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

Abstract

The invention discloses a wide-output low-ripple 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 input diode DRS, an input diode DRC and an output capacitor Co. The SEPIC circuit unit comprises a switching tube SS, an input inductor LS1, an intermediate capacitor CS, a diode DS and an inductor LS2; the Cuk circuit unit comprises a switching tube SC, an input inductor LC1, an intermediate capacitor CC, a diode DC and an inductor LC2; and the SEPIC circuit unit and the Cuk circuit unit are in input parallel connection and output parallel connection, so that voltage boost-buck output is realized. The invention provides the cascaded topology of the PFC converter based on the SEPIC and the Cuk, diode devices are reduced, so that the running loss of the converter is reduced, and other main elements of the SEPIC and the Cuk are reserved, namely, the LC filter network characteristics of input and output of the two converters and the corresponding low output ripple characteristics are reserved.

Description

Technical Field

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

[0002] With the wider application of new energy power generation technology, battery packs, as energy storage systems for renewable energy (such as solar or wind energy, etc.), will be more widely used. However, when the DC power input from the new energy source is not available, such as when there is no sunlight or available wind power, a low-power AC-DC buck-boost battery charger with power factor correction (PFC) function is usually required to power the battery pack through the AC mains. These battery charging systems may face a wide range of input voltage fluctuations, especially under different weather and load conditions. In global power systems and mobile power applications, some power supply devices may need to support a wide voltage range from 85V to 265V. Therefore, a PFC converter with buck-boost function is required to effectively adjust the input voltage and output voltage, ensure the stability of the charging process and improve the energy conversion efficiency. In practical applications, it is of great help to improve the energy efficiency of the power supply and reduce the load on the power grid. Therefore, a power factor correction converter with a wide voltage operating range and buck-boost function has a good application prospect.

[0003] Traditional battery charger front-end circuits ranging from hundreds of watts to thousands of watts usually use boost PFC converters with rectifier bridges. The boost PFC converter needs to be equipped with a post-stage DC-DC buck converter to meet the wide voltage operating range requirements of the battery pack, and its power conversion requires a two-stage circuit. On the other hand, the buck-boost PFC converter with buck-boost output capability has problems such as high switch tube voltage stress, large switch tube conduction loss, and large electromagnetic interference. Therefore, it is usually only suitable for LED lighting applications of tens of watts.

[0004] like Figure 1 As shown in the figure, the traditional SEPIC PFC converter topology can be regarded as the integrated circuit of boost and buck-boost, and the traditional Cuk PFC converter topology can be regarded as the integrated circuit of boost and buck. Therefore, both the traditional SEPIC and Cuk PFC converters have wide output voltage capability; and because both the input and output sides have inductor and capacitor networks, they also have natural low output ripple capability.

[0005] Therefore, based on two converter topology circuits, the present invention proposes a bridgeless PFC converter with low output ripple by connecting the two conversion units in parallel in input and output. The converter has high-efficiency operation capability and good voltage step-up and step-down capability, and can achieve smoother energy input through the characteristics of multiple inductors and intermediate capacitors of SEPIC and Cuk conversion units to achieve low output ripple characteristics. Summary of the invention

[0006] The purpose of the present invention is to provide a wide output low ripple bridgeless PFC converter based on SEPIC and Cuk to solve the problems of the existing buck-boost PFC converter with step-up and step-down output capability proposed in the above background technology, which requires two-stage circuits for power conversion and has high switch tube voltage stress, large switch tube conduction loss, large electromagnetic interference and other problems.

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

[0008] The present invention proposes a wide output low ripple bridgeless PFC converter based on SEPIC and Cuk. The topology of the PFC converter includes a SEPIC circuit unit, a Cuk circuit unit, an input diode D RS , Input diode D RC and output capacitor C o ;

[0009] The SEPIC circuit unit includes a switch tube S S , input inductance L S1 、Intermediate capacitor C S 、Diode D S and inductor L S2 The Cuk circuit unit includes a switch tube S C , input inductance L C1 、Intermediate capacitor C C 、Diode D C and inductor L C2 ;

[0010] The SEPIC circuit unit and the Cuk circuit unit are connected in parallel in input and output to achieve voltage step-up and step-down output.

[0011] Preferably, one end of the AC input side is connected to the input diode D RS The anode connection of the input diode D RC The cathode of the input diode D RS 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 connection, the intermediate capacitor C SThe positive connection of the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S The anode is connected;

[0012] Input diode D RC The anode and 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 C The cathode, inductance L C2 One end of the inductor is connected to C2 The other end of the output capacitor C o The positive electrode of diode D S Cathode, load R L One end is connected;

[0013] The other end of the AC input side is connected to the switch tube S S The source of the switch tube S C The drain of diode D C Anode, inductor L S2 The other end of the output capacitor C o The negative electrode, load R L The other end of the connection.

