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

Abstract

The invention discloses a wide-output low-voltage stress bridgeless PFC converter based on SEPIC and Cuk, and relates to the technical field of PFC converters. The topological structure of the PFC converter comprises an SEPIC circuit unit, a Cuk circuit unit, an output capacitor Cp and an output capacitor Cn, the SEPIC circuit unit comprises a switching tube SS, an input inductor LS1, an inductor LS2, an intermediate capacitor CS, an input diode DS1 and a diode DS2; the Cuk circuit unit comprises a switching tube SC, an input inductor LC1, an inductor LC2, an intermediate capacitor CC, an input diode DC1 and a diode DC2; the SEPIC circuit unit and the Cuk circuit unit are connected in parallel at the input end and are connected in series at the output end, so that the voltage stress of a switching tube is reduced. Two circuit units are subjected to input parallel connection, output series connection and PFC converter cascade topology based on SEPIC and Cuk, diode devices are reduced, so that the converter operation loss is reduced, other main elements of SEPIC and Cuk are reserved, and the LC filter network characteristics of input and output of the two converters are reserved.

Description

Technical Field

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

[0002] In the context of the wide application of renewable energy power generation technologies such as solar energy and wind energy, batteries, as key components of energy storage systems, play an increasingly important role in energy storage and scheduling. However, for charging devices, variable grid conditions require them to be able to adapt to a wide voltage range to ensure that the battery charging system can operate efficiently at various input voltages. In addition, in many cases, the DC power input from new energy sources cannot be directly obtained, which requires a small-power AC-DC converter with power factor correction (PFC) that can operate stably within a wide voltage range. The buck-boost function and the power factor correction closed-loop control loop enable the AC-DC PFC converter to stably adjust the output voltage within different input voltage ranges, ensuring that the battery pack always receives an appropriate charging voltage. In the case of large fluctuations in the grid voltage, the PFC converter can also maintain a constant output voltage, thereby avoiding severe fluctuations in the grid load and effectively reducing the instability of the grid. Therefore, an AC-DC PFC converter with a buck-boost function and a wide voltage operating range has broad application prospects, especially in new energy applications and charging devices connected to the power system with high development potential.

[0003] Traditionally, the front-stage circuit of battery chargers in the range of hundreds of watts to several kilowatts usually adopts a boost PFC converter and is equipped with a rectifier bridge. And to meet the wide voltage operating range requirements of the battery pack, the boost PFC converter usually needs to be cascaded with a DC-DC buck converter at the subsequent stage to form a two-stage power conversion circuit. In contrast, although the buck-boost PFC converter has the ability to step up and step down the output, due to its high switch voltage stress (the sum of the input voltage and the output voltage), large switch conduction loss, and significant electromagnetic interference, it is usually only applicable to LED lighting applications with a power of dozens of watts. Therefore, developing a PFC converter with a buck-boost function and low voltage stress has good application prospects.

[0004] Such as Figure 1As shown in the figure, the traditional SEPIC PFC converter topology can be regarded as an integrated circuit of boost and buck-boost respectively, and the traditional Cuk PFC converter topology can be regarded as an integrated circuit of boost and buck respectively. Therefore, both the traditional SEPIC and Cuk PFC converters have the ability of wide output voltage. However, the topologies used in the traditional SEPIC and Cuk PFC converters use multiple diodes for rectification in multiple operating modes, which results in operating losses.

[0005] The present invention proposes a bridge-less PFC converter. Based on the SEPIC and Cuk PFC conversion circuits, the present invention reduces the diode devices and thus reduces the converter operating losses by input-parallel connecting and output-series connecting two conversion units through a PFC converter cascade topology based on SEPIC and Cuk, and retains other main components of SEPIC and Cuk, that is, retains the LC filter network characteristics of the input and output of these two converters. Summary of the Invention

[0006] The purpose of the present invention is to provide a wide-output low-voltage stress bridge-less PFC converter based on SEPIC and Cuk to solve the problems in the prior art that the buck-boost PFC converter has high voltage stress of its switching tubes, large on-state loss of the switching tubes and significant electromagnetic interference, and is only applicable to LED lighting occasions with a power of dozens of watts as mentioned in the above background technology.

[0007] To achieve the above purpose, the present invention is implemented by adopting the following technical solutions:

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

[0009] The SEPIC circuit unit includes switching 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 switching 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 to reduce the voltage stress of the switching tube.

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

[0012] The anode of the input diode D C1 is connected to the anode of the input diode D S1 , the source of the switching tube S C , the source of the switching tube S S , the other end of the inductor L S2 , the cathode of the diode D C2 , the negative electrode of the output capacitor C p , and the positive electrode of the output inductor C n .

[0013] The other end of the AC input side is connected to the cathode of the input diode D S1 and one end of the input inductor L C1 ; the other end of the input inductor L C1 is connected to the drain of the switching tube S C and the positive electrode of the intermediate capacitor C C ; the negative electrode of the intermediate capacitor C C is connected to the anode of the diode D C2 and one end of the inductor L C2 ; the other end of the inductor L C2 is connected to the negative electrode of the output capacitor C n and the other end of the load R L .

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

[0015] The cathode of the input diode D C1 is connected to the cathode of the input diode D S1 and the drain of the switching transistor S C ; the drain of the switching transistor S S is connected to the drain of the switching transistor S S2 and one end of the inductor L C2 ; the anode of the diode D p is connected to the negative electrode of the output capacitor C n ; the positive electrode of the output capacitor C

[0016] The other end of the AC input side is connected to the anode of the input diode D S1 and one end of the input inductor L S1 ; one end of the input inductor L S1 is connected to the source of the switching transistor S S and the negative electrode of the intermediate capacitor C S ; the negative electrode of the intermediate capacitor C S is connected to the other end of the inductor L S2 and the cathode of the diode D S2 ; the anode of the diode D S2 is connected to the negative electrode of the output capacitor C n and the other end of the load R L .

[0017] Preferably, the working mode of the PFC converter in the positive half-cycle of the AC input based on the SEPIC circuit unit is as follows:

[0018] Working mode 1: The switching transistor S S and the input diode D S1 are in the conducting state, and the switching transistor S C is in the conducting state but no current flows through; the input terminal charges the input inductor L S1 through the input diode D S and the switching transistor S S1 ; meanwhile, the intermediate capacitor C S charges the inductor L S through the switching transistor S S2 , and the output capacitor C p and the output capacitor C n supply energy to the load R L ; in this stage, the input inductor current i LS1 and the inductor current i LS2 rise linearly;

[0019] Operating mode 2: Switching transistor S S Turns off, and the input diode D S1 and diode D S2 are in the conducting state; the input terminal transfers the energy stored in the input inductor L S1 to the intermediate capacitor C S , the subsequent-stage output capacitor C p and the load R L ; meanwhile, the current i S2 of the inductor L LS2 flows through the diode D S2 for freewheeling and transfers energy to the subsequent-stage output capacitor C p and the load R L ; during this stage, the input inductor current i LS1 , the inductor current i LS2 linearly decreases; meanwhile, the output capacitor C n keeps supplying power to the load R L ;

[0020] Operating mode 3: The switching transistor S S remains off. This operating mode starts when both the input inductor current i LS1 and the inductor current i LS2 linearly decrease to zero, at which time i LS1 = i LS2 = 0, and the output capacitor C p and the output capacitor C n supply energy to the subsequent-stage circuit.

[0021] Preferably, the operating modes of the PFC converter mainly based on the Cuk circuit in the negative half-cycle of the AC input are as follows:

[0022] Operating mode 4: The switching transistor S C , the input diode D C1 are in the conducting state, and the switching transistor S S is in the conducting state but no current flows through it; the input terminal charges the input inductor L C1 through the input diode D C and the switching transistor S C1 ; meanwhile, the intermediate capacitor C C charges the inductor L C through the switching transistor S C2 , and the output capacitor C p , the output capacitor C n supply energy to the load R L ; during this stage, the input inductor current i LC1 , the inductor current i LC2 linearly increases;

[0023] Operating mode 5: The switching transistor S CTurn off, input diode D C1 and diode D C2 are in the conducting state; the input terminal transfers the energy stored in the input inductor L C1 to the intermediate capacitor C C , the subsequent-stage output capacitor C n and the load R L ; meanwhile, the current i C2 of the inductor L LC2 flows through the diode D C2 for freewheeling and transfers energy to the subsequent-stage output capacitor C n and the load R L ; during this stage, the input inductor current i LC1 , the inductor current i LC2 linearly decreases; meanwhile, the output capacitor C p keeps supplying power to the load R L .

[0024] Operating mode 6: The switch S C remains off. This operating mode starts when both the input inductor current i LC1 and the inductor current i LC2 linearly decrease to zero. At this time, i LC1 = i LC2 = 0, and the output capacitor C p and the output capacitor C n supply energy to the subsequent-stage circuit.

[0025] Preferably, the PFC converter adopts single-voltage closed-loop control and controls the switch S C and the switch S S with the same control drive signal.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) In the present invention, the PFC converter reduces the number of input diodes and uses only one input diode in a single operating mode, reducing energy loss and simplifying the circuit structure of the present invention.

[0028] (2) In the present invention, the PFC converter performs input parallel connection and output series connection on the SEPIC converter and the Cuk converter, retains the smooth power conversion of the SEPIC and Cuk converters, improves the light-load efficiency, and reduces the voltage stress of the switch. It realizes the ability to operate with high efficiency and good voltage step-up / step-down ability, and can achieve smoother energy input through the characteristics of multiple inductors and intermediate capacitors of the SEPIC and Cuk conversion units.

[0029] (3) In the present invention, the PFC converter has relatively low switching device stress and corresponding switching losses. Specifically, the voltage stress of the MOSFET switching device is only the sum of the input voltage V in,pk and 1 / 2 of the output voltage V o , that is, V in,pk + 1 / 2V o .

[0030] (4) In the present invention, the PFC converter circuit can achieve closed-loop control by using a simple single-voltage-loop feedback, and the two switching devices can achieve closed-loop control by using completely identical drive signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of the topologies of traditional SEPIC and Cuk PFC converters in the background art of the present invention;

[0032] Figure 2 is a schematic diagram of the topology of the bridgeless PFC converter with wide output and low voltage stress based on SEPIC and Cuk in the present invention;

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

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

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

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

[0037] Figure 7 is a simulation waveform diagram of key devices of the bridgeless PFC converter with wide output and low voltage stress based on SEPIC and Cuk in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1:

[0040] Refer to Figure 2 , Figure 2 , which presents two hybrid input parallel output series bridgeless circuits of the present invention based on SEPIC and Cuk. The circuit topology mainly includes a SEPIC circuit unit and a Cuk circuit unit. In the figure, the switching transistor S S , the input inductor L S1 , the inductor L S2 , the intermediate capacitor C S , the input diode D S1 , the diode D S2 constitute the SEPIC circuit unit; the switching transistor S C , the input inductor L C1 , the inductor L C2 , the intermediate capacitor C C , the input diode D C1 , the diode D C2 constitute the Cuk circuit unit.

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

[0042] The anode of the input diode D C1 is connected to the anode of the input diode D S1 , the source of the switching transistor S C , the source of the switching transistor S S , the other end of the inductor L S2 , the cathode of the diode D C2 , the negative electrode of the output capacitor C p , and the positive electrode of the output inductor C n .

[0043] The other end of the AC input side is connected to the cathode of the input diode D S1 and one end of the input inductor L C1 . The other end of the input inductor L C1 is connected to the switching transistor SC The drain of C is connected to the positive electrode of the inductor L C2 One end of C is connected to the negative electrode of the intermediate capacitor C C2 and the anode of the diode D C2 The other end of the inductor L n is connected to the negative electrode of the output capacitor C L and the other end of the load R

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

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

[0046] Figure 2Two hybrid input parallel output series bridgeless circuits based on SEPIC and Cuk proposed by the present invention. Since Figure 2 (a) and Figure 2 (b) have circuit symmetry and performance similarity, therefore, mainly taking the circuit in Figure 2 (a) to introduce 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 shown in Figure 3 shown. Figure 3 (a) is the equivalent circuit of the working mode 1 of the AC-DC bridgeless PFC converter mainly based on the SEPIC circuit in the positive half cycle of the AC input. Figure 3 (b) is the equivalent circuit of the working mode 2 of the AC-DC bridgeless PFC converter mainly based on the SEPIC circuit in the positive half cycle of the AC input. Figure 3 (c) is the equivalent circuit of the working mode 3 of the AC-DC bridgeless PFC converter mainly based on the SEPIC circuit in the positive half cycle of the AC input.

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

[0049] Working mode 1: The switching tubes S S and the input diode D S1 are in the conducting state, and the switching tube S C is in the conducting state but no current flows through. The input terminal charges the input inductor L S1 through the input diode D S and the switching tube S S1 ; meanwhile, the intermediate capacitor C S charges the inductor L S through the switching tube S S2 , and the output capacitors C p , C n supply energy to the load R L . At this stage, the input inductor current i LS1 , the inductor current i LS2 rise linearly.

[0050] Working mode 2: The switching tube S STurn off, input diode D S1 , diode D S2 is in the conducting state. The input terminal transfers the energy stored in the input inductor L S1 to the intermediate capacitor C S , the subsequent-stage output capacitor C p and the load R L ; meanwhile, the current i S2 of the inductor L LS2 flows through the diode D S2 for freewheeling and transfers energy to the subsequent-stage output capacitor C p and the load R L . During this stage, the input inductor current i LS1 , the inductor current i LS2 linearly decreases; meanwhile, the output capacitor C n continues to supply power to the load R L .

[0051] Operating mode 3: The switch S S remains turned off. This operating mode starts when both the input inductor current i LS1 and the inductor current i LS2 linearly decrease to zero, at which time i LS1 = i LS2 = 0, and the output capacitors C p and C n supply energy to the subsequent-stage circuit.

[0052] Operating mode 4: The switch S C , the input diode D C1 are in the conducting state. The switch S S is in the conducting state but no current flows through it. The input terminal charges the input inductor L C1 through the input diode D C and the switch S C1 ; meanwhile, the intermediate capacitor C C charges the inductor L C through the switch S C2 , and the output capacitors C p , C n supply energy to the load R L . During this stage, the input inductor current i LC1 , the inductor current i LC2 linearly increases.

[0053] Operating mode 5: The switch S C turns off, and the input diode D C1 , diode D C2 are in the conducting state. The input terminal transfers the energy stored in the input inductor L C1 to the intermediate capacitor C C, the post-stage output capacitor C n and the load R L transfer; meanwhile, the current i C2 of the inductor L LC2 flows through the diode D C2 for freewheeling and transfers energy to the post-stage output capacitor C n and the load R L During this stage, the input inductor current i LC1 , the inductor current i LC2 decreases linearly; meanwhile, the output capacitor C p continues to supply power to the load R L .

[0054] Operating mode 6: The switch S C remains off. This operating mode starts when both the input inductor current i LC1 and the inductor current i LC2 have linearly decreased to zero, at which time i LC1 = i LC2 = 0, and the output capacitor C p and the output capacitor C n supply energy to the post-stage circuit.

[0055] The closed-loop control circuit of the circuit of the present invention is as 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 uses a simple single-voltage closed-loop control to achieve the control of the two switches. Moreover, the two switches S C and the switch S S adopt the same control drive signal, avoiding complex control.

[0056] Figure 6 This is the key device theoretical waveform diagram of the bridgeless PFC converter of the present invention. Among them, d on is the conduction duty cycle, d off is the freewheeling turn-off duty cycle of the inductor current, and T s is a switching period. As Figure 6 can be seen, the key devices of the conversion unit mainly operate within half of the power frequency cycle and do not interfere with each other.

[0057] Experimental verification:

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

[0059] Figure 7 is the waveform simulation diagram of the key devices of the bridgeless PFC converter. From Figure 7 it can be seen that under the condition of an AC input of 220 Vac (i.e., the peak value of the AC input voltage is 311 V) and a frequency of 50 Hz, the bridgeless PFC converter realizes a regulated output of 160 V. Moreover, the switching tube S S and the switching tube S C are simultaneously turned on and off during the positive and negative half - cycles of the input voltage v in , realizing the bridgeless operation of the AC - DC circuit of the present invention. In addition, the double - conversion unit circuit only works during each half power - frequency cycle, and the inductor currents do not interfere with each other, which is consistent with the theoretical key device waveforms shown in Figure 6 , verifying the working principle of the converter without a rectifier bridge. At the same time, it also shows that the converter can achieve closed - loop stable operation through the system closed - loop control scheme shown in Figure 5 .

[0060] Table 1 gives the operation simulation results of the present invention under a wide output voltage. From Table 1, it can be seen that the PF value of the converter proposed by the present invention is much higher than 0.9 in a wide operating range, and has a better PF value with the increase of power and output voltage. At the same time, it also has good THDi performance. Moreover, the voltage stress V ds of the MOSFET switching tube is low, only the sum of the input voltage V in,pk and 1 / 2 of the output voltage V o , that is, V ds = V in,pk + 1 / 2V o .

[0061] Table 1 Comparison of the performance of the converter of the present invention under 220 Vac input

[0062]

[0063] According to the above - mentioned theoretical analysis and simulation results, it can be seen that the bridgeless PFC converter based on SEPIC and Cuk circuits proposed by the present invention can achieve a wide output voltage of 100 - 200 V through simple single - voltage closed - loop control under an AC input voltage of 220 Vac. And the two switching tubes can use exactly the same drive signals, and the circuit control scheme is simple and reliable.

[0064] The above is only used to help understand the method of the present invention and its core concept. However, the protection scope of the present invention is not limited thereto. For those of ordinary skill in the art within the technical scope disclosed by the present invention, any equivalent substitution or change made according to the technical solution of the present invention and its inventive concept should be covered within the protection scope of the present invention. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk, characterized in that: The topological structure 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 inductance L S1 、Inductance L S2 、Intermediate capacitor C S , Input diode D S1 、Diode D S2 The Cuk circuit unit includes a switch tube S C , input inductance L C1 、Inductance 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.

2. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 1, characterized in that: One end of the AC input side is connected to the input diode D C1 The cathode of the 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 The cathode of the 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 the diode D C2 Anode, inductor L C2 One end of the inductor L C2 The other end of the 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, characterized in that: 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 middle capacitor C C The negative pole of the middle capacitor C C The positive electrode of the diode D C2 The cathode of the inductor L C2 One end of the inductor L 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, 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; 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 middle capacitor C S The negative pole 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.

4. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 2 or 3, characterized in that: The PFC converter is mainly based on the SEPIC circuit unit and its working 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 middle capacitor C S Through the switch tube S S To inductor L S2 Charging, output capacitor C p , output capacitor C n To load R L Energy supply; at this stage, the input inductor current i LS1 , inductor current i LS2 Linear rise; Working mode 2: Switching 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; at this stage, the input inductor current i LS1 , inductor current i LS2 Linearly decrease; 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 energy for subsequent circuits.

5. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 4, characterized in that: The working 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 middle capacitor C C Through the switch tube S C To inductor L C2 Charging, output capacitor C p , output capacitor C n To load R L Energy supply; at 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; at this stage, the input inductor current i LC1 , inductor current i LC2 Linearly decrease; 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 energy for subsequent circuits.

6. The wide output low voltage stress bridgeless PFC converter based on SEPIC and Cuk according to claim 5, characterized in that: The PFC converter adopts a 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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