CN113541476B - Symmetric double-Boost circuit based on soft switch and implementation method - Google Patents

Abstract

The invention discloses a soft switch-based symmetric double-Boost circuit and an implementation method thereof, and the symmetric double-Boost circuit comprises a symmetric soft switch topological circuit and a symmetric double-Boost topological circuit, wherein the symmetric double-Boost topological circuit comprises two symmetrical same-type Boost basic topological circuits, the two Boost basic topological circuits are symmetrically connected to realize medium-high power DC-DC rectification, the symmetric soft switch topological structure comprises two symmetric soft switch topological structures, and the two soft switch topological structures are respectively correspondingly arranged in the two Boost basic topological circuits. The symmetrical soft switching topological circuit is built in the symmetrical double-Boost topological circuit, so that the power tube S is realized _b The zero current turn-off condition and the zero voltage turn-on condition, and the symmetrical soft switch topological circuit enables the power diode VD ₁ 、VD ₂ Working in the zero-current turn-off and zero-voltage turn-on state, reducing the power switch device S as a whole _b And a power two tube VD ₁ 、VD ₂ Loss and converter efficiency are improved.

Description

A Symmetrical Double Boost Circuit Based on Soft Switching and Its Realization Method

technical field

The invention relates to the technical field of rectifier circuits, in particular to a soft-switch-based symmetrical double Boost circuit and an implementation method.

Background technique

A "rectifying circuit" is a circuit that converts AC power into DC power. Most rectification circuits are composed of transformers, rectification main circuits and filters. It is widely used in speed regulation of DC motors, excitation regulation of generators, electrolysis, electroplating and other fields. After the 1970s, the main circuit was mostly composed of silicon rectifier diodes and thyristors. The filter is connected between the main circuit and the load, and is used to filter out the AC component in the pulsating DC voltage. Whether the transformer is set or not depends on the specific situation. The role of the transformer is to achieve the matching between the AC input voltage and the DC output voltage and the electrical isolation between the AC grid and the rectifier circuit.

The function of the rectifier circuit is to convert the low-voltage alternating current output by the AC step-down circuit into unidirectional pulsating direct current. This is the rectification process of alternating current. The rectifier circuit is mainly composed of rectifier diodes. The voltage after the rectifier circuit is no longer an AC voltage, but a mixed voltage containing DC voltage and AC voltage.

The existing symmetrical dual BOOST circuit has fewer switching devices and can operate in a low switching frequency and high power mode. It can not only be independently applied to DC-DC step-up applications, but also can be applied to three-phase single-switch uncontrolled BOOST rectifiers that constitute hybrid rectifiers in AC-DC medium and high voltage applications. However, the current symmetrical dual BOOST circuit lacks soft switching design, which cannot reduce the power loss of the symmetrical dual BOOST converter, and the operating efficiency of its own circuit or a new circuit formed with other converters is limited. The loss is high and the converter efficiency is low.

Contents of the invention

The purpose of the present invention is to provide a symmetrical double Boost circuit based on soft switching to solve the technical problems of high power tube loss and low conversion efficiency in the prior art.

In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

A symmetrical double Boost circuit based on soft switching, including a symmetrical soft switching topology circuit and a symmetrical dual Boost topology circuit, the symmetrical dual Boost topology circuit includes two symmetrical Boost basic topology circuits of the same type, and the two The symmetrical connection of the Boost basic topology circuit can realize medium and high power DC-DC rectification. The symmetrical soft switching topology includes two symmetrical soft switching topological structures, and the two soft switching topological structures are respectively built into the two In the Boost basic topology circuit, the two soft-switching topological structures respectively realize the zero-voltage turn-on and zero-current turn-off of the power transistor and the power diode in the two Boost basic topology circuits to reduce the power loss of the two Boost basic topology circuits And improve the rectification conversion efficiency of the two Boost basic topology circuits.

As a preferred solution of the present invention, the symmetrical dual Boost topology circuit includes a power supply E, a power transistor S _b , an inductor L _{1 ,} an inductor L ₂ , a power diode VD ₁ , a power diode VD ₂ , and a capacitor C ₁ , Capacitor C ₂ , load resistance R, the inductance L _1, are equal to the inductance L ₂ , the power diode VD ₁ is equal to the power diode VD ₂ , wherein,

The anode of the power supply E is electrically connected to _one end of the inductor L1, and the other end of the inductor L1 is electrically connected to the second leg of the power transistor Sb and _one end _of the power diode _VD1 respectively. connected, the other end of the power diode _VD1 is electrically connected to _one end of the capacitor C1 and _one end of the load resistor R respectively, and the negative pole of the power supply E is electrically connected to one end of the inductor L2, so _The other end of the inductor L2 is electrically connected to the third pin of the power transistor Sb and one end of the power diode _VD2 , and the other end of the power diode _VD2 is respectively connected to one end of the _{capacitor C2} , the other end of the load resistor R is electrically connected, and the other end of the capacitor _C1 is electrically connected to the other end of the capacitor _C2 .

As a preferred solution of the present invention, the symmetrical soft switching topology circuit includes inductor L _r1 , inductor L _r2 , capacitor C _s1 , capacitor C _s2 , capacitor C _r1 , capacitor C _r2 , diode D ₁ , diode D ₂ , diode D ₃ , diode D ₄ , diode D ₅ , diode D ₆ , the inductance L _r1 is equal to the inductance L _r2 , the capacitance C _s1 is equal to the capacitance C _s2 , the capacitance C _r1 is equal to the The capacitance C _r2 is equal, the diode D ₁ is equal to the diode D ₄ , the diode D ₂ is equal to the diode D ₅ , the diode D ₃ is equal to the diode D ₆ , the capacitance C _s1 , Capacitor C _s2 provides zero-current turn-off conditions for the power transistor S _b , the inductor L _r1 and inductor L _r2 provide zero-voltage turn-on conditions for the power transistor S _b , and the two soft-switching topologies are power diodes VD ₁ and VD ₂ provide zero-current turn-off conditions and zero-voltage turn-on conditions, where,

One end of the inductor L _r1 and _one end of the diode D1 are respectively electrically connected to the second leg of the power transistor S _b , and the other end of the inductor L _r1 is electrically connected to _one end of the power diode VD1. _The other end of the diode D1 is electrically connected to _one end of the diode D2 and one end of the capacitor C _s1 respectively, the other end of the capacitor C _s1 is electrically connected to the other end of the capacitor _C1 , and the diode D The other end of ₂ is electrically connected to one end of the capacitor C _r1 and one end of the diode _D3 , the other end of the capacitor C _r1 is electrically connected to the other end of the inductor L _r1 , and the diode _{D3 The} other end is electrically connected to the other end of the power diode VD1;

_One end of the inductor L _r2 and one end of the first diode _D4 are respectively electrically connected to the pin of the power transistor S2, and the other end of the inductor L _r2 is electrically connected to one end of the power diode _VD2 . The other end of the diode D ₄ is electrically connected to one end of the diode D ₅ and one end of the capacitor C _s2 respectively, the other end of the capacitor C _s2 is electrically connected to the other end of the capacitor C ₂ , and the diode D The other end of ₅ is electrically connected to one end of the capacitor C _r2 and one end of the diode _D6 respectively, the other end of the capacitor C _r2 is electrically connected to the other end of the inductor L _r2 , and the diode _{D6 The} other end is electrically connected to the other end of the power diode VD2.

As a preferred solution of the present invention, the switching period of the symmetrical soft switching topology circuit includes seven working stages, wherein,

Phase t ₀ ~ t ₁ including the switching period of the first working stage: during the time t ₀ ~ t ₁ , the switching tube S _b remains in the off state, and the power diode VD1, power diode VD2 Maintain zero voltage conduction state;

The second working stage includes the switching period t ₁ ~ t ₂ stage, the power transistor S _b changes from the off state to the zero current on state, and the power diode VD ₁ and power diode VD ₂ change from zero voltage to The on-state changes to the zero-current off-state, and the capacitors C _r1 and C _r2 are kept in a fully discharged state;

In the stage t ₂ -t ₃ including the switching period of the third working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ is kept in the off state, and the inductor L _r1 and the capacitor C _r1 , capacitor C _r2 , and inductor L _r2 are kept in a series resonance state, the capacitors C _s1 and C _s2 are kept in a discharging state, and the capacitors C _r1 and C _r2 are kept in a charging state;

In the stage t ₃ -t ₄ including the switching period of the fourth working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₁ and diode D ₄ are kept in a conducting state, the inductor L _r1 and capacitor C _r1 are kept in a series resonant state, the capacitor C _r2 and inductance L _r2 are kept in a series resonant state, the capacitor C _s1 , capacitor C _s2 is kept in a fully discharged state, and the capacitors C _r1 and C _r2 are kept in a charged state;

In the stage t ₄ -t ₅ including the switching cycle of the fifth working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₁ , diode D ₂ , diode D ₄ , and diode D ₅ are kept in an off state, and the capacitors C _r1 and C _r2 are kept in a full state;

In the _sixth working stage, which includes the switching period t5 _- t6 stage, the power transistor S _b changes from the on state to the zero current off state, and the power diode VD ₁ and power diode VD ₂ remain in the off state. In the off state, the diode D ₁ , diode D ₃ , diode D ₄ , and diode D ₆ are kept in the on state, the capacitor C _s1 and the capacitor C _s2 are kept in the charged state, and the capacitors C _r1 and C _r2 are kept at discharge state;

In the stage t ₆ -t ₇ including the switching cycle of the seventh working stage, the power transistor S _b is kept in the off state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₃ and diode D ₆ are kept in a conduction state, the capacitors C _s1 and C _s2 are kept in a charged state, and the capacitors C _r1 and C _r2 are kept in a discharged state.

As a preferred solution of the present invention, the duration periods of the second, third and fourth working stages in the seven working stages are determined by electrical components, and the second working stage, the third working stage The mathematical expressions of the duration periods in the stage and the fourth working stage are respectively:

The duration of the t ₁ ~ t ₂ stage in the second working stage is t _{1 ~ 2} , and the quantitative expression of the t _{1 ~ 2} is:

In the formula, L _r ＝L _r1 ＝L _r2 , L _r1 , L _r2 are characterized by inductance L _r1 , L _r2 respectively, I _in is the input current of the power supply E, U _o is the voltage across the load resistance R;

The duration of t ₂ to t ₃ in the working phase is t _{2 to 3} , and the quantitative expression of t _{2 to 3} is:

C_r＝C_r1＝C_r2，C_s＝C_s1＝C_s2，L_r＝L_r1＝L_r2，C_r1、C_r2分别表征为电容C_r1、C_r2，C_s1、C_s2表分别征为电容C_s1、C_s2，L_r1、L_r2分别表征为电感L_r1、L_r2；In the formula,

C _r ＝C _r1 ＝C _r2 , C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 and C _r2 are represented by capacitances C _r1 and C _r2 respectively, and C _s1 and C _s2 represent are capacitors C _s1 and C _s2 , and L _r1 and L _r2 are respectively represented as inductances L _r1 and L _r2 ;

The duration of the t3~t4 stage in the working stage is _{t3 ~4 ,} and the quantitative expression of the t3 _~4 is:

In the formula, C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 C _r1 , C _r2 are represented as capacitances C _r1 , C _r2 , respectively, and L _r1 , L _r2 are represented as inductances L _r1 , L _r2 .

As a preferred solution of the present invention, the present invention provides a method for realizing the symmetrical dual Boost circuit based on soft switching, comprising the following steps:

Step S1, quantifying the turn-on time and turn-off time of the power transistor S _b based on the seven working stages;

Step S2, quantifying the resonant angular frequency of the symmetrical soft-switching topology circuit based on the principle of ensuring that the resonant circuit is completed in a limited time and stably;

Step S3, based on the principle of ensuring that D ₁ and D ₂ , D ₄ and D ₅ can be turned off reliably and reduce losses, quantify the component parameters in the symmetrical soft switching topology circuit.

As a preferred solution of the present invention, in the step S1, the specific methods for quantifying the turn-on time and turn-off time of the power transistor S _b include:

Analyze the energy conversion process between the inductor L _r1 , capacitor C _s1 and capacitor C _r1 in the t ₁ ~ t ₄ stage of the symmetrical soft switching topology circuit, and based on the inductance L _r1 , capacitor C _s1 and capacitor C _r1 The energy conversion process quantifies the minimum turn-on time of the power transistor _Sb , and the minimum turn-on time is:

T _min(on) = T·D _min ,

In the formula, T _min(on) >t ₄ -t ₁ , T is the switching period, and D _min is the minimum duty cycle;

Analyze the energy conversion process between the inductor L _r1 , the capacitor C _s1 , the capacitor C _r1 , and the load resistor R in the t ₅ stage of the previous switching cycle to the t ₀ stage of the next switching cycle of the symmetrical soft switching topology circuit, and according to the The energy conversion process between the inductor L _r1 , the capacitor C _s1 , the capacitor C _r1 , and the load resistor R quantifies the minimum off time of the power transistor S _b , and the minimum off time is:

T _min(off) = T·(1-D _max ),

In the formula, T _min(on) >t ₀ ′-t ₅ , T is the switching period, and D _max is the maximum duty cycle.

As a preferred solution of the present invention, in the step S2, the specific method for quantifying the resonant angular frequency of the symmetrical soft-switching topology circuit includes:

Obtain the switching frequency of the switching tube S _b , and ensure that the resonant angular frequency of the resonant circuit is greater than the switching frequency so that the resonant response of the resonant circuit is completed within a limited time, and the quantification formula of the resonant angular frequency is:

ω ₂ >2πf _s ;

C_r＝C_r1＝C_r2，L_r＝L_r1＝L_r2，ω₂是谐振角频率，f_s是开关频率，C_r1、C_r2分别表征为电容C_r1、C_r2，L_r1、L_r2分别表征为电感L_r1、L_r2。In the formula,

C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 , ω ₂ is the resonant angular frequency, f _s is the switching frequency, C _r1 , C _r2 are characterized by capacitances C _r1 , C _r2 , L _r1 , L _r2 is characterized by inductance L _r1 and L _r2 respectively.

As a preferred solution of the present invention, in the step S3, the specific method for quantifying the component parameters in the symmetrical soft switching topology circuit includes:

Before the capacitor C _r1 or C _r2 is discharged to 0, the diode D ₁ and the diode D ₂ or the diode D ₄ and the diode D ₅ can be turned off reliably, and the basic relational expression of the components of the symmetrical soft switching topology circuit is constructed:

In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 , C _r2 are represented by capacitance C _r1 , C _r2 respectively, and L _r1 , L _r2 are represented by inductance L _r1 , L _r2 respectively , I _in is the input current of the power supply E, and U _o is the voltage across the load resistor R.

As a preferred solution of the present invention, the value range of capacitance C _r , capacitance C _s , and inductance L _r is obtained by using the basic relational formula of the soft switching element and the quantization formula of the resonant angular frequency:

分别表征为电容C_r1、C_r2两端电压U_Cr1、U_Cr2的最大值，I_{in max}为供电电源E的输入电流I_in的最大值，C_r1、C_r2分别表征为电容C_r1、C_r2，C_s1、C_s2分别表征为电容C_s1、C_s2，L_r1、L_r2分别表征为电感L_r1、L_r2。In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r ＝C _r1 ＝C _r2 ,

Respectively represented as the maximum value of the voltage U _Cr1 and U _Cr2 across the capacitors C _r1 and C _r2 , I _{in max} is the maximum value of the input current I _in of the power supply E, and C _r1 and C _r2 are respectively represented by the capacitors C _r1 and C _r2 , C _s1 , C _s2 are respectively represented as capacitors C _s1 , C _s2 , and L _r1 , L _r2 are respectively represented as inductances L _r1 , L _r2 .

Compared with the prior art, the present invention has the following beneficial effects:

In the present invention, a symmetrical soft-switching topological circuit is built in a symmetrical dual-Boost topology circuit, and capacitors C _s1 and capacitors C _s2 in the symmetrical soft-switching topological circuit are respectively responsible for providing the zero-current shutdown condition of power tube S _b , inductance L _r1 , inductance L _r2 is responsible for providing the zero-voltage turn-on condition of the power tube S _b , which reduces the loss of the power tube S _b as a whole. At the same time, the soft switching circuit also makes the power diodes VD ₁ and VD ₂ work in the zero-current off and zero-voltage turn-on state. The symmetrical double Boost converter with soft switching function reduces the loss of the power switching device S _b and power diodes VD ₁ and VD ₂ as a whole, and improves the efficiency of the converter. The soft switching circuit is applied to the three-phase single-switch Boost rectifier in the hybrid rectifier to reduce the switching loss of the hybrid rectifier and improve the energy conversion efficiency.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that are required in the description of the embodiments or the prior art. Apparently, the drawings in the following description are only exemplary, and those skilled in the art can also obtain other implementation drawings according to the provided drawings without creative work.

1 is a schematic diagram of a symmetrical dual Boost circuit based on soft switching provided by an embodiment of the present invention;

Fig. 2 is the equivalent circuit diagram of the symmetrical dual Boost circuit based on soft switching in the switching period provided by the embodiment of the present invention;

Fig. 2 (a) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t0～t1 stage provided by the embodiment of the present invention;

Fig. 2 (b) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t1～t2 stage provided by the embodiment of the present invention;

Fig. 2 (c) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t2～t3 stage provided by the embodiment of the present invention;

Fig. 2 (d) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t3-t4 stage provided by the embodiment of the present invention;

Fig. 2 (e) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t4～t5 stage provided by the embodiment of the present invention;

Fig. 2 (f) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t5-t6 stage provided by the embodiment of the present invention;

Fig. 2 (g) is the equivalent circuit diagram of the symmetric dual Boost circuit based on soft switching in the t6-t7 stage provided by the embodiment of the present invention;

3 is a voltage and current waveform diagram of a symmetrical dual Boost circuit based on soft switching provided by an embodiment of the present invention;

Fig. 4 is a flowchart of an implementation method provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figures 1-4, the present invention provides a symmetrical dual Boost circuit based on soft switching, including a symmetrical soft switching topology circuit and a symmetrical dual Boost topology circuit. The symmetrical dual Boost topology circuit includes two symmetrical The same type of Boost basic topology circuit, the symmetrical connection of two Boost basic topology circuits can realize medium and high power DC-DC rectification, the symmetrical soft switching topology includes two symmetrical soft switching topological structures, and the two soft switching topological structures correspond to the built-in In the two Boost basic topology circuits, the two soft-switching topologies realize the zero-voltage turn-on and zero-current turn-off of the power transistor and the power diode in the two Boost basic topology circuits respectively, so as to reduce the power loss of the two Boost basic topology circuits and improve The rectification conversion efficiency of two Boost basic topological circuits.

Symmetrical dual Boost topology circuit includes power supply E, power tube S _b , inductor L _1, inductor L ₂ , power diode VD ₁ , power diode VD ₂ , capacitor C ₁ , capacitor C ₂ , load resistor R, inductor L1, Equal to inductor L2, power diode _VD1 and power diode _{VD2 are} equal, where,

The positive pole of the power supply E is electrically connected to _one end of the inductor L1, and the other end of the inductor L1 is electrically connected to the second leg of the power transistor Sb and _one end _of the power diode _VD1 respectively, and the other end _of the power diode VD1 is respectively It is electrically connected to one end of the capacitor C1 and _one end of the load resistor R, the negative pole of the power supply E is electrically connected to one end of the _{inductor L2} , and the other end of the inductor L2 is respectively connected to the third leg of the power transistor S _b and the power diode One end of the VD ₂ is electrically connected, the other end of the power diode VD ₂ is electrically connected to one end of the capacitor C ₂ and the other end of the load resistor R, and the other end of the capacitor C ₁ is electrically connected to the other end of the capacitor C ₂ .

The symmetrical soft switching topology circuit includes inductor L _r1 , inductor L _r2 , capacitor C _s1 , capacitor C _s2 , capacitor C _r1 , capacitor C _r2 , diode D ₁ , diode D ₂ , diode D ₃ , diode D ₄ , diode D ₅ , Diode D ₆ , inductance L _r1 is equal to inductance L _r2 , capacitance C _s1 is equal to capacitance C _s2 , capacitance C _r1 is equal to capacitance C _r2 , diode D ₁ is equal to diode D ₄ , diode D ₂ is equal to diode D ₅ , Diode D ₃ and diode D ₆ are equal, capacitor C _s1 and capacitor C _s2 provide zero current turn-off conditions for power tube S _b , inductance L _r1 and inductance L _r2 provide zero voltage turn-on conditions for power tube S _b , two soft switches The topology provides zero-current turn-off and zero-voltage turn-on conditions for power diodes VD ₁ , VD ₂ , where,

One end of the inductor L _r1 and _one end of the diode D1 are respectively electrically connected to the second leg of the power transistor S _b , the other end of the inductor L _r1 is electrically connected to _one end of the power diode VD1, and the other end _of the diode D1 is respectively connected to One end of the diode D ₂ is electrically connected to one end of the capacitor C _s1 , the other end of the capacitor C _s1 is electrically connected to the other end of the capacitor C ₁ , and the other end of the diode D ₂ is respectively connected to one end of the capacitor C _r1 and the diode D ₃ One end is electrically connected, the other end of the capacitor C _r1 is electrically connected to the other end of the inductor L _r1 , and the other end of the diode _D3 is electrically connected to the other end of the power diode VD ₁ ;

_One end of the inductor L _r2 and one end of the first diode _D4 are respectively electrically connected to the pin of the power transistor S2, the other end of the inductor L _r2 is electrically connected to one end of the power diode _VD2 , and the other end of the first diode _D4 is respectively connected to _One end of the diode D5 is electrically connected to one end of the capacitor _Cs2 , the other end of the capacitor _Cs2 is electrically connected to the other end of the capacitor _C2 , and the other end of the diode _{D5 is respectively connected to one end of the capacitor Cr2 and} the diode _D6 One end is electrically connected, the other end of the capacitor C _r2 is electrically connected to the other end of the inductor L _r2 , and the other end of the diode D ₆ is electrically connected to the other end of the power diode VD ₂ .

The switching cycle of the symmetrical soft-switching topology circuit includes seven working stages. The following seven working stages are analyzed in detail. In the analysis process, it is assumed that all devices in the circuit are ideal devices, C _s1 <C _r1 , C _s2 <C _r2 , the working process of the symmetrical soft-switching topology circuit in one switching cycle is shown in Figure 2, and the voltage and current waveforms of the Boost soft-switching circuit are shown in Figure 3, so the electrical parameter data and energy conversion of components within one switching cycle of the soft-switching circuit can be analyzed and obtained process, where

The first working stage includes the t ₀ ~ t ₁ stage of the switching cycle: the equivalent circuit diagram of the soft switching circuit working in the Boost basic topology circuit is shown in Figure 2(a). During the time t ₀ ~ t ₁ , the switch The tube S _b is kept in the off state, and the power diode VD ₁ and the power diode VD ₂ are kept in the zero-voltage conduction state;

The second working stage includes the t ₁ ~ t ₂ stage of the switching cycle: the equivalent circuit diagram of the symmetrical soft switching circuit working in the Boost basic topology circuit is shown in Figure 2(b), and the power transistor S _b transitions from the off state In the zero-current conduction state, the power diode VD ₁ and the power diode VD ₂ change from the zero-voltage conduction state to the zero-current off state, and the capacitor C _r1 and capacitor C _r2 remain in a fully discharged state;

The third working stage includes the _t2 ~ _t3 stage of the switching cycle. The equivalent circuit diagram of the symmetrical soft switching circuit working in the Boost basic topology circuit is shown in Figure 2( _c ), and the power transistor Sb remains in the on state , the power diode VD ₁ and the power diode VD ₂ are kept in the off state, the inductor L _r1 , the capacitor C _r1 , the capacitor C _r2 , and the inductor L _r2 are kept in the series resonance state, the capacitor C _s1 and the capacitor C _s2 are kept in the discharge state, and the capacitor C _r1 and capacitor C _r2 are kept in a charged state;

The _fourth working stage includes the _t3 ~t4 stage of the switching cycle. The equivalent circuit diagram of the symmetrical soft switching circuit operating in the Boost basic topology circuit is shown in Fig. 2(d), and the power transistor S _b remains in the on state , the power diode VD ₁ and the power diode VD ₂ are kept in the off state, the diode D ₁ and the diode D ₄ are kept in the on state, the inductor L _r1 and the capacitor C _r1 are kept in the series resonance state, and the capacitor C _r2 and the inductor L _r2 are kept In the series resonance state, the capacitors C _s1 and C _s2 are kept in a fully discharged state, and the capacitors C _r1 and C _r2 are kept in a charged state;

The fifth working stage includes the t ₄ ~ t ₅ stage of the switching cycle. The equivalent circuit diagram of the symmetrical soft switching circuit operating in the Boost basic topology circuit is shown in Figure 2(e), and the power transistor S _b remains in the on state , the power diode VD ₁ and the power diode VD ₂ are kept in the off state, the diode D ₁ , diode D ₂ and diode D ₄ , and the diode D ₅ are kept in the off state, and the capacitor C _r1 and the capacitor C _r2 are kept in the full state;

The sixth working stage includes the t ₅ ~ t ₆ stage of the switching cycle. The equivalent circuit diagram of the symmetrical soft switching circuit operating in the Boost basic topology circuit is shown in Figure 2(f). The power transistor S _b transitions from the on state It is in the zero-current off state, power diode VD ₁ and power diode VD ₂ remain in the off state, diode D ₁ , diode D ₃ , diode D ₄ , and diode D ₆ remain in the on state, and capacitor C _s1 and capacitor C _s2 Keep in charging state, capacitors C _r1 and C _r2 keep in discharging state;

The seventh working stage includes the t ₆ ~ t ₇ stage of the switching cycle. The equivalent circuit diagram of the symmetrical soft switching circuit operating in the Boost basic topology circuit is shown in Fig. 2(g), and the power transistor S _b is kept in the off state , power diode VD ₁ and power diode VD ₂ are kept in off state, diode D ₃ and diode D ₆ are kept in on state, capacitor C _s1 and capacitor C _s2 are kept in full state, capacitor C _r1 and capacitor C _r2 are kept in discharge state.

Specifically, as shown in Figure 2(a), during the t ₀ ~ t ₁ stage: the switch tube S ₁ remains in the off state, at the time t ₀ , the discharge process of C _r1 and C _r2 ends, and the voltages U _Cr1 and U _Cr2 at both ends are equal to zero , at this time the power diodes VD1 and VD2 are turned on, and they are turned on in a zero-voltage state. The terminal voltages of C _s1 and C _s2 in series are approximately equal to the load voltage U _O , while the current I _Lr on L _r1 and L _r2 is equal to the input current I _L =I _in .

As shown in Figure 2(b), in the stage t ₁ ~ t ₂ : the pulse signal is triggered at time t ₁ , and the power switch tube S _b becomes in the conduction state. At this time, due to the addition of the conduction branch of the switch tube, the current I _Lr1 , I _Lr2 begins to decline linearly, the branch current of the switch tube increases slowly, and the voltage drops to zero at the moment when the power device is turned on. At this time, the conduction current is very small, and it is basically zero-voltage conduction. As the power device is fully turned on, the branch current increases gradually, and the currents of I _Lr1 and I _Lr2 gradually decrease until the currents I _Lr1 and I _Lr2 drop to zero at time t ₂ , at which point the power diodes VD ₁ and VD ₂ are zero current off. The expression for this period is:

In the formula, L _r =L _r1 =L _r2 .

As shown in Fig. 2(c), stage t ₂ ~ t ₃ : at time t ₂ , since the current of power diodes VD ₁ and VD ₂ is zero at this time, the load is supplied with power by output filter capacitors C ₁ and C ₂ . When the I _Lr1 current drops to zero, the voltages of the symmetrical capacitors C _s1 and C _s2 start to discharge through the loop formed by D ₂ , C _r1 , L _r1 , S ₁ and the symmetrical circuit D ₅ , C _r12 , and L _r2 . The series connected capacitor and inductor resonate. In this process, C _r1 and C _r2 start to charge, U _Cr1 and U _Cr2 start to increase from zero, and the currents of L _r1 and L _r2 increase from zero to the opposite direction. When time _t3 is reached, the electric energy on C _s1 and C _s2 are all released, and U _Cs1 =U _Cs2 =0 at this time. The expression of the duration of the C _s1 discharge process is:

C_s＝C_s1＝C_s2，C_r＝C_r1＝C_r2。in,

C _s =C _s1 =C _s2 , C _r =C _r1 =C _r2 .

As shown in Figure 2(d), stage t ₃ ~ t ₄ : time t ₃ , because at this time the capacitor voltage U _Cs1 = 0, U _Cs2 = 0, so that diodes D ₁ and D ₄ are turned on, respectively in the symmetrical Boost circuit A resonant circuit is formed in the middle, as shown in figure (d), a resonant circuit is formed between L _r1 and C _r1 , and a resonant circuit is formed between L _r2 and C _r2 . The inductor current I _Lr1 charges C _r1 through D ₁ and D ₂ , U _Cr1 continues to rise, and at time t ₄ I _Lr1 decreases to zero, and the inductor electric energy is fully released, and U _Cr1 reaches the maximum value U _Cr1max at this time. The other way of resonance is the same. The duration of this process is equal to the resonance period of the inductor and capacitor, and the corresponding expression is as follows:

In the formula, L _r =L _r1 =L _r2 , C _r =C _r1 =C _r2 .

As shown in Figure 2(e), stage t ₄ ~ t ₅ : In the two resonant circuits in the previous period, at time t ₄ , the voltages of U _Cr1 and U _Cr2 reached the resonance peak value, and the voltage across the capacitors C _r1 and C _r2 made D ₁ , D ₂ and D ₄ , D ₅ are turned off, and U _Cr1 , U _Cr2 are kept at the maximum value U _Cr1max . At this time, the switch tube S _b is kept in a stable conduction stage, and the currents of the inductors L ₁ and L ₂ are I _in =I _L . I _L is the current flowing through the inductors L ₁ and L ₂ .

As shown in Fig. 2(f), stage t ₅ ~ t ₆ : At time t ₅ , the switching tube S _b is sent to turn off the pulse command, at this time the power supply is given by L ₁ , D ₁ and D ₄ , L ₂ in the symmetrical circuit. C _s1 and C _s2 start to charge, the voltages U _Cs1 and U _Cs2 connected in series at both ends of the switch tube S _b gradually increase from zero, and the voltage at both ends of the power switch S _b gradually increases during the turn-off process, which is beneficial to reduce the switching calculation consumption. At the same time, the power supply also supplies power to the load through L ₁ , L _r1 , C _r1 , D ₃ and their symmetrical circuits D ₆ , C _r2 , L _r2 , and L ₂ , and also charges the output filter capacitor; at this time, C _r1 , C _r2 is in the discharge state respectively, U _Cr1 and U _Cr2 decrease gradually, I _L =I _in =I _Lr +I _Cs (I _Cs is the charging current of Cs ₁ and Cs ₂ ). At time t ₆ , the capacitor voltages U _Cs1 and U _Cs2 of C _s1 and C _s2 respectively reach their maximum values, U _Cs1max ≈ U _o .

As shown in Figure 2(g), stage t ₆ ~ t ₇ : at time t ₆ , the inductor current I _Lr = I _L = I _in , the voltages U _Cr1 and U _Cr2 at both ends of C _r1 and C _r2 are driven by the power diode VD ₁ , VD ₂ are clamped. The power supply still provides electric energy to the load end through L ₁ , L _r1 , C _r1 , D ₃ and its symmetrical circuit D ₆ , C _r2 , L _r2 , L ₂ , but C _r1 , C _r2 have not been fully discharged. Until t ₇ moment, C _r1 , C _r2 are fully discharged, U _Cr1 , U _Cr2 drop to zero, that is, return to the initial state of t ₀ .

Through the above analysis: when the switch tube S _b is turned on, since the inductor current cannot change suddenly, at this time I _L = I _Lr1 = I _in , the voltage at both ends of S _b drops rapidly, while the current rises slowly, which ensures the zero-voltage turn-on Realize the conditions and reduce the turn-on loss; when the switch tube S _b is turned off, because C _s1 and C _s2 have a clamping effect on S _b , the voltage of S _b needs to increase slowly. This is due to the nature of the capacitor. The capacitor voltage cannot change suddenly. Compared with the voltage, the current drops faster, thus ensuring the realization condition of zero current turn-off and reducing the turn-off loss.

It can also be seen from Figure 3 that when the _first power transistor S1 is turned on at time _t1 , the voltage U _s1 drops rapidly to zero, while the current I _s1 rises slowly from zero, thereby avoiding the problem caused by the simultaneous existence of voltage and current. loss _; at time t5, the trigger signal disappears, and when the _first power tube S1 is turned off, the current I _s1 drops rapidly until its value is equal to zero, and at the same time the voltage U _s1 begins to rise slowly, and this process is also avoided In the same way, when the _second power transistor S2 is turned on at _t1 , the voltage U _s2 drops rapidly to zero, while the current I _s2 rises slowly from zero, thereby avoiding the simultaneous existence of voltage and current. _The loss caused; at time t5, the trigger signal disappears, when the _second power tube S2 is turned off at time _t1 , the current I _s2 drops rapidly until its value is equal to zero, and at the same time the voltage U _s2 begins to rise slowly, This process also avoids unnecessary losses.

The duration of the second, third and fourth working stages in the seven working stages is determined by electrical components, and the mathematics of the duration of the second, third and fourth working stages The expressions are:

The duration of the t ₁ ~ t ₂ stage in the second working stage is t _{1 ~ 2} , and the quantitative expression of t _{1 ~ 2} is:

In the formula, L _r ＝L _r1 ＝L _r2 , L _r1 , L _r2 are characterized by inductance L _r1 , L _r2 respectively, I _in is the input current of the power supply E, U _o is the voltage across the load resistance R;

The duration of stage t ₂ ~ t ₃ in the working stage is t _{2 ~ 3} , and the quantitative expression of t _{2 ~ 3} is:

C_r＝C_r1＝C_r2，C_s＝C_s1＝C_s2，L_r＝L_r1＝L_r2，C_r1、C_r2分别表征为电容C_r1、C_r2，C_s1、C_s2表分别征为电容C_s1、C_s2，L_r1、L_r2分别表征为电感L_r1、L_r2；In the formula,

C _r ＝C _r1 ＝C _r2 , C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 and C _r2 are represented by capacitances C _r1 and C _r2 respectively, and C _s1 and C _s2 represent are capacitors C _s1 and C _s2 , and L _r1 and L _r2 are respectively represented as inductances L _r1 and L _r2 ;

The duration of t ₃ ~ t ₄ stage in the working stage is t _{3 ~ 4} , and the quantitative expression of t _{3 ~ 4} is:

In the formula, C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 C _r1 , C _r2 are represented as capacitances C _r1 , C _r2 , respectively, and L _r1 , L _r2 are represented as inductances L _r1 , L _r2 .

The design of the symmetrical soft-switching circuit is mainly to configure the parameters of the inductance and capacitance components in the circuit. The design principle is to realize the zero-current turn-off and zero-voltage turn-on of the soft-switch circuit without affecting the operation of the original circuit. influences. Among them, the inductance L _r1 and L _r2 can affect the rise time of the turn-on current. If L _r1 and L _r2 are too large, the loss of the circuit will be increased, so L _r1 and L _r2 should be appropriately reduced; but the smaller the L _r1 and L _r2 , The shorter the rise time, it will be difficult to realize the zero-current turn-on of the power transistor _Sb , so L _r1 and L _r2 should not be too small. In addition, capacitors C _s1 and C _s2 will have an impact on the rise time of the shutdown voltage, so the present invention provides a method for implementing a symmetrical double Boost circuit based on soft switching, and provides parameters of inductance and capacitance elements for The configuration process is as follows.

As shown in Figure 4, based on the schematic diagram of the above-mentioned symmetrical dual Boost circuit based on soft switching, the present invention provides an implementation method, including the following steps:

Step S1, quantifying the turn-on time and turn-off time of the power transistor _Sb based on seven working stages;

Step S2, quantifying the resonant angular frequency of the symmetrical soft-switching topology circuit based on the principle of ensuring the time-limited and stable completion of the resonant circuit;

Step S3, based on the principle of ensuring that D ₁ and D ₂ can be turned off reliably to reduce loss, quantify the component parameters in the symmetrical soft-switching topology circuit.

In step S1, specific methods for quantifying the turn-on time and turn-off time of the power transistor S _b include:

Analyze the energy conversion process between the inductor L _{r1 , the capacitor C s1 and the capacitor C r1 in the symmetric soft switching topology circuit in the t 1 ~ t 4 stage, and quantify it according to the energy conversion process between the inductor L r1 , the capacitor C s1 and} the capacitor C _r1 The minimum turn-on time of power tube _Sb , the minimum turn-on time is:

T _min(on) = T·D _min ,

In the formula, T _min(on) >t ₄ -t ₁ , T is the switching period, and D _min is the minimum duty cycle;

Analyze the energy conversion process among the inductor L _r1 , capacitor C _s1 , capacitor C _r1 , and load resistance R in the symmetric soft switching topology circuit from the t ₅ stage of the previous switching cycle to the next switching cycle t ₀ stage, and according to the inductance L _r1 , the energy conversion process between capacitor C _s1 and capacitor C _r1 , and load resistance R quantifies the minimum off time of power tube S _b , and the minimum off time is:

T _min(off) = T·(1-D _max ),

In the formula, T _min(on) >t ₀ ′-t ₅ , T is the switching period, and D _max is the maximum duty cycle.

In step S2, specific methods for quantifying the resonant angular frequency of the symmetrical soft-switching topology circuit include:

_Obtain the switching frequency of the switching tube Sb, and ensure that the resonant angular frequency of the resonant circuit is greater than the switching frequency so that the resonant response of the resonant circuit is completed within a limited time. The quantification formula of the resonant angular frequency is:

ω ₂ >2πf _s ;

C_r＝C_r1＝C_r2，L_r＝L_r1＝L_r2，ω₂是谐振角频率，f_s是开关频率，C_r1、C_r2分别表征为电容C_r1、C_r2，L_r1、L_r2分别表征为电感L_r1、L_r2。In the formula,

C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 , ω ₂ is the resonant angular frequency, f _s is the switching frequency, C _r1 , C _r2 are characterized by capacitances C _r1 , C _r2 , L _r1 , L _r2 is characterized by inductance L _r1 and L _r2 respectively.

In step S3, specific methods for quantifying component parameters in the symmetrical soft-switching topology circuit include:

Using the diode D ₁ and diode D ₂ or diode D ₄ and diode D ₅ to be turned off reliably before the capacitor C _r1 or C _r2 is discharged to 0, the basic relationship of the components of the symmetrical soft switching topology circuit is constructed:

In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 , C _r2 are represented by capacitance C _r1 , C _r2 respectively, and L _r1 , L _r2 are represented by inductance L _r1 , L _r2 respectively , I _in is the input current of the power supply E, and U _o is the voltage across the load resistor R.

Using the basic relational formula of the soft switching element and the quantitative formula of the resonant angular frequency, the value range of the capacitance C _r , capacitance C _s , and inductance L _r is obtained:

分别表征为电容C_r1、C_r2两端电压U_Cr1、U_Cr2的最大值，I_{in max}为供电电源E的输入电流I_in的最大值，C_r1、C_r2分别表征为电容C_r1、C_r2，C_s1、C_s2分别表征为电容C_s1、C_s2，L_r1、L_r2分别表征为电感L_r1、L_r2。In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r ＝C _r1 ＝C _r2 ,

Respectively represented as the maximum value of the voltage U _Cr1 and U _Cr2 across the capacitors C _r1 and C _r2 , I _{in max} is the maximum value of the input current I _in of the power supply E, and C _r1 and C _r2 are respectively represented by the capacitors C _r1 and C _r2 , C _s1 , C _s2 are respectively represented as capacitors C _s1 , C _s2 , and L _r1 , L _r2 are respectively represented as inductances L _r1 , L _r2 .

Specifically, if the basic relationship of the components does not hold, then the diode D ₁ , diode D ₂ and diode D ₃ will conduct simultaneously with the power diode VD ₁ until L _r1 can bear all the input current again. Therefore, this situation should be avoided, otherwise the turn-on loss of the diode will increase, resulting in unnecessary waste of energy.

Solve the capacitance C _r , capacitance C _s , and inductance L _r by using the basic relational formula of the components and the quantization formula of the resonant angular frequency, specifically:

由于

则

利用

再由于I_in＜I_{in max}，则

可得：Transform the basic relational expression of the component to obtain

because

but

use

Since I _in <I _{in max} , then

Available:

再由于I_in＜I_{in max}，则

可得：use

Since I _in <I _{in max} , then

Available:

Among them, since the symmetrical soft-switching topology circuit has a _{symmetrical type , the capacitance C r1 and the capacitance} C _s1 , inductance L _r1 , equivalently obtain capacitance C _r2 , capacitance C _s2 , and inductance L _r2 .

The symmetrical double Boost topology circuit of the present invention is evolved from the three-phase single-switch Boost rectifier connected in parallel in the hybrid rectifier. The structure includes two basic Boost circuits of the same type. The circuit structure can be applied to medium and high power occasions .

In the present invention, a symmetrical soft-switching topological circuit is built in a symmetrical double-Boost topological circuit. The symmetrical double-Boost topological circuit has L ₁ =L ₂ , VD ₁ =VD ₂ , and its symmetrical soft-switching topological circuit has C ₁ =C ₂ , C _s1 ＝C _s2 , L _r1 ＝L _r2 , D ₁ ＝D ₄ , D ₂ ＝D ₅ , D ₃ ＝D ₆ , the capacitors C _s1 and C _s2 in the symmetrical soft switching topology circuit are responsible for providing the power transistor S _b zero-current turn-off condition, inductance L _r1 and inductance L _r2 are responsible for providing the zero-voltage turn-on condition of power tube S _b , reducing the loss of power tube S _b as a whole, and at the same time, the soft switching circuit also makes power diodes VD ₁ and VD ₂ work In the state of zero-current turn-off and zero-voltage turn-on, the symmetrical dual-boost converter with soft switching function reduces the loss of power switching device S _b and power diodes VD ₁ and VD ₂ as a whole, and improves the efficiency of the converter. The soft switching circuit is applied to the three-phase single-switch Boost rectifier in the hybrid rectifier to reduce the switching loss of the hybrid rectifier and improve the energy conversion efficiency.

The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent replacements to the present application within the spirit and protection scope of the present application, and such modifications or equivalent replacements shall also be deemed to fall within the protection scope of the present application.

Claims (6)

1. A symmetrical double Boost circuit based on soft switching, characterized in that: comprise symmetrical soft switching topological circuit, and symmetrical double Boost topological circuit, said symmetrical double Boost topological circuit comprises two symmetrical same type Boost foundations Topological circuit, the symmetrical connection of the two Boost basic topological circuits can realize medium and high power DC-DC rectification, the symmetrical soft switching topological circuit includes two symmetrical soft switching topological structures, and the two soft switching topological structures respectively correspond to Built into the two Boost basic topology circuits, the two soft switching topologies respectively realize the zero-voltage turn-on and zero-current turn-off of the power transistor and the power diode in the two Boost basic topology circuits to reduce the two Boost The power loss of the basic topology circuit and the improvement of the rectification conversion efficiency of the two Boost basic topology circuits; the symmetrical dual Boost topology circuit includes a power supply E, a power tube S _b , an inductor L ₁ , an inductor L ₂ , a power diode VD ₁ , power diode VD ₂ , capacitor C ₁ , capacitor C ₂ , load resistor R, the inductance L ₁ is equal to the inductance L ₂ , the power diode VD ₁ is equal to the power diode VD ₂ , wherein, The anode of the power supply E is electrically connected to _one end of the inductor L1, and the other end of the inductor L1 is electrically connected to the second leg of the power transistor Sb and _one end _of the power diode _VD1 respectively. connected, the other end of the power diode _VD1 is electrically connected to _one end of the capacitor C1 and _one end of the load resistor R respectively, and the negative pole of the power supply E is electrically connected to one end of the inductor L2, so _The other end of the inductor L2 is electrically connected to the third pin of the power transistor Sb and one end of the power diode _VD2 , and the other end of the power diode _VD2 is respectively connected to one end of the _{capacitor C2} , the other end of the load resistor R is electrically connected, the other end of the capacitor _C1 is electrically connected to the other end of the capacitor C2 _; the symmetrical soft switching topology circuit includes an inductor L _r1 , an inductor L _r2 , and a capacitor C _s1 , capacitor C _s2 , capacitor C _r1 , capacitor C _r2 , diode D ₁ , diode D ₂ , diode D ₃ , diode D ₄ , diode D ₅ , diode D ₆ , the inductance L _r1 is equal to the inductance L _r2 , the capacitance C _s1 is equal to the capacitance C _s2 , the capacitance C _r1 is equal to the capacitance C _r2 , the diode D ₁ is equal to the diode D ₄ , the diode D ₂ is equal to the diode D ₅ are equal, the diode D ₃ and the diode D ₆ are equal, the capacitor C _s1 and capacitor C _s2 provide the zero current shutdown condition for the power transistor S _b , and the inductance L _r1 and the inductance L _r2 are the The power transistor S _b provides zero-voltage turn-on conditions, and the two soft-switching topologies provide zero-current turn-off conditions and zero-voltage turn-on conditions for power diodes VD ₁ and VD ₂ , wherein, One end of the inductor L _r1 and _one end of the diode D1 are respectively electrically connected to the second leg of the power transistor S _b , and the other end of the inductor L _r1 is electrically connected to _one end of the power diode VD1. _The other end of the diode D1 is electrically connected to _one end of the diode D2 and one end of the capacitor C _s1 respectively, the other end of the capacitor C _s1 is electrically connected to the other end of the capacitor _C1 , and the diode D The other end of ₂ is electrically connected to one end of the capacitor C _r1 and one end of the diode _D3 , the other end of the capacitor C _r1 is electrically connected to the other end of the inductor L _r1 , and the diode _{D3 The} other end is electrically connected to the other end of the power diode VD1; _One end of the inductance _Lr2 and one end of the first diode D4 are respectively electrically connected to the third pin of the power transistor _Sb , and the other end of the inductance _Lr2 is electrically connected to one end of the power diode _VD2 , so _The other end of the first diode D4 is electrically connected to one end of the diode _{D5 and one end of the capacitor C s2 ,} and the other end of the capacitor C ₂ is electrically connected to the other end of the capacitor _C2 . _The other end of the diode D5 is electrically connected to one end of the capacitor C _r2 and one end of the diode _D6 respectively, the other end of the capacitor C _r2 is electrically connected to the other end of the inductor L _r2 , and the diode D The other end of ₆ is electrically connected to the other end of the power diode VD ₂ ; the switching cycle of the symmetrical soft switching topology circuit includes seven working stages, wherein, The stage t ₀ ~ t ₁ including the switching period of the first working stage: during the time t ₀ ~ t ₁ , the power transistor S _b remains in the off state, and the power diode VD1, power diode VD2 Maintain zero voltage conduction state; The second working stage includes the switching period t ₁ ~ t ₂ stage, the power transistor S _b changes from the off state to the zero current on state, and the power diode VD ₁ and power diode VD ₂ change from zero voltage to The on-state changes to the zero-current off-state, and the capacitors C _r1 and C _r2 are kept in a fully discharged state; In the stage t ₂ -t ₃ including the switching period of the third working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ is kept in the off state, and the inductor L _r1 and the capacitor C _r1 , capacitor C _r2 , and inductor L _r2 are kept in a series resonance state, the capacitors C _s1 and C _s2 are kept in a discharging state, and the capacitors C _r1 and C _r2 are kept in a charging state; In the stage t ₃ -t ₄ including the switching period of the fourth working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₁ and diode D ₄ are kept in a conducting state, the inductor L _r1 and capacitor C _r1 are kept in a series resonant state, the capacitor C _r2 and inductance L _r2 are kept in a series resonant state, the capacitor C _s1 , capacitor C _s2 is kept in a fully discharged state, and the capacitors C _r1 and C _r2 are kept in a charged state; In the stage t ₄ -t ₅ including the switching cycle of the fifth working stage, the power transistor S _b is kept in the on state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₁ , diode D ₂ , diode D ₄ , and diode D ₅ are kept in an off state, and the capacitors C _r1 and C _r2 are kept in a full state; In the _sixth working stage, which includes the switching period t5 _- t6 stage, the power transistor S _b changes from the on state to the zero current off state, and the power diode VD ₁ and power diode VD ₂ remain in the off state. In the off state, the diode D ₁ , diode D ₃ , diode D ₄ , and diode D ₆ are kept in the on state, the capacitor C _s1 and the capacitor C _s2 are kept in the charged state, and the capacitors C _r1 and C _r2 are kept at discharge state; In the stage t ₆ -t ₇ including the switching cycle of the seventh working stage, the power transistor S _b is kept in the off state, the power diode VD ₁ and the power diode VD ₂ are kept in the off state, and the diode D ₃ and diode D ₆ are kept in a conduction state, the capacitor C _s1 and capacitor C _s2 are kept in a full state, and the capacitor C _r1 and capacitor C _r2 are kept in a discharge state; the second working stage in the seven working stages The duration periods in the stage, the third working stage and the fourth working stage are determined by electrical components, and the mathematical expressions of the duration periods in the second working stage, the third working stage and the fourth working stage are respectively: The duration of the t ₁ ~ t ₂ stage in the second working stage is t _{1 ~ 2} , and the quantitative expression of the t _{1 ~ 2} is:

In the formula, L _r ＝L _r1 ＝L _r2 , L _r1 , L _r2 are characterized by inductance L _r1 , L _r2 respectively, I _in is the input current of the power supply E, U _o is the voltage across the load resistance R; The duration of t ₂ to t ₃ in the working phase is t _{2 to 3} , and the quantitative expression of t _{2 to 3} is:

In the formula,

C _r ＝C _r1 ＝C _r2 , C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 and C _r2 are represented by capacitances C _r1 and C _r2 respectively, and C _s1 and C _s2 represent are capacitances C _s1 and C _s2 , and L _r1 and L _r2 are respectively represented as inductances L _r1 and L _r2 ; The duration of the t ₃ ~ t ₄ phase in the working phase is t _{3 ~ 4} , and the quantitative expression of the t _{3 ~ 4} is:

In the formula, C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 , C _r1 , C _r2 are represented by capacitance C _r1 , C _r2 respectively, and L _r1 , L _r2 are represented by inductance L _r1 , L _r2 respectively . 2. a kind of realization method based on the symmetrical double Boost circuit of soft switch according to claim 1, it is characterized in that: comprise the following steps: Step S1, quantifying the turn-on time and turn-off time of the power transistor S _b based on the seven working stages; Step S2, quantifying the resonant angular frequency of the symmetrical soft-switching topology circuit based on the principle of ensuring the time-limited and stable completion of the resonant circuit; Step S3, based on the principle of ensuring that D ₁ and D ₂ , D ₄ and D ₅ can be turned off reliably and reduce losses, quantify the component parameters in the symmetrical soft switching topology circuit. 3. A kind of realization method according to claim 2, is characterized in that, in described step S1, the turn-on time of described power transistor _Sb and the concrete method of turn-off time quantization comprise: Analyze the energy conversion process between the inductor L _r1 , capacitor C _s1 and capacitor C _r1 in the t ₁ ~ t ₄ stage of the symmetrical soft switching topology circuit, and based on the inductance L _r1 , capacitor C _s1 and capacitor C _r1 The energy conversion process quantifies the minimum turn-on time of the power transistor _Sb , and the minimum turn-on time is: T _min(on) = T·D _min , In the formula, T _min(on) >t ₄ -t ₁ , T is the switching period, and D _min is the minimum duty cycle; Analyze the energy conversion process between the inductor L _r1 , the capacitor C _s1 , the capacitor C _r1 , and the load resistor R in the t ₅ stage of the previous switching cycle to the t ₀ stage of the next switching cycle of the symmetrical soft switching topology circuit, and according to the The energy conversion process between the inductor L _r1 , the capacitor C _s1 , the capacitor C _r1 , and the load resistor R quantifies the minimum off time of the power transistor S _b , and the minimum off time is: T _min(off) = T·(1-D _max ), In the formula, T _min(off) >t ₀ ′-t ₅ , T is the switching period, and D _max is the maximum duty cycle. 4. a kind of implementation method according to claim 3, is characterized in that, in described step S2, the concrete method of quantifying the resonant angular frequency of described symmetrical soft-switching topological circuit comprises: Obtain the switching frequency of the power tube S _b , and ensure that the resonant angular frequency of the resonant circuit is greater than the switching frequency so that the resonant response of the resonant circuit is completed within a limited time, and the quantification formula of the resonant angular frequency is: ω ₂ >2πf _s ; In the formula,

C _r ＝C _r1 ＝C _r2 , L _r ＝L _r1 ＝L _r2 , ω ₂ is the resonant angular frequency, f _s is the switching frequency, C _r1 , C _r2 are characterized by capacitances C _r1 , C _r2 , L _r1 , L _r2 is characterized by inductance L _r1 and L _r2 respectively. 5. a kind of implementation method according to claim 4, is characterized in that, in described step S3, the concrete method of quantifying the element parameter in the symmetrical soft-switching topological circuit comprises: Before the capacitor C _r1 or C _r2 is discharged to 0, the diode D ₁ and the diode D ₂ or the diode D ₄ and the diode D ₅ can be turned off reliably, and the basic relational expression of the components of the symmetrical soft switching topology circuit is constructed:

In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r1 , C _r2 are represented by capacitance C _r1 , C _r2 respectively, and L _r1 , L _r2 are represented by inductance L _r1 , L _r2 respectively , I _in is the input current of the power supply E, U _o is the voltage across the load resistor R, and I _r is the inductor current. 6. A kind of realization method according to claim 5, it is characterized in that, described using described soft switching element basic relational formula and the quantitative formula of resonant angular frequency, obtain electric capacity C _r , electric capacity C _s , inductance L _r Ranges:

In the formula, C _s ＝C _s1 ＝C _s2 , L _r ＝L _r1 ＝L _r2 , C _r ＝C _r1 ＝C _r2 ,

Respectively represented as the maximum value of the voltage U _Cr1 and U _Cr2 across the capacitors C _r1 and C _r2 , I _{in max} is the maximum value of the input current I _in of the power supply E, and C _r1 and C _r2 are respectively represented by the capacitors C _r1 and C _r2 , C _s1 , C _s2 are respectively represented as capacitors C _s1 , C _s2 , and L _r1 , L _r2 are respectively represented as inductances L _r1 , L _r2 .

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