CN113541486A

CN113541486A - Interleaved diode capacitor network high-gain ZVT (zero voltage zero volt) direct current converter and auxiliary circuit

Info

Publication number: CN113541486A
Application number: CN202110697676.0A
Authority: CN
Inventors: 张岩; 李新颖; 程钰杰
Original assignee: Nanjing Junyao Technology Co ltd; Xian Jiaotong University
Current assignee: Nanjing Junyao Technology Co ltd; Xian Jiaotong University
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2021-10-22
Anticipated expiration: 2041-06-23
Also published as: CN113541486B

Abstract

The invention discloses a high-gain ZVT (zero voltage variation) direct-current converter and an auxiliary circuit of an interleaved diode capacitor network, wherein the ZVT auxiliary circuit comprises a first auxiliary circuit, a second auxiliary circuit and a resonant inductor, the first auxiliary circuit comprises a first auxiliary switching tube and a first auxiliary diode, the second auxiliary circuit comprises a second auxiliary switching tube and a second auxiliary diode, the first auxiliary circuit and the second auxiliary circuit share one resonant inductor and are used for realizing ZVS (zero voltage switching) switching-on and switching-off of the first controllable switching tube and the second controllable switching tube in the direct-current converter, the first auxiliary switching tube and the second auxiliary switching tube realize ZCS switching-on, and all diodes realize ZCS switching-off. The high-efficiency high-power-density switch has the characteristics of expandable high-voltage gain, low input current ripple, low voltage stress, wide-range soft switching and simple parameter design while realizing high efficiency and high power density.

Description

Interleaved diode capacitor network high-gain ZVT (zero voltage zero volt) direct current converter and auxiliary circuit

Technical Field

The invention belongs to the field of converters, and particularly relates to a high-gain ZVT (zero voltage zero volt) direct current converter of an interleaved diode capacitor network and an auxiliary circuit.

Background

Due to exhaustion of fossil fuels and environmental pollution, new energy sources are increasingly attracting attention. The photovoltaic and fuel cell technology in new energy is an ideal way for future household new energy power generation due to wide application region range, short construction period, cleanness and no pollution. However, both of the two energy sources have the remarkable characteristics of low output voltage and wide fluctuation range, so that a front-level high-gain direct-current converter is required to perform boost conversion and simultaneously ensure the voltage stability of a direct-current bus, and the direct-current bus is connected to a power grid through a grid-connected inverter.

The main technical challenge currently faced is how to handle incoming large currents and outgoing high voltages with a minimum of power devices and passive components. Input-parallel output series LLC or dual active bridge converters are the preferred solutions to achieve high gain and high efficiency. However, the coordinated control of voltage and current sharing among modules significantly increases the cost and complexity of the system, making it more suitable for high-power applications. In applications where forced isolation is not required, non-isolated DC-DC converters have the potential advantage of achieving higher efficiency and power density. The two-phase interleaved boost diode-capacitor (TIBD) converter is composed of two parts, namely two-phase interleaved boost input and a diode-capacitor boost unit (VMC), and has similar excellent performance. The staggered boost input part enables input current to be continuous and ripples to be reduced, the current stress of the controllable switch tube is reduced, the diode capacitor boosting unit achieves high gain and simultaneously reduces the voltage stress of all semiconductor devices, and therefore low-on-state resistance power devices can be used for reducing conduction loss. In addition, fewer magnetic elements may enable high power density integration. However, for the TIBD converter, as the number of semiconductor devices increases, hard switching causes higher power loss and severe electromagnetic interference, and soft switching is particularly necessary. Unlike an isolated DC-DC converter which naturally implements soft switching using transformer leakage inductance, all the inductor current and capacitor voltage in the TIBD converter are constant DC components, and there is no voltage current zero crossing, so soft switching is difficult to implement. Existing soft-switching solutions for TIBD converters are more limited to a specific TIBD topology, and there is a lack of systematic soft-switching design solutions for this type of excellent topology.

Zero voltage switching is more suitable for high frequency power converters employing MOSFETs or GaN than zero current switching. The simplest and straightforward approach is critical conduction mode, where a small boost inductor is designed to achieve current return to zero at the end of a switching cycle. However, the high peak-to-average current ratio and input ripple limit its application in very low power conversion. For a quasi-resonant TIBD converter, a small inductor is inserted into the switched capacitor network and then the large capacitor is replaced with a small resonant capacitor. But the energy transferred to the load by the resonant capacitor is limited at this time, and the voltage gain is low. Unlike the ZVS approach, the ZVT topology removes the auxiliary leg from the main circuit and only acts when the main switch switches. Therefore, the additional voltage stress and power loss are small. Although there are ZVT methods for TIBD converters, each method is only suitable for a specific topology, and the ZVS range is limited and varies with different resonance parameters.

The staggered non-isolated diode capacitor network high-gain direct current converter adopts a double boost circuit staggered working mode, which is beneficial to reducing input current ripples and prolonging the service lives of a fuel cell and a photovoltaic panel. The high gain characteristic of the diode capacitor network enables the voltage stress of the semiconductor device to be greatly reduced, and the low-voltage switch tube can improve the efficiency of the circuit while reducing the cost and conduction loss of the circuit. The reduction of the number of the magnetic pieces and the switching tubes is beneficial to reducing the circuit volume and the driving cost, and has the advantage of high power density. However, the hard switching mode of this type of converter limits further improvement of the switching frequency of this type of converter, and the power density is limited, so that the goals of miniaturization and light weight cannot be achieved.

Disclosure of Invention

The invention aims to provide a high-gain ZVT (zero volt-ampere) direct current converter and an auxiliary circuit of an interleaved diode capacitor network, which have the characteristics of expandable high voltage gain, low input current ripple, low voltage stress, wide-range soft switching and simple parameter design while realizing high efficiency and high power density.

The technical solution for realizing the purpose of the invention is as follows:

a high-gain direct current converter ZVT auxiliary circuit of an interleaved diode capacitor network comprises a first auxiliary circuit, a second auxiliary circuit and a resonant inductor, wherein the first auxiliary circuit comprises a first auxiliary switching tube and a first auxiliary diode, the second auxiliary circuit comprises a second auxiliary switching tube and a second auxiliary diode, the first auxiliary circuit and the second auxiliary circuit share one resonant inductor and are used for realizing ZVS (zero voltage switching) switching-on and switching-off of a first controllable switching tube and a second controllable switching tube in a direct current converter, the first auxiliary switching tube and the second auxiliary switching tube realize ZCS switching-on, and all diodes realize ZCS switching-off.

Further, the drain of the first auxiliary switch tube is connected with one end of the resonant inductor and is also connected with the anode of the first auxiliary diode, the drain of the second auxiliary switch tube is connected with the other end of the resonant inductor and is also connected with the anode of the second auxiliary diode, the source of the first auxiliary switch tube is connected with the drain of one of the controllable switch tubes of the converter, the source of the second auxiliary switch tube is connected with the drain of the other controllable switch tube, the cathode of the first auxiliary diode is connected with one end of a certain capacitor in the diode capacitor boosting unit in the converter, and the cathode of the second auxiliary diode is connected with one end of a certain capacitor in the diode capacitor boosting unit in the converter.

Preferably, the source of the first auxiliary switching tube is connected to the source of the second auxiliary switching tube, the drain of the first auxiliary switching tube is connected to one end of the resonant inductor, and is also connected to the anode of the first auxiliary diode and the cathode of the second auxiliary diode, the other end of the resonant inductor is connected to the drain of one of the controllable switching tubes of the converter, the drain of the second auxiliary switching tube is connected to the drain of the other controllable switching tube, the cathode of the first auxiliary diode is connected to one end of the first capacitor in the diode capacitor boosting unit in the converter, and the anode of the second auxiliary diode is connected to one end of the second capacitor in the diode capacitor boosting unit.

A high-gain ZVT direct current converter based on a staggered diode capacitor network of a ZVT auxiliary circuit comprises two staggered input ends, a diode capacitor boosting unit and an output end load, wherein the two staggered input ends comprise an input end power supply, a first staggered inductor, a second staggered inductor, a first controllable switch tube, a second controllable switch tube, a first resonant capacitor and a second resonant capacitor, the positive pole of the input end power supply is simultaneously connected with one ends of the first staggered inductor and the second staggered inductor, the other end of the first staggered inductor is connected with the drain electrode of the first controllable switch tube, and the source electrode of the first controllable switch tube is connected with the negative pole of the input end power supply; the other end of the second interleaved inductor is connected with the drain electrode of a second controllable switching tube, the source electrode of the second controllable switching tube is connected with the negative electrode of the input end power supply, the capacitor is connected with the switching tube in parallel, and the capacitor is connected with the switching tube in parallel; a ZVT auxiliary circuit is added between the two-phase staggered input end and the diode capacitor boosting unit to realize soft switching of the first controllable switching tube and the second controllable switching tube, and the ZVT auxiliary circuit comprises a first auxiliary switching tube, a second auxiliary switching tube, a first auxiliary diode, a second auxiliary diode and a resonant inductor.

