Isolated converter

Abstract

To solve a problem in which, heat generated from a primary circuit board and a secondary circuit board during use of an isolated converter or the like may not be able to be sufficiently dissipated from a casing.SOLUTION: In an isolated converter 1, an inverter circuit board (primary side circuit board) 4A faces one side wall 21A of a casing at a distance so as to extend along the one side wall 21A, and a rectifier circuit board (secondary side circuit board) 4B faces the other side wall 21B of the casing 20 at a distance so as to extend along the other side wall 21B. An insulating molding material M is filled into an internal space S of the casing 20, thereby sealing the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B in the internal space S of the casing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an isolated converter including a transformer. [Background technology]

[0002] For example, Patent Document 1 discloses an isolated converter including a transformer. The transformer is housed in an insulating housing, and is electrically connected to an inverter circuit board and a rectifier circuit board outside the housing. The transformer, the inverter circuit board (primary side circuit board), and the rectifier circuit board (secondary side circuit board) are housed in a metal casing. [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, when the transformer, primary circuit board, and secondary circuit board are housed in a single insulating casing, the heat generated from the primary circuit board and secondary circuit board during use of the isolated converter may not be able to be sufficiently dissipated from the casing.

[0005] The present invention has been made in consideration of the above, and has an object to provide an isolated converter that can ensure heat dissipation within a housing while ensuring insulation of the transformer, even when a transformer, a primary side circuit board, and a secondary side circuit board are accommodated in a single housing. [Means for solving the problem]

[0006] In view of the above problems, an isolated converter according to the present invention is an isolated converter including: a transformer including a coil substrate having a first coil pattern serving as a primary coil and a second coil pattern serving as a secondary coil, and a core that electromagnetically couples the first coil pattern and the second coil pattern; a primary-side circuit substrate electrically connected to the first coil pattern at one end of the coil substrate; and a secondary-side circuit substrate electrically connected to the second coil pattern at the other end of the coil substrate, the primary circuit board faces one of a pair of side walls of the casing at a distance so as to extend along the one side wall, and the secondary circuit board faces the other of the pair of side walls of the casing at a distance so as to extend along the other side wall, and an internal space of the casing is filled with an insulating molding material, such that the transformer, the primary circuit board, and the secondary circuit board are sealed in the internal space of the casing with the molding material.

[0007] According to the present invention, when the isolated converter is used, heat is generated because a current flows through the primary circuit board and the secondary circuit board. Here, the primary circuit board faces one of the pair of side walls of the casing at a distance so as to extend along one of the side walls, and a molding material is filled between the primary circuit board and the other side wall. Therefore, heat generated by the primary circuit board is easily dissipated from one of the side walls of the casing via the molding material. Similarly, the secondary circuit board faces the other of the pair of side walls of the casing at a distance so as to extend along the other of the pair of side walls of the casing, and a molding material is filled between the secondary circuit board and the other side wall. Therefore, heat generated by the secondary circuit board is easily dissipated from the other side wall of the casing via the molding material. Even when the transformer, primary circuit board, and secondary circuit board are housed within a single casing, the heat generated from the primary circuit board and the secondary circuit board can be efficiently dissipated from a pair of side walls of the casing.

[0008] In a more preferred embodiment, an input board having an electrolytic capacitor and an input terminal electrically connected to the primary circuit board is attached to the outer surface of one side wall of the casing, and an output board having an electrolytic capacitor and an output terminal electrically connected to the secondary circuit board is attached to the outer surface of the other side wall of the casing.

[0009] According to this embodiment, by mounting the electrolytic capacitors on the input board and the output board and positioning them outside the casing, it is possible to prevent the heat generated when filling the casing with molding material and the heat generated inside the casing when the isolated converter is in use from being transmitted to the electrolytic capacitors.

[0010] In a further preferred embodiment, a pair of mounting members for mounting the casing are arranged between the input board and one of the side walls, and between the output board and the other side wall, and a space is formed in each of the mounting members in a portion where the electrolytic capacitor is located.

