Single-stage bridgeless alternating-current / direct-current conversion circuit

Abstract

Provided in the present application is a single-stage bridgeless alternating-current / direct-current conversion circuit. The circuit comprises an input-side circuit and an output-side circuit, wherein the input-side circuit comprises a three-phase circuit, each individual-phase circuit in the three-phase circuit comprises a first switch circuit, a filter circuit and a first single-stage energy transmission circuit, and the first single-stage energy transmission circuit comprises a second switch circuit and a transformer; and the output-side circuit comprises a first output rectifier and filter circuit. Compared with a two-stage circuit, the circuit has a higher conversion efficiency.

Description

Single-stage bridgeless AC-DC conversion circuit

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 8, 2023, with application number 202311676435.3 and application name “Single-stage bridgeless AC / DC conversion circuit”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of power supply circuits, and in particular to a single-stage bridgeless AC-DC conversion circuit. Background Art

[0003] Currently, the circuit topologies for charging modules in electronic devices primarily include single-phase and three-phase inputs. Regardless of whether single-phase or three-phase input is used, a two-stage topology is employed. For example, with single-phase input, the front stage uses a boost chopper circuit, while the back stage uses a resonant circuit or a phase-shifted full-bridge circuit to achieve efficient DC-DC isolation and energy transfer. For example, with three-phase input, the front stage typically uses a three-phase Vienna circuit for power factor calibration and AC-DC conversion, while the back stage also uses a resonant circuit or a phase-shifted full-bridge circuit to achieve a wide range of DC output voltages and high-efficiency soft-switching operation. However, the existing two-stage approach results in low overall conversion efficiency for the charging module.

[0004] Summary of the Invention

[0005] The present application provides a single-stage bridgeless AC-DC conversion circuit, which realizes the regulation of input current through a single-stage circuit, and simultaneously realizes the adjustment of power factor correction and input and output isolation, and has a higher conversion efficiency than a two-stage circuit.

[0006] The present application provides a single-stage bridgeless AC-DC conversion circuit, which includes an input side circuit and an output side circuit. The input side circuit includes a three-phase circuit, each phase circuit in the three-phase circuit includes a first switching circuit, a filtering circuit, and a first single-stage energy transfer circuit. The first single-stage energy transfer circuit includes a second switching circuit and a transformer. The output side circuit includes a first output rectifier and filter circuit.

[0007] For each phase circuit, the first fixed terminal of the first switch circuit is connected to the second port of the input voltage source, and the second fixed terminal of the first switch circuit is connected to the first port of the input voltage source of another phase circuit other than the phase circuit, so that each phase circuit is input with a different line voltage. The movable terminal of the first switch circuit is connected to the second port of the filter circuit and the second input terminal of the second switch circuit, the first port of the input voltage source is connected to the first port of the filter circuit and the first input terminal of the second switch circuit, and the output terminal of the second switch circuit is connected to the first port of the primary winding of the transformer.

[0008] The second ports of the primary windings of the transformers in the three-phase circuit are connected to each other, the second ports of the first secondary windings of the transformers in the three-phase circuit are connected to each other, the first port of the first secondary winding of the transformers in the three-phase circuit is respectively connected to the three input terminals of the first output rectifier and filter circuit, and the output terminal of the first output rectifier and filter circuit serves as the output terminal of the single-stage bridgeless AC-DC conversion circuit;

[0009] The first switch circuit is configured to control conduction between the second fixed terminal and the moving terminal when the line voltage input to each phase circuit is not greater than a first preset voltage; and to control conduction between the first fixed terminal and the moving terminal when the line voltage input to each phase circuit is greater than the first preset voltage;

[0010] A filter circuit, configured to filter the input first AC signal;

[0011] A second switching circuit is used to convert the AC signal output by the filter circuit into a second AC signal, wherein the current of the second AC signal is controlled by a bidirectional switch in the second switching circuit;

[0012] a transformer, configured to adjust the voltage of the second AC signal;

[0013] The first output rectification and filtering circuit is used to rectify and filter the AC signal output by the transformer.

[0014] As can be seen, the present application proposes a single-stage bridgeless AC / DC conversion circuit. Since the present application is a single-stage circuit, it can achieve higher conversion efficiency compared to a two-stage circuit. In addition, the input side of the present circuit controls the input current through a bridgeless circuit, which can reduce the number of power devices and thus improve the corresponding conversion efficiency on the input side. At the same time, since the present circuit switches between the three-phase input line voltage and the phase voltage through the first switching circuit, it solves the problem of high voltage stress on semiconductor devices when the input line voltage is high, and also solves the problem of large conduction loss and reduced conversion efficiency of semiconductor devices when the input line voltage is low. In addition, by combining the intelligent input switching strategy of line voltage and phase voltage, the input voltage range can be increased, thereby increasing the output voltage range.

[0015] In a feasible example, the second switching circuit includes a filter inductor, a DC blocking capacitor and two switching tubes, and the two switching tubes constitute a bidirectional switching tube; the first port of the filter inductor serves as the first input end of the second switching circuit, the second port of the filter inductor is connected to the first port of the bidirectional switching tube and the first port of the DC blocking capacitor, and the second port of the bidirectional switching tube serves as the second input end of the second switching circuit.

[0016] In a feasible example, the single-stage bridgeless AC / DC conversion circuit also includes a second output rectifier and filter circuit, a switch Sw1, a switch Sw2, and a switch Sw3, and each phase circuit also includes a second single-stage energy transfer circuit; the first input end and the second input end of the second single-stage energy transfer circuit in each phase circuit are respectively connected to the first input end and the second input end of the first single-stage energy transfer circuit, the first output ends of the three second single-stage energy transfer circuits are respectively connected to the three input ends of the second output rectifier and filter circuit, the second output ends of the three second single-stage energy transfer circuits are connected to each other, and the second output end of the first output rectifier and filter circuit is connected to the first port of switch Sw1 and the switch The first output rectifier and filter circuit is connected to the first port of switch Sw2, the first output end of the first output rectifier and filter circuit is connected to the first port of switch Sw3, the first output end of the second output rectifier and filter circuit is connected to the second port of switch Sw1 and the second port of switch Sw3, and the second output end of the second output rectifier and filter circuit is connected to the second port of switch Sw2; when switch Sw1 is turned on and switch Sw3 and switch Sw2 are turned off, the first output rectifier and filter circuit are connected in series; when switch Sw3 and switch Sw2 are turned on and switch Sw1 is turned off, the first output rectifier and filter circuit are connected in parallel.

[0017] In the present application, a single-stage energy transfer circuit is added to each phase circuit so that the current ripple period of the sum of the output currents is twice the switching frequency period ripple, thereby reducing the total output current ripple.

