Transformers and Power Converters

Abstract

To obtain a transformer having high heat dissipation.SOLUTION: A transformer 3 includes: a core that forms a magnetic circuit; and a primary winding 3a and secondary windings 3b, 3d wound about the core. Each of the primary winding 3a and secondary windings 3b, 3d has at least one winding member. One of the winding members constituting the primary winding 3a or the secondary windings 3b, 3d having a smaller number of turns is provided on one of outermost layers in a direction of a winding axis 100. A metallic plate 40 is provided on the other of the outermost layers in the direction of the winding axis.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Electrically powered vehicles that use a motor as a drive source, such as electric vehicles or hybrid vehicles, are equipped with multiple power converters. Examples of power converters include a charger that converts commercial AC power into DC power to charge a high-voltage battery, a DC / DC converter that converts the DC power of the high-voltage battery into a voltage (e.g., 12 V) for a battery for auxiliary equipment, and an inverter that converts DC power from the battery into AC power for the motor. In recent years, with the spread of electric vehicles and the expansion of vehicle interior space, there has been a demand for smaller and less expensive power converters.

[0003] As a transformer used in a power converter, for example, a transformer has been disclosed that has a core that forms a magnetic circuit, a primary winding on the high-voltage side, and a secondary winding on the low-voltage side, with the primary winding and secondary winding arranged coaxially in layers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-207919 Summary of the Invention [Problem to be solved by the invention]

[0005] When a transformer operates, current flows through its primary and secondary windings, generating heat. To counter this heat, transformers are fixed to a metal case, which provides a heat dissipation path from the transformer's exterior. However, it is difficult to provide an even heat dissipation path on all of the transformer's exterior surfaces, which hinders miniaturization. Furthermore, in transformers in which the primary and secondary windings are divided into multiple pieces and stacked coaxially, it is difficult to dissipate heat from windings located on layers far from the heat dissipation surface. Windings with a large number of turns in particular generate high heat density, making heat dissipation even more difficult.

[0006] The present application discloses a technique for solving the above-mentioned problems, and has an object to provide a transformer and a power conversion device with high heat dissipation properties. [Means for solving the problem]

[0007] Book Disclosure Lance is A transformer comprising a core that forms a magnetic circuit, and a primary winding and a secondary winding wound around the core, the primary winding and the secondary winding each include at least one winding member; one of the winding members constituting the primary winding or the secondary winding with the fewer number of turns is provided on one of the outermost layers in the winding axis direction, a transformer having a laminated arrangement in which a metal plate is provided on the other of the outermost layers in the winding axis direction, the winding member of the lowermost layer of the primary winding or the secondary winding having the fewer number of turns is connected to at least a part of the metal plate; A portion of the primary winding or secondary winding with the fewer turns is connected in parallel with the metal plate to form one winding. It is something. Book Disclosure a force transducer including the transformer; Through the transformer It transmits power from the primary circuit to the secondary circuit. [Effects of the Invention]

[0008] According to the transformer disclosed in the present application, a transformer with high heat dissipation properties can be obtained. According to the power conversion device disclosed in the present application, a power conversion device with high heat dissipation properties can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram of a power conversion device according to a first embodiment. [Figure 2] 1 is a perspective view showing the configuration of a transformer according to a first embodiment. [Figure 3] 1 is a perspective development view showing the configuration of a winding of a transformer according to Embodiment 1. FIG. [Figure 4] 1 is a perspective view showing a configuration of a primary winding of a transformer according to a first embodiment. [Figure 5] 1 is a perspective view showing a configuration of a primary winding of a transformer according to a first embodiment. [Figure 6] 2 is a perspective view showing the configuration of a secondary winding of the transformer according to the first embodiment. FIG. [Figure 7] 2 is a perspective view showing the configuration of a secondary winding of the transformer according to the first embodiment. FIG. [Figure 8] 2 is a perspective view showing a configuration of a metal plate of the transformer according to the first embodiment. FIG. [Figure 9] 3A and 3B are explanatory diagrams illustrating a configuration of a resin part of the transformer according to the first embodiment. [Figure 10] 10A and 10B are cross-sectional views illustrating the configuration of the transformer according to embodiment 1. [Figure 11] FIG. 10 is a perspective development view showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 12] FIG. 10 is a perspective development view showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 13] FIG. 10 is a circuit diagram showing a modified example of the secondary side circuit of the power conversion device according to the second embodiment. [Figure 14] FIG. 10 is a perspective development view showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 15] FIG. 10 is a perspective development view showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 16] FIG. 10 is a circuit diagram showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 17] FIG. 10 is a circuit diagram showing a modified example of the secondary side circuit of the power conversion device according to the second embodiment. [Figure 18] FIG. 10 is a circuit diagram showing a modified example of the winding configuration of the transformer according to the second embodiment. [Figure 19]FIG. 10 is a perspective development view showing a modified example of the winding configuration of the transformer according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 Embodiment 1 relates to a transformer having a core forming a magnetic circuit and a primary winding and a secondary winding wound around the core, in which the primary winding and secondary winding each have at least one flat winding member, and one of the winding members constituting the secondary winding with a smaller number of turns is provided on one of the outermost layers in the winding axis direction, and a metal plate is provided on the other outermost layer in the winding axis direction, and a power conversion device including this transformer.

[0011] The configuration and operation of a power conversion device equipped with a transformer according to embodiment 1 will be described below with reference to Figure 1, which is a circuit diagram of the power conversion device, Figure 2, which is a perspective view showing the configuration of the transformer, Figure 3, which is a perspective development view showing the configuration of the transformer windings, Figures 4 and 5, which are perspective views showing the configuration of the primary winding of the transformer, Figures 6 and 7, which are perspective views showing the configuration of the secondary winding of the transformer, Figure 8, which is a perspective view showing the configuration of the metal plate of the transformer, Figure 9, which is an explanatory diagram of the configuration of the resin part of the transformer, and Figure 10, which is a cross-sectional view explaining the configuration of the transformer. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted.

