A bidirectional co-current dc / dc converter and method using coupled inductors

Abstract

A bidirectional co-flow DC / DC converter and method using coupled inductors includes two secondary coupled inductor branches to achieve higher voltage conversion factor, current sharing characteristics and soft switching; due to the use of a double current path inductor structure, the voltage conversion ratio is improved, and the current can be shared in all operating modes; all active switches use soft switching of the synchronous rectification concept, which helps to reduce conduction loss; the converter in the application does not require additional circuit elements to achieve soft switching, and can achieve higher efficiency operation. The converter in the application uses two parallel inductor current paths to share input current in boost and buck modes, thereby reducing the rated current of a single coil, which helps to reduce input current ripple. Due to the advantages of the topology, the leakage energy is directly transmitted to the load, and the maximum measured efficiency in the buck mode under the condition of 170W and the boost mode under the condition of 190W is 96.12% and 96.63% respectively.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronic soft switching, and particularly relates to a bidirectional co-flow DC / DC converter and method using coupled inductors. BACKGROUND

[0002] Bidirectional DC / DC converters are widely used in storage interfaces and electric vehicle fields. Since it requires high voltage gain in the boost mode and the interface low voltage battery can reach the high voltage side in the buck mode, the traditional double-switch non-isolated bidirectional DC / DC is not suitable for these applications, and the efficiency and voltage stress performance of the traditional bidirectional DC / DC converter are poor. In order to solve the problem that it is difficult to achieve the required conversion ratio in both buck and boost modes, bidirectional DC / DC converters are divided into two categories: isolated bidirectional DC / DC converters and non-isolated bidirectional DC / DC converters. In order to achieve high conversion ratio, the isolated bidirectional DC / DC converter adopts a transformer as an isolation element. However, in the full-bridge isolated bidirectional DC / DC converter, the number of active switches is generally greater than or equal to 8. In order to reduce the number of active switches in the circuit, some scholars use a half-bridge topology to achieve it. However, the main problem faced by these converters is the complexity of soft switching and control.

[0003] Non-isolated bidirectional DC / DC uses different circuit concepts, such as SEPIC, voltage multiplier, switched capacitor, and coupled inductor, to achieve high conversion ratio. The BDCS derived from SEPIC has low efficiency due to its cascaded structure. Voltage multipliers can be used to design bidirectional DC / DC converters, but they generate a large voltage stress between switches. The bidirectional DC / DC converter based on switched capacitor has a simple structure, low control complexity, and good performance in essence. However, the switching loss and large switching current stress of this type of converter are still major problems. The zero voltage switching of active switches in these converters can be achieved through auxiliary circuits, but the gain and control complexity are limited. SUMMARY

[0004] In view of the problems in the prior art, the application provides a bidirectional co-flow DC / DC converter and method using coupled inductors

[0005] The application is achieved by the following technical solutions:

[0006] A bidirectional co-flow DC / DC converter using coupled inductors, characterized by comprising a first coupled inductor branch and a second coupled inductor branch, the first coupled inductor branch comprising a same name end of a coupled inductor magnetic coil L1 and a capacitor C4 and a first coupled branch magnetic coil L2 connected in sequence to the same name end of the coupled inductor magnetic coil L1.

[0007] The second coupling inductance branch includes the opposite end of the coupling inductance magnetic ring L1 and the capacitor C2 and the second coupling branch magnetic ring L3 connected in sequence to the opposite end of the coupling inductance magnetic ring L1.

[0008] The first coupling inductance branch and the second coupling inductance branch are parallel inductance current paths for sharing input current in the boost and buck modes.

[0009] Further, the same end of the coupling inductance magnetic ring L1 is connected with the input battery VLV, the capacitor C4 and the opposite end of the first coupling branch magnetic ring L2, and the opposite end of the coupling inductance magnetic ring L1 is respectively connected with the capacitor C2, the same end of the second coupling branch magnetic ring L2, the drain of the switch tube S1 and the source of the switch tube S2.

[0010] The same end of the first coupling branch magnetic ring L2 is respectively connected with the drain of the switch tube S4 and the source of the switch tube S5.

[0011] The opposite end of the second coupling branch inductance L3 is respectively connected with the negative electrode of the output capacitor C3 and the drain of the switch tube S3.

