Transformer unit, and power conversion device

Abstract

To provide a technique for reducing a DC magnetic flux of a transformer and reducing the size of the transformer.SOLUTION: A transformer unit includes a core having a first column part and a second column part, a first transformer which is provided on the first column part and has a primary side coil and a secondary side coil, and a second transformer which is provided on the second column part and has a primary side coil and a secondary side coil, wherein the core has a common column part which is arranged with a gap between itself and at least one of the first column part and the second column part, as a common magnetic path for commonly passing a first DC magnetic flux generated by the first transformer and a second DC magnetic flux generated by the second transformer, and the respective coils of the first transformer and the second transformer are provided on the core so that the direction of the first DC magnetic flux and the direction of the second DC magnetic flux in the common column part are reversed from each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, research and development has been conducted on secondary batteries that contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable, and advanced energy. A converter (power conversion device) is required when transmitting power using secondary batteries such as lithium-ion batteries. Lithium-ion batteries have a characteristic in which their open-circuit voltage varies significantly depending on their state of charge. Therefore, converters are required to perform highly efficient power conversion over a wide range of input / output voltage ratios. 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] Converters are required to be compact as well as to perform high-efficiency power conversion over a wide range of input / output voltage ratios. To miniaturize converters, miniaturization of the transformer (transformer unit) is crucial. However, when a boost chopper is used in the primary circuit of a transformer, as proposed in Non-Patent Document 1, DC magnetic flux is generated in the transformer, which places a limit on how much the transformer can be miniaturized by increasing the frequency.

[0005] Therefore, an object of the present invention is to propose a technique that can reduce the DC magnetic flux of a transformer and thereby reduce the size of the transformer. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention provides a transformer unit comprising: a core having a first pillar portion and a second pillar portion; a first transformer having a primary winding and a secondary winding provided on the first pillar portion; and a second transformer having a primary winding and a secondary winding provided on the second pillar portion, wherein the core has a common pillar portion arranged with a gap from at least one of the first pillar portion and the second pillar portion as a common magnetic path for passing a first DC magnetic flux generated by the first transformer and a second DC magnetic flux generated by the second transformer, and the respective windings of the first transformer and the second transformer are provided on the core so that the direction of the first DC magnetic flux and the direction of the second DC magnetic flux at the common pillar portion are opposite to each other. [Effects of the Invention]

[0007] According to the present invention, for example, it is possible to propose a technique that enables the DC magnetic flux of a transformer to be reduced, thereby making it possible to reduce the size of the transformer. [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 schematic diagram illustrating a configuration example of a transformer unit according to a first embodiment; [Figure 3]FIG. 1 is a diagram for explaining a DC magnetic flux and an excitation magnetic flux generated in a core of a transformer unit according to a first embodiment; [Figure 4] A circuit diagram showing a configuration example of a power conversion device according to a second embodiment. [Figure 5] FIG. 10 is a schematic diagram illustrating a configuration example of a transformer unit 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 isolated 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 isolated 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 unit 10 (transformer), 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 this embodiment, an example will be described in which the transformer unit 10 is configured using two-phase transformers 10a to 10b.

[0013] First, the configuration of the transformer unit 10 will be described. The transformer unit 10 of this embodiment includes multiple transformers (first transformer 10a, second transformer 10b). The first transformer 10a includes a primary winding 12a and a secondary winding 13a wound around a first pillar portion 11a of a core 11, which will be described later. The primary winding 12a of the first transformer 10a has a number of turns n pa The first leg LG of the primary circuit 20 pa The secondary winding 13a of the first transformer 10a has a number of turns n sa and the inductor L sa The second leg LG of the secondary circuit 30 sa Similarly, the second transformer 10b includes a primary winding 12b and a secondary winding 13b wound around a second post portion 11b of the core 11, which will be described later. The primary winding 12b of the second transformer 10b has a number of turns npb The first leg LG of the primary circuit 20 pb The secondary winding 13b of the second transformer 10b has a number of turns n sb and the inductor L sb The second leg LG of the secondary circuit 30 sb is connected to.

