Patent Description:
An inductor is one of electronic components that are used in printed circuit boards, and may be applied to resonance circuits, filter circuits, power circuits, etc. due to the electromagnetic characteristics thereof.

Recently, various electronic devices such as communication devices or display devices have been developed to become smaller and thinner, and according to this trend, an inductor used in these electronic devices is required to be smaller, thinner and highly efficient.

An electromagnetic interference (EMI) filter used in a power board serves to transmit a signal necessary for the operation of a circuit and to remove noise.

<FIG> is a block diagram showing a construction in which a general power board equipped with an EMI filter is connected to a power source and a load.

Noise transmitted from the power board of the EMI filter shown in <FIG> may be largely classified into radiative noise of <NUM> to <NUM> radiated from the power board and conductive noise of <NUM> to <NUM> conducted via a power line.

A conductive noise transmission mode may include a differential mode and a common mode. Among these modes, common-mode noise travels and returns along a large loop. Thus, the common-mode noise may affect electronic devices that are located far away even when the amount thereof is small. Such common-mode noise is generated by impedance imbalance of a wiring system and becomes remarkable at a high frequency.

In order to remove common-mode noise, an inductor that is applied to the EMI filter shown in <FIG> generally uses a toroidal-shaped magnetic core that includes a Mn-Zn-based ferrite material. Since Mn-Zn-based ferrite has a high magnetic permeability within a range from <NUM> to <NUM>, it is capable of effectively removing common-mode noise.

As the power of the power board, to which the EMI filter is applied, is higher, a magnetic core having a higher inductance is required. To this end, a magnetic core having a high magnetic permeability µ, e.g. a magnetic core having relative permeability µ of <NUM>,<NUM>/m to <NUM>,<NUM>/m or higher, is required. However, Mn-Zn-based ferrite having such a high magnetic permeability is expensive. Further, because Mn-Zn-based ferrite has a low core loss ratio due to the material property thereof, the noise removal efficiency within a band of <NUM> to <NUM> is low.

<CIT>, <CIT> and <CIT> disclose a noise suppresion filter. <CIT> discloses a magnetic device capable of suppressing flux saturation. <CIT> discloses an interference suppressor. In particular, <CIT> discloses a power board with an EMI filter that comprises a ferrite core that is provided with a core made from a plurality of metal ribbons on its inside or its outside in order 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.

Embodiments provide a power board comprising an inductor, which is capable of receiving high power and which is compact and has excellent noise removal performance and a constant inductance, and comprising an EMI filter including the same.

In the present description and drawings, any examples and technical descriptions of apparatuses, products and/or methods which are not covered by the claims should be taken as background art or examples useful for understanding the invention.

An inductor that may be used in embodiments of the present invention includes a first magnetic body having a toroidal shape, the first magnetic body including ferrite, and a second magnetic body configured to be different from the first magnetic body, the second magnetic body including a metal ribbon, wherein the second magnetic body includes an outer magnetic body disposed on the outer circumferential surface of the first magnetic body and an inner magnetic body disposed on the inner circumferential surface of the first magnetic body, and each of the outer magnetic body and the inner magnetic body is wound in multiple layers in a circumferential direction of the first magnetic body.

For example, the metal ribbon included in the outer magnetic body and the inner magnetic body may be a Fe-based nanocrystalline metal ribbon.

According to the invention, the thickness of the first magnetic body is greater than the thickness of each of the outer magnetic body and the inner magnetic body in a diameter direction of the first magnetic body.

For example, a thickness ratio between the inner magnetic body and the first magnetic body in the diameter direction may range from <NUM>:<NUM> to <NUM>:<NUM>, and a thickness ratio between the outer magnetic body and the first magnetic body in the diameter direction may range from <NUM>:<NUM> to <NUM>:<NUM>.

According to the invention, the magnetic permeability of each of the outer magnetic body and the inner magnetic body is different from the magnetic permeability of the first magnetic body, the thickness of each of the outer magnetic body and the inner magnetic body is less than the thickness of the first magnetic body in the diameter direction of the first magnetic body, and the saturation magnetic flux density of each of the outer magnetic body and the inner magnetic body may be greater than the saturation magnetic flux density of the first magnetic body.

For example, the thickness of the outer magnetic body and the thickness of the inner magnetic body may be the same as each other in the diameter direction.

An EMI filter that may be used in embodiments of the present invention includes an inductor and a capacitor, wherein the inductor includes a first magnetic body having a toroidal shape, the first magnetic body including ferrite, a second magnetic body configured to be different from the first magnetic body, the second magnetic body including a metal ribbon, the second magnetic body including an outer magnetic body disposed on the outer circumferential surface of the first magnetic body and an inner magnetic body disposed on the inner circumferential surface of the first magnetic body, and coils wound around the first magnetic body, the outer magnetic body and the inner magnetic body, and each of the outer magnetic body and the inner magnetic body is wound in multiple layers in a circumferential direction of the first magnetic body.

