Transformer coil board

Abstract

To solve a problem in which the parasitic capacitance between a first coil pattern and a second coil pattern becomes large.SOLUTION: A coil substrate 3 is a laminated substrate formed by laminating a plurality of single-layer substrates 35 (35A, 35B, ...), and the single-layer substrates 35 have first conductive patterns 36A, 36B, ... formed along the periphery of a first insertion hole 31, and the first conductive patterns 36A, 36B, ... of the adjacent single-layer substrates 35 (35A, 35B, ...) are electrically connected to each other to form a first coil pattern 36. The single-layer substrate 35 has second conductive patterns 37A, 37B, ... formed along the periphery of a second insertion hole 32, and a second coil pattern 37 is formed by electrically connecting the second conductive patterns 37A, 37B, ... of the adjacent single-layer substrates 35 (35A, 35B, ...).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a coil substrate for a transformer. [Background technology]

[0002] For example, Patent Document 1 proposes a coil substrate for a transformer having a first spiral coil pattern that serves as a primary coil on one side and a second spiral coil pattern that serves as a secondary coil on the other side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-4928 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the coil substrate shown in Patent Document 1 has the first coil pattern and the second coil pattern formed on both sides of the coil substrate, and therefore it is expected that the parasitic capacitance between the first coil pattern and the second coil pattern will become large.

[0005] The present invention has been made in view of the above, and has an object to provide a coil substrate for a transformer that can reduce the parasitic capacitance of the coil substrate. [Means for solving the problem]

[0006] In consideration of the above problem, a coil substrate for a transformer has a first insertion hole that is inserted into a first magnetic part of a core that forms a magnetic circuit, and a second insertion hole that is inserted into a second magnetic part of the core, wherein the coil substrate has a first coil pattern that is either a primary coil or a secondary coil around the first insertion hole, and a second coil pattern that is the other of the primary coil or the secondary coil around the second insertion hole, the coil substrate is a laminated substrate in which a plurality of single-layer substrates are laminated, a first conductive pattern is formed in the single-layer substrate along the periphery of the first insertion hole, and the first coil pattern is formed by electrically connecting the first conductive patterns of adjacent single-layer substrates, and a second conductive pattern is further formed in the single-layer substrate along the periphery of the second insertion hole, and the second coil pattern is formed by electrically connecting the second conductive patterns of adjacent single-layer substrates.

[0007] According to the present invention, the coil substrate has a first coil pattern around the first insertion hole and a second coil pattern around the second insertion hole, so that the primary coil and the secondary coil can be provided separately. This makes it possible to suppress parasitic capacitance between the primary coil and the secondary coil. Furthermore, by stacking single-layer substrates on which the first conductive pattern is formed and electrically connecting adjacent first conductive patterns, a primary coil having a shape similar to that of a winding can be formed. Similarly, by stacking single-layer substrates on which the second conductive pattern is formed and electrically connecting adjacent second conductive patterns, a secondary coil having a shape similar to that of a winding can be formed.

[0008] In a more preferred embodiment, the first coil pattern is formed on the single-layer substrate by a first conductive via that electrically connects the first conductive patterns to each other, and the second coil pattern is formed on the single-layer substrate by a second conductive via that electrically connects the second conductive patterns to each other.

[0009] According to this aspect, by using the first conductive via and the second conductive via provided in the single-layer substrate, the first and second coil patterns can be formed with a simpler structure.

[0010] In a more preferred embodiment, a through hole is formed in the coil substrate so as to penetrate the coil substrate and separate the first insertion hole and the second insertion hole.

[0011] According to this aspect, by providing a through hole to separate the first insertion hole and the second insertion hole, a gap is formed between the first coil pattern and the second coil pattern, thereby reducing the parasitic capacitance between them compared to when no through hole is provided.

[0012] In a more preferred embodiment, among the plurality of single-layer substrates, there is a first single-layer substrate on which the first conductive pattern and the second conductive pattern are formed, and a second single-layer substrate on which only the first conductive pattern is formed, and in a planar view of the coil substrate, an area of ​​the first conductive pattern formed on the first single-layer substrate is larger than an area of ​​the second conductive pattern formed on the first single-layer substrate.

[0013] According to the present invention, the thickness of the coil substrate can be reduced by forming the first conductive pattern and the second conductive pattern on the first single-layer substrate. Furthermore, by laminating the second single-layer substrate on which only the first conductive pattern is formed, the number of turns of the first coil pattern becomes greater than the number of turns of the second coil pattern, and the first coil pattern is more likely to generate heat than the second coil pattern. However, according to this aspect, the area of ​​the first conductive pattern is greater than the area of ​​the second conductive pattern on the first single-layer substrate, and therefore the heat dissipation of the first coil pattern can be improved.