[0014] Here, each inductor L sa ~L sb is used to prevent a large current from flowing through the secondary circuit 30 by providing a phase difference between the voltages generated by the secondary windings 13a to 13b. sa ~L sb can be set to different values. In the transformer unit 10 of this embodiment, in order to obtain a wide range of input / output voltage ratios, the turns ratio (n sa / n pa , n sb / n pb ) are different from each other, but may be the same. A specific configuration example of the transformer unit 10 will be described later.

[0015] The primary side circuit 20 is a circuit (first circuit) for transmitting power between the primary side windings 12a-12b of each of the transformers 10a-10b and the first device D1. The primary side circuit 20 is provided on the primary side of each of the transformers 10a-10b, and is connected to the primary side windings 12a-12b of each of the transformers 10a-10b and the first device D1 (battery). The primary side circuit 20 of this embodiment is made up of a plurality of first legs LG pa ~LG pb and capacitor C pdc A plurality of first legs LG pa ~LG pb 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 pb are connected in parallel.

[0016] 1st Leg LG pa is the electrical contact J pa Two first switch elements S pa1 ~S pa2 are connected in series, and electrical contact J pa One end of the primary winding 12a of the first transformer 10a is connected to the first device D1. The other end of the primary winding 12a of the first transformer 10a is connected to the first device D1. Similarly, the first leg LG pb is the electrical contact J pb Two first switch elements S pb1 ~S pb2 are connected in series, and electrical contact J pb One end of the primary winding 12b of the second transformer 10b is connected to the line a2. The other end of the primary winding 12b of the second transformer 10b is connected to the first device D1. The terminal of the first device D1 opposite to the terminal connected to the primary windings 12a-12b of each of the transformers 10a-10b is connected to the line a2. The primary circuit 20 configured in this manner can also operate as a boost chopper.

[0017] The secondary side circuit 30 is a circuit (second circuit) for transmitting power between the secondary side windings 13a to 13b of the transformers 10a to 10b and the second device D2. The secondary side circuit 30 is provided on the secondary side of each of the transformers 10a to 10b, and is connected to the secondary side windings 13a to 13b of each of the transformers 10a to 10b and the second device D2. The secondary side circuit 30 of this embodiment is provided on the secondary side of each of the transformers 10a to 10b, and is connected to the secondary side windings 13a to 13b of each of the transformers 10a to 10b and the second device D2. sa ~LG sb and capacitor C sdc and capacitor C sm A plurality of second legs LG sa ~LG sb 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 sb is connected in parallel to the capacitor C sm is the electrical contact J m and line b2, and electrical contact J mThe second device D2 is connected between the line b1 and the line b2, and is connected in series to the secondary windings 13a and 13b of the transformers 10a and 10b via the sa ~LG sb and capacitor C sdc are connected in parallel.

[0018] 2nd Leg LG sa is the electrical contact J sa Two second switch elements S sa1 ~S sa2 are connected in series, and electrical contact J sa One end of the secondary winding 13a of the first transformer 10a is connected to the inductor L sa The other end of the secondary winding 13a of the first transformer 10a is connected to the electrical contact J m (i.e., capacitor C sm Similarly, the second leg LG sb is the electrical contact J sb Two second switch elements S sb1 ~S sb2 are connected in series, and electrical contact J sb One end of the secondary winding 13b of the second transformer 10b is connected to the inductor L sb The other end of the secondary winding 13b of the second transformer 10b is connected to the electrical contact J m (i.e., capacitor C sm (connected to line b2 via

[0019] Here, each first switch element S pa1 ~S pa2 , S pb1 ~S pb2 , and each second switch element S sa1 ~S sa2 , S sb1 ~S sb2 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.

[0020] The control unit 40 controls the first switch elements of the primary side circuit 20 and the second switch elements of the secondary side circuit 30, thereby controlling power transmission (i.e., power conversion) between the first device D1 and the second device D2. 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, and the like. Here, in this embodiment, the control unit 40 is provided as a component of the power conversion device 100A, but this is not limiting, 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.

[0021] Power conversion devices are required to not only convert power efficiently across a wide range of input / output voltage ratios but also to be compact. To achieve this, miniaturization of the transformer unit containing multiple transformers is important. However, when configuring the primary circuit as a boost chopper as described above, DC magnetic flux is generated in each transformer due to the DC current in the primary circuit, which can make miniaturization of the transformer unit difficult. Specifically, because DC magnetic flux is always generated in each transformer in a fixed direction, simply integrating multiple transformers to reduce their size can result in excessive DC bias magnetization, reducing excitation inductance and causing excessive current flow in the circuit, leading to damage to switching elements. Therefore, the transformer unit 10 of this embodiment has a configuration that reduces DC magnetic flux and enables miniaturization.

