A bridgeless step-down power factor correction circuit

Abstract

The utility model discloses a kind of bridgeless buck type power factor correction circuit, belong to electric energy conversion technical field, including first switch, second switch, third switch, fourth switch, first winding, second winding, third winding, fourth winding, first inductance, first capacitor, second capacitor, third capacitor, alternating current, first switch, first winding, second winding, third winding, fourth winding, second switch are in series;Second winding, first inductance, first capacitor, third switch are in series;Third winding, first inductance, first capacitor, fourth switch are in series.The utility model discloses a kind of bridgeless buck type power factor correction circuit, solve the problem that bridgeless buck type power factor correction circuit when input voltage is much greater than output voltage, duty cycle is too small, switch loss is big.

Description

Technical Field

[0001] This utility model relates to the field of power conversion technology, and in particular to a bridgeless buck power factor correction circuit. Background Technology

[0002] With the continuous development of power electronics technology, the application of input capacitive filters in various power electronic devices is becoming increasingly widespread. The extensive use of these filters leads to severe harmonic pollution on the power grid side, thus affecting the power supply quality and stability. To address this harmonic pollution problem, most AC / DC converters now require power factor correction (PFC) circuits. The core function of this circuit is to correct the input current, making its waveform closer to a sine wave, thereby improving the power factor and suppressing harmonics. Among existing PFC circuits, boost PFC is widely used due to its relatively simple structure and stable correction effect. While it effectively improves the current power factor and reduces current harmonics, it requires a large voltage gain in wide-range input applications, resulting in a significant reduction in circuit efficiency and making it difficult to meet the demands of high-efficiency applications.

[0003] Compared to traditional boost power factor correction circuits, buck power factor correction circuits (BFC) maintain higher efficiency across a wide input voltage range. For example... Figure 1 The bridgeless buck power factor correction circuit shown includes switches Q1, Q2, D1, D2, winding Na, winding Nb, and inductor L. o Inductor L m Capacitor C o Capacitors C1 and C2 are connected, with the first terminal of capacitor C1 connected to an AC power supply. ac The first terminal of capacitor C1 is connected to the first terminal of switch Q1, the second terminal of capacitor C1 is connected to the second terminal of capacitor C2 and the second terminal of switch D2, and the first terminal of capacitor C2 is connected to AC power supply U. ac The second terminal of switch Q1 is connected to the first terminal of switch Q2. The second terminal of switch Q1 is connected to the first terminal of winding Na. The second terminal of winding Na is connected to the first terminal of winding Nb and inductor L. o The first terminal, inductor L m The inductor L is connected in parallel across the two ends of winding Na, and the second end of winding Nb is connected to the second end of switch Q2. o The second terminal is connected to capacitor C o The first terminal, capacitor C o The second terminal is connected to the second terminal of switch D1, and the first terminal of switch D1 is connected to the second terminal of switch Q1. Capacitor C o The second terminal of the capacitor is connected to the second terminal of switch D2, and the first terminal of switch D2 is connected to the second terminal of switch Q2; capacitor Co A load R is also connected in parallel at both ends. load Capacitor C o The two ends are the output voltage V o .However, Figure 1 When the input and output voltages differ significantly, especially when the output voltage is low, the buck power factor correction circuit in the circuit has a very small duty cycle. This small duty cycle results in a very short turn-on time for the switching transistor, leading to a large turn-off loss for the main switch. Utility Model Content

[0004] The present invention aims to provide a bridgeless buck power factor correction circuit to solve the problem of large input-output voltage differences in traditional bridgeless buck power factor correction circuit technology.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows: A bridgeless buck power factor correction circuit includes: a first switch, a second switch, a third switch, a fourth switch, a first winding, a second winding, a third winding, a fourth winding, a first inductor, a first capacitor, a second capacitor, and a third capacitor; an AC current, the first switch, the first winding, the second winding, the third winding, the fourth winding, and the second switch connected in series; the second winding, the first inductor, the first capacitor, and the third switch connected in series; the third winding, the first inductor, the first capacitor, and the fourth switch connected in series; a first terminal of the second capacitor is connected to a second terminal of the AC current, a second terminal of the second capacitor is connected to a second terminal of the fourth switch, a first terminal of the third capacitor is connected to a first terminal of the AC current, and a second terminal of the third capacitor is connected to a second terminal of the fourth switch.

