Power conversion device

Abstract

To provide a power conversion device capable of efficiently converting power with a simpler configuration when accommodating multiple types of voltage levels.SOLUTION: A power conversion device that performs power conversion between a first apparatus and a second apparatus includes a transformer having a primary coil and a secondary coil, a first circuit, and a second circuit. The second circuit includes a secondary-side leg formed by two secondary-side switching elements connected in series, and a first capacitor and a second capacitor, both connected in parallel with the secondary-side leg. The secondary coil is connected in parallel with one of the two secondary-side switching elements via the second capacitor. The second circuit further includes a switching mechanism for selectively switching between a first connection state in which the second apparatus is connected in parallel with the first capacitor, and a second connection state in which the second apparatus is connected in parallel with the second capacitor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] In recent years, research and development has been conducted on secondary batteries that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. When fixed or portable secondary batteries such as lithium-ion batteries are used as power sources of multiple voltage levels (e.g., 100V, 200V), a DC / DC converter (power conversion device) is required to boost the voltage of the power source. Such converters are required to perform highly efficient power conversion over a wide input / output voltage ratio. Non-Patent Document 1 proposes a current-fed dual active bridge converter using a three-phase transformer with an asymmetric turns ratio. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Chen Yiyu, Ota Ryosuke, and Hoshi Shinichi, "Current-fed Dual Active Bridge Converter Using Asymmetric Three-Phase Transformer," Institute of Electrical Engineers of Japan, December 1-2, 2022, EDD-22-046, SPC-22-186, pp. 87-92 Summary of the Invention [Problem to be solved by the invention]

[0004] The converter proposed in Non-Patent Document 1 requires a large difference in the turn ratio of each phase to accommodate multiple voltage levels, so a converter that can perform highly efficient power conversion with a simpler configuration is desired.

[0005] Therefore, an object of the present invention is to provide a power conversion device that can perform power conversion with high efficiency using a simpler configuration when compatible with a plurality of voltage levels, thereby contributing to improved energy efficiency. [Means for solving the problem]

[0006] In order to achieve the above object, a power conversion device as one aspect of the present invention is a power conversion device that performs power conversion between a first device and a second device, and includes: a transformer having a primary coil and a secondary coil wound around a core; a first circuit that transmits power between the primary coil and the first device; and a second circuit that transmits power between the secondary coil and the second device, wherein the second circuit has a secondary leg formed by two secondary switch elements connected in series, a first capacitor connected in parallel to the secondary leg, and a second capacitor, and the secondary coil is connected in parallel to one of the two secondary switch elements via the second capacitor, and the second circuit further includes a switching mechanism for selectively switching between a first connection state in which the second device is connected in parallel to the first capacitor and a second connection state in which the second device is connected in parallel to the second capacitor. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a power conversion device that can perform highly efficient power conversion with a simpler configuration, for example, when dealing with a plurality of voltage levels. [Brief explanation of the drawings]

[0008] [Figure 1] A circuit diagram showing a configuration example of a power conversion device according to a first embodiment. [Figure 2] FIG. 1 is a diagram illustrating a first connection state and a second connection state. [Figure 3] A circuit diagram showing a configuration example of a power conversion device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and includes modifications and variations of the configuration within the scope of the present invention. Furthermore, not all of the combinations of features described in the present embodiments are necessarily essential to the present invention. Note that the same reference numerals are used to designate the same components, and their description will be omitted.

[0010] First Embodiment A power conversion device 100A according to a first embodiment of the present invention will be described. The power conversion device 100A according to this embodiment is an insulating converter (DC / DC converter) that performs power conversion for transmitting (supplying) power between a first device D1 and a second device D2, and may be configured as a bidirectional insulating converter that can transmit power bidirectionally between the first device D1 and the second device D2. That is, the power conversion device 100A is configured to be able to transmit (supply) power from the first device D1 to the second device D2 and to transmit (supply) power from the second device D2 to the first device D1. The first device D1 may be, for example, a rechargeable battery such as a lithium-ion battery. The second device D2 may be a load to which power is supplied from the battery serving as the first device D1, or a power source (for example, a charger) that supplies power to the battery serving as the first device D1.

