Three-phase LLC power conversion circuit and control method thereof

Abstract

The invention relates to a three-phase LLC power conversion circuit and a control method thereof. The three-phase LLC power conversion circuit is configured to receive an input voltage and output an output voltage, and comprises a three-phase transformer, an input switch group, an output switch group and a resonant circuit group. The input switch group comprises a plurality of input switches, and the output switch group comprises a plurality of rectification switches. The control method disclosed by the invention comprises the following steps: (S1) detecting input voltage, output voltage and a zero-crossover point of output current of each phase of the three-phase LLC power conversion circuit; and (S2) controlling the switching state of at least one rectification switch to lead or lag the switching state of the same corresponding input switch according to the ratio of the output voltage to the input voltage and / or adjusting the duty cycle of all the input switches to be increased, and adjusting the switching frequency of all the input switches according to the output voltage, the reference voltage and the soft switching setting condition.

Description

Technical Field

[0001] The present disclosure relates to the field of power conversion circuits, and in particular to a three-phase LLC power conversion circuit and a control method thereof. Background Art

[0002] The rapid development of information technology, particularly cloud computing, big data, and artificial intelligence, is driving increased energy consumption in data centers. Consequently, the power levels and power densities of the power conversion circuits that provide power to data centers have also increased significantly. Compared to unidirectional power conversion circuits, three-phase LLC power conversion circuits have become widely used in data centers due to their lower RMS current, lower peak current, and improved magnetic integration.

[0003] However, due to the interaction between the three phases, the control of a three-phase LLC power conversion circuit is more complex than that of a unidirectional power conversion circuit. For example, in a unidirectional power conversion circuit, phase shift control can be used to narrow the switching frequency range, making the unidirectional power conversion circuit suitable for applications with a wide voltage range. However, in a three-phase LLC power conversion circuit, it has two control variables. Using a single control variable, phase shift control, cannot address changes in the resonant frequency, which will result in significant reactive current and cannot accurately control the switches for soft switching. Therefore, there is still room for improvement in the control of three-phase LLC power conversion circuits.

[0004] Furthermore, a three-phase LLC power conversion circuit typically includes a three-phase transformer and a three-phase inductor. To reduce core and copper losses, the three-phase inductor and three-phase transformer are often integrated into a single magnetic component. However, conventional magnetic components integrating a three-phase inductor and three-phase transformer still have room for improvement in core losses and size reduction due to poor flux cancellation.

[0005] Therefore, it is necessary to develop a three-phase LLC power conversion circuit and a control method thereof to solve the problems and deficiencies faced by the prior art. Summary of the Invention

[0006] The present disclosure provides a three-phase LLC power conversion circuit and control method thereof, which not only reduces the switching frequency range of the three-phase power conversion circuit, but also achieves lower RMS current, lower peak current, and improved magnetic integration. Furthermore, because the control unit of the three-phase power conversion circuit controls two control variables, namely the phase shift and frequency of the switches, it can address the increase in reactive current caused by changes in resonant frequency and enable more precise soft switching of the switches.

[0007] To achieve the above-mentioned objectives, a preferred embodiment of the present disclosure is a control method applied to a three-phase LLC power conversion circuit. The three-phase LLC power conversion circuit receives an input voltage and outputs an output voltage, and includes a three-phase transformer, an input switch group, an output switch group, and a resonant circuit group. The input switch group is electrically connected to multiple primary-side windings of the three-phase transformer and includes multiple input switches. The output switch group is electrically connected to multiple secondary-side windings of the three-phase transformer and includes multiple rectifier switches. The resonant circuit group is electrically connected between the input switch group and the multiple primary-side windings. The control method disclosed herein includes the steps of: (S1) detecting the zero crossing point of the input voltage, the output voltage, and the output current of each phase of a three-phase LLC power conversion circuit; and (S2) controlling a plurality of input switches to perform switching operations based on the detection result of step (S1), controlling a plurality of rectifier switches to perform synchronous rectification switching operations, and controlling the switching state of at least one rectifier switch of the output switch group of each phase to lead or lag the switching state of the corresponding input switch based on the ratio of the output voltage to the input voltage and / or adjusting the duty cycle of all input switches of each phase to increase so that the ratio of the output voltage to the input voltage is increased, and adjusting the switching frequency of all input switches based on the output voltage, the reference voltage, and the soft switching setting conditions so that all input switches perform soft switching switching.

[0008] To achieve the above-mentioned purpose, another preferred embodiment of the present disclosure is a three-phase LLC power conversion circuit, which is structured to receive an input voltage and output an output voltage, and includes an input switch group, a three-phase transformer, a resonant circuit group, and an output switch group. The input switch group receives the input voltage and includes a plurality of input switches. The three-phase transformer includes a plurality of primary-side windings and a plurality of secondary-side windings, wherein the input switch group is electrically connected to the plurality of primary-side windings. The resonant circuit group is electrically connected between the input switch group and the plurality of primary-side windings, and includes a plurality of first resonant elements and a plurality of second resonant elements, wherein the plurality of first resonant elements are star-connected and are respectively composed of inductors or respectively composed of capacitors, and the plurality of second resonant elements are delta-connected and are respectively composed of inductors. The output switch group is electrically connected to the plurality of secondary-side windings and outputs the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 1 is a flowchart of the steps of a control method according to an embodiment of the present disclosure.

[0010] Figure 2 for Figure 1 The circuit topology diagram of the first embodiment of the three-phase LLC power conversion circuit to which the control method is applicable is shown.

[0011] Figures 3 to 6 They are Figure 2The diagram shows some waveform timing diagrams of the operation of the three-phase LLC power conversion circuit when the control unit of the three-phase LLC power conversion circuit is controlled under different implementation modes.

[0012] Figure 7 This is a circuit topology diagram of the second embodiment of the three-phase LLC power conversion circuit disclosed in the present invention.

[0013] Figure 8 This is a circuit topology diagram of the third embodiment of the three-phase LLC power conversion circuit disclosed in the present invention.

[0014] Figure 9 This is a circuit topology diagram of the fourth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention.

[0015] Figures 10 and 11 They are Figure 9 The diagram shows some waveform timing diagrams of the operation of the three-phase LLC power conversion circuit when the control unit of the three-phase LLC power conversion circuit is controlled under different implementation modes.

[0016] Figure 12 This is a circuit topology diagram of the fifth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention.

[0017] Figure 13 for Figure 12 FIG. 1 is a waveform timing diagram of a control unit of a three-phase LLC power conversion circuit when in operation.

[0018] Figure 14 This is a circuit topology diagram of the sixth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention.

[0019] Figure 15A FIG. 1 is a circuit topology diagram of a first embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0020] Figure 15B for Figure 15A The figure shows the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0021] Figure 15C for Figure 15B Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0022] Figure 16A for Figure 15A FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component. FIG.

[0023] Figure 16B for Figure 16A Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0024] Figure 17A FIG. 4 is a circuit topology diagram of a second embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0025] Figure 17B FIG. 4 is a circuit topology diagram of a third embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0026] Figure 17C for Figure 17A or Figure 17B The figure shows the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0027] Figure 17D for Figure 17C Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0028] Figure 18A for Figure 17A or Figure 17B FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component. FIG.

[0029] Figure 18B for Figure 18A Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0030] Figure 19A This is a circuit topology diagram of a fourth embodiment of the magnetic component of the present disclosure applicable to a three-phase LLC power conversion circuit.

[0031] Figure 19B for Figure 19A The figure shows the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0032] Figure 19C for Figure 19B Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0033] Figure 20A Figure 19A FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component. FIG.

[0034] Figure 20B for Figure 20A Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0035] Figure 21A FIG. 5 is a circuit topology diagram of a fifth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0036] Figure 21B for Figure 21AThe figure shows the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0037] Figure 21C for Figure 21B Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0038] Figure 22A for Figure 21A FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component. FIG.

[0039] Figure 22B for Figure 22A Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0040] Figure 23A This is a circuit topology diagram of a sixth embodiment of the magnetic component of the present disclosure applicable to a three-phase LLC power conversion circuit.

[0041] Figure 23B FIG. 4 is a circuit topology diagram of a seventh embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0042] Figure 23C FIG. 4 is a circuit topology diagram of an eighth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0043] Figure 23D FIG. 4 is a circuit topology diagram of a ninth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure.

[0044] Figure 23E for Figure 23A 、 Figure 23B 、 Figure 23C or Figure 23D The figure shows the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0045] Figure 23F for Figure 23E Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown.

[0046] Figure 24 for Figure 15A FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component.