Furthermore, the diode capacitor boosting unit is a Bi-fold Dickson boosting unit and comprises 6 capacitors and 6 diodes, the drain electrode of the first controllable switch tube is connected with one ends of the first capacitor, the third capacitor, the fourth capacitor and the sixth capacitor and one end of a resonance inductor, the other end of the resonance inductor is connected with the drain electrode of the first auxiliary switch tube, the anode of the first auxiliary diode and the cathode of the second auxiliary diode, the drain electrode of the second controllable switch tube is connected with the anode of the first diode, one end of the second capacitor, one end of the fifth capacitor and the drain electrode of the second auxiliary switch tube, and the source electrode of the second auxiliary switch tube is connected with the source electrode of the first auxiliary switch tube; the other end of the first capacitor is connected with the cathode of the first diode, the cathode of the first auxiliary diode and the anode of the second diode, the other end of the second capacitor is connected with the cathode of the second diode and the anode of the third diode, the other end of the third capacitor is connected with the cathode of the third diode and one end of a load, the other end of the fourth capacitor is connected with the anode of the fourth diode, the anode of the second auxiliary diode and the cathode of the fifth diode, the other end of the fifth capacitor is connected with the anode of the fifth diode and the cathode of the sixth diode, the other end of the sixth capacitor is connected with the anode of the sixth diode and the other end of the load, and the cathode of the fourth diode is connected with the cathode of the input end power supply.

A control method based on the interleaved diode capacitor network high-gain ZVT direct current converter is characterized in that a control cycle of the control method is divided into a first half cycle and a second half cycle, and the first half cycle and the second half cycle are symmetrical, and the control method comprises the following steps:

t₀～t₁in the stage, the first controllable switch tube is turned off, the first resonant capacitor is connected in parallel to cause zero voltage to be turned off, the voltage of the first resonant capacitor rapidly rises to the voltage at two ends of the fourth capacitor, the second diode, the fourth diode and the sixth diode are turned on, and the first diode, the third diode and the fifth diode are turned off in a reverse bias mode; the first auxiliary switch tube and the second auxiliary switch tube are in an off state, and the second controllable switch tube is kept on;

t₁～t₂step one, the first auxiliary switch tube is turned on, and other semiconductor devices keep the state of the previous step; the voltage of the resonant inductor is equal to the voltage across the fourth capacitor, and the current of the resonant inductor starts from zero with a slope V_C4/L_rThe voltage rises linearly, and the first auxiliary switch tube is switched on for zero current;

t₂～t₃step one, the resonant inductor current rises to the first inductor current, and at the moment, the second diode, the fourth diode and the sixth diode are turned off at zero current; the resonance inductor starts to resonate with the first resonance capacitor;

t₃～t₄in the stage, the voltage at two ends of the first resonant capacitor is reduced to zero, the resonant inductive current is larger than the first inductive current, the current starts to reversely flow through the switch tube, and all diodes are reversely biased and turned off;

t₄～t₅the first auxiliary switching tube is turned off, the first auxiliary diode is turned on, and other semiconductor devices keep the state of the previous stage;

t₅～t₆step, the resonant inductor current is reduced to zero, and the first auxiliary diode realizes zero current turn-off; the input end power supply linearly magnetizes the first inductor and the second inductorThe inductor is linearly magnetized by the power supply of the input end all the time in the first half of the switching period;

t₆and at the moment, the second controllable switch tube is turned off, the first half cycle is finished, the second half cycle is symmetrically executed, and the next cycle is repeated after the second half cycle is finished.

Compared with the prior art, the invention has the following remarkable effects:

1) the auxiliary circuit comprises a first auxiliary switching tube, a second auxiliary switching tube, a first auxiliary diode, a second auxiliary diode and a resonant inductor, wherein the auxiliary circuit is added into a converter circuit, the voltage gain is adjusted by controlling the duty ratio of a controllable switching tube in topology, ZVS (zero voltage switching) switching-on of the two controllable switching tubes, ZCS (zero voltage switching) switching-on of the auxiliary switching tube and ZCS (zero voltage switching) switching-off of all diodes are realized under the condition that the voltage stress of a main circuit semiconductor device is not changed, so that the efficiency and the power density of the converter are further improved, and the problem of electromagnetic interference is effectively inhibited;

2) the modularized diode capacitor boosting unit has simple working principle, parameter design and controller design, high voltage gain and is beneficial to engineering application;

3) the converter provided by the invention has the advantages that the input current ripple is remarkably reduced through the ZVT auxiliary circuit, and the service lives of a photovoltaic panel and a fuel cell are prolonged;

4) all main circuit semiconductor devices of the invention keep low voltage when the voltage stress is unchanged, and auxiliary circuit semiconductor devices have low voltage stress, so that low-voltage devices can be used for reducing conduction loss;

5) the ZVT auxiliary circuit design is suitable for TIBD converters, realizes soft switching of all semiconductor devices, has universality, and has wide application prospect in a new energy distributed power generation system due to the zero-voltage conversion soft switching topology.

Drawings

Fig. 1 is a general topology diagram of a TIBD converter.

FIG. 2 is a typical topology diagram of a TIBD converter with different diode-capacitor boosting units, wherein (a) is a topology diagram of the diode-capacitor boosting unit being an interleaved voltage doubling unit; (b) the diode capacitance boosting unit is a topological diagram of a Cockcroft-Walton boosting unit; (c) a topological diagram of a diode capacitor boosting unit as a Dickson boosting unit; (d) the method is a topological diagram of a diode capacitor boosting unit which is a Bi-fold Dickson boosting unit; (e) the method is a topological diagram of a diode capacitor boosting unit which is a Bi-fold Dickson boosting unit; (f) - (i) is a topological diagram of a diode capacitance boosting unit which is a Cockcroft-Walton and Dickson derivative boosting unit.

FIG. 3 is an equivalent circuit diagram of the TIBD converter of FIG. 2(d), wherein (a) is the first controllable switch tube S₁OFF, the second controllable switching tube S₂An equivalent circuit diagram of ON; (b) is a first controllable switch tube S₁ON, the second controllable switch tube S₂Equivalent circuit diagram of OFF.

FIG. 4 is a functional block circuit diagram of the TIBD converter of FIG. 2(d), wherein (a) is a circuit with a first controllable switch S₁A boost circuit diagram of (a); (b) is provided with a second controllable switch tube S₂A boost circuit diagram of (a); (c) a load charging loop diagram is provided.

Fig. 5 is a simplified diagram of a universal topology of the TIBD converter according to the three functional blocks of fig. 4.

FIG. 6(a) shows the converter of FIG. 2(d) including a first controllable switch S₁ZVT auxiliary circuit diagram of the boost circuit of (1); in the drawing (b), is S₁＝OFF，S₂An equivalent circuit diagram of the circuit of fig. 6(a) when ON and Sa OFF.

FIGS. 7(a) - (f) show the converter of FIG. 2(d) including S₁From S₁And turning off to each mode equivalent circuit diagram for realizing ZVS turning-on.

FIG. 8 shows the converter of FIG. 2(d) including S₁Other ZVT auxiliary circuit diagrams of the boost circuit of (1).

FIG. 9 shows the converter of FIG. 2(d) including S₁The ZVT auxiliary circuit general topology structure diagram of the boost circuit.

FIG. 10(a) shows the converter of FIG. 2(d) including S₂The optimum ZVT auxiliary circuit diagram of the boost circuit of (1); (b) the converter of fig. 2(d) contains an optimal ZVT auxiliary circuit diagram of two boost circuits.

Fig. 11 is a simplified optimized ZVT auxiliary circuit for the converter of fig. 2 (d).

FIG. 12(a) is a diagram of an optimal ZVT assist circuit for the converter of FIG. 2(a) including two boost circuits; (b) the optimized ZVT auxiliary circuit diagram is simplified for the converter of fig. 2 (a).

Fig. 13 is another TIBD converter of fig. 2 with a simplified optimal ZVT auxiliary circuit.

FIG. 14 is a general topology diagram of a TIBD converter with a simplified optimal ZVT auxiliary circuit.

Fig. 15 is a theoretical waveform diagram for constructing the ZVT converter of fig. 11.

Fig. 16(a) to (f) are equivalent circuit diagrams of the respective operation modes of the converter modes 1 to 6 in fig. 11.

FIG. 17 shows the difference in R_LAnd the relationship graph of the voltage gain ratio M and the duty ratio D under the influence.

Fig. 18 is a graph comparing the efficiency of different ZVT IDBD converters.

Fig. 19 is a comparative evaluation graph of several typical ZVT IDBD converters.

Fig. 20 is a diagram of driving signals of the controllable switch tube in the experiment.

Fig. 21 is a power loss distribution diagram of the converter of fig. 11.

FIG. 22 shows the input voltage V_in＝25V，V_o＝400V，R_LGraph of experimental results at 1000 Ω.

FIG. 23 shows the input voltage V_in＝25V，V_o＝400V，R_LGraph of experimental results at 500 Ω.

FIG. 24 shows the input voltage V_in＝15V，V_o＝400V，R_LGraph of experimental results at 1000 Ω.

FIG. 25(a) shows R_LA dynamic response graph of the input voltage stepped from 15V to 25V at 800 Ω; (b) is a V_inDynamic response graph of load step from 0.4A to 0.8A at 20V.

FIG. 26(a) is a graph of efficiency at different loads; (b) the voltage gain ratio under different loads is shown.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. It is to be understood that the described examples are only a few, not all examples of the present invention, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. All other examples, which can be obtained by a person skilled in the art without making any creative effort based on the examples in the present invention, shall fall within the protection scope of the present invention.