[0022] An example of the configuration of the transformer unit 10 of this embodiment will be described below. Fig. 2 is a schematic diagram showing an example of the configuration of the transformer unit 10 of this embodiment. Fig. 3 shows a DC magnetic flux M generated in the core 11 of the transformer unit 10 of this embodiment. DCa ~M DCb and the excitation magnetic flux M ACa ~M ACb 3(a) is a diagram for explaining (AC magnetic flux). DCa ~M DCb 3(b) shows the excitation magnetic flux M generated in the core 11. ACa ~M ACb3, the reference numerals of the parts of the core 11 are omitted for ease of viewing, so please refer to FIG. 2 for the reference numerals of the parts of the core 11. Also, in FIGS. 2 and 3, the transformer unit 10 is shown in an XYZ coordinate system in which the direction in which each pillar part of the core 11 extends is the Z direction.

[0023] The transformer unit 10 of this embodiment includes a core 11, a first transformer 10a having a primary winding 12a and a secondary winding 13a, and a second transformer 10b having a primary winding 12b and a secondary winding 13b.

[0024] The core 11 has a plurality of pillar portions (first pillar portion 11a, second pillar portion 11b) and a common pillar portion 11m. The plurality of pillar portions 11a-11b and the common pillar portion 11m are arranged to extend in one direction (Z direction) and are spaced apart from each other. For example, the plurality of pillar portions 11a-11b and the common pillar portion 11m may be arranged approximately parallel to each other. Here, the core 11 is a member for passing magnetic flux (magnetic field) and may be made of a material with high magnetic permeability and low loss. The core 11 may be made of, for example, an iron core, but is not limited to this and may also be made of a magnetic material such as a silicon hard plate, permalloy, or ferrite.

[0025] The first pillar portion 11a of the core 11 is configured as an I-shaped core on which the primary winding 12a and secondary winding 13a of the first transformer 10a are provided. One end 11a1 (end on the +Z direction side) of the first pillar portion 11a is configured to protrude toward one end (end on the +Z direction side) of the common pillar portion 11m and is magnetically coupled to one end of the common pillar portion 11m. The other end 11a2 (end on the -Z direction side) of the first pillar portion 11a is configured to protrude toward the other end (end on the -Z direction side) of the common pillar portion 11m and is magnetically coupled to the other end of the common pillar portion 11m. With this configuration, as shown in FIG. 3(a), the first DC magnetic flux M generated in the first pillar portion 11a by the first transformer 10a (primary winding 12a) DCacan also be passed through the common pillar portion 11m. Here, a gap Ga is provided between one end 11a1 of the first pillar portion 11a and one end of the common pillar portion 11m, and between the other end 11a2 of the first pillar portion 11a and the other end of the common pillar portion 11m. This gap Ga can reduce the influence of excitation magnetic flux (AC magnetic flux) and DC magnetic flux generated by other transformers (for example, the second transformer 10b) on the first transformer 10a.

[0026] In addition, the first columnar portion 11a of this embodiment has a protrusion 11a3 between the portion where the primary winding 12a is provided and the portion where the secondary winding 13a is provided. As shown in FIG. 3(a), this protrusion 11a3 prevents leakage magnetic flux M La Such an inductance is called leakage inductance, and the inductor L connected to the secondary winding 13a of the first transformer 10a functions as an inductance. sa That is, the inductor L sa At least a part of the inductor L can be included in the first pillar portion 11a. Therefore, the leakage inductance obtained by the protrusion 11a3 of the first pillar portion 11a sa This reduces the size of the transformer unit 10, thereby reducing the size of the transformer unit 10. The leakage inductance of the protrusion 11a3 can be changed as desired by adjusting the thickness (width) and length of the protrusion 11a3.

