Current-mode soft-switching push-pull bridge bidirectional dc-dc converter

Abstract

The application discloses a current-mode soft-switching push-pull bridge bidirectional DC-DC converter in the field of data noise reduction, which comprises a high-frequency transformer T r , a direct-current voltage source V in and a direct-current voltage source V o ; the high-frequency transformer T r is provided with a secondary winding N s and a first winding N1 and a second winding N2 connected with each other; the direct-current voltage source V in is connected in series with an input inductor l b , and then is connected in parallel with a first primary branch, a second primary branch and an auxiliary branch; the first winding N1 and a first control unit are arranged in series on the first primary branch; the second winding N2 and a second control unit are arranged in series on the second primary branch; a clamping capacitor C c and an auxiliary control unit are arranged in series on the auxiliary branch; the secondary winding N s is connected with a series inductor l s through an active half-bridge circuit and the direct-current voltage source V o ; the application reduces circulation loss and eliminates voltage spikes of power tubes caused by high-frequency transformer leakage inductance.

Description

Technical Field

[0001] This invention belongs to the field of converters, specifically relating to a current-mode soft-switching push-pull bridge bidirectional DC-DC converter. Background Technology

[0002] The world's energy sector is undergoing a major transformation, with the large-scale development and utilization of clean and renewable energy sources becoming the norm, and countries around the world are vigorously developing new energy sources. To achieve its "dual-carbon" goals, my country is developing a new power system based on renewable energy sources. Hydrogen energy, as a renewable energy source, differs from solar and wind energy in that it has excellent storage performance and is also environmentally friendly, efficient, safe, and highly portable. Therefore, building an integrated wind / solar / hydrogen and energy storage power supply system has excellent application prospects. The DC-DC converter is a crucial component of this integrated system, boosting the low voltage generated by renewable energy generation units to a DC bus ranging from 200 to 800V. A portion of this electrical energy is then transmitted via a bidirectional DC-DC converter to the battery storage end to balance the load demand at different times.

[0003] Current-source push-pull converters offer advantages such as low input current ripple, simple structure, self-boosting capability, and electrical isolation, making them suitable for wind / solar / hydrogen and energy storage boost power supply systems. However, traditional current-source push-pull converters suffer from high switching losses and high electrical stress on power transistors, necessitating further optimization and improvement for practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a current-mode soft-switching push-pull bridge bidirectional DC-DC converter and system, which effectively solves the problem of poor noise reduction effect when the noise energy changes greatly, and reduces circulating current loss.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a current-mode soft-switching push-pull bridge bidirectional DC-DC converter, comprising: a high-frequency transformer T r DC voltage source V in and DC voltage source V o ;

[0007] The high-frequency transformer T r There is a secondary winding N s and the first winding N1 and the second winding N2 connected to each other; the DC voltage source V in With input inductance l bAfter being connected in series, the first primary branch, the second primary branch, and the auxiliary branch are connected in parallel. A first winding N1 and a first control unit are connected in series on the first primary branch. A second winding N2 and a second control unit are connected in series on the second primary branch. A clamping capacitor C is connected in series on the auxiliary branch. c and auxiliary control unit;

[0008] The DC voltage source V o A first secondary circuit and a second secondary circuit are connected in parallel on both sides; a capacitor C is connected in series on the first secondary circuit. o1 and capacitor C o2 The second secondary circuit has a third control unit and a fourth control unit connected in series; the secondary winding N s One end is connected in series with an inductor l s On the circuit connected between the third control unit and the fourth control unit, the secondary winding N s The other end is connected to capacitor C. o1 and capacitor C o2 On the circuit between them.

[0009] Preferably, the first primary side branch is provided with a primary side equivalent leakage inductance l. lk1 The original equivalent leakage inductance l lk1 It is disposed between the first winding N1 and the first control unit; the second primary side branch is provided with a primary side equivalent leakage inductance l. lk2 The original equivalent leakage inductance l lk2 It is located between the second winding N2 and the second control unit.

[0010] Preferably, the DC voltage source V in The positive terminal and the input inductor l b After being connected in series, it is connected between the first winding N1 and the second winding N2; the first winding N1 and the second winding N2 have the same number of turns.

[0011] Preferably, the first control unit, the second control unit, the third control unit, the fourth control unit, and the auxiliary control unit include power transistors, diodes, and control capacitors connected in parallel; the power transistors are MOSFET power transistors.

