JPH04318906A - Composite toroidal core for common mode choke excellent in magnetic property - Google Patents

Abstract

PURPOSE:To provide a core in such shape that it is excellent in noise attenuating property and pulse attenuating property and which is used for a noise filter for a common mode choke, etc., being used for a switching power source, etc. CONSTITUTION:In a toroidal core which consists of at least two or more kinds of magnetic materials A and B different in the frequency property of the permeability in respect of magnetic property, this is a composite toroidal core for common mode excellent in magnetic property, characterized in that two or more kinds of materials are arranged coaxially and in the shape of nest structure. Efficient inductance property can be materialized from low frequency to high frequency with high degree of freedom, and the saturation magnetic flux density of the material can be made the best use of. Space saving and the reduction of total winding are great as effect.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core having excellent noise attenuation characteristics and pulse attenuation characteristics for use in noise filters such as common mode chokes used in switching power supplies and the like.

0002

2. Description of the Related Art Currently, various common mode chokes are widely used as EMC components related to switching power supplies. Conventionally, ferrite has been used as a material for this common mode choke due to its cost and stable impedance characteristics up to a high frequency range.

[0003] However, due to recent EMC regulations moving toward lower frequencies, ferrite common mode chokes usually have two cores: a core with a large number of turns for low frequencies, and a core with a small number of turns for high frequencies. It is commonly used. However, 2
By arranging two cores, a large amount of space in the power supply circuit is occupied, which is a major obstacle to downsizing the power supply.

0004

[Problems to be Solved by the Invention] In order to solve the above problems, the present invention reduces the number of common mode choke coils, which conventionally functioned with two or more, to one, thereby saving space and achieving a total The object of the present invention is to provide a highly reliable core that has a reduced number of windings and has efficient inductance characteristics, and is applicable from a low frequency range to a high frequency range.

[0005]

[Means for Solving the Problems] The present invention provides a toroidal core made of at least two types of magnetic materials having different magnetic permeability frequency characteristics, in which the two or more types of materials are concentrically adjacent to each other. This composite toroidal core for common mode chokes has excellent magnetic properties and is characterized by being arranged in a symmetrical structure.

[0006] At least one type of magnetic material is Mn.
- Ferrite such as Zn, Ni-Zn, or at least one other magnetic material is a metallic magnetic material such as amorphous, silicon steel, or amorphous heat-treated material, or
By arranging the magnetic material with higher saturation magnetic flux density adjacently on the inside, even more excellent magnetic properties can be enjoyed.

[0007] The present inventors conventionally attempted to use ferrite with similar magnetic properties, that is, similar frequency dependence of magnetic permeability, to be functionalized for low frequency and high frequency use by winding. For low-frequency applications with the same number of wires, we focused on using an iron-based metal magnetic material with excellent low-frequency characteristics compared to ferrite, and tried various combinations.

In general, in order to combine different types of cores so that they can be treated as one core, two types of combinations as shown in FIG. 1 can be considered. (a) has a concentrically adjacent structure (nested structure); (b)
) has a concentric stacked structure, and materials A and B each have different magnetic properties. The present inventors have experimentally discovered that the former is significantly superior in practice from the viewpoint of effective utilization of saturation magnetic flux density, and have completed the invention.

By employing the core compositing method proposed by the present invention, it is possible to adjust two different magnetic properties, for example, magnetic permeability, to the most practically preferred frequency characteristic. That is, μ(f) is expressed as a linear combination of μ1 (f) and μ2 (f), μ(f)=a・μ1 (f)+b・μ2 (f) where μ(f): composite core Frequency characteristics of magnetic permeability, f: frequency μ1 (f): magnetic permeability μ2 of material 1 (f): magnetic permeability a and b of material 2 are constants determined by the ratio of the inner and outer diameters of the coil, and Fig. 2
If we define r1, r2, r3 as follows, and place material 1 inside the concentric center and material 2 outside the concentric center, a=ln
(r2 /r1)/ln(r3/r1)b=ln
(r3/r2)/ln(r3/r1). That is, by selecting the inner and outer diameter ratios r1, r2, r3, arbitrary a and b can be taken, and μ(f) can be optimally selected according to the frequency f.

The above advantages can also be achieved by a stacked composite core as shown in FIG. 1(b). However, the nested method shown in FIG. 1(a) is significantly superior to the stacked method shown in FIG. 1(b) in terms of magnetic flux distribution.

[0011] The magnetic flux distribution in the toroidal core is not uniform in the radial direction, and the magnetic flux density becomes higher toward the inner side of the core. In other words, arranging a material with a high saturation magnetic flux density, such as an iron-based metallic magnetic material, inside the core makes it possible to fully utilize the characteristics of the material. what if,
If the stacking method is used, the characteristics of the material, which has a high magnetic flux density, will only be able to exhibit about half of its properties.

In other words, the only combination of composite cores that can design the magnetic permeability μ(f) with a high degree of freedom and make maximum use of the saturation magnetic flux density characteristics is the nested method.

[0013]

[Operation] According to the present invention, in a composite toroidal core made of two or more types of magnetic materials having different magnetic properties, it is possible to realize a combination that takes full advantage of the properties of the materials in terms of the degree of freedom of magnetic permeability and the distribution of magnetic flux density.

[0014]

[Example] In the dimensions shown in Figure 2, r1 = 10m
m, r2 = 15mm, r3 = 20mm, t = 10m
m, and the ferrite was placed on the outside and the iron-based amorphous heat-treated magnetic material was placed on the inside. Ferrite saturation magnetic flux density 0
．． The iron-based amorphous heat-treated magnetic material has a saturation magnetic flux density of 1.35 T and a magnetic permeability of 20,000 (at 1 kHz).

[0015] The number of windings was 12 turns, and noise attenuation characteristics were obtained in the range of 10 kHz to 10 MHz, which was approximately the same as that of two conventional ferrite cores. In other words, it was possible to obtain the same characteristics in half the space of conventional products. Furthermore, the pulse attenuation characteristics are different from that of the conventional ferrite core 2.
The saturation starting point of the input pulse voltage is 10
The voltage increased from 0V to about 300V. In addition, the total number of windings in the core is 12, which is 66% less than the 24+12=36 windings in the case of two conventional ferrite cores, leading to a significant reduction in man-hours.

[0016]

[Effects of the Invention] The present invention makes it possible to manufacture common mode chokes for EMC, for example, which require only half the space and have excellent pulse attenuation characteristics, compared to conventional chokes where two cores are placed side by side to ensure the characteristics. This greatly contributes to reducing the cost of cores by downsizing switching power supplies and reducing the number of man-hours in the winding process.

[Brief explanation of the drawing]

FIG. 1 shows an explanatory diagram of combinations of composite toroidal cores, in which (a) shows a concentrically adjacent structure (nested structure) and (b) shows a stacked structure.

FIG. 2(a) is a plan view showing the dimensions of each part of the nested composite toroidal core, and FIG. 2(b) is a front view.

Claims (3)

[Claims] [Claim 1] A toroidal core made of at least two or more types of magnetic materials having different frequency characteristics of magnetic permeability, characterized in that the two or more types of materials are arranged in a concentrically adjacent structure. Composite toroidal core for common mode chokes with excellent magnetic properties. [Claim 2] At least one type of magnetic material is Mn-Z.
2. The common mode choke according to claim 1, wherein the ferrite such as n, Ni-Zn, or at least one other magnetic material is a metallic magnetic material such as amorphous, silicon steel, or amorphous heat-treated material. Composite toroidal core. [Claim 3] Claim 1, characterized in that the cores are arranged from the inside to the outside of the nest in the order of the height of the saturation magnetic flux density of the core.
Or the composite toroidal core for common mode choke described in 2.