[0027] The second pillar portion 11b of the core 11 is configured as an I-shaped core in which the primary winding 12b and secondary winding 13b of the second transformer 10b are provided, similar to the first pillar portion 11a. One end 11b1 (end on the +Z direction side) of the second pillar portion 11b is configured to protrude toward one end (end on the +Z direction side) of the common pillar portion 11m and is magnetically coupled to one end of the common pillar portion 11m. The other end 11b2 (end on the -Z direction side) of the second pillar portion 11b is configured to protrude toward the other end (end on the -Z direction side) of the common pillar portion 11m and is magnetically coupled to the other end of the common pillar portion 11m. With this configuration, as shown in FIG. 3(a), the second DC magnetic flux M generated in the second pillar portion 11b by the second transformer 10b (primary winding 12b) DCb can also be passed through the common pillar portion 11m. Here, a gap Gb is provided between one end 11b1 of the second pillar portion 11b and one end of the common pillar portion 11m, and between the other end 11b2 of the second pillar portion 11b and the other end of the common pillar portion 11m. This gap Gb can reduce the influence of excitation magnetic flux (AC magnetic flux) and DC magnetic flux generated by other transformers (e.g., the first transformer 10a) on the second transformer 10b.

[0028] Similarly to the first columnar portion 11a, the second columnar portion 11b of this embodiment has a protrusion 11b3 between the portion where the primary winding 12b is provided and the portion where the secondary winding 13b is provided. As shown in FIG. 3(a), this protrusion 11b3 prevents leakage magnetic flux M Lb This inductance (leakage inductance) functions as an inductance. sb That is, the inductor L sb At least a part of the inductor L can be included in the second pillar section 11b. Therefore, the leakage inductance obtained by the protrusion 11b3 of the second pillar section 11b sb This reduces the size of the transformer unit 10, thereby reducing the size of the transformer unit 10. The leakage inductance of the protrusion 11b3 can be changed as desired by adjusting the thickness (width) and length of the protrusion 11b3.

[0029] The common pole portion 11m is magnetically coupled to the first pole portion 11a and the second pole portion 11b. As a result, the common pole portion 11m is axially coupled to the first DC magnetic flux M DCa and the second DC magnetic flux M generated by the second transformer 10b. DCb The gap Ga between the first column portion 11a and the common column portion 11m and the gap Gb between the second column portion 11b and the common column portion 11m may be the same width as the gap Ga between the first column portion 11a and the common column portion 11m and the gap Gb between the second column portion 11b and the common column portion 11m.

[0030] As shown in FIG. 3(a), the windings of the first transformer 10a and the second transformer 10b are connected to the first DC magnetic flux M DCa and the direction of the second DC magnetic flux M DCb The windings of the first transformer 10a (primary winding 12a, secondary winding 13a) on the first pillar portion 11a of the core 11 are opposite to each other. Specifically, the primary winding 12a and secondary winding 13a of the first transformer 10a are provided on the first pillar portion 11a of the core 11 with the same polarity (winding direction). The primary winding 12b and secondary winding 13b of the second transformer 10b are provided on the second pillar portion 11b of the core 11 with the same polarity (winding direction). The winding direction of the windings of the first transformer 10a (primary winding 12a, secondary winding 13a) on the first pillar portion 11a is opposite to the winding direction of the windings of the second transformer 10b (primary winding 12b, secondary winding 13b) on the second pillar portion 11b. As a result, the first DC magnetic flux M DCa and the direction of the second DC magnetic flux M DCb , and the direction of the first DC magnetic flux M can be reversed, thereby reducing the DC magnetic flux in the transformer unit 10. For example, DCa and the second DC magnetic flux MDCb When the magnitudes of the first DC magnetic flux M DCa and the second DC magnetic flux M DCb and cancel each other out.

[0031] On the other hand, the excitation magnetic flux generated in the core 11 for use in power transmission between the first device D1 and the second device D2 can be controlled independently by the first transformer 10a and the second transformer 10b. Specifically, as shown in FIG. 3(b), the excitation magnetic flux M generated (excited) in the first column portion 11a by the first transformer 10a (primary winding 12a) is ACa The direction of the first leg LG of the primary circuit 20 pa The two first switch elements S pa1 ~S pa2 Similarly, the excitation magnetic flux M generated (excited) in the second column portion 11b by the second transformer 10b (primary winding 12b) is ACb The direction of the first leg LG of the primary circuit 20 pb The two first switch elements S pb1 ~S pb2 Therefore, by shifting the phase of the input to the first transformer 10a (primary winding 12a) from the phase of the input to the second transformer 10b (primary winding 12a), the first transformer 10a and the second transformer 10b can be controlled independently.

