CN113410990B - High-efficiency high-gain quasi-Z-source soft switching DC-DC converter - Google Patents

Abstract

The invention discloses a high-efficiency high-gainThe quasi Z source soft switch DC-DC converter comprises a DC power supply V _g Energy storage inductor L ₁ The clamping unit, the coupling inductance unit and the load side; the DC power supply V _g For an energy-storing inductor L ₁ Providing energy; a clamping unit clamping a voltage peak generated by a leakage inductance of a coupling inductance of the coupling inductance unit to a fixed value and transferring energy to a load side; the coupling inductance unit utilizes the charging and discharging of the coupling inductance to adjust the duty ratio D and the turn ratio n, so as to realize high-voltage conversion. The invention can realize the arbitrary double regulation of the voltage gain through the direct duty ratio and the turn ratio of the coupling inductor; the active elements all realize soft switching; relatively few passive components; under the action of the active clamping circuit, the efficiency and the electromagnetic interference are improved, and the working reliability of the circuit is improved.

Description

A high-efficiency and high-gain quasi-Z source soft-switching DC-DC converter

technical field

The invention belongs to the technical field of DC-DC conversion equipment, and in particular relates to a high-efficiency and high-gain quasi-Z source soft-switching DC-DC converter.

Background technique

In recent years, high-gain DC-DC boost converters have played an increasingly important role in many industrial applications, such as uninterruptible power supplies, renewable energy systems, distributed photovoltaic power generation systems, and DC microgrids. In applications such as grid-tied systems or UPS, use a high-gain converter as an interface between low-voltage input sources (photovoltaic panels, fuel cells, and battery packs) and the inverter to meet high-voltage requirements at the inverter input . This application requires a high-gain converter capable of delivering high efficiency and continuous input current.

Paper "H Ardi, A Ajami, and M Sabahi. A novel high step-up DC–DC converter with continuous input current integrating coupled inductor for renewableenergy applications [J]. IEEE transactions on industrial electronics, 2018, 65(2):1306– 1315" proposed a coupled-inductance converter with continuous input current, but this converter is hard-switched with high switching losses. Using soft switching technology is an effective method to overcome switching losses and improve the efficiency of power converters. Literature “M Forouzesh, Y Shen, K Yari, Y P Siwakoti, and F Blaabjerg. High-efficiency high step-up DC–DC converter with dual coupled inductors for grid-connected photovoltaic systems [J]. IEEE transactions on power electronics, 2018 , 33(7):5967–5982" proposed a soft-switching converter with an active clamp circuit with a snubber capacitor. Although it has excellent performance, it contains four switching tubes, which complicates the structure and increases the cost. The document "S W Lee and H L Do.Highstep-up coupled-inductor cascade boost DC–DC converter with lossless passivesnubber[J].IEEE transactions on industrial electronics,2018,65(10):7753–7761" proposes a method with coupling Inductive secondary boost converter using passive lossless snubber circuit to achieve soft switching performance. Although it contains only one switch, a relatively large number of passive components are used. The quasi-impedance source (QZS) network provides continuous input current and its input and output common ground, so it is widely used. The document "M M Haji-Esmaeili, E Babaei, and M Sabahi. High step-up quasi-Z source DC-DC converter[J]. IEEE transactionson power electronics, 2018, 33(12):10563-10571" proposes a High-gain converters based on QZS networks, despite their high voltage gain, contain many passive components, and hard-switching operation will also limit efficiency.

Therefore, seeking a DC-DC converter with simple structure, continuous input current, high efficiency and high gain has become a research focus in this field.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to aim at the deficiencies of the above-mentioned prior art, and to provide a high-efficiency and high-gain quasi-Z source soft-switching DC-DC converter, which integrates a coupled inductor and a quasi-Z source structure, and has a simple structure and continuous input current. The voltage gain is high, and the quasi-Z source diode is replaced by a synchronous switch tube in the converter of the present invention, and the switch tube realizes the zero-voltage switching (ZVS) characteristic; at the same time, the first diode and the second diode are turned on and off. Occurring in zero-voltage zero-current switching (ZVZCS) conditions, both improve the efficiency of the converter.

In order to realize the above-mentioned technical purpose, the technical scheme adopted in the present invention is:

A high-efficiency and high-gain quasi-Z source soft-switching DC-DC converter, comprising a DC power supply V _g , an energy storage inductor L ₁ , a clamping unit, a coupled inductor unit and a load side;

The DC power supply V _g provides energy for the energy storage inductor L ₁ ;

The clamping unit clamps the voltage spike generated by the leakage inductance of the coupled inductance of the coupled inductance unit to a fixed value, and transfers the energy to the load side;

The coupled inductance unit uses the coupled inductance to charge and discharge to adjust the duty cycle D and the turns ratio n to realize high voltage conversion.

In order to optimize the above technical solutions, the specific measures taken also include:

The above-mentioned clamping unit includes a first switch tube S ₁ and its anti-parallel diode D _S1 and buffer capacitor C _S1 , a second switch tube S ₂ and its anti-parallel diode D _S2 and buffer capacitor C _S2 , the first capacitor C ₁ and the second capacitor C ₂ ;

The coupled inductor unit includes a first winding L _2a , a second winding L _2b , a third capacitor C ₃ and a first diode D ₁ of the coupled inductor;

the load side includes a second diode D _o , an output capacitor C _o and a load R;

The current difference and current sum between the energy storage inductor L1 and the _first winding _L2a of the coupled inductor make the buffer capacitor connected in parallel with the _first switch S1 and the _second switch S2 completely charged and discharged, and a dead zone is added. Time control, so that the first diode D ₁ and the second diode D _o work in a zero voltage switching (ZVS) environment;

The first winding L _2a and the second winding L _2b of the coupled inductor are used to achieve high gain of the circuit;

The clamping unit collects the leakage inductance energy of the coupled inductor, and finally transfers it to the load side, so as to realize the lossless absorption of the energy of the clamping capacitor.

_One end of the above-mentioned energy storage inductance L1 is connected with the DC power supply _Vg , and the other end is connected with the negative electrode of the _second capacitor C2 of the clamping unit and the common end of the negative electrode of the _second switch tube S2;

In the clamping unit, the positive pole of the _first switch tube S1 is connected to the positive pole of the _second capacitor C2, the negative pole of the _second capacitor C2 is connected to the negative pole of the second switch tube S2, and the _second switch tube S2 is connected to the negative pole of the _second switch tube S2. The positive pole is connected to the positive pole of the first capacitor _C1 , and the negative pole of the first capacitor _C1 is connected to the negative pole _of the _first switch tube S1 and the negative _pole of the DC power supply _Vg . The gate source is used to receive the control signal of the external main control chip, and control the on or off of the switch tube through the change of the duty ratio to realize the switching of different working states of the circuit;

In the coupled inductance unit, the first winding and the second winding have the same name as each other, and the turns ratio is 1:n. After the first winding L _2a , the second winding L _2b and the third capacitor are connected in series, they are connected to the first The diode D1 is connected in parallel, the common terminal of the anode of the _first winding _L2a and the cathode of the _first diode D1 is connected to the common terminal of the anode of the first capacitor _C1 and the anode of the _second switch tube S2, the first winding _L2a The negative pole and the common terminal of the negative pole of the _third capacitor C3 are connected to the positive pole of the _first switch tube S1 and the common terminal of the positive pole of the _second capacitor C2, and the common terminal of the negative pole of the second winding _L2b and the anode of the _first diode D1 is connected to The cathode of the second diode D _o on the output side is connected to transfer the energy to the load side;

On the load side, after the output capacitor C _o is connected in parallel with the load R, it is connected in series with the second diode D _o .

The above-mentioned first switch transistor S ₁ and second switch transistor S ₂ are both N-channel MOS transistors, and their gate and source electrodes can both receive control signals from an external main control chip.

The unipolar PWM control method is used to control the first switch S ₁ and the second switch S ₂ to be turned on or off, so as to improve the working efficiency of the switches and reduce the switching loss, thereby improving the working efficiency of the entire circuit .

In the above-mentioned direct-on state of the DC-DC converter, the _first switch tube S1 is turned on, the _second switch tube S2 is turned off, the _first diode D1 is turned on, and the second diode _D0 is connected by the output voltage and the output voltage. The difference between the voltage of the first capacitor V _o -V _C1 is reverse biased; the first and second capacitors C ₁ and C ₂ are discharged; the excitation inductor current i _Lm of the first winding of the coupled inductor has been reduced to zero, and then reversely increased. is large positive; the leakage inductance L _2k of the second winding of the coupled inductor and the capacitor C ₁ always resonate, and the sum of the current i _in , the excitation inductor current i _Lm and the resonant current flows through the first switch tube S ₁ ; when the resonant current drops to zero, The _first diode D1 is turned off in ZVZCS condition.