[0014] In a more preferred embodiment, the first insertion hole and the second insertion hole are circular, and in a planar view of the coil substrate, when only the first conductive patterns of the multiple single-layer substrates are viewed, the first coil pattern forms a circular, continuous edge along the first insertion hole due to the first conductive patterns of the multiple single-layer substrates, and in a planar view of the coil substrate, when only the second conductive patterns of the multiple single-layer substrates are viewed, the second coil pattern forms a circular, continuous edge along the second insertion hole due to the second conductive patterns of the multiple single-layer substrates.

[0015] According to this aspect, the first coil pattern forms a continuous circular edge along the first insertion hole due to the first conductive patterns of the multiple single-layer substrates, so that the distribution of the electric field formed by the first coil pattern can be made uniform and the generated electric field can be stabilized. Furthermore, the second coil pattern forms a continuous circular edge along the second insertion hole due to the second conductive patterns of the multiple single-layer substrates, so that the distribution of the electric field formed by the second coil pattern can be made uniform and the generated electric field can be stabilized.

[0016] In a more preferred embodiment, the first insertion hole and the second insertion hole are circular, and in a planar view of the coil substrate, an outer edge of the first conductive pattern and an outer edge of the second conductive pattern are approximately rectangular, and the first conductive pattern and the second conductive pattern are formed such that one side of the outer edge of the first conductive pattern faces one side of the outer edge of the second conductive pattern.

[0017] According to this embodiment, the current-carrying portions where the first and second conductive patterns face each other can be made narrower than other portions, thereby reducing the parasitic capacitance in these portions. Furthermore, triangular portions are formed at the corners of the first and second conductive patterns, and these portions can act as heat dissipation portions.

[0018] In a more preferred embodiment, in a plan view of the coil substrate, a center of the first insertion hole is formed closer to the second insertion hole than a center of the first conductive pattern.

[0019] In a more preferred embodiment, both surfaces of the coil substrate are covered with an insulating layer.

[0020] This makes it possible to prevent discharge between the first conductive pattern and the core and between the second conductive pattern and the core. Effect of the Invention

[0021] According to the coil substrate for a transformer according to the present invention, the parasitic capacitance of the coil substrate can be reduced. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic perspective view of an isolated converter according to an embodiment of the present invention. [Diagram 2] 2 is a central cross-sectional view of the isolated converter shown in FIG. 1. [Diagram 3] FIG. 2 is a perspective view including the transformer shown in FIG. [Figure 4] 2 is a perspective view of a substrate including the coil substrate shown in FIG. 1. [Diagram 5] FIG. 2 is a schematic perspective view of the coil substrate shown in FIG. [Figure 6] 6 is a schematic perspective view for explaining first and second coil patterns of the coil substrate shown in FIG. 5. FIG. [Figure 7] 7 is a plan view for explaining first and second coil patterns of the coil substrate shown in FIG. 6. FIG. [Figure 8] 1(a) to 1(c) are plan views of a first to a third single-layer substrate of a coil substrate. [Figure 9] 13(a) to 13(c) are plan views of the fifth to seventh single-layer substrates of the coil substrate. [Figure 10]13(a) to 13(c) are plan views of the 10th to 12th single-layer substrates of the coil substrate. [Figure 11] 5 is a conceptual diagram illustrating a current flow in a coil substrate. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A coil substrate for a transformer according to an embodiment of the present invention will be described below with reference to FIGS.

[0024] 1. About the isolated converter 1 including the coil board 3 for the transformer The isolated converter 1 according to this embodiment is a DC-DC converter and includes a transformer 3A as shown in Fig. 1 and Fig. 2. The transformer 3A is a core-type transformer including a coil substrate 3 and a core 10. As will be described later with reference to Fig. 6, the coil substrate 3 has a first coil pattern 36 which serves as a primary coil of the transformer 3A, and a second coil pattern 37 which serves as a secondary coil of the transformer 3A. The core 10 electromagnetically couples the first coil pattern 36 and the second coil pattern 37.

[0025] The insulating converter 1 further includes a primary side circuit board and a secondary side circuit board. In this embodiment, the primary side circuit board is an inverter circuit board 4A, and the inverter circuit board 4A is electrically connected to the first coil pattern 36 at one end of the coil board 3. In this embodiment, the secondary circuit board is a rectifier circuit board 4B, and the other end of the coil board 3 is electrically connected to the second coil pattern 37.

[0026] The inverter circuit board 4A is a board body (for example, a glass epoxy board) on which a wiring pattern is provided, and electronic components 42 such as switching elements are mounted to form an inverter circuit. The inverter circuit board 4A converts DC power into AC power by the switching elements, and the AC power is supplied to the coil board 3.