[0012] First, the overall configuration of a power conversion device 10 according to the first embodiment will be described with reference to FIG. 1, which is a circuit configuration diagram of the power conversion device 10. As shown in FIG. The power conversion device 10 includes a DC power supply 1, an inverter 2, a transformer 3, a rectifier circuit 4, a smoothing reactor 5, and a smoothing capacitor 6, and has a load 7 connected to the output.

[0013] The power conversion device 10 converts a DC voltage Vin of a DC power supply 1 into a secondary side DC voltage insulated by a transformer 3, and outputs a DC voltage Vout to a load 7 such as a battery. The insulated transformer 3 includes a primary winding 3a and secondary windings 3b and 3d. The inverter 2 is a single-phase inverter that is connected to the primary winding 3a of the transformer 3 and has a full-bridge configuration of semiconductor switching elements 2a, 2b, 2c, and 2d, each of which is a metal-oxide-semiconductor field-effect transistor (MOSFET) with a diode built in between its source and drain, to convert the DC voltage Vin of the DC power supply 1 into an AC voltage. The rectifier circuit 4 includes diodes 4a and 4b as rectifier elements (semiconductor elements) connected to the secondary windings 3b and 3d of the transformer 3. A smoothing reactor 5 and a smoothing capacitor 6 are connected to the output of the rectifier circuit 4 , and a DC voltage Vout is output to a load 7 .

[0014] The transformer 3 has a center-tapped secondary side, and the center-tap terminal 3e is connected to GND. The secondary side terminals other than the center-tap terminal 3e are connected to the anode terminals of diodes 4a and 4b, respectively, and the cathode terminals of the diodes 4a and 4b are connected to a smoothing reactor 5.

[0015] Although a DC / DC converter with a center tapped secondary side has been described as an example of the power conversion device 10, the secondary side may have a full-bridge configuration. Also, although an example of a DC / DC converter with a full-bridge primary side has been described, any isolated converter with an isolation transformer, such as a forward type, flyback type, or LLC type, may be used. Although the semiconductor switching elements 2a, 2b, 2c, and 2d are MOSFETs in the example shown, they may be self-extinguishing semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors) with diodes connected in antiparallel.

[0016] For ease of understanding, the transformer 3 according to the first embodiment is an example in which the power conversion device 10 is a step-down DC / DC converter, and voltage is stepped down according to the turns ratio between the primary winding 3a and the secondary windings 3b and 3d. The voltage input to the primary winding 3a is stepped down and output from the secondary windings 3b and 3d. That is, the number of turns of the secondary windings 3b and 3d is smaller than that of the primary winding 3a. Furthermore, by stepping down the voltage in the transformer 3, the voltage of the secondary windings 3b and 3d decreases while the current increases.

[0017] Next, the configuration of the transformer 3 according to the first embodiment will be described with reference to FIG. 2, which is a perspective view showing the configuration of the transformer 3. In the description of the present application, as shown in the drawing, the direction of winding axis 100 of transformer 3 is defined as the z direction, and two directions that are perpendicular to the z direction and perpendicular to each other are defined as the x direction and the y direction. The clockwise or counterclockwise rotation of the primary winding 3a and secondary windings 3b and 3d, which will be explained later, is determined by looking from the minus side to the plus side of the z-axis. Furthermore, the reference numerals of each component are generally assigned from the negative side to the positive side of the z-axis (increasing the number).

[0018] The transformer 3 is an example of a planar shape made of laminated metal sheets, and includes a lower core 11, an upper core 12, and a winding 13, which form a magnetic circuit. Note that Fig. 2 also shows a cooler 14 (only the cooler 14 attached to the transformer 3 is shown), which is closely related to the configuration and function of the transformer 3.

[0019] The transformer 3 is constructed by assembling the lower core 11 and the upper core 12 to the winding body 13. After assembling, the lower core 11 and the upper core 12 may be fixed with, for example, heat-resistant tape or adhesive. The transformer 3 is assembled into a housing equipped with a cooler 14 together with other components (not shown) that constitute the power conversion device 10, thereby forming the power conversion device 10. The method of assembling the cooler 14 is, for example, by fixing it using screws and springs.

[0020] 2 shows an example in which the lower core 11 and the upper core 12 are configured by combining the same E-shaped cores. However, different shapes may be combined, for example, an E-shaped core and an I-shaped core. The lower core 11 is composed of a flat plate-shaped abdomen 111, and a middle leg 112 and outer leg portions 113 and 114 protruding from the abdomen 111. The upper core 12 is composed of a flat plate-shaped abdomen 121, and a middle leg 122 and outer leg portions 123 and 124 protruding from the abdomen 121. The center leg 112 (122) and outer leg portions 113, 114 (123, 124) are formed so as to protrude from the abdomen 111 (121) in the thickness direction of the abdomen. The lower core 11 and the upper core 12 are assembled so that their protruding surfaces butt against each other. The cross-sectional shape of the butting surfaces may be square or rectangular. A magnetic material such as ferrite is used as the material.

[0021] The configurations of the primary winding 3a, the secondary windings 3b and 3d, and the metal plate 40 will be described with reference to FIG. 3, which is a perspective development view showing the configuration of the windings of the transformer. In the transformer 3, the primary winding 3a and the secondary windings 3b, 3d are arranged in a stacked configuration, and a metal plate 40 is also arranged in a stacked configuration. A sealing resin that can ensure the necessary insulating performance is applied to fill the gaps between the windings and the metal plate 40 and to cover the outer periphery, and a part or all of the windings are sealed with sealing resin to form the winding body 13. The sealing of the primary winding 3a, the secondary windings 3b, 3d, and the metal plate 40 with sealing resin will be described later.

[0022] The primary winding 3a, secondary windings 3b and 3d, and metal plate 40 are formed by winding a metal plate in a circular or spiral shape. For example, copper or aluminum plates are used as materials. The primary winding 3a, which has a large number of turns, may be made of an insulated winding. An insulated winding is a linear conductor insulated by an insulating layer, and may be made of, for example, magnet wire.

[0023] The primary winding 3a is composed of a first primary winding 21 and a second primary winding 22. In Fig. 3, the first primary winding 21 and the second primary winding 22 are each composed of a single layer, but each may be composed of multiple layers. Here, each of the secondary windings 3b and 3d is made up of one winding member, but may be made up of multiple winding members. The first primary winding 21, the second primary winding 22, and the secondary windings 3b and 3d are stacked in the order of the first primary winding 21, the secondary winding 3d, and the second primary winding 22, with the secondary winding 3b having the fewest number of turns being the bottom layer, starting from the negative Z-axis side, so that the primary windings and secondary windings overlap each other alternately.