[0047] Figure 25 for Figure 23E FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic component. FIG.

[0048] Explanation of symbols

[0049] 1, 1a, 1b, 1c, 1d, 1e: Three-phase LLC power conversion circuit

[0050] DC: Input power

[0051] V in : Input voltage

[0052] R: Load

[0053] V o : Output voltage

[0054] V ref : Reference voltage

[0055] T: three-phase transformer

[0056] 2: Input switch group

[0057] 3: Output switch group

[0058] 4: Control unit

[0059] Q1: First upper input switch

[0060] Q2: First input switch

[0061] Q3: Second upper input switch

[0062] Q4: Second input switch

[0063] Q5: Third upper input switch

[0064] Q6: The third input switch

[0065] T1, T A 、T AB :First transformer

[0066] T2, T B 、T BC : Second transformer

[0067] T3, T C 、T CA :Third transformer

[0068] L m1 , L m2 , L m3 : Magnetizing inductance

[0069] RE A1 、RE B1、 RE C1 : The first resonant element

[0070] RE A2 、RE B2、 RE C2 : The second resonant element

[0071] S R1 、S R1a :First upper rectifier switch

[0072] S R2 、S R2a :First lower rectifier switch

[0073] S R3 、S R3a :Second upper rectifier switch

[0074] S R4 、S R4a :Second lower rectifier switch

[0075] S R5 、S R5a :The third upper rectifier switch

[0076] S R6 、S R6a :The third lower rectifier switch

[0077] S R7 :Fourth upper rectifier switch

[0078] S R8 :Fourth lower rectifier switch

[0079] S R9 :Fifth upper rectifier switch

[0080] S R10 :Fifth lower rectifier switch

[0081] S R11 :Sixth upper rectifier switch

[0082] S R12 :Sixth lower rectifier switch

[0083] △T1: First time

[0084] △T2: Second time

[0085] I p1 , I M1 , I s1 , I s2 , I s3 , I C1 , I C2 , I C3 , I L1 , I L2 , I L3 :Current 41:Zero current detection circuit

[0086] 42: Gain control circuit

[0087] 43: First Drive

[0088] 44: Subtractor

[0089] 45: Compensation circuit

[0090] 46: Voltage Controlled Oscillator

[0091] 47: Second Drive

[0092] S1~S2: Steps of control method

[0093] T 1p 、T 2p 、T 3p : Primary side winding

[0094] T 1s 、T 2s 、T 3s : Secondary side winding

[0095] C r1 、C r2 、C r3 :capacitance

[0096] L r1 , L r2 and L r3 : Resonant inductor

[0097] L rBC , L rA , L rA1 : First resonant inductor

[0098] L rCA , L rB , L rB1 : Second resonant inductor

[0099] L rAB , L rC , L rC1 : The third resonant inductor

[0100] 5, 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h: Magnetic components

[0101] 6: Magnetic core

[0102] 6a: First magnetic core

[0103] 6b: Second magnetic core

[0104] 6c: Third core

[0105] L mA , L mAB : First magnetizing inductance

[0106] L mB , LmBC : Second magnetizing inductance

[0107] L mC , L mCA : The third excitation inductor

[0108] Φ LrBC , Φ LrCA , Φ LrAB , Φ mA , Φ mB , Φ mC , Φ LrA , Φ LrB , Φ LrC , Φ ΣA , Φ ΣB , Φ ΣC , Φ mAB , Φ mBC , Φ mCA , Φ LrA1 , Φ LrB1 , Φ LrC1 , Φ LrA2 , Φ LrB2 , Φ LrC2 :magnetic flux

[0109] L rA2 : Fourth resonant inductor

[0110] L rB2 : Fifth resonant inductor

[0111] L rC2 : Sixth resonant inductor DETAILED DESCRIPTION

[0112] Some typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure is capable of various variations in different implementations without departing from the scope of the present disclosure, and the descriptions and drawings are intended to be illustrative rather than limiting of the present disclosure.

[0113] Figure 1 1 is a flowchart of the steps of a control method according to an embodiment of the present disclosure. Figure 2 for Figure 1 The circuit topology diagram of the first embodiment of the three-phase LLC power conversion circuit to which the control method is applicable is shown. Figures 3 to 6 They are Figure 2 The following is a schematic diagram of some waveform timings of the operation of the three-phase LLC power conversion circuit when the control unit of the three-phase LLC power conversion circuit is controlled in different implementation modes. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 As shown, in this embodiment, the control method disclosed in the present invention can be applied to a common three-phase LLC power conversion circuit, or can be applied to Figure 2 As shown in the three-phase LLC power conversion circuit 1. Since there are many implementation methods of the three-phase LLC power conversion circuit, it is impossible to describe them one by one. Figure 2 The three-phase LLC power conversion circuit 1 is an exemplary embodiment to illustrate the control method of the present disclosure. The input end of the three-phase LLC power conversion circuit 1 is electrically connected to the input power DC and receives the input voltage V in The output end of the three-phase LLC power conversion circuit 1 is electrically connected to the load R to provide an output voltage V o to a load R. The three-phase LLC power conversion circuit 1 includes a three-phase transformer T, an input switch group 2, an output switch group 3, a control unit 4 and a resonant circuit group.

[0114] The input switch group 2 is electrically connected to the input terminals of the three-phase LLC power conversion circuit 1 and includes a first upper input switch Q1, a first lower input switch Q2, a second upper input switch Q3, a second lower input switch Q4, a third upper input switch Q5, and a third lower input switch Q6. The first upper input switch Q1 and the first lower input switch Q2 are connected in series to form a first input switch arm, and the first upper input switch Q1 and the first lower input switch Q2 are connected in series to form a second input switch arm, and the second upper input switch Q3 and the second lower input switch Q4 are connected in series to form a second input switch arm, and the second upper input switch Q3 and the second lower input switch Q4 are connected in series to form a third input switch arm, and the third upper input switch Q5 and the third lower input switch Q6 are connected in series to form a third input switch arm, and the third upper input switch Q5 and the third lower input switch Q6 are connected in series to form a third input switch arm. Furthermore, the first input switch arm, the second input switch arm, and the third input switch arm are connected in parallel to each other.

[0115] The three-phase transformer T includes a first transformer T1, a second transformer T2, and a third transformer T3. The first transformer T1, the second transformer T2, and the third transformer T3 each include a primary winding and a secondary winding. In some embodiments, the first transformer T1, the second transformer T2, and the third transformer T3 each include a magnetizing inductor L. m1 、L m2 、L m3 , respectively connected in parallel with the primary side windings of the first transformer T1, the second transformer T2, and the third transformer T3.

[0116] The resonant circuit group is electrically connected between the input switch group 2 and the primary windings of the three-phase transformer T, and includes a plurality of first resonant elements RE A1 、RE B1、 RE C1 and a plurality of second resonant elements REA2 、RE B2、 RE C2 . A plurality of first resonant elements RE A1 、RE B1、 RE C1 The first resonant element RE is star-connected (ie, Y-connected) and can be composed of inductors or capacitors. A1 The first resonant element RE is electrically connected between the first connection point and the first end of the primary winding of the first transformer T1. B1 The first resonant element RE is electrically connected between the second connection point and the first end of the primary winding of the second transformer T2. C1 The second resonant elements RE are electrically connected between the third connection point and the first end of the primary winding of the third transformer T3. A2 、RE B2、 RE C2 The second resonant elements RE are connected in a triangle (i.e., △ connection) and are respectively composed of inductors, and the respective endpoints of any two second resonant elements are electrically connected to each other and electrically connected to the second end of the primary winding of the corresponding transformer in the first transformer T1, the second transformer T2, and the third transformer T3. A2 、RE B2、 RE C2 The second resonant element RE is connected in a triangle (ie, △ connection) and is composed of inductors. A2 、RE B2、 RE C2 Compared with the star connection, the inductance value increases by 3 times, the current decreases by √3 times, the cross-sectional area of the wire decreases by 3 times, the number of winding turns increases by only √3 times, and the loss and volume remain unchanged. A2 、RE B2、 RE C2 They can also be composed of capacitors respectively.

[0117] The output switch group 3 is electrically connected between the multiple secondary windings of the three-phase transformer T and the output terminal of the three-phase LLC power conversion circuit 1. The output switch group 3 includes a first synchronous rectification switch group, a second synchronous rectification switch group, and a third synchronous rectification switch group, which are respectively coupled to the secondary windings of the corresponding transformers in the first transformer T1, the second transformer T2, and the third transformer T3. In some embodiments, the first synchronous rectification switch group includes a first upper rectifier switch S R1 , the first lower rectifier switch S R2 , the second upper rectifier switch S R3 And the second lower rectifier switch S R4 The first upper rectifier switch S R1With the first lower rectifier switch S R2 The first rectifier bridge arm is connected in series, and the second upper rectifier switch S R3 With the second lower rectifier switch S R4 The first rectifier bridge arm and the second rectifier bridge arm are connected in series to form a second rectifier bridge arm, wherein the first rectifier bridge arm and the second rectifier bridge arm are connected in parallel. The second synchronous rectifier switch group includes a third upper rectifier switch S R5 , the third lower rectifier switch S R6 , the fourth upper rectifier switch S R7 And the fourth lower rectifier switch S R8 The third upper rectifier switch S R5 With the third lower rectifier switch S R6 The third rectifier bridge arm is connected in series, and the fourth upper rectifier switch S R7 With the fourth lower rectifier switch S R8 The third rectifier bridge arm is connected in series to form a fourth rectifier bridge arm, wherein the third rectifier bridge arm and the fourth rectifier bridge arm are connected in parallel. The third synchronous rectifier switch group includes a fifth upper rectifier switch S R9 , the fifth lower rectifier switch S R10 , the sixth upper rectifier switch S R11 and the sixth lower rectifier switch S R12 The fifth upper rectifier switch S R9 With the fifth lower rectifier switch S R10 The fifth rectifier bridge arm is connected in series, and the sixth upper rectifier switch S R11 With the sixth lower rectifier switch S R12 The fifth and sixth rectifier bridge arms are connected in series to form the sixth rectifier bridge arm, and the fifth and sixth rectifier bridge arms are connected in parallel. R1 , the first lower rectifier switch S R2 , the second upper rectifier switch S R3 , the second lower rectifier switch S R4 , the third upper rectifier switch S R5 , the third lower rectifier switch S R6 , the fourth upper rectifier switch S R7 And the fourth lower rectifier switch S R8 And the fifth upper rectifier switch S R9 , the fifth lower rectifier switch S R10 , the sixth upper rectifier switch S R11 and the sixth lower rectifier switch S R12They can be active switches, such as metal oxide semiconductor field effect transistors. Since the first synchronous rectification switch group, the second synchronous rectification switch group and the third synchronous rectification switch group of the output switch group 3 of the three-phase LLC power conversion circuit 1 are full-bridge structures, the voltage stress of each rectifier switch in the first synchronous rectification switch group, the second synchronous rectification switch group and the third synchronous rectification switch group can be reduced, and the control freedom of the output switch group 3 can be increased. In the above embodiment, the first input switch bridge arm, the first transformer T1, the first resonant element RE A1 , the second resonant element RE A2 The first synchronous rectifier switch group and the first phase of the three-phase LLC power conversion circuit 1. The second input switch bridge arm, the second transformer T2, the first resonant element RE B1 , the second resonant element RE B2 The third input switch bridge arm, the third transformer T3, the first resonant element RE C1 , the second resonant element RE C2 and the third synchronous rectification switch group constitute the third phase in the three-phase LLC power conversion circuit 1.

[0118] The control unit 4 is electrically connected to the input switch group 2 and the output switch group 3 to detect the input voltage V in , output voltage V o And the zero crossing point of the output current of each phase, and according to the detection result, the first upper input switch Q1 to the third lower input switch Q6 of the input switch group 2 are controlled to switch, and the first upper rectifier switch S of the output switch group 3 are controlled. R1 To the sixth lower rectifier switch S R12 Perform synchronous rectification switching operation. Preferably, but not limited to, the switching actions of any two upper input switches in the input switch group 2 are 120 degrees apart; the switching actions of the upper input switch and the lower input switch in each input switch bridge arm of the input switch group 2 are complementary, and there is a dead time; the switching actions of the upper rectifier switch and the lower rectifier switch in each rectifier bridge arm of the output switch group 3 are complementary, and there is a dead time. In addition, the control unit 4 also controls the output voltage V o and input voltage V in The ratio of controls the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead or lag the switching state of the corresponding input switch in the input switch bridge arm of the same phase (i.e., the input switch phase angle corresponding to the at least one rectifier switch leading or lagging the conduction), and / or adjusts the duty cycle of all input switches of each input switch bridge arm in the input switch group 2 to be larger, so that the output voltage V o and input voltage V in In addition, the control unit 4 also increases according to the output voltage Vo , reference voltage V ref The switching frequencies of all input switches of the input switch group 2 are adjusted according to the soft switching setting conditions, so that all input switches of the input switch group 2 perform soft switching.

[0119] Since each phase of the three-phase LLC power conversion circuit 1 operates with a phase difference of 120 degrees, and the two switches of each phase's switch bridge arm operate in a complementary relationship, Figure 3 Only some operating parameters of the three-phase LLC power conversion circuit 1 are illustrated to exemplify the disclosed technology. Figures 3 to 6 In FIG, symbols Q1, Q3, and Q5 respectively represent the switching states of the first upper input switch Q1, the second upper input switch Q3, and the third upper input switch Q5 in the input switch group 2. Symbol Q 7A , Q 8A They represent the synchronous rectifier switches (i.e. the first upper rectifier switch S R1 With the second lower rectifier switch S R4 ) switching state, wherein the first upper rectifier switch S R1 The switching state of the first upper input switch Q1 leads the switching state of the first time △T1, and the second lower rectifier switch S R4 The switching state of the first input switch Q1 lags behind the switching state of the first input switch Q1 by a second time △T2. Symbol Q 9A , Q 10A They represent the synchronous rectifier switches (i.e. the third upper rectifier switch S R5 With the fourth lower rectifier switch S R8 ) switching state, wherein the third upper rectifier switch S R5 The switching state of the second upper input switch Q3 leads the switching state of the fourth lower rectifier switch S R8 The switching state of Q1 lags behind the switching state of the second upper input switch Q3. Symbol Q 11A , Q 12A They represent the synchronous rectifier switches (i.e. the diagonal fifth rectifier switch S) that are in phase with and corresponding to the third upper input switch Q5. R9 With the sixth lower rectifier switch S R12 ) switching state, wherein the fifth upper rectifier switch S R9 The switching state of the third upper input switch Q5 leads the switching state of the sixth lower rectifier switch S R12 The switching state of the third upper input switch Q5 lags behind the switching state of the third upper input switch Q5. p1 is the current flowing through the primary winding of the first transformer T1 of the first phase in the three-phase LLC power conversion circuit 1, I M1 is the magnetizing inductance L of the first transformer T1 of the first phase in the three-phase LLC power conversion circuit 1m1 Current, I s1 is the current flowing through the secondary winding of the first transformer T1 of the first phase in the three-phase LLC power conversion circuit 1 .

[0120] Depend on Figure 3 As shown in the figure, the control unit 4 outputs the voltage V o and input voltage V in The ratio of controls the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead the switching state of the corresponding input switch in the input switch bridge arm of the same phase, and controls the switching state of the remaining at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lag the switching state of the corresponding input switch in the input switch bridge arm of the same phase. Figure 4 As shown, the control unit 4 can also be changed to control at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to perform synchronous rectification switching, and control the switching state of the remaining at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lag behind the switching state of the corresponding input switch in the input switch bridge arm of the same phase. Figure 5 and Figure 6 As shown, the control unit 4 can also be changed to control at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to perform synchronous rectifier switching, and control the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead the switching state of the corresponding input switch in the input switch bridge arm of the same phase by a third time ΔT. In addition, Figure 6 As shown, the control unit 4 further adjusts the switching frequencies of all input switches of the input switch group 2 according to the soft switching setting conditions, so that all input switches of the input switch group 2 perform soft switching.

[0121] As can be seen from the above, the three-phase LLC power conversion circuit 1 of the present disclosure not only reduces the switching frequency range, but also has lower RMS current, peak current, and better magnetic integration. Moreover, because the control unit 4 controls two control variables, namely the phase and switching frequency of the switch, it can solve the problem of increased reactive current due to changes in the resonant frequency and enable the switch to perform soft switching more accurately.

[0122] In some embodiments, the control unit 4 includes a zero current detection circuit 41, a gain control circuit 42, a first driver 43, a subtractor 44, a compensation circuit 45, a voltage controlled oscillator 46, and a second driver 47. The first driver 43 is configured to drive the first upper rectifier switch S of the output switch group 3. R1 To the sixth lower rectifier switch S R12Operation. The zero current detection circuit 41 is electrically connected to the secondary windings of the first transformer T1, the second transformer T2, and the third transformer T3, respectively, to detect the zero crossing point of the output current of each phase of the three-phase LLC power conversion circuit 1. The gain control circuit 42 is configured to detect the input voltage V in And the output voltage V o , and receive the detection result of the zero current detection circuit 41, and according to the input voltage V in , output voltage V o The detection result of the zero crossing point of the output current of each phase is used to control the first driver 43 to drive the first upper rectifier switch S of the output switch group 3. R1 To the sixth lower rectifier switch S R12 The gain control circuit 42 also performs synchronous rectification switching operation according to the output voltage V o and input voltage V in The ratio of controls the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead or lag the switching state of the corresponding input switch in the input switch bridge arm of the same phase (i.e., the input switch phase angle corresponding to the at least one rectifier switch leading or lagging the conduction), and / or adjusts the duty cycle of all input switches of each input switch bridge arm in the input switch group 2 to be larger, so that the output voltage V o and input voltage V in The subtractor 44 is configured to convert the output voltage V o With reference voltage V ref Perform a subtraction operation. Compensation circuit 45 is configured to receive soft switching setting conditions and the calculation result of subtractor 44, and output a compensation signal based on the soft switching setting conditions and the calculation result of subtractor 44. Voltage-controlled oscillator 46 generates a switching signal having a frequency corresponding to first upper input switch Q1 through third lower input switch Q6 based on the compensation signal. Second driver 47 is configured to drive first upper input switch Q1 through third lower input switch Q6 of input switch group 2 of output switch group 3 to perform soft switching operations based on the switching signal.

[0123] Please refer to Figure 1 , the control method disclosed herein includes the following steps.

[0124] Step S1: The control unit 4 detects the input voltage V received by the three-phase LLC power conversion circuit 1. in , the output voltage V output by the three-phase LLC power conversion circuit 1 o And the zero crossing point of the output current of each phase of the three-phase LLC power conversion circuit.

[0125] Step S2, the control unit 4 controls the input voltage V in , output voltage Vo The detection result of the zero crossing point of the output current of each phase of the three-phase LLC power conversion circuit controls the first upper input switch Q1 to the third lower input switch Q6 of the input switch group 2 to switch, and controls the first upper rectifier switch S of the output switch group 3. R1 To the sixth lower rectifier switch S R12 Perform synchronous rectification switching operation and also according to the output voltage V o and input voltage V in The ratio of controls the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead or lag the switching state of the corresponding input switch in the input switch bridge arm of the same phase and / or adjusts the duty cycle of all input switches of all input switch bridge arms in the input switch group 2 of each phase to be larger, so that the output voltage V o and input voltage V in In addition, the control unit 4 also increases according to the output voltage V o , reference voltage V ref The switching frequencies of all input switches of the input switch group 2 are adjusted according to the soft switching setting conditions, so that all input switches of the input switch group 2 perform soft switching.

[0126] Figure 7 The circuit topology diagram of the second embodiment of the three-phase LLC power conversion circuit disclosed in this invention is shown in FIG. In this embodiment, the circuit structure of the three-phase LLC power conversion circuit 1a is similar to that of Figure 2 The three-phase LLC power conversion circuit 1 is shown, and its circuit structure is not further described. However, the first upper input switch Q1, the first lower input switch Q2, the second upper input switch Q3, the second lower input switch Q4, the third upper input switch Q5, and the third lower input switch Q6 in the input switch group 2 of the three-phase LLC power conversion circuit 1a of this embodiment are electrically connected in cascade.

[0127] Figure 8 FIG3 is a circuit topology diagram of the third embodiment of the three-phase LLC power conversion circuit disclosed in the present invention. In this embodiment, the circuit structure of the three-phase LLC power conversion circuit 1b is similar to that of Figure 2 The three-phase LLC power conversion circuit 1 is shown in FIG. 1 , so its circuit structure is not described in detail. The first synchronous rectifier switch group of the output switch group 3 of the three-phase LLC power conversion circuit 1b of this embodiment is changed to include a first upper rectifier switch S connected in series. R1a With the first lower rectifier switch S R2a In the half-bridge structure, the second synchronous rectification switch group of the output switch group 3 is changed to include a second upper rectification switch S connected in series. R3a With the second lower rectifier switch S R4aFor a half-bridge structure, the third synchronous rectification switch group of the output switch group 3 is changed to include a third upper rectification switch S connected in series. R5a With the third lower rectifier switch S R6a It is a half-bridge structure.

[0128] See also Figure 9 、 Figure 10 and Figure 11 ,in Figure 9 : is a circuit topology diagram of the fourth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention, Figures 10 and 11 They are Figure 9 The following is a schematic diagram of some waveform timings of the operation of the three-phase LLC power conversion circuit when the control unit of the three-phase LLC power conversion circuit is controlled under different implementations. In this embodiment, the circuit structure of the three-phase LLC power conversion circuit 1c is similar to that of Figure 8 The three-phase LLC power conversion circuit 1b is shown, so its circuit structure is not described in detail. The three-phase LLC power conversion circuit 1c of this embodiment has multiple primary windings T of the three-phase transformer T. 1p 、T 2p 、T 3p It is a triangle connection (i.e. △ connection), with multiple secondary windings T 1s 、T 2s 、T 3s It is a triangle connection (i.e. △ connection).

[0129] Depend on Figure 10 As shown in the figure, the control unit 4 outputs the voltage V o and input voltage V in The ratio of controls the switching state of at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lead the switching state of the corresponding input switch in the input switch bridge arm of the same phase (that is, the first upper rectifier switch S R1a , the second upper rectifier switch S R3a , the third upper rectifier switch S R5a The switching states of the first upper input switch Q1, the second upper input switch Q3, and the third upper input switch Q5 are respectively ahead of the switching states of the first upper input switch Q1, the second upper input switch Q3, and the third upper input switch Q5. Figure 11 As shown in the figure, the control unit 4 can also be changed to control at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to perform synchronous rectification switching according to the ratio of the output voltage Vo and the input voltage Vin, and control the switching state of the remaining at least one rectifier switch of the synchronous rectifier switch group of each phase output switch group 3 to lag behind the switching state of the corresponding input switch in the input switch bridge arm of the same phase (the first upper rectifier switch S R1a The switching state of the first upper input switch Q1 lags behind the switching state of the first upper input switch Q1).

[0130] See also Figure 12and Figure 13 ,in Figure 12 : is a circuit topology diagram of the fifth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention, Figure 13 for Figure 12 The waveform timing diagram of the control unit of the three-phase LLC power conversion circuit shown in FIG. Figure 8 The detailed circuit architecture of the three-phase LLC power conversion circuit 1b is shown as follows: Figure 8 The first resonant elements RE of the three-phase LLC power conversion circuit 1c are shown as follows: A1 、RE B1、 RE C1 It is a star connection (ie Y connection), and can be connected by capacitors C r1 、C r2 、C r3 constituted, such as Figure 12 As shown. The second resonant element RE A2 、RE B2、 RE C2 It is a triangle connection (i.e. △ connection), and is composed of resonant inductance L r1 、L r2 and L r3 I c1 , I c2 , I c3 The current flowing through the capacitor C r1 、C r2 、C r3 Current, I L1 , I L2 , I L3 The current flowing through the resonant inductor L is r1 、L r2 and L r3 The current, and I s1 , I s2 , I s3 are the currents flowing through the secondary windings of the first transformer T1 , the second transformer T2 , and the third transformer T3 , respectively.

[0131] Figure 14 FIG. 1 is a circuit topology diagram of the sixth embodiment of the three-phase LLC power conversion circuit disclosed in the present invention. In this embodiment, the circuit structure of the three-phase LLC power conversion circuit 1e is similar to that of FIG. Figure 8 The three-phase LLC power conversion circuit 1b is shown, and its circuit structure is not described in detail here. However, the first upper input switch Q1, first lower input switch Q2, second upper input switch Q3, second lower input switch Q4, third upper input switch Q5, and third lower input switch Q6 in the input switch group 2 of the three-phase LLC power conversion circuit 1e of this embodiment are electrically connected in cascade.

[0132] From the above, it can be seen that the input switch group 2 of the three-phase LLC power conversion circuit can be Figure 2 The circuit structure of the input switch group of the three-phase LLC power conversion circuit 1 shown in FIG. Figure 7 The input switch group 2 of the three-phase LLC power conversion circuit 1a shown in FIG. 1 is one of the two circuit structures. The output switch group of the three-phase LLC power conversion circuit can be Figure 2 The circuit structure of the output switch group 3 of the three-phase LLC power conversion circuit 1 is shown as follows: Figure 8 The output switch group 3 of the three-phase LLC power conversion circuit 1b shown in FIG. A1 、RE B1、 RE C1 It can be a star connection (ie, Y connection) or a triangle connection (ie, △ connection), and can be composed of capacitors or resonant inductors respectively. A2 、RE B2、 RE C2 The circuits can be star-connected (i.e., Y-connected) or delta-connected (i.e., △-connected), and can be composed of capacitors or resonant inductors, respectively. It should be emphasized that the circuit structures of the input switch group 2, the output switch group 3, and the resonant circuit group are not limited to the aforementioned embodiments and can be adjusted according to actual application requirements.

[0133] In order to improve the three-phase transformer (for example Figure 2 The three-phase transformer T) and the three-phase resonant inductor (such as Figure 2 The second resonant element RE shown A2 、RE B2、 RE C2 ) to improve core loss and reduce volume. The present disclosure also performs corresponding position matching between the three-phase transformer and the resonant inductor in the resonant element to achieve flux cancellation, thereby achieving the aforementioned purpose. Different implementation methods of position matching between the three-phase transformer and the resonant inductor in the resonant element are given below for illustration, wherein the numbers A, B, and C appearing in the subsequent specifications represent the first phase A, the second phase B, and the third phase C of the three phases, respectively. The first phase A leads the second phase B by 120 degrees, the second phase B leads the third phase C by 120 degrees, and the third phase C leads the first phase A by 120 degrees.

[0134] See also Figure 15A 、 Figure 15B and Figure 15C ,in Figure 15A This is a circuit topology diagram of the first embodiment of the magnetic component of the present disclosure applicable to a three-phase LLC power conversion circuit. Figure 15B for Figure 15A The schematic diagram of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 15C for Figure 15B Schematic diagram of partial magnetic flux vector of the magnetic component shown. The magnetic component 5 of this embodiment includes a three-phase transformer, a three-phase resonant inductor and a magnetic core group. The magnetic core group includes a single magnetic core 6. The three-phase transformer includes a first transformer T A , the second transformer T B And the third transformer T C , the first transformer T A , the second transformer T B And the third transformer T C The primary winding of the three-phase resonant inductor is connected in star (Y). rBC (BC phase inductance), second resonant inductance L rCA (CA phase inductance) and the third resonant inductance L rAB (AB phase inductance), respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected, and the first resonant inductor L rBC , the second resonant inductor L rCA and the third resonant inductor L rAB In some embodiments, the three-phase transformer further includes a first magnetizing inductor L. mA , the second excitation inductor L mB and the third magnetizing inductor L mC , respectively, with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary windings of the transformers are connected in parallel.

[0135] In the magnetic component 5, the first resonant inductor L rBC , the second resonant inductor L rCA and the third resonant inductor L rAB The first transformer T is arranged horizontally adjacent to the first side of the magnetic core 6. A , the second transformer T B And the third transformer T C The first side of the magnetic core 6 is adjacent to the second side thereof, wherein the first side is opposite to the second side. In addition, when the ratio of the inductance value of the resonant inductor to the inductance value of the corresponding excitation inductor is greater than a set value, for example, 10, the resonant inductor located in different phases is adjacent to the transformer, i.e., the first transformer T A With the first resonant inductor L rBC The second transformer T B With the second resonant inductor LrCA The third transformer T C and the third resonant inductor L rAB Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductor and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductor and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductor is opposite to that of the transformer.

[0136] exist Figure 15C In the figure, the first resonant inductor L is shown. rBC , the second resonant inductor L rCA and the third resonant inductor L rAB The respective magnetic flux Φ LrBC , Φ LrCA , Φ LrAB , also shows the first transformer T A , the second transformer T B And the third transformer T C The respective magnetic flux Φ mA , Φ mB , Φ mC , and shows the magnetic flux Φ of the resonant inductor in phase A, phase B and phase C respectively LrA , Φ LrB , Φ LrC Through the first transformer T A , the second transformer T B And the third transformer T C With the first resonant inductor L rBC , the second resonant inductor L rCA and the third resonant inductor L rAB The configuration mode can make the resonant inductance and transformer of different phases cancel each other out. For example, the first transformer T A The magnetic flux and the first resonant inductance L rBC The magnetic flux of phase A is partially offset to form the total magnetic flux Φ ΣA , thereby improving the loss of the magnetic core 6 and reducing the volume of the magnetic core 6.

[0137] See also Figure 16A and Figure 16B ,in Figure 16A for Figure 15A The schematic diagram of another variation of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component shown in FIG. Figure 16B for Figure 16A In some embodiments, when the ratio of the inductance of the resonant inductor to the inductance of the corresponding magnetizing inductor is less than a set value, the resonant inductor and the transformer located in the same phase are adjacent to each other, that is, the first transformer T A With the second resonant inductor LrCA The second transformer T B and the third resonant inductor L rAB The third transformer T C With the first resonant inductor L rBC The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0138] See also Figure 17A 、 Figure 17B 、 Figure 17C and Figure 17D ,in Figure 17A This is a circuit topology diagram of a second embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 17B FIG. 1 is a circuit topology diagram of a third embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 17C for Figure 17A or Figure 17B The schematic diagram of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 17D for Figure 17C Schematic diagram of the partial flux vector of the magnetic component shown. Figure 17A In the magnetic assembly 5a shown, the first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The primary winding of the three-phase resonant inductor is connected in star (Y). rA , the second resonant inductor L rB and the third resonant inductor L rC Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected, and the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC It is a star connection (Y connection).

[0139] exist Figure 17B In the magnetic assembly 5b shown, the first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The first resonant inductor L of the three-phase resonant inductor is 120 degrees apart. rA , the second resonant inductor LrB and the third resonant inductor L rC are independent and have a phase difference of 120 degrees, and the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC Respectively with the first transformer T A , the second transformer T B And the third transformer T C The primary side winding of the corresponding transformer is electrically connected.

[0140] In the magnetic component 5a or 5b, the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC The first transformer T is arranged horizontally adjacent to the first side of the magnetic core 6. A , the second transformer T B And the third transformer T C The first side of the magnetic core 6 is adjacent to the second side thereof, wherein the first side is opposite to the second side. In addition, the resonant inductor located in a different phase is adjacent to the transformer, i.e., the first transformer T A and the third resonant inductor L rC The second transformer T B With the first resonant inductor L rA The third transformer T C With the second resonant inductor L rB The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0141] exist Figure 17D In the figure, the first resonant inductor L is shown. rA , the second resonant inductor L rB and the third resonant inductor L rC The respective magnetic flux Φ LrA , Φ LrB , Φ LrC , also shows the first transformer T A , the second transformer T B And the third transformer T C The respective magnetic flux Φ mA , Φ mB , Φ mC Through the first transformer T A , the second transformer T B And the third transformer T C With the first resonant inductor L rA, the second resonant inductor L rB and the third resonant inductor L rC The configuration mode can make the resonant inductance and transformer of different phases cancel each other out. For example, the first transformer T A The magnetic flux and the third resonant inductor L rC The magnetic flux of phase A is partially offset to form the total magnetic flux Φ ΣA , thereby improving the loss of the magnetic core 6 and reducing the volume of the magnetic core 6.

[0142] See also Figure 18A and Figure 18B ,in Figure 18A for Figure 17A or Figure 17B The schematic diagram of another variation of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component shown in FIG. Figure 18B for Figure 18A Schematic diagram of partial magnetic flux vector of magnetic component shown in FIG. In some embodiments, the resonant inductor located in the same phase is adjacent to the transformer, that is, the first transformer T A With the first resonant inductor L rA The second transformer T B With the second resonant inductor L rB The third transformer T C and the third resonant inductor L rC The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0143] See also Figure 19A 、 Figure 19B and Figure 19C ,in Figure 19A FIG. 1 is a circuit topology diagram of a fourth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 19B for Figure 19A The schematic diagram of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 19C for Figure 19B The magnetic component 5c of this embodiment includes a three-phase transformer, a three-phase resonant inductor and a magnetic core 6. The three-phase transformer includes a first transformer T AB , the second transformer T BC And the third transformer T CA , the first transformer T AB , the second transformer T BC And the third transformer T CAThe primary winding of the three-phase resonant inductor is connected in a triangle (△ connection). The three-phase resonant inductor includes the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC , respectively, with the first transformer T AB , the second transformer T BC And the third transformer T CA The primary windings of the two corresponding transformers are electrically connected, and the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC In some embodiments, the three-phase transformer further includes a first magnetizing inductor L mAB , the second excitation inductor L mBC and the third magnetizing inductor L mCA , respectively with the first transformer T AB , the second transformer T BC And the third transformer T CA The corresponding primary windings of the transformers are connected in parallel.

[0144] In the magnetic component 5c, the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC The first transformer T is arranged horizontally adjacent to the first side of the magnetic core 6. AB , the second transformer T BC And the third transformer T CA The first side of the magnetic core 6 is adjacent to the second side thereof, wherein the first side is opposite to the second side. In addition, the resonant inductor located in a different phase is adjacent to the transformer, i.e., the first transformer T AB and the third resonant inductor L rC The second transformer T BC With the first resonant inductor L rA The third transformer T CA With the second resonant inductor L rB The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0145] exist Figure 19C In the figure, the first resonant inductor L is shown. rA , the second resonant inductor L rB and the third resonant inductor L rC The respective magnetic flux Φ LrA , Φ LrB , ΦLrC , also shows the first transformer T AB , the second transformer T BC And the third transformer T CA The respective magnetic flux Φ mAB , Φ mBC , Φ mCA , and shows the magnetic flux Φ of the resonant inductor in phase AB, phase BC and phase CA respectively LrAB , Φ LrBC , Φ LrCA Through the first transformer T AB , the second transformer T BC And the third transformer T CA With the first resonant inductor L rA , the second resonant inductor L rB and the third resonant inductor L rC The configuration mode can make the resonant inductance and transformer of different phases cancel each other out. For example, the first transformer T AB The magnetic flux and the third resonant inductor L rC The magnetic flux is partially offset, thereby improving the loss of the magnetic core 6 and reducing the volume of the magnetic core 6.

[0146] See also Figure 20A and Figure 20B ,in Figure 20A for Figure 19A The schematic diagram of another variation of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component shown in FIG. Figure 20B for Figure 20A Schematic diagram of partial magnetic flux vector of magnetic component shown in FIG. In some embodiments, the resonant inductor located in the same phase is adjacent to the transformer, that is, the first transformer T AB With the first resonant inductor L rA The second transformer T BC With the second resonant inductor L rB The third transformer T CA and the third resonant inductor L rC The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0147] See also Figure 21A 、 Figure 21B and Figure 21C ,in Figure 21A FIG. 5 is a circuit topology diagram of a fifth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 21B for Figure 21AThe schematic diagram of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 21C for Figure 21B The magnetic component 5d of this embodiment includes a three-phase transformer, a three-phase resonant inductor and a magnetic core 6. The three-phase transformer includes a first transformer T AB , the second transformer T BC And the third transformer T CA , the first transformer T AB , the second transformer T BC And the third transformer T CA The primary winding of the three-phase resonant inductor is connected in a triangle (△ connection). The three-phase resonant inductor includes the first resonant inductor L rBC , the second resonant inductor L rCA and the third resonant inductor L rAB , the third resonant inductor L rAB , the first resonant inductor L rBC , the second resonant inductor L rCA Respectively with the first transformer T AB , the second transformer T BC And the third transformer T CA The primary windings of the two corresponding transformers are electrically connected, and the first resonant inductor L rBC , the second resonant inductor L rCA and the third resonant inductor L rAB In some embodiments, the three-phase transformer further includes a first magnetizing inductor L. mAB , the second excitation inductor L mBC and the third magnetizing inductor L mCA , respectively, with the first transformer T AB , the second transformer T BC And the third transformer T CA The corresponding primary windings of the transformers are connected in parallel.

[0148] In the magnetic component 5d, the third resonant inductor L rAB , the first resonant inductor L rBC and the second resonant inductor L rCA The first transformer T is arranged horizontally adjacent to the first side of the magnetic core 6. AB , the second transformer T BC And the third transformer T CA The first side of the magnetic core 6 is adjacent to the second side thereof, wherein the first side is opposite to the second side. In addition, the resonant inductor located in a different phase is adjacent to the transformer, i.e., the first transformer T AB With the second resonant inductor L rCA The second transformer T BC and the third resonant inductor L rABThe third transformer T CA With the first resonant inductor L rBC The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0149] exist Figure 21C In the figure, the third resonant inductor L is shown. rAB , the first resonant inductor L rBC and the second resonant inductor L rCA The respective magnetic flux Φ LrAB , Φ LrBC , Φ LrCA , also shows the first transformer T AB , the second transformer T BC And the third transformer T CA The respective magnetic flux Φ mAB , Φ mBC , Φ mCA Through the first transformer T AB , the second transformer T BC And the third transformer T CA and the third resonant inductor L rAB , the first resonant inductor L rBC and the second resonant inductor L rCA The configuration mode can make the resonant inductance and transformer of different phases cancel each other out. For example, the first transformer T AB The magnetic flux and the second resonant inductance L rCA The magnetic flux is partially offset, thereby improving the loss of the magnetic core 6 and reducing the volume of the magnetic core 6.

[0150] See also Figure 22A and Figure 22B ,in Figure 22A for Figure 21A The schematic diagram of another variation of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component shown in FIG. Figure 22B for Figure 16A Schematic diagram of partial magnetic flux vector of magnetic component shown in FIG. In some embodiments, the resonant inductor located in the same phase is adjacent to the transformer, that is, the first transformer T AB and the third resonant inductor L rAB The second transformer T BC With the first resonant inductor L rBC The third transformer T CA With the second resonant inductor L rCAThe resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0151] See also Figure 23A 、 Figure 23B 、 Figure 23C 、 Figure 23D 、 Figure 23E and Figure 23F ,in Figure 23A 1 is a circuit topology diagram of a sixth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 23B FIG. 1 is a circuit topology diagram of a seventh embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 23C FIG. 8 is a circuit topology diagram of an eighth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 23D FIG. 1 is a circuit topology diagram of a ninth embodiment of a magnetic component applicable to a three-phase LLC power conversion circuit according to the present disclosure. Figure 23E for Figure 23A 、 Figure 23B 、 Figure 23C or Figure 23D The schematic diagram of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 23F for Figure 23E Schematic diagram of some of the magnetic flux vectors of the magnetic assembly shown. Figure 23A The magnetic component 5e shown includes a three-phase transformer, a first set of three-phase resonant inductors, a second set of three-phase resonant inductors and a magnetic core 6. The first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The primary winding of the three-phase transformer is connected in star (Y). A , the second transformer T B And the third transformer T C The secondary winding of is star-connected (Y-connected). The first set of three-phase resonant inductors includes the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 , the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected, and the first resonant inductor LrA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 The second set of three-phase resonant inductors includes the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 , the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding secondary winding of the transformer is electrically connected, and the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 It is a star connection (Y connection).

[0152] exist Figure 23B In the magnetic assembly 5f shown, the first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The first resonant inductor L of the first three-phase resonant inductor is 120 degrees apart and independent of each other. rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 are independent and have a phase difference of 120 degrees, and the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected. The fourth resonant inductor L of the second group of three-phase resonant inductors rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 are independent and have a phase difference of 120 degrees, and the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The secondary windings of the corresponding transformers are electrically connected.

[0153] Figure 23CIn the magnetic component 5g shown, the magnetic component 5g includes a three-phase transformer, a first set of three-phase resonant inductors, a second set of three-phase resonant inductors and a magnetic core 6. The first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The primary winding of is connected in star (Y). The first set of three-phase resonant inductors includes the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 , the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected, and the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 The second set of three-phase resonant inductors includes the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 , the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 are electrically connected to the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 The corresponding resonant inductor and the first transformer T A , the second transformer T B And the third transformer T C Between the primary windings of the corresponding transformer, and the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 It is a star connection (Y connection).

[0154] exist Figure 23D In the magnetic assembly 5h shown, the first transformer T of the three-phase transformer A , the second transformer T B And the third transformer T C The first resonant inductor L of the first three-phase resonant inductor is 120 degrees apart and independent of each other. rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 are independent and have a phase difference of 120 degrees, and the first resonant inductor LrA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 Respectively with the first transformer T A , the second transformer T B And the third transformer T C The corresponding primary winding of the transformer is electrically connected. The fourth resonant inductor L of the second group of three-phase resonant inductors rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 are independent and have a phase difference of 120 degrees, and the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 are electrically connected to the first resonant inductor L rA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 The corresponding resonant inductor and the first transformer T A , the second transformer T B And the third transformer T C Between the corresponding primary windings of the transformer.

[0155] In the magnetic component 5e, 5f, 5g or 5h, the first resonant inductor L rA1 , the second resonant inductor L rB2 and the third resonant inductor L rC2 The fourth resonant inductor L is arranged horizontally adjacent to the first side of the magnetic core 6. rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 The first transformer T is arranged horizontally adjacent to the second side of the magnetic core 6. A , the second transformer T B And the third transformer T C The first and second sides of the magnetic core 6 are arranged horizontally between the first and second sides and between the first and second three-phase resonant inductors, wherein the first side is opposite to the second side. In addition, the resonant inductors located in different phases are adjacent to the transformer, i.e., the first transformer T A and the third resonant inductor L rC1 and the sixth resonant inductor L rC2 The second transformer T B With the first resonant inductor L rA1 and the fourth resonant inductor L rA2 The third transformer T C With the second resonant inductor L rB1 and the fifth resonant inductor L rB2The resonant inductors are arranged horizontally adjacent to each other. Furthermore, the phase angle between the magnetic flux direction of the adjacent resonant inductors and the magnetic flux direction of the transformer is greater than 90 degrees and less than 270 degrees. Furthermore, because the adjacent resonant inductors and the transformer are arranged horizontally, the winding direction of the adjacent resonant inductors is opposite to the winding direction of the transformer.

[0156] exist Figure 23F In the figure, the first resonant inductor L is shown. rA1 , the second resonant inductor L rB1 , the third resonant inductor L rC1 , the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 The respective magnetic flux Φ LrA1 , Φ LrB1 , Φ LrC1 , Φ LrA2 , Φ LrB2 , Φ LrC2 , also shows the first transformer T A , the second transformer T B And the third transformer T C The respective magnetic flux Φ mA , Φ mB , Φ mC Through the first transformer T A , the second transformer T B And the third transformer T C With the first resonant inductor L rA1 , the second resonant inductor L rB1 , the third resonant inductor L rC1 , the fourth resonant inductor L rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 The configuration mode can make the resonant inductance and transformer of different phases cancel each other out. For example, the first transformer T A The magnetic flux and the third resonant inductor L rC1 The magnetic flux and the sixth resonant inductor L rC2 The magnetic flux of phase A is partially offset to form the total magnetic flux Φ ΣA , the second transformer T B The magnetic flux and the first resonant inductance L rA1 The magnetic flux and the fourth resonant inductance L rA2 The magnetic flux of phase B is partially offset to form the total magnetic flux Φ ΣB , the third transformer T C The magnetic flux and the second resonant inductance L rB1 The magnetic flux and the fifth resonant inductance L rB2 The magnetic flux of phase C is partially offset to form the total magnetic flux Φ ΣC, thereby improving the loss of the magnetic core 6 and reducing the volume of the magnetic core 6.

[0157] In the above-mentioned embodiments, the three-phase transformer and the three-phase resonant inductor of the magnetic component can also be stacked and arranged vertically on the magnetic core group, and the winding direction of the adjacent resonant inductors is the same as that of the transformer. Several possible implementation methods are listed below for exemplary explanation. Figure 24 , which is Figure 15A FIG. 1 is a schematic diagram showing another variation of the arrangement positions of the three-phase transformer and the three-phase resonant inductor of the magnetic assembly of the embodiment shown in FIG. Figure 24 As shown, the circuit structure of the magnetic component of this embodiment is similar to Figure 15A The magnetic component 5 shown in the figure, wherein the magnetic core assembly of the magnetic component of this embodiment comprises a first magnetic core 6a and a second magnetic core 6b, and the first magnetic core 6a is vertically arranged above the second magnetic core 6b. rBC , the second resonant inductor L rCA and the third resonant inductor L rAB The first transformer T is provided on the first magnetic core 6a. A , the second transformer T B And the third transformer T C In addition, the resonant inductor located in different phases is adjacent to the transformer, that is, the first transformer T A With the first resonant inductor L rBC The second transformer T is set vertically adjacent to B With the second resonant inductor L rCA The third transformer T is set vertically adjacent to C and the third resonant inductor L rAB The resonant inductors are arranged vertically adjacent to each other, and the phase angle between the magnetic flux direction of the vertically adjacent resonant inductors and the magnetic flux direction of the transformer is between -90 degrees and +90 degrees, wherein the positive direction of the magnetic flux direction is from bottom to top, and the winding direction of the adjacent resonant inductors is the same as the winding direction of the transformer.

[0158] Figure 25 for Figure 23E The schematic diagram of another variation of the arrangement position of the three-phase transformer and the three-phase resonant inductor of the magnetic component is shown. Figure 25 As shown, the circuit structure of the magnetic component of this embodiment is similar to Figure 23A 、 Figure 23B 、 Figure 23C or Figure 23D In the magnetic components 5e, 5f, 5g or 5h shown in FIG, the magnetic core assembly of the magnetic component of this embodiment comprises a first magnetic core 6a, a second magnetic core 6b, and a third magnetic core 6c. The first magnetic core 6a is vertically arranged above the second magnetic core 6b, and the second magnetic core 6b is vertically arranged above the third magnetic core 6c. The first resonant inductor LrA1 , the second resonant inductor L rB1 and the third resonant inductor L rC1 The first transformer T is provided on the first magnetic core 6a. A , the second transformer T B And the third transformer T C The fourth resonant inductor L is provided on the second magnetic core 6b. rA2 , the fifth resonant inductor L rB2 and the sixth resonant inductor L rC2 In addition, the resonant inductor located in different phases is adjacent to the transformer, that is, the first transformer T A and the third resonant inductor L rC1 and the sixth resonant inductor L rC2 The second transformer T is set vertically adjacent to B With the first resonant inductor L rA1 and the fourth resonant inductor L rA2 The third transformer T is set vertically adjacent to C With the second resonant inductor L rB1 and the fifth resonant inductor L rB2 The phase angle between the magnetic flux direction of the vertically adjacent resonant inductor and the magnetic flux direction of the transformer is between -90 degrees and +90 degrees, wherein the positive direction of the magnetic flux is from bottom to top, and the winding direction of the adjacent resonant inductor is the same as the winding direction of the transformer.

[0159] In summary, the present disclosure provides a three-phase LLC power conversion circuit and control method thereof, which not only reduces the switching frequency range of the three-phase power conversion circuit, but also achieves lower RMS current, lower peak current, and improved magnetic integration. Furthermore, because the control unit of the three-phase power conversion circuit controls two control variables: the phase shift and frequency of the switches, it can address the increase in reactive current caused by changes in the resonant frequency and enable more precise soft switching of the switches.

Claims

1. A control method, applied to a three-phase LLC power conversion circuit, the three-phase LLC power conversion circuit receiving an input voltage and outputting an output voltage, and comprising a three-phase transformer, an input switch group, an output switch group, and a resonant circuit group, wherein the input switch group is electrically connected to a plurality of primary-side windings of the three-phase transformer and comprises a plurality of input switches, the output switch group is electrically connected to a plurality of secondary-side windings of the three-phase transformer and comprises a plurality of rectifier switches, and the resonant circuit group is electrically connected between the input switch group and the plurality of primary-side windings, the control method comprising: Step S1: Detecting a zero crossing point of the input voltage, the output voltage, and an output current of each phase of the three-phase LLC power conversion circuit; and Step S2: Controlling the plurality of input switches to perform switching operations based on the detection result of step S1, controlling the plurality of rectifier switches to perform synchronous rectification switching operations, and controlling the switching state of at least one rectifier switch of the output switch group of each phase to lead or lag the switching state of the corresponding input switch based on the ratio of the output voltage to the input voltage, and / or adjusting the duty cycle of all the input switches of each phase to increase so as to increase the ratio of the output voltage to the input voltage, and adjusting the switching frequency of all the input switches based on the output voltage, a reference voltage, and a soft switching setting condition so that all the input switches perform soft switching.

2. The control method of claim 1 , wherein in step S2, the switching state of at least one rectifier switch of each phase is controlled to lead the switching state of the corresponding input switch according to the ratio of the output voltage to the input voltage, and the switching state of the remaining at least one rectifier switch of each phase is controlled to lag the switching state of the corresponding input switch.

3. The control method of claim 1 , wherein in step S2 , at least one rectifier switch of each phase is controlled to perform synchronous rectification switching, and the switching state of the remaining at least one rectifier switch of each phase is controlled to lead the switching state of the corresponding input switch.

4. The control method of claim 1 , wherein in step S2 , at least one rectifier switch of each phase is controlled to perform synchronous rectification switching, and a switching state of the remaining at least one rectifier switch of each phase is controlled to lag behind a switching state of the corresponding input switch.

5. The control method of claim 1 , wherein the plurality of input switches include a first upper input switch, a first lower input switch, a second upper input switch, a second lower input switch, a third upper input switch, and a third lower input switch, wherein the first upper input switch and the first lower input switch are connected in series to form a first input switch bridge arm, the second upper input switch and the second lower input switch are connected in series to form a second input switch bridge arm, and the third upper input switch and the third lower input switch are connected in series to form a third input switch bridge arm, wherein the first input switch bridge arm, the second input switch bridge arm, and the third input switch bridge arm are connected in parallel with each other.

6. The control method of claim 1 , wherein the plurality of input switches comprises a first upper input switch, a first lower input switch, a second upper input switch, a second lower input switch, a third upper input switch, and a third lower input switch, wherein the first upper input switch is connected in series with the first lower input switch, the second upper input switch is connected in series with the second lower input switch, and the third upper input switch is connected in series with the third lower input switch, wherein the first upper input switch, the first lower input switch, the second upper input switch, the second lower input switch, the third upper input switch, and the third lower input switch are electrically connected in a cascade manner.

7. The control method according to claim 1 , wherein the plurality of rectifier switches include a first upper rectifier switch, a first lower rectifier switch, a second upper rectifier switch, a second lower rectifier switch, a third upper rectifier switch, a third lower rectifier switch, a fourth upper rectifier switch, a fourth lower rectifier switch, a fifth upper rectifier switch, a fifth lower rectifier switch, a sixth upper rectifier switch, and a sixth lower rectifier switch, wherein the first upper rectifier switch and the first lower rectifier switch are connected in series to form a first rectifier bridge arm, and the second upper rectifier switch and the second lower rectifier switch are connected in series to form a first rectifier bridge arm. Two rectifier bridge arms, the first rectifier bridge arm is connected in parallel with the second rectifier bridge arm, wherein the third upper rectifier switch is connected in series with the third lower rectifier switch to form a third rectifier bridge arm, the fourth upper rectifier switch is connected in series with the fourth lower rectifier switch to form a fourth rectifier bridge arm, the third rectifier bridge arm is connected in parallel with the fourth rectifier bridge arm, wherein the fifth upper rectifier switch is connected in series with the fifth lower rectifier switch to form a fifth rectifier bridge arm, the sixth upper rectifier switch is connected in series with the sixth lower rectifier switch to form a sixth rectifier bridge arm, and the fifth rectifier bridge arm is connected in parallel with the sixth rectifier bridge arm. 8 . The control method according to claim 7 , wherein the plurality of rectifier switches are respectively constituted by active switches.

9. The control method according to claim 1 , wherein the resonant circuit comprises a plurality of first resonant elements and a plurality of second resonant elements, the plurality of first resonant elements being star-connected and each consisting of an inductor or a capacitor, and the plurality of second resonant elements being delta-connected and each consisting of another inductor or another capacitor. 10 . The control method according to claim 9 , wherein the plurality of primary-side windings of the three-phase transformer are connected in a delta configuration, and the plurality of secondary-side windings are connected in a delta configuration.

11. A three-phase LLC power conversion circuit, receiving an input voltage and outputting an output voltage, comprising: an input switch group, receiving the input voltage and comprising a plurality of input switches; a three-phase transformer comprising a plurality of primary-side windings and a plurality of secondary-side windings, wherein the input switch group is electrically connected to the plurality of primary-side windings; a resonant circuit group electrically connected between the input switch group and the plurality of primary-side windings, and comprising a plurality of first resonant elements and a plurality of second resonant elements, wherein the plurality of first resonant elements are star-connected and each comprised of an inductor or a capacitor, and the plurality of second resonant elements are delta-connected and each comprised of another inductor or another capacitor; and An output switch group is electrically connected to the plurality of secondary side windings and includes a plurality of rectifier switches for outputting the output voltage.

12. The three-phase LLC power conversion circuit of claim 11 , further comprising a control unit electrically connected to the input switch group and the output switch group, configured to detect a zero crossing point of the input voltage, the output voltage, and an output current of each phase of the three-phase LLC power conversion circuit, and to control the plurality of input switches to perform switching operations based on the detection results, control the plurality of rectifier switches to perform synchronous rectification switching operations, and control the switching state of at least one rectifier switch of the output switch group of each phase to lead or lag the switching state of the corresponding input switch based on a ratio of the output voltage to the input voltage, and / or adjust the duty cycle of all the input switches of each phase to increase the ratio of the output voltage to the input voltage, and adjust the switching frequency of all the input switches based on the output voltage, a reference voltage, and a soft switching setting condition, so that all the input switches perform soft switching.

13. The three-phase LLC power conversion circuit as described in claim 12, wherein the control unit controls the switching state of at least one rectifier switch of each phase to lead the switching state of the corresponding input switch according to the ratio of the output voltage to the input voltage, and controls the switching state of the remaining at least one rectifier switch of each phase to lag the switching state of the corresponding input switch.

14. The three-phase LLC power conversion circuit as claimed in claim 12, wherein the control unit controls at least one rectifier switch of each phase to perform synchronous rectification switching, and controls the switching state of the remaining at least one rectifier switch of each phase to lead the switching state of the corresponding input switch.

15. The three-phase LLC power conversion circuit as claimed in claim 12, wherein the control unit controls at least one rectifier switch of each phase to perform synchronous rectification switching, and controls the switching state of the remaining at least one rectifier switch of each phase to lag behind the switching state of the corresponding input switch.

16. The three-phase LLC power conversion circuit of claim 11 , wherein the plurality of input switches include a first upper input switch, a first lower input switch, a second upper input switch, a second lower input switch, a third upper input switch, and a third lower input switch, wherein the first upper input switch and the first lower input switch are connected in series to form a first input switch arm, the second upper input switch and the second lower input switch are connected in series to form a second input switch arm, and the third upper input switch and the third lower input switch are connected in series to form a third input switch arm, wherein the first input switch arm, the second input switch arm, and the third input switch arm are connected in parallel with each other.

17. The three-phase LLC power conversion circuit of claim 11 , wherein the plurality of input switches include a first upper input switch, a first lower input switch, a second upper input switch, a second lower input switch, a third upper input switch, and a third lower input switch, wherein the first upper input switch is connected in series with the first lower input switch, the second upper input switch is connected in series with the second lower input switch, and the third upper input switch is connected in series with the third lower input switch, wherein the first upper input switch, the first lower input switch, the second upper input switch, the second lower input switch, the third upper input switch, and the third lower input switch are electrically connected in a cascade relationship.

18. The three-phase LLC power conversion circuit of claim 11 , wherein the plurality of rectifier switches include a first upper rectifier switch, a first lower rectifier switch, a second upper rectifier switch, a second lower rectifier switch, a third upper rectifier switch, a third lower rectifier switch, a fourth upper rectifier switch, a fourth lower rectifier switch, a fifth upper rectifier switch, a fifth lower rectifier switch, a sixth upper rectifier switch, and a sixth lower rectifier switch, wherein the first upper rectifier switch and the first lower rectifier switch are connected in series to form a first rectifier bridge arm, and the second upper rectifier switch and the second lower rectifier switch are connected in series to form a first rectifier bridge arm. A second rectifier bridge arm is formed, the first rectifier bridge arm is connected in parallel with the second rectifier bridge arm, wherein the third upper rectifier switch is connected in series with the third lower rectifier switch to form a third rectifier bridge arm, the fourth upper rectifier switch is connected in series with the fourth lower rectifier switch to form a fourth rectifier bridge arm, the third rectifier bridge arm is connected in parallel with the fourth rectifier bridge arm, wherein the fifth upper rectifier switch is connected in series with the fifth lower rectifier switch to form a fifth rectifier bridge arm, the sixth upper rectifier switch is connected in series with the sixth lower rectifier switch to form a sixth rectifier bridge arm, and the fifth rectifier bridge arm is connected in parallel with the sixth rectifier bridge arm.

19. The three-phase LLC power conversion circuit as claimed in claim 18, wherein the plurality of rectifier switches are respectively constituted by active switches.

20. The three-phase LLC power conversion circuit of claim 11 , wherein the resonant circuit comprises a plurality of first resonant elements and a plurality of second resonant elements, the plurality of first resonant elements being star-connected and each consisting of an inductor or a capacitor, and the plurality of second resonant elements being delta-connected and each consisting of the inductor.

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