JP2002299132A - Power transformer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take measures against a noise and the miniaturization of a power supply which are compatible in a power transformer device. SOLUTION: A transformer body 2 is attached to a board 1, and it is covered with a shielding case 3. In the shielding case 3, a metal-containing conductive film 5 is formed at least in a part on the inner circumferential face of a plastic case 4. In the power transformer device constituted in this manner, the insulating plastic, case 4 faces the outer circumferential face of the shielding case 3, and the insulation from a hot-line part of the power supply is ensured fully. The transformer body 2 is shielded with the metal-containing conductive film, and its measures against noise are taken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transformer device used for various switching power supplies and the like.

[0002]

2. Description of the Related Art Generally, a power supply transformer is used for a switching power supply of an electronic device. However, this power supply transformer has a problem that noise emitted from a coil adversely affects other electronic devices and peripheral circuits. I have

Therefore, as a countermeasure against the noise of the switching power supply, a metal shield plate or a shield case is often attached to a noise source such as the power transformer to suppress the generation of the noise.

[0004]

However, for example, when the shield case is made of metal, there is a problem of insulation from the live part of the power supply.

More specifically, it is necessary to increase the distance from other components in order to ensure insulation, resulting in inconveniences such as an increase in the size of the power supply and a restriction on the arrangement of components.

The present invention has been proposed for the purpose of solving such a drawback, and an object of the present invention is to provide a power supply transformer device capable of achieving both noise suppression and downsizing of a power supply. .

[0007]

In order to achieve the above object, a power transformer device according to the present invention is a power transformer device wherein a transformer body mounted on a substrate is covered with a shield case. Is characterized in that a conductive film containing a metal is formed on at least a part of the inner peripheral surface of the plastic case.

In the power transformer apparatus of the present invention constructed as described above, a plastic case having an insulating property faces the outer peripheral surface of the shield case, and the insulation of the power supply from the live part is sufficiently ensured. You. Therefore, it is possible to arrange the components in close proximity to other components, and there is no restriction on the component arrangement, which greatly contributes to downsizing of the power supply.

On the other hand, the transformer main body is shielded by a conductive film containing a metal, so that sufficient noise countermeasures can be taken.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power transformer device according to the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the power transformer device of the present invention basically comprises a transformer body 2 mounted on a substrate 1, and the transformer body 2 is housed in a shield case 3. The surrounding area is covered and shielded.

The transformer body 2 includes, for example, a primary coil,
It is composed of a secondary coil, an iron core, and the like, and may have any structure.

A terminal pin 2a connected to each coil is erected on the bottom surface of the transformer main body 2. The terminal pin 2a is inserted into a through-hole provided in the substrate 1 and soldered to form a mechanical pin. In addition to that, it is electrically connected to a wiring pattern formed on the surface of the substrate 1 and is connected to an external circuit.

On the other hand, as shown in FIG. 2, the shield case 3 is a case-like case having an open bottom surface, and is mainly composed of a plastic case 4 formed of an insulating synthetic resin.

As the synthetic resin material constituting the plastic case 4, any material can be used, and examples thereof include ABS resin, acetal resin, vinyl resin and the like.

On the inner peripheral surface of the plastic case 4, a conductive film 5 is formed, which plays a role of a shield. The conductive film 5 may be formed on the entire inner peripheral surface of the plastic case 4,
It may be partially formed only in a necessary part. In this example, the structure is such that the conductive film 5 is formed on the entire inner peripheral surface of the plastic case 4.

The conductive film 5 contains a metal material which is nonmagnetic and has excellent conductivity, and can be formed by various methods.

For example, it can be formed by plating a metal material such as copper plating or silver plating. In this case, since the plastic case is insulative, a certain thickness may be obtained by electroplating after electroless plating.

Alternatively, the conductive film 5 can be formed by painting. Specifically, a paint or paste mixed with fine metal powder such as copper powder or silver powder is applied to the inner peripheral surface of the plastic case by an arbitrary method.

Further, vacuum evaporation, sputtering, etc.
It is also possible to directly apply a metal film to the inner peripheral surface of the plastic case by the so-called PVD technique.

It is preferable that the conductive film 5 is grounded by some means. The grounding method is such that when the shield case 3 is attached to the substrate 1, the end of the conductive film 5 formed on the inner peripheral surface of the shield case 3 comes into contact with the wiring pattern formed on the surface of the substrate 1. And grounding via the wiring pattern. Alternatively, the lead wire 6 may be connected to an arbitrary position of the conductive film 5 by soldering or the like, and may be taken out to ground.

In the power transformer apparatus having the above-described configuration, the insulating plastic case 4 faces the outer peripheral surface of the shield case 3, so that the insulation from other components is sufficiently achieved. Further, the shielding effect on the transformer main body 2 is sufficiently ensured by the conductive film 5 formed on the inner peripheral surface of the shield case 2.

Therefore, when the switching power supply transformer is installed in a small space such as an AC adapter, the objects of shielding and insulation can be simultaneously and effectively solved.

The above is the basic structure of the power supply transformer device to which the present invention is applied. However, the present invention is not limited to this example, and the shape, the material, the dimensions, and the like do not depart from the gist of the present invention. It can be changed arbitrarily.

FIG. 3 shows an example of a shield case used in an actual power supply transformer of a switching power supply.

The shield case 10 has a relatively flat casing shape, and a large number of slits 11 for heat radiation are provided on the upper surface and peripheral side surfaces. The basic structure is the same as that of the previous example. Yes, a conductive film is formed on the inner peripheral surface of a plastic case.

[0027]

As is clear from the above description, in the present invention, since the shield case has a structure in which the conductive film is formed on the inner peripheral surface of the plastic case, the shield and the insulation can be solved by one component. This makes it possible to achieve both noise suppression and downsizing of the power supply.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one configuration example of a power transformer device to which the present invention is applied.

FIG. 2 is a schematic perspective view showing an example of a shield case.

FIG. 3 is a schematic perspective view showing another example of the shield case.

[Explanation of symbols]

 1 board, 2 transformer body, 3 shield case, 4 plastic case 5 conductive film

Claims (4)

[Claims] 1. A power transformer device wherein a transformer main body attached to a substrate is covered by a shield case, wherein the shield case is formed by forming a conductive film containing a metal on at least a part of an inner peripheral surface of a plastic case. A power transformer device. 2. The power transformer device according to claim 1, wherein said conductive film is formed by plating. 3. The power transformer device according to claim 1, wherein said conductive film is formed by painting. 4. The power transformer according to claim 1, wherein the conductive film is grounded via the substrate.