KR102569684B1 - Magnetic core, inductor and emi filter comprising the same - Google Patents

Abstract

An inductor according to an embodiment of the present invention includes a magnetic core and a coil wound on the magnetic core, wherein the magnetic core includes a first magnetic body and a second magnetic body of different kinds, wherein the second magnetic body It is accommodated in the first magnetic body.

Description

Magnetic core, inductor and EMI filter including the same {MAGNETIC CORE, INDUCTOR AND EMI FILTER COMPRISING THE SAME}

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

An inductor is one of electronic components applied on a printed circuit board, and may be applied to a resonant circuit, a filter circuit, a power circuit, etc. due to its electromagnetic characteristics.

Recently, since miniaturization and thinning of various electronic devices such as communication devices and display devices have become important issues, miniaturization, thinning, and high efficiency of inductors applied to these electronic devices are required.

Meanwhile, an EMI (ElectroMagnetic Interference) filter applied to the power board serves to pass signals necessary for circuit operation and remove noise. 1 shows a power board to which an EMI filter is applied, and FIG. 2 is an example of a circuit diagram of the EMI filter. Referring to FIGS. 1 and 2 , the EMI filter 10 may include a plurality of capacitors Cx and Cy and an inductor L. Types of noise generated from the power board can be largely divided into radiated noise of 30Mhz to 1Ghz radiated from the power board and conductive noise of 150Khz to 30Mhz conducted through a power line. A transmission method of conductive noise may be divided into a differential mode and a common mode. Among them, even a small amount of common mode noise returns in a large loop, so it can affect electronic devices that are far away. Such common mode noise is sometimes caused by impedance unbalance in a wiring system, and becomes more prominent in a high-frequency environment.

In order to remove common mode noise, an inductor applied to an EMI filter generally uses a toroidal-shaped magnetic core including an Mn-Zn-based ferrite material. Since Mn-Zn-based ferrite has a high permeability at 100 Khz to 1 Mhz, it is effective in removing common mode noise. As the power of the power board to which the EMI filter is applied increases, a magnetic core having a high inductance is required. Mn-Zn-based ferrite having such a high magnetic permeability has a high unit price, and since the core loss rate is low due to the material characteristics of the Mn-Zn-based ferrite, noise removal efficiency in the 6 to 30 MHz band is still low.

A technical problem to be achieved by the present invention is to provide a coil component applicable to an EMI filter.

An inductor according to an embodiment of the present invention includes a magnetic core and a coil wound on the magnetic core, wherein the magnetic core includes a first magnetic body and a second magnetic body of different kinds, wherein the second magnetic body It is accommodated in the first magnetic body.

The first magnetic body may be a molded body including ferrite powder, and the second magnetic body may include a metal ribbon stacked in multiple layers.

The first magnetic body may have a toroidal shape and include a groove formed between an inner circumferential surface and an outer circumferential surface, and the second magnetic body may be accommodated in the groove.

The first magnetic body may include a lower first magnetic body including the groove and an upper first magnetic body covering the lower first magnetic body.

The groove may include a first groove and a second groove spaced apart from the first groove, and the second magnetic material may be accommodated in the first groove and the second groove, respectively.

Each of the first groove and the second groove may have a toroidal shape, and the first groove may be disposed closer to the outer circumferential surface than the second groove.

An EMI filter according to an embodiment of the present invention includes at least one inductor and at least one capacitor, the inductor includes a magnetic core, and a coil wound on the magnetic core, and the magnetic core includes a heterogeneous It includes a first magnetic body and the second magnetic body, and the second magnetic body is accommodated in the first magnetic body.

According to an embodiment of the present invention, it is possible to obtain an EMI filter having excellent noise removal performance in a wide frequency band, being compact, and having a large power capacity. In particular, the EMI filter according to the embodiment of the present invention has high removal performance for common mode noise and differential mode noise among conductive noise. In addition, according to an embodiment of the present invention, it is possible to obtain an EMI filter capable of adjusting noise removal performance for each frequency band. In addition, according to an embodiment of the present invention, a separate bonding process for assembling heterogeneous magnetic materials is not required.

