A power factor correction circuit, control method and electrical apparatus

Abstract

The application provides a power factor correction circuit, a control method and a power utilization device, and relates to the technical field of power management. The circuit comprises at least one first switching unit, at least one second switching unit and a power inductor. The first switching unit comprises two conduction directions, and the second switching unit comprises one conduction direction. The first switching unit is electrically connected with the power inductor and an alternating current power supply respectively. The second switching unit is electrically connected with the power inductor, the first switching unit and a load respectively. The conduction path of the circuit has one first switching unit and one second switching unit, or has two first switching units. The circuit cooperates between the first switching unit, the second switching unit and the power inductor, so that the number of power devices in series conduction in the conduction path of the circuit is not more than two, the number of semiconductor devices on the power transmission path is effectively reduced, the conduction loss of the whole circuit is reduced, and the system power conversion efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of power management technology, and in particular to a power factor correction circuit, control method, and electrical equipment. Background Technology With the increasing demands for power quality from various electronic devices, harmonic standards established by the International Electrotechnical Commission (IEC) and other relevant organizations have imposed strict limitations on the input current waveform of AC power supply equipment. To meet this requirement, power factor correction circuits must be incorporated into AC-DC converters to suppress current harmonics and improve the power factor. Therefore, high-performance, low-loss power factor correction topologies have always been a research hotspot in the field of power electronics.

[0002] The most widely used solution currently is a cascaded structure of a front-end rectifier bridge and a rear-end boost converter. The AC input voltage is first converted into DC voltage by a rectifier bridge composed of multiple diodes, and then the rear-end boost converter is controlled by a high-frequency switch to make the waveform and phase of the input current follow the changes in the input voltage, thereby achieving power factor correction.

[0003] However, in this structure, at any given moment when the current flows from the AC power source to the load, the current will inevitably flow through at least two diodes in the rectifier bridge in sequence, and then through at least one power switch or freewheeling diode in the subsequent converter. The entire power transmission path has a large number of power semiconductor devices connected in series, a complex structure, high conduction losses, and high power consumption, which is not conducive to improving the overall system efficiency. Summary of the Invention

[0004] This application provides a power factor correction circuit, control method, and electrical device, which aims to reduce the on-state voltage drop, reduce conduction losses, and improve power conversion efficiency by reducing the number of power devices connected in series in the conductive path of the circuit.

[0005] The embodiments of this application adopt the following technical solutions: In a first aspect, embodiments of this application provide a power factor correction circuit, the circuit comprising: at least one first switching unit, at least one second switching unit, and a power inductor; the first switching unit includes two conduction directions, and the second switching unit includes one conduction direction; The first switching unit is electrically connected to the power inductor and the AC power supply respectively; the second switching unit is electrically connected to the power inductor, the first switching unit and the load respectively. The first switching unit is used to control the power inductor to generate an induced current with changing direction by turning itself on and off; the second switching unit is used to conduct the induced current to the load when the first switching unit is off. The closed current path formed by the AC power supply, the power inductor, the load, the first switch unit in the on state, and the second switch unit is a conductive path. The conductive path has one first switch unit and one second switch unit, or has two first switch units.

[0006] Secondly, embodiments of this application provide a control method for a power factor correction circuit, the method comprising: Obtain the power signal output from the AC power supply and the load voltage across the load terminals; A control signal is generated based on the polarity of the power signal and the error between the load voltage and the preset reference voltage. The first switching unit is turned on according to the control signal so that the power inductor generates a current in one direction; The first switching unit is controlled to turn off according to the control signal, so that the power inductor generates an induced current in another direction, and the second switching unit conducts the induced current unidirectionally to the load. The closed current path formed by the AC power supply, the power inductor, the first switch unit in the conducting state, and the second switch unit is a conductive path. The conductive path has one first switch unit and one second switch unit, or has two first switch units.

[0007] Thirdly, embodiments of this application provide an electrical device including a power factor correction circuit as described in any one of the first aspects; and a control method for performing the power factor correction circuit as described in any one of the second aspects.

[0008] Beneficial effects In this embodiment, by electrically connecting the first switching unit to the power inductor and the AC power supply respectively, and electrically connecting the second switching unit to the power inductor and the load respectively, and with the first switching unit having bidirectional conduction capability and the second switching unit having unidirectional conduction capability, in any operating process of the AC power supply charging the power inductor and the power inductor discharging the load, the semiconductor devices connected in series in the conductive path formed by the AC power supply, the power inductor, the load, and the first and second switching units in the conduction state are always one first switching unit and one second switching unit, or two first switching units. Compared to the prior art scheme where the current must flow sequentially through two diodes in the rectifier bridge and at least one power switch or freewheeling diode in the subsequent converter, i.e., at least three power semiconductor devices need to be connected in series, this application significantly reduces the number of semiconductor devices in the power transmission path. Since each semiconductor device has a forward voltage drop and generates corresponding power consumption when it is turned on, reducing the number of devices can directly eliminate the conduction loss of this part, thereby effectively reducing the overall conduction loss of the circuit, reducing power consumption, and improving the power conversion efficiency. This solves the problem of complex structure and high conduction loss caused by too many series devices in the power path in the existing power factor correction circuit. Attached Figure Description

[0009] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the current flow of the first power factor correction circuit provided in the embodiments of this application; Figure 2 This is a schematic diagram of the current flow direction of the second power factor correction circuit provided in the embodiments of this application; Figure 3 This is a schematic diagram of the current flow of the third power factor correction circuit provided in the embodiments of this application; Figure 4 This is a schematic diagram of the current flow of the fourth power factor correction circuit provided in the embodiments of this application; Figure 5 This is a schematic diagram of a power factor correction circuit provided in an embodiment of this application; Figure 6 This is an equivalent circuit topology diagram of the first power factor correction circuit provided in the embodiments of this application; Figure 7 This is an equivalent circuit topology diagram of the second power factor correction circuit provided in the embodiments of this application; Figure 8 This is an equivalent circuit topology diagram of the third power factor correction circuit provided in the embodiments of this application; Figure 9This is an equivalent circuit topology diagram of the fourth power factor correction circuit provided in the embodiments of this application; Figure 10 This is a schematic diagram of another power factor correction circuit provided in an embodiment of this application; Figure 11 This is a flowchart of a control method for a power factor correction circuit provided in an embodiment of this application; Figure 12 This is a schematic diagram of an electrical device structure provided in an embodiment of this application. Detailed Implementation

[0010] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0011] In the embodiments of this application, the terms "first", "second", "third", "fourth" are used to distinguish the same or similar items with essentially the same function and effect, only for the purpose of clearly describing the technical solution of the embodiments of this application, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0012] In the embodiments of this application, the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0013] In the description of this specification, the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this application. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0014] In the embodiments of this application, "multiple" means two or more, and "at least one" means one or more, unless otherwise explicitly specified.

[0015] The features such as "parallel," "perpendicular," and "identical" used in the embodiments of this application include features in the strict sense of "parallel," "perpendicular," and "identical," as well as cases where "approximately parallel," "approximately perpendicular," and "approximately identical" include certain tolerances. Taking into account the measurement and the tolerances associated with the measurement of a specific quantity (e.g., limitations of the measurement system), they represent the acceptable deviation range for a specific value as determined by a person skilled in the art. For example, "approximately" can mean within one or more standard deviations, or within 10% or 5% of the value.

[0016] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open and encompassing, that is, "including, but not limited to".