[0006] In one specific embodiment, the first terminal of the first switch is connected to the first terminal of the alternating current; the second terminal of the first switch is connected to the first terminal of the first winding; the second terminal of the first winding is connected to the first terminal of the second winding; the second terminal of the second winding is connected to the first terminal of the third winding and the first terminal of the first inductor; the second terminal of the third winding is connected to the second terminal of the fourth winding; the first terminal of the fourth winding is connected to the second terminal of the second switch; the first terminal of the second switch is connected to the second terminal of the alternating current; the second terminal of the first inductor is connected to the first terminal of the first capacitor; the second terminal of the first capacitor is connected to the second terminal of the third switch; the first terminal of the third switch is connected to the second terminal of the first winding; the second terminal of the first capacitor is connected to the second terminal of the fourth switch; the first terminal of the fourth switch is connected to the second terminal of the fourth winding; and the two terminals of the first capacitor are connected in parallel with the load.

[0007] In one specific embodiment, the first end of the first winding is connected to the first end of the alternating current and the first end of the third capacitor; the second end of the first winding is connected to the first end of the first switch; the second end of the first switch is connected to the first end of the second winding; the second end of the second winding is connected to the first end of the third winding and the first end of the first inductor; the second end of the third winding is connected to the second end of the second switch; the first end of the second switch is connected to the second end of the fourth winding; the first end of the fourth winding is connected to the second end of the alternating current; the second end of the first inductor is connected to the first end of the first capacitor; the second end of the first capacitor is connected to the second end of the third switch; the first end of the third switch is connected to the second end of the first switch; the second end of the first capacitor is connected to the second end of the fourth switch; the first end of the fourth switch is connected to the second end of the second switch; and the two ends of the first capacitor are connected in parallel with the load.

[0008] Furthermore, the first winding and the second winding form a first tapped inductor, and the third winding and the fourth winding form a second tapped inductor.

[0009] Furthermore, the number of turns ratio Defined as: , in, The number of turns for the first and fourth windings. This refers to the number of turns in the second and third windings.

[0010] Furthermore, the first winding has the same number of turns as the fourth winding; the second winding has the same number of turns as the third winding.

[0011] Furthermore, the circuit is in a charging state, with the first and second windings working together or the third and fourth windings working together.

[0012] Furthermore, the current is in a discharge state, with the second winding acting alone or the third winding acting alone.

[0013] In one specific embodiment, the system further includes a first diode, a second diode, a third diode, a fourth diode, a fourth capacitor, and a fifth capacitor. The cathode of the first diode is connected to a first end of the first winding, the anode of the first diode is connected to the cathode of the second diode and a first end of the fourth capacitor, the anode of the second diode is grounded, and a second end of the fourth capacitor is connected to a second end of the first winding. The cathode of the third diode is connected to a first end of the fourth winding, the anode of the third diode is connected to the cathode of the fourth diode and a first end of the fifth capacitor, the anode of the fourth diode is grounded, and a second end of the fifth capacitor is connected to a second end of the fourth winding.

[0014] Furthermore, the first switch and the second switch are MOSFETs, with the first terminal of the first switch being the drain of the MOSFET and the second terminal of the first switch being the source of the MOSFET; the first terminal of the second switch is the drain of the MOSFET and the second terminal of the second switch is the source of the MOSFET; the third switch and the fourth switch are diodes, with the first terminal of the third switch being the cathode of the diode and the second terminal of the third switch being the anode of the diode; the first terminal of the fourth switch is the cathode of the diode and the second terminal of the fourth switch is the anode of the diode.

[0015] Beneficial effects: This utility model discloses a bridgeless step-down power factor correction circuit where the turns ratio of the tapped inductor is related to the duty cycle, and the duty cycle increases with the turns ratio. Increase by adjusting the turns ratio It can solve Figure 1 The bridgeless buck power factor correction circuit suffers from high switching losses due to an excessively small duty cycle when the input voltage is much greater than the output voltage. By arranging tapped inductors and power devices with different connection methods, the driving problem caused by the negative voltage at the source of the main switch when it is turned off can be avoided, enabling the circuit to achieve bootstrap drive. The addition of a clamping circuit can clamp the voltage stress of the main switch within a safe range, preventing leakage inductance energy from being transferred to its junction capacitance when the main switch is turned off, thus avoiding the generation of high voltage spikes and damage to the devices, and solving the leakage inductance energy problem.

