the power control chip, the emitter is grounded, and the anode is connected to the resistor. R One end of 13; the cathode of the isolation optocoupler U1, the cathode of the voltage regulator TL431, and the resistor R One end of 14 and the resistor R One end of 15 is connected to the resistor R The other end of 15 and the capacitor C One end of 8 is connected to the capacitor C The other end of 8, the reference electrode of the voltage regulator TL431, the resistor R One end of 11 and the resistor R One end of 12 is connected to the resistor R The other end of 13, the resistor R The other end of 14 and the resistor R The other end of 11 is connected to one end of the load; the anode of the voltage regulator TL431 and the resistor R The other end of 12 is connected to the other end of the load.

[0051] resistance R 11 and resistor R 12 divides the voltage of the secondary power supply output circuit and processes it through the voltage regulator TL431. R 15 and capacitor C 8. Perform loop compensation on the voltage collected by the system to reduce the ripple of the output voltage. Under dynamic load conditions, when the isolation optocoupler U1 does not pass current, it passes through the resistor R 14 provides a current path for the voltage regulator TL431. R Reference numeral 13 denotes a current-limiting resistor for the feedback loop of the isolation optocoupler U1. The isolation optocoupler U1 outputs the feedback signal through the FB pin of the power control chip for use by the power control chip.

[0052] In this application, the primary high-voltage DC input power circuit distributes the high-voltage DC input to multiple N-channel MOSFETs, and the secondary power output circuit provides a DC output voltage. The control circuit drives the N-channel MOSFETs and provides protection. A voltage regulator circuit provides a stable voltage for the control circuit. The primary high-voltage DC input power circuit employs a voltage-sharing topology with multiple N-channel MOSFETs connected in series. The drain-source terminals of the N-channel MOSFETs are connected in series with the primary winding, and the input voltage is distributed via resistors and capacitors in the input circuit. This reduces voltage stress on the N-channel MOSFETs and improves system reliability. The secondary power output circuit actually consists of multiple output windings and corresponding rectifier circuits, providing outputs at multiple independent voltage levels. When processing a high-voltage DC input, a traditional single-switch flyback converter requires the main switch to withstand significant voltage stress, which increases power loss and reduces system reliability. In contrast, the input voltage in this application is processed by the voltage-sharing circuit in the primary high-voltage DC input power circuit and then transmitted to the secondary power output circuit via a transformer, outputting a stable DC voltage. The first auxiliary winding supplies power to the control chip via the voltage regulator circuit, ensuring stable circuit operation. The power control chip implements overcurrent protection, overvoltage protection, and dynamic regulation, ensuring safe and stable operation of the system under high-voltage input. This application has broad application value in large-scale energy storage equipment and medium- and high-voltage power electronic systems, effectively improving operating performance in high-voltage input scenarios, reducing design costs and energy consumption, and improving system operating efficiency and reliability.

[0053] This application also proposes a control method for a flyback converter with a high-voltage DC input, which may include controlling the on-time of N-channel MOSFETs in multiple input sub-circuits to achieve output voltage stability in a secondary power supply output circuit that meets preset requirements. The specific implementation method will not be further described.

[0054] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A flyback converter for high voltage DC input, characterized in that: include: Primary high-voltage DC input power circuit, secondary power output circuit and auxiliary winding power supply circuit; The auxiliary winding power supply circuit includes multiple coil windings on the primary side and at least one coil winding on the secondary side, which respectively constitute the primary winding and secondary winding of the transformer; The primary high-voltage DC input power loop includes multiple input sub-loops, each input sub-loop includes a voltage equalizing loop, an N-channel MOSFET, an RC cascade loop and a Schottky diode; the drain of the N-channel MOSFET is connected to the anode of the Schottky diode, the RC cascade loop, and one end of the voltage equalizing loop in sequence, the source of the N-channel MOSFET is connected to the other end of the voltage equalizing loop, and the gate of the N-channel MOSFET is used to receive a control signal for controlling the N-channel MOSFET to be turned on or off; the two ends of the first primary winding are respectively connected to the drain of the first N-channel MOSFET and one end of the voltage equalizing circuit, the two ends of the other primary windings are respectively connected to the source of the previous N-channel MOSFET and the drain of the next N-channel MOSFET, and the source of the last N-channel MOSFET is grounded; one end of the first voltage equalizing circuit is connected to the positive electrode of the high-voltage DC input, and the other end of the last voltage equalizing circuit is connected to the negative electrode of the high-voltage DC input; The secondary power output loop includes an output diode, the anode of the output diode is connected to one end of the secondary winding, and the cathode of the output diode and the other end of the secondary winding are connected to two ends of the load respectively.

