Buck-boost converter integrated with short-circuit protection function

Abstract

This invention discloses a Buck-Boost converter with integrated short-circuit protection. Based on the Buck-Boost circuit, a discharge branch consisting of a capacitor and an inductor is added to the Buck-Boost converter with protection function. The inductor in the Buck-Boost circuit is coupled to the inductor in the discharge branch, and the anode of the thyristor is connected in series with the source of the MOSFET. This solves the problem of power quality degradation caused by series loads of circuit breakers and reduces the overall system size.

Description

Technical Field

[0001] This invention belongs to the field of DC circuit breaker technology and relates to a Buck-Boost converter with integrated short-circuit protection function. Background Technology

[0002] Against the backdrop of "carbon neutrality and carbon peaking," the continuous promotion of new energy power generation and utilization has become a hot topic in the electrical industry. DC microgrids possess advantages such as simple structure, high transmission efficiency, and good power quality. Since new energy sources are connected to the grid in DC form, converter devices can be reduced, and there is no need to consider voltage, frequency, and phase control issues. Therefore, DC microgrids are an effective way to integrate new energy sources. DC microgrids require a large number of DC-DC converters to support various electrical appliances. At the same time, the extensive use of converters and appliances places higher demands on the safe operation of DC microgrids. However, DC current does not have a natural zero-crossing point, which increases the difficulty of protecting DC systems. Therefore, short-circuit protection of DC systems is currently an important research direction in DC power systems.

[0003] DC circuit breakers isolate faults and extinguish arcs by creating artificial current zero-crossing points, which is currently an effective method of DC protection. DC circuit breakers can be classified into three types according to their structure: mechanical, hybrid, and solid-state. Mechanical circuit breakers have high withstand voltage and current ratings, but are limited by mechanical switches, resulting in relatively slow switching speeds. Hybrid circuit breakers, building upon this, form a working mode where mechanical switches conduct normal operating current while solid-state devices interrupt short-circuit current. Although they have good dynamic and static characteristics, they are too large and heavy. Solid-state circuit breakers use power electronic devices as switching elements; they are not only small and lightweight but can also eliminate faults without arcing, light, or sound, thus attracting widespread attention.

[0004] Corzine KA et al., in the paper "Corzine KA, Ashton R W. Structure and analysis of the Z-source MVDC breaker [C] / / 2011 IEEE Electric Ship Technologies Symposium. IEEE, 2011: 334-338," proposed a Z-source solid-state circuit breaker developed based on a Z-source converter. It can achieve typical short-circuit fault isolation that meets system parameter design requirements simply by adjusting the parameters of the circuit breaker components, without requiring external detection and control circuits. KA Corzine et al., in the paper "KA Corzine and R W Ashton, A New Z-Source DC Circuit Breaker [J]. IEEE Transactions on Power Electronics, 2012, 27(6): 2796-2804," proposed interleaved and parallel Z-source solid-state DC circuit breakers. However, the interleaved type circuit breaker has the problem of the power supply and load not sharing a common ground, while the parallel type has the problem of a large fault current. Arthur H. Chang et al. proposed a series-type Z-source circuit breaker in “CHANG AH, SENNETT BR, AVESTRUZ AT, et al. Analysis and design of DC system protection using Z-source circuit breaker[J].IEEE Transactions on Power Electronics, 2015, 31(2):1036-1049.”, which solved the problems of the two circuit breakers mentioned above, but still generated reflected current to the power supply during short circuits. To address this, Li Weilin et al. proposed a solid-state circuit breaker based on coupled inductors in “LI W, WANG Y, WU X, et al. A novel solid-state circuit breaker for on-board DC microgrid system[J].IEEE Transactions on Industrial Electronics, 2018, 66(7):5715-5723.”, which has the advantages of supporting common ground for power supply and load, no reflected current to the power supply, and avoiding false triggering caused by load changes.