[0027] The rectifier circuit board 4B has electronic components 44 such as diodes mounted on a board body (for example, a glass epoxy board) on which a wiring pattern is provided, forming a rectifier circuit that rectifies the current (voltage) output from the coil board 3. Note that the inverter circuit and rectifier circuit in a DC-DC converter are generally known circuits, and detailed description thereof will be omitted. In this embodiment, a DC-DC converter is exemplified as the insulating converter 1, but if the insulating converter 1 is a switching type AC-DC converter, the primary side circuit board will be a rectifier circuit board including an electric circuit for AC-DC conversion further including, for example, four diodes. As a result, the AC-DC converter is configured to include an electric circuit for AC-DC conversion and a DC-DC converter.

[0028] The isolated converter 1 further includes an insulating casing 20. The casing 20 houses the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B. In Fig. 1, the casing 20 is in a state where a front cover (not shown) is removed. The cover is attached to the casing 20 by screwing a fastener (not shown) into a screw hole 23.

[0029] In this embodiment, the casing 20 is made of a resin material having insulating properties. The resin material is not particularly limited as long as it can ensure insulating properties, and examples thereof include engineering plastics. The engineering plastic may be a crystalline plastic such as polyphenylene sulfide (PPS). Furthermore, from the viewpoint of ensuring heat resistance and strength, it is preferable that the resin material be a non-crystalline plastic made of polyetherimide (PEI) such as Ultem (registered trademark).

[0030] An input board 61A having an electrolytic capacitor 63A and an input terminal 64A electrically connected to the inverter circuit board 4A mounted thereon is attached to the outer surface of one side wall 21A of the casing 20. An output board 61B having an electrolytic capacitor 63B and an output terminal 64B electrically connected to the rectifier circuit board 4B mounted thereon is attached to the outer surface of the other side wall 21A of the casing 20. The electrolytic capacitor 63A constitutes a part of a smoothing circuit that smoothes the pulsating flow of the current input to the inverter circuit board 4A, and the electrolytic capacitor 63B constitutes a part of a smoothing circuit that smoothes the pulsating flow of the current output from the rectifier circuit board 4B.

[0031] In this embodiment, a pair of mounting members 50A, 50B for mounting the casing 20 to an external structure (not shown) is disposed between the input board 61A and one of the side walls 21A and between the output board 61B and the other of the side walls 21B. Each mounting member 50A (50B) is attached to the casing 20 together with the input board 61A (output board 61B) by screwing (fastening) a fastener 72 to the casing 20. In this embodiment, the fastener 73 is inserted without being screwed into the casing 20 and is screwed and fastened to a spacer 45A (45B) fixed to the inverter circuit board 4A (rectifier circuit board 4B).

[0032] Each mounting member 50A (50B) has a frame-shaped main body 51A (51B) in which a space 52A (52B) is formed, and a leg 53A (53B) protruding from the main body 51A (51B) and in which a mounting hole 53a is formed, as shown in Fig. 2. The space 52A (52B) accommodates an electrolytic capacitor 63A (63B), and wiring connecting an input terminal 64A (output terminal 64B) to the inverter circuit board 4A (rectifier circuit board 4B), etc.

[0033] 2. About Core 10 3, the core 10 electromagnetically couples the first coil pattern 36 and the second coil pattern 37 of the coil substrate 3. The core 10 has U-shaped divided bodies 11 and 12, and the divided bodies 11 and 12 are compacts (e.g., powder magnetic cores) made of a soft magnetic material such as ferrite (iron).

[0034] One divided body 11 has a first magnetic portion 11a inserted into a first insertion hole 31 formed in the coil substrate 3, and a second magnetic portion 11b inserted into a second insertion hole 32. The first magnetic portion 11a and the second magnetic portion 11b are connected by a connecting portion 11c. The other divided body 12 has a first magnetic portion 12a and a second magnetic portion 12b at positions facing the first magnetic portion 11a and the second magnetic portion 11b, respectively, and the first magnetic portion 12a and the second magnetic portion 12b are connected by a connecting portion 12c. An insulating washer 19 is sandwiched between one divided body 11 and the other divided body 12, thereby forming a gap G between them.

[0035] When assembling the core 10, the segments 11 and 12 are sandwiched between a pair of presser blocks 15 and 16 with the washer 19 in place, the shaft portion 14b is screwed into the screw hole 15a that penetrates the other presser block 15, and the connecting bolt 14 is tightened. The pair of presser blocks 15 and 16 and the connecting bolt (fastener) 14 are made of a non-magnetic material such as resin or ceramics. In this way, the segments 11 and 12 can form a magnetic circuit (magnetic path) between the primary coil and secondary coil of the transformer 3A.