1 shows a power board to which an EMI filter is applied.
2 is an example of a circuit diagram of an EMI filter.
3 is a perspective view of an inductor according to an embodiment of the present invention.
4 is a perspective view and a cross-sectional view of a magnetic core according to an embodiment of the present invention.
5 and 6 are perspective and cross-sectional views of a magnetic core according to another embodiment of the present invention.
7 is a graph illustrating the skin effect theory.
8 is a graph showing magnetic flux versus skin depth of a ferrite material.
9 is a graph showing magnetic flux versus skin depth of a ferrite material and a metal ribbon material.
10 is a graph showing magnetic permeability and inductance of a ferrite material and a metal ribbon material.
11 shows a top view and a cross-sectional view of a magnetic core manufactured according to Comparative Examples and Examples.
12 is a graph showing noise removal performance of Comparative Examples and Examples.
13 shows differential mode noise improvement effects according to Comparative Examples and Examples.
14 shows a common mode noise improvement effect according to a comparative example and an embodiment.
15 shows a perspective view and a cross-sectional view of a magnetic core according to an embodiment of the present invention.
16 is an exploded view of the magnetic core of FIG. 15;
17 shows a perspective view and a cross-sectional view of a magnetic core according to another embodiment of the present invention.
18 shows a perspective view and a cross-sectional view of a magnetic core according to another embodiment of the present invention.
19 is an exploded view of the magnetic core of FIG. 18;
20 to 22 show a perspective view and a cross-sectional view of a magnetic core according to another embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers such as second and first may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a second element may be termed a first element, and similarly, a first element may be termed a second element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

In the description of the embodiments, each layer (film), region, pattern or structure is "on" or "under" the substrate, each layer (film), region, pad or pattern. The substrate formed on includes all those formed directly or through another layer. The criteria for upper/upper or lower/lower of each layer will be described based on drawings. In addition, since the thickness or size of each layer (film), region, pattern, or structure in the drawing may be modified for clarity and convenience of description, it does not entirely reflect the actual size.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings, but the same or corresponding components regardless of reference numerals are given the same reference numerals, and overlapping descriptions thereof will be omitted.

3 is a perspective view of an inductor according to an embodiment of the present invention.

Referring to FIG. 3 , the inductor 100 includes a magnetic core 110 and a coil 120 wound on the magnetic core 110 . At this time, the magnetic core 110 may have a toroidal shape, and the coil 120 is wound symmetrically with the first coil 122 wound on the magnetic core 110 and the first coil 122. A second coil 124 may be included. The first coil 122 and the second coil 124 may be wound on the upper surface S1, the outer circumferential surface S2, the lower surface S3, and the inner circumferential surface S4 of the toroidal-shaped magnetic core 110, respectively. A bobbin for insulating the magnetic core 110 and the coil 120 may be further disposed between the magnetic core 110 and the coil 120, or the surface of the magnetic core 110 may be coated with insulation. The coil 120 may be formed of a conducting wire whose surface is coated with an insulating material. The conducting wire may be made of copper, silver, aluminum, gold, nickel, tin, etc. whose surface is coated with an insulating material, and the cross section of the conducting wire may have a circular or prismatic shape.

According to an embodiment of the present invention, the magnetic core 110 includes a heterogeneous magnetic material.

4 is a perspective view and cross-sectional view of a magnetic core according to one embodiment of the present invention, and FIGS. 5 and 6 are perspective and cross-sectional views of a magnetic core according to another embodiment of the present invention.

4, the magnetic core 110 includes a first magnetic body 112 and a second magnetic body 114, the first magnetic body 112 and the second magnetic body 114 are heterogeneous, and the second magnetic body ( 114) may be disposed on at least a portion of the surface of the first magnetic body 112. At this time, the second magnetic body 114 may have a higher saturation magnetic flux density than the first magnetic body 112 .

Here, the first magnetic body 112 may include ferrite, and the second magnetic body 114 may include a metal ribbon. Here, the magnetic permeability (μ) of ferrite may be 2,000 to 15,000, and the magnetic permeability (μ) of the metal ribbon may be 100,000 to 150,000. For example, the ferrite may be Mn—Zn-based ferrite, and the metal ribbon may be Fe-based nanocrystalline metal ribbon. The Fe-based nanocrystalline metal ribbon may be a nanocrystalline metal ribbon containing Fe and Si.

At this time, the first magnetic body 112 and the second magnetic body 114 each have a toroidal shape, and the second magnetic body 114 is disposed on the outer circumferential surface S2 of the first magnetic body 112. 1) and an internal second magnetic body 114-2 disposed on the inner circumferential surface S4 of the first magnetic body 112.

At this time, the thickness of the second magnetic body 114 is thinner than the thickness of the first magnetic body 112 . By adjusting the ratio between the thickness of the second magnetic body 114 and the thickness of the first magnetic body 112, the permeability of the magnetic core 110 can be adjusted.

To this end, the second magnetic material 114 may include a metal ribbon wound in multiple layers.

