JPH07153613A - Core for choke coil and nonlinear choke coil - Google Patents

Abstract

PURPOSE:To obtain a nonlinear choke coil having superior nonlinear characteristics and a temperature stability by a method wherein the nonlinear choke coil consists of a core formed by constituting integrally a nanocrystal high-magnetic permeability closed magnetic circuit core, a nanocrystal alloy core and a gapped core or a gapped dust core. CONSTITUTION:A core for choke coil consists of a core formed by constituting integrally a nanocrystal high-magnetic permeability closed magnetic circuit core, a nanocrystal alloy core and a gapped core or a gapped dust core. The nanocrystal alloy core is an alloy core containing Fe as its main component and the composition of the core for choke coil is constituted in the compositional ratio of at least one kind of an element selected from between Cu and Cu to at least one kind of an element selected from among Ti, Zr, Hf, V, Nb, Ta, Mo, and W to Si to B = a content of 0.1at% or higher to 3at% of lower to a content of 1at% or higher to 7at% or lower to a content of 10at% or higher to 17at% or lower to a content of 4at% or higher to 10at% or lower and a nonlinear choke coil is formed by winding at least one conductor wire on this core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil magnetic core having a non-linear characteristic and a non-linear choke coil used in an output side smoothing circuit of a switching power supply.

[0002]

2. Description of the Related Art As a choke coil used in a smoothing circuit such as a switching power supply, a ferrite core with a gap, a silicon steel core with a gap, a Fe-based amorphous core with a gap, and a no-gap Fe core are used.
A choke coil using a base amorphous magnetic core, an Fe powder magnetic core, an Fe-Al-Si alloy powder magnetic core, or the like is used. However, a choke coil using a ferrite core is likely to saturate, and in order to exert a sufficient effect, it is necessary to increase the gap, increase the number of windings, increase the shape of the magnetic core, and the like. is there. Increasing the number of windings leads to an increase in copper loss, which causes a problem that the coil heats up and the temperature rises sharply. On the other hand, if the choke coil is made larger,
As a matter of course, it is disadvantageous in terms of downsizing the entire circuit.

The choke coil using a silicon steel magnetic core has a large magnetic core loss at a high frequency, and therefore has a problem that the temperature rises sharply and the switching frequency cannot be raised so much.
In a choke coil using a Fe-based amorphous magnetic core with a gap, it is necessary to mold the magnetic core with resin when cutting the magnetic core to form the gap, but the magnetic loss of the material is large because the magnetostriction of the material is large. There is a problem of noise due to increase or magnetostriction vibration. When a no-gap Fe-based amorphous magnetic core is used, resonance occurs due to magnetostrictive vibration, which causes unstable operation depending on the frequency, and there is a problem of noise due to magnetostrictive vibration depending on the frequency band. The Fe dust core is inexpensive, but has a problem that the magnetic permeability is low at less than 100, the core loss is large, and the choke coil cannot be downsized so much. The choke coil using the Fe-Al-Si alloy dust core is also superior in characteristics to the one using the Fe dust core, but has the same problem in terms of downsizing. As described above, the choke coils used in the conventional smoothing circuit have their respective problems and cannot be said to have sufficient characteristics.

[0004]

By the way, in the smoothing circuit on the output side of the switching power supply, it becomes difficult to obtain a constant voltage at a critical current or less. Therefore, a resistor is inserted in parallel to the output circuit or a low current is superimposed. Non-linear choke coil (swinging choke)
Is used. Further, the choke coil used in the active filter is preferably a choke which exhibits a non-linear characteristic. As a method of obtaining such a characteristic with a choke coil, a method is known in which a wedge-shaped gap is provided so that saturation occurs partially. However, this method has a problem of cost increase and a problem that it is difficult to accurately adjust the gap. There is also a method in which choke coils having different gaps are made into a series, or cores having different gaps are simultaneously wound to manufacture choke coils. In addition to this, there is known a composite of a nanocrystalline alloy magnetic core having a gap and a high-permeability magnetic core having no gap described in JP-A-1-169905. However, in a non-linear choke coil in which a gap-formed core or a dust core and a high-permeability core such as an amorphous alloy are combined, the high permeability core is more easily magnetized than the gap-formed nanocrystalline alloy core, and thus the high permeability is high. There is a problem that the ratio of the core loss of the magnetic core is large and the temperature rise becomes large when the Fe-based amorphous alloy magnetic core is used. When a Co-based amorphous alloy is used as a high-permeability closed magnetic circuit core, there is a problem that the characteristics deteriorate when used in an environment where the temperature change is large and the ambient temperature is high.

Further, the conventional ferrite using a high-permeability closed magnetic circuit core has a problem that the temperature characteristic of the choke coil is inferior because the magnetic characteristic of the ferrite changes greatly with temperature.

