40results about How to "Simple topology" patented technology

The invention discloses a single-stage bidirectional DC converter and a single-phase household storage inverter based on the single-stage bidirectional DC converter, the single-stage bidirectional DC converter is used for bidirectional charging and discharging of a battery and energy storage of household users, a DC bus side of the single-stage bidirectional DC converter is connected between a photovoltaic MPPT and the inverter or connected with other loads, a low-voltage side of the single-stage bidirectional DC converter is connected with the battery, and the single-phase household storage inverter is connected with the single-stage bidirectional DC converter. The topological structure of the single-stage bidirectional DC converter is simple, the number of components is small, and the equipment cost is reduced. The high-voltage side of the single-stage bidirectional DC converter can be connected in series with a single-phase inverter circuit, a half-bridge inverter circuit, a three-phase inverter circuit, a three-phase three-level inverter circuit or a split-phase inverter circuit, the neutral-point voltage can be balanced, the output bus voltage is stable, and the application scene of the household storage inverter is expanded.

The invention provides a current excitation system for battery impedance spectroscopy measurement and a control method thereof.The current excitation system comprises a power conversion circuit and a control circuit, the power conversion circuit is connected to the two ends of a battery system in parallel, and the control circuit is connected with the power conversion circuit; the control circuit is used for acquiring a closed-loop sampling signal monitored from the power conversion circuit, and then generating a feedback control signal for controlling the power conversion circuit through a PID (Proportion Integration Differentiation) double-loop indirect control method based on the closed-loop sampling signal and the initial control signal; the power conversion circuit generates an excitation current required for battery impedance spectroscopy measurement based on the feedback control signal. The excitation current is generated by power supply of the battery system, a large amount of electric energy does not need to be consumed from the battery, and the overall implementation cost is effectively reduced through the novel circuit structure and the logic control process capable of saving computing power. According to the invention, the technical effects of simplifying the circuit topological structure and realizing low-power-consumption current excitation are achieved.

The invention discloses a bidirectional CLLC resonant converter and a control method thereof, which are used for solving the technical problem that the topological structure is too complicated due to the existing bidirectional CLLC resonant converter. The circuit comprises a primary side full-bridge circuit, a primary side resonance network, a secondary side resonance network, a secondary side full-bridge circuit, a primary side direct current source, a primary side filter capacitor, a secondary side direct current source and a secondary side filter capacitor. The primary side direct current source, the primary side filter capacitor and the primary side full-bridge circuit are connected in parallel; the primary side full-bridge circuit is electrically connected with one end of the primary side resonance network, and the other end of the primary side resonance network is coupled with one end of the secondary side resonance network; the other end of the secondary side resonance network is connected with the secondary side full-bridge circuit; and the secondary DC source, the secondary filter capacitor and the secondary full-bridge circuit are connected in parallel.

This invention discloses a voltage source static frequency converter system for pumped hydro storage and its grid-connected control method. The system includes an input reactor, a phase-shifting transformer, a high-voltage frequency converter, an output reactor, a grid-connection switch, an output switch, a signal acquisition unit, and a control unit. The input terminal of the phase-shifting transformer is connected to the power grid through the input reactor, and its output terminal is connected to the input terminal of the high-voltage frequency converter. The output terminal of the high-voltage frequency converter is connected to a motor through the output reactor. The output switch is located between the output reactor and the motor. The grid-connection switch is located between the motor and the power grid. The signal acquisition unit is used to acquire the three-phase voltage and current signals at the input terminal of the phase-shifting transformer, and the output voltage and current signals at the output side of the high-voltage frequency converter. The control unit is connected to the signal acquisition unit and is used to perform grid-connected control based on the signals acquired by the signal acquisition unit. This invention has advantages such as low cost and no motor idling during grid connection.

The application discloses a Marx high-voltage pulse power supply based on a high-gain boost type DC-DC converter, and the circuit is composed of an input DC power supply, two power switching tubes, a switching inductor and a cascaded Marx generator; the cascaded Marx generator can be expanded to n levels, and can be used in application occasions requiring high-voltage pulse power supplies, such as cancer treatment in medical treatment, water treatment, waste gas treatment, sterilization, electron and ion beam generation and acceleration, electrostatic dust removal and the like. Under the same working condition, the Marx high-voltage pulse power supply can realize high-gain pulses, and compared with the existing Marx high-voltage pulse power supply, can realize lower switching power loss and higher voltage gain. Meanwhile, the Marx high-voltage pulse power supply also has the advantages of simple topological structure, few modules, few electronic devices and low cost. Therefore, the Marx high-voltage pulse power supply has important economic value and practical engineering significance.