[0018] In a feasible example, the single-stage bridgeless AC / DC conversion circuit also includes a third output rectifier filter circuit, a switch Sw4, a switch Sw5, and a switch Sw6, and the transformer in each phase circuit also includes a second secondary winding; the first ports of the second secondary windings of the three transformers in the three-phase circuit are respectively connected to the three input ends of the third output rectifier filter circuit, the second ports of the second secondary windings of the three transformers are connected to each other, the second output end of the first output rectifier filter circuit is connected to the first port of the switch Sw4 and the first port of the switch Sw5, and the first output rectifier filter circuit is connected to the first port of the switch Sw4 and the first port of the switch Sw5. The first output end of the circuit is connected to the first port of switch Sw6, the first output end of the third output rectifier and filter circuit is connected to the second port of switch Sw4 and the second port of switch Sw6, and the second output end of the third output rectifier and filter circuit is connected to the second port of switch Sw5; when switch Sw4 is turned on and switch Sw6 and switch Sw5 are turned off, the first output rectifier and filter circuit are connected in series with the third output rectifier and filter circuit; when switch Sw6 and switch Sw5 are turned on and switch Sw4 is turned off, the first output rectifier and filter circuit are connected in parallel with the third output rectifier and filter circuit.

[0019] In the present application, the output voltage range can be increased by using the above-mentioned single-stage bridgeless AC-DC conversion circuit.

[0020] In a feasible example, the single-stage bridgeless AC / DC conversion circuit also includes a fourth output rectifier and filter circuit, a switch Sw7, a switch Sw8, and a switch Sw9, and each phase circuit also includes a second DC blocking capacitor and a second transformer; the first port of the second DC blocking capacitor in each phase circuit is connected to the first port of the DC blocking capacitor, and the second port of the second DC blocking capacitor is connected to the first port of the primary winding of the second transformer, the second ports of the primary windings of the three second transformers in the three-phase circuit are connected to each other, the first ports of the secondary windings of the three second transformers are respectively connected to the three input ends of the fourth output rectifier and filter circuit, the second ports of the secondary windings of the three second transformers are connected to each other, and the first output rectifier and filter circuit are respectively connected to the three input ends of the fourth output rectifier and filter circuit, and the second ports of the secondary windings of the three second transformers are connected to each other. The second output end of the wave circuit is connected to the first port of switch Sw7 and the first port of switch Sw8, the first output end of the first output rectifier and filter circuit is connected to the first port of switch Sw9, the first output end of the fourth output rectifier and filter circuit is connected to the second port of switch Sw7 and the second port of switch Sw9, and the second output end of the fourth output rectifier and filter circuit is connected to the second port of switch Sw8; when switch Sw7 is turned on and switch Sw9 and switch Sw8 are turned off, the first output rectifier and filter circuit is connected in series with the fourth output rectifier and filter circuit; when switch Sw9 and switch Sw8 are turned on and switch Sw7 is turned off, the first output rectifier and filter circuit is connected in parallel with the fourth output rectifier and filter circuit.

[0021] In the present application, the above-mentioned single-stage bridgeless AC-DC conversion circuit can not only increase the output voltage range but also increase the output power.

[0022] In a feasible example, the bidirectional switch tube in the single-stage energy transfer circuit in each phase circuit is controlled according to a control signal, the control signal is determined according to a first control result, the first control result is determined after loop control based on the deviation between the input current of each phase circuit and the corresponding input current control amount, the input current control amount is determined based on the minimum value between the second control result and the third control result, and the absolute value of the voltage input to each phase circuit, the second control result is determined after loop control based on the current output by the single-stage bridgeless AC / DC conversion circuit and the external required current, and the third control result is determined after loop control based on the voltage output by the single-stage bridgeless AC / DC conversion circuit and the external required voltage.

[0023] In the present application, the control signal of the bidirectional switch tube in the three-phase circuit is determined, thereby controlling the conduction and disconnection of the bidirectional switch tube in the three-phase circuit, thereby realizing the input power factor correction of the circuit.

[0024] In a feasible example, the first output rectifier and filter circuit includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6 and a filter capacitor Co1; the first port of the diode D1 serves as the first input terminal of the first output rectifier and filter circuit and is connected to the second port of the diode D2; the second port of the diode D2 serves as the first output terminal of the first output rectifier and filter circuit and is connected to the second port of the diode D3, the second port of the diode D5 and the first port of the filter capacitor Co1; the first port of the diode D2 serves as the second output terminal of the first output rectifier and filter circuit and is connected to the first port of the diode D4, the first port of the diode D6 and the second port of the filter capacitor Co1; the first port of the diode D3 serves as the second input terminal of the first output rectifier and filter circuit and is connected to the second port of the diode D4; the first port of the diode D5 serves as the third input terminal of the first output rectifier and filter circuit and is connected to the second port of the diode D6.

[0025] In a feasible example, the driving times of the control signals corresponding to the switch tubes in the three first single-stage energy transfer circuits in the three-phase circuit are respectively spaced apart by one-third of the switching cycle.

[0026] In the present application, the output current ripple can be reduced by spacing the driving times of the control signals corresponding to the switch tubes in the three first single-stage energy transfer circuits by one-third of the switching cycle.

[0027] In a feasible example, the first single-stage energy transfer circuit in each phase circuit and the bidirectional switch tube in the second single-stage energy transfer circuit are controlled according to the control signal, and the driving time of the control signal corresponding to the bidirectional switch tube in the first single-stage energy transfer circuit in each phase circuit is separated from the driving time of the control signal corresponding to the bidirectional switch tube in the second single-stage energy transfer circuit by half a switching cycle.

[0028] In the present application, the driving time of the control signals corresponding to the two bidirectional switch tubes in each phase circuit is separated by half a switching cycle, which can reduce the output current ripple.

[0029] In a possible example, the filtering circuit includes a filtering capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] FIG1 is a schematic diagram of a single-stage bridgeless AC-DC conversion circuit structure provided in an embodiment of the present application;

[0032] FIG2 is a topological diagram of a single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application;

[0033] FIG3 is a schematic diagram of a positive half-axis current waveform provided in an embodiment of the present application;

[0034] FIG4 is a schematic diagram of a negative half-axis current waveform provided in an embodiment of the present application;

[0035] FIG5 is a topological diagram of another single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application;

[0036] FIG6 is a topological diagram of another single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application;

[0037] FIG7 is a topological diagram of another single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application;

[0038] FIG8 is a control block diagram of a single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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 this application.

[0040] The terms "first," "second," and the like in the specification, claims, and drawings of this application are used to distinguish between different objects rather than to describe a specific order. In addition, the terms "include," "include," and "have," and any variations thereof, are intended to cover non-exclusive inclusions.