[0016] To make the above-mentioned features and advantages of the utility model more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a traditional bridgeless buck power factor correction circuit.

[0018] Figure 2 This is a circuit diagram of a first specific embodiment of a bridgeless buck power factor correction circuit according to the present invention.

[0019] Figure 3 This is a circuit diagram of a second specific embodiment of a bridgeless buck power factor correction circuit according to the present invention.

[0020] Figure 4 This is a circuit diagram of a third specific embodiment of a bridgeless buck power factor correction circuit according to the present invention.

[0021] Figure 5 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when the switch Q1 is turned on during the positive half-cycle.

[0022] Figure 6 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when the switch Q1 is turned off during the positive half-cycle.

[0023] Figure 7 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when switch Q2 is turned on during the negative half-cycle.

[0024] Figure 8 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when switch Q2 is turned off during the negative half-cycle. Detailed Implementation

[0025] To make the objectives and technical solutions of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0026] Figure 2 This is a circuit diagram of a first specific embodiment of a bridgeless buck power factor correction circuit according to this utility model. Figure 2 As shown, the bridgeless buck power factor correction circuit of this utility model includes switches Q1, Q2, D1, D2, capacitors C1 and C2, windings N1, N2, N3, and N4, and inductor L. o With capacitor C o Alternating current u ac Switch Q1, windings N1, N2, N3, N4, and switch Q2 are connected in series; winding N2 and inductor L o Capacitor C o Switch D1 is connected in series; winding N3 and inductor L o Capacitor C o Switch D2 is connected in series; the first terminal of switch Q1 is connected to AC power u. ac The first terminal of the circuit is connected to the first terminal of capacitor C2, the second terminal of switch Q1 is connected to the first terminal of winding N1, the second terminal of winding N1 is connected to the first terminal of winding N2, the second terminal of winding N2 is connected to the first terminal of winding N3 and inductor L. o The first end of winding N3 is connected to the second end of winding N4, the first end of winding N4 is connected to the second end of switch Q2, and the first end of switch Q2 is connected to AC power supply u. ac The second terminal and the first terminal of capacitor C1; inductor Lo The second terminal is connected to capacitor C o The first terminal, capacitor C o The second terminal is connected to the second terminal of switch D1, and the first terminal of switch D1 is connected to the second terminal of winding N1. Capacitor C o The second terminal is connected to the second terminal of switch D2, and the first terminal of switch D2 is connected to the second terminal of winding N4; the second terminal of capacitor C1 is connected to the second terminal of capacitor C2 and capacitor C o The second terminal, capacitor C o A load R is also connected in parallel at both ends. load Capacitor C o The two ends are the output voltage V o .

[0027] Among them, switches D1 and D2 serve as freewheeling current.

[0028] Among them, capacitors C1 and C2 play the role of suppressing voltage spikes.

[0029] Furthermore, windings N1 and N2 form a tapped inductor L1, which facilitates adjustment of the turns ratio between windings N1 and N2.

[0030] Furthermore, windings N3 and N4 together form a tapped inductor L2, which facilitates adjustment of the turns ratio between windings N3 and N4.

[0031] Furthermore, the number of turns in winding N1 is equal to that in winding N4.

[0032] Furthermore, the number of turns in winding N2 is equal to that in winding N3.

[0033] Optionally, switches Q1 and Q2 are MOSFETs, with the first terminal of switch Q1 being the drain of the MOSFET and the second terminal of switch Q1 being the source of the MOSFET; the first terminal of switch Q2 is the drain of the MOSFET and the second terminal of switch Q2 is the source of the MOSFET.

[0034] Alternatively, switches Q1 and Q2 can be other semiconductor devices.

[0035] Optionally, switches D1 and D2 can be diodes, with the first terminal of switch D1 being the cathode of the diode and the second terminal of switch D1 being the anode of the diode, and the first terminal of switch D2 being the cathode of the diode and the second terminal of switch D2 being the anode of the diode.

[0036] Alternatively, switches D1 and D2 can also be other semiconductor devices.

[0037] The working principle of a bridgeless step-down power factor correction circuit of this utility model will be further described below with reference to the first specific embodiment. Figure 5This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram is shown when switch Q1 is on during the positive half-cycle. Switch Q1 is on, switch Q2 is off, and switches D1 and D2 are off. For input current, For the current flowing through winding N2, This is the output current. The current flows along the alternating current u ac Switch Q1, winding N1, winding N2, inductor L o Capacitor C o Capacitor C1, AC current u ac A circuit is formed, and the circuit is in a charging state at this time, with windings N1 and N2 working together.