The invention discloses a small-size high-efficiency large-current lithium battery active equalization circuit and a control method thereof, the small-size high-efficiency large-current lithium battery active equalization circuit comprises active equalization modules which are connected in parallel between two connected battery cells, and each active equalization module is composed of four switching tubes and a group of resonance branch circuit which is formed by connecting an inductor and a capacitor in series; n-1 active equalization modules are needed for a battery pack composed of N battery cells. The LC series branch serves as an energy temporary storage unit to replace a traditional inductance type single inductor or capacitance type multiple capacitors, the number of elements is reduced, meanwhile, low-loss energy transfer is achieved through resonance characteristics, and the equalization scheme has the advantages of being small in size, large in equalization current, small in equalization energy loss between battery cells, high in efficiency and the like.

The application provides a charger assembly, a vehicle charging method and a vehicle, and belongs to the technical field of automobiles. The core is that the on-off execution unit of the main circuit, namely, the positive electrode relay and the negative electrode relay, is accommodated and integrated in the vehicle-mounted charger assembly. On the physical connection, the passage from the battery positive electrode to the positive electrode of the charging pile through the positive electrode relay and the passage from the battery negative electrode to the negative electrode of the charging pile through the negative electrode relay are formed, so that the charging control logic is internalized in the charger assembly. Since the relays are no longer scattered in the battery or the external distribution box, but are uniformly designed and packaged as internal components of the charger assembly, the development of the external distribution box and the complex wire harness is avoided at the physical level, the number of external connectors and wire harnesses is reduced, the topology of the whole vehicle is effectively simplified, the development cycle of the whole vehicle is shortened, and the hardware cost of the whole vehicle is reduced.

The invention discloses a cloth posture determination method, device and equipment and a readable storage medium, and belongs to the technical field of cloth simulation. The method comprises the steps that a two-dimensional plane where a cloth model in a flattened state is located is evenly divided, and background grids are obtained; obtaining first motion information of each grid vertex in the background grid; acquiring an elastic energy function of the background grid; constructing a to-be-solved target function based on the elastic energy function of the background grid and the first motion information of each grid vertex; solving the objective function to obtain second motion information of each grid vertex; and determining first attitude information of the cloth model based on the second motion information of each grid vertex. The motion of the cloth model is simulated through the background grid, and the topological structure of the background grid is simple, so that the efficiency of calculating the second motion information of the grid vertex can be accelerated, the attitude of the cloth model can be quickly determined, and the real-time performance is ensured.

The application relates to an intensive transient disturbance regulation circuit, which comprises a three-phase bridge arm unit, a common DC side unit and a zero sequence bridge arm unit; the three-phase bridge arm unit is connected with each phase power supply branch of a three-phase power grid, a common neutral end of the common DC side unit and an input end of the zero sequence bridge arm unit, and an output end of the zero sequence bridge arm unit is grounded; the zero sequence bridge arm unit is used for generating a first current for offsetting a fault zero sequence component based on a power grid voltage, a power grid current and a common neutral end voltage of the three-phase power grid; the three-phase bridge arm unit is used for determining a three-phase reactive compensation current based on the common neutral end voltage and the first current input by the zero sequence bridge arm unit, and sending the three-phase reactive compensation current to a corresponding phase distribution line of the three-phase power grid; and the common DC side unit is used for providing common DC voltage support for the three-phase bridge arm unit and the zero sequence bridge arm unit. The zero sequence disturbance of the distribution network can be inhibited, and the voltage deviation and power fluctuation problems caused by the power grid transient disturbance can be weakened.

The present invention relates to a method, system, device and medium for detecting residual current of a low-voltage AC cable for a station. The method comprises: arranging a topological structure including a host and a plurality of slaves in a low-voltage AC power supply system; the host is used to collect electrical parameter information of the low-voltage AC cable, and the slave is used to collect residual current measurement values ​​of each circuit in the system; the host and the slave perform data synchronous acquisition through a working mode of switching between asynchronous and synchronous modes; and based on the synchronous data sets collected by the host and the slave, perform residual current vector synthesis calculation based on a phase angle reference system of two sections of low-voltage AC cables. Compared with the traditional method, the present invention does not increase other external hardware costs, has no auxiliary components and cables, reuses existing communication lines, and realizes high-precision synchronous acquisition through asynchronous and synchronous mode switching. The present invention adopts a residual current vector synthesis calculation method based on a phase angle reference system of two sections of low-voltage AC cables, which can avoid calculation errors between different coordinate systems.