Various schematic structural diagrams in accordance with disclosed examples of the invention are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1, a two-phase interleaved structure on an input side of a classic interleaved diode capacitor network high-gain dc converter reduces input current ripples and current stress of a switching tube. The output side of the diode capacitor network is composed of two basic diode capacitor boosting units, namely Cockcroft-Walton and Dickson, and a diode boosting structure derived from the diode capacitor boosting units. The converter has the advantages, high efficiency and high power density are further realized, the working principle, the parameter design and the control structure are simple, and the modular boosting unit structure is adopted, so that the converter is particularly suitable for the preceding-stage direct current boosting conversion occasion of new energy power generation. However, the hard switching operation mode of this type of converter limits further improvement of the switching frequency of this type of converter, and the goal of miniaturization and light weight cannot be achieved. On the basis of analyzing the converter, the invention finds that the converter can be divided into three parts according to the circuit function: comprising S₁And L₁Comprises S₂And L₂The capacitor and the load form a discharge loop, as shown in fig. 4. Since the circuit works in the staggered mode, when one of the switch tubes is actuated, the other switch tube is actuatedOne switch tube is always conducted, so that the two boost circuits do not influence each other. To realize the inclusion of S₁And L₁The soft switching of all semiconductor devices in the boost circuit of (1), adding a ZVT auxiliary circuit as shown in FIG. 9, according to L_rIn the implementation of S₁The energy feedback loop after ZVS is turned on, and the auxiliary circuit structure is shown in fig. 9(a) or fig. 9 (b). First auxiliary diode D_aOne end of (1) and a resonant inductor L_rAnd a one-way switch tube S_aAnd the other end of the capacitor is connected with one capacitor in the diode capacitor boosting network. Since the auxiliary circuit is only at S₁Operating around the turn-on time, including S₂And L₂All semiconductors in the boost circuit of (1) are still operating in hard switching mode. Also, to implement the inclusion of S₂And L₂The soft switching of all semiconductor devices in the boost circuit of (1) adds a ZVT auxiliary circuit similar to the structure of FIG. 9. At the same time, includes S₁And L₁All semiconductor devices in the boost circuit of (1) operate in a hard switching mode. In order to realize the soft switching of all semiconductor devices of the two boost circuits, the auxiliary circuits of the two boost circuits are added into the hard switching main circuit at the same time, and all the semiconductor devices of the circuits realize the soft switching. Because the two auxiliary circuits only work near the turn-on time of the corresponding controllable switch tubes and the two controllable switch tubes work in the staggered mode, the two auxiliary circuits can share one resonant inductor, the two auxiliary circuits can be simplified into one auxiliary circuit, and the two unidirectional switch tubes can be replaced by bidirectional switch tubes. The simplified auxiliary circuit structure has two forms depending on whether the resonant inductors of the two auxiliary circuits have a common connection. The final simplified ZVT assist circuit structure is shown in fig. 14. The simplified auxiliary circuit is composed of a first auxiliary switch tube S_aAnd a second auxiliary switch tube S_bA first auxiliary diode D_aAnd a second auxiliary diode D_bResonant inductance L_rAnd (4) forming. In order to realize ZVS turn-off of the controllable switching tubes, two small capacitors C are connected in parallel at two ends of the two controllable switching tubes_s1And C_s2. Finally, the controllable switching tube realizes ZVS on and off, the auxiliary switching tube realizes ZCS on, and all diodes realize ZCS off.

The invention is described in detail below with reference to the figures and specific examples.

Fig. 1 shows a general topology of a two-phase interleaved boost diode-capacitor (TIBD) converter, which consists of two-phase interleaved input and diode-capacitor boost units. Fig. 2 shows several typical hard-switched (HS) TIBD converters, with basic diode-capacitor voltage boosting cells (VMC) in the dashed box, with increased cell count to improve voltage gain. The topologies in fig. 2(b) and (c) are composed of two most basic Cockcroft-Walton and Dickson diode capacitance boosting units, and diode capacitance boosting units of other topologies can be derived from the two basic boosting units. The operation of the TIBD converter in fig. 2(a), (d), (e), (f) and (i) is explained in detail in the prior art. In order to better explain the design idea of ZVT auxiliary soft switching of this type of topology, the basic operation principle of this type of topology hard switching topology needs to be introduced, and the converter of the Bi-fold Dickson boost unit in fig. 2(d) is taken as an example for analysis. In order to obtain high voltage gain, the duty ratio of the two controllable switching tubes is larger than 0.5, and the phase of the two controllable switching tubes is shifted by 180 degrees, so that three circuit states exist in one switching period. When both switches are turned on simultaneously, all diodes are reverse biased and both inductors are charged by the input voltage source. The two circuit states are shown in fig. 3(a) and (b). The converter can be considered to consist of two interleaved boost circuits. One of the boost circuits is composed of V_in、L₁、S₁、D₂、D₄、D₆、C₁、C₂、C₄、C₅、C₆And (4) forming. Another boost circuit is composed of V_in、L₂、S₂、D₁、D₃、D₅、C₁、C₂、C₃、C₄、C₅And (4) forming. For containing S₁When S is a boost circuit₁When conducting, L₁Is supplied by voltage source V_inIs magnetized and is not influenced by the switch tube S₂The effect of the switching on or off action. When one switch tube is turned on or off, the other switch tube is always kept in a conducting state, so that the two switch tubes are in a conducting stateThe individual boost circuits do not affect each other. When S is₁When disconnected, the circuit state is as shown in FIG. 3(a), V_inAnd L₁Three diode capacitor parallel branches are charged, and the state simplifies the circuit structure as shown in fig. 4 (a). For another boost circuit, when S₂When the switch is turned off, the circuit state is as shown in fig. 3(b), and the simplified circuit configuration is as shown in fig. 4 (b). Thus, the circuit in fig. 2(d) can be considered to be composed of three functional parts as shown in fig. 4, the third part being a discharge loop composed of an output capacitor and a load. As can be seen from fig. 4(a) and (b), the two boost circuits share part of the capacitance without the semiconductor device and the inductance overlapping. Therefore, the general structure of this type of converter can be further summarized as fig. 5, and the dotted line portion connected to the point G indicates that the connection branch may or may not exist according to different structures of the diode-capacitor boosting unit.

To realize the inclusion of S₁The soft switching of all semiconductor devices in the boost circuit of (a), adding a ZVT auxiliary circuit to the topology of fig. 2(d) is shown in fig. 6 (a). Due to the first auxiliary switch tube S_aIs a one-way switch tube and is only at S₁Conducting near the turn-on time, so that a second controllable switch tube S is included₂All semiconductor devices in the boost circuit of (1) are still operating in a hard switching state. Wherein the dotted line is S₁L after ZVS switching on_rTransferring energy to a first capacitor C₁The passage of (2). To illustrate the working principle of the auxiliary circuit, a first controllable switch tube S₁＝OFF，S₂ON and a first auxiliary switching tube S_aThe equivalent circuit when OFF is given as shown in fig. 6 (b). At the switch tube S₁The second controllable switch tube S is turned on from the off state₂Always kept on, inductor L₂Is always by V_inIs magnetized, and therefore comprises a second controllable switching tube S₂The boost circuit does not affect the circuit comprising the first controllable switch tube S₁The operating state of the boost circuit. Comprises a first controllable switch tube S₁The equivalent circuit of the boost circuit in each mode is shown in fig. 7, and the shaded area in fig. 7(a) is an added auxiliary circuit. FIG. 6(b) includes a first controllable switch tube S₁The boost circuit is simplified as shown in the figure7(b), input terminal power supply V_inAnd a first inductance L₁Three diode capacitor branches are charged in series. Once S is present_aOn, the circuit operates as shown in fig. 7 (c). Due to L_rVoltage at both ends is V_C4，i_LrIncrease linearly from zero, S_aZCS is turned on, and the current flowing through the three diode capacitor branches begins to decrease. When i is_Lr＝I_L1While the current through the three diode-capacitor branches is reduced to zero, D₂、D₄And D₆ZCS off is achieved and the circuit state changes as shown in fig. 7 (d). L is_rStart and C_S1Occurrence of resonance, V_CS1From V at the end of the state with a sinusoidal law_C4Reducing to zero. When V is_CS1When 0, the circuit state changes as shown in fig. 7(e) and the current starts to flow in reverse through the switching tube S₁. During this state, the first controllable switch tube S₁Achieving ZVS turn-on. In order to reduce the frequency of the power supply due to i_LrConduction losses due to circulating currents, first auxiliary switching tube S_aIs turned off and the circuit enters the state shown in fig. 7 (f). L is_rEnergy of (D) through_aIs transferred to C₁. When i is_LrReduced to zero, D_aZCS off is achieved and the state ends. The next state is that the two controllable switching tubes are simultaneously conducted, which is the same as the hard switching topology. Similarly, the above-described ZVT auxiliary circuit design method may also be applied to the other hard-switched TIBD converters in fig. 2. Since this type of converter can be functionally decomposed into three parts as shown in fig. 4, the different parts are the multiple parallel diode capacitor branches in the two boost circuits and the capacitors in the load supply loop. But whether containing S₁The boost circuit has a plurality of diode capacitance branches, because the auxiliary branch L_r-S_aIn the first auxiliary switch tube S_aAfter being turned on, to I_L1All diodes in the boost circuit can achieve ZCS turn-off when the current transfer is completed. After that, C_S1And L_rOnset of resonance, V_CS1Eventually resonating to zero. Thus, S₁The ZVS conduction condition is provided. Thus, comprising S₁In the boost circuit ofAll semiconductor devices of (2) realize soft switching.