[0012] Preferably, the power transistors of the first and second control units use square wave drive signals with a 180-degree phase difference and a duty cycle greater than 0.5. The power transistor of the auxiliary control unit is driven by a NAND gate square wave signal from the power transistors of the first and second control units. The power transistors of the third and fourth control units use square wave drive signals with a 180-degree phase difference and a duty cycle of 0.5, and the square wave drive signals input to the power transistors of the first and fourth control units have a phase difference.

[0013] Preferably, the soft-switching condition of the power transistor in the first control unit is as follows:

[0014]

[0015] Where I0 represents the output current of the converter, U o DC voltage source V o The voltage value, D S1 This is expressed as the duty cycle of the power transistor in the first control unit. L s For inductor l s L is the inductance value. b For inductor l b f is the inductance value. S1 The switching frequency of the power transistor in the first control unit;

[0016] Preferably, the soft-switching condition of the power transistor in the second control unit is as follows:

[0017]

[0018] Among them, D S2 This is expressed as the duty cycle of the power transistor in the second control unit. f S2 The switching frequency of the power transistor in the second control unit;

[0019] Preferably, the soft-switching condition of the power transistor in the auxiliary control unit is:

[0020]

[0021] Among them, D sc This represents the duty cycle of the power transistor in the auxiliary control unit; f sc The switching frequency of the power transistor in the auxiliary control unit.

[0022] Preferably, the power transmitted by the bidirectional DC-DC converter is:

[0023]

[0024] Where n is the high-frequency transformer T r The coil turns ratio, U in DC voltage source V in The voltage value is D, and D is the duty cycle of the power transistor of the first control unit.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The current-mode soft-switching push-pull bridge bidirectional DC-DC converter of this invention transfers energy from the primary side to the secondary side using a series inductor l. s The voltages at both ends are controlled to be equal in magnitude to reduce circulating current losses and reduce the current stress on all power transistors.

[0027] The auxiliary circuit in this invention can absorb the energy of the leakage inductance of the high-frequency transformer, and can eliminate the voltage spikes of the power transistors caused by the leakage inductance of the high-frequency transformer; thereby reducing the voltage stress of the power transistors of the first control unit and the second control unit; the voltages across the power transistors of the first control unit and the second control unit on the secondary side are clamped by the output voltage, so the voltage spikes of each power transistor are small, which also makes it easier to select power semiconductor devices with low withstand voltage stress. Attached Figure Description

[0028] Appendix Figure 1 This is a schematic diagram of the current-mode soft-switching push-pull bridge bidirectional DC-DC converter proposed in this invention.

[0029] Appendix Figure 2 This is a schematic diagram of the main waveforms of the current-mode soft-switching push-pull bridge bidirectional DC-DC converter implementation circuit of the present invention.

[0030] Appendix Figure 3 ~Attached Figure 15 This is a schematic diagram of various switching modes of the current-mode soft-switching push-pull bridge bidirectional DC-DC converter embodiment of the present invention.

[0031] Appendix Figure 16 ~Attached Figure 20 The waveform diagrams are used to demonstrate the current-mode soft-switching push-pull bridge bidirectional DC-DC converter of the present invention based on the PLECS simulation platform.

[0032] The main symbol name in the above figures is: V in This is the primary side DC voltage source voltage; l b For input inductance; v Lb For input inductance l b Voltage across terminals; i Lb For the flow through the input inductor l b Current; S1, S2, S c S4 and S5 represent the power transistors of the first control unit, second control unit, auxiliary control unit, third control unit, and fourth control unit, respectively; C s1 C s2 C sc C s4 C s5 These are respectively connected to power transistors S1, S2, and S... c The capacitors S4 and S5 are connected in parallel; D1, D2, and D3 are capacitors connected in parallel. scD4 and D5 are connected to power transistors S1, S2, and S3 respectively. c A diode consisting of S4 and S5 connected in parallel; C c For resonant capacitor; T r For high-frequency transformers; L lk1 L lk2 These represent the equivalent leakage inductances of the primary windings N1 and N2, respectively; C o1 C o2 The capacitor connected in series in the first secondary circuit; V o This is the DC voltage source for the secondary side of the converter; v Ls For secondary winding N s Series inductor L s Voltage across terminals; i Ls I is the current in inductor Ls; Ls_peak i is the peak current of inductor Ls; s1 i s2 i is the current flowing through power transistors S1 and S2; Sc For the current flowing through the power transistor S c The current; i s4 The current flowing through power transistor S4; v ab For transformer T r Secondary voltage; v cd The voltage at the midpoint of the half-bridge arm is v. Cc For capacitor C c The clamping voltage; Ts is the switching period, and D is the duty cycle. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0034] Appendix Figure 1 This is a schematic diagram of the current-mode soft-switching push-pull bridge bidirectional DC-DC converter structure proposed in this invention.

