JP2000228319A - Choke coil and noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized chock coil capable of obtaining a satisfactory noise attenuating effect over a wide frequency band, and a noise filter using it. SOLUTION: In this chock coil, a magnetic core 1 is composed by combining a nanocrystal soft magnetic alloy core 2 made into a toroidal shape of a nanocrystal soft magnetic alloy, in which nanocrystal grains whose crystal grain diameters are 50 nm or smaller occupy 50% or more of the whole volume of its structure, and a ferrite core 3 made of ferrite into a toroidal shape to be coaxial, and lead wires 4, 4' are wound about the magnetic core 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil used to attenuate noise affecting electronic equipment and the like, and a noise filter using the choke coil, and particularly exhibits a noise attenuation effect in a wide frequency band. It is a technology that makes it possible.

[0002]

2. Description of the Related Art As semiconductor switching elements have become more sophisticated, switching power supplies and inverter devices using the semiconductor switching elements have rapidly become widespread. In particular, with the development of high-output semiconductor switch elements corresponding to high frequencies represented by IGBTs, the frequency of large-capacity inverters, including low-noise inverters whose switching frequency is higher than the upper limit of the audible frequency band, is rapidly increasing. It is planned.

With the widespread use of such switching power supplies and high-frequency inverter devices, high-frequency noise generated by the semiconductor switching operation of these devices enters other electronic devices connected to this power line via the power line. There is a problem in that an obstacle such as a malfunction of an electronic device is caused.

In order to cope with such an obstacle, a noise filter using a choke coil formed by winding a conductive wire around a magnetic core is interposed between the lines to reduce noise.

[0005] The above-mentioned noise is roughly classified into a normal mode noise reciprocating between lines and a common mode noise flowing between the line and the earth. A normal mode choke coil and a common mode choke coil corresponding to each are developed. Are appropriately used to form a noise filter.

As the noise filter, a choke coil using ferrite for a magnetic core is generally known.
However, although a choke coil using ferrite for a magnetic core exhibits a good noise attenuation effect in a middle frequency range, a sufficient noise attenuation effect cannot be expected in a high frequency range and a low frequency range.

The frequency band of the generated noise often ranges from a high frequency band to a low frequency band depending on the noise source and the like. In order to widen the noise attenuation band even a little, for example, a high frequency band is used. In general, a choke coil a having a good noise attenuation effect and a choke coil b having a good noise attenuation effect in a low frequency region are connected in series to form a noise filter (FIG. 6).
reference).

As the magnetic core material, various materials such as amorphous alloys are used in addition to the ferrite. One of the magnetic permeability and the saturation magnetic flux density is high.
Since the other has the characteristic of being low, it is difficult to configure a choke coil that can cover a wide frequency band with only one magnetic core material, and a plurality of choke coils are connected in series as described above. .

Examples of combining choke coils having different noise attenuation frequency bands include an example in which ferrite and an amorphous alloy are used for a magnetic core, an example in which different types of amorphous alloys are combined, and an example in which a dust core and a silicon steel plate are combined. Etc. are known.

FIG. 6 shows a circuit configuration when a noise filter is configured by connecting two choke coils in series. The circuit configuration shown in FIG. 6 does not show a circuit constituting an actual noise filter as it is, but shows an equivalent circuit thereof for easy understanding.

On the other hand, recently, there has been reported an example in which a nanocrystalline soft magnetic alloy having characteristics not found in the past and satisfying both a high magnetic permeability and a high saturation magnetic flux density is used for a choke coil (Japanese Patent Laid-Open No. Hei 8 (1996)). -115830).

In this example, a common mode choke coil having a magnetic core formed in a toroidal shape using Finemet (registered trademark) made by Hitachi Metals, Ltd. as a nanocrystalline soft magnetic alloy, and an outer iron type coil using ferrite. Is connected in series with a common mode choke coil having a magnetic core configured in accordance with CISPRPub. Eleven Cla
It is reported that a result satisfying both ssA or both Class A and Class B is obtained.