When S is₁After ZVS turn-on is achieved, if L_rTransfer energy to other capacitors, to contain S₁The added ZVT assist circuit of the boost circuit of (a) is shown in fig. 8. For these circuits, only the operating state of fig. 7(f) differs among the corresponding simplified equivalent circuits. The dotted line in FIG. 8 is L_rFeeding back energy to the current paths of the different capacitors. The conduction loss of the auxiliary circuit in fig. 8(a), (c) and (d) is larger than that of the auxiliary circuit in fig. 6(a), 8(b) and (e) because two controllable switching tubes are added in the energy feedback loop. Since the voltage stress of Sa in fig. 6(a) and 8(a) is lower than that of other circuits, a low on-resistance switch tube can be selected to reduce the conduction loss of the auxiliary circuit. Therefore, in the case of including S₁The auxiliary circuit in fig. 6(a) is the most preferable design scheme among the auxiliary circuits of the boost circuit design of (a). Comparing all the auxiliary circuits in fig. 6(a) and fig. 8, the general structure of the ZVT auxiliary circuit designed for one boost circuit in the TIBD converter is shown in fig. 9. In the design of the auxiliary circuit, the shaded area in FIG. 10(a) includes S₂The dotted line is the resonant inductor energy feedback loop. Likewise, containing S₂All semiconductor devices in the boost circuit of (1) realize soft switching but contain S₁All semiconductor devices in the boost circuit of (1) are still operating in a hard switching state. In order to realize soft switching of all semiconductor devices in fig. 2(d), a ZVT auxiliary circuit designed for two boost circuits is added at the same time, and the soft switching topology is shown in fig. 10 (b). The two auxiliary circuits only act in a short time near the turn-on time of the corresponding controllable switch tube and the two controllable switch tubes work in a staggered mode, so that the two auxiliary circuits do not influence each other. Considering the staggered working mode of the two auxiliary circuits, the two auxiliary circuits can share one resonant inductor, the two unidirectional switching tubes can be replaced by bidirectional switching tubes, and further the two unidirectional switching tubes are simplified into one auxiliary circuit, and the simplified soft switching circuit is shown in fig. 11. The diode capacitor boosting unit is a Bi-fold Dickson boosting unit and a first controllable switch tube S₁Drain electrode of the first capacitor C₁A third capacitor C₃A fourth capacitor C₄A sixth capacitor C₆And a resonant inductor L_rAnd a resonant inductor L_rAnd the other end of the first auxiliary switch tube S_aDrain electrode of (1), first auxiliary diode D_aAnd a second auxiliary diode D_bIs connected to the cathode of a second controllable switching tube S₂Has a drain connected with a first diode D₁Anode of, a second capacitor C₂A fifth capacitor C₅And a second auxiliary switching tube S_bAnd a second auxiliary switching tube S_bSource electrode and first auxiliary switch tube S_aIs connected to the source of (a); a first capacitor C₁And the other end of the first diode D₁Cathode of (1), first auxiliary diode D_aAnd a second diode D₂Is connected to the anode of a second capacitor C₂And the other end of the second diode D₂And a third diode D₃Is connected to the anode of a third capacitor C₃And the other end of the first diode D and a third diode D₃Cathode and load R_LOne end connected to a fourth capacitor C₄And the other end of the fourth diode D₄Anode of (2), second auxiliary diode D_bAnd a fifth diode D₅Is connected to the cathode of a fifth capacitor C₅And the other end of the first diode D and a fifth diode D₅And a sixth diode D₆Is connected to the cathode of a sixth capacitor C₆And the other end of the first diode D and a sixth diode D₆Anode and load R_LIs connected to the other end of the fourth diode D₄Cathode and input terminal power supply V_inAnd connecting the negative electrode.

According to the same design concept, an optimal ZVT auxiliary circuit of two boost circuits is added to the hard-switching TIBD topology in fig. 2(a), and the soft-switching circuit topology is shown in fig. 12 (a). Since the resonant inductances in the two auxiliary circuits do not have a common termination point, the final simplified auxiliary circuit is shown in FIG. 12(b), L_rThe energy feedback loop is shown in dashed lines. The diode capacitor boosting unit is a staggered voltage-multiplying unit and comprises 3 capacitors and 4 diodes, and the first controllable switch tube S₁Drain electrode of the first diode D is connected with the second diode D₂Anode of, a second capacitor C₂And a second auxiliary switching tube S_bSource electrode of (1), second controllable switch tube S₂Has a drain connected with a first diode D₁Anode of, first capacitor C₁And a first auxiliary switching tube S_aA source electrode of (a); resonant inductor L_rOne terminal and a second auxiliary diode D_bAn anode and a second auxiliary switch tube S_bA drain connected to the first auxiliary diode D_aAnode and first auxiliary switch tube S_aDrain electrode connected to a first capacitor C₁And the other end of the second diode D₂Cathode, third diode D₃Anode and second auxiliary diode D_bCathode connection, second capacitor C₂And the other end of the first diode D₁Cathode, fourth diode D₄Anode and first auxiliary diode D_aIs connected to the cathode of a third diode D₃Cathode and fourth diode D₄Cathode, tenth capacitor C_oOne end and a load R_LOne end connected to input end power supply V_inNegative electrode and tenth capacitor C_oThe other end and a load R_LThe other end is connected.

Applying the above-mentioned design idea of the ZVT auxiliary circuit to other topologies in fig. 2, and finally designing an optimal soft switching topology as shown in fig. 13, where fig. 13(a) is a topology diagram of the converter with the ZVT auxiliary circuit in fig. 2(b), and the diode capacitor boosting unit is a Cockcroft-Walton boosting unit, and includes 4 capacitors and 4 diodes; first controllable switch tube S₁Drain electrode of the first capacitor C₁And a second auxiliary switching tube S_bSource electrode of (1), second controllable switch tube S₂Has a drain connected with a first diode D₁Anode of, a second capacitor C₂And a first auxiliary switching tube S_aA source electrode of (a); resonant inductor L_rOne terminal and a second auxiliary diode D_bAn anode and a second auxiliary switch tube S_bA drain connected to the first auxiliary diode D_aAnode and first auxiliary switch tube S_aDrain electrode connected to a first capacitor C₁Is connected with the first auxiliary diode D_aCathode, second auxiliary diode D_bCathode, first diode D₁Cathode, second diode D₂Anode and third capacitor C₃One terminal of (C), a second capacitor C₂The other end of the first diode D is connected with a second diode D₂Cathode and third diode D₃Anode, third capacitor C₃The other end of the second diode D is connected with a third diode D₃Cathode and fourth diode D₄Anode, fourth diode D₄Cathode is connected with tenth capacitor C_oOne end and a load R_LOne end, input end power supply V_inNegative pole connected to tenth capacitor C_oThe other end and a load R_LThe other end;

fig. 13(b) is a topology diagram of the converter with ZVT auxiliary circuit in fig. 2(c), and the diode capacitor boosting unit is a Dickson boosting unit, and includes 4 capacitors and 4 diodes; the first controllable switch tube S₁Has a drain connected with a first diode D₁Anode and second capacitor C₂And a second auxiliary switching tube S_bSource electrode of (1), second controllable switch tube S₂Drain electrode of the first capacitor C₁One terminal, a third capacitor C₃And a first auxiliary switching tube S_aA source electrode of (a); resonant inductor L_rOne terminal and a second auxiliary diode D_bAn anode and a second auxiliary switch tube S_bA drain connected to the first auxiliary diode D_aAnode and first auxiliary switch tube S_aDrain electrode connected to a first capacitor C₁Is connected with the first auxiliary diode D_aCathode, second auxiliary diode D_bCathode, first diode D₁Cathode, second diode D₂Anode, second capacitor C₂The other end of the first diode D is connected with a second diode D₂Cathode and third diode D₃Anode, third capacitor C₃The other end of the second diode D is connected with a third diode D₃Cathode and fourth diode D₄Anode, fourth diode D₄Cathode is connected with tenth capacitor C_oOne end and a load R_LOne end, input end power supply V_inNegative electrode connected with capacitor C_oThe other end and a load R_LThe other end;

FIG. 13(c) is a converter topology of FIG. 2(e) with ZVT auxiliary circuit, the two polesThe tube capacitor boosting unit is a Bi-fold Dickson boosting unit and comprises 4 capacitors and 4 diodes; the first controllable switch tube S₁Has a drain connected with a first diode D₁Anode and third capacitor C₃One terminal, a fourth capacitor C₄One end and a first auxiliary switch tube S_aThe drain electrode of the first controllable switch tube S₂Drain electrode of the first capacitor C₁One terminal, a second capacitor C₂One terminal and a resonant inductor L_rOne terminal, resonant inductor L_rThe other end is connected with a first auxiliary diode D_aCathode, second auxiliary diode D_bAn anode and a second auxiliary switch tube S_bDrain electrode of (1), second auxiliary switch tube S_bSource and S of_aIs connected to the source of the first capacitor C₁The other end of the first diode D₁Cathode, second diode D₂Anode and second auxiliary diode D_bCathode, second capacitor C₂The other end of the second diode D is connected with a third diode D₃Anode, fourth diode D₄Cathode and first auxiliary diode D_aAnode, second diode D₂Cathode is connected with third capacitor C₃The other end and a load R_LOne terminal, a fourth diode D₄Anode connected to fourth capacitor C₄The other end and a load R_LThe other end, a third diode D₃Cathode and input power supply V_inConnecting the negative electrodes;