[0011] According to this aspect, the casing can be attached to an external device by the pair of mounting members. Furthermore, since the mounting members have a space formed in the portion where the electrolytic capacitor is located, this space acts as a heat insulating layer, and the effect of heat transferred from the casing to the electrolytic capacitor can be suppressed when the molding material is filled and when the isolated converter is used.

[0012] In a more preferred embodiment, the internal space of the casing is filled with a molding material having a relative dielectric constant lower than the relative dielectric constant of an insulating material of a substrate body constituting the coil substrate.

[0013] According to this aspect, the molding material filled inside the casing ensures the voltage resistance of the transformer while having a lower dielectric constant than the insulating material of the substrate body, thereby suppressing an increase in parasitic capacitance caused by the molding material.

[0014] In a more preferred embodiment, the isolated converter is a DC-DC converter, the primary side circuit board is an inverter circuit board equipped with switching elements that convert DC power into AC power and supply the AC power to the coil board, and the secondary side circuit board is a rectifier circuit board that rectifies a current output from the coil board.

[0015] According to this embodiment, the inverter circuit board and the rectifier circuit board are prone to heat generation when current is applied, but by arranging the inverter circuit board and the rectifier circuit board facing a pair of side walls of the casing, the heat dissipation properties of the DC-DC converter can be ensured. Effect of the Invention

[0016] According to the isolated converter of the present invention, it is possible to ensure the insulation of the transformer and also ensure the heat dissipation within the housing even when the transformer, the primary side circuit board, and the secondary side circuit board are accommodated within one housing. [Brief description of the drawings]

[0017] [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 schematic perspective view of the isolated converter shown in FIG. 1 as viewed from the other side. [Diagram 3] 2 is a central cross-sectional view of the isolated converter shown in FIG. 1. [Figure 4] 2 is a cross-sectional view for explaining an attachment state of the coil substrate shown in FIG. 1. [Diagram 5] FIG. 2 is a schematic perspective view of a core of the isolated converter shown in FIG. [Figure 6] FIG. 6 is an exploded perspective view of the core shown in FIG. 5. [Figure 7] FIG. 2 is a schematic perspective view of the coil substrate shown in FIG. [Figure 8] 8 is a schematic perspective view for explaining first and second coil patterns of the coil substrate shown in FIG. 7. FIG. [Figure 9] 2 is a perspective view of a substrate including the coil substrate shown in FIG. 1. [Figure 10] FIG. 2 is a perspective view including the transformer shown in FIG. [Figure 11] 2 is a perspective view for explaining attachment of the rectifier circuit board shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An isolated converter according to an embodiment of the present invention will be described below with reference to FIGS.

[0019] 1. Overall structure of isolated converter 1 The isolated converter 1 according to this embodiment is a DC-DC converter and includes a transformer 3A. The transformer 3A is a core-type transformer including a coil substrate 3 and a core 10. As described later with reference to Figs. 7 and 8, the coil substrate 3 has a first coil pattern 36 that serves as a primary coil of the transformer 3A, and a second coil pattern 37 that serves as a secondary coil of the transformer 3A. As described later with reference to Figs. 7 and 10, the core 10 electromagnetically couples the first coil pattern 36 and the second coil pattern 37.

[0020] The isolated converter 1 further includes a primary circuit board and a secondary circuit board. In this embodiment, the primary 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.

[0021] 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.

[0022] 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 therefore detailed description thereof will be omitted.

[0023] In this embodiment, a DC-DC converter is exemplified as the isolated converter 1, but if the isolated converter 1 is a switching type AC-DC converter, the primary side circuit board is a rectifier circuit board including an electric circuit for AC-DC conversion further including four diodes, for example. As a result, the AC-DC converter includes an electric circuit for AC-DC conversion and a DC-DC converter.

[0024] 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 and Fig. 2, 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.

[0025] 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).

[0026] The inverter circuit board 4A faces one side wall 21A of the casing 20 at a distance so as to extend along the one side wall 21A. On the other hand, the rectifier circuit board 4B faces the other side wall 21B of the casing 20 at a distance so as to extend along the other side wall 21B. An input board 61A is mounted on the outer surface of one side wall 21A of the casing 20, on which an electrolytic capacitor 63A electrically connected to the inverter circuit board 4A and an input terminal 64A are mounted. An output board 61B is mounted on the outer surface of the other side wall 21B of the casing 20, on which an electrolytic capacitor 63B electrically connected to the rectifier circuit board 4B and an output terminal 64B are mounted. 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.

[0027] 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. Note that in this embodiment, as described later with reference to Figs. 4 and 11, the fastener 73 is inserted through the casing 20 without being screwed, and is screwed (fastened) to a spacer 45A (45B) fixed to the inverter circuit board 4A (rectifier circuit board 4B).

[0028] 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. 3. The space 52A (52B) accommodates an electrolytic capacitor 63A (63B), and wiring and the like that connects an input terminal 64A (output terminal 64B) to the inverter circuit board 4A (rectifier circuit board 4B).

[0029] 2. About Core 10 The core 10 electromagnetically couples the first coil pattern 36 and the second coil pattern 37 of the coil substrate 3 (see FIG. 8). As shown in FIG. 5 and FIG. 6, 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).

[0030] One divided body 11 has a first magnetic portion 11a inserted into a first insertion hole 31 formed in the coil substrate 3 shown in Fig. 10, and a second magnetic portion 11b inserted into a second insertion hole 32. As shown in Fig. 5, 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.

[0031] 6, a gap G (see FIG. 3, etc.) is formed between one divided body 11 and the other divided body 12 by sandwiching an insulating washer 19 between them. In the divided bodies 11 and 12, a groove portion 11d is formed along the first magnetic portions 11a, 12a and the second magnetic portions 11b, 12b.

[0032] When assembling the core 10, with the washer 19 in place, the segments 11, 12 are sandwiched between a pair of presser blocks 15, 16, and the shaft portion 14b of the connecting bolt 14 is inserted into the hole portion 16a of one of the presser blocks 16. At this time, the shaft portion 14b is further inserted through the washer 19 and accommodated in the grooves 12d, 11d. While maintaining this state, 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.

[0033] In this embodiment, the screw hole 15a is a screw hole that penetrates the other pressing block 15, so that the size of the gap G formed between the divided bodies 11, 12 can be adjusted to a desired size by adjusting the amount of tightening of the connecting bolt 14. Furthermore, the portion of the other pressing block 15 where the screw hole 15a is formed is recessed from the contact surface 15c described below. This recessed portion acts as an escape portion when the tip of the connecting bolt 14 protrudes due to tightening. The pair of pressing blocks 15, 16 and the connecting bolt (fastener) 14 are made of a non-magnetic material such as resin or ceramics.

[0034] In this manner, a magnetic circuit (magnetic path) between the primary coil and secondary coil of transformer 3A can be formed by split bodies 11 and 12. When assembling core 10, coil substrate 3 is placed on core 10, and then core 10 is assembled as shown in FIG.

[0035] 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.

[0036] As a result, the flat contact surface 15c of the other pressing block 15 comes into contact with the top wall 22 of the casing 20, and the core 10 can be attached to the casing 20 with high precision, and the core 10 is suspended above the bottom wall 24 of the casing 20. Furthermore, when the connecting bolt 14 is fastened, stress acts on one pressing block 16 in a direction that pushes the head 14a of the connecting bolt 14 into one pressing block 16. As a result, a larger stress acts on one pressing block 16 than on the other pressing block 15 due to the connecting bolt 14. A stress due to the fastening of the fixing screw 71 acts on the other pressing block 15. In this way, the stress caused by the head 14a of the connecting bolt 14 and the fixing screw 71 can be distributed to the pair of pressing blocks 15 and 16, so that the strength of the isolated converter can be stably ensured when the core 10 is assembled to the casing 20.

[0037] 3. Coil board 3 The coil substrate 3 has a first insertion hole 31 through which the first magnetic portion 11a of the core 10 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.

[0038] 8, in this embodiment, the coil substrate 3 has a conductive first coil pattern 36 around the first insertion hole 31, and has a second coil pattern 37 around the second insertion hole 32. Specifically, the coil substrate 3 is a laminated substrate in which a plurality of single-layer substrates 35 are laminated.