[0017] In this specification, "electrical connection" and "coupling" include situations where constituent elements are connected together by a component having some electrical function. There are no particular limitations on the "component having some electrical function" as long as it enables the transmission and reception of electrical signals between the connected constituent elements.

[0018] In this application, a transistor refers to a device that includes at least three terminals: a gate, a drain, and a source. A transistor has a channel region between its drain (drain terminal, drain region, or drain) and its source (source terminal, source region, or source), and current can flow through the drain, the channel region, and the source. In this disclosure, the channel region refers to the region through which current primarily flows.

[0019] In this application, the first electrode can be the drain and the second electrode can be the source, or vice versa. When using transistors with opposite polarities or when the current direction changes during circuit operation, the functions of the "source" and "drain" are sometimes interchanged. Therefore, in this application, the "source" and "drain" can be interchanged.

[0020] With increasingly stringent mandatory requirements for harmonics and power factor of input current in commercial AC-DC power supplies as stipulated by international standards such as IEC 61000-3-2 developed by the International Electrotechnical Commission, power factor correction (PFC) circuits have become a core component of AC power supply equipment. At the same time, power electronic devices continue to evolve towards higher efficiency and smaller size. Therefore, how to further simplify circuit topology and reduce system power consumption while achieving power factor correction functionality has become an important research direction in this field.

[0021] Currently, power factor correction circuits mainly employ two mainstream architectures. The first is the traditional Boost PFC topology, which uses a cascaded structure of a front-end full-wave rectifier bridge and a rear-end boost converter. The AC input is first converted into a pulsating DC voltage by a rectifier bridge composed of four diodes, and then the Boost converter circuit, which includes power switches, freewheeling diodes, and energy storage inductors, completes the power conversion and power factor correction. The second is an improved bridgeless or common-ground PFC topology. The bridgeless scheme eliminates the front-end rectifier bridge, directly forming the switching network on the AC input side with power switches and diodes, thereby eliminating the conduction losses caused by the rectifier bridge diodes. The common-ground scheme directly connects the output ground to the AC input neutral line, providing a low-impedance return path for high-frequency common-mode current to suppress common-mode interference. However, both of these schemes still require a relatively large number of power devices, such as four switches, or additional auxiliary circuits such as voltage stress balancing and polarity compensation, resulting in a relatively large overall number of components.

[0022] In traditional Boost PFC topologies, at any given time, at least two diodes in the rectifier bridge and one power switch or freewheeling diode in the subsequent stage are connected in series along the power transmission path. This results in a significant forward voltage drop and conduction losses. Furthermore, the hierarchical structure of the rectification and boost stages increases the number of passive components and the complexity of circuit wiring, further enhancing the overall system power consumption. In existing improved bridgeless or common-ground schemes, the additional power transistors, auxiliary circuits, and balancing components also increase the total number of components without fundamentally reducing the number of series-connected components in the main power circuit, making it difficult to achieve low-power operation while simplifying the structure.

[0023] Based on this, embodiments of this application provide a power factor correction circuit, such as... Figures 1-5 As shown, the power factor correction circuit includes at least one first switching unit S, at least one second switching unit D, and a power inductor LB. The first switching unit S has two conduction directions, and the second switching unit D has one conduction direction. The first switching unit S is electrically connected to the power inductor LB and the AC power supply Vi, respectively. The second switching unit D is electrically connected to the power inductor LB, the first switching unit S, and the load Vo, respectively. The first switching unit S is used to control the power inductor LB to generate an induced current with changing direction by its own conduction and cutoff. The second switching unit D is used to conduct the induced current to the load Vo when the first switching unit S is turned off. The closed current path formed by the AC power supply Vi, the power inductor LB, the load Vo, the first switching unit S in the conduction state, and the second switching unit D in the conduction state is a conductive path. The conductive path has one first switching unit S and one second switching unit D, or has two first switching units S.

[0024] The first switching unit S refers to a power semiconductor device with controllable switching capability and bidirectional conductivity. Its conductivity characteristics are divided into two states: in the on state, it can achieve bidirectional conductivity, and the current can flow freely in both directions; in the off state, it can only achieve unidirectional conductivity through its integrated body diode, and is cut off in the reverse direction. This unit is used to switch the on / off state according to control commands to control the energy stored or released by the power inductor LB.

[0025] For example, the first switching unit S can be a field-effect crystal (MOSFET).

[0026] Choosing a MOSFET as the first switching unit S leverages its bidirectional conductivity of the channel in the on-state and the unidirectional conductivity of its internal body diode in the off-state. This eliminates the need for additional independent rectifier diodes in the charging and discharging phases. During charging, the on-channel of one MOSFET and the body diode of another MOSFET form a circuit. During discharging, the body diode of the MOSFET and the second switching unit D form a freewheeling circuit. The body diode, being an inherent parasitic structure of the MOSFET, requires no additional components. Therefore, while achieving power factor correction, this effectively reduces the number of independent semiconductor devices connected in series in the main power circuit, lowering the on-state voltage drop and conduction losses.

[0027] The second switching unit D refers to a semiconductor device with unidirectional conductivity, which only allows current to pass through in a preset direction and cuts off in the reverse direction.

[0028] For example, the second switching unit D can be a Schottky diode, which is used to form a freewheeling circuit for the power inductor LB when the first switching unit S is turned off, so as to unidirectionally transfer the magnetic field energy stored in the power inductor LB to the load Vo side. Its forward conduction voltage is lower than that of traditional silicon diodes, the switching speed is fast, and the reverse recovery loss is extremely low, which can significantly reduce the conduction loss.

[0029] The power inductor LB is an energy storage element in the circuit. By turning the first switching unit S on and off, the AC power supply Vi charges the power inductor LB, converting electrical energy into magnetic field energy and storing it in the power inductor LB. Alternatively, the power inductor LB discharges to the load Vo, converting the magnetic field energy stored in the power inductor LB into electrical energy and transferring it to the load Vo.

[0030] A conductive path is a closed current loop consisting of an AC power source Vi, a power inductor LB, a semiconductor device in a conducting state, and a load Vo. It is the current flow path for power transmission and conversion.

[0031] The specific structure and working process of the power factor correction circuit provided in the embodiments of this application will be described in detail below, in conjunction with the above structure.

[0032] The operation of this power factor correction circuit naturally switches according to the polarity change of the AC power supply Vi. Both the positive and negative half-cycles of the AC voltage include a power conversion cycle in which the power inductor LB stores and releases energy. Specifically, the positive half-cycle of the AC voltage is the period when the live wire voltage is greater than the neutral wire voltage, and the negative half-cycle is the period when the neutral wire voltage is greater than the live wire voltage.

[0033] When the output voltage of the AC power supply Vi is in the positive half-cycle, the circuit alternately performs the process of charging the power inductor LB and discharging the load Vo through the high-frequency switching control of the first switching unit S.

[0034] During the stage where AC power supply Vi charges power inductor LB, AC power supply Vi, power inductor LB and two first switching units S form a closed conductive path. AC power supply Vi charges power inductor LB through this conductive path. In this conductive path, one of the first switching units S is in the on state and the other first switching unit S is in the off state, with current flowing through its body diode.

[0035] During the discharge phase from the power inductor LB to the load Vo, the power inductor LB, a first switching unit S, a second switching unit D, and the load Vo form a closed conductive path. The power inductor LB discharges to the load Vo through this conductive path, which is composed of a first switching unit S and a second switching unit D. The first switching unit S can be in the off state, and the current flows through its body diode.