[0041] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] Please refer to Figure 1, which is a schematic diagram of the structure of a single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application. As shown in Figure 1, the single-stage bridgeless AC-DC conversion circuit includes an input side circuit and an output side circuit. The input side circuit includes input voltage sources Va, Vb, and Vc corresponding to the three phases, a first switching circuit, a filter circuit 101, 102, and 103, and a single-stage energy transfer circuit 111, 112, and 113; the output side circuit includes a first output rectifier filter circuit 121. The single-stage energy transfer circuits 111, 112, and 113 each include a second switching circuit and a transformer. The first switching circuit is implemented by single-pole double-throw relay switches S1, S2, and S3. Switches S1, S2, and S3 include a moving end and a fixed end. The fixed ends include a first fixed end and a second fixed end, respectively corresponding to port 1 and port 2 in the figure.

[0043] The moving end of switch S1 is connected to the second input end of filter circuit 101. The first input end of filter circuit 101 is connected to the first port of input voltage source Va and the second fixed end of switch S3. The first fixed end of switch S1 is connected to the second port of input voltage source Va, the second port of input voltage source Vb, the first fixed end of switch S2, the second port of input voltage source Vc, and the first fixed end of switch S3. The first port of input voltage source Vb is connected to the second fixed end of switch S1 and the first input end of filter circuit 102. The moving end of switch S2 is connected to the second input end of filter circuit 102. The first port of input voltage source Vc is connected to the second fixed end of switch S2 and the first input end of filter circuit 103. The moving end of switch S3 is connected to the second input end of filter circuit 103. Point N is the center point of the three-phase AC input phase voltage.

[0044] The first output terminal and the second output terminal of the filter circuit 101 are respectively connected to the first input terminal and the second input terminal of the second switch circuit in the single-stage energy transfer circuit 111, and the output terminal of the second switch circuit in the single-stage energy transfer circuit 111 is connected to the first port of the primary winding of the transformer in the single-stage energy transfer circuit 111; the first output terminal and the second output terminal of the filter circuit 102 are respectively connected to the first input terminal and the second input terminal of the second switch circuit in the single-stage energy transfer circuit 112, and the output terminal of the second switch circuit in the single-stage energy transfer circuit 112 is connected to the first port of the primary winding of the transformer in the single-stage energy transfer circuit 112. The first port of the primary winding is connected; the first output terminal and the second output terminal of the filter circuit 103 are respectively connected to the first input terminal and the second input terminal of the second switching circuit in the single-stage energy transfer circuit 113, and the output terminal of the second switching circuit in the single-stage energy transfer circuit 113 is connected to the first port of the primary winding of the transformer in the single-stage energy transfer circuit 113; the second port of the primary winding of the transformer in the single-stage energy transfer circuit 111 is connected to the second port of the primary winding of the transformer in the single-stage energy transfer circuit 112 and the second port of the primary winding of the transformer in the single-stage energy transfer circuit 113.

[0045] The first port of the secondary winding of the transformer in the single-stage energy transfer circuit 111 is connected to the first input terminal of the first output rectifier and filter circuit 121. The first port of the secondary winding of the transformer in the single-stage energy transfer circuit 112 is connected to the second input terminal of the first output rectifier and filter circuit 121. The first port of the secondary winding of the transformer in the single-stage energy transfer circuit 113 is connected to the third input terminal of the first output rectifier and filter circuit 121. The second port of the secondary winding of the transformer in the single-stage energy transfer circuit 111 is connected to the second port of the secondary winding of the transformer in the single-stage energy transfer circuit 112 and the second port of the secondary winding of the transformer in the single-stage energy transfer circuit 113. The output terminal of the first output rectifier and filter circuit 121 serves as the output terminal of the single-stage bridgeless AC / DC converter circuit.

[0046] The filter circuits 101 , 102 and 103 are respectively used to filter the input first AC signal, where the first AC signal is determined according to the conduction states of the switches S1 , S2 and S3 .

[0047] Specifically, in the initial stage, the moving terminals of switches S1, S2, and S3 all contact the second fixed terminal, achieving conduction between the second fixed terminal and the moving terminal. At this time, the voltage signals corresponding to the first AC signal input to the three-phase circuit are the three-phase line voltages Vab, Vbc, and Vca. When the line voltage input to each phase circuit is greater than a first preset voltage, the moving terminals of switches S1, S2, and S3 all contact the first fixed terminal, achieving conduction between the first fixed terminal and the moving terminal. At this time, the voltage signals corresponding to the first AC signal input to the three-phase circuit are the three-phase voltages Van, Vbn, and Vcn. Similarly, when the line voltage input to each phase circuit is no greater than the first preset voltage, the moving terminals of switches S1, S2, and S3 all contact the second fixed terminal again, achieving conduction between the second fixed terminal and the moving terminal. At this time, the voltage signals corresponding to the first AC signal input to the circuit are the three-phase line voltages Vab, Vbc, and Vca. Wherein, the line voltage Vab = Van - Vbn, the line voltage Vbc = Vbn - Vcn, and the line voltage Vca = Vcn - Van.

[0048] The line voltage input to each phase circuit being greater than the first preset voltage may mean that the line voltage input to all phase circuits in the three-phase circuit is greater than the first preset voltage, and the corresponding line voltage input to each phase circuit is not greater than the first preset voltage, or that the line voltage input to one or more phase circuits in the three-phase circuit is not greater than the first preset voltage. Furthermore, the line voltage input to each phase circuit being greater than the first preset voltage may mean that the line voltage input to one or more phase circuits in the three-phase circuit is greater than the first preset voltage, and the corresponding line voltage input to each phase circuit is not greater than the first preset voltage, or that the line voltage input to all phase circuits in the three-phase circuit is not greater than the first preset voltage.

[0049] The second switch circuit in the single-stage energy transfer circuits 111, 112, and 113 is used to convert the AC signal output by the filter circuit into a second AC signal, wherein the current of the second AC signal is controlled by the bidirectional switch in the second switch circuit;

[0050] The transformers in the single-stage energy transfer circuits 111, 112, and 113 are used to adjust the voltage of the second AC signal;

[0051] The first output rectification and filtering circuit 121 is used to rectify and filter the AC signal output by the transformer.

[0052] Since this circuit is a single-stage circuit, it can achieve higher conversion efficiency compared to a two-stage circuit. In addition, the input side of this circuit controls the input current through a bridgeless circuit, which can reduce the number of power devices and also improve conversion efficiency. At the same time, this circuit can also achieve a wider input voltage range by switching between phase voltage input and line voltage input.