FIG. 13(d) is a converter topology of FIG. 2(f) with ZVT auxiliary circuit, the diode capacitor boost unit is a Cockcroft-Walton and Dickson derived boost unit, which includes 7 capacitors and 7 diodes; first controllable switch tube S₁Drain electrode of the first capacitor C₁One terminal, a third capacitor C₃One terminal, a fifth capacitor C₅One end and a first auxiliary switch tube S_aThe drain electrode of the first controllable switch tube S₂Drain electrode of the first capacitor is connected with the second capacitor C₂One terminal, a fourth capacitor C₄One terminal, a sixth capacitor C₆One terminal, a first diode D₁Anode and resonant inductor L_rOne terminal, resonant inductor L_rThe other end is connected with a first auxiliary diode D_aCathode, second auxiliary diode D_bAnode and secondary auxiliarySwitch tube S_bDrain electrode of (1), second auxiliary switch tube S_bSource electrode and first controllable switch tube S_aIs connected to the source of the first capacitor C₁The other end of the first diode D₁Cathode, second diode D₂Anode and second auxiliary diode D_bCathode, fourth capacitor C₄The other end of the second diode D is connected with a fourth diode D₄Anode, fifth diode D₅Cathode and first auxiliary diode D_aAnode, second capacitor C₂The other end of the first diode D is connected with a second diode D₂Cathode and third diode D₃Anode, fifth capacitor C₅The other end of the second diode D is connected with a fifth diode D₅Anode and sixth diode D₆Cathode, third capacitor C₃The other end of the second diode D is connected with a third diode D₃Cathode and diode D_oAnode, sixth capacitor C₆The other end of the second diode D is connected with a sixth diode D₆Anode, tenth capacitor C_oAnd a load R_LOne terminal, diode D_oCathode is connected with tenth capacitor C_oAnd a load R_LThe other end, a fourth diode D₄Cathode connected with input end power supply V_inAnd a negative electrode.

FIG. 13(e) is a converter topology of FIG. 2(g) with ZVT auxiliary circuit, the diode capacitor boost unit is a Cockcroft-Walton and Dickson derived boost unit, comprising 7 capacitors and 7 diodes; first controllable switch tube S₁Drain electrode of the first capacitor is connected with the second capacitor C₂One terminal, a fourth capacitor C₄One terminal and a resonant inductor L_rOne end, the second controllable switch tube S₂Drain electrode of the first capacitor C₁One terminal of (1), a fifth capacitor C₅One end of (1), a first diode D₁Anode, fifth diode D₅Cathode and second auxiliary switch tube S_bDrain electrode of (1), second auxiliary switch tube S_bSource electrode and first auxiliary switch tube S_aSource connection of, a resonant inductor L_rIs connected with the first auxiliary diode D_aAnode, second auxiliary diode D_bCathode and first auxiliary switch tube S_aThe drain electrode of (1), the first capacitor C₁The other end of the first diode D is connected with a second diode D₂Cathode and third diode D₃Anode, second capacitor C₂The other end of the first diode D₁Cathode, second diode D₂An anode, the other end of the third capacitor C3 and a first auxiliary diode D_aCathode, third capacitor C₃The other end of the second diode D is connected with a third diode D₃Cathode and fourth diode D₄Anode, fourth diode D₄Cathode is connected with tenth capacitor C_oOne end and a load R_LOne terminal, a fourth capacitor C₄The other end of the second diode D is connected with a fifth diode D₅Anode and sixth diode D₆Cathode and sixth capacitor C₆One terminal and a second auxiliary diode D_bAnode, fifth capacitor C₅The other end of the second diode D is connected with a sixth diode D₆Anode and diode D₇Cathode, sixth capacitor C₆Another end of the diode D₇Anode, tenth capacitor C_oAnother end of (1) and a load R_LAnd the other end of the same.

FIG. 13(f) is the converter topology of FIG. 2(h) with ZVT auxiliary circuit, the diode capacitance boost unit is Cockcroft-Walton and Dickson derived boost unit, which includes 3 capacitors and 3 diodes, the first controllable switch tube S₁Drain electrode of the first capacitor is connected with the second capacitor C₂One terminal, a third diode D₃Cathode and first auxiliary switch tube S_aThe drain electrode of the first controllable switch tube S₂Drain electrode of the first capacitor C₁One end of (1), a first diode D₁Anode and resonant inductor L_rOne terminal, resonant inductor L_rThe other end is connected with a first auxiliary diode D_aCathode, second auxiliary diode D_bAn anode and a second auxiliary switch tube S_bThe first auxiliary switch tube S_aAnd a second auxiliary switch S_bIs connected to the source of the first capacitor C₁Is connected with the first auxiliary diode D_aAnode, third diode D₃Anode and third capacitor C₃And a load R_LOne terminal of (C), a second capacitor C₂The other end of the first auxiliary diode D is connected with a second auxiliary diode D_bCathode, first diode D₁Cathode and second diode D₂Anode, third capacitor C₃The other end of the first diode is connected with the second diodeD₂Cathode and load R_LThe other end; the topology of the auxiliary circuits of fig. 2(i) and 2(h) are similar.

Comparing the above soft switching topologies, it can be seen that there are two basic configurations of the ZVT auxiliary circuit, as shown in fig. 14, the circuit configuration of the ZVT auxiliary circuit in fig. 14(a) is: the first auxiliary switch tube S_aDrain and resonant inductor L_rOne end of the first auxiliary diode is connected with the first auxiliary diode D_aAnode connected, a second auxiliary switching tube S_bDrain and resonant inductor L_rThe other end is connected with a second auxiliary diode D_bAnode connection, first auxiliary switching tube S_aA source connected to the drain of one of the controllable switching tubes of the converter, a second auxiliary switching tube S_bA source connected to the drain of another controllable switch tube, a first auxiliary diode D_aA cathode connected to one end of a capacitor in a diode-capacitor boosting unit in the converter, and a second auxiliary diode D_bThe cathode is connected with one end of a certain capacitor in the diode capacitor boosting unit in the converter. The circuit structure of the ZVT auxiliary circuit in fig. 14(b) is: the first auxiliary switch tube S_aSource electrode and second auxiliary switch tube S_bIs connected to the source of the first auxiliary switching tube S_aDrain electrode of and resonant inductor L_rIs connected to one end of the first auxiliary diode D_aAnd a second auxiliary diode D_bIs connected to the cathode of the resonant inductor L_rThe other end of the first auxiliary switch tube S is connected with the drain electrode of one controllable switch tube of the converter_bIs connected with the drain of another controllable switching tube, a first auxiliary diode D_aA cathode connected to one end of the first capacitor in the diode capacitor boosting unit in the converter, and a second auxiliary diode D_bAnd the anode is connected with one end of a second capacitor in the diode capacitor boosting unit. Due to L in the topology of FIG. 12(b)_rThe energy feedback loop has one more switching tube compared with the energy feedback loop in the topology of fig. 11, so the conduction loss of the auxiliary circuit in fig. 11 is lower. For the same reason, the simplified auxiliary circuit structure in fig. 14(b) is superior to the simplified auxiliary circuit structure in fig. 14 (a).

The operation principle and parameter design of the ZVT converters with 3 VMC units in fig. 11 are illustrated as a general case. The driving signals of the two controllable switching tubes are the same, the conduction duty ratio is larger than 0.5, and the phase difference between the two controllable switching tubes is 180 degrees so as to realize high voltage gain. FIG. 15 shows the switching period T_sThe theoretical waveforms for the converter of fig. 11, and the operating mode in the first half of the switching cycle are shown in fig. 16. D and D are the duty cycles of the main and auxiliary switches, respectively. α represents a phase shift angle between the main switch and the auxiliary switch. There are 12 modes in one switching cycle. However, due to the symmetrical working principle, only the first six modes were analyzed. At t₆To t₇During a time interval of (1), flows through S₁Is equal to S₂Input current I at turn-off_in. And at t₀To t₁Due to part of the input current flowing through D₄Thus at S₁Flows through S when turned off₂Current of less than I_in. This asymmetric state between the two half switching cycles does not affect the current and voltage relationships in the main circuit. C_S1And C_S2Same capacity value C_S1＝C_S2＝C_S。

To simplify the steady state operation analysis, the following assumptions were made:

1) the capacitance and boost inductance in the VMC are large enough so they can be considered as a constant voltage source and a constant current source.

2) All semiconductor devices are ideal devices.

The working process of the topology is as follows:

mode 1: (t)₀～t₁):t₀At any moment, switch tube S₁Turn-off, shunt capacitance C_S1Resulting in zero voltage turn-off, capacitor voltage V_Cs1Rises rapidly to V_C4A second diode D₂、D₄、D₆On and the first diode D₁、D₃、D₅Reverse bias turn-off; first auxiliary switch tube S_a、S_bIs in an off state and switches the transistor S₂Kept on, and the equivalent circuit is as shown in fig. 16 (a);

therefore, the two resonant capacitor voltages, the resonant inductor currents and the duration expressions are respectively:

mode 2: (t)₁～t₂):t₁At the moment, the first auxiliary switch tube S_aTurning on, and keeping other semiconductor devices in the state of the previous mode; resonant inductor voltage equal to V_C4Resonant inductance L_rCurrent i of_LrStarting from zero with a slope V_C4/L_rLinearly rises due to the sum of L_rIn the same branch, S_aZero current switching-on is realized, and an equivalent circuit is shown in fig. 16 (b);

mode 3: (t)₂～t₃):t₂Time of day, resonant inductor current i_LrUp to the inductor current I_L1At this time, the second diode D₂、D₄、D₆Zero current turn-off is realized; resonant inductor L_rStart and capacitance C_S1Resonance, the equivalent circuit is shown in fig. 16 (c);

the expressions of two resonance capacitor voltages, resonance inductance currents and duration time obtained by the resonance equivalent circuit are respectively as follows:

wherein:

mode 4: (t)₃～t₄):t₃Time of day, capacitor voltage V_Cs1Decreases to zero and resonates the inductor current i_LrIs greater than I_L1The current starts to flow reversely through the switch tube S₁All diodes are reverse biased off; in this mode S₁Zero voltage turn-on can be achieved with an equivalent circuit as shown in fig. 16 (d);

mode 5: (t)₄～t₅):t₄At the moment, the first auxiliary switch tube S_aIs turned off and the first auxiliary diode D_aTurning on, and keeping other semiconductor devices in the state of the previous mode; resonant inductor voltage equal to-V_C1Thus i_LrWith a slope V_C1/L_rThe linearity decreases, and the equivalent circuit is shown in fig. 16 (e);

mode 6: (t)₅～t₆):t₅Time, i_LrReduced to zero, D_aZero current turn-off is realized; input end power supply V_inFor inductor L₁Linear magnetization and inductance L₂Always from input supply V during the first half of the switching cycle_inLinear magnetization is carried out; third capacitor C₃And a sixth capacitance C₆The series connection supplies power to the load in the whole switching period; t is t₆Time of day, S₂Off, the second half of the switching cycle begins and the equivalent circuit is as shown in fig. 16 (f).

considering the symmetry of the circuit operation in the front and back half periods

According to the principle of volt-second equilibrium, L₁The average value of the voltages across the period is zero, so the following equation can be obtained:

according to the charge balance principle, flows through D_aAnd D₁Is the load current, from D_a、D₂、D₄And D₆The following equation can be obtained for the charge relationship of (a):

wherein:

according to the equivalent circuit of mode 1, the series of voltage relationships between different capacitances is written as follows:

from equation (7) to equation (10), the voltage gain can be expressed as:

wherein:

for a converter with N VMC cells, the voltage gain can be derived as:

wherein:

to visually display the voltage gain characteristic, the gain curve of M as a function of D under different load conditions is shown in fig. 17. As the duty cycle and the number of VMC units increase, the voltage gain increases significantly. It can be seen that the voltage gain is affected by the load.

To reduce the turn-off loss of the main switch, v_CS1And v_CS2Should have a rise time of more than 3t_offWherein t is_offIs the switch off time obtained from device data sheets or experimental tests. Thus, C_sIs calculated as follows:

in order to reduce the influence of the auxiliary branch on the main circuit, the time interval t₁₃Should be less than 1/10 of a half switching cycle. Thus, L_rDesigned by the following formula:

in FIG. 16(C) C_S1In a resonant state, v_CS1Is derived as equation (15). From this formula, it can be seen that v_CS1Is always reduced to zero over a period of pi/2 electrical degrees under any load and input voltage conditions. In other words，S₁ZVT can be always switched on under any load and input voltage condition, and wide-range soft switching is realized. Due to the symmetry of the working principle, S₂Also has a wide range ZVT turn-on characteristic.

v_CS1(t)＝V_C4cosω_r(t-t₂) (15)

According to FIG. 15, S₁Must be at t₃And then switched on to achieve ZVT. Thus, the time interval t₁To a switching tube S₁The turn-on time should be greater than t₁₃. From this relationship, α:

in FIG. 15, at S₁Turn off S after the turn-on moment_aTo ensure S₁ZVT of is on. Therefore, d/f must be satisfied_s>(1-α/2π)/f_s. The duty cycle d of the auxiliary switch can be given by the following equation:

the time interval t being reduced when the duty cycle D is reduced₆To t₇Increases and the operating mode 6 disappears first. Thus, during mode 5, S₂Is turned off and the first diode D₁，D₃，D₅After turning on, the energy of the resonant inductor still passes through D_aIs fed back to C₁. However, this operational difference does not affect the voltage, current relationship in the main circuit. Therefore, when at t₄Is turned off at a moment S₂When D is obtained_min：

According to fig. 15, the duration of mode 1 decreases as D increases. When it is reduced to 0, D is obtained_max：

The maximum voltage and current ratings of the switching tube and diode are listed in table 1 according to fig. 15 and the operating principle. The effective current values of the switching tube and the diode are calculated by applying the equation (20).

TABLE 1

For large capacitors and inductors, the voltage and current ripple coefficients are used to design their parameters. Then, for a given current ripple factor δ_LL can be obtained by emulating a converter circuit₁And L₂. Another method is to calculate according to the formula in table 2. Also, a formula or simulation result may be applied to design the capacitance.

TABLE 2

Compared with other soft switching design methods, the ZVT circuit design method has small additional voltage stress and power loss. Therefore, to evaluate the performance of the converter constructed in fig. 11, a comparison was made with the latest other converters of different boost technologies and soft switching technologies in table 3. The Switching Device Power (SDP) of a semiconductor is expressed as the product of voltage stress and current stress. The total SDP is a measure of the total semiconductor device requirements and is an important cost indicator for the converter. The peak voltage and current of the power device under experimental operating conditions were used to calculate SDP. Also, the power densities were compared under the same operating conditions. By using SIMETrix software, different loads are given in FIG. 18And (5) comparing the efficiencies. Although the inverter auxiliary circuit in fig. 11 has one more switching tube, the number of other elements is smaller than that of the conventional inverter. Moreover, the converter has the advantages of scalable high voltage gain, higher efficiency, lower SDP, higher power density, lower voltage stress and wider ZVS range than other converters. Documents [ T.Nouri, N.Vosouughi Kurdkandi and M.Shaneh, "A Novel ZVS High-Step-Up Converter With build-In Transformer Voltage Multiplier Cell," In IEEE Transactions on Power Electronics, vol.35, No.12, pp.12871-12886, Dec.2020.]Is a typical non-isolated coupled inductor ZVS high gain dc converter with limited soft switching range, although the converter has similar performance to the ZVT converter constructed in fig. 11. Prior documents [ M.Jabbari and M.Mokhdar, "" High-Frequency Resonant ZVS Boost Converter With group Switches and Continuous Input Current, "" in IEEE Transactions on Industrial Electronics, vol.67, No.2, pp.1059-1067, Feb.2020]The ZVS converter of the resonant cascade structure of (a) has the worst performance due to the transfer of energy to the load in a resonant mode of operation. Although documents [ S.Li, Y.ZHEN, B.Wu and K.M.Smidley, "A Family of resource Two-Switch Boosting Switch With ZVS Operation and a Line Regulation Range," in IEEE Transactions on Power Electronics, vol.33, No.1, pp.448-459, Jan.2018]The switched capacitor ZVS converter in (1) has the potential advantages of high efficiency and high power density, but the voltage gain is too low to be applied in experimental conditions. Documents [ Z.Liao, Y.Lei and R.C.N.Pilawa-Podgurski, "" Analysis and Design of a High Power sensitivity Flying-Capacitor Multi level Boost Converter for High Step-Up Conversion, "" in IEEE Transactions on Power Electronics, vol.34, No.5, pp.4087-4099, May 2019]The medium multilevel converter operates on hard switching with the switching frequency set to 100kHz for fair comparison. The converter also has poor performance. Documents [ L.Shih, Y.Liu and H.Chiu, "" A Novel Hybrid Mode Control for a Phase-Shift Full-Bridge Converter reforming High Efficiency Over a Full-Load Range, "" in IEEE Transactions on Power Electronics, vol.34, No.3, pp.2794-2804, March2019]The phase-shifted full-bridge converter can represent an isolated bridge soft switching converter, and the converter has the advantages of less device number, low voltage stress of a low-voltage side switching tube and low current stress of a high-voltage side diode. However, high gain applications are inefficient and the algorithm is complex to achieve wide range ZVS control. V_in＝20V，V_o＝400V，P_oA comparison of the overall performance between these converters at 320W is shown in figure 19, where 5 indicates best, 4 indicates excellent, 3 indicates normal, 2 indicates poor, 1 indicates very poor and the parameters refer to table 3. It is evident from this figure that the converter in fig. 11 has better performance than the other converters.

TABLE 3

Example 1

Based on the auxiliary circuit and the converter in the embodiment, it is considered that the hardware circuit operates at V_in＝15V～25V，V_o＝400V，f_s＝500kHz，R_L＝500Ω～1000Ω，δ_L＝0.3，δ_CIn the case of 0.02, the detailed parameters are designed as follows:

1) resonance parameter C_sAnd L_r: due to I_in＝6.4A～21.3A，V_o＝400V，t_off3ns, according to formula (13), C_sIs 1.44nF, C is selected accordingly_sWas 1.5 nF. Then, L is calculated from the formula (14)_rThe design value was 1 uH.

2) Control variables α, D: by applying the expressions (16) to (19) in this order, α ═ 16 pi/9, D ═ 0.12, and D can be calculated_min＝0.51，D_max＝0.89。

3) A semiconductor device: the resonance parameter L_rAnd C_sSubstituting table 1, the maximum voltage and current stress of the main switch was calculated to be 66.7V and 23.9A. Therefore, the main switch is selected as GaN device GS61008T and the diode is selected as NTSB40200 CTG.

4) Large capacitance and inductance: passive element meter according to table 2 and operating rangeCalculated values are respectively L₁＝L₂＝33.6uH，C₁＝C₄＝1.2uH，C₂＝C₅＝0.6uH，C₃＝C₆0.3 uH. Finally, the device specifications of the converter in fig. 11 are listed in table 4.

At S_aAt the turn-on instant of (2), the current flows in reverse direction through S_b. From the reverse conduction characteristic of the data sheet GS61008T, the tube drop on the positive voltage drive signal is much less than the tube drop on the zero voltage drive signal. Therefore, when one auxiliary switch is turned on, a positive drive signal should also be applied to the other auxiliary switch to reduce conduction losses. FIG. 20 shows the drive signals applied during the experiment, with the converter of FIG. 11 at nominal condition V_in＝20V，V_o＝400V，R_LThe power loss distribution at 500 Ω is shown in fig. 21. Since the main power loss is mainly due to conduction losses of the semiconductor devices, in order to further improve the converter efficiency, semiconductor devices with low on-resistance may be used in the hardware design.

In order to verify the theoretical analysis and evaluate the performance of the constructed transducer, a 320W hardware prototype was constructed with the specifications as shown in table 4. The control board is realized by the DSP TMS320F 28335. The efficiency was measured using a digital power meter YOKOGAWA WT 1804E.

TABLE 4

Fig. 22-24 show experimental waveforms at steady state at different input voltages and loads. The voltage stresses of the main switch and the diode measured in these figures are 67V and 133V, which are substantially in accordance with the theoretical values of 66.7V and 133.3V. In fig. 22(a), it can be seen that the controllable switch S is turned on before the gate drive signal is turned on₁And S₂Has been reduced to zero, so that the main switch realizes ZVT turn-on, thereby greatly reducing the switching losses of the two switches. FIGS. 22(b) and (c) show D₁，D₂，D₅And D₆ZCS is turned off, thus eliminating reverse recovery losses and suppressing EMI noise. And is tuned toVibrating inductor current i_LrThe effectiveness of the theoretical analysis is further demonstrated, as is the theoretical waveform in fig. 15. To verify parametric design, fig. 23 and 24 show soft switching waveforms for different loads and input voltages. It can be seen that soft switching of all semiconductor devices is achieved over the entire input voltage and load range.

The dynamic response of the output voltage when the load and input voltage are stepped is shown in fig. 25. A conventional PI controller is used to regulate the output voltage. It is apparent that the converter of fig. 11 is capable of regulating the output voltage over a wide range of load and input voltage variations.

To validate the loss profile analysis, fig. 26(a) plots the efficiency curves at different power levels. The measured curve is very close to the theoretical efficiency curve. Thus, the efficiency advantage of the ZVT converter is verified. Under this operating condition, the efficiency of the converter in fig. 11 peaks at 94.9%. Fig. 26(b) shows a comparison of the voltage gain ratio between the theoretical value and the experimental result. The two curves are also very close. Therefore, the effectiveness of the above theoretical analysis and parameter design was verified.

On the basis of the topology of the high-gain direct-current converter of the prior staggered diode capacitor network, the switching-on and switching-off of all switching tubes ZVS and all diodes ZCS of the converter are realized by the soft switch design scheme of the universal ZVT auxiliary circuit. The auxiliary switching tube realizes ZCS on, and the auxiliary diode realizes ZCS off. Therefore, the efficiency is improved while the switching frequency is increased, the high power density is realized, and the electromagnetic interference is restrained.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical solution according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A high-gain DC converter ZVT auxiliary circuit with staggered diode capacitor network is characterized by comprising a first auxiliary circuit, a second auxiliary circuit and a resonant inductor (L)_r) First assistanceThe circuit comprises a first auxiliary switching tube (S)_a) And a first auxiliary diode (D)_a) The second auxiliary circuit comprises a second auxiliary switch tube (S)_b) And a second auxiliary diode (D)_b) The first and second auxiliary circuits share a resonant inductor (L)_r) For realizing ZVS on and off of the first controllable switch tube and the second controllable switch tube in the DC converter, and the first auxiliary switch tube (S)_a) And a second auxiliary switch tube (S)_b) ZCS is turned on, and ZCS is turned off by all diodes.

2. The ZVT auxiliary circuit of claim 1, wherein the first auxiliary switch tube (S) is connected to the ZVT auxiliary circuit_a) Drain and resonant inductance (L)_r) One end of the first auxiliary diode is connected with the first auxiliary diode (D)_a) Anode connected, second auxiliary switching tube (S)_b) Drain and resonant inductance (L)_r) The other end is connected with a second auxiliary diode (D)_b) Anode connection, first auxiliary switching tube (S)_a) A source connected to the drain of one of the controllable switching tubes of the converter, a second auxiliary switching tube (S)_b) A source connected to the drain of another controllable switching tube, a first auxiliary diode (D)_a) A cathode and a second auxiliary diode (D)_b) The cathode is connected to a diode capacitor boosting unit in the converter.

3. The ZVT auxiliary circuit of claim 1, wherein the first auxiliary switch tube (S) is connected to the ZVT auxiliary circuit_a) Source electrode and second auxiliary switch tube (S)_b) Is connected to the source of the first auxiliary switching tube (S)_a) Drain and resonant inductance (L)_r) Is connected to one end of the first auxiliary diode (D)_a) And a second auxiliary diode (D)_b) Is connected to the cathode, a resonant inductance (L)_r) Is connected to the drain of one of the controllable switching tubes of the converter, a second auxiliary switching tube (S)_b) The drain electrode of the first auxiliary diode is connected with the drain electrode of the other controllable switch tubePolar tube (D)_a) A cathode and a second auxiliary diode (D)_b) The anode is connected to a diode capacitor boosting unit in the converter.

4. A high-gain ZVT DC converter based on the staggered diode capacitor network of the ZVT auxiliary circuit of claim 1, which comprises two staggered input terminals, a diode capacitor boosting unit and an output terminal load (R)_L) The two-phase interleaved input terminal comprises an input terminal power supply (V)_in) A first interleaved inductor (L)₁) A second interleaved inductor (L)₂) A first controllable switch tube (S)₁) A second controllable switch tube (S)₂) A first resonant capacitor (C)_s1) And a second resonance capacitor (C)_s2) Said input terminal power supply (V)_in) The positive electrode is simultaneously connected with the first interleaved inductor (L)₁) And a second interleaved inductance (L)₂) Is connected to a first interleaved inductance (L)₁) The other end and the first controllable switch tube (S)₁) Is connected to the drain of the first controllable switching tube (S)₁) Source of (2) is connected with an input end power supply (V)_in) A negative electrode; second interleaved inductance (L)₂) The other end is connected with a second controllable switch tube (S)₂) Is connected to the drain of the second controllable switching tube (S)₂) Source of (2) is connected with an input end power supply (V)_in) Negative electrode, capacitor (C)_s1) And a switching tube (S)₁) Parallel connection, a capacitor (C)_s2) And a switching tube (S)₂) Parallel connection; it is characterized in that a ZVT auxiliary circuit is added between the two-phase staggered input end and the diode capacitance boosting unit to realize a first controllable switch tube (S)₁) And a second controllable switch tube (S)₂) The ZVT auxiliary circuit comprises a first auxiliary switch tube (S)_a) A second auxiliary switch tube (S)_b) A first auxiliary diode (D)_a) A second auxiliary diode (D)_b) And a resonant inductor (L)_r)；

The first controllable switch tube (S)₁) And a second controllable switch tube (S)₂) The phase difference of the driving signals is 180 DEG, the conduction duty ratio of the two is the same and is more than 0.5, and a first auxiliary switch tube (S)_a) And a second auxiliary switch tube (S)_b) Has a phase difference of 180 DEG and is only in pairsThe controllable switch tube is conducted before being switched on.

5. The interleaved diode capacitor network high-gain ZVT (zero volt Current) DC converter as recited in claim 4, wherein the diode capacitor boosting unit is a Bi-fold Dickson boosting unit comprising 6 capacitors and 6 diodes, and the first controllable switch tube (S)₁) Is connected to the first capacitor (C)₁) A third capacitor (C)₃) A fourth capacitor (C)₄) A sixth capacitor (C)₆) One terminal of (a) and a resonant inductor (L)_r) And a resonant inductance (L)_r) And the other end of the first auxiliary switch tube (S)_a) Drain electrode of (1), first auxiliary diode (D)_a) And a second auxiliary diode (D)_b) Is connected to the cathode of a second controllable switching tube (S)₂) Is connected to a first diode (D)₁) Anode of (2), second capacitor (C)₂) A fifth capacitor (C)₅) And a second auxiliary switching tube (S)_b) And a second auxiliary switching tube (S)_b) Source electrode and first auxiliary switch tube (S)_a) Is connected to the source of (a); a first capacitor (C)₁) And the other end of the first diode (D)₁) Cathode of (2), first auxiliary diode (D)_a) And a second diode (D)₂) Is connected to the anode of a second capacitor (C)₂) And the other end of the first diode (D) and a second diode (D)₂) And a third diode (D)₃) Is connected to the anode of a third capacitor (C)₃) And the other end of the first diode (D) and a third diode (D)₃) Cathode and load (R)_L) One end connected to a fourth capacitor (C)₄) And the other end of the first diode (D) and a fourth diode (D)₄) Anode of (D), second auxiliary diode (D)_b) And a fifth diode (D)₅) Is connected to the cathode of a fifth capacitor (C)₅) And the other end of the first diode (D) and a fifth diode (D)₅) And a sixth diode (D)₆) Is connected to the cathode of a sixth capacitor (C)₆) And the other end of the first diode (D) and a sixth diode (D)₆) Anode and load (R)_L) Is connected at the other end with a fourth diode (D)₄) Cathode and input terminal power supply (V)_in) And connecting the negative electrode.

6. The interleaved diode-capacitor network high-gain ZVT (zero volt Current) DC converter as claimed in claim 4, wherein the diode-capacitor voltage boosting unit is an interleaved voltage doubling unit comprising 3 capacitors and 4 diodes, and the first controllable switch tube (S)₁) Is connected to the second diode (D)₂) Anode of (2), second capacitor (C)₂) And a second auxiliary switching tube (S)_b) Source electrode of (1), second controllable switch tube (S)₂) Is connected to a first diode (D)₁) Anode of (2), first capacitor (C)₁) And a first auxiliary switching tube (S)_a) A source electrode of (a); resonance inductance (L)_r) One terminal and a second auxiliary diode (D)_b) An anode and a second auxiliary switching tube (S)_b) A drain electrode connected to the first auxiliary diode (D)_a) An anode and a first auxiliary switching tube (S)_a) Drain electrode connected to a first capacitor (C)₁) And the other end of the first diode (D) and a second diode (D)₂) Cathode, third diode (D)₃) An anode and a second auxiliary diode (D)_b) Cathode connection, second capacitance (C)₂) And the other end of the first diode (D)₁) Cathode, fourth diode (D)₄) An anode and a first auxiliary diode (D)_a) Is connected to the cathode of a third diode (D)₃) Cathode and fourth diode (D)₄) Cathode, tenth capacitance (C)_o) One end and a load (R)_L) One end connected to input end power supply (V)_in) Negative electrode and tenth capacitor (C)_o) The other end and the load (R)_L) The other end is connected.

7. The interleaved diode capacitor network high gain ZVT direct current converter according to claim 4, wherein the diode capacitor boosting unit is a Cockcroft-Walton boosting unit comprising 4 capacitors and 4 diodes; a first controllable switch tube (S)₁) Is connected to the first capacitor (C)₁) And a second auxiliary switching tube (S)_b) Source electrode of (1), second controllable switch tube (S)₂) Is connected to a first diode (D)₁) Anode of (2), second capacitor (C)₂) And a first auxiliary switchPipe (S)_a) A source electrode of (a); resonance inductance (L)_r) One terminal and a second auxiliary diode (D)_b) An anode and a second auxiliary switching tube (S)_b) A drain electrode connected to the first auxiliary diode (D)_a) An anode and a first auxiliary switching tube (S)_a) Drain electrode connected to a first capacitor (C)₁) Is connected to the first auxiliary diode (D)_a) Cathode, second auxiliary diode (D)_b) Cathode, first diode (D)₁) Cathode, second diode (D)₂) An anode and a third capacitor (C)₃) One terminal of (C), a second capacitor (C)₂) Is connected to a second diode (D)₂) Cathode and third diode (D)₃) Anode, third capacitor (C)₃) The other end of the second diode (D) is connected with a third diode (D)₃) Cathode and fourth diode (D)₄) Anode, fourth diode (D)₄) Cathode is connected with tenth capacitor (C)_o) One end and a load (R)_L) One terminal, input terminal power supply (V)_in) Negative pole connected to tenth capacitor (C)_o) The other end and the load (R)_L) And the other end.

8. The interleaved diode capacitor network high gain ZVT direct current converter according to claim 4, wherein the diode capacitor boosting unit is a Dickson boosting unit comprising 4 capacitors and 4 diodes; the first controllable switch tube (S)₁) Is connected to a first diode (D)₁) Anode, second capacitor (C)₂) And a second auxiliary switching tube (S)_b) Source electrode of (1), second controllable switch tube (S)₂) Is connected to the first capacitor (C)₁) One terminal, a third capacitor (C)₃) And a first auxiliary switching tube (S)_a) A source electrode of (a); resonance inductance (L)_r) One terminal and a second auxiliary diode (D)_b) An anode and a second auxiliary switching tube (S)_b) A drain electrode connected to the first auxiliary diode (D)_a) An anode and a first auxiliary switching tube (S)_a) Drain electrode connected to a first capacitor (C)₁) Is connected to the first auxiliary diode (D)_a) Cathode, second auxiliary diode (D)_b) Cathode, first diode (D)₁) Cathode, second diode (D)₂) Anode, second capacitor (C)₂) Is connected to a second diode (D)₂) Cathode and third diode (D)₃) Anode, third capacitor (C)₃) The other end of the second diode (D) is connected with a third diode (D)₃) Cathode and fourth diode (D)₄) Anode, fourth diode (D)₄) Cathode is connected with tenth capacitor (C)_o) One end and a load (R)_L) One terminal, input terminal power supply (V)_in) Negative electrode connecting capacitor (C)_o) The other end and the load (R)_L) And the other end.

9. The interleaved diode capacitor network high gain ZVT direct current converter according to claim 4, wherein the diode capacitor boosting unit is a Bi-fold Dickson boosting unit comprising 4 capacitors and 4 diodes; the first controllable switch tube (S)₁) Is connected to a first diode (D)₁) Anode and third capacitor C₃One terminal, a fourth capacitor C₄One end and a first auxiliary switch tube (S)_a) A second controllable switch tube (S)₂) Is connected to the first capacitor (C)₁) One terminal, a second capacitor (C)₂) One terminal and resonance inductance (L)_r) One terminal, resonant inductor (L)_r) The other end is connected with a first auxiliary diode (D)_a) Cathode, second auxiliary diode (D)_b) An anode and a second auxiliary switching tube (S)_b) Drain electrode of (1), second auxiliary switching tube (S)_b) Source of (S) and_a) Is connected to the source of the first capacitor (C)₁) Is connected to the first diode (D)₁) Cathode, second diode (D)₂) An anode and a second auxiliary diode (D)_b) Cathode, second capacitor (C)₂) The other end of the second diode (D) is connected with a third diode (D)₃) Anode, fourth diode (D)₄) A cathode and a first auxiliary diode (D)_a) Anode, second diode (D)₂) The cathode is connected with a third capacitor (C)₃) The other end and the load (R)_L) One terminal, a fourth diode (D)₄) Anode is connected with fourth capacitor (C)₄) The other end and the load (R)_L) The other end, a third diode (D)₃) Cathode and input power supply (V)_in) And connecting the negative electrode.

10. The interleaved diode capacitor network high gain ZVT direct current converter according to claim 4, wherein the diode capacitor boosting unit is a Cockcroft-Walton and Dickson derived boosting unit comprising 7 capacitors and 7 diodes; a first controllable switch tube (S)₁) Is connected to the first capacitor (C)₁) One terminal, a third capacitor (C)₃) One terminal, a fifth capacitor (C)₅) One end and a first auxiliary switch tube (S)_a) The drain electrode of the first controllable switch tube S₂Is connected to the second capacitor (C)₂) One terminal, a fourth capacitor (C)₄) One terminal, a sixth capacitor (C)₆) One terminal, the first diode (D)₁) Anode and resonance inductance (L)_r) One terminal, resonant inductor (L)_r) The other end is connected with a first auxiliary diode (D)_a) Cathode, second auxiliary diode (D)_b) An anode and a second auxiliary switching tube (S)_b) Drain electrode of (1), second auxiliary switching tube (S)_bSource electrode and first controllable switch tube (S)_a) Is connected to the source of the first capacitor (C)₁) Is connected to the first diode (D)₁) Cathode, second diode (D)₂) An anode and a second auxiliary diode (D)_b) Cathode, fourth capacitor (C)₄) Is connected with a fourth diode (D)₄) Anode, fifth diode (D)₅) A cathode and a first auxiliary diode (D)_a) Anode, second capacitor (C)₂) Is connected to a second diode (D)₂) Cathode and third diode (D)₃) Anode, fifth capacitor (C)₅) Is connected with a fifth diode (D)₅) An anode and a sixth diode (D)₆) Cathode, third capacitor (C)₃) The other end of the second diode (D) is connected with a third diode (D)₃) Cathode and diode (D)_o) Anode, sixth capacitor (C)₆) The other end of the second diode (D) is connected with a sixth diode (D)₆) Anode, tenth capacitor (C)_o) And a load (R)_L) One terminal, diode (D)_o) Cathode is connected with tenth capacitor (C)_o) And a load (R)_L) The other end, a fourth diode (D)₄) Cathode is connected with input end power supply (V)_in) And a negative electrode.