[0036] The core 10 thus assembled is attached to the casing 20. Specifically, the other pressing block 15 is formed with a flat contact surface 15c that contacts the inner surface (flat surface) of the top wall 22 of the casing 20, and a screw hole 15b is formed in the contact surface 15c. A fixing screw (fixing tool) 71 is inserted through the top wall 22 of the casing, screwed into the screw hole 15b, and then tightened.

[0037] 3. Regarding the board structure including the coil board 3 and its mounting structure 3 and 4, the inverter circuit board 4A is attached integrally to the coil board 3 at one end 3a of the coil board 3 so as to extend in a direction perpendicular to the coil board 3. In this embodiment, the inverter circuit board 4A and the coil board 3 (the first coil pattern 36 of the coil board 3) are integrally and electrically connected by soldering via connection terminals 41 connected to each other.

[0038] Similarly, the rectifier circuit board 4B is attached integrally to the coil board 3 so as to extend in a direction perpendicular to the coil board 3 at the other end 3b of the coil board 3. The rectifier circuit board 4B and the coil board 3 (the second coil pattern 37) are integrally and electrically connected by soldering via a connection terminal 43 that connects them together. According to this embodiment, the coil board 3, the inverter circuit board 4A, and the rectifier circuit board 4B can be handled as a single compact board structure, and the isolated converter 1 can be made compact.

[0039] In this embodiment, the inverter circuit board 4A and the rectifier circuit board 4B are fixed to opposing side walls 21A, 21B of the casing 20, thereby holding the coil board 3 within the casing 20. The coil board 3 is supported by the casing 20 in a suspended state within the casing 20. This allows the inverter circuit board 4A and the rectifier circuit board 4B to absorb deformation and distortion due to dimensional errors and the like during installation, and allows the coil board 3 to be held within the casing 20.

[0040] Here, as shown in FIG. 2, spacers 45A, 45B are arranged between the inverter circuit board 4A and the rectifier circuit board 4B, respectively, and the inner surfaces of the pair of side walls 21A, 21B, to position the first insertion hole 31 relative to the first magnetic portion 11a and to position the second insertion hole 32 relative to the second magnetic portion 11b.

[0041] Specifically, a spacer 45A is fixed to the inverter circuit board 4A, and a spacer 45B is fixed to the rectifier circuit board 4B. The inverter circuit board 4A and the rectifier circuit board 4B are attached to the casing 20 by screwing and tightening fasteners 73 that have passed through the side walls 21A and 21B into the spacers 45A and 45B.

[0042] In this manner, the spacer 45A is sandwiched between one side wall 21A of the casing 20 and the inverter circuit board 4A, and the spacer 45B is sandwiched between the other side wall 21B of the casing 20 and the rectifier circuit board 4B. Thus, simply by tightening the fastener 73, the first insertion hole 31 can be positioned in the casing 20 with respect to the first magnetic portion 11a of the core 10 to minimize the parasitic capacitance, and the second insertion hole 32 can be positioned with respect to the second magnetic portion 11b of the core 10 to minimize the parasitic capacitance.

[0043] Specifically, the first insertion hole 31 and the second insertion hole 32 are circular through holes. Therefore, in a plan view, the opening of the first coil pattern 36 and the opening of the second coil pattern 37 are also circular. In addition, the first magnetic parts 11a, 12a and the second magnetic parts 11b, 12b of the core 10 are substantially cylindrical. In this case, the parasitic capacitance between the core 10 and the first coil pattern 36 and the parasitic capacitance between the core 10 and the second coil pattern 37 can be minimized by positioning the first coil pattern 36 so that the center of the opening of the first coil pattern 36 coincides with the axis of the first magnetic part 11a and the axis of the first magnetic part 12a, and by positioning the second coil pattern 37 so that the center of the opening of the second coil pattern 37 coincides with the axis of the second magnetic part 11b and the axis of the second magnetic part 12b. In addition to this, discharge between the core 10 and the first coil pattern 36 and discharge between the core 10 and the second coil pattern 37 can be suppressed.

[0044] 4. Coil board 3 As shown in FIG. 3 and FIG. 5, the coil substrate 3 has a first insertion hole 31 through which the first magnetic portion 11a of the core 10 forming the magnetic circuit is inserted, and a second insertion hole 32 through which the second magnetic portion 11b of the core 10 is inserted. The first insertion hole 31 and the second insertion hole 32 are circular through holes. The first magnetic portion 11a is substantially cylindrical, and the first insertion hole 31 is larger than the circular cross section of the first magnetic portion 11a. As a result, a clearance for assembly adjustment is formed between the periphery of the first insertion hole 31 and the first magnetic portion 11a. Similarly, the second magnetic portion 11b is substantially cylindrical, and the second insertion hole 32 is larger than the circular cross section of the second magnetic portion 11b. As a result, a clearance for assembly adjustment is formed between the periphery of the second insertion hole 32 and the second magnetic portion 11b.