Although the outer second magnetic body 114-1 and the inner second magnetic body 114-2 are illustrated as having the same material and thickness, it is not limited thereto. The outer second magnetic body 114-1 and the inner second magnetic body 114-2 may have different materials or magnetic permeability, and may have different thicknesses. Accordingly, the permeability of the magnetic core 110 may have various ranges.

Alternatively, as shown in FIG. 5, the second magnetic body 114 is disposed only on the outer circumferential surface S2 of the first magnetic body 112, or as shown in FIG. 6, the second magnetic body 114 is disposed on the inner circumferential surface of the first magnetic body 112. It may be arranged only in (S4).

In this way, if the magnetic core 110 includes heterogeneous magnetic materials having different permeability, it is possible to remove noise in a wide frequency band. In particular, compared to toroidal-type magnetic cores made of only Mn-Zn-based ferrite, magnetic flux is prevented from being concentrated on the surface, so the effect of removing high-frequency noise is high, and internal saturation is lowered, so it can be applied to high-power products. In addition, the performance of the magnetic core 110 can be adjusted by adjusting the magnetic permeability and volume ratio of the first magnetic body 112 and the second magnetic body 114 .

Hereinafter, the effect of the embodiment in which the magnetic core 110 includes a heterogeneous magnetic material will be described in more detail.

7 is a graph showing skin effect theory, FIG. 8 is a graph showing magnetic flux with respect to skin depth of a ferrite material, and FIG. 9 is a graph showing magnetic flux with respect to skin depth of a ferrite material and a metal ribbon material. 10 is a graph showing magnetic permeability and inductance of a ferrite material and a metal ribbon material.

Referring to FIG. 7 and Equation 1 below, the higher the specific permeability of the material and the higher the frequency, the smaller the skin depth value. Accordingly, a phenomenon in which the magnetic flux gathers on the surface of the material appears.

where δ is the skin depth, ρ is the resistivity, μ _s is the relative permeability, and f is the frequency.

Referring to FIG. 8 , the thinner the skin depth δ, the higher the magnetic flux Bm. Since the saturation magnetic flux density of the ferrite material is 0.47T, when the magnetic core is a ferrite core, the magnetic core becomes saturated when the magnetic flux exceeds 0.47T, and thus noise removal performance may deteriorate.

Referring to FIG. 9, when a material having a saturation magnetic flux density greater than the saturation magnetic flux density of the ferrite material, for example, a metal ribbon material is disposed on the surface of the ferrite material, it can withstand high magnetic flux at a thin skin depth, improving noise performance. can be maintained

In this way, if the second magnetic material having a higher saturation magnetic flux density than the first magnetic material is disposed on at least a portion of the surface of the first magnetic material, the effective sectional area of the magnetic core can be increased at a high frequency.

Meanwhile, referring to FIG. 10 , it can be seen that a magnetic core including both a ferrite material and a metal ribbon material having different magnetic permeability for each frequency has high inductance in a predetermined frequency range, and thus high noise removal performance can be obtained.

Hereinafter, further explanation is made using comparative examples and examples.

11 is a top view and cross-sectional view of a magnetic core manufactured according to Comparative Examples and Examples, FIG. 12 is a graph showing noise removal performance of Comparative Examples and Examples, and FIG. 13 is a differential mode according to Comparative Examples and Examples A noise improvement effect is shown, and FIG. 14 shows a common mode noise improvement effect according to a comparative example and an embodiment.

Referring to FIG. 11, in Comparative Example and Examples 1 to 3, the first magnetic material has an inner diameter (ID), an outer diameter (OD), and a height (T) of 15 mm, 25 mm, and 15 mm, respectively, and has a toroidal Mn-Zn A ferrite core was used. And, in Examples 1 to 3, Fe—Si-based metal ribbon was used as the second magnetic material, and it was laminated to have a thickness of 2 mm.

In Comparative Example, the second magnetic body was not disposed. In Example 1, the second magnetic body was disposed on the outer circumferential surface of the first magnetic body, and in Example 2, the second magnetic body was disposed on the inner circumferential surface of the first magnetic body. In Example 3, the second magnetic body was disposed on the outer and inner circumferential surfaces of the first magnetic body.

A coil was wound with 21 turns on the magnetic core according to Comparative Example and Examples 1 to 3, and noise removal performance was simulated under the conditions of an applied current of 1A and a power of 220W.

As a result, referring to FIG. 12 , it can be seen that the larger the area where the second magnetic material is disposed, the higher the noise removal performance.