[0014] Preferably, one end of the AC input side is connected to the input diode D RS The cathode connection of the input diode D RC Anode connection of input diode D RS The anode and input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source connection, the intermediate capacitor C S The negative pole of the middle capacitor C S The positive electrode and the inductor L S2 One end of the diode D S The cathode of is connected;

[0015] Input diode D RC 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 C Anode, inductor L C2One end of the inductor is connected to C2 The other end of the output capacitor C o The cathode of diode D S Anode, load R L One end is connected;

[0016] The other end of the AC input side is connected to the switch tube S C The source of the switch tube S S The drain of diode D C The cathode, inductance L S2 The other end of the output capacitor C o The positive electrode, load R L The other end of the connection.

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

[0018] Working mode 1: switch tube S S , Input diode D RS In the on state, the switch tube S C It is in the on state during the entire positive half cycle but no current flows through it; the input terminal is connected through the input diode D RS , 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 o To load R L Energy supply; at this stage, the input inductor current i LS1 , inductor current i LS2 Linear increase; output capacitance C o To load R L Energy supply;

[0019] Working mode 2: switch tube S S Turn off, input diode D RS 、Diode D S 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 Charged and passed through diode D S To the next stage output capacitor C o and load R L supply energy; at the same time, the inductor current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C o and load R L Transfer energy; at this stage, the input inductor current iLS1 , inductor current i LS2 Linear decline;

[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, only output capacitor C o For load R L Energy supply.

[0021] Preferably, the working mode of the PFC converter in the negative half AC input cycle is mainly based on the Cuk circuit unit, which is as follows:

[0022] Working mode 4: switch tube S C , Input diode D RC In the on state, the switch tube S S It is in the on state during the entire negative half cycle but no current flows through it; the input terminal passes through the input diode D RC , 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 , output capacitor C o Charge and supply load R L Energy supply; at this stage, the input inductor current i LC1 , inductor current i LC2 Linear rise;

[0023] Working mode 5: switch tube S C Turn off, input diode D RC 、Diode D C 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 Charged and passed through diode D S To the next stage output capacitor C o and load R L supply energy; at the same time, the inductor current i LC2 Through diode D C Freewheeling, to the next stage output capacitor C o and load R L Transfer energy; at this stage, the input inductor current i LC1 , inductor current i LC2 Linear decline;

[0024] Working mode 6: switch tube SC 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, only output capacitor C o For load R L Energy supply.

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

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

[0027] (1) The topology used in traditional SEPIC and Cuk PFC converters uses multiple diodes for rectification in multiple working modes, resulting in operating losses. Based on this, the present invention proposes a PFC converter cascade topology based on SEPIC and Cuk, which reduces diode devices and thus reduces converter operating losses, 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, and their corresponding low output ripple characteristics. Therefore, 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 present invention connects the SEPIC converter and the Cuk converter in parallel in input and output, thereby retaining the smooth power conversion of the SEPIC and Cuk converters and their corresponding low output ripple characteristics.

[0029] (3) The 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

[0030] Figure 1 A topological structure diagram of a conventional SEPIC and Cuk PFC converter in the background technology of the present invention;

[0031] Figure 2 A topological structure diagram of a wide output low ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0032] Figure 3It is the working modal diagram of the positive half AC input cycle of the wide output low ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0033] Figure 4 It is a working modal diagram of the negative half AC input cycle of the wide output low ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0034] Figure 5 It is a schematic diagram of a closed-loop control circuit of a wide-output low-ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0035] Figure 6 The waveform diagram of key components in half a power frequency cycle of the wide output low ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention;

[0036] Figure 7 This is a simulation waveform diagram of key components of the wide output low ripple bridgeless PFC converter based on SEPIC and Cuk in the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1:

[0039] See also Figure 2-7 , Wide output low ripple bridgeless PFC converter based on SEPIC and Cuk, Figure 2 Two hybrid input parallel output parallel bridgeless circuits based on SEPIC and Cuk are provided in the present invention. The circuit topology mainly includes SEPIC circuit unit and Cuk circuit unit. The switch tube S S , input inductance L S1 、Intermediate capacitor C S , Input diode D RS 、Diode D S 、Inductance L S2 The switch tube S C , input inductance L C1 、Intermediate capacitor C C , Input diode D RC 、Diode D C 、Inductance L C2 Form a Cuk circuit unit.

[0040] Specifically, Figure 2 In (a), one end of the AC input side is connected to the input diode D RS The anode connection of the input diode D RC The cathode of the input diode D RS 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 connection, the intermediate capacitor C S The positive terminal of the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S The anode of the input diode D RC The anode and 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 and the inductor L C2 One end of the diode D C The output capacitor C o The positive electrode and the inductor L C2 The other end of the diode D S Cathode, load R L The other end of the AC input side is connected to the switch tube S S The source of the switch tube S C The drain of diode D C Anode, inductor L S2 The other end of the output capacitor C o The negative electrode, load R L The other end of the connection.

