Transformer

Abstract

To provide a transformer, formed on a printed circuit board, which can suppress the volume of the printed circuit board.SOLUTION: A transformer disclosed in the present specification comprises: a printed circuit board having a first coil made of a wiring pattern on a conductor layer; and a second coil, located outside the printed circuit board, which faces the first coil. Unlike transformers according to prior arts where all the coils are formed on a printed circuit board, the transformer disclosed herein is designed such that only the first coil is formed by the wiring pattern on the printed circuit board, and that the second coil is prepared separately from the printed circuit board. This structure can reduce the volume of the printed circuit board provided in the transformer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a transformer, and more particularly to a transformer that utilizes a wiring pattern on a printed circuit board. [Background technology]

[0002] Transformers that utilize wiring patterns on printed circuit boards are known (for example, Patent Document 1). In the transformer of Patent Document 1, one coil is made by connecting wiring patterns on one or more conductor layers. The transformer includes two or more coils. In the transformer of Patent Document 1, the wiring patterns on one or more conductor layers form the primary coil, and the wiring patterns on another one or more other conductor layers form the secondary coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-198246 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional transformers using printed circuit boards, all coils are formed on conductor layers. Adopting a printed circuit board with multiple conductor layers increases the volume of the printed circuit board. This specification provides a transformer with a small volume of printed circuit board. [Means for solving the problem]

[0005] The transformers (100, 200, 300) disclosed in this specification include a printed circuit board (110) with a first coil (120) formed as a wiring pattern on conductor layers (111a, 111b), and a second coil (130, 330) disposed outside the printed circuit board and facing the first coil. In conventional transformers, all coils are formed on the printed circuit board, whereas in the transformers disclosed in this specification, only the first coil is formed as a wiring pattern on the printed circuit board, and the second coil is prepared separately from the printed circuit board. This structure makes it possible to reduce the volume of the printed circuit board provided in the transformer. The first coil may be the primary coil, or the second coil may be the primary coil.

[0006] A typical second coil may be a flat wire wound edgewise more than one turn. When the second coil is made of flat wire, the second coil does not include a substrate. Furthermore, by using a second coil made of flat wire wound more than one turn, a thin transformer with high inductance can be realized.

[0007] The second coil may be bonded to the conductor layer on which the first coil is formed, allowing the first coil to be bonded without increasing the number of layers of the printed circuit board.

[0008] The rectangular wire is covered with an insulating coating (133), and it is preferable that the breakdown voltage of the insulating coating is higher than the breakdown voltage of the insulating layer (112) of the printed circuit board. The insulation between the rectangular wire and the printed circuit board can be ensured by the thin insulating coating.

[0009] It is preferable that a gap (201) is provided between the second coil and the printed circuit board, and insulation between the second coil and the printed circuit board can be ensured by the air gap.

[0010] Another typical example of the second coil may be a coil formed by a wiring pattern on a sub-board (350) that is smaller than the printed circuit board. By employing a second coil on a sub-board that is smaller than the printed circuit board, the volume of the printed circuit board can also be made smaller than that of conventional transformers.

[0011] A protrusion (338) may be provided on one of the printed circuit board and the sub-board, and the other may be in contact with the protrusion, ensuring an air gap between the printed circuit board with the first coil and the sub-board with the second coil.

[0012] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a transformer 100 according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the transformer of the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the transformer 100 taken along line III-III in FIG. [Figure 4] 4 is a cross-sectional view of the transformer 100 taken along line IV-IV in FIG. [Figure 5] FIG. 10 is a cross-sectional view of a transformer 200 according to a second embodiment. [Figure 6] FIG. 10 is a perspective view of a transformer 300 according to a third embodiment. [Figure 7] FIG. 10 is an exploded perspective view of a transformer 300 according to a third embodiment. [Figure 8] 8 is a cross-sectional view of the transformer taken along line VIII-VIII in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First Embodiment) A transformer 100 of a first embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view of the transformer 100. FIG. 2 is an exploded perspective view of the transformer 100. FIG. 3 is a cross-sectional view of the transformer 100 taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view of the transformer 100 taken along line IV-IV in FIG. 1.

[0015] Transformer 100 includes a printed circuit board 110, a first coil 120, a second coil 130, and a core 140. As shown in the cross-sectional views of Figures 3 and 4, printed circuit board 110 has a three-layer structure in which an insulating layer 112 is sandwiched between two conductor layers 111a and 111b. For ease of explanation, one surface of printed circuit board 110 (the side of conductor layer 111a) will be referred to as the front surface, and the other surface (the side of conductor layer 111b) will be referred to as the back surface of printed circuit board 110.