[0005] In practical applications, circuit breakers are typically connected in series between the converter and the load. However, passive components in the converter may oscillate with passive components in the circuit breaker, reducing the output power quality. To address this, Xiaoguang Diao et al. proposed a DC-DC converter with integrated short-circuit protection in "Diao X, Zhu W, Song Y, et al. An Integrated Design of the Solid-State Circuit Breaker and the DC-DC Converter [C] / / 2020 IEEE Applied Power Electronics Conference and Exposition (APEC). IEEE, 2020: 3419-3423.", which reduces the power loss caused by the circuit breaker. Kwen Chong et al. proposed a Buck converter with integrated short-circuit protection in "A Buck Converter with Integrated Circuit Breaker", which reduces the system size while ensuring short-circuit protection and power output quality. Yuyang Liu et al. proposed a Boost converter with integrated short-circuit protection in their paper "Liu Y, Wang Y, Ding S, et al. A Boost Converter Integrated With DC CircuitBreaker [C] / / IECON 2021–47th Annual Conference of the IEEE Industrial Electronics Society. IEEE, 2021: 1-6." This converter provides short-circuit protection and low-pass filtering without affecting the normal operation of the Boost circuit. However, research on integrating short-circuit protection in Buck-Boost converters is currently scarce. Therefore, this patent introduces a Buck-Boost converter with integrated short-circuit protection. Summary of the Invention

[0006] This invention primarily solves the problem of power quality degradation caused by series loads on circuit breakers, and also reduces the overall system size.

[0007] To address the aforementioned problems, this invention discloses a Buck-Boost converter with integrated short-circuit protection. The technical solution is as follows: The Buck-Boost converter with integrated short-circuit protection adds a discharge branch consisting of a capacitor and an inductor to the Buck-Boost circuit. The inductor in the Buck-Boost circuit is coupled to the inductor in the discharge branch, and the anode of the thyristor is connected in series with the source of the MOSFET. Specifically, the topology of a Buck-Boost converter with integrated short-circuit protection includes: a DC power supply, a MOSFET, a thyristor, a first diode, a coupling inductor module, a primary winding of the coupling inductor, a secondary winding of the coupling inductor, a first capacitor, a second capacitor, a load resistor, a first resistor, a second resistor, a second diode, and a third diode. The positive terminal of the DC power supply is connected to the drain of the MOSFET; the source of the MOSFET is connected to the anode of the thyristor; the cathode of the thyristor is connected to the cathode of the first diode, the first terminal of the first resistor, and the first terminal of the coupled inductor module; the anode of the first diode is connected to the positive terminal of the first capacitor, the positive terminal of the second capacitor, and the first terminal of the load resistor; the negative terminal of the first capacitor is connected to the second terminal of the coupled inductor module and the first terminal of the second resistor; the second terminal of the first resistor is connected to the cathode of the second diode; the anode of the second diode is connected to the third terminal of the coupled inductor module, the fourth terminal of the coupled inductor module, the anode of the third diode, the negative terminal of the DC power supply, the negative terminal of the second capacitor, and the second terminal of the load resistor; the second terminal of the second resistor is connected to the cathode of the third diode; the first resistor and the second diode constitute the energy absorption branch of the primary winding of the coupled inductor; the second resistor and the third diode constitute the energy absorption branch of the secondary winding of the coupled inductor.

[0008] To improve the performance of the Buck-Boost converter with protection functions, appropriate coupling inductor parameters need to be selected. If the turns ratio of the primary winding to the secondary winding of the coupling inductor is too large, the fault current will be insufficient to turn off the thyristor; if the turns ratio is too small, it will interfere with the normal operation of the Buck-Boost converter. Analysis of simulation and experimental results shows that a turns ratio of 16:5 for the primary winding to the secondary winding of the coupling inductor is more suitable.

[0009] The working process of the Buck-Boost converter with protection function can be divided into four steps: steady-state operation, short-circuit fault instantaneous operation, resonant operation, and energy absorption operation.

[0010] Step 1: When the system is in normal operating condition, it operates according to the Buck-Boost circuit principle. When the MOSFET is turned on, the primary winding of the coupling inductor is charged, and the voltages of the primary winding L1 and the secondary winding L2 are V respectively. L1 VL2 .

[0011]

[0012] V in V is the input voltage. C1 V is the voltage across the first capacitor. o For the output voltage, L m Let be the mutual inductance of the coupled inductors, and k be the coupling coefficient of the coupled inductors.

[0013] The voltage difference of the primary winding L1 during the conduction time is ΔV L1 .