[0041] Specifically, Figure 2 In (b), one end of the AC input side is connected to the input diode D RS The cathode connection of the input diode D RC The anode of the input diode D RS The anode and input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source connection, the intermediate capacitor C S The negative pole of the middle capacitor C S The positive electrode and the inductor L S2 One end of the diode D S The cathode of the input diode D RC The cathode of the input inductor L C1One end of the input inductor L C1 The other end of the switch tube S C The drain, intermediate capacitance C C The positive terminal of the middle capacitor C C The negative electrode and the inductor L C2 One end of the diode D C The output capacitor C o The negative electrode and the inductor L C2 The other end of the diode D S Anode, load R L The other end of the AC input side is connected to the switch tube S C The source of the switch tube S S The drain of diode D C The cathode, inductance L S2 The other end of the output capacitor C o The positive electrode, load R L The other end of the connection.

[0042] Figure 2 The present invention proposes two hybrid input parallel output parallel 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.

[0043] 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 AC-DC bridgeless PFC converter based on SEPIC circuit in working mode 1 in the positive half cycle of AC input; Figure 3 (b) is the equivalent circuit of AC-DC bridgeless PFC converter based on SEPIC circuit in working mode 2 in 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 in the positive half cycle of AC input.

[0044] 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 AC-DC bridgeless PFC converter based on Cuk circuit in working mode 4 in the negative half cycle of AC input; Figure 4 (b) is the equivalent circuit of AC-DC bridgeless PFC converter based on Cuk circuit in working mode 5 in the negative half cycle of 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.

[0045] Working mode 1: switch tube S S , Input diode D RS In the on state, the switch tube S C It is in the on state during the entire positive half cycle but no current flows through it. The input terminal is connected through the input diode D RS , 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 o To load R L In this stage, the input inductor current i LS1 , inductor current i LS2 Linear increase. Output capacitor C o To load R L Energy supply.

[0046] Working mode 2: switch tube S S Turn off, input diode D RS , output diode D S The input terminal is connected to the input inductor L S1 The energy is transferred to the middle capacitor C S Charged and passed through diode D S To the next stage output capacitor C o and load R L At the same time, the inductor L S2 The current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C o and load R L Transfer energy. In this stage, the input inductor current i LS1 , inductor current i LS2 Linear decrease.

[0047] Working mode 3: switch tube S S Keep off, the working mode is in the inductor current i LS1 and the inductor current i LS2 All linearly decrease to zero, at this time i LS1 =i LS2 = 0, only output capacitor C o For load R L Energy supply.

[0048] Working mode 4: switch tube S C, Input diode D RC In the on state, the switch tube S S It is in the on state during the entire negative half cycle but no current flows through it. The input terminal is connected through the input diode D RC , 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 , output capacitor C o Charge and supply load R L In this stage, the input inductor current i LC1 , inductor current i LC2 Linear increase.

[0049] Working mode 5: switch tube S C Turn off, input diode D RC 、Diode D C 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 Charged and passed through diode D S To the next stage output capacitor C o and load R L At the same time, the inductor L C2 The current i LC2 Through diode D C Freewheeling, to the next stage output capacitor C o and load R L Transfer energy. In this stage, the input inductor current i LC1 , inductor current i LC2 Linear decrease.

[0050] Working mode 6: switch tube S C Keep off, the working mode is in the inductor current i LC1 and the inductor current i LC2 All linearly decrease to zero, at this time i LC1 =i LC2 = 0, only output capacitor C o For load R L Energy supply.

[0051] The closed-loop control circuit of the circuit of the present invention is as follows Figure 5 As 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.

[0052] Figure 6 The theoretical waveform diagram of the key components of the bridgeless PFC converter of the present invention. on is the on-duty ratio, 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 of the power frequency cycle and do not interfere with each other.

[0053] System simulation results:

[0054] In order to verify the feasibility of the present invention under 220Vac input, the circuit is simulated and verified using PSIM simulation software. Specific parameters: AC input voltage peak value is 311V, effective value is 220Vac, frequency is 50Hz, input inductance L S1 is 2mH, input inductance L C1 is 500uH, inductor L S2 =L C2 is 25uH, the middle capacitor C C =C S The resistor is 1uF, the switching frequency of the PFC converter is 50kHz, the P in the PI parameters is 1, I is 0.005, and the output voltage of the converter can be 100~200V.

[0055] Figure 7 This is a waveform simulation diagram of the key components of the bridgeless PFC converter. 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 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 be Figure 5 The system closed-loop control scheme shown achieves closed-loop stable operation.

