Buck power factor correction circuit and power supply
By integrating rectification and buck functions into one, the Buck power factor correction circuit solves the problems of complex circuit topology and low efficiency in the prior art, and realizes circuit simplification and efficient power conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-13
AI Technical Summary
In existing power systems, the two-stage design of AC rectification and step-down circuits results in complex circuit topology, low integration, and low power conversion efficiency.
The rectification and buck functions are integrated into one unit. A Buck power factor correction circuit is used. The rectification and buck processing of electrical energy are achieved through H-bridge circuit, inductor, capacitor and controller. The controller controls the rectification and stopping of rectification of H-bridge circuit under different voltage conditions. The switching transistor of Buck circuit reuses the switching transistor of H-bridge circuit.
It simplifies the circuit topology, improves the circuit integration and power conversion efficiency, reduces hardware costs, and enhances power conversion efficiency.
Smart Images
Figure CN121663975A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, specifically to a Buck power factor correction circuit and a power supply. Background Technology
[0002] In power systems, in certain scenarios, AC power needs to be rectified and stepped down before being supplied to the load. Generally, rectification is performed first, followed by step-down, which involves two stages of circuits connected in series: a rectifier circuit and a step-down circuit. This architecture not only results in a complex circuit topology and low integration, but also relatively low power conversion efficiency. Summary of the Invention
[0003] In view of this, this application provides a Buck power factor correction circuit and power supply that integrates rectification and step-down functions to achieve rectification and step-down processing of electrical energy. The circuit topology is simple, the integration is high, and the power conversion efficiency is improved.
[0004] To solve the above problems, the technical solution provided in this application is as follows:
[0005] This application provides a Buck power factor correction circuit, including: an H-bridge circuit, an inductor, a capacitor, and a controller; the midpoint of the first arm of the H-bridge circuit is used to connect to the positive terminal of an AC source, and the midpoint of the second arm of the H-bridge circuit is used to connect to the negative terminal of the AC source; the first end of the inductor is connected to the first end of the first arm and the first end of the second arm; the first end of the capacitor is connected to the second end of the inductor; the second end of the capacitor is connected to the second end of the first arm and the second end of the second arm; the controller is used to control the H-bridge circuit to perform rectification when the absolute value of the voltage of the AC source is greater than the voltage of the capacitor, and to control the H-bridge circuit to stop rectification when the absolute value of the voltage of the AC source is less than or equal to the voltage of the capacitor.
[0006] In one possible implementation, the first bridge arm includes a first upper transistor and a first lower transistor, and the second bridge arm includes a second upper transistor and a second lower transistor; the controller is configured to control both the first upper transistor and the second lower transistor to be turned on and to control both the first lower transistor and the second upper transistor to be turned off when the voltage of the AC source is greater than the voltage of the capacitor during the positive half-cycle of the AC source; and to control the first upper transistor to be turned off and the second upper transistor and the second lower transistor to be turned on when the pulse width timing time of one cycle is reached.
[0007] In one possible implementation, the controller is configured to control the first lower transistor and the second upper transistor to conduct when the absolute value of the voltage of the AC source is greater than the voltage of the capacitor during the negative half-cycle of the AC source; and to control the second upper transistor to turn off and control both the first upper transistor and the first lower transistor to conduct when the pulse width timing time of one cycle is reached.
[0008] One possible implementation is that the body diodes of the first upper transistor and the first lower transistor have opposite conduction directions; the body diodes of the second upper transistor and the second lower transistor have opposite conduction directions.
[0009] In one possible implementation, the first upper transistor includes a first switch and a second switch connected in series; the first switch and the second switch are connected top to top; the second upper transistor includes a third switch and a fourth switch connected in series, the third switch and the fourth switch are connected top to top.
[0010] One possible implementation further includes: a fifth switching transistor; the first end of the fifth switching transistor is connected to the first end of the inductor, and the second end of the fifth switching transistor is connected to the second end of the second bridge arm; the controller is further configured to control the fifth switching transistor to conduct when the inductor is freewheeling.
[0011] In one possible implementation, the controller is used to control all the switches in the H-bridge to turn off, or to control the upper switches of two arms of the H-bridge to turn off, so that the H-bridge circuit stops rectification.
