Single-stage alternating current to direct current resonant converter

Abstract

A single-stage alternating current to direct current resonant converter, which is used for converting a three-phase alternating-current power supply into a direct-current power supply. The single-stage alternating current to direct current resonant converter comprises a primary-side circuit, a resonant circuit and a secondary-side circuit, wherein the primary-side circuit comprises three sets of primary-side switching circuits, each primary-side switching circuit being coupled to one phase of the three-phase alternating-current power supply; and the resonant circuit comprises three sets of transformers, primary-side windings of the transformers being respectively coupled to the primary-side switching circuits, and secondary-side windings of the transformers being coupled to the secondary-side circuit.

Description

Single-stage AC / DC resonant converter Technical Field

[0001] This invention relates to an AC / DC resonant converter, and more particularly to a single-stage AC / DC resonant converter. Background Technology

[0002] Due to the power supply or battery charging needs of various electronic devices, AC / DC converters have always been indispensable power conversion devices. Traditional AC / DC converters, as shown in Figure 1, typically have a two-stage circuit structure. Specifically, a traditional AC / DC converter 100A includes an AC / DC conversion circuit 100B, an intermediate capacitor CI, and a DC / DC conversion circuit 100C. The AC / DC conversion circuit 100B converts single-phase or three-phase AC power into an intermediate power source and stores the intermediate power in the intermediate capacitor CI. The DC / DC conversion circuit 100C uses the intermediate power stored in the intermediate capacitor CI as an input source and converts it into an output power source with a specific voltage level to power (or charge) the load 200 coupled to the downstream end.

[0003] On the other hand, if the input power supply of the AC / DC converter 100A is a three-phase AC power supply, each phase usually requires a complete set of conversion circuits for power conversion. Therefore, most three-phase AC / DC converters 100A include three sets of AC / DC conversion circuits 100B, an intermediate capacitor CI, and a DC / DC conversion circuit 100C. Since the intermediate capacitor CI is generally used to store a large amount of power and requires a large configuration space, the size of the AC / DC converter 100A will be too large, which is not conducive to miniaturization design.

[0004] Therefore, how to design a single-stage AC / DC resonant converter, using a single-stage circuit structure to replace the traditional two-stage circuit structure, is a major research topic that the creators of this project intend to undertake. Summary of the Invention

[0005] To address the aforementioned problems, this disclosure provides a single-stage AC / DC resonant converter to overcome the limitations of existing technologies. Therefore, the single-stage AC / DC resonant converter of this disclosure is used to convert three-phase AC power into DC power, and includes a primary-side circuit, a resonant circuit, and a secondary-side circuit. The primary-side circuit includes three sets of primary-side switching circuits, each coupled to one phase of the three-phase AC power supply, and each primary-side switching circuit includes a rectifier circuit and a switching circuit. The rectifier circuit includes rectifier bridge arms and capacitors connected in parallel with the rectifier bridge arms, and the switching circuit is coupled to the capacitors. The resonant circuit includes three sets of transformers, the primary windings of which are coupled to the switching circuits of the primary-side switching circuits, and the secondary windings of the transformers form a common secondary winding. The secondary-side circuit includes one set of secondary-side switching circuits, and these secondary-side switching circuits are coupled to the common secondary winding.

[0006] To address the aforementioned problems, this disclosure provides a single-stage AC / DC resonant converter to overcome the limitations of existing technologies. Therefore, the single-stage AC / DC resonant converter of this disclosure is used to convert three-phase AC power into DC power, and includes a primary-side circuit, a resonant circuit, and a secondary-side circuit. The primary-side circuit includes three sets of primary-side switching circuits, each of which includes a filter circuit and a switching circuit. The filter circuit is coupled to one phase of the three-phase AC power supply, and the switching circuit is coupled to the filter circuit. The resonant circuit includes three transformers, the primary windings of which are coupled to the switching circuits of the primary-side switching circuits, and the secondary windings of the transformers form a common secondary winding. The secondary-side circuit includes a set of secondary-side switching circuits, which are coupled to the common secondary winding.

[0007] To address the aforementioned problems, this disclosure provides a single-stage AC / DC resonant converter to overcome the limitations of existing technologies. Therefore, the single-stage AC / DC resonant converter of this disclosure is used to convert three-phase AC power into DC power, and includes a primary-side circuit, a resonant circuit, and a secondary-side circuit. The primary-side circuit includes three sets of primary-side switching circuits, each coupled to one phase of the three-phase AC power supply, and each primary-side switching circuit includes a switching circuit. The resonant circuit includes three transformers, the primary windings of which are coupled to the switching circuits of the primary-side switching circuits. The secondary-side circuit includes three sets of secondary-side switching circuits, the input terminals of which are coupled to the secondary windings of the transformers, and the output terminals of which are connected in parallel.

[0008] The main purpose and effect of this disclosure is that, since the single-stage AC / DC resonant converter of this disclosure uses a single-stage circuit structure to replace the traditional two-stage circuit structure, and the method of converting three-phase input to output power mainly uses multiple switches for switching, the single-stage AC / DC resonant converter of this disclosure does not require intermediate energy storage components.

[0009] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit this invention. Attached Figure Description

[0010] Figure 1 shows an existing two-stage AC / DC converter;

[0011] Figure 2 is a circuit diagram of a first embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0012] Figure 3 is a circuit diagram of a second embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0013] Figure 4 is a circuit diagram of the third embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0014] Figure 5 is a circuit diagram of the fourth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0015] Figure 6 is a circuit diagram of the fifth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0016] Figure 7 is a circuit diagram of the sixth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0017] Figure 8 is a circuit diagram of the seventh embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0018] Figure 9 is a circuit diagram of the eighth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0019] Figure 10 is a circuit diagram of the ninth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0020] Figure 11 is a circuit diagram of the tenth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0021] Figure 12 is a circuit diagram of the eleventh embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0022] Figure 13 is a circuit diagram of the twelfth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0023] Figure 14 is a circuit diagram of the thirteenth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0024] Figure 15 is a circuit diagram of the fourteenth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0025] Figure 16 is a circuit diagram of the fifteenth embodiment of the single-stage AC / DC resonant converter of this disclosure;

[0026] Figure 17 is a circuit diagram of the sixteenth embodiment of the single-stage AC / DC resonant converter of this disclosure; and

[0027] Figure 18 is a circuit diagram of the seventeenth embodiment of the single-stage AC / DC resonant converter of this disclosure.

[0028] Explanation of reference numerals in the attached figures

[0029] 100A: AC / DC converter

[0030] 100B: AC / DC conversion circuit

[0031] CI: Intermediate capacitor

[0032] 100C: DC / DC converter circuit

[0033] 100: Resonant Converter

[0034] A: Primary side circuit

[0035] 1: Primary-side switching circuit

[0036] 2: Rectifier circuit

[0037] L: Inductance

[0038] Cf: Capacitor

[0039] 22: Rectifier bridge arm

[0040] 222: First rectifier bridge arm

[0041] Qr1: First rectifier switch

[0042] Qr2: Second rectifier switch

[0043] 224: Second rectifier bridge arm

[0044] Qr3: Third rectifier switch

[0045] Qr4: Fourth rectifier switch

[0046] 3: Filtering circuit

[0047] 4: Switching circuit

[0048] L1: First Inductor

[0049] L2: Second Inductor

[0050] 42: First switching bridge arm

[0051] Q1: First switching switch

[0052] Q2: Second switch

[0053] 422: First switch module

[0054] 424: Second Switch Module

[0055] 44: Second switching bridge arm

[0056] Q3: Third switch

[0057] Q4: Fourth switch

[0058] 442: Third switch module

[0059] 444: Fourth Switch Module

[0060] Pgnd1, Pgnd2, Pgnd3: Primary side grounding terminals

[0061] B: Resonant circuit

[0062] Lr1, Lr2: Resonant inductors

[0063] Cr1, Cr2: Resonant capacitors

[0064] T: Transformer

[0065] Wp: Primary winding

[0066] Wp1: First primary winding

[0067] Wp2: Second primary winding

[0068] Pc: Center tap end

[0069] Ws: Secondary winding

[0070] WCs: Common winding on the secondary side

[0071] C: Secondary side circuit

[0072] 5: Secondary-side switching circuit

[0073] 52: First-stage side bridge arm

[0074] Qs1: Primary side switch

[0075] Qs2: Secondary side switch

[0076] 54: Secondary side bridge arm

[0077] Qs3: Third-stage side switch

[0078] Qs4: Fourth secondary side switch

[0079] 56: Third-stage side bridge arm

[0080] Qs5: Fifth secondary side switch

[0081] Qs6: Sixth secondary side switch

[0082] Co: Output capacitor

[0083] Sgnd: Secondary side grounding terminal

[0084] P: Node

[0085] P1: First node

[0086] P2: Second node

[0087] P3: Third Node

[0088] Pr1: First rectifier node

[0089] Pr2: Second rectifier node

[0090] Pp1: First primary side node

[0091] Pp2: Second primary side node

[0092] Pp3: Third primary side node

[0093] Ps1: First-level side node

[0094] Ps2: Secondary side node

[0095] Ps3: Third-level side node

[0096] 6: Controller

[0097] 200: Load

[0098] R, Y, B: Three-phase AC power supply

[0099] Pac: AC power supply

[0100] N: Neutral end

[0101] Pdc: DC power supply

[0102] Sc: Control signal Detailed Implementation

[0103] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings:

[0104] The single-stage AC / DC resonant converter disclosed herein differs from the existing two-stage AC / DC converter shown in Figure 1, which requires an intermediate energy storage element to store energy into DC power before converting the DC power into DC output power. Specifically, the single-stage AC / DC resonant converter of this disclosure is suitable for three-phase / single-phase extended topology (unfolded topology), primarily for matrix converter topology applications. Matrix converters convert three-phase input to output power mainly using multiple switches for switching. Like voltage and current source inverters, matrix converters handle voltage and current conversion in several stages, but the DC link lacks an intermediate energy storage element; therefore, voltage and current conversion can be completed in a single-stage converter. Thus, the capacitors between the three-phase AC power supply R, Y, B and the output capacitor Co are primarily used for filtering, not energy storage. Therefore, the single-stage AC / DC resonant converter can process the three-phase AC power supply R, Y, B in a phase-by-phase manner.

[0105] Please refer to Figure 2, which is a circuit diagram of a first embodiment of the single-stage AC / DC resonant converter of this disclosure, and also refer to Figure 1. The single-stage AC / DC resonant converter 100 can use a circuit architecture consisting of resonant tanks composed of inductors and capacitors (e.g., but not limited to LC, CLLC, etc.), and is particularly suitable for using dual-active-bridge (DAB) and series resonant dual-active-bridge (SR DAB) circuit architectures. That is, the single-stage AC / DC resonant converter 100 of this disclosure can process the three-phase AC power supply R, Y, B in a phase-by-phase manner to convert it into DC power supply Pdc, and the voltage level of the converted DC power supply Pdc can be set by the controller 6 to be increased or decreased. On the other hand, in order to avoid the circuit structure being too complicated, this disclosure mainly focuses on the circuit architecture of series resonant dual-active-bridge (SR DAB), and other circuit architectures can be deduced from the circuit structure shown in this disclosure, and will not be described in detail.

[0106] Referring again to Figure 2, a single-stage AC / DC resonant converter (hereinafter referred to as resonant converter 100) is used to convert a three-phase AC power supply R, Y, B into a DC power supply Pdc. The resonant converter 100 includes a primary-side circuit A, a resonant circuit B, and a secondary-side circuit C. The primary-side circuit A includes three sets of primary-side switching circuits 1, and each set of primary-side switching circuits 1 includes a rectifier circuit 2 and a switching circuit 4. The rectifier circuit 2 includes a rectifier bridge arm 22 and a capacitor Cf connected in parallel to the rectifier bridge arm 22, and the switching circuit 4 is coupled to the capacitor Cf. As mentioned above, the capacitor Cf is not an intermediate energy storage element (i.e., it is not an electrolytic capacitor or other element that can be used to store large amounts of electricity), so it is mainly used for filtering rather than storing energy.

[0107] The resonant circuit B mainly includes three sets of resonant slots and three sets of transformers T, and the resonant slots can vary depending on the circuit architecture of the resonant converter 100. This disclosure primarily focuses on the SR DAB circuit architecture, where the resonant slots include primary-side resonant slots and secondary-side resonant slots. The primary-side resonant slot includes a series-connected resonant inductor Lr1 and a resonant capacitor Cr1, and the secondary-side resonant slot includes a series-connected resonant inductor Lr2 and a resonant capacitor Cr2. Each transformer T includes a primary-side winding Wp and a secondary-side winding Ws, and the primary-side winding Wp is coupled to the switching circuit 4 of the primary-side switching circuit 1 via the primary-side resonant slot. When the circuit architecture of the resonant converter 100 is the SR DAB circuit architecture, the secondary-side winding Ws and the secondary-side resonant slot form a secondary-side common winding WCs. Furthermore, when the circuit architecture of the resonant converter 100 does not have a secondary-side resonant slot, the secondary-side winding Ws forms the secondary-side common winding WCs. It is worth mentioning that, in one embodiment, the turns ratio of the primary winding Wp to the secondary winding Ws is indicated by n:1, but it is not limited thereto and can be any ratio that can be implemented in the resonant converter 100.

[0108] The secondary-side circuit C differs from the primary-side circuit A, comprising only one set of secondary-side switching circuits 5, which are coupled to the secondary-side common winding WCs and the load 200. The load 200 is preferably a battery, particularly for electric vehicles, but is not limited thereto. The resonant converter 100 also includes a controller 6, which provides control signals Sc to control the primary-side circuit A and the secondary-side circuit C, thereby dividing the three-phase AC power supply R, Y, and B into several stages to process voltage and current conversions and convert them into DC power supply Pdc.

[0109] Furthermore, referring to Figure 2, the rectifier circuit 2 includes not only the rectifier bridge arm 22 and the capacitor Cf connected in parallel with the rectifier bridge arm 22, but also an inductor L, which is also used for filtering. The inductor L of each primary-side switching circuit 1 is coupled to one end of one phase of the three-phase AC power supply Pac (R, Y, B). The rectifier bridge arm 22 includes a first rectifier bridge arm 222 and a second rectifier bridge arm 224 connected in parallel with the capacitor Cf. One of the first rectifier bridge arms 222 is coupled to the inductor L, and the other of the first rectifier bridge arm 222 is coupled to the other end of the AC power supply Pac.

[0110] Specifically, taking the first rectifier bridge arm 222 coupled to inductor L as an example, the first rectifier bridge arm 222 may include a first rectifier switch Qr1 and a second rectifier switch Qr2 connected in series, and a first rectifier node Pr1 is formed between the first rectifier switch Qr1 and the second rectifier switch Qr2. The second rectifier bridge arm 224 may also include a third rectifier switch Qr3 and a fourth rectifier switch Qr4 connected in series, and a second rectifier node Pr2 is formed between the third rectifier switch Qr3 and the fourth rectifier switch Qr4. Therefore, the first rectifier node Pr1 is coupled to the other end of inductor L, and the second rectifier node Pr2 is coupled to the neutral terminal N of the three-phase AC power supply R, Y, B.

[0111] The switching circuit 4 includes a first switching bridge arm 42 and a second switching bridge arm 44, with a capacitor Cf connected in parallel between the first switching bridge arm 42 and the second switching bridge arm 44. The first switching bridge arm 42 may include a first switching switch Q1 and a second switching switch Q2 connected in series, forming a first primary-side node Pp1 between the first switching switch Q1 and the second switching switch Q2. The second switching bridge arm 44 may include a third switching switch Q3 and a fourth switching switch Q4 connected in series, forming a second primary-side node Pp2 between the third switching switch Q3 and the fourth switching switch Q4. One of the first primary-side node Pp1 and the second primary-side node Pp2 is coupled to the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3 (here, the first primary-side node Pp1 is used as an example), and the other of the first primary-side node Pp1 and the second primary-side node Pp2 is coupled to the primary-side winding Wp of the transformer T. In this embodiment, the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3 coupled to each primary-side switching circuit 1 are different. Therefore, each first primary-side node Pp1 is coupled to a different primary-side ground terminal Pgnd1, Pgnd2, and Pgnd3. The coupling relationship in the following embodiments is the same, and will not be repeated here.

[0112] Since one end of the primary winding Wp is also coupled to the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3, the two ends of the primary winding Wp are respectively coupled to the first primary-side node Pp1 and the second primary-side node Pp2. Furthermore, the resonant inductor Lr1 and resonant capacitor Cr1 of the primary-side resonant slot can be coupled between the first primary-side node Pp1 and one end of the primary winding Wp (as illustrated in Figure 2), or coupled between the primary winding Wp and the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3. Besides these, there are many other structures for the primary-side resonant slot (such as, but not limited to, a single resonant inductor structure) and feasible coupling methods (such as, but not limited to, the resonant inductor Lr1 and resonant capacitor Cr1 being respectively configured on both sides of the primary winding Wp), which will not be elaborated upon here.

[0113] On the secondary side of Figure 2, the secondary windings Ws are coupled to the primary windings Wp and are connected to the same node to form a structure of shared secondary windings WCs. Specifically, the first end of each secondary winding Ws is coupled to the secondary ground terminal Sgnd, and the second end of each secondary winding Ws is connected to a node P. The secondary-side switching circuit 5 includes a primary-side bridge arm 52, a secondary-side bridge arm 54, and an output capacitor Co, with the primary-side bridge arm 52 and the secondary-side bridge arm 54 connected in parallel with the output capacitor Co. Furthermore, the load 200 can receive DC power Pdc by coupling to the output capacitor Co. The primary-side bridge arm 52 includes a primary-side switch Qs1 and a secondary-side switch Qs2 connected in series, and a primary-side node Ps1 is formed between the primary-side switch Qs1 and the secondary-side switch Qs2. The second-stage side arm 54 includes a third-stage side switch Qs3 and a fourth-stage side switch Qs4 connected in series, and a second-stage side node Ps2 is formed between the third-stage side switch Qs3 and the fourth-stage side switch Qs4.

[0114] Node P of the secondary winding Ws is coupled to one of the primary winding nodes Ps1 and Ps2 (illustrated here as primary winding node Ps1), and the other of primary winding node Ps1 and Ps2 is coupled to the secondary ground terminal Sgnd. Since one end of the secondary winding Ws is also coupled to the secondary ground terminal Sgnd, the two ends of the secondary winding Ws are coupled to primary winding node Ps1 and secondary winding node Ps2, respectively. Furthermore, the resonant inductance Lr2 and resonant capacitor Cr2 of the secondary resonant slot can be configured similarly to those of the primary resonant slot, and will not be elaborated further here.

[0115] In summary, the controller 6 provides a control signal Sc, enabling the rectifier bridge arm 22 of the resonant converter 100 to perform full-wave rectification. The rectified power is then converted into a specific level DC power supply Pdc via the switching circuit 4, the resonant circuit B, and the secondary side circuit C. Furthermore, the resonant converter 100 can also provide power factor correction (PFC) functionality through the settings and operation of the controller 6, thereby improving the power conversion efficiency of the resonant converter 100. It is worth noting that in one embodiment, the rectifier bridge arm 22 primarily rectifies the AC power supply Pac; therefore, the switching speed of the switches within the controller 6 (e.g., but not limited to the mains frequency) is slower than the switching speed of the switches within the switching circuit 4 (e.g., but not limited to 400kHz–600kHz). Therefore, the rectifier bridge arm 22 can also be referred to as the slow arm, and the switching bridge arms 42 and 44 within the switching circuit 4 can be referred to as the fast arms. This will be the case in subsequent disclosures and will not be elaborated further here.

[0116] Furthermore, in the resonant converter 100 of Figure 2, since the secondary windings Ws of the transformer T are directly connected in parallel and uniformly coupled to the same node P, and a single set of secondary-side switching circuits 5 are coupled through this node P, the number of secondary-side switches can be reduced (at least 8 switches can be reduced if compared with a three-set separately converted architecture), thereby reducing the power loss of the switches and reducing the number of control signal outputs of the controller 6. On the other hand, the switches in this disclosure are all illustrated with metal-oxide-semiconductor field-effect transistors, but this is not a limitation. Any electronic component that can be used as a switch should be included in the scope of this embodiment (e.g., but not limited to, insulated-gate bipolar transistors, gallium nitride transistors, etc.).

[0117] Please refer to Figure 3, which is a circuit diagram of a second embodiment of the single-stage AC / DC resonant converter of this disclosure, and also refer to Figure 2. The primary-side circuit A in Figure 3 is exactly the same as that in Figure 2, and the structure and coupling method of the primary-side winding Wp of the transformer T are also the same as those in Figure 2. The difference lies in the structure of the secondary-side common winding WCs and the secondary-side circuit C in Figure 3, which are different from those in Figure 2. Specifically, the secondary-side winding Ws in Figure 3 is a delta-connected structure. Therefore, the secondary-side winding Ws is coupled end-to-end in sequence to form the first node P1, the second node P2, and the third node P3.

[0118] In addition to the first secondary-side bridge arm 52 and the second secondary-side bridge arm 54 shown in Figure 2, the secondary-side switching circuit 5 also includes a third secondary-side bridge arm 56. The third secondary-side bridge arm 56 is connected in parallel to the first secondary-side bridge arm 52, and includes a fifth secondary-side switch Qs5 and a sixth secondary-side switch Qs6 connected in series. A third secondary-side node Ps3 is formed between the fifth secondary-side switch Qs5 and the sixth secondary-side switch Qs6, and the first node P1, the second node P2, and the third node P3 are respectively coupled to the first secondary-side node Ps1, the second secondary-side node Ps2, and the third secondary-side node Ps3. The delta connection structure shown in Figure 3 also reduces the number of secondary-side switches. Furthermore, since the secondary-side winding Ws is wound as a three-phase winding and can be formed by a single iron core to create a three-phase transformer, the size of the three-phase transformer can be reduced (compared to the use of three transformers in traditional converters).

[0119] Please refer to Figure 4, which is a circuit diagram of the third embodiment of the single-stage AC / DC resonant converter of this disclosure, and in conjunction with Figures 2 and 3. The primary-side circuit A in Figure 4 is exactly the same as that in Figure 2. The structure and coupling method of the primary-side winding Wp of the transformer T are also the same as those in Figure 2, and the structure of the secondary-side circuit C is the same as that in Figure 3. The difference between Figure 4 and Figures 2 and 3 is that the structures of the secondary-side common winding WCs and the secondary-side circuit C are different from those in Figures 2 and 3. Specifically, the secondary-side winding Ws in Figure 4 has a Y-shaped connection structure. Therefore, the first end of each secondary-side winding is coupled to the first primary-side node Ps1, the second primary-side node Ps2, and the third primary-side node Ps3 of the switching circuit 5, and the second end of each secondary-side winding Ws is similar to that in Figure 2, being commonly coupled to a single node P. Therefore, the circuit architecture of Figure 4 provides similar benefits to that of Figure 3, and can also reduce the number of secondary-side switches and the size of the three-phase transformer.

[0120] Please refer to Figure 5, which is a circuit diagram of the fourth embodiment of the single-stage AC / DC resonant converter of this disclosure, and also refer to Figures 2 to 4. The rectifier circuit 2 in Figure 5 is exactly the same as that in Figure 2, except that the secondary-side circuit C includes three sets of secondary-side switch circuits 5, and the circuit architecture of the switching circuit 4 is also different from that in Figure 2. Specifically, the switching circuit 4 includes a first switching switch Q1 and a second switching switch Q2. One end of the first switching switch Q1 and the second switching switch Q2 is coupled to one end of the capacitor Cf, and the other end of the capacitor Cf is coupled to the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3.

[0121] On the other hand, the circuit architecture of resonant circuit B is also different from that in Figure 2. Furthermore, the resonant circuit B in Figure 5 is shown without a primary-side resonant slot, and the secondary side includes a secondary-side resonant slot formed by the resonant inductor Lr2 and the resonant capacitor Cr2. Specifically, the primary winding Wp of each transformer T includes a first primary winding Wp1 and a second primary winding Wp2 connected in series, with a center tap Pc formed between the first primary winding Wp1 and the second primary winding Wp2. One end of the first primary winding Wp1 is coupled to the other end of the first switching switch Q1, one end of the second primary winding Wp2 is coupled to the other end of the second switching switch Q2, and the center tap Pc of the transformer T is coupled to the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3.

[0122] In Figure 5, the circuit architecture of the three sets of secondary-side switching circuits 5 is the same as that in Figure 2, and the input terminal of the secondary-side switching circuit 5 is coupled to the secondary-side winding Ws of the transformer T. Specifically, one of the first-side node Ps1 and the second-side node Ps2 of each set of secondary-side switching circuits 5 (here, the first-side node Ps1 is used as an example) is coupled to one end of each set of secondary-side windings Ws, and the other of the first-side node Ps1 and the second-side node Ps2 of each set of secondary-side switching circuits 5 is coupled to the secondary-side ground terminal Sgnd. Since one end of the secondary-side winding Ws is also coupled to the secondary-side ground terminal Sgnd, the two ends of the secondary-side winding Ws are coupled to the first-side node Ps1 and the second-side node Ps2, respectively. Furthermore, the resonant inductance Lr2 and resonant capacitor Cr2 of the secondary-side resonant slot can be configured similarly to the secondary-side resonant slot in Figure 2, and will not be described in detail here.

[0123] Referring again to Figure 5, the three sets of secondary-side switching circuits 5 are independent of each other, and their output terminals are connected in parallel to jointly supply power to the load 200. Specifically, one end of the output capacitor Co of the three sets of secondary-side switching circuits 5 is jointly coupled to form a positive output terminal, and the other end of the output capacitor Co is jointly coupled to form a negative output terminal. The positive and negative output terminals can be coupled to the load 200 to supply power to the load 200. In summary, since each phase switching circuit 4 in Figure 5 uses only two switches (i.e., the first switching switch Q1 and the second switching switch Q2), it can reduce the number of switches in the primary-side switching circuit 1.

[0124] Please refer to Figure 6, which is a circuit diagram of the fifth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 5, and repeatedly refer to Figures 3 and 5. The circuit architecture of Figure 6 is a combination of some circuit architectures of Figures 2 and 5, and can achieve the corresponding effects described above. Specifically, the primary side circuit A of Figure 6 is the same as the primary side circuit A of Figure 5, and the secondary side circuit C of Figure 6 is the same as the secondary side circuit C of Figure 2. Furthermore, the circuit structure of the primary side winding Wp of Figure 6 is the same as that of Figure 5, which is also a center-tapped structure. The secondary side winding Ws is the same as that of Figure 2, which is connected to the same node P. Other detailed circuit structures and features can be referred to in conjunction with Figures 3 and 5, and will not be described in detail here.

[0125] Please refer to Figure 7, which is a circuit diagram of the sixth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 6, and repeatedly refer to Figures 3 and 5. Figure 7 is similar to Figure 6, and the circuit architecture is a combination of some circuit architectures of Figures 3 and 5, achieving the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 3, with a delta connection structure. Other detailed circuit structures and features can be referred to in conjunction with Figures 3 and 5, and will not be repeated here.

[0126] Please refer to Figure 8, which is a circuit diagram of the seventh embodiment of the single-stage AC / DC resonant converter of this disclosure, in conjunction with Figures 2 to 7, and repeatedly refer to Figures 4 to 5. Figure 8 is also similar to Figure 6, and the circuit architecture is a combination of some circuit architectures of Figures 4 and 5, achieving the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 4, with a Y-shaped connection structure. Other detailed circuit structures and features can be referred to Figures 4 and 5, and will not be repeated here.

[0127] Please refer to Figure 9, which is a circuit diagram of the eighth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer to Figures 2 to 8 in conjunction. The main feature of Figure 9 is that the fast arm and slow arm in the primary side circuit A are integrated to form a circuit with three sets of bridge arms connected in parallel. Specifically, Figure 9 is based on the switching circuit 4 in Figure 2, which includes a first switching bridge arm 42 and a second switching bridge arm 44, and further includes a rectifier bridge arm 22 connected in parallel to form a circuit with three sets of bridge arms connected in parallel. Furthermore, the rectifier bridge arm 22 is connected in parallel with a capacitor Cf, and the rectifier bridge arm 22 includes a first rectifier switch Qr1 and a second rectifier switch Qr2 connected in series, and a third primary side node Pp3 is formed between the first rectifier switch Qr1 and the second rectifier switch Qr2. One end of the first rectifier switch Qr1 is coupled to one end of the capacitor Cf, and one end of the second rectifier switch Qr2 is coupled to the other end of the first rectifier switch Qr1 to form the third primary side node Pp3, and the other end of the second rectifier switch Qr2 is coupled to the other end of the capacitor Cf.

[0128] In addition, the switching circuit 4 also includes a first inductor L1 and a second inductor L2. One end of the first inductor L1 is coupled to one end of the AC power supply Pac, and the other end of the first inductor L1 is coupled to the first primary-side node Pp1. One end of the second inductor L2 is coupled to one end of the AC power supply Pac, and the other end of the second inductor L2 is coupled to the second primary-side node Pp2. Similar to Figure 2, one of the first primary-side node Pp1 and the second primary-side node Pp2 is coupled to the primary-side winding Wp, and the other is coupled to the primary-side ground terminals Pgnd1, Pgnd2, and Pgnd3. Furthermore, the third primary-side node Pp3 is coupled to the other end of the AC power supply Pac. The circuit structure in Figure 9 is based on a boost converter circuit, which is similar to a totem pole power factor corrector. That is, the primary-side circuit A mainly boosts the AC power supply Pac, and it also reduces one set of slow bridge arms. Apart from this, the remaining circuit structure and function are similar to those in Figure 2, and will not be described in detail here.

[0129] Please refer to Figure 10, which is a circuit diagram of the ninth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 9, and repeatedly refer to Figures 3 and 9. The circuit architecture of Figure 10 is mainly a combination of some circuit architectures of Figures 3 and 9, and can achieve the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 3, which is a delta connection structure. Other detailed circuit structures and features can be referred to in conjunction with Figures 3 and 9, and will not be repeated here.

[0130] Please refer to Figure 11, which is a circuit diagram of the tenth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 10, and repeatedly refer to Figures 4 and 9. The circuit architecture of Figure 11 is mainly a combination of some circuit architectures of Figures 4 and 9, and can achieve the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 4, which is a Y-connected structure. Other detailed circuit structures and features can be referred to in conjunction with Figures 4 and 9, and will not be repeated here.

[0131] Please refer to Figure 12, which is a circuit diagram of the eleventh embodiment of the single-stage AC / DC resonant converter of this disclosure, and in conjunction with Figures 2 to 11. The main feature of Figure 12 is that the primary-side circuit A does not have a slow-speed arm; instead, a bidirectional on / off fast arm is used. Furthermore, the resonant circuit B and the secondary-side circuit C are the same as in Figure 2. Specifically, the three primary-side switching circuits 1 in Figure 12 each include a filter circuit 3 and a switching circuit 4. The filter circuit 3 is coupled to one phase of the three-phase AC power supply R, Y, and B, Pac, and the switching circuit 4 is coupled to the filter circuit 3 and the primary-side winding Wp. Specifically, the filter circuit 3 includes an inductor L and a capacitor Cf. Similar to the description in Figure 2, the inductor L and capacitor Cf primarily function as filters, rather than as intermediate energy storage elements (i.e., not as electrolytic capacitors or other elements that can store large amounts of electricity).

[0132] Furthermore, one end of inductor L is coupled to one end of AC power supply Pac, and one end of capacitor Cf is coupled to the other end of inductor L. The other end of capacitor Cf is coupled to the other end of AC power supply Pac, and capacitor Cf is connected in parallel with switching circuit 4. Switching circuit 4 is similar to that in Figure 2, and also includes a first switching bridge arm 42 and a second switching bridge arm 44, but the switching switches Q1 to Q4 of switching bridge arms 42 and 44 are replaced with switch modules 422 to 444, and each set of switch modules 422 to 444 is a bidirectional switch. Therefore, when both switches of the bidirectional switch are turned off, their paths can be completely disconnected. Specifically, the first switching bridge arm 42 includes a first switch module 422 and a second switch module 424 connected in series, and the first switch module 422 and the second switch module 424 each include switches connected in reverse series (i.e., the directions of the junction diodes are exactly opposite). Therefore, the first switching bridge arm 42 includes more than four switches. One end of the first switching module 422 is coupled to the other end of the second switching module 424 and connected to the filter circuit 3 (specifically, the first switching bridge arm 42 is connected to the parallel capacitor Cf), and the other end of the first switching module 422 is coupled to one end of the second switching module 424 to form the first primary side node Pp1.

[0133] The second switching bridge arm 44 includes a third switch module 442 and a fourth switch module 444 connected in series, and the third switch module 442 and the fourth switch module 444 also each include switches connected in reverse series. Therefore, the second switching bridge arm 44 also includes more than four switches. One end of the third switch module 442 and the other end of the fourth switch module 444 are coupled to the filter circuit 3 (specifically, the capacitor Cf connected in parallel to the second switching bridge arm 44), and the other end of the third switch module 442 is coupled to one end of the fourth switch module 444 to form the second primary side node Pp2. The coupling relationship between the first primary side node Pp1 and the second primary side node Pp2 is similar to that in Figure 2. One of them is coupled to one end of the primary side winding Wp, and the other is coupled to the other end of the primary side winding Wp and the primary side ground terminals Pgnd1, Pgnd2, and Pgnd3. The remaining detailed coupling methods are similar to those in Figure 2 and will not be described in detail here.

[0134] It is worth mentioning that, in one embodiment, besides the implementation of two switches connected in reverse series, the bidirectional switch has several other implementations with different structures but the same function. Therefore, the structure of switch modules 422-444 can be selectively replaced according to actual needs. That is, any bidirectional switch with bidirectional conduction / turn-off function should be included in the scope of this embodiment. In addition, the circuit structure and coupling relationship not mentioned in Figure 12 are similar to those in Figure 2 and can achieve similar effects, so they will not be described in detail here.

[0135] Please refer to Figure 13, which is a circuit diagram of the twelfth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 12, and repeatedly refer to Figures 3 and 12. The circuit architecture of Figure 13 is mainly a combination of some circuit architectures of Figures 3 and 12, and can achieve the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 3, which is a delta connection structure. Other detailed circuit structures and features can be referred to in conjunction with Figures 3 and 12, and will not be described again here.

[0136] Please refer to Figure 14, which is a circuit diagram of the thirteenth embodiment of the single-stage AC / DC resonant converter of this disclosure, and refer in conjunction with Figures 2 to 13, and repeatedly refer to Figures 4 and 12. The circuit architecture of Figure 14 is mainly a combination of some circuit architectures of Figures 4 and 12, and can achieve the corresponding effects described above. The main difference is that the secondary winding Ws is the same as in Figure 4, which is a Y-connected structure. Other detailed circuit structures and features can be referred to in conjunction with Figures 4 and 12, and will not be described again here.

[0137] Please refer to Figure 15, which is a circuit diagram of the fourteenth embodiment of the single-stage AC / DC resonant converter of this disclosure, and in conjunction with Figures 2 to 14. The secondary-side circuit C in Figure 15 is exactly the same as that in Figure 5, and the filter circuit 3 is exactly the same as that in Figure 12. The difference lies in the switching circuit 4. Specifically, the switching circuit 4 in Figure 15 is similar to that in Figure 5, but the first switching switch Q1 and the second switching switch Q2 are replaced by the first switching module 422 and the second switching module 424, respectively. Furthermore, the first switching module 422 and the second switching module 424 are also bidirectional switches, each including switches connected in reverse series (i.e., the directions of the junction diodes are exactly opposite). Similarly, in addition to the implementation of two switches connected in reverse series, there are many other implementations with different structures but the same function, which will not be described in detail here.

[0138] Furthermore, one end of the first switch module 422 and the second switch module 424 are coupled to the filter circuit 3 (specifically, one end of the capacitor Cf, and the other end of the capacitor Cf is coupled to the primary side ground terminals Pgnd1, Pgnd2, and Pgnd3), and the other ends of the first switch module 422 and the second switch module 424 are respectively coupled to one end of the first primary side winding Wp1 and the second primary side winding Wp2. Other coupling relationships and their achievable effects can be seen in Figures 5 and 12, and will not be elaborated further here.

[0139] Please refer to Figures 16, 17, and 18, which are circuit diagrams of the fifteenth to seventeenth embodiments of the single-stage AC / DC resonant converter of this disclosure, and also refer to Figures 2 to 14, and repeatedly refer to Figures 2 to 4 and 15. The circuit architectures of Figures 16, 17, and 18 are mainly combinations of some circuit architectures of Figures 2 and 15, 3 and 15, and 4 and 15, respectively, and can achieve the corresponding effects described above. Other detailed circuit structures and features can be referred to Figures 2 to 4 and 15, and will not be repeated here.

[0140] However, the above description is only a detailed description and accompanying drawings of preferred embodiments of the present invention. The features of the present invention are not limited thereto and are not intended to limit the present invention. The full scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims.

Claims

1. A single-stage AC-DC resonant converter for converting a three-phase AC power source into a DC power source, the single-stage AC-DC resonant converter comprising: a primary side circuit including three sets of primary side switching circuits, each of the three sets of primary side switching circuits coupled to one of the three-phase AC power source, and each of the three sets of primary side switching circuits including: a rectifying circuit including a rectifying bridge arm and a capacitor connected in parallel to the rectifying bridge arm; a switching circuit coupled to the capacitor; a resonant circuit including three sets of transformers, primary side windings of the three sets of transformers coupled to the switching circuit of the three sets of primary side switching circuits, respectively, and secondary side windings of the three sets of transformers forming a common secondary side winding; a secondary side circuit including a set of secondary side switching circuits coupled to the common secondary side winding.

2. The single-stage AC-DC resonant converter of claim 1, wherein the set of secondary side switching circuits includes: a first secondary side bridge arm including a first secondary side switch and a second secondary side switch connected in series, and a first secondary side node formed between the first secondary side switch and the second secondary side switch; and a second secondary side bridge arm connected in parallel to the first secondary side bridge arm, and including a third secondary side switch and a fourth secondary side switch connected in series, a second secondary side node formed between the third secondary side switch and the fourth secondary side switch; wherein first ends of the secondary side windings of the three sets of transformers are coupled to a secondary side ground, and second ends of the secondary side windings of the three sets of transformers are commonly coupled to a node, the node coupled to one of the first secondary side node and the second secondary side node, and the other of the first secondary side node and the second secondary side node coupled to the secondary side ground.

3. The single-stage AC-DC resonant converter of claim 1, wherein the set of secondary side switching circuits includes: a first secondary side bridge arm including a first secondary side switch and a second secondary side switch connected in series, wherein a first secondary side node is formed between the first secondary side switch and the second secondary side switch; a second secondary side bridge arm connected in parallel to the first secondary side bridge arm, and including a third secondary side switch and a fourth secondary side switch connected in series, wherein a second secondary side node is formed between the third secondary side switch and the fourth secondary side switch; and a third secondary side bridge arm connected in parallel to the first secondary side bridge arm, and including a fifth secondary side switch and a sixth secondary side switch connected in series, wherein a third secondary side node is formed between the fifth secondary side switch and the sixth secondary side switch; wherein first ends of the secondary side windings of the three sets of transformers are coupled to the first secondary side node, the second secondary side node, and the third secondary side node, respectively, and second ends of the secondary side windings of the three sets of transformers are commonly coupled to a node.

4. The single-stage AC-DC resonant converter of claim 1, wherein the set of secondary side switching circuits includes: a first secondary side bridge arm including a first secondary side switch and a second secondary side switch connected in series, and a first secondary side node formed between the first secondary side switch and the second secondary side switch; a second secondary side bridge arm connected in parallel to the first secondary side bridge arm, and including a third secondary side switch and a fourth secondary side switch connected in series, a second secondary side node formed between the third secondary side switch and the fourth secondary side switch; a third secondary side bridge arm connected in parallel to the first secondary side bridge arm, and including a fifth secondary side switch and a sixth secondary side switch connected in series, a third secondary side node formed between the fifth secondary side switch and the sixth secondary side switch; wherein first ends of the secondary side windings of the three sets of transformers are coupled to the first secondary side node, the second secondary side node, and the third secondary side node, respectively, and second ends of the secondary side windings of the three sets of transformers are commonly coupled to a node. a second secondary side leg parallel to the first secondary side leg and comprising a third secondary side switch and a fourth secondary side switch connected in series, a second secondary side node formed between the third secondary side switch and the fourth secondary side switch; and a third secondary side leg parallel to the first secondary side leg and comprising a fifth secondary side switch and a sixth secondary side switch connected in series, a third secondary side node formed between the fifth secondary side switch and the sixth secondary side switch; wherein the three sets of secondary side windings of the transformers are coupled in series to form a first node, a second node and a third node, and the first node, the second node and the third node are coupled to the first secondary side node, the second secondary side node and the third secondary side node, respectively.

5. The single-stage AC / DC resonant converter of claim 1, wherein the rectifying circuit further comprises: an inductor coupled to one end of the one phase AC power source; wherein the rectifying legs comprise a first rectifying leg and a second rectifying leg parallel to the capacitor, and the first rectifying leg and the second rectifying leg are coupled to the inductor and the other end of the one phase AC power source, respectively.

6. The single-stage AC / DC resonant converter of claim 1, wherein the switching circuit comprises: a first switching switch coupled to one end of the capacitor, and the other end of the capacitor is coupled to a primary side ground terminal; and a second switching switch coupled to one end of the capacitor. wherein the primary side winding of each transformer comprises a first primary side winding and a second primary side winding connected in series, and a center tap terminal formed between the first primary side winding and the second primary side winding; one end of the first primary side winding is coupled to the other end of the first switching switch, one end of the second primary side winding is coupled to the other end of the second switching switch, and the center tap terminal is coupled to the primary side ground terminal.

7. The single-stage AC / DC resonant converter of claim 1, wherein the switching circuit comprises: a first switching leg parallel to the capacitor and comprising a first switching switch and a second switching switch connected in series, a first primary side node formed between the first switching switch and the second switching switch; and a second switching leg parallel to the capacitor and comprising a third switching switch and a fourth switching switch connected in series, a second primary side node formed between the third switching switch and the fourth switching switch; wherein one of the first primary side node and the second primary side node is coupled to a primary side ground terminal, and the other of the first primary side node and the second primary side node is coupled to the primary side winding of one of the transformers.

8. The single-stage AC / DC resonant converter of claim 7, wherein the rectifying legs are parallel to the capacitor and comprise: a first rectifying switch coupled to one end of the capacitor; and a second rectifying switch coupled to the other end of the first rectifying switch to form a third primary side node, and coupled to the other end of the capacitor; the switching circuit further comprises: ​ ​ ​ a first inductor having one end coupled to one end of one of the three-phase AC power sources and the other end coupled to the first primary-side node; and a second inductor having one end coupled to one end of one of the three-phase AC power sources and the other end coupled to the second primary-side node; wherein the third primary-side node is coupled to the other end of one of the three-phase AC power sources.

9. A single-stage AC-DC resonant converter for converting three-phase AC power sources into DC power sources, the single-stage AC-DC resonant converter comprising: a primary-side circuit including three sets of primary-side switching circuits, and each of the three sets of primary-side switching circuits including: a filter circuit coupled to one of the three-phase AC power sources, respectively; a switching circuit coupled to the filter circuit; a resonant circuit including three sets of transformers, primary-side windings of the three sets of transformers coupled to the switching circuits of the three sets of primary-side switching circuits, respectively, and secondary-side windings of the three sets of transformers forming a secondary-side common winding; a secondary-side circuit including one set of secondary-side switching circuits coupled to the secondary-side common winding.

10. The single-stage AC-DC resonant converter of claim 9, wherein the secondary-side switching circuits include: a first secondary-side bridge arm including a first secondary-side switch and a second secondary-side switch connected in series, and a first secondary-side node formed between the first secondary-side switch and the second secondary-side switch; and a second secondary-side bridge arm connected in parallel to the first secondary-side bridge arm, and including a third secondary-side switch and a fourth secondary-side switch connected in series, and a second secondary-side node formed between the third secondary-side switch and the fourth secondary-side switch; wherein first ends of the secondary-side windings of the three sets of transformers are coupled to a secondary-side ground, and second ends of the secondary-side windings of the three sets of transformers are commonly coupled to a node, and the node is coupled to one of the first secondary-side node and the second secondary-side node, and the other of the first secondary-side node and the second secondary-side node is coupled to the secondary-side ground.

11. The single-stage AC-DC resonant converter of claim 9, wherein the secondary-side switching circuits include: a first secondary-side bridge arm including a first secondary-side switch and a second secondary-side switch connected in series, and a first secondary-side node formed between the first secondary-side switch and the second secondary-side switch; a second secondary-side bridge arm connected in parallel to the first secondary-side bridge arm, and including a third secondary-side switch and a fourth secondary-side switch connected in series, and a second secondary-side node formed between the third secondary-side switch and the fourth secondary-side switch; and a third secondary-side bridge arm connected in parallel to the first secondary-side bridge arm, and including a fifth secondary-side switch and a sixth secondary-side switch connected in series, and a third secondary-side node formed between the fifth secondary-side switch and the sixth secondary-side switch; wherein first ends of the secondary-side windings of the three sets of transformers are coupled to the first secondary-side node, the second secondary-side node, and the third secondary-side node, respectively, and second ends of the secondary-side windings of the three sets of transformers are commonly coupled to a node.

12. The single-stage AC-DC resonant converter of claim 9, wherein the secondary-side switching circuit comprises: a first secondary-side bridge leg comprising a first secondary-side switch and a second secondary-side switch connected in series, and a first secondary-side node formed between the first secondary-side switch and the second secondary-side switch; a second secondary-side bridge leg connected in parallel with the first secondary-side bridge leg, and comprising a third secondary-side switch and a fourth secondary-side switch connected in series, a second secondary-side node formed between the third secondary-side switch and the fourth secondary-side switch; and a third secondary-side bridge leg connected in parallel with the first secondary-side bridge leg, and comprising a fifth secondary-side switch and a sixth secondary-side switch connected in series, a third secondary-side node formed between the fifth secondary-side switch and the sixth secondary-side switch; wherein the three sets of secondary-side windings of the transformers are sequentially coupled end-to-end to form a first node, a second node, and a third node, and the first node, the second node, and the third node are coupled to the first secondary-side node, the second secondary-side node, and the third secondary-side node, respectively.

13. The single-stage AC-DC resonant converter of claim 9, wherein the filter circuit comprises: an inductor having one end coupled to one end of one of the phase AC power sources; and a capacitor having one end coupled to the other end of the inductor, and the other end coupled to the other end of the one of the phase AC power sources; wherein the switching circuit is connected in parallel with the capacitor.

14. The single-stage AC-DC resonant converter of claim 9, wherein the switching circuit comprises: a first switching bridge leg comprising a first switch module and a second switch module connected in series, wherein one end of the first switch module and the other end of the second switch module are coupled to the filter circuit, and the other end of the first switch module is coupled to one end of the second switch module to form a first primary-side node; a second switching bridge leg connected in parallel with the first switching bridge leg, and comprising a third switch module and a fourth switch module connected in series, wherein one end of the third switch module and the other end of the fourth switch module are coupled to the filter circuit, and the other end of the third switch module is coupled to one end of the fourth switch module to form a second primary-side node; wherein one of the first primary-side node and the second primary-side node is coupled to one end of the primary-side winding, and the other of the first primary-side node and the second primary-side node is coupled to the other end of the primary-side winding and a primary-side ground.

15. The single-stage AC-DC resonant converter of claim 9, wherein the switching circuit comprises: a first switch module having one end coupled to the filter circuit; and a second switch module having one end coupled to the filter circuit; wherein the primary-side winding of each transformer comprises a first primary-side winding and a second primary-side winding connected in series, and a center tap formed between the first primary-side winding and the second primary-side winding; one end of the first primary-side winding is coupled to the other end of the first switch module, one end of the second primary-side winding is coupled to the other end of the second switch module, and the center tap is coupled to a primary-side ground. ​ 16. A single-stage AC-DC resonant converter for converting a three-phase AC power source into a DC power source, the single-stage AC-DC resonant converter comprising: a primary side circuit including three sets of primary side switching circuits, each of the three sets of primary side switching circuits coupled to one of the three-phase AC power source, and each of the three sets of primary side switching circuits including a switching circuit; a resonant circuit including three sets of transformers, primary side windings of the three sets of transformers coupled to the switching circuits of the three sets of primary side switching circuits, respectively; a secondary side circuit including three sets of secondary side switching circuits, input terminals of the three sets of secondary side switching circuits coupled to secondary side windings of the three sets of transformers, and output terminals of the three sets of secondary side switching circuits coupled in parallel.

17. The single-stage AC-DC resonant converter of claim 16, wherein each of the three sets of secondary side switching circuits includes: a first secondary side leg including a first secondary side switch and a second secondary side switch connected in series, and a first secondary side node formed between the first secondary side switch and the second secondary side switch; and a second secondary side leg connected in parallel to the first secondary side leg, and including a third secondary side switch and a fourth secondary side switch connected in series, a second secondary side node formed between the third secondary side switch and the fourth secondary side switch; wherein one of the first secondary side node and the second secondary side node is coupled to a secondary side winding of one of the transformers, and the other of the first secondary side node and the second secondary side node is coupled to a secondary side ground terminal.

18. The single-stage AC-DC resonant converter of claim 16, wherein each of the three sets of primary side switching circuits further includes: a rectifying circuit including a rectifying leg and a capacitor connected in parallel to the rectifying leg; an inductor having one end coupled to the one of the three-phase AC power source; a first switch module having one end coupled to the capacitor; and a second switch module having one end coupled to the capacitor; wherein the primary side winding of each of the transformers includes a first primary side winding and a second primary side winding connected in series, and a center tap terminal formed between the first primary side winding and the second primary side winding, one end of the first primary side winding coupled to the other end of the first switch module, one end of the second primary side winding coupled to the other end of the second switch module, and the center tap terminal coupled to a primary side ground terminal.

19. The single-stage AC-DC resonant converter of claim 16, wherein each of the three sets of primary side switching circuits further includes: a filter circuit including an inductor and a capacitor, one end of the inductor and the other end of the capacitor coupled to two ends of the one of the three-phase AC power source, respectively, and the other end of the inductor coupled to one end of the capacitor; wherein one end of the capacitor is coupled to the switching circuit, and the other end of the capacitor is coupled to a primary side ground terminal.

20. The single-stage AC-DC resonant converter of claim 19, wherein the switching circuit includes: a first switch module having one end coupled to the capacitor; and a second switch module having one end coupled to the capacitor. ​ ​ The primary side winding of each transformer comprises a first primary side winding and a second primary side winding connected in series, and a center tap end is formed between the first primary side winding and the second primary side winding; one end of the first primary side winding is coupled to the other end of the first switch module, one end of the second primary side winding is coupled to the other end of the second switch module, and the center tap end is coupled to a primary side ground end.

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