Single-stage isolated unidirectional and bidirectional AC-DC conversion circuit based on Vienna bridgeless PFC

Abstract

The invention provides a single-stage isolation type unidirectional and bidirectional AC-DC conversion circuit based on Vienna bridgeless PFC. The single-stage isolation type unidirectional and bidirectional AC-DC conversion circuit is used for mutual conversion between AC voltage and DC voltage. A primary side of the AC-DC conversion circuit is of a structure combining a Vienna bridgeless PFC and a half-bridge push-pull circuit, a transformer and an inductor and a capacitor of a secondary side form a series resonance circuit, and the primary side can realize zero-voltage soft switching of a switching tube. According to the converter, the structure of a conversion circuit and the number of switching tubes are reduced, so that the efficiency and the size of the whole converter are improved; according to the single-stage isolation type unidirectional and bidirectional AC-DC conversion circuit provided in the design, the characteristic that a PFC circuit is combined with a DC-DC conversion primary side circuit is utilized, the function of mutual conversion of single-stage AC-DC electric energy is achieved, the function is achieved only through a simple circuit and a small size, and a complex control mode is avoided. And the AC-DC conversion is flexibly realized, so that the performance of the circuit is improved, and the cost of the circuit is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and particularly designs a single-stage isolated single-phase and three-phase AC-DC conversion circuit based on Vienna bridgeless PFC. Background Art

[0002] With the development of communication technologies, electric vehicles, and power systems, etc., higher requirements are put forward for the performance, weight, volume, efficiency, and reliability of switching power supplies for communication, electric vehicle chargers, and power operation power supplies. The power supplies in these fields usually draw power from the AC grid and output DC electrical energy. Considering the impact on the power quality of the grid and safety, it is required that the converter simultaneously has the functions of power factor correction and electrical isolation.

[0003] In the traditional bridge-type power factor correction circuit (commonly known as Boost PFC), since more power semiconductor devices conduct current at the same time, the improvement of the circuit efficiency is limited. With the development of power semiconductor devices, especially the application of wide-bandgap semiconductor devices, the bridgeless PFC circuit has received more and more attention because only two power semiconductor devices conduct current at the same time, which can improve the efficiency of the converter. Among them, the Vienna-type bridgeless PFC circuit has received more and more research from experts and scholars due to reasons such as small common-mode interference.

[0004] In the Vienna-type power factor correction circuit, the power factor correction circuit operates alternately in each half power frequency cycle, and the structure is simple. In the reverse inverter working state, the switching tubes are turned on in sequence, which can effectively achieve synchronous freewheeling and improve the efficiency. The series resonant DC-DC converter has a simple structure, the bridge arm switching tubes can achieve soft switching, the switching loss is small, and it also has a high-frequency transformer, which is widely used in DC conversion occasions.

[0005] Traditional switching power supplies for communication, commercial energy storage power supplies, electric vehicle chargers, and power operation power supplies, etc. are two-stage circuits. The front stage is a power factor correction circuit, and the rear stage is an isolated DC-DC circuit. However, the two-stage circuit uses more devices, has a higher cost, a complex control circuit, and a larger volume. Summary of the Invention

[0006] In view of the above technical problems existing in the prior art, the present invention proposes a single-stage isolated single / double-direction AC-DC conversion circuit based on Vienna bridgeless PFC. By combining the power factor correction technology and the DC-DC conversion circuit, this circuit realizes the single-stage integrated function of power factor correction and DC-DC conversion; the conversion circuit, the transformer and the secondary LC form a series resonance network, enabling the bridge arm switching tubes to operate under soft switching, reducing the switching loss; meanwhile, the two-way conversion circuit structure has the function of mutual conversion between AC and DC, enhancing the practicality of use; the conversion circuit uses a high-frequency transformer to transfer energy, which can achieve the function of electrical isolation.