[0012] In one possible implementation, the controller is further configured to obtain an AC current reference value based on the voltage of the capacitor and the instantaneous voltage of the AC source, and control the AC input current based on the AC current reference value.
[0013] In one possible implementation, the controller is configured to perform PI regulation on the voltage of the capacitor to obtain a voltage reference value, multiply the voltage reference value by the instantaneous voltage of the AC source, and divide the product by the square of the effective voltage value of the AC source to obtain the AC current reference value.
[0014] This application also provides a power supply including the Buck power factor correction circuit described in any of the above implementations.
[0015] The Buck power factor correction circuit provided in this application includes an H-bridge circuit, an inductor, a capacitor, and a controller. The controller is used to control the H-bridge circuit to rectify when the absolute value of the AC source voltage is greater than the capacitor voltage, and to control the H-bridge circuit to stop rectifying when the absolute value of the AC source voltage is less than or equal to the capacitor voltage. In this application embodiment, the switching transistor of the Buck circuit reuses the switching transistor in the H-bridge circuit. Therefore, the solution provided in this application embodiment is not a simple two-stage circuit connected in series. It has high circuit integration and improves power conversion efficiency. Attached Figure Description
[0016] Figure 1A schematic diagram of a first type of Buck power factor correction circuit provided in an embodiment of this application;
[0017] Figure 2a A signal waveform diagram before rectification is provided in an embodiment of this application;
[0018] Figure 2b The figure is a waveform diagram of a rectified signal provided in an embodiment of this application;
[0019] Figure 3 A schematic diagram of a second type of Buck power factor correction circuit provided in an embodiment of this application;
[0020] Figure 4 A schematic diagram of a third type of Buck power factor correction circuit provided in an embodiment of this application;
[0021] Figure 5 A schematic diagram of a fourth Buck power factor correction circuit provided in an embodiment of this application;
[0022] Figure 6 This is a schematic diagram of a fifth Buck power factor correction circuit provided in an embodiment of this application. Detailed Implementation
[0023] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0024] See Figure 1 The figure is a schematic diagram of a Buck power factor correction circuit provided in an embodiment of this application.
[0025] The Buck power factor correction (PFC) circuit provided in this application includes an H-bridge circuit 100, an inductor L, a capacitor C, and a controller 200.
[0026] This application does not specifically limit the type of controller 200. It can be specifically set according to the actual application needs. For example, it may include a microcontroller unit (MCU), a digital signal processor (DSP), a digital signal controller (DSC), a field-programmable gate array (FPGA), or other application-specific integrated circuits (ASICs).
[0027] The midpoint of the first arm 10 of the H-bridge circuit 100 is used to connect to the positive terminal of the AC source, and the voltage of the positive terminal of the AC source is denoted by VacL. The midpoint of the second arm 20 of the H-bridge circuit is used to connect to the negative terminal of the AC source, and the voltage of the negative terminal of the AC source is denoted by VacN.
[0028] The embodiments of this application do not specifically limit the type of AC power output by the AC source. For example, it may include single-phase AC power and multi-phase AC power. The following description takes the output of single-phase AC power as an example.
[0029] The first end of the inductor L is connected to the first end of the first bridge arm 10 and the first end of the second bridge arm 20. The first end of the capacitor C is connected to the second end of the inductor L, and the second end of the capacitor C is connected to the second end of the first bridge arm 10 and the second end of the second bridge arm 20.
[0030] The Buck-type PFC circuit provided in this application reuses the switching transistor (not shown in the figure) of the Buck circuit in the H-bridge circuit 100, integrating the rectification function and the step-down function into one, simplifying the circuit topology, improving the integration degree, and improving the power conversion efficiency.
[0031] The controller 200 is used to collect the voltage of the AC source and the voltage of the capacitor C, and to control the H-bridge circuit 100 to perform rectification when the absolute value of the AC source voltage is greater than the voltage of the capacitor C.
[0032] Since the buck circuit requires the output voltage to be lower than the input voltage, the controller 200 is also used to control the H-bridge circuit 100 to stop rectification when the absolute value of the AC source voltage is less than or equal to the voltage of capacitor C.
[0033] For ease of understanding, the operating time of the Buck-type PFC circuit provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0034] See Figure 2a The figure is a signal waveform diagram before rectification provided in an embodiment of this application.