[0024] The metal plates 40 are stacked so that the second primary winding 22, one of the primary windings 3a with the larger number of turns, is sandwiched between the secondary winding 3d, one of the secondary windings with the smaller number of turns. Furthermore, the metal plates 40 are arranged in the uppermost layer in the winding axis direction, and are arranged so as to sandwich the secondary winding 3b, which is arranged in the lowermost layer, and the other windings. The arrangement order of the layers is an example, and other arrangements may be used. If P is the primary winding and S is the secondary winding, the transformer configuration in Figure 3 corresponds to SPSP.

[0025] The primary winding 3a, secondary windings 3b and 3d, and metal plate 40 are configured so that the external dimensions of the windings in the x and y directions, which will be described later, are uniform. Note that uniform external dimensions allow for errors within the dimensional tolerances of each winding.

[0026] The configuration of the primary winding 3a will be described with reference to FIGS. 4 and 5, which are perspective views showing the configuration of the primary winding of the transformer. The first primary winding 21 constituting the primary winding 3a has a winding part 211 formed by winding in a circular or spiral shape, an inner winding end 212, and an outer winding end 213. The second primary winding 22 has a winding part 221 formed by winding in a circular or spiral shape, an inner winding end 222, and an outer winding end 223. The cross section of each of the primary windings 21 and 22 is formed into a substantially rectangular shape having long and short sides, with the long sides facing each other. The cross-sectional shape of the primary windings 21, 22 may be formed into a substantially elliptical shape. For example, when they are made of magnet wire, they may be formed into a round cross-section as is, or they may be formed into a substantially elliptical shape by pressing or the like so that long and short sides are formed, and the surfaces facing each other are the long sides.

[0027] Each winding portion 211, 221 has an extension portion 214, 224 extending outward from the outermost portion of the winding portion. The extension portion 214, 224 is formed integrally with the outermost winding portion. The extension portion 214, 224 is formed so that its outer shape matches that of extension portions 313, 323 of the secondary windings 3b, 3d, which will be described later. As long as the outer shapes are matched, the shape and position may be changed as desired. For example, as shown in FIG. 5, the extension portion can be set as desired using a first primary winding 21A and a second primary winding 22A that do not have the extension portion 214, 224.

[0028] An inner end 212 of the first primary winding 21, which is closer to the winding axis 100, has a bent structure toward the second primary winding 22, while an inner end 222 of the second primary winding 22 does not have a bent structure toward the first primary winding 21. The bent structure may be changed as desired. For example, both ends may have a bent structure.

[0029] The outer ends 213, 223 of the first primary winding 21 and the second primary winding 22, which are located farther from the winding axis, have a bent structure. The bent structure may be changed as desired. The inner end 212 of the first primary winding 21 and the inner end 222 of the second primary winding 22 are connected, for example by welding, to the first primary winding 21 so that the second primary winding 22 is connected in series to the first primary winding 21, thereby forming the primary winding 3a.

[0030] The primary winding 3a is made up of a first primary winding 21 and a second primary winding 22, which are wound in opposite directions. The first primary winding 21 is spirally wound clockwise around the winding axis 100, from the side farther from the winding axis 100 to the side closer to the winding axis 100. The second primary winding 22 is spirally wound counterclockwise from the side farther from the winding axis 100 to the side closer to the winding axis 100. In this way, the primary winding 3a is formed by combining windings formed by winding in opposite directions. In other words, when the first primary winding 21 and the second primary winding 22 are connected, they become a single series-connected winding that rotates in the same direction, forming the primary winding 3a. The configuration of the primary winding 3a is one example, and other configurations are also possible. Here, the first primary winding 21 corresponds to a first winding member, and the second primary winding 22 corresponds to a second winding member.

[0031] The first primary winding 21 and the second primary winding 22 according to the first embodiment have the same number of turns, 4. The first primary winding 21 and the second primary winding 22 are connected in series to form a primary winding 3a with 8 turns. In this way, the first primary winding 21 and the second primary winding 22 are configured with the same number of turns, and by combining them, it is possible to create a desired number of turns for the primary winding 3 a. Note that, as will be explained later, the number of turns is not limited to an even number or an integer.

[0032] Secondary windings 3b and 3d will be described with reference to FIGS. 6 and 7, which are perspective views showing the configuration of the secondary windings of the transformer. Secondary winding 3b is formed by winding part 31 formed by winding in a circular or spiral shape, end 311 closer to winding axis 100, and end 312 farther from winding axis 100. Secondary winding 3d is formed by winding part 32 formed by winding in a circular or spiral shape, end 321 closer to winding axis 100, and end 322 farther from winding axis 100. Here, the secondary windings 3b and 3d are each composed of one winding member, but may be composed of multiple winding members. The cross-sectional shape of the winding portions 31 and 32 is formed as a substantially rectangular shape having long and short sides. The secondary windings 3b and 3d are formed so that the surfaces facing each other are the long sides. For example, "end 311 closer to winding axis 100" will be referred to as "end 311" as appropriate.

[0033] The winding portions 31, 32 of the secondary windings 3b, 3d are formed with extensions 313, 323 extending outward from the outermost portion of the winding portion. The extensions 313, 323 are formed integrally with the outermost winding portion. The extensions 313, 323 are formed to have the same outer shape as the extensions 214, 224 of the primary winding 3a. As long as the outer shapes are the same, the shape and position may be changed as desired. For example, as shown in FIG. 7, the extensions can be set as desired using secondary windings 3bA, 3dA that do not have the extensions 313, 323.

[0034] Ends 311 and 321 of secondary windings 3b and 3d, respectively, closer to winding axis 100 have a bent structure. The bent structure may be changed as desired. Similarly, ends 312 and 322 of secondary windings 3b and 3d, respectively, farther from winding axis 100 also have a bent structure. Ends 311 and 321 of secondary windings 3b and 3d that are closer to winding axis 100 are connected by welding, for example, and are formed so that their heights in the Z direction are the same when connected.

