LLC resonant circuit for DC-DC charging module

By adopting four sets of resonant modules, transformers and rectifier modules in the LLC resonant circuit, combining the connection method between the drive module and the power switch tube, the problems of insufficient voltage gain range and instability in the prior art are solved, and the voltage gain range is widened and the loss is reduced.

CN119921560APending Publication Date: 2025-05-02SUZHOU XINYUAN ELECTRONIC TECH CO LTD
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Patent Information

Application Number
CN202510045722.7
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-01-13
Publication Date
2025-05-02

AI Technical Summary

Technical Problem

In the case of wide voltage input, in order to achieve high gain, the quality factor Q value and voltage ratio need to be very small, resulting in large frequency changes, unstable system and increased loss, and the method of widening the voltage gain range is complex to control.

Method used

Four sets of resonance modules, transformers and rectifier modules are used to connect to the gate of the power switch tube through the signal output end of the driving module to realize the on-off of the power switch tube, and adjust each power switch tube to broaden the voltage gain range and reduce losses.

Benefits of technology

It achieves widening of the voltage gain range, reduces losses, ensures efficient and stable operation of the system, and is suitable for different application scenarios.

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Abstract

According to the LLC resonant circuit for the DC-DC charging module provided by the invention, the voltage gain range can be widened, the loss is reduced, and the stability is good; comprising a resonant cavity, transformers and rectification modules, the resonant cavity comprises a first resonance module to a fourth resonance module, the transformers are divided into a first transformer to a fourth transformer, and the rectification modules are divided into a first rectification module to a fourth rectification module; each of the first resonance module to the fourth resonance module comprises two power switch tubes, and a signal output end of the driving module is connected with grid electrodes of the power switch tubes so as to drive the power switch tubes to realize corresponding on-off; the first resonance module is connected with the first transformer and the first rectification module in sequence, the second resonance module is connected with the second transformer and the second rectification module in sequence, the third resonance module is connected with the third transformer and the third rectification module in sequence, and the fourth resonance module is connected with the fourth transformer and the fourth rectification module in sequence. The first transformer is connected with the second transformer, and the third transformer is connected with the fourth transformer.
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Description

Technical Field

[0001] The invention relates to the technical field of DC-DC direct current charging, in particular to an LLC resonant circuit for a DC-DC charging module. Background Art

[0002] With the rapid development and widespread use of new energy vehicles, the demand for stable and fast charging is also increasing. Among them, the DC-DC charging module used to realize DC power level conversion is widely used in new energy vehicle charging equipment. The DC-DC charging module needs to work at a certain switching frequency and requires a resonant circuit to stabilize the output voltage of DCDC. The LLC resonant circuit can achieve soft switching characteristics within the full load range and is widely used in high-frequency situations. For this reason, the LLC resonant circuit is widely used in wide voltage input conditions, but when the input voltage is too wide, in order to achieve high gain, the quality factor Q value and voltage ratio in the LLC resonant circuit need to be very small, which leads to slight frequency changes. If the voltage regulation is too wide, it will cause system instability and increase losses. In addition, the current method to widen the voltage gain range of the LLC resonant circuit is to obtain a wider output voltage range by switching the switch mode, but this method is more complicated to control. Summary of the invention

[0003] In view of the defects existing in the prior art, the present invention provides an LLC resonant circuit for a DC-DC charging module, which can not only broaden the voltage gain range and reduce the loss, but also has good stability.

[0004] The present invention adopts the following technical scheme: an LLC resonant circuit for a DC-DC charging module, comprising a resonant cavity, a transformer, and a rectifier module. The resonant cavity comprises a first resonant module, a second resonant module, a third resonant module, and a fourth resonant module. The transformer is divided into a first transformer, a second transformer, a third transformer, and a fourth transformer. The rectifier module is divided into a first rectifier module, a second rectifier module, a third rectifier module, and a fourth rectifier module. The first resonant module, the second resonant module, the third resonant module, and the fourth resonant module have the same circuit structure and all include two power switch tubes. The signal output end of the driving module is connected to the gate of the power switch tube to drive the power switch tube to realize corresponding switching. The first resonant module is connected to the first transformer and the first rectifier module in sequence, the second resonant module is connected to the second transformer and the second rectifier module in sequence, the third resonant module is connected to the third transformer and the third rectifier module in sequence, the fourth resonant module is connected to the fourth transformer and the fourth rectifier module in sequence, the first transformer is connected to the second transformer, and the third transformer is connected to the fourth transformer.