[0035] A current-mode soft-switching push-pull bridge bidirectional DC-DC converter includes: a high-frequency transformer T r DC voltage source V in and DC voltage source V o ;

[0036] The high-frequency transformer T r There is a secondary winding N s and the first winding N1 and the second winding N2 connected to each other; the DC voltage source V in With input inductance l bAfter being connected in series, the first primary side branch, the second primary side branch, and the auxiliary branch are connected in parallel; a first winding N1 and a first control unit are connected in series on the first primary side branch; a second winding N2 and a second control unit are connected in series on the second primary side branch; the number of turns of the first winding N1 and the second winding N2 are equal; the DC voltage source V in The positive terminal and the input inductor l b After being connected in series, it is connected to the same-name terminals of the first winding N1 and the second winding N2; the first primary side branch is provided with primary side equivalent leakage inductance l. lk1 The original equivalent leakage inductance l lk1 It is disposed between the first winding N1 and the first control unit; the second primary side branch is provided with a primary side equivalent leakage inductance l. lk2 The original equivalent leakage inductance l lk2 A clamping capacitor C is disposed between the second winding N2 and the second control unit; a clamping capacitor C is connected in series on the auxiliary branch. c and auxiliary control unit; the first control unit, the second control unit, and the auxiliary control unit are connected to the DC voltage source V. in The negative electrode is directly connected.

[0037] The first control unit includes a power transistor S1, a diode D1, and a control capacitor C connected in parallel. S1 The first control unit includes a power transistor S2, a diode D2, and a control capacitor C connected in parallel. S2 The conduction direction of diodes D1 and D2 is that of the DC voltage source V. in The negative terminal points to the DC voltage source V. in The positive terminal; the auxiliary control unit includes a power transistor S connected in parallel. c Diode D sc and control capacitor C sc The diode D sc The conduction direction is that of the DC voltage source V in The positive terminal points to the DC voltage source V. in The negative electrode.

[0038] The DC voltage source V o An active half-bridge circuit is connected on both sides; the active half-bridge circuit includes a first secondary circuit and a second secondary circuit connected in parallel; a capacitor C is connected in series on the first secondary circuit. o1 and capacitor C o2 The second secondary circuit has a third control unit and a fourth control unit connected in series; the secondary winding N s Series inductor l with the same name s On the circuit connected between the third control unit and the fourth control unit, the secondary winding N s The other end is connected to capacitor C. o1 and capacitor C o2On the circuit between them.

[0039] The third control unit includes a power transistor S4, a diode D4, and a control capacitor C4 connected in parallel; the fourth control unit includes a power transistor S5, a diode D5, and a control capacitor C5 connected in parallel; the conduction direction of diodes D4 and D5 is the same as that of the DC voltage source V. o The negative terminal points to the DC voltage source V. o Positive electrode; power transistors S1, S2, and S... c Power transistors S4 and S5 are MOSFET power transistors.

[0040] Appendix Figure 2 This is a schematic diagram of the main waveforms of the current-mode soft-switching push-pull bridge bidirectional DC-DC converter proposed in this invention. The power transistors S1 and S2 are driven by square wave signals with a phase difference of 180 degrees and a duty cycle greater than 0.5. c The circuit is driven by square wave signals from NAND gates of power transistors S1 and S2; power transistors S4 and S5 use square wave drive signals with a 180-degree phase difference and a duty cycle of 0.5, and the square wave drive signals input to power transistors S1 and S5 have a phase difference. As a phase shift angle, there is a certain dead time between the drive signals of each power transistor to achieve zero-voltage turn-on.

[0041] The soft-switching condition for the power transistor S1 is:

[0042]

[0043] Where I0 represents the output current of the converter, U o DC voltage source V o The voltage value, D S1 This is expressed as the duty cycle of power transistor S1. L s For inductor l s L is the inductance value. b For inductor l b f is the inductance value. S1 The switching frequency of the power transistor in the first control unit;

[0044] The soft-switching condition for the power transistor S2 is:

[0045]

[0046] Among them, D s2 This is expressed as the duty cycle of power transistor S2. f S2 The switching frequency of the power transistor in the second control unit;

[0047] The power transistor S c The soft-switching condition is:

[0048]

[0049] Among them, D Sc Represented as power transistor S c duty cycle; f Sc The switching frequency of the power transistor in the auxiliary control unit.