A kind of high gain magnetic integrated DC-DC converter for photovoltaic power generation system, it is characterized in that, including CDDC unit, the CDDC unit is connected with power supply V IN Connection, the CDDC unit is connected with magnetic integrated inductance unit, the magnetic integrated inductance unit is connected with fast recovery diode D3, the fast recovery diode D3 is connected with power switch tube Q1, the magnetic integrated inductance unit is connected with fast recovery diode D4, the fast recovery diode D4 is connected with output filter capacitor C3, EE magnetic core upper portion is arranged in the magnetic integrated inductance unit, EE magnetic core lower portion is arranged in the magnetic integrated inductance unit, topology structure is simple, device is less, control is convenient, especially modular design is carried out, the CDDC unit is introduced, so that system obtains higher gain, while the magnetic integrated inductance unit introduced improves the power density of converter, the application helps to promote the performance improvement of high gain magnetic integrated DC-DC converter for photovoltaic power generation system.

The invention belongs to the technical field of electronic equipment, and discloses a diode driving circuit and a control method thereof, and the diode driving circuit comprises an inductor, a switching tube S1, a switching tube S2, a laser diode assembly, an input capacitor, a voltage stabilizing capacitor, a diode D1, a diode D2, a control module 1 and a control module 2. One end of the input capacitor is connected with one end of the inductor and connected with the anode of the diode D1, the other end of the input capacitor is connected to GND, the other end of the inductor is connected with the drain electrode of the switching tube S1 and the anode of the diode D2, and the cathode of the diode D1 is connected with the anode of the laser diode assembly and the cathode of the diode D2. The cathode of the laser diode assembly is connected with the drain electrode of the switch tube S2, one end of the voltage stabilizing capacitor is connected with the anode of the diode D1, and the other end of the voltage stabilizing capacitor is connected with the cathode of the diode D1. According to the invention, the voltage withstanding value of the voltage stabilizing capacitor is effectively reduced while the high frequency, quick response and large current change rate performance of the pulse laser driver are met.

The application relates to the technical field of pre-charging circuits, and discloses a pre-charging circuit and a charging method, wherein the pre-charging circuit comprises a switching unit, a constant-current generating unit and a comparison control unit; the switching unit comprises an input end, an output end and a control end; the constant-current generating unit is connected in parallel with the input end and the output end, and generates a pre-charging current which is constant in size and is input to the output end when the input end and the output end are disconnected; the comparison control unit generates a control signal which is input to the control end based on the voltage difference between the input end and the output end; when in use, when initially powered on, the application provides the output end of the switching unit with a constant pre-charging current through the constant-current generating unit, guarantees that the current is constant and does not attenuate during the pre-charging process, can shorten the pre-charging time and inhibit the impact current in the initial power-on period, and protects the switching unit and the battery pack; and by adjusting the size of the pre-charging current output by the constant-current generating unit, the bus capacitor with different capacitances and the battery with different voltage grades can be adapted, and the generality is high.

The invention discloses a motor locked-rotor protection driving circuit, which relates to the field of motor locked-rotor protection, and is characterized in that a first thermosensitive detection unit and a second thermosensitive detection unit are respectively connected between two output ends of a motor and a corresponding power switch unit in series; and the control module automatically pulls down the control end of the connected power switch unit to be below a cut-off threshold value during stalling, so that a corresponding current path is cut off, and automatic stalling protection is realized. Although the scheme is realized on the basis of discrete electronic elements, a current sampling resistor, a voltage comparator and a latch logic circuit which are necessary in a traditional discrete scheme are omitted through a thermal-electric direct linkage mechanism, and self-triggering protection can be completed only through few devices such as a thermistor, a bipolar transistor and a bias resistor; according to the invention, customization limitation of a special driving chip is avoided, defects of large size, high cost and low reliability of a traditional discrete circuit are overcome, a topological structure is obviously simplified, and system cost, size and failure rate are reduced.