[0007] To achieve the above-mentioned invention purposes, the present invention provides the following technical solutions:

[0008] The capacitors C1 and C2 on the primary side are connected in series, and one end of the connection point of the capacitors C1 and C2 is connected to the input AC2; the power switching tubes Q1 and Q2 are connected in series to form a half-bridge; one end of the connection point of the power switching tubes Q1 and Q2 is connected to the input AC2; the anode of the power switching tube Q1 is connected in series with the same-name end of the transformer winding T1A and is connected to the other end of the capacitor C1; the cathode of the power switching tube Q2 is connected in series with the same-name end of the transformer winding T1B and is connected to the other end of the capacitor C2; after the anodes of the diodes D1 and D2 are connected in series with the cathodes of the diodes D1 and D2, the cathode of the diode D1 is connected to the anode of the power switching tube Q1; the anode of the diode D2 is connected to the cathode of the power switching tube Q2; the anodes of the diodes D3 and D4 are connected in series or the cathode of the power switching tube Q3 is connected in series with the anode of the power switching tube Q4, the cathode of the diode D3 or the anode of the power switching tube Q3 is connected to the other end of the capacitor C1, and the anode of the diode D4 or the cathode of the power switching tube Q4 is connected to the other end of the capacitor C2; the inductor L2 is connected between the connection ends of the diodes D1 and D2 and the connection ends of the diodes D3 and D4; the inductor L1 is connected between the connection ends of the diodes D3 and D4 and the input AC1;

[0009] The secondary side is a full-bridge full-wave rectifier circuit or a half-bridge full-wave rectifier circuit.

[0010] The winding on the secondary side is connected in series with the capacitor C3 and the inductor L3 and then connected to the rectifier circuit on the secondary side.

[0011] The said full-bridge full-wave rectifier circuit includes:

[0012] A first secondary side branch connected in parallel with the load. The first secondary side branch is composed of the first diode D5 and the second diode D6 connected in series, or composed of the first power switching tube Q5 and the second power switching tube Q6 connected in series; the cathode of the first diode D5 or the anode of the first power switching tube Q5 is connected to one end of the output load, and the anode of the second diode D6 or the cathode of the second power switching tube Q6 is connected to the other end of the output load;

[0013] A second secondary branch in parallel with the load, the second secondary branch is composed of a third diode D7 and a fourth diode D8 connected in series, or composed of a third power switch Q7 and a fourth power switch Q8 connected in series; the cathode of the third diode D7 or the anode of the third power switch Q7 is connected to one end of the output load, and the anode of the fourth diode D8 or the cathode of the third power switch Q8 is connected to the other end of the output load;

[0014] A third secondary branch in parallel with the output load is an output filter capacitor C4.

[0015] The half-bridge full-wave rectifier circuit includes:

[0016] The same-named end of the winding T1C of the circuit is connected in series with the different-named end of the winding T1D, and the connection point is connected to one end of the output load after being connected in series with the capacitor C3 and the inductor L3; the other end of the load is connected to the different-named end of the winding T1C through the cathode of the power switch Q5, and at the same time is connected to the same-named end of the winding T1D through the cathode of the power switch Q6.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) By combining the power factor correction technology and the DC-DC conversion circuit, the present invention realizes the function of single-stage integration of power factor correction and DC-DC conversion, reduces the number of power switches, specifically reduces 4 power switches, reduces the cost of the converter, reduces the first-stage conversion control circuit, and improves the efficiency of the conversion circuit.

[0019] (2) The primary half-bridge switch and transformer in the conversion circuit of the present invention and the secondary LC form a series resonance network, which makes it easy for the power switch tubes of the bridge arm to achieve soft switching, reduces the switching loss, avoids various electromagnetic interference problems caused by hard switching of the switch tubes, is easy to realize the high-frequency operation of the circuit, and is beneficial to improving the efficiency of the circuit.

[0020] (3) The two-way conversion circuit structure of the present invention has the function of mutual conversion between AC and DC, which enhances the practicability of use. The two-way DC-DC conversion circuit and the half-bridge full-wave rectifier structure of the two-way DC-DC conversion circuit are suitable for the low-voltage and large-current working mode, and the full-bridge full-wave rectifier structure of the two-way DC-DC conversion circuit is suitable for the high-voltage working mode.

