JP2010118486A - Inductor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductor which has higher core strength, higher insulation resistance, and lower core loss as compared with the conventional art. <P>SOLUTION: The inductor 100 includes a compact 1 containing a solidified mixture of mixed powder composed of amorphous soft magnetic powder and crystalline soft magnetic powder, and an insulating material, and a coil 2 provided in the compact 1. The mixed powder preferably comprises 90 to 98%, by mass, of the amorphous soft magnetic powder and 2 to 10% by mass of the crystalline soft magnetic powder. When the compounding ratio of the crystalline soft magnetic powder is more than 10% by mass, the insulation resistance decreases and the core loss increases, and when the compounding ratio of the crystalline soft magnetic powder is less than 2% by mass, the magnetic permeability and core strength decrease. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inductor, a manufacturing method thereof, an inductor using a toroidal core and a toroidal coil, a choke coil using an inductor, and a power supply circuit.

  In recent years, the demand for improvement in power efficiency and miniaturization of elements used in these power supply circuits has increased due to the increase in current accompanying the performance enhancement of CPUs (Central Processing Units) for notebook personal computers and PDAs.

  A core formed of soft magnetic metal powder having a high saturation magnetic flux density, which hardly causes magnetic saturation, is used for the magnetic core of an inductor used as a choke coil in a power supply circuit that requires a large current.

  In recent years, an inductor in which a dust core and a coil portion are integrally formed has been proposed (patent document 1) with a request for miniaturization of an element.

  These integrally molded inductors exhibit excellent DC superposition characteristics by molding a soft magnetic metal powder having a high saturation magnetic flux density together with a resin binder, but on the other hand, since a coil is arranged inside the magnetic core, It is difficult to perform heat treatment at a high temperature to improve the magnetic properties after molding in the powder magnetic core, and there is a problem that the core loss is larger than that of the conventional powder magnetic core and the efficiency when used as a power supply element is reduced. .

  As a solution to these problems, a method has been proposed in which amorphous metal magnetic powder having no magnetocrystalline anisotropy and low core loss is used as a raw material for the core (Patent Document 2).

  However, in general, an amorphous metal has a significantly higher hardness than a crystalline metal, and there is a problem that an improvement in filling rate due to plastic deformation cannot be expected during compression molding, resulting in a low magnetic permeability.

  In addition, since the amount of deformation during molding of the amorphous powder is small, there is a problem that the strength is lowered because the bonding between the powders generated in the molded body is reduced.

  As a solution to these problems, a technique has been proposed in which a crystalline metal powder is mixed with an amorphous metal powder to form a core material (Patent Documents 3 and 4).

  In these techniques, the crystalline powder is added to the amorphous powder to improve the filling rate and increase the magnetic permeability.

  Furthermore, since the crystalline metal powder is deformed, it plays the role of a binder for bonding the amorphous powders together, so that the core strength is improved.

JP 2003-309024 A JP 2004-22814 A JP 2004-197218 A JP 2004-363466 A

  However, when a crystalline powder having a large magnetocrystalline anisotropy is added to an amorphous powder, there is a concern that the core loss increases as the coercive force of the core increases.

  In the examples of Patent Documents 3 and 4, the core loss when produced with only amorphous powder is not so small as compared with the core loss produced with only crystalline powder, so the coercive force increases when crystalline powder is added. The effect of increasing the magnetic permeability is greater than the effect of the above, and the core loss is reduced by the mixing ratio. However, if amorphous powder with significantly superior soft magnetic properties compared to the crystalline material is used, the crystalline powder It is estimated that the core loss is greatly increased by the addition.

  In addition, when crystalline powder is added to amorphous powder, there is a problem that the crystalline powder is excessively deformed due to friction between the surface of the molded body and the mold, the core surface is conducted, and the insulation resistance as an element is lowered. there were.

  The present invention has been made in view of such problems, and a problem thereof is to provide an inductor having higher core strength and insulation resistance and lower core loss than conventional ones.

  In order to solve the above-described problems, a first aspect of the present invention includes a magnetic core and a coil disposed inside the magnetic core, and the magnetic core is 90 to 98 mass% amorphous soft magnetic. An inductor comprising a solidified mixture of a powder and a mixed powder of 2 to 10 mass% crystalline soft magnetic powder and an insulating material.