The present invention discloses a DC converter topology with output voltage regulation capability, which belongs to the technical field of DC-DC converter topology, and includes two transmission paths for transferring energy from an input port to an output port. The main channel is an LLC resonant converter, which operates at a fixed switching frequency and transfers most of the input energy to a load. The auxiliary channel includes two stages, the first stage uses a small LLC resonant converter to achieve efficient isolation conversion, and then a non-isolated PWM DC converter is cascaded therewith, and the output voltage is adjusted by adjusting the PWM DC converter. The main channel and the auxiliary channel are connected in parallel at the input port and in series at the output port. The present invention simplifies the control strategy and synchronous rectification logic, and most of the input energy is transferred to the load by a single-stage main channel, which significantly reduces energy loss. Therefore, the proposed converter topology achieves high efficiency and high power density.

This invention discloses a broadband impedance measurement device for high-voltage systems and a voltage regulation method for its sub-modules. Each sub-module of the device consists of a cascaded H-bridge and a floating DC / DC converter connected in series on the DC side. One end of the cascaded H-bridge is connected to the current of each phase of the high-voltage system, and the AC side of the cascaded H-bridges in each sub-module is cascaded. The other end of the cascaded H-bridge is connected to the floating DC / DC converter. One end of the floating DC / DC converter is connected to the cascaded H-bridge, and the other end is floating. The device of this invention controls the energy balance on the bus capacitor of the cascaded H-bridge connected to the DC / DC converter in real time, so that the DC bus voltage remains stable when implementing current injection functions at different frequencies, thereby improving the impedance measurement effect. Through three-phase active and reactive power control, the energy loss on the floating side of the high-frequency DC / DC converter is compensated, a certain voltage range is maintained, and the voltage regulation and balance control effect between phases within the sub-module is improved.

An isolated bipolar output self-voltage balancing DC-DC converter, the converter comprising a forward converter, a bipolar voltage balancing unit; the forward converter comprises a DC input source u in , a power switch S1, a reset inductor L p1 , a transformer T, a reset diode D p1 , a rectifier diode D1, a freewheeling diode D2, an inductor L 1, an output capacitor C 1; the bipolar voltage balancing unit comprises a rectifier diode D3, a freewheeling diode D4, an inductor L 2, an inductor L 3, an output capacitor C 2, a voltage balancing capacitor C p The application can effectively reduce the voltage imbalance problem caused by cross regulation ratio of the traditional forward converter in bipolar output, reduce voltage deviation, and the circuit control is simple, the automatic voltage balancing of the bipolar output is realized through the bipolar voltage balancing unit, without complex sampling and control algorithm, the control system design and implementation difficulty is low, and the application is suitable for the occasions requiring bipolar voltage power supply.

The invention discloses a dual-frequency flyback converter with high dynamic response. The dual-frequency flyback converter comprises a basic flyback converter, a synchronous Buck converter and a diode D2, the basic flyback converter comprises a direct current input source uin, a power switch S1, an excitation inductor Lm, a leakage inductor Lk, a transformer T, a rectifier diode D1 and an output capacitor Co; the synchronous Buck converter comprises an auxiliary capacitor Cvt, a power switch S2, a power switch S3 and an inductor Lvt. The circuit is simple in structure, a traditional flyback converter and the synchronous Buck converter are reasonably connected through the diode D2, the leakage inductance energy utilization rate of the flyback converter is effectively improved, the dynamic response performance of the traditional flyback converter can be effectively improved on the occasion with high output precision, and the reliability of the flyback converter is improved. The overshoot and the adjustment time of the voltage when the load changes are greatly reduced, and the stability of the system is improved.

The application discloses a kind of long and narrow channel-oriented wireless access device and method, device includes a plurality of sequentially connected access point units, access point unit includes: directional antenna, for realizing the signal coverage of specified channel area;Photoelectric converter group, for completing the photoelectric / electro-optical conversion of serial signal;Environment sensor, for monitoring the environment in channel;Central processing unit, for receiving, processing and forwarding data;External interface, for the connection of host computer and central processing unit, realizes data transceiving;Access point unit is connected by photoelectric converter group each other.The long and narrow channel of the application is split into multiple sections, each long and narrow channel is covered by directional antenna on wireless access device, and wireless access device is connected by optical fiber, supports multiple connection modes, designs special network configuration frame, solves the problem that existing wireless router or base station is high in cost and poor in reliability in long and narrow channel environment.