[0039] The single-layer substrate 35 is composed of a single-layer substrate on which a first conductive pattern 36A is formed around the first through-hole 31 and a second conductive pattern 37A is formed around the second through-hole 32, and a single-layer substrate on which only the first conductive pattern 36A is formed. The first conductive pattern 36A and the second conductive pattern 37A are rectangular patterns formed in a planar shape on a substrate body having insulation properties such as a glass epoxy substrate. The first conductive pattern 36A and the second conductive pattern 37A have openings 31a and 32a formed in accordance with the first through-hole 31 and the second through-hole 32.

[0040] In this embodiment, among the multiple stacked first conductive patterns 36A, only a pair of first conductive patterns 36A located at the outermost positions are connected to the terminal portion 34A of the inverter circuit board 4A. The first conductive patterns 36A of adjacent single-layer boards 35 are insulated from each other by the board body having the above-mentioned insulating properties. The first conductive patterns 36A of adjacent single-layer boards 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 each first conductive pattern 36A. This forms a first coil pattern 36 corresponding to the primary coil of the transformer 3A.

[0041] In this embodiment, a plurality of groups of the first conductive vias 38 (four in FIG. 8) arranged at equal intervals are arranged at intervals from the terminal portion 34A toward the opening 31a. The first conductive pattern 36A located in the top layer shown in FIG. 8 and the first conductive pattern 36A located in the layer below (second layer) are connected by a group of four first conductive vias 38 closest to the terminal portion 34A. Furthermore, the first conductive pattern 36A located in the lower layer (second layer) and the first conductive pattern 36A located in the layer further below (third layer) are connected by a group of four first conductive vias 38 adjacent to the opening 31a side with respect to the group of four first conductive vias 38 described above. In this way, as the number of layers increases, the group of the first conductive vias 38 connecting the first conductive patterns 36A is sequentially shifted toward the opening 31a side. In this way, as described later, 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.

[0042] In the present embodiment, similarly, among the plurality of second conductive patterns 37A, only a pair of second conductive patterns 37A located at the outermost positions are connected to the terminal portion 34B to the rectifier circuit board 4B. The second conductive patterns 37A of adjacent single-layer boards 35 are insulated from each other by the board body having the above-mentioned insulating properties. The second conductive patterns 37A of adjacent single-layer boards 35 are electrically connected to each other through the second conductive vias 39 so that current flows in the same circumferential direction around the openings 32a of each second conductive pattern 37A. This forms a second coil pattern 37 corresponding to the secondary coil of the transformer 3A. In the present 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 boards 35 on which only the first conductive pattern 36A is formed.

[0043] In this embodiment, a group of a plurality of evenly spaced second conductive vias 39 (three in FIG. 8) are arranged at intervals from the terminal portion 34B toward the opening 32a. As the number of layers increases, the group of a plurality of second conductive vias 39 connecting the second conductive patterns 37A to each other is sequentially shifted toward the opening 32a. In this way, as described later, 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 37 can be stabilized.

[0044] Furthermore, as shown in FIG. 7, the coil substrate 3 is formed with a through hole 33 penetrating the coil substrate 3 so as to separate the first through hole 31 and the second through hole 32. As described later, the coil substrate 3 may be filled with a molding material M having a relative dielectric constant lower than that of the insulating material of the substrate body 35a constituting the coil substrate 3. As a result, the through hole 33 is also filled with the molding material M having a relative dielectric constant lower than that 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. Furthermore, the surfaces on both sides of the coil substrate 3 are covered with an insulating layer 3c. By providing the insulating layer 3c, it is possible to prevent discharge between the first conductive pattern 36A and the second conductive pattern 37A and the core 10.

