A interleaved parallel LLC resonant inverter

Abstract

The application belongs to the technical field of electronic circuits and provides an interleaved parallel LLC resonant inverter, which comprises a first half-bridge LLC converter, a second half-bridge LLC converter, a first switch tube, a second switch tube, a control loop, a load and an output capacitor; the input end of the first half-bridge LLC converter and the second half-bridge LLC converter are in an interleaved structure, the load samples an output voltage, compares the output voltage with a reference voltage through the control loop, and forms four-way driving to drive the first half-bridge LLC converter and the second half-bridge LLC converter respectively; when the first half-bridge LLC converter flows through forward or reverse current, the first switch tube is controlled to be turned on; when the second half-bridge LLC converter flows through forward or reverse current, the first switch tube is controlled to be turned on, and the load obtains a complete waveform. The application provides an inverter and a circuit thereof with high efficiency and high power density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuit, and particularly relates to an interleaved parallel LLC resonant inverter. BACKGROUND

[0002] With the continuous development of industry, the efficiency requirement of the inverter is also continuously improved. The traditional inverter adopts a two-stage inverter mode of a front-stage boost and a rear-stage inversion, involves more inverter elements, and has disadvantages in efficiency and power density.

[0003] For example, the volume proportion of the inductive element is large, which limits the improvement of the inverter power density. The volume of the inductive element can be reduced by increasing the switching frequency, but the increase of the switching frequency will increase the conduction and turn-off loss, and reduce the inverter overall efficiency. In addition, the LLC resonant circuit can realize the zero-voltage (ZVS) turn-on of the primary side main switch tube and the zero-current (ZCS) turn-off of the secondary rectifier diode in the entire load range within a certain frequency range, meets the demand of high frequency and low loss, and the resonant inductance and the excitation inductance can be integrated through the transformer magnetism, which can further improve the power density. However, the pure LLC resonant converter can only perform DC-DC conversion, and cannot realize inversion. SUMMARY

[0004] The main purpose of the present application is to provide an interleaved parallel LLC resonant inverter to solve the problem that the traditional inverter does not meet the demand in efficiency and power density.

[0005] To achieve the above purpose, the embodiment of the present application provides an interleaved parallel LLC resonant inverter, comprising: a first half-bridge LLC converter, a second half-bridge LLC converter, a first switch tube, a second switch tube, a control loop, a load and an output capacitor.

[0006] The input end of the first half-bridge LLC converter and the input end of the second half-bridge LLC converter are connected to a direct current power supply, and the output end of the first half-bridge LLC converter and the output end of the second half-bridge LLC converter are connected in series.

[0007] One end of the load and the output capacitor connected in parallel is connected in series with the output end of the first half-bridge LLC converter and the first switch tube, and the other end of the load and the output capacitor connected in parallel is connected to the midpoint of the rectifier bridge of the first half-bridge LLC converter and the second half-bridge LLC converter.

[0008] One end of the second switch tube is connected in series with the output end of the second half-bridge LLC converter, and the other end of the second switch tube is connected to one end of the output end of the first half-bridge LLC converter which is not connected to the first switch tube.

[0009] The load sampling output voltage is compared with a reference voltage through the control loop, and a four-way drive is formed, the four-way drive including a first drive, a second drive, a third drive and a fourth drive, the first drive and the second drive being used to drive a first half-bridge LLC converter, and the third drive and the fourth drive being used to drive a second half-bridge LLC converter.

[0010] When the first half-bridge LLC converter flows through forward or reverse current, the first switch tube is controlled to be turned on, when the second half-bridge LLC converter flows through forward or reverse current, the first switch tube is controlled to be turned on, and the load obtains a complete waveform.

[0011] Optionally, the first half-bridge LLC converter includes a first LLC converter half-bridge switch tube, a second LLC converter half-bridge switch tube, a first inductor, a second inductor, a first capacitor, a first transformer, a first diode, a second diode, a third diode and a fourth diode.

[0012] The first LLC converter half-bridge switch tube and the second LLC converter half-bridge switch tube are connected in series, an output end of the first LLC converter half-bridge switch tube is connected with a positive pole of a direct current power supply, and an input end of the second LLC converter half-bridge switch tube is connected with a negative pole of the direct current power supply.

[0013] The second LLC converter half-bridge switch tube, the first inductor, the second inductor and the first capacitor are connected in sequence, and the first transformer is connected in parallel across the second inductor.

[0014] The first diode and the third diode are connected in series, the second diode and the fourth diode are connected in series, and the first diode and the third diode in series and the second diode and the fourth diode in series are connected in parallel.

[0015] A secondary coil of the first transformer is connected between the second diode and the fourth diode.

[0016] Optionally, the second half-bridge LLC converter includes a third LLC converter half-bridge switch tube, a fourth LLC converter half-bridge switch tube, a third inductor, a fourth inductor, a second capacitor, a second transformer, a fifth diode, a sixth diode, a seventh diode and an eighth diode.

[0017] The third LLC converter half-bridge switch tube and the fourth LLC converter half-bridge switch tube are connected in series, an output end of the third LLC converter half-bridge switch tube is connected with a positive pole of a direct current power supply, and an input end of the fourth LLC converter half-bridge switch tube is connected with a negative pole of the direct current power supply.

[0018] The fourth LLC converter half-bridge switch tube, the third inductor, the fourth inductor and the second capacitor are connected in sequence, and the second transformer is connected in parallel across the fourth inductor;

[0019] The fifth diode and the seventh diode are connected in series, and the sixth diode and the eighth diode are connected in series, and the fifth diode and the seventh diode connected in series and the sixth diode and the eighth diode connected in series are connected in parallel;

[0020] The secondary coil of the second transformer is connected between the sixth diode and the eighth diode.

[0021] Optionally, the third diode and the fifth diode are connected, and the fourth diode and the sixth diode are connected to form the rectifier bridge.

[0022] Optionally, the first transformer includes a first secondary coil and a second secondary coil, and the second transformer includes a third secondary coil and a fourth secondary coil;

[0023] One end of the first secondary coil is connected between the second diode and the fourth diode, and the other end of the first secondary coil is connected in series with the third secondary coil;

[0024] One end of the second secondary coil is connected between the fifth diode and the seventh diode, and the other end of the second secondary coil is connected in series with the fourth secondary coil;

[0025] The fourth secondary coil is connected between the sixth diode and the eighth diode at one end not connected in series with the second secondary coil.

[0026] Optionally, by changing the transformer turns ratio of the first transformer and the transformer turns ratio of the second transformer, the voltage level across the load is adjusted.

[0027] Optionally, the control loop includes a proportional transformation module, a rectification module, a zero comparator, a PI controller, and a phase shifter connected in sequence;

[0028] The input end of the proportional transformation module serves as the input end of the control loop and is connected with the load to receive the output voltage of the load;

[0029] The zero comparator also accesses a reference voltage;

[0030] The zero comparator compares the reference voltage with the output voltage after the proportional transformation module and the rectification module;

[0031] The comparison result passes through the PI controller and the phase shifter to form the four-way drive.

[0032] Optionally, the reference voltage passes through the zero-crossing comparator to form a complementary signal, which is used to drive the first switch and the second switch.

[0033] Optionally, the output voltage of the four-way drive changes with the parameter change of the reference voltage.

[0034] Optionally, the phase shift angle of the phase shifter is 0-π.

[0035] The embodiment of the present application provides a single-pole inverter based on an LLC converter, a group of switch tubes are added between a first half-bridge LLC converter, a second half-bridge LLC converter and an output capacitor, when forward or reverse current flows through a rectifier bridge of the first half-bridge LLC converter and the second half-bridge LLC converter, the corresponding switch tube is controlled to be turned on, so that the forward or reverse current passing through the load is synthesized into a complete waveform, and the effect of inversion is achieved, meanwhile, the present application also adopts two groups of LLC converters which are connected in a staggered parallel mode, the phase shift angle is controlled through a control loop, output voltage closed-loop control is realized, the characteristics of high frequency, high efficiency and high power density are achieved, and the output voltage stability can be effectively ensured. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A component structure diagram of a single-pole inverter based on an LLC converter is provided for the embodiment of the present application.

[0037] Figure 2 A circuit structure diagram of a single-pole inverter based on an LLC converter is provided for the embodiment of the present application.

[0038] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0039] It should be understood that the specific embodiments described herein merely serve to explain the present application and do not serve to limit the present application.

[0040] It should be noted that, in this document, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or further include elements inherent in such processes, methods, articles or devices. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0041] In the present document, the suffixes such as "module", "part", or "unit" used for an element are merely used to facilitate the explanation of the present application, and have no particular meaning by themselves. Thus, "module" and "part" can be used interchangeably.

[0042] As shown in Figure 1 An embodiment of the present application provides an interleaved parallel LLC resonant inverter 100, comprising a first half-bridge LLC converter 10, a second half-bridge LLC converter 20, a first switch tube K1, a second switch tube K2, a control loop 30, a load R0 and an output capacitor C0.

[0043] Figure 1 In the present embodiment, the connection relationship of the components of the interleaved parallel LLC resonant inverter 100 is as follows:

[0044] The input end of the first half-bridge LLC converter 10 and the input end of the second half-bridge LLC converter 20 are connected to a DC power supply Vin, and the output end A of the first half-bridge LLC converter 10 and the output end C of the second half-bridge LLC converter 20 are connected in series; one end of the load R0 and the output capacitor C0 connected in parallel is connected in series with the output end A of the first half-bridge LLC converter 10 and the first switch tube K1, and the other end of the load R0 and the output capacitor C0 connected in parallel is connected to the midpoint B of the rectifier bridge of the first half-bridge LLC converter 10 and the second half-bridge LLC converter 20; one end of the second switch tube K2 is connected in series with the output end C of the second half-bridge LLC converter 20, and the other end of the second switch tube K2 is connected to the end of the output end A of the first half-bridge LLC converter 10 which is not connected to the first switch tube K1.

[0045] In the present embodiment, the first half-bridge LLC converter 10 and the second half-bridge LLC converter 20 are interleaved structures with parallel input and series output, and more specifically, the anode of the first switch tube K1 is connected to the output end A of the first half-bridge LLC converter 10, and the cathode of the first switch tube K1 is connected to the D end of the output capacitor C0; the cathode of the second switch tube K2 is connected to the output end C of the second half-bridge LLC converter 20, and the anode of the second switch tube K2 is connected to the cathode of the first switch tube K1, i.e. the D end of the output capacitor C0; the E end of the output capacitor C0 is connected to the midpoint of the rectifier bridge.

[0046] The load R0 samples the output voltage Vo, compares it with the reference voltage Vref through the control loop 30, and forms four-way drive, which includes first drive, second drive, third drive and fourth drive, the first drive and the second drive are used to drive the first half-bridge LLC converter 10, and the third drive and the fourth drive are used to drive the second half-bridge LLC converter 20.

[0047] In the embodiment of the present application, when the first half-bridge LLC converter 10 flows forward or reverse current, the first switch K1 is controlled to be turned on, when the second half-bridge LLC converter 20 flows forward or reverse current, the first switch K1 is controlled to be turned on, and the load R0 obtains complete waveform, thereby realizing that when the DC power Vin is connected, the current flowing through the load is the inverter effect of the alternating current.

[0048] The implementation principle is as follows:

[0049] Firstly, the two groups of LLC converters in parallel, i.e., the first half-bridge LLC converter 10 and the second half-bridge LLC converter 20, work at the first resonance point f r1 , which is expressed by the formula as follows:

[0050]

[0051] Wherein, L r1 =L r2 =L r , C r1 =C r2 =C r ;

[0052] L r1 is the inductance value of the first inductor L1, L r2 is the inductance value of the third inductor L3, C r1 is the capacitance value of the first capacitor C1, and C r2 is the capacitance value of the second capacitor C2.

[0053] When at the first resonance point, the LLC converter secondary output current is a sine wave, and the rectifier bridge output current is a positive half cycle, i.e., the current is output by the first half-bridge LLC converter 10 and input by the second half-bridge LLC converter 20, the first switch K1 is triggered to be turned on, and the positive half cycle current will flow through the load, when the positive half cycle current is zero, the second switch K2 is turned off; similarly, when the rectifier bridge output current is a negative half cycle, i.e., the current is input by the first half-bridge LLC converter 10 and output by the second half-bridge LLC converter 20, the second switch K2 is triggered to be turned on, and the negative half cycle current will flow through the load, when the negative half cycle current is zero, the second switch K2 is turned off. In a cycle, the current on the load is the combination of the positive half cycle current and the negative cycle current, which is a periodic current, thereby achieving the inverter effect.

[0054] It should be noted that the turn-on and turn-off of the first switch K1 and the second switch K2 are driven by the reference voltage Vref, and the driving principle is described below.

[0055] As Figure 2As shown, the embodiment of the present application also shows the detailed circuit structure of the first half-bridge LLC converter 10, the second half-bridge LLC converter 20 and the control loop 30, and continues to explain the circuit structure and circuit principle of the interleaved parallel LLC resonant inverter 100.

[0056] Figure 2 In the embodiment of the present application, the first half-bridge LLC converter 10 comprises a first LLC converter half-bridge switch S1, a second LLC converter half-bridge switch S2, a first inductor L1, a second inductor L2, a first capacitor C1, a first transformer T1, a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4, and the circuit structure of the first half-bridge LLC converter 10 is as follows:

[0057] The first LLC converter half-bridge switch S1 and the second LLC converter half-bridge switch S2 are connected in series, the output end of the first LLC converter half-bridge switch S1 is connected with the positive pole of the direct current power supply Vin, and the input end of the second LLC converter half-bridge switch S2 is connected with the negative pole of the direct current power supply Vin; the second LLC converter half-bridge switch S2, the first inductor L1, the second inductor L2 and the first capacitor C1 are connected in sequence, the first transformer T1 is connected in parallel across the second inductor L2; the first diode D1 and the third diode D3 are connected in series, the second diode D2 and the fourth diode D4 are connected in series, the series-connected first diode D1 and third diode D3 and the series-connected second diode D2 and fourth diode D4 are connected in parallel; the secondary coil of the first transformer T1 is connected between the second diode D2 and the fourth diode D4.

[0058] In the embodiment of the present application, the second half-bridge LLC converter 20 is completely identical in structure with the first half-bridge LLC converter 10.

[0059] Figure 2 In the embodiment of the present application, the second half-bridge LLC converter 20 comprises a third LLC converter half-bridge switch S3, a fourth LLC converter half-bridge switch S4, a third inductor L3, a fourth inductor L4, a second capacitor C2, a second transformer T2, a fifth diode D5, a sixth diode D6, a seventh diode D7 and an eighth diode D8, and the circuit structure of the second half-bridge LLC converter 20 is as follows:

[0060] The third LLC converter half-bridge switch S3 and the fourth LLC converter half-bridge switch S4 are connected in series, the output end of the third LLC converter half-bridge switch S3 is connected with the positive pole of the direct current power supply Vin, and the input end of the fourth LLC converter half-bridge switch S4 is connected with the negative pole of the direct current power supply Vin; the fourth LLC converter half-bridge switch S4, the third inductor L3, the fourth inductor L4 and the second capacitor C2 are connected in sequence, and the second transformer T2 is connected in parallel across the fourth inductor L4; the fifth diode D5 and the seventh diode D7 are connected in series, the sixth diode D6 and the eighth diode D8 are connected in series, and the fifth diode D5 and the seventh diode D7 connected in series and the sixth diode D6 and the eighth diode D8 connected in series are connected in parallel; the secondary coil of the second transformer T2 is connected between the sixth diode D6 and the eighth diode D8.

[0061] The third diode D3 and the fifth diode D5 are connected, and the fourth diode D4 and the sixth diode D6 are connected to form a rectifier bridge. Figure 2 The E end of the output capacitor C0 is connected to the midpoint between the third diode D3 and the fifth diode D5, and the midpoint between the fourth diode D4 and the sixth diode D6.

[0062] As shown in the figure, Figure 2 The detailed structure of the first transformer T1 and the second transformer T2 is also part of the above-mentioned interleaved structure, the first transformer T1 includes a first secondary coil and a second secondary coil, and the second transformer T2 includes a third secondary coil and a fourth secondary coil; one end of the first secondary coil is connected between the second diode D2 and the fourth diode D4; the other end of the first secondary coil is connected in series with the third secondary coil; one end of the second secondary coil is connected between the fifth diode D5 and the seventh diode D7, and the other end of the second secondary coil is connected in series with the fourth secondary coil; the end of the fourth secondary coil which is not connected in series with the second secondary coil is connected between the sixth diode D6 and the eighth diode D8.

[0063] In the embodiment of the application, the first transformer T1 and the second transformer T2 directly affect the voltage across the load R0, and therefore, the voltage level across the load R0 can be adjusted by changing the transformer turns ratio of the first transformer T1 and the transformer turns ratio of the second transformer T2.

[0064] As shown in the figure, Figure 2 In the embodiment of the application, the circuit structure of the control loop 30 is as follows:

[0065] The control loop 30 includes a proportional transformation module 31, a rectification module 32, a zero comparator 33, a PI controller 34 and a phase shifter 35 connected in sequence.

[0066] The input terminal of the proportional conversion module 31 serves as the input terminal of the control loop 30 and is connected to the load R0 to receive the output voltage Vo of the load R0. The proportional conversion module 31 and the rectifier module 32 perform proportional conversion and rectification on the output voltage Vo.

[0067] The zero comparator 33 is also connected to the reference voltage Vref, thereby comparing the reference voltage Vref with the output voltage Vo after being processed by the proportional converter module 31 and the rectifier module 32. The comparison result is then processed by the PI controller 34 and the phase shifter 35 to form a four-way drive.

[0068] The comparison result is adjusted by the PI controller and then enters the phase shifter 35. The phase shifter 35 adjusts the phase shift according to the comparison result to drive the LLC half-bridge switch to achieve wide voltage gain. The phase shift angle of the phase shifter 35 is between 0 and π.

[0069] Combination Figure 1 As shown, the first and second drives are used to drive the first half-bridge LLC converter 10, and the third and fourth drives are used to drive the second half-bridge LLC converter 20. Figure 2 In this process, the first drive acts on the first LLC converter half-bridge switch S1, the second drive acts on the second LLC converter half-bridge switch S2, the third drive acts on the third LLC converter half-bridge switch S3, and the fourth drive acts on the fourth LLC converter half-bridge switch S4.

[0070] It should be noted that in this embodiment of the invention, the output voltage Vo of the four-channel drive changes with the parameter changes of the reference voltage Vref.

[0071] Figure 2 In this embodiment, the reference voltage, after passing through the zero-crossing comparator 33, forms complementary signals VT1 and VT2, which are used to drive the first switch K1 and the second switch K2. That is, in this embodiment, the driving of the first switch K1 and the second switch K2 is controlled by the reference voltage Vref. The reference voltage Vref forms a set of complementary symmetrical signals VT1 and VT2 through the zero-crossing comparator 33, which drive K1 and K2 respectively. When the rectifier bridge is in positive output, the VT1 signal is used to drive the first switch K1 to conduct. When the rectifier bridge is in reverse output, the VT2 signal is used to drive the second switch K2 to conduct.

[0072] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the foregoing embodiments are described in detail, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent replacements; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. An interleaved parallel LLC resonant inverter, characterized by, include: The system consists of a first half-bridge LLC converter, a second half-bridge LLC converter, a first switching transistor, a second switching transistor, a control loop, a load, and an output capacitor. The input terminals of the first half-bridge LLC converter and the second half-bridge LLC converter are both connected to a DC power supply, and the output terminal of the first half-bridge LLC converter is connected in series with the output terminal of the second half-bridge LLC converter. One end of the load and the output capacitor connected in parallel is connected in series to the output terminal of the first half-bridge LLC converter and in series with the first switching transistor. The other end of the load and the output capacitor connected in parallel is connected to the midpoint of the rectifier bridge of the first half-bridge LLC converter and the second half-bridge LLC converter. One end of the second switch is connected in series with the output of the second half-bridge LLC converter, and the other end of the second switch is connected to the end of the first switch that is not connected to the output of the first half-bridge LLC converter. The load sampling output voltage is compared with the reference voltage through the control loop to form a four-way drive. The four-way drive includes a first drive, a second drive, a third drive, and a fourth drive. The first drive and the second drive are used to drive the first half-bridge LLC converter, and the third drive and the fourth drive are used to drive the second half-bridge LLC converter. By turning the first and second switching transistors on and off, the current on the load is made to combine positive half-cycle current and negative cycle current into a periodic current, thereby achieving inversion, including: When at the first resonant point, the secondary output current of the LLC converter is sinusoidal. When the rectifier bridge output current is in the positive half-cycle, the current is output from the first half-bridge LLC converter and input from the second half-bridge LLC converter. The first switch is triggered to turn on, and the positive half-cycle current will flow through the load. When the positive half-cycle current crosses zero, the second switch is turned off. When the rectifier bridge output current is in the negative half-cycle, the current is input from the first half-bridge LLC converter and output from the second half-bridge LLC converter. The second switch is triggered to turn on, and the negative half-cycle current will flow through the load. When the negative half-cycle current crosses zero, the second switch is turned off.

2. The interleaved parallel LLC resonant inverter of claim 1, wherein, The first half-bridge LLC converter includes a first LLC converter half-bridge switch, a second LLC converter half-bridge switch, a first inductor, a second inductor, a first capacitor, a first transformer, a first diode, a second diode, a third diode, and a fourth diode; The first LLC converter half-bridge switch and the second LLC converter half-bridge switch are connected in series. The output terminal of the first LLC converter half-bridge switch is connected to the positive terminal of the DC power supply, and the input terminal of the second LLC converter half-bridge switch is connected to the negative terminal of the DC power supply. The second LLC converter half-bridge switch, the first inductor, the second inductor and the first capacitor are connected in sequence, and the first transformer is connected in parallel across the second inductor; The first diode and the third diode are connected in series, the second diode and the fourth diode are connected in series, and the first diode and the third diode connected in series and the second diode and the fourth diode connected in series are connected in parallel; The secondary coil of the first transformer is connected between the second diode and the fourth diode.

3. The interleaved parallel LLC resonant inverter of claim 2, wherein, The second half-bridge LLC converter comprises a third LLC converter half-bridge switch tube, a fourth LLC converter half-bridge switch tube, a third inductor, a fourth inductor, a second capacitor, a second transformer, a fifth diode, a sixth diode, a seventh diode and an eighth diode; The third LLC converter half-bridge switch tube and the fourth LLC converter half-bridge switch tube are connected in series, the output end of the third LLC converter half-bridge switch tube is connected to the positive pole of the DC power supply, and the input end of the fourth LLC converter half-bridge switch tube is connected to the negative pole of the DC power supply; The fourth LLC converter half-bridge switch tube, the third inductor, the fourth inductor and the second capacitor are connected in sequence, and the second transformer is connected across the fourth inductor; The fifth diode and the seventh diode are connected in series, the sixth diode and the eighth diode are connected in series, and the fifth diode and the seventh diode connected in series and the sixth diode and the eighth diode connected in series are connected in parallel; The secondary coil of the second transformer is connected between the sixth diode and the eighth diode.

4. The interleaved parallel LLC resonant inverter of claim 3, wherein, The third diode and the fifth diode are connected, and the fourth diode and the sixth diode are connected to form the rectifier bridge.

5. The interleaved parallel LLC resonant inverter of claim 3, wherein, The first transformer comprises a first secondary coil and a second secondary coil, and the second transformer comprises a third secondary coil and a fourth secondary coil; One end of the first secondary coil is connected between the second diode and the fourth diode, and the other end of the first secondary coil is connected in series with the third secondary coil; One end of the second secondary coil is connected between the fifth diode and the seventh diode, and the other end of the second secondary coil is connected in series with the fourth secondary coil; The end of the fourth secondary coil which is not connected in series with the second secondary coil is connected between the sixth diode and the eighth diode.

6. The interleaved parallel LLC resonant inverter of any one of claims 3 to 5, wherein, By changing the transformer turns ratio of the first transformer and the transformer turns ratio of the second transformer, the voltage level across the load is adjusted.

7. The interleaved parallel LLC resonant inverter of claim 1, wherein, The control loop comprises a proportional transformation module, a rectification module, a zero comparator, a PI controller and a phase shifter connected in sequence; The input end of the proportional transformation module serves as the input end of the control loop and is connected to the load to receive the output voltage of the load; The zero comparator is also connected to a reference voltage; The zero comparator compares the reference voltage with the output voltage after the proportional transformation module and the rectification module; The comparison result passes through the PI controller and the phase shifter to form the four-way drive.

8. The interleaved parallel LLC resonant inverter of claim 7, wherein, The reference voltage after passing through the zero comparator also forms a complementary signal for driving the first switch tube and the second switch tube.

9. The interleaved parallel LLC resonant inverter of claim 7, wherein, The output voltage of the four-way drive changes with the change of the parameters of the reference voltage.

10. The interleaved parallel LLC resonant inverter of claim 7, wherein, The phase shifter has a phase shift angle of .

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