[0035] This application uses an example where the effective value of the single-phase AC power output from the AC source is 220Vac, corresponding to a peak voltage of 311V. The curve in the figure represents the AC source input voltage signal, and the straight line represents the 220V DC signal.
[0036] See Figure 2b The figure is a waveform diagram of a rectified signal provided in an embodiment of this application.
[0037] The curve in the figure represents the AC input signal after rectification by the H-bridge circuit, which is the input signal of the inductor in the Buck-type PFC circuit.
[0038] Since the Buck-type PFC circuit provided in this embodiment is a step-down PFC circuit, and step-down Buck circuits require the output voltage to be lower than the input voltage, one possible implementation is that when the output voltage of the Buck circuit is lower than 220Vdc, 220 / 311 = 1 / The corresponding arcsine value is 45 degrees. When the output voltage of the Buck circuit is approximately 220Vdc, the output operating angle of the Buck-type PFC circuit is 90°. The other 90° corresponding to this 90° is suspended because the AC input voltage is lower than 220V, which is lower than the output voltage of the Buck circuit. Therefore, the lower the output voltage of the Buck circuit, the larger the output operating angle of the Buck-type PFC circuit, the higher the output power factor of the Buck-type PFC circuit, the higher the proportion of active power to total power, and the lower the reactive power and harmonic losses.
[0039] Figure 2a and Figure 2b The corresponding embodiments are for ease of understanding only and are not intended to be limiting. The Buck-type PFC circuit provided in this application is applicable to any single-phase AC input power supply.
[0040] The Buck power factor correction circuit provided in this application includes an H-bridge circuit, an inductor, a capacitor, and a controller. The controller is used to control the H-bridge circuit to rectify when the absolute value of the AC source voltage is greater than the capacitor voltage, and to control the H-bridge circuit to stop rectifying when the absolute value of the AC source voltage is less than or equal to the capacitor voltage. In this application embodiment, the switching transistor of the Buck circuit reuses the switching transistor in the H-bridge circuit. Therefore, the solution provided in this application embodiment is not a simple two-stage circuit connected in series. It has high circuit integration and improves power conversion efficiency.
[0041] The Buck-type PFC circuit provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0042] The Buck-type PFC circuit provided in this application embodiment has a first bridge arm including a first upper transistor and a first lower transistor, and a second bridge arm including a second upper transistor and a second lower transistor.
[0043] This application does not specifically limit the number of switching transistors included in the first upper transistor, the first lower transistor, the second upper transistor, and the second lower transistor. The following describes the specific implementation of these transistors. Figure 3 The following is an example of how the first upper transistor, the first lower transistor, the second upper transistor, and the second lower transistor all include a switching transistor.
[0044] See Figure 3 The figure is a schematic diagram of the second Buck power factor correction circuit provided in the embodiment of this application.
[0045] The Buck-type PFC circuit provided in this application embodiment includes a first upper transistor including a first power transistor Q1, a first lower transistor including a second power transistor Q2, a second upper transistor including a third power transistor Q3, and a second lower transistor including a fourth power transistor Q4.
[0046] This application does not specifically limit the type of switching transistor in the Buck-type PFC circuit. For example, it can be at least one of the following: an Insulated Gate Bipolar Transistor (IGBT) or a Metal Oxide Semiconductor Field-Effect Transistor (MOSFET). For ease of description and understanding, the following embodiments of this application use IGBTs as examples where the first power transistor Q1, the second power transistor Q2, the third power transistor Q3, and the fourth power transistor Q4 are all IGBTs.
[0047] The second end of the first power transistor Q1 and the first end of the second power transistor Q2 are used to connect to the positive terminal of the AC source, and the second end of the third power transistor Q3 and the first end of the fourth power transistor Q4 are used to connect to the negative terminal of the AC source.
[0048] The Buck-type PFC circuit provided in this application embodiment can reuse the switching transistor (not shown in the figure) of the Buck circuit with the first power transistor Q1 or with the third power transistor Q3. This application embodiment does not make specific limitations, as long as it can realize the reuse of the rectifier circuit and the buck circuit.
[0049] The working principle of the Buck-type PFC circuit is explained below using one cycle of an AC source as an example.
