A staggered incomplete series soft switch forward-flyback circuit topology

Abstract

The present invention discloses a staggered incomplete series soft switch forward and flyback circuit topology structure, which belongs to the technical field of power electronic devices, and includes: an input power supply module, a capacitor voltage divider module, a first main power module, a first clamping circuit module, a second main power module, a second clamping circuit module, a dual-channel shared rectifier module, and an output circuit. The circuit topology structure of the present invention realizes the soft switching of the main power switch tube through the clamping circuit, and the two channels work staggered to achieve equivalent frequency doubling, and both channels are soft switches and can work at high frequencies; at the same time, only one magnetic component is used, including two channels of forward and flyback, and no filtering inductance is required. The secondary side of the transformer is shared by two channels, which reduces a set of windings on the secondary side. The converter can transmit power to the dual-channel shared rectifier module and the output circuit in the whole cycle, and achieve high conversion efficiency and high power density of the converter.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic devices, and in particular to a staggered incomplete series soft switch forward-flyback circuit topology structure. Background Art

[0002] The forward-flyback converter combines the characteristics of the forward converter and the flyback converter. It is a high-efficiency, high-power density converter that works in both forward and flyback modes. As the market's requirements for converter power density and efficiency continue to increase, the forward-flyback converter has been widely researched and applied.

[0003] The forward-flyback combined converter (also known as the Weinberg circuit) was first proposed by German Brain E. Taylor, and there are many derived circuit topologies. Among them, the forward-flyback combined converter with a single transformer structure has the advantages of small secondary copper loss and output current ripple compared to the forward converter, but has the disadvantages of large primary copper loss, large iron loss and large switch tube conduction loss. The advantage of the dual transformer structure is that the number of primary turns of a single transformer is reduced, thereby reducing the primary copper loss, and also making low-profile design possible, but the disadvantage of this structure is that the voltage stress on the main switch tube and the active clamp tube is large.

[0004] Therefore, it is of great significance to further study and improve the efficiency and power density of the forward-flyback combination converter. Summary of the invention

[0005] The problem to be solved by the present invention is to provide an interleaved incomplete series soft switch forward-flyback circuit topology structure, by which the two forward-flyback main power circuits formed together with the transformer are connected in series and interleaved to achieve equivalent frequency doubling and improve the efficiency and power density of the transformer.

[0006] The present invention adopts the following technical solution: a staggered incomplete series soft switch forward and flyback circuit topology structure, including: an input power module, a capacitor voltage divider module, a first main power module, a first clamping circuit module, a second main power module, a second clamping circuit module, and a dual-channel shared rectifier module.

[0007] The input power module provides a DC voltage V in , through the capacitor voltage divider module to convert the DC voltage V in Decomposed into two DC voltages V in1 and V in2 ;

[0008] The first main power module includes a first main power tube Q1 and upper half windings LP1 and LP2 of the primary side of the transformer T, LP1 and LP2 and two windings LS1 and LS2 of the secondary side of the transformer T, forming a first group of forward-flyback transformers;

[0009] The second main power module includes a second main power tube Q2 and lower half windings LP3 and LP4 of the primary side of the transformer T. LP3 and LP4 and two windings LS1 and LS2 of the secondary side of the transformer T form a second forward-flyback transformer.

[0010] The first clamping circuit module includes a first clamping switch tube Q4 and a first clamping capacitor C C1 , the first clamping capacitor C C1 The upper end is connected to the source of the first main power tube Q1, the lower end is connected to the drain of the first clamp switch tube Q4, and the source of the first clamp switch tube Q4 is connected to the negative electrode of the input power module;

[0011] The second clamping circuit module includes a second clamping switch tube Q3 and a second clamping capacitor C C2 The second clamping capacitor C C2 The upper end is connected to the source of the second clamp switch tube Q3, the lower end is connected to the drain of the second main power tube Q2, and the drain of the second clamp switch tube Q3 is connected to the positive electrode of the input power module;

[0012] The dual-path shared rectifier module comprises secondary windings LS1 and LS2 of a transformer T, and dual-path forward-flyback multiplexing diodes D1 and D2, and is used to rectify the AC voltage of the transformer T into a DC voltage.