[0045] The coil substrate 3 has a through hole 33 formed therethrough to separate the first insertion hole 31 and the second insertion hole 32. When the through hole 33 is not filled with a molding material described later, the through hole 33 forms a space (air is present) between the first coil pattern 36 and the second coil pattern 37, so that the parasitic capacitance between them can be reduced compared to when the through hole 33 is not provided. However, as described later, when filling the internal space S of the casing 20 with a molding material, the molding material having a relative dielectric constant lower than the relative dielectric constant of the insulating material of the substrate body 35a constituting the coil substrate 3 is filled. As a result, the through hole 33 is also filled with a molding material having a relative dielectric constant lower than the relative dielectric constant of the insulating material of the substrate body 35a, so that the parasitic capacitance between the first coil pattern 36 and the second coil pattern 37 can be reduced.

[0046] In this embodiment, as shown in Figures 6 to 10, the coil substrate 3 has a conductive first coil pattern 36 around the first insertion hole 31, and a second coil pattern 37 around the second insertion hole 32. As shown in Figure 5, both surfaces of the coil substrate 3 are covered with an insulating layer 3c. This makes it possible to prevent discharge between the core 10 and the first coil pattern 36 and the second coil pattern 37.

[0047] Specifically, the coil substrate 3 is a laminated substrate formed by stacking a plurality of (e.g., 12 layers) single-layer substrates 35 (35A-35L). In the drawings, the numbers of layers of the single-layer substrates 35 correspond to the reference characters A-L, and the fourth, eighth, and ninth single-layer substrates 35 (35D, 35H, 35I) are not shown.

[0048] The single layer substrate 35 is composed of a plurality of (for example, seven layers) first single layer substrates 35A-35G and a plurality of (for example, five layers) second single layer substrates 35H-35L. The first single layer substrates 35A-35G are single layer substrates on which the first conductive patterns 36A-36G are formed around the first insertion holes 31 and the second conductive patterns 37A-37G are formed around the second insertion holes 32. The second single layer substrates 35H-35L are single layer substrates on which only the first conductive patterns 36H-36L are formed. In this embodiment, the number of turns of the first coil pattern 36 is greater than the number of turns of the second coil pattern 37 by the number of single layer substrates 35 on which only the first conductive patterns 36H-36L are formed.

[0049] The first conductive patterns 36A-36L and the second conductive patterns 37A-37G are rectangular patterns formed in a planar shape on an insulating substrate body 35a such as a glass epoxy substrate. The first conductive patterns 36A-36L and the second conductive patterns 37A-37G have openings 31a, 32a formed therein in accordance with the first insertion hole 31 and the second insertion hole 32.

[0050] In this embodiment, among the multiple stacked first conductive patterns 36A-36L, only a pair of outermost first conductive patterns 36A, 36L are connected to terminal portions 34A, 34A of the inverter circuit board 4A (see FIGS. 8(a) and 10(c)). The first conductive patterns 36A-36L of adjacent single-layer boards 35 are insulated from each other by the board body 35a having the above-mentioned insulating properties.

[0051] The first conductive patterns 36A-36L of adjacent single-layer substrates 35 are electrically connected to each other through first conductive vias 38 so that current flows in the same circumferential direction around the openings 31a of the first conductive patterns 36A-36L. This allows the first coil pattern 36, which corresponds to the primary coil of the transformer 3A, to be formed with a simpler structure. The first coil pattern 36 becomes a primary coil that is similar to the form of a winding.

[0052] Specifically, as shown in Fig. 7, groups 38A-38K of a plurality of (for example, four in Fig. 8) evenly spaced first conductive vias 38 are arranged at intervals from the terminal portion 34A toward the opening 31a. The plurality of (for example, four) first conductive vias 38 constituting each group 38A-38K are formed at intervals on a straight line. In this embodiment, the first conductive vias 38 connect adjacent ones of the 12 adjacent first conductive patterns 36A-36K, so that 11 groups 38A-38K of first conductive vias 38 exist inside the coil substrate 3.

[0053] As shown in Fig. 8(a) and (b), the first conductive pattern 36A of the uppermost (first layer) single-layer substrate 35 (35A) is connected to one terminal portion 34A of the inverter circuit substrate 4A. Furthermore, the first conductive pattern 36A located in the first layer and the first conductive pattern 36B located in the layer below (second layer) are connected by a group 38A of four first conductive vias 38 closest to the terminal portion 34A. As shown in Fig. 8(b) and (c), the first conductive pattern 36B located in the layer below (second layer) and the first conductive pattern 36C located in the layer below (third layer) are connected to the group 38A of four first conductive vias 38 described above by a group 38B of four first conductive vias 38 adjacent to the opening 31a side.

