JPS5833814A - Magnetic core - Google Patents

Abstract

PURPOSE:To obtain the magnetic core which provides a very large inductance at a low current region but rapidly reduces such inductance at a preset constant current value by providing stacked magnetic materials at the region near the gap provided at a part of the magnetic core. CONSTITUTION:A gap Ga is formed between the centers 3a and 4a of a pair of E type core 3, 4 combined and simultaneously a thin magnetic material sheet 6 is wound around this gap Ga in such a way that the insulator 5 is sandwiched by such sheet in order to form a laminate. In case of forming a chock coil using this magnetic core, a combined magnetic permeability at the coupling area of the gap Ga and magnetic material 6 is determined depending on that of magnetic material 6 at the low current region where the magnetic material 6 is not magnetically saturated and its value becomes very large. Meanwhile, when a load increases and a choke current exceeds a specified value, the magnetic material 6 is saturated magnetically and therefore said combined magnetic permeability comes close to that of air forming the gap Ga.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention primarily relates to a magnetic core suitable for constructing coils that are used with superimposed direct current.

For example, in coils that are used with DC current superimposed, such as choke coils, output filters of switching power supplies, or power transformers of flyback converters, the method shown in Figure 1 is used to improve the DC superimposition characteristics. It is common to use a ferrite magnetic core provided with a C2 gap Ga in a part of the magnetic circuit such as the C2 and core center portions. If such a gap Ga is provided, a flat DC superposition characteristic in which the coil inductance L remains constant with respect to changes in the ampere turns IN over a certain width can be obtained, as shown in FIG.

It should be noted that the % DC superimposition characteristic transitions as the curve A1→A2→A5 as the gap Ga becomes larger.

However, when this magnetic core is used in the choke coil of a switching power supply, it becomes difficult to install the load in the switching power supply. The relationship between and the output voltage v0 is as shown in Figure 6, and the load power is applied. When V is small, that is, in the region of choke current discontinuity, the output voltage V. There was a drawback that the amount of liquid became abnormally high and the stability of the output became poor.

In addition, when the magnetic core is used as a power transformer for a frequency position m-type flyback converter, the DC superimposition characteristic of the magnetic core becomes a flat characteristic as shown in Fig. 2, and the inductance decreases despite the load fluctuation C2. Because the frequency remains constant, the frequency becomes extremely high (2) at light loads, causing intermittent oscillations, increasing the burden on the transistors that are switching elements, increasing losses, and making heat dissipation measures stricter. Ta.

As a conventional technique for eliminating these drawbacks, an inductance adjustment method disclosed in Japanese Patent Publication No. 56-24565 is known. This conventional technology is based on an inductor in which a magnetic air gap is provided in a part of the magnetic circuit, a magnetic core is arranged in the air gap circle with a permanent magnet that provides a magnetic bias to the magnetic circuit, and a common coil is wound around the magnetic core without magnetic bias. , which adjusts the inductance value by changing the air gap between the two types of magnetic cores, and has an extremely high inductance value in the low current region.
As described above, the inductance value decreases sharply at a certain current value, and an inductor that maintains the small inductance value up to a large current range can be realized.

However, this prior art requires a permanent magnet to apply a magnetic bias, which is accompanied by a demagnetization phenomenon, and therefore has a drawback in that it lacks reliability.

The present invention solves the above-mentioned conventional technical problem, and has an extremely large inductance in a low current range, whose value decreases sharply at a certain current value, and maintains that small inductance value until a large current range, Moreover, it is an object of the present invention to provide a magnetic core with which it is possible to easily adjust the inductance value in a low current region to increase or decrease it, and to obtain a highly reliable inductor that does not cause characteristic fluctuations due to aging.