[0038] Figure 6 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when switch Q1 is turned off during the positive half-cycle is shown. Switches Q1 and Q2 are off, switch D1 is on, and switch D2 is off. The current flowing through switch D1, For the current flowing through winding N2, This is the output current. The current flows along winding N2 and inductor L. o Capacitor C o Switch D1 and winding N2 form a circuit. At this time, the circuit is in a discharge state, and winding N2 acts alone.

[0039] Figure 7 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram is shown when switch Q2 is on during the negative half-cycle. Switch Q1 is off, switch Q2 is on, and switches D1 and D2 are off. For the current flowing through winding N3, This is the output current. The current flows along the alternating current u ac Switch Q2, winding N4, winding N3, inductor L o Capacitor C o Capacitor C2, AC current u ac A circuit is formed, and the circuit is in a charging state at this time, with windings N3 and N4 working together.

[0040] Figure 8 This is the first specific embodiment of the present invention in the alternating current u ac The current flow path diagram when switch Q2 is turned off during the negative half-cycle is shown. Switches Q1 and Q2 are off, switch D1 is cut off, and switch D2 is turned on. The current flowing through switch D2, For the current flowing through winding N3, This is the output current. The current flows along winding N3 and inductor L. o Capacitor C o Switch D2 and winding N3 form a circuit, and the circuit is in a discharge state at this time, with winding N3 acting alone.

[0041] Furthermore, the number of turns ratio Defined as: , in, The number of turns for the first and fourth windings. This refers to the number of turns in the second and third windings.

[0042] Furthermore, by using inductor volt-second balance, the duty cycle and turns ratio of the bridgeless buck power factor correction circuit can be derived. related.

[0043] More specifically, the duty cycle of a bridgeless buck power factor correction circuit varies with the turns ratio. It increases as it increases.

[0044] By using a center tap, the number of winding turns connected to the inductor can be switched between charging and discharging states, thus exhibiting different inductance values. This structure introduces a degree of freedom, allowing for the selection of the turns ratio. To optimize performance. Adjust the turns ratio based on the actual duty cycle requirements. ,solve Figure 1 The bridgeless buck power factor correction circuit suffers from problems such as excessively small duty cycle and high switching losses when the input voltage is much greater than the output voltage.

[0045] This utility model also provides a second specific embodiment of a bridgeless buck power factor correction circuit, such as... Figure 3 As shown, the connection method of the tapped inductor and power devices is rearranged. Specifically, the first terminal of winding N1 is connected to AC power u. ac The first terminal of winding N1 is connected to the first terminal of capacitor C2, the second terminal of winding N1 is connected to the first terminal of switch Q1, the second terminal of switch Q1 is connected to the first terminal of winding N2, and the second terminal of winding N2 is connected to the first terminal of winding N3 and inductor L. o The first end of winding N3 is connected to the second end of switch Q2, the first end of switch Q2 is connected to the second end of winding N4, and the first end of winding N4 is connected to AC power supply u. ac The second terminal and the first terminal of capacitor C1, inductor L o The second terminal is connected to capacitor C o The first terminal, capacitor C o The second terminal is connected to the second terminal of switch D1, and the first terminal of switch D1 is connected to the second terminal of switch Q1. Capacitor C oThe second terminal of capacitor C1 is connected to the second terminal of switch D2, and the first terminal of switch D2 is connected to the second terminal of switch Q2; the second terminal of capacitor C1 is connected to the second terminal of capacitor C2 and capacitor C... o The second terminal, capacitor C o A load R is also connected in parallel at both ends. load Capacitor C o The two ends are the output voltage V o .

[0046] Optionally, switches Q1 and Q2 are MOSFETs, with the first terminal of switch Q1 being the drain of the MOSFET and the second terminal of switch Q1 being the source of the MOSFET; the first terminal of switch Q2 is the drain of the MOSFET and the second terminal of switch Q2 is the source of the MOSFET.

[0047] Alternatively, switches Q1 and Q2 can be other semiconductor devices.

[0048] Optionally, switches D1 and D2 can be diodes, with the first terminal of switch D1 being the cathode of the diode and the second terminal of switch D1 being the anode of the diode, and the first terminal of switch D2 being the cathode of the diode and the second terminal of switch D2 being the anode of the diode.