In the above report, various combinations of magnetic cores are verified. However, when a magnetic core using both finemet and ferrite materials is configured in a toroidal shape and connected in series, the above noise standard is not satisfied. It is also reported that a result satisfying neither Class A nor B is obtained.

[0014]

As described above, conventionally, there has been proposed a configuration in which choke coils having different noise attenuation frequency bands are connected in series so that a noise attenuation effect can be obtained in a slightly wide frequency band. However, it is still not enough, and there is a demand for the development of a choke coil having a good noise attenuation effect over a wider band.

Further, in accordance with recent downsizing of electronic devices and the like, downsizing of the noise filter itself is strongly demanded. However, as long as a plurality of choke coils are connected in series, the number of components is inevitably increased, which is bulky and cannot sufficiently meet the demand for miniaturization.

Furthermore, the large number of parts requires a lot of time for assembling work, and there is a strong demand for an improvement in the conventional configuration in terms of production cost.

On the other hand, as described above, from the viewpoint of magnetic characteristics,
It is desirable to use a nanocrystalline soft magnetic alloy such as Finemet in terms of magnetic permeability and saturation magnetic flux density, but it is difficult to use the nanocrystalline soft magnetic alloy abundantly because it is expensive.

Therefore, the present inventor has proposed that a composite magnetic core using another magnetic material and an appropriate amount of a nanocrystalline soft magnetic alloy can be used in a wide frequency band while keeping the material price within an allowable range. We thought it was necessary to develop a product that exhibited a noise attenuation effect.

An object of the present invention is to provide a small-sized choke coil of a composite magnetic core using a nanocrystalline soft magnetic alloy capable of obtaining a good noise attenuation effect in a wide frequency band.

An object of the present invention is to provide a noise filter using a small-sized choke coil of a composite magnetic core using a nanocrystalline soft magnetic alloy capable of obtaining a good noise attenuation effect in a wide frequency band.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0022]

The present invention provides a choke coil formed by winding a conductive wire around a toroidal magnetic core, wherein the toroidal magnetic core has a crystal grain size of 50 nm.
The present invention is characterized in that a nanocrystalline soft magnetic alloy in which the following nanocrystalline grains occupy 50% or more of the entire volume of the structure and ferrite are used as a core material.

The toroidal magnetic core is formed so that the toroidal nanocrystalline soft magnetic alloy core formed of the nanocrystalline soft magnetic alloy and the toroidal ferrite core formed of the ferrite are coaxial. It is characterized by being combined.

[0024] The toroidal core is characterized in that a ribbon of the nanocrystalline soft magnetic alloy is wound around a toroidal ferrite core formed of the ferrite.

A noise filter according to the present invention is characterized in that the noise filter is configured by using the choke coil having any one of the above-described structures.

By making the core of the choke coil a composite core using a nanocrystalline soft magnetic alloy such as finemet and ferrite, a finemet having high magnetic permeability and high saturation magnetic flux density can be obtained with high performance, material cost and Thus, it is possible to manufacture a choke coil having a good noise attenuating effect in a wider frequency band than in the related art by suppressing the usage amount within a range that can be balanced on both sides.

By appropriately changing the ratio between the nanocrystalline soft magnetic alloy and the ferrite used in the composite magnetic core, the frequency characteristic can be set to an arbitrary characteristic, and even in a wide frequency band, the noise attenuation particularly in a desired frequency band can be increased. The choke coil can also be used.

As described above, since a nanocrystalline soft magnetic alloy having high magnetic permeability and high saturation magnetic flux density is used for the magnetic core,
Compared to using a magnetic material having a lower magnetic permeability and a lower saturation magnetic flux density, the same cross-sectional area can be reduced even in order to ensure the same noise attenuation, further promoting the miniaturization of choke coils. can do.