[0012] The positive electrode of the output capacitor C3 is connected with the drain of the switch tube S5 and further the source of the switch tube S6, and the drain of the main switch S6 is connected with the bidirectional DC / DC output end.

[0013] Further, the drain of the switch tube S2 is respectively connected with the source of the switch tube S3 and the capacitor C1.

[0014] Further, a power supply VHL is arranged between the drain of the switch tube S6 and the capacitor C1, for verifying the boost operation.

[0015] Further, the switch tube S1, the switch tube 2, the switch tube 3, the switch tube S4, the switch tube S5 and the switch tube S6 are all active switch MOSFETs.

[0016] Further, the switch tube S1 and the switch tube S6 are active switch main switches.

[0017] Further, the switch tube 2, the switch tube 3, the switch tube S4 and the switch tube S5 are active switch auxiliary switches.

[0018] A bidirectional common-flow DC / DC conversion method with high gain and high efficiency by using coupling inductance, characterized by comprising the following steps:

[0019] Boost process:

[0020] S1: Close the switch tube S4 and the switch tube S6 under the ZVS condition, and the current passes through the anti-parallel body diode of the switch tube S4 and the switch tube S6, so that the current of the switch tube S1 is zero.

[0021] S2: The body diode of switch S1 is turned on, switch S1 is turned on to realize ZVS on-off, the polarity of the secondary winding and the tertiary winding of the coupled inductor makes the antiparallel body diodes of switch S3 and switch S5 forward-biased, and capacitors C1 and C4 release their energy to capacitors C2 and C3 through the secondary winding and the tertiary winding of the coupled inductor;

[0022] S3: Switch S3 and switch S5 are turned on under ZVS conditions, capacitors C1 and C4 continue to release their energy to capacitors C2 and C3 together with the coupled secondary winding and the tertiary winding of the inductor in this mode, the capacitance values of capacitors C1 and C2 and the inductance of the coupled secondary winding are adjusted to complete the DTs interval half-cycle quasi-resonant current (tr) process;

[0023] S4: The polarity of the primary winding of the coupled inductor and the leakage inductance is reversed, the body diodes of switch S2, switch S4 and switch S6 are naturally opened, the magnetization energy stored in the leakage inductor is transferred to capacitor C1 through the body diode of switch S2, and the magnetization current begins to decrease;

[0024] S5: Switch S2, switch S4 and switch S6 are turned on under ZVS conditions, the magnetization current continues to decrease until the magnetization energy stored in the leakage inductor is transferred to capacitor C1, and the boost process is completed;

[0025] Buck process:

[0026] S1: Switch S1, switch S3 and switch S5 are turned off, the body diodes of switch S1, switch S5 and switch S6 are forward-biased, and the current of the secondary winding and the tertiary winding of the coupled inductor enters the high-voltage side through the body diode of switch S6;

[0027] S2: Switch S6 is turned on under ZVS conditions, the reverse current flowing into the high-voltage side decreases to zero, and the free rotation stage of the buck operation stops;

[0028] S3: Capacitors C1 and C4 are charged through the body diodes of switch S2 and switch S4, respectively;

[0029] S4: When switch S2 and switch S4 are turned on under ZVS conditions, capacitor C1 is fully charged;

[0030] S5: Switch S2 is turned on, capacitor C1 begins to discharge until switch S6 is turned off;

[0031] S6: The polarity of the coupled inductor is changed to maintain the continuity of the inductor current, the body diodes of switch S1, switch S3 and switch S5 are forward-biased and begin to conduct, and capacitors C2 and C3 begin to charge;

[0032] S7: when the switch tube S1, the switch tube S3 and the switch tube S5 are opened under the ZVS condition, the capacitor C2 and the capacitor C3 continue to charge, when the switch tube S3, the switch tube S5 and the switch tube S1 are closed, the step S1 is repeated, and the step S1 is repeated, and the step S1 is repeated.