[0006]

As a result of intensive studies to solve the above problems, the present inventors have integrated a nanocrystal high magnetic permeability closed magnetic circuit core with a magnetic core having a gap or a dust core. A choke coil made of a magnetic core and wound with at least one conducting wire exhibits excellent non-linear characteristics in a wide range on the low DC superposition side where particularly high inductance is exhibited, and is suitable as a choke coil because the temperature rise due to iron loss is also small. The present invention has been found out, and the present invention has been devised.

According to the present invention, a nanocrystalline high magnetic permeability closed magnetic circuit core having no gap and a magnetic core having a gap other than a nanocrystalline alloy magnetic core are integrated or a nanocrystalline high magnetic permeability closed magnetic circuit core and a dust core having no gap are integrated. Is a choke coil magnetic core showing a non-linear characteristic. An example of the structure of the choke coil magnetic core of the present invention is shown in FIGS. 1 (a), (b), (c), (d), and (e), and FIG.
Another aspect of the present invention is a non-linear choke coil in which at least one conductive wire is wound around the magnetic core. This choke coil has a non-linear characteristic in which the inductance changes in two steps with respect to the superimposed current as shown in FIG. 2, and high inductance can be obtained in a region where the current is small. Therefore, the choke coil is small and has stable characteristics over a wide output range. Can be realized. Considering the characteristics of the magnetic core, this is due to the incremental relative permeability μ △ and the DC superimposed magnetic field H
Expressed as a _DC relationship. If the number of turns and the effective area are constant, the inductance L is proportional to the incremental relative permeability μΔ, and the DC superimposed current I _DC and the DC superimposed magnetic field H _DC are proportional. Examples of the nanocrystalline alloy according to the present invention include alloys described in Japanese Patent Publication No. 4393/1992 and Japanese Patent Laid-Open No. 242755/1992. At least 50% of the structures of these alloys are alloys having a fine grain size of 100 nm or less. The preferred crystal grain size is 50 nm or less, particularly preferably 30 nm or less. The balance mainly consists of an amorphous phase, but may be substantially 100% crystal. The nanocrystalline alloy used for the magnetic core has a ribbon thickness of about 1 μm to 40 μm made by the ultra-quenching method such as the single roll method, but 1 μm to 25 μm if the loss needs to be particularly reduced. It is desirable that the plate thickness is about the same. It is more preferable that the plate thickness is 1 μm to 15 μm.

The nanocrystalline alloy according to the present invention is an alloy mainly composed of Fe and at least 1 selected from Cu and Au.
Content of seed elements is 0.1 at% or more and 3 at% or less, Ti, Zr, Hf, V, N
b, Ta, Mo, the content of at least one element selected from W is 1 at% or more and 5 at% or less, the Si content is 10 at% or more and 17 at% or less, the B content is 4 at% or more and 10 at% or less of the composition In particular, the temperature rise can be suppressed to a low level. In addition, nanocrystalline alloy
Fe-based alloy, the content of at least one element selected from Cu, Au 0at% or more 3at% or less, Ti, Zr, H
The content of at least one element selected from f, V, Nb, Ta, Mo, W is 2 at% or more and 10 at% or less, and the Si content is 0 at% or more and 10 at%
In the following, in the case of an alloy having a composition of B content of 2 at% or more and 10 at% or less, the region showing high inductance can be expanded when the input current is small, so that it exhibits particularly excellent characteristics as a choke coil. A material having a magnetostriction of substantially zero or positive is suitable for the magnetic core material according to the present invention. When the magnetostriction is zero, the core loss is low and the temperature rise is the lowest, but when the magnetostriction is positive, the method of decreasing the inductance with respect to the superimposed current becomes gentle.

As the magnetic core to be combined with the nanocrystalline alloy closed magnetic circuit magnetic core constituting the magnetic core for choke coil of the present invention, a Fe-based amorphous magnetic core with a gap, a nanocrystalline alloy magnetic core with a gap, a ferrite magnetic core with a gap, Fe-Al-Si dust core, Mo permalloy dust core, Fe
There are dust cores, Fe-Si dust cores, nanocrystal dust cores, and the like. In addition, since the magnetic cores that are configured are integrated, they are usually put in a resin or ceramic core case, or the surroundings are resin coated, but when using a bobbin for winding, the magnetic core is not necessarily the case. There is no need to insert it in or resin coat it. Further, the magnetic cores to be combined are usually bonded so that they do not move, or fixed so that they do not move with each other by a case or band, but they need not be completely bonded. Further, each magnetic core may be impregnated with resin as needed.

[0010]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. (Example 1) Cu: 1%, Nb: 2.5%, Si: 15.5%, B in atomic%
Is cooled to 6.5% and the balance is substantially Fe.
An amorphous alloy ribbon having a thickness of 2.5 mm and a thickness of 10 μm was produced.
Next, this alloy ribbon was wound around an outer diameter of 33 mm and an inner diameter of 20 mm to produce a toroidal magnetic core. This magnetic core in an argon atmosphere 55
Heat treatment was performed at 0 ° C for 1 hour. As a result of microstructure observation by X-ray diffraction and a transmission electron microscope, it was confirmed that 50% or more of the microstructure of the heat-treated alloy was a nanocrystalline alloy composed of a fine bccFe phase. Moreover, the magnetostriction was measured, and it was confirmed to be very low magnetostriction, which was less than 1 × 10 ⁻⁶ .