To form a composite magnetic core with ferrite using a nanocrystalline soft magnetic alloy, a nanocrystalline soft magnetic alloy core formed using a nanocrystalline soft magnetic alloy and a ferrite formed using ferrite are used. Both the magnetic core and the magnetic core may be formed in, for example, a toroidal shape having the same diameter, and may be formed by overlapping them in the axial direction.

The nanocrystalline soft magnetic alloy is currently manufactured as a so-called thin ribbon in the form of a thin film. Therefore, the nanocrystalline soft magnetic alloy is formed by winding the ribbon or punching it into a toroidal shape and laminating the punched ribbons. The magnetic alloy core and the ferrite core may be overlapped with each other with an adhesive. Furthermore, when superimposing, a plurality of ferrite cores and a plurality of nanocrystalline soft magnetic alloy cores may be alternately superposed.

When the magnetic cores are integrated with each other, for example, instead of using an adhesive to bond the magnetic cores together, the winding force of a conductive wire wound around the magnetic cores can be used.

Since the respective magnetic cores using ferrite and a nanocrystalline soft magnetic alloy are integrated as described above to form one toroidal magnetic core, and a lead wire is wound around the magnetic core to form a choke coil. Compared with the conventional configuration in which choke coils are connected in series, the number of components is reduced, the size can be reduced, and the work can be reduced.

[0033]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1A is a perspective view showing the configuration of a toroidal magnetic core of a choke coil according to the present invention. FIG.
FIG. 2B is a plan view showing a state in which a coil is wound around the magnetic core of FIG. 1A to form a choke coil. FIG. 2 shows FIG.
FIG. 4 is a circuit diagram showing a circuit configuration of a noise filter using the choke coil having the above configuration.

As shown in FIG. 1 (a), a core 1 of a choke coil is formed by solidifying a nanocrystalline soft magnetic alloy core 2 formed of a nanocrystalline soft magnetic alloy in a toroidal shape and a ferrite powder in a toroidal shape. And the ferrite core 3
It is configured to be stacked vertically. The nanocrystalline soft magnetic alloy core 2 and the ferrite core 3 may be laminated so as to be bonded via an adhesive.

As shown in FIG. 1 (b), the conductors 4, 4 'are bifilar-wound around the toroidal-shaped magnetic core 1 thus formed to form a choke coil.

In the case shown in FIG. 1, the core 1 of the choke coil comprises a nanocrystalline soft magnetic alloy core 2 and a ferrite core 3
Each of the outer diameter to φ37mm, inner diameter φ19mm,
It is formed in a toroidal shape with a thickness of 11 mm, and both are laminated. In addition, the size of the magnetic core 1 does not need to be limited to such a size, and may be appropriately set according to the use situation.

In the circuit configuration of the noise filter using the choke coil of the present invention, the conductive wire 4 wound around the magnetic core 1,
Reference numeral 4 'is connected via a capacitor 5, each of which has input terminals 6, 6' and output terminals 7, 7 ', and is grounded 8, 8'. Such a configuration is shown in a circuit diagram in FIG.

As shown in FIG. 2, the configuration of the noise filter circuit using the choke coil of the present invention is different from that of a conventional noise filter configured by connecting in series choke coils of different frequency bands (see FIG. 6). Since the magnetic core is formed as a composite magnetic core, the circuit configuration is simplified. The size can be reduced accordingly.

The nanocrystalline soft magnetic alloy used for the nanocrystalline soft magnetic alloy core 2 constituting the magnetic core 1 of the choke coil having the above configuration has the following configuration.

The nanocrystalline soft magnetic alloy mainly comprises iron (Fe), and silicon (Si), boron (B), copper (C)
u) and niobium (Nb) as alloy components, and fine nanocrystalline grains account for 50% or more of the entire volume of the alloy structure. The fine nanocrystal grains have an average particle size of 10
It is less than 00 $.

