Wide output and low voltage stress bridgeless PFC converter based on SEPIC and Cuk

Abstract

The present invention discloses a wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk, which relates to the technical field of PFC converters. The topology of the PFC converter includes a SEPIC circuit unit, a Cuk circuit unit, an output capacitor C p and output capacitor C n ; SEPIC circuit unit includes switch tube S S , input inductor L S1 、Inductor L S2 , intermediate capacitor C S , input diode D S1 , diode D S2 ; Cuk circuit unit includes switch tube S C , input inductor L C1 、Inductor L C2 , intermediate capacitor C C , input diode D C1 , diode D C2 The SEPIC circuit unit and the Cuk circuit unit are connected in parallel at the input and in series at the output, reducing the voltage stress on the switch tube. By connecting the two circuit units in parallel at the input and in series at the output, the present invention utilizes a SEPIC and Cuk PFC converter cascade topology, reducing diode components and thus converter operating losses, while retaining the other key components of the SEPIC and Cuk converters, namely, the LC filter network characteristics of the input and output of the two converters.

Description

Technical Field

[0001] The present invention belongs to the technical field of PFC converters, and in particular relates to a wide-output, low-voltage stress bridgeless PFC converter based on SEPIC and Cuk. Background Art

[0002] With the widespread adoption of renewable energy generation technologies (such as solar and wind power), batteries, as a key component of energy storage systems, are playing an increasingly important role in energy storage and dispatch. However, for charging equipment, variable grid conditions require adaptability to a wide voltage range to ensure efficient operation of battery charging systems under various input voltages. Furthermore, direct current (DC) from renewable energy sources is often unavailable directly, necessitating the development of low-power AC-DC converters with power factor correction (PFC) that can operate stably over a wide voltage range. The buck-boost function and closed-loop power factor correction control circuit enable AC-DC PFC converters to stably adjust the output voltage across a wide input voltage range, ensuring that the battery pack always receives the appropriate charging voltage. Even in the presence of large grid voltage fluctuations, the PFC converter can maintain a constant output voltage, thereby mitigating drastic fluctuations in grid load and effectively reducing grid instability. Therefore, AC-DC PFC converters with a wide voltage operating range and buck-boost functionality have broad application prospects, particularly in renewable energy applications and charging equipment connected to power systems.

[0003] Traditionally, the front-stage circuits of battery chargers ranging from hundreds of watts to several kilowatts typically use a boost PFC converter and are equipped with a rectifier bridge. Furthermore, to meet the wide voltage operating range requirements of the battery pack, the boost PFC converter typically requires a subsequent cascade connection with a DC-DC step-down converter, forming a two-stage power conversion circuit. In contrast, while the buck-boost PFC converter has the ability to boost and buck outputs, it is generally only suitable for LED lighting applications with a power of tens of watts due to its high switching tube voltage stress (the sum of the input and output voltages), large switching tube conduction losses, and significant electromagnetic interference. Therefore, the development of a low-voltage stress PFC converter with boost and buck functionality has good application prospects.

[0004] like Figure 1As shown in Figure 2, the traditional SEPIC PFC converter topology can be viewed as a combination of boost and buck-boost circuits, while the traditional Cuk PFC converter topology can be viewed as a combination of boost and buck circuits. Therefore, both traditional SEPIC and Cuk PFC converters have wide output voltage capabilities. However, both topologies utilize multiple diodes for rectification in various operating modes, resulting in operational losses.

[0005] The present invention proposes a bridgeless PFC converter. Based on the SEPIC and Cuk PFC conversion circuits, the present invention connects the two conversion units in parallel at the input and in series at the output. Through a PFC converter cascade topology based on SEPIC and Cuk, the present invention reduces diode devices and thus reduces converter operating losses, while retaining other key components of SEPIC and Cuk, that is, retaining the LC filter network characteristics of the input and output of these two converters. Summary of the Invention

[0006] The present invention aims to provide a wide-output, low-voltage-stress bridgeless PFC converter based on SEPIC and Cuk circuits, thereby resolving the problems mentioned in the background art above. The buck-boost PFC converter in the prior art is only suitable for LED lighting applications with a power of tens of watts due to its high switch voltage stress, large switch conduction loss, and significant electromagnetic interference.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] The present invention proposes a wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk. The topology of the PFC converter includes a SEPIC circuit unit, a Cuk circuit unit, an output capacitor C p and output capacitor C n ;

[0009] The SEPIC circuit unit includes a switch tube S S , input inductor L S1 、Inductor L S2 , intermediate capacitor C S , input diode D S1 , diode D S2 The Cuk circuit unit includes a switch tube S C , input inductor L C1 、Inductor L C2 , intermediate capacitor C C , input diode D C1 , diode D C2 ;

[0010] The SEPIC circuit unit and the Cuk circuit unit are connected in parallel at the input end and in series at the output end, thereby reducing the voltage stress of the switch tube.

[0011] Preferably, one end of the AC input side is connected to the input diode D C1 cathode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The drain, intermediate capacitance C S The positive connection of the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S2 The anode of diode D S2 The cathode and output capacitor C p The positive electrode, load R L One end is connected;

[0012] Input diode D C1 The anode of the input diode D S1 Anode, switch tube S C The source of the switch tube S S The source, inductor L S2 The other end of the diode D C2 cathode, output capacitor C p The negative pole of the output inductor C n The positive pole is connected;

[0013] The other end of the AC input side is connected to the input diode D S1 cathode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube S C The drain, intermediate capacitance C C The positive connection of the middle capacitor C C The cathode of diode D C2 Anode, inductor L C2 One end of the inductor L is connected C2 The other end of the output capacitor C n The negative electrode, load R L The other end is connected.

[0014] Preferably, one end of the AC input side is connected to the input diode D C1 Anode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube S C The source, the intermediate capacitor C C The negative connection of the middle capacitor C C The positive electrode of the diode DC2 cathode, inductor L C2 One end of the inductor L is connected C2 The other end of the output capacitor C p The positive electrode, load R L One end is connected;

[0015] Input diode D C1 The cathode of the input diode D S1 The cathode of the switch tube S C The drain of the switch tube S S The drain, inductance L S2 One end of the diode D C2 Anode, output capacitor C p The negative pole of the output capacitor C n The positive pole is connected;

[0016] The other end of the AC input side is connected to the input diode D S1 Anode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source, the intermediate capacitor C S The negative connection of the middle capacitor C S The positive electrode and the inductor L S2 The other end of the diode D S2 The cathode of the diode D is connected S2 The anode and output capacitor C n The negative electrode, load R L The other end is connected.

[0017] Preferably, the PFC converter mainly uses a SEPIC circuit unit and operates in the following mode during the positive half cycle of the AC input:

[0018] Working mode 1: switch tube S S , input diode D S1 In the on state, the switch tube S C In the on state but no current flows; the input terminal passes through the input diode D S1 , switch tube S S Give the input inductor L S1 Charging; at the same time, the intermediate capacitor C S Through the switch tube S S To inductor L S2 Charging, output capacitor C p , output capacitor C n Give load R L Energy supply; in this stage, the input inductor current i LS1 , inductor current i LS2 linear rise;

[0019] Working mode 2: switch tube S S Turn off, input diode D S1 , diode D S2 In the on state; the input terminal is connected to the input inductor L S1 The energy is transferred to the middle capacitor C S , the output capacitor C p and load R L transfer; at the same time, the inductor L S2 The current i LS2 Through diode D S2 Freewheeling, to the next stage output capacitor C p and load R L Transfer energy; in this stage, the input inductor current i LS1 , inductor current i LS2 linearly decreases; at the same time, the output capacitor C n Keep the load R L powered by;

[0020] Working mode 3: switch tube S S Keep off, the working mode is when the input inductor current i LS1 and the inductor current i LS2 All linearly decrease to zero, at this time i LS1 =i LS2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

[0021] Preferably, the PFC converter mainly uses a Cuk circuit and operates in the following mode during the negative half cycle of the AC input:

[0022] Working mode 4: switch tube S C , input diode D C1 In the on state, the switch tube S S In the on state but no current flows; the input terminal passes through the input diode D C1 , switch tube S C Give the input inductor L C1 Charging; at the same time, the intermediate capacitor C C Through the switch tube S C To inductor L C2 Charging, output capacitor C p , output capacitor C n Give load R L Energy supply; in this stage, the input inductor current i LC1 , inductor current i LC2 linear rise;

[0023] Working mode 5: switch tube S CTurn off, input diode D C1 , diode D C2 In the on state; the input terminal is connected to the input inductor L C1 The energy is transferred to the middle capacitor C C , the output capacitor C n and load R L transfer; at the same time, the inductor L C2 The current i LC2 Through diode D C2 Freewheeling, to the next stage output capacitor C n and load R L Transfer energy; in this stage, the input inductor current i LC1 , inductor current i LC2 linearly decreases; at the same time, the output capacitor C p Keep the load R L powered by;

[0024] Working mode 6: switch tube S C Keep off, the working mode is when the input inductor current i LC1 and the inductor current i LC2 All linearly decrease to zero, at this time i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

[0025] Preferably, the PFC converter adopts single voltage closed loop control to control the switch tube S C and switch tube S S The same control drive signal is used for control.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The PFC converter of the present invention reduces the number of input diodes and uses only one input diode in a single working mode. The circuit of the present invention reduces energy loss and simplifies the circuit structure.

[0028] (2) The PFC converter of the present invention connects the SEPIC converter and the Cuk converter in parallel and in series, retaining the smooth power conversion of the SEPIC and Cuk converters while improving light-load efficiency and reducing the voltage stress of the switch tube. This achieves high-efficiency operation and good voltage step-up and step-down capabilities, and can achieve smoother energy input by utilizing the characteristics of multiple inductors and intermediate capacitors in the SEPIC and Cuk conversion units.

[0029] (3) The PFC converter of the present invention has low switch tube stress and corresponding switching loss. Specifically, the voltage stress of the MOSFET switch tube is only the input voltage V in,pk With 1 / 2 output voltage V o The sum of V in,pk +1 / 2V o .

[0030] (4) The PFC converter circuit of the present invention can use a simple single voltage loop feedback to achieve closed-loop control, and the two switching tubes can use exactly the same driving signal to achieve closed-loop control. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the topology of traditional SEPIC and Cuk PFC converters in the background technology of the present invention;

[0032] Figure 2 Schematic diagram of the topology of the wide-output, low-voltage-stress bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0033] Figure 3 This is the operating mode diagram of the wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk in the present invention during the positive half AC input cycle;

[0034] Figure 4 This is the operating mode diagram of the negative half AC input cycle of the wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0035] Figure 5 This is a closed-loop control circuit diagram of a wide-output, low-voltage-stress bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0036] Figure 6 The theoretical waveform diagram of the key components of the wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0037] Figure 7 This is a simulation waveform diagram of the key components of the wide-output, low-voltage stress bridgeless PFC converter based on SEPIC and Cuk in the present invention. DETAILED DESCRIPTION

[0038] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1:

[0040] See also Figure 2 , Figure 2 Two hybrid input parallel output series bridgeless circuits based on SEPIC and Cuk are presented. The circuit topology mainly includes SEPIC circuit unit and Cuk circuit unit. S , input inductor L S1 、Inductor L S2 , intermediate capacitor C S , input diode D S1 , diode D S2 Composed of SEPIC circuit unit; switch tube S C , input inductor L C1 、Inductor L C2 , intermediate capacitor C C , input diode D C1 , diode D C2 Form a Cuk circuit unit.

[0041] Specifically, see Figure 2 (a), one end of the AC input side and the input diode D C1 cathode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The drain, intermediate capacitance C S The positive pole of the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S2 The output capacitor C p The positive electrode of the diode D S2 cathode, load R L One end is connected.

[0042] Input diode D C1 The anode of the input diode D S1 Anode, switch tube S C The source of the switch tube S S The source, inductor L S2 The other end of the diode D C2 cathode, output capacitor C p The negative pole of the output inductor C n The positive pole is connected.

[0043] The other end of the AC input side is connected to the input diode D S1 cathode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube SC The drain, intermediate capacitance C C The positive terminal of the inductor L C2 One end and the middle capacitor C C The cathode of diode D C2 The anode connection, inductor L C2 The other end of the output capacitor C n The negative electrode, load R L The other end is connected.

[0044] Specifically, see Figure 2 (b), one end of the AC input side and the input diode D C1 Anode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube S C The source, the intermediate capacitor C C The negative terminal of the inductor L C2 One end and the middle capacitor C C The positive electrode of diode D C2 The cathode connection of the inductor L C2 The other end of the output capacitor C p The positive electrode, load R L One end of the input diode D C1 The cathode of the input diode D S1 The cathode of the switch tube S C The drain of the switch tube S S The drain, inductance L S2 One end of the diode D C2 Anode, output capacitor C p The negative pole of the output capacitor C n The positive pole is connected.

[0045] The other end of the AC input side is connected to the input diode D S1 Anode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source, the intermediate capacitor C S The negative terminal of the inductor L S2 The other end of the middle capacitor C S The positive electrode of diode D S2 The cathode of the diode D is connected S2 The anode and output capacitor C n The negative electrode, load R L The other end is connected.

[0046] Figure 2The present invention proposes two hybrid input parallel output series bridgeless circuits based on SEPIC and Cuk. Figure 2 (a) and Figure 2 The circuit in (b) has symmetry and similar performance, so this paper mainly uses Figure 2 The circuit in (a) mainly introduces the working principle of the converter.

[0047] The working mode diagram of the positive half AC input cycle of the circuit of the present invention is as follows: Figure 3 shown. Figure 3 (a) is the equivalent circuit of the AC-DC bridgeless PFC converter based on SEPIC circuit in working mode 1 during the positive half cycle of AC input. Figure 3 (b) is the equivalent circuit of the AC-DC bridgeless PFC converter based on SEPIC circuit in working mode 2 during the positive half cycle of AC input. Figure 3 (c) is the equivalent circuit of the AC-DC bridgeless PFC converter based on SEPIC circuit in working mode 3 during the positive half cycle of AC input.

[0048] The working mode diagram of the negative half AC input cycle of the circuit of the present invention is as follows: Figure 4 shown. Figure 4 (a) is the equivalent circuit of the AC-DC bridgeless PFC converter based on the Cuk circuit in working mode 4 during the negative half cycle of the AC input. Figure 4 (b) is the equivalent circuit of the AC-DC bridgeless PFC converter based on the Cuk circuit in working mode 5 during the negative half cycle of the AC input. Figure 4 (c) is the equivalent circuit of the AC-DC bridgeless PFC converter based on the Cuk circuit in working mode 6 during the negative half cycle of the AC input.

[0049] Working mode 1: switch tube S S , input diode D S1 In the on state, the switch tube S C In the on state but no current flows through. The input terminal is connected to the input diode D S1 , switch tube S S Give the input inductor L S1 Charging; at the same time, the intermediate capacitor C S Through the switch tube S S To inductor L S2 Charging, output capacitor C p , output capacitor C n Give load R L In this stage, the input inductor current i LS1 , inductor current i LS2 Linear increase.

[0050] Working mode 2: switch tube S STurn off, input diode D S1 , diode D S2 The input terminal is connected to the input inductor L S1 The energy is transferred to the middle capacitor C S , the output capacitor C p and load R L transfer; at the same time, the inductor L S2 The current i LS2 Through diode D S2 Freewheeling, to the next stage output capacitor C p and load R L Transfer energy. In this stage, the input inductor current i LS1 , inductor current i LS2 linearly decreases; at the same time, the output capacitor C n Keep the load R L powered by.

[0051] Working mode 3: switch tube S S Keep off, the working mode is when the input inductor current i LS1 and the inductor current i LS2 All linearly decrease to zero, at this time i LS1 =i LS2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

[0052] Working mode 4: switch tube S C , input diode D C1 In the on state, the switch tube S S In the on state but no current flows through. The input terminal is connected to the input diode D C1 , switch tube S C Give the input inductor L C1 Charging; at the same time, the intermediate capacitor C C Through the switch tube S C To inductor L C2 Charging, output capacitor C p , output capacitor C n Give load R L In this stage, the input inductor current i LC1 , inductor current i LC2 Linear increase.

[0053] Working mode 5: switch tube S C Turn off, input diode D C1 , diode D C2 The input terminal is connected to the input inductor L C1 The energy is transferred to the middle capacitor C C, the output capacitor C n and load R L transfer; at the same time, the inductor L C2 The current i LC2 Through diode D C2 Freewheeling, to the next stage output capacitor C n and load R L Transfer energy. In this stage, the input inductor current i LC1 , inductor current i LC2 linearly decreases; at the same time, the output capacitor C p Keep the load R L powered by.

[0054] Working mode 6: switch tube S C Keep off, the working mode is when the input inductor current i LC1 and the inductor current i LC2 All linearly decrease to zero, at this time i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

[0055] The closed-loop control circuit of the circuit of the present invention is as follows Figure 5 shown. Figure 5 This is the main control principle of the bridgeless PFC converter of the present invention. It can be seen that the present invention mainly adopts a simple single voltage closed loop control to realize the control of the dual switch tubes. Moreover, the two switch tubes S C and switch tube S S The same control drive signal is used to avoid complex control.

[0056] Figure 6 The theoretical waveform diagram of the key components of the bridgeless PFC converter of the present invention. on is the on-duty cycle, d off is the inductor current freewheeling turn-off duty cycle, T s is a switching cycle. Figure 6 It can be seen that the key components of the conversion unit mainly work within half the power frequency cycle and do not interfere with each other.

[0057] Experimental verification:

[0058] To verify the feasibility of the circuit under 220Vac input, the circuit was simulated using PSIM simulation software. Specific parameters: AC input voltage peak value 311V, effective value 220Vac, frequency 50Hz, input inductance L S1 is 3mH, input inductor L C1 is 500uH, inductor L S2 =LC2 is 20uH, the middle capacitor C C =C S The resistor is 1uF, the switching frequency of the PFC converter is 50kHz, P in the PI parameters is 1, I is 0.005, and the output voltage of the converter can be 100~200V.

[0059] Figure 7 The waveform simulation diagram of the key components of the bridgeless PFC converter is shown in Figure 2. Figure 7 It can be seen that under the condition of AC input 220Vac (i.e. AC input voltage peak 311V) and frequency 50Hz, the bridgeless PFC converter achieves a 160V regulated output. S and switch tube S C At the input voltage v in In the positive and negative half cycles, the inductor currents are turned on and off at the same time, thus realizing the bridgeless operation of the AC-DC circuit of the present invention. In addition, the dual conversion unit circuit only works in each half of the power frequency cycle, and the inductor currents do not interfere with each other. Figure 6 The waveforms of the theoretical key components are consistent with those shown in the figure, which verifies the working principle of the converter without a rectifier bridge. It also shows that the converter can Figure 5 The system closed-loop control scheme shown achieves closed-loop stable operation.

[0060] Table 1 shows the simulation results of the present invention under a wide output voltage range. As can be seen from Table 1, the PF value of the converter proposed in the present invention is much higher than 0.9 in a wide operating range, and with the increase of power and output voltage, the PF value is better, and the THDi performance is also better. In addition, the voltage stress V ds Low, only the input voltage V in,pk With 1 / 2 output voltage V o The sum of V ds =V in,pk +1 / 2V o .

[0061] Table 1 Performance comparison of the converter of the present invention at 220Vac input

[0062]

[0063] The theoretical analysis and simulation results above demonstrate that the proposed bridgeless PFC converter based on SEPIC and Cuk circuits can achieve a wide output voltage range of 100-200V at a 220V AC input voltage through simple single-voltage closed-loop control. Furthermore, the two switching transistors can use identical drive signals, making the circuit control scheme simple and reliable.

[0064] The above description is only used to help understand the method and core essence of the present invention, but the scope of protection of the present invention is not limited thereto. For those skilled in the art, equivalent replacements or modifications based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention should be included in the scope of protection of the present invention. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk, characterized by: The topology of the PFC converter includes a SEPIC circuit unit, a Cuk circuit unit, an output capacitor C p and output capacitor C n ; The SEPIC circuit unit includes a switch tube S S , input inductor L S1 、Inductor L S2 , intermediate capacitor C S , input diode D S1 , diode D S2 The Cuk circuit unit includes a switch tube S C , input inductor L C1 、Inductor L C2 , intermediate capacitor C C , input diode D C1 , diode D C2 ; The SEPIC circuit unit and the Cuk circuit unit are connected in parallel at the input end and in series at the output end, thereby reducing the voltage stress of the switch tube; One end of the AC input side is connected to the input diode D C1 cathode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The drain, intermediate capacitance C S The positive connection of the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S2 The anode of diode D S2 The cathode and output capacitor C p The positive electrode, load R L One end is connected; Input diode D C1 The anode of the input diode D S1 Anode, switch tube S C The source of the switch tube S S The source, inductor L S2 The other end of the diode D C2 The cathode of the output capacitor C p The negative pole of the output inductor C n The positive pole is connected; The other end of the AC input side is connected to the input diode D S1 cathode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube S C The drain, intermediate capacitance C C The positive connection of the middle capacitor C C The cathode of diode D C2 Anode, inductor L C2 One end of the inductor L is connected C2 The other end of the output capacitor C n The negative electrode, load R L The other end is connected; The PFC converter is mainly based on the SEPIC circuit unit and its operating mode in the positive half cycle of the AC input is as follows: Working mode 1: switch tube S S , input diode D S1 In the on state, the switch tube S C In the on state but no current flows; The input terminal passes through the input diode D S1 , switch tube S S Give the input inductor L S1 Charging; at the same time, the intermediate capacitor C S Through the switch tube S S To inductor L S2 Charging, output capacitor C p , output capacitor C n Give load R L Energy supply; in this stage, the input inductor current i LS1 , inductor current i LS2 linear rise; Working mode 2: switch tube S S Turn off, input diode D S1 , diode D S2 In the on state; the input terminal is connected to the input inductor L S1 The energy is transferred to the middle capacitor C S , the output capacitor C p and load R L transfer; at the same time, the inductor L S2 The current i LS2 Through diode D S2 Freewheeling, to the next stage output capacitor C p and load R L Transfer energy; in this stage, the input inductor current i LS1 , inductor current i LS2 linearly decreases; at the same time, the output capacitor C n Keep the load R L powered by; Working mode 3: switch tube S S Keep off, the working mode is when the input inductor current i LS1 and the inductor current i LS2 All linearly decrease to zero, at this time i LS1 =i LS2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

2. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 1, characterized in that: The topology of the PFC converter is replaced by: One end of the AC input side is connected to the input diode D C1 Anode, input inductor L C1 One end of the input inductor L C1 The other end of the switch tube S C The source, the intermediate capacitor C C The negative connection of the middle capacitor C C The positive electrode of the diode D C2 cathode, inductor L C2 One end of the inductor L is connected C2 The other end of the output capacitor C p The positive electrode, load R L One end is connected; Input diode D C1 The cathode of the input diode D S1 The cathode of the switch tube S C The drain of the switch tube S S The drain, inductor L S2 One end of the diode D C2 Anode, output capacitor C p The negative pole of the output capacitor C n The positive pole is connected; The other end of the AC input side is connected to the input diode D S1 Anode, input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source, the intermediate capacitor C S The negative connection of the middle capacitor C S The positive electrode and the inductor L S2 The other end of the diode D S2 The cathode of the diode D is connected S2 The anode and output capacitor C n The negative electrode, load R L The other end is connected.

3. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 1 or 2, characterized in that: The operating mode of the PFC converter based on the Cuk circuit in the negative half cycle of the AC input is as follows: Working mode 4: switch tube S C , input diode D C1 In the on state, the switch tube S S In the on state but no current flows; The input terminal passes through the input diode D C1 , switch tube S C Give the input inductor L C1 Charging; at the same time, the intermediate capacitor C C Through the switch tube S C To inductor L C2 Charging, output capacitor C p , output capacitor C n Give load R L Energy supply; in this stage, the input inductor current i LC1 , inductor current i LC2 linear rise; Working mode 5: switch tube S C Turn off, input diode D C1 , diode D C2 In the on state; the input terminal is connected to the input inductor L C1 The energy is transferred to the middle capacitor C C , the output capacitor C n and load R L transfer; at the same time, the inductor L C2 The current i LC2 Through diode D C2 Freewheeling, to the next stage output capacitor C n and load R L Transfer energy; in this stage, the input inductor current i LC1 , inductor current i LC2 linearly decreases; at the same time, the output capacitor C p Keep the load R L powered by; Working mode 6: switch tube S C Keep off, the working mode is when the input inductor current i LC1 and the inductor current i LC2 All linearly decrease to zero, at this time i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides power to subsequent circuits.

4. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 3, characterized in that: The PFC converter adopts single voltage closed loop control to control the switch tube S C and switch tube S S The same control drive signal is used for control.

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