[0021] (4) The primary side of the present invention combines a deformed Vienna bridge-less PFC circuit with a half-bridge resonance circuit, boosts the voltage with one inductor, balances the voltage values of the upper and lower capacitors with one inductor, and preferably uses wide-bandgap power devices, providing an example for the application of wide-bandgap power devices.

[0022] (5) The conversion circuit of the present invention can convert an AC voltage into a desired DC voltage, and can also convert a DC voltage into a desired AC voltage, while achieving electrical isolation. This function has a very wide range of applications. For example: switching power supplies for communication, electric vehicle chargers, LED drivers, commercial and household energy storage inverters, bidirectional OBCs, etc. It shows that the solution of this converter has a very broad application prospect. Description of the Drawings

[0023] Figure 1 Schematic diagram of the unidirectional AC-DC conversion circuit structure of a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC provided for Embodiment 1;

[0024] Figure 2 Schematic diagram of the bidirectional AC-DC conversion circuit (full-bridge full-wave rectification) structure of a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC provided for Embodiment 2;

[0025] Figure 3 Schematic diagram of the bidirectional AC-DC conversion circuit (half-bridge full-wave rectification) structure of a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC provided for Embodiment 3;

[0026] Figure 4 Single-stage isolated unidirectional AC-DC working waveform diagram of a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC in Embodiment 1;

[0027] Figure 5 Single-stage isolated bidirectional AC-DC working waveform diagram of a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC in Embodiment 2; Detailed Embodiments

[0028] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0029] Embodiment 1

[0030] Referring to Figure 1 , a single-stage isolated single-bidirectional AC-DC conversion circuit based on Vienna bridge-less PFC includes a primary side and a secondary side, and is characterized in that: the primary side half-bridge push-pull resonant circuit includes a bridge-less PFC; the primary side switching tubes, transformer, and secondary side inductor and capacitor form a series resonant circuit; specifically:

[0031] The capacitors C1 and C2 on the primary side are connected in series. One end of the connection point of capacitors C1 and C2 is connected to the input AC2. The power switch tubes Q1 and Q2 are connected in series to form a half-bridge. One end of the connection point of power switch tubes Q1 and Q2 is connected to the input AC2. The anode of power switch tube Q1 is connected in series with the same-name end of the transformer winding T1A and is connected to the other end of capacitor C1. The cathode of power switch tube Q2 is connected in series with the same-name end of the transformer winding T1B and is connected to the other end of capacitor C2. After the anodes of diode D1 and the cathode of diode D2 are connected in series, the cathode of diode D1 is connected to the anode of power switch tube Q1. The anode of diode D2 is connected to the cathode of power switch tube Q2. The anodes of diode D3 and the cathode of diode D4 are connected in series. The cathode of diode D3 is connected to the other end of capacitor C1, and the anode of diode D4 is connected to the other end of capacitor C2. The inductor L2 is connected between the connection ends of diodes D1 and D2 and the connection ends of diodes D3 and D4. The inductor L1 is connected between the connection ends of diodes D3 and D4 and the input AC1.

[0032] The secondary side is a full-bridge full-wave rectifier circuit. The winding on the secondary side is connected in series with capacitor C3 and inductor L3 and then connected to the rectifier circuit on the secondary side.

[0033] The full-bridge full-wave rectifier circuit includes:

[0034] A first secondary side branch connected in parallel with the load. The first secondary side branch is composed of a series connection of a first diode D5 and a second diode D6, or is composed of a series connection of a first power switch tube Q5 and a second power switch tube Q6. The cathode of the first diode D5 or the anode of the first power switch tube Q5 is connected to one end of the output load, and the anode of the second diode D6 or the cathode of the second power switch tube Q6 is connected to the other end of the output load.

[0035] A second secondary side branch connected in parallel with the load. The second secondary side branch is composed of a series connection of a third diode D7 and a fourth diode D8, or is composed of a series connection of a third power switch tube Q7 and a fourth power switch tube Q8. The cathode of the third diode D7 or the anode of the third power switch tube Q7 is connected to one end of the output load, and the anode of the fourth diode D8 or the cathode of the third power switch tube Q8 is connected to the other end of the output load.