More specifically, the nanocrystalline soft magnetic alloy is prepared by, for example, rotating an alloy melt containing 13 atomic% of silicon, 9 atomic% of boron, 1 atomic% of copper, 5 atomic% of niobium and the balance iron as an alloy component. It is formed in the shape of a ribbon by a super-quenching method such as a single roll method in which it is wound on by spraying. Such a nanocrystalline soft magnetic alloy is commercially available from Hitachi Metals, Ltd. under the name of Finemet.

On the other hand, in this embodiment, Mn-Zn ferrite is used for the ferrite core 3. Mn, Zn
Such a ferrite component may be formed in a toroidal shape. The ferrite of the ferrite core 3 combined with the nanocrystalline soft magnetic alloy core 2 is not limited to Mn-Zn ferrite.

The choke coil having the above-described configuration was put in a measuring circuit shown in FIG. 3 to confirm a noise attenuation effect. Magnetic core 1
One ends of the conductive wires 4 and 4 ′ are connected to an AC power supply 9. The other end of the conductor 4 is the spectrum analyzer 1
0 and grounded. The other end of the conductor 4 ′ is grounded via a resistor 11.

The resistance 11 is equal to the internal resistance of each of the AC power supply 9 and the spectrum analyzer 10, and is set to 50Ω in the case shown in FIG.

As shown in FIG. 4, the noise attenuation effect (indicated by A in the figure) of the choke coil of the present invention was confirmed using the above measuring circuit. In FIG. 4, as a comparative example,
A choke coil having a configuration in which two ferrite cores 3 each having a toroidal shape are stacked in the same manner as shown in FIG. 1 is formed, and this choke coil is put into a measurement circuit shown in FIG. 4 and B).

FIG. 4 shows that 100 kHz to 100 MHz
In a wide frequency band, the noise attenuation curve A using the choke coil having the above configuration according to the present invention is
As a comparative example, it can be seen that the noise attenuation amount is larger than the noise attenuation curve B in the case where the choke coil constituted only of the ferrite core 3 is used.

In particular, in the frequency band of 100 kHz to 1 MHz, it can be seen that the noise attenuation curve A has a larger noise attenuation effect than the noise attenuation curve B as the frequency approaches 100 kHz. Incidentally, at 100 kHz, the noise attenuation of the case using the choke coil of the present invention is about 9 dB larger than that of the comparative example.

FIG. 4 shows that the noise decay curves A and B
It can also be seen that the noise attenuation is maximum in a frequency range slightly lower than 1 MHz.

On the other hand, in the frequency band of 1 MHz to 100 MHz, the noise attenuation of the comparative example (see noise attenuation curve B in the figure) decreases almost linearly, whereas the choke coil of the present invention is used. In the case (see noise attenuation curve A in the figure), it can be seen that the attenuation level is almost flat up to around 10 MHz, and then the attenuation gradually decreases.

By the way, at 10 MHz, the use of the choke coil of the present invention is about 6 d higher than that of the comparative example.
The noise attenuation is as large as B.

From the above results, it can be seen that the choke coil of the present invention has a large noise attenuation effect in a wide frequency band, for example, by removing noise from the power supply line and removing the noise from other electronic devices connected to this power supply line. It can be seen that it can be effectively used for a noise filter or the like for preventing a malfunction in the above.

The present invention is not limited to the above embodiment, but can be variously modified without departing from the gist thereof.

In the above configuration, the nanocrystalline soft magnetic alloy core 2
And the ferrite core 3 were each formed in the same toroidal core, and the two were laminated. For example, Mn-Zn ferrite, which is easy to form, was formed into a small cylindrical shape, and the periphery was formed. The nanocrystalline soft magnetic alloy formed in a ribbon shape in the above-described manner may be wound a predetermined number of times, and the magnetic core 1 may be configured so that the whole becomes a toroidal shape as shown in FIG.

Alternatively, a nanocrystalline soft magnetic alloy core 2 is formed by winding a nanocrystalline soft magnetic alloy ribbon in a hollow shape so that its outer diameter matches the inner diameter of the ferrite core 3. 2 may be fitted into the hollow of the ferrite core 3 formed in a toroidal shape.

By adjusting the ratio of the nanocrystalline soft magnetic alloy core 2 and the ferrite core 3 constituting the magnetic core 1, a noise attenuation frequency band in which a particularly large noise attenuation effect is desired can be arbitrarily selected. .

In the above-described embodiment, the structure in which the nanocrystalline soft magnetic alloy core 2 and the ferrite core 3 are bonded via an adhesive has been described. However, the conductive wire 4 wound around the magnetic core 1 without bonding with the adhesive. The nanocrystalline soft magnetic alloy core 2 and the ferrite core 3 may be fixed by simultaneously binding the nanocrystalline soft magnetic alloy core 2 and the ferrite core 3 at 4 ′.

The configuration of the choke coil according to the above embodiment can be applied to any of a common mode choke coil and a normal mode choke coil.

[0059]

According to the present invention, a noise attenuation effect can be obtained in a wide frequency band.

Since a toroidal core in which a nanocrystalline soft magnetic alloy core and a ferrite core are integrated is used,
The configuration of the noise filter circuit can be simplified as compared with the case where the choke coils are connected in series.

Since the circuit configuration of the noise filter can be simplified, the size can be further reduced.

In addition, since the number of parts can be reduced as compared with the configuration in which the choke coils are connected in series, a low-cost, small-sized noise filter that does not require any manufacturing work can be provided.

In the noise filter of the present invention, unlike the conventional configuration, the choke coils used are not connected in series, so that the size is further reduced. In particular, since a nanocrystalline soft magnetic alloy and ferrite are used for the magnetic core of the choke coil used, the noise attenuation effect in a wide frequency band is greater than that of a noise filter having a conventional configuration.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a magnetic core of a choke coil according to an embodiment of the present invention. FIG. 2B is a plan view showing a state where a conductive wire is wound around FIG.

FIG. 2 is a circuit diagram showing a configuration of a noise filter using the choke coil of the present invention.

FIG. 3 is a circuit diagram showing a measurement circuit for examining a noise attenuation effect.

FIG. 4 is a graph showing a noise attenuation effect of the choke coil of the present invention.

FIG. 5A is a plan sectional view showing a toroidal core in which a nanocrystalline soft magnetic alloy core is provided outside a ferrite core. (B) is a plan sectional view showing a toroidal core in which a ferrite core is provided outside a nanocrystalline soft magnetic alloy core.

FIG. 6 is a circuit diagram showing a circuit configuration of a noise filter having a conventional configuration in which choke coils are connected in series.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic core 2 Nanocrystal soft magnetic alloy core 3 Ferrite core 4 Conductor 4 'Conductor 5 Capacitor 5' Capacitor 6 Input terminal 6 'Input terminal 7 Output terminal 7' Output terminal 8 Earth 8 'Earth 9 AC power supply 10 Spectrum analyzer 11 Resistance A Noise attenuation curve B Noise attenuation curve a Choke coil b Choke coil

Claims (4)

[Claims] 1. A choke coil formed by winding a conductive wire around a toroidal magnetic core, wherein the toroidal magnetic core has nanocrystalline grains having a crystal grain size of 50 nm or less in a volume of 50% or more of the entire structure. A choke coil characterized in that a nanocrystalline soft magnetic alloy occupying the same and ferrite are used as a magnetic core material. 2. The choke coil according to claim 1, wherein the toroidal magnetic core comprises: a toroidal nanocrystalline soft magnetic alloy core formed of the nanocrystalline soft magnetic alloy;
A choke coil characterized by being coaxially combined with a toroidal ferrite core formed of ferrite. 3. The choke coil according to claim 1, wherein the toroidal core is formed by winding a ribbon of the nanocrystalline soft magnetic alloy around a toroidal ferrite core formed of the ferrite. A choke coil characterized in that: 4. A noise filter comprising the choke coil according to claim 1. Description: