JPH0799121A - Core for choke coil - Google Patents

Abstract

PURPOSE:To downsize the shape of core corresponding to the material property by giving a specified relation between the specific permeability and the saturation magnetic flux density of the material constitution the core and the window area to the winding of the core and the length of an average magnetic path. CONSTITUTION:When defined that the specific permeability of the material constituting the core is mur and the density of saturation magnetic flux is Bs [T], and that the window area to the winding of the core 1 is Aw [m<2>] and the average length of magnetic paths is I [m], these fulfills the relation of mur=K.Bs.1/Aw [K shows the number in the range of 0.34-0.55]. And, in case that the core material to be used is predetermined, the shape of the core, that is the area Aw of a window to winding and the average length of magnetic paths are determined so that they may fulfill the relation of the formula, according to the material property (mur, Bs), that is, so that the value of K may be in the range of 0.34-0.55. Moreover, in case that the shape (Aw, 1) of the core is predetermined, a core material, which has the permeability mur and the density of saturation magnetic flux Bs fulfilling the relation of the formula, according to the shape, is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil core.

[0002]

2. Description of the Related Art In choke coils used for switching power supplies and the like, crystalline materials such as permalloy and ferrite have been mainly used as core materials. Also,
As the core shape, various shapes such as a toroidal core, an EI core and a PQ core have been used.

By the way, as demands for downsizing and weight reduction of various electronic devices such as switching power supplies have increased, switching frequencies and operating frequencies tend to be higher year by year. In response to such higher operating frequencies, choke coil cores made of conventional crystalline materials have drawbacks such as large loss in the high frequency range and insufficient magnetic flux density. However, there is a problem that it is not possible to sufficiently meet the demand for miniaturization of electronic devices.

On the other hand, Co-based and Fe-based amorphous magnetic alloys have attracted attention because they exhibit excellent soft magnetic characteristics such as high magnetic permeability, low loss, and high saturation magnetic flux density, and are partially used as core materials. It has been put to practical use. In this way, various improvements in material properties for the core have been made, and although core materials satisfying low loss, high saturation magnetic flux density, etc. have been obtained,
Since the study on the core shape has not been sufficiently conducted, the material properties have not been fully utilized, and downsizing of the core in accordance with the material properties has not been achieved. That is, since the core shape according to the characteristics of the core material is not defined, it is not possible to fully utilize the saturation magnetic flux density of the core material, etc. There are problems such as use, or conversely, the core shape is made too small to reduce the inductance and reduce the actual current.

[0005]

As described above, in the conventional choke coil core, although the loss of the material characteristics and the saturation magnetic flux density have been increased, the core suitable for the core material has been promoted. Since the study of the shape was insufficient, there was a problem that the core was not sufficiently miniaturized by taking advantage of the material characteristics.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a core for a choke coil capable of downsizing the core shape in accordance with material characteristics.

[0007]

The choke coil core according to the present invention has a relative permeability of the core constituent material of μ _r , a saturation magnetic flux density of B _s [T], and a window for the winding of the core. When the area is A _w [m ² ] and the average magnetic path length is 1 [m], μ _r = K · B _s · l / A _w ………… (1) (where K is 0.34 to 0.55) (Indicating the number of ranges) is satisfied.

As the constituent material of the core for the choke coil of the present invention, various core materials can be applied, but an amorphous magnetic alloy having a small loss particularly in a high frequency range and a high saturation magnetic flux density can be obtained. It is preferable to use an Fe-based soft magnetic alloy having fine crystal grains (hereinafter referred to as Fe-based fine crystal alloy). As the amorphous magnetic alloy, for example, a general formula: (M _1-a M ′ _a ) _100-b X _b (wherein M is at least one element selected from Fe and Co, M ′ is Ti, V 2, Cr, Mn, Ni, Cu, Zr, Nb, Mo, Ta,
At least one element selected from W etc., X is B, S
i, C, P, etc., at least one element is selected, and a and b each represent a number satisfying 0 ≦ a ≦ 0.5 and 10 ≦ b ≦ 35). It is illustrated.

Further, as the Fe-based fine crystal alloy, a general formula: Fe _100-cdefgh A _c D _d E _e Si _f B _g Z _h (In the formula, A is at least one element selected from Cu and Au) , D is at least one element selected from 4A group elements, 5A group elements, 6A group elements and rare earth elements, E is Mn,
At least one element selected from Al, Ga, Ge, In, Sn and platinum group elements, Z represents at least one element selected from C, N and P, and c, d, e, f, g And h are 0 ≦ c ≦ 8, 0.1 ≦ d ≦ 15, 0 ≦ e ≦ 10, 0 ≦
It is a number that satisfies the following formulas: f≤25, 1≤g≤12, 0≤h≤10, 1≤f + g + h≤30. However, all the numbers in the above formula indicate at%), the composition is substantially represented, and an alloy having fine crystal grains with an average grain size of, for example, 50 nm or less is included.