[0036] The third secondary side branch connected in parallel with the output load is the output filter capacitor C4.

[0037] The anode of power switch tube Q1 is connected in series with the same-name end of the transformer winding T1A and is connected to capacitor C1 to form positive half-wave drive or rectification. The cathode of power switch tube Q2 is connected in series with the same-name end of the transformer winding T1B and is connected to capacitor C2 to form negative half-wave drive or rectification. Diode D1 and power switch tube Q1 are connected in series to form a positive half-wave BOOST boost power switch, and diode D2 and power switch tube Q2 are connected in series to form a negative half-wave BOOST boost power switch.

[0038] Diodes D3 and D4 are used for step-up positive and negative half-wave rectification, capacitors C1 and C2 are used for filtering, capacitor L1 is a BOOST step-up inductor, and inductor L2 is a voltage balancing inductor for capacitors C1 and C2. Inductor L1 and inductor L2 can share a magnetic core or not, and the inductance of inductor L1 or inductor L2 can be 0.

[0039] The power switch tubes Q1 and Q2 are connected in series with the windings T1C of the primary and secondary sides of the transformer T1, and capacitors C3 and inductor L3 to form an LLC series resonance. The diodes D5, D6, D7, and D8 on the secondary side form a full-bridge full-wave rectification.

[0040] Embodiment 2

[0041] Refer to Figure 2 , compared with Embodiment 1, a single-stage isolated single-phase and three-phase AC-DC conversion circuit based on Vienna bridgeless PFC in this embodiment has the following differences:

[0042] The cathode of power switch tube Q3 is connected in series with the anode of power switch tube Q4. The anode of power switch tube Q3 is connected to the other end of capacitor C1, and the cathode of power switch tube Q4 is connected to the other end of capacitor C2. When operating in inversion, power switch tubes Q3 and Q4 form a half-bridge inversion circuit, and power switch tubes Q1 and Q2 form a freewheeling circuit.

[0043] The power switch tubes Q1 and Q2 are connected in series with the windings T1C of the primary and secondary sides of the transformer T1, capacitors C3 and inductor L3 to form an LLC series resonance. The power switch tubes Q5, Q6, Q7, and Q8 on the secondary side form a full-bridge rectification circuit or a full-bridge inversion circuit.

[0044] Embodiment 3

[0045] Refer to Figure 3 , compared with Embodiment 1, a single-stage isolated single-phase and three-phase AC-DC conversion circuit based on Vienna bridgeless PFC in this embodiment has the following differences:

[0046] The cathode of power switch tube Q3 is connected in series with the anode of power switch tube Q4. The anode of power switch tube Q3 is connected to the other end of capacitor C1, and the cathode of power switch tube Q4 is connected to the other end of capacitor C2. When operating in inversion, power switch tubes Q3 and Q4 form a half-bridge inversion circuit, and power switch tubes Q1 and Q2 form a freewheeling circuit.

[0047] The power switch tubes Q1 and Q2 are connected in series with the primary sides T1A and T1B of the transformer T1, and the windings T1C and T1D of the secondary side, capacitors C3 and inductor L3 to form an LLC series resonance. The power switch tubes Q5 and Q6 on the secondary side form a half-bridge rectification circuit or a half-bridge inversion circuit.

[0048] Compared with the existing conversion circuit, the isolated AC-DC conversion circuit provided in this embodiment reduces the number of switching tubes. The bridgeless PFC and the push-pull conversion circuit adopt the control mode of PFM or PWM.

[0049] For describing the commutation process of the working mode, the following assumptions are made:

[0050] (1) The power switching tubes Q1 and Q2 work complementarily at an adjustable switching frequency, and the duty cycles are equal or complementary.

[0051] (2) The inductor L1 works in the BOOST boost mode. The number of turns of the primary transformer windings T1A and T1B is equal, and they work in a coupled manner.

[0052] (3) The inductor L1 and the inductor L2 can share the same magnetic core or different magnetic cores; the inductance of the inductor L1 or the inductor L2 can be 0, and the inductor L3 can be the leakage inductance of the transformer.