  According to a second aspect of the present invention, there is provided a coil inside a mixture of a mixed powder comprising a blending ratio of 90 to 98 mass% amorphous soft magnetic powder and 2 to 10 mass% crystalline soft magnetic powder, and an insulating material. And a step of solidifying the mixture. A method for manufacturing an inductor.

  In the third aspect of the present invention, a mixture of a mixed powder composed of a blending ratio of 90 to 98 mass% amorphous soft magnetic powder and 2 to 10 mass% crystalline soft magnetic powder and an insulating material is solidified. A toroidal core characterized in that

  According to a fourth aspect of the present invention, there is provided an inductor formed by winding a toroidal core according to the third aspect.

  According to a fifth aspect of the present invention, there is provided a choke coil including the inductor according to the first aspect or the fourth aspect.

  According to a sixth aspect of the present invention, there is provided a power supply circuit including the inductor according to the first aspect or the fourth aspect.

  According to the present invention, it is possible to provide an inductor having higher core strength and insulation resistance and lower core loss than conventional ones.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the inductor 100 according to the present embodiment will be briefly described with reference to FIG.

  As shown in FIG. 1, an inductor 100 includes a molded body 1 including a solidified mixture of a mixed powder made of an amorphous soft magnetic powder and a crystalline soft magnetic powder, which will be described later, and an insulating material, and a molded body 1. The coil 2 is provided inside.

  As is apparent from FIG. 1, the inductor 100 is an integrally molded inductor, the molded body 1 constitutes the magnetic core portion 3, and both ends of the coil 2 are exposed from the molded body 1 to constitute the terminal portions 4a and 4b. ing.

  Next, each member constituting the inductor 100 will be described.

The amorphous soft magnetic powder is an indispensable material for reducing the core loss of the inductor 100. For example, the formula: (Fe _1-a TM _a ) _100-w-xy-Z P _{WB x} L _y Si _Z (However, inevitable impurities are included, TM is one or more selected from Co and Ni, L is one or more selected from Al, V, Cr, Y, Zr, Mo, Nb, Ta, and W. And 0 ≦ a ≦ 0.98, 2 ≦ w ≦ 16 atomic%, 2 ≦ x ≦ 16 atomic%, 0 <y ≦ 10 atomic%, 0 ≦ z ≦ 8 atomic%).

  More specifically, amorphous Fe—P—B—Nb—Cr powder, amorphous Fe—Si—B powder, amorphous Fe—Si—B—Cr powder, etc. satisfying the above composition ratio Fe-based amorphous powder or Co-based amorphous powder is used.

  The crystalline soft magnetic powder is essential because it improves the filling rate of the mixed powder, increases the magnetic permeability, and acts as a binder for bonding the amorphous soft magnetic powders together.

  The crystalline soft magnetic powder is, for example, crystalline Fe-Si-Cr powder, crystalline carbonyl Fe powder, crystalline Fe-Si powder, crystalline Fe-Ni powder, crystalline Fe-Al powder, crystalline Fe-Si-Al Examples thereof include crystalline soft magnetic powder such as powder.

The particle size (average particle size D ₅₀ ) of the crystalline soft magnetic powder is preferably 1 to ₅ μm. This is because if the average particle size is further increased, the core loss of the magnetic core portion 3 increases due to an increase in eddy current, and the superiority over the core (magnetic core portion) made only of crystalline soft magnetic powder is lost. .

  Here, the mixing ratio of the mixed powder composed of the amorphous soft magnetic powder and the crystalline soft magnetic powder is 90 to 98 mass% for the amorphous soft magnetic powder and 2 to 10 mass% for the crystalline soft magnetic powder. desirable. That is, the mixed powder is composed of an amorphous soft magnetic powder and a crystalline soft magnetic powder, and the amount of the crystalline soft magnetic powder added to the total amount of the mixed powder is preferably 2 to 10 mass%.

  This is because when the blending ratio of the crystalline soft magnetic powder is further increased, the insulation resistance of the magnetic core portion 3 is decreased and the core loss is increased. On the other hand, when the blending ratio of the crystalline soft magnetic powder is further decreased, the magnetic core is decreased. This is because the magnetic permeability and core strength of the portion 3 are reduced.

  The insulating material serves as a binder for adhering the mixed powder, and examples thereof include various resins such as phenol resin, epoxy resin, acrylic resin, silicone resin, polyimide resin, polyamide resin, and inorganic glass.

  As the coil 2, for example, a conductor made of metal or the like with an insulating coating is used.

