JP2000077239A - Shield thin transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce leak flux and the entire height by fitting primary and secondary coil to the coil accommodation part of a dish core, by forming a closed magnetic circuit by a flat core at an area to the center leg of the dish core, by blocking the opening surface of the dish core, and by uniformly mounting two bases flush with the flat core. SOLUTION: Primary and secondary coils 12 and 13 are inserted into a center leg 2 of a dish core 1, and is concentrically fitted to a coil accommodation part. A dish core 7 is engaged and fitted across stage recessed parts formed at the outer-periphery frame of the dish core 1, and is fixed by an adhesive. At this time, a gap (g) is formed between the rear side of the flat core 7 and the tip surface of the center leg 2, and a closed magnetic circuit is formed by the dish core 1 and the flat core 7 through the gap (g). Then, a base 8 is positioned and fixed at the outer-periphery frame of the dish core 1, and the opening surface of the dish core 1 is closed by the flat core 7 and two bases 8. Also, the flat core 7 is allowed to be nearly flush with the base 8.

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.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been reduced in size and weight, transformers and coils used in them have also been required to be reduced in size, thickness, and height.

[0003]

A conventional transformer is shown in FIG.
A drum core having upper and lower flanges, a primary winding and a secondary winding concentrically wound around a winding shaft portion of the drum core,
It is composed of a base for mounting and fixing the drum core and a ring core mounted on the outer periphery of the drum core. The base is provided with terminals for connecting the primary winding and the secondary winding. -Is a gap formed by the upper flange of the drum core and the upper end of the ring core. In the transformer having the above configuration, the magnetic flux easily leaks to the outside from the upper gap portion, and there is a high possibility that the surrounding electronic components are magnetically damaged. In order to reduce the leakage magnetic flux, a shield sheet is placed on the upper surface of the transformer. However, if the shield sheet is placed, there arises a problem that the electrical characteristics of the transformer change.

On the other hand, in the transformer shown in FIG. 2 in which the same reference numerals are given to the same parts as in FIG. 1, a drum core having a primary winding and a secondary winding wound thereon is covered with a bottomed cylindrical cap core, and a gap is formed. Since it is formed between the lower flange of the drum core and the inner periphery of the opening of the cap core, the leakage magnetic flux to the outside can be reduced, but the height of the entire transformer is increased by the thickness t of the upper surface of the cap core, and the height is low. There was a problem that goes against the conversion.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional transformer, and has as its object to reduce the leakage magnetic flux to the outside and to reduce the entire transformer. To reduce the height (thickness).

According to a first aspect of the present invention, there is provided a thin transformer, wherein a dish-shaped core having a concave winding accommodating portion formed between a central leg protruding from an opening surface and an outer peripheral frame; Primary and secondary windings concentrically mounted in the winding accommodating section of the core and the upper surface of the central leg of the dish-shaped core and straddling the two opposite sides of the frame. A plate-shaped core which is mounted and forms a closed magnetic path between the plate-shaped core and the central leg of the plate-shaped core, and sandwiches the plate-shaped core and closes an opening surface of the plate-shaped core to be flush with the plate-shaped core. It is characterized by comprising two attached bases. With this configuration, the height of the entire transformer can be reduced, and the leakage magnetic flux can be reduced.

According to a second aspect of the present invention, there is provided a thin transformer, wherein a hole or a step is formed in an outer peripheral frame portion of a dish-shaped core, and an engaging portion corresponding to the hole or the step is formed in each of two bases. It is characterized in that the two bases are positioned and mounted on the outer peripheral frame of the dish-shaped core. With this configuration, the mounting positions of the bases can be kept constant.

According to a third aspect of the present invention, there is provided a thin transformer in which step recesses are formed on two opposing sides of an outer peripheral frame of a dish-shaped core, and a plate-shaped core is fitted. By doing so, the connection between the dish-shaped core and the plate-shaped core is ensured.

According to a fourth aspect of the present invention, there is provided a thin transformer using a ferrite core having an insulating property as a material of a dish-shaped core and a plate-shaped core, and a bobbin for mounting a primary winding and a secondary winding. Can be omitted.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. The magnetic-shield type thin transformer of the present invention comprises:
Dish-shaped core 1, plate-shaped core 7, two bases 8, primary winding 1
And a secondary winding 13. The dish-shaped core 1 and the plate-shaped core 7 are formed of an insulating ferrite core, for example, a nickel-based ferrite core. A concave winding storage part 4 is formed between the central leg part 2 and the outer peripheral frame part 3 protruding from the opening surface, and the winding storage part 4 is preliminarily wound into a flat shape by a self-fusing insulated wire. The primary winding 12 and the secondary winding 13 are mounted concentrically. Reference numeral 5 denotes a stepped recess formed on two opposing sides of the outer peripheral frame 3 of the dish-shaped core 1, and 6 denotes a step or a hole formed in the outer peripheral frame. The plate-shaped core 7 has a width that fits into the stepped recess 5 of the dish-shaped core 1, and when fitted into the stepped recess 5, a gap g is formed between the inner side surface and the center leg 2. It is.
The base 8 is a flat plate, and has a plurality of terminals 9 and a primary winding 12.
And a groove 10 for pulling out an end of the secondary winding 13 and an engaging portion 11 such as a projection engaging with a step or a hole 6 formed in the outer peripheral frame 3 of the dish-shaped core 1.

