High-power flyback power supply short-circuit protection circuit with wide input voltage range

Abstract

The invention discloses a high-power flyback power supply short-circuit protection circuit with a wide input voltage range, which is applied to a high-voltage side series flyback power supply and comprises a time delay circuit, a threshold comparison circuit and an action logic circuit, the threshold comparison circuit takes a feedback (FB) pin signal as a fault signal and compares the fault signal with a protection threshold, and when the FB signal is greater than the protection threshold, a comparator outputs a high level to trigger the fault signal holding circuit to work; and the action logic circuit pulls a current sampling (CS) pin to a high level, the PWM outputs a sealed wave until the voltage of the VCC pin is reduced to a chip under-voltage protection threshold, and the power supply is restarted. If the short-circuit fault is not eliminated, the protection circuit acts, and the power supply is always in a hiccup mode; and if the short-circuit fault is eliminated, the power supply is restarted. Finally, experiments prove that the provided short-circuit protection circuit can reliably and quickly protect the power supply.

Description

Technical Field

[0001] This invention relates to the field of short-circuit protection circuits, and in particular to a short-circuit protection circuit for a high-power flyback power supply with a wide input voltage range. Background Technology

[0002] Used in auxiliary power supply systems for photovoltaic and energy storage modules. With the continuous increase in voltage and power levels of photovoltaic and energy storage systems, traditional single-tube flyback power supplies can no longer meet the auxiliary power supply requirements. Therefore, a primary-side series flyback power supply topology suitable for high voltage and high power has emerged. As a core component of the entire system, the stability and reliability of the auxiliary power supply are crucial. Auxiliary power supplies are typically required to prevent damage from internal or external interference, necessitating comprehensive protection functions. Commonly used protection functions include overvoltage / undervoltage protection, overload protection, and short-circuit protection. However, under high voltage and high power output conditions, because the peak current during a short-circuit fault is similar to the peak current during high power transmission, the existing cycle-by-cycle current limiting mode of the chip cannot release the energy of the electrolytic capacitor in the VCC power supply branch below the undervoltage protection threshold of the power chip, making it particularly difficult to implement short-circuit protection at the power output.

[0003] The voltage levels and transmission power of photovoltaic and energy storage modules are constantly increasing, with current system voltage levels ≥1.5kV and transmission power ≥320kW. This has led to a corresponding increase in the input voltage and power requirements of the auxiliary power supply. The auxiliary power supply system is crucial for maintaining the stable operation of the entire system, which places higher demands on power supply protection. Short-circuit faults are among the most common faults in power supply systems. When a short-circuit fault occurs in the load, the power supply system must provide fast and reliable protection to prevent further propagation of the fault. Existing literature has conducted research on short-circuit protection for single-tube flyback power supply topologies, but these protection circuits lack fault signal holding circuits and cannot guarantee reliable protection of the power supply when a short-circuit fault occurs under high-voltage, high-power operating conditions.

[0004] To address the aforementioned issues, a short-circuit protection circuit for a high-power flyback power supply with a wide input voltage range is disclosed based on a high-voltage side series flyback power supply topology. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is that the power supply cannot reliably protect itself when a short circuit fault occurs under high voltage and high power operating conditions.

[0006] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a short-circuit protection circuit for a high-power flyback power supply with a wide input voltage range, which is applied to a series-type flyback power supply on the high-voltage side. The short-circuit protection circuit includes a delay circuit, a threshold comparison circuit and an action logic circuit.

[0007] The delay circuit is used to avoid the situation where the feedback FB pin signal is greater than the protection threshold during the start-up phase of the flyback power supply, thus preventing the protection circuit from malfunctioning.

[0008] The input terminal of the threshold comparison circuit is connected to the FB pin signal, which is used to compare the FB pin signal with a preset protection threshold. When the FB pin signal is greater than the protection threshold, a high-level trigger signal is output.