[0032] As described above, in the transformer unit 10 of this embodiment, the core 11 has the first column portion 11a on which the windings of the first transformer 10a are provided, the second column portion 11b on which the windings of the second transformer 10b are provided, and the common column portion 11m. The common column portion 11m is magnetically coupled to each of the first column portion 11a and the second column portion 11b, and is connected to the first DC magnetic flux M generated by the first transformer 10a. DCa and the second DC magnetic flux M generated by the second transformer 10b. DCb The windings of the first transformer 10a and the second transformer 10b are configured as a common magnetic path for passing the first DC magnetic flux M DCa and the direction of the second DC magnetic flux M DCband the second transformer 10b are provided on the core 11 so that their directions are opposite to each other. This configuration reduces excessive DC bias magnetism due to the DC magnetic flux of each transformer (first transformer 10a, second transformer 10b), making it possible to miniaturize the transformer unit 10 having multiple transformers.

[0033] Second Embodiment A second embodiment of the present invention will now be described. In the above first embodiment, an example in which the transformer unit 10 is configured using two-phase transformers 10a to 10b has been described, but in this embodiment, an example in which the transformer unit 10 is configured using three-phase transformers 10a to 10c 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.

[0034] Fig. 4 is a circuit diagram showing a configuration example of a power conversion device 100B of this embodiment. Fig. 5 is a schematic diagram showing a configuration example of the transformer unit 10 of this embodiment, showing the transformer unit 10 of this embodiment as viewed from above (+Z direction side). Fig. 5(a) shows the DC magnetic flux M generated in the common pole part 11m of the core 11 by each transformer 10a to 10c. DCa ~M DCc 5(b) shows the DC magnetic flux M generated in the common pole portion 11m of the core 11. DCa ~M DCc 5(a) and 5(b), the winding direction of each winding provided on each of the pillar portions 11a to 11c of the core 11 is indicated by a dashed arrow.

[0035] In the power conversion device 100B of this embodiment, the transformer unit 10 is configured by three-phase transformers 10a to 10c. In addition, in the power conversion device 100B of this embodiment, three first legs LG are provided to operate the three-phase transformers 10a to 10c, respectively. pa ~LG pc are provided in the primary side circuit 20, and three second legs LG are provided to operate the three-phase transformers 10a to 10c, respectively. sa ~LG scare provided in the secondary side circuit 30. The following describes elements that are newly added to the power conversion device 100B of this embodiment compared to the power conversion device 100A of the first embodiment.

[0036] The transformer unit 10 further includes a third post portion 11c on the core 11, and further includes a third transformer 10c. The third transformer 10a includes a primary winding 12c and a secondary winding 13c wound around the third post portion 11c of the core 11. The primary winding 12a of the third transformer 10c has a number of turns n pc The first leg LG of the primary circuit 20 pc The secondary winding 13c of the third transformer 10c has n turns. sc and the inductor L sc The second leg LG of the secondary circuit 30 sc 5, the third pillar portion 11c is disposed with a gap between it and the common pillar portion 11m, and is magnetically coupled to the common pillar portion 11m through the gap. As a result, the third DC magnetic flux M generated in the third pillar portion 11c by the third transformer 10c (primary winding 12c) is transmitted to the common pillar portion 11m. DCc It can also be passed through the common pillar section of 11m.

[0037] The third pillar portion 11c may have a configuration similar to that of the first pillar portion 11a and the second pillar portion 11b. Specifically, one end (end on the +Z direction side) of the third pillar portion 11c protrudes toward one end (end on the +Z direction side) of the common pillar portion 11m, and the other end (end on the -Z direction side) protrudes toward the other end (end on the -Z direction side) of the common pillar portion 11m. In addition, the third pillar portion 11c may have a protrusion between the portion where the primary winding 12c is provided and the portion where the secondary winding 13c is provided, the protrusion functioning as an inductance (leakage inductance) due to leakage flux linking each of the primary winding 12c and the secondary winding 13c. In this case, the leakage inductance obtained by the protrusion sc This allows the size of the transformer unit 10 to be reduced.