[0036] When the output voltage of the AC power supply Vi is in the negative half-cycle, the circuit alternately performs the process of charging the power inductor LB and discharging the load Vo through the high-frequency switching control of the first switching unit S.

[0037] During the charging phase of AC power source Vi to power inductor LB, AC power source Vi, power inductor LB and two first switching units S form a closed conductive path. AC power source Vi charges power inductor LB in reverse through this conductive path. In this conductive path, the first switching unit S is in the on state, the other first switching unit S is in the off state, and the current flows through its body diode.

[0038] During the discharge phase from the power inductor LB to the load Vo, the power inductor LB, the first switching unit S, the second switching unit D, and the load Vo form a closed conductive path. The power inductor LB discharges to the load Vo through this conductive path, which is composed of a first switching unit S and a second switching unit D. The first switching unit S can be in the off state, and the current flows through its body diode.

[0039] In the embodiments of this application, by electrically connecting the first switching unit S to the power inductor LB and the AC power supply Vi respectively, and electrically connecting the second switching unit D to the power inductor LB and the load Vo respectively, the conductive path during the charging phase of the AC power supply Vi to the power inductor LB is composed of two first switching units S, and the conductive path during the discharging phase of the power inductor LB to the load Vo is composed of one first switching unit S and one second switching unit D. The number of semiconductor devices connected in series in the main power circuit never exceeds two. In a conventional bridge PFC circuit composed of four diodes, the two diodes in the rectifier bridge are always connected in series in the main power circuit. Regardless of whether the subsequent switching transistor is in the on or off state, the main circuit current must flow through these two diodes. In addition, there is a power switching transistor or freewheeling diode in the subsequent converter. At any given time, there are at least three semiconductor devices connected in series in the main power circuit. In this embodiment, the body diode integrated within the first switching unit S in the conductive path is an inherent parasitic structure, not an additional independent device. Therefore, no additional independent diode is introduced into the conductive path during the charging phase, and the conductive path during the discharging phase only requires one first switching unit S and one second switching unit D. The number of semiconductor devices connected in series throughout the entire operating cycle remains two. Thus, this application reduces the number of semiconductor devices connected in series in the main power circuit from a circuit topology perspective, effectively reducing on-state voltage drop and conduction losses, and improving system efficiency.

[0040] Optionally, in some power factor correction circuits provided in this application, such as Figures 1-5 As shown, at least one first switching unit S includes a first switching transistor S1 and a second switching transistor S2; the first end of the first switching transistor S1 is electrically connected to the live wire of the AC power supply Vi, and the second end of the first switching transistor S1 is electrically connected to the first end of the power inductor LB; the first end of the second switching transistor S2 is electrically connected to the neutral wire of the AC power supply Vi, and the second end of the second switching transistor S2 is electrically connected to the second end of the power inductor LB.

[0041] In this embodiment, the first switch S1 and the second switch S2 are both specific implementations of the first switch unit S described in the above embodiments, that is, power semiconductor devices with controllable switching capability and bidirectional conductivity.

[0042] Taking a MOSFET as an example, the first switch S1 and the second switch S2 can conduct bidirectionally through their channels when they are on, and can conduct unidirectionally through their internally integrated body diodes when they are off. The first terminal of the first switch S1 and the second switch S2 can be the drain and the second terminal can be the source, or the first terminal can be the source and the second terminal can be the drain, which can be determined according to the actual circuit design.

[0043] At least one second switching unit D includes a first diode D1 and a second diode D2; the first terminal of the first diode D1 is electrically connected to the first terminal of the power inductor LB, and the second terminal of the first diode D1 is electrically connected to the first terminal of the load Vo; the first terminal of the second diode D2 is electrically connected to the second terminal of the power inductor LB, and the second terminal of the second diode D2 is electrically connected to the first terminal of the load Vo.

[0044] Both the first diode D1 and the second diode D2 are specific implementations of the second switching unit D described in the above embodiments, i.e., semiconductor devices with unidirectional conductivity. Taking a Schottky diode as an example, the first end of the first diode D1 and the second diode D2 are anodes, and the second end is anode. When the anode potential is higher than the cathode potential, the diode conducts in the forward direction, and the current flows from the anode to the cathode; when the anode potential is lower than the cathode potential, the diode is reverse-biased and the current is blocked. Both the first diode D1 and the second diode D2 are connected between the power inductor LB and the load Vo, and are used to provide a freewheeling path for the power inductor LB when both the first switch S1 and the second switch S2 are turned off, so as to unidirectionally transfer the energy stored in the power inductor LB to the load Vo side.

[0045] The working process of this embodiment will be described in detail below with reference to the above structure.

[0046] like Figure 1 and 6 As shown, when the live wire voltage of AC power supply Vi is greater than the neutral wire voltage, the first switch S1 is turned off, and the second switch S2 is turned on, it is in the stage where AC power supply Vi is charging power inductor LB.

[0047] At this time, the channel of the first switch S1 is turned off because there is no driving signal. However, the anode of its body diode T1 is connected to the live wire of the AC power supply Vi, and the cathode is connected to the first terminal of the power inductor LB. The potential of the live wire is higher than the potential of the neutral wire. The first terminal of the power inductor LB is connected to the neutral wire through the conduction channel of the second switch S2. Therefore, the anode potential of the body diode T1 of the first switch S1 is higher than the cathode potential, and it is forward conducting.

[0048] The second switch S2 forms a conductive channel due to the driving signal, allowing current to flow through it. The body diode T2 of the second switch S2 has its anode connected to the neutral line of the AC power supply Vi and its cathode connected to the second terminal of the power inductor LB. At this time, the conductive channel of the second switch S2 short-circuits the second terminal of the power inductor LB to the neutral line. The anode and cathode potentials at both ends of the body diode T2 are essentially equal, failing to meet the forward conduction condition, and therefore the switch is in the off state.

[0049] At this time, the charging current flows out from the live wire of the AC power supply Vi, flows sequentially through the body diode T1 of the first switching transistor S1, the power inductor LB, and the conduction channel of the second switching transistor S2, and returns to the neutral wire of the AC power supply Vi, forming the first conductive path. The AC power supply Vi charges the power inductor LB through the first conductive path, and the electrical energy is converted into magnetic field energy and stored in the power inductor LB.

[0050] During this charging phase, the first conductive path is formed by the body diode T1 of the first switching transistor S1 and the conduction channel of the second switching transistor S2, i.e., two first switching units S, and the number of semiconductor devices connected in series on the main power circuit is two.

[0051] like Figure 2 and Figure 7 As shown, when the live wire voltage of AC power supply Vi is greater than the neutral wire voltage, the first switch S1 is turned off, and the second switch S2 is turned off, it is in the stage of power inductor LB discharging to load Vo.

[0052] At this time, neither the first switch S1 nor the second switch S2 has a drive signal, and both channels are turned off. Since the current in the power inductor LB cannot change abruptly, an induced electromotive force is generated across its terminals, causing the potential at the second terminal of the power inductor LB to rise. The anode of the second diode D2 is connected to the second terminal of the power inductor LB, and the cathode is connected to the load Vo. At this time, the anode potential is higher than the cathode potential, and the second diode D2 is forward-biased.

[0053] Meanwhile, the anode of the body diode T1 of the first switching transistor S1 is connected to the live wire of the AC power supply Vi, and the cathode is connected to the first terminal of the power inductor LB, so that the anode potential of the body diode T1 of the first switching transistor S1 is higher than the cathode potential, and the body diode T1 of the first switching transistor S1 remains forward conducting.

