CN109742939B - Bidirectional PFC soft switch and control method thereof - Google Patents

Abstract

The invention relates to a bidirectional PFC soft switch and a control method thereof, belonging to the field of circuit topology; the bidirectional PFC soft switch and the control method thereof are provided, which can improve the overall efficiency of the converter; the technical scheme is as follows: a bidirectional PFC soft switch comprises a main loop and an auxiliary branch, wherein the main loop comprises a first switch tube S and a second switch tube S₁、S₂First and second resonant capacitors C₁、C₂Inductor L, first and second filter capacitors C_o1、C_o2The auxiliary branch comprises a third switching tube S and a fourth switching tube S₃、S₄Resonant inductance L_rThe main loop of the transformer T and the full-bridge rectifier bridge is a bidirectional half-bridge PFC converter, the auxiliary branch assists in completing soft switching of the main loop in a boosting mode and a voltage reduction mode, and a switching tube of the auxiliary branch also realizes soft switching.

Description

Bidirectional PFC soft switch and control method thereof

Technical Field

The invention discloses a bidirectional PFC soft switch and a control method thereof, and belongs to the technical field of power electronic circuit topologies.

Background

In recent years, with the increasing importance of energy utilization and consumption in China, higher requirements are put on power supply systems, and direct-current power converters play an indispensable role. The power supply system capable of charging and discharging is widely applied to numerous industries greatly supported by the nation, such as electric vehicles, uninterruptible power supplies, photovoltaic power generation, aviation power and other occasions, energy can be required to freely circulate in two directions, and therefore the application prospect of the bidirectional converter is wider. The high frequency of the bidirectional converter is the development direction, and the high frequency enables the converter to be miniaturized, and particularly promotes the miniaturization and the lightness of high and new technology products in the application of the high and new technology fields. However, the switching loss of the hard switching converter increases with the increase of the switching frequency, the on-off loss of the switching tube due to the output capacitor and the turn-off loss due to the reverse recovery characteristic of the diode become more serious at high frequency, and the electromagnetic interference also increases. Therefore, it is important to reduce the on-off loss of the switching tube and the reverse recovery loss of the diode.

At present, the more mature method for solving the above-mentioned losses is to apply soft switching technology. One or more auxiliary loops are added on the basis of the traditional bidirectional converter, so that the energy stored in a parasitic capacitor and the energy stored in the forward conduction of a freewheeling diode during inductive freewheeling are transferred to the auxiliary loops before the main switching tube is switched on, and the main switching tube is switched on softly.

Although the above methods based on soft switching technology can successfully solve the problem of energy loss of the main circuit, the energy in the added auxiliary circuit cannot be fed back to the input or the output, and only the energy is transferred formally, and the energy loss is not substantially reduced; in addition, the auxiliary switching tube is switched on and off under the condition of hard switching, and the switching loss is also relatively large. Thus, the overall efficiency of the system is still not improved.

Disclosure of Invention

The invention discloses a bidirectional PFC soft switch and a control method thereof, overcomes the defects in the prior art, and provides a bidirectional PFC soft switch implementation method and a control method thereof for improving the overall efficiency of a converter.

In order to solve the technical problem, the technical scheme adopted by the invention is a bidirectional PFC soft switch, which comprises a main loop and an auxiliary branch; the main loop comprises a first and a second switch tube S₁、S₂First and second resonant capacitors C₁、C₂Inductor L, first and second filter capacitors C_o1、C_o2(ii) a The auxiliary branch comprises a third switching tube S and a fourth switching tube S₃、S₄Resonant inductance L_rA transformer T and a full bridge rectifier bridge;

first resonant capacitor C₁And a first switch tube S₁Parallel second resonant capacitor C₂And a second switch tube S₂Parallel connection; first switch tube S₁Source electrode of and the second switch tube S₂The other end of the inductor L is respectively connected with the anode output end m of the full-bridge rectifier bridge and the second filter capacitor C_o2Is connected to a second filter capacitor C_o2And the other end of the first switch tube S₂The source electrodes of the two-way transistor are connected; a first filter capacitor C_o1Are respectively connected with the first switch tube S₁Drain electrode of the first switching tube S₂The source electrodes of the two-way transistor are connected; first and third switch tubes S₁、S₃Is connected with the drain of the third switching tube S₃Source electrode and fourth switch tube S₄Is connected with the drain electrode of the first switching tube S and the fourth switching tube S₂、S₄The source electrodes of the two-way transistor are connected; negative output end n of full-bridge rectifier bridge and fourth switching tube S₄The source electrodes of the two-way transistor are connected; resonant inductor L_rOne end of (1) and a first switch tube S₁Is connected with the source electrode of the resonant inductor L_rThe other end of the first switch tube is connected with the different name end of the primary side of the transformer T, the same name end of the primary side of the transformer T is connected with the third switch tube S₃The source electrodes of the two-way transistor are connected; the dotted terminal of the secondary side of the transformer T is connected with the first alternating current input terminal p of the full-bridge rectifier bridge, and the dotted terminal of the secondary side of the transformer T is connected with the full-bridge rectifier bridgeThe second ac inputs q of the current bridge are connected.

Further, the first, second, third and fourth switch tubes S₁、S₂、S₃、S₄All are power switch tubes with anti-parallel diode characteristics.

Further, the device also comprises a first diode D, a second diode D, a third diode D and a fourth diode D₁、D₂、D₃、D₄A first, a second, a third and a fourth diode D₁、D₂、D₃、D₄A first switch tube S, a second switch tube S, a third switch tube S and a fourth switch tube S in sequence₁、S₂、S₃、S₄An anti-parallel diode.