[0038] The primary circuit 20 includes a first leg LGpc 1st Leg LG pc is the electrical contact J pc Two first switch elements S pc1 ~S pc2 are connected in series, and electrical contact J pc One end of the primary winding 12c of the third transformer 10c is connected to the first device D1. The other end of the primary winding 12c of the third transformer 10c is connected to the first device D1. The secondary circuit 30 is also connected to the second leg LG. sc Second Leg LG sc is the electrical contact J sc Two second switch elements S sc1 ~S sc2 are connected in series, and electrical contact J sc One end of the secondary winding 13c of the third transformer 10c is connected to the inductor L sc The other end of the secondary winding 13c of the third transformer 10c is connected to the electrical contact J m (i.e., capacitor C sm (connected to line b2 via

[0039] In this embodiment, each winding of the third transformer 10c is connected to the third DC magnetic flux M DCc The direction of the first DC magnetic flux M DCa or the direction of the second DC magnetic flux M DCb In the example of FIG. 5, each winding of the third transformer 10c is provided on the core 11 (third pillar portion 11c) so that the direction of the third DC magnetic flux M DCc The direction of the first DC magnetic flux M DCa The direction of the second DC magnetic flux M DCb As a result, the common pole portion 11m is provided with two-phase DC magnetic flux M DCa , M DCc and the DC magnetic flux M for one phase oriented in the +Z direction. DCb These current magnetic fluxes M DCa ~M DCcWhen these are integrated, the DC magnetic fluxes in the opposite directions are reduced, so that the DC magnetic flux in the common pole portion 11m can be reduced. For example, when the DC magnetic flux M DCa ~M DCc Assuming that the magnitudes of the DC magnetic fluxes are the same, as shown in Fig. 5(b), only one phase of DC magnetic flux remains in the common pole portion 11m. In other words, the DC magnetic flux in the transformer unit 10 can be reduced.

[0040] The excitation magnetic flux generated in the core 11 for use in power transmission between the first device D1 and the second device D2 can be controlled independently by each of the transformers 10a to 10c. Specifically, the direction of the excitation magnetic flux generated (excited) in the first column portion 11a by the first transformer 10a (primary winding 12a) is controlled by the first leg LG of the primary circuit 20. pa The two first switch elements S pa1 ~S pa2 The direction of the excitation magnetic flux generated (excited) in the second column portion 11b by the second transformer 10b (primary winding 12b) is periodically reversed by controlling the first leg LG of the primary circuit 20. pb The two first switch elements S pb1 ~S pb2 Similarly, the direction of the excitation magnetic flux generated (excited) in the third column portion 11c by the third transformer 10c (primary winding 12c) is periodically reversed by controlling the first leg LG of the primary circuit 20. pc The two first switch elements S pc1 ~S pc2 Therefore, by shifting the phases of the inputs to the transformers 10a to 10c from one another, the transformers 10a to 10c can be controlled independently. For example, the phases of the inputs to the transformers 10a to 10c are shifted by 60 degrees from one another.

[0041] Here, in the transformer unit 10, the turn ratio between the primary winding and the secondary winding (n sa / n pa , n sb / n pb , n sc / n pc) among the multiple transformers 10a to 10c, highly efficient power conversion can be achieved over a wide range of input / output voltage ratios. When the multiple transformers 10a to 10c have different turn ratios, the magnetic flux of the common pole portion 11m may become saturated when switching the inputs of the multiple transformers 10a to 10c. Therefore, when the second transformer 10b has a larger turn ratio than the first transformer 10a, and the third transformer 10c has a larger turn ratio than the second transformer 10b (i.e., n sa / n pa <n sb / n pb <n sc / n pc In this case, each winding of each transformer 10a to 10c is connected to the second DC magnetic flux M DCb The direction of the first DC magnetic flux M DCa and the third DC magnetic flux M DCc It is preferable that the common post portion 11m is provided in the core 11 so that the direction of the common post portion 11m is opposite to that of the common post portion 11m. This can reduce saturation of the magnetic flux in the common post portion 11m.