Next, this magnetic core, a Fe-based amorphous magnetic core having a gap, and a Mo permalloy powder magnetic core are combined and laminated and adhered to the structure shown in FIGS. 1 (a) and 1 (b). -The coil of the present invention is put in a coil and wound with 50 turns.
A coil coil was made. Figure 3 shows the DC superposition characteristics at 10kHz. For comparison, DC superposition characteristics are also shown when a choke coil made of Mo permalloy powder magnetic core, a ferrite and a Fe-based amorphous magnetic core with a gap are integrated. The choke coil of the present invention exhibits non-linear characteristics and is suitable for the secondary smooth choke of the switching power supply. Further, the inductance is remarkably improved particularly on the low current side as compared with the choke coil of the same type using ferrite as a high magnetic permeability core.

Next, the temperature rise was actually measured by incorporating it into the smoothing circuit of the switching power supply. The choke coil of the present invention
In contrast to 32 ° C. to 38 ° C., the nonlinear choke coil using a ferrite core as the high magnetic permeability core has a temperature of 43 ° C., and the choke coil of the present invention has a smaller temperature rise.

(Example 2) Nanocrystalline alloy magnetic cores having the compositions shown in Table 1 were prepared in the same manner as in Example 1 and were compounded with magnetic cores made of other materials, as shown in FIGS. 1 (a) (b) (c). A magnetic core having the structure shown in was prepared and wound with a formal wire. The DC superposition characteristics were measured. All choke coils showed a non-linear DC superposition characteristic. Next, the temperature rise ΔT was actually measured by incorporating it in the smoothing circuit of the switching power supply. The results obtained are shown in Table 1.
The temperature rise ΔT is smaller and superior in the choke coil of the present invention than in the conventional non-linear choke coil.

[0014]

[Table 1]

(Example 3) Nanocrystalline alloy magnetic cores having the compositions shown in Table 2 were prepared in the same manner as in Example 1 and were compounded with magnetic cores of other materials. A magnetic core having the structure shown in Fig. 3 was prepared, and a formal wire was wound around it, and the DC superposition characteristics at 25 ° C and 120 ° C were measured. Incremental relative permeability at 25 ° C, frequency 10kHz, superimposed magnetic field 4A / m is μ △ ₁ (25), 120 ° C, incremental relative permeability at frequency 10kHz, superimposed magnetic field 4A / m is μ △ ₁ (120). The temperature coefficient was defined as α = (μΔ ₁ (25) -μΔ ₁ (120)) × 100 / μΔ ₁ (25). The obtained results are shown in Table 2. All choke coils showed non-linear DC superposition characteristics. The temperature coefficient α of the choke coil of the present invention is smaller and superior than that of the conventional non-linear choke coil.

[0016]

[Table 2]

[0017]

According to the present invention, a magnetic core for a choke coil and a non-linear choke coil exhibiting a high inductance when the current is small, a small temperature rise and an excellent temperature stability can be realized. There is something remarkable.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of the structure of a choke coil core according to the present invention.

FIG. 2 is a diagram schematically showing an example of DC superposition characteristics of a nonlinear choke coil.

FIG. 3 is a diagram showing an example of a DC superimposition characteristic of the choke coil magnetic core of the present invention.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01F 3/04 17/06 G 8123-5E

Claims (4)

[Claims] 1. A core for a choke coil, characterized in that a nano-crystal high magnetic permeability closed magnetic circuit core and a magnetic core having a gap other than a nano-crystal alloy magnetic core or a powder magnetic core are integrated. 2. The nanocrystalline alloy is an alloy mainly composed of Fe, wherein the content of at least one element selected from Cu and Au is 0.1 at% or more and 3 at% or less, Ti, Zr, Hf, V, Content of at least one element selected from Nb, Ta, Mo, W is 1 at% or more and 7 at% or less, Si content is 10 at% or more and 17 at% or less, B content is 4 at%
The composition is not less than 10 at% and not more than 10.
A magnetic core for a choke coil according to 1. 3. The nanocrystalline alloy is an alloy mainly composed of Fe, wherein the content of at least one element selected from Cu and Au is 0 at% or more and 3 at% or less, Ti, Zr, Hf, V, Nb. , Ta, Mo, W content of at least one element is 2 at% or more and 10 at% or less, Si content is 0 at% or more and 10 at% or less, B content is 2 at% or more and 10 at% or less The magnetic core for a choke coil according to claim 1, wherein 4. A non-linear choke coil characterized in that at least one conductor is wound around the magnetic core according to any one of claims 1 to 3.