[0035] Additionally, the secondary winding 3d, which is the upper layer of the secondary winding, is formed with connecting portions 324 and 325. The connecting portions 324 and 325 are formed so as to protrude outward from the winding portion 32, have a bent structure, and extend so that their ends are parallel to the secondary winding 3d. The connecting portion 324 is connected to the cooler 14 via a heat dissipation member (not shown). In the first embodiment, the connecting portion 325 is directly connected to the cooler 14 using, for example, a screw. That is, it becomes the center tap terminal 3e in FIG. 1 and is connected to the cooler 14 as a GND. That is, the connecting portion 325 is used both for the GND connection and for fixing the transformer 3 to the cooler 14. The shapes, positions, and numbers of the connecting portions 324 and 325 may be changed as desired. The thickness of the secondary windings 3b and 3d in the Z direction is greater than the thickness of the primary winding 3a, that is, the secondary windings 3b and 3d are formed to have a larger cross-sectional area than the primary winding 3a. The number of turns of each of the secondary windings 3b and 3d according to the present embodiment 1 is 1. As will be described later, the secondary windings 3b and 3d may be connected in series without providing a center tap terminal.

[0036] Next, the metal plate 40 will be described with reference to FIG. 8, which is a perspective view showing the configuration of the metal plate of the transformer. Metal plate 40 includes a winding portion 41 formed by winding in a circular shape, and connecting portions 42, 43, and 44. Connecting portions 42, 43, and 44 are formed so as to protrude outward from winding portion 41, have a bent structure, and extend so that their ends are parallel to metal plate 40. The shape, position, and number of connecting portions 42, 43, and 44 may be changed as desired. Winding section 41 has a notch 45 formed therein that extends from the side closer to winding axis 100 toward the outside so as to have a substantially C-shape. It is sufficient that notch 45 is formed so as to prevent communication between winding portions 41. For example, winding portion 41 may be divided into two parts, and metal plate 40 may be formed from a plurality of parts. The shape and position of notch 45 may be changed as desired, as long as it prevents communication between winding portions 41.

[0037] Furthermore, since metal plate 40 has no electrical connections and no current flows through it, connecting portions 42, 43, and 44 are directly connected to cooler 14. For example, they are fixed using screws. That is, connecting portions 42, 43, and 44 also share the same metal fittings as those used to fix transformer 3 to cooler 14.

[0038] Next, the configuration of the sealing resin will be described with reference to FIG. 9, which is an explanatory diagram of the configuration of the resin portion of the transformer. The sealing resin is formed so as to fill gaps in the lamination direction between the primary winding 3a, secondary windings 3b, 3d and metal plate 40, and to cover the outer periphery so as to ensure the necessary insulating performance. For example, a thin plate-shaped resin (not shown) may be prepared to fill the gaps between the primary winding 3a, the secondary windings 3b, 3d, and the metal plate 40, and placed between each layer to form a stacked configuration, with the outer periphery covered with another resin. Part of each of the surfaces of connecting portions 324 and 325 formed on secondary windings 3b and 3d that come into contact with heat dissipation member or cooler 14 is exposed from the sealing resin. Also, part of each of the surfaces of connecting portions 42, 43, and 44 formed on metal plate 40 that come into contact with heat dissipation member or cooler 14 is exposed from the sealing resin. In other words, part of the surface that serves as the heat dissipation surface of transformer 3 is exposed. In FIG. 9, the shaded area including secondary winding 3b represents the part that is exposed from the sealing resin.

[0039] The laminated structure of winding body 13 will be described with reference to FIGS. 10A and 10B, which are cross-sectional views illustrating the structure of the transformer. 10A and 10B explain the relationship in height between the surfaces that serve as heat dissipation surfaces of the primary winding 3a, secondary windings 3b and 3d, and metal plate 40. Note that FIG. 10A corresponds to the cross section AA in FIG. 9, and FIG. 10B corresponds to the cross section BB in FIG. 9. 10A and 10B show the relationship between secondary winding 3b of winding body 13, winding portion 211 of primary winding 3a, secondary winding 3d, winding portion 221 of primary winding 3a, and metal plate 40 in the up-down direction.

[0040] 9, connection portions 324 (not shown) and 325 of secondary winding 3d and connection portions 42, 43, and 44 of metal plate 40 are formed so as to be partially exposed from the sealing resin. The surfaces of connection portion 325 of secondary winding 3d and connection portions 42, 43, and 44 of metal plate 40, which are also used to fix transformer 3, are formed to be on the same plane. Furthermore, the surfaces of the connection portions 324 of the secondary windings 3b and 3d, which are connected to the cooler 14 via the heat dissipation member, are formed to be flush with each other. That is, the cooler 14 is formed so that a gap 60 is formed between the surface that serves as the fixing surface of the transformer 3 and the surface that is connected via the heat dissipation member. The thickness of the gap 60 in the Z direction is set to be equal to or smaller than the thickness of the secondary windings 3b and 3d.

[0041] Here, the effects of the first embodiment will be described. The transformer 3 includes a first primary winding 21 and a second primary winding 22 that constitute the primary winding 3a, secondary windings 3b and 3d, and a metal plate 40, which are stacked in the following order: the secondary winding 3b is the bottom layer, the first primary winding 21, the secondary winding 3d, the second primary winding 22, and the metal plate 40 as the top layer. The first primary winding 21 and the second primary winding 22 have a large number of turns, which makes the heat density high and makes it difficult to dissipate heat. However, the first primary winding 21 can dissipate heat efficiently by being sandwiched between the secondary windings 3b and 3d, each of which has a heat dissipation path. Furthermore, the second primary winding 22 is sandwiched between the secondary winding 3d and the metal plate 40, which also have heat dissipation paths, and thus can dissipate heat efficiently. In other words, the second primary winding 22 has high heat dissipation properties, and the transformer 3 can be made smaller.