The assembling process of the magnetic-shield type thin transformer having the above configuration will be described with reference to FIG. First, the primary winding 12 and the secondary winding 13 are inserted through the central leg 2 of the dish-shaped core 1, and are mounted concentrically on the winding housing 4. Next, the plate-shaped core 7 is fitted and mounted across the stepped recesses 5 formed in the outer peripheral frame portion 3 of the dish-shaped core 1 and fixed with an adhesive. At this time, a gap g is formed between the back side of the plate-shaped core 7 and the front end surface of the center leg 2, so that the dish-shaped core 1 and the plate-shaped core 7 form a closed magnetic path through the gap g. And the terminals 9 of the two bases 8
Is fixed to the side 16 of the plate-shaped core 7, the engaging portion 11 is engaged with the step portion or the hole 6 of the plate-shaped core 1, and the base 8 is attached to the outer peripheral frame of the plate-shaped core 1. The opening surface of the dish-shaped core 1 is sealed by the plate-shaped core 7 and the two bases 8 while being positioned and fixed to the portion 3. In addition, the plate-shaped core 7 and the base 8
Is almost flush. Also, the primary winding 12
Each terminal of the secondary winding 13 is drawn out of the dish-shaped core 1 from the winding housing 4 through the groove 10 of the base 8 and connected to the terminal 9.

[0012]

As described above, according to the present invention, the dish-shaped core 1 and the plate-shaped core 7 are formed of an insulative ferrite core, and the primary winding 12 and the secondary winding 13 are self-contained. It is formed in a flat shape using a fusion-bonded insulated wire, and has a central leg 2 of a dish-shaped core 1.
The plate-shaped core 7 is fitted directly into the stepped concave portion 5 formed on the opposite side of the outer peripheral frame portion 3 of the dish-shaped core 1, so that the conventional bobbin or drum core can be used. There is no need to use them, the number of parts can be reduced, and the height (thickness) can be reduced by the thickness of the flanges because no bobbin or drum core is used. The opening surface of the dish-shaped core 1 is composed of a plate-shaped core 7 and a base 8.
Therefore, the leakage magnetic flux to the outside can be reduced. Further, since the plate-shaped core 7 only needs to be large enough to cover the upper surface of the central leg 2 of the dish-shaped core 1, the overall manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing one example of a conventional transformer, FIG. 2 is a cross-sectional explanatory view showing another example of a conventional transformer, and FIG. 3 shows one example of a dish-shaped core related to the thin transformer of the present invention.
(A) is a sectional side view, and (b) is a front view. 4A and 4B show a plate-shaped core relating to the thin transformer of the present invention, wherein FIG. 4A is a sectional side view and FIG. 4B is a front view. 5A and 5B are views showing an assembled state of the thin transformer of the present invention, wherein FIG. 5A is a sectional side view and FIG. 5B is a bottom view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dish-shaped core 2 ... Central leg part 3 ... Outer peripheral frame part 4 ... Winding storage part 5 ... Step recessed part 6 ... Step part or hole 7 ... Plate core DESCRIPTION OF SYMBOLS 8 ... Base 9 ... Terminal 10 ... Groove 11 ... Locking part 12 ... Primary winding 13 ... Secondary winding

Claims (4)

[Claims] 1. A dish-shaped core having a concave winding accommodating portion formed between a central leg portion protruding from an opening surface and an outer peripheral frame portion; The concentrically mounted flat primary and secondary windings, and the upper surface of the central leg of the dish-shaped core, are mounted over two opposing sides of the frame-shaped part, and are mounted on the dish-shaped core. A plate-shaped core that forms a closed magnetic path between the plate-shaped core and the two bases that sandwich the plate-shaped core and cover the opening surface of the dish-shaped core and are flush with the plate-shaped core. A magnetic-shield type transformer characterized by being configured. 2. A dish-shaped core having a hole or a step formed in an outer peripheral frame portion, and an engaging portion corresponding to the hole or the step formed in each of two bases. 2. The magnetically shielded thin transformer according to claim 1, wherein the transformer is positioned and mounted on an outer peripheral frame portion of the transformer. 3. The magnetically shielded thin type according to claim 1, wherein stepped recesses are formed on two opposing sides of the outer peripheral frame portion of the dish-shaped core, and the plate-shaped core is fitted. Trance. 4. The magnetically shielded thin transformer according to claim 1, wherein a ferrite core having an insulating property is used as a material of the dish-shaped core and the plate-shaped core.