In the soft magnetic material as described above, various relative magnetic permeabilities μ _r and saturation magnetic flux densities B _s can be obtained by adjusting the composition and heat treatment conditions. In the present invention, the soft magnetic material (core material) used in advance is used.
, The material properties (μ _r , B _s )
To satisfy the relation of equation (1), that is, K
The core shape, that is, the window area A _w for the winding and the average magnetic path length 1 are determined so that the value of is in the range of 0.34 to 0.55. Further, when the core shape (A _w , l) is determined in advance, a core material having a magnetic permeability μ _r and a saturation magnetic flux density B _s that satisfy the relationship of the equation (1) is selected according to the shape. select.

Here, when the material characteristics (μ _r , B _s ) are determined and the core shape is such that the value of K becomes smaller than 0.34, a sufficient inductance L cannot be obtained,
DC superimposition characteristics (for example, current (I _max ) at which L becomes 1/2)
Is good, the actual current will be reduced. Also, K
If the core shape is such that the value of is larger than 0.55, the inductance L becomes too large, and the core shape is set larger than the material characteristics. That is, the value of K is
By determining the core shape so that it is in the range of 0.34 to 0.55, it is possible to make full use of the characteristics of the core material, obtain good characteristics as a choke coil, and then downsize the choke coil core. Becomes The more preferable range of the value of K is 0.38 to 0.48.

Further, when the core shape (A _w , l) and the saturation magnetic flux density B _s are constant, if the relative permeability μ _r is set so that the value of K becomes smaller than 0.34, the direct current superposition characteristic, for example, I _{Although max} increases, a sufficient inductance L cannot be obtained and the actual current decreases. On the contrary, if the relative permeability μ _r is set so that the value of K is larger than 0.55, the DC superposition characteristic, for example, I _max, is lowered even though the sufficient inductance L is obtained, and the sufficient function as the choke coil is obtained. Will not be obtained. In other words, for example, the optimum relative permeability μ _r varies depending on the core shape, but good characteristics as a choke coil can be obtained when the K value is in the range of 0.34 to 0.55, regardless of the core shape. That is, both high inductance and excellent direct current superposition characteristics can be satisfied, and further, the core shape can be downsized according to the material characteristics.

Amorphous magnetic alloy or Fe as described above
The core for a choke coil using a base fine crystal alloy may be obtained by winding a ribbon of these alloys into a desired shape or punching the ribbon into a desired shape and then stacking the core into a desired core shape. Can be obtained by

The choke coil core of the present invention is
By satisfying the relationship of the above formula (1), excellent DC superposition characteristics can be obtained without providing a substantial air gap due to cutting or the like. As a result, it is not necessary to form a magnetic gap by cutting or the like, so that the manufacturing cost can be reduced and the leakage magnetic flux generated due to the formation of the gap can be prevented.

The choke coil core of the present invention can be applied to various shaped cores such as a toroidal core, an EI core and a PQ core. Here, when the present invention is applied to a toroidal core, for example, as shown in FIG. 1, the cross-sectional area of the air-core portion 1a of the toroidal core 1 is the window area A.
_w , and the average magnetic path length l is a value obtained from the average value of the outer diameter and the inner diameter. When applied to an EI core, as shown in FIG. 2, for example, the cross-sectional area of one air-core portion 2a of the EI core 2 becomes the window area A _w , and the average magnetic path length l
Is the average magnetic path length around the one air-core portion 2a. P
The Q core is based on the EI core.

The choke coil core of the present invention is
The present invention can be applied to any choke coil such as a normal mode choke coil, a common mode choke coil, and a smooth choke coil.

[0017]

EXAMPLES Examples of the present invention will be described below.

Example 1 First, a Fe ₇₉ B ₁₃ Si ₈ alloy ribbon having a saturation magnetic flux density B _s of 1.50 T was wound into an outer diameter of 18 mm × an inner diameter of 12 mm × a height of 4.5 mm. Finished shape is outer diameter 20 mm × inner diameter 10.6 mm
A core for choke coil was produced by performing a mold treatment so that the height was 6.8 mm. At this time, the heat treatment conditions were changed to obtain choke coil cores having various relative magnetic permeability μ _r .

The average magnetic path length l of the choke coil core is 47.1 × 10 ^-3 m, and the window area A _w is 81.7 × 10 ^-6.
m ² , effective area S is 10.8 × 10 ⁻⁶ m ² .