[0013] Preferably, the capacitive voltage divider module is connected to the input power module and includes a capacitor C A and capacitor C B , the DC voltage V in Decomposed into two DC voltages V in1 and V in2 , V in1 and V in2 The value is equal to V in / 2, the center tap of transformer T is connected to capacitor C A and capacitor C B The midpoint of .

[0014] Preferably, the drain of the first main power tube Q1 is connected to the capacitor C A and connected to the positive polarity input terminal of the input power module;

[0015] The source of the first main power tube Q1 is connected to the top of the transformer T, and a first soft switch auxiliary branch is formed between the source of the first main power tube Q1 and the negative polarity input end of the input power module.

[0016] Preferably, the source of the second main power tube Q2 is connected to the capacitor C Band connected to the negative terminal of the input power module;

[0017] The drain of the second main power tube Q2 is connected to the bottom end of the transformer T, and a second soft switch auxiliary branch is formed between the drain of the second main power switch tube Q2 and the positive polarity input end of the input power module.

[0018] Preferably, the primary sides of the first group of forward-flyback transformers and the second group of forward-flyback transformers are connected in series and work alternately, and the first soft-switch auxiliary branch and the second soft-switch auxiliary branch are connected to the second soft-switch auxiliary branch and the first soft-switch auxiliary branch bus respectively.

[0019] Preferably, the transformer T includes six sets of windings, namely: two windings LP1 and LP2 connected in sequence in the upper half of the primary side of the transformer T, two windings LP3 and LP4 connected in sequence in the lower half of the primary side of the transformer T, and two windings LS1 and LS2 on the secondary side of the transformer T. According to the relationship between the same-name ends, the two windings on the secondary side also serve as the forward and flyback windings of the two-way forward and flyback circuits.

[0020] Preferably, the upper half of the primary side of the transformer T is from the end connected to the source of the first main power tube Q1 to the center tap of the transformer T, and the lower half of the primary side of the transformer T is from the end connected to the drain of the second main power tube Q2 to the center tap of the transformer T.

[0021] Preferably, in the dual-path shared rectifier module, the dual-path forward-flyback multiplexing diode D1 is connected between the like-name end of the secondary side of the transformer and the load, and the dual-path forward-flyback multiplexing diode D2 is connected between the opposite-name end of the secondary side of the transformer T and the load, and the dual-path forward-flyback multiplexing diodes D1 and D2 also serve as forward and flyback rectifiers for the outputs of the first and second groups of forward-flyback transformers.

[0022] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0023] 1. The circuit topology structure of the present invention contains only one magnetic component, including two-way forward and flyback, and does not require a filter inductor. The two-way forward and flyback main power circuits formed together with the transformer are connected in series and work in an interleaved manner to achieve equivalent frequency doubling.

[0024] 2. In the circuit topology of the present invention, the secondary side of the transformer is shared by two paths, which can reduce a set of secondary windings. Both paths are soft switches and can work at high frequencies. At the same time, the voltage stress of the switch tube is significantly reduced, which can reduce switching losses and meet the needs of high-frequency operation. It has the advantages of high efficiency and high power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a topological structure diagram of the staggered incomplete series soft switch forward-flyback circuit of the present invention;

[0026] Figure 2 It is a signal timing diagram of the interleaved incomplete series soft switch forward-flyback circuit of the present invention;

[0027] Figure 3 is a structural diagram of circuit topology mode 1 of an embodiment of the present invention;

[0028] Figure 4 is a structural diagram of circuit topology mode 2 of an embodiment of the present invention;

[0029] Figure 5 is a structural diagram of circuit topology mode 3 of an embodiment of the present invention;

[0030] Figure 6 is a structural diagram of circuit topology mode 4 of an embodiment of the present invention;

[0031] Figure 7 is a structural diagram of circuit topology mode 5 of an embodiment of the present invention;

[0032] Figure 8 is a structural diagram of circuit topology mode 6 of an embodiment of the present invention;

[0033] Fig. 9 is a structural diagram of circuit topology mode 7 of an embodiment of the present invention;

[0034] Fig.10 is a circuit topology mode 8 structure diagram of an embodiment of the present invention;

[0035] Fig.11 is a structural diagram of a circuit topology mode 9 of an embodiment of the present invention;

[0036] Fig.12 is a structural diagram of a circuit topology mode 10 according to an embodiment of the present invention;

[0037] Fig.13 It is a structural diagram of the circuit topology mode 11 of an embodiment of the present invention;

