A phase-shifted dual full-bridge DC-DC converter based on soft switching technology

Abstract

The present invention provides a phase-shifted dual full-bridge DC-DC converter based on soft switching technology, which belongs to the field of power electronics technology. The phase-shifted dual full-bridge DC-DC converter based on soft switching technology includes an input dual full-bridge inverter circuit, a high-frequency transformer assembly, an output rectifier circuit and an output filter circuit. The present invention can realize soft switching of the switch tube when adopting the phase-shift control method, which can effectively reduce the switching loss and increase the operating frequency of the converter; at the same time, the secondary windings of the high-frequency transformers T1 and T2 can operate in the output series mode, and the output voltage of the converter when the output is connected in series is twice the output voltage of the traditional phase-shifted single full-bridge, and the output power can also be greatly improved. The circuit described in the present invention adopts a new dual full-bridge topology, and applies soft switching technology to reduce the switching loss of the switch tube, which can effectively solve the problem of low output voltage and low power of the traditional single full-bridge converter.

Description

Technical Field

[0001] The invention relates to the field of power electronics, and in particular to a phase-shifted dual full-bridge DC-DC converter based on soft switching technology. Background Art

[0002] With the popularization of power electronics technology, as an important application branch of power electronics conversion devices, the DC converter converts the input DC voltage into the required amplitude DC voltage after high-frequency chopping or inversion, rectification and filtering. As an important component of the switching power supply, people have put forward higher requirements for its volume, weight, efficiency and reliability, and high efficiency and high power density are one of its mainstream development directions.

[0003] Improving efficiency is of great significance in saving electricity, reducing heat dissipation requirements, and reducing the size and weight of the radiator. Higher power density requires the converter to be smaller in size when outputting the same power, which is very important in applications such as aerospace that have strict volume requirements. High reliability requires the device to be able to work for a long time in different states, with a low failure rate and a long average time between failures. At present, with the development of power products towards high efficiency and high power density, the phase-shifted full-bridge circuit has developed rapidly and has been widely used and studied, and the phase-shifted full-bridge soft-switching converter has gradually matured. Compared with the traditional hard-switching circuit, the switch tube of the phase-shifted full-bridge soft-switching circuit can operate in a zero voltage and zero current state, which can effectively reduce switching losses, is conducive to increasing the switching frequency, and can achieve miniaturization and lightweight of power products.

[0004] The inventor has discovered through research that the current research focuses on single phase-shifted full-bridge converters, which have low output voltage and small power. They are mostly used in scenarios with small and medium power requirements and are difficult to adapt to high-voltage and high-power application scenarios required for aerospace applications such as spacecraft ion electric propulsion power supplies. How to invent a phase-shifted dual full-bridge DC-DC converter based on soft switching technology to improve these problems has become an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] In order to make up for the above shortcomings, the present invention provides a phase-shifted dual full-bridge DC-DC converter based on soft switching technology, aiming to improve the problem that the existing single phase-shifted full-bridge converter has low output voltage and small power, which is difficult to meet the needs of scenarios with relatively large power requirements.

[0006] The present invention is achieved in that:

[0007] The invention provides a phase-shifted dual full-bridge DC-DC converter based on soft switching technology, comprising an input dual full-bridge inverter circuit, a high-frequency transformer component, an output rectifier circuit and an output filter circuit.

[0008] The input dual full-bridge inverter circuit includes a single full-bridge A and a single full-bridge B, wherein the single full-bridge A and the single full-bridge B include 8 switch tubes Q1-Q8, anti-parallel diodes D1, D3, D5 and D7 of 4 switch tubes, 4 switch tube parallel absorption capacitors C1, C3, C5, C7, and 4 lag arm series diodes D2, D4, D6 and D8, the diodes D1, D3, D5 and D7 are parasitic diodes or external diodes, and the absorption capacitors C1, C3, C5 and C7 are parasitic capacitors or external capacitors.

[0009] The high-frequency transformer assembly includes a high-frequency transformer T1 and a high-frequency transformer T2. The two single full bridges A and B are respectively connected to the primary windings of the high-frequency transformer T1 and the high-frequency transformer T2. The leading bridge arm of the single full bridge A is composed of switch tubes Q1 and Q3 connected in series, and the lagging bridge arm is composed of D2, Q2, D4, and Q4 connected in series in sequence. The leading bridge arm of the single full bridge B is composed of switch tubes Q5 and Q7 connected in series, and the lagging bridge arm is composed of D6, Q6, D8, and Q8 connected in series in sequence; one end of the primary winding of the high-frequency transformer T1 is connected to the leading bridge arm of the single full bridge A through a resonant circuit, and the other end of the primary winding of the high-frequency transformer T1 is connected to the lagging bridge arm of the single full bridge A.

[0010] The output rectifier circuit is connected to the secondary windings of the high-frequency transformers T1 and T2.

[0011] The output filter circuit is composed of a filter inductor Lf and a filter capacitor Cf. One end of the filter inductor Lf is connected to the cathodes of three diodes D01, D11, and D21, the other end of the filter inductor Lf is connected to one end of the filter capacitor Cf, and the other end of the filter capacitor Cf is connected to the anodes of three diodes D02, D12, and D22.

[0012] In an embodiment of the present invention, the single full bridge A and the single full bridge B are completely identical, and the model parameters of the components corresponding to the two single full bridges A and the single full bridge B are completely identical.

[0013] In one embodiment of the present invention, Q1, Q3 of the single full bridge A and their parallel diodes and capacitors form an advanced bridge arm and a resonant circuit is provided between one end of the primary winding of the high-frequency transformer T1, and Q2, Q4, D2, and D4 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T1; Q5, Q7 of the single full bridge B and their parallel diodes and capacitors form an advanced bridge arm and a resonant circuit is provided between one end of the primary winding of the high-frequency transformer T2, and Q6, Q8, D6, and D8 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T2.

[0014] In one embodiment of the present invention, the resonant circuit of the single full bridge A is composed of a resonant inductor Lk1 and a blocking capacitor Cb1, and the resonant circuit of the single full bridge B is composed of a resonant inductor Lk2 and a blocking capacitor Cb2.

[0015] In one embodiment of the present invention, the output rectifier circuit is composed of 6 diodes D11, D12, D01, D02, D21 and D22, the same-name end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D11 and the cathode of D12, the other end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D01 and the cathode of D02, the same-name end of the secondary winding of the high-frequency transformer T2 is connected to the anode of D21 and the cathode of D22, and the other end of the secondary winding of T2 is connected to the anode of D11 and the cathode of D12.

[0016] In one embodiment of the present invention, the driving signals of Q1 and Q5 are the same, the driving signals of Q2 and Q6 are the same, the driving signals of Q3 and Q7 are the same, the driving signals of Q4 and Q8 are the same, and the driving signals of the same bridge arm switch tubes are complementary, the interval time is the dead time, the driving signals of the leading bridge arm switch tubes Q1 and Q3 are respectively ahead of the lagging bridge arm switch tubes Q4 and Q2 by one phase, and the driving signals of the leading bridge arm switch tubes Q5 and Q7 are respectively ahead of the lagging bridge arm switch tubes Q8 and Q6 by one phase.

[0017] The beneficial effects of the present invention are as follows: the present invention obtains a phase-shifted dual full-bridge DC-DC converter based on soft switching technology through the above-mentioned design. When in use, soft switching is realized on the new dual full-bridge topology, which effectively reduces the switching loss of the main power tube, is beneficial to increase the operating frequency of the converter, and can improve the working efficiency of the converter; in addition, the use of the dual full-bridge topology can solve the problems of low output voltage and low output power of the traditional single phase-shifted full-bridge converter, which is convenient for adapting to high-voltage and high-power application scenarios required by aerospace, such as spacecraft ion electric propulsion power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 Schematic diagram of the circuit structure of a phase-shifted dual full-bridge DC-DC converter based on soft switching technology provided by an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of main waveforms provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0026] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. Example

[0028] See also Figure 1-2 The present invention provides a technical solution: a phase-shifted dual full-bridge DC-DC converter based on soft switching technology, including an input dual full-bridge inverter circuit 100, a high-frequency transformer assembly 200, an output rectifier circuit 300 and an output filter circuit 400.

[0029] The input dual full-bridge inverter circuit 100 includes a single full-bridge A and a single full-bridge B. The single full-bridge A and the single full-bridge B include 8 switch tubes Q1-Q8, 4 anti-parallel diodes D1, D3, D5 and D7 of the switch tubes, 4 switch tube parallel absorption capacitors C1, C3, C5, C7, and 4 lagging arm series diodes D2, D4, D6 and D8. The diodes D1, D3, D5 and D7 are parasitic diodes or external diodes, and the absorption capacitors C1, C3, C5 and C7 are parasitic capacitors or external capacitors.

[0030] The high-frequency transformer assembly 200 includes a high-frequency transformer T1 and a high-frequency transformer T2. Two single full bridges A and B are respectively connected to the primary windings of the high-frequency transformer T1 and the high-frequency transformer T2. The leading bridge arm of the single full bridge A is composed of switch tubes Q1 and Q3 connected in series, and the lagging bridge arm is composed of D2, Q2, D4, and Q4 connected in series in sequence. The leading bridge arm of the single full bridge B is composed of switch tubes Q5 and Q7 connected in series, and the lagging bridge arm is composed of D6, Q6, D8, and Q8 connected in series in sequence; one end of the primary winding of the high-frequency transformer T1 is connected to the leading bridge arm of the single full bridge A through a resonant circuit, and the other end of the primary winding of the high-frequency transformer T1 is connected to the lagging bridge arm of the single full bridge A.

[0031] The output rectifier circuit 300 is connected to the secondary windings of the high-frequency transformers T1 and T2. Specifically, the output rectifier circuit 300 is composed of 6 diodes D11, D12, D01, D02, D21 and D22. The same-name end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D11 and the cathode of D12, the other end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D01 and the cathode of D02, the same-name end of the secondary winding of the high-frequency transformer T2 is connected to the anode of D21 and the cathode of D22, and the other end of the secondary winding of T2 is connected to the anode of D11 and the cathode of D12.

[0032] The output filter circuit 400 is composed of a filter inductor Lf and a filter capacitor Cf. One end of the filter inductor Lf is connected to the cathodes of three diodes D01, D11, and D21, the other end of the filter inductor Lf is connected to one end of the filter capacitor Cf, and the other end of the filter capacitor Cf is connected to the anodes of three diodes D02, D12, and D22.

[0033] In the present application, the single full bridge A and the single full bridge B are exactly the same, and the model parameters of the devices corresponding to the two single full bridges A and the single full bridge B are exactly the same.

[0034] It should be noted that Q1, Q3 of the single full bridge A and their parallel diodes and capacitors form an advanced bridge arm and there is a resonant circuit between one end of the primary winding of the high-frequency transformer T1, and Q2, Q4, D2, and D4 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T1; Q5, Q7 of the single full bridge B and their parallel diodes and capacitors form an advanced bridge arm and there is a resonant circuit between one end of the primary winding of the high-frequency transformer T2, and Q6, Q8, D6, and D8 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T2.

[0035] In one embodiment of the present application, the resonant circuit of the single full bridge A is composed of a resonant inductor Lk1 and a blocking capacitor Cb1, and the resonant circuit of the single full bridge B is composed of a resonant inductor Lk2 and a blocking capacitor Cb2.

[0036] In some specific implementation schemes, the driving signals of Q1 and Q5 are the same, the driving signals of Q2 and Q6 are the same, the driving signals of Q3 and Q7 are the same, the driving signals of Q4 and Q8 are the same, and the driving signals of the same bridge arm switches are complementary, the interval time is the dead time, the driving signals of the leading bridge arm switches Q1 and Q3 are ahead of the lagging bridge arm switches Q4 and Q2 by one phase respectively, and the driving signals of the leading bridge arm switches Q5 and Q7 are ahead of the lagging bridge arm switches Q8 and Q6 by one phase respectively.

[0037] As can be seen from the above, in the present invention, the two single full bridges A and B on the input side are connected in parallel, and the secondary windings of the high-frequency transformers T1 and T2 are connected in series under the control mode in which the single full bridges A and B have the same corresponding switch tube drive signals, that is, the drive signals of Q1 and Q5 are the same, the drive signals of Q2 and Q6 are the same, the drive signals of Q3 and Q7 are the same, and the drive signals of Q4 and Q8 are the same. At the same time, the drive signals of the switch tubes in the same bridge arm are required to be complementary, and the interval time is the dead time, that is, the drive signals of Q1 and Q3 are complementary, the drive signals of Q2 and Q4 are complementary, the drive signals of Q5 and Q7 are complementary, and the drive signals of Q6 and Q8 are complementary. In order to realize the zero current switching of the lagging bridge arm switch tube, it is also necessary to require that there is a phase shift angle between the driving signal of the leading bridge arm switch tube and the driving signal of the lagging bridge arm switch tube, that is, the driving signals of the leading bridge arm switch tubes Q1 and Q3 of the single full bridge A are respectively ahead of the lagging bridge arm switch tubes Q4 and Q2 by one phase; the driving signals of the leading bridge arm switch tubes Q5 and Q7 of the single full bridge B are respectively ahead of the lagging bridge arm switch tubes Q8 and Q6 by one phase.

[0038] The present invention can realize soft switching of the switch tube when adopting the phase shift control mode, which can effectively reduce the switching loss and increase the operating frequency of the converter; at the same time, the secondary windings of the high-frequency transformers T1 and T2 can work in the output series mode, and the output voltage of the converter when the output series connection is twice the output voltage of the traditional phase-shifted single full-bridge, and the output power can also be greatly improved. The circuit described in the present invention adopts a new dual full-bridge topology, and applies soft switching technology to reduce the switching loss of the switch tube, which can effectively solve the problem of low output voltage and low power of the traditional single full-bridge converter, and is suitable for high-voltage and high-power application scenarios such as aerospace.

[0039] Please continue reading Figure 2 The working principle of the phase-shifted dual full-bridge DC-DC converter based on soft switching technology is as follows:

[0040] Working mode 1: t0-time, energy transmission. Before t0, Q1, Q4, Q5, and Q8 are turned on, and the primary current charges the blocking capacitor. The voltage across the capacitor continues to rise, and the secondary side works in the rectification state to output energy to the load.

[0041] Working mode 2: [t0, t1] time period, charging and discharging, at t0, Q1 and Q5 are turned off. For single full bridge A, its primary current Ip1 is transferred from Q1 to C1 and C3 branches. Due to the existence of C1, the voltage across it cannot change suddenly, so Q1 is turned off at zero voltage. The secondary side is in the rectification state, outputting energy to the load. At t1, C1 is fully charged, C3 is discharged to zero, and D3 is naturally turned on. For single full bridge B, its primary current Ip2 is transferred from Q5 to C5 and C7 branches. Due to the existence of C5, the voltage across it cannot change suddenly, so Q5 is turned off at zero voltage. The secondary side is in the rectification state, outputting energy to the load. At t1, C5 is fully charged, C7 is discharged to zero, and D7 is naturally turned on.

[0042] Working mode 3: [t1, t2] time period, the primary current is reset. After D3 and D7 are turned on, Q3 and Q7 are turned on at this time, and Q3 and Q7 are turned on with zero voltage. The primary current decreases linearly under the action of the blocking capacitor voltage. At this time, the polarity of the primary voltage of the high-frequency transformer changes, the secondary induced potential is positive and negative, and the secondary starts to work in the freewheeling state. At t2, the primary current is reduced to zero, ending working mode 3.

[0043] Working mode 4: [t2, t3] time period, primary side intermittent. When the primary current is zero, due to the reverse blocking effect of D4 and D8, the primary current continues to remain zero. At this time, Q4 and Q8 are turned off, and Q4 and Q8 are turned off with zero current. At t3, Q2 and Q6 are turned on. Due to the existence of resonant inductance, the primary current cannot change suddenly, and Q2 and Q6 are turned on with zero current. At this time, the secondary side continues to work in the freewheeling state.

[0044] Working mode 5: [t3, t4] time period, the duty cycle is lost. After turning on Q2 and Q6, the blocking capacitor is reversely charged. Due to the existence of the resonant inductor, the primary current increases linearly. Before t4, the primary current cannot provide the load current, and the secondary side is still in the freewheeling stage. At this time, the secondary side duty cycle is lost.

[0045] Working mode 6: [t4, t5] time period, energy transfer. At t4, the primary current can provide the load current, the secondary side resumes the rectification state, and the primary side continues to transfer energy to the secondary side. Then the circuit starts working in another half switching cycle, and its working condition is similar to the first half cycle.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A phase-shifted dual full-bridge DC-DC converter based on soft switching technology, characterized in that: include An input dual full-bridge inverter circuit (100), the input dual full-bridge inverter circuit (100) comprising a single full-bridge A and a single full-bridge B, the single full-bridge A and the single full-bridge B comprising eight switch tubes Q1-Q8, four switch tube anti-parallel diodes D1, D3, D5 and D7, four switch tube parallel absorption capacitors C1, C3, C5, C7, and four lagging arm series diodes D2, D4, D6 and D8, the diodes D1, D3, D5 and D7 being parasitic diodes or external diodes, and the absorption capacitors C1, C3, C5 and C7 being parasitic capacitors or external capacitors; A high-frequency transformer assembly (200), the high-frequency transformer assembly (200) comprising a high-frequency transformer T1 and a high-frequency transformer T2, the two single full bridges A and B being connected to the primary windings of the high-frequency transformer T1 and the high-frequency transformer T2 respectively, the leading bridge arm of the single full bridge A being composed of switch tubes Q1 and Q3 being connected in series, the lagging bridge arm being composed of D2, Q2, D4, and Q4 being connected in series in sequence, the leading bridge arm of the single full bridge B being composed of switch tubes Q5 and Q7 being connected in series, the lagging bridge arm being composed of D6, Q6, D8, and Q8 being connected in series in sequence; one end of the primary winding of the high-frequency transformer T1 being connected to the leading bridge arm of the single full bridge A via a resonant circuit, and the other end of the primary winding of the high-frequency transformer T1 being connected to the lagging bridge arm of the single full bridge A; An output rectifier circuit (300), the output rectifier circuit (300) being connected to secondary windings of high-frequency transformers T1 and T2; The output rectifier circuit (300) is composed of 6 diodes D11, D12, D01, D02, D21 and D22, the same-name end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D11 and the cathode of D12, the other end of the secondary winding of the high-frequency transformer T1 is connected to the anode of D01 and the cathode of D02, the same-name end of the secondary winding of the high-frequency transformer T2 is connected to the anode of D21 and the cathode of D22, and the other end of the secondary winding of T2 is connected to the anode of D11 and the cathode of D12; An output filter circuit (400), the output filter circuit (400) being composed of a filter inductor Lf and a filter capacitor Cf, one end of the filter inductor Lf being connected to the cathodes of three diodes D01, D11 and D21, the other end of the filter inductor Lf being connected to one end of the filter capacitor Cf, and the other end of the filter capacitor Cf being connected to the anodes of three diodes D02, D12 and D22; The single full bridge A and the single full bridge B are completely identical, and the model parameters of the components corresponding to the two single full bridges A and the single full bridge B are completely identical; Q1, Q3 of the single full bridge A and the diode and capacitor connected in parallel form an advanced bridge arm, which has a resonant circuit with one end of the primary winding of the high-frequency transformer T1; Q2, Q4, D2, and D4 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T1; Q5, Q7 of the single full bridge B and the diode and capacitor connected in parallel form an advanced bridge arm, which has a resonant circuit with one end of the primary winding of the high-frequency transformer T2; Q6, Q8, D6, and D8 form a lagging bridge arm connected to the other end of the primary winding of the high-frequency transformer T2; The resonant circuit of the single full bridge A is composed of a resonant inductor Lk1 and a blocking capacitor Cb1, and the resonant circuit of the single full bridge B is composed of a resonant inductor Lk2 and a blocking capacitor Cb2; The driving signals of Q1 and Q5 are the same, the driving signals of Q2 and Q6 are the same, the driving signals of Q3 and Q7 are the same, the driving signals of Q4 and Q8 are the same, and the driving signals of the same bridge arm switch tubes are complementary, the interval time is the dead time, the driving signals of the leading bridge arm switch tubes Q1 and Q3 are respectively ahead of the lagging bridge arm switch tubes Q4 and Q2 by one phase, and the driving signals of the leading bridge arm switch tubes Q5 and Q7 are respectively ahead of the lagging bridge arm switch tubes Q8 and Q6 by one phase.

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