A plurality of cores having different relative magnetic permeabilities μ _r were respectively wound, and the characteristics as a choke coil were measured and evaluated as follows. First, the inductance (AL value) of each core was measured under the condition of 100 kHz. In addition, as an evaluation of the DC superposition characteristics, the inductance is 1/2
The current (I _max ) at which Next, the AL (I _max ) ² value was calculated as the characteristic value of the choke coil from the obtained AL value and I _max value. Also, B _s , μ _r ,
The value of K (= μ _r · A _w / B _s · l) was calculated from the respective values of 1 and A _w based on the above-mentioned formula (1).

With the relative permeability μ _r and K value of each core,
Table 1 shows each measurement result. In addition, K value and AL (I _max )
The relationship with ² is shown in FIG.

[0022]

[Table 1] As is clear from FIG. 3, in the choke coil using the core of the first embodiment, the value of K is about 0.43 and the maximum A
It can be seen that an L (I _max ) ² value (= 2000) is obtained, and K = 0.34 to 0.55 is necessary to obtain a capacity of 80% or more.

Further, when a choke coil for 2A is manufactured with the core of the above Example 1, in the core of K = 0.463 (sample No. 4)
A choke coil of 460 μH can be manufactured, but K = 0.2
In the core of 31 (Sample No. 6), 268 μH, K = 0.925 (Sample No. 2)
With the core, only 226 μH choke coil can be obtained.
From these facts, it is important to set the core shape using the value of K as an index, and by setting the value of K to 0.34 to 0.55, good characteristics as a choke coil can be obtained, and It turns out that miniaturization is possible.

Example 2 An Fe ₇₂ B ₁₄ Si ₁₄ alloy ribbon having a saturation magnetic flux density B _s of 1.0 T was
The outer diameter is 26 mm, the inner diameter is 16 mm, and the height is 9.5 mm.
The finish shape of this winding body is 29.5 mm outer diameter x 13 mm inner diameter x height
Molding treatment was performed so that the thickness was 13 mm, and a choke coil core was produced. Then, in the same manner as in Example 1,
Cores for choke coils with various relative permeability μ _r were obtained. The average magnetic path length l of the choke coil core is 66.0 ×
A 10 ^-3 m, the window area A _w is 132.7 × 10 ^-6 m ^2, the effective area S is 38 × 10 ^-6 m ^2.

A plurality of cores having different relative magnetic permeabilities μ _r were wound, and the characteristics as a choke coil were measured and evaluated in the same manner as in Example 1. The AL value of each core is
It was measured under the condition of 100 kHz. Table 2 shows the respective measurement results together with the relative magnetic permeability μ _r and K value of each core. Further, the relationship between the K value and the AL (I _max ) ² value is shown in FIG.

[0026]

[Table 2] As is clear from FIG. 4, even in the choke coil using the core of the second embodiment, the value of K is about 0.43 and the maximum A
It can be seen that an L (I _max ) ² value (= 7500) is obtained, and K = 0.34 to 0.55 is necessary to obtain a capacity of 80% or more. Further, from the results of Example 1 and Example 2, the optimum relative permeability changes depending on the core shape, but K is 0.43.
You can see that the maximum ability can be drawn out in the vicinity.

Among the cores of the second embodiment, for example, the core having a relative magnetic permeability μ _r of 800 (Sample No. 10) can obtain only a choke coil of 489 μH, and the core shape can be set using the value of K as an index. It turns out to be important.

[0028]

As described above, according to the present invention, it is possible to easily and easily reproduce a choke coil core whose shape is made smaller according to the material characteristics, or a choke coil core having material characteristics suitable for the shape. It is possible to provide it with good performance.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a core shape in a choke coil core of the present invention.

FIG. 2 is a diagram for explaining another core shape in the choke coil core of the present invention.

FIG. 3 is a diagram showing a relationship between a K value and a choke ability of a choke coil using a core according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a K value and a choke ability of a choke coil using a core according to another embodiment of the present invention.

[Explanation of symbols]

 1 ... Toroidal core 1a, 2a ... Air core 2 ... EI core

Claims (2)

[Claims] 1. In a core for a choke coil, the relative magnetic permeability of the constituent material of the core is μ _r , the saturation magnetic flux density is B _s [T], and the window area of the core with respect to the winding is A _w [m ² ], And the average magnetic path length is 1 [m], it is necessary to satisfy the relationship of μ _r = K · B _s · l / A _w (where K represents a number in the range of 0.34 to 0.55). Characteristic core for choke coil. 2. The choke coil core according to claim 1, wherein the core is formed of a wound body or a laminated body of an amorphous alloy ribbon or an Fe-based soft magnetic alloy ribbon having fine crystal grains, and is substantially Core for choke coil, which has no special air gap.