The invention provides a power supply circuit of an LED projector. The power supply circuit comprises a first peripheral circuit, a second peripheral circuit, an isolation transformer and a control circuit, the first end of the control circuit is connected with the first end of the first peripheral circuit, the second end of the control circuit is connected with the first end of the second peripheral circuit, the third end of the control circuit is connected with the LED, the second end of the first peripheral circuit is connected with the second end of the second peripheral circuit through the isolation transformer, and the third end of the second peripheral circuit is connected with the LED; the control circuit is used for outputting a constant-voltage power supply and a constant-current power supply to the first peripheral circuit and the second peripheral circuit. Compared with the prior art, the power supply has the advantages that the topology is simple, the cost is low, the decisive advantage on equipment miniaturization is achieved, the volt-ampere characteristic of an LED light source and the voltage coupling characteristic of a transformer winding are utilized, constant voltage and constant current output can be achieved only through one control chip, and the production cost is reduced by simplifying the power supply topology structure.

This utility model discloses a clamping absorption circuit and a DC power supply system. The clamping absorption circuit includes a boost switch K1, a buck switch K2, a first clamping absorption branch, and a second clamping absorption branch. The first clamping absorption branch includes a first diode D1, a first capacitor C1, and a first resistor R1. The first diode D1 and the first capacitor C1 are connected in series and then in parallel with the boost switch K1, forming a first node between the first diode D1 and the first capacitor C1. The first resistor R1 is connected between the first node and the positive bus. The second clamping absorption branch includes a second diode D2, a second capacitor C2, and a second resistor R2. The second diode D2 and the second capacitor C2 are connected in series and then in parallel with the buck switch K2, forming a second node between the second diode D2 and the second capacitor C2. The second resistor R2 is connected between the second node and the negative bus.

The invention discloses an all-digital phased array active silencing loudspeaker system based on storage bus multiplexing, which comprises a network digital audio acquisition module, a central processing control module, a signal distribution module and a driving array module, the network digital audio acquisition module is used for receiving a digital audio data packet from the Ethernet, performing protocol unpacking and data buffering on the digital audio data packet, recovering a high-precision global master clock signal and a frame synchronization signal from a network data stream to form a serial digital audio signal, and transmitting the serial digital audio signal to the central processing control module; the central processing control module processes the audio data to obtain a high-speed parallel bus data stream; the signal distribution module is used for receiving a high-speed parallel bus data stream and expanding the high-speed parallel bus data stream into a multi-partition array control signal; and the driving array module is used for receiving the pulse control signal and carrying out chopping modulation on the high-voltage direct-current bus through a GaN power device. According to the invention, the hardware topology is simplified, the silencing effect is optimized, and the sound wave superposition is more accurate.

The present invention relates to a high-power broadband nonlinear transmission line comb generator chip. The comb generator chip is composed of 40 levels of nonlinear transmission line units in periodic cascade, wherein each nonlinear transmission line unit is composed of a high-resistance microstrip line and three base-emitter short-circuited transistors. A certain degree of waveform compression can be achieved after the radio frequency signal passes through each level of nonlinear transmission unit. After passing through a certain number of nonlinear transmission units, a DC-100GHz series of harmonic pulse signals can be obtained at the chip output port, and then the required harmonic components in the solitary wave can be filtered out through a frequency selection network to realize a high-order frequency multiplication function. The present invention has a wide operating frequency, and reduces the energy reflection of harmonics by bending and folding the routing, thereby achieving higher harmonic power output and smaller chip size, filling the gap in domestic high-order frequency multiplication comb generator chips.

The utility model provides a sensor testboard based on Ethernet control. The sensor testboard comprises an Ethernet network, a motor servo system, a channel switching system, an upper computer and a sensor, the channel switching system comprises a power supply and a signal interface, and the sensor is in electrical signal connection with the channel switching system through the power supply and the signal interface; the sensor is in signal connection with the upper computer; the topology architecture of the Ethernet network is a bus type topology architecture, and the motor servo system, the channel switching system and the upper computer are respectively in signal connection with the Ethernet network. The sensor testboard based on Ethernet control is simple and reasonable in structure, strong in adaptability, simple in topology, easy to maintain, high in subsystem integration, fast in test response speed, high in test efficiency, high in system stability, high in maintainability and expansibility, capable of being carried at a high speed and supporting remote test, and suitable for popularization and application. The requirements of an axle detection system can be met, and the rail transit detection control efficiency is effectively improved.