2. A flyback converter for high voltage DC input according to claim 1, characterized in that: It also includes a control circuit; the primary winding of the transformer also includes a first auxiliary winding; The control loop includes a control resistor R 10. Resistors R 4. Resistors R 5. Diode D 6. Power control chip, resistor R 8. Capacitor C 4. Resistors R 7. Resistors R 9. Capacitor C 5. Capacitor C 6. Capacitor C 7 and resistor R 6; One end of the first auxiliary winding is grounded, and the other end is connected to a resistor R One end of 10, diode D 6 and resistor R 4 parallel resistors R The other end of 10 is connected to the diode D 6 anode; The ZCD pin of the power control chip is connected to a resistor R One end of 5 and the diode D 6 cathode, resistor R The other end of 5 is grounded; the FB pin of the power control chip is connected to the voltage feedback circuit; the CS pin of the power control chip is used to monitor the current peak of the primary high-voltage DC input power loop for overcurrent protection; the GND pin of the power control chip is grounded; the CT pin of the power control chip is connected to the capacitor C One end of 4, capacitor C The other end of 4 is grounded; the FAULT pin of the power control chip is connected to a resistor R One end of 9, resistor R The other end of 9 is connected to the resistor R 7. The cathode of diode D10 and the VCC pin of the power control chip; resistor R One end of 8 is connected to the capacitor C 4, and the other end is connected to the high voltage DC input; the VCC pin of the power control chip is connected to the capacitor in turn C 5 and ground; the DRV pin of the power control chip serves as the MOS drive output pin of the power control chip, connected to the gate of the N-channel MOSFET, and is used to receive the control signal that controls the N-channel MOSFET to turn on or off; the capacitor C 6. One end of the resistor is connected to the VCC pin of the power control chip and the other end is grounded. R 6 and capacitor C 7 After parallel connection, one end is connected to the resistor R 9 and resistor R 7, and the other end is grounded.

3. A flyback converter for high voltage DC input according to claim 2, characterized in that: Also includes a voltage stabilizing circuit; One end of the voltage stabilizing circuit is connected to one end of the first auxiliary winding, and the other end is connected to the VCC pin of the power control chip and the capacitor C Between 6.

4. A flyback converter for high voltage DC input according to claim 3, characterized in that: The voltage stabilizing circuit includes an electrolytic capacitor C 10. Diode D 9. Diode D 7. Transistor Q 4. Schottky diode D 8. Resistors R 16. Resistors R 17. Diode D 7 and capacitor C 9; The electrolytic capacitor C 10's positive terminal and diode D The cathode of 9 is connected to the VCC pin of the power control chip; the diode D 9's anode is connected to the transistor Q 4 emitter, Schottky diode D 8 anode and electrolytic capacitor C The negative poles of 10 are grounded; Schottky diodes D 8 cathode, triode Q 4 base and resistor R One end of 16 is connected to the resistor R The other end of 16, transistor Q 4 collector, resistor R One end of 17 and the diode D 7's cathode is connected; resistor R The other end of 17 and the capacitor C One end of 9 is connected to the diode D 7 anode, capacitor C The other end of 9 is connected to the other end of the first auxiliary winding.

5. The flyback converter for high voltage DC input according to claim 4, characterized in that: The voltage feedback circuit includes an isolation optocoupler U1, a resistor R 13. Resistors R 14. Resistors R 15. Capacitor C 8. TL431 voltage regulator, resistor R 11 and resistor R 12; The collector of the isolation optocoupler U1 is connected to the FB pin of the power control chip, the emitter is grounded, and the anode is connected to the resistor R One end of 13; the cathode of the isolation optocoupler U1, the cathode of the voltage regulator TL431, and the resistor R One end of 14 and the resistor R One end of 15 is connected to the resistor R The other end of 15 and the capacitor C One end of 8 is connected to the capacitor C The other end of 8, the reference electrode of the voltage regulator TL431, the resistor R One end of 11 and the resistor R One end of 12 is connected to the resistor R The other end of 13, the resistor R The other end of 14 and the resistor R The other end of 11 is connected to one end of the load; the anode of the voltage regulator TL431 and the resistor R The other end of 12 is connected to the other end of the load.

6. The flyback converter for high voltage DC input according to claim 1, characterized in that: The voltage-sharing circuit includes a resistor and an electrolytic capacitor connected in parallel.

7. The flyback converter for high voltage DC input according to claim 1, characterized in that: The secondary power output circuit also includes an electrolytic capacitor; The electrolytic capacitor is connected in parallel with the load.

8. The flyback converter for high voltage DC input according to claim 1, characterized in that: The N-channel MOSFET withstand voltage The calculation method includes: in, is the maximum DC input voltage of the primary high-voltage DC input power circuit, is the reflected voltage of the secondary power supply output loop, is the voltage margin set.

9. The flyback converter for high voltage DC input according to claim 8, characterized in that: The reflected voltage of the secondary power supply output loop The calculation method includes: in, is the transformer turns ratio, is the output voltage of the secondary power output circuit, It is the conduction voltage of the output diode of the secondary power supply output circuit.

10. A control method for a flyback converter for high voltage DC input according to any one of claims 1 to 9, characterized in that: include: By controlling the on-time of the N-channel MOSFETs in multiple input sub-loops, the output voltage stability of the secondary power supply output loop can meet the preset requirements.

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