[0038] Fig.14 It is a structural diagram of the circuit topology mode 12 of an embodiment of the present invention;

[0039] Fig.15 It is a structural diagram of the circuit topology mode 13 of an embodiment of the present invention;

[0040] Fig.16 It is a structural diagram of the circuit topology mode 14 of an embodiment of the present invention;

[0041] Fig.17 is a structural diagram of a circuit topology mode 15 of an embodiment of the present invention;

[0042] Fig.18 is a structural diagram of a circuit topology mode 16 according to an embodiment of the present invention;

[0043] Description of the numbers in the figure:

[0044] 1-input power module, 2-capacitor voltage divider module, 3-first main power module, 4-first clamping circuit module, 5-second main power module, 6-second clamping circuit module, 7-dual-way shared rectifier module. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the application is further elaborated in detail below in conjunction with the accompanying drawings. The described embodiments are only a part of the embodiments involved in the present invention. All non-innovative embodiments of other researchers in the field on this embodiment belong to the protection scope of the present invention. At the same time, for the step numbering in the embodiment of the present invention, it is only set for the convenience of explanation, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0046] The present invention provides a staggered incomplete series soft switch forward and flyback circuit topology structure, such as Figure 1 As shown, it includes: an input power module 1, a capacitor voltage divider module 2, a first main power module 3, a first clamping circuit module 4, a second main power module 5, a second clamping circuit module 6, and a dual-channel shared rectifier module 7.

[0047] The input power module 1 is used to provide a DC voltage V in ;

[0048] Capacitor voltage divider module 2, including voltage divider capacitor C A ,C B ; C A The positive pole is connected to the positive polarity end of the input power module, and the negative pole of CB is connected to the negative polarity end of the input power module; the capacitor voltage divider module 2 is used to convert the DC voltage V in Decomposed into two DC voltages V in1 and V in2， V in1 and V in2 The value is equal to V in / 2.

[0049] The first main power module 3 includes the first main power tube Q1 and the upper half of the primary side of the transformer T (i.e., the end connected to the source of Q1 to the center tap of the transformer), denoted as T1. The two windings contained in T1 and the secondary winding T3 of the transformer form a forward-flyback transformer.

[0050] The first clamping circuit module 4 includes a first clamping switch tube Q4 and a first clamping capacitor C C1 ,C C1The upper terminal is connected to the source of Q1, the lower terminal is connected to the drain of Q4, and the source of Q4 is connected to the negative pole of the power module. The soft switching technology can be realized through the active clamping circuit. The soft switching technology can reduce the voltage and current stress during the switching process, reduce switching losses and electromagnetic interference (EMI), and improve the overall efficiency of the system, which is especially important for high-frequency switching applications.

[0051] The second main power module 5 includes the second main power tube Q2 and the lower half of the primary side of the transformer T (i.e., the end connected to the drain of Q2 to the center tap of the transformer), denoted as T2. The two windings contained in T2 and the secondary winding T3 of the transformer form a forward-flyback transformer.

[0052] The second clamping circuit module 6 includes a second clamping switch tube Q3 and a second clamping capacitor C C2 ,C C2 The upper end is connected to the source of the second clamp switch tube Q3, the lower end is connected to the drain of the second main power tube Q2, and the drain of the second clamp switch tube Q3 is connected to the positive electrode of the power module.

[0053] The dual-path shared rectifier module 7 includes a transformer secondary side T3 and dual-path forward-flyback multiplexing diodes D1 and D2. The diode D1 is connected between the like-name end of the transformer secondary side and the load. When the main switch tube is turned on, the branch where the diode D1 is located transfers energy from the input power supply to the load. The diode D2 is connected between the opposite-name end of the transformer secondary side and the load. When the main switch tube is closed and the transformer is magnetically reset, the branch where the diode D2 is located transfers the excitation inductance energy to the load. The dual-path shared rectifier module is used to rectify the AC voltage of the main transformer T into a DC voltage.

[0054] In the circuit topology of the present invention, the driving signals of the staggered incomplete series soft switch forward and flyback circuit are Vgs1, Vgs2, Vgs3, and Vgs4 respectively, the output capacitor voltage of the first main switch tube is Vcr1, the output capacitor voltage of the second main switch tube is Vcr2, the currents of the first and second main power tubes Q1 and Q2 are iQ1 and iQ2 respectively, the currents flowing through the first and second clamping capacitors are icc1 and icc2 respectively, the currents of the secondary side diodes D1 and D2 are iD1 and iD2 respectively, the output current is io, and the specific output timing of each signal is as follows: Figure 2 shown.