[0014] ΔV L1 =DT s V in

[0015] D is the duty cycle, T s The switching cycle.

[0016] When the MOSFET is turned off, the primary winding L1 of the coupling inductor discharges, and the second capacitor C... L During charging, a voltage V is generated across the load resistor. o The voltages of the primary winding L1 and the secondary winding L2 are V' and V', respectively. L1 ,V' L2 .

[0017]

[0018] The voltage difference of the primary winding L1 during the turn-off time is ΔV' L1 .

[0019] ΔV' L1 =(1-D)T s V o

[0020] According to the volt-second balance principle, we can conclude that:

[0021]

[0022] When the switching frequency is very high, the current through the secondary winding branch of the coupling inductor can be ignored, and the discharge branch has no impact on the normal operating state.

[0023] Step Two: When a short-circuit fault occurs, the load current will change significantly in a short period of time. The first and second capacitors begin to discharge to provide fault current. When the fault current flows through the secondary winding of the coupling inductor, the primary winding of the coupling inductor induces a current in the opposite direction to the steady-state operating current. The induced current gradually cancels out the positive steady-state current, and the current flowing through the thyristor gradually decreases. When the thyristor current is less than 0, reaching the reverse bias condition, the thyristor turns off.

[0024] During this process, because the capacitor discharges very quickly, the induced voltage generated by the primary coil can be ignored. The reverse bias of the diode allows the load, the complex coil inductance 7, and the first capacitor 8 to be considered a passive RLC circuit. Before the fault occurred, the voltage across the first capacitor was V. o The inductor current is negligible. The RLC circuit exhibits three different behaviors depending on the selected values:

[0025] 1. When Δ = R 2 At -4L / C, it is overdamped, and the current induced in the primary coil is:

[0026]

[0027] 2. When Δ = 0, the critical damping is reached, and the current induced in the primary coil is:

[0028]

[0029] 3. When Δ < 0, it is the critical damping, and the current induced in the primary coil is:

[0030]

[0031] To successfully turn off the thyristor, the maximum value of the reverse current induced on the primary side must be greater than the average value of the thyristor current. Let the thyristor current be i. SCR ,have

[0032] i L1·max >i SCR

[0033] Step 3: After the thyristor is turned off, the first capacitor, the second capacitor, and the secondary winding of the coupled inductor form a passive resonant circuit. The system enters the passive LC resonant operating state. At this time, the first and second capacitors finish discharging, and the secondary winding of the coupled inductor begins to discharge.

[0034] Step 4: When the secondary winding of the coupled inductor begins to discharge, part of the current flows through the energy-absorbing circuit composed of the second resistor and the third diode, and part of the current charges the first capacitor; the induced current in the primary winding of the coupled inductor flows through the energy-absorbing circuit composed of the first resistor and the second diode. Repeat steps 3 and 4 until the energy in the circuit is completely consumed and the fault isolation is completed.

[0035] The advantages of this invention are:

[0036] The circuit topology incorporates a circuit breaker structure, enabling the circuit to have both energy conversion capabilities and self-protection capabilities.

[0037] This circuit topology reduces the system size by multiplexing the inductive components of the converter and the circuit breaker.

[0038] This circuit topology solves the resonance problem that may exist when the circuit breaker and converter are connected in series, and improves the output power quality. Attached Figure Description

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 This is a schematic diagram of the circuit topology of the present invention.

[0041] Figure 2 This is to simulate the voltage waveforms across the load during its entire operating phase and during a short-circuit fault.

[0042] Figure 3 This is to simulate the voltage waveforms across the thyristor during its entire operating phase and during a short-circuit fault.

[0043] Figure 4 This is to simulate the current waveform of the thyristor during the entire operating phase and under short-circuit fault conditions.

[0044] Figure 5 This is to simulate the current waveform of the primary winding of the coupled inductor during the entire operating phase and under short-circuit fault conditions.