[0053] Analysis of the AC-DC conversion process (taking the positive half-cycle as an example, AC1>AC2) is as Figure 4 :

[0054] Mode 1: [t1~t2] At this time, the power switching tube Q1 is conducting and the power switching tube Q2 is cut off. The current flows from the positive pole of the capacitor C1 through the transformer winding T1A to the negative pole of the capacitor C1. The secondary winding T1C generates an electromotive force with the lower part positive and the upper part negative. The secondary diodes D5 and D8 are conducting, and a current is generated on the secondary side, forming a full-bridge rectification; at the same time, AC1 passes through the inductors L1, L2, and the diode D1, and then through the power switching tube Q1 to AC2, and the inductors L1 and L2 store energy.

[0055] Mode 2: [t2~t3] At this time, the power switching tube Q1 is conducting and the power switching tube Q2 is cut off. The current of the inductor L3 starts to decrease from the maximum value. The secondary rectifying diodes D5 and D8 are turned off. At this time, it is considered that the exciting inductance is large enough. In this stage, the current is approximately constant. Therefore, the working waveform in the [t2~t3] stage is obtained, and the inductors L1 and L2 store energy.

[0056] Mode 3: [t3~t4] At this time, the power switching tubes Q1 and Q2 are cut off. The inductor L1 charges the capacitor C1 after being rectified by the diode D3. The current of the inductor L2 is coupled to the winding T1B through the winding T1A and charges the capacitor C2 through the anti-parallel diode of the power switching tube Q2. The dead time of the work is very short, and the current of the inductor L2 is almost constant. Therefore, the working waveform [t3~t4] can be obtained:

[0057] Mode 4: [t4~t5] At this time, the power switching tube Q1 is cut off. At this time, the current of the inductor L2 passes through the anti-parallel diode of the power switching tube Q2 of the full-bridge inverter circuit until the power switching tube Q2 is conducting, forming a zero-voltage turn-on.

[0058] [t5~t7] Repeat the above process; the working mode in the negative half cycle is the same;

[0059] Analysis of the DC-AC conversion process (taking the full-bridge inverter circuit as an example) is as Figure 5 :

[0060] DC-DC conversion process: At this time, the output becomes the input. The power switch tubes Q5 and Q8 are turned on, and the power switch tubes Q6 and Q7 are turned off. The current flows from the positive pole of OUT+ to the power switch tube Q5, through the transformer winding T1C to the capacitor C3 and the inductor L3, forming a series resonance, and then through the power switch tube Q8 to the negative pole of OUT-. The winding T1A of the circuit generates an induced electromotive force with the lower part positive and the upper part negative. The power switch tube Q1 is turned on, and a current is generated in the primary side to charge the capacitor C1, forming a positive half-wave rectification; the negative half cycle is opposite. The power switch tubes Q6 and Q7 are turned on, and the power switch tubes Q5 and Q8 are turned off. The whole process forms a full-bridge LLC circuit, and the driving waveform is as Figure 5 shown.

[0061] DC-AC conversion process: As Figure 5 shown, the power switch tube Q3 works in the entire positive half cycle of the AC, and the power switch tube Q4 is turned off. The current flows from the positive pole of the capacitor C1 through the power switch tube Q3 through the inductor L1 to AC1 and AC2 and then back to the negative pole of the capacitor C1. At this time, the power switch tube Q2 can be turned on when the inductor L3 is freewheeling; the power switch tube Q4 works in the entire negative half cycle of the AC, and the power switch tube Q3 is turned off. The current flows out from the positive pole of the capacitor C2 through AC1, through AC2 and back to the inductor L1 through the power switch tube Q4 and back to the negative pole of the capacitor C1. At this time, the power switch tube Q1 can be turned on when the inductor L3 is freewheeling, as Figure 5 shown, and finally an AC voltage waveform is formed between AC1 and AC2.

[0062] The conversion process of the DC-AC half-bridge inverter circuit. The working processes of Q5 and Q6 are the same as those of Figure 5 the driving waveform and the working modes are also the same.