[0054] The body diode T2 of the second switch S2 has its anode connected to the neutral line of the AC power supply Vi and its cathode connected to the second terminal of the power inductor LB. At this time, due to the increase in the induced electromotive force potential at the second terminal of the power inductor LB, the cathode potential of the body diode T2 of the second switch S2 is higher than the anode potential, which does not meet the forward conduction condition. Therefore, the body diode T2 of the second switch S2 is in the reverse cutoff state.

[0055] The induced current flows out from the second terminal of the power inductor LB, passes through the second diode D2, the load Vo, the AC power supply Vi, and the body diode T1 of the first switching transistor S1, and returns to the first terminal of the power inductor LB, forming a second conductive path. The power inductor LB discharges to the load Vo through the second conductive path, releasing the stored magnetic field energy to the load Vo.

[0056] At this time, the second conductive path is formed by the second diode D2 and the body diode T1 of the first switching transistor S1, that is, a first switching unit S and a second switching unit D, and the number of semiconductor devices connected in series on the main power circuit is two.

[0057] like Figure 3 and Figure 8 As shown, when the neutral voltage of the AC power supply Vi is greater than the live voltage, the first switch S1 is turned on, and the second switch S2 is turned off, the AC power supply Vi is in the charging stage of the power inductor LB.

[0058] At this time, the channel of the second switch S2 is turned off due to the lack of a driving signal, but the anode of its body diode T2 is connected to the neutral line of the AC power supply Vi and the cathode is connected to the second terminal of the power inductor LB. The neutral line potential is higher than the live line potential, and the second terminal of the power inductor LB is connected to the live line through the power inductor LB and the conducting channel of the first switch S1. Therefore, the anode potential of the body diode T2 of the second switch S2 is higher than the cathode potential, and it is forward conducting.

[0059] The first switching transistor S1 is fully conducting due to the driving signal, allowing current to flow bidirectionally. The body diode T1 of the first switching transistor S1 has its anode connected to the AC power supply Vi (live wire) and its cathode connected to the first terminal of the power inductor LB. At this time, the conducting channel of the first switching transistor S1 has short-circuited the first terminal of the power inductor LB to the live wire. The anode and cathode potentials at both ends of the body diode T1 of the first switching transistor S1 are essentially equal, which does not meet the forward conduction condition, therefore it is in the cutoff state.

[0060] The charging current flows out from the neutral wire of the AC power supply Vi, sequentially through the body diode T2 of the second switch S2, the power inductor LB, and the conduction channel of the first switch S1, before returning to the live wire of the AC power supply Vi, forming a third conductive path. The AC power supply Vi charges the power inductor LB in reverse through this third conductive path, converting electrical energy into magnetic field energy stored in the power inductor LB.

[0061] At this time, the third conductive path is formed by the body diode T2 of the second switch S2 and the conduction channel of the first switch S1, that is, two first switch units S, and the number of semiconductor devices connected in series on the power main circuit is two.

[0062] like Figure 4 and Figure 9As shown, when the neutral voltage of the AC power supply Vi is greater than the live voltage, the first switch S1 is turned off, and the second switch S2 is turned off, it is in the stage of the power inductor LB discharging to the load Vo.

[0063] At this time, neither the first switch S1 nor the second switch S2 has a drive signal, and both channels are turned off. Since the current in the power inductor LB cannot change abruptly, an induced electromotive force is generated across its terminals, causing the potential at the first terminal of the power inductor LB to rise. The anode of the first diode D1 is connected to the first terminal of the power inductor LB, and the cathode is connected to the load Vo. At this time, the anode potential is higher than the cathode potential, and the first diode D1 is forward-biased.

[0064] Meanwhile, the anode of the body diode T2 of the second switch S2 is connected to the neutral line of the AC power supply Vi, and the cathode is connected to the second terminal of the power inductor LB. The discharge current flows into the neutral line of the AC power supply Vi after passing through the load Vo, so that the anode potential of the body diode T2 of the second switch S2 is higher than the cathode potential, and the body diode T2 of the second switch S2 remains forward conducting.

[0065] The body diode T1 of the first switching transistor S1 has its anode connected to the live wire of the AC power supply Vi and its cathode connected to the first terminal of the power inductor LB. At this time, due to the increase in the induced electromotive force potential at the first terminal of the power inductor LB, the cathode potential of the body diode T1 of the first switching transistor S1 is higher than the anode potential, which does not meet the forward conduction condition. Therefore, the body diode T1 of the first switching transistor S1 is in the reverse cutoff state.

[0066] The induced current flows out from the first terminal of the power inductor LB, passes through the first diode D1, the load Vo, the AC power supply Vi, and the body diode T2 of the second switch S2, and returns to the second terminal of the power inductor LB, forming a fourth conductive path. The power inductor LB discharges to the load Vo through the fourth conductive path, releasing the stored magnetic field energy to the load Vo.

[0067] At this time, the fourth conductive path is formed by the body diode T2 of the first diode D1 and the second switch S2, that is, a first switch unit S and a second switch unit D, and the number of semiconductor devices connected in series on the main power circuit is two.

[0068] In the embodiments of this application, the first terminal of the first switching transistor S1 is electrically connected to the live wire of the AC power supply Vi, and the second terminal is electrically connected to the first terminal of the power inductor LB. The first terminal of the second switching transistor S2 is electrically connected to the neutral wire of the AC power supply Vi, and the second terminal is electrically connected to the second terminal of the power inductor LB. The anode of the first diode D1 is electrically connected to the first terminal of the power inductor LB, and the cathode is electrically connected to the first terminal of the load Vo. The anode of the second diode D2 is electrically connected to the second terminal of the power inductor LB, and the cathode is electrically connected to the first terminal of the load Vo.

[0069] With the above configuration, during the positive half-cycle charging phase, the charging circuit is formed by the body diode T1 of the first switch S1 and the conduction channel of the second switch S2; during the positive half-cycle discharging phase, the discharging circuit is formed by the second diode D2 and the body diode T1 of the first switch S1; during the negative half-cycle charging phase, the charging circuit is formed by the body diode T2 of the second switch S2 and the conduction channel of the first switch S1; during the negative half-cycle discharging phase, the discharging circuit is formed by the first diode D1 and the body diode T2 of the second switch S2.

[0070] In each operating phase, the current path is determined solely by the voltage polarity of the AC power supply Vi and the drive signal of the switching transistors: During the charging phase, the channel of the on-state switching transistor and the body diode of the off-state switching transistor are connected in series to form a charging circuit; During the discharging phase, both switching transistors are off, and the power inductor LB induces an electromotive force that causes the anode potential of the corresponding diode to be higher than the cathode potential, thus turning it on and forming a discharge circuit with the body diode of the corresponding switching transistor. The entire process only requires providing a set of complementary drive signals to the first switching transistor S1 and the second switching transistor S2. During the positive half-cycle, the first switching transistor S1 is kept off and high-frequency on / off control is applied to the second switching transistor S2. During the negative half-cycle, the second switching transistor S2 is kept off and high-frequency on / off control is applied to the first switching transistor S1. This completes the power factor correction throughout the entire cycle without the need for complex multi-channel timing coordination or polarity switching logic. The control logic is simple and reliable, which can reduce the complexity and implementation cost of the control circuit and improve the stability and reliability of the system operation.