[0054] 9(a) to 9(c), the first conductive pattern 36E of the fifth-layer single-layer substrate 35 (35E) and the first conductive pattern 36F of the sixth-layer single-layer substrate 35 (35F) are connected by a group 38E of first conductive vias 38, and the first conductive pattern 36E of the sixth-layer single-layer substrate 35 (35F) and the first conductive pattern 36G of the seventh-layer single-layer substrate 35 (35G) are connected by a group 38F of first conductive vias 38. As shown in FIGS. 10(a) and 10(b), the first conductive pattern 36J of the tenth-layer single-layer substrate 35J and the first conductive pattern 36K of the eleventh-layer single-layer substrate 35 (35K) are connected by a group 38J of first conductive vias 38. Finally, as shown in Figures 10(b) and (c), the first conductive pattern 36K of the 11th layer single-layer substrate 35 (35K) and the first conductive pattern 36L of the 12th layer single-layer substrate 35 (35L) are connected by a group 38L of first conductive vias 38, and the first conductive pattern 36L of the 12th layer single-layer substrate 35L is connected to the other terminal portion 34A of the inverter circuit substrate 4A.

[0055] In this way, as shown in FIG. 11, the first conductive patterns 36A-36J are electrically connected in the order of one terminal 34A, through the groups 38A-38K of the first conductive vias 38, to the other terminal 34A so that a current flows in the same circumferential direction. In this way, the first coil pattern 36 corresponding to the primary coil of the transformer 3A is formed. As the number of layers increases, the groups 38A-38K of the first conductive vias 38 connecting the first conductive patterns 36A-36L are sequentially shifted toward the opening 31a. In this way, the current flowing through the first coil pattern 36 flows along the periphery (circumferential edge) of the circular first insertion hole 31, so that the electric field formed in the first coil pattern 36 can be stabilized.

[0056] In this embodiment, among the multiple stacked second conductive patterns 37A-37G, only a pair of second conductive patterns 37A, 37G located at the outermost positions are connected to terminal portions 34B, 34B of the rectifier circuit board 4B (see FIGS. 8(a) and 9(c)). The second conductive patterns 37A-37G of adjacent single-layer boards 35 are insulated from each other by the board body 35a having the above-mentioned insulating properties.

[0057] The second conductive patterns 37A-37G of adjacent single-layer substrates 35 are electrically connected to each other through second conductive vias 39 so that current flows in the same circumferential direction around the openings 32a of the second conductive patterns 37A-37G. This allows the second coil pattern 37, which corresponds to the secondary coil of the transformer 3A, to be formed with a simpler structure. The second coil pattern 37 is a secondary coil that is similar to a winding.

[0058] 7, groups 39A-39F of a plurality (e.g., three) of second conductive vias 39 arranged at equal intervals are arranged at intervals from the terminal portion 34B toward the opening 32a. The plurality (e.g., three) of second conductive vias 39 constituting each group 39A-39F are formed at intervals on a straight line. In this embodiment, the second conductive vias 39 connect adjacent ones of the seven adjacent second conductive patterns 37A-37G, and six groups 39A-39F of second conductive vias 39 exist inside the coil substrate 3.

[0059] As shown in Fig. 8(a) and (b), the second conductive pattern 37A of the uppermost (first) layer single-layer substrate 35 (35A) is connected to one terminal portion 34B of the rectifier circuit substrate 4B. Furthermore, the second conductive pattern 37A located in the first layer and the second conductive pattern 37B located in the layer below (second layer) are connected by a group 39A of three second conductive vias 39 closest to the terminal portion 34B. As shown in Fig. 8(b) and (c), the second conductive pattern 37B located in the layer below (second layer) and the second conductive pattern 37C located in the layer below (third layer) are connected to the group 39A of three second conductive vias 39 described above by a group 39B of three second conductive vias 39 adjacent to the opening 32a side.

[0060] 9(a) and (b), the second conductive pattern 37E of the fifth-layer single-layer substrate 35 (35E) and the second conductive pattern 37F of the sixth-layer single-layer substrate 35 (35F) are connected by a group 39E of second conductive vias 39. Finally, as shown in FIG. 9(b) and (c), the second conductive pattern 37F of the sixth-layer single-layer substrate 35 (35F) and the second conductive pattern 37G of the eighth-layer single-layer substrate 35 (35G) are connected by a group 39F of second conductive vias 39, and the second conductive pattern 37G of the eighth-layer single-layer substrate 35 (35G) is connected to the other terminal portion 34B of the rectifier circuit substrate 4B.

