A bridgeless power factor correction (PFC) circuit

Abstract

A bridgeless PFC correction circuit comprises a control module, which collects current flowing through a current sampling element and controls a switching element to be closed when the current flowing through the current sampling element is greater than a first threshold. The closing of the switching element can be controlled according to the current flowing through the current sampling element, so that the switching element can be turned on at zero voltage. Since the collected current does not change abruptly, the requirement for the time delay of a sampling control circuit included in the control module is reduced, and the signal anti-interference capability of the control module is stronger.

Description

Technical Field

[0001] This application relates to the field of circuits, and more particularly to a bridgeless power factor correction (PFC) circuit. Background Technology

[0002] Currently, green, energy-saving, and high-efficiency technologies have become an inevitable trend in power supply development. Bridgeless PFC circuits, due to their high efficiency and high power density, have become the mainstream technology in the industry.

[0003] In bridgeless boost PFC circuits, switching transistors with lower on-resistance can replace low-frequency rectifier diodes, making them more suitable for high-efficiency, high-power-density applications. When the AC power supply operates at different cycles, the PFC circuit needs to control the closing or opening of different switching elements accordingly to achieve its rectification function. In existing solutions, a first control signal is generated by detecting the voltage of the switching element, and a second control signal is generated by detecting the AC input voltage. These two control signals are then combined to form a final control signal, which controls the closing or opening of the switching element to achieve zero-voltage switching.

[0004] However, the voltage changes of the switching element are quite drastic, which places high demands on the sampling control circuit, and the sampling control circuit has weak signal anti-interference capability. Summary of the Invention

[0005] This application provides a bridgeless PFC correction circuit. The control module collects the current flowing through the current sampling element. When the current flowing through the current sampling element is greater than a first threshold, the control module controls the switching element to close. In this way, the closing of the switching element can be controlled based on the current flowing through the current sampling element, thereby achieving zero-voltage switching of the switching element. Since the collected current does not change abruptly, the time delay requirement of the sampling control circuit included in the control module is reduced, and the signal anti-interference capability of the control module is strong.

[0006] This application provides a PFC circuit, comprising: an AC power supply, a low-frequency switching module, a power module, and a control module. The low-frequency switching module includes a switching element, the power module includes a first inductor, and the control module includes a current sampling element. The AC power supply is connected to the low-frequency switching module via the switching element, the AC power supply is connected to the power module via the first inductor, the low-frequency switching module and the power module are connected via the switching element, the control module is connected to the power module via the current sampling element, and / or the control module is connected to the low-frequency switching module via the current sampling element. The control module controls the switching element included in the low-frequency switching module to close or open. The control module collects the current flowing through the current sampling element. When the current flowing through the current sampling element is greater than a first threshold, the control module controls the switching element to close or open.

[0007] This application provides a bridgeless PFC correction circuit. The control module collects the current flowing through the current sampling element. When the current flowing through the current sampling element is greater than a first threshold, the control module controls the switching element to close. In this way, the closing of the switching element can be controlled based on the current flowing through the current sampling element, thereby achieving zero-voltage switching of the switching element. Since the collected current does not change abruptly, the time delay requirement of the sampling control circuit included in the control module is reduced, and the signal anti-interference capability of the control module is strong.

[0008] In one possible implementation of the first aspect, the circuit described above comprises: the switching element including a first low-frequency switch and a second low-frequency switch; the power module further including a first power switch, a second power switch, and a first capacitor; the current sampling element including a first sampling element; a first terminal of the AC power supply connected to a first terminal of the first inductor; a second terminal of the AC power supply connected to a first terminal of the first low-frequency switch and a first terminal of the second low-frequency switch; a second terminal of the first inductor connected to a first terminal of the first power switch and a first terminal of the second power switch; a second terminal of the first low-frequency switch connected to a second terminal of the first power switch; a second terminal of the second low-frequency switch connected to a second terminal of the second power switch; the first capacitor connected in parallel with a bridge arm branch including the first power switch and the second power switch; an input terminal of the control module connected to the first sampling element; and an output terminal of the control module connected to a third terminal of the first low-frequency switch and a third terminal of the second low-frequency switch; the position of the first sampling element differs when the AC power supply is in different output states.

[0009] One possible implementation provides an optional circuit topology where the first sampling element can be connected to different branches when the AC power supply is in different output states. In this way, the control module can collect the current of different branches through the first sampling element and then control the low-frequency switching element based on the current of each branch.

[0010] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the positive half-cycle and the first power switch is in the closed state, the first sampling element is connected in series in the branch where the first power switch is located; when the current flowing through the first sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

[0011] In this possible implementation, when the AC power supply is operating in the positive half-cycle and the first power switch is in the closed state, the first sampling element is connected in series to the branch where the first power switch is located. Then, the control module can control the first low-frequency switch according to the current flowing through the first power switch.

[0012] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the positive half-cycle and the first power switch is in the off state, the first sampling element is connected in series in the branch where the second power switch is located; when the current flowing through the first sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

[0013] In this possible implementation, when the AC power supply is operating in the positive half-cycle and the first power switch is in the off state, the first sampling element is connected in series to the branch where the second power switch is located. Then, the control module can control the first low-frequency switch according to the current flowing through the second power switch.

[0014] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the negative half-cycle and the second power switch is in the closed state, the first sampling element is connected in series in the branch where the second power switch is located; when the current flowing through the first sampling element is greater than a first threshold, the control module controls the second low-frequency switch to close.

[0015] In this possible implementation, when the AC power supply is operating in the negative half-cycle and the second power switch is in the closed state, the first sampling element is connected in series to the branch where the second power switch is located. Then, the control module can control the second low-frequency switch according to the current flowing through the second power switch.

[0016] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the negative half-cycle and the second power switch is in the off state, the first sampling element is connected in series in the branch where the first power switch is located; when the current flowing through the first sampling element is greater than the first threshold, the control module controls the second low-frequency switch to close.

[0017] In this possible implementation, when the AC power supply is operating in the negative half-cycle and the second power switch is in the off state, the first sampling element is connected in series to the branch where the first power switch is located. Then, the control module can control the second low-frequency switch according to the current flowing through the first power switch.