[0016] The printed circuit board 110 is provided with a circular through-hole 113a and rectangular through-holes 113b, 113b. The first coil 120 is formed by a wiring pattern on the conductor layers 111a, 111b. The first coil 120 is formed so as to surround the circular through-hole 113a of the printed circuit board 110. Coils are formed by wiring patterns on each of the conductor layers 111a, 111b, and these are connected in series through vias 116a (FIG. 4) that penetrate the printed circuit board 110. The first coil 120 is connected to a control element 119a by another wiring pattern formed on both sides of the printed circuit board 110. The control element 119a controls the current flowing through the first coil 120.

[0017] The second coil 130 is composed of two coils 130a and 130b. The coils 130a and 130b are arranged on the front and back sides of the printed circuit board 110, respectively. The coil 130a is connected to supporting portions 131 and 132, respectively. The supporting portions 131 and 132 are connected to terminals 115a and 115b formed on the conductor layer 111a of the printed circuit board 110. The supporting portions 131 and 132 are joined to the terminals 115a and 115b, thereby fixing the coil 130a to the printed circuit board 110. The same is true for the coil 130b. The two coils 130a and 130b are connected in series to one of the terminals 115a and 115b via the via 116b (FIG. 4). The series-connected coils 130a and 130b form the second coil 130. The second coil 130 is disposed so as to surround the through-hole 113a of the printed circuit board 110, and faces the first coil 120. Both ends of the second coil 130 are connected to the control element 119b by wiring patterns formed on the conductor layers 111a and 111b.

[0018] The first coil 120 and the second coil 130 face each other and form a transformer. When a current flows through the first coil 120, an induced current flows through the second coil 130. The control element 119b rectifies the induced current generated in the second coil 130.

[0019] The core 140 includes an E-shaped core 141 and a flat core 142. The E-shaped core 141 includes a cylinder 141a and a pair of rectangular pillars 141b. The cylinder 141a passes through a through-hole 113a in the printed circuit board 110, and the pair of rectangular pillars 141b pass through a pair of through-holes 113b. The flat core 142 connects the tips of the cylinder 141a and the rectangular pillars 141b, which pass through the through-holes 113a and 113b. As shown in FIG. 3, the core 140 passes through the first coil 120 and the second coil 130 and surrounds them. When a current flows through the first coil 120, a magnetic field is generated in the core 140. The magnetic field generated in the core 140 generates a strong induced current in the second coil 130.

[0020] The transformer 100 of the first embodiment includes a printed circuit board 110, a first coil 120, a second coil 130, and a core 140. The printed circuit board 110 has a pair of conductor layers 111a and 111b and an insulating layer 112 sandwiched between them. The first coil 120 is formed by the wiring pattern of the conductor layers 111a and 111b on both sides of the printed circuit board 110. The second coil 130 is formed by edgewise wound rectangular wire. The second coil 130 is fixed to the printed circuit board 110 and is disposed outside the printed circuit board 110. In other words, the second coil 130 is adjacent to the printed circuit board 110 in the normal direction of the printed circuit board 110. The second coil 130 faces the first coil 120. A core 140 passes through the first coil 120 and the second coil 130. The transformer 100 includes a first coil 120 formed by a wiring pattern on the printed circuit board 110 and a second coil 130 arranged outside the printed circuit board 110, thereby enabling the volume of the printed circuit board 110 to be reduced.

[0021] As shown in FIG. 2, the second coil 130 is composed of two coils 130a and 130b wound edgewise in two turns. The two coils 130a and 130b are connected in series. That is, the second coil 130 is composed of a rectangular wire wound four turns. By using a rectangular wire wound multiple times, the second coil 130 is thin and has a large inductance. Furthermore, by using a rectangular wire, the second coil 130 can withstand a large current.

[0022] The rectangular wire of the second coil 130 is covered with an insulating coating 133 (FIGS. 3 and 4). The breakdown voltage of the insulating coating 133 is higher than the breakdown voltage of the insulating layer 112 of the printed circuit board 110. The thin insulating coating 133 ensures insulation between the rectangular wire of the second coil 130 and the printed circuit board 110.

[0023] The second coil 130 is joined to the conductor layers 111a and 111b of the printed circuit board 110 via support portions 131 and 132. The first coil 120 is formed on the conductor layers 111a and 111b. The second coil 130 is fixed to the conductor layers 111a and 111b on which the first coil 120 is formed. By joining the second coil 130 to the conductor layers 111a and 111b on which the first coil 120 is formed, there is no need to add another layer to the printed circuit board 110 to fix the second coil 130.

[0024] (Second Embodiment) Figure 5 shows a cross-sectional view of a transformer 200 of a second embodiment. The transformer 200 differs from the transformer 100 of the first embodiment in that an air gap 201 is provided between the printed circuit board 110 and the second coil 130. The rest of the structure of the transformer 200 is the same as that of the transformer 100 of the first embodiment.