[0055] In one embodiment of the present invention, to simplify the analysis, the following assumptions are made:

[0056] 1. The first and second clamping capacitors C c1 , C c2 and output capacitor C O Large enough so that through C c1 , C c2 , C OThe voltage can be regarded as a constant.

[0057] 2. All leakage inductances are reflected to the primary side.

[0058] 3. The leakage inductance of the transformer is much smaller than the magnetizing inductance.

[0059] For the circuit topology of this embodiment, operating mode 1 (t0 < t < t1) is as Figure 3 shown:

[0060] Before time t0, the body diode Dr1 of the first main power transistor Q1 conducts, preparing for the ZVS conduction of the first main power transistor Q1. At time t0, the main power switch transistor Q2 is in the conducting state, the commutation on the secondary side ends, the diode D1 conducts, and the current flowing through Q1 is the sum of the output reflected secondary current and the magnetizing current.

[0061] P1 and S1 function the same as a normal transformer, transferring energy from the primary side to the secondary side. During this period, P2 and S2 act as an inductor and support the reflected secondary current, and the reflected magnetizing inductance acts as a filter inductor.

[0062] Operating mode 2 (t1 < t < t2) is as Figure 4 shown:

[0063] The first main power transistor Q1 turns off at t1, and the voltage on the equivalent output capacitor Vcr1 increases almost linearly until it rises to Vin / 2. When Vcr1 reaches the input voltage, the secondary side diode D2 starts to conduct.

[0064] Operating mode 3 (t2 < t < t3) is as Figure 5 shown:

[0065] At time t2, the commutation of the transformer starts, and the transformer is equivalent to being short-circuited. The leakage inductance L k resonates with the output capacitor Cr1 of the first main power transistor Q1. Therefore, the leakage inductance current i Lk decreases in a resonant manner, and Vcr1 increases in a resonant manner at the same time. At time t3, Vcr1 increases to Vin / 2 + Vcc1.

[0066] Operating mode 4 (t3 < t < t4) is as Figure 6 shown:

[0067] At time t3, the body diode Dr4 of the first clamping switch transistor Q4 turns on, preparing for the ZVS conduction of the clamping switch transistor. The commutation on the secondary side continues, and the leakage inductance current decreases linearly.

[0068] Operating mode 5 (t4 < t < t5) is as Figure 7 shown:

[0069] At time t4, turn on the first clamping switch transistor Q4, and the secondary side diode D l turns off and D2 turns on. The commutation on the secondary side ends. The output current is supported by the DC magnetization current of the transformer P2, S2. During this period, the transformer P1, S1 operates as an inductor and the magnetization current decreases linearly.

[0070] Operating mode 6 (t5 < t < t6), as Figure 8 shown:

[0071] At time t5, the first clamping switch transistor Q4 is turned off, and the output capacitor voltage of the first main power transistor Q1 decreases from Vin / 2 + Vcc1 to Vin / 2 with an almost constant discharge current.

[0072] Operating mode 7 (t6 < t < t7), as Fig. 9 shown:

[0073] At time t6, the secondary side diode D1 turns on, and commutation on the secondary side starts. The transformer is short-circuited at this time. The leakage inductance L k resonates with the output capacitance Cr1 of the main switch Q1, and the leakage inductance current i Lk increases resonantly, and VCr1 decreases resonantly.

[0074] Until VCr1 drops to zero, the body diodes of the first main power transistor Q1 and the second main power transistor Q2 start to conduct.

[0075] Operating mode 8 (t7 < t < t8), as Fig.10 shown:

[0076] The output capacitance voltages Vcr1 and Vcr2 of the first main power transistor Q1 and the second main power transistor Q2 are maintained at zero, and the leakage inductance current i Lk and the switch current i Ql , i Q2 both increase linearly. During this period, the second main power transistor Q2 should be turned on to achieve ZVS operation.

[0077] Operating mode 9 (t8 < t < t9), as Fig.11 shown:

[0078] Before time t8, the body diode Dr2 of the second main power transistor Q2 conducts to prepare for the ZVS conduction of the second main power transistor Q2. At time t8, the second main power transistor Q2 is in the conducting state, the commutation on the secondary side ends, the diode D1 conducts, and the current flowing through the second main power transistor Q2 is the sum of the output reflected secondary current and the magnetization current. The functions of P3 and S1 are the same as those of an ordinary transformer, transferring energy from the primary side to the secondary side.

[0079] During this period, P4 and S2 act as an inductor and support the reflected secondary current, and the reflected magnetizing inductor operates as a filter inductor.

[0080] Operating mode 10 (t9 < t < t10), as Fig.12 shown:

[0081] The second main power transistor Q2 turns off at t9, and the voltage on the equivalent output capacitor Vcr2 increases almost linearly until it rises to Vin / 2. When Vcr1 reaches the input voltage, the secondary diode D2 starts to conduct.

[0082] Operating mode 11 (t10 < t < t11), as Fig.13 shown:

[0083] At time t10, the commutation of the transformer starts, and the transformer is equivalent to being short-circuited. The leakage inductance L k resonates with the output capacitor Cr2 of the second main power transistor Q2. Therefore, the leakage inductance current i Lk decreases in a resonant manner, and Vcr2 increases in a resonant manner at the same time. At time t11, Vcr2 increases to Vin / 2 + Vcc1.

[0084] Operating mode 12 (t11 < t < t12), as Fig.14 shown:

[0085] At time t11, the body diode Dr3 of the second clamping switch transistor Q3 turns on, preparing for the ZVS conduction of the clamping switch transistor. The commutation on the secondary side continues, and the leakage inductance current decreases linearly.

[0086] Operating mode 13 (t12 < t < t13), as Fig.15 shown:

[0087] At time t12, the second clamping switch transistor Q3 is turned on, the secondary diode D1 turns off, and D2 conducts, and the commutation on the secondary side ends. The output current is supported by the DC magnetizing current of the transformer P4, S2. During this period, the transformer P3, S1 operates as an inductor, and the magnetizing current decreases linearly.

[0088] Operating mode 14 (t13 < t < t14), as Fig.16 shown:

[0089] At time t13, the second clamping switch transistor Q3 turns off, and the output capacitor voltage of the second main power transistor Q2 decreases from Vin / 2 + Vcc1 to Vin / 2 with an almost constant discharge current.

[0090] Operating mode 15 (t14 < t < t15), as Fig.17 shown:

[0091] At time t14, the secondary diode D1 conducts, and the secondary side starts commutation. At this time, the transformer is short-circuited. The leakage inductance L k resonates with the output capacitance Cr2 of the second main power transistor Q2. The leakage inductance current i Lk increases in a resonant manner, and Vcr2 decreases in a resonant manner until Vcr2 drops to zero. The body diodes of the first and second main power transistors Q1 and Q2 start to conduct.

[0092] Operating mode 16 (t15 < t < t16), as Fig.18 shown:

[0093] The output capacitance voltages Vcr1 and Vcr2 of the first and second main power transistors Q1 and Q2 remain zero, and the leakage inductance current i Lk and the switch current i Ql , iQ2 all increase linearly.

[0094] During this period, the first main power transistor Q1 should be turned on to achieve ZVS operation, and the next switching cycle starts at the end of this period.

[0095] It can be seen that the present invention proposes an interleaved incomplete series soft-switching forward and flyback circuit topology, which significantly reduces the voltage stress of the main switch transistor and the clamping switch transistor; the two main power switch transistors conduct alternately, and the control is convenient. Therefore, it can be widely applied to the occasions with high input voltage. The switching transistors of the interleaved incomplete series soft-switching forward and flyback circuit can use MOS transistors, so that the switching frequency can be further increased. The flyback converter also serves as a filter inductor, eliminating the output filter inductor, so there is only one magnetic component in the circuit. By the series interleaved operation of the primary sides of the two forward and flyback main power circuits formed together with the transformer, equivalent frequency doubling is achieved. Both paths are soft-switching, significantly reducing the switching loss and meeting the requirements of high-frequency operation. As described above, the interleaved incomplete series soft-switching forward and flyback circuit has the advantages of high efficiency and high power density.

[0096] The above is only the preferred embodiment of the present invention. It should be noted that: for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A staggered incomplete series soft switch forward-flyback circuit topology structure, characterized in that: include: Input power module, capacitor voltage divider module, first main power module, first clamping circuit module, second main power module, second clamping circuit module, dual-channel shared rectifier module; The input power module provides a DC voltage V in , through the capacitor voltage divider module to convert the DC voltage V in Decomposed into two DC voltages V in1 and V in2 ; The first main power module includes a first main power tube Q1 and upper half windings LP1 and LP2 of the primary side of the transformer T, LP1 and LP2 and two windings LS1 and LS2 of the secondary side of the transformer T, forming a first group of forward-flyback transformers; The second main power module includes a second main power tube Q2 and lower half windings LP3 and LP4 of the primary side of the transformer T. LP3 and LP4 and two windings LS1 and LS2 of the secondary side of the transformer T form a second forward-flyback transformer. The first clamping circuit module includes a first clamping switch tube Q4 and a first clamping capacitor C C1 , the first clamping capacitor C C1 The upper end is connected to the source of the first main power tube Q1, the lower end is connected to the drain of the first clamp switch tube Q4, and the source of the first clamp switch tube Q4 is connected to the negative electrode of the input power module; The second clamping circuit module comprises a second clamping switch tube Q3 and a second clamping capacitor C C2 The second clamping capacitor C C2 The upper end is connected to the source of the second clamp switch tube Q3, the lower end is connected to the drain of the second main power tube Q2, and the drain of the second clamp switch tube Q3 is connected to the positive electrode of the input power module; The dual-path shared rectifier module includes secondary windings LS1 and LS2 of a transformer T, and dual-path forward-flyback multiplexing diodes D1 and D2, which are used to rectify the AC voltage of the transformer T into a DC voltage; The transformer T comprises six sets of windings, namely: two windings LP1 and LP2 connected in sequence at the upper half of the primary side of the transformer T, two windings LP3 and LP4 connected in sequence at the lower half of the primary side of the transformer T, and two windings LS1 and LS2 at the secondary side of the transformer T. According to the same-name terminal relationship, the two windings at the secondary side also serve as the forward and flyback windings of the two-way forward and flyback circuits; In the dual-path shared rectifier module, the dual-path forward-flyback multiplexing diode D1 is connected between the like-name end of the secondary side of the transformer and the load, and the dual-path forward-flyback multiplexing diode D2 is connected between the opposite-name end of the secondary side of the transformer T and the load. The dual-path forward-flyback multiplexing diodes D1 and D2 also serve as forward and flyback rectifier tubes for the output of the first and second groups of forward-flyback transformers.

2. The interleaved incomplete series soft switch forward-flyback circuit topology structure according to claim 1 is characterized in that: The capacitor voltage divider module is connected to the input power module and includes a capacitor C A and capacitor C B , the DC voltage V in Decomposed into two DC voltages V in1 and V in2 , V in1 and V in2 The value is equal to V in / 2, the center tap of transformer T is connected to capacitor C A and capacitor C B The midpoint of .

3. The interleaved incomplete series soft switch forward-flyback circuit topology structure according to claim 1, characterized in that: The drain of the first main power tube Q1 and the capacitor C A and connected to the positive polarity input terminal of the input power module; The source of the first main power tube Q1 is connected to the top of the transformer T, and a first soft switch auxiliary branch is formed between the source of the first main power tube Q1 and the negative polarity input end of the input power module.

4. The interleaved incomplete series soft switch forward-flyback circuit topology structure according to claim 3 is characterized in that: The source of the second main power tube Q2 and the capacitor C B and connected to the negative terminal of the input power module; The drain of the second main power tube Q2 is connected to the bottom end of the transformer T, and a second soft switch auxiliary branch is formed between the drain of the second main power switch tube Q2 and the positive polarity input end of the input power module.

5. The interleaved incomplete series soft switch forward-flyback circuit topology structure according to claim 4, characterized in that: The primary sides of the first group of forward-flyback transformers and the second group of forward-flyback transformers are connected in series and work alternately. The first soft-switch auxiliary branch and the second soft-switch auxiliary branch are connected to the second soft-switch auxiliary branch and the first soft-switch auxiliary branch bus respectively.

6. The interleaved incomplete series soft switch forward-flyback circuit topology structure according to claim 5, characterized in that: The upper half of the primary side of the transformer T is connected to the source of the first main power tube Q1 to the center tap of the transformer T, and the lower half of the primary side of the transformer T is connected to the drain of the second main power tube Q2 to the center tap of the transformer T.

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