Cuk and SEPIC-based wide-output PFC converter without input diode

Abstract

The invention discloses an input-diode-free wide-output PFC converter based on Cuk and SEPIC, 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 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; 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 buck-boost of the output voltage is realized. According to the input-diode-free wide-output PFC converter based on the Cuk and the SEPIC, a diode rectifier bridge is completely eliminated, so that the energy loss of the circuit is reduced, and the circuit structure is simplified; meanwhile, the voltage stress of the switching tube is greatly reduced compared with that of a traditional Buck-boost PFC converter, and the buck-boost capability of the output voltage is still achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of PFC converters, and in particular relates to a Cuk and SEPIC-based PFC converter without input diode and with wide output. Background Art

[0002] With the widespread application of new energy power generation technology, batteries, as an important carrier of new energy storage applications, are expected to be more widely used. Battery packs usually operate in a large voltage range. For example, when the energy consumption of the battery pack is large, the terminal voltage of its components will drop significantly; and when charging the battery pack, an AC-DC charging converter with a wide output voltage operating range is required to cope with the voltage rise during the battery pack charging process. Moreover, during the charging process of the battery pack, the front-stage AC-DC charging converter is required to operate in two modes: constant voltage charging and constant current charging. Especially in the constant current charging process, the charging converter needs to achieve a wide output voltage range. Therefore, a wide voltage operating range power factor correction (PFC) converter with buck-boost function has a good application prospect.

[0003] The traditional buck-boost PFC converter with buck-boost output capability has the following problems: high switch voltage stress, large switch conduction loss, and relatively large electromagnetic interference compared to buck PFC and boost PFC. Other traditional Cuk and SEPIC PFC converters, such as Figure 1 As shown, there are also problems such as large electromagnetic interference.

[0004] The present invention proposes a Cuk and SEPIC-based wide output PFC converter without input diode, combined with Figure 1 The traditional Cuk and SEPIC PFC converter topology shown in the figure realizes a new topology without a rectifier bridge by connecting the output ends of the two converter topology circuits in series and the input ends in parallel. The bridgeless PFC converter without input diode based on Cuk and SEPIC circuits has high efficiency operation capability, good voltage step-up and step-down capability, and can realize smoother energy input through the characteristics of multiple inductors and intermediate capacitors of Cuk and SEPIC conversion units. Summary of the invention

[0005] The purpose of the present invention is to provide a Cuk and SEPIC-based input diode-free wide output PFC converter to solve the problems of high switch tube voltage stress, large switch tube conduction loss, and relatively large electromagnetic interference compared to buck PFC and boost PFC in the conventional buck-boost PFC converter with step-up and step-down output capability in the prior art proposed in the above background technology.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention proposes a Cuk and SEPIC-based PFC converter without input diode and with wide output. The topology structure includes a SEPIC circuit unit, a Cuk circuit unit, an output capacitor C p and output capacitor C n ;

[0008] The SEPIC circuit unit includes a switch tube S S , input inductance L S1 、Intermediate capacitor C S 、Diode D S 、Inductance L S2 The Cuk circuit unit includes a switch tube S C , input inductance L C1 、Intermediate capacitor C C 、Diode D C 、Inductance L C2 ;

[0009] 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 achieve step-up and step-down of the output voltage.

[0010] Preferably, one end of the AC input side is connected to the input inductor L S1 The same-name terminal is connected to the input inductor L S1 The opposite end of the switch tube S S The drain, intermediate capacitance C S The positive electrode is connected to the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S The anode of the diode D S The cathode and output capacitor C p The positive electrode, load R L One end of the connection;

[0011] The other end of the AC input side is connected to the input inductor L C1 The opposite end is connected, the input inductor L C1 The same-name terminal and the switch tube S C The drain, intermediate capacitance C C The positive electrode is connected to the middle capacitor C C The negative electrode and the inductor L C2 One end of the diode D C 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;

[0012] The switch tube S S The source and inductor L S2 The other end of the output capacitor C p The negative pole of the output capacitor C n The positive electrode of diode D C The cathode of the switch tube S C Source connection.