[0033] Compared with the prior art, the application has the following beneficial technical effects:

[0034] A bidirectional co-flow DC / DC converter and method using coupled inductors, including two secondary coupled inductor branches to achieve higher voltage conversion factor, current sharing characteristics and soft switching; due to the use of a double current path inductor structure, the voltage conversion ratio is improved, and the current can be shared in all operating modes; all active switches use soft switching of the synchronous rectification concept, which helps to reduce conduction loss; the converter in the application does not require additional circuit elements to achieve soft switching, and can achieve higher efficiency operation. The converter in the application uses two parallel inductor current paths to share input current in boost and buck modes, thereby reducing the rated current of a single coil, which helps to reduce input current ripple. Due to the advantages of the topology, the leakage energy is directly transmitted to the load, and the maximum measured efficiency in the buck mode under the condition of 170W and the boost mode under the condition of 190W is 96.12% and 96.63% respectively. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0036] Figure 2 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0037] Figure 3 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0038] Figure 4 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0039] Figure 5 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0040] Figure 6 A bidirectional co-flow DC / DC converter using coupled inductors is shown in the specific embodiment of the application;

[0041] Figure 7A high-gain and high-efficiency bidirectional co-current DC / DC step-up schematic diagram using coupled inductance in a specific embodiment of the present application;

[0042] Figure 8 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0043] Figure 9 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0044] Figure 10 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0045] Figure 11 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0046] Figure 12 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0047] Figure 13 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application;

[0048] Figure 14 A high-gain and high-efficiency bidirectional co-current DC / DC step-down schematic diagram using coupled inductance in a specific embodiment of the present application. DETAILED DESCRIPTION

[0049] The present application will be further described below in connection with specific embodiments, which are intended to explain the present application but not to limit it.

[0050] In order to make the personnel in the art better understand the present application scheme, the technical solutions in the embodiments of the present application will be clearly and completely described below in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0051] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above-described drawings are intended to distinguish similar objects and are not necessarily intended to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged, where appropriate, so that the embodiments of the application described herein can be carried out in other than the order illustrated or described herein. Furthermore, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, processes, methods, systems, products, or devices that include a series of steps or units are not necessarily limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0052] The present application provides a bidirectional co-flow DC / DC converter using coupled inductance, such as Figure 1 The first coupled inductance branch includes the same name end of the coupled inductance magnetic coil L1 and the capacitor C4 and the first coupled branch magnetic coil L2 connected in sequence to the same name end of the coupled inductance magnetic coil L1, and specifically, the coupled inductance turns ratio n = N2 / N1.

[0053] The second coupled inductance branch includes the opposite name end of the coupled inductance magnetic coil L1 and the capacitor C2 and the second coupled branch magnetic coil L3 connected in sequence to the opposite name end of the coupled inductance magnetic coil L1.

[0054] The first coupled inductance branch and the second coupled inductance branch are parallel inductance current paths for sharing input current in boost and buck modes.

[0055] Further, the same name end of the coupled inductance magnetic coil L1 is connected with the input battery VNV and the capacitor C4 and the opposite name end of the first coupled branch magnetic coil L2, and the opposite name end of the coupled inductance magnetic coil L1 is respectively connected with the capacitor C2 and the same name end of the second coupled branch magnetic coil L2, the drain of the switch tube S1 and the source of the switch tube S2.

[0056] The same name end of the first coupled branch magnetic coil L2 is respectively connected with the drain of the switch tube S4 and the source of the switch tube S5.

[0057] The opposite name end of the second coupled branch inductance L3 is respectively connected with the negative electrode of the output capacitor C3 and the drain of the switch tube S3.

[0058] The positive electrode of the output capacitor C3 is connected with the drain of the switch tube S5 and further the source of the switch tube S6, and the drain of the main switch S6 is connected with the bidirectional DC / DC output end.

[0059] Further, the negative electrode of the input battery VLV is respectively connected with the source of the switch tube S2 and the capacitor C1.

[0060] Further, the drain of the switch tube S2 is connected with the source of the switch tube S3 and the capacitor C1 respectively.

[0061] Further, the power supply VHL is arranged between the drain of the switch tube S6 and the capacitor C1, so as to verify the boost operation.

[0062] Further, the switch tube S1, the switch tube S2, the switch tube S3, the switch tube S4, the switch tube S5 and the switch tube S6 are all active switch MOSFETs.

[0063] Further, the switch tube S1 and the switch tube S6 are active switch main switches.

[0064] Further, the switch tube S2, the switch tube S3, the switch tube S4 and the switch tube S5 are active switch auxiliary switches.

[0065] Specifically, the application adopts a double-current path inductance structure, improves the voltage conversion ratio, can share the current in all working modes, all active switches use the soft switching concept of synchronous rectification, and do not need additional circuit elements to realize soft switching, so as to realize higher efficiency operation.