[0045] 4. Regarding the substrate structure including the coil substrate 3 As shown in FIG. 9, 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 is disposed along one side wall 21A of the casing 20, and one end (one side edge) 3a of the coil board 3 is joined to the surface (surface of the board body) on which the electronic components 42 of the inverter circuit board 4A are mounted. The coil board 3 and the inverter circuit board 4A may be joined by adhesion, or may be integrated by a connecting jig or the like. In this embodiment, the inverter circuit board 4A and the coil board 3 (the first coil pattern 36 of the inverter circuit board 4A) are integrally and electrically connected by soldering via the connecting terminals 41 connected to each other.

[0046] 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. In this embodiment, the rectifier circuit board 4B is disposed along the other side wall 21B of the casing 20, and the other end (other side edge) 3b of the coil board 3 is joined to the surface (surface of the board body) on which the electronic components 44 of the rectifier circuit board 4B are mounted. The coil board 3 and the rectifier circuit board 4B may be joined by adhesion, or may be integrated by a connecting jig or the like. In this embodiment, the rectifier circuit board 4B and the coil board 3 (the second coil pattern 37) are integrally and electrically connected by soldering via a connecting terminal 43 that connects them to each other.

[0047] Here, "attached to the coil substrate 3 extending in a direction perpendicular to the inverter circuit substrate 4A (rectifier substrate 4B) and the coil substrate 3" means that the inverter circuit substrate 4A (rectifier substrate 4B) is attached to the coil substrate 3 so that the normal line of the flat-shaped inverter circuit substrate 4A (rectifier substrate 4B) is perpendicular or substantially perpendicular to the normal line of the flat-shaped coil substrate 3. In this embodiment, the inverter circuit substrate 4A and the rectifier substrate 4B are attached to both ends of the coil substrate 3, forming an H-shaped substrate structure in a side view. However, the substrate structure is not limited to this structure, and these substrates may be attached to the coil substrate 3 so as to form a C-shaped or U-shaped substrate structure, for example.

[0048] According to this embodiment, the coil substrate 3, the inverter circuit substrate 4A, and the rectifier circuit substrate 4B can be handled as a single compact substrate structure. This makes it easier to manage the relative positions of the coil substrate 3, the inverter circuit substrate 4A, and the rectifier circuit substrate 4B with respect to the core 10, and improves the workability of assembling the isolated converter 1.

[0049] Furthermore, since the inverter circuit board 4A and the rectifier circuit board 4B are attached integrally to the coil board 3 so as to extend in a direction perpendicular to the coil board 3, the internal space S of the casing 20 can be utilized more effectively than in the case where these boards are arranged on the same plane. As a result, the casing 20 can be made compact, and the isolated converter 1 can be made smaller, thereby realizing a small footprint.

[0050] 5. Mounting structure of coil substrate 3 to casing 20 In this embodiment, the inverter circuit board 4A and the rectifier circuit board 4B are fixed to opposing side walls 21A and 21B of the casing 20, thereby holding the coil board 3 within the casing 20. Specifically, the inverter circuit board 4A is fixed to one side wall 21A, and the rectifier circuit board 4B is fixed to the other side wall 21B. As a result, the coil board 3 is supported by the casing 20 in a suspended state within the casing 20.

[0051] In this manner, the inverter circuit board 4A and the rectifier circuit board 4B are fixed to a pair of opposing side walls 21A, 21B of 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 attachment, and the coil board 3 can be held within the casing 20. This makes it possible to suppress deformation and distortion of the coil board 3 caused by directly attaching the coil board 3 to the casing 20, and therefore allows the coil board 3 to be attached to the core 10 with high precision.

[0052] Here, as shown in FIG. 4, 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.

[0053] Specifically, a spacer 45A is fixed to the inverter circuit board 4A with an adhesive or the like, and a spacer 45B is fixed to the rectifier circuit board 4B with an adhesive or the like. As shown in FIG. 11, the spacer 45A is a stepped cylindrical body having a large diameter portion 45a and a small diameter portion 45b. The spacer 45A is fixed to the inverter circuit board 4A in a state where the large diameter portion 45a abuts against the inverter circuit board 4A and the small diameter portion 45b is accommodated in the mounting hole 47 of the inverter circuit board 4A at the stepped portion. Although not shown, the spacer 45B also has the same shape as the spacer 45A, and the spacer 45B is fixed to the rectifier circuit board 4B in the same manner as the spacer 45A.