[0053] The single-stage bridgeless AC-DC conversion circuit is described in detail below using FIG2 :

[0054] Specifically, please refer to FIG2 , which is a topological diagram of a single-stage bridgeless AC / DC converter circuit provided in an embodiment of the present application. As shown in FIG2 , the circuit includes input voltage sources Va, Vb, and Vc corresponding to the three phases, and single-pole double-throw relay switches S1, S2, and S3. Filter circuit 101 includes filter capacitor Ci1; filter circuit 102 includes filter capacitor Ci2; and filter circuit 103 includes filter capacitor Ci3. Single-stage energy transfer circuit 111 includes filter inductor Lf1, blocking capacitor C1, switch tubes Q1 and Q2, and transformer T1; single-stage energy transfer circuit 112 includes filter inductor Lf3, blocking capacitor C3, switch tubes Q3 and Q4, and transformer T3; and single-stage energy transfer circuit 113 includes filter inductor Lf5, blocking capacitor C5, switch tubes Q5 and Q6, and transformer T5. The first output rectifier and filter circuit 121 includes diodes D1, D2, D3, D4, D5, D6, and filter capacitor Co1. Switches Q1 and Q2 form a bidirectional switch, while switches Q3 and Q4 form a bidirectional switch. Switches Q5 and Q6 form a bidirectional switch. These diodes are rectifier diodes.

[0055] The moving end of switch S1 is provided with an input current terminal ia, and is connected to the second port of filter capacitor Ci1 and the second port of switch Q2. The first port of filter capacitor Ci1 is connected to the first port of input voltage source Va, the second fixed terminal of switch S3, and the first port of filter inductor Lf1. The first fixed terminal of switch S1 is connected to the second port of input voltage source Va, the second port of input voltage source Vb, the first fixed terminal of switch S2, the second port of input voltage source Vc, and the first fixed terminal of switch S3. The first port of input voltage source Vb is connected to the second fixed terminal of switch S1, the first port of filter capacitor Ci2, and the first port of filter inductor Lf3. The moving end of switch S2 is provided with an input current terminal ib, and is connected to the second port of filter capacitor Ci2 and the second port of switch Q4. The first port of input voltage source Vc is connected to the second fixed terminal of switch S2, the first port of filter capacitor Ci3, and the first port of filter inductor Lf5. The moving end of switch S3 is provided with an input current terminal ic, and is connected to the second port of filter capacitor Ci3 and the second port of switch Q6.

[0056] The second port of filter inductor Lf1 is connected to the second port of switch Q1 and the first port of DC blocking capacitor C1. The first port of switch Q1 is connected to the first port of switch Q2. The second port of DC blocking capacitor C1 is connected to the first port of the primary winding of transformer T1. The second port of filter inductor Lf3 is connected to the second port of switch Q3 and the first port of DC blocking capacitor C3. The first port of switch Q3 is connected to the first port of switch Q4. The second port of DC blocking capacitor C3 is connected to the first port of the primary winding of transformer T3. The second port of filter inductor Lf5 is connected to the second port of switch Q5 and the first port of DC blocking capacitor C5. The first port of switch Q5 is connected to the first port of switch Q6. The second port of DC blocking capacitor C5 is connected to the first port of the primary winding of transformer T5. The second port of the primary winding of transformer T1 is connected to the second port of the primary winding of transformer T3 and the second port of the primary winding of transformer T5.

[0057] The second port of the secondary winding of transformer T1 is connected to the second port of the secondary winding of transformer T3 and the second port of the secondary winding of transformer T5. The first port of the secondary winding of transformer T1 is connected to the first port of diode D1 and the second port of diode D2; the first port of the secondary winding of transformer T3 is connected to the first port of diode D3 and the second port of diode D4; the first port of the secondary winding of transformer T5 is connected to the first port of diode D5 and the second port of diode D6. The second port of diode D1 is connected to the second port of diode D3, the second port of diode D5, and the first port of filter capacitor Co1, and the first port of diode D2 is connected to the first port of diode D4, the first port of diode D6, and the second port of filter capacitor Co1. The second port of filter capacitor Co1 is provided with output current terminal io1, and the first and second ports of filter capacitor Co1 serve as the first and second output terminals, respectively, of the single-stage bridgeless AC / DC converter circuit.

[0058] The switching tube may be a triode or a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0059] Among them, when the line voltage input to each phase circuit is not greater than the first preset voltage, the moving ends of the three switches S1, S2 and S3 contact the second fixed end, achieving conduction between the second fixed end and the moving end. At this time, the voltage input to the circuit corresponds to the three-phase line voltages Vab, Vbc, and Vca. At this time, the current transmitting energy in the circuit is the line current. The voltage stress of the switch tubes Q1, Q2, Q3, Q4, Q5, Q6 and the diodes D1, D2, D3, D4, D5, and D6 depends on the peak voltage of the input line voltage and the output power. The greater the peak voltage of the input line voltage, the higher the stress of the semiconductor device; under the same input line voltage, the greater the output power, the greater the duty cycle of the above-mentioned switch tubes. At this time, after the above-mentioned switch tubes are turned off, the voltage stress superimposed on the two ends will also be higher.

[0060] When the input line voltage is at a high value, the system intelligently switches to phase voltage energy extraction mode, bringing the active terminals of the three switches S1, S2, and S3 into contact with the first fixed terminal, achieving conduction between the first fixed terminal and the active terminal. At this point, the circuit input voltage corresponds to the three-phase voltages Van, Vbn, and Vcn. The voltage stress on the switches and diodes depends on the peak input phase voltage and the output power. Because the peak input phase voltage is much lower than the peak input line voltage, the voltage stress on the semiconductor devices is reduced, and the switching losses of the power module are reduced. Even if the output power increases, the voltage stress on the switches and diodes remains within a safe range.

[0061] When the circuit input voltage corresponds to the phase voltage, the input current for transmitting electrical energy corresponds to the phase current. The current flowing through the main power components (such as the aforementioned switches) increases accordingly, leading to increased conduction losses in the components. Therefore, when the corresponding line voltage is low, the circuit's conversion efficiency is low when the input voltage is the phase voltage. Therefore, when the line voltage is low, the active terminals of the three single-pole double-throw switches S1, S2, and S3 are intelligently connected to the second fixed terminal. The first preset voltage can be determined based on the voltage stress of the main power components (such as the aforementioned switches).

[0062] The above circuit adjusts the input current of each phase circuit by controlling the on and off of the switch tube in the single-stage energy transfer circuit, thereby achieving power factor correction of the above circuit.

[0063] This circuit achieves power factor correction by controlling the on / off switching of the bidirectional switching transistor in the second switching circuit of each phase circuit to adjust the input current of each phase circuit. Bidirectional switching transistors are used because the AC power input includes positive and negative half-axis currents, and both positive and negative half-axis currents must flow through the circuit.

[0064] The bidirectional switch tube is driven and controlled according to a control signal. For example, the switch tube Q1 and the switch tube Q2 are driven and controlled according to the same control signal, which can be a pulse width modulation (PWM) signal. The duty cycle corresponding to the control signal is determined according to a first control result. The first control result is determined by loop control (current loop) based on the deviation between the input current of each phase circuit and the corresponding input current control amount. The input current control amount is determined according to the minimum value between the second control result and the third control result, and the absolute value of the voltage input to each phase circuit. The second control result is determined by loop control (current loop) based on the current output by the single-stage bridgeless AC / DC converter circuit and the external required current. The third control result is determined by loop control (voltage loop) based on the voltage output by the single-stage bridgeless AC / DC converter circuit and the external required voltage. The loop control includes proportional integral controller (PI) control or proportional integral differential (PID) control.

[0065] It can be seen that the transformers in the three-phase circuit shown in the present application are connected in a star shape, so that the rectification and filtering of the output of the three-phase circuit can be achieved through an output rectification and filtering circuit, thereby reducing the number of components and improving the conversion efficiency.

[0066] The current waveform of the circuit is explained below through Figures 3 and 4:

[0067] For example, please refer to Figure 3, which is a schematic diagram of a positive half-axis current waveform provided in an embodiment of the present application. As shown in Figure 3, it includes a drive waveform diagram of the control signal (Vgs) of the switches Q1 and Q2, a waveform diagram of the current (iLf1) of the filter inductor Lf1, a waveform diagram of the current (iD1) of the diode D1, and a waveform diagram of the current (iD2) of the diode D2.

[0068] When the input line voltage is in the positive half-axis voltage wave sequence, when switches Q1 and Q2 are turned on, the AC input voltage is superimposed on the two ends of filter inductor Lf1, and the current in filter inductor Lf1 increases. At this time, DC blocking capacitor C1 discharges through the star-connected circuit of transformer T1. At this time, diode D1 is in the reverse blocking state, and diode D2 is in the conducting freewheeling state. When switches Q1 and Q2 are turned off, the current in filter inductor Lf1 decreases, and the inductor current transfers energy to the secondary winding of transformer T1 through DC blocking capacitor C1 and the primary winding of transformer T1, while also charging DC blocking capacitor C1. At this time, diode D1 is in the forward conducting state, and diode D2 is in the reverse blocking state.

[0069] For example, please refer to Figure 4, which is a schematic diagram of a negative half-axis current waveform provided in an embodiment of the present application. As shown in Figure 4, it includes a drive waveform diagram of the control signal (Vgs) of the switches Q1 and Q2, a waveform diagram of the current (iLf1) of the filter inductor Lf1, a waveform diagram of the current (iD1) of the diode D1, and a waveform diagram of the current (iD2) of the diode D2.

[0070] When the input line voltage is in the negative half-axis voltage wave sequence, when switches Q1 and Q2 are turned on, the negative AC input voltage is superimposed on the two ends of filter inductor Lf1, causing the current in filter inductor Lf1 to increase in a negative direction. At this time, DC blocking capacitor C1 is reversely discharged through the star-connected circuit of transformer T1. At this time, diode D2 is in the reverse blocking state, and diode D1 is in the conducting freewheeling state. When switches Q1 and Q2 are turned off, the current in filter inductor Lf1 decreases in a negative direction. The inductor current transfers energy to the secondary winding of transformer T1 through DC blocking capacitor C1 and the primary winding of transformer T1, and also reversely charges DC blocking capacitor C1. At this time, diode D2 is in the forward conducting state, and diode D1 is in the reverse blocking state.

[0071] In addition, the single-stage bridgeless AC-DC conversion circuit may also include other circuits, which are described in detail below with reference to FIG5 :

[0072] For example, please refer to Figure 5, which is a topological diagram of another single-stage bridgeless AC-DC conversion circuit provided in an embodiment of the present application. As shown in Figure 5, compared with the single-stage bridgeless AC-DC conversion circuit shown in Figure 2, the single-stage bridgeless AC-DC conversion circuit further includes a second output rectifier and filter circuit, a switch Sw1, a switch Sw2, and a switch Sw3, and each phase circuit further includes a second single-stage energy transfer circuit, wherein the second output rectifier and filter circuit includes a diode D11, a diode D12, a diode D13, a diode D14, a diode D15, a diode D16, and a filter capacitor Co2; the second single-stage energy transfer circuit of the first phase includes a filter inductor Lf2, a DC blocking capacitor C2, a switch tube Q11, a switch tube Q12, and a transformer T2; the second single-stage energy transfer circuit of the second phase includes a filter inductor Lf4, a DC blocking capacitor C4, a switch tube Q13, a switch tube Q14, and a transformer T4; the second single-stage energy transfer circuit of the third phase includes a filter inductor Lf6, a DC blocking capacitor C6, a switch tube Q15, a switch tube Q16, and a transformer T6. The remaining components are identical to the single-stage bridgeless AC / DC converter circuit shown in FIG2 and are not further described here. Similarly, switches Q11 and Q12 form a bidirectional switch, switches Q13 and Q14 form a bidirectional switch, and switches Q15 and Q16 form a bidirectional switch.

[0073] The first port of the filter inductor Lf2 is connected to the first port of the filter inductor Lf1, the second port of the filter inductor Lf2 is connected to the first port of the DC blocking capacitor C2 and the second port of the switch tube Q11, the first port of the switch tube Q11 is connected to the first port of the switch tube Q12, the second port of the switch tube Q12 is connected to the second port of the switch tube Q2, and the second port of the DC blocking capacitor C2 is connected to the first port of the primary winding of the transformer T2; the first port of the filter inductor Lf4 is connected to the first port of the filter inductor Lf3, the second port of the filter inductor Lf4 is connected to the first port of the DC blocking capacitor C4 and the second port of the switch tube Q13, the first port of the switch tube Q13 is connected to the first port of the switch tube Q14, and the switch tube Q14 The second port of is connected to the second port of the switch tube Q4, the second port of the DC blocking capacitor C4 is connected to the first port of the primary winding of the transformer T4; the first port of the filter inductor Lf6 is connected to the first port of the filter inductor Lf5, the second port of the filter inductor Lf6 is connected to the first port of the DC blocking capacitor C6 and the second port of the switch tube Q15, the first port of the switch tube Q15 is connected to the first port of the switch tube Q16, the second port of the switch tube Q16 is connected to the second port of the switch tube Q6, and the second port of the DC blocking capacitor C6 is connected to the first port of the primary winding of the transformer T6; the second port of the primary winding of the transformer T2 is connected to the second port of the primary winding of the transformer T4 and the second port of the primary winding of the transformer T6.