[0042] The effect of stacking the primary and secondary windings so that they alternately overlap each other on the proximity effect that causes bias in current density will be explained below. Proximity effect is a phenomenon in which, when current flows through the primary and secondary windings, the magnetic fields emitted by both windings cause the current to concentrate in areas close to each other if the current directions are opposite, and conversely, causes the current to concentrate in areas farther apart if the current directions are the same, creating a bias in the current density and increasing the resistance value. In the configuration of the transformer 3 according to the first embodiment, the primary winding 3a and the secondary windings 3b, 3d are stacked and arranged so as to alternately overlap, which increases the number of surfaces of the primary winding 3a and the secondary windings 3b, 3d that face each other, thereby suppressing bias in current density due to proximity effect. In other words, bias in current density can be suppressed more effectively than when the primary winding 3a and the secondary windings 3b, 3d are not stacked and arranged so as to alternately overlap. This reduces losses in the transformer 3 and allows the transformer 3 to be made smaller.

[0043] Next, the characteristics of the secondary windings 3b and 3d will be described. One of the secondary windings, secondary winding 3b, which has a low voltage but a high current, is arranged on the lowest layer. As a result, the insulation distance required for secondary winding 3b is smaller than that for primary winding 3a, which has a high voltage, so there is no need to ensure insulation with sealing resin, which makes heat dissipation difficult. In addition, there is no need to use an expensive, special heat dissipation member with high insulating performance; the secondary winding can be exposed from the heat dissipation resin and directly abutted against the heat dissipation member to dissipate heat to cooler 14. In other words, the secondary winding, which has a high current and high loss, can efficiently dissipate heat.

[0044] The thickness of the secondary windings 3b and 3d in the Z direction is greater than that of the primary winding 3a. In other words, the cross-sectional area of ​​the secondary windings is greater than that of the primary winding. This allows for efficient diffusion of heat in the planar direction, enabling efficient heat dissipation from the secondary windings 3b and 3d, which carry a large current. Furthermore, this serves as a heat dissipation path for the primary winding 3a, allowing efficient heat dissipation from the primary winding 3a, which has a large number of turns and is difficult to dissipate heat from.

[0045] The secondary winding 3d has a connection part 324 connected to the cooler 14 via a heat dissipation member and a connection part 325 connected to GND as a circuit configuration (i.e., directly connected to the cooler 14). This allows for efficient heat dissipation from both the secondary winding 3d and the primary winding 3a, which has a large number of turns and is difficult to dissipate heat from. Furthermore, by using the connection part 325 both for GND connection and for fixing the transformer 3, a GND circuit can be configured without providing a separate component.

[0046] Next, the features of the metal plate 40 will be described. The metal plate 40, which has no electrical connection and through which no current flows, is arranged on an adjacent layer to the second primary winding 22 that constitutes the primary winding 3a, and is sandwiched between the second primary winding 22 and the secondary winding 3d, and is directly connected to the cooler 14. As a result, the primary winding 3a, which has a large number of turns and is difficult to dissipate heat, is sandwiched between the metal plate 40 and the secondary windings 3b and 3d, each of which has its own heat dissipation path, and the primary winding 3a can dissipate heat efficiently through each of them.

[0047] Metal plate 40 has connecting portions 42, 43, and 44. This allows it to be in direct contact with cooler 14, enabling efficient heat dissipation from primary winding 3a. Also, by sharing the fixing of transformer 3, there is no need to prepare a separate member. The metal plate 40 has a notch 45 formed in the winding portion 41. This makes it possible to prevent the generation of an induced current due to the magnetic field from the primary winding 3a and the secondary windings 3b and 3d, that is, a so-called one-turn short circuit. Metal plate 40 is disposed on the top layer. As a result, metal plate 40 is directly connected to cooler 14 and is at GND potential, allowing the upper surface of the portion of metal plate 40 that overlaps upper core 12 to be exposed. In other words, the thickness of winding body 13 including metal plate 40 in the z direction can be reduced, thereby reducing the thickness of outer legs 113, 114, 123, and 124 of lower core 11 and upper core 12. As a result, the height of transformer 3 can be reduced.

[0048] Next, the winding of the primary winding 3a and the secondary windings 3b and 3d will be described. Primary winding 3a is configured by combining first primary winding 21, which is wound in a clockwise spiral shape from the side farther from winding axis 100 to the side closer to winding axis 100, with second primary winding 22, which is wound in a counterclockwise spiral shape from the side farther from winding axis 100 to the side closer to winding axis 100. This makes it easy to configure a single series-connected winding by connecting the ends closer to winding axis 100. In the above description, an example has been given in which one winding is constructed by connecting the ends closer to winding axis 100, but the ends connected to construct one winding may also be those farther from winding axis 100.

[0049] Secondary windings 3b and 3d are configured by combining secondary winding 3b, which is spirally wound clockwise from the side far from winding axis 100 to the side near to it, with secondary winding 3d, which is spirally wound counterclockwise from the side far from winding axis 100 to the side near to it, thereby making it easy to configure a center tap circuit.

[0050] Next, the extensions of the primary winding 3a and the secondary windings 3b and 3d will be described. In the primary winding 3a, extension portions 214 and 224 extending outward from the outermost shapes of the winding portions 211 and 221 are formed integrally with the winding portions 211 and 221. In addition, in the secondary windings 3b and 3d, extension portions 313 and 323 extending outward from the outermost shapes of the winding portions 31 and 32 are formed integrally with the winding portions 31 and 32. This allows the heat generated outside the winding portions to be efficiently diffused and dissipated in the planar direction.

[0051] Next, the cross-sectional shapes of the primary winding 3a and the secondary windings 3b and 3d will be described. The cross-sectional shape of the primary winding 3a and the secondary windings 3b and 3d is a rectangle with long and short sides, and the opposing surfaces of adjacent winding layers are formed so that they face the long sides, and the opposing surfaces of the winding parts are formed to be the same size. By making the cross-sectional shape of the primary winding 3a and secondary windings 3b and 3d rectangular, the effect of the so-called skin effect (current moving closer to the surface of the conductor) can be reduced, and the increase in loss can be suppressed.