[0054] As shown in Fig. 4, in this embodiment, the fasteners 73 inserted through the side walls 21A, 21B are screwed into the spacers 45A, 45B and tightened, thereby attaching the inverter circuit board 4A and the rectifier circuit board 4B to the casing 20. Specifically, as shown in Fig. 11, the side wall 21A, the mounting member 50A, and the input board 61A of the casing 20 are each formed with mounting holes 21a, 51b, and 61b through which the fasteners 73 are inserted. The mounting holes 21a, 51b, and 61b are circular through holes that do not engage with the fasteners 73.

[0055] In this embodiment, a fastener 73 is inserted through the mounting holes 21a, 51b, and 61b of the side wall 21A, the mounting member 50A, and the input board 61A, and is screwed into the spacer 45A fixed to the inverter circuit board 4A, and the fastener 73 is tightened. Furthermore, a fastener 72 is inserted through the mounting holes 51a and 61a of the mounting member 50A and the input board 61A, and is screwed into the side wall 21A, and the fastener 72 is tightened. This makes it possible to fix the inverter circuit board 4A to the casing 20, as well as the mounting member 50A and the input board 61A.

[0056] Similarly, mounting holes are formed in the side wall 21B of the casing 20, the mounting member 50B, and the output board 61B, and fasteners 72, 73 can be used to fix the rectifier circuit board 4B to the casing 20, as well as to fix the mounting member 50B and the output board 61B.

[0057] 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. This allows the first insertion hole 31 to be positioned appropriately relative to the first magnetic portion 11a of the core 10 in the casing 20, and allows the second insertion hole 32 to be positioned relative to the second magnetic portion 11b of the core 10 so as to minimize the parasitic capacitance. In particular, by simply fastening the fastener 73, the first magnetic portion 11a and the second magnetic portion 11b of the core 10 (split body 11) can be positioned so as to minimize the parasitic capacitance of the first insertion hole 31 and the second insertion hole 32 of the coil board 3.

[0058] Specifically, the first through-hole 31 and the second through-hole 32 are circular through-holes. Therefore, the opening 31a of the first conductive pattern 36A and the opening 32a of the second conductive pattern 37A are also circular. The first magnetic portions 11a, 12a and the second magnetic portions 11b, 12b of the core 10 are substantially cylindrical. In this case, the parasitic capacitance between the core 10 and the first conductive pattern 36A and the parasitic capacitance between the core 10 and the second conductive pattern 37A can be minimized by positioning the opening 31a of the first conductive pattern 36A so that the center of the opening 31a coincides with the axis of the first magnetic portion 11a and the axis of the first magnetic portion 12a, and by positioning the opening 32a of the second conductive pattern 37A so that the center of the opening 32a coincides with the axis of the second magnetic portion 11b and the axis of the second magnetic portion 12b. In addition, 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.

[0059] 6. Molding into the casing 20 The internal space S of the casing 20 is filled with an insulating molding material M, and thereby the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B are sealed in the internal space S of the casing 20 with the molding material M. The molding material M is made of a thermosetting resin such as a silicone resin, an epoxy resin, or a urethane resin, and the molding material M is filled into the internal space S in a state where it is heated to a temperature lower than the curing start temperature, as necessary.

[0060] After the molding material M is filled in the internal space S, the insulating converter 1 is accommodated in a space in a reduced pressure or vacuum state, and a process is performed to remove air bubbles present inside the molding material M filled in the internal space S of the casing 20. Since the temperature of the molding material M during this process is relatively low (for example, about 25 to 40°C), the workability is good and the thermal influence on the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B is small. Furthermore, the thermal influence on the electrolytic capacitors mounted on the input board 61A and the output board 61B is small. After the process to remove the air bubbles, the molding material M is heated to a temperature (for example, about 40 to 120°C) equal to or higher than the thermal curing start temperature, so that the thermosetting resin of the molding material M can be thermally cured. As a result, the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B can be sealed in the internal space S of the casing 20 with the molding material M.