[0071] Throughout the entire operating cycle, the number of semiconductor devices connected in series in the main power circuit remains constant at two. Compared to the structure of traditional PFC circuits, this reduces the number of devices and lowers the overall forward voltage drop. The Schottky diode has a low forward voltage drop and minimal reverse recovery loss, further reducing conduction losses at each stage. Simultaneously, the body diode in the charging circuit is an inherent parasitic structure of the MOSFET itself, not requiring an additional independent device, which is beneficial for the circuit's development towards higher integration. Therefore, the embodiments of this application effectively reduce the overall system power consumption while simplifying the circuit structure.

[0072] Optionally, in some power factor correction circuits provided in this application, the neutral wire of the AC power supply Vi and the second terminal of the load Vo are both electrically connected to the ground terminal GND.

[0073] The ground terminal GND refers to the node in the circuit that serves as a common reference potential. It is usually connected to the system ground and provides a zero potential reference for the circuit.

[0074] The working process of this embodiment will be described below in conjunction with the above structure.

[0075] It should be noted that the connection method in which the neutral wire of AC power supply Vi and the second terminal of load Vo are both electrically connected to the ground terminal GND mainly involves the discharge stage. The conductive path in the charging stage consists of AC power supply Vi, power inductor LB and the first switching unit S. The current forms a loop between the live wire and the neutral wire of AC power supply Vi, without involving the participation of the ground terminal GND. This will not be described in detail here.

[0076] During the positive half-cycle discharge phase, both the first switch S1 and the second switch S2 are turned off, generating an induced electromotive force across the power inductor LB. The potential at its second terminal rises, and the second diode D2 is forward-biased. At this time, the output voltage of the AC power supply Vi and the induced electromotive force of the power inductor LB are superimposed in series, supplying power to the load Vo through the second diode D2. The current flows through the second diode D2, the load Vo, and the ground terminal GND into the neutral line of the AC power supply Vi, then returns to the first terminal of the power inductor LB through the body diode T1 of the first switch S1 within the AC power supply Vi, forming a closed loop. Since the second terminal of the load Vo and the neutral line of the AC power supply Vi are both electrically connected to the ground terminal GND, the supply current flows directly back to the neutral line of the AC power supply Vi through the ground terminal GND after passing through the load Vo, forming a low-impedance power supply path.

[0077] During the negative half-cycle discharge phase, both the first switch S1 and the second switch S2 are turned off, generating an induced electromotive force across the power inductor LB. The potential at its first terminal rises, and the first diode D1 is forward-biased. At this time, the output voltage of the AC power supply Vi and the induced electromotive force of the power inductor LB are connected in series and superimposed, supplying power to the load Vo through the first diode D1. The current flows through the first diode D1, the load Vo, and the ground terminal GND into the neutral line of the AC power supply Vi, then returns to the second terminal of the power inductor LB through the body diode T2 of the second switch S2 inside the AC power supply Vi, forming a closed loop. Similarly, by utilizing the connection method where both the neutral line of the AC power supply Vi and the second terminal of the load Vo are electrically connected to the ground terminal GND, low-impedance return current is achieved.

[0078] In the embodiments of this application, by electrically connecting both the neutral wire of the AC power supply Vi and the second terminal of the load Vo to the ground terminal GND, the following advantages are achieved: In traditional non-common-ground power factor correction circuits, a diode or MOSFET is connected in series between the AC power supply Vi neutral line and the ground terminal GND. When these devices are off, the connection between the neutral line and the ground terminal GND is broken. At this time, during the high-frequency switching process of the DC-side power switch, the parasitic capacitance between its drain and the heat sink generates a high-frequency parasitic current. After this parasitic current flows to the ground terminal GND, it cannot return directly to the AC power supply Vi neutral line through the internal circuit because the path between the neutral line and the ground terminal GND is blocked by the off devices. Instead, it forms a loop through external paths such as the chassis and input cables, which can easily interfere with other sensitive circuits. In this embodiment, the neutral wire of the AC power supply Vi is directly connected to the grounding terminal GND, providing a low-impedance internal return path for the parasitic current. After passing through the grounding terminal GND, the parasitic current can return directly to the neutral wire of the AC power supply Vi without having to detour through an external path, thereby effectively reducing interference to other circuits. Therefore, in addition to reducing the number of series devices in the main power circuit and reducing the overall power consumption of the circuit in the above embodiments, the embodiments of this application can also reduce electromagnetic interference to other circuits and improve the electromagnetic compatibility performance of the system.

[0079] Optionally, in some power factor correction circuits provided in this application, such as Figure 10 As shown, the power factor correction circuit also includes a voltage regulator capacitor C0, the first end of which is electrically connected to the first end of the load Vo; the second end of the voltage regulator capacitor C0 is electrically connected to the second end of the load Vo.

[0080] A Zener capacitor C0 is an energy storage element connected across the load Vo to smooth the output voltage. The Zener capacitor C0 stores energy while the power inductor LB discharges to the load Vo, and releases energy back to the load Vo when the power inductor LB stops discharging, thus maintaining the stability of the voltage across the load Vo and reducing output voltage fluctuations.

[0081] The working process of this embodiment will be described below in conjunction with the above structure. It should be noted that the voltage regulator capacitor C0 mainly participates in the energy transfer during the discharge stage and the discharge interval. During the charging stage, the conductive path is composed of the AC power supply Vi, the power inductor LB and the first switching unit S. The current does not flow through the load Vo branch. The voltage regulator capacitor C0 does not participate in the energy transfer during this stage, which will not be discussed in detail here.

[0082] During the positive half-cycle of the AC power supply Vi, and when the power inductor LB is in the discharge phase, both the first switch S1 and the second switch S2 are turned off. An induced electromotive force (EMF) is generated across the power inductor LB, causing its second terminal potential to rise, and the second diode D2 to conduct in the forward direction. At this time, the output voltage of the AC power supply Vi and the induced EMF of the power inductor LB are connected in series and superimposed, jointly supplying power to the load Vo through the second diode D2. Part of the supply current flows to the load Vo, and the other part flows to the voltage regulator capacitor C0 to charge it. The electrical energy is stored in the voltage regulator capacitor C0 in the form of electric field energy. When the first switch unit S1 turns on again and the circuit enters the charging phase, the power inductor LB stops discharging to the load Vo. At this time, the voltage regulator capacitor C0 releases the stored electrical energy to the load Vo to maintain the voltage stability across the load Vo.

[0083] During the negative half-cycle of the AC power supply Vi, and when the power inductor LB is in the discharge phase, both the first switch S1 and the second switch S2 are turned off. An induced electromotive force is generated across the power inductor LB, causing its first terminal potential to rise, and the first diode D1 to conduct in the forward direction. At this time, the output voltage of the AC power supply Vi and the induced electromotive force of the power inductor LB are connected in series and superimposed, jointly supplying power to the load Vo through the first diode D1. This also charges the voltage regulator capacitor C0, which maintains the voltage of the load Vo during the subsequent charging phase.

[0084] Due to the high-frequency switching control of the first switching unit S in the power factor correction circuit, the discharge of the power inductor LB to the load Vo is intermittent. During the switching process of the first switching unit S, the AC power supply Vi and the power inductor LB jointly supply power to the load Vo during the discharge phase. During the charging phase, the power inductor LB and the load Vo are isolated by the turned-off first switching unit S, and the AC power supply Vi only charges the power inductor LB. If a voltage-stabilizing capacitor C0 is not connected in parallel across the load Vo, the load Vo current will be interrupted during the charging phase, resulting in large fluctuations in the output voltage.