When the above-mentioned DC-DC converter is in the off state, the _first switch S1 is turned off, the _second switch S2 is turned on, the second diode D _o starts to conduct under the condition of ZVZCS, and the first diode D ₁ is reverse biased by the difference between the output voltage and the first capacitor voltage V _o -V _C1 , the first capacitor C ₁ is always charged, the input voltage V _g and the third capacitor C ₃ together are the excitation inductance of the first winding of the coupled inductor , the energy storage inductor L ₁ , the second winding L _2b of the coupled inductor and the load side provide energy, the excitation inductance of the first winding of the coupled inductor charges the second capacitor C ₂ , and the excitation inductor current i _Lm decreases until zero, at this time, the input The voltage V _g and the second and third capacitors C ₂ and C ₃ together provide energy for the energy storage inductor L ₁ , the _second winding L _2b of the coupled inductor and the load side. When charging, the excitation inductor current i _Lm increases in the opposite direction. When the magnitude of the negative excitation inductor current i _Lm is greater than the current i _in , the current begins to flow through the second switch tube S ₂ in the reverse direction. In order to ensure that the buffer capacitors C _S1 and C _S2 continue to charge and discharge in the next cycle, the first The current of the _second switch tube S2 is positive before it is turned off. When the current of the second diode Do becomes zero, the diode is turned off under the condition of _ZVZCS .

The expression of the above-mentioned output voltage V ₀ on the load side is:

Among them, B is the voltage gain of the converter, D is the duty cycle, n is the turns ratio, and V _g is the DC power supply voltage.

The present invention has the following beneficial effects:

Aiming at the shortcomings of the existing high-gain DC-DC circuit with relatively many active components and low efficiency, the present invention can realize any dual adjustment of the voltage gain through the through duty cycle and the turns ratio of the coupled inductor, avoiding the switching tube when the voltage gain is high. The limit duty cycle ensures the overall safety of the converter; the active components all realize soft switching, that is, all active components work in a soft switching environment, which improves the efficiency of the converter; relatively few passive components , further improves the efficiency and power density of the converter; under the action of the active clamp circuit, the efficiency and electromagnetic interference are improved, and the reliability of the circuit operation is increased; its structure is simple, easy to use, low design cost, The electrical principle is reliable and the output efficiency is high, which can reach 96.92% of the whole machine efficiency.

Description of drawings

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

FIG. 2 is a schematic diagram of control signals of two switch tubes according to the present invention.

FIG. 3 is a schematic diagram of a working state when the main power switch tube of the present invention is turned on.

FIG. 4 is a schematic diagram of the working state when the main power switch tube of the present invention is turned off.

Detailed ways

The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

Referring to FIG. 1 , a high-efficiency and high-gain quasi-Z source soft-switching DC-DC converter includes a DC power supply V _g , an energy storage inductor L ₁ , a clamping unit, a coupled inductor unit and a load side;

The DC power supply V _g provides energy for the energy storage inductor L ₁ ;

The clamping unit clamps the voltage spike generated by the leakage inductance of the coupled inductance of the coupled inductance unit to a fixed value, and transfers the energy to the load side;

The coupled inductance unit uses the coupled inductance to charge and discharge to adjust the duty cycle D and the turns ratio n to realize high voltage conversion.

In the embodiment, the clamping unit includes a first switch tube S ₁ and its anti-parallel diode D _S1 and buffer capacitor C _S1 , a second switch tube S ₂ and its anti-parallel diode D _S2 and buffer capacitor C _S2 , the first a capacitor C ₁ and a second capacitor C ₂ ;

The coupled inductor unit includes a first winding L _2a , a second winding L _2b , a third capacitor C ₃ and a first diode D ₁ of the coupled inductor;

the load side includes a second diode D _o , an output capacitor C _o and a load R;

The working principle of the present invention is:

The current difference and current sum between the energy storage inductor L1 and the _first winding _L2a of the coupled inductor make the buffer capacitor connected in parallel with the _first switch S1 and the _second switch S2 completely charge and discharge, and add a dead time control, so that the first diode D ₁ and the second diode D _o work in a zero voltage switching (ZVS) environment;

The first winding L _2a and the second winding L _2b of the coupled inductor are used to achieve high gain of the circuit;

The clamping unit collects the leakage inductance energy of the coupled inductor, and finally transfers it to the load side, so as to realize the lossless absorption of the energy of the clamping capacitor.