[0050] In one possible implementation, controller 200 is configured to turn on both the first power transistor Q1 and the fourth power transistor Q4, and turn off both the second power transistor Q2 and the third power transistor Q3, when VacL is greater than VacN and the voltage of the AC source is greater than the voltage of capacitor C during the positive half-cycle of the AC source. At this time, the AC current is forward-biased, and the positive AC input of the AC source is used to power the output. Controller 200 then controls the H-bridge circuit to perform rectification. Alternatively, controller 200 may be configured to turn off the first power transistor Q1 and turn on both the third power transistor Q3 and the fourth power transistor Q4 when the pulse width timing period of one cycle is reached, placing the Buck circuit in freewheeling mode.
[0051] The embodiments of this application do not specifically limit the pulse width timing time of the AC source in one cycle, and can be specifically set according to the actual application needs.
[0052] In one possible implementation, controller 200 is used to turn on the second power transistor Q2 and the third power transistor Q3 when VacL is less than VacN and the absolute value of the AC source voltage is greater than the voltage of capacitor C during the negative half-cycle of the AC source. At this time, the AC current is negatively conducted, and the negative AC input of the AC source is used to supply power to the output terminal. Controller 200 controls the H-bridge circuit to perform rectification. Controller 200 is also used to turn off the third power transistor Q3 and turn on both the first power transistor Q1 and the second power transistor Q2 when the pulse width timing time of one cycle is reached, and the Buck circuit is in freewheeling mode.
[0053] At this point, one communication cycle of the communication source is complete.
[0054] The following details the method by which controller 200 performs PFC.
[0055] The controller 200 is used to obtain the AC current reference value based on the voltage of capacitor C and the instantaneous voltage of AC source, and to control the AC input current based on the AC current reference value to realize loop operation. It can stabilize the output voltage of AC source and improve the stability of Buck type PFC circuit.
[0056] One possible implementation is that the controller 200 is used to perform PI regulation on the voltage of capacitor C to obtain a voltage reference value, multiply the voltage reference value by the instantaneous voltage of the AC source, and divide the product of the voltage reference value and the instantaneous voltage of the AC source by the square of the effective value of the AC source voltage to obtain the AC current reference value.
[0057] In one possible implementation, the Buck-type PFC circuit provided in this application embodiment, when the absolute value of the AC source voltage is less than or equal to the voltage of capacitor C, and the output voltage of the buck-type Buck circuit cannot meet the requirement of being lower than the input voltage, the controller 200 controls all the switches in the H-bridge to turn off, that is, controls the first power transistor Q1, the second power transistor Q2, the third power transistor Q3, and the fourth power transistor Q4 to turn off, or the controller 200 controls the upper transistors of two bridge arms in the H-bridge to turn off, that is, controls the first power transistor Q1 and the third power transistor Q3 to turn off, so that the H-bridge circuit stops rectification and prevents current backflow. At this time, capacitor C supplies power to the output of the Buck-type PFC circuit to maintain the output voltage of the circuit.
[0058] One possible implementation is the Buck-type PFC circuit provided in this application embodiment. The controller detects the input current of the inductor L to determine whether an overcurrent has occurred in the Buck power factor correction circuit. When an overcurrent occurs in the Buck power factor correction circuit, the controller 200 controls all the switches in the H-bridge to turn off, that is, controls the first power transistor Q1, the second power transistor Q2, the third power transistor Q3, and the fourth power transistor Q4 to turn off, so that the H-bridge circuit stops rectification. Alternatively, the controller 200 controls the upper transistors of two arms in the H-bridge to turn off, that is, controls the first power transistor Q1 and the third power transistor Q3 to turn off, so that the H-bridge circuit stops rectification, thereby achieving overcurrent protection.
[0059] See Figure 4 The figure is a schematic diagram of the third Buck power factor correction circuit provided in the embodiment of this application.
[0060] Existing PFC circuits, when performing overcurrent protection, rely on subsequent circuits or additional circuits for overcurrent protection because the body diode of the power transistor can continue to supply power to the downstream circuits after the power transistor is turned off. This results in complex circuit topologies, low integration, and increased hardware costs. Therefore, this application provides another Buck power factor correction circuit that can solve the problems of the prior art.