[0052] Next, the fixing of the transformer 3 and the cooler 14 will be described. A gap 60 is formed between the fixing surface for fixing the transformer 3 to the cooler 14 and the surface serving as the heat dissipation surface connected to the cooler 14 via a heat dissipation member. By placing the heat dissipation member in the gap 60, the thickness of the heat dissipation member can be controlled to a constant value. Also, when viewed from the cooler 14, the fixing surface of the transformer 3 and the installation surface of the heat dissipation member can be made flush with each other, which reduces variations in processing. In particular, when using a sheet-shaped heat dissipation member formed to a constant thickness and hardness, the variation in compression of the heat dissipation member in the Z direction can be efficiently controlled, which means that the variation in heat dissipation can be suppressed. The heat dissipation member is assumed to be a sheet-like heat dissipation member made of silicone, etc. However, even if a conductive adhesive, grease, or hardening grease is used, the effect of suppressing variations in heat dissipation is the same because they are arranged to fill the gap 60.

[0053] A small-sized transformer with high heat dissipation properties can be provided by configuring the transformer 3 as in the present embodiment 1. Furthermore, by including this transformer 3 and transmitting power between the primary side circuit and the secondary side circuit via this transformer, a small-sized power conversion device with high heat dissipation properties can be provided.

[0054] As described above, the transformer of the first embodiment includes a core forming a magnetic circuit and primary and secondary windings wound around the core, each of which includes at least one flat winding member, and which has a laminated configuration in which one of the winding members constituting the secondary winding with fewer turns is provided on one of the outermost layers in the winding axis direction, and a metal plate is provided on the other outermost layer in the winding axis direction. The power conversion device of the first embodiment includes this transformer. Therefore, the transformer and the power conversion device according to the first embodiment have high heat dissipation properties.

[0055] Embodiment 2 In the second embodiment, a modification of the power conversion device and the transformer described in the first embodiment will be described. The variations of the second embodiment can be implemented in combination with each other to the extent that no technical contradiction occurs. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in this application. For example, this includes cases in which at least one component is modified, added, or omitted. In the variations, the same reference numerals are used for the same or equivalent parts as those in the first embodiment. Furthermore, detailed descriptions of configurations that provide the same effects as those in the first embodiment will not be repeated.

[0056] A modification of the configuration of FIG. 3, which differs from the configuration of FIG. 3 in the number of turns of the primary winding, the shape of the core, etc., will be described with reference to FIG. 11, which is a perspective development view showing a modification of the winding configuration of the transformer. 11, the first primary winding 21 and the second primary winding 22 may be combined to form an odd number of turns, 5. In this case, the first primary winding 21 and the second primary winding 22 may be formed with the same number of turns, 2.5 turns including one decimal place, for example, by making two and a half turns starting from the inner ends 212 and 222 of the windings, and connected in series. Furthermore, if the cross section of the mating surfaces of upper core 12 and lower core 11 is rectangular, the winding shape can be configured to fit the cross section of the cores. This allows the winding to have the same effect regardless of whether the number of turns is odd or even.

[0057] Here, the differences from the configuration in FIG. 3 will be supplemented. The position of the connecting portion 325 of the secondary winding 3d is different, and the winding directions of the secondary windings 3b and 3d are reversed. In Fig. 11, the connection portion 324 of the secondary winding 3d is formed as a contiguous portion with the end portion 322. This may be changed as desired depending on the arrangement space, etc. 11, the connection portion 44 of the metal plate 40 is not present. For example, it may be attached in the opposite direction as viewed from the y direction, but this is not shown. The small holes (only one of which is marked "sh" in FIG. 11) on the metal plate 40 in FIG. 11 are provided for positioning the plate-shaped resin and the mold when molding the sealing resin. In FIG. 11, only one is marked "positioning hole sh." This is not shown in FIG. 3.

[0058] A modified example in which the first and second primary windings are each made up of a plurality of winding members will be described with reference to FIG. 12, which is a perspective development view showing a modified example of the winding configuration of the transformer. 12, the first primary winding 21 and the second primary winding 22 may each be configured with multiple layers. In this case, the first primary winding 21 and the second primary winding 22 are configured by combining winding members 51 and 53, and 52 and 54, respectively, where winding members 51 and 52 are spirally wound clockwise from the side farther from the winding axis 100 to the side closer to the winding axis 100, and winding members 53 and 54 are spirally wound counterclockwise from the side farther from the winding axis 100 to the side closer to the winding axis 100. The winding members 51 and 53, and 52 and 54 are connected by welding, for example, so that the inner ends of the windings are connected in series to form the first primary winding 21 and the second primary winding 22, respectively. The outer ends of the winding members 52 and 53 constituting the first primary winding 21 and the second primary winding 22 may be connected by welding, for example, to form a single primary winding 3a connected in series.

[0059] The case where the secondary side of the transformer has a full-bridge configuration will be described with reference to FIG. 13, which is a circuit diagram showing a modified example of the secondary side circuit of the power conversion device, and FIG. 14, which is a perspective development view showing a modified example of the winding configuration of the transformer. 13, a transformer 3 includes a primary winding 3a and a secondary winding 3f. A rectifier circuit 4 includes diodes 4c, 4d, 4e, and 4f connected to the secondary winding 3f of the transformer 3 in a full bridge configuration. 14, the winding with fewer turns may be formed by a single secondary winding 3b, and the primary winding 3a may be formed by two windings, a first primary winding 55 and a second primary winding 56. In this case, the first primary winding 55 is wound in a clockwise spiral shape from the side farther from the winding axis 100 to the side closer to the winding axis 100, and the second primary winding 56 is wound in a counterclockwise spiral shape from the side farther from the winding axis 100 to the side closer to the winding axis 100. The inner ends of the first primary winding 55 and the second primary winding 56 may be connected by welding, for example, so that they are in series to form the primary winding 3a. If P is the primary winding and S is the secondary winding, the configuration of the transformer in FIG. 14 corresponds to SPP.

[0060] A modification in which the secondary side of the transformer has a center tap configuration will be described with reference to FIG. 15, which is a perspective development view showing a modification in the configuration of the windings of the transformer. 1, the winding with fewer turns may be configured as secondary windings 3b and 3d using a single winding member, and primary winding 3a may be configured as two windings, first primary winding 55 and second primary winding 56, as shown in Fig. 15. In this case, secondary winding 3d may be configured as end 312 remote from winding axis 100 and intermediate end 328, and secondary winding 3b may be configured as end 311 closer to winding axis 100 and intermediate end 328.