  In FIG. 1, the inductor 100 is configured as an integral inductor in which the coil 2 is provided inside the magnetic core portion 3, but the magnetic core portion 3 is a toroidal core, and the coil 2 is wound around the toroidal core to configure the inductor. May be.

  Next, a method for manufacturing the inductor 100 will be briefly described.

  First, an amorphous soft magnetic powder and a crystalline soft magnetic powder are prepared using a water atomization method or the like, and mixed at the above-described mixing ratio to obtain a mixed powder.

  Next, an insulating material is mixed with the obtained mixed powder in a proportion of, for example, 2 to 10 mass%, preferably 5 mass%, with respect to the total amount of the mixture to obtain a mixture.

  Next, the coil 2 is placed in the mold, and the granulated powder (mixture) is filled in the mold and pressure-molded, and then, for example, 300 to 400 ° C., preferably 350 ° C. for about 1 hour. 1 is completed, the integrally molded inductor 100 shown in FIG. 1 is completed.

  As described above, the coil 2 and the magnetic core portion 3 may not be integrally formed, but the magnetic core portion 3 may be configured as a toroidal core, and a winding may be applied to the magnetic core portion 3 to form an inductor.

  Thus, according to the present embodiment, the inductor 100 includes the magnetic core portion 3 and the coil 2 disposed inside the magnetic core, and the magnetic core portion 3 is 90 to 98 mass% amorphous soft magnetic. This includes a solidified mixture of a mixed powder and an insulating material composed of a powder and a blending ratio of 2 to 10 mass% crystalline soft magnetic powder.

  Therefore, the inductor 100 has higher core strength and insulation resistance and lower core loss than the conventional inductor.

  Next, the present invention will be described in more detail with specific examples.

  First, toroidal cores and monolithic inductors in which crystalline soft magnetic powder and amorphous soft magnetic powder were mixed at various mixing ratios were manufactured.

  First, crystalline soft magnetic powder and amorphous soft magnetic powder were produced.

First, as a crystalline soft magnetic powder, a crystalline Fe-6.5 wt% Si-3 wt% Cr powder was prepared using a water atomization method, and then an average particle diameter D ₅₀ of 5.0 μm and 10. Fine powders of 1.0 μm and 2.5 μm were obtained from 0 μm and 20.8 μm powder using air classification.

Similarly, amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ and amorphous Fe ₇₆ Si ₉ B ₁₃ Cr ₂ powders were produced by the water atomization method as amorphous soft magnetic powders, both having an average particle size of 10 A powder of 0.0 μm was obtained.

Next, the amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder, amorphous Fe ₇₆ Si ₉ B ₁₃ Cr ₂ produced using Perkin Elmer PYRIS Diamond DSC at a heating rate of 40 ° C./min. The DSC (Differential Scanning Calorimetry) curve of the powder was measured.

  FIG. 2A shows the DSC curve measured.

As shown in FIG. 2A, in the amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder, an endotherm indicating a glass transition temperature Tg is confirmed at 471 ° C., and this composition is reduced to a crystallization temperature Tx or less. It was found to be a metallic glass having a transition temperature Tg.

Next, the prepared amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder and crystalline Fe-6.5wt% Si-3wt% Cr powder were thoroughly mixed in various proportions using a V-type mixer. As a result, a mixed powder was obtained. Similarly, a mixed powder was prepared for the Fe ₇₆ Si ₉ B ₁₃ Cr ₂ powder.

  Next, the obtained mixed powder is mixed with a phenol resin as an insulating material at a ratio of 5 mass% with respect to the total amount, and passed through a sieve having an opening of 500 μm, whereby a granulated powder having an average particle size of 500 μm or less ( Mixture).

The measurement of the average particle size D ₅₀ of any powder was also carried out using a laser particle size distribution analyzer.

The produced granulated powder (mixture) was filled in a mold having an outer diameter of 13 mm and an inner diameter of 8 mm, and molded at a surface pressure of 7 Ton / cm ² (7 × 10 ⁹ Pa) to obtain a toroidal molded body having a height of 5 mm. .

  The obtained molded body was subjected to a curing treatment at 150 ° C. for 2 hours in a nitrogen atmosphere, and further subjected to a strain relief heat treatment at 350 ° C. for 1 hour in a nitrogen atmosphere to obtain a toroidal core.