[0013] Furthermore, the operating mode of the Cuk and SEPIC-based input diode-free wide output PFC converter in the positive half cycle is mainly determined by the input inductance L of the SPEIC circuit unit and the Cuk circuit unit. C1 And switch tube S C The implementation is as follows:

[0014] Working mode 1: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C S Through the switch tube S S To inductor L S2 Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply;

[0015] Working mode 2: Switching tube S S , switch tube S C Turn off, diode D S is turned on and stored in the input inductor L S1 and input inductance L C1 The energy passes through the diode D S And switch tube S C The body diode of the S , the output capacitor C p and load R L Transfer; inductor current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C p and load R L Transfer energy; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2Linearly decrease; at the same time, the output capacitor C n Keep the load R L powered by;

[0016] Working mode 3: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LS2 The linear decrease starts when it reaches zero, at which time i LS1 =i LS2 =i LC1 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0017] Furthermore, the operating mode of the Cuk and SEPIC-based input diode-free wide output PFC converter in the negative half cycle is mainly determined by the input inductance L of the Cuk circuit unit and the SEPIC circuit unit. S1 And switch tube S S The implementation is as follows:

[0018] Working mode 4: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C C Through the switch tube S C To inductor L C2 and output capacitor C n Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply;

[0019] Working mode 5: switch tube S S , switch tube S C Turn off, diode D C is turned on and stored in the input inductor L C1 and input inductance L S1 The energy passes through the diode D C And switch tube S S The body diode of the C Transferred and stored in the inductor LC2 The energy passes through the diode D C To the next stage output capacitor C n and load R L Transfer; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C p Keep the load R L powered by;

[0020] Working mode 6: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LC2 The linear decrease starts when it reaches zero, at which time i LS1 =i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0021] Preferably, one end of the AC input side is connected to the input inductor L C1 The same-name terminal is connected to the input inductor L C1 The opposite 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 cathode connection, inductor L C2 The other end of the output capacitor C p The positive electrode, load R L One end of the connection;

[0022] The other end of the AC input side is connected to the input inductor L S1 The opposite end is connected, the input inductor L S1 The same-name terminal and 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 One end of the diode D S The cathode of the diode D is connected S The anode and output capacitor C n The negative electrode, load R L The other end is connected;

[0023] The switch tube S S The drain and inductance LS2 The other end of the output capacitor C n The positive electrode, output capacitor C p The cathode of diode D C Anode, switch tube S C Drain connection.

[0024] Furthermore, the operating mode of the Cuk and SEPIC-based input diode-free wide output PFC converter in the positive half cycle is mainly determined by the input inductance L of the SPEIC circuit unit and the Cuk circuit unit. C1 And switch tube S C The implementation is as follows:

[0025] Working mode 1: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C S Through the switch tube S S To inductor L S2 Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply;

[0026] Working mode 2: Switching tube S S , switch tube S C Turn off, diode D S is turned on and stored in the input inductor L S1 and input inductance L C1 The energy passes through the diode D S And switch tube S C The body diode of the S , the output capacitor C n and load R L Transfer; Inductance L S2 The current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C n and load R L Transfer energy; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor Cp Keep the load R L powered by;

[0027] Working mode 3: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LS2 The linear decrease starts when it reaches zero, at which time i LS1 =i LS2 =i LC1 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0028] Furthermore, the operating mode of the Cuk and SEPIC-based input diode-free wide output PFC converter in the negative half cycle is mainly determined by the input inductance L of the Cuk circuit unit and the SEPIC circuit unit. S1 And switch tube S S The implementation is as follows:

[0029] Working mode 4: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C C Through the switch tube S C To inductor L C2 and output capacitor C p Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C n The subsequent load R L Energy supply;

[0030] Working mode 5: switch tube S S , switch tube S C Turn off, diode D C is turned on and stored in the input inductor L C1 and input inductance L S1 The energy passes through the diode D C And switch tube S S The body diode of the C Transferred and stored in the inductor L C2 The energy passes through the diode D CTo the next stage output capacitor C p and load R L Transfer; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C n Keep the load R L powered by;

[0031] Working mode 6: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LC2 The linear decrease starts when it reaches zero, at which time i LS1 =i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0032] Preferably, the PFC converters of the above two circuit structures adopt single voltage closed-loop control and generate the same control drive signal to the switch tube S C And switch tube S S Take control.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The Cuk and SEPIC-based input diode-free wide output PFC converter of the present invention completely eliminates the diode rectifier bridge, thereby reducing energy loss and simplifying the circuit structure.