[0018] In one possible implementation of the first aspect, the circuit described above includes a second sampling element, wherein when the AC power supply is operating in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the second power switch is located; when the sum of the currents flowing through the first sampling element and the second sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

[0019] In this possible implementation, the control module can control the first low-frequency switch by the sum of the currents flowing through the first sampling element and the second sampling element, providing a specific implementation method.

[0020] In one possible implementation of the first aspect, the circuit described above includes: the current sampling element further includes a second sampling element; when the AC power supply is operating in the negative half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the second power switch is located; when the sum of the currents flowing through the first sampling element and the second sampling element is greater than a first threshold, the control module controls the second low-frequency switch to close.

[0021] In this possible implementation, the control module can control the second low-frequency switch by the sum of the currents flowing through the first sampling element and the second sampling element, providing a specific implementation method.

[0022] In one possible implementation of the first aspect, the circuit described above includes: the low-frequency switching module further comprising a first diode and a second diode; the cathode of the first diode is connected to a first terminal of the AC power supply and the anode of the second diode, and the anode of the first diode is connected to a second terminal of the first low-frequency switch and a second terminal of the first power switch; the anode of the second diode is connected to a first terminal of the AC power supply, and the cathode of the second diode is connected to a second terminal of the second low-frequency switch and a second terminal of the second power switch; the control module acquires the current of a third sampling element, wherein the current flowing through the third sampling element is the current flowing through the first diode or the second diode; when the current flowing through the third sampling element is greater than a second threshold, the control module controls the first low-frequency switch or the second low-frequency switch to disconnect.

[0023] In this possible implementation, the low-frequency switching module includes a first diode and a second diode. When the current in the first or second diode exceeds a first threshold, the control module can turn off the low-frequency switch to protect it, thereby improving the reliability of the PFC circuit.

[0024] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the positive half-cycle and the first low-frequency switch is in the on state, the third sampling element is connected in series in the branch where the first diode is located, or the third sampling element is connected in series in the branch between the first terminal of the AC power supply and the first connection point, where the first connection point is the connection point between the first diode and the second diode; when the current flowing through the third sampling element is greater than the first threshold, the control module controls the first low-frequency switch to turn off.

[0025] In one possible implementation, the third sampling element is connected in series in the branch where the first diode is located, or the third sampling element is connected in series in the branch between the first terminal of the AC power supply and the first connection point. The control module collects the current flowing through the first diode. When the control module confirms that the current in the third sampling element is greater than the first threshold, the control module can disconnect the first low-frequency switch to protect it.

[0026] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply operates in the negative half-cycle and the second low-frequency switch is in the on state, the third sampling element is connected in series in the branch where the second diode is located, or the third sampling element is connected in the branch between the first terminal of the AC power supply and the first connection point, where the first connection point is the connection point between the first diode and the second diode; when the current flowing through the third sampling element is greater than the first threshold, the control module controls the second low-frequency switch to turn off, thereby improving the reliability of the PFC circuit.

[0027] In this possible implementation, the third sampling element is connected in series in the branch where the second diode is located, or the third sampling element is connected in the branch between the first terminal of the AC power supply and the first connection point. The control module collects the current flowing through the second diode. When the control module confirms that the current in the third sampling element is greater than the first threshold, in order to protect the second low-frequency switch, the control module can disconnect the second low-frequency switch, thereby improving the reliability of the PFC circuit.

[0028] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply is operating in the positive half-cycle and the first low-frequency switch is in the on state, the third sampling element is connected in series between the second connection point and the third connection point, the second connection point being the connection point between the first diode and the first power switch, and the third connection point being the connection point between the first low-frequency switch and the first capacitor, and the third sampling element is the same as the first sampling element; when the current flowing through the third sampling element is greater than a first threshold, the control module controls the first low-frequency switch to turn off.

[0029] In this possible implementation, the third sampling element is connected in series between the second connection point and the third connection point. The control module can collect the current flowing through the first diode. When the control module confirms that the current in the third sampling element is greater than the first threshold, the control module can disconnect the first low-frequency switch, thereby improving the reliability of the PFC circuit.

[0030] In one possible implementation of the first aspect, the circuit is as follows: when the AC power supply operates in the negative half-cycle and the second low-frequency switch is in the on state, the third sampling element is connected in series between the fourth connection point and the fifth connection point, the fourth connection point being the connection point between the second diode and the second power switch, and the fifth connection point being the connection point between the second low-frequency switch and the first capacitor, and the third sampling element is the same as the first sampling element; when the current flowing through the third sampling element is greater than the first threshold, the control module controls the second low-frequency switch to turn off.

[0031] In this possible implementation, the third sampling element is connected in series between the fourth and fifth connection points. The control module can collect the current flowing through the second diode. When the control module confirms that the current in the third sampling element is greater than the first threshold, the control module can disconnect the second low-frequency switch, thereby improving the reliability of the PFC circuit.

[0032] In one possible implementation of the first aspect, the circuit described above includes: the power module further comprising a second inductor, a third power switch, and a fourth power switch; a first terminal of the second inductor being connected to a first terminal of the AC power supply, and a second terminal of the second inductor being connected to a first terminal of the third power switch; a first capacitor being connected in parallel with a bridge arm branch including the third power switch and the fourth power switch; a second terminal of the third power switch being connected to a second terminal of the first power switch; and a first terminal of the fourth power switch being connected to a first terminal of the second power switch, and a second terminal of the fourth power switch being connected to a first terminal of the third power switch.

[0033] In this possible implementation, the PFC circuit includes multiple boost circuits, which can improve the rectification efficiency of the PFC circuit.

[0034] In one possible implementation of the first aspect, the circuit described above includes: the current sampling element further comprising a second sampling element; when the AC power supply is operating in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the third power switch is located; or, the first sampling element is connected in series in the branch where the second power switch is located, and the second sampling element is connected in series in the branch where the fourth power switch is located; when the sum of the currents flowing through the first sampling element and the second sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

[0035] In one possible implementation, the first sampling element is connected in series in the branch containing the first power switch, and the second sampling element is connected in series in the branch containing the third power switch; alternatively, the first sampling element is connected in series in the branch containing the second power switch, and the second sampling element is connected in series in the branch containing the fourth power switch. The control module can control the closing of the first low-frequency switch by collecting the sum of the currents of the first and third power switches, or by collecting the sum of the currents of the second and fourth power switches.