[0049] Alternatively, switches D1 and D2 can also be other semiconductor devices. Figure 2 The working principle of the circuit and Figure 3 The same in the circuit, Figure 3 I will not go into details here.

[0050] exist Figure 2 In the first specific embodiment, switch Q1, winding N1, and winding N2 are connected in sequence, and switch Q2, winding N3, and winding N4 are connected in sequence. Since windings N1 and N2 are connected after main switches Q1 and Q2 respectively, the source of the main switches may be negatively charged when turned off, causing the drive voltage to rise and potentially exceed the safe range. In this embodiment, however, by changing the connection method of the tap inductor and power devices, and connecting windings N1 and N4 to the drains of switches Q1 and Q2 respectively, the problem of the main switch source being negatively charged when turned off is avoided, thus solving the drive problem and enabling the circuit to achieve bootstrap drive.

[0051] This utility model provides a third specific embodiment of a bridgeless buck power factor correction circuit, such as... Figure 4 As shown, a clamping circuit is added, in Figure 3Diodes Dc1, Dc2, Dc3, and Dc4, and capacitors Cc1 and Cc2 are added to the circuit. The cathode of diode Dc1 is connected to the first terminal of winding N1, and the anode of diode Dc1 is connected to the cathode of diode Dc2 and the first terminal of capacitor Cc1. The anode of diode Dc2 is grounded, and the second terminal of capacitor Cc1 is connected to the second terminal of winding N1. The cathode of diode Dc3 is connected to the first terminal of winding N4, and the anode of diode Dc3 is connected to the cathode of diode Dc4 and the first terminal of capacitor Cc2. The anode of diode Dc4 is grounded, and the second terminal of capacitor Cc2 is connected to the second terminal of winding N4.

[0052] Figure 2 The working principle of the circuit and Figure 4 The same in the circuit, Figure 4 I will not go into details here.

[0053] Figure 4 The clamping circuit is also applicable to Figure 2 Working principle and Figure 2 The circuit is the same, so I will not repeat it here.

[0054] This embodiment adds a lossless clamping circuit. When switch Q1 is off, the leakage inductance current passes through capacitor Cc1 and diode Dc1, storing the leakage inductance energy in capacitor Cc1. When switch Q1 is on, the energy in capacitor Cc1 is released to the output through diode Dc2 and winding N2, achieving energy recovery. The clamping circuit principle of switch Q2 is the same as that of switch Q1, and will not be described again here.

[0055] for Figure 3 In a second specific embodiment of a bridgeless buck power factor correction circuit, the tapped inductor cannot achieve complete coupling. Leakage inductance energy is transferred to its junction capacitance when the main switch is turned off, generating a high-voltage spike that may damage the device. This embodiment solves the leakage inductance energy problem by adding a clamping circuit. The main switch voltage stress is clamped within a safe range, preventing leakage inductance energy from transferring to its junction capacitance when the main switch is turned off, thus avoiding the high-voltage spike and device damage.

[0056] This invention relates to a bridgeless step-down power factor correction circuit where the turns ratio of the tapped inductor is related to the duty cycle, and the duty cycle increases with the turns ratio. Increase by adjusting the turns ratio It can solve Figure 1The bridgeless buck power factor correction circuit suffers from high switching losses due to an excessively small duty cycle when the input voltage is much greater than the output voltage. By arranging tapped inductors and power devices with different connection methods, the driving problem caused by the negative voltage at the source of the main switch when it is turned off can be avoided, enabling the circuit to achieve bootstrap drive. The addition of a clamping circuit can clamp the voltage stress of the main switch within a safe range, preventing leakage inductance energy from being transferred to its junction capacitance when the main switch is turned off, thus avoiding the generation of high voltage spikes and damage to the devices, and solving the leakage inductance energy problem.

[0057] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A bridgeless buck power factor correction circuit, characterized in that, It includes a first switch, a second switch, a third switch, a fourth switch, a first winding, a second winding, a third winding, a fourth winding, a first inductor, a first capacitor, a second capacitor, and a third capacitor; an alternating current, the first switch, the first winding, the second winding, the third winding, the fourth winding, and the second switch are connected in series; the second winding, the first inductor, the first capacitor, and the third switch are connected in series; the third winding, the first inductor, the first capacitor, and the fourth switch are connected in series; the first terminal of the second capacitor is connected to the second terminal of the alternating current, the second terminal of the second capacitor is connected to the second terminal of the fourth switch, the first terminal of the third capacitor is connected to the first terminal of the alternating current, and the second terminal of the third capacitor is connected to the second terminal of the fourth switch.