In FIGS. 13 and 14 , differential mode noise rejection performance and common mode noise rejection performance were verified by measuring a magnetic field after connecting the magnetic core according to Comparative Example and Example 3 to the power board.

Referring to FIG. 13 , it can be seen that the degree of saturation inside the magnetic core is lowered in the magnetic core according to Example 3 compared to the magnetic core according to the comparative example. Accordingly, it can be seen that the magnetic core according to the embodiment of the present invention is suitable for high-power products.

Referring to FIG. 14, in the magnetic core according to Comparative Example, as the frequency increases, the surface of the magnetic core is saturated and the area efficiency decreases. However, the magnetic core according to Example 3 has a second magnetic body disposed on the surface of the first magnetic body. Therefore, it can be seen that the surface of the magnetic core is not saturated, the area efficiency is improved, and the noise removal effect at high frequency is great.

However, the second magnetic material 114, which is a metal ribbon, is thin and requires winding several times. In addition, an bonding process is required to arrange the wound metal ribbon on the inner or outer circumferential surface of the first magnetic material 112, and this bonding process is not easy to work with.

Accordingly, in the embodiment of the present invention, the second magnetic body is intended to be accommodated in the first magnetic body that has been molded in advance.

15 is a perspective view and cross-sectional view of a magnetic core according to one embodiment of the present invention, FIG. 16 is an exploded view of the magnetic core of FIG. 15, and FIG. 17 is a perspective view and cross-sectional view of a magnetic core according to another embodiment of the present invention. indicates

Referring to FIGS. 15 and 16 , the magnetic core 110 includes a first magnetic body 112 and a second magnetic body 114 of different kinds. The first magnetic body 112 may be a molded body including ferrite powder, and the second magnetic body 114 may be a metal ribbon stacked in multiple layers.

The first magnetic body 112 has a toroidal shape and may include a lower first magnetic body 300 for accommodating the second magnetic body 114 and an upper first magnetic body 310 covering the lower first magnetic body 300. there is. The lower first magnetic material 300 includes a groove G formed between an inner circumferential surface and an outer circumferential surface. Here, the groove (G) may be formed in a toroidal shape. To this end, the lower first magnetic body 300 includes a bottom surface 302, an outer wall 304 extending from the bottom surface 302 and including an outer circumferential surface, and extending from the bottom surface 302 and including an inner circumferential surface, and an outer wall ( 304 and an inner wall 306 spaced apart from each other, and a space between the outer wall 304 and the inner wall 306 may be a groove G for accommodating the second magnetic material 114 .

In this case, the outer wall 304 may be thinner than the inner wall 306 . According to this, the inner wall 306 is larger than the outer wall 304 ?緞? Compared to the case where the second magnetic body 114 is formed, the circumference of the groove G for accommodating the second magnetic body 114 may be formed longer, and the area of the second magnetic body 114 may be widened. Accordingly, it is possible to increase the noise removal performance.

According to an embodiment of the present invention, the second magnetic body 114, which is a multi-layered metal ribbon pre-wound, may be inserted into the groove G of the lower first magnetic body 300 formed in advance. Accordingly, the second magnetic body 114 can be easily accommodated in the first magnetic body 112 . As described above, according to an embodiment of the present invention, a process for bonding the first magnetic material 112 and the second magnetic material 114 and a process for winding the second magnetic material 114 around the outer circumferential surface of the first magnetic material 112. Since this is not required, the fabrication process is simple.

On the other hand, referring to FIG. 17, unlike the embodiment shown in FIGS. 15 to 16, the grooves G are not formed in a toroidal shape, but may be formed in symmetrical shapes over a part of the circumference. Accordingly, the second magnetic material 114 can be disposed only in the region where the coil 120 is wound.

18 is a perspective view and a cross-sectional view of a magnetic core according to another embodiment of the present invention, FIG. 19 is an exploded view of the magnetic core of FIG. 18, and FIGS. 20 to 22 are magnetic cores according to another embodiment of the present invention. Shows a perspective view and a cross-sectional view of.

18 to 19 , the magnetic core 110 includes a first magnetic body 112 and a second magnetic body 114 of different kinds. The first magnetic body 112 may be a molded body including ferrite powder, and the second magnetic body 114 may be a metal ribbon stacked in multiple layers.