[0036] In one possible implementation of the first aspect, the circuit described above includes a second sampling element. When the AC power supply operates in the negative half-cycle, the first sampling element is connected in series in the branch containing the second power switch, and the second sampling element is connected in series in the branch containing the fourth power switch; or, the first sampling element is connected in series in the branch containing the first power switch, and the second sampling element is connected in series in the branch containing the third power switch. When the sum of the currents flowing through the first sampling element and the second sampling element exceeds a first threshold, the control module controls the second low-frequency switch to close.

[0037] In one possible implementation, the first sampling element is connected in series in the branch containing the second power switch, and the second sampling element is connected in series in the branch containing the fourth power switch; alternatively, the first sampling element is connected in series in the branch containing the first power switch, and the second sampling element is connected in series in the branch containing the third power switch. The control module can control the closing of the second low-frequency switch by collecting the sum of the currents of the second and fourth power switches, or by collecting the sum of the currents of the first and third power switches.

[0038] In one possible implementation of the first aspect, the circuit described above includes: the current sampling element further comprising a second sampling element, a fourth sampling element, and a fifth sampling element; when the AC power supply operates in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, the second sampling element is connected in series in the branch where the second power switch is located, the fourth sampling element is connected in series in the branch where the third power switch is located, and the fifth sampling element is connected in series in the branch where the fourth power switch is located; when the sum of the currents flowing through the first sampling element, the second sampling element, the fourth sampling element, and the fifth sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

[0039] In this possible implementation, the control module can collect the sum of the currents flowing through the first power switch, the second power switch, the third power switch, and the fourth power switch to control the closing of the first low-frequency switch.

[0040] In one possible implementation of the first aspect, the circuit described above includes: the current sampling element further comprising a second sampling element, a fourth sampling element, and a fifth sampling element; when the AC power supply operates in the negative half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, the second sampling element is connected in series in the branch where the second power switch is located, the fourth sampling element is connected in series in the branch where the third power switch is located, and the fifth sampling element is connected in series in the branch where the fourth power switch is located; when the sum of the currents flowing through the first sampling element, the second sampling element, the fourth sampling element, and the fifth sampling element is greater than a first threshold, the control module controls the second low-frequency switch to close.

[0041] In this possible implementation, the control module can collect the sum of the currents flowing through the first power switch, the second power switch, the third power switch, and the fourth power switch to control the closing of the second low-frequency switch.

[0042] In one possible implementation of the first aspect, the control module further includes a controller, which is composed of discrete components, or the controller is composed of logic devices.

[0043] In one possible implementation of the first aspect, the logic device includes a complex programmable logic device (CPLD), a microcontroller unit (MCU), a field programmable gate array (FPGA), a central processing unit (CPU), or a digital signal processor (DSP).

[0044] In one possible implementation of the first aspect, the power module may operate in Critical Conduction Mode (CRM), Continuous Current Mode (CCM), Triangular Current Mode (TCM), or Discontinuous Current Mode (DCM).

[0045] In one possible implementation of the first aspect, the switching element includes an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a gallium nitride field-effect transistor (GaN FET).

[0046] In one possible implementation of the first aspect, the current sampling element is a resistor or a computed tomography (CT).

[0047] A second aspect of this application provides a communication power supply, the communication power supply including the PFC circuit, the PFC circuit including an AC power supply, a low-frequency switching module, a power module and a control module, the PFC circuit being the PFC circuit described in the first aspect or any possible implementation of the first aspect. Attached Figure Description

[0048] Figure 1 This is a basic topology diagram of a bridgeless PFC circuit provided in an embodiment of this application;

[0049] Figure 2 This is a basic topology diagram of another bridgeless PFC circuit provided in the embodiments of this application;

[0050] Figure 3 This is a schematic diagram of a bridgeless PFC circuit provided in an embodiment of this application;

[0051] Figure 4 This is a schematic diagram of an embodiment of a bridgeless PFC circuit provided in this application;

[0052] Figure 4a This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0053] Figure 5 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0054] Figure 6 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0055] Figure 7 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0056] Figure 8This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0057] Figure 9 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0058] Figure 9a This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0059] Figure 10 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0060] Figure 11 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0061] Figure 12 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0062] Figure 13 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0063] Figure 14 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application;

[0064] Figure 15 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0066] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0067] Currently, green, energy-saving, and high-efficiency technologies have become an inevitable trend in power supply development. Bridgeless PFC circuits, due to their high efficiency and high power density, have become the mainstream technology in the industry.

[0068] Optionally, this bridgeless PFC circuit can be used in communication power supplies, in boost rectifiers, and in other electronic devices; specific applications are not limited here.

[0069] Figure 1 This is a basic topology diagram of a bridgeless PFC circuit provided in an embodiment of this application.

[0070] Please see Figure 1 , Figure 1 The basic topology of a bridgeless PFC circuit is shown. This basic topology includes an AC power supply, two rectifier diodes A1 and A2 connected in series, two switching elements S3 and S4 connected in series, an inductor L1, and a capacitor C. The series-connected switching elements S3 and S4 can be metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0071] Optionally, a bridgeless PFC circuit can operate with a single bridge arm, or with two bridge arms staggered by 180 degrees, or with three bridge arms staggered by 120 degrees. Specific limitations are not specified here.

[0072] For example, the working principle of a bridgeless PFC circuit is illustrated using a single-bridge arm operation. If the switching elements S3 and S4 are MOSFETs, the AC power supply is considered to be operating in the positive half-cycle when the current output is in the positive half-cycle. At this time, MOSFET S4 acts as the main conductor and MOSFET S3 acts as the synchronizing transistor. During the on-time Ton of MOSFET S4, the current loop flows through inductor L1, MOSFET S4, and diode D2. Inductor L1 stores energy during this time. During the off-time Toff of MOSFET S4, the current loop flows through inductor L1, MOSFET S3, capacitor C, and diode A2. Inductor L1 outputs energy during this time. The AC power supply and inductor L1 charge capacitor C. Similarly, when the current output is in the negative half-cycle, the AC power supply is considered to be operating in the negative half-cycle. MOSFET S3 acts as the main conductor and MOSFET S4 acts as the synchronizing transistor. During the on-time Ton of MOSFET S3, the current loop flows through inductor L1, MOSFET S3, and diode A1. Inductor L1 stores energy during this time. During the off-time Toff of MOSFET S3, the current loop flows through inductor L1, MOSFET S4, capacitor C, and diode D1, while the AC power supply and inductor L1 charge capacitor C.