[0035] (2) The voltage stress of the switch tube in the Cuk and SEPIC-based input diode-free wide output PFC converter of the present invention is greatly reduced compared with the traditional Buck-boost PFC converter, and still has the ability to step up and down the output voltage.

[0036] (3) The Cuk and SEPIC-based input diode-free wide output PFC converter circuit of the present invention can use a simple single voltage loop feedback to achieve closed-loop control, and the two switch tubes can use exactly the same driving signal to achieve closed-loop control. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The topological structure diagram of the traditional Cuk and SEPIC PFC converters in the background technology of the present invention ((a) is SEPIC PFC, (b) is Cuk PFC);

[0038] Figure 2 A topological structure diagram of a wide output PFC converter without input diode based on Cuk and SEPIC in the present invention;

[0039] Figure 3 This is an operation mode diagram of the Cuk and SEPIC-based input diode-free wide output PFC converter in the present invention, which is mainly based on the SEPIC circuit in the positive half cycle;

[0040] Figure 4 It is an operation mode diagram of the Cuk circuit-based and SEPIC-based PFC converter without input diode and with wide output in the negative half cycle;

[0041] Figure 5 It is a closed-loop control circuit diagram of a wide-output PFC converter without input diode based on Cuk and SEPIC in the present invention;

[0042] Figure 6 The waveform diagram of key components in half a power frequency cycle of the Cuk and SEPIC-based input diode-free wide output PFC converter of the present invention;

[0043] Figure 7 This is a simulation waveform diagram of key components when the input diode-free wide output PFC converter based on Cuk and SEPIC in the present invention outputs 160V / 100W. DETAILED DESCRIPTION

[0044] 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.

[0045] Embodiment 1:

[0046] The circuit topology of the Cuk and SEPIC-based input diode-free wide output PFC converter mainly includes the SEPIC circuit unit and the Cuk circuit unit. S , input inductance L S1 、Intermediate capacitor C S 、Diode D S 、Inductance L S2 Forming a SEPIC circuit; switch tube S C , input inductance L C1 、Intermediate capacitor C C 、Diode D C 、Inductance L C2 Form a Cuk circuit.

[0047] Figure 2 Two bridgeless circuit diagrams of the input diode-free wide output PFC converter based on Cuk and SEPIC in the present invention are given.

[0048] Specifically, Figure 2 As shown in (a), one end of the AC input side is connected to the input inductor L S1 The input inductor L S1 The opposite end of the switch tube S S The drain, intermediate capacitance 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 diode D is connected. S The cathode and output capacitor C p The positive electrode, load R L one end of the .

[0049] The other end of the AC input side is connected to the input inductor L C1 The input inductor L C1 The same-name terminal and 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 anode of the inductor is connected. C2 The other end of the output capacitor C n The negative electrode, load R L The other end of the connection.

[0050] Switching tube S S The source and inductor L S2 The other end of the output capacitor C p The negative pole of the output capacitor C n The positive electrode of diode D C The cathode of the switch tube S C Source connection.

[0051] Specifically, Figure 2 As shown in (b), one end of the AC input side is connected to the input inductor L C1 The input inductor L C1 The opposite 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 cathode of the inductor is connected. C2The other end of the output capacitor C p The positive electrode, load R L one end of the .

[0052] The other end of the AC input side is connected to the input inductor L S1 The input inductor L S1 The same-name terminal and 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 One end of the diode D S The cathode of diode D is connected. S The anode and output capacitor C n The negative electrode, load R L The other end of the connection.

[0053] Switching tube S S The drain and inductance L S2 The other end of the output capacitor C n The positive electrode, output capacitor C p The cathode of diode D C Anode, switch tube S C Drain connection.

[0054] because Figure 2 (a) and Figure 2 The circuit in (b) has symmetry and similar performance. Therefore, the present invention is mainly based on Figure 2 The circuit in (a) mainly introduces the working principle of the converter.

[0055] It should be noted that in order to better illustrate the working principle, the coupled inductor L S1 and L C1 An ideal transformer primary side T1 and secondary side T2 are introduced to illustrate the coupling relationship and working principle.

[0056] 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.

[0057] The working mode diagram of the negative half AC input cycle of the circuit of the present invention is as follows: Figure 4shown. 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.

