CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2018/001856, filed Feb. 13, 2018, which claims priority to Korean Patent Application No. 10-2017-0019999, filed Feb. 14, 2017, whose entire disclosures are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a magnetic core, an inductor, and an electromagnetic interference (EMI) filter including the same.

BACKGROUND ART

An inductor is one of electronic parts applied to a printed circuit board and is applicable to a resonance circuit, a filter circuit, a power circuit, and the like due to its electromagnetic characteristics.

Recently, miniaturization and thinning of various electronic devices such as communication devices and display devices are important issues. Therefore, inductors applied to such electronic devices need to be miniaturized and thinned and to have high efficiency.

Meanwhile, an electromagnetic interference (EMI) filter which is applied to an inside of a power board serves to pass a signal, which is necessary for circuit operation, and remove noise.FIG. 1is an example of a circuit diagram of an EMI filter. Referring toFIG. 1, an EMI filter10may include a plurality of capacitors Cx and Cy and inductors L. Types of noise generated from a power board may be broadly classified into radio noise ranging from 30 MHz to 1 GHz radiated from the power board and conductive noise ranging from 150 kHz to 30 MHz conducted through a power line. Transmission modes of conductive noise may be divided into a differential mode and a common mode. Among them, common mode noise, even a small amount of noise, is reflected back while drawing a large loop and thus can affect electronic devices that are far away. The common mode noise is generated due to impedance imbalance of a wiring system and is significantly generated in a high-frequency environment.

In order to remove the common mode noise, in the inductor applied to the EMI filter, a toroidal magnetic core including a Mn—Zn based ferrite material is generally used. The Mn—Zn based ferrite has a high permeability at a frequency ranging from 100 kHz to 1 MHz and thus is effective for removing the common mode noise. A magnetic core having high inductance is required as power of a power board, to which the EMI filter is applied, increases. To this end, a magnetic core having a high permeability, for example, a magnetic core having a permeability (L) ranging from 10,000 to 15,000, should be used. Since the Mn—Zn based ferrite having such a high permeability has a high unit price and a core loss rate is low due to material characteristics of the Mn—Zn based ferrite, noise removal efficiency in a frequency band ranging from 6 to 30 MHz is still low.

DISCLOSURE

Technical Problem

The present invention is directed to providing a coil part applicable to an electromagnetic interference (EMI) filter.

Technical Solution

One aspect of the present invention provides an inductor including a magnetic core, and a coil wound around the magnetic core, wherein the magnetic core includes a plurality of stacked sub-magnetic cores, each of the sub-magnetic cores includes a first magnetic body and a second magnetic body, the first magnetic body and the second magnetic body are different types of magnetic bodies, the second magnetic body is disposed on at least a portion of a surface of the first magnetic body, each of the sub-magnetic cores has a toroidal shape, and a permeability of the first magnetic body differs from a permeability of the second magnetic body.

A ratio of a thickness of the second magnetic body disposed on an outer circumferential surface of the first magnetic body in a radial direction of the first magnetic body to a thickness of the first magnetic body may range from 1:16 to 1:80.

A ratio of a thickness of the second magnetic body disposed on an inner circumferential surface of the first magnetic body in the radial direction of the first magnetic body to the thickness of the first magnetic body may range from 1:16 to 1:80.

The permeability of the second magnetic body may be greater than the permeability of the first magnetic body.

The first magnetic body may include ferrite and the second magnetic body may include a metal ribbon.

The first magnetic body may include a Mn—Zn based ferrite and the second magnetic body may include an Fe—Si based metal ribbon.

The first magnetic body may have a toroidal shape, and the second magnetic body may be disposed to surround all of an upper surface, an outer circumferential surface, a lower surface, and an inner circumferential surface of the first magnetic body.

The second magnetic body which surrounds at least one of the outer circumferential surface and the inner circumferential surface of the first magnetic body may include a metal ribbon in which a plurality of layers are wound.