In the embodiment, one end of the energy storage inductor L ₁ is connected to the DC power supply V _g , and the other end is connected to the common end of the negative electrode of the second capacitor C ₂ of the clamping unit and the negative electrode of the second switch tube S ₂ ;

In the clamping unit, the positive pole of the _first switch tube S1 is connected to the positive pole of the _second capacitor C2, the negative pole of the _second capacitor C2 is connected to the negative pole of the second switch tube S2, and the _second switch tube S2 is connected to the negative pole of the _second switch tube S2. The positive pole is connected to the positive pole of the first capacitor _C1 , and the negative pole of the first capacitor _C1 is connected to the negative pole _of the _first switch tube S1 and the negative _pole of the DC power supply _Vg . The gate source is used to receive the control signal of the external main control chip, and control the on or off of the switch tube through the change of the duty ratio to realize the switching of different working states of the circuit;

In the coupled inductance unit, the first winding and the second winding have the same name as each other, and the turns ratio is 1:n. After the first winding L _2a , the second winding L _2b and the third capacitor are connected in series, they are connected to the first The diode D1 is connected in parallel, the common terminal of the anode of the _first winding _L2a and the cathode of the _first diode D1 is connected to the common terminal of the anode of the first capacitor _C1 and the anode of the _second switch tube S2, the first winding _L2a The negative pole and the common terminal of the negative pole of the _third capacitor C3 are connected to the positive pole of the _first switch tube S1 and the common terminal of the positive pole of the _second capacitor C2, and the common terminal of the negative pole of the second winding _L2b and the anode of the _first diode D1 is connected to The cathode of the second diode D _o on the output side is connected to transfer the energy to the load side;

On the load side, after the output capacitor C _o is connected in parallel with the load R, it is connected in series with the second diode D _o .

In the embodiment, the first switch transistor S ₁ and the second switch transistor S ₂ are both N-channel MOS transistors, and their gate and source electrodes can both receive control signals from an external main control chip.

In the embodiment, the unipolar PWM control method is used to control the _first switch S1 and the _second switch S2 to be turned on or off, so as to improve the working efficiency of the switch and reduce the switching loss, thereby improving the overall performance of the switch. circuit efficiency.

A schematic diagram of the control signals of the two switches is shown in FIG. 2 , and a unipolar PWM control method is used to control the switches to be in an on or off state. Through the control of dead time, the buffer capacitors C _S1 and C _S2 of the switch tube are fully charged and discharged, so that the switch tube can work in a zero voltage switching (ZVS) environment.

In one steady-state working cycle, the converter mainly has two working modes.

The schematic diagram of the working state in the through state is shown in Figure 3. Since the diode of the _first switch S1 has been turned on, a conduction signal is applied to the gate of the _first switch S1 at this time, so that the _first switch S1 Zero voltage (ZVS) conduction.

In this state, the _first switch S1 is turned on, the _second switch S2 is turned off, the _first diode D1 is turned on, and the second diode D _o is output by the difference between the voltage and the first capacitor voltage V _o -V _C1 is reverse biased; the first and second capacitors C ₁ and C ₂ are discharged; the excitation inductance current i _Lm of the first winding of the coupled inductor has been reduced to zero, and then reversely increased to positive; the second coupled inductor The winding leakage inductance L _2k and the capacitor C ₁ resonate all the time, and the sum of the current i _in , the excitation inductor current i _Lm and the resonant current flows through the first switch tube S ₁ ; when the resonant current drops to zero, the first diode D ₁ is in Shutdown under ZVZCS condition.