Further, the full-bridge rectifier bridge comprises a fifth diode D, a sixth diode D, a seventh diode D and an eighth diode D₅、D₆、D₇、D₈Fifth and sixth diodes D₅、D₆A branch formed by series connection with a seventh diode D and an eighth diode D₇、D₈The branches formed by the series connection are connected in parallel.

A control method of a bidirectional PFC soft switch is completed based on the bidirectional PFC soft switch and comprises a buck mode control method and a boost mode control method; the PFC soft switch is under the voltage reduction mode, the first voltage source V₁And the first filter capacitor C_o1In parallel, the first filter capacitor C_o1Is a voltage input terminal, and the second filter capacitor C_o2The two ends of the voltage-stabilizing switch are voltage output ends; the PFC soft switch is in a boost mode, and the second voltage source V₂And the second filter capacitor C_o2In parallel, the second filter capacitor C_o2The two ends of the first filter capacitor C are voltage input ends_o1Are voltage output terminals.

Further, the buck mode control method includes nine modes, and the nine modes sequentially complete one cycle, specifically including:

the first mode of the buck mode occurs at t₀-t₁Stage t of₀Moment, resonance inductance L_rCurrent i of_Lr0, only the first switchPipe S₁In the conducting state, the current direction of the inductor L is controlled by the first voltage source V₁To a second voltage source V₂The first voltage source V of the mode₁The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁Soft shutdown is realized, and the mode is finished;

buck mode the second mode occurs at t₁-t₂Stage t of₁First switch tube S is turned off in a soft mode at any moment₁The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L1Approximately constant when the second resonant capacitance C is₂Terminal voltage is defined by V₁When the voltage drops to 0V, the mode ends, and the duration is: t is t₁₂＝V₁·2C_r/I_L1Wherein, C_r＝C₁＝C₂，C_rIs a resonant capacitor;

the third mode of the buck mode occurs at t₂-t₃Stage t of₂Time second resonance capacitor C₂The end voltage is reduced to 0V, and the second diode D₂Naturally conducting follow current, and connecting the second switch tube S₂The drain-source voltage is clamped to be close to 0V, and the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

the fourth mode of the buck mode occurs at t₃-t₄Stage t of₃Second switch tube S is switched on softly at any moment₂The energy stored in the inductor L passes through the second switch tube S₂Release, turning off the second switch tube S₂The third switch tube S is switched in the short time before₃Conducting due to the opening of the third switch tube S₃The current in the front auxiliary branch is 0A, and the third switch tube S₃Soft switching on is realized, and the mode is finished;

the fifth mode of the buck mode occurs at t₄-t₅Stage t of₄Third switching tube S capable of being switched on at any moment₃The dotted terminal of the primary winding Np of the transformer T is positive, the dotted terminal of the secondary winding Ns is induced by positive electromotive force, and the fifth diode D and the eighth diode D₅、D₈Conducting, clamping the secondary winding Ns voltage of the transformer T at the voltage source V₂Voltage V of₂The Np voltage of the primary winding of the transformer T is clamped at V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing the turns of the secondary winding and the primary winding, and the resonance inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrA linear increase; when resonance inductance L_rCurrent i_LrCurrent i increases to inductor L_LI.e. i_Lr＝i_LWhile the second switch tube S is turned off₂Due to the second resonant capacitance C₂In the presence of a second switching tube S₂And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

buck mode the sixth mode occurs at t₅-t₆Stage t of₅Second switch tube S is turned off at soft moment₂Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonant, resonant inductance L_rCurrent i in_LrContinuing to increase, the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging the first resonant capacitor C₁Terminal voltage gradually decreases, and second resonant capacitor C₂Terminal voltage gradually increases when C₂Terminal voltage increase to V₁-V₂at/K, resonant inductance L_rCurrent i in_LrMaximum is reached, this modality ends, duration:

the seventh mode of the buck mode occurs at t₆-t₇Stage t of₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuous discharge and second resonant capacitor C₂Continuing to charge, resonating the inductor current i_LrInitially reduced, the first resonant capacitance C₁Terminal voltage gradually decreases, and second resonant capacitor C₂The terminal voltage gradually increases when the first resonant capacitor C₁Terminal voltage is reduced to 0V, and a second resonant capacitor C₂Terminal voltage increase to V₁When this modality ends, the duration is:

the eighth mode of the buck mode occurs at t₇-t₈Stage t of₇Moment first resonance capacitor C₁The terminal voltage is reduced to 0V, the first diode D₁Starting to naturally conduct follow current, and switching the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

the ninth mode of the buck mode occurs at t₈-t₉Stage t of₈First switch tube S is switched on softly at any moment₁The inductor L stores energy; resonant inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i in_LrContinue to decrease as the resonant inductance L_rCurrent i in_LrThe third switching tube S is switched off when the voltage is reduced to 0A₃A third switching tube S₃Realize soft shutoff, turn off the third switch tube S₃When this modality ends, the duration is:

further, the boost mode control method includes nine modes, and the nine boost modes sequentially complete one cycle, specifically including:

boost mode the first mode occurs at t₀-t₁Stage (2):t₀moment, resonance inductance L_rMedium current i_LrIs 0, only the second switch tube S₂On, the current direction in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁In this mode, the second voltage source V₂The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the second switch tube S is turned off₂Due to the second resonant capacitance C₂In the presence of a second switching tube S₂Realize soft turn-off, turn-off second switch tube S₂When so, this mode ends;

boost mode the second mode occurs at t₁-t₂Stage t of₁Second switch tube S is turned off at soft moment₂The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L2Approximately constant when the first resonant capacitor C₁When the terminal voltage drops to 0V, this mode ends, and the duration is: t is t₁₂＝V₂·2C_r/I_L2Wherein, C_r＝C₁＝C₂，C_rIs a resonant capacitor;

boost mode the third mode occurs at t₂-t₃Stage (2): t is t₂Moment first resonance capacitor C₁The voltage at both ends is reduced to 0V, the first diode D₁Naturally conducting follow current, and connecting the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

boost mode the fourth mode occurs at t₃-t₄Stage (2): t is t₃First switch tube S is switched on softly at any moment₁The energy stored in the inductor L passes through the first switch tube S₁To a first voltage source V₁Transfer, turning off the first switch tube S₁The fourth switch tube S is turned on in the short time₄Is conducted due to the conduction ofFour-switch tube S₄The current in the front auxiliary branch is 0A, and the fourth switch tube S₄Soft switching on is realized, and the mode is finished;

boost mode the fifth mode occurs at t₄-t₅Stage (2): t is t₄Fourth switching tube S capable of being turned on softly at any moment₄The dotted terminal of the primary winding Np of the transformer T is negative, the dotted terminal of the secondary winding Ns is induced with negative electromotive force, and the sixth diode D and the seventh diode D₆、D₇Conducting, the voltage of the secondary winding Ns of the transformer T is clamped at V₂The Np voltage of the primary winding of the transformer T is V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing the number of turns of the secondary winding and the primary winding, so that the resonant inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrLinear increase when resonant inductance L_rCurrent i_LrWhen the current is equal to the L current of the inductor, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

boost mode the sixth mode occurs at t₅-t₆Stage (2): t is t₅First switch tube S is turned off in a soft mode at any moment₁Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonance occurs, resonance inductance L_rCurrent i_LrContinuing to increase, the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging the first resonant capacitor C₁Terminal voltage gradually increases, and the second resonant capacitor C₂The terminal voltage gradually decreases when the second resonant capacitor C₂Terminal voltage reduction to V₁-V₂At/n, resonant inductance L_rCurrent i in_LrThe maximum is reached and the modality ends for a duration of:

boost mode the seventh mode occurs at t₆-t₇Stage (2): t is t₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuously charging and second resonant capacitor C₂Continuing to discharge, resonant inductor L_rCurrent i_LrInitially reduced, the first resonant capacitance C₁The terminal voltage continues to increase, and the second resonant capacitor C₂The terminal voltage continues to decrease when the second resonant capacitor C₂When the terminal voltage is reduced to 0V, the mode ends, and the duration is as follows:

boost mode the eighth mode occurs at t₇-t₈Stage (2): t is t₇Time second resonance capacitor C₂When the terminal voltage is reduced to 0, the second diode D2 starts to naturally conduct and freewheel, and the second switch tube S₂Is clamped to be close to 0, and then the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

boost mode the ninth mode occurs at t₈-t₉Stage (2): t is t₈Second switch tube S is switched on softly at any moment₂The direction of the current in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁The inductor L stores energy and resonates the inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i_LrContinue to decrease as the resonant inductance L_rCurrent i_LrTurning off the fourth switching tube S when the voltage is reduced to 0₄Fourth switch tube S₄And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

compared with the prior art, the invention has the following beneficial effects:

the invention solves the problem that the traditional bidirectional half-bridge PFC converter is conducted at the moment of the main switching tubeIn the meantime, the body diode of the rectifier switch tube has the problem of overlarge conduction loss of the main switch tube due to the reverse recovery characteristic and the fact that the energy stored before the parasitic capacitance of the main switch tube cannot be released when the main switch tube is switched on, and the two parts of energy loss are successfully fed back to the voltage source V through the resonant inductor of the auxiliary branch circuit and the transformer₂Meanwhile, zero voltage conduction and disconnection of the main circuit switch tube and zero current conduction and disconnection of the auxiliary branch circuit switch tube are achieved, and the efficiency of the converter is remarkably improved.

Drawings

FIG. 1 is a schematic diagram of a circuit configuration of an embodiment of the present invention;

FIG. 2 is an equivalent circuit diagram of the embodiment operating in the buck mode in the first mode;

FIG. 3 is an equivalent circuit diagram of the embodiment operating in the second mode in buck mode;

FIG. 4 is an equivalent circuit diagram of the third mode of operation of the embodiment in buck mode;

FIG. 5 is an equivalent circuit diagram of the fourth mode of operation of the embodiment in buck mode;

FIG. 6 is an equivalent circuit diagram of the fifth mode of operation of the embodiment in buck mode;

fig. 7 is an equivalent circuit diagram of the sixth mode and the seventh mode when the embodiment operates in the buck mode;

FIG. 8 is an equivalent circuit diagram of the embodiment operating in the eighth mode in buck mode;

FIG. 9 is an equivalent circuit diagram of the ninth mode of operation of the embodiment in buck mode;

FIG. 10 is a waveform signal diagram of the current flowing through the inductor and the voltage applied to the switching tube when the embodiment is operated in the buck mode;

FIG. 11 is an equivalent circuit diagram of the embodiment operating in the first mode in the boost mode;

FIG. 12 is an equivalent circuit diagram of the embodiment operating in the second mode in the boost mode;

FIG. 13 is an equivalent circuit diagram of the embodiment operating in the third mode in the boost mode;

FIG. 14 is an equivalent circuit diagram of the embodiment operating in the fourth mode in the boost mode;

FIG. 15 is an equivalent circuit diagram of the embodiment operating in the fifth mode in boost mode;

fig. 16 is an equivalent circuit diagram of the sixth mode and the seventh mode in the boost mode;

FIG. 17 is an equivalent circuit diagram of the embodiment operating in the eighth mode in the boost mode;

FIG. 18 is an equivalent circuit diagram of the ninth mode of operation of the embodiment in boost mode;

fig. 19 is a waveform signal diagram of the current flowing through the inductor and the voltage applied to the switching tube when the embodiment is operated in the boosting process.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in FIG. 1, a bidirectional PFC soft switch (PFC: power factor correction) comprises a main loop and an auxiliary branch, wherein the main loop comprises a first switching tube S and a second switching tube S₁、S₂First and second resonant capacitors C₁、C₂Inductor L, first and second filter capacitors C_o1、C_o2The auxiliary branch comprises a third switching tube S and a fourth switching tube S₃、S₄Resonant inductance L_rA transformer T and a full bridge rectifier bridge;

first resonant capacitor C₁And a first switch tube S₁Parallel second resonant capacitor C₂And a second switch tube S₂Parallel connection; first switch tube S₁Source electrode of and the second switch tube S₂The other end of the inductor L is respectively connected with the anode output end m of the full-bridge rectifier bridge and the second filter capacitor C_o2Is connected to a second filter capacitor C_o2And the other end of the first switch tube S₂The source electrodes of the two-way transistor are connected; a first filter capacitor C_o1Are respectively connected with the first switch tube S₁Drain electrode of the first switching tube S₂The source electrodes of the two-way transistor are connected; first and third switch tubes S₁、S₃Is connected with the drain of the third switching tube S₃Source and fourthSwitch tube S₄Is connected with the drain electrode of the first switching tube S and the fourth switching tube S₂、S₄The source electrodes of the two-way transistor are connected; negative output end n of full-bridge rectifier bridge and fourth switching tube S₄The source electrodes of the two-way transistor are connected; resonant inductor L_rOne end of (1) and a first switch tube S₁Is connected with the source electrode of the resonant inductor L_rThe other end of the first switch tube is connected with the different name end of the primary side of the transformer T, the same name end of the primary side of the transformer T is connected with the third switch tube S₃The source electrodes of the two-way transistor are connected; the dotted terminal of the secondary side of the transformer T is connected with a first alternating current input terminal p of the full-bridge rectifier bridge, and the dotted terminal of the secondary side of the transformer T is connected with a second alternating current input terminal q of the full-bridge rectifier bridge.

The PFC soft switch also comprises a first diode D, a second diode D, a third diode D and a fourth diode D₁、D₂、D₃、D₄A first, a second, a third and a fourth diode D₁、D₂、D₃、D₄A first switch tube S, a second switch tube S, a third switch tube S and a fourth switch tube S in sequence₁、S₂、S₃、S₄An anti-parallel diode. First switch tube S₁Source electrode of and the second switch tube S₂The drain electrodes of the two bridge arms are connected in series to form a main bridge arm, and the connection point is marked as a point A; third switch tube S₃Source electrode and fourth switch tube S₄The drain electrodes of the two bridge arms are connected in series to form an auxiliary bridge arm, and the connection point is marked as a point B; upper end of main arm (first switch tube S)₁Drain electrode of) and upper end point of auxiliary arm (third switching tube S)₃Drain of (d) and is denoted as point C; lower end point of main bridge arm (second switch tube S)₂Source electrode of) and the lower end point (fourth switching tube S) of the auxiliary bridge arm₄Source of (D) and is denoted as point D.

The full bridge rectifier bridge comprises a fifth diode D, a sixth diode D, a seventh diode D and an eighth diode D₅、D₆、D₇、D₈Fifth and sixth diodes D₅、D₆A branch formed by series connection with a seventh diode D and an eighth diode D₇、D₈The branches formed by the series connection are connected in parallel.

The invention also provides a control method of the bidirectional PFC soft switch, which is completed based on the bidirectional PFC soft switch and comprises a voltage reduction mode control method and a voltage reduction mode control methodBoost mode control method, first voltage source V when PFC soft switch is in buck mode₁And a first filter capacitor C_o1Parallel connection, a first filter capacitor C_o1Has two ends as voltage input ends and a second filter capacitor C_o2The two ends of the voltage-stabilizing switch are voltage output ends; in boost mode, the second voltage source V₂And a second filter capacitor C_o2Parallel second filter capacitor C_o2Has two ends as voltage input ends, a first filter capacitor C_o1Are voltage output terminals.

The voltage reduction mode control method comprises nine modes, wherein the nine voltage reduction modes are sequentially performed to complete one cycle, and the method specifically comprises the following steps:

as shown in fig. 2, the buck mode first mode occurs at t₀-t₁Stage t of₀Moment resonance inductance L_rCurrent i of_Lr0, only the first switching tube S₁In the conducting state, the current direction of the inductor L is controlled by the first voltage source V₁To a second voltage source V₂The first voltage source V of the mode₁The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁Soft shutdown is realized, and the mode is finished;

as shown in FIG. 3, the second mode of buck mode occurs at t₁-t₂Stage t₁First switch tube S is turned off in a soft mode at any moment₁The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L1Approximately constant when the second resonant capacitance C is₂Terminal voltage is defined by V₁When the voltage drops to 0V, the mode ends, and the duration is: t is t₁₂＝V₁·2C_r/I_L1Wherein, C_r＝C₁＝C₂，C_rIs a resonant capacitor;

as shown in fig. 4, the boost mode third mode occurs at t₂-t₃Stage t₂Time second resonance capacitor C₂The end voltage is reduced to 0V, and the second diode D₂Naturally conducting follow current, second diode D₂Is conducted to the second switch tube S₂The drain-source voltage is clamped to be close to 0V, and the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

as shown in fig. 5, the fourth mode of the buck mode occurs at t₃-t₄Stage t of₃Second switch tube S is switched on softly at any moment₂The energy stored in the inductor L passes through the second switch tube S₂Release, turning off the second switch tube S₂The third switch tube S is switched in the short time before₃Conducting due to the opening of the third switch tube S₃The current in the front auxiliary branch is 0A, and the third switch tube S₃Soft switching on is realized, and the mode is finished;

as shown in fig. 6, t₄Third switching tube S capable of being switched on at any moment₃The dotted terminal of the primary winding Np of the transformer T is positive, the dotted terminal of the secondary winding Ns is induced by positive electromotive force, and the fifth diode D and the eighth diode D₅、D₈Conducting, clamping the secondary winding Ns voltage of the transformer T at the voltage source V₂Voltage V of₂The Np voltage of the primary winding of the transformer T is clamped at V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing the turns of the secondary winding and the primary winding, and the resonance inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrA linear increase; when resonance inductance L_rCurrent i_LrCurrent i increases to inductor L_LI.e. i_Lr＝i_LWhile the second switch tube S is turned off₂Due to the second resonant capacitance C₂In the presence of a second switching tube S₂And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

as shown in fig. 7, buck modeThe sixth mode occurs at t₅-t₆Stage t of₅Second switch tube S is turned off at soft moment₂Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonant, resonant inductance L_rCurrent i in_LrContinuing to increase, the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging the first resonant capacitor C₁Terminal voltage gradually decreases, and second resonant capacitor C₂Terminal voltage gradually increases when C₂Terminal voltage increase to V₁-V₂at/K, resonant inductance L_rCurrent i in_LrMaximum is reached, this modality ends, duration:

the seventh mode of the buck mode occurs at t₆-t₇Stage t of₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuous discharge and second resonant capacitor C₂Continuing to charge, resonating the inductor current i_LrInitially reduced, the first resonant capacitance C₁Terminal voltage gradually decreases, and second resonant capacitor C₂The terminal voltage gradually increases when the first resonant capacitor C₁Terminal voltage is reduced to 0V, and a second resonant capacitor C₂Terminal voltage increase to V₁When this modality ends, the duration is:

as shown in fig. 8, the eighth mode of the buck mode occurs at t₇-t₈Stage t of₇Moment first resonance capacitor C₁The terminal voltage is reduced to 0V, the first diode D₁Starting to naturally conduct a follow current, the first diode D₁Is conducted to the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

as shown in fig. 9, the ninth buck mode occurs at t₈-t₉Stage t of₈First switch tube S is switched on softly at any moment₁The inductor L stores energy; resonant inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i in_LrContinue to decrease as the resonant inductance L_rCurrent i in_LrThe third switching tube S is switched off when the voltage is reduced to 0A₃A third switching tube S₃Realize soft shutoff, turn off the third switch tube S₃When this modality ends, the duration is:

FIG. 10 shows the first, second and third switch tubes S₁、S₂、S₃Under the whole voltage reduction mode, the grid source voltage, the drain source voltage, the inductor L and the resonant inductor L_rA waveform diagram of (a). When the main loop is in the voltage reduction mode, the fourth switch tube S₄Not in operation, only the third switching tube S₃And has an auxiliary function. A second switch tube S₂Before the switch-off, the third switch tube S is firstly switched on₃Conducting, resonant inductance L_rWhen the current in the second switch tube increases from 0 to the load current, the second switch tube S is turned off₂(ii) a Then the current in the resonant inductor Lr continues to increase, and the resonant inductor L_rA first and a second resonant capacitor C₁、C₂The energy in the resonance capacitor is transferred to the resonance inductor L_rThe potential at the point A rises until the resonant inductor L_rWhen the voltage at the two ends is 0, the current of the resonant inductor reaches the maximum value; then the potential of the point A continuously rises until the first switch tube S₁The drain-source voltage of (1) is 0, at this time the first diode D₁Follow current, first switching tube S₁Can be conducted under ZVS (zero voltage switch), and the resonant inductor L_rThe current in (1) is always reduced from the maximum value; first switch tube S₁After conduction, the resonant inductor L_rThe current in the transformer is continuously reduced, and the energy is totally fed into the second voltage source V by the transformer T₂Until the current is reduced to 0, the third switch tube S₃Can be switched off under ZCS.

The boost mode control method includes nine boost modes, and the nine buck modes sequentially complete one cycle, and specifically includes:

as shown in fig. 11, the boost mode first mode occurs at t₀-t₁Stage t₀Moment, resonance inductance L_rMedium current i_LrIs 0, only the second switch tube S₂On, the current direction in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁In this mode, the second voltage source V₂The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the second switch tube S is turned off₂Due to the second resonant capacitance C₂In the presence of a second switching tube S₂Realize soft turn-off, turn-off second switch tube S₂When so, this mode ends;

as shown in fig. 12, the boost mode second mode occurs at t₁-t₂Stage t of₁Second switch tube S is turned off at soft moment₂The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L1Approximately constant when the first resonant capacitor C₁When the terminal voltage drops to 0V, this mode ends, and the duration is: t is t₁₂＝V₂·2Cr/I_L2Wherein, C1 ═ C2 ═ Cr, Cr is resonance capacitance, I_L2Is the load current in boost mode;

as shown in fig. 13, the boost mode third mode occurs at t₂-t₃Stage (2): t is t₂Moment first resonance capacitor C₁The voltage at both ends is reduced to 0V, the first diode D₁Naturally conducting a follow current, a first diode D₁Is conducted to the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

as shown in figure 14, boost mode fourth mode occurs at t₃-t₄Stage (2): t is t₃First switch tube S is switched on softly at any moment₁The energy stored in the inductor L passes through the first switch tube S₁To a first voltage source V₁Transfer, turning off the first switch tube S₁The fourth switch tube S is turned on in the short time₄Conducting due to the fourth switching tube S being turned on₄The current in the front auxiliary branch is 0A, and the fourth switch tube S₄Soft switching on is realized, and the mode is finished;

as shown in fig. 15, the boost mode fifth mode occurs at t₄-t₅Stage (2): t is t₄Fourth switching tube S capable of being turned on softly at any moment₄The dotted terminal of the primary winding Np of the transformer T is negative, the dotted terminal of the secondary winding Ns is induced with negative electromotive force, and the sixth diode D and the seventh diode D₆、D₇Conducting, the voltage of the secondary winding Ns of the transformer T is clamped at V₂The Np voltage of the primary winding of the transformer T is V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing the number of turns of the secondary winding and the primary winding, so that the resonant inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrLinear increase when resonant inductance L_rCurrent i_LrWhen the current is equal to the L current of the inductor, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

as shown in fig. 16, the boost mode sixth mode occurs at t₅-t₆Stage (2): t is t₅First switch tube S is turned off in a soft mode at any moment₁Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonance occurs, resonance inductance L_rCurrent i_LrContinuing to increase, the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging the first resonant capacitor C₁Terminal voltage gradually increases, secondResonant capacitor C₂The terminal voltage gradually decreases when the second resonant capacitor C₂Terminal voltage reduction to V₁-V₂At/n, resonant inductance L_rCurrent i in_LrThe maximum is reached and the modality ends for a duration of:

boost mode the seventh mode occurs at t₆-t₇Stage (2): t is t₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuously charging and second resonant capacitor C₂Continuing to discharge, resonant inductor L_rCurrent i_LrInitially reduced, the first resonant capacitance C₁The terminal voltage continues to increase, and the second resonant capacitor C₂The terminal voltage continues to decrease when the second resonant capacitor C₂When the terminal voltage is reduced to 0V, the mode ends, and the duration is as follows:

as shown in fig. 17, the eighth mode of the boost mode occurs at t₇-t₈Stage (2): t is t₇Time second resonance capacitor C₂The terminal voltage is reduced to 0, the second diode D2 starts to naturally conduct and freewheel, and the conduction of the second diode D2 leads the second switch tube S₂Is clamped to be close to 0, and then the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

as shown in fig. 18, the ninth mode of the boost mode occurs at t₈-t₉Stage (2): t is t₈Second switch tube S is switched on softly at any moment₂The direction of the current in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁The inductor L stores energy and resonates the inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i_LrContinue to decrease as the resonant inductance L_rCurrent i_LrTurn off the fourth switch tube when the voltage is reduced to 0S₄Fourth switch tube S₄And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

FIG. 19 shows the first, second and fourth switch tubes S₁、S₂、S₃Under the whole boosting mode, the grid source voltage, the drain source voltage, the inductor L and the resonant inductor L_rA waveform diagram of (a). When the main circuit is in the boosting mode, the third switch tube S₃Not working, only the fourth switching tube S₄And has an auxiliary function. First switch tube S₁Before the switch-off, the fourth switch tube S is firstly switched on₄Conducting, resonant inductance L_rWhen the current in the first switch tube increases from 0 to the load current, the first switch tube S is turned off₁(ii) a Thereafter resonant inductor L_rThe current in (1) continues to increase, and the resonant inductance L_rA first and a second resonant capacitor C₁、C₂The energy in the resonance capacitor is transferred to the resonance inductor L_rThe potential at the point A is reduced until the resonant inductor L_rWhen the voltage at both ends is 0, the resonant inductor L_rThe current of (2) reaches a maximum value; then the potential of the point A continuously decreases until the second switch tube S₂Is 0, when the second diode D is connected to the source₂Follow current, second switching tube S₂Can be conducted under ZVS, and the resonant inductor L_rThe current in (1) is always reduced from the maximum value; a second switch tube S₂After conduction, the resonant inductor L_rThe current in the transformer is continuously reduced, and the energy is totally fed into the second voltage source V by the transformer T₂Until the current drops to 0, the fourth switch tube S₄Can be switched off under ZCS.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims (2)

1. A control method of bidirectional PFC soft switch is characterized in thatCharacterized in that: the method is completed based on a bidirectional PFC soft switch, wherein the bidirectional PFC soft switch comprises a main loop and an auxiliary branch; the main loop comprises a first and a second switch tube S₁、S₂First and second resonant capacitors C₁、C₂Inductor L, first and second filter capacitors C_o1、C_o2(ii) a The auxiliary branch comprises a third switching tube S and a fourth switching tube S₃、S₄Resonant inductance L_rTransformer T, first, second, third and fourth diodes D₁、D₂、D₃、D₄And a full bridge rectifier bridge;

first resonant capacitor C₁And a first switch tube S₁Parallel second resonant capacitor C₂And a second switch tube S₂Parallel connection; first switch tube S₁Source electrode of and the second switch tube S₂The other end of the inductor L is respectively connected with the anode output end m of the full-bridge rectifier bridge and the second filter capacitor C_o2Is connected to a second filter capacitor C_o2And the other end of the first switch tube S₂The source electrodes of the two-way transistor are connected; a first filter capacitor C_o1Are respectively connected with the first switch tube S₁Drain electrode of the first switching tube S₂The source electrodes of the two-way transistor are connected; first and third switch tubes S₁、S₃Is connected with the drain of the third switching tube S₃Source electrode and fourth switch tube S₄Is connected with the drain electrode of the first switching tube S and the fourth switching tube S₂、S₄The source electrodes of the two-way transistor are connected; negative output end n of full-bridge rectifier bridge and fourth switching tube S₄The source electrodes of the two-way transistor are connected; resonant inductor L_rOne end of (1) and a first switch tube S₁Is connected with the source electrode of the resonant inductor L_rThe other end of the first switch tube is connected with the different name end of the primary side of the transformer T, the same name end of the primary side of the transformer T is connected with the third switch tube S₃The source electrodes of the two-way transistor are connected; the homonymous end of the secondary side of the transformer T is connected with a first alternating current input end p of the full-bridge rectifier bridge, and the synonym end of the secondary side of the transformer T is connected with a second alternating current input end q of the full-bridge rectifier bridge;

first, second, third and fourth switch tubes S₁、S₂、S₃、S₄Are all provided with anti-parallel diodesA linear power switch tube; first, second, third and fourth diodes D₁、D₂、D₃、D₄A first switch tube S, a second switch tube S, a third switch tube S and a fourth switch tube S in sequence₁、S₂、S₃、S₄The anti-parallel diode of (1);

the full bridge rectifier bridge comprises a fifth diode D, a sixth diode D, a seventh diode D and an eighth diode D₅、D₆、D₇、D₈Fifth and sixth diodes D₅、D₆A branch formed by series connection with a seventh diode D and an eighth diode D₇、D₈The branches formed by the series connection are connected in parallel;

the control method of the bidirectional PFC soft switch comprises a buck mode control method and a boost mode control method; the first voltage source V is under the voltage reduction mode of the PFC soft switch₁And a first filter capacitor C_o1Parallel connection, a first filter capacitor C_o1Has two ends as voltage input ends and a second filter capacitor C_o2The two ends of the voltage-stabilizing switch are voltage output ends; the second voltage source V is used for the PFC soft switch in a boost mode₂And a second filter capacitor C_o2Parallel second filter capacitor C_o2Has two ends as voltage input ends, a first filter capacitor C_o1The two ends of the voltage-stabilizing switch are voltage output ends;

the voltage reduction mode control method comprises nine modes, wherein the nine modes sequentially complete one cycle, and the method specifically comprises the following steps:

the first mode of the buck mode occurs at t₀-t₁Stage t of₀Moment, resonance inductance L_rCurrent i of_Lr0, only the first switching tube S₁In the conducting state, the current direction of the inductor L is controlled by the first voltage source V₁To a second voltage source V₂The first voltage source V of the mode₁The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁Soft shutdown is realized, and the mode is finished;

buck mode the second mode occurs at t₁-t₂Stage t of₁First switch tube S is turned off in a soft mode at any moment₁The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L1Approximately constant when the second resonant capacitance C is₂Terminal voltage is defined by V₁When the voltage drops to 0V, the mode ends, and the duration is: t is t₁₂＝V₁·2C_r/I_L1Wherein, C_r＝C₁＝C₂，C_rIs a resonant capacitor;

the third mode of the buck mode occurs at t₂-t₃Stage t of₂Time second resonance capacitor C₂The end voltage is reduced to 0V, and the second diode D₂Naturally conducting follow current, and connecting the second switch tube S₂The drain-source voltage is clamped to be close to 0V, and the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

the fourth mode of the buck mode occurs at t₃-t₄Stage t of₃Second switch tube S is switched on softly at any moment₂The energy stored in the inductor L passes through the second switch tube S₂Release, turning off the second switch tube S₂The third switch tube S is switched in the short time before₃Conducting due to the opening of the third switch tube S₃The current in the front auxiliary branch is 0A, and the third switch tube S₃Soft switching on is realized, and the mode is finished;

the fifth mode of the buck mode occurs at t₄-t₅Stage t of₄Third switching tube S capable of being switched on at any moment₃The dotted terminal of the primary winding Np of the transformer T is positive, the dotted terminal of the secondary winding Ns is induced by positive electromotive force, and the fifth diode D and the eighth diode D₅、D₈Conducting, clamping the secondary winding Ns voltage of the transformer T at the voltage source V₂Voltage V of₂The Np voltage of the primary winding of the transformer T is clamped at V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing secondary windings and primary windingsNumber of turns of (1), resonant inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrA linear increase; when resonance inductance L_rCurrent i_LrCurrent i increases to inductor L_LI.e. i_Lr＝i_LWhile the second switch tube S is turned off₂Due to the second resonant capacitance C₂In the presence of a second switching tube S₂And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

buck mode the sixth mode occurs at t₅-t₆Stage t of₅Second switch tube S is turned off at soft moment₂Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonant, resonant inductance L_rCurrent i in_LrContinuing to increase, the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging the first resonant capacitor C₁Terminal voltage gradually decreases, and second resonant capacitor C₂Terminal voltage gradually increases when C₂Terminal voltage increase to V₁-V₂at/K, resonant inductance L_rCurrent i in_LrMaximum is reached, this modality ends, duration:

the seventh mode of the buck mode occurs at t₆-t₇Stage t of₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuous discharge and second resonant capacitor C₂Continuing to charge, resonating the inductor current i_LrInitially reduced, the first resonant capacitance C₁Terminal voltage gradually decreases, and second resonant capacitor C₂The terminal voltage gradually increases when the first resonant capacitor C₁Terminal voltage is reduced to 0V, and a second resonant capacitor C₂Terminal voltage increase to V₁When this modality ends, the duration is:

the eighth mode of the buck mode occurs at t₇-t₈Stage t of₇Moment first resonance capacitor C₁The terminal voltage is reduced to 0V, the first diode D₁Starting to naturally conduct follow current, and switching the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

the ninth mode of the buck mode occurs at t₈-t₉Stage t of₈First switch tube S is switched on softly at any moment₁The inductor L stores energy; resonant inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i in_LrContinue to decrease as the resonant inductance L_rCurrent i in_LrThe third switching tube S is switched off when the voltage is reduced to 0A₃A third switching tube S₃Realize soft shutoff, turn off the third switch tube S₃When this modality ends, the duration is:

2. the method of claim 1, wherein the step of controlling the bidirectional PFC soft switch comprises: the boost mode control method comprises nine modes, wherein the nine boost modes sequentially complete one cycle, and specifically comprises the following steps:

boost mode the first mode occurs at t₀-t₁Stage (2): t is t₀Moment, resonance inductance L_rMedium current i_LrIs 0, only the second switch tube S₂On, the current direction in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁In this mode, the second voltage source V₂The energy of the first switch tube S is transferred to the inductor L, and when the energy stored in the inductor L reaches the maximum, the second switch tube S is turned off₂Due to second harmonicVibration capacitor C₂In the presence of a second switching tube S₂Realize soft turn-off, turn-off second switch tube S₂When so, this mode ends;

boost mode the second mode occurs at t₁-t₂Stage t of₁Second switch tube S is turned off at soft moment₂The direction of the current flowing through the inductor L cannot change suddenly, so that the first resonant capacitor C₁Discharging, second resonant capacitor C₂Charging, the inductance value of the inductor L is opposite to the first and second resonant capacitors C₁、C₂Large capacitance value, current I through inductor L_L2Approximately constant when the first resonant capacitor C₁When the terminal voltage drops to 0V, this mode ends, and the duration is: t is t₁₂＝V₂·2C_r/I_L2Wherein, C_r＝C₁＝C₂，C_rIs a resonant capacitor;

boost mode the third mode occurs at t₂-t₃Stage (2): t is t₂Moment first resonance capacitor C₁The voltage at both ends is reduced to 0V, the first diode D₁Naturally conducting follow current, and connecting the first switch tube S₁The drain-source voltage of the first switching tube S is clamped to be close to 0V, and the first switching tube S is switched on under zero voltage₁A first switch tube S₁Realize soft switching on, switch on the first switch tube S₁When so, this mode ends;

boost mode the fourth mode occurs at t₃-t₄Stage (2): t is t₃First switch tube S is switched on softly at any moment₁The energy stored in the inductor L passes through the first switch tube S₁To a first voltage source V₁Transfer, turning off the first switch tube S₁The fourth switch tube S is turned on in the short time₄Conducting due to the fourth switching tube S being turned on₄The current in the front auxiliary branch is 0A, and the fourth switch tube S₄Soft switching on is realized, and the mode is finished;

boost mode the fifth mode occurs at t₄-t₅Stage (2): t is t₄Fourth switching tube S capable of being turned on softly at any moment₄The dotted terminal of the primary winding Np of the transformer T is negative, the dotted terminal of the secondary winding Ns is induced with negative electromotive force, and the sixth and the fourthSeven diode D₆、D₇Conducting, the voltage of the secondary winding Ns of the transformer T is clamped at V₂The Np voltage of the primary winding of the transformer T is V₂K, where K ═ n_s/n_p，n_s、n_pRespectively representing the number of turns of the secondary winding and the primary winding, so that the resonant inductance L_rThe voltage across is clamped at V₁-V₂K, resonant inductance L at this time_rCurrent i_LrLinear increase when resonant inductance L_rCurrent i_LrWhen the current is equal to the L current of the inductor, the first switch tube S is turned off₁Due to the first resonant capacitor C₁In the presence of a first switching tube S₁And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

boost mode the sixth mode occurs at t₅-t₆Stage (2): t is t₅First switch tube S is turned off in a soft mode at any moment₁Resonant inductance L_rStart and first and second resonant capacitors C₁、C₂Resonance occurs, resonance inductance L_rCurrent i_LrContinuing to increase, the first resonant capacitor C₁Charging, second resonant capacitor C₂Discharging the first resonant capacitor C₁Terminal voltage gradually increases, and the second resonant capacitor C₂The terminal voltage gradually decreases when the second resonant capacitor C₂Terminal voltage reduction to V₁-V₂At/n, resonant inductance L_rCurrent i in_LrThe maximum is reached and the modality ends for a duration of:

boost mode the seventh mode occurs at t₆-t₇Stage (2): t is t₆Moment resonance inductance L_rCurrent i_LrReaches a maximum value, after which the first resonant capacitor C₁Continuously charging and second resonant capacitor C₂Continuing to discharge, resonant inductor L_rCurrent i_LrInitially reduced, the first resonant capacitance C₁The terminal voltage continues to increase, and the second resonant capacitor C₂The terminal voltage continues to decrease when the second resonant capacitor C₂When the terminal voltage is reduced to 0V, the mode ends, and the duration is as follows:

boost mode the eighth mode occurs at t₇-t₈Stage (2): t is t₇Time second resonance capacitor C₂When the terminal voltage is reduced to 0, the second diode D2 starts to naturally conduct and freewheel, and the second switch tube S₂Is clamped to be close to 0, and then the second switch tube S is switched on under zero voltage₂A second switch tube S₂Realize soft switching on, switch on the second switch tube S₂When so, this mode ends;

boost mode the ninth mode occurs at t₈-t₉Stage (2): t is t₈Second switch tube S is switched on softly at any moment₂The direction of the current in the inductor L is controlled by a second voltage source V₂To the first voltage source V₁The inductor L stores energy and resonates the inductor L_rThe voltage at both ends becomes-V₂K, resonant inductance L_rCurrent i_LrContinue to decrease as the resonant inductance L_rCurrent i_LrTurning off the fourth switching tube S when the voltage is reduced to 0₄Fourth switch tube S₄And realizing soft turn-off, wherein the mode is ended and the duration is as follows:

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