[0085] In the embodiments of this application, by setting a voltage regulator capacitor C0, and electrically connecting its first terminal to the first terminal of the load Vo and its second terminal to the second terminal of the load Vo, the voltage regulator capacitor C0 can be charged and store energy by the AC power supply Vi and the power inductor LB during the discharge phase, and release energy to the load Vo during the charging phase, providing a continuous current supply to the load Vo. Since the voltage regulator capacitor C0 can independently supply power to the load Vo during the charging phase, the load Vo can obtain a continuous energy supply throughout the entire cycle, avoiding output voltage fluctuations caused by power supply interruptions due to high-frequency switching, thereby effectively improving the output stability and reliability of the circuit.

[0086] Optionally, in some power factor correction circuits provided in this application, the power factor correction circuit further includes a filter inductor L1 and a filter capacitor C1; the first end of the filter inductor L1 is electrically connected to the live wire of the AC power supply Vi, and the second end is electrically connected to the first end of the first switching unit S; the first end of the filter capacitor C1 is electrically connected to the second end of the filter inductor L1, and the second end is electrically connected to the neutral wire of the AC power supply Vi.

[0087] The filter inductor L1 and filter capacitor C1 form the input filter network. The filter inductor L1 presents a larger impedance to high-frequency currents and a smaller impedance to low-frequency currents, thus hindering the conduction of high-frequency signals between the AC power supply Vi and the first switching unit S. The filter capacitor C1 presents a smaller impedance to high-frequency currents, providing a low-impedance bypass path for high-frequency signals, allowing them to flow directly into the ground terminal GND instead of being conducted between the AC power supply Vi and the first switching unit S.

[0088] The working process of this embodiment will be described below in conjunction with the above structure.

[0089] During circuit operation, the first switching unit S switches on and off at high frequency. Each switching action causes the input current to rise or fall rapidly, resulting in high-frequency current fluctuations. These current fluctuations may flow into the AC power supply Vi and be conducted to other devices on the power grid through the AC power supply Vi line. At the same time, there may also be high-frequency interference signals generated by other devices on the AC power supply Vi side. If these interference signals directly enter subsequent stages of this circuit, they will affect the control accuracy of the power factor correction.

[0090] In this embodiment, the filter inductor L1 is connected in series between the live wire of the AC power supply Vi and the first switching unit S, and the filter capacitor C1 is connected in parallel between the second terminal of the filter inductor L1 and the neutral wire of the AC power supply Vi, forming a low-pass filter network. For the high-frequency pulsating current generated by the high-frequency switching of the first switching unit S, the filter inductor L1, due to its large impedance to high-frequency signals, hinders its conduction to the AC power supply Vi side. Simultaneously, the filter capacitor C1, due to its small impedance to high-frequency signals, provides a low-impedance bypass path for the high-frequency current, allowing it to flow through the filter capacitor C1 to the ground terminal GND, thereby preventing high-frequency noise from being conducted to other devices on the power grid through the AC power supply Vi line. For high-frequency interference signals transmitted from the AC power supply Vi side, the filter inductor L1, also due to its large impedance to high-frequency signals, hinders their entry into subsequent circuits, while the filter capacitor C1 bypasses them to the ground terminal GND, thereby filtering out high-frequency interference from the AC power supply Vi side and reducing the high-frequency electromagnetic interference components entering subsequent circuits.

[0091] For the AC input current of the frequency required by the load Vo, the impedance presented by the filter inductor L1 is extremely small and the impedance presented by the filter capacitor C1 is extremely large. The current passes through the filter inductor L1 with almost no attenuation and enters the subsequent circuit. After power factor correction, it is supplied to the load Vo.

[0092] By setting up a filter inductor L1 and a filter capacitor C1, and connecting the first terminal of the filter inductor L1 to the live wire of the AC power supply Vi and the second terminal to the first terminal of the first switching unit S, and connecting the first terminal of the filter capacitor C1 to the second terminal of the filter inductor L1 and the second terminal to the neutral wire of the AC power supply Vi, a low-pass filter network can be formed. This filter network effectively suppresses current fluctuations generated by the high-frequency switching of the first switching unit S from being conducted to other devices on the power grid through the AC power supply Vi, reducing the conducted interference of this circuit to the power grid; on the other hand, it prevents current fluctuations from entering the subsequent discharge circuit, reducing the high-frequency ripple in the load Vo current and improving the power supply quality; at the same time, it can also filter out high-frequency interference signals transmitted from the AC power supply Vi side, ensuring the quality of the current waveform entering the subsequent circuit and improving the accuracy and effect of power factor correction.

[0093] Optionally, in some power factor correction circuits provided in this application, such as Figure 10 As shown, the power factor correction circuit further includes a reference unit 1, a comparison unit 2, and a drive unit 3. The reference unit 1 is electrically connected to the AC power supply Vi, the load Vo, and the comparison unit 2, respectively. The drive unit 3 is electrically connected to the comparison unit 2 and the switching unit, respectively. The comparison unit 2 is electrically connected to the AC power supply Vi. The reference unit 1 is used to generate a reference voltage signal based on the difference between the voltage across the load Vo and a preset reference voltage. The comparison unit 2 is used to generate a control signal based on the comparison result between the reference voltage signal and the output current signal of the AC power supply Vi. The drive unit 3 is used to control the switching unit to turn on and off according to the control signal.

[0094] The reference unit 1 includes an error calculator 11, an error adjuster 12, a first absolute value arithmetic unit 13, and a multiplier 14.

[0095] The error calculator 11 is used to obtain the voltage across the load Vo, and subtract the voltage across the load Vo from the preset reference voltage to obtain the error signal between the two.

[0096] The error regulator 12 is used to perform proportional-integral regulation on the error signal to generate an amplitude signal, which is dynamically adjusted according to the change of the error signal: when the error increases, the amplitude signal increases; when the error decreases, the amplitude signal decreases.

[0097] The first absolute value arithmetic unit 13 is used to take the absolute value of the output voltage waveform of the AC power supply Vi, and convert the alternating positive and negative AC voltage signal into a unidirectional voltage signal.

[0098] Multiplier 14 is used to multiply the amplitude signal with the output voltage waveform of AC power supply Vi to generate an instantaneous reference voltage signal. The waveform of the reference voltage signal is in phase and frequency with the output voltage of AC power supply Vi, and its amplitude is determined by the amplitude signal output by error regulator 12.

[0099] The reference voltage signal is used to compare with the actual output current signal. By controlling the on and off of the first switching unit S, the waveform and amplitude of the AC power supply Vi output current are adjusted so that the input current and input voltage are in phase and frequency, thereby matching the input power with the load Vo power, and finally adjusting the load Vo voltage to near the preset reference voltage.

[0100] Comparison unit 2 includes a low-pass filter 21, a second absolute value arithmetic unit 22, a voltage error detector 23, and a current compensator 24. The low-pass filter 21 extracts the average value of the output current signal and filters out high-frequency switching noise. The second absolute value arithmetic unit 22 takes the absolute value of the filtered output current signal, converting the alternating positive and negative AC current signal into a unidirectional signal. The voltage error detector 23 subtracts the absolute value of the AC power supply Vi output voltage signal from the first absolute value arithmetic unit 13 from the reference voltage signal to obtain the voltage error signal between the two. The current compensator 24 performs compensation processing based on the voltage error signal output by the voltage error detector 23 to generate a control signal.