[0073] In this embodiment, the bridgeless PFC circuit can operate in CRM mode, TCM mode, CCM mode, and DCM mode. It can also operate in other modes, which are not limited here. The characteristics of each operating mode are briefly described below.

[0074] When the bridgeless PFC circuit operates in CRM mode, the reverse recovery current of the synchronous transistor's body diode is used to turn on the main transistor's body diode, thus achieving zero-voltage turn-on of the main transistor. When the bridgeless PFC circuit operates in TCM mode, the negative current of the synchronous transistor is sampled and controlled to turn on the main transistor's body diode, thus achieving zero-voltage turn-on of the main transistor. When the bridgeless PFC circuit operates in CCM mode, if the switching element is a GaN transistor, there is no reverse recovery problem, and GaN transistors can be directly used in the bridgeless PFC circuit. If the switching element is an IGBT or MOSFET, taking MOSFET as an example, a diode with the opposite polarity to its body diode is usually connected in series with the MOSFET switching element, and another diode is connected in parallel with its positive and negative terminals connected to the source of the MOSFET and the cathode of the series diode, respectively. The parallel diode is usually a silicon carbide (SiC) diode, a GaN diode, or a fast recovery diode. This solves the reverse recovery problem in CCM mode. DCM mode will not be discussed in detail here.

[0075] Figure 2 This is a basic topology diagram of another bridgeless PFC circuit provided in the embodiments of this application.

[0076] like Figure 2 As shown, to further improve the power density and efficiency of bridgeless PFC circuits, commonly used methods include... Figure 2 The switch elements S1 and S2 shown are replaced as follows: Figure 1 The rectifier diodes A1 and A2 are shown.

[0077] When the AC power supply operates in different cycles, the PFC circuit needs to control S1 and S2 to close or open accordingly, thereby achieving the rectification function of the PFC circuit. In existing technical solutions, a first control signal is generated by detecting the voltage of the switching element, and a second control signal is generated by detecting the AC input voltage. The first and second control signals are combined to form a final control signal, which then controls the closing or opening of the switching element.

[0078] However, the voltage changes of the switching element are relatively drastic, and the sampling control circuit used to sample the voltage of the switching element has low delay requirements and weak signal anti-interference capability.

[0079] To address the aforementioned problems in the control of existing bridgeless PFC circuits, this application provides a bridgeless PFC circuit. The control module collects the current flowing through a current sampling element. When the current flowing through the current sampling element exceeds a first threshold, the control module controls the switching element to close. Thus, the closing of the switching element can be controlled based on the current flowing through the current sampling element, thereby achieving zero-voltage switching of the switching element. Since the collected current does not change abruptly, the time delay requirement of the sampling control circuit included in the control module is reduced, and the control module has strong signal anti-interference capability.

[0080] Figure 3 This is a schematic diagram of a bridgeless PFC circuit provided in an embodiment of this application.

[0081] like Figure 3 As shown, the bridgeless PFC circuit includes: an AC power supply, a low-frequency switching module, a power module, and a control module. The low-frequency switching module includes switching elements, the power module includes a first inductor, and the control module includes a current sampling element. It is understood that this bridgeless PFC circuit may also include other modules; specific details are not limited here.

[0082] In this embodiment, the modules included in the bridgeless PFC circuit are interconnected. The AC power supply and the low-frequency switching module are connected via a switching element, the AC power supply and the power module are connected via a first inductor, the low-frequency switching module and the power module are connected via a switching element, the control module and the power module are connected via a current sampling element, and / or the control module and the low-frequency switching module are connected via a current sampling element. The control module controls the switching elements included in the low-frequency switching module to close or open.

[0083] In this embodiment, the control module collects the current flowing through the current sampling element. Thus, when the current flowing through the current sampling element exceeds a first threshold, the control module can control the switching element to close. Therefore, the control module can control the switching element based on the current flowing through the sampling element.

[0084] based on Figure 3 The following is a schematic diagram of the bridgeless PFC circuit described in the embodiments of this application.

[0085] Figure 4 This is a schematic diagram of an embodiment of a bridgeless PFC circuit provided in this application.

[0086] In this application embodiment, one possible implementation is as follows: Figure 4 As shown. The switching elements included in the bridgeless PFC circuit may include a first low-frequency switch and a second low-frequency switch, and may also include other low-frequency switches, which are not limited here. The power module included in the bridgeless PFC circuit also includes a first power switch, a second power switch and a first capacitor. The current sampling element includes a first sampling element, and may also include other elements, which are not limited here.

[0087] In the embodiments of this application, such as Figure 4 As shown, the first terminal of the AC power supply is connected to the first terminal of the first inductor, and the second terminal of the AC power supply is connected to the first terminals of the first and second low-frequency switches. The second terminal of the first inductor is connected to the first terminals of the first and second power switches. The second terminal of the first low-frequency switch is connected to the second terminal of the first power switch. The second terminal of the second low-frequency switch is connected to the second terminal of the second power switch. The first capacitor is connected in parallel with the bridge arm branch including the first and second power switches. The input terminal of the control module is connected to the first sampling element, and the output terminal of the control module is connected to the third terminals of the first and second low-frequency switches.

[0088] In this embodiment, when the AC power supply is in different output states, the position of the first sampling element is different, and the control module can collect the current of different branches, and then control the closing of the first low-frequency switch and the second low-frequency switch according to the current of different branches.

[0089] In this embodiment, the control module may further include a controller, which may be composed of discrete components or logic devices. The control module may also be composed of other devices, which are not specifically limited here.

[0090] In the embodiments of this application, the logic device may include a complex CPLD, MCU, FPGA, CPU, DSP, or other devices, which are not limited here.

[0091] In this embodiment, the power module can operate in critical conduction mode (CRM), continuous current mode (CCM), delta current mode (TCM), or discontinuous current mode (DCM). The power module can also operate in other modes, which are not limited here.

[0092] In the embodiments of this application, the switching element may include IGBT, MOSFET or GaN FET, and the switching element may also be other elements, which are not limited here.

[0093] In this embodiment, the current sampling element is a resistor or a current transformer (CT). The current sampling element can also be other devices, which are not limited here.