[0061] The Buck-type PFC circuit provided in this application embodiment has the following characteristics: the body diode T1 of the first power transistor Q1 and the body diode T2 of the second power transistor Q2 have opposite conduction directions; the body diode T3 of the third power transistor Q3 and the body diode T4 of the fourth power transistor Q4 have opposite conduction directions. In this application embodiment, when performing overcurrent protection and the controller 200 controls all switches in the H-bridge to be turned off, it can prevent the output AC of the AC source from flowing to the Buck circuit, prevent short circuit of the AC input, protect the Buck circuit, simplify the circuit topology, have high integration, and reduce hardware costs.
[0062] Furthermore, since the Buck circuit and the PFC circuit in the embodiment of this application share the same switching transistor, when performing overcurrent protection, it is only necessary to ensure that the body diodes of the first upper transistor and the first lower transistor in the H-bridge circuit have opposite conduction directions; and that the body diodes of the second upper transistor and the second lower transistor have opposite conduction directions. There is no need to consider the switching transistors outside the H-bridge circuit, and the circuit topology is simple.
[0063] For example, for ease of understanding, the figure shows a possible implementation of this application embodiment, in which the negative terminal of body diode T1 is connected to the positive terminal of body diode T2, and the negative terminal of body diode T3 is connected to the positive terminal of body diode T4.
[0064] This application also provides another implementation method that can prevent the output AC of the AC source from flowing to the Buck circuit when all the switches in the H-bridge are turned off. The following is a detailed description in conjunction with the accompanying drawings.
[0065] See Figure 5 The figure is a schematic diagram of the fourth Buck power factor correction circuit provided in the embodiments of this application.
[0066] In the Buck-type PFC circuit provided in this application embodiment, the first upper transistor includes a first switch transistor M1 and a second switch transistor M2 connected in series, with the first switch transistor M1 and the second switch transistor M2 connected to each other. The second upper transistor includes a third switch transistor M3 and a fourth switch transistor M4 connected in series, with the third switch transistor M3 and the fourth switch transistor M4 connected to each other.
[0067] When all switches in the H-bridge are turned off by the controller 200, since the first switch M1 and the second switch M2 are connected to each other, and the third switch M3 and the fourth switch M4 are connected to each other, the Buck-type PFC circuit provided in this application embodiment can prevent the output current of the H-bridge from flowing to the Buck circuit, prevent short circuit of AC input, and protect the Buck circuit.
[0068] The embodiments of this application do not specifically limit the number of switching transistors included in the first lower transistor and the second lower transistor, nor do they specifically limit the specific settings of the body diode of the switching transistor in the first lower transistor and the body diode of the switching transistor in the second lower transistor. The settings can be made according to the actual application needs.
[0069] As shown in the figure, in one possible implementation, the first lower transistor includes a second power transistor Q2, and the direction of the body diode of the second power transistor Q2 is the same as the direction of the body diode of the second switch transistor M2; the second lower transistor includes a fourth power transistor Q4, and the direction of the body diode of the fourth power transistor Q4 is the same as the direction of the body diode of the fourth switch transistor M4.
[0070] To improve the operating efficiency of the Buck-type PFC circuit, the Buck-type PFC circuit provided in this application embodiment may further include a fifth switching transistor.
[0071] See Figure 6 The figure is a schematic diagram of the fifth Buck power factor correction circuit provided in the embodiments of this application.
[0072] This application does not specifically limit the implementation of the H-bridge circuit in the Buck-type PFC circuit where the fifth switch is located. It can be any of the implementation methods described in the above embodiments. For ease of understanding, this application uses... Figure 5 Based on the corresponding embodiments, the fifth switching transistor will be introduced.
[0073] Figure 6 and Figure 5 The difference is Figure 6 It also includes the fifth switching transistor M5.
[0074] In the Buck-type PFC circuit provided in this application embodiment, the first end of the fifth switch M5 is connected to the first end of the inductor L, and the second end of the fifth switch M5 is connected to the second end of the second bridge arm, that is, the second end of the fifth switch M5 is connected to the second end of the fourth power transistor Q4.
[0075] The controller 200 is also used to control the fifth switch M5 to be turned on, and to control all switches on the first and second arms of the H-bridge to be turned off, that is, to control the first switch M1, the second switch M2, the third switch M3, the fourth switch M4, the second power transistor Q2 and the fourth power transistor Q4 to be turned off, and the inductor L to be in freewheeling state, which can improve the working efficiency of the Buck type PFC circuit.
[0076] Based on the Buck power factor correction circuit provided in the above embodiments, this application also provides a power supply.