[0101] The driving unit 3 compares the control signal output by the comparison unit 2 with a sawtooth wave of fixed frequency. When the amplitude of the control signal is greater than the amplitude of the sawtooth wave, a high-level driving signal is output to turn on the first switching unit S; when the amplitude of the control signal is less than the amplitude of the sawtooth wave, a low-level driving signal is output to turn off the first switching unit S. Through this pulse width modulation method, the continuously changing control signal is converted into a driving pulse with a duty cycle varying according to the amplitude of the control signal, which is then output to the first switching unit S to control the on / off state of the first switching unit S.

[0102] In the embodiments of this application, by setting a reference unit 1, a comparison unit 2, and a drive unit 3, and electrically connecting the reference unit 1 to the AC power supply Vi, the load Vo, and the comparison unit 2 respectively, electrically connecting the drive unit 3 to the comparison unit 2 and the first switch unit S respectively, and electrically connecting the comparison unit 2 to the AC power supply Vi, closed-loop control of the first switch unit S can be realized. The closed-loop control obtains the error between the load voltage Vo and the preset reference voltage through the error calculator 11. After proportional-integral regulation by the error regulator 12, the amplitude signal is dynamically adjusted. Then, it is multiplied by the absolute value of the AC power supply Vi output voltage waveform by the multiplier 14 to generate a reference voltage signal that is in phase and frequency with the input voltage and whose amplitude is determined by the voltage error. The current regulation layer extracts the average value of the output current through the low-pass filter 21. The AC current signal is converted into a unidirectional signal by the second absolute value arithmetic unit 22. The voltage error detector 23 calculates the error between the AC power supply Vi output voltage and the reference voltage. The current compensator 24 controls the on / off state of the first switching unit S according to the error, so that the waveform and amplitude of the actual AC input current are consistent with the current corresponding to the reference voltage signal. This makes the input voltage and input current in phase and frequency, and the input power matches the load voltage Vo power, thereby adjusting the load voltage Vo to near the preset reference voltage. The dual-layer control structure enables the circuit to achieve power factor correction while responding quickly to changes in load Vo and input voltage, maintaining the stability of the output voltage, and improving the dynamic response speed and output voltage stability of the system.

[0103] Embodiments of this application provide a control method for a power factor correction circuit, such as... Figure 11 As shown, the method includes steps S1 to S4.

[0104] Step S1: Obtain the power signal output by the AC power supply and the load voltage at both ends of the load.

[0105] The voltage sampling circuit acquires the power signal output from the AC power supply and the load voltage across the load terminals in real time. The power signal includes the voltage polarity and value information of the AC power supply, used to determine whether the current AC power supply is in the positive half-cycle (live wire voltage greater than neutral wire voltage) or the negative half-cycle (neutral wire voltage greater than live wire voltage), so as to select the corresponding control strategy for the switching transistor based on the voltage polarity. The load voltage is used to compare with a preset reference voltage to determine the deviation between the current output voltage and the target value. When the load voltage deviates from the preset reference voltage, it indicates that the current input power and load power are mismatched, and subsequent steps are needed to adjust the duty cycle of the first switching unit to change the magnitude of the input power, thereby restoring the load voltage to near the preset reference voltage.

[0106] Step S2: Generate a control signal based on the polarity of the power supply signal and the error between the load voltage and the preset reference voltage.

[0107] The load voltage obtained in step S1 is subtracted from the preset reference voltage to obtain an error signal, which reflects the deviation between the current output voltage and the target value. The error signal is then proportional-integral (PI) adjustment to generate an amplitude signal: the amplitude signal increases when the error increases and decreases when the error decreases. Simultaneously, the absolute value of the AC power supply's output voltage waveform is taken, converting the alternating positive and negative AC voltage signal into a unidirectional voltage waveform signal. The amplitude signal is multiplied by the AC power supply's output voltage waveform after taking its absolute value to generate an instantaneous reference voltage signal. This reference voltage signal has the same frequency and phase as the AC power supply's output voltage, and its amplitude is determined by the magnitude of the error.

[0108] Then, the output current signal of the AC power supply is low-pass filtered to extract the average value and filter out high-frequency switching noise. Its absolute value is then taken to convert the AC current signal into a unidirectional signal. The AC power supply output voltage signal after taking the absolute value is subtracted from the reference voltage signal to obtain the voltage error signal. This voltage error signal is then compensated to generate the control signal.

[0109] Depending on the polarity of the power supply signal, the control signal acts on different switching transistors: during the positive half-cycle, the first switching transistor remains off, and the control signal controls the high-frequency switching of the second switching transistor; during the negative half-cycle, the second switching transistor remains off, and the control signal controls the high-frequency switching of the first switching transistor.

[0110] Step S3: Control the first switching unit to turn on according to the control signal so that the power inductor generates a current in one direction.

[0111] When the control signal is a conduction signal, the corresponding first switching unit is driven to conduct. During the positive half-cycle, the second switching transistor is turned on, and the live wire of the AC power supply forms a closed loop through the body diode of the first switching transistor, the power inductor, the conduction channel of the second switching transistor to the neutral wire of the AC power supply. The AC power supply charges the power inductor, and the current of the power inductor rises linearly. The electrical energy is converted into magnetic field energy and stored in the power inductor.

[0112] During the negative half-cycle, the first switch is turned on, and the neutral wire of the AC power supply forms a closed loop through the body diode of the second switch, the power inductor, the conduction channel of the first switch, and the live wire of the AC power supply. The AC power supply charges the power inductor in reverse.

[0113] Step S4: Control the first switching unit to turn off according to the control signal so that the power inductor generates an induced current in another direction, and the second switching unit conducts the induced current unidirectionally to the load.

[0114] When the control signal is a turn-off signal, the corresponding first switching unit is turned off. During the positive half-cycle, both the first and second switching transistors are turned off. Since the current in the power inductor cannot change abruptly, an induced electromotive force is generated across its terminals, causing the potential at the second terminal of the power inductor to rise. The second diode is forward-biased, and the energy stored in the power inductor forms a closed loop through the second diode, the load, the AC power supply, and the body diode of the first switching transistor. The power inductor discharges to the load, releasing the stored magnetic field energy to the load.

[0115] During the negative half-cycle, both the first and second switching transistors are turned off, generating an induced electromotive force across the power inductor, causing the potential at the first terminal of the power inductor to rise. The first diode is forward-biased, and the energy stored in the power inductor forms a closed loop through the first diode, the load, the AC power supply, and the body diode of the second switching transistor, allowing the power inductor to discharge to the load.

[0116] Throughout the entire operation in steps S3 and S4, the closed current path formed by the AC power supply, the power inductor, and the first and second switching units in their on-state constitutes the conductive path. During the charging phase, the conductive path consists of two first switching units, i.e., the conduction channel of one switching transistor is connected in series with the body diode of another switching transistor. During the discharging phase, the conductive path consists of one first switching unit and one second switching unit, i.e., the body diode of one switching transistor is connected in series with another diode. Throughout the entire operating cycle, the number of semiconductor devices connected in series in the conductive path remains constant at two, effectively reducing the on-state voltage drop and conduction losses.