[0094] Figure 4a The diagram shows the driving waveform of the first low-frequency switch S2, the current waveform of the first inductor L1, and the voltage waveform of the AC input during the positive half-cycle of the AC input. Figure 9 As can be seen, when the current flowing through the first inductor L1 rises to the preset threshold, the controller turns on the first low-frequency switch S2. When the positive half-cycle is about to end and the AC input voltage is lower than the preset value, the controller turns off the first low-frequency switch S2. This achieves zero-voltage turn-on of the first low-frequency switch S2 and synchronous rectification at the power frequency.

[0095] Figure 5 This is a schematic diagram of an embodiment of a bridgeless PFC circuit provided in this application.

[0096] In this application embodiment, one possible implementation is as follows: Figure 5 As shown. When the AC power supply is operating in the positive half-cycle and the first power switch is in the closed state, the first sampling element is connected in series in the branch where the first power switch is located. Optionally, the first sampling element can be connected in series in the branch where the first power switch is located at position a1, or at position b1. The first sampling element can also be connected in other equivalent ways to the branch where the first power switch is located; specific details are not limited here.

[0097] In this embodiment, when the AC power supply is operating in the positive half-cycle and the first power switch is closed, current flows through the first inductor L1, the first power switch S4, and the first low-frequency switch S2. At this time, the first inductor L1 stores energy. When the controller in the control module confirms that the current flowing through the first sampling element M1 is greater than the first threshold, the control module can control the first low-frequency switch S2 to close, thus achieving zero-voltage switching and power frequency synchronous rectification of the first low-frequency switch S2.

[0098] Figure 6 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0099] In this application embodiment, one possible implementation is as follows: Figure 6 As shown, when the AC power supply is operating in the positive half-cycle and the first power switch is in the off state, the first sampling element is connected in series in the branch where the second power switch is located. Optionally, the first sampling element M1 can be connected in series in the branch where the second power switch S3 is located at position a2, or at position b2. The first sampling element M1 can also be connected in other equivalent ways to the branch where the second power switch S3 is located; the specific method is not limited here.

[0100] In this embodiment, when the AC power supply is operating in the positive half-cycle and the first power switch S4 is in the open state, current flows through the first inductor L1, the second power switch S3, the first capacitor C1, and the first low-frequency switch S2. At this time, the first inductor L1 outputs energy, and the AC power supply and the first inductor L1 together charge the first capacitor C1. When the controller in the control module confirms that the current flowing through the first sampling element M1 is greater than the first threshold, the control module can control the first low-frequency switch S2 to close, thus realizing the zero-voltage turn-on of the first low-frequency switch S2 and synchronous rectification at the power frequency.

[0101] Figure 7 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0102] In this application embodiment, one possible implementation is as follows: Figure 7 As shown, when the AC power supply operates in the negative half-cycle and the second power switch S3 is in the closed state, the first sampling element M1 is connected in series in the branch where the second power switch S3 is located. Optionally, the first sampling element M1 can be connected in series in the branch where the second power switch S3 is located at position a3, the first sampling element M1 can be connected in series in the branch where the second power switch S3 is located at position b3, or the first sampling element M1 can be connected in other equivalent ways, which are not limited here.

[0103] In this embodiment, when the AC power supply operates in the negative half-cycle and the second power switch S3 is closed, current flows through the second low-frequency switch S1, the second power switch S3, and the first inductor L1. When the controller in the control module confirms that the current flowing through the first sampling element M1 is greater than the first threshold, the control module controls the second low-frequency switch S1 to close, thus realizing zero-voltage switching and power frequency synchronous rectification of the second low-frequency switch S1.

[0104] Figure 8 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0105] In this application embodiment, one possible implementation is as follows: Figure 8 As shown, when the AC power supply is operating in the negative half-cycle and the second power switch S3 is in the open state, the first sampling element M1 is connected in series in the branch where the first power switch S4 is located. Optionally, the first sampling element M1 can be connected in series in the branch where the first power switch S4 is located at position a4, the first sampling element M1 can be connected in series in the branch where the first power switch S4 is located at position b4, or the first sampling element M1 can be connected in other equivalent ways, which are not limited here.

[0106] In this embodiment, when the AC power supply operates in the negative half-cycle and the second power switch S3 is in the open state, current flows through the second low-frequency switch S1, the first capacitor C, the first power switch S4, and the first inductor L1. When the controller in the control module confirms that the current flowing through the first sampling element M1 is greater than the first threshold, the control module controls the second low-frequency switch S1 to close, thus realizing the zero-voltage turn-on of the second low-frequency switch S1 and synchronous rectification at the power frequency.

[0107] Figure 9 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0108] In this application embodiment, one possible implementation is as follows: Figure 9 As shown, optionally, the current sampling element may also include a second sampling element M2.

[0109] When the AC power supply is operating in the positive half-cycle, the first sampling element M1 is connected in series in the branch where the first power switch S4 is located. Optionally, the first sampling element M1 can be connected in series at position d1, or at position c1, or in other equivalent ways; specific details are not limited here.

[0110] The second sampling element M2 is connected in series in the branch where the second power switch S3 is located. Optionally, the second sampling element M2 is connected in series in the branch where the second power switch S3 is located. Optionally, the second sampling element M2 can be connected in series in the branch where the second power switch S3 is located at position a5, the second sampling element M2 can be connected in series in the branch where the second power switch S3 is located at position b5, or the second sampling element M2 can be connected in other equivalent ways, which are not limited here.

[0111] When the controller in the control module confirms that the sum of the currents flowing through the first sampling element M1 and the second sampling element M2 is greater than the first threshold, the control module controls the first low-frequency switch S2 to close, thus realizing the zero-voltage turn-on of the first low-frequency switch S2 and the power frequency synchronous rectification.

[0112] When the AC power supply is operating in the negative half-cycle, the first sampling element M1 is connected in series in the branch where the first power switch is located, and the second sampling element M2 is connected in series in the branch where the second power switch is located. The specific series connection method is the same as in the above embodiment. Figure 9 The methods shown are similar, and will not be elaborated here.

[0113] When the controller in the control module confirms that the sum of the currents flowing through the first sampling element M1 and the second sampling element M2 is greater than the first threshold, the control module controls the second low-frequency switch S1 to close, thus realizing the zero-voltage turn-on of the second low-frequency switch S1 and the power frequency synchronous rectification.