[0025] The transformer 200 includes two coils 130a and 130b that constitute the second coil 130. Support portions 231 and 232 are connected to the coil ends of the two coils 130a and 130b, respectively. The heights of the support portions 231 and 232 (lengths in the normal direction to the printed circuit board) are higher than the support portions 131 and 132 of the transformer of the first embodiment. The two coils 130a and 130b are supported by the higher support portions 231 and 232, thereby ensuring an air gap 201 between the second coil 130 and the printed circuit board 110. The air gap 201 ensures insulation between the second coil 130 and the printed circuit board 110 (first coil 120).

[0026] (Third Embodiment) Figures 6-8 show a transformer 300 of a third embodiment. Figure 6 is a perspective view of the transformer 300, and Figure 7 is an exploded perspective view of the transformer 300. Figure 8 is a cross-sectional view of the transformer 300 taken along line VIII-VIII in Figure 6. The transformer 300 differs from the second coil 130 of the transformer 100 of the first embodiment in the configuration of the second coil 330. The other configurations of the transformer 300 are the same as those of the transformer 100 of the first embodiment.

[0027] The second coil 330 of the transformer 300 is formed on sub-substrates 350a and 350b. The transformer 300 includes a pair of sub-substrates 350a and 350b. The sub-substrate 350a is disposed on the front side of the printed circuit board 110, and the sub-substrate 350b is disposed on the back side of the printed circuit board 110. Similar to the printed circuit board 110, the sub-substrates 350a and 350b have a three-layer structure in which an insulating layer 352 is sandwiched between a pair of conductor layers 351a and 351b.

[0028] 7 and 8, coils 330a are formed as wiring patterns on each of a pair of conductor layers 351a and 351b of sub-substrate 350a, and are connected in series by vias 302. Coils 330b are also formed as wiring patterns on each of a pair of conductor layers 351a and 351b of sub-substrate 350b, and are connected in series by vias 302.

[0029] Four protrusions 358 are formed on the surface of sub-substrate 350b facing printed circuit board 110. The tips of the four protrusions 358 contact printed circuit board 110, and sub-substrate 350b is held parallel to printed circuit board 110. The four protrusions 358 also form an air gap 301 between sub-substrate 350b and printed circuit board 110. Sub-substrate 350a also has four protrusions 358, the tips of which contact printed circuit board 110, and air gap 301 is formed between sub-substrate 350a and printed circuit board 110. The four protrusions 358 also hold sub-substrate 350a parallel to printed circuit board 110, with gap 301 between them.

[0030] Protrusion 358 is a conductive land. One land (protrusion 358a shown in FIG. 8) is connected to coil 330a via wiring pattern 331. Protrusion 358a is connected to terminal 115a on the front surface of printed circuit board 110. Terminal 115a is electrically connected to terminal 115b on the back side of printed circuit board 110 via via 116b. Protrusion 358b of sub-board 350b is in contact with terminal 115b. Protrusion 358b is also a conductive land. Protrusion 358b is connected to wiring pattern 332 formed on the conductor layer of sub-board 350b, and wiring pattern 332 is connected to coil 330b. Coils 330a and 330b are connected in series via wiring patterns 331 and 332, protrusions 358a and 358b, terminals 115a and 115b, and via 116b, and they constitute one second coil 330. The protrusions 358 other than the protrusions 358a and 358b only need to function as spacers to ensure the gap 301 between the printed circuit board 110 and the sub-boards 350a and 350b, and do not need to be connected to other conductor patterns.

[0031] Sub-boards 350a and 350b including second coil 330 are fixed to printed circuit board 110 and are arranged outside printed circuit board 110. Sub-boards 350a and 350b are smaller than printed circuit board 110. Therefore, compared to when all coils are formed on a printed circuit board, the volume of the printed circuit board for the entire transformer can be made smaller than conventional.

[0032] The first coil 120 and the second coil 330 face each other. A gap 301 between the first coil 120 and the second coil 330 insulates the first coil 120 from the second coil 330.

[0033] First coil 120 and second coil 330 face each other, with the cylindrical core 140 passing through their centers. Core 140 also surrounds first coil 120 and second coil 330. A magnetic field is generated in core 140 by the current flowing through first coil 120, and this magnetic field generates an induced current in second coil 330.

[0034] The features and advantages of the transformer 300 of the third embodiment will be described. The transformer 300 includes a first coil 120 formed by a wiring pattern on a printed circuit board 110, and a second coil 330 formed by a wiring pattern on sub-boards 350a and 350b disposed outside the printed circuit board 110. The sub-boards 350a and 350b are smaller than the printed circuit board 110. This structure allows the volume of the printed circuit boards that make up the transformer to be smaller than when the second coil is formed by a wiring pattern inside the printed circuit board 110.