[0066] Further, in the case of unit turn ratio (n=1), a high conversion coefficient of boost≥10 and buck≤1 / 10 can be obtained. In the two working modes of boost and buck, the current and voltage stress of the main MOSFET switch are small, and the low-voltage and low-pass state resistance MOSFET is matched, so that the conduction loss can be reduced. Similarly, all active switches are soft switches, i.e. zero voltage switching, so that the switching loss can be ignored, thereby further improving the conversion efficiency.

[0067] The application utilizes two parallel inductance current paths to share the input current in the boost and buck modes, thereby reducing the rated current of a single coil and helping to reduce the input current ripple. Due to the topological advantage, the leakage energy is directly transmitted to the load. The maximum measured efficiencies in the buck mode under the condition of 170W and the boost mode under the condition of 190W are 96.12% and 96.63% respectively, and the application is a bidirectional common-flow DC / DC converter with high gain and high efficiency.

[0068] The application provides a high-gain and high-efficiency bidirectional common-flow DC / DC conversion method using coupled inductance, comprising the following steps:

[0069] In order to simplify the analysis, the coupled inductance is modeled as an ideal transformer with two secondary windings and magnetizing inductance Lm. The leakage inductance L lk , the circuit parameters such as the capacitor inter-wavelength voltage are very small, and are ignored for the purpose of simplifying the analysis. The active MOSFET switch is considered as an ideal switch, and the magnetizing inductance Lm is Lm+L_lk The ratio is considered as the coupling coefficient k, the winding turns ratio is n, and it adopts two working modes in continuous conduction (CCM): boost and buck.

[0070] The boost process:

[0071] In boost mode, power is drawn from the low-voltage power supply V. _LV Flow to high voltage bus V _HV The CIBDC mode proposed in this invention is divided into 6 sub-intervals according to the switching state, specifically the high-voltage side V _HV The circuit model is considered to be a combination of output capacitors and resistors to verify boost operation;

[0072] S1: Under ZVS conditions, switching transistors S4 and S6 are turned off. Current flows through the anti-parallel body diodes of switching transistors S4 and S6, making the current in switching transistor S1 zero; further, such as Figure 2 As shown, at time t1, when switch S1 is turned on, this step S1 ends;

[0073] S2: The body diode of switch S1 is turned on, and switch S1 is turned on to achieve ZVS switching. The polarity of the secondary and tertiary windings of the coupling inductor causes the anti-parallel body diodes of switch S3 and switch S5 to be forward biased. Capacitors C1 and C4 release their energy to capacitors C2 and C3 along with the secondary and tertiary windings of the coupling inductor.

[0074] Specifically, such as Figure 3 As shown, when the switch S1 is turned on at this time, ZVS switching operation is achieved, coupling the inductor magnetizing current (i lm The load current begins to rise, and the output high-voltage side capacitor C... HV Provided, at this time, the soft switching operation of the switching transistor S1 is similar to that of synchronous rectification, and is implemented during the turn-on process.

[0075] S3: Switches S3 and S5 are turned on under ZVS conditions. Capacitors C1 and C4, along with the secondary and tertiary windings of the coupled inductor, continue to release their energy to capacitors C2 and C3 in this mode. Adjusting the capacitance values ​​of C1 and C2, as well as the inductance of the secondary winding of the coupled inductor, completes the DTs interval half-cycle quasi-resonant current (tr) process; furthermore, such as... Figure 4 As shown, the current stress of switch S1 is reduced at this time; similarly, the soft switching operation of switch S3 and switch S5 is also completed under synchronous rectification.

[0076] S4: As Figure 5As shown, first switch S1, switch S3 and switch S5 are closed, at this time, the polarity of the coupling inductance primary winding and leakage inductance is reversed, the high voltage side of switch S2, switch S4 and the body diode of switch S6 are naturally opened, at this time, the switch voltage is zero, the magnetization energy stored in the leakage inductance is transferred to the capacitor C1 through the body diode of switch S2, specifically, the capacitor C4 is in the charging mode, storing the energy of the coupling inductance third winding, the energy stored in the capacitor C2, capacitor C3 and the coupling inductance secondary winding is released to the high voltage capacitor and the load side, and the magnetization current starts to decrease;