[0114] In one possible implementation, the low-frequency switching module may optionally include a first diode D2 and a second diode D1.

[0115] In this embodiment, the cathode of the first diode D2 is connected to the first terminal of the AC power supply and the anode of the second diode D1. The anode of the first diode D2 is connected to the second terminal of the first low-frequency switch S2 and the second terminal of the first power switch S4. The anode of the second diode D1 is connected to the first terminal of the AC power supply, and the cathode of the second diode D1 is connected to the second terminal of the second low-frequency switch S1 and the second terminal of the second power switch S3. The control module collects the current of the third sampling element, and the current flowing through the third sampling element is the current flowing through the first diode or the second diode.

[0116] When the controller in the control module confirms that the current flowing through the third sampling element is greater than the first threshold, the controller in the control module controls the first low-frequency switch or the second low-frequency switch to open.

[0117] In this embodiment, the protection of the first low-frequency switch S2 is used as an example for explanation. Under severe conditions such as lightning strikes, excessive reverse current in the channel direction of the low-frequency switch element can easily lead to device damage. Figure 9a The diagram shows the driving waveform of the first low-frequency switch S2, the current waveform of the first inductor L1, the current waveform of the first low-frequency switch S2, and the AC input voltage waveform. From... Figure 9a As can be seen from this, when the negative current flowing through the first low-frequency switch S2 rises to a preset value, the controller included in the control module will quickly turn off the first low-frequency switch S2, thus realizing the negative overcurrent protection of the first low-frequency switch S2.

[0118] Figure 10 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0119] In this application embodiment, one possible implementation is as follows: Figure 10 As shown, optionally, when the AC power supply is operating in the positive half-cycle and the first low-frequency switch S2 is in the conducting state, the third sampling element M3 is connected in series in the branch where the first diode D2 is located. Optionally, the third sampling element M3 can be connected in series in the branch where the first diode D2 is located at position a6, or at position b6. The third sampling element M3 can also be connected in other equivalent ways to the branch where the first diode D2 is located; specific details are not limited here.

[0120] Alternatively, the third sampling element M3 can also be connected in series at position c2 as shown in the figure in the branch between the first end of the AC power supply and the first connection point, where the first connection point is the connection point d2 between the first diode and the second diode.

[0121] When the controller in the control module confirms that the current flowing through the third sampling element M3 is greater than the first threshold, the controller in the control module controls the first low-frequency switch S2 to open.

[0122] Figure 11 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0123] In this application embodiment, one possible implementation is as follows: Figure 11As shown. Optionally, when the AC power supply operates in the negative half-cycle and the second low-frequency switch S1 is in the on state, the third sampling element M3 is connected in series in the branch where the second diode D1 is located. Optionally, the third sampling element M3 can be connected in series in the branch where the second diode D1 is located at position a7, the third sampling element M3 can be connected in series in the branch where the second diode D1 is located at position b7, or the third sampling element M3 can be connected in other equivalent ways, which are not limited here.

[0124] Alternatively, the third sampling element M3 can also be connected in series at position c3 as shown in the figure in the branch between the first end of the AC power supply and the first connection point, where the first connection point is the connection point d3 between the first diode and the second diode.

[0125] When the controller in the control module confirms that the current flowing through the third sampling element M3 is greater than the first threshold, the controller in the control module controls the second low-frequency switch S1 to open.

[0126] Figure 12 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0127] In this application embodiment, one possible implementation is as follows: Figure 12 As shown. Optionally, when the AC power supply is operating in the positive half-cycle and the first low-frequency switch S2 is in the conducting state, the third sampling element M3 is connected in series between the second connection point a8 and the third connection point b8. The second connection point a8 is the connection point between the first diode D2 and the first power switch S4, and the third connection point b8 is the connection point between the first low-frequency switch S2 and the first capacitor C. The third sampling element M3 is the same as the first sampling element M1.

[0128] When the controller in the control module confirms that the current flowing through the third sampling element M3 is greater than the first threshold, the controller in the control module controls the first low-frequency S2 switch to open.

[0129] Figure 13 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0130] In this application embodiment, one possible implementation is as follows: Figure 13 As shown. Optionally, when the AC power supply is operating in the negative half-cycle and the second low-frequency switch S1 is in the conducting state, the third sampling element M3 is connected in series between the fourth connection point a9 and the fifth connection point b9. The fourth connection point a9 is the connection point between the second diode D1 and the second power switch S3, and the fifth connection point b9 is the connection point between the second low-frequency switch S1 and the first capacitor C. The third sampling element M3 is the same as the first sampling element M1.

[0131] When the controller in the control module confirms that the current flowing through the third sampling element M3 is greater than the first threshold, the controller in the control module controls the second low-frequency switch S1 to open.

[0132] In one possible implementation, the power module may also include a second inductor L2, a third power switch S6, and a fourth power switch S5.

[0133] The first terminal of the second inductor L2 is connected to the first terminal of the AC power supply, and the second terminal of the second inductor L2 is connected to the first terminal of the third power switch S6. The first capacitor C is connected in parallel with the bridge arm branch including the third power switch S6 and the fourth power switch S5. The second terminal of the third power switch S6 is connected to the second terminal of the first power switch S4. The first terminal of the fourth power switch S5 is connected to the first terminal of the second power switch S3, and the second terminal of the fourth power switch S5 is connected to the first terminal of the third power switch S6.

[0134] Figure 14 This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0135] In this application embodiment, one possible implementation is as follows: Figure 14 As shown. Optionally, the current sampling element may also include a second sampling element M2.

[0136] When the AC power supply is operating in the positive half-cycle, the first sampling element M1 is connected in series to the branch where the first power switch S4 is located, and the second sampling element M2 is connected in series to the branch where the third power switch S6 is located; or, the first sampling element M1 is connected in series to the branch where the second power switch S3 is located, and the second sampling element M2 is connected in series to the branch where the fourth power switch S5 is located.

[0137] When the controller in the control module confirms that the sum of the currents flowing through the first sampling element M1 and the second sampling element M2 is greater than the first threshold, the controller in the control module controls the first low-frequency switch S2 to close.