[0077] The power supply provided in this application includes the Buck power factor correction circuit described in any of the above embodiments. The power supply can use the Buck power factor correction circuit to control the H-bridge circuit to rectify when the absolute value of the AC source voltage is greater than the capacitor voltage, and to control the H-bridge circuit to stop rectifying when the absolute value of the AC source voltage is less than or equal to the capacitor voltage. The switching transistor of the Buck circuit reuses the switching transistor in the H-bridge circuit. Therefore, the solution provided in this application is not a simple two-stage circuit series connection. It has high circuit integration and improves power conversion efficiency.
[0078] In this application, the terms "first," "second," etc., are used to distinguish identical or similar items that have essentially the same function. It should be understood that there is no logical or temporal dependency between "first," "second," and "nth," nor does it limit the quantity or order of execution. It should also be understood that although the following description uses the terms "first," "second," etc., to describe various elements, these elements should not be limited by the terms. These terms are merely used to distinguish one element from another.
[0079] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0080] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A Buck power factor correction circuit, characterized in that, include: H-bridge circuit, inductors, capacitors, and controller; The midpoint of the first arm of the H-bridge circuit is used to connect to the positive terminal of the AC source, and the midpoint of the second arm of the H-bridge circuit is used to connect to the negative terminal of the AC source; the first end of the inductor is connected to the first end of the first arm and the first end of the second arm; the first end of the capacitor is connected to the second end of the inductor; the second end of the capacitor is connected to the second end of the first arm and the second end of the second arm. The controller is configured to control the H-bridge circuit to perform rectification when the absolute value of the voltage of the AC source is greater than the voltage of the capacitor, and to control the H-bridge circuit to stop rectification when the absolute value of the voltage of the AC source is less than or equal to the voltage of the capacitor.
2. The circuit according to claim 1, characterized in that, The first bridge arm includes a first upper tube and a first lower tube, and the second bridge arm includes a second upper tube and a second lower tube; The controller is configured to, during the positive half-cycle of the AC source, when the voltage of the AC source is greater than the voltage of the capacitor, control both the first upper transistor and the second lower transistor to be turned on, and control both the first lower transistor and the second upper transistor to be turned off; when the pulse width timing time of one cycle is reached, control the first upper transistor to be turned off, and control both the second upper transistor and the second lower transistor to be turned on.
3. The circuit according to claim 2, characterized in that, The controller is configured to control the first lower transistor and the second upper transistor to conduct when the absolute value of the voltage of the AC source is greater than the voltage of the capacitor during the negative half-cycle of the AC source; and to control the second upper transistor to turn off and control both the first upper transistor and the first lower transistor to conduct when the pulse width timing time of one cycle is reached.
4. The circuit according to any one of claims 1-3, characterized in that, The conduction directions of the body diodes of the first upper transistor and the first lower transistor are opposite; the conduction directions of the body diodes of the second upper transistor and the second lower transistor are opposite.
5. The circuit according to any one of claims 1-3, characterized in that, The first upper tube includes a first switch and a second switch connected in series; the first switch and the second switch are connected to each other at the top; the second upper tube includes a third switch and a fourth switch connected in series, the third switch and the fourth switch are connected to each other at the top.
6. The circuit according to any one of claims 1-3, characterized in that, Also includes: Fifth switching transistor; The first end of the fifth switch is connected to the first end of the inductor, and the second end of the fifth switch is connected to the second end of the second bridge arm; The controller is also configured to control the fifth switch to turn on when the inductor is freewheeling.
7. The circuit according to any one of claims 1-3, characterized in that, The controller is used to control all the switches in the H-bridge to turn off, or to control the upper switches of two arms of the H-bridge to turn off, so that the H-bridge circuit stops rectification.
8. The circuit according to any one of claims 1-3, characterized in that, The controller is also configured to obtain an AC current reference value based on the voltage of the capacitor and the instantaneous voltage of the AC source, and control the AC input current based on the AC current reference value.
9. The circuit according to claim 8, characterized in that, The controller is used to perform PI regulation on the voltage of the capacitor to obtain a voltage reference value, multiply the voltage reference value by the instantaneous voltage of the AC source, and divide the product by the square of the effective value of the AC source voltage to obtain the AC current reference value.
10. A power supply, characterized in that, Includes the Buck power factor correction circuit as described in any one of claims 1-9.