[0011] The second device D2 serving as a load may include, for example, a home appliance or an in-vehicle motor. When a home appliance is used as the second device D2, the power conversion device 100A is used for a home or a building. In this case, the second device D2 may include an inverter that performs DC / AC conversion of the power output from the power conversion device 100A. On the other hand, when an in-vehicle motor is used as the second device D2, the power conversion device 100A may be mounted on an electric vehicle, a hybrid vehicle, or the like. The vehicle on which the power conversion device 100A is mounted may be a four-wheeled vehicle, or may be a vehicle other than a four-wheeled vehicle, such as a saddle-type vehicle (motorcycle, tricycle). The power conversion device 100A may be mounted on a moving body other than a vehicle, such as a ship or an aircraft.

[0012] Fig. 1 is a circuit diagram showing a configuration example of a power conversion device 100A of this embodiment. As shown in Fig. 1, the power conversion device 100A of this embodiment may include a transformer 10, a primary side circuit 20 (first circuit), a secondary side circuit 30 (second circuit), and a control unit 40. In this embodiment, an example will be described in which a battery is used as the first device D1 and a load is used as the second device D2. In addition, in this embodiment, an example will be described in which a one-phase transformer 10 is used.

[0013] First, the configuration of the transformer 10 will be described. The transformer 10 has a core 11, a primary coil 12, and a secondary coil 13. The core 11 is a member for passing magnetic flux (magnetic field) and can be made of a material with high magnetic permeability and low loss. The core 11 can be made of, for example, an iron core, but is not limited to this and may be made of a magnetic material such as silicon steel plate, permalloy, or ferrite. The primary coil 12 and the secondary coil 13 are wound around the same (common) core 11. The turn ratio (n s / n p ) is the desired input / output voltage ratio (i.e., the voltage E p and the voltage E of the second device D2 s The transformer 10 of this embodiment is set in accordance with, for example, the turn ratio (n s / n p ) is configured to be greater than 1.

[0014] Next, the configurations of the primary side circuit 20 and the secondary side circuit 30 will be described. In this embodiment, an example will be described in which the power conversion device 100A (transformer 10, primary side circuit 20, secondary side circuit 30) is configured as an isolated bidirectional DC / DC converter of a current-fed DAB (Dual Active Bridge) system. However, the power conversion device 100A is not limited to a current-fed DAB system, and may be configured as an isolated bidirectional DC / DC converter of another system, such as a voltage-fed DAB system.

[0015] The primary side circuit 20 is a circuit (first circuit) for transmitting power between the primary side coil 12 of the transformer 10 and the first device D1. The primary side circuit 20 is provided on the primary side of the transformer 10 and is connected to the primary side coil 12 of the transformer 10 and the first device D1 (battery). The primary side circuit 20 of this embodiment is p (primary leg) and capacitor C pdc First Leg LG p is the electrical contact J p (third contact) through the two first switch elements S p1 ~S p2 (two primary side switch elements) are connected in series and are connected between line a1 and line a2. pdc 1st leg LG p That is, the capacitor C pdc 1st leg LG p Similarly, one end of the primary coil 12 of the transformer 10 is connected to an electrical contact J p and the other end of the primary coil 12 is connected to the first device D1. The other end of the primary coil 12 in the first device D1 is connected to the line a2. The primary circuit 20 configured in this way can also operate as a boost chopper.

[0016] The secondary circuit 30 is a circuit (second circuit) for transmitting power between the secondary coil 13 of the transformer 10 and the second device D2. The secondary circuit 30 is provided on the secondary side of the transformer 10 and is connected to the secondary coil 13 of the transformer 10 and the second device D2. The secondary circuit 30 of this embodiment is s (secondary leg) and capacitor C sdc (first capacitor) and capacitor C sm (second capacitor). s is the electrical contact J s (first contact) through the two second switch elements S s1 ~S s2 (two secondary side switch elements) are connected in series and are connected between line b1 (first line) and line b2 (second line). sdcThe second leg LG s That is, the capacitor C sdc The second leg LG s Similarly, a capacitor C is connected between the line b1 and the line b2. sm is the electrical contact J m (second contact) and is connected in series to the secondary coil 13 of the transformer 10 through the electrical contact J m and line b2. One end of the secondary coil 13 of the transformer 10 is connected to the inductor L s Electrical contact J via s The other end of the secondary coil 13 is connected to an electrical contact J m That is, the secondary coil 13 is connected to the capacitor C sm 2nd leg via LG s The two second switch elements S s1 ~S s2 One of the switch elements S s2 ) is connected in parallel with the inductor L s can also be substituted by the leakage inductance of the primary coil 12 or the secondary coil 13.