2. The bridgeless buck power factor correction circuit as described in claim 1, characterized in that, The first terminal of the first switch is connected to the first terminal of the AC power supply. The second terminal of the first switch is connected to the first terminal of the first winding. The second terminal of the first winding is connected to the first terminal of the second winding. The second terminal of the second winding is connected to the first terminal of the third winding and the first terminal of the first inductor. The second terminal of the third winding is connected to the second terminal of the fourth winding. The first terminal of the fourth winding is connected to the second terminal of the second switch. The first terminal of the second switch is connected to the second terminal of the AC power supply. The second terminal of the first inductor is connected to the first terminal of the first capacitor. The second terminal of the first capacitor is connected to the second terminal of the third switch. The first terminal of the third switch is connected to the second terminal of the first winding. The second terminal of the first capacitor is connected to the second terminal of the fourth switch. The first terminal of the fourth switch is connected to the second terminal of the fourth winding. The two terminals of the first capacitor are connected in parallel with the load.

3. The bridgeless buck power factor correction circuit as described in claim 1, characterized in that, The first end of the first winding is connected to the first end of the AC power supply and the first end of the third capacitor. The second end of the first winding is connected to the first end of the first switch. The second end of the first switch is connected to the first end of the second winding. The second end of the second winding is connected to the first end of the third winding and the first end of the first inductor. The second end of the third winding is connected to the second end of the second switch. The first end of the second switch is connected to the second end of the fourth winding. The first end of the fourth winding is connected to the second end of the AC power supply. The second end of the first inductor is connected to the first end of the first capacitor. The second end of the first capacitor is connected to the second end of the third switch. The first end of the third switch is connected to the second end of the first switch. The second end of the first capacitor is connected to the second end of the fourth switch. The first end of the fourth switch is connected to the second end of the second switch. The two ends of the first capacitor are connected in parallel with the load.

4. The bridgeless buck power factor correction circuit as described in claim 2 or 3, characterized in that, The first winding and the second winding form a first tap inductor, and the third winding and the fourth winding form a second tap inductor.

5. The bridgeless buck power factor correction circuit as described in claim 4, characterized in that, Turns ratio Defined as: ， in, The number of turns for the first and fourth windings. This refers to the number of turns in the second and third windings.

6. The bridgeless buck power factor correction circuit as described in claim 5, characterized in that, Duty cycle and turns ratio of the bridgeless buck power factor correction circuit Regarding the duty cycle of the bridgeless buck power factor correction circuit as a function of the turns ratio... It increases as it increases.

7. The bridgeless buck power factor correction circuit as described in claim 6, characterized in that, The circuit is in a charging state, with the first and second windings working together or the third and fourth windings working together.

8. The bridgeless buck power factor correction circuit as described in claim 7, characterized in that, The circuit is in a discharging state, with either the second winding or the third winding acting alone.

9. The bridgeless buck power factor correction circuit as described in claim 1, characterized in that, It also includes a first diode, a second diode, a third diode, a fourth diode, a fourth capacitor, and a fifth capacitor. The cathode of the first diode is connected to the first end of the first winding, the anode of the first diode is connected to the cathode of the second diode and the first end of the fourth capacitor, the anode of the second diode is grounded, and the second end of the fourth capacitor is connected to the second end of the first winding. The cathode of the third diode is connected to the first end of the fourth winding, the anode of the third diode is connected to the cathode of the fourth diode and the first end of the fifth capacitor, the anode of the fourth diode is grounded, and the second end of the fifth capacitor is connected to the second end of the fourth winding.

10. The bridgeless buck power factor correction circuit as described in claim 1, characterized in that, The first switch and the second switch are MOSFETs. The first terminal of the first switch is the drain of the MOSFET, and the second terminal of the first switch is the source of the MOSFET. The first terminal of the second switch is the drain of the MOSFET, and the second terminal of the second switch is the source of the MOSFET. The third switch and the fourth switch are diodes. The first end of the third switch is the cathode of the diode, and the second end of the third switch is the anode of the diode. The first end of the fourth switch is the cathode of the diode, and the second end of the fourth switch is the anode of the diode.

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