[0009] The action logic circuit is connected to the output of the threshold comparison circuit. It is used to receive the high-level trigger signal, latch the fault signal, and pull the current sampling CS pin of the PWM controller in the flyback power supply to the reference voltage VREF, so that the output OUT pin of the PWM controller stops outputting the PWM drive signal. The PWM controller restarts when the voltage VCC of the chip power supply circuit in the flyback power supply drops to the undervoltage protection threshold of the PWM controller. If the short circuit fault is not eliminated, the flyback power supply enters hiccup mode. If the short circuit fault is eliminated, the flyback power supply resumes normal operation.

[0010] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the delay circuit includes a resistor R5 and a capacitor C9. One end of the resistor R5 is connected to the reference voltage VREF, and the other end is connected to one end of the capacitor C9, with the other end of the capacitor C9 grounded. The resistor R5 is used to adjust the charging time of the capacitor C9, and the charging time is greater than the time during the flyback power supply startup phase when the compensation COMP port signal of the PWM controller is greater than the protection threshold.

[0011] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the threshold comparison circuit includes a low-pass filter, a comparator, and a voltage divider circuit;

[0012] The low-pass filter includes a resistor R4 and a capacitor C8. One end of the resistor R4 is connected to the FB pin signal, and the other end is connected to one end of the capacitor C8 and the non-inverting input of the comparator. The other end of the capacitor C8 is grounded.

[0013] The voltage divider circuit includes resistors R12 and R13. One end of resistor R12 is connected to the reference voltage VREF, and the other end is connected to one end of resistor R13 and the inverting input of the comparator. The other end of resistor R13 is grounded. The voltage division value of resistors R12 and R13 is the preset protection threshold.

[0014] The output of the comparator is connected to the action logic circuit.

[0015] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the operating logic circuit includes thyristor Q4, PMOS transistor Q3, resistor R6, resistor R8, resistor R7, resistor R9 and resistor R10.

[0016] One end of resistor R6 is connected to the output of the threshold comparison circuit, and the other end is connected to one end of resistor R8 and the gate of thyristor Q4. The other end of resistor R8 is connected to one end of capacitor C9 in the delay circuit. One end of resistor R7 is connected to the anode of thyristor Q4, and the other end is connected to the reference voltage VREF. The cathode of thyristor Q4 is grounded.

[0017] One end of resistor R9 is connected to the reference voltage VREF, and the other end is connected to one end of resistor R10 and the gate of PMOS transistor Q3. The other end of resistor R10 is connected to the anode of thyristor Q4. The source of PMOS transistor Q3 is connected to the reference voltage VREF, and the drain is connected to the CS pin of PWM controller. The CS pin is also connected to a protection resistor R11.

[0018] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the power stage of the high-voltage side series-type flyback power supply includes two series-connected single-tube flyback circuits, namely a first single-tube flyback circuit and a second single-tube flyback circuit.

[0019] The first single-transistor flyback circuit includes a capacitor C3, a resistor R1, a first primary winding N1 of a transformer T1, a diode D1, and a first SiCMOS transistor Q1;

[0020] The second single-transistor flyback circuit includes a capacitor C4, a resistor R2, the second primary winding N2 of a transformer T1, a diode D2, and a second SiCMOS transistor Q2;

[0021] The input voltage of the first single-transistor flyback circuit is taken from the upper half bus voltage, and the input voltage of the second single-transistor flyback circuit is taken from the lower half bus voltage.

[0022] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the power stage of the high-voltage side series-type flyback power supply further includes a voltage-equalizing capacitor bank, which includes capacitor C1 and capacitor C2. The capacitors C1 and C2 are connected in series and then connected to the two ends of the DC input voltage Vin, and the series connection node is the boundary point between the upper half bus voltage and the lower half bus voltage; the voltage-equalizing capacitor bank is used to equalize the bus voltage and absorb high-frequency voltage signals from the circuit.

[0023] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the first single-transistor flyback circuit further includes a first RCD snubber circuit, which is composed of the capacitor C3, the resistor R1 and the diode D1; the second single-transistor flyback circuit further includes a second RCD snubber circuit, which is composed of the capacitor C4, the resistor R2 and the diode D2.