[0138] When the AC power supply is operating in the negative half-cycle, the first sampling element M1 is connected in series in the branch containing the second power switch S3, and the second sampling element M2 is connected in series in the branch containing the fourth power switch S5; or, the first sampling element M1 is connected in series in the branch containing the first power switch S4, and the second sampling element M2 is connected in series in the branch containing the third power switch S6.

[0139] When the controller in the control module confirms that the sum of the currents flowing through the first sampling element M1 and the second sampling element M2 is greater than the first threshold, the controller in the control module controls the second low-frequency switch S1 to close.

[0140] Figure 15This is a schematic diagram of another embodiment of a bridgeless PFC circuit provided in this application.

[0141] In this application embodiment, one possible implementation is as follows: Figure 15 As shown. Optionally, the current sampling element may also include a second sampling element M2, a fourth sampling element M4, and a fifth sampling element M5.

[0142] When the AC power supply is operating in the positive half-cycle, the first sampling element M1 is connected in series in the branch where the first power switch S4 is located, the second sampling element M2 is connected in series in the branch where the second power switch S3 is located, the fourth sampling element M4 is connected in series in the branch where the third power switch S6 is located, and the fifth sampling element M5 is connected in series in the branch where the fourth power switch S5 is located.

[0143] When the controller in the control module confirms that the sum of the currents flowing through the first sampling element M1, the second sampling element M2, the fourth sampling element M4, and the fifth sampling element M5 is greater than the first threshold, the control module controls the first low-frequency switch S2 to close.

[0144] When the AC power supply is operating in the negative half-cycle, the first sampling element M1 is connected in series in the branch where the first power switch S4 is located, the second sampling element M2 is connected in series in the branch where the second power switch S3 is located, the fourth sampling element M4 is connected in series in the branch where the third power switch S6 is located, and the fifth sampling element M5 is connected in series in the branch where the fourth power switch S5 is located.

[0145] When the sum of the currents flowing through the first sampling element M1, the second sampling element M2, the fourth sampling element M4, and the fifth sampling element M5 in the control module exceeds a first threshold, the control module controls the second low-frequency switch S1 to close. The bridgeless PFC circuit provided in this application uses an indirect method for acquiring the current of the low-frequency switch tube, thereby reducing the size of the current sampling element and ensuring zero-voltage turn-on and rapid negative overcurrent protection under any operating condition. By acquiring the current flowing simultaneously through the power switch element, the inductor, and the body diode of the low-frequency switch element, the low-frequency switch element is quickly turned on. Since the inductor current cannot change abruptly, the requirement for ultra-low delay of the detection and control circuit signal is reduced, thus achieving zero-voltage turn-on under any operating condition. By acquiring the current flowing simultaneously through the first switch element and the first diode in the low-frequency switch module, the low-frequency switch element is quickly turned off, preventing overcurrent damage. This invention achieves zero-voltage turn-on and negative overcurrent suppression of the low-frequency switch element in the bridgeless PFC circuit, improving the reliability of the bridgeless PFC circuit.

Claims

1. A bridgeless power factor correction (PFC) circuit, characterized in that, include: The system includes an AC power supply, a low-frequency switching module, a power module, and a control module. The low-frequency switching module includes a switching element, a first diode, and a second diode. The switching element includes a first low-frequency switch and a second low-frequency switch. The power module includes a first inductor, a first power switch, and a second power switch. The control module includes a current sampling element. The negative terminal of the first diode is connected to a first terminal of the AC power supply and the positive terminal of the second diode. The positive terminal of the first diode is connected to a second terminal of the first low-frequency switch and a second terminal of the first power switch. The positive terminal of the second diode is connected to a first terminal of the AC power supply, and the negative terminal of the second diode is connected to a second terminal of the second low-frequency switch and a second terminal of the second power switch. The AC power supply is connected to the low-frequency switching module through the switching element, the AC power supply is connected to the power module through the first inductor, the low-frequency switching module and the power module are connected through the switching element, the control module is connected to the power module through the current sampling element and / or the control module is connected to the low-frequency switching module through the current sampling element, and the control module controls the switching element included in the low-frequency switching module to close or open; The control module collects the current flowing through the current sampling element; When the current flowing through the current sampling element is greater than the first threshold, the control module controls the switching element to close or open. The control module collects the current of the third sampling element, and the current flowing through the third sampling element is the current flowing through the first diode or the second diode; When the current flowing through the third sampling element is greater than the first threshold, the control module controls the first low-frequency switch or the second low-frequency switch to disconnect.

2. The PFC circuit according to claim 1, characterized in that, The power module further includes a first capacitor, and the current sampling element includes a first sampling element; The first end of the AC power supply is connected to the first end of the first inductor, and the second end of the AC power supply is connected to the first end of the first low-frequency switch and the first end of the second low-frequency switch. The second end of the first inductor is connected to the first end of the first power switch and the first end of the second power switch; The second terminal of the first low-frequency switch is connected to the second terminal of the first power switch; The second terminal of the second low-frequency switch is connected to the second terminal of the second power switch; The first capacitor is connected in parallel with the bridge arm branch that includes the first power switch and the second power switch; The input terminal of the control module is connected to the first sampling element, and the output terminal of the control module is connected to the third terminal of the first low-frequency switch and the third terminal of the second low-frequency switch.

3. The PFC circuit according to claim 2, characterized in that, When the AC power supply is operating in the positive half-cycle and the first power switch is in the closed state, the first sampling element is connected in series to the branch where the first power switch is located. When the current flowing through the first sampling element is greater than the first threshold, the control module controls the first low-frequency switch to close.

4. The PFC circuit according to claim 2, characterized in that, When the AC power supply is operating in the positive half-cycle and the first power switch is in the off state, the first sampling element is connected in series to the branch where the second power switch is located; When the current flowing through the first sampling element is greater than the first threshold, the control module controls the first low-frequency switch to close.

5. The PFC circuit according to claim 2, characterized in that, When the AC power supply is operating in the negative half-cycle and the second power switch is in the closed state, the first sampling element is connected in series to the branch where the second power switch is located; When the current flowing through the first sampling element is greater than the first threshold, the control module controls the second low-frequency switch to close.

6. The PFC circuit according to claim 2, characterized in that, When the AC power supply is operating in the negative half-cycle and the second power switch is in the off state, the first sampling element is connected in series to the branch where the first power switch is located; When the current flowing through the first sampling element is greater than the first threshold, the control module controls the second low-frequency switch to close.