[0061] When the molding material M is made of a thermoplastic resin such as polystyrene resin, polyethylene resin, or polypropylene resin, it is necessary to melt the thermoplastic resin by heating it to a temperature equal to or higher than its softening point. Since the temperature of the molding material M at this time is high (for example, 100 to 150°C), the heat may affect not only the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B, but also the electrolytic capacitors 63A and 63B mounted on the input board 61A and the output board 61B.

[0062] In addition, it is necessary to house the isolated converter 1 in a space under reduced pressure or vacuum and perform a process to remove air bubbles inside the molding material M while the molding material M is melting. This requires an expensive vacuum furnace, and the workability is not good. For this reason, it is preferable to use a thermosetting resin for the molding material M.

[0063] When the isolated converter 1 is in use, heat is generated because a current flows through the inverter circuit board 4A and the rectifier circuit board 4B. Here, the inverter circuit board 4A faces one side wall of the casing 20 at a distance so as to extend along the one side wall 21A, and a molding material M is filled between the inverter circuit board 4A and the other side wall. Therefore, the heat generated by the inverter circuit board 4A is easily dissipated from the one side wall 21A of the casing 20 via the molding material M.

[0064] Similarly, the rectifier circuit board 4B faces the other side wall 21B of the casing 20 at a distance so as to extend along the other side wall 21B, and a molding material M is filled between the rectifier circuit board 4B and the other side wall 21B. Therefore, heat generated by the rectifier circuit board 4B is easily dissipated from the other side wall 21B of the casing 20 via the molding material M.

[0065] In this way, even when the transformer 3A, the inverter circuit board 4A, and the rectifier circuit board 4B are housed in a single casing 20, the heat generated by the inverter circuit board 4A and the rectifier circuit board 4B can be efficiently dissipated from a pair of side walls 21A, 21B of the casing.

[0066] In this embodiment, among the molding materials M made of the resins exemplified above, it is preferable that the internal space S of the casing 20 is filled with a molding material M having a relative dielectric constant lower than that of the insulating material of the substrate body constituting the coil substrate 3. It is more preferable that the relative dielectric constant of the molding material M is lower than that of the insulating material of the substrate body constituting the inverter circuit substrate 4A and the rectifier circuit substrate 4B.

[0067] The molding material M filled in the internal space S of the casing 20 ensures the withstand voltage of the transformer 3A, while the dielectric constant of the molding material M is set lower than that of the insulating material of the substrate body, thereby suppressing an increase in parasitic capacitance caused by the molding material M. When the insulating material of the substrate body is glass epoxy, its dielectric constant is 4.0, so that the dielectric constant of the molding material M is preferably less than 4.0 (for example, 2.0 to 3.0).

[0068] Furthermore, as described above, an input board 61A on which an electrolytic capacitor 63A and an input terminal 64A electrically connected to the inverter circuit board 4A are mounted is attached to the outer surface of one side wall 21A of the casing 20. An output board 61B on which an electrolytic capacitor 63B and an output terminal 64B electrically connected to the rectifier circuit board 4B are mounted is attached to the outer surface of the other side wall 21B of the casing 20.

[0069] The electrolytic capacitors 63A and 63B have a lower heat resistance temperature compared to other electronic components because they contain an electrolyte. In view of this, in this embodiment, the electrolytic capacitors 63A and 63B are mounted on the input board 61A and the output board 61B, and are disposed outside the casing 20. This makes it possible to suppress the influence of heat transferred from the molding material M to the electrolytic capacitors 63A and 63B when the molding material M is filled into the casing 20. If a thermosetting resin such as epoxy resin is used for the molding material M, it is sufficient to thermally cure it before attaching the input board 61A and the output board 61B to the casing 20.

[0070] Furthermore, a pair of mounting members 50A, 50B for mounting the casing 20 are 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. A space 52A is formed in the mounting member 50A in a portion where the input terminal 64A and the electrolytic capacitor 63A are located.

[0071] Specifically, a space 52A is formed in the mounting member 50A at a portion where the input terminal 64A and the electrolytic capacitor 63A are located. The input terminal 64A and the electrolytic capacitor 63A are connected in the space 52A by inserting wiring (not shown) from the inverter circuit board 4A into an insertion hole (not shown) formed in one side wall 21A of the casing 20.