[0024] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the wide input voltage range is 500V to 1500V.

[0025] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: when a short-circuit fault occurs, the FB pin signal reaches the protection threshold within 3 operating cycles, triggering the threshold comparison circuit to output a high-level trigger signal.

[0026] In a preferred embodiment of the high-power flyback power supply short-circuit protection circuit with a wide input voltage range described in this invention: the output parameters of the high-power flyback power supply are 24V / 400W.

[0027] The beneficial effects of this invention are as follows: By setting up three parts—a delay circuit, a threshold comparison circuit, and an action logic circuit—the delay circuit is used to avoid the situation where the COMP port signal is higher than the protection threshold during the startup phase. The threshold comparison circuit takes the feedback (FB) pin signal as a fault signal and compares it with the protection threshold. When the FB signal is greater than the protection threshold, the comparator outputs a high level, triggering the fault signal holding circuit to work. The action logic circuit pulls the current sampling (CS) pin to a high level and blocks the PWM output until the VCC pin voltage drops to the chip's undervoltage protection threshold, at which point the power supply restarts. If the short-circuit fault is not eliminated, the protection circuit operates, and the power supply remains in hiccup mode; if the short-circuit fault is eliminated, the power supply restarts. Finally, experiments demonstrate that the proposed short-circuit protection circuit can reliably and quickly protect the power supply. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein:

[0029] Figure 1 A block diagram of the flyback power supply and protection circuit structure of the present invention is shown;

[0030] Figure 2 The high-voltage side series flyback topology of the present invention is shown. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0032] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0033] Reference Figure 1 This embodiment provides a short-circuit protection circuit for a high-power flyback power supply with a wide input voltage range, which is applied to a series-type flyback power supply on the high-voltage side. The short-circuit protection circuit includes a delay circuit, a threshold comparison circuit, and an action logic circuit.

[0034] The delay circuit is used to avoid the situation where the feedback FB pin signal is greater than the protection threshold during the start-up phase of the flyback power supply, thus preventing the protection circuit from malfunctioning.

[0035] The input terminal of the threshold comparison circuit is connected to the FB pin signal, which is used to compare the FB pin signal with a preset protection threshold. When the FB pin signal is greater than the protection threshold, a high-level trigger signal is output.

[0036] The action logic circuit is connected to the output of the threshold comparison circuit. It is used to receive the high-level trigger signal, latch the fault signal, and pull the current sampling CS pin of the PWM controller in the flyback power supply to the reference voltage VREF, so that the output OUT pin of the PWM controller stops outputting the PWM drive signal. The PWM controller restarts when the voltage VCC of the chip power supply circuit in the flyback power supply drops to the undervoltage protection threshold of the PWM controller. If the short circuit fault is not eliminated, the flyback power supply enters hiccup mode. If the short circuit fault is eliminated, the flyback power supply resumes normal operation.

[0037] The circuit includes a delay circuit, a threshold comparison circuit, and an action logic circuit. During the start-up phase of the flyback power supply, the delay circuit plays a role in preventing the feedback FB pin signal from exceeding the protection threshold, thereby avoiding malfunction of the protection circuit. The input of the threshold comparison circuit is connected to the FB pin signal, which is compared with a preset protection threshold. When the FB pin signal exceeds the protection threshold, a high-level trigger signal is output. The action logic circuit is connected to the output of the threshold comparison circuit. After receiving the high-level trigger signal, it latches the fault signal and pulls the current sampling CS pin of the PWM controller in the flyback power supply to the reference voltage VREF, causing the output OUT pin of the PWM controller to stop outputting the PWM drive signal. This continues until the voltage VCC of the chip power supply circuit in the flyback power supply drops to the undervoltage protection threshold of the PWM controller, at which point the PWM controller restarts. If the short-circuit fault is not eliminated, the flyback power supply enters a hiccup mode. If the short-circuit fault is eliminated, the flyback power supply resumes normal operation. Its beneficial effects are as follows: This short-circuit protection circuit addresses the difficulty of short-circuit protection in high-voltage, high-power applications of series-type flyback power supplies on the high-voltage side. Through a delay circuit, it effectively avoids malfunctions during startup, ensuring normal power supply startup. The threshold comparison circuit accurately detects the relationship between the FB pin signal and the protection threshold, outputting a trigger signal in a timely manner. The action logic circuit, by latching the fault signal, ensures that the CS pin is reliably pulled to VREF when a short-circuit fault occurs, stopping the PWM drive signal output and achieving fast and reliable short-circuit protection. Simultaneously, through a restart mechanism after the VCC voltage drops to the undervoltage protection threshold, the power supply enters a hiccup mode before the fault is cleared, preventing device damage due to prolonged exposure to fault current. After the fault is cleared, the power supply can resume normal operation. The entire circuit has a simple structure, few components, low cost, and rapid protection action. It is suitable for high-power flyback power supplies with a wide input voltage range (500V~1500V) and can meet the high requirements for auxiliary power supply stability and reliability in fields such as photovoltaics and energy storage modules.