[0045] Figure 6 This is to simulate the current waveform of the secondary winding of the coupled inductor during the entire operating phase and under short-circuit fault conditions. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0048] Figure 1 In the diagram, 1—DC power supply, 2—MOSFET, 3—thyristor, 4—first diode, 5—coupled inductor module, 6—primary winding of coupled inductor, 7—secondary winding of coupled inductor, 8—first capacitor, 9—second capacitor, 10—load resistor, 11—first resistor, 12—second resistor, 13—second diode, 14—third diode, 15, 18—connection points of thyristor cathode to first diode, first resistor, and first terminal of coupled inductor module, 16—connection point of first diode anode to first capacitor positive terminal, second capacitor positive terminal, and first terminal of load resistor, 17—connection point of first capacitor negative terminal to second terminal of coupled inductor module and first terminal of second resistor, 18—connection point of second diode anode to third diode anode, third terminal of coupled inductor module, fourth terminal of coupled inductor module, negative terminal of DC power supply, second terminal of second capacitor, and second terminal of load resistor.

[0049] A topology of a Buck-Boost converter with integrated short-circuit protection includes: a DC power supply (1), a MOSFET (2), a thyristor (3), a first diode (4), a coupled inductor module (5), a primary winding of the coupled inductor (6), a secondary winding of the coupled inductor (7), a first capacitor (8), a second capacitor (9), a load resistor (10), a first resistor (11), a second resistor (12), a second diode (13), and a third diode (14). The positive terminal of the DC power supply (1) is connected to the drain of the MOSFET (2); the source of the MOSFET (2) is connected to the anode of the thyristor (3); the cathode of the thyristor (3) is connected to the cathode of the first diode (4), the first terminal of the first resistor (11), and the first terminal of the coupling inductor module (5); the anode of the first diode (4) is connected to the positive terminal of the first capacitor (8), the positive terminal of the second capacitor (9), and the first terminal of the load resistor (10); the negative terminal of the first capacitor (8) is connected to the second terminal of the coupling inductor module (5) and the first terminal of the second resistor (12); the second terminal of the first resistor (11) is connected to the second diode. The cathode of tube (13) is connected; the anode of the second diode (13) is connected to the third terminal of the coupling inductor module (5), the fourth terminal of the coupling inductor module (5), the anode of the third diode (14), the negative terminal of the DC power supply (1), the negative terminal of the second capacitor (9), and the second terminal of the load resistor (10); the second terminal of the second resistor (12) is connected to the cathode of the third diode (14); the first resistor (11) and the second diode (13) form the energy absorption branch of the primary winding (6) of the coupling inductor; the second resistor (12) and the third diode (14) form the energy absorption branch of the secondary winding (7) of the coupling inductor.

[0050] To improve the performance of the Buck-Boost converter with protection function, appropriate coupling inductor parameters are selected. If the turns ratio of the primary winding (6) to the secondary winding (7) of the coupling inductor is too large, the fault current will be insufficient to turn off the thyristor (3); if the turns ratio of the primary winding (6) to the secondary winding (7) of the coupling inductor is too small, it will interfere with the normal operation of the Buck-Boost converter. Through simulation and experimental results analysis, it is found that a turns ratio of 16:5 for the primary winding (6) to the secondary winding (7) of the coupling inductor is more suitable.

[0051] The working process of the Buck-Boost converter with protection function can be divided into four steps: steady-state operation, short-circuit fault instantaneous operation, resonant operation, and energy absorption operation.

[0052] Step 1: When the system is in normal operating condition, it operates according to the Buck-Boost circuit principle. When the MOSFET is turned on, the primary winding of the coupling inductor is charged, and the voltages of the primary winding L1 and the secondary winding L2 are V respectively. L1 V L2 .

[0053]

[0054] V in V is the input voltage. C1 V is the voltage across the first capacitor. o For the output voltage, L m Let be the mutual inductance of the coupled inductors, and k be the coupling coefficient of the coupled inductors.

[0055] The voltage difference of the primary winding L1 during the conduction time is ΔV L1 .

[0056] ΔV L1 =DT s V in (2)

[0057] D is the duty cycle, T s The switching cycle.

[0058] When the MOSFET is turned off, the primary winding L1 of the coupling inductor discharges, and the second capacitor C... L During charging, a voltage V is generated across the load resistor. o The voltages of the primary winding L1 and the secondary winding L2 are V' and V', respectively. L1 ,V' L2 .

[0059]

[0060] The voltage difference of the primary winding L1 during the turn-off time is ΔV' L1 .

