JPH06104129A - Transformer - Google Patents

Abstract

PURPOSE:To realize a low-cost transformer manufacturable without winding work, by providing parts of primary and secondary windings on a printed board beforehand in the shape of conductive patterns. CONSTITUTION:A plurality of bobbins 14 and 16 having tabular resin parts 24 and 26, formed by coating the central horizontal parts 20a and 22a of a plurality of U-shaped winding terminals 20 and 22 by resin molding respectively, are laminated in the direction of the board thickness of the resin parts 24 and 26, and recessions 24a are formed on one contact surface of the resin parts 24 and 26, and protrusions 26a fittable to the recessions 24a are formed on the other. A transformer unit 12 is formed by fitting a pair of cores 18a and 18b to the bobbins 14 and 16 laminated so as to interpose the central horizontal parts 20a and 22a of the winding terminals 20 and 22, and the transformer unit 12 is mounted on a printed wiring board 34 having conductive patterns. And their respective winding terminals 20 and 22 are properly short-circuited with the conductive patterns to form primary and secondary windings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer used for a switching power supply or the like. In recent years, power transformers are becoming more compact and less costly, and there is a growing demand for high safety and support for automatic mounting. In response to these needs, resin-filled types with cases are often used. Is starting to appear.

This resin-filled transformer has a high heat dissipation performance by being filled with a resin, so that it can be miniaturized, and it does not emit smoke in the event of overload and is highly safe. In addition, it has the feature that it can easily comply with safety standards due to improved insulation.

On the other hand, due to the recent demand for high-density mounting, electronic parts have been switched to surface mounting type, and transformers for power supplies are no exception, and there is a demand for development of a transformer that can be miniaturized and can be surface mounted. ing.

[0004]

2. Description of the Related Art FIG. 6 shows a perspective view of a conventional general transformer, in which primary and secondary windings are wound around a bobbin 2 and a pair of E-shaped cores 6 are inserted into the bobbin 2. It is fixed with metal fittings 8. The terminal 10 is inserted into the through hole and attached to the printed wiring board.

This transformer requires (a) winding work,
(B) It is impossible to clean the entire surface because the winding is exposed.
(C) Since the core and windings are structurally floated from the printed wiring board, there is a problem that it is difficult to dissipate heat using a metal core printed wiring board or the like.

Therefore, in order to improve the wettability of the solder by cleaning the entire surface and to improve the moisture resistance after mounting, the resin formed by molding the entire transformer including the core excluding the terminals is made of insulating plastic. A filling type transformer has been proposed (Jitsuko 54-7320).

However, as described in this publication, when the entire part including the core is molded with a resin, the characteristics are deteriorated due to the stress caused by the hardening of the resin and the expansion / contraction stress due to the temperature change. Since there is a problem, a transformer in which a coil winding body is covered with a heat-resistant resin mold and a core is assembled to the coil winding body through the resin mold is disclosed in Japanese Utility Model Laid-Open No. 1-67706. ing.

[0008]

The transformer described in the above-mentioned publication has the advantage that the entire surface can be cleaned before mounting because the coil winding body is covered with the resin mold. However, there is a problem that the winding work is still required and that the core and the winding are structurally floated from the printed wiring board, so that it is difficult to dissipate heat using the metal core printed wiring board.

The present invention has been made in view of the above points, and an object thereof is to provide a low-cost transformer in which winding work can be omitted.

[0010]

A transformer for a switching power supply which operates at several hundreds of KHz can have a very small number of turns on both the primary side and the secondary side. Therefore, in the present invention, a conductive pattern forming part of the primary and secondary windings is provided on the printed wiring board, and a transformer unit having no winding is mounted on the printed wiring board. It was completed as a transformer.

That is, according to the present invention, a plurality of bobbins each having a plate-shaped resin portion formed by coating a central horizontal portion of each of a plurality of substantially U-shaped winding terminals with a resin mold are provided. The plurality of bobbins are laminated in the thickness direction, and a concave portion is formed on one of the contact surfaces of the resin portions and a convex portion is formed on the other surface so as to be fitted in the concave portion, and the central horizontal portion of the winding terminal is sandwiched therebetween. A pair of cores are attached to form a transformer unit.

Then, this transformer unit is mounted on a printed wiring board having a conductive pattern, and the winding terminals are appropriately short-circuited by the conductive pattern to form primary and secondary windings. .

[0013]

In the transformer of the present invention, by mounting a transformer unit having no winding on a printed wiring board, a part of the winding terminals and a part of the conductive pattern form the primary winding. Then, the secondary winding is formed by the other part of the winding terminal and the other part of the conductive pattern to complete the transformer.

Therefore, the manufacturing of the transformer unit does not require a complicated transformer winding process, and the transformer manufacturing can be facilitated and the cost can be reduced. In addition, each bobbin having winding terminals is formed independently, and is integrated by fitting a convex portion into a concave portion facing each other at the time of assembly. The cutting can be performed without being interfered by other bobbins, and the relative position of each bobbin can be easily determined, which facilitates manufacturing.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. With reference to FIGS. 1 to 3, reference numeral 12 denotes a transformer unit of the present invention, which does not have windings which are essential in conventional transformers.

The transformer unit 12 includes a first bobbin 14, a second bobbin 16, and a pair of cores 18a, 18b.
Composed of. The first and second bobbins 14 and 16 are plate-shaped by covering the central horizontal portions 20a and 22a of the first and second winding terminals 20 and 22 formed in a plurality of substantially U-shapes with a resin mold. The resin portions 24 and 26 are formed.