[0061] 11 to 15, the layer configuration is such that one of the secondary windings with fewer turns is placed at the bottom, and metal plate 40 is placed in the top layer. This allows efficient heat dissipation from primary winding 3a, which has a large number of turns and is difficult to dissipate heat from. That is, as long as one of the secondary windings is placed at the bottom and the metal plate 40 is placed on the top layer, any layer configuration of the windings sandwiched between them is acceptable. Furthermore, if the primary winding 3a, which has a large number of turns and is difficult to dissipate heat, is arranged on an adjacent layer of the metal plate 40, heat can be dissipated more efficiently. Furthermore, loss can be reduced by alternately arranging the primary winding and secondary winding in the stacked configuration of the windings sandwiched between them.

[0062] The case where the secondary windings are connected in series will be described with reference to FIG. 16, which is a circuit diagram showing a modified example of the winding configuration of the transformer. As shown in Figure 16, a secondary winding 3d may be connected in series with the secondary winding 3b. By connecting the secondary windings 3b and 3d in series, the number of turns of the secondary winding increases. In this case, the number of turns of the secondary winding is the sum of the numbers of turns of the secondary windings 3b and 3d. That is, in the case of Figure 16, the number of turns of the secondary winding is 2, and the transformation ratio of the transformer 3 is 8:2.

[0063] A modification in which the secondary side of the transformer is of a center tap type will be described with reference to FIG. 17, which is a circuit diagram showing a modification of the secondary side circuit of the power conversion device. In a DC / DC converter with a center-tapped secondary side, a secondary circuit configuration such as that shown in Fig. 17 may be used. In this case, the connection part 325 of the secondary winding 3d, i.e., the center tap terminal 3e, is not connected to GND but is brought into contact with the cooler 14 via a heat dissipation member and connected to the smoothing reactor 5 by, for example, welding. Alternatively, the secondary winding 3d of the transformer 3 may be configured integrally with the winding of the smoothing reactor 5 via the connection part 325.

[0064] An example of using a metal plate as a secondary winding will be described with reference to FIG. 18, a circuit diagram showing a modified example of the winding configuration of a transformer, and FIG. 19, a perspective development view showing a modified example of the winding configuration of a transformer. As shown in Figures 18 and 19, metal plate 40 may be deformed to serve as secondary winding 3c. In this case, ends 311, 321, and 331 of secondary windings 3b, 3d, and 3c, respectively, that are closer to winding axis 100, are connected by welding, for example. Furthermore, ends 322 and 332 of secondary windings 3d and 3c, which are upper layers of the secondary windings and that are farther from winding axis 100, are connected by welding, for example. In other words, secondary windings 3d and 3c are parallel windings. The ends are formed so that their heights in the Z direction are the same when connected.

[0065] Secondary winding 3c is formed to protrude outward from winding portion 33, has a bent structure, and has connecting portions 326 and 327 extending parallel to secondary winding 3c. Because metal plate 40 becomes part of the secondary winding and electricity flows through connecting portions 326 and 327, they may be connected to cooler 14 via a heat dissipation member (not shown).

[0066] Furthermore, it is expected that the use of secondary winding 3c will suppress bias in current density due to proximity effect and reduce losses occurring in transformer 3. Therefore, if connections 326 and 327 of secondary winding 3c are eliminated or their size is adjusted, the effect of miniaturization will not be lost even if a fixed point of transformer 3 is provided separately.

[0067] Furthermore, it is not necessary to form extensions 214, 224 and 313, 323 as in the first primary winding 21A, the second primary winding 22A, and the secondary windings 3bA, 3dA. In this case, the transformer 3 can be made smaller by, for example, arranging the connection parts 42, 43 of the metal plate 40, which is also used to fix the transformer 3, closer to each other toward the center of the y-axis in the freed up space.

[0068] The arrangement of the notches 45 of the metal plate 40 may be changed as desired depending on the temperature distribution of the metal plate 40. In this case, for example, by arranging the notches 45 near areas with high temperatures, the heat can be dispersed and efficiently transferred to the connection parts 42, 43, and 44, which serve as heat dissipation paths, thereby enabling heat dissipation. As another example, by arranging the connectors in the vicinity of a low temperature, heat can be efficiently transferred to the connecting portions 42, 43, and 44 and dissipated without impeding heat dissipation. In practice, the position of the notch 45 is determined to allow for more efficient heat dissipation, taking into consideration the temperature distribution in the metal plate 40 and the arrangement of the cooler 14 and the connecting portions 42, 43, and 44.

[0069] Furthermore, the connection portions 42, 43, and 44 of the metal plate 40 may not be used to fix the transformer 3. In this case, they may be formed so as to be flush with the surface of the connection portion 324 of the secondary windings 3b and 3d, which are connected to the cooler 14 via a heat dissipation member. This allows the number of fixing points of the transformer 3 to be arbitrarily arranged, and allows for efficient heat dissipation.

[0070] Furthermore, the surface of the cooler 14 to which the transformer 3 is fixed and the surface connected via the heat dissipation member may be the same surface. In this case, a gap 60 may be formed in the cooler 14. This provides the same effect as when the gap 60 is provided in the transformer 3.

[0071] As described above, in each of the modifications described in the second embodiment, the transformer and the power conversion device also have high heat dissipation properties.

[0072] Although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are conceivable within the scope of the technology disclosed in this application, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with a component of another embodiment.

[0073] Various aspects of the present disclosure are summarized below as appendices.