[0038] As an optional embodiment, the delay circuit includes a resistor R5 and a capacitor C9. One end of the resistor R5 is connected to the reference voltage VREF, and the other end is connected to one end of the capacitor C9, with the other end of the capacitor C9 grounded. The resistor R5 is used to adjust the charging time of the capacitor C9, and the charging time is greater than the time during the flyback power supply startup phase when the compensation COMP port signal of the PWM controller is greater than the protection threshold.

[0039] Specifically, the delay circuit consists of a resistor R5 and a capacitor C9. One end of resistor R5 is connected to the reference voltage VREF, and the other end is connected to one end of capacitor C9. The other end of capacitor C9 is grounded. During the flyback power supply startup phase, the reference voltage VREF charges capacitor C9 through resistor R5. Resistor R5 is used to adjust the charging time, which is set to be longer than the time during the startup phase when the compensation COMP port signal of the PWM controller exceeds the protection threshold. This avoids potential malfunctions of the protection circuit due to abnormally high COMP port signal during startup, ensuring that the protection circuit does not respond to abnormal signals during startup. After the power supply has stabilized and started up, it will enter normal operation. By utilizing the RC charging characteristics of resistor R5 and capacitor C9, the time period during which the COMP port signal is greater than the protection threshold during the startup phase is precisely avoided. This effectively prevents the protection circuit from being falsely triggered during the power supply startup process, ensuring that the flyback power supply can successfully complete startup and enter a stable operating state. At the same time, this delay circuit has a simple structure, consisting only of resistors and capacitors. It has few components, low cost, is easy to implement, and has high reliability. It can adapt to high-power flyback power supplies with a wide input voltage range (500V~1500V), meeting the requirements of photovoltaic and energy storage modules for the stability and anti-interference of auxiliary power supply protection circuits.

[0040] As an optional embodiment, the threshold comparison circuit consists of a low-pass filter, a comparator, and a voltage divider circuit. The low-pass filter includes a resistor R4 and a capacitor C8. One end of resistor R4 is connected to the FB pin signal, and the other end is connected to one end of capacitor C8 and the non-inverting input of the comparator. The other end of capacitor C8 is grounded. The voltage divider circuit includes resistors R12 and R13. One end of resistor R12 is connected to the reference voltage VREF, and the other end is connected to one end of resistor R13 and the inverting input of the comparator. The other end of resistor R13 is grounded. The voltage division value of resistors R12 and R13 is a preset protection threshold. The output of the comparator is connected to the action logic circuit. Its operation is as follows: the FB pin signal first passes through the low-pass filter composed of resistor R4 and capacitor C8 to remove high-frequency interference. The filtered FB signal is then connected to the same input of the comparator. Simultaneously, the reference voltage VREF, after being divided by resistors R12 and R13, obtains the preset protection threshold and is connected to the inverting input of the comparator. The FB signal at the non-inverting input is compared with the preset protection threshold at the inverting input in real time. When the FB signal is greater than the preset protection threshold, the comparator outputs a high-level trigger signal to the action logic circuit, triggering subsequent protection actions. The low-pass filter effectively filters out high-frequency noise in the FB pin signal, improving the accuracy of signal detection and avoiding misjudgments caused by noise interference. The voltage divider circuit, through the reasonable configuration of resistors R12 and R13, can accurately set the protection threshold to adapt to the protection requirements under different operating conditions. The comparator can quickly respond to signal changes and output the trigger signal in a timely manner, ensuring the sensitivity and reliability of short-circuit fault detection. The entire threshold comparison circuit has a simple structure, conventional component selection, and low cost. It can also work in conjunction with the delay circuit and action logic circuit to ensure accurate detection of short-circuit faults in high-power flyback power supplies with a wide input voltage range (500V~1500V), laying the foundation for the reliable execution of subsequent protection actions and meeting the high-performance requirements of auxiliary power supply protection circuits in photovoltaic and energy storage modules and other fields.