[0058] Working mode 1: In this stage, the switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C S Through the switch tube S S To inductor L S2 Charging; the ideal transformer T1 has a current i at the same end T1 Inflow, the ideal transformer T2 has a current i T2 At this stage, the inductor current i LS1 , inductor current i LC1 , inductor current i LS2 Linear increase. Output capacitor C p and output capacitor C n Provide energy for subsequent loads.

[0059] Working mode 2: Switching tube S S , switch tube S C Turn off, diode D S is turned on and stored in the input inductor L S1 and input inductance L C1 The energy passes through the diode D S And switch tube S C The body diode of the S , the output capacitor C p and load R L Transfer; inductor current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C p and load R L Transfer energy; inductor current i LS1 , inductor current i LC1 , inductor current i LS2 At the same time, the output capacitor C n Keep the load R L powered by.

[0060] Working mode 3: switch tube S C And switch tube S S Keep off, the working mode is in the inductor current i LS1 , inductor current i LC1 and the inductor current i LS2 The linear decrease starts when it reaches zero, at which time i LS1 =i LS2 =i LC1 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0061] Working mode 4: In this stage, the switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C C Through the switch tube S C To inductor L C2 and output capacitor C n Charging; the ideal transformer T2 has a current i at the same end T2 The ideal transformer T1 has a current i at the same end. T1 In this stage, the inductor current i LS1 , inductor current i LC1 , inductor current i LS2 Linear increase. Output capacitor C p and output capacitor C n Provide energy for subsequent loads.

[0062] Working mode 5: switch tube S S , switch tube S C Turn off, diode D C is turned on and stored in the input inductor L C1 and input inductance L S1 The energy passes through the diode D C And switch tube S S The body diode of the C Transferred and stored in the inductor L C2 The energy passes through the diode D C To the next stage output capacitor C n and load R L Transfer; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C pKeep the load R L powered by.

[0063] Working mode 6: switch tube S C And switch tube S S Keep off, the working mode is in the inductor current i LS1 , inductor current i LC1 and the inductor current i LC2 The linear decrease starts when it reaches zero, at which time i LS1 =i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0064] In the present invention Figure 2 The working principle of the converter in (b) is as follows:

[0065] Working mode 1: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C S Through the switch tube S S To inductor L S2 Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply;

[0066] Working mode 2: Switching tube S S , switch tube S C Turn off, diode D S is turned on and stored in the input inductor L S1 and input inductance L C1 The energy passes through the diode D S And switch tube S C The body diode of the S , the output capacitor C n and load R L Transfer; Inductance L S2 The current i LS2 Through diode D S Freewheeling, to the next stage output capacitor C n and load R LTransfer energy; input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C p Keep the load R L powered by;

[0067] Working mode 3: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LS2 The linear decrease starts when it reaches zero, at which time i LS1 =i LS2 =i LC1 =0, and the output capacitor C p and output capacitor C n Provide energy for the subsequent circuits;

[0068] Working mode 4: switch tube S S , switch tube S C In the on state, the input end passes through the switch tube S S , switch tube S C , to the input inductor L S1 , input inductance L C1 Charging; at the same time, the middle capacitor C C Through the switch tube S C To inductor L C2 and output capacitor C p Charging; in this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C n The subsequent load R L Energy supply;

[0069] Working mode 5: switch tube S S , switch tube S C Turn off, diode D C is turned on and stored in the input inductor L C1 and input inductance L S1 The energy passes through the diode D C And switch tube S S The body diode of the C Transferred and stored in the inductor L C2 The energy passes through the diode D C To the next stage output capacitor C p and load R L Transfer; input inductor current i LS1, input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C n Keep the load R L powered by;

[0070] Working mode 6: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LC2 The linear decrease starts when it reaches zero, at which time i LS1 =i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

[0071] 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 S S The same control drive signal is used to avoid complex control.

[0072] 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.

[0073] System simulation results:

[0074] In order to verify the operational feasibility of the circuit of the present invention under 220Vac input, the circuit was simulated and verified using PSIM simulation software.

[0075] Specific parameters: AC input voltage peak value is 311V, effective value is 220Vac, frequency is 50Hz, input inductance L S1 is 3mH, input inductance L C1 is 200uH, inductor L S2 =L C2 is 20uH, the middle capacitor C C =C SThe inductor is 1uF, the switching frequency of the PFC converter is 50kHz, the P in the PI parameter is 1, I is 0.005, and the converter output voltage can be 100-200V. In addition, to ensure the continuity of the input current, an electromagnetic filter inductor L is added on the input side. f With input capacitor C f , respectively set to L f =0.4mH, C f =0.1uF.