[0077] S5: as Figure 6 shown, switch S2, switch S4 and switch S6 are opened under ZVS condition, the magnetization current ilm continues to decrease, specifically, the energy stored in the capacitor C2, capacitor C3 and the coupling inductance secondary winding is released to the high voltage capacitor and the load side, until the magnetization energy stored in the leakage inductance is transferred to the capacitor C1, when the stored energy is transferred to the capacitor C1, switch S2 stops conducting; then, as Figure 7 shown, when the switch S2 will no longer deliver current to the capacitor C1, the boost process is completed;

[0078] Buck process:

[0079] In the buck mode operation, the power flows from the high voltage V HV to the low voltage V LV In a working cycle, the buck is divided into the following 7 steps:

[0080] S1: as Figure 8 shown, switch S1, switch S3 and switch S5 are closed, due to the polarity of the coupling inductance coil, the body diode of switch S1, switch S5 and switch S6 is forward biased, the current of the secondary winding and the tertiary winding of the coupling inductance enters the high voltage side through the body diode of switch S6; so that switch S6 can be opened under ZVS condition, when ZVS ends at t1, the current of switch S1 and switch S5 decreases to zero value, at the same time, switch S1 and switch S5 are closed under ZVS condition due to the conduction of the body diode;

[0081] S2: as Figure 9 shown, when switch S6 is opened under ZVS condition, at T1, the reverse current flowing into the high voltage side decreases to zero value, the free rotation stage of the buck operation stops;

[0082] S3: as Figure 10 shown, the capacitor C1 and the capacitor C4 are charged through the body diode of switch S2 and switch S4 respectively;

[0083] Specifically, because switch S1 is turned on, current flows more easily through the coupling inductor and capacitor C3, while capacitor C2 flows from the high-voltage side to the low-voltage side, achieving an active voltage reduction process; due to the polarity coupling of the inductor, the body diodes of switches S2 and S3 are turned on, and the magnetizing current i m In contrast to the voltage boost process, which rises in the opposite direction, capacitors C1 and C4 are charged in this mode through the body diodes of switching transistors S2 and S4, respectively. Since the body diodes of switching transistors S2 and S4 are conductive, these switches can be turned on under ZVS conditions. Meanwhile, in this step, the low-voltage side capacitor and load current are provided by the high-voltage side.

[0084] S4: As Figure 11 As shown, when switches S2 and S4 are turned on in ZVS state, and the current through S2 is zero, capacitor C1 is fully charged.

[0085] S5: As Figure 12 As shown, when switch S2 is turned on, capacitor C1 begins to discharge until switch S6 is turned off.

[0086] S6: As Figure 13 As shown, when switch S6 is off, the polarity of the coupling inductor changes to maintain the continuity of the inductor current. The body diodes of switches S1, S3, and S5 are forward biased and begin to conduct. At this time, capacitor C1 begins to discharge, capacitors C2 and C3 begin to charge, and the magnetizing current begins to decrease. When the body diodes conduct, switches S1, S3, and S5 will turn on under ZVS conditions.

[0087] S7: As Figure 14 As shown, when switches S1, S3, and S5 are turned on under ZVS conditions, capacitors C2 and C3 are continuously charged. When switches S3, S5, and S1 are turned off, step S1 is repeated to complete the step-down process.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional co-flow DC / DC converter utilizing coupled inductors, characterized by, The first coupled inductor branch includes the same name end of the coupled inductor magnetic ring L1 and the capacitor C4 and the first coupled branch magnetic ring L2 connected in sequence to the same name end of the coupled inductor magnetic ring L1; The second coupled inductor branch includes the different name end of the coupled inductor magnetic ring L1 and the capacitor C2 and the second coupled branch magnetic ring L3 connected in sequence to the different name end of the coupled inductor magnetic ring L1; The first coupled inductor branch and the second coupled inductor branch are parallel inductor current paths for sharing input current in boost and buck modes; The same name end of the coupled inductor magnetic ring L1 is connected with the input battery VLV, the capacitor C4 and the different name end of the first coupled branch magnetic ring L2, and the different name end of the coupled inductor magnetic ring L1 is respectively connected with the capacitor C2, the same name end of the second coupled branch magnetic ring L2, the drain of the switch tube S1 and the source of the switch tube S2; The same name end of the first coupled branch magnetic ring L2 is respectively connected with the drain of the switch tube S4 and the source of the switch tube S5; The different name end of the second coupled branch inductor L3 is respectively connected with the negative electrode of the output capacitor C3 and the drain of the switch tube S3; The positive electrode of the output capacitor C3 is connected with the drain of the switch tube S5 and the source of the switch tube S6, and the drain of the switch tube S6 is connected with the bidirectional DC / DC output end; The source of the switch tube S1 is connected with the negative electrode of the input battery VLV, the bidirectional DC / DC output end, the drain of the switch tube S2 and the source of the switch tube S3; the source of the switch tube S4 is connected with the different name end of the coupled inductor magnetic ring L1; and the same name end of the second coupled branch inductor L3 is connected with the capacitor C2.