[0061] ΔV' L1 =(1-D)T s V o (4)

[0062] According to the volt-second balance principle, we can conclude that:

[0063]

[0064] When the switching frequency is very high, the current through the secondary winding branch of the coupling inductor can be ignored, and the discharge branch has no impact on the normal operating state.

[0065] Step Two: When a short-circuit fault occurs, the load current will change significantly in a short period of time. The first and second capacitors begin to discharge to provide fault current. When the fault current flows through the secondary winding of the coupling inductor, the primary winding of the coupling inductor induces a current in the opposite direction to the steady-state operating current. The induced current gradually cancels out the positive steady-state current, and the current flowing through the thyristor gradually decreases. When the thyristor current is less than 0, reaching the reverse bias condition, the thyristor turns off.

[0066] During this process, because the capacitor discharges very quickly, the induced voltage generated by the primary coil can be ignored. The reverse bias of the diode allows the load, the complex coil inductance 7, and the first capacitor 8 to be considered a passive RLC circuit. Before the fault occurred, the voltage across the first capacitor was V. o The inductor current is negligible. The RLC circuit exhibits three different behaviors depending on the selected values:

[0067] 1. When Δ = R 2 At -4L / C, it is overdamped, and the current induced in the primary coil is:

[0068]

[0069] 2. When Δ = 0, the critical damping is reached, and the current induced in the primary coil is:

[0070]

[0071] 3. When Δ < 0, it is the critical damping, and the current induced in the primary coil is:

[0072]

[0073] To successfully turn off the thyristor, the maximum value of the reverse current induced on the primary side must be greater than the average value of the thyristor current. Let the thyristor current be i. SCR ,have

[0074] i L1·max >i SCR (9)

[0075] Step 3: After the thyristor is turned off, the first capacitor, the second capacitor, and the secondary winding of the coupled inductor form a passive resonant circuit. The system enters the passive LC resonant operating state. At this time, the first and second capacitors finish discharging, and the secondary winding of the coupled inductor begins to discharge.

[0076] Step 4: When the secondary winding of the coupled inductor begins to discharge, part of the current flows through the energy-absorbing circuit composed of the second resistor and the third diode, and part of the current charges the first capacitor; the induced current in the primary winding of the coupled inductor flows through the energy-absorbing circuit composed of the first resistor and the second diode. Repeat steps 3 and 4 until the energy in the circuit is completely consumed and the fault isolation is completed.

[0077] A simulation experiment was conducted on the Simulink platform for the example. The DC power supply (1) voltage was set to 12V, the inductance of the primary winding (6) of the coupled inductor was 160μH, the inductance of the secondary winding (7) of the coupled inductor was 50μH, the first capacitor (8) was 1000μF, the second capacitor (9) was 600μF, the load resistor (10) was set to 50Ω, and the short-circuit fault resistance was 0.3Ω. The experimental waveform is shown below. Figure 2 As shown in 3, 4, 5, and 6.

[0078] In this simulation experiment, a load short-circuit fault occurred at t = 0.15s. During normal operation, the current in the first capacitor (8) is almost zero, and the discharge branch formed by the first capacitor (8) and the secondary winding (7) of the coupled inductor does not affect normal circuit operation. When a short-circuit fault occurs at the load end, the load current changes significantly in a very short time, and the second capacitor (9) discharges rapidly, with a maximum discharge current of 46A. The thyristor (3) current begins to decrease until the thyristor (3) turns off, a process that takes approximately 0.2μs. After the thyristor (3) turns off, the energy absorption circuit absorbs the remaining energy, and the fault is completely isolated in approximately 3μs. These results verify the functionality of the Buck-Boost converter with integrated short-circuit protection.