In order to achieve the above object, the present invention is characterized in that, in a magnetic core partially having a C gap, a magnetic material is laminated and provided near the gap.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. IR4 diagram (Al is a front sectional view of the magnetic core according to the present invention, FIG. 4 (Bl is a sectional diagram of FIG. 4 (Al on line 8l-B1). In this example, two E-type cores 5% 4 are combined to form a gap Ga between both center portions 5a-4a, and a thin sheet-like magnetic material 6 is wound and laminated multiple times around this gap Ga with an insulating layer 5 in between. In such a structure, the insulating layer 5 can be formed by thinly coating the surface of the magnetic body 6 with an insulating material such as an insulating resin, or by adhering or interposing an insulating resin film, an insulating paper, or the like. Further, the magnetic material 6 may be an amorphous alloy, a ferrite,
Composite resin ferrite formed by mixing ferrite powder and synthetic resin, permalloy, silicon steel plate, etc. are suitable.

As mentioned above, when the magnetic body 6 is provided near the gap G&, when this magnetic core is used to configure a choke coil, etc., in the low current region where the magnetic body 6 is not magnetically saturated, the gap GI!L and the magnetic The composite magnetic permeability at the joint part with the magnetic body 6 is determined depending on the magnetic permeability 6 of the magnetic body 6, and its value becomes extremely (:ii6). Therefore, as shown in FIG.
The inductance value in the low current region (A) where the choke current is discontinuous is extremely high. On the other hand, when the load increases and the choke current exceeds a certain value 4:, the magnetic body 6 becomes magnetically saturated. When the current reaches a certain constant value C2, the inductance value decreases rapidly, and in the continuous choke current region (b), the characteristics become flat as in the case of only the gap Ga.

According to the present invention, the inductance value can be rapidly increased during light loads, so when the magnetic core is used to configure a choke coil, an output filter of a switching power supply, a power transformer, etc. As shown in Figure 6C2, conventionally, the output voltage V had a tendency to abnormally increase at light load. However, as the inductance value increases, the increase is suppressed as shown in (i), and the output stability becomes very good.

In addition, when the power transformer I of the magnetic core frequency modulation type flyback converter is used, the inductance value increases at light loads, suppressing abnormal increases in frequency, reducing the load on the switching transistor, and reducing losses. descend. Furthermore, since the leakage magnetic flux is reduced, the leakage inductance is also reduced.

Furthermore, unlike the one disclosed in Japanese Patent Publication No. 56-24565, it does not have a permanent magnet and there is no room for unstable factors such as demagnetization, so it is a high-speed magnet that operates stably over a long period of time. A highly reliable inductor can be realized.

Another important feature of the present invention is that the pre-magnetic material 6 is provided in a stacked manner. With such a structure, the inductance in the low current region can be easily adjusted to increase or decrease by increasing or decreasing the number of laminated magnetic bodies 6. FIG. 7 is an ampere turn-inductance characteristic diagram of each choke coil when the number of laminated layers (number of turns) of the magnetic material 6 is changed, and the horizontal axis is ↓ 2 ampere turns Idc (AT)
, and the vertical axis is the inductance L according to the logarithmic scale C-
(mH). Curve C0 is the characteristic of the choke coil using 0% layer count, that is, the conventional magnetic core, and curve O5, C
1,04%C6 and C8 are each 1 number 1.214
．． 6.8, each characteristic is shown. In addition, the magnetic material 6
An amorphous alloy coated with a resin of 2 pm to form the C insulating layer 5 on both sides was used.

As is clear from Fig. 7, the conventional choke coil using a magnetic core with only a gap has a flat characteristic (curve C8) with a constant width change in coil current (in contrast, the inductance L is about 0°9mH). However, the choke coil used with the magnetic core according to the present invention has curves a1.c2, C4,06,
As shown by C8, when the coil current decreases and the ampere turns drops below approximately 50 (*T) 32, the inductance L
increases rapidly. It can be seen that the inductance L increases as the number of layers of the magnetic body 6 increases C2, such as 1, 2, and 4.6%8, and that the inductance L can be adjusted by increasing or decreasing the number of laminated layers C2.

In addition, in the embodiment shown in FIG. 4 (4), (Bll=), the structure is such that the magnetic material 6 is wound and laminated with an insulating layer 115 made of an insulating coat, insulating paper, etc. sandwiched therebetween. Due to the magnetic flux passing between the center parts 5a and 4a, the magnetic body 6 becomes an open circuit in contrast to the electromotive force C2 that should be generated.In other words, since the magnetic body 6 does not constitute a short ring, its loss and heat generation can be prevented.

FIG. 8 is a sectional view of another embodiment of the magnetic core according to the present invention.The feature of this embodiment is that the magnetic material 6t gap g
, is formed. This gap g may be provided at multiple locations. In addition, the gap section is not limited to two, and may be formed of an insulating material such as an insulating resin. In the case of this embodiment, an open circuit is formed by the gaps g and C for the electromotive force 6 to be generated by the magnetic body 5 (2).
(Different from the embodiment shown in FIG.

FIG. 9 shows a sectional view of another embodiment of the magnetic core according to the present invention. The features of this embodiment are that the center portions 5a, 4a''4I forming the gap G& are square;
The magnetic material 6 is laminated and provided on a part or all of the outer surface. In the case of a rectangular magnetic core, when a magnetic body 6 made of an amorphous alloy or the like is wound and laminated, the magnetic body 6 swells outward between the ridge corners of the magnetic core as shown in (e) in FIG.
It is difficult to make close contact. On the other hand, as shown in the embodiment shown in FIG.
:Can be installed in close contact. Moreover, since the magnetic bodies 6 are separated by the gap g2 extending between each outer surface C: the ridge portion, there is an advantage that formation of a short ring by the magnetic bodies 6 can be prevented. Note that the magnetic body 6 may be further divided into 6 parts on each outer surface C2.

As described above, the present invention is characterized in that a magnetic core layer having a gap in a part is provided with a magnetic material laminated near the gap, so that an extremely large inductance can be achieved in a low current region. The value decreases sharply at a certain current value, and the small inductance value is maintained up to a large current range. Moreover, it is easy to increase or decrease the inductance value in the low current range C, and the characteristics change due to aging. It provides a magnetic core that makes it possible to obtain highly reliable coils that do not cause any It is possible to suppress abnormal increases in output voltage and frequency, improve output stability, and reduce loss.

[Brief explanation of drawings]

Figure 1 is a front view of a conventional magnetic core. Figure 2 is its DC superimposition characteristic diagram. Figure 3 is an output current-output voltage characteristic diagram of a switching power supply configured using the magnetic core, which is the first factor. Figure sI4 ( A
j is a front partial sectional view of the magnetic core according to the present invention, FIG.
is a cross-sectional view at B, -B, and line C2 in Figure 4 ((Rotation)),
FIG. 5 is the ampere-turn-inductance characteristic diagram of the coil using the magnetic core according to the present invention %i! Figure 6 is an output current-output voltage characteristic diagram when using the magnetic core according to the present invention, and the seventh
The figure is an ampere turn-inductance characteristic diagram when the number of layers of magnetic material is changed in the magnetic core according to the present invention, and Figure 8 is another embodiment of the magnetic core according to the present invention (cross-sectional view at
FIG. 9 is a cross-sectional view of still another embodiment C2, the first
Figure 0 is a diagram illustrating a drawback when a bimagnetic material is wound around a rectangular magnetic core. G... Gap 5... Insulating layer 6... Magnetic material Figure 1 N.

Claims (1)

[Scope of Claims] (1) A magnetic core having a gap in a part thereof, characterized in that a magnetic material is laminated in the vicinity of the gap. (2) The magnetic core according to claim 131, characterized in that the magnetic body is provided so as to surround the gap. 6) The magnetic body is arranged to surround the gap with an insulating layer in between. 184. The magnetic core according to claim 183, wherein the magnetic core is wound around the core. (4) Claim 1, characterized in that the Illlltj magnetic body is provided in an end shape with a gap in the direction of one station.
The magnetic core according to item 81 or item 2. 61? ] The end of the magnetic core that makes up the distribution gap has a square new curve, and! The magnetic core according to Claim 1 or WJ2C:, wherein the magnetic body 11 is divided and provided for each outward direction of the magnetic core end portion. (61lpl) The magnetic material is made of at least one of an amorphous alloy, ferrite, composite resin ferrite, permalloy, or silicon steel plate. The magnetic core according to item 4 or 5.