[0050] The converter's operation within one switching cycle can be divided into nine sub-modes: [t0~t0′], [t0′~t0″], [t0″~t1], [t1~t1′], [t1′~t1″], [t1″~t2], [t2~t2′], [t2′~t3], and [t3~t4]. The operation process of each sub-mode is analyzed in detail below.

[0051] For ease of analysis, let's make the following assumptions: 1) Power transistors S1, S2, and S... c 1) S4 and S5 are ideal devices with zero on-state voltage drop; 2) Clamping capacitor C c With output capacitor C o1 C o2 Large enough, clamping voltage V Cc It can be regarded as a constant voltage source; 3) The capacitors of the half-bridge circuit are equal in size and are C. o1 =C o2 =C o ;4) High-frequency transformer T r The turns ratio of the primary and secondary windings is n and its value is: n = N S / N1=N S / N2, the primary leakage inductance of the transformer is L lk1 =L lk2 And all leakage inductance is refracted to the secondary side of the transformer, and in series with the inductor l s 5) Combined together; with power transistors S1, S2, S c The direction of the conduction current i is the direction of the current i. Ls i s1 i s2 6) The direction of the conduction current of the diodes D4 and D5 connected in anti-parallel to the power transistors S4 and S5 is the direction of the current i. Lb i s4 i s5 Positive direction. Based on this, the modal analysis is as follows:

[0052] 1. As attached Figure 3 Mode 1 of the converter shown has a time period of [t0~t0′];

[0053] Before t0, through inductor ls current i Ls The direction is positive, power transistors S2 and S c When the transformer is turned on, the secondary current flows through the anti-parallel diode D4 of the power transistor S4. At time t0, diode D1 turns on, the auxiliary control unit turns off, and the input voltage acts on the input inductor L. b Above, i.e., v Lb =U in DC voltage source V in Give input inductance l b Charging, i Lb Increase, at this time i s1 Decrease in the opposite direction, i s2 The voltage v of the transformer primary winding decreases in the positive direction. ab =0, secondary voltage v cd =0.5U o Series inductor l s The voltage across the terminals is v Ls =-0.5U o At this time, inductor l s Release energy to DC voltage source U o Charging, i Ls Decrease, that is:

[0054]

[0055] At time t0′, the current i flowing through power transistor S1 s1 When the value decreases to zero, this mode ends.

[0056] 2. As attached Figure 4 and attached Figure 5 Mode 2 of the converter shown has a time period of [t0′~t0″];

[0057] At time t0′, i s1 =0, S1 conducts with zero voltage. Then i s1 Continue to increase positively, i s2 Continue to decrease positively, i Lb i Ls i s1 i s2 The mathematical equation for the change is the same as that for mode 1; at time t0″, i Ls The mode ends when the value drops to zero.

[0058] 3. As attached Figure 6 and attached Figure 7 Mode 3 of the converter shown has a time period of [t0″~t1];

[0059] At time t0″, power transistor S4 is turned on with zero voltage, i Ls Reduced to 0, power transistor current i s1 =is2 Subsequently, the secondary side DC voltage source V o Give series inductor l s Energy storage, i Ls The voltage continues to increase in the opposite direction. At time t1, power transistor S2 is turned off, and this mode ends.

[0060] 4. As attached Figure 8 and attached Figure 9 Mode 4 of the converter shown has a time period of [t1~t1′];

[0061] At time t1, S2 is turned off. At this time, i Lb The maximum value is reached. This is due to the input inductance L. b The current on the transistor cannot change abruptly, and the junction capacitance C of power transistor S1... s1 Charging, C Sc Discharge. Before time t1′, power transistor S... c body diode D sc When the circuit is turned on, the current is transferred to S. c The body diode, i.e., the power transistor S c Zero-voltage turn-on can be achieved. In this mode, the secondary inductor current cannot change abruptly, and the primary current will be redistributed. The instant before time t1 is defined as t. 1- Then, in an instant, it is defined as t. 1+ Specifically, these include:

[0062]

[0063] Subsequently, due to the voltage v across the input inductor Lb =U in -v Cc , i.e. i Lb Decrease, v Cc Clamping capacitor C c The voltage across the terminals. Furthermore, V ab =-v Cc v Ls =-nv Cc -0.5U0, U in Together with U0, they supply power to inductor L. s Energy storage includes:

[0064]

[0065] At time t1, power transistor S is turned on. c This mode ends.

[0066] 5. As attached Figure 10 Mode 5 of the converter shown has a time interval of [t1′~t1″].

[0067] At time t1′, diode D scWhen in the ON state, zero-voltage turn-on can be achieved. At time t1″, S4 turns off, and this mode ends.

[0068] 6. As attached Figure 11 Mode 6 of the converter shown has a time interval of [t1″~t2].

[0069] At time t1″, power transistor S4 is turned off, due to the series inductor current i Ls The current cannot change abruptly; this current supplies the junction capacitance C of the power transistor S4. S4 Charging, C S5 Discharge occurs, and diode D5 conducts at time t2. Afterwards, v Ls =nv Cc -0.5U o =0, secondary current i s4 The body diode transitions from S4 to S5 and remains at the maximum reverse current I. Ls_peak V remains unchanged during this stage. in Give V o Transfer energy.

[0070] 7. As attached Figure 12 Mode 7 of the converter shown has a time interval of [t2~t2′].

[0071] At time t2, since diode D5 has already turned on, S5 can achieve zero-voltage turn-on. This mode has i s1 =ni Ls And remain unchanged, i s1 =i Sc +i Lb , i.e. i Lb Decrease, i Sc Decrease in the opposite direction. At time t2′, i Sc When the value decreases to 0, this mode ends.

[0072] 8. As attached Figure 13 and attached Figure 14 The converter shown has mode 8, with a time interval of [t2′~t3].

[0073] After time t2′, power transistor S c Turn on. Afterwards, taking the direction of the power transistor's on-current flow as the positive direction, i... sc Increasing from zero in a positive direction, i Lb Continue to decrease. At time t3, turn off S. c This mode ends.

[0074] 9. As attached Figure 15 Mode 9 of the converter shown has a time interval of [t3~t4].

[0075] At time t3, power transistor S c When turned off, since the inductor current cannot change abruptly, the power transistor S...c Junction capacitance C sc Charging, C S2 Discharge. Sc The current rapidly decreases to 0. Before time t4, the current transfers to the body diode of S2, i.e., diode D2 conducts, creating conditions for zero-voltage turn-on of S2. In this mode, since the secondary-side series inductor current cannot change abruptly, the primary-side current is redistributed again. With time t3 as the boundary, the instant before time t3 is defined as t. 3- Then, in an instant, it is defined as t. 3+ That is:

[0076]

[0077] At time t4, power transistor S2 is turned on, achieving zero-voltage turn-on. The main energy for S2 to achieve zero-voltage turn-on is provided by the series inductor on the secondary side. After time t4, the second half of the cycle begins, which is similar to the first half and will not be described again. Furthermore, energy is transferred from the output side to the input side, and the analysis method is similar.

[0078] Under the above operating modes, based on the volt-second balance principle satisfied by the series inductor on the secondary side, the power transmitted by the converter can be deduced as follows:

[0079]

[0080] Where n is the high-frequency transformer T r The coil turns ratio, U in DC voltage source V in The voltage value, D S1 This represents the duty cycle of power transistor S1.

[0081] With attachment Figure 3 Based on the analysis of the nine modes of the converter in Appendix 15, the soft-switching characteristics of the invented converter were simulated and verified using PLECS simulation software. The converter parameters are 40V DC input, 200V DC output, switching frequency of power transistors S1 and S2 of 100kHz, and output power of 500W. The key parameters of the converter's main circuit topology are: input inductance L... d =40μH, transformer turns ratio n=1:1:1, transformer primary leakage inductance L lk1 =L lk2 =600nH, transformer secondary series inductance L s =10μH, clamping capacitor C c =10μF, half-bridge circuit capacitor C o1 =C o2 =50μF.

[0082] Appendix Figure 16The graphs show the output voltage, output current, and input inductor current waveforms. The values ​​shown meet the converter parameter requirements. (Attached) Figure 17 The voltage and current waveforms of the clamping capacitor verify that the converter can achieve the clamping function. There are no voltage spikes in the power transistors. The auxiliary clamping circuit can absorb the energy from the transformer leakage inductance and the junction capacitance of the power transistors. All power transistors exhibit small voltage spikes during turn-off, which is beneficial for selecting power semiconductor devices with low withstand voltage stress. (Attached) Figure 18 The waveforms of the driving voltage, current, and terminal voltage of the main power transistor S1 are shown, verifying that it can achieve zero-voltage turn-on; (Attached) Figure 19 For auxiliary power transistor S c The waveforms of the driving voltage, current, and terminal voltage are shown to verify that it can achieve zero-voltage turn-on; (attached) Figure 20 The waveforms of the driving voltage, current, and terminal voltage of the power transistor S4 are shown to verify that it can achieve zero-voltage turn-on.

[0083] In summary, the converter of the present invention has fewer power transistors with isolation drive on the primary side and does not require isolation drive; the transformer secondary side is connected in series with an inductor to achieve wide load soft switching conditions for the main power transistors, and the soft switching conditions can be flexibly adjusted according to the output power; the converter can achieve bidirectional transmission and has low circulating current loss.

[0084] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A current-fed soft-switching push-pull bridge bidirectional DC-DC converter, characterized in that, The application relates to a soft-switching multi-phase power supply, which comprises a first control unit, a second control unit, a third control unit, a fourth control unit and an auxiliary control unit. High frequency transformer T r DC voltage source V in and DC voltage source V o ; The high-frequency transformer T r The secondary winding N s And the first winding N1 and the second winding N2 are connected to each other; the direct-current voltage source V in In series with the input inductor l b In parallel with the first primary branch, the second primary branch and the auxiliary branch; the first winding N1 and the first control unit are arranged in series on the first primary branch; the second winding N2 and the second control unit are arranged in series on the second primary branch; the clamping capacitor C c And the auxiliary control unit are arranged in series on the auxiliary branch; The direct current voltage source V o Two sides are connected in parallel with the first secondary circuit and the second secondary circuit; the first secondary circuit is connected in series with the capacitor C o1 And the capacitor C o2 ; the second secondary circuit is connected in series with the third control unit and the fourth control unit; the secondary winding N s One end of the inductor l s Is connected to the circuit between the third control unit and the fourth control unit, and the other end of the secondary winding N s Is connected to the circuit between the capacitor C o1 And the capacitor C o2 ; The first control unit, the second control unit, the third control unit, the fourth control unit and the auxiliary control unit comprise power tubes, diodes and control capacitors which are connected in parallel with each other; the power tubes are MOSFET power tubes; The power tube of the first control unit and the power tube of the second control unit are driven by square wave signals with a phase difference of 180 degrees and a duty ratio greater than 0.5; the power tube of the auxiliary control unit is driven by NAND square wave signals of the power tube of the first control unit and the power tube of the second control unit; the power tube of the third control unit and the power tube of the fourth control unit are driven by square wave signals with a phase difference of 180 degrees and a duty ratio of 0.5; and the square wave signals inputted by the power tube of the first control unit and the power tube of the fourth control unit are provided with a phase difference phi. The soft-switching condition of the power tube of the first control unit is that: ； Where I0 represents the output current of the converter. DC voltage source V o voltage value, This is expressed as the duty cycle of the power transistor in the first control unit. , For inductor l s inductance value, For inductor l b The inductance value; n is the switching frequency of the power transistor in the first control unit; n is the high-frequency transformer T. r The turns ratio of the primary and secondary windings; The soft-switching condition of the power tube of the second control unit is that: ； wherein, represents a duty cycle of the power tube of the second control unit, ; is a switching frequency of the power tube of the second control unit.

2. The current-fed soft-switching push-pull bridge bidirectional DC-DC converter of claim 1, wherein, The first primary branch is provided with a primary equivalent leakage inductance l lk1 The primary equivalent leakage inductance l lk1 is arranged between the first winding N1 and the first control unit. The second primary branch is provided with a primary equivalent leakage inductance l lk2 The primary equivalent leakage inductance l lk2 is arranged between the second winding N2 and the second control unit.

3. The current-fed soft-switching push-pull bridge bidirectional DC-DC converter of claim 1, wherein, The DC voltage source V in The positive terminal and the input inductor l b After being connected in series, it is connected between the first winding N1 and the second winding N2; the first winding N1 and the second winding N2 have the same number of turns.

4. The current-fed soft-switching push-pull bridge bidirectional DC-DC converter of claim 1, wherein, The soft-switching condition of the power tube of the auxiliary control unit is that: ； wherein, duty cycle of the power tube of the auxiliary control unit; switching frequency of the power tube of the auxiliary control unit.

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