[0042] Furthermore, in this embodiment, an example has been described in which the transformer unit 10 has three-phase transformers 10a to 10c, but the same applies when the transformer unit 10 has four or more phase transformers. For example, by reversing the direction of the DC magnetic flux in the common pole portion 11m for at least one of the four or more phase transformers from the direction of the DC magnetic flux in the other transformers, the DC magnetic flux in the transformer unit 10 can be reduced. However, it is desirable that four or more phase transformers be provided in the core 11 so that the DC magnetic flux in the common pole portion 11m is reduced as much as possible. For example, it is desirable to make the number of transformers whose DC magnetic flux direction in the common pole portion 11m is the +Z direction and the number of transformers whose DC magnetic flux direction in the common pole portion 11m is the -Z direction as close as possible.

[0043] As described above, in the power conversion device 100B of this embodiment, which includes three-phase transformers 10a to 10c, as in the power conversion device 100A of the first embodiment, excessive DC bias magnetism due to the DC magnetic flux of each of the transformers 10a to 10c is reduced, making it possible to miniaturize the transformer unit 10 having multiple transformers.

[0044] <Summary of the embodiment> (Item 1) A core (e.g., 11) having a first columnar portion (e.g., 11a) and a second columnar portion (e.g., 11b), a first transformer (e.g., 10a) having a primary winding (e.g., 12a) and a secondary winding (e.g., 13a) provided on the first pillar portion; a second transformer (e.g., 10b) having a primary winding (e.g., 12b) and a secondary winding (e.g., 13b) provided on the second pillar portion; Equipped with The core is connected to a first DC magnetic flux (e.g., M DCa ) and a second DC magnetic flux (e.g., M DCb a common pole portion (for example, 11 m) arranged with a gap from at least one of the first pole portion and the second pole portion as a common magnetic path for passing the first pole portion and the second pole portion together; a transformer unit characterized in that each winding of the first transformer and the second transformer is provided in the core so that the direction of the first DC magnetic flux and the direction of the second DC magnetic flux in the common column portion are opposite to each other. According to this item, excessive DC bias magnetism due to the DC magnetic flux of each transformer is reduced, making it possible to miniaturize a transformer unit having multiple transformers.

[0045] (Item 2) 2. The transformer unit according to claim 1, wherein the winding direction of the first transformer in the first pole section and the winding direction of the second transformer in the second pole section are opposite to each other. According to this item, the DC magnetic flux within the transformer unit can be easily reduced simply by setting the winding direction of the windings of each transformer relative to the core.

[0046] (Item 3) 3. The transformer unit according to item 1 or 2, wherein one end of each of the first pillar portion and the second pillar portion (e.g., 11a1, 11b1) is magnetically coupled to one end of the common pillar portion, and the other end of each of the first pillar portion and the second pillar portion (e.g., 11a2, 11b2) is magnetically coupled to the other end of the common pillar portion. According to this item, each pole part on which the windings of each transformer are provided can be magnetically coupled to a common pole part.

[0047] (Item 4) The transformer unit described in item 3 is characterized in that the gaps (e.g., Ga, Gb) are provided between one end (e.g., 11a1, 11b1) of at least one of the first pillar portion and the second pillar portion and one end of the common pillar portion, and between the other end (e.g., 11a2, 11b2) of the one of the first pillar portion and the second pillar portion and the other end of the common pillar portion. According to this item, the influence of the excitation magnetic flux and the DC magnetic flux generated by other transformer units can be reduced.

[0048] (Item 5) 5. The transformer unit according to any one of items 1 to 4, wherein each of the first pillar portion and the second pillar portion has a protrusion (e.g., 11a3, 11b3) between a portion around which the primary winding is wound and a portion around which the secondary winding is wound, to function as a leakage inductance. According to this item, the leakage inductance obtained from the protrusion acts as part of the inductor connected in series to the secondary winding of each transformer, thereby making it possible to miniaturize the inductor and, ultimately, the transformer unit.

[0049] (Item 6) 6. A transformer unit according to any one of items 1 to 5, characterized in that the first transformer and the second transformer have different turn ratios between the primary winding and the secondary winding. According to this item, a transformer unit having a wide range of input / output voltage ratios is provided.