[0061] In this way, as shown in FIG. 11, the second conductive patterns 37A-37G are electrically connected in this order from one terminal 34B to the other terminal 34B through the groups 39A-39F of the second conductive vias 39 so that the current flows in the same circumferential direction. This forms the second coil pattern 37 corresponding to the secondary coil of the transformer 3A. As the number of layers increases, the groups 39A-39F of the second conductive vias 39 connecting the second conductive patterns 37A-37G are sequentially shifted toward the opening 32a. In this way, the current flowing through the second coil pattern 37 flows along the periphery (circumferential edge) of the circular second insertion hole 32, so that the electric field formed in the second coil pattern 36 can be stabilized.

[0062] The area of ​​the first conductive patterns 36A-36G formed on the first single-layer substrates 35A-35G is larger than the area of ​​the second conductive patterns 37A-37G formed on the first single-layer substrates 35A-35G. Thus, by forming the first conductive patterns 36A-36G and the second conductive patterns 37A-37G on the first single-layer substrates 35A-35G, the thickness of the coil substrate 3 can be reduced.

[0063] Furthermore, by stacking the second single-layer substrates 35H-35L on which only the first conductive patterns 36H-36L are formed, the number of turns of the first coil pattern 36 becomes greater than the number of turns of the second coil pattern 37, and the first coil pattern 36 is more likely to generate heat than the second coil pattern 37. However, in this embodiment, the area of ​​the first conductive patterns 36A-36G is greater than the area of ​​the second conductive patterns 37A-37G in the first single-layer substrates 35A-35G, so that the heat dissipation property of the first coil pattern 36 can be improved.

[0064] 7, in a plan view of the coil substrate 3, when only the first conductive patterns 36A-36L of the multiple single-layer substrates 35 are viewed, the first coil pattern 36 forms a continuous circular edge along the first insertion hole 31 by the first conductive patterns 36A-36L of the multiple single-layer substrates 35. Similarly, in a plan view of the coil substrate 3, when only the second conductive patterns 37A-37G of the multiple single-layer substrates 35 are viewed, the second conductive patterns 37A-37G of the multiple single-layer substrates 35 form a continuous circular edge along the second insertion hole 32.

[0065] In this way, because the first coil pattern 36 forms a continuous circular edge along the first insertion hole 31 due to the first conductive patterns 36A-36L of the multiple single-layer substrates 35, it is possible to make the distribution of the electric field formed by the first coil pattern 36 uniform. Furthermore, because the second coil pattern 37 forms a continuous circular edge along the second insertion hole 32 due to the second conductive patterns 37A-37G of the multiple single-layer substrates 35, it is possible to make the distribution of the electric field formed by the second coil pattern 37 uniform.

[0066] As described above, the outer edges of the first conductive patterns 36A-36L and the outer edges of the second conductive patterns 37A-37G are approximately rectangular, and in each of the first single-layer substrates 35A-35G, the first conductive patterns 36A-36L and the second conductive patterns 37A-37G are formed so that one side of the outer edge of the first conductive patterns 36A-36L faces one side of the outer edge of the second conductive patterns 37A-37G.

[0067] With this configuration, the current-carrying portions 36b, 37b where the first conductive patterns 36A-36L and the second conductive patterns 37A-37G face each other can be made narrower than other portions, and the parasitic capacitance in these portions can be reduced. Furthermore, triangular portions are formed at the corners 36a, 37a of the first conductive patterns and the second conductive patterns, and these portions can function as heat dissipation portions. In particular, by forming the center of the first through-hole 31 closer to the second through-hole 32 than the center of the first conductive patterns 36A-36G in a plan view of the coil substrate 3, this effect can be further exhibited.

[0068] The internal space S of the casing 20 may be filled with a molding material having insulating properties. As long as the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B can be sealed with the molding material M in the internal space S of the casing 20 by filling the molding material, the material of the molding material is not particularly limited to a thermoplastic resin or a thermosetting resin. Examples of the thermosetting resin include silicone resin, epoxy resin, and urethane resin. Among these, it is preferable to fill the molding material having a relative dielectric constant lower than that of the insulating material of the substrate body 35a constituting the coil substrate 3. The molding material filled in the internal space S of the casing 20 ensures the pressure resistance of the transformer 3A, while making the relative dielectric constant of the molding material lower than that of the insulating material of the substrate body, thereby suppressing an increase in parasitic capacitance caused by the molding material. When the insulating material of the substrate body 35a is glass epoxy, its relative dielectric constant is 4.0, so that the relative dielectric constant of the molding material is preferably less than 4.0 (for example, 2.0 to 3.0).