[0017] Here, each first switch element S p1 ~S p2 , and each second switch element S s1 ~S s2 As the lines a1 to a2, b1 to b2, etc., transistors (power elements) that perform switching operations, such as IGBTs and MOSFETs, can be used. Each of the lines a1 to a2 and b1 to b2 may be understood as a current path or an electrical contact.

[0018] The control unit 40 controls each of the first switch elements S of the primary side circuit 20. p1 ~S p2 and each second switch element S of the secondary side circuit 30 s1 ~S s2The control unit 40 controls the power transmission (i.e., power conversion) from the first device D1 to the second device D2 by controlling the power conversion device 100A. The control unit 40 can be configured by a computer including a processor such as a CPU, a storage device such as a semiconductor memory, an interface with an external device, etc. Here, in this embodiment, the control unit 40 is provided as a component of the power conversion device 100A, but this is not limitative, and for example, an external control device such as an ECU (Electronic Control Unit) provided in a vehicle may function as the control unit 40.

[0019] Incidentally, a DC / DC converter may be used at a plurality of voltage levels (for example, 100V, 200V), and even in this case, it is required to convert power with high efficiency over a wide input / output voltage ratio. sdc and a first connection state in which the second device D2 is connected in parallel with the capacitor C sm The switching mechanism SW is configured to selectively switch between a first connection state in which the secondary side circuit 30 is connected in parallel with the first connection state and a second connection state in which the secondary side circuit 30 is connected in parallel with the first connection state. The switching mechanism SW may be understood as a mechanism that switches whether or not the secondary side circuit 30 is operated as a step-down chopper.

[0020] In the first connection state, as shown in FIG. 2(a), the second device D2 is connected between the line b1 and the line b2, and the capacitor C sdc In this first connection state, the secondary side circuit 30 can be operated to supply power to the second device D2 at a high voltage. For example, in this embodiment, the primary side circuit 20 operates as a step-up chopper, so when the voltage of the first device D1 (power supply) is 50 V, the voltage between the line a1 and the line a2 in the primary side circuit 20 becomes 100 V. Therefore, the turns ratio (n s / n p ) is 2, the secondary side circuit 30 in the first connection state can supply power to the second device D2 at a high voltage of 200V.

[0021] In the second connection state, as shown in FIG. 2(b), the second device D2 is connected to the electrical contact Jm and line b2, and a capacitor C sm In this second connection state, the secondary side circuit 30 can be operated as a step-down chopper so as to supply power to the second device D2 at a low voltage. For example, in this embodiment, the primary side circuit 20 operates as a step-up chopper, so that when the voltage of the first device D1 (power supply) is 50V, the voltage between the line a1 and the line a2 in the primary side circuit 20 becomes 100V. The turns ratio (n s / n p ) is 2, the secondary side circuit 30 in the second connection state operates as a step-down chopper, so that it is possible to supply power to the second device D2 at a low voltage of 100V.

[0022] The switching mechanism SW may be a mechanical switch or an electrical switch (e.g., a semiconductor switch element). As an example, a three-terminal mechanical switch such as a toggle switch may be used as the switching mechanism SW. Furthermore, the switching mechanism SW may be configured as a mechanism that switches between the first connection state and the second connection state under the control of the control unit 40, or may be configured as a mechanism that manually switches between the first connection state and the second connection state.

[0023] As described above, the power conversion device 100A of this embodiment includes a switching mechanism SW in the secondary side circuit 30 that selectively switches between the first connection state and the second connection state. This allows the power conversion device 100A to support multiple voltage levels with a simpler configuration and to perform highly efficient power conversion when used at each voltage level. Furthermore, because the power conversion device 100A can support multiple voltage levels simply by providing the switching mechanism SW, it can also be advantageous in terms of the number of components in the power conversion device 100A.

[0024] Second Embodiment A second embodiment of the present invention will be described. In the above first embodiment, an example in which one transformer 10 (one-phase transformer) is used has been described, but in this embodiment, an example in which multiple transformers 10 are used will be described. Note that this embodiment basically follows on from the first embodiment, and can follow the first embodiment except for the matters mentioned below.