On the lower surface of the resin portion 24 of the first bobbin 14,
A plurality of concave portions 24a are formed, and the concave portion 24a is formed on the upper surface of the resin portion 26 of the second bobbin 16 so as to face the concave portions 24a.
Is formed with a plurality of protrusions 26a.

The first and second bobbins 14 and 16 are
Resin parts 24, 26 are formed by resin-molding by exposing the vicinity of both sides of the ladder of the intermediate terminal member obtained by punching the sheet metal into a ladder shape.
After forming, the tip of the exposed portion is cut and bent to be manufactured.

After the first and second bobbins 14 and 16 are manufactured independently, the convex portion 26a is formed in the facing concave portion 24a.
Are integrated with each other by inserting the cores 18a, 18 into the bobbins 14, 16 such that the central horizontal portions 20a, 22a of the first and second winding terminals 20, 22 are sandwiched therebetween.
The transformer unit 12 is constructed by attaching b.

As is apparent from FIG. 1, the first winding terminal 2
0 is longer than the second winding terminal 22, and the first and second winding terminals 22
With the bobbins 14 and 16 integrated, the first winding terminal 2
The vertical portion 20b of 0 is arranged outside the vertical portion 22b of the second winding terminal 22.

On the upper surface of the resin portion 24 of the first bobbin 14 and the lower surface of the resin portion 26 of the second bobbin 16, respectively, the step portion 2 is formed.
4b, 26b are formed, and the stepped portions 24b, 26 are formed.
cores 18a and 18b are fitted in the core 1b
8a and 18b are attached to the first and second bobbins 14 and 16. The cores 18a and 18b are fixed by winding, for example, a polyester film.

The transformer unit 12 configured as described above is provided with a plurality of lands 28 as shown in FIG.
The printed wiring board 34 having the first conductive pattern 30 and the second conductive pattern 32 is mounted as shown in FIG.

As described above, when the transformer unit 12 is mounted on the printed wiring board 34, a part of the first winding terminal 20 is short-circuited by the first conductive pattern 30 of the printed wiring board 34 to form the secondary winding. Similarly, each of the second winding terminals 22 is short-circuited by the second conductive pattern 32 to form a primary winding, thereby forming a transformer.

One core 18b of the transformer unit 12
Is mounted in close contact with the printed wiring board 34. Therefore, when a metal core printed wiring board is used for the printed wiring board, the heat generated by the transformer can be released to the metal core printed wiring board via the core 18b, resulting in a heat dissipation effect. Can be expected.

By fixing the core 18b with a silicone rubber adhesive or an epoxy adhesive, a further heat dissipation effect and a reliable fixing can be achieved. According to this embodiment, since the first bobbin 14 and the second bobbin 16 are manufactured independently, they are integrated by fitting the convex portion 26a into the concave portion 24a.
There is no risk of the relative positions of the two being displaced, and the intermediate terminal member can be easily cut and bent during the bobbin manufacturing process, facilitating the manufacturing.

It is also possible to easily achieve various types of voltage conversion by preparing a plurality of types of bobbins having the same structure as the first and second bobbins 14 and 16 and changing the combination thereof.

Further, as shown in FIG. 5, a transformer having various characteristics can be constructed by changing the conductive pattern on the printed wiring board. In addition, in the above-described embodiment, the configuration of the transformer suitable for surface mounting is shown, but it goes without saying that an insertion mounting type transformer can be obtained by changing the shape of the exposed portions of the winding terminals 20 and 22. Yes.

Although the bobbin has two stages in the above-mentioned embodiment, it may have three or more stages.

[0029]

Since the transformer of the present invention is constructed as described above in detail, the winding work can be omitted and the cost can be reduced. Further, since the entire surface can be washed, it can be mounted on the surface, and heat can be easily radiated, so that the transformer can be made smaller and thinner.

Further, each bobbin having a winding terminal is formed independently, and is integrated by fitting a convex portion into a concave portion facing each other at the time of assembly. Bending and cutting can be performed without being interfered by other bobbins, and the relative positions of the bobbins can be easily determined, which facilitates manufacturing.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of the present invention.

FIG. 3 is a side view of the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a conductive pattern on a printed wiring board.

FIG. 5 is a diagram showing another example of a conductive pattern on a printed wiring board.

FIG. 6 is a perspective view of a conventional general transformer.

[Explanation of symbols]

 12 transformer unit 14,16 bobbin 18a, 18b core 20,22 winding terminal 24,26 resin part 24a concave part 26a convex part 30,32 conductive pattern 34 printed wiring board

Claims (1)

[Claims] 1. A plurality of substantially U-shaped winding terminals (2
A plurality of bobbins (14, 26) in which a plate-shaped resin portion (24, 26) is formed by covering the central horizontal portion (20a, 22a) of (0, 22) with a resin mold.
16) is laminated in the plate thickness direction of the resin part (24, 26), and the concave part (24a) is provided on one of the contact surfaces of each resin part (24, 26) and the concave part (24a) is provided on the other side. A pair of cores (18a) is formed on the plurality of bobbins (14, 16) that are formed by forming a protrusion (26a) to be fitted and sandwiching the central horizontal portion (20a, 22a) of the winding terminal (20, 22). , 18b) to form a transformer unit (12), the transformer unit (12) is mounted on a printed wiring board (34) having conductive patterns (30, 32), and each of the winding terminals ( A transformer in which primary and secondary windings are formed by appropriately shorting 20,22) with conductive patterns (30,32).