The schematic diagram of the working state at the end of the state is shown in Figure 4. The _first switch S1 is turned off, the _second switch S2 is turned on, and the second diode Do starts to conduct under the condition of _ZVZCS . The tube D ₁ is reverse biased by the difference between the output voltage and the first capacitor voltage V _o -V _C1 , the first capacitor C ₁ is always charged, and the input voltage V _g and the third capacitor C ₃ together are the output voltage of the first winding of the coupled inductor. The excitation inductance, the energy storage inductance L ₁ , the second winding L _2b of the coupled inductance and the load side provide energy, the excitation inductance of the first winding of the coupled inductance charges the second capacitor C ₂ , and the excitation inductance current i _Lm decreases until zero, at this time , the input voltage V _g and the second and third capacitors C ₂ and C ₃ together provide energy for the energy storage inductor L ₁ , the second winding L _2b of the coupled inductor and the load side, and the second capacitor C ₂ is the excitation of the first winding of the coupled inductor The inductor is charged in the reverse direction, and the excitation inductor current i _Lm increases in the reverse direction. When the magnitude of the negative excitation inductor current i _Lm is greater than the current i _in , the current begins to flow through the second switch tube S ₂ in the reverse direction. In order to ensure that the buffer capacitors C _S1 and C _S2 continue to charge and discharge in the next cycle, the first The current of the _second switch tube S2 is positive before it is turned off. When the current of the second diode Do becomes zero, the diode is turned off under the condition of _ZVZCS .

In the embodiment, using the energy storage inductor L ₁ and the inductance volt-second balance rule of the first and second windings L _2a and L _2b of the coupled inductors, the expression of the output voltage V ₀ is obtained as:

Among them, B is the voltage gain of the converter, D is the duty cycle, n is the turns ratio, and V _g is the DC power supply voltage.

Since the converter increases the degree of freedom of the turns ratio n, when the turns ratio is 2 and the duty cycle is 0.3, the gain B can reach 9.5 times, which avoids the existence of the limit duty cycle of the switch tube at high voltage gain, and ensures the the overall safety of the converter.

In this embodiment, the output voltage is 380V and the output power is 200W. The experimental verification is carried out. The switches all realize zero voltage (ZVS) conduction, and the diodes realize the soft switching (ZVZCS) phenomenon, and the efficiency can reach 96.92%.

The above analysis and experimental results can show that the DC converter of the present invention has a high boost capability, realizes the soft switching function of the active device, and improves the efficiency of the converter. Invention effect.

The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions that belong to the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (6)

1. A high-efficiency high-gain quasi-Z source soft switch DC-DC converter is characterized by comprising a DC power supply V _g Energy storage inductor L ₁ The clamping unit, the coupling inductance unit and the load side;

the DC power supply V _g For an energy-storing inductor L ₁ Providing energy;

the clamping unit clamps a voltage peak generated by the leakage inductance of the coupling inductor unit to a fixed value and transfers energy to a load side;

the coupling inductance unit is used for regulating the duty ratio D and the turn ratio n by utilizing the charge and discharge of the coupling inductance to realize high-voltage conversion;

the clamping unit comprises a first switch tube S ₁ And its anti-parallel diode D _S1 And a buffer capacitor C _S1 A second switch tube S ₂ And its anti-parallel diode D _S2 And a buffer capacitor C _S2 A first capacitor C ₁ And a second capacitor C ₂ ；

The coupling inductance unit comprises a first winding L of a coupling inductance _2a A second winding L _2b A third capacitor C ₃ And a first diode D ₁ ；

The load side comprises a second diode D _o An output capacitor C _o And a load R;

the energy storage inductor L ₁ And a first winding L of a coupling inductor _2a The current difference and the current sum between the first switch tube S ₁ And a second switching tube S ₂ The parallel buffer capacitors are fully charged and discharged and are controlled by dead time, so that the first diode D ₁ And a second diode D _o Working in a zero voltage switching environment;

a first winding L of the coupling inductor _2a A second winding L _2b For achieving high gain of the circuit;

the clamping unit collects the leakage inductance energy of the coupling inductor and finally transfers the leakage inductance energy to the load side to realize the lossless absorption of the energy of the clamping capacitor;

the energy storage inductor L ₁ Is connected to a DC power supply V _g Connected to the other end of the first capacitor C of the clamping unit ₂ Negative pole and second switch tube S ₂ The common end of the negative electrode is connected;

in the clamping unit, a first switch tube S ₁ Positive electrode of (1) and a second capacitor C ₂ Is connected to the positive pole of a second capacitor C ₂ And a second switch tube S ₂ Is connected with the negative pole of the first switch tube S ₂ Positive electrode of and first capacitor C ₁ Is connected to the positive pole of a first capacitor C ₁ And the first switch tube S ₁ Negative electrode and DC power supply V _g Is connected with the negative pole of the first switching tube S ₁ And a second switching tube S ₂ The gate source electrode of the switch tube is used for receiving a control signal of an external main control chip and controlling the conduction or the disconnection of the switch tube through the change of the duty ratio to realize the switching of different working states of the circuit;