[0079] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A Buck-Boost converter with integrated short-circuit protection, characterized in that: The Buck-Boost converter with protection function adds a discharge branch consisting of a capacitor and an inductor to the Buck-Boost circuit, couples the inductor in the Buck-Boost circuit with the inductor in the discharge branch, and connects the anode of the thyristor to the source of the MOSFET in series. The Buck-Boost converter with integrated short-circuit protection includes the following topology. The topology includes: a DC power supply, a MOSFET, a thyristor, a first diode, and a coupling inductor module. The coupling inductor module includes a primary winding and a secondary winding of the coupling inductor, a first capacitor, a second capacitor, a load resistor, a first resistor, a second resistor, a second diode, and a third diode. The positive terminal of the DC power supply is connected to the drain of the MOSFET; the source of the MOSFET is connected to the anode of the thyristor; the cathode of the thyristor is connected to the cathode of the first diode, the first terminal of the first resistor, and the first terminal of the coupling inductor module; the anode of the first diode is connected to the positive terminals of the first and second capacitors. The first terminal of the load resistor is connected; the negative terminal of the first capacitor is connected to the second terminal of the coupled inductor module and the first terminal of the second resistor; the second terminal of the first resistor is connected to the cathode of the second diode; the anode of the second diode is connected to the third terminal of the coupled inductor module, the fourth terminal of the coupled inductor module, the anode of the third diode, the negative terminal of the DC power supply, the negative terminal of the second capacitor, and the second terminal of the load resistor; the second terminal of the second resistor is connected to the cathode of the third diode; the first resistor and the second diode form the energy absorption branch of the primary winding of the coupled inductor; the second resistor and the third diode form the energy absorption branch of the secondary winding of the coupled inductor.

2. A Buck-Boost converter with integrated short-circuit protection function according to claim 1, characterized in that: The turns ratio of the primary winding to the secondary winding of the coupled inductor is 16:

5.

3. A Buck-Boost converter with integrated short-circuit protection function according to claim 2, characterized in that: The working process of a Buck-Boost converter can be divided into four steps.

4. A Buck-Boost converter with integrated short-circuit protection function according to claim 3, characterized in that: Of the four steps in the described working process, step one is: When the MOSFET is turned on, the primary winding of the coupled inductor is charged, and the voltages of the primary winding L1 and the secondary winding L2 are V, respectively. L1 V L2 , V in V is the input voltage. C1 V is the voltage across the first capacitor. o For the output voltage, L m Let be the mutual inductance of the coupled inductors, and k be the coupling coefficient of the coupled inductors. The voltage difference of the primary winding L1 during the conduction time is , D is the duty cycle, T s The switching cycle.

5. A Buck-Boost converter with integrated short-circuit protection function according to claim 4, characterized in that: Of the four steps in the described working process, step one further includes, When the MOSFET is turned off, the primary winding L1 of the coupling inductor discharges, and the second capacitor C... L During charging, a voltage V is generated across the load resistor. o The voltages of the primary winding L1 and the secondary winding L2 are respectively , , The voltage difference of the primary winding L1 during the turn-off time is , According to the volt-second balance principle, we can conclude that: When the switching frequency is very high, the current through the secondary winding branch of the coupling inductor can be ignored, and the discharge branch has no impact on the normal operating state.

6. A Buck-Boost converter with integrated short-circuit protection function according to claim 5, characterized in that: Of the four steps in the described working process, step two is: When a short-circuit fault occurs, the load current will change significantly in a short period of time, and the first and second capacitors will start to discharge to provide fault current. When the fault current flows through the secondary winding of the coupled inductor, the primary winding of the coupled inductor induces a current in the opposite direction to the steady-state operating current. The induced current gradually cancels out the positive steady-state current, and the current flowing through the thyristor gradually decreases. When the thyristor current is less than 0 and the reverse bias condition is met, the thyristor turns off.

7. A Buck-Boost converter with integrated short-circuit protection function according to claim 6, characterized in that: Of the four steps in the described work process, step three is: When the thyristor is turned off, the first capacitor, the second capacitor, and the secondary winding of the coupling inductor form a passive resonant circuit. The system enters the passive LC resonant operating state. At this time, the first and second capacitors finish discharging, and the secondary winding of the coupled inductor begins to discharge.

8. A Buck-Boost converter with integrated short-circuit protection function according to claim 7, characterized in that: Of the four steps in the described working process, step four is: When the secondary winding of the coupled inductor begins to discharge, part of the current flows through the energy-absorbing circuit composed of the second resistor and the third diode, and part of the current charges the first capacitor. The induced current in the primary winding of the coupled inductor flows through the energy-absorbing circuit composed of the first resistor and the second diode. Steps three and four are repeated until the energy in the circuit is completely consumed and the fault isolation is completed.

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