[0050] (Item 7) The core further includes a third pillar portion (e.g., 11c), The transformer unit further includes a third transformer (e.g., 10c) having a primary winding (e.g., 12c) and a secondary winding (e.g., 13c) provided on the third pole portion, The common pillar portion is configured to transmit a third DC magnetic flux (e.g., M DCc ) is arranged with a gap between it and the third pillar portion so that it can pass through, 7. The transformer unit according to any one of items 1 to 6, wherein each winding of the third transformer is provided in the core so that the direction of the third DC magnetic flux in the common pole portion is opposite to the direction of the first DC magnetic flux or the direction of the second DC magnetic flux. According to this item, in a transformer unit having three or more phase transformers, excessive DC bias magnetism due to the DC magnetic flux of each transformer is reduced, making it possible to reduce the size of the transformer unit.

[0051] (Item 8) a turns ratio between a primary winding and a secondary winding of the second transformer is larger than that of the first transformer, and is also larger than that of the third transformer; 8. The transformer unit according to item 7, wherein the windings of the first transformer, the second transformer, and the third transformer are provided on the core so that the direction of the second DC magnetic flux is opposite to the directions of the first DC magnetic flux and the third DC magnetic flux in the common column portion. According to this item, it is possible to reduce saturation of magnetic flux in the common pillar portion 11m.

[0052] (Item 9) 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), 9. A power conversion device comprising the transformer unit according to any one of items 1 to 8. According to this item, a power conversion device that can be made smaller is provided.

[0053] 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]

[0054] 10a to 10c: transformer, 11: core, 11a to 11c: pole section, 11m: common pole section, 12a to 12c: primary winding, 13a to 13c: secondary winding, 20: primary circuit (first circuit), 30: secondary circuit (second circuit), 40: control section, 100A, 100B: power conversion device

Claims

1. a core having a first columnar portion and a second columnar portion; a first transformer having a primary winding and a secondary winding provided on the first pillar portion; a second transformer having a primary winding and a secondary winding provided on the second pillar portion; Equipped with the core has a common pillar portion disposed with a gap from at least one of the first pillar portion and the second pillar portion, as a common magnetic path through which a first DC magnetic flux generated by the first transformer and a second DC magnetic flux generated by the second transformer commonly pass, a transformer unit characterized in that each winding of the first transformer and the second transformer is provided on the core so that the direction of the first DC magnetic flux and the direction of the second DC magnetic flux in the common column portion are opposite to each other.

2. 2. The transformer unit according to claim 1, wherein the winding direction of the first transformer in the first column section and the winding direction of the second transformer in the second column section are opposite to each other.

3. 2. The transformer unit of claim 1, wherein one end of each of the first and second pillars is magnetically coupled to one end of the common pillar, and the other end of each of the first and second pillars is magnetically coupled to the other end of the common pillar.

4. The transformer unit according to claim 3, characterized in that the gap is provided between one end of at least one of the first column portion and the second column portion and one end of the common column portion, and between the other end of the one of the first column portion and the second column portion and the other end of the common column portion.

5. 2. The transformer unit according to claim 1, wherein each of the first pillar portion and the second pillar portion has a protrusion between a portion around which the primary winding is wound and a portion around which the secondary winding is wound, the protrusion functioning as a leakage inductance.

6. 2. The transformer unit according to claim 1, wherein the first transformer and the second transformer have different turn ratios between the primary winding and the secondary winding.

7. The core further includes a third pillar portion, the transformer unit further includes a third transformer having a primary winding and a secondary winding provided on the third pole portion; the common pillar portion is disposed with a gap between it and the third pillar portion so as to pass a third DC magnetic flux generated by the third pillar portion; 2. The transformer unit according to claim 1, wherein each winding of the third transformer is provided on the core so that the direction of the third DC magnetic flux in the common column portion is opposite to the direction of the first DC magnetic flux or the direction of the second DC magnetic flux.

8. a turns ratio between a primary winding and a secondary winding of the second transformer is larger than that of the first transformer, and is also larger than that of the third transformer; 8. The transformer unit according to claim 7, wherein the windings of the first transformer, the second transformer, and the third transformer are provided on the core so that the direction of the second DC magnetic flux is opposite to the directions of the first DC magnetic flux and the third DC magnetic flux in the common column portion.

9. A power conversion device that performs power conversion between a first device and a second device, A power conversion device comprising the transformer unit according to any one of claims 1 to 8.

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