For example, a thickness ratio between the inner magnetic body and the first magnetic body in a diameter direction of the first magnetic body may range from <NUM>:<NUM> to <NUM>:<NUM>, and a thickness ratio between the outer magnetic body and the first magnetic body in the diameter direction may range from <NUM>:<NUM> to <NUM>:<NUM>.

For example, the thickness of each of the inner magnetic body and the outer magnetic body in the diameter direction may range from <NUM> to <NUM>.

An inductor according to embodiments and an EMI filter including the same have excellent noise removal performance over a wide frequency band, a reduced size, a large power receiving capacity, and improved performance of removing conductive noise including common-mode noise and differential-mode noise, and is capable of adjusting the noise removal performance for each frequency band.

Out of the following figures, only <FIG> concerns an embodiment of the magnetic core that may be used in a power board as defined in independent claim <NUM>. The remaining figures and their description only serve as background information helpful for understanding the present invention but they do not actually form part of the invention.

Exemplary embodiments can be variously changed and embodied in various forms, in which illustrative embodiments are shown. However, exemplary embodiments should not be construed as being limited to the embodiments set forth herein and any changes, equivalents or alternatives which are within the spirit and scope of the embodiments should be understood as falling within the scope of the embodiments.

It will be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be termed a second element and a second element may be termed a first element without departing from the teachings of the embodiments.

It will be understood that when an element is referred to as being "connected to" or "coupled to" another element, it may be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements present.

In the description of the embodiments, it will be understood that when an element, such as a layer (film), a region, a pattern or a structure, is referred to as being "on" or "under" another element, such as a substrate, a layer (film), a region, a pad or a pattern, the term "on" or "under" means that the element is "directly" on or under another element or is "indirectly" formed such that an intervening element may also be present. It will also be understood that criteria of on or under is on the basis of the drawing. The thickness or size of a layer (film), a region, a pattern, or a structure shown in the drawings may be exaggerated, omitted or schematically drawn for the convenience and clarity of explanation, and may not utterly reflect the actual size.

The terms used in the present specification are used for explaining a specific exemplary embodiment, not limiting the present inventive concept. Thus, the singular expressions in the present specification include the plural expressions unless clearly specified otherwise in context. In the specification, the terms "comprising" or "including" shall be understood to designate the presence of particular features, numbers, steps, operations, elements, parts, or combinations thereof but not to preclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept pertains.

The same elements are denoted by the same reference numerals in the drawings, and a repeated explanation thereof will not be given. Embodiments will be described using a Cartesian coordinate system. However, other different coordinate systems may be used. In the drawings, an x-axis, a y-axis, and a z-axis of the Cartesian coordinate system are perpendicular to each other. However, the disclosure is not limited thereto. The x-axis, the y-axis, and the z-axis may intersect each other.

<FIG> is a perspective view of an inductor <NUM> according to an embodiment.

Referring to <FIG>, the inductor <NUM> may include a magnetic core <NUM> and a coil <NUM> wound around the magnetic core <NUM>.

The magnetic core <NUM> may have a toroidal shape, and the coil <NUM> may include a first coil <NUM> wound around the magnetic core <NUM> and a second coil <NUM> wound so as to be opposite the first coil <NUM>. Each of the first coil <NUM> and the second coil <NUM> may be wound around a top surface TS, a bottom surface BS and a side surface OS of the toroidal-shaped magnetic core <NUM>.

A bobbin (not illustrated) for insulating the magnetic core <NUM> and the coil <NUM> may be further provided between the magnetic core <NUM> and the coil <NUM>.

The coil <NUM> may be configured as a conductive wire coated on the surface thereof with an insulating material. The conductive wire coated on the surface thereof with an insulating material may include copper, silver, aluminum, gold, nickel, tin, or the like, and may have a circular-shaped or polygonal-shaped cross-section. However, the disclosure is not limited to any particular material of the conductive wire or to any particular shape of the cross-section of the conductive wire.

In the embodiment, the magnetic core <NUM> may include first and second magnetic bodies. The first and second magnetic bodies are mutually different, and the second magnetic body may be disposed on at least a portion of the surface of the first magnetic body. The magnetic core <NUM> may be embodied in various forms depending on the configuration in which the second magnetic body is disposed on the surface of the first magnetic body. That is, the second magnetic body may be disposed on at least a portion of the top surface, the bottom surface or the side surface of the first magnetic body.

Hereinafter, various embodiments 400A, 400B, 800A to 800E and <NUM> of the magnetic core <NUM> shown in <FIG> will be described below with reference to the accompanying drawings.

<FIG> is an exploded perspective view of an embodiment 400A of the magnetic core <NUM> shown in <FIG>, <FIG> are perspective views showing a process of forming the magnetic core 400A shown in <FIG>, and <FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of the magnetic core 400A shown in <FIG>, from which the illustration of a bobbin <NUM> is omitted.

Referring to <FIG>, an embodiment 400A of the magnetic core may include a first magnetic body <NUM> