CN110350800B - Ship cathode protection isolation type switching power supply converter from shore power - Google Patents

Abstract

The utility model relates to a ship cathodic protection isolated switching power supply converter obtained from shore power, which belongs to the field of power distribution. It includes at least one flyback transformer, two main control switch tubes and two auxiliary switch tubes; it uses the secondary winding of the flyback transformer and the switch capacitor connected in series with it to improve the output power level of the converter; The series circuit composed of the auxiliary switch tube and the clamping capacitor and the series circuit composed of the secondary side auxiliary switch tube and the clamping capacitor can absorb and transfer most of the leakage inductance energy of the flyback transformer without loss, and realize the two main control switch tubes. The zero-current conduction of the two main control switches is used to realize the zero-voltage turn-off of the first and second main control switches by using the parasitic parallel capacitance of the two main control switches. The reasonable matching of the auxiliary switches realizes zero-voltage turn-on and zero-voltage turn-off of the two auxiliary switches. It reduces the voltage and current stress of the switch tube, has high conversion efficiency, and can increase the output of the converter.

Description

A ship cathodic protection isolated switching power converter from shore power

technical field

The invention belongs to the field of power distribution, and in particular relates to a ship cathodic protection isolated switching power supply converter.

Background technique

Ships docked at the dock need shore power to supply energy. If the hull does not take effective anti-corrosion measures, it will lead to severe galvanic corrosion.

Cathodic protection is an effective measure for metal anticorrosion widely used in seawater environment. The advantage of the impressed current cathodic protection system is that it adopts automatic control, and the output current can be adjusted automatically so that the surface of the protected structure is within the protection potential range. The impressed current cathodic protection system has high reliability; the output current of the cathodic protection system can be adaptively changed according to the working conditions, so that the ship's metal materials are in a better protection state.

It is a promising new technology to use a switching potentiostat from shore power as an impressed current cathodic protection power supply, mainly because the switching power supply uses modern power electronic technology to control the time ratio of switching on and off. , a power supply that maintains a stable output voltage. With the advantages of small size, light weight, low power consumption and high efficiency, it has gradually replaced the traditional linear power supply.

The flyback converter power supply, which has been widely used at present, stores energy when the switch tube is turned on, and releases energy to the load when the switch tube is turned off, which not only stores energy as an inductance, but also realizes voltage conversion and electrical isolation as a transformer. , has the dual role of inductor and transformer.

However, although the flyback converter reduces the number of circuit magnetics, the voltage and current stress of the switching devices increases. Moreover, when the switch tube is turned off, due to the oscillation of the parasitic capacitance of the switch tube and transformer, the leakage inductance and voltage peak of the switch tube of the flyback converter are large, the duty cycle is low, the turn-off loss is large, and the electromagnetic interference is serious, so it cannot be used. for high voltage input and high performance conditions.

Therefore, how to make the cathodic protection isolated switching power supply can realize the current opening of all switching tubes while maintaining low current stress, small loss of switching tubes, greater than 50% duty cycle, high conversion efficiency, and stable output current is a practical work. problems to be solved urgently.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a ship cathodic protection isolated switching power supply converter from shore power. Aiming at the shortcomings of the current flyback converter, such as serious switching loss, high switching voltage and current stress, low conversion efficiency, and serious switching loss, it provides a reasonable control method, low switching current stress, and can achieve zero switching. Cathodic protection isolated switching power supply with current conduction and stable output current.

The technical scheme of the present invention is to provide a ship cathodic protection isolated switching power supply converter obtained from shore power, which is characterized by:

The switching power supply converter includes a flyback transformer T, and both ends of the primary winding _Lp of the flyback transformer are respectively connected to the positive and negative terminals of the input DC voltage V _In ; terminal, which is respectively connected with the positive and negative terminals of the output DC voltage V _OUT ;

Between the primary winding Lp and the input DC voltage V _In , a first main switch tube S ₁ and a second main switch tube S ₂ are respectively set, and the first and second main switch tubes S ₁ and S ₂ are respectively corresponding to the series Connected to both ends of the primary winding Lp;

Between the first main switch tube S ₁ and the primary winding Lp, a leakage inductance coil L _1K is connected in series;

At both ends of the primary winding Lp, first and second clamping diodes D1 and D2 are respectively connected in parallel;

Between the secondary winding LS and the positive end of the output DC voltage V _OUT , a secondary total leakage inductance _{L l} and a rectifier diode D3 are connected in series;

In the primary winding Lp, a primary side auxiliary unit is provided;

At the output end of the secondary winding LS, a resonant capacitor _{C a} and a secondary side auxiliary unit are connected in parallel;

The flyback transformer T transmits power from the primary winding side to the secondary winding side;

_The first and second clamping diodes D1 and D2 transfer the energy stored in the leakage inductance _L1k and the secondary total leakage inductance L1 to the input terminal;

The said primary side auxiliary unit is used to realize the condition of zero current conversion ZCT;

The secondary side auxiliary unit is responsible for the operation of the zero current conversion ZCT;

The first and second main switch tubes S1 and S2 are turned on and off at the same time;

When the first and second main switch tubes are turned off, the leakage inductance exchanges energy twice through the primary side auxiliary unit, so that the leakage inductance current is reversed before the main switch tubes are turned on, and then acts on the parasitic capacitance of the switch tubes to reduce The purpose of the drain-source voltage dropping to zero before the arrival of the driving signal of the main switch tube is achieved, thereby realizing the soft-switching function.

Specifically, the primary-side auxiliary unit includes a primary-side auxiliary switch tube S3 and _two diodes D31 and D32; one end of the auxiliary switch tube S3 is connected to an end _of the same name of the _second main switch tube S2, and the other end It is connected to the other end of the same name of the _second main switch tube S2 through diodes D31 and D32;

The secondary side auxiliary unit includes a secondary side auxiliary switch tube S _a , one end of the secondary side auxiliary switch tube S _a is correspondingly connected to the positive end of the rectifier diode D3; the other end of the secondary side auxiliary switch tube S _a is The resonant capacitor C _a is connected to the negative end of the output DC voltage V _OUT , and the secondary side auxiliary switch tube is connected in parallel to the secondary winding L _S through the resonant capacitor C _a ;

Said ship cathodic protection isolated switching power converter uses the secondary side auxiliary switch _S3 and the _first main switch S1 to conduct complementary conduction, and the first and second clamping diodes D1 and D2 connect the first main switch S3. _The voltage between the switch tube S1 and the second main switch tube S2 is controlled at the input voltage V _In ; the clamping diodes D1 and D2 transfer the energy stored in the leakage inductance _L1k and the secondary total leakage inductance L1 to the input end; using The bidirectional conduction characteristic of the primary side auxiliary switch tube S3 provides a path for the reverse conduction of the resonant current.

Further, the described marine cathodic protection isolated switching power supply converter utilizes the series circuit composed of the primary side auxiliary switch tube and the clamping capacitor and the series circuit composed of the secondary side auxiliary switch tube and the clamping capacitor to absorb losslessly. And transfer most of the leakage inductance energy of the flyback transformer, and realize the zero current conduction of the two main switches;

At the same time, the parasitic parallel capacitance of the first and second main switch tubes S ₁ and S ₂ is used to realize the zero-voltage turn-off of the first and second main switch tubes. The reasonable matching of the auxiliary switches _realizes zero-voltage turn-on and zero-voltage turn-off of the two secondary side auxiliary switches S3 and _Sa.

Specifically, the first and second main switch tubes S1 and S2, the primary side auxiliary switch tube S3 and the secondary side auxiliary switch tube Sa each have a parasitic capacitance;

A DC blocking capacitor Cr and a resonant inductor Lr are connected in series on the primary side of the flyback transformer T;

On the secondary winding side of the flyback transformer T, an inductor L _l , a diode D ₃ , a load resistor _RL and a filter capacitor C _O are arranged;

Wherein, the inductor _L1 , the diode _D3 and the resistor _RL are connected in series in sequence, and the filter capacitor _CO is connected in parallel with the load resistor _RL .

Further, the ship cathodic protection isolated switching power converter adopts a soft-switching flyback converter topology that reduces switching voltage stress to achieve zero current transition, which can effectively reduce switching overvoltage and eliminate output current. volatility.

Further, the ship cathodic protection isolated switching power converter from shore power introduces resonance before and after the switching process, so that the voltage drops to zero before the switch is turned on, and the current drops to zero before the switch is turned off, eliminating the need for The overlapping of voltage and current during the switching process greatly reduces or even eliminates the switching loss. At the same time, the resonance process limits the rate of change of the voltage and current during the switching process, so that the switching noise is also significantly reduced.

Further, the on-off of the first and second main switch tubes S ₁ and S ₂ is controlled by an external drive unit, and they are turned on or off at the same time;

The switching period Ts of the first and second main switching tubes is given by 1/f _s , where f _s is the switching frequency;

The duty cycle D of the first and second main switch tubes is the ratio of the power-on time of the main switch tubes to the total time period T _s .

The ship cathodic protection isolated switching power supply converter from shore power according to the technical solution of the present invention does not require additional inductive elements, thereby improving current stability, reducing switching tube voltage and current stress, high conversion efficiency, and reduced loss , which can increase the output of the converter.

Compared with the prior art, the advantages of the present invention are:

1. The technical solution of the present invention utilizes the secondary winding of a flyback transformer and a switched capacitor connected in series with it to improve the output power level of the converter;

2. The technical solution of the present invention uses the series circuit composed of the primary side auxiliary switch tube and the clamping capacitor and the series circuit composed of the secondary side auxiliary switch tube and the clamping capacitor to absorb and transfer most of the flyback transformer without loss. Leakage inductance energy, and realize zero current conduction of two power switch tubes;

3. The technical scheme of the present invention uses the parasitic parallel capacitance of the two power switch tubes S ₁ and S ₂ to realize the zero-voltage turn-off of the first and second power switch tubes, and uses the first and second power switch tubes. The reasonable matching with the primary and secondary auxiliary switches realizes the zero-voltage turn-on and zero-voltage turn-off of the two auxiliary switches S ₃ and S _a ;

4. The technical solution of the present invention does not require additional inductive elements, thereby improving current stability, reducing switching tube voltage and current stress, high conversion efficiency, reduced loss, and increasing the output of the converter.

5. The technical solution of the present invention can realize switching input under higher voltage and high-performance working conditions, realize the current conduction of all switch tubes while maintaining low current stress, small switch tube loss, and the duty cycle is greater than 50. %, high conversion efficiency, stable output current.

Description of drawings

FIG. 1 is a schematic diagram of the circuit topology principle of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

In Fig. 1, the technical scheme of the present invention provides a ship cathodic protection isolated switching power supply converter taken from shore power, the invention of which is:

The switching power converter includes a flyback transformer T, the two ends of the primary winding (also known as the primary winding or the primary winding, referred to as the primary side) Lp of the flyback transformer, and the positive and negative terminals of the input DC voltage V _In . The two ends of the secondary winding of the flyback transformer (also known as the secondary winding or the load side winding, referred to as the load side or the secondary side) L _S are respectively connected correspondingly to the positive and negative ends of the output DC voltage V _OUT ;

Between the primary winding Lp and the input DC voltage V _In , a first main switch tube S ₁ and a second main switch tube S ₂ are respectively set, and the first and second main switch tubes S ₁ and S ₂ are respectively corresponding to the series Connected to both ends of the primary winding Lp;

Between the first main switch tube S ₁ and the primary winding Lp, a leakage inductance coil L _1K is connected in series;

At both ends of the primary winding Lp, first and second clamping diodes D1 and D2 are respectively connected in parallel;

Between the secondary winding LS and the positive end of the output DC voltage V _OUT , a secondary total leakage inductance _{L l} and a rectifier diode D3 are connected in series;

In the primary winding Lp, a primary side auxiliary unit is provided;

At the output end of the secondary winding LS, a resonant capacitor _{C a} and a secondary side auxiliary unit are connected in parallel;

The flyback transformer T transmits power from the primary winding side to the secondary winding side;

_The first and second clamping diodes D1 and D2 transfer the energy stored in the leakage inductance _L1k and the secondary total leakage inductance L1 to the input terminal;

The said primary side auxiliary unit is used to realize the condition of zero current conversion ZCT;

The secondary side auxiliary unit is responsible for the operation of the zero current conversion ZCT;

The first and second main switch tubes S1 and S2 are turned on and off at the same time;

When the first and second main switch tubes are turned off, the leakage inductance exchanges energy twice through the primary side auxiliary unit, so that the leakage inductance current is reversed before the main switch tubes are turned on, and then acts on the parasitic capacitance of the switch tubes to reduce The purpose of the drain-source voltage dropping to zero before the arrival of the driving signal of the main switch tube is achieved, thereby realizing the soft-switching function.

It can be seen from the figure that the switch tubes S1 and S2 are the main switch tubes, the switch tubes _S3 and _Sa are the auxiliary switch tubes, _S1 , _S2 , _S3 and _Sa each have _a parasitic capacitance, and the inductance coil Lm is _a transformer The excitation inductance, the small resonant inductance Lr is the added inductance, and the capacitor Cr is the clamping capacitor.

Obviously, the two primary winding side main switch tubes (referred to as the main switch) S ₁ and S ₂ , the parallel rectified diode D ₃ on the secondary winding side and the flyback transformer T constitute the main part of the power supply circuit, responsible for the power from the primary Transmission from the winding side to the load side.

_The diodes D1 and D2 _on the primary side act as clamping diodes to transfer the energy stored in the leakage inductance _L1k and the secondary total leakage inductance _L1 to the input; the primary side auxiliary unit contains an auxiliary switch S3 and _two Diodes (D31 and D32) are used to realize the condition of zero current conversion ZCT (Zero Current Transition). When the main switch is turned off, the leakage inductance exchanges energy twice through the auxiliary branch, so that the leakage inductance current is turned on in the main switch. Forward and reverse, and then act on the parasitic capacitance of the switch tube to achieve the purpose of the drain-source voltage dropping to zero before the arrival of the main switch drive signal, thereby realizing the soft switching function.

On the secondary side (also known as the load side) of the exciter transformer, the auxiliary circuit composed of the auxiliary switch tube Sa and the resonant capacitor Ca is responsible for the operation of zero-current conversion, and resonance is introduced before and after the switching process, so that the voltage drops to zero before the switch is turned on. The current drops to zero before turning off, which eliminates the overlap of voltage and current during the switching process, thereby greatly reducing or even eliminating the switching loss. At the same time, the resonance process limits the rate of change of voltage and current during the switching process, which makes switching noise also significantly reduced.

There are eight operating modes in one switching cycle.

The output filter capacitor and the load resistance are assumed by the capacitor C _o and the resistor _RL respectively, and the input DC voltage and the output voltage are represented by V _In and V _Out respectively.

The _two main switches S1 and S2 are switched _on and off by the external drive unit controller, simultaneously on or off, and the switching period _Ts is given by 1/fs, where _fs is the switching frequency. The switch duty cycle D is the ratio of the power-on time of the main switch to the total time period Ts.

In the topology diagram, the transformer T is modeled as an ideal transformer with primary magnetizing inductance L _m and secondary total leakage inductance L _l .

The technical scheme of the present invention improves the output power level of the converter by using the secondary winding of a flyback transformer and the switches and capacitors connected in series with it; using a series circuit composed of an auxiliary switch tube on the primary side and a clamping capacitor and two The series circuit composed of the secondary side auxiliary switch tube and the clamping capacitor absorbs and transfers most of the leakage inductance energy of the flyback transformer losslessly, and realizes the zero current conduction of the two power switch tubes; using the main switch S ₁ The parasitic parallel capacitance of the two power switch tubes and S ₂ itself realizes the zero-voltage turn-off of the first and second main switch tubes; the rational use of the first and second main switch tubes and the main and secondary auxiliary switch tubes is reasonable. Matching, the zero-voltage turn-on and zero-voltage turn-off of the two auxiliary switches S ₃ and S _a are realized.

In the whole technical solution, no additional inductive element is needed, thereby improving the current stability, reducing the voltage and current stress of the switch, high conversion efficiency, reduced loss, and increasing the output of the converter.

Example:

Example 1:

According to the electrical principle topology diagram shown in Figure 1, a cathodic protection isolated switching power converter with an output power of 60W and an output voltage of 24V is designed. The parameters of the switching power converter are: input voltage V _In = 250V, output power V _Out = 60W, output voltage 24V, excitation inductance L _m is 600μH, resonant inductance is 15μH, DC blocking capacitor 3.5μF, switching frequency 80kHz, output filter Capacitor 480µF.

The experimental waveforms of the switching tube driving voltage V _gs , the switching tube drain-source voltage V _ds , the resonant inductor current i _Lr and the secondary side rectifier tube current i _Dr and voltage V _Dr are detected by an oscilloscope and other instruments. The voltage stress of all switches is clamped to the input voltage, and the zvs conduction of all switches is realized. The reverse peak value of the resonant inductor current i _Lr is much smaller than its forward peak value, which reduces the resonance loss and turn-off loss.

The maximum efficiency of the cathodic protection isolated switching power converter can reach 92%.

Example 2:

According to the electrical principle topology diagram shown in Figure 1, a cathodic protection isolated switching power supply converter with an output power of 48W and an output voltage of 12V is designed. The parameters of the switching power supply converter are input voltage V _In = 130V, output power V _Out = 48W, output voltage 12V, excitation inductance L _m is 600μH, resonance inductance is 15μH, DC blocking capacitor 3.5μF, switching frequency 65kHz, output filter Capacitor 480µF.

The experimental waveforms of the switching tube driving voltage V _gs , the switching tube drain-source voltage V _ds , the resonant inductor current i _Lr and the secondary side rectifier tube current i _Dr and voltage V _Dr are detected by an oscilloscope and other instruments. The voltage stress of all switches is clamped to the input voltage, and the zvs conduction of all switches is realized. The reverse peak value of the resonant inductor current i _Lr is much smaller than its forward peak value, which reduces the resonance loss and turn-off loss.

The maximum efficiency of the cathodic protection isolated switching power converter can reach 92.5%.

The technical scheme of the present invention improves the output power level of the converter by using the secondary winding of a flyback transformer and the switch capacitor connected in series with it; using the series circuit composed of the auxiliary switch tube on the primary side and the clamping capacitor and the secondary side The series circuit composed of the auxiliary switch tube and the clamping capacitor absorbs and transfers most of the leakage inductance energy of the flyback transformer without loss, and realizes the zero _- current conduction of the _two power switch tubes; The parasitic parallel capacitance of each main switch tube itself realizes the zero-voltage turn-off of the first and second main switch tubes; Zero-voltage turn-on and zero-voltage turn-off of the two auxiliary switches S ₃ and S _a . It does not require additional inductive components, the control method is reasonable, the current stress of the switch tube is low, and the zero-current conduction of the switch tube can be realized; at the same time, the output current is stable, thereby improving the current stability, reducing the voltage and current stress of the switch tube, and high conversion efficiency. The loss is reduced and the output of the converter can be increased.

The invention can be widely used in the field of design and operation management of shore power distribution network.

Claims (7)

1. A ship cathode protection isolation type switching power supply converter from shore power is characterized in that:

the switching power supply converter comprises a flyback transformer T, two ends of a primary winding Lp of the flyback transformer and an input direct-current voltage V_InThe positive and negative terminals are respectively and correspondingly connected; flyback transformer secondary winding L_SAnd output a direct voltage V_OUTThe positive and negative terminals are respectively and correspondingly connected;

at the primary winding Lp and the input DC voltage V_InBetween, respectively setting a first main switch tube S₁And a second main switching tube S₂The first and the second main switch tubes S₁And S₂Are respectively and correspondingly connected in series with the two ends of the primary winding Lp;

in the first main switch tube S₁A leakage inductance coil L is connected in series between the primary winding Lp and the transformer_1K；

A first clamping diode D and a second clamping diode D are respectively connected in parallel at two ends of the primary winding Lp₁And D₂Wherein the first clamping diode D₁Is connected to the negative terminal of the first main switch tube S_lA first clamping diode D connected to one end of the primary winding Lp₁The positive end of the primary winding is connected with the other end of the primary winding Lp; second clamping diode D₂Is connected with the positive end of the second main switch tube S₂A second clamping diode D connected to the other end of the primary winding Lp₂The negative terminal of the primary winding is connected with one end of the primary winding Lp;

in the secondary winding L_SAnd output DC voltage V_OUTBetween the positive terminals of the secondary total leakage inductor L_lAnd a rectifier diode D₃；

In the primary winding Lp, a primary side auxiliary unit is provided;

the primary side auxiliary unit comprises a primary side auxiliary switch tube S₃And two diodes D₃₁And D₃₂(ii) a Auxiliary switch tube S₃Source terminal and second main switch tube S₂Source terminal of the auxiliary switching tube S₃Drain terminal of via diode D₃₁And D₃₂The drain end of the second main switching tube S2 is connected;

in the secondary winding L_SIs connected in parallel with a resonant capacitor C_aAnd a secondary side auxiliary unit;

wherein, the secondary side auxiliary unit comprises a secondary side auxiliary switch tube S_aSecondary side auxiliary switch tube S_aDrain terminal of and rectifier diode D₃The positive ends of the two are correspondingly connected; secondary side auxiliary switch tube S_aSource terminal of the capacitor C_aAnd output DC voltage V_OUTIs connected with the negative terminal of the power supply; resonant capacitor C_aThe secondary side auxiliary unit is connected in series and then is connected to the output end of the secondary winding in parallel;

the flyback transformer T transmits power from the primary winding side to the secondary winding side;

first and second clamping diodes D_lAnd D₂Will be stored in the leakage inductance L_lkAnd secondary total leakage inductance L_lThe energy in (1) is transferred to the input end;

the primary side auxiliary unit is used for realizing the condition of zero current conversion ZCT;

the secondary side auxiliary unit is responsible for the operation of zero current conversion ZCT;

the first and the second main switch tubes S₁And S₂Simultaneously open and close;

when the first main switching tube and the second main switching tube are switched off, the leakage inductance carries out secondary energy exchange through the primary side auxiliary unit, so that the leakage inductance current is reversed before the main switching tube is switched on, and then acts on the parasitic capacitance of the switching tube, so that the purpose that the leakage source voltage is reduced to zero before a driving signal of the main switching tube comes is achieved, and the soft switching function is realized.

2. The shore power derived switching power converter as defined in claim 1, wherein said marine cathodic protection isolation switching power converter utilizes a secondary side auxiliary switching tube S₃And a first main switch tube S₁Complementary conducting, first and second clamping diodes D₁And D₂A first main switch tube S₁And a second main switching tube S₂The voltage between the input voltage V and the output voltage V is controlled_In(ii) a Clamping diode D_lAnd D₂Will be stored in the leakage inductance L_lkAnd secondary total leakage inductance L_lThe energy in (1) is transferred to the input end; using a primary side auxiliary switching tube S₃The bidirectional conductive characteristic of the resonant circuit provides a path for reverse conduction of the resonant current.

3. The shore power derived marine cathodic protection isolated switching mode power converter as defined in claim 2, wherein said marine cathodic protection isolated switching mode power converter absorbs and transfers most of the leakage inductance energy of the flyback transformer without loss by using the series circuit of the primary side auxiliary switching tube and the clamping capacitor and the series circuit of the secondary side auxiliary switching tube and the clamping capacitor, and realizes zero current conduction of the two main switching tubes;

at the same time, the first and the second main switch tubes S are utilized₁And S₂Parasitic parallel capacitance existing in the first and second capacitorsThe zero voltage of the main switch tube is cut off, and the reasonable matching of the first and second main switch tubes and the main and auxiliary switch tubes is utilized to realize the two secondary side auxiliary switch tubes S₃And S_aZero voltage on and zero voltage off.

4. The shore power derived switching power converter according to claim 1 or 2, wherein the first and second main switching tubes S are connected to each other by a connecting line₁、S₂Primary side auxiliary switch tube S₃And secondary side auxiliary switch tube S_aEach with a parasitic capacitance;

a DC blocking capacitor Cr and a resonant inductor Lr are connected in series with the primary side of the flyback transformer T;

an inductor L is arranged on the secondary winding side of the flyback transformer T_lDiode D₃Load resistance R_LAnd a filter capacitor C_O；

Wherein, the inductance L_lDiode D₃And a resistance R_LAre connected in series in sequence and filter capacitor C_OAnd a load resistance R_LAnd (4) connecting in parallel.

5. The shore power derived marine cathodic protection isolated switching power supply converter as defined in claim 1 wherein said marine cathodic protection isolated switching power supply converter utilizes a soft switching flyback converter topology to reduce switching voltage stress to achieve zero current transitions.

6. The shore power based switching power converter according to claim 1, wherein the shore power based switching power converter introduces resonance before and after the switching process to eliminate the voltage and current overlap during the switching process.

7. The shore power derived switching power converter of claim 1, wherein said first and second main switching tubes S₁And S₂Is switched on and off from the outsideThe driving unit controls the opening or closing of the switch;

the switching period T of the first and second main switching tubes_sFrom 1/f_sGiven therein, f_sIs the switching frequency;

the duty ratio D of the first main switching tube and the second main switching tube is the electrifying time of the main switching tube relative to the total time period T_sThe ratio of the active ingredients to the total amount of the active ingredients.

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