in the coupling inductance unit, the first winding and the second winding are dotted terminals, and the turn ratio is 1: n, the first winding L _2a A second winding L _2b Connected in series with a third capacitor and then connected with a first diode D ₁ Parallel, first winding L _2a Positive electrode and first diode D ₁ Common terminal of cathode and first capacitor C ₁ Positive and second switch tube S ₂ The common end of the positive electrodes is connected, and a first winding L _2a Negative pole and third capacitor C ₃ The common terminal of the negative electrode and the first switch tube S ₁ Positive electrode and second capacitor C ₂ The common terminal of the positive electrodes are connected, and a second winding L _2b Cathode and first diode D ₁ Second diode D of anode common terminal and output side _o The cathodes are connected to transfer energy to the load side;

in the load side, an output capacitor C _o Connected in parallel with the load R and then connected with a second diode D _o Are connected in series.

2. A high efficiency high gain quasi-Z source soft switching DC-DC converter as claimed in claim 1,

the first switch tube S ₁ A second switch tube S ₂ The MOS tubes with N channels are adopted, and the grid and the source electrodes of the MOS tubes can receive control signals of an external main control chip.

3. A high efficiency high gain quasi-Z source soft switching DC-DC converter as claimed in claim 1, characterized in that the first switch tube S is controlled by unipolar PWM control method ₁ A second switch tube S ₂ The on-state or the off-state is achieved, the working efficiency of the switch tube is improved, the switching loss is reduced, and therefore the working efficiency of the whole circuit is improved.

4. The high-efficiency high-gain quasi-Z-source soft-switching DC-DC converter according to claim 1, wherein the first switch tube S is in a through state of the DC-DC converter ₁ Conducting the second switch tube S ₂ Off, the first diode D ₁ Conducting, second diode D _o Difference V between the output voltage and the first capacitor voltage _o -V _C1 Reverse biasing; a first capacitor C ₁ A second capacitor C ₂ Discharging; exciting inductor current i of first winding of coupling inductor _Lm Decrease all the way to zero and then reverseIncreasing to positive; leakage inductance L of second winding of coupling inductor _2k And a first capacitor C ₁ Always resonant, current i _in Exciting inductance current i _Lm The sum of the resonant currents flows through the first switching tube S ₁ (ii) a When the resonant current drops to zero, the first diode D ₁ Shut down under ZVZCS conditions.

5. A high efficiency high gain quasi-Z source soft switching DC-DC converter as claimed in claim 1, wherein when the DC-DC converter is in OFF state, the first switch tube S ₁ Turning off the second switch tube S ₂ On, the second diode D _o Starting to conduct under ZVZCS condition, the first diode D ₁ Difference V between the output voltage and the first capacitor voltage _o -V _C1 Reverse bias, first capacitor C ₁ Charging at all times, input voltage V _g And a third capacitance C ₃ Excitation inductor and energy storage inductor L which are both a first winding of a coupling inductor ₁ Second winding L of coupled inductor _2b And the load side supplies energy, and the excitation inductor of the first winding of the coupling inductor is a second capacitor C ₂ Charging and exciting inductive current i _Lm Decreases until zero, at which time the input voltage V _g And a second capacitor C ₂ A third capacitor C ₃ Together being an energy-storing inductor L ₁ A second winding L of the coupled inductor _2b And a load side for supplying energy, a second capacitor C ₂ Reversely charging the exciting inductor of the first winding of the coupling inductor by the exciting inductor current i _Lm Increasing reversely; when negative excitation inductance current i _Lm Is greater than the current i _in Time, exciting an inductive current i _Lm Start to reversely flow through the second switch tube S ₂ To ensure a buffer capacitor C _S1 、C _S2 Charging and discharging are continued in the next cycle, so that the second switch tube S ₂ Before turning off, when the second diode D is positive _o The current goes to zero and the diode turns off under ZVZCS conditions.

6. A high efficiency high gain quasi-Z source soft switching DC-DC converter as claimed in claim 1, whichCharacterized in that the output voltage V of the load side ₀ The expression of (a) is:

wherein B is the voltage gain of the converter, D is the duty ratio, n is the turn ratio, and V _g Is the input voltage.

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