The number of layers of the metal ribbon disposed in a region in which the coil is wound may differ from the number of layers of the metal ribbon disposed in a region in which the coil is not wound.

Each of a thickness of the second magnetic body disposed on the upper surface of the first magnetic body and a thickness of the second magnetic body disposed on the lower surface of the first magnetic body may be smaller than a distance between the upper surface of the first magnetic body and the lower surface of the first magnetic body, and each of a thickness of the second magnetic body disposed on the outer circumferential surface of the first magnetic body and a thickness of the second magnetic body disposed on the inner circumferential surface of the first magnetic body may be smaller than a distance between the outer circumferential surface of the first magnetic body and the inner circumferential surface of the first magnetic body.

The magnetic core may have a toroidal shape, the first magnetic body may include a first region in which the second magnetic body is disposed to surround an upper surface, an outer circumferential surface, a lower surface, and an inner circumferential surface of the first magnetic body and a second region in which the second magnetic body is not disposed, and the coil is wound around at least a portion of a surface of the first region.

The second region and the coil may be spaced apart from each other.

The first magnetic body may include a pair of first regions disposed symmetrically to each other and a pair of second regions disposed symmetrically to each other.

The magnetic core may further include a lower sub-magnetic core disposed on a lowermost sub-magnetic core of the plurality of sub-magnetic cores and an upper sub-magnetic core disposed on an uppermost sub-magnetic core of the plurality of sub-magnetic cores. The lower sub-magnetic core and the upper sub-magnetic core may be made of a first magnetic body.

Another aspect of the present invention provides a magnetic core including a first sub-magnetic core and a second sub-magnetic core stacked on the first sub-magnetic core, wherein each of the first sub-magnetic core and the second sub-magnetic core includes a first magnetic body and a second magnetic body, the first magnetic body and the second magnetic body are different types of magnetic bodies, the second magnetic body is disposed on at least a portion of a surface of the first magnetic body, each of the first sub-magnetic core and the second sub-magnetic core has a toroidal shape, and a permeability of the first magnetic body differs from a permeability of the second magnetic body.

The first magnetic body may have a toroidal shape, and the second magnetic body may be disposed to surround all of an upper surface, an outer circumferential surface, a lower surface, and an inner circumferential surface of the first magnetic body.

The second magnetic body which surrounds at least one of the outer circumferential surface and the inner circumferential surface of the first magnetic body may include a metal ribbon in which a plurality of layers are wound.

The first magnetic body may have a toroidal shape, and the first magnetic body may include a first region in which the second magnetic body is disposed to surround the upper surface, the outer circumferential surface, the lower surface, and the inner circumferential surface of the first magnetic body and a second region in which the second magnetic body is not disposed.

The magnetic core may further include a lower sub-magnetic core disposed below the first sub-magnetic core and an upper sub-magnetic core disposed above the second sub-magnetic core, and the lower sub-magnetic core and the upper sub-magnetic core are made of a first magnetic body.

Still another aspect of the present invention provides an EMI filter including at least one inductor and at least one capacitor, wherein the inductor includes a magnetic core and a coil wound around the magnetic core, the magnetic core includes a plurality of stacked sub-magnetic cores, each of the sub-magnetic cores includes a first magnetic body and a second magnetic body, the first magnetic body and the second magnetic body are different types of magnetic bodies, the second magnetic body is disposed on at least a portion of a surface of the first magnetic body, each of the sub-magnetic cores has a toroidal shape, and a permeability of the first magnetic body differs from a permeability of the second magnetic body.

Advantageous Effects

According to embodiments of the present invention, an electromagnetic interference (EMI) filter having high noise removal performance in a wide frequency band, a small size, and a large power capacity can be obtained. Specifically, EMI filters according to the embodiments of the present invention can have high removal performance with respect to both of common mode noise and differential mode noise among conductive noise. In addition, according to the embodiments of the present invention, EMI filters of which noise removal performance is adjustable for each frequency band can be obtained.