2. The bidirectional co-current DC / DC converter with coupled inductors of claim 1, wherein, The drain of the switch tube S2 is respectively connected with the source of the switch tube S3 and the capacitor C1.

3. The bidirectional co-current DC / DC converter with coupled inductors of claim 1, wherein, A power supply VHL is arranged between the drain of the switch tube S6 and the capacitor C1, for verifying boost operation.

4. The bidirectional co-current DC / DC converter with coupled inductors of claim 1, wherein, The switch tube S1, the switch tube S2, the switch tube S3, the switch tube S4, the switch tube S5 and the switch tube S6 are all active switch MOSFETs.

5. The bidirectional co-current DC / DC converter with coupled inductors of claim 1, wherein, The switch tube S1 and the switch tube S6 are active switch main switches.

6. The bidirectional co-current DC / DC converter with coupled inductors of claim 1, wherein, The switch tube S2, the switch tube S3, the switch tube S4 and the switch tube S5 are active switch auxiliary switches.

7. A bidirectional co-current DC / DC conversion method using coupled inductors, characterized by, The bidirectional common-flow DC / DC converter using coupled inductor according to any one of claims 1-6 comprises the following steps: Boost process: S1: under ZVS condition, the switch tube S4 and the switch tube S6 are closed, the current passes through the anti-parallel body diode of the switch tube S4 and the switch tube S6, so that the current of the switch tube S1 is zero; S2: the body diode of the switch tube S1 is turned on, the switch tube S1 is turned on to realize ZVS on-off, the polarity of the coupled inductor secondary winding and the tertiary winding makes the anti-parallel body diode of the switch tube S3 and the switch tube S5 forward biased, and the capacitor C1 and the capacitor C4 release energy to the capacitor C2 and C3 with the coupled inductor secondary winding and the tertiary winding; S3: Switch S3 and switch S5 are turned on under ZVS condition, capacitor C1 and capacitor C4 together with coupled inductor secondary winding, tertiary winding continue to release their energy to capacitor C2 and C3 in this mode, adjust the capacitance value of capacitor C1 and capacitor C2 and the inductance of coupled inductor secondary winding, complete the DTs interval half cycle quasi-resonant current (tr) process; S4: The polarity of the coupled inductor primary winding and the leakage inductance is reversed, the body diode of switch S2, switch S4 and switch S6 is naturally turned on, the magnetization energy stored in the leakage inductance is transferred to capacitor C1 through the body diode of switch S2, and the magnetization current begins to decrease; S5: Switch S2, switch S4 and switch S6 are turned on under ZVS condition, the magnetization current continues to decrease until the magnetization energy stored in the leakage inductance is transferred to capacitor C1, completing the boost process; Buck process: S1: Switch S1, switch S3 and switch S5 are turned off, the body diodes of switch S1, switch S5 and switch S6 are forward biased, the current of the secondary winding and the tertiary winding of the coupled inductor enters the high voltage side through the body diode of switch S6; S2: Switch S6 is turned on under ZVS condition, the reverse current flowing into the high voltage side decreases to zero, and the free rotation stage of the buck operation stops; S3: Capacitor C1 and capacitor C4 are charged through the body diodes of switch S2 and switch S4 respectively; S4: When switch S2 and switch S4 are turned on under ZVS state, capacitor C1 is fully charged; S5: Switch S2 is turned on, capacitor C1 starts to discharge until switch S6 is turned off; S6: The polarity of the coupled inductor is changed to maintain the continuity of the inductor current, the body diodes of switch S1, switch S3 and switch S5 are forward biased and start to conduct, and capacitor C2 and capacitor C3 start to charge; S7: When switch S1, switch S3 and switch S5 are turned on under ZVS condition, capacitor C2 and capacitor C3 continue to charge, and when switch S3, switch S5 and switch S1 are turned off, repeat step S1, completing the buck process.

Images