[0069] According to this embodiment, the coil substrate 3 has the first coil pattern 36 around the first insertion hole 31 and the second coil pattern 37 around the second insertion hole 32, so that the primary coil and secondary coil of the transformer 1A can be provided separately. This makes it possible to suppress the parasitic capacitance between the primary coil and secondary coil in the coil substrate 3.

[0070] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as described in the claims.

[0071] In this embodiment, the first coil pattern with a large number of turns is the primary coil, and the second coil pattern with a small number of turns is the secondary coil, but depending on the application of the transformer, the first coil pattern with a large number of turns may be the secondary coil, and the second coil pattern with a small number of turns may be the primary coil. Furthermore, the first conductive pattern and the second conductive pattern are electrically connected by the first conductive via and the second conductive via so that the currents flowing in the first coil pattern and the second coil pattern are in the same circumferential direction, but the first conductive pattern and the second conductive pattern may be electrically connected by the first conductive via and the second conductive via so that the currents flowing in the first coil pattern and the second coil pattern are in the opposite directions. [Explanation of symbols]

[0072] 1: isolated converter, 3: coil substrate, 3A: transformer, 3c: insulating layer, 4A: inverter circuit board (primary circuit board), 4B: rectifier circuit board (secondary circuit board), 10: core, 11a: first magnetic portion, 11b: second magnetic portion, 31: first through hole, 32: second through hole, 35: single-layer substrate, 35a: substrate body, 35A to 35G: first single-layer substrate, 35H to 35K: second single-layer substrate, 36: first coil pattern, 36A to 36K: first conductive pattern, 37: second coil pattern, 37A to 37G: second conductive pattern, 38: first conductive via, 39: second conductive via

Claims

1. A coil substrate for a transformer, the coil substrate having a first insertion hole inserted through a first magnetic portion of a core forming a magnetic circuit, and a second insertion hole inserted through a second magnetic portion of the core, the coil substrate has a first coil pattern around the first insertion hole, the first coil pattern being one of a primary coil or a secondary coil, and has a second coil pattern around the second insertion hole, the second coil pattern being the other of the primary coil or the secondary coil, the coil substrate is a laminated substrate formed by laminating a plurality of single-layer substrates, a first conductive pattern is formed along a periphery of the first insertion hole on the single-layer substrate, and the first conductive patterns of adjacent single-layer substrates are electrically connected to each other to form the first coil pattern; A coil substrate for a transformer, characterized in that a second conductive pattern is further formed along the periphery of the second insertion hole on the single-layer substrate, and the second coil pattern is formed by electrically connecting the second conductive patterns of adjacent single-layer substrates to each other.

2. the first coil pattern is formed on the single-layer substrate by a first conductive via that electrically connects the first conductive patterns to each other; 2. The coil substrate for a transformer according to claim 1, wherein the second coil pattern is formed on the single-layer substrate by a second conductive via that electrically connects the second conductive patterns to each other.

3. 2. The coil substrate for a transformer according to claim 1, wherein a through hole is formed in the coil substrate so as to penetrate the coil substrate and separate the first insertion hole and the second insertion hole.

4. Among the plurality of single-layer substrates, there is a first single-layer substrate on which the first conductive pattern and the second conductive pattern are formed, and a second single-layer substrate on which only the first conductive pattern is formed, 2. The coil substrate for a transformer according to claim 1, characterized in that, in a plan view of the coil substrate, an area of ​​a first conductive pattern formed on the first single-layer substrate is larger than an area of ​​a second conductive pattern formed on the first single-layer substrate.

5. The first insertion hole and the second insertion hole are circular, when only the first conductive patterns of the plurality of single-layer substrates are viewed in a plan view of the coil substrate, the first coil pattern forms a circular, continuous edge portion along the first insertion hole due to the first conductive patterns of the plurality of single-layer substrates, 3. A coil substrate for a transformer as described in claim 2, characterized in that when only the second conductive patterns of the plurality of single-layer substrates are viewed in a planar view of the coil substrate, the second coil pattern forms a circular, continuous edge portion along the second insertion hole due to the second conductive patterns of the plurality of single-layer substrates.

6. The first insertion hole and the second insertion hole are circular, In a plan view of the coil substrate, an outer edge of the first conductive pattern and an outer edge of the second conductive pattern have a substantially rectangular shape, 2. The coil substrate for a transformer according to claim 1, wherein the first conductive pattern and the second conductive pattern are formed such that one side of an outer edge of the first conductive pattern faces one side of an outer edge of the second conductive pattern.

7. 2. The coil substrate for a transformer according to claim 1, wherein both surfaces of said coil substrate are covered with an insulating layer.

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