[0041] As an optional embodiment, the action logic circuit includes a thyristor Q4, a PMOS transistor Q3, resistors R6, R8, R7, R9, R10, and a protection resistor R11. One end of resistor R6 is connected to the output of the threshold comparison circuit, and the other end is connected to one end of resistor R8 and the gate of thyristor Q4. The other end of resistor R8 is connected to one end of capacitor C9 in the delay circuit. One end of resistor R7 is connected to the anode of thyristor Q4, and the other end is connected to the reference voltage VREF. The cathode of thyristor Q4 is grounded. One end of resistor R9 is connected to the reference voltage VREF, and the other end is connected to... One end of resistor R10 is connected to the gate of PMOS transistor Q3, and the other end of resistor R10 is connected to the anode of thyristor Q4. The source of PMOS transistor Q3 is connected to the reference voltage VREF, and the drain is connected to the CS pin of the PWM controller. The CS pin is also connected to a protection resistor R11. Its operation is as follows: When the threshold comparator circuit outputs a high-level trigger signal, this signal is transmitted to the gate of thyristor Q4 via resistor R6. Simultaneously, resistor R8 introduces the voltage of capacitor C9 in the delay circuit, jointly driving thyristor Q4 to conduct. After thyristor Q4 conducts, its anode voltage decreases, which in turn lowers the gate voltage of PMOS transistor Q3 through resistor R10. When the source of PMOS transistor Q3 is connected to the reference voltage VREF, the voltage difference between the gate and source meets the conduction condition, causing PMOS transistor Q3 to conduct. This pulls the CS pin of the PWM controller to the reference voltage VREF, and the fault signal is latched by the self-locking characteristic of thyristor Q4 until the VCC voltage drops to the chip's undervoltage protection threshold. The fault signal is then cleared. The protection resistor R11 limits the current to the CS pin. The self-locking characteristic of thyristor Q4 ensures reliable latching of the fault signal, guaranteeing continuous triggering of protection actions during short-circuit faults and preventing device damage caused by protection interruption. PMOS transistor Q3 can quickly... Pulling the CS pin to the reference voltage VREF causes the PWM controller to quickly stop outputting drive signals, ensuring rapid protection action. Each resistor (R6, R8, R7, R9, R10, R11) serves to divide voltage, limit current, and regulate drive signals, respectively, ensuring reasonable circuit parameter matching and stable operation. The entire action logic circuit has a simple structure, few components, and low cost. It can work in conjunction with delay circuits and threshold comparison circuits to achieve reliable short-circuit protection in high-power flyback power supplies with a wide input voltage range (500V~1500V), meeting the high reliability requirements of auxiliary power supply protection circuits in photovoltaic and energy storage modules and other fields.