[0074] The second port of the secondary winding of transformer T2 is connected to the second port of the secondary winding of transformer T4 and the second port of the secondary winding of transformer T6. The first port of the secondary winding of transformer T2 is connected to the first port of diode D11 and the second port of diode D12; the first port of the secondary winding of transformer T4 is connected to the first port of diode D13 and the second port of diode D14; and the first port of the secondary winding of transformer T6 is connected to the first port of diode D15 and the second port of diode D16. The second port of diode D11 is connected to the second port of diode D13, the second port of diode D15, and the first port of filter capacitor Co2. The first port of diode D12 is connected to the first port of diode D14, the first port of diode D16, and the second port of filter capacitor Co2. The second port of filter capacitor Co2 is provided as output current terminal io2. The output terminals of the first and second output rectifier filter circuits serve as the output terminals of the single-stage bridgeless AC / DC converter circuit.

[0075] Among them, when switch Sw1 is turned on and switch Sw3 and switch Sw2 are turned off, the first output rectifier and filter circuit are connected in series with the second output rectifier and filter circuit; when switch Sw3 and switch Sw2 are turned on and switch Sw1 is turned off, the first output rectifier and filter circuit are connected in parallel with the second output rectifier and filter circuit.

[0076] It can be seen that since the present application adopts a single-stage circuit, the output current of the circuit is a discontinuous current, that is, when the bidirectional switch tube in the three-phase circuit is disconnected, energy is transmitted to the output side through the transformer in the three-phase circuit; when the bidirectional switch tube in the three-phase circuit is turned on, the primary winding of the transformer is magnetically reset, and the primary winding stops transmitting energy to the secondary winding. Intermittent energy transmission will cause the output current ripple to be large. Therefore, the present application adds a single-stage energy transmission circuit to each phase circuit, so that the current ripple period of the sum of the output currents is twice the switching frequency period ripple, thereby reducing the total output current ripple.

[0077] In addition, for example, please refer to Figure 6, which is another single-stage bridgeless AC-DC conversion circuit topology diagram provided in an embodiment of the present application. As shown in Figure 6, compared with the single-stage bridgeless AC-DC conversion circuit shown in Figure 2, the single-stage bridgeless AC-DC conversion circuit also includes a third output rectifier filter circuit, switch Sw4, switch Sw5 and switch Sw6, and the transformer in each phase circuit also includes a second secondary winding. The third output rectifier filter circuit includes a diode D21, a diode D22, a diode D23, a diode D24, a diode D25, a diode D26 and a filter capacitor Co3.

[0078] The second port of the second secondary winding of transformer T1 is connected to the second port of the second secondary winding of transformer T3 and the second port of the second secondary winding of transformer T5. The first port of the second secondary winding of transformer T1 is connected to the first port of diode D21 and the second port of diode D22; the first port of the second secondary winding of transformer T3 is connected to the first port of diode D23 and the second port of diode D24; and the first port of the second secondary winding of transformer T5 is connected to the first port of diode D25 and the second port of diode D26. The second port of diode D21 is connected to the second port of diode D23, the second port of diode D25, and the first port of filter capacitor Co3. The first port of diode D22 is connected to the first port of diode D24, the first port of diode D26, and the second port of filter capacitor Co3. The second port of filter capacitor Co3 is provided as output current terminal io3. The output terminals of the first and third output rectifier and filter circuits serve as the output terminals of the single-stage bridgeless AC / DC converter circuit.

[0079] Similarly, when switch Sw4 is turned on and switch Sw6 and switch Sw5 are turned off, the first output rectifier and filter circuit are connected in series with the third output rectifier and filter circuit; when switch Sw6 and switch Sw5 are turned on and switch Sw4 is turned off, the first output rectifier and filter circuit are connected in parallel with the third output rectifier and filter circuit.

[0080] It can be seen that the output voltage range can be increased through the above-mentioned single-stage bridgeless AC-DC conversion circuit.

[0081] In addition, for example, please refer to Figure 7, which is another single-stage bridgeless AC-DC conversion circuit topology diagram provided in an embodiment of the present application. As shown in Figure 7, compared with the single-stage bridgeless AC-DC conversion circuit shown in Figure 2, the single-stage bridgeless AC-DC conversion circuit also includes a fourth output rectifier filter circuit, switch Sw7, switch Sw8, and switch Sw9. The three-phase circuit also includes a DC blocking capacitor C7, a DC blocking capacitor C8, a DC blocking capacitor C9, a transformer T7, a transformer T8, and a transformer T9. The fourth output rectifier filter circuit includes a diode D31, a diode D32, a diode D33, a diode D34, a diode D35, a diode D36, and a filter capacitor Co4.

[0082] A first port of the DC blocking capacitor C7 is connected to the first port of the DC blocking capacitor C1, and a second port of the DC blocking capacitor C7 is connected to the first port of the primary winding of the transformer T7; a first port of the DC blocking capacitor C8 is connected to the first port of the DC blocking capacitor C3, and a second port of the DC blocking capacitor C8 is connected to the first port of the primary winding of the transformer T8; a first port of the DC blocking capacitor C9 is connected to the first port of the DC blocking capacitor C5, and a second port of the DC blocking capacitor C9 is connected to the first port of the primary winding of the transformer T9; and a first port of the primary winding of the transformer T7 is connected to the first port of the primary winding of the transformer T8 and the first port of the primary winding of the transformer T9.

[0083] The second port of the secondary winding of transformer T7 is connected to the second port of the secondary winding of transformer T8 and the second port of the secondary winding of transformer T9. The first port of the secondary winding of transformer T7 is connected to the first port of diode D31 and the second port of diode D32; the first port of the secondary winding of transformer T8 is connected to the first port of diode D33 and the second port of diode D34; and the first port of the secondary winding of transformer T9 is connected to the first port of diode D35 and the second port of diode D36. The second port of diode D31 is connected to the second port of diode D33, the second port of diode D35, and the first port of filter capacitor Co4. The first port of diode D32 is connected to the first port of diode D34, the first port of diode D36, and the second port of filter capacitor Co4. The second port of filter capacitor Co4 is provided as output current terminal io4. The output terminals of the first and fourth output rectifier and filter circuits serve as the output terminals of the single-stage bridgeless AC / DC converter circuit.

[0084] It can be seen that the above-mentioned single-stage bridgeless AC-DC conversion circuit can not only improve the output voltage range but also improve the output power.

[0085] The determination of the control signal of the bidirectional switch in the above three-phase circuit is specifically described below with reference to FIG8 :

[0086] Please refer to Figure 8, which is a control block diagram of a single-stage bridgeless AC-DC converter circuit provided in an embodiment of the present application. As shown in Figure 8, the output voltage Vo and output current io of the single-stage bridgeless AC-DC converter circuit are sampled, and the set value of the output voltage (demand voltage) Voref and the set value of the output current (demand current) Ioref are determined according to the external load demand. The output voltage Vo and the set value of the output voltage Voref are input into the output voltage loop for calculation to obtain the output result Vpi of the output voltage loop; the output current io and the set value of the output current Ioref are input into the output current loop for calculation to obtain the output current loop result Ipi; the output voltage loop result and the output current loop result are taken as the smaller to obtain the final output loop control result Minpi. In this way, the voltage control and current control of the above circuit can be realized respectively.