[0074] (Appendix 1) A transformer comprising a core that forms a magnetic circuit, and a primary winding and a secondary winding wound around the core, the primary winding and the secondary winding each include at least one winding member; one of the winding members constituting the primary winding or the secondary winding with the fewer number of turns is provided on one of the outermost layers in the winding axis direction, A transformer having a laminated arrangement in which a metal plate is provided on the other of the outermost layers in the winding axis direction. (Appendix 2) The primary winding or the secondary winding includes at least two winding members, each of which has two or more turns. At least one first winding member wound clockwise from the side farther from the winding axis to the side closer to the winding axis; At least one second winding member wound counterclockwise from the side farther from the winding axis to the side closer to the winding axis; 2. The transformer according to claim 1, comprising: (Appendix 3) The primary winding or the secondary winding, which includes at least two of the winding members, 2. The transformer according to claim 1, wherein at least one first winding member and at least one second winding member are connected on the side closer to or farther from the winding axis to form one winding. (Appendix 4) the primary winding and the secondary winding each include a plurality of winding members; one of the winding members constituting the primary winding or the secondary winding with the fewer number of turns is provided on one of the outermost layers in the winding axis direction, and the metal plate is provided on the other outermost layer, 2. The transformer according to claim 1, wherein the winding members of the primary winding and the secondary winding are alternately stacked in the winding axis direction. (Appendix 5) the primary winding or the secondary winding with the fewer number of turns includes at least one of the winding members; the primary winding or the secondary winding with a larger number of turns has one or more winding members more than the primary winding or the secondary winding with a smaller number of turns, one of the winding members of the primary winding or the secondary winding having the fewer number of turns is provided on one of the outermost layers, and the metal plate is provided on the other outermost layer; 2. The transformer according to claim 1, wherein the winding members of the primary winding and the secondary winding are stacked in the direction of the winding axis. (Appendix 6) 10. The transformer according to claim 1, wherein the winding member constituting the primary winding or the secondary winding having the fewer number of turns and a portion of the metal plate are connected to a cooler via a heat dissipation member or directly. (Appendix 7) the winding member of the lowermost layer of the primary winding or the secondary winding having the fewer number of turns is connected to at least a part of the metal plate; 2. The transformer according to claim 1, wherein a portion of the primary winding or the secondary winding with the fewer number of turns is connected in parallel with the metal plate to form a single winding. (Appendix 8) the metal plate includes a winding portion wound around the core, 8. The transformer according to claim 1, wherein the winding portion includes a notch extending from a side closer to the winding axis toward an outer side. (Appendix 9) 8. The transformer according to claim 1, wherein a cross-sectional area of ​​the primary winding or the secondary winding with a smaller number of turns is larger than a cross-sectional area of ​​the primary winding or the secondary winding with a larger number of turns. (Appendix 10) 8. The transformer according to claim 1, wherein the primary winding and the secondary winding each have an extension portion extending outward from the outermost edge of the wound winding portion. (Appendix 11) 8. The transformer according to any one of Supplementary Note 1 to Supplementary Note 7, wherein the primary winding and the secondary winding each have a rectangular or elliptical cross-sectional shape having long sides and short sides, and the surfaces facing each other are the long sides. (Appendix 12) 8. The transformer according to claim 1, further comprising a sealing resin that seals at least a part or all of the primary winding, the secondary winding, and the metal plate. (Appendix 13) 13. The transformer according to claim 12, wherein the sealing resin is formed so that at least a portion of the surface of the metal plate connected to the primary winding or the secondary winding and the heat dissipation member or the cooler is exposed. (Appendix 14) A power conversion device comprising the transformer according to any one of Supplementary Note 1 to Supplementary Note 13, and performing power transmission between a primary side circuit and a secondary side circuit via the transformer. [Explanation of symbols]

[0075] 1 DC power supply, 2 inverter, 2a, 2b, 2c, 2d semiconductor switching elements, 3 transformer, 3a primary winding, 3b, 3c, 3f, 3d, 3bA, 3dA secondary winding, 3e center tap terminal, 4 rectifier circuit, 4a, 4b, 4c, 4d, 4e, 4f diodes, 5 smoothing reactor, 6 smoothing capacitor, 7 load, 10 power converter, 11 lower core, 12 upper core, 13 winding body, 14 cooler, 21, 21A first primary winding, 22, 22A second primary winding, 31, 32, 33 winding portion, 40 metal plate, 41 winding portion, 42, 43, 44 connection portion, 45 notch portion, 51, 52, 53, 54 winding members, 55 first primary winding, 56 second primary winding, 60 gap, 100 winding axis, 111,121 abdomen, 112,122 mid-leg, 113,114,123,124 Outer legs, 211,221 Windings, 212,222 inner end of winding, 213,223 outer end of winding, 214,224 extension, 311,321,331 end closer to winding axis; 312, 322, 332 the end remote from the winding axis, 313, 323 the extension; 324, 325 Connections, 326, 327 Connections, 328 Intermediate ends, sh Positioning hole.

Claims

1. A transformer comprising a core that forms a magnetic circuit, and a primary winding and a secondary winding wound around the core, the primary winding and the secondary winding each include at least one winding member; one of the winding members constituting the primary winding or the secondary winding having the fewer number of turns is provided on one of the outermost layers in the winding axis direction, a transformer having a laminated arrangement in which a metal plate is provided on the other of the outermost layers in the winding axis direction, the winding member of the lowermost layer of the primary winding or the secondary winding having the fewer number of turns is connected to at least a part of the metal plate; A transformer in which a part of the primary winding or the secondary winding with the fewer number of turns is connected in parallel with the metal plate to form one winding.

2. the metal plate includes a winding portion wound around the core, The transformer according to claim 1 , wherein the winding portion is provided with a notch extending from a side closer to the winding axis toward an outer side.

3. 2. The transformer according to claim 1, wherein the cross-sectional area of ​​the primary winding or the secondary winding with a smaller number of turns is larger than the cross-sectional area of ​​the primary winding or the secondary winding with a larger number of turns.

4. 2. The transformer according to claim 1, wherein the primary winding and the secondary winding each include an extension portion extending outward from the outermost edge of the wound winding portion.

5. 2. The transformer according to claim 1, wherein the primary winding and the secondary winding each have a rectangular or elliptical cross section having long and short sides, with the long sides being the surfaces facing each other.

6. The transformer according to claim 1 , further comprising a sealing resin that seals at least a part or all of the primary winding, the secondary winding, and the metal plate.

7. 7. The transformer according to claim 6, wherein the sealing resin is formed so that at least a part of the surface of the metal plate connected to the primary winding or the secondary winding and the heat dissipation member or the cooler is exposed.

8. A power conversion device comprising the transformer according to any one of claims 1 to 7, wherein power is transmitted between a primary side circuit and a secondary side circuit via the transformer.

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