JPS6032311A - Magnetic core for choke coil - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic core of excellent DC superpositional characteristics having small irregularity which can be manufactured at reduced manhours by a method wherein a ferromagnetic thin belt is cut or grounded at one or more parts so that the inside of the core is linked together by performing a toroidal winding or a punching photoetching. CONSTITUTION:After a toroidal winding or punching photoetching and the like has been performed on the ferromagnetic thin belt and lamination or impregnation has also been conducted thereon, it is cut at one or more parts or gounded so that it will be connected on the internal side of the core. A closed magnetic circuit, a cut core, an EI core, an EE core and the like are used as a magnetic core. When amorphous is used for the ferromagnetic thin belt, its DC superpositional characteristics are excellent due to having high Bs when compared with ferrite, and its iron loss is small when compared with silicon steel, thereby enabling to obtain desirable results. Also, when the core is cut, leakage magnetic flux can be reduced through the intermediary of the core of the cut part and a spacer, or by assembling without the spacer, and as the DC superpositional characteristics can be changed, desirable results can be obtained when the device is used for proper purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a magnetic core for a choke coil.

Conventionally, as magnetic cores for choke coils, gap f1 magnetic cores such as ferrite and silicon steel, powder magnetic cores, and the like have been mainly used. However, ferrite has drawbacks such as poor DC Φ characteristics due to low [3s], and silicon steel has large iron loss.

Recently, advances in electronic devices have been very remarkable, and miniaturization of the power supplies used in these devices has become important, and nuiting currents, which can be miniaturized, are being widely used.

However, in conventional chokes, the inductance never decreases at low currents;
1 is constant, so if the output current decreases lζ,
There was a drawback that the output voltage fluctuated.

For this reason, switching power supplies prevent this by allowing a certain amount of current to flow even when there is no load. Therefore, the efficiency decreases by this amount of current, which is undesirable.

To prevent this, a choke that exhibits nonlinear characteristics with large inductance at low currents is required.

For this purpose, conventionally nonlinear characteristics have been obtained by adding a step to the gap of the magnetic core or arranging a soft magnetic material near the gap.

However, these methods require many man-hours to process the gap portion. It has drawbacks such as a slow drop in inductance on the low current side.

In order to prevent the inductance from dropping suddenly as the current increases, a proposal has been made to insert a V-shaped groove in the magnetic core, but this method is difficult to increase processing accuracy and results in large variations. There are drawbacks to this.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks of the prior art, and to provide a magnetic core for a choke coil that has excellent DC superimposition characteristics, has small variations, and requires less man-hours.

The key points of the present invention are to obtain a magnetic core for a coil by toroidally winding a ferromagnetic ribbon or punching and photo-etching it, cutting or polishing it at one or more places so that the inside of the core is connected, and improving the inductance at low currents. That's true.

If amorphous is used for the ferromagnetic ribbon,

Since it has a higher Bs than Lie (-), it has excellent DC superimposition characteristics, and has a smaller iron loss than silicon steel, so more favorable results can be obtained.

In addition, when the core is cut, the DC superimposition characteristics that can reduce leakage magnetic flux can be changed by combining the cut portion of the core with or without a spacer, so depending on the application, the DC superposition characteristic can be changed. You can get good results.

In particular, the magnetic core according to the present invention has improved inductance on the low current side, and is therefore most suitable as a magnetic core for a switching power supply choke coil.

Hereinafter, the present invention will be explained based on examples.

Embodiment 1 FIG. 1 is not a schematic diagram showing an example of the structure of a magnetic core for a choke coil according to the present invention. For the magnetic core, a closed magnetic circuit magnetic core, a cut core, an El core, an EE cocoa, etc. are used.

Embodiment 2 FIG. 2 is a diagram comparing an example of the LIoc characteristics of the magnetic core of the present invention with the L-1oQ characteristics of a conventional magnetic core with a grip. According to the present invention, the DC superimposition characteristics are improved particularly on the low current side.

The present invention solves the conventional problem of A1 and low current 1II1.
The inductance of 1 is improved and the man-hours are reduced.hX/JX
The effect is significantly reduced and the variation is reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the structure of a magnet 1G according to the present invention, and FIG. 2G is a schematic diagram showing an example of the structure of a magnet 4. >Noshi-I, is a diagram showing an example of o characteristics.

Claims (1)

[Claims] 1. Toroidally wound or punched ferromagnetic ribbon
A magnetic core for a choke coil characterized by etching, laminating or impregnating, and then cutting or polishing at one or more places so that the inner sides of the core are connected. 2. A magnetic core for a choke coil according to claim 1, characterized in that cut cores are combined with each other with or without a spacer. 3. A magnetic core for a choke coil according to claims 1 and 2, characterized in that an amorphous ribbon is used as the ferromagnetic ribbon. 4. Claims 1 and 27, characterized in that they are used in smoothing chokes for switching power supplies. The magnetic core for a choke coil according to item 3.