[0056] Table 1 shows the operation simulation results of the present invention under a wide output voltage. As can be seen from Table 1, the PF value of the converter proposed by the present invention is higher than 0.94 in a wide operating range, and has a good PF value and THDi performance; and its output voltage ripple (peak-to-peak value) is low in a wide operating range, indicating that the converter still has a low output voltage ripple characteristic.

[0057] Table 1 Performance comparison of the converter of the present invention at 220Vac input

[0058]

[0059] According to the above theoretical analysis and simulation results, it can be seen that the bridgeless PFC converter based on Cuk and SEPIC circuits proposed in the present invention can achieve a wide output voltage of 100-200V under 220Vac AC input voltage through simple single voltage closed-loop control. In addition, the two switch tubes can use exactly the same driving signal, and the circuit control scheme is simple and reliable.

[0060] The above description is only used to help understand the method of the present invention and its core essence, but the protection scope of the present invention is not limited thereto. For those skilled in the art in the art, equivalent replacement or change according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A wide output low ripple 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 input diode D RS , Input diode D RC and output capacitor C o ; The SEPIC circuit unit includes a switch tube S S , input inductance L S1 、Intermediate capacitor C S 、Diode D S and inductor L S2 The Cuk circuit unit includes a switch tube S C , input inductance L C1 、Intermediate capacitor C C 、Diode D C and inductor L C2 ; The SEPIC circuit unit and the Cuk circuit unit are connected in parallel in input and output to achieve voltage step-up and step-down output.

2. The wide output low ripple 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 RS The anode connection of the input diode D RC The cathode of the input diode D RS 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 connection, the intermediate capacitor 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 S The anode is connected; Input diode D RC The anode and 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 C The cathode of the inductor L C2 One end of the inductor is connected to C2 The other end of the output capacitor C o The positive electrode of diode D S Cathode, load R L One end is connected; The other end of the AC input side is connected to the switch tube S S The source of the switch tube S C The drain of diode D C Anode, inductor L S2 The other end of the output capacitor C o The negative electrode, load R L The other end of the connection.

3. The wide output low ripple 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 RS The cathode of the input diode D RC Anode connection of input diode D RS The anode and input inductor L S1 One end of the input inductor L S1 The other end of the switch tube S S The source connection, the intermediate capacitor C S The negative pole of the middle capacitor C S The positive electrode and the inductor L S2 One end of the diode D S The cathode of is connected; Input diode D RC 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 C Anode, inductor L C2 One end of the inductor is connected to C2 The other end of the output capacitor C o The cathode of diode D S Anode, load R L One end is connected; The other end of the AC input side is connected to the switch tube S C The source of the switch tube S S The drain of diode D C The cathode of the inductor L S2 The other end of the output capacitor C o The positive electrode, load R L The other end of the connection.

4. The wide output low ripple bridgeless PFC converter based on SEPIC and Cuk according to claim 2 or 3, characterized in that: The working mode of the PFC converter in the positive half AC input cycle is mainly based on the SEPIC circuit unit, which is as follows: Working mode 1: switch tube S S , Input diode D RS In the on state, the switch tube S C It is in the on state during the entire positive half cycle but no current flows; The input terminal passes through the input diode D RS , 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 o To load R L Energy supply; at this stage, the input inductor current i LS1 , inductor current i LS2 Linear increase; output capacitance C o To load R L Energy supply; Working mode 2: switch tube S S Turn off, input diode D RS 、Diode D S 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 Charged and passed through diode D S To the next stage output capacitor C o and load R L supply energy; at the same time, the inductor current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C o and load R L Transfer energy; at this stage, the input inductor current i LS1 , inductor current i LS2 Linear decline; 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, only output capacitor C o For load R L Energy supply.

5. The wide output low ripple bridgeless PFC converter based on SEPIC and Cuk according to claim 4, characterized in that: The working mode of the PFC converter in the negative half AC input cycle is mainly based on the Cuk circuit unit, as follows: Working mode 4: switch tube S C , Input diode D RC In the on state, the switch tube S S It is in the on state during the entire negative half cycle but no current flows; The input terminal passes through the input diode D RC , 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 , output capacitor C o Charge and supply 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 RC 、Diode D C 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 Charged and passed through diode D S To the next stage output capacitor C o and load R L supply energy; at the same time, the inductor current i LC2 Through diode D C Freewheeling, to the next stage output capacitor C o and load R L Transfer energy; at this stage, the input inductor current i LC1 , inductor current i LC2 Linear decline; 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, only output capacitor C o For load R L Energy supply.

6. The wide output low ripple bridgeless PFC converter based on SEPIC and Cuk according to claim 5, characterized in that: The PFC converter adopts single voltage closed loop control to realize the switching tube S C And switch tube S S The control of the switch tube S C And switch tube S S The same control drive signal is used.

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