This utility model discloses an optocoupler-based isolated sampling circuit. The input terminal is connected to the target AC / DC circuit, and the output terminal is connected to an HDD (High-Speed ​​ADC). It includes resistors R1-R9, capacitors C1-C2, operational amplifier U1, and two optocouplers. The target circuit is connected to the positive input terminal of U1 via R1, grounded via parallel connection C2 and R2, and its common terminal is connected to the HDD via R9. The negative input terminal of U1 is connected to R3 and the output terminal 3 of U2. The control terminal 1 of U2 is connected to the output of U1 via R4, and the control terminal 2 is connected to the control terminal 1 of U3. The control terminal 2 of U3 is grounded. The input terminals 4 of the two optocouplers are connected to the drive power supply via R5 and R6 respectively. The output terminal 3 of U3 is connected to R8, R7, and C1 in parallel. Its topology is simple, it is compatible with both AC and DC circuits, has low cost, good dynamic response, strong anti-interference, reliable isolation, and high sampling accuracy.

This invention discloses an equivalent aggregation method applicable to networks containing new energy sources. The method preprocesses the network topology and parameter information of the network containing new energy sources. When the short-circuit current of the network containing new energy sources is a linear function of voltage, the influence of the acquired topology parameters on the short-circuit current is analyzed, and an equivalent aggregation model of the network containing new energy sources is established. Based on the type of new energy source and combined with a practical expression for the actual short-circuit current of the new energy source, the corresponding equivalent aggregation model is obtained. This method establishes an equivalent aggregation model of the network containing new energy sources based on the influence of new energy sources and network topology parameters on the short-circuit current, simplifying the network topology and reducing new energy coupling nodes. It avoids the problems of long computation time and non-convergence caused by iterative calculation of the entire new energy network and excessive network dimensions.

The utility model discloses an off-grid green electricity hydrogen production micro-grid regulation and control system which comprises a photovoltaic power generation unit, energy storage units, a standby energy supply unit, a power supply and distribution tandem execution unit, a hydrogen production system and an upper energy management unit. And the power of the photovoltaic module is transmitted to the power supply and distribution tandem execution unit through the inverter for power supply and distribution. In order to ensure that the two groups of energy storage devices supply energy uninterruptedly and stably in the switching process, an additional standby energy supply unit is added. The hydrogen production system is used as a terminal device of photovoltaic power generation local consumption, can adjust the imbalance of hydrogen production instantaneous power through the energy storage unit, and reduces the influence of power generation volatility; the upper energy management unit mainly carries out overall coordination on all the subunits, through reasonable distribution and scheduling of energy, the influence of randomness and volatility of renewable energy on a hydrogen production system is reduced, hydrogen production continuity and hydrogen production efficiency are maintained, and maximum absorption is achieved.

The present invention discloses a power data acquisition method, system, readable storage medium and program product, which relates to the field of computer application technology, including: controlling a microcontroller and a baseboard management controller to enter a power-on sequence by powering on a server; when the microcontroller is started, the microcontroller is used to acquire current power data; after the baseboard management controller is started, the baseboard management controller is used to acquire current power data from the microcontroller through a first data acquisition channel; when the input-output system in the server is in the startup process, the input-output system is used to acquire current power data from the microcontroller through a second data acquisition channel. The power data acquisition method provided by the present invention avoids the problem of occupying physical pins, simplifies the topological structure, and realizes the timely acquisition of hot-swap information of the power supply.

The present invention discloses a single-ended forward converter fault diagnosis method based on output voltage differential value. The method is based on the single-ended forward converter, including a switch device and a magnetic reset circuit on the primary side and an output rectifier diode D1, a freewheeling diode D2, an inductor and a capacitor on the secondary side. The method includes the following steps: obtaining the relationship between the output voltage and the duty cycle according to a small signal model corresponding to the single-ended forward converter, and calculating the differential value of the output voltage; judging the open-short circuit fault of the switch device and / or the open-short circuit fault of the capacitor according to the differential value; and also calculating the second-order differential value of the output voltage, and judging the open-short circuit fault of the freewheeling diode according to the second-order differential value.