[0087] The conduction state of switches S1, S2, and S3 is switched by the size of the three-phase input line voltage. When the line voltage is greater than a first preset voltage, switches S1, S2, and S3 are switched to conduction between the moving end and the first fixed end. At this time, the three-phase phase voltages Van, Vbn, and Vcn are taken to obtain the absolute values ​​of the voltage samples of the three-phase input phase voltages |Vac1|, |Vac2|, and |Vac3|; when the line voltage is not greater than the first preset voltage, switches S1, S2, and S3 are switched to conduction between the moving end and the second fixed end. At this time, the three-phase line voltages Vab, Vbc, and Vca are taken to obtain the absolute values ​​of the voltage samples of the three-phase input line voltages |Vac1|, |Vac2|, and |Vac3|.

[0088] The absolute values ​​of the sampled three-phase input AC voltage signals, |Vac1|, |Vac2|, and |Vac3|, are multiplied by the loop output Minpi to obtain the current reference values ​​Iac1ref, Iac2ref, and Iac3ref, respectively. At this point, the first-phase input current is sampled to obtain the first-phase input current Iac1. The first-phase input current Iac1 and the corresponding first-phase current reference value Iac1ref are input into the first input current loop for calculation, resulting in the duty cycle DR1 of the control signal for the switch in the single-stage energy transfer circuit in that phase circuit.

[0089] The second-phase input current Iac2 is obtained by sampling the second-phase input current. This second-phase input current Iac2 and the corresponding second-phase current reference value Iac2ref are input into the second input current loop for calculation to obtain the duty cycle DR2 of the control signal for the switch in the single-stage energy transfer circuit in the phase circuit. The third-phase input current Iac3 is obtained by sampling the third-phase input current. This third-phase input current Iac3 and the corresponding third-phase current reference value Iac3ref are input into the third input current loop for calculation to obtain the duty cycle DR3 of the control signal for the switch in the single-stage energy transfer circuit in the phase circuit.

[0090] The duty cycles DR1, DR2, and DR3 are input into the PWM wave generation calculation unit to obtain pulse width modulation signals PWM1, PWM2, and PWM3 corresponding to the first bidirectional switch tube (switch tube Q1 and switch tube Q2), the second bidirectional switch tube (switch tube Q3 and switch tube Q4), and the third bidirectional switch tube (switch tube Q5 and switch tube Q6), respectively. The driving time corresponding to PWM1, PWM2, and PWM3 is separated by one-third of the switching cycle.

[0091] When two single-stage energy transfer circuits are present in each phase as shown in FIG5 , a six-way interleaved design is implemented for the pulse width modulation signals PWM1, PWM2, and PWM3 to generate control signals SQ1, SQ2, SQ3, SQ4, SQ5, and SQ6 corresponding to the first bidirectional switch (switches Q1 and Q2), the second bidirectional switch (switches Q3 and Q4), the third bidirectional switch (switches Q5 and Q6), the fourth bidirectional switch (switches Q11 and Q12), the fifth bidirectional switch (switches Q13 and Q14), and the sixth bidirectional switch (switches Q15 and Q16), respectively. The control signals SQ1 and SQ4 are phase-staggered by 180°, the control signals SQ2 and SQ5 are phase-staggered by 180°, and the control signals SQ3 and SQ6 are phase-staggered by 180°. Furthermore, the control signals SQ1, SQ2, and SQ3 are phase-staggered by 120° to reduce output current ripple.

[0092] The control signal of the bidirectional switch tube in the three-phase circuit is determined by the above scheme, thereby controlling the conduction and disconnection of the bidirectional switch tube in the three-phase circuit, thereby realizing input power factor correction of the circuit.

[0093] As can be seen, the present application proposes a single-stage bridgeless AC / DC conversion circuit. Since the present application is a single-stage circuit, it can achieve higher conversion efficiency than a two-stage circuit. In addition, the input side of the present circuit controls the input current through a bridgeless circuit, which can reduce the number of power devices and thus improve the corresponding conversion efficiency on the input side. At the same time, since the present circuit switches between the three-phase input line voltage and the phase voltage through the first switching circuit, it solves the problem of high voltage stress on semiconductor devices when the input line voltage is high. It also solves the problem of large conduction losses in semiconductor devices and reduced conversion efficiency when the input line voltage is low. In addition, by combining the intelligent input switching strategy of line voltage and phase voltage, the input voltage range can be increased, thereby increasing the output voltage range.

[0094] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0095] The above is a detailed introduction to the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A single-stage bridgeless AC-DC conversion circuit, characterized in that: The single-stage bridgeless AC / DC conversion circuit comprises an input side circuit and an output side circuit, wherein the input side circuit comprises a three-phase circuit, each phase circuit of the three-phase circuit comprises a first switch circuit, a filter circuit and a first single-stage energy transfer circuit, wherein the first single-stage energy transfer circuit comprises a second switch circuit and a transformer, and the output side circuit comprises a first output rectifier filter circuit; For each phase circuit, the first fixed end of the first switch circuit is connected to the second port of the input voltage source, and the second fixed end of the first switch circuit is connected to the first port of the input voltage source in another phase circuit other than the phase circuit, so that different line voltages are input to each phase circuit respectively, the moving end of the first switch circuit is connected to the second port of the filter circuit and the second input end of the second switch circuit, the first port of the input voltage source is connected to the first port of the filter circuit and the first input end of the second switch circuit, and the output end of the second switch circuit is connected to the first port of the primary winding of the transformer; The second ports of the primary windings of the transformers in the three-phase circuit are connected to each other, the second ports of the first secondary windings of the transformers in the three-phase circuit are connected to each other, the first port of the first secondary winding of the transformers in the three-phase circuit is respectively connected to the three input ends of the first output rectifier and filter circuit, and the output end of the first output rectifier and filter circuit serves as the output end of the single-stage bridgeless AC / DC conversion circuit; The first switch circuit is used to control the conduction between the second fixed end and the moving end when the line voltage input to the each-phase circuit is not greater than the first preset voltage; and to control the conduction between the first fixed end and the moving end when the line voltage input to the each-phase circuit is greater than the first preset voltage; The filtering circuit is used to filter the input first AC signal; The second switch circuit is used to convert the AC signal output by the filter circuit into a second AC signal, wherein the current of the second AC signal is controlled by a bidirectional switch in the second switch circuit; The transformer is used to adjust the voltage of the second AC signal; The first output rectifying and filtering circuit is used to rectify and filter the AC signal output by the transformer.

2. The circuit according to claim 1, characterized in that The second switch circuit includes a filter inductor, a DC blocking capacitor and two switch tubes, and the two switch tubes constitute the bidirectional switch tube; The first port of the filter inductor serves as the first input end of the second switch circuit, the second port of the filter inductor is connected to the first port of the bidirectional switch tube and the first port of the DC blocking capacitor, and the second port of the bidirectional switch tube serves as the second input end of the second switch circuit.

3. The circuit according to claim 1 or 2, characterized in that: The single-stage bridgeless AC / DC conversion circuit further includes a second output rectification and filtering circuit, a switch Sw1, a switch Sw2, and a switch Sw3, and each phase circuit further includes a second single-stage energy transfer circuit; The first input end and the second input end of the second single-stage energy transfer circuit in each phase circuit are respectively connected to the first input end and the second input end of the first single-stage energy transfer circuit, the first output ends of the three second single-stage energy transfer circuits are respectively connected to the three input ends of the second output rectification and filtering circuit, the second output ends of the three second single-stage energy transfer circuits are connected to each other, the second output end of the first output rectification and filtering circuit is connected to the first port of the switch Sw1 and the first port of the switch Sw2, the first output end of the first output rectification and filtering circuit is connected to the first port of the switch Sw3, the first output end of the second output rectification and filtering circuit is connected to the second port of the switch Sw1 and the second port of the switch Sw3, and the second output end of the second output rectification and filtering circuit is connected to the second port of the switch Sw2; When the switch Sw1 is turned on, and the switch Sw3 and the switch Sw2 are turned off, the first output rectifying and filtering circuit is connected in series with the second output rectifying and filtering circuit; When the switch Sw3 and the switch Sw2 are turned on and the switch Sw1 is turned off, the first output rectifying and filtering circuit is connected in parallel with the second output rectifying and filtering circuit.

4. The circuit according to claim 1 or 2, characterized in that: The single-stage bridgeless AC / DC conversion circuit further includes a third output rectifier filter circuit, a switch Sw4, a switch Sw5, and a switch Sw6, and the transformer in each phase circuit further includes a second secondary winding; The first ports of the second secondary windings of the three transformers in the three-phase circuit are respectively connected to the three input ends of the third output rectifying and filtering circuit, the second ports of the second secondary windings of the three transformers are connected to each other, the second output end of the first output rectifying and filtering circuit is connected to the first port of the switch Sw4 and the first port of the switch Sw5, the first output end of the first output rectifying and filtering circuit is connected to the first port of the switch Sw6, the first output end of the third output rectifying and filtering circuit is connected to the second port of the switch Sw4 and the second port of the switch Sw6, and the second output end of the third output rectifying and filtering circuit is connected to the second port of the switch Sw5; When the switch Sw4 is turned on, and the switch Sw6 and the switch Sw5 are turned off, the first output rectifying and filtering circuit is connected in series with the third output rectifying and filtering circuit; When the switch Sw6 and the switch Sw5 are turned on and the switch Sw4 is turned off, the first output rectifying and filtering circuit is connected in parallel with the third output rectifying and filtering circuit.

5. The circuit according to claim 2, characterized in that The single-stage bridgeless AC-DC conversion circuit further includes a fourth output rectifier filter circuit, a switch Sw7, a switch Sw8, and a switch Sw9, and each phase circuit further includes a second DC blocking capacitor and a second transformer; The first port of the second DC blocking capacitor in each phase circuit is connected to the first port of the DC blocking capacitor, and the second port of the second DC blocking capacitor is connected to the first port of the primary winding of the second transformer, the second ports of the primary windings of the three second transformers in the three-phase circuit are connected to each other, the first ports of the secondary windings of the three second transformers are respectively connected to the three input ends of the fourth output rectifier and filter circuit, the second ports of the secondary windings of the three second transformers are connected to each other, the second output end of the first output rectifier and filter circuit is connected to the first port of the switch Sw7 and the first port of the switch Sw8, the first output end of the first output rectifier and filter circuit is connected to the first port of the switch Sw9, the first output end of the fourth output rectifier and filter circuit is connected to the second port of the switch Sw7 and the second port of the switch Sw9, and the second output end of the fourth output rectifier and filter circuit is connected to the second port of the switch Sw8; When the switch Sw7 is turned on, and the switch Sw9 and the switch Sw8 are turned off, the first output rectifying and filtering circuit is connected in series with the fourth output rectifying and filtering circuit; When the switch Sw9 and the switch Sw8 are turned on and the switch Sw7 is turned off, the first output rectifying and filtering circuit is connected in parallel with the fourth output rectifying and filtering circuit.

6. The circuit according to claim 1 or 2, characterized in that: The bidirectional switch tube in the single-stage energy transfer circuit in each phase circuit is controlled according to a control signal, and the control signal is determined according to a first control result, and the first control result is determined after loop control based on a deviation between an input current of each phase circuit and a corresponding input current control amount, and the input current control amount is determined according to a minimum value between a second control result and a third control result, and an absolute value of a voltage input to each phase circuit, and the second control result is determined after loop control based on a current output by the single-stage bridgeless AC / DC conversion circuit and an external required current, and the third control result is determined after loop control based on a voltage output by the single-stage bridgeless AC / DC conversion circuit and an external required voltage.

7. The circuit according to claim 1 or 2, characterized in that: The first output rectification and filtering circuit includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6 and a filtering capacitor Co1; The first port of the diode D1 serves as the first input end of the first output rectification and filtering circuit and is connected to the second port of the diode D2. The second port of the diode D2 serves as the first output end of the first output rectification and filtering circuit and is connected to the second port of the diode D3, the second port of the diode D5 and the first port of the filter capacitor Co1. The first port of the diode D2 serves as the second output end of the first output rectification and filtering circuit and is connected to the first port of the diode D4, the first port of the diode D6 and the second port of the filter capacitor Co1. The first port of the diode D3 serves as the second input end of the first output rectification and filtering circuit and is connected to the second port of the diode D4. The first port of the diode D5 serves as the third input end of the first output rectification and filtering circuit and is connected to the second port of the diode D6.

8. The circuit according to claim 1 or 2, characterized in that: The driving times of the control signals corresponding to the bidirectional switch tubes in the three first single-stage energy transfer circuits in the three-phase circuit are respectively spaced apart by one third of the switching cycle.

9. The circuit according to claim 3, characterized in that The first single-stage energy transfer circuit in each phase circuit and the bidirectional switch tube in the second single-stage energy transfer circuit are controlled according to the control signal, and the driving time of the control signal corresponding to the bidirectional switch tube in the first single-stage energy transfer circuit in each phase circuit is separated from the driving time of the control signal corresponding to the bidirectional switch tube in the second single-stage energy transfer circuit by half a switching cycle.

10. The circuit according to claim 1 or 2, characterized in that: The filter circuit includes a filter capacitor.

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