7. The PFC circuit according to claim 2, wherein the current sampling element further comprises a second sampling element, characterized in that, When the AC power supply is operating in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the second power switch is located. When the sum of the currents flowing through the first sampling element and the second sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

8. The PFC circuit according to claim 2, characterized in that, The current sampling element further includes a second sampling element. When the AC power supply is operating in the negative half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the second power switch is located. When the sum of the currents flowing through the first sampling element and the second sampling element is greater than the first threshold, the control module controls the second low-frequency switch to close.

9. The PFC circuit according to any one of claims 1 to 8, characterized in that, When the AC power supply is operating in the positive half-cycle and the first low-frequency switch is in the conducting state, the third sampling element is connected in series in the branch where the first diode is located, or the third sampling element is connected in series in the branch between the first terminal of the AC power supply and the first connection point, where the first connection point is the connection point between the first diode and the second diode. When the current flowing through the third sampling element is greater than the first threshold, the control module controls the first low-frequency switch to disconnect.

10. The PFC circuit according to any one of claims 1 to 8, characterized in that, When the AC power supply is operating in the negative half-cycle and the second low-frequency switch is in the conducting state, the third sampling element is connected in series in the branch where the second diode is located, or the third sampling element is connected in the branch between the first terminal of the AC power supply and the first connection point, where the first connection point is the connection point between the first diode and the second diode. When the current flowing through the third sampling element is greater than the first threshold, the control module controls the second low-frequency switch to disconnect.

11. The PFC circuit according to any one of claims 2 to 8, characterized in that, When the AC power supply is operating in the positive half-cycle and the first low-frequency switch is in the conducting state, the third sampling element is connected in series between the second connection point and the third connection point. The second connection point is the connection point between the first diode and the first power switch, and the third connection point is the connection point between the first low-frequency switch and the first capacitor. The third sampling element is the same as the first sampling element. When the current flowing through the third sampling element is greater than the first threshold, the control module controls the first low-frequency switch to disconnect.

12. The PFC circuit according to any one of claims 2 to 8, characterized in that, When the AC power supply is operating in the negative half-cycle and the second low-frequency switch is in the conducting state, the third sampling element is connected in series between the fourth connection point and the fifth connection point. The fourth connection point is the connection point between the second diode and the second power switch, and the fifth connection point is the connection point between the second low-frequency switch and the first capacitor. The third sampling element is the same as the first sampling element. When the current flowing through the third sampling element is greater than the first threshold, the control module controls the second low-frequency switch to disconnect.

13. The PFC circuit according to claim 2, characterized in that, The power module also includes a second inductor, a third power switch, and a fourth power switch. The first end of the second inductor is connected to the first end of the AC power supply, and the second end of the second inductor is connected to the first end of the third power switch; The first capacitor is connected in parallel with the bridge arm branch including the third power switch and the fourth power switch; The second terminal of the third power switch is connected to the second terminal of the first power switch; The second terminal of the fourth power switch is connected to the second terminal of the second power switch, and the first terminal of the fourth power switch is connected to the first terminal of the third power switch.

14. The PFC circuit according to claim 13, characterized in that, The current sampling element further includes a second sampling element. When the AC power supply is operating in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, and the second sampling element is connected in series in the branch where the third power switch is located; or, the first sampling element is connected in series in the branch where the second power switch is located, and the second sampling element is connected in series in the branch where the fourth power switch is located. When the sum of the currents flowing through the first sampling element and the second sampling element is greater than a first threshold, the control module controls the first low-frequency switch to close.

15. The PFC circuit according to claim 13, characterized in that, The current sampling element further includes a second sampling element. When the AC power supply is operating in the negative half-cycle, the first sampling element is connected in series to the branch where the second power switch is located, and the second sampling element is connected in series to the branch where the fourth power switch is located; or, the first sampling element is connected in series to the branch where the first power switch is located, and the second sampling element is connected in series to the branch where the third power switch is located. When the sum of the currents flowing through the first sampling element and the second sampling element is greater than the first threshold, the control module controls the second low-frequency switch to close.

16. The PFC circuit according to claim 13, characterized in that, The current sampling element further includes a second sampling element, a fourth sampling element, and a fifth sampling element; When the AC power supply is operating in the positive half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, the second sampling element is connected in series in the branch where the second power switch is located, the fourth sampling element is connected in series in the branch where the third power switch is located, and the fifth sampling element is connected in series in the branch where the fourth power switch is located. When the sum of the currents flowing through the first sampling element, the second sampling element, the fourth sampling element, and the fifth sampling element exceeds a first threshold, the control module controls the first low-frequency switch to close.

17. The PFC circuit according to claim 13, characterized in that, The current sampling element further includes a second sampling element, a fourth sampling element, and a fifth sampling element; When the AC power supply is operating in the negative half-cycle, the first sampling element is connected in series in the branch where the first power switch is located, the second sampling element is connected in series in the branch where the second power switch is located, the fourth sampling element is connected in series in the branch where the third power switch is located, and the fifth sampling element is connected in series in the branch where the fourth power switch is located. When the sum of the currents flowing through the first sampling element, the second sampling element, the fourth sampling element, and the fifth sampling element exceeds the first threshold, the control module controls the second low-frequency switch to close.

18. The PFC circuit according to any one of claims 1 to 8, characterized in that, The control module further includes a controller, which is composed of discrete components, or the controller is composed of logic devices.

19. The PFC circuit according to claim 18, characterized in that, The logic devices include complex programmable logic devices (CPLDs), microcontroller units (MCUs), field-programmable gate arrays (FPGAs), central processing units (CPUs), or digital signal processors (DSPs).

20. The PFC circuit according to any one of claims 1 to 8, characterized in that, The power module can operate in critical conduction mode (CRM), continuous current mode (CCM), delta current mode (TCM), or discontinuous current mode (DCM).

21. The PFC circuit according to any one of claims 1 to 8, characterized in that, The switching element includes an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a gallium nitride (GaN) FET.

22. The PFC circuit according to any one of claims 1 to 8, characterized in that, The current sampling element is a resistor or a current transformer (CT).

23. A communication power supply, characterized in that, The communication power supply includes the PFC circuit, which includes an AC power supply, a low-frequency switching module, a power module, and a control module. The PFC circuit is the PFC circuit as described in any one of claims 1 to 22.

Images