[0072] Similarly, a space 52B is formed in the mounting member 50B in a portion where the output terminal 64B and the electrolytic capacitor 63B are located. The output terminal 64B and the electrolytic capacitor 63B are connected in the space 52B by inserting wiring (not shown) from the rectifier circuit board 4B into an insertion hole (not shown) formed in the other side wall 21A of the casing 20.

[0073] Furthermore, the mounting members 50A, 50B have spaces 52A, 52B formed in the portions where the electrolytic capacitors 63A, 63B are located, and these spaces 52A, 52B act as heat insulating layers. As a result, the influence of heat transferred from the casing 20 to the electrolytic capacitors 63A, 63B can be suppressed. Note that, when the isolated converter is in use, the heat generated by the inverter circuit board 4A and the rectifier circuit board 4B has a lower amount of heat per unit time than the heat generated during molding, and therefore, even if these spaces 52A, 52B are formed, the heat is dissipated from the mounting members 50A, 50B.

[0074] 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.

[0075] In this embodiment, the core is a split core consisting of a pair of U-shaped segments, and a coil board is arranged on this split core, but as long as a primary circuit board and a secondary circuit board can be attached to the coil board, the shape of the split core and the shapes of the first and second coil patterns of the coil board are not particularly limited. [Explanation of symbols]

[0076] 1: isolated converter, 3: coil board, 3A: transformer, 3c: insulating layer, 4A: inverter circuit board (primary circuit board), 4B: rectifier circuit board (secondary circuit board), 10: core, 11a: first magnetic part, 11b: second magnetic part, 20: casing, 21A, 21B: side wall, 31: first insertion hole, 32: second insertion hole, 36: first coil pattern, 37: second coil pattern, 45A, 45B: spacer, 50A, 50B: mounting member, 52A, 52B: space, 61A: input board, 61B: output board, 63A, 63B: electrolytic capacitor, 64A: input terminal, 64B: output terminal, 73: fastener, M: molding material, S: internal space

Claims

1. a transformer including a coil substrate having a first coil pattern serving as a primary coil and a second coil pattern serving as a secondary coil, and a core that electromagnetically couples the first coil pattern and the second coil pattern; a primary side circuit board electrically connected to the first coil pattern at one end of the coil board; a secondary circuit board electrically connected to the second coil pattern at the other end of the coil board; An isolated converter comprising: the isolated converter includes an insulating casing that houses the transformer, the primary circuit board, and the secondary circuit board; the primary side circuit board faces one of a pair of side walls of the casing at a distance so as to extend along the one side wall, the secondary circuit board faces the other of the pair of side walls of the casing at a distance so as to extend along the other of the pair of side walls, an insulating molding material is filled into the internal space of the casing, and thereby the transformer, the primary side circuit board, and the secondary side circuit board are sealed in the internal space of the casing with the molding material.

2. an input board having an input terminal and an electrolytic capacitor electrically connected to the primary circuit board attached to an outer surface of the one side wall; 2. The isolated converter according to claim 1, wherein an output board is attached to an outer surface of the other side wall, the output board including an electrolytic capacitor electrically connected to the secondary circuit board and an output terminal.

3. a pair of mounting members for mounting the casing are disposed between the input board and the one side wall and between the output board and the other side wall; 3. The isolated converter according to claim 2, wherein each of the mounting members has a space formed in a portion where the electrolytic capacitor is located.

4. 2. The isolated converter according to claim 1, wherein the internal space of the casing is filled with a molding material having a relative dielectric constant lower than a relative dielectric constant of an insulating material of a substrate body constituting the coil substrate.

5. the isolated converter is a DC-DC converter, the primary side circuit board is an inverter circuit board having a switching element mounted thereon, which converts DC power into AC power by the switching element and supplies the AC power to the coil board; 2. The isolated converter according to claim 1, wherein the secondary side circuit board is a rectifier circuit board that rectifies a current output from the coil board.

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