[0005] Furthermore, the driving module has 8 signal output terminals, and the 8 signal output terminals are connected to the gates of the power switch tubes one by one; the driving module is connected to the controller, and outputs corresponding on or off signals according to the 8 PWM driving signals of the controller;

[0006] Furthermore, the first resonance module further includes capacitor C1, capacitor C2, capacitor C3, and inductor L1; the second resonance module further includes capacitor C4, capacitor C5, capacitor C6, and inductor L2; the third resonance module further includes capacitor C7, capacitor C8, capacitor C9, and inductor L3; the fourth resonance module further includes capacitor C10, capacitor C11, capacitor C12, and inductor L4; the power switch tube is divided into power switch tube Q1 to power switch tube Q8, and the gates of the power switch tubes Q1 to power switch tube Q8 are respectively connected to the driving module The eight signal output ends are connected correspondingly; one end of the capacitor C1 is connected to the drain of the power switch tube Q1, the source of the power switch tube Q1 is connected to one end of the inductor L1 and the drain of the power switch tube Q2, the other end of the inductor L1 is connected to one end of the capacitor C3, the other end of the capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the source of the power switch tube Q2; one end of the capacitor C4 is connected to the drain of the power switch tube Q3, the source of the power switch tube Q3 is connected to the drain of the power switch tube Q3, and the drain of the power switch tube Q3 is connected to the drain of the power switch tube Q3. One end of the inductor L2 is connected to one end of the inductor L2 and the drain of the power switch tube Q4, the other end of the inductor L2 is connected to one end of the capacitor C6, the other end of the capacitor C4 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the source of the power switch tube Q4; one end of the capacitor C7 is connected to the drain of the power switch tube Q5, the source of the power switch tube Q5 is connected to one end of the inductor L3 and the drain of the power switch tube Q6, the other end of the inductor L3 is connected to one end of the capacitor C9, and the The other end of the capacitor C7 is connected to one end of the capacitor C8, and the other end of the capacitor C8 is connected to the source of the power switch tube Q6; one end of the capacitor C10 is connected to the drain of the power switch tube Q7, and the source of the power switch tube Q7 is connected to one end of the inductor L4 and the drain of the power switch tube Q8, the other end of the inductor L4 is connected to one end of the capacitor C12, the other end of the capacitor C10 is connected to one end of the capacitor C11, and the other end of the capacitor C11 is connected to the source of the power switch tube Q8;

[0007] Further, the first rectifier module includes a capacitor C13 and diodes D11 to D14; the second rectifier module includes a capacitor C14 and diodes D21 to D24; the third rectifier module includes a capacitor C15 and diodes D31 to D34; the fourth rectifier module includes a capacitor C16 and diodes D41 to D44; one end of the primary coil of the first transformer is connected to the other end of the capacitor C3, the other end of the primary coil of the first transformer is connected to one end of the primary coil of the second transformer, the other end of the primary coil of the second transformer is connected to the other end of the capacitor C6, one end of the secondary coil of the first transformer is connected to the positive electrode of the diode D11, the positive electrode of the diode D21, and the positive electrode of the diode D31. The cathode of the diode D13 is connected to each other, the other end of the secondary coil of the first transformer is connected to the anode of the diode D12 and the cathode of the diode D14, the cathode of the diode D11 and the cathode of the diode D12 are connected to one end of the capacitor C13, the anode of the diode D13 and the anode of the diode D14 are connected to the other end of the capacitor C13; one end of the secondary coil of the second transformer is connected to the anode of the diode D21 and the cathode of the diode D23, the other end of the secondary coil of the second transformer is connected to the anode of the diode D22 and the cathode of the diode D24, the cathode of the diode D21 and the cathode of the diode D22 are connected to the cathode of the diode D23. The negative electrode of the diode D23 and the positive electrode of the diode D24 are connected to one end of the capacitor C14, and the positive electrode of the diode D23 and the positive electrode of the diode D24 are connected to the other end of the capacitor C14; one end of the primary coil of the third transformer is connected to the other end of the capacitor C9, the other end of the primary coil of the third transformer is connected to one end of the primary coil of the fourth transformer, and the other end of the primary coil of the fourth transformer is connected to the other end of the capacitor C12, one end of the secondary coil of the third transformer is connected to the positive electrode of the diode D31 and the negative electrode of the diode D33, and the other end of the secondary coil of the third transformer is connected to the positive electrode of the diode D32 and the negative electrode of the diode D34. The cathode of the diode D31 and the cathode of the diode D32 are connected to one end of the capacitor C15, and the anode of the diode D33 and the anode of the diode D34 are connected to the other end of the capacitor C15; one end of the secondary coil of the fourth transformer is connected to the anode of the diode D41 and the cathode of the diode D43, and the other end of the secondary coil of the fourth transformer is connected to the anode of the diode D42 and the cathode of the diode D44, the cathode of the diode D41 and the cathode of the diode D42 are connected to one end of the capacitor C16, and the anode of the diode D43 and the anode of the diode D44 are connected to the other end of the capacitor C16;