Claims

1. A single-stage isolated single-phase and two-phase AC-DC conversion circuit based on Vienna bridgeless PFC, comprising a primary side and a secondary side, characterized in that: The primary-side half-bridge push-pull resonant circuit includes a bridgeless PFC; the primary-side switching transistors, the transformer, and the secondary-side inductor and capacitor form a series resonant circuit; specifically: The capacitors C1 and C2 on the primary side are connected in series, and one end of the connection point of the capacitors C1 and C2 is connected to the input AC2; the power switching transistors Q1 and Q2 are connected in series to form a half-bridge; one end of the connection point of the power switching transistors Q1 and Q2 is connected to the input AC2; the anode of the power switching transistor Q1 is connected in series with the same-name end of the transformer winding T1A and is connected to the other end of the capacitor C1; the cathode of the power switching transistor Q2 is connected in series with the same-name end of the transformer winding T1B and is connected to the other end of the capacitor C2; after the anodes of the diodes D1 and D2 are connected in series with the cathodes of the diodes D1 and D2, the cathode of the diode D1 is connected to the anode of the power switching transistor Q1; the anode of the diode D2 is connected to the cathode of the power switching transistor Q2; the anodes of the diodes D3 and D4 are connected in series or the cathode of the power switching transistor Q3 is connected in series with the anode of the power switching transistor Q4, the cathode of the diode D3 or the anode of the power switching transistor Q3 is connected to the other end of the capacitor C1, and the anode of the diode D4 or the cathode of the power switching transistor Q4 is connected to the other end of the capacitor C2; the inductor L2 is connected between the connection ends of the diodes D1 and D2 and the connection ends of the diodes D3 and D4; the inductor L1 is connected between the connection ends of the diodes D3 and D4 and the input AC1; The secondary side is a full-bridge full-wave rectifier circuit or a half-bridge full-wave rectifier circuit.

2. The single-stage isolated single-phase and single-direction AC-DC conversion circuit based on Vienna bridgeless PFC according to claim 1, characterized in that, The winding on the secondary side is connected in series with the capacitor C3 and the inductor L3 and then connected to the rectifier circuit on the secondary side.

3. The single-stage isolated single-phase and three-phase AC-DC conversion circuit based on Vienna bridgeless PFC according to claim 1, wherein The full-bridge full-wave rectifier circuit includes: A first secondary-side branch connected in parallel with the load, and the first secondary-side branch is composed of a series connection of a first diode D5 and a second diode D6, or is composed of a series connection of a first power switching transistor Q5 and a second power switching transistor Q6; the cathode of the first diode D5 or the anode of the first power switching transistor Q5 is connected to one end of the output load, and the anode of the second diode D6 or the cathode of the second power switching transistor Q6 is connected to the other end of the output load; A second secondary-side branch connected in parallel with the load, and the second secondary-side branch is composed of a series connection of a third diode D7 and a fourth diode D8, or is composed of a series connection of a third power switching transistor Q7 and a fourth power switching transistor Q8; the cathode of the third diode D7 or the anode of the third power switching transistor Q7 is connected to one end of the output load, and the anode of the fourth diode D8 or the cathode of the third power switching transistor Q8 is connected to the other end of the output load; The third secondary-side branch connected in parallel with the output load is the output filter capacitor C4.

4. The single-stage isolated single-phase and two-phase AC-DC conversion circuit based on Vienna bridgeless PFC according to claim 1, characterized in that, The half-bridge full-wave rectifier circuit includes: The same-name end of the winding T1C of the circuit is connected in series with the different-name end of the winding T1D, and the connection point is connected to one end of the output load after being connected in series with the capacitor C3 and the inductor L3; the other end of the load is connected to the different-name end of the winding T1C through the cathode of the power switching transistor Q5 and is simultaneously connected to the same-name end of the winding T1D through the cathode of the power switching transistor Q6.

5. The single-stage isolated single-phase and two-phase AC-DC conversion circuit based on Vienna bridgeless PFC as claimed in claim 1, wherein, The power switching transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are power metal-oxide semiconductor field effect transistors.

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