[0042] As an optional embodiment, the power stage of the high-voltage side series-type flyback power supply includes two series-connected single-transistor flyback circuits, namely a first single-transistor flyback circuit and a second single-transistor flyback circuit. The first single-transistor flyback circuit consists of capacitor C3, resistor R1, the first primary winding N1 of transformer T1, diode D1, and a first SiCMOS transistor Q1. The second single-transistor flyback circuit consists of capacitor C4, resistor R2, the second primary winding N2 of transformer T1, diode D2, and a second SiCMOS transistor Q2. The first single-transistor flyback circuit... The input voltage of the first single-transistor flyback circuit is taken from the upper half bus voltage, and the input voltage of the second single-transistor flyback circuit is taken from the lower half bus voltage. Its operation is as follows: When the DC input voltage Vin (500V~1500V) is connected, the upper half bus voltage is input to the first single-transistor flyback circuit, and the lower half bus voltage is input to the second single-transistor flyback circuit. Under the drive signal output by the PWM controller, the first SiCMOS transistor Q1 and the second SiCMOS transistor Q2 alternately turn on and off. When Q1 and Q2 are on, the primary windings N1 and N2 of transformer T1 store... When Q1 and Q2 are turned off, the energy stored in the primary winding is transferred to the output side through the secondary winding to power the load. At the same time, the first RCD absorption circuit composed of capacitor C3, resistor R1 and diode D1 and the second RCD absorption circuit composed of capacitor C4, resistor R2 and diode D2 absorb the voltage spikes in the corresponding single-transistor flyback circuits, protecting SiCMOS transistors and other devices. The high-voltage side series topology is formed by two series-connected single-transistor flyback circuits, which can effectively adapt to a wide input voltage range of 500V to 1500V, meeting the needs of photovoltaic and energy storage modules for high-voltage auxiliary power supplies. Compared with traditional single-transistor flyback power supplies, it can withstand higher input voltages and transmit greater power (such as 24V / 400W output). At the same time, by using the upper and lower half bus voltages of the two single-transistor flyback circuits respectively, the voltage stress on individual devices is reduced, improving the reliability and safety of the circuit. The setting of the RCD absorption circuit further suppresses voltage spikes during the switching process, protects key devices such as SiCMOS transistors, and extends the service life of the power supply.

[0043] As an optional embodiment, the power stage of the high-voltage side series-type flyback power supply includes a voltage-equalizing capacitor bank composed of capacitors C1 and C2. Capacitors C1 and C2 are connected in series across the DC input voltage Vin, with the series connection point serving as the boundary between the upper and lower bus voltages. The working process is as follows: when the DC input voltage Vin (500V~1500V) is connected, capacitors C1 and C2, due to their series connection, share the input voltage. Through their capacitance characteristics, they evenly distribute the total input voltage to the upper and lower bus, enabling the first single-transistor flyback circuit and the second single-transistor flyback circuit to operate smoothly. The voltage across each of the excitation circuits remains balanced. Meanwhile, during circuit operation, capacitors C1 and C2 absorb high-frequency voltage signals generated by switching actions, reducing voltage fluctuations. The voltage-equalizing capacitor group effectively solves the voltage balancing problem of the two series-connected single-tube flyback circuits under high-voltage input, preventing damage to individual circuits due to excessive voltage, improving circuit safety and reliability. Simultaneously, the absorption of high-frequency voltage signals reduces electromagnetic interference, ensuring the stability of the power supply operation. This structure is simple, achieving voltage equalization and filtering functions solely through the series connection of two capacitors, making it low-cost and easy to implement.

[0044] As an optional embodiment, the first single-transistor flyback circuit includes a first RCD snubber circuit composed of capacitor C3, resistor R1, and diode D1, and the second single-transistor flyback circuit includes a second RCD snubber circuit composed of capacitor C4, resistor R2, and diode D2. The operation is as follows: In the first single-transistor flyback circuit, when the first SiCMOS transistor Q1 is turned off, the first primary winding N1 of transformer T1 will generate a voltage spike due to leakage inductance. At this time, diode D1 conducts, introducing this spike voltage into capacitor C3, causing capacitor C3 to charge and store energy. Subsequently, capacitor C3 discharges through resistor R1, consuming the stored energy as heat, thereby suppressing the voltage spike; in the second single-transistor flyback circuit, when the second SiCMOS transistor... When Q2 is turned off, the voltage spike generated by the second primary winding N2 of transformer T1 is introduced into capacitor C4 through diode D2. After capacitor C4 is charged, it discharges through resistor R2, thus suppressing the voltage spike. The beneficial effect is that the first RCD absorption circuit and the second RCD absorption circuit can effectively absorb the voltage spike generated when the corresponding single-transistor flyback circuit is turned off, avoiding damage to the SiCMOS transistor due to excessive voltage, significantly improving the reliability and service life of the device, while reducing electromagnetic interference in the circuit, ensuring the stable operation of the high-power flyback power supply with a wide input voltage range (500V~1500V). The absorption circuit has a simple structure, consisting only of capacitors, resistors and diodes, and is low in cost and easy to integrate.

[0045] As an optional embodiment, when a short-circuit fault occurs, the output voltage drops sharply. The feedback loop adjusts the FB pin signal to gradually increase. Within three operating cycles, this signal reaches the protection threshold. At this time, the FB signal, filtered by a low-pass filter (resistor R4 and capacitor C8) in the threshold comparison circuit, is input to the non-inverting input of the comparator and compared with the preset protection threshold obtained by voltage division by resistors R12 and R13 at the inverting input. Since the FB signal is greater than the protection threshold, the comparator outputs a high-level trigger signal to the action logic circuit. The FB pin signal can reach the protection threshold and trigger protection within three operating cycles, ensuring the rapid detection of short-circuit faults. This allows the protection circuit to respond quickly to the fault, reducing the fault duration and preventing device damage due to prolonged exposure to fault current. It also improves the safety and reliability of the high-power flyback power supply under high-voltage and high-power conditions. This fast response characteristic, in conjunction with the delay circuit and action logic circuit of the entire short-circuit protection circuit, ensures that the power supply can quickly enter the protection state after a short-circuit fault occurs within a wide input voltage range (500V~1500V).

[0046] As an optional embodiment, the output parameters of the high-power flyback power supply are 24V / 400W. Its operation is as follows: When the DC input voltage is within the range of 500V to 1500V, the power stage of the high-voltage side series-type flyback power supply works collaboratively through two series-connected single-tube flyback circuits. After isolation and transformation by transformer T1, the energy is transferred to the low-voltage side output circuit, ultimately achieving a stable output of 24V voltage and 400W power to supply power to loads such as the photovoltaic and energy storage module control systems. During this process, the feedback circuit monitors the output voltage of 24V in real time and adjusts it through a PI loop to achieve F... The signal from pin B is fed into the PWM control circuit, which, together with the current sampling signal, generates a drive signal to regulate the on / off state of the power stage SiC MOSFET, ensuring that the output voltage is stable at 24V and the power is stable at 400W. At the same time, the short-circuit protection circuit monitors the circuit status at all times and acts quickly when a short-circuit fault occurs to protect the power supply and load. Its beneficial effect is that the 24V / 400W output parameters can accurately match the voltage and power requirements of the photovoltaic and energy storage module auxiliary power supply system, providing stable power to key components such as the control system and ensuring the normal operation of the entire system.

[0047] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A short-circuit protection circuit for a high-power flyback power supply with a wide input voltage range, characterized in that: Applied to a high-voltage side series-type flyback power supply, the short-circuit protection circuit includes a delay circuit, a threshold comparison circuit, and an action logic circuit. The delay circuit is used to avoid the situation where the feedback FB pin signal is greater than the protection threshold during the start-up phase of the flyback power supply, thus preventing the protection circuit from malfunctioning. The input terminal of the threshold comparison circuit is connected to the FB pin signal, which is used to compare the FB pin signal with a preset protection threshold. When the FB pin signal is greater than the protection threshold, a high-level trigger signal is output. The action logic circuit is connected to the output of the threshold comparison circuit. It is used to receive the high-level trigger signal, latch the fault signal, and pull the current sampling CS pin of the PWM controller in the flyback power supply to the reference voltage VREF, so that the output OUT pin of the PWM controller stops outputting the PWM drive signal. The PWM controller restarts when the voltage VCC of the chip power supply circuit in the flyback power supply drops to the undervoltage protection threshold of the PWM controller. If the short circuit fault is not eliminated, the flyback power supply enters hiccup mode. If the short circuit fault is eliminated, the flyback power supply resumes normal operation.

2. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The delay circuit includes a resistor R5 and a capacitor C9. One end of the resistor R5 is connected to the reference voltage VREF, and the other end is connected to one end of the capacitor C9. The other end of the capacitor C9 is grounded. The resistor R5 is used to adjust the charging time of the capacitor C9, and the charging time is greater than the time when the compensation COMP port signal of the PWM controller is greater than the protection threshold during the start-up phase of the flyback power supply.

3. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The threshold comparison circuit includes a low-pass filter, a comparator, and a voltage divider circuit; The low-pass filter includes a resistor R4 and a capacitor C8. One end of the resistor R4 is connected to the FB pin signal, and the other end is connected to one end of the capacitor C8 and the non-inverting input of the comparator. The other end of the capacitor C8 is grounded. The voltage divider circuit includes resistors R12 and R13. One end of resistor R12 is connected to the reference voltage VREF, and the other end is connected to one end of resistor R13 and the inverting input of the comparator. The other end of resistor R13 is grounded. The voltage division value of resistors R12 and R13 is the preset protection threshold. The output of the comparator is connected to the action logic circuit.

4. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The operation logic circuit includes thyristor Q4, PMOS transistor Q3, resistors R6, R8, R7, R9 and R10; One end of resistor R6 is connected to the output of the threshold comparison circuit, and the other end is connected to one end of resistor R8 and the gate of thyristor Q4. The other end of resistor R8 is connected to one end of capacitor C9 in the delay circuit. One end of resistor R7 is connected to the anode of thyristor Q4, and the other end is connected to the reference voltage VREF. The cathode of thyristor Q4 is grounded. One end of resistor R9 is connected to the reference voltage VREF, and the other end is connected to one end of resistor R10 and the gate of PMOS transistor Q3. The other end of resistor R10 is connected to the anode of thyristor Q4. The source of PMOS transistor Q3 is connected to the reference voltage VREF, and the drain is connected to the CS pin of PWM controller. The CS pin is also connected to a protection resistor R11.

5. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The power stage of the high-voltage side series-type flyback power supply includes two series-connected single-transistor flyback circuits, namely a first single-transistor flyback circuit and a second single-transistor flyback circuit. The first single-transistor flyback circuit includes a capacitor C3, a resistor R1, a first primary winding N1 of a transformer T1, a diode D1, and a first SiCMOS transistor Q1; The second single-transistor flyback circuit includes a capacitor C4, a resistor R2, the second primary winding N2 of a transformer T1, a diode D2, and a second SiCMOS transistor Q2. The input voltage of the first single-transistor flyback circuit is taken from the upper half bus voltage, and the input voltage of the second single-transistor flyback circuit is taken from the lower half bus voltage.

6. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 5, characterized in that: The power stage of the high-voltage side series-type flyback power supply also includes a voltage equalization capacitor bank, which includes capacitor C1 and capacitor C2. The capacitors C1 and C2 are connected in series and connected to the two ends of the DC input voltage Vin. The series connection node is the boundary point between the upper half bus voltage and the lower half bus voltage. The voltage equalization capacitor bank is used to equalize the bus voltage and absorb high-frequency voltage signals in the circuit.

7. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 5, characterized in that: The first single-transistor flyback circuit further includes a first RCD snubber circuit, which is composed of the capacitor C3, the resistor R1 and the diode D1; the second single-transistor flyback circuit further includes a second RCD snubber circuit, which is composed of the capacitor C4, the resistor R2 and the diode D2.

8. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The wide input voltage range is 500V to 1500V.

9. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: When a short-circuit fault occurs, the FB pin signal reaches the protection threshold within 3 operating cycles, triggering the threshold comparison circuit to output a high-level trigger signal.

10. The high-power flyback power supply short-circuit protection circuit with a wide input voltage range according to claim 1, characterized in that: The output parameters of the high-power flyback power supply are 24V / 400W.

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