[0117] The above control method provides high-frequency on / off control signals to the corresponding first switching unit according to the polarity of the power signal. This ensures that the conductive path during the AC power supply charging the power inductor consists of two first switching units, while the conductive path during the power inductor discharging the load consists of one first switching unit and one second switching unit. The number of semiconductor devices connected in series in the main power circuit never exceeds two. Compared to the traditional structure where at least three devices are connected in series, this control method reduces the series voltage drop of one device in any operating phase, effectively lowering the on-state voltage drop and conduction losses, and improving power conversion efficiency. Furthermore, this control method only requires keeping the first switch off and applying high-frequency on / off control to the second switch during the positive half-cycle, and keeping the second switch off and applying high-frequency on / off control to the first switch during the negative half-cycle. It eliminates the need for complex multi-channel timing coordination or polarity switching logic, resulting in simple and reliable control logic. This reduces the complexity and implementation cost of the control circuit, and improves the stability and reliability of the system operation.

[0118] Embodiments of this application provide an electrical device, such as... Figure 12As shown, the electrical equipment includes a power factor correction circuit as described in any of the preceding embodiments; and a control method for executing the power factor correction circuit as described in any of the preceding embodiments.

[0119] In this embodiment, electrical equipment refers to electronic devices that are powered by AC power and need to convert AC power to DC power to provide power to internal loads, including but not limited to power adapters, chargers, inverter home appliances, industrial power supplies, communication power supplies, uninterruptible power supplies, etc.

[0120] In the embodiments of this application, by applying the power factor correction circuit and control method described in the foregoing embodiments to the electrical equipment, the electrical equipment achieves power factor correction while also possessing advantages such as a small number of series-connected devices in the main power circuit, low conduction losses, and high power conversion efficiency. Simultaneously, the electrical equipment also exhibits beneficial effects such as strong common-mode interference immunity, stable output voltage, and low conducted interference to the power grid. The specific implementation principles of these technical effects have been detailed in the above embodiments and will not be repeated here.

[0121] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A power factor correction circuit, characterized in that, include: The device includes at least one first switching unit, at least one second switching unit, and a power inductor; the first switching unit includes two conduction directions, and the second switching unit includes one conduction direction. The first switching unit is electrically connected to the power inductor and the AC power supply respectively; the second switching unit is electrically connected to the power inductor, the second switching unit and the load respectively. The first switching unit is used to control the power inductor to generate an induced current with changing direction by turning itself on and off; the second switching unit is used to conduct the induced current to the load when the first switching unit is off. The closed current path formed by the AC power supply, the power inductor, the load, the first switch unit in the on state, and the second switch unit is a conductive path. The conductive path has one first switch unit and one second switch unit, or has two first switch units.

2. The power factor correction circuit according to claim 1, characterized in that, The at least one first switching unit includes a first switching transistor and a second switching transistor; The first terminal of the first switching transistor is electrically connected to the live wire of the AC power supply, and the second terminal of the first switching transistor is electrically connected to the first terminal of the power inductor. The first terminal of the second switching transistor is electrically connected to the neutral wire of the AC power supply, and the second terminal of the second switching transistor is electrically connected to the second terminal of the power inductor.

3. The power factor correction circuit according to claim 1, characterized in that, The at least one second switching unit includes a first diode and a second diode; The first terminal of the first diode is electrically connected to the first terminal of the power inductor, and the second terminal of the first diode is electrically connected to the first terminal of the load. The first terminal of the second diode is electrically connected to the second terminal of the power inductor, and the second terminal of the second diode is electrically connected to the first terminal of the load.

4. The power factor correction circuit according to claim 3, characterized in that, The neutral wire of the AC power supply and the second terminal of the load are both electrically connected to the grounding terminal.

5. The power factor correction circuit according to any one of claims 1 to 4, characterized in that, The first switching unit is a field-effect transistor; The second switching unit is a Schottky diode.

6. The power factor correction circuit according to claim 1, characterized in that, The at least one first switching unit includes a first switching transistor and a second switching transistor; the at least one second switching unit includes a first diode and a second diode; When the live wire voltage of the AC power supply is greater than the neutral wire voltage, the first switch is off, and the second switch is on, the conductive current flows from the live wire of the AC power supply through the body diode of the first switch, the power inductor, and the second switch to the neutral wire, forming a first conductive path; the AC power supply charges the power inductor through the first conductive path. When the live wire voltage of the AC power supply is greater than the neutral wire voltage, the first switch is off, and the second switch is off, the induced current of the power inductor flows from the second terminal of the power inductor, the second diode, the load, the AC power supply, the body diode of the first switch to the first terminal of the power inductor, forming a second conductive path; the power inductor discharges to the load through the second conductive path.

7. The power factor correction circuit according to claim 1, characterized in that, The switching module includes a first switching transistor and a second switching transistor; the at least one second switching unit includes a first diode and a second diode; When the live wire voltage of the AC power supply is less than the neutral wire voltage, and the first switch is turned on and the second switch is turned off, the conductive current flows from the neutral wire of the AC power supply through the body diode of the second switch unit, the power inductor, and the live wire of the AC power supply from the first switch unit, forming a third conductive path; the AC power supply charges the power inductor through the third conductive path. When the live wire voltage of the AC power supply is less than the neutral wire voltage, the first switch unit is off, and the second switch unit is off, the induced current of the power inductor flows from the first end of the power inductor through the first diode, the load, the body diode of the second switch tube, and to the second end of the power inductor, forming a fourth conductive path; the power inductor discharges to the load through the fourth conductive path.

8. The power factor correction circuit according to claim 1, characterized in that, It also includes a voltage regulator capacitor; The first terminal of the voltage-stabilizing capacitor is electrically connected to the first terminal of the load; the second terminal of the voltage-stabilizing capacitor is electrically connected to the second terminal of the load. The voltage stabilizing capacitor is used to provide current to the load when the first switching unit is turned off and the power inductor stops discharging to the load, so as to maintain the voltage stability across the load.

9. The power factor correction circuit according to claim 1, characterized in that, It also includes a filter inductor and a filter capacitor; the switching module includes a first switching unit; The first end of the filter inductor is electrically connected to the live wire of the AC power supply, and the second end is electrically connected to the first end of the first switching unit. The first end of the filter capacitor is electrically connected to the second end of the filter inductor, and the second end is electrically connected to the neutral wire of the AC power supply.

10. The power factor correction circuit according to claim 9, characterized in that, It also includes a reference unit, a comparison unit, and a drive unit; The reference unit is electrically connected to the AC power supply, the load, and the comparison unit, respectively. The driving unit is electrically connected to the comparison unit and the switching unit respectively; The comparison unit is electrically connected to an AC power supply; The reference unit is used to generate a reference voltage signal based on the difference between the voltage across the load and a preset reference voltage. The comparison unit is used to generate a control signal based on the comparison result between the reference voltage signal and the output current signal of the AC power supply; The drive unit is used to control the switching unit to open or close according to the control signal.

11. A control method for a power factor correction circuit, characterized in that, include: Obtain the power signal output from the AC power supply and the load voltage across the load terminals; A control signal is generated based on the polarity of the power signal and the difference between the load voltage and the preset reference voltage; The first switching unit is turned on according to the control signal so that the power inductor generates a current in one direction; The first switching unit is controlled to turn off according to the control signal, so that the power inductor generates an induced current in another direction, and the second switching unit conducts the induced current unidirectionally to the load. The closed current path formed by the AC power supply, the power inductor, the first switch unit in the conducting state, and the second switch unit is a conductive path. The conductive path has one first switch unit and one second switch unit, or has two first switch units.

12. An electrical appliance, comprising a power factor correction circuit as described in any one of claims 1 to 10; and a control method for executing the power factor correction circuit as described in claim 11.

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