[0076] Figure 7 This is the 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.

[0077] 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 in this patent is higher than 0.9 in a wide operating range, and has better PF value and THDi performance as the power and output voltage increase.

[0078] Table 1 PF and THDi parameters of the converter of the present invention at 220Vac input

[0079]

[0080] 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.

[0081] 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 PFC converter without input diode based on Cuk and SEPIC, 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 、Intermediate capacitor C S 、Diode D S 、Inductance L S2 The Cuk circuit unit includes a switch tube S C , input inductance L C1 、Intermediate capacitor C C 、Diode D C 、Inductance L 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 to achieve step-up and step-down of the output voltage.

2. The Cuk and SEPIC-based input diode-free wide output PFC converter according to claim 1, characterized in that: One end of the AC input side and the input inductor L S1 The same-name terminal is connected to the input inductor L S1 The opposite end of the switch tube S S The drain, intermediate capacitance C S The positive electrode is connected to the middle capacitor C S The negative electrode and the inductor L S2 One end of the diode D S The anode of the diode D S The cathode and output capacitor C p The positive electrode, load R L One end of the connection; The other end of the AC input side is connected to the input inductor L C1 The opposite end is connected, the input inductor L C1 The same-name terminal and the switch tube S C The drain, intermediate capacitance C C The positive electrode is connected to the middle capacitor C C The negative electrode and the inductor L C2 One end of the diode D C 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; The switch tube S S The source and inductor L S2 The other end of the output capacitor C p The negative pole of the output capacitor C n The positive electrode of diode D C The cathode of the switch tube S C Source connection.

3. The Cuk and SEPIC-based input diode-free wide output PFC converter according to claim 1, characterized in that: One end of the AC input side and the input inductor L C1 The same-name terminal is connected to the input inductor L C1 The opposite 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 cathode connection, inductor L C2 The other end of the output capacitor C p The positive electrode, load R L One end of the connection; The other end of the AC input side is connected to the input inductor L S1 The opposite end is connected, the input inductor L S1 The same-name terminal and 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 One end of the diode D S The cathode of the diode D is connected S The anode and output capacitor C n The negative electrode, load R L The other end is connected; The switch tube S S The drain and inductance L S2 The other end of the output capacitor C n The positive electrode, output capacitor C p The cathode of diode D C Anode, switch tube S C Drain connection.

4. The Cuk and SEPIC-based input diode-free wide output PFC converter according to claim 2 or 3, characterized in that: Its working mode in the positive half cycle is mainly composed of the input inductance L of the SPEIC circuit unit and the Cuk circuit unit. C1 And switch tube S C The implementation is as follows: Working mode 1: switch tube S S , switch tube S C In the on state, at this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply; Working mode 2: Switching tube S S , switch tube S C Turn off, diode D S conduction, input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C p or output capacitor C n Keep the load R L powered by; Working mode 3: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LS2 The linear decrease starts when it reaches zero, at which time i LS1 =i LS2 =i LC1 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

5. The Cuk and SEPIC-based input diode-free wide output PFC converter according to claim 4, characterized in that: Its working mode in the negative half cycle is mainly composed of the input inductance L of the Cuk circuit unit and the SEPIC circuit unit. S1 And switch tube S S The implementation is as follows: Working mode 4: switch tube S S , switch tube S C In the on state, at this stage, the input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linear increase; output capacitance C p and output capacitor C n The subsequent load R L Energy supply; Working mode 5: switch tube S S , switch tube S C Turn off, diode D C conduction, input inductor current i LS1 , input inductor current i LC1 , inductor current i LS2 Linearly decrease; at the same time, the output capacitor C p or output capacitor C n Keep the load R L powered by; Working mode 6: switch tube S C And switch tube S S Keep off, the working mode is when the input inductor current i LS1 , input inductor current i LC1 and the inductor current i LC2 The linear decrease starts when it reaches zero, at which time i LS1 =i LC1 =i LC2 =0, and the output capacitor C p and output capacitor C n Provides energy for subsequent circuits.

6. The Cuk and SEPIC-based input diode-free wide output PFC converter according to claim 5, characterized in that: The PFC converter adopts single voltage closed loop control and generates the same control drive signal to the switch tube S C And switch tube S S Take control.

Images