[0025] 3 is a circuit diagram showing a configuration example of a power conversion device 100B of this embodiment. The power conversion device 100B of this embodiment is provided with a plurality of transformers 10a to 10c. In addition, the power conversion device 100B of this embodiment includes a plurality of first legs LGs that operate the plurality of transformers 10a to 10c, respectively. pa ~LG pc are provided in the primary side circuit 20, and a plurality of second legs LG are provided to operate the plurality of transformers 10a to 10c, respectively. sa ~LG sc are provided in the secondary side circuit 30. By providing a plurality of transformers 10a-10c in this manner, even if the terminal voltage of the first device D1 fluctuates due to the SOC (State Of Charge) of the first device D1 as a power source (battery), the power supplied to the second device D2 can be stabilized and power can be converted with high efficiency. Here, in this embodiment, an example configuration of a three-phase transformer having three transformers 10a-10c will be described, but the number of transformers 10 is not limited to three, and may be two or four or more.

[0026] The transformer 10a has a core 11a, and a primary coil 12a and a secondary coil 13a wound around the core 11a. Similarly, the transformer 10b has a core 11b, and a primary coil 12b and a secondary coil 13b wound around the core 11b. The transformer 10c has a core 11c, and a primary coil 12c and a secondary coil 13c wound around the core 11c. The turns ratio (n sa / n pa , n sb / n pb , n sc / n pc) may be the same or different from each other. When the transformers 10a to 10c have the same turn ratio, ripples can be suppressed and power can be supplied to the second device D2 more stably. When the transformers 10a to 10c have different turn ratios from each other, highly efficient power conversion can be performed over a wider input / output voltage ratio.

[0027] The primary circuit 20 includes a plurality of first legs LG pa ~LG pc and capacitor C pdc A plurality of first legs LG pa ~LG pc is connected in parallel between the line a1 and the line a2. pdc is connected between the line a1 and the line a2, and each first leg LG pa ~LG pc are connected in parallel.

[0028] 1st Leg LG pa is the electrical contact J pa (third contact) through the two first switch elements S pa1 ~S pa2 are connected in series, and electrical contact J pa One end of the primary coil 12a of the transformer 10a is connected to the first leg LG. pb is the electrical contact J pb (third contact) through the two first switch elements S pb1 ~S pb2 are connected in series, and electrical contact J pb One end of the primary coil 12b of the transformer 10b is connected to the first leg LG pc is the electrical contact J pc (third contact) through the two first switch elements S pc1 ~S pc2 are connected in series, and electrical contact J pc One end of the primary coil 12c of the transformer 10c is connected to the first device D1. The other end of each of the primary coils 12a to 12c is connected to the first device D1. The primary circuit 20 configured in this manner can operate as a boost chopper.

[0029] The secondary circuit 30 includes a plurality of second legs LG sa ~LG sc and capacitor C sdc and (first capacitor), capacitor C sm (second capacitor). sa ~LG sc is connected in parallel between the line b1 and the line b2. sdc is connected between line b1 and line b2, and each second leg LG sa ~LG sc is connected in parallel to the capacitor C sm is the electrical contact J m (second contact) and is connected in series to the secondary coil 13 of the transformer 10 through the electrical contact J m and line b2.

[0030] 2nd Leg LG sa is the electrical contact J sa (first contact) through the two second switch elements S sa1 ~S sa2 are connected in series, and electrical contact J sa One end of the secondary coil 13a of the transformer 10a is connected to the inductor L sa Similarly, the second leg LG sb is the electrical contact J sb (first contact) through the two second switch elements S sb1 ~S sb2 are connected in series, and electrical contact J sb One end of the secondary coil 13b of the transformer 10b is connected to the inductor L sb The second leg LG is connected via sc is the electrical contact J sc (first contact) through the two second switch elements S sc1 ~S sc2 are connected in series, and electrical contact J sc One end of the secondary coil 13c of the transformer 10c is connected to the inductor L sc The other end of each of the secondary coils 13a to 13c is connected to an electrical contact J. m, and each of the secondary coils 13a to 13c is connected to the corresponding second leg LG sa ~LG sc The two second switch elements S sa1 ~S sa2 , S sb1 ~S sb2 , S sc1 ~S sc2 One of the switch elements S sa2 , S sb2 , S sb2 ) is connected in parallel with the inductor L sa The inductor L can be substituted by the leakage inductance of the primary coil 12a or the secondary coil 13a. sb ~L sc The same is true.