[0008] Further, the gate terminal signals of the power switch tube Q1 and the power switch tube Q2 are out of phase by 180°, and the duty cycles of the power switch tubes Q1 and Q2 are both 15% to 50%; the gate terminal signals of the power switch tubes Q3 and Q4 are out of phase by 180°, and the duty cycles of the power switch tubes Q3 and Q4 are both 50%; the gate terminal signals of the power switch tubes Q5 and Q6 are out of phase by 180°, and the duty cycles of the power switch tubes Q5 and Q6 are both 15% to 50%; the gate terminal signals of the power switch tubes Q7 and Q8 are out of phase by 180°, and the duty cycles of the power switch tubes Q7 and Q8 are both 50%; the gate terminal signals of the power switch tubes Q1 and Q5 are out of phase by 90°;

[0009] Furthermore, the gate-end signal of the power switch tube Q1 has the same phase as the gate-end signal of the power switch tube Q4; the gate-end signal of the power switch tube Q2 has the same phase as the gate-end signal of the power switch tube Q3; the gate-end signal of the power switch tube Q5 has the same phase as the gate-end signal of the power switch tube Q8; the gate-end signal of the power switch tube Q6 has the same phase as the gate-end signal of the power switch tube Q7.

[0010] The beneficial effect of the present invention is that by setting four groups of resonance modules, transformers, and rectifier modules, the signal output end of the driving module is correspondingly connected to the power switch tube in the resonance module to realize the corresponding on and off of the power switch tube. Each power switch tube can be easily adjusted to widen the voltage gain range, reduce losses, meet the needs of different application scenarios, and ensure efficient and stable operation, and has good use value. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural block diagram of the present invention;

[0012] Figure 2 It is a circuit schematic diagram of the present invention. DETAILED DESCRIPTION

[0013] like Figure 1 , Figure 2As shown, an LLC resonant circuit for a DC-DC charging module of the present invention includes a resonant cavity, a transformer, and a rectifier module. The resonant cavity includes a first resonant module, a second resonant module, a third resonant module, and a fourth resonant module. The transformer is divided into a first transformer T1, a second transformer T2, a third transformer T3, and a fourth transformer T4. The rectifier module is divided into a first rectifier module, a second rectifier module, a third rectifier module, and a fourth rectifier module. The circuit structures of the first resonant module, the second resonant module, the third resonant module, and the fourth resonant module are the same, and all include two power switch tubes. The signal output end of the driving module is connected to the gate of the power switch tube to drive the power switch tube to realize corresponding switching. The first resonant module is connected to the first transformer T1 and the first rectifier module in sequence, the second resonant module is connected to the second transformer T2 and the second rectifier module in sequence, the third resonant module is connected to the third transformer T3 and the third rectifier module in sequence, the fourth resonant module is connected to the fourth transformer T4 and the fourth rectifier module in sequence, the first transformer T1 is connected to the second transformer T2, and the third transformer T3 is connected to the fourth transformer T4.

[0014] The driving module has 8 signal output terminals, and the 8 signal output terminals are connected to the gates of the power switch tubes one by one; the driving module is connected to the controller, and outputs corresponding on or off signals according to the 8 PWM drive signals of the controller; the controller and the driving module adopt existing circuit modules or devices, and the controller can output 8 PWM drive signals (i.e. PWM1~PWM8), and can adjust the frequency, duty cycle and phase shift angle of these 8 PWM drive signals; the gate terminal signal of the power switch tube refers to the corresponding PWM drive signal, so that the power switch tube is turned on and off accordingly according to the corresponding PWM drive signal.

[0015] The first resonance module also includes capacitor C1, capacitor C2, capacitor C3, and inductor L1; the second resonance module also includes capacitor C4, capacitor C5, capacitor C6, and inductor L2; the third resonance module also includes capacitor C7, capacitor C8, capacitor C9, and inductor L3; the fourth resonance module also includes capacitor C10, capacitor C11, capacitor C12, and inductor L4; the power switch tube is divided into power switch tube Q1 to power switch tube Q8, and the gates of the power switch tube Q1 to power switch tube Q8 are respectively connected to the 8 signal output terminals of the driving module; one end of the capacitor C1 is connected to the drain of the power switch tube Q1, the source of the power switch tube Q1 is connected to one end of the inductor L1 and the drain of the power switch tube Q2, the other end of the inductor L1 is connected to one end of the capacitor C3, the other end of the capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the source of the power switch tube Q2; one end of the capacitor C4 is connected to the drain of the power switch tube Q3, and the power switch tube Q The source of the power switch tube Q3 is connected to one end of the inductor L2 and the drain of the power switch tube Q4, the other end of the inductor L2 is connected to one end of the capacitor C6, the other end of the capacitor C4 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the source of the power switch tube Q4; one end of the capacitor C7 is connected to the drain of the power switch tube Q5, the source of the power switch tube Q5 is connected to one end of the inductor L3 and the drain of the power switch tube Q6, and the other end of the inductor L3 is connected to one end of the capacitor C9. , the other end of capacitor C7 is connected to one end of capacitor C8, and the other end of capacitor C8 is connected to the source of power switch tube Q6; one end of capacitor C10 is connected to the drain of power switch tube Q7, the source of power switch tube Q7 is connected to one end of inductor L4 and the drain of power switch tube Q8, the other end of inductor L4 is connected to one end of capacitor C12, the other end of capacitor C10 is connected to one end of capacitor C11, and the other end of capacitor C11 is connected to the source of power switch tube Q8.

[0016] The first rectifier module includes a capacitor C13 and diodes D11 to D14; the second rectifier module includes a capacitor C14 and diodes D21 to D24; the third rectifier module includes a capacitor C15 and diodes D31 to D34; the fourth rectifier module includes a capacitor C16 and diodes D41 to D44; one end of the primary coil of the first transformer T1 is connected to the other end of the capacitor C3, the other end of the primary coil of the first transformer T1 is connected to one end of the primary coil of the second transformer T2, the other end of the primary coil of the second transformer T2 is connected to the other end of the capacitor C6, one end of the secondary coil of the first transformer T1 is connected to the positive electrode of the diode D11, the The negative electrode of D13 is connected to each other, the other end of the secondary coil of the first transformer T1 is connected to the positive electrode of the diode D12 and the negative electrode of the diode D14, the negative electrode of the diode D11 and the negative electrode of the diode D12 are connected to one end of the capacitor C13, the positive electrode of the diode D13 and the positive electrode of the diode D14 are connected to the other end of the capacitor C13; one end of the secondary coil of the second transformer T2 is connected to the positive electrode of the diode D21 and the negative electrode of the diode D23, the other end of the secondary coil of the second transformer T2 is connected to the positive electrode of the diode D22 and the negative electrode of the diode D24, the negative electrode of the diode D21 and the positive electrode of the diode D22 are connected The negative electrode is connected to one end of the capacitor C14, the positive electrode of the diode D23 and the positive electrode of the diode D24 are connected to the other end of the capacitor C14; one end of the primary coil of the third transformer T3 is connected to the other end of the capacitor C9, the other end of the primary coil of the third transformer T3 is connected to one end of the primary coil of the fourth transformer T4, the other end of the primary coil of the fourth transformer T4 is connected to the other end of the capacitor C12, one end of the secondary coil of the third transformer T3 is connected to the positive electrode of the diode D31 and the negative electrode of the diode D33, and the other end of the secondary coil of the third transformer T3 is connected to the positive electrode of the diode D32 and the negative electrode of the diode D34 The cathode of the diode D31 and the cathode of the diode D32 are connected to one end of the capacitor C15, and the anode of the diode D33 and the anode of the diode D34 are connected to the other end of the capacitor C15; one end of the secondary coil of the fourth transformer T4 is connected to the anode of the diode D41 and the cathode of the diode D43, the other end of the secondary coil of the fourth transformer T4 is connected to the anode of the diode D42 and the cathode of the diode D44, the cathode of the diode D41 and the cathode of the diode D42 are connected to one end of the capacitor C16, and the anode of the diode D43 and the anode of the diode D44 are connected to the other end of the capacitor C16.

[0017] The gate terminal signals of the power switch tubes Q1 and Q2 are out of phase by 180°, and the duty ratios of the power switch tubes Q1 and Q2 are both 15% to 50%; the gate terminal signals of the power switch tubes Q3 and Q4 are out of phase by 180°, and the duty ratios of the power switch tubes Q3 and Q4 are both 50%; the gate terminal signals of the power switch tubes Q5 and Q6 are out of phase by 180°, and the duty ratios of the power switch tubes Q5 and Q6 are both 15% to 50%; the gate terminal signals of the power switch tubes Q7 and Q8 are out of phase by 180°, and the duty ratios of the power switch tubes Q5 and Q6 are both 15% to 50%. 180°, the duty cycles of the power switch tubes Q7 and Q8 are both 50%; the gate terminal signals of the power switch tubes Q1 and Q5 are out of phase by 90°; further, the gate terminal signal of the power switch tube Q1 has the same phase as the gate terminal signal of the power switch tube Q4; the gate terminal signal of the power switch tube Q2 has the same phase as the gate terminal signal of the power switch tube Q3; the gate terminal signal of the power switch tube Q5 has the same phase as the gate terminal signal of the power switch tube Q8; the gate terminal signal of the power switch tube Q6 has the same phase as the gate terminal signal of the power switch tube Q7.

[0018] The control method in the present invention is relatively simple, and can allow the frequency and duty cycle of each PWM drive signal to be adjusted, and the voltage gain range to be widened by accurately controlling 8 power switch tubes, so as to achieve efficient and stable operation of the entire circuit and reduce driving losses. Four voltage outputs are achieved through the first rectifier module, the second rectifier module, the third rectifier module, and the fourth rectifier module.

[0019] Figure 2 The Drive in is used as the drive module.

[0020] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0021] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An LLC resonant circuit for a DC-DC charging module, comprising a resonant cavity, a transformer, and a rectifier module, characterized in that: The resonant cavity includes a first resonant module, a second resonant module, a third resonant module, and a fourth resonant module. The transformer is divided into a first transformer, a second transformer, a third transformer, and a fourth transformer. The rectifier module is divided into a first rectifier module, a second rectifier module, a third rectifier module, and a fourth rectifier module. The first resonant module, the second resonant module, the third resonant module, and the fourth resonant module have the same circuit structure and all include two power switch tubes. The signal output end of the driving module is connected to the gate of the power switch tube to drive the power switch tube to achieve corresponding switching. The first resonant module is connected to the first transformer and the first rectifier module in sequence, the second resonant module is connected to the second transformer and the second rectifier module in sequence, the third resonant module is connected to the third transformer and the third rectifier module in sequence, the fourth resonant module is connected to the fourth transformer and the fourth rectifier module in sequence, the first transformer is connected to the second transformer, and the third transformer is connected to the fourth transformer.

2. The LLC resonant circuit for a DC-DC charging module according to claim 1, characterized in that: The driving module has 8 signal output terminals, and the 8 signal output terminals are connected to the gates of the power switch tubes in a one-to-one correspondence; the driving module is connected to the controller and outputs corresponding on or off signals according to the 8 PWM driving signals of the controller.

3. The LLC resonant circuit for a DC-DC charging module according to claim 2, characterized in that: The first resonance module also includes capacitor C1, capacitor C2, capacitor C3, and inductor L1; the second resonance module also includes capacitor C4, capacitor C5, capacitor C6, and inductor L2; the third resonance module also includes capacitor C7, capacitor C8, capacitor C9, and inductor L3; the fourth resonance module also includes capacitor C10, capacitor C11, capacitor C12, and inductor L4; the power switch tube is divided into power switch tube Q1 to power switch tube Q8, and the gates of the power switch tubes Q1 to Q8 are respectively connected to the 8 gates of the driving module. The signal output end is connected accordingly; one end of the capacitor C1 is connected to the drain of the power switch tube Q1, the source of the power switch tube Q1 is connected to one end of the inductor L1 and the drain of the power switch tube Q2, the other end of the inductor L1 is connected to one end of the capacitor C3, the other end of the capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the source of the power switch tube Q2; one end of the capacitor C4 is connected to the drain of the power switch tube Q3, the source of the power switch tube Q3 is connected to the drain of the power switch tube Q3, and the drain of the power switch tube Q2 is connected to the drain of the power switch tube Q3. One end of the inductor L2 and the drain of the power switch tube Q4 are connected, the other end of the inductor L2 is connected to one end of the capacitor C6, the other end of the capacitor C4 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the source of the power switch tube Q4; one end of the capacitor C7 is connected to the drain of the power switch tube Q5, the source of the power switch tube Q5 is connected to one end of the inductor L3 and the drain of the power switch tube Q6, the other end of the inductor L3 is connected to one end of the capacitor C9, and the The other end of capacitor C7 is connected to one end of capacitor C8, and the other end of capacitor C8 is connected to the source of power switch tube Q6; one end of capacitor C10 is connected to the drain of power switch tube Q7, and the source of power switch tube Q7 is connected to one end of inductor L4 and the drain of power switch tube Q8, the other end of inductor L4 is connected to one end of capacitor C12, the other end of capacitor C10 is connected to one end of capacitor C11, and the other end of capacitor C11 is connected to the source of power switch tube Q8.

4. The LLC resonant circuit for a DC-DC charging module according to claim 3, characterized in that: The first rectifier module includes a capacitor C13 and diodes D11 to D14; the second rectifier module includes a capacitor C14 and diodes D21 to D24; the third rectifier module includes a capacitor C15 and diodes D31 to D34; the fourth rectifier module includes a capacitor C16 and diodes D41 to D44; one end of the primary coil of the first transformer is connected to the other end of the capacitor C3, the other end of the primary coil of the first transformer is connected to one end of the primary coil of the second transformer, the other end of the primary coil of the second transformer is connected to the other end of the capacitor C6, one end of the secondary coil of the first transformer is connected to the positive electrode of the diode D11, the positive electrode of the diode D1 3 are connected, the other end of the secondary coil of the first transformer is connected to the positive electrode of the diode D12 and the negative electrode of the diode D14, the negative electrode of the diode D11 and the negative electrode of the diode D12 are connected to one end of the capacitor C13, the positive electrode of the diode D13 and the positive electrode of the diode D14 are connected to the other end of the capacitor C13; one end of the secondary coil of the second transformer is connected to the positive electrode of the diode D21 and the negative electrode of the diode D23, the other end of the secondary coil of the second transformer is connected to the positive electrode of the diode D22 and the negative electrode of the diode D24, the negative electrode of the diode D21 and the negative electrode of the diode D22 and one end of the capacitor C14, the anode of the diode D23 and the anode of the diode D24 are connected to the other end of the capacitor C14; one end of the primary coil of the third transformer is connected to the other end of the capacitor C9, the other end of the primary coil of the third transformer is connected to one end of the primary coil of the fourth transformer, the other end of the primary coil of the fourth transformer is connected to the other end of the capacitor C12, one end of the secondary coil of the third transformer is connected to the anode of the diode D31 and the cathode of the diode D33, the other end of the secondary coil of the third transformer is connected to the anode of the diode D32 and the cathode of the diode D34, The cathode of the diode D31 and the cathode of the diode D32 are connected to one end of the capacitor C15, and the anode of the diode D33 and the cathode of the diode D34 are connected to the other end of the capacitor C15; one end of the secondary coil of the fourth transformer is connected to the anode of the diode D41 and the cathode of the diode D43, and the other end of the secondary coil of the fourth transformer is connected to the anode of the diode D42 and the cathode of the diode D44, the cathode of the diode D41 and the cathode of the diode D42 are connected to one end of the capacitor C16, and the anode of the diode D43 and the cathode of the diode D44 are connected to the other end of the capacitor C16.

5. The LLC resonant circuit for a DC-DC charging module according to claim 3, characterized in that: The gate terminal signals of the power switch tubes Q1 and Q2 are out of phase by 180°, and the duty cycles of the power switch tubes Q1 and Q2 are both 15% to 50%; the gate terminal signals of the power switch tubes Q3 and Q4 are out of phase by 180°, and the duty cycles of the power switch tubes Q3 and Q4 are both 50%; the gate terminal signals of the power switch tubes Q5 and Q6 are out of phase by 180°, and the duty cycles of the power switch tubes Q5 and Q6 are both 15% to 50%; the gate terminal signals of the power switch tubes Q7 and Q8 are out of phase by 180°, and the duty cycles of the power switch tubes Q7 and Q8 are both 50%; the gate terminal signals of the power switch tubes Q1 and Q5 are out of phase by 90°.

6. The LLC resonant circuit for a DC-DC charging module according to claim 3, characterized in that: The gate terminal signal of the power switch tube Q1 has the same phase as the gate terminal signal of the power switch tube Q4; the gate terminal signal of the power switch tube Q2 has the same phase as the gate terminal signal of the power switch tube Q3; the gate terminal signal of the power switch tube Q5 has the same phase as the gate terminal signal of the power switch tube Q8; the gate terminal signal of the power switch tube Q6 has the same phase as the gate terminal signal of the power switch tube Q7.