[0035] Here are some points to note regarding the technology described in the embodiments. In the transformers 100-300, coils are formed as wiring patterns on each of a pair of conductor layers 111a and 111b of the printed circuit board 110, and these coils constitute a first coil. The first coil may be formed by only a coil on one conductor layer of the printed circuit board, or may be formed by coils on three or more conductor layers.

[0036] 2 and 7, the coil 130a is a wiring pattern wound two times around the through-hole 113a on the conductor layer 111a of the printed circuit board 110. The coil 130a may be a wiring pattern wound only once around the through-hole 113a, or may be a wiring pattern wound three or more times.

[0037] The second coil 130 is joined to the conductor layers 111a and 111b on which the first coil 120 is formed. By joining the second coil 130 to the conductor layers 111a and 111b on which the first coil 120 is formed, there is no need to provide another conductor layer for joining the second coil.

[0038] In the transformers 100 and 200, coils 130a and 130b are arranged on both sides of the printed circuit board 110, and their series connection forms the second coil 130. The second coil may be arranged on only one side of the printed circuit board.

[0039] The first coil 120 has four turns. The first coil may have more than four turns or less than four turns. The second coil 130 (330) also has four turns, but the second coil may have more than four turns or less than four turns.

[0040] The first coil 120 may correspond to a primary coil of a transformer, and the second coil 130 (330) may correspond to a secondary coil of the transformer. Alternatively, the first coil 120 may correspond to a secondary coil of a transformer, and the second coil 130 (330) may correspond to a primary coil of the transformer.

[0041] In transformer 300, protrusions 358 are provided on sub-boards 350a and 350b, and their tips abut against printed circuit board 110. Protrusions 358 may also be provided on printed circuit board 110, and their tips may abut against sub-board 350a (350b). That is, it is sufficient that a protrusion is provided on one of the printed circuit board and the sub-board, and the tip of protrusion 358 abuts against the other of the printed circuit board and the sub-board.

[0042] The cross-sectional areas of the first coil 120 and the second coil 130 (330) are determined according to the magnitude of the expected current. It is preferable that a low current flows through the first coil 120 formed by a wiring pattern on the printed circuit board 110, and a large current flows through the second coil 130 made of rectangular wire or the second coil 330 formed by a wiring pattern on the sub-board 350.

[0043] The terminals 115a and 115b are plated with a conductive material and are joined to the printed circuit board 110 with solder.

[0044] The second coil 130 of the transformer 100 may be fixed to the printed circuit board 110 with an insulating adhesive. The thickness of the adhesive and the distance between the windings may be determined according to the upper limit of the allowable inter-winding capacitance between the first coil and the second coil. The thickness of the insulating layers of the printed circuit board and the sub-board may also be determined based on the upper limit of the allowable inter-winding capacitance.

[0045] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0046] 100, 200, 300: transformer 110: printed circuit board 111a, 111b: conductor layer 112: insulating layer 113a, 113b: through hole 115a, 115b: terminal 116a, 116b, 302: via 119a, 119b: control element 120: first coil 130, 330: second coil 130a, 130b, 330a, 330b: coil 131, 132, 231, 232: support portion 133: insulating coating 140: core 141: E-shaped core 142: flat core 201, 301: gap 331, 332: wiring pattern 350a, 350b: sub-board 351a, 351b: conductor layer 352: insulating layer 358, 358a, 358b: Protrusion

Claims

1. a printed circuit board (110) having a first coil (120) formed by a wiring pattern on conductor layers (111a, 111b); a second coil (130, 330) disposed outside the printed circuit board and facing the first coil; A transformer (100, 200, 300) comprising:

2. 2. The transformer (100, 200) of claim 1, wherein the second coil (130) is a rectangular wire wound edgewise for more than one turn.

3. 3. The transformer (100, 200) according to claim 2, wherein the second coil (130) is bonded to the conductor layer (111a, 111b) on which the first coil is formed.

4. 3. The transformer according to claim 2, wherein the rectangular wire is covered with an insulating coating (133), and the dielectric breakdown voltage of the insulating coating is higher than the dielectric breakdown voltage of the insulating layer (112) of the printed circuit board.

5. The transformer (200) according to claim 2, wherein a gap (201) is secured between the second coil and the printed circuit board.

6. 2. The transformer (300) according to claim 1, wherein the second coil (330) is formed as a wiring pattern on a sub-board (350) that is smaller than the printed circuit board (110).

7. 7. The transformer (300) according to claim 6, wherein one of the printed circuit board (110) and the sub-board (350) has a projection (338), and the other is in contact with the projection.

8. The transformer (100, 200, 300) according to any one of claims 1 to 7, further comprising a core (140) passing through the first coil and the second coil and surrounding the first coil and the second coil.

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