[0031] The secondary circuit 30 is further provided with a switching mechanism SW. The switching mechanism SW switches the second device D2 to the capacitor C sdc and a first connection state in which the second device D2 is connected in parallel with the capacitor C sm The switching mechanism SW is a mechanism for selectively switching between the first connection state in which the power supply is connected in parallel with the power supply, and the second connection state in which the power supply is connected in parallel with the power supply. The configuration and function of the switching mechanism SW are the same as those described in the first embodiment, and therefore will not be described here.

[0032] As described above, the power conversion device 100B of this embodiment, which includes multiple transformers 10a to 10c, can accommodate multiple voltage levels with a simple configuration that simply includes a switching mechanism SW, similar to the power conversion device 100A of the first embodiment, and can perform highly efficient power conversion when used at each voltage level. This can also be advantageous in terms of the number of parts in the power conversion device 100B.

[0033] <Summary of the embodiment> (Item 1) A power conversion device (e.g., 100A, 100B) that performs power conversion between a first device (e.g., D1) and a second device (e.g., D2), a transformer (e.g., 10) having a primary coil (e.g., 12) and a secondary coil (e.g., 13) wound around a core (e.g., 11); a first circuit (e.g., 20) that transmits power between the primary coil and the first device; a second circuit (e.g., 30) that transmits power between the secondary coil and the second device; Equipped with The second circuit includes two secondary side switch elements (e.g., S s1 ~S s2 ) are connected in series to form a secondary leg (e.g., LG s ) and a first capacitor (e.g., C sdc ) and a second capacitor (e.g., C sm ) and the secondary coil is connected in parallel to one of the two secondary switch elements via the second capacitor; The power conversion device is characterized in that the second circuit further has a switching mechanism (e.g., a SW) for selectively switching between a first connection state in which the second device is connected in parallel to the first capacitor and a second connection state in which the second device is connected in parallel to the second capacitor. According to this item, it is possible to support multiple voltage levels with a simpler configuration and achieve highly efficient power conversion when used at each voltage level. Furthermore, since it is possible to support multiple voltage levels simply by providing a switching mechanism, it can also be advantageous in terms of the number of parts required for the power conversion device.

[0034] (Item 2) the two secondary-side switch elements in the secondary-side leg are connected in series via first contacts, 2. The power conversion device according to item 1, wherein one end of the secondary coil is connected to the first contact, and the other end of the secondary coil is connected to the second capacitor. According to this item, when the power conversion device is adapted to handle a plurality of voltage levels, it is possible to perform power conversion with high efficiency using a simpler configuration.

[0035] (Item 3) The secondary leg and the first capacitor are each connected between a first line (e.g., b1) and a second line (e.g., b2), The second capacitor has a second contact (e.g., J m ) connected in series with the secondary coil via a second contact and connected between the second contact and the second line, the first connection state is a state in which the second device is connected between the first line and the second line, 3. The power conversion device according to item 1 or 2, wherein the second connection state is a state in which the second device is connected between the second contact and the second line. According to this item, whether or not the second circuit functions as a step-down chopper can be switched by the switching mechanism.

[0036] (Item 4) The first circuit includes two primary side switch elements (e.g., S p1 ~S p2 ) are connected in series to form a primary leg (e.g., LG p ) and The power conversion device according to any one of items 1 to 3, characterized in that the primary coil is connected in parallel with one of the two primary switch elements via the first device. According to this item, the first circuit can be configured using two switch elements.

[0037] (Item 5) The first circuit includes a capacitor (e.g., C pdc 5. The power conversion device according to item 4, further comprising: According to this item, the first circuit can be operated as a boost chopper.

[0038] (Item 6) The two primary-side switch elements in the primary-side legs have third contacts (e.g., J p ) are connected in series, 6. The power conversion device according to item 4 or 5, wherein one end of the primary coil is connected to the third contact and the other end of the primary coil is connected to the first device. According to this item, when the power conversion device is adapted to handle a plurality of voltage levels, it is possible to perform power conversion with high efficiency using a simpler configuration.

[0039] (Item 7) The power conversion device includes a plurality of the transformers (e.g., 10a to 10c), The first circuit includes a plurality of primary legs (e.g., LG) that respectively operate the plurality of transformers. pa ~LG pc ) and The second circuit includes a plurality of secondary legs (e.g., LG) that respectively operate the plurality of transformers. sa ~LG sc ) 7. The power conversion device according to any one of items 4 to 6, wherein: According to this item, a power conversion device having a multi-phase transformer can be realized, and power can be converted with high efficiency over a wide input / output voltage ratio between a first device and a second device.

[0040] (Item 8) 8. The power conversion device according to item 7, wherein the plurality of transformers have different turn ratios between the primary coil and the secondary coil. According to this item, highly efficient power conversion can be performed over a wider input / output voltage ratio.

[0041] (Item 9) 9. The power conversion device according to any one of items 1 to 8, wherein the switching mechanism is a mechanical switch having three terminals. According to this item, the power conversion device can be made compatible with a plurality of voltage levels with a simpler configuration.

[0042] (Item 10) the first device is a battery; 10. The power conversion device according to any one of items 1 to 9, wherein the second device is a load to which power is supplied from the first device, or a power source that supplies power to the first device. According to this item, power can be transferred from a battery serving as the first device to a load serving as the second device, and power can be transferred from a power source serving as the second device to a battery serving as the first device.

[0043] (Item 11) 11. The power conversion device according to any one of items 1 to 10, wherein the power conversion device is capable of transmitting power bidirectionally between the first device and the second device. According to this item, power can be transferred from the first device to the second device, and from the second device to the first device.

[0044] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0045] 10: transformer, 11: core, 12: primary coil, 13: secondary coil, 20: primary circuit (first circuit), LG p : 1st leg, S p1 ~S p2 : first switch element, 30: secondary side circuit (second circuit), LG s :2nd leg, S s1 ~S s2 : second switch element, 40: control unit, 100A, 100B: power conversion device

Claims

1. A power conversion device that performs power conversion between a first device and a second device, a transformer having a primary coil and a secondary coil wound around a core; a first circuit that transfers power between the primary coil and the first device; a second circuit that transfers power between the secondary coil and the second device; Equipped with the second circuit includes a secondary leg formed by connecting two secondary switch elements in series, and a first capacitor and a second capacitor connected in parallel to the secondary leg; the secondary coil is connected in parallel with one of the two secondary switch elements via the second capacitor, the second circuit further has a switching mechanism for selectively switching between a first connection state in which the second device is connected in parallel to the first capacitor and a second connection state in which the second device is connected in parallel to the second capacitor.

2. the two secondary-side switch elements in the secondary-side leg are connected in series via first contacts, 2. The power conversion device according to claim 1, wherein one end of the secondary coil is connected to the first contact, and the other end of the secondary coil is connected to the second capacitor.

3. the secondary leg and the first capacitor are each connected between a first line and a second line; the second capacitor is connected in series with the secondary coil via a second contact and is connected between the second contact and the second line; the first connection state is a state in which the second device is connected between the first line and the second line, 3. The power conversion device according to claim 1, wherein the second connection state is a state in which the second device is connected between the second contact and the second line.

4. the first circuit has a primary leg formed by connecting two primary switch elements in series, 3. The power conversion device according to claim 1, wherein the primary coil is connected in parallel with one of the two primary switch elements via the first device.

5. 5. The power conversion device according to claim 4, wherein the first circuit further includes a capacitor connected in parallel with the primary leg.

6. the two primary-side switch elements in the primary-side leg are connected in series via a third contact; 5. The power conversion device according to claim 4, wherein one end of the primary coil is connected to the third contact, and the other end of the primary coil is connected to the first device.

7. the power conversion device includes a plurality of the transformers, the first circuit has a plurality of the primary legs that respectively operate the plurality of the transformers; the second circuit has a plurality of secondary legs that respectively operate a plurality of the transformers; 5. The power conversion device according to claim 4.

8. The power conversion device according to claim 7 , wherein the plurality of transformers have mutually different turn ratios between the primary coil and the secondary coil.

9. 3. The power conversion device according to claim 1, wherein the switching mechanism is a mechanical switch having three terminals.

10. the first device is a battery, 3. The power conversion device according to claim 1, wherein the second device is a load to which power is supplied from the first device, or a power source that supplies power to the first device.

11. The power conversion device according to claim 1 or 2, wherein the power conversion device is capable of transmitting power bidirectionally between the first device and the second device.

Images