The first magnetic body 112 has a toroidal shape and may include a lower first magnetic body 300 for accommodating the second magnetic body 114 and an upper first magnetic body 310 covering the lower first magnetic body 300. there is. The lower first magnetic material 300 includes a first groove G1 and a second groove G2 formed between an inner circumferential surface and an outer circumferential surface. Here, each of the first groove G1 and the second groove G2 may be formed in a toroidal shape. To this end, the lower first magnetic body 300 includes a bottom surface 302, an outer wall 304 extending from the bottom surface 302 and including an outer circumferential surface, and extending from the bottom surface 302 and including an inner circumferential surface, and an outer wall ( 304) and an inner wall 306 spaced apart, extending from the bottom surface 302 and spaced apart from the outer wall 304 and the inner wall 306 between the outer wall 304 and the inner wall 306, respectively. can include A space between the outer wall 304 and the partition wall 308 may become a first groove G1 for accommodating the second magnetic material 114-1, and a space between the partition wall 308 and the inner wall 306 may be It may be a second groove G2 for accommodating the two magnetic materials 114-2.

In this case, the thickness of the outer wall 304 and the inner wall 306 may be thinner than the thickness of the partition wall 308 . According to this, the circumferences of the grooves G1 and G2 for accommodating the second magnetic material 114 can be formed longer than when the barrier rib 308 is formed to be thinner than the thickness of the outer wall 304 and the inner wall 306. , the area of the second magnetic material 114 may be increased. Accordingly, it is possible to increase the noise removal performance.

According to the embodiment of the present invention, the second magnetic body 114-1 is a plurality of layers of metal ribbons each pre-wound in the first groove G1 and the second groove G2 of the lower first magnetic body 300 formed in advance. , 114-2). Accordingly, the second magnetic bodies 114 - 1 and 114 - 2 can be easily accommodated in the first magnetic body 112 . As described above, according to an embodiment of the present invention, a process for bonding the first magnetic material 112 and the second magnetic material 114 and a process for winding the second magnetic material 114 around the outer circumferential surface of the first magnetic material 112. Since this is not required, the fabrication process is simple.

On the other hand, referring to FIG. 20, unlike the embodiment shown in FIGS. 18 to 19, the first groove G1 and the second groove G2 are not formed in a toroidal shape, and are symmetrical to each other over a part of the circumference. It may be formed into a shape. Accordingly, the second magnetic material 114 can be disposed only in the region where the coil 120 is wound.

Alternatively, referring to FIGS. 21 and 22, one of the first groove G1 and the second groove G2 may be formed in a toroidal shape, and the other may be formed in a shape symmetrical to each other over a portion of the circumference. there is. According to this, one of the second magnetic bodies 114-1 and 114-2 may be disposed in a toroidal shape, and the other may be disposed only in a region where the coil 120 is wound.

Here, the second magnetic bodies 114-1 and 114-2 are exemplified as being of the same material, but are not limited thereto, and the second magnetic bodies 114-1 and 114-2 may be of different types of materials. The type of the second magnetic material 114-1, 114-2, the thickness and spacing of the outer wall 304, the inner wall 306, and the partition wall 308, and the shape of the first groove G1 and the second groove G2 By adjusting, it is possible to obtain an inductor applicable to various frequency bands.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

300: lower first magnetic body
310: upper first magnetic body
302: bottom
304: outer wall
306: inner wall
308 bulkhead
114: second magnetic body

Claims (7)

magnetic core, and
A coil wound on the magnetic core,
The magnetic core includes a first magnetic body and a second magnetic body of different kinds,
The second magnetic body is accommodated in the first magnetic body,
The first magnetic body is a toroidal shaped body including ferrite, and the second magnetic body includes a metal ribbon stacked in multiple layers.
The first magnetic material includes a groove formed between an inner circumferential surface and an outer circumferential surface,
The second magnetic body is accommodated in the groove,
The first magnetic body includes a lower first magnetic body including the groove and an upper first magnetic body covering the lower first magnetic body. delete delete delete magnetic core, and
A coil wound on the magnetic core,
The magnetic core includes a first magnetic body and a second magnetic body of different kinds,
The second magnetic body is accommodated in the first magnetic body,
The first magnetic body is a toroidal shaped body including ferrite, and the second magnetic body includes a metal ribbon stacked in multiple layers.
The first magnetic material includes a groove formed between an inner circumferential surface and an outer circumferential surface,
The second magnetic body is accommodated in the groove,
The groove includes a first groove and a second groove spaced apart from the first groove,
The second magnetic material is accommodated in the first groove and the second groove, respectively. According to claim 5,
The first groove and the second groove each have a toroidal shape, and the first groove is disposed closer to the outer circumferential surface than the second groove. An EMI filter comprising the inductor according to claim 1 or 5 and at least one capacitor.

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