Similarly, the coil 2 is placed in a 10 mm square mold, and the granulated powder (mixture) is further filled, and a surface pressure of 7 Ton / cm ² (7 × 10 ⁹ Pa) is added, and the integral molding shown in FIG. Molded into the shape of a mold inductor 100.

  Similarly to the toroidal shape, the molded body 1 thus obtained was subjected to a heat treatment for removing stress in a temperature range of 350 ° C. for 1 hour after curing at 150 ° C. for 2 hours in a nitrogen atmosphere, and then the terminal portions 4a and 4b. By soldering, a surface mount inductor (inductor 100, that is, an integrally formed inductor) was obtained.

  Through the above steps, a toroidal core and an integrally molded inductor in which crystalline soft magnetic powder and amorphous soft magnetic powder were mixed at various mixing ratios were manufactured.

  Next, the physical properties of the prepared core and the integrally molded inductor were investigated.

First, the difference in core strength depending on the mixing ratio of crystalline Fe-6.5wt% Si-3wt% Cr powder and amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder as an amorphous material investigated.

Specifically, the crystalline Fe-6.5wt% Si-3wt% Cr powder having an average particle size of 5 [mu] m, with respect to toroidal core prepared by adding the amorphous _{Fe 75 P 12 B 8 Nb 3} Cr 2 A strength test according to a method for testing the crushing strength of a sintered oil-impregnated bearing (JIS Z2507) was performed to evaluate the crushing strength.

  FIG. 2B shows the relationship between the amount of crystalline soft magnetic powder added and the crushing strength.

As shown in FIG. 2B, the crushing strength in the case where the toroidal core was produced using only the amorphous soft magnetic powder was 23.1 N / mm ² .

On the other hand, when the addition amount of the crystalline soft magnetic powder with respect to the total amount of the mixed powder is 2 mass%, the crushing strength is 38.5 N / mm ² , an increase of 1.7 times compared to the case of the amorphous soft magnetic powder alone. It was.

  From the above results, it was found that it is useful to add crystalline soft magnetic powder to amorphous soft magnetic powder. In addition, the crushing strength increased as the addition amount was further increased.

  Next, similarly, the core loss when the crystalline soft magnetic powder was added to the amorphous soft magnetic powder was evaluated.

The average particle diameter D ₅₀ of crystalline Fe-6.5wt% Si-3wt% Cr powder _{5μm Fe 75 P 12 B 8 Nb} 3 Cr 2 ( metallic glasses) and amorphous _{Fe 76 Si 9 B 13 Cr 2} ( metal FIG. 3 shows the core loss of a toroidal core produced by adding to an amorphous material that is not glass. A commercially available BH analyzer was used for the measurement, and the excitation conditions were 50 mT and 300 kHz.

As shown in FIG. 3, when a toroidal core is made of only amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder, the core loss is 800 kW / m ³ and amorphous Fe ₇₆ Si ₉ B ₁₃ Cr ₂ powder. 1400 kW / m ³ was shown in the case of producing only by the above method.

When amorphous Fe ₇₅ P ₁₂ B ₈ Nb ₃ Cr ₂ powder, which is metallic glass, is used, amorphous Fe ₇₆ Si ₉ B ₁₃ Cr ₂ powder, which is an amorphous material that is not metallic glass, is used. The core loss was lower than that in the case of using a metal glass, and it was found that a low core loss can be realized by using metallic glass.

  On the other hand, when the crystalline Fe-6.5wt% Si-3wt% Cr powder, which is a crystalline soft magnetic powder, is added to these amorphous powders, the core loss increases as the amount added increases. I went.

In addition, the core loss was 2500 kW / m ³ when a toroidal core was produced using only crystalline soft magnetic powder.

  From the above results, there is a proportional relationship between the core loss and the amount of crystalline soft magnetic powder added, and as the amount added increases, the core loss increases and the advantages of the amorphous material are lost. It was found that the addition amount of the crystalline soft magnetic powder with respect to the total amount of the mixed powder is better.

Then Similarly crystalline Fe-6.5wt% Si-3wt% Cr powder of amorphous _{Fe 75 P 12 B 8 Nb 3} Cr 2 surface mount inductors powder was prepared by adding in various ratios of (inductor 100) The insulation resistance at 50 V was measured using an insulation resistance tester TOS7200 manufactured by Kikusui Electronics Corporation. The results are shown in FIG.

  As shown in FIG. 4, the amount of crystalline Fe-6.5 wt% Si-3 wt% Cr (crystalline soft magnetic powder) with respect to the total amount of the mixed powder shows a high insulation resistance of 3000 MΩ or more up to 10 mass%, When the addition amount was 20 mass%, the resistance decreased greatly to 80 MΩ, and thereafter the insulation resistance decreased as the addition amount increased. This is probably because the crystalline soft magnetic powder was deformed by molding and current conduction occurred.

  In the examination so far, in order to produce an element that increases the core strength, has a low core loss, and exhibits a sufficient insulation resistance as a circuit element, the amount of the crystalline soft magnetic powder added to the total amount of the mixed powder is 2 to 2. It was shown that it is desirable to set it to 10 mass% or less.

Next, the influence of the particle size of the crystalline soft magnetic powder to be added was examined. The average particle diameter _{D 50} 1.0μm fabricated by classification, 2.5μm, 5.0μm, 10.0μm, crystalline Fe-6.5wt% Si-3wt% Cr powder of amorphous Fe ₇₅ P of 20.8μm ₁₂ B ₈ Nb ₃ Cr ₂ powder was added at a rate of 10 mass%, and the core loss (core loss) was compared using a commercially available BH analyzer. The results are shown in FIG.

As shown in FIG. 5, 1.0 .mu.m average particle diameter _{D 50,} 2.5 [mu] m, in the core of adding crystalline Fe-6.5wt% Si-3wt% Cr powder 5.0 .mu.m, the core loss is 900 back and forth against indicate the low value, the average particle diameter D ₅₀ of 10.0 [mu] m, the core loss increases in core added with powder of 20.8Myuemu, superior to cores formed using only the crystalline soft magnetic powder Lost. An increase in eddy current can be considered as a cause of an increase in core loss. Therefore, the average particle diameter _{D 50} of the crystalline soft magnetic powder to be added 5.0μm is considered appropriate from 1.0 .mu.m.

  From the above examination, it was shown that the present invention can provide an inductor with high core strength and insulation resistance and low core loss.

  The inductor and the manufacturing method thereof according to the present invention can be applied to a choke coil, a power supply circuit, and the manufacture thereof.

  The technical scope of the present invention does not depend on the above-described embodiments and examples. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

It is a perspective view of inductor 100 concerning this embodiment, Comprising: The magnetic core part 3 represents the outer periphery with the dotted line, and has drawn the inside transparently. Is a diagram showing an amorphous _{Fe 75 P 12 B 8 Nb 3} Cr 2 powder and amorphous Fe ₇₆ Si ₉ B ₁₃ Cr ₂ powder DSC curve. It is a figure which shows the relationship between the addition amount of crystalline soft magnetic powder, and crushing strength. It is a figure which shows the relationship between the addition amount of crystalline soft magnetic powder, and a core loss. It is a figure which shows the relationship between the addition amount of crystalline soft magnetic powder, and insulation resistance. It is a diagram showing the relationship between the average particle diameter D ₅₀ and the core loss of the crystalline soft magnetic powder (core loss).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Molded object 2 ......... Coil 3 ......... Magnetic core part 4a ... Terminal part 4b ... Terminal part 100 ... Inductor

Claims (24)

With magnetic core,
A coil disposed inside the magnetic core;
Have
The magnetic core is
An inductor comprising a solidified mixture of a mixed powder composed of a blend ratio of 90 to 98 mass% amorphous soft magnetic powder and 2 to 10 mass% crystalline soft magnetic powder and an insulating material. The crystalline soft magnetic powder is:
The inductor according to claim 1, wherein the average particle diameter D ₅₀ is 1 to ₅ μm. The amorphous soft magnetic powder has the _{formula: (Fe 1-a TM a} ) 100-w-x-y-z P W B x L y Si Z ( provided that includes unavoidable impurities, TM is Co, Ni L is one or more selected from Al, V, Cr, Y, Zr, Mo, Nb, Ta, W, and 0 ≦ a ≦ 0.98, 2 ≦ w ≦ 16 atoms 3, 2 ≦ x ≦ 16 atomic%, 0 <y ≦ 10 atomic%, 0 ≦ z ≦ 8 atomic%).   The inductor according to claim 3, wherein the amorphous soft magnetic powder is a metallic glass exhibiting a glass transition point. The amorphous soft magnetic powder is
The inductor according to claim 3, wherein the inductor is a Co-based amorphous powder.   The crystalline soft magnetic powder includes crystalline Fe-Si-Cr powder, crystalline carbonyl Fe powder, crystalline Fe-Si powder, crystalline Fe-Ni powder, crystalline Fe-Al powder, crystalline Fe-Si- The inductor according to claim 1, wherein the inductor is any one of Al powders. The insulating material is
The inductor according to any one of claims 1 to 6, comprising any one of a phenol resin, an epoxy resin, an acrylic resin, a silicone resin, a polyimide resin, a polyamide resin, and an inorganic glass.   A coil is arranged inside a mixture of a mixed powder composed of 90 to 98 mass% amorphous soft magnetic powder and 2 to 10 mass% crystalline soft magnetic powder and an insulating material, and the mixture is solidified. A method of manufacturing an inductor comprising a step. The crystalline soft magnetic powder is:
The method for manufacturing an inductor according to claim 8, wherein the average particle diameter D ₅₀ is 1 to ₅ μm. The amorphous soft magnetic powder has the _{formula: (Fe 1-a TM a} ) 100-w-x-y-z P W B x L y Si Z ( provided that includes unavoidable impurities, TM is Co, Ni L is one or more selected from Al, V, Cr, Y, Zr, Mo, Nb, Ta, W, and 0 ≦ a ≦ 0.98, 2 ≦ w ≦ 16 atoms 10. The method for manufacturing an inductor according to claim 8, wherein: 2 ≦ x ≦ 16 atomic%, 0 <y ≦ 10 atomic%, 0 ≦ z ≦ 8 atomic%).   The method of manufacturing an inductor according to claim 10, wherein the amorphous soft magnetic powder is a metallic glass exhibiting a glass transition point. The amorphous soft magnetic powder is
The method of manufacturing an inductor according to claim 10, wherein the inductor is a Co-based amorphous powder.   The crystalline soft magnetic powder includes crystalline Fe-Si-Cr powder, crystalline carbonyl Fe powder, crystalline Fe-Si powder, crystalline Fe-Ni powder, crystalline Fe-Al powder, crystalline Fe-Si- The method for manufacturing an inductor according to claim 8, wherein the inductor is any one of Al powders. The insulating material is
The method for manufacturing an inductor according to any one of claims 8 to 13, comprising any one of a phenol resin, an epoxy resin, an acrylic resin, a silicone resin, a polyimide resin, a polyamide resin, and an inorganic glass.   A toroidal core obtained by solidifying a mixture of an insulating material and a mixed powder comprising a blending ratio of 90 to 98 mass% amorphous soft magnetic powder and 2 to 10 mass% crystalline soft magnetic powder. The crystalline soft magnetic powder is:
The toroidal core according to claim 15, wherein the average particle diameter D ₅₀ is 1 to ₅ μm. The amorphous soft magnetic powder has the _{formula: (Fe 1-a TM a} ) 100-w-x-y-z P W B x L y Si Z ( provided that includes unavoidable impurities, TM is Co, Ni L is one or more selected from Al, V, Cr, Y, Zr, Mo, Nb, Ta, W, and 0 ≦ a ≦ 0.98, 2 ≦ w ≦ 16 atoms %, 2 ≦ x ≦ 16 atomic%, 0 <y ≦ 10 atomic%, 0 ≦ z ≦ 8 atomic%). The toroidal core according to claim 15 or 16, wherein   The toroidal core according to claim 17, wherein the amorphous soft magnetic powder is a metallic glass exhibiting a glass transition point. The amorphous soft magnetic powder is
The toroidal core according to claim 17, which is a Co-based amorphous powder.   The crystalline soft magnetic powder includes crystalline Fe-Si-Cr powder, crystalline carbonyl Fe powder, crystalline Fe-Si powder, crystalline Fe-Ni powder, crystalline Fe-Al powder, crystalline Fe-Si- The toroidal core according to any one of claims 15 to 19, wherein the toroidal core is any one of Al powders. The insulating material is
The toroidal core according to any one of claims 15 to 20, comprising any one of a phenol resin, an epoxy resin, an acrylic resin, a silicone resin, a polyimide resin, a polyamide resin, and an inorganic glass.   An inductor obtained by winding a toroidal core according to any one of claims 15 to 21.   A choke coil comprising the inductor according to claim 1.   A power supply circuit comprising the inductor according to claim 1.

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