阅读说明：本技术 一种新型的无桥集成ac-dc整流电路及整流方法 (Novel bridgeless integrated AC-DC rectifying circuit and rectifying method ) 是由 潘尚智 王明龙 宫金武 查晓明 于 2019-09-16 设计创作，主要内容包括：本发明提出了一种新型的无桥集成AC-DC整流电路及整流方法,包括：单相交流电源,第一电感等。其中,后级DC-DC电路包括但不限于半桥LLC谐振电路,全桥LLC谐振电路,双有源全桥变换电路,双有源半桥变换电路等。本发明拥有两个控制自由度,包括：前级控制：控制对象为第一个桥臂(低频),通过正弦脉宽调制方法,实时调节该桥臂开关管的占空比以实现功率因数校正的功能和PFC输出直流侧电压的调节；后级控制：控制对象为第二个桥臂(高频),通过变频控制或者移相控制,实时调节后级DC-DC电路输出电压；控制方法使得前后级可以分别控制。同时可以实现与后级DC-DC变换电路共享桥臂,从而达到提高效率的目的。(The invention provides a novel bridgeless integrated AC-DC rectifying circuit and a rectifying method, comprising the following steps: single-phase ac power, first inductor, etc. The post-stage DC-DC circuit includes, but is not limited to, a half-bridge LLC resonant circuit, a full-bridge LLC resonant circuit, a dual-active full-bridge conversion circuit, a dual-active half-bridge conversion circuit, and the like. The invention possesses two degrees of freedom of control, including: preceding stage control: the control object is a first bridge arm (low frequency), and the duty ratio of a switch tube of the bridge arm is adjusted in real time by a sine pulse width modulation method so as to realize the function of power factor correction and the adjustment of voltage on the direct current side output by the PFC; and (3) post-stage control: the control object is a second bridge arm (high frequency), and the output voltage of the rear-stage DC-DC circuit is adjusted in real time through frequency conversion control or phase-shift control; the control method enables the front and rear stages to be controlled separately. Meanwhile, the bridge arm can be shared with a post-stage DC-DC conversion circuit, so that the aim of improving the efficiency is fulfilled.)

1. A novel bridgeless integrated AC-DC rectification circuit and method are characterized by comprising the following steps: the single-phase alternating current power supply, a first inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube and a rear-stage DC-DC circuit;

one end of the single-phase alternating current power supply is connected with one end of the first inductor; the other end of the single-phase alternating current power supply is connected with a drain electrode of the fourth switching tube; the other end of the first inductor and the first switch tube S₁Is connected to the source of (a); the drain electrode of the first switching tube is connected with the drain electrode of the third switching tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the third switching tube is connected with the drain electrode of the second switching tube; the source electrode of the second switching tube is connected with the source electrode of the fourth switching tube; the rear-stage DC-DC circuit is connected with the drain electrode of the third switching tube and the source electrode of the fourth switching tube;

the latter stage DC-DC circuit adopts half-bridge LLC resonant circuit, includes: the single-phase alternating-current power supply comprises a single-phase alternating-current power supply, a first inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a dc capacitor, a first capacitor, a second capacitor, a first transformer, a first diode, a second diode, a third capacitor and a first load resistor;

one end of the single-phase alternating current power supply is connected with one end of the first inductor; the other end of the single-phase alternating current power supply is connected with a drain electrode of the fourth switching tube; the other end of the first inductor and the first switch tube S₁Is connected to the source of (a); the drain electrode of the first switching tube, the drain electrode of the third switching tube and the dc capacitor are connected with the anode of the first capacitor; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the third switching tube and the drain electrode of the second switching tube are connected with one end of the primary side of the first transformer; the negative electrode of the first capacitor and the positive electrode of the second capacitor are connected with the other end of the primary side of the first transformer; the source electrode of the second switch tube, the source electrode of the fourth switch tube and the dc capacitor are connected with the negative electrode of the second capacitor; one end of the secondary side of the first transformer is connected with the anode of the first diode; the middle end of the first transformer is connected with the negative electrode of the third capacitor and one end of the first resistor; the third end of the secondary side of the first transformer is connected with the anode of a second diode; and the anodes of the first diode, the second diode and the third capacitor are connected with the other end of the first resistor.

2. The novel bridgeless integrated AC-DC rectification circuit according to claim 1, wherein the post-stage DC-DC circuit is a half-bridge LLC resonant circuit, a full-bridge LLC resonant circuit, a dual-active full-bridge conversion circuit, or a dual-active half-bridge conversion circuit.

3. A method of rectification using the novel bridgeless integrated AC-DC rectifier circuit of claim 1, comprising:

preceding stage control: the control object is a first bridge arm, the first bridge arm is low-frequency, and the duty ratio of a switch tube of the bridge arm is adjusted in real time by a sine pulse width modulation method so as to realize the function of power factor correction and the adjustment of voltage on a PFC output direct current side;

and (3) post-stage control: the control object is a second bridge arm, the second bridge arm is high-frequency, and the output voltage of the rear-stage DC-DC circuit is adjusted in real time through frequency conversion control or phase-shift control;

the control method enables the front stage and the rear stage to be controlled respectively; meanwhile, the bridge arm can be shared with a rear-stage DC-DC conversion circuit, so that the aim of improving the efficiency is fulfilled;

the expression of the voltage on the DC side of the PFC output is as follows:

wherein, V_dcRepresents the output voltage of the PFC direct current side; v_iRepresents an alternating-current-side input voltage; d₁Bridge arm switch tube S with low frequency representation₂Duty cycle of (d); d₂Indicating high frequency bridge arm switch tube S₃The duty cycle of (c).

Technical Field

The invention relates to the technical field of power electronic conversion, in particular to a novel bridgeless integrated AC-DC rectifying circuit and a method.

Background

At present, a large amount of bridge type uncontrolled rectification is used, so that not only is serious harmonic pollution caused to a power grid, but also waste of electric energy is caused due to low power factor of an alternating current side. The power factor correction technology can realize that the alternating current side current tracks the alternating current side voltage, and can improve the power factor of the alternating current side.

Power factor correction techniques must be able to achieve high power factor and low input current harmonics to meet IEC61000-3-2 harmonic standards. Therefore, a conventional power supply generally includes a two-stage power conversion structure, a Boost circuit used as a Power Factor Correction (PFC) circuit for realizing a high power factor and a low input current harmonic, and a DC-DC conversion circuit for outputting a required DC voltage. The two-stage circuit topology can enable the circuit to achieve optimal performance, such as high power factor, stable PFC output DC side voltage, and stable DC-DC output voltage. However, the two-stage structure has too many components, so that the power consumption is high, the efficiency is relatively low, the circuit control is complex, and most of the system loss is consumed in the rectifier diode.

Aiming at the problem of efficiency reduction caused by excessive number of components, two solutions are mainly provided, one is to improve the topological structure of the first-stage power factor correction circuit to form a bridgeless PFC structure so as to reduce the number of diodes and switching tubes as much as possible. At present, various bridgeless PFC circuits are available, such as a double-Boost PFC circuit, a double-inductor PFC circuit, a totem-pole PFC circuit and the like; the other method is to integrate the first-stage PFC circuit and the second-stage DC-DC circuit by sharing one bridge arm.

The learners combine the two solutions together, and provide a topological structure in which the totem-pole PFC and the post-stage DC-DC conversion circuit are integrated by sharing one bridge arm, so that the number of switching devices can be further reduced, but the circuit topology has only one control degree of freedom, the voltage on the output direct current side of the PFC is uncontrollable, and when the input voltage is increased to a certain degree, the voltage stress on the output direct current side of the PFC and the voltage stress on the switching devices are too high, so that the devices are easily damaged; in addition, because the voltage of the output direct current side of the PFC is uncontrollable, the voltage change is too large, and the parameter design of a post-stage DC-DC circuit is poor.

In order to solve the problem that the output dc voltage of the PFC is not controllable, some researchers have proposed a solution to achieve the purpose of controlling the output dc voltage of the PFC by combining pulse frequency modulation and pulse width modulation. When the voltage of the direct current side output by the PFC does not exceed a specified limit value, pulse frequency modulation is adopted; when the voltage of the output direct current side of the PFC approaches or exceeds a specified limit value, the purpose of reducing the voltage of the output direct current side of the PFC is achieved by changing the duty ratio in a mode of combining pulse frequency modulation and pulse width modulation, however, input harmonic current is increased, the power factor is reduced, and the duty ratio is limited by input voltage change, so that the working condition of a rear-stage DC-DC circuit is deteriorated, the design cannot be optimized, and the efficiency of the whole circuit is influenced to a certain extent.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned problems, and provides 1. a novel bridgeless integrated AC-DC rectifier circuit and method, comprising: the single-phase alternating current power supply, a first inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube and a rear-stage DC-DC circuit;

one end of the single-phase alternating current power supply is connected with one end of the first inductor; the other end of the single-phase alternating current power supply is connected with a drain electrode of the fourth switching tube; the other end of the first inductor and the first switch tube S₁Is connected to the source of (a); the drain electrode of the first switching tube is connected with the drain electrode of the third switching tube; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the third switching tube is connected with the drain electrode of the second switching tube; the source electrode of the second switching tube is connected with the source electrode of the fourth switching tube; the rear-stage DC-DC circuit is connected with the drain electrode of the third switching tube and the source electrode of the fourth switching tube;

the latter stage DC-DC circuit adopts half-bridge LLC resonant circuit, includes: the single-phase alternating-current power supply comprises a single-phase alternating-current power supply, a first inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a dc capacitor, a first capacitor, a second capacitor, a first transformer, a first diode, a second diode, a third capacitor and a first load resistor;

one end of the single-phase alternating current power supply is connected with one end of the first inductor; the other end of the single-phase alternating current power supply is connected with a drain electrode of the fourth switching tube; the other end of the first inductor and the first switch tube S₁Is connected to the source of (a); the drain electrode of the first switching tube, the drain electrode of the third switching tube and the dc capacitor are connected with the anode of the first capacitor; the source electrode of the first switch tube is connected with the drain electrode of the second switch tube; the source electrode of the third switching tube and the drain electrode of the second switching tube are connected with one end of the primary side of the first transformer; the negative electrode of the first capacitor and the positive electrode of the second capacitor are connected with the other end of the primary side of the first transformer; the source electrode of the second switch tube, the source electrode of the fourth switch tube and the dc capacitor are connected with the negative electrode of the second capacitor; one end of the secondary side of the first transformer is connected with the anode of the first diode; the middle end of the first transformer is connected with the negative electrode of the third capacitor and one end of the first resistor; the third end of the secondary side of the first transformer is connected with the anode of a second diode; and the anodes of the first diode, the second diode and the third capacitor are connected with the other end of the first resistor.

2. The novel bridgeless integrated AC-DC rectification circuit according to claim 1, wherein the post-stage DC-DC circuit is a half-bridge LLC resonant circuit, a full-bridge LLC resonant circuit, a dual-active full-bridge conversion circuit, or a dual-active half-bridge conversion circuit.

The single-phase alternating current power supply is used for providing input alternating current power supply; the first inductor is used for storing and releasing energy; the first switching tube is used for controlling the output of direct-current voltage; the second switching tube is used for controlling the output of direct-current voltage; the third switching tube is used for controlling the output of direct-current voltage; the fourth switching tube is used for controlling the output of direct-current voltage; the dc capacitor is used for filtering and outputting direct-current voltage ripples; the first capacitor and the second capacitor are used for generating resonance with the inductor; the first load resistor is used for providing direct current voltage output; the first transformer is used for transmitting energy to an output side; the first diode is used for providing a current circulation path; the second diode is used for providing a current circulation path; and the third capacitor is used for filtering the direct-current voltage ripple at the output side.

A method of rectification using a novel bridgeless integrated AC-DC rectifier circuit, comprising:

preceding stage control: the control object is a first bridge arm, the first bridge arm is low-frequency, and the duty ratio of a switch tube of the bridge arm is adjusted in real time by a sine pulse width modulation method so as to realize the function of power factor correction and the adjustment of voltage on a PFC output direct current side;

and (3) post-stage control: the control object is a second bridge arm, the second bridge arm is high-frequency, and the output voltage of the rear-stage DC-DC circuit is adjusted in real time through frequency conversion control or phase-shift control;

the control method enables the front stage and the rear stage to be controlled respectively; meanwhile, the bridge arm can be shared with a rear-stage DC-DC conversion circuit, so that the aim of improving the efficiency is fulfilled;

the expression of the voltage on the DC side of the PFC output is as follows:

wherein, V_dcRepresents the output voltage of the PFC direct current side; v_iRepresents an alternating-current-side input voltage; d₁Bridge arm switch tube S with low frequency representation₂Duty cycle of (d); d₂Indicating high frequency bridge arm switch tube S₃The duty cycle of (c).

Compared with the prior art, the invention has the following advantages:

the invention has two degrees of freedom of control. The first bridge arm is a low-frequency bridge arm, and the duty ratio of a switch tube of the bridge arm is adjusted in real time by a sine pulse width modulation method so as to realize the function of power factor correction and the adjustment of voltage on a PFC output direct current side; the second bridge arm is a high-frequency bridge arm, the duty ratio is fixed, the second bridge arm can share the bridge arm with a half-bridge LLC resonant DC-DC circuit, integration is realized, a soft switching effect is brought, and the purpose of improving efficiency is achieved.

Drawings

Fig. 1 is a circuit diagram of the system of the present invention.

Fig. 2 is a typical circuit diagram of a half-bridge LLC resonant DC-DC circuit followed by the system of the present invention.

FIG. 3: the driving signals of the switching tubes S3 and S4, input inductive current, resonant current, excitation inductive current and current waveforms flowing through the first diode and the second diode are in a stable working state of a typical circuit of the system.

Fig. 4 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 1 of operation.

Fig. 5 is an equivalent circuit diagram of an exemplary circuit of the system of the present invention during mode 2 of operation.

Fig. 6 is an equivalent circuit diagram of an exemplary circuit of the system of the present invention during mode 3 of operation.

Fig. 7 is an equivalent circuit diagram of an exemplary circuit of the system of the present invention during mode 4 of operation.

Fig. 8 is an equivalent circuit diagram of an exemplary circuit of the system of the present invention during mode 5 of operation.

Fig. 9 is an equivalent circuit diagram of an exemplary circuit of the system of the present invention during mode of operation 6.

Detailed Description

In order to facilitate the understanding and implementation of the present invention for those of ordinary skill in the art, the present invention is further described in detail with reference to the accompanying drawings and examples, it is to be understood that the embodiments described herein are merely illustrative and explanatory of the present invention and are not restrictive thereof.

The circuit of this embodiment is shown in figure 1,

single phase ac power supply v_inFirst inductance L₁A first switch tube S₁A second switch tube S₂A third switching tube S₃Fourth switch tube S₄Dc capacitor C_dcFirst capacitor C₁First capacitor C₂First transformer T₁First diode D₁Second, secondDiode D₂Third capacitor C₃And a first load resistor R₁；

The single-phase AC power supply v_inOne end of (1) and the first inductor L₁Is connected with one end of the connecting rod; the single-phase AC power supply v_inAnd the other end of the second switch tube S₄Is connected with the drain electrode of the transistor; the first inductor L₁And the other end of the first switch tube S₁Is connected to the source of (a); the first switch tube S₁The drain electrode of the third switching tube S₃The positive electrode of the dc capacitor and the first capacitor C₁The positive electrode of (1) is connected; the first switch tube S₁Source electrode of and the second switch tube S₂Is connected with the drain electrode of the transistor; the third switch tube S₃Source electrode of, the fourth switching tube S₄And the first transformer T₁One end of the primary side is connected; the first capacitor C₁Negative pole of (1), the second capacitor C₂And the first transformer T₁The other end of the primary side is connected; the second switch tube S₂Source electrode of, the fourth switching tube S₄Source of the dc capacitor, a cathode of the dc capacitor and the second capacitor C₂The negative electrode of (1) is connected; the first transformer T₁One end of the secondary side and the first diode D₁The anode of (2) is connected; the first transformer T₁An intermediate terminal and the third capacitor C₃Negative electrode of (1), first resistor R₁Is connected with one end of the connecting rod; the first transformer T₁The third end of the secondary side and a second diode D₂The anode of (2) is connected; the first diode D₁The second diode D₂The third capacitor C₃And the first resistor R₁The other end of the connecting rod is connected.

The following describes the embodiments of the present invention with reference to fig. 2 to 9:

setting a first inductance L₁Has a current of i_inAt a voltage v_LFirst capacitor C₁Has a voltage of v_C1A second capacitor C₂Has a voltage of v_C2Third capacitor C₃Has a voltage of v_C3Output power from the DC side of PFCPressure v_dc，v_dc＝v_C1+v_C2Flows through the first diode D₁Has a current of i_D1Flows through the first diode D₂Has a current of i_D2Flows through the first transformer T₁Current of leakage inductance is i_LrFlows through the first transformer T₁Current of exciting inductor is i_mFirst load resistance R₁A voltage v_o。

Due to S₁，S₂The working processes of the upper pipe and the lower pipe are symmetrical, so that only S is analyzed₁6 working stages when the upper pipe is opened. FIGS. 4-9 are circuit diagrams S of the circuit shown in FIG. 1₁A schematic diagram of an equivalent circuit of a working mode when the upper tube is turned on, wherein FIG. 4 is a first switch tube S₁A third switch tube S₃Conducting the second switch tube S₂And a fourth switching tube S₄Off, the first diode D₁Forward conducting, second diode D₂An equivalent circuit schematic diagram when reverse turn-off is performed; FIG. 5 shows the first switch tube S₁A third switch tube S₃Conducting the second switch tube S₂And a fourth switching tube S₄Off, the first diode D₁A second diode D₂An equivalent circuit schematic diagram when reverse turn-off is performed; FIG. 6 shows the first switch tube S₁Conducting the second switch tube S₂A third switch tube S₃Turn-off and fourth switch tube S₄Off, the first diode D₁A second diode D₂An equivalent circuit schematic diagram when reverse turn-off is performed; FIG. 7 shows the first switch tube S₁And a fourth switching tube S₄Conducting the second switch tube S₂A third switch tube S₃Turn-off, first diode D₁Reverse turn-off, second diode D₂An equivalent circuit schematic diagram when conducting in the forward direction; FIG. 8 shows the first switch tube S₁A second switch tube S₂A third switch tube S₃Turn-off, fourth switch tube S₄Conducting the first diode D₁A second diode D₂An equivalent circuit schematic diagram when reverse turn-off is performed; FIG. 9 shows the first switch tube S₁A second switch tube S₂A third switch tube S₃And a fourth switching tube S₄Off, the first diode D₁A second diode D₂And an equivalent circuit schematic diagram in reverse turn-off.

The working conditions of the modes are specifically analyzed, and the adjustment of the output voltage at the direct current side can be realized by adjusting the duty ratio of the low-frequency bridge arm, so that the first inductor L₁Average current i in a single switching cycle of_LaveIs constant and i will not be listed again in each modal analysis_inAnd v_C1、v_C2、v_C3Using i in the steady state analysis_LaveInstead of the first inductor L₁Current value i of_in. It is to be noted that the following processes or parameters, if any, which are not specifically described in detail are understood or implemented by those skilled in the art with reference to the prior art.

As shown in FIG. 4, modality 1 corresponds to t of FIG. 3₀～t₁Time period:

at t ═ t₀While, the first switch tube S₁A third switch tube S₃Zero voltage on, second switch tube S₂And a fourth switching tube S₄Off, input current i_inPasses through the first inductor L once₁A first switch tube S₁A third switch tube S₃Then returns to the single-phase AC power supply v_in. At this time, the inductor energy is increased and the inductor current i_inLinearly rising, inductor current i_inCan be expressed as:

at the same time, the first capacitor C₁A third switch tube S₃First transformer leakage inductance L_rA first transformer resonant inductor L_mA second capacitor C₂Forming a resonant circuit, resonant current i_LrSpecific exciting inductance current i_mLarge so that the current flowing through the primary side of the transformer is positive and negative, and the amplitude is the difference between the resonant current and the exciting current, therefore, the first diode D on the secondary side of the transformer₁And conducting. The primary voltage of the transformer is clamped at nV_oExciting inductance current is linearly increased, exciting inductance current i_LrCan be expressed as:

at this stage, the resonant frequency is:at t₁And at the moment, when the resonant inductor current is equal to the excitation inductor current, ending the mode 1 working mode.

As shown in FIG. 5, modality 2 corresponds to t of FIG. 3₁～t₂Time period:

at t ═ t₁While, the first switch tube S₁A third switch tube S₃Continuously turning on, inputting an inductive current i_inThe linear increase continues until t is reached₂The time reaches a maximum value. In addition, at t₁Time of day, resonant inductor current i_LrEqual to exciting inductance current i_mWhen the first diode is turned off, the first diode is turned off with zero current. In this mode, the first capacitor C₁A third switch tube S₃First transformer leakage inductance L_rA first transformer resonant inductor L_mA second capacitor C₂Forming a resonant circuit, wherein the resonant frequency is as follows:in this mode, since the resonant current is equal to the exciting inductor current, the first and second diodes on the secondary side of the transformer are turned off in reverse directions, so that no energy is transferred to the secondary side. At t ═ t₂While, the third switch tube S₃Off, modality 2 ends.

As shown in FIG. 6, modality 3 corresponds to t of FIG. 3₂～t₃Time period:

in this mode, corresponding to the dead time of the switching signal, the third switch tube S is now in the process₃And a fourth switching tube S₄Turn off, input of inductor current i_inLinear decrease, the relation of the relevant electrical parameters in this modeComprises the following steps:

due to the third switch tube S₃And a fourth switching tube S₄The presence of parasitic capacitances, to which the excitation current is discharged, thus realizes the fourth switching tube S₄The zero voltage of (2) turns on. When t is equal to t₃While, the fourth switch tube S₄And (4) opening.

As shown in FIG. 7, modality 4, corresponding to t of FIG. 3₃～t₄Time period:

at t ═ t₃While, the fourth switch tube S₄The drain-source voltage will be zero, therefore, the fourth switch tube S₄The zero voltage turns on. In this mode, the inductor current i is input_inContinuing to linearly decrease; because the fourth switch tube S₄Conducting so that the input voltage of the resonant tank is zero. In this mode, the resonance current is larger than the exciting inductance current, and the secondary side of the transformer is provided with a second diode D according to the polarity relation of the transformer₂The forward direction is conducted, the primary voltage of the transformer is clamped at-nV_oExcitation inductance current i_mThe linear decrease, the magnetizing inductor current can be expressed as:

at t ═ t₄When the resonant current is equal to the exciting inductance current, the mode 4 is finished.

As shown in FIG. 8, modality 5 corresponds to t of FIG. 3₄～t₅Time period:

fourth switch tube S₄Keeping on state, when t is t₄While the resonance current is equal to the exciting inductor current, a second diode D₂Zero current turn-off, at t ═ t₅While, the fourth switch tube S₄The switch-off, the mode 5 end,

as shown in FIG. 9, modality 6, corresponding to t of FIG. 3₅～t₆Time period:

in this mode, all the primary side switching tubes and the secondary side diodes are in the off state, which is the same as mode 3, because the third switching tube S₃And a fourth switching tube S₄Due to the existence of the parasitic capacitors, the excitation current discharges to the parasitic capacitors, and zero-voltage switching-on of the third switching tube is realized. When t is equal to t₆While, the third switch tube S₃And (4) opening.

The 6 working stages when the second switch tube is switched on are similar to the above, and are not described in detail herein.

According to the analysis of the above modes, the first inductance L is₁And analyzing the relation among all parameters of the system under the steady state condition by using a volt-second balance principle, wherein variables represented by capital characters below are steady state values of corresponding variables. Provided with a first switch tube S₁The time of opening is (1-D)₁)T_s1A second switch tube S₂Time of opening is D₁T_s1A third switching tube S₃Time of opening is D₂T_s2Fourth switch tube S₄The time of opening is (1-D)₂)T_s2Wherein D is₁Is a first switch tube S₁Duty cycle of (1-D)₁) Is a second switch tube S₂Duty ratio of D₂For a third switching tube S₃Duty cycle of (1-D)₄) Is a fourth switching tube S₄The duty cycle of (c). T is_s1，T_s2Is a switching period, and T_s1Greater than T_s2. For the first inductance L₁The method is obtained by applying a volt-second balance principle:

finishing the formula (5) to obtain:

the above-mentioned embodiment is a typical circuit of the system of the present invention, but the implementation manner of the present invention is not limited by the above-mentioned embodiment, and a typical circuit formed by changing the DC-DC circuit (including but not limited to a half-bridge LLC resonant circuit, a full-bridge LLC resonant circuit, a dual-active full-bridge inverter circuit, a dual-active half-bridge inverter circuit, etc.) of the latter stage of the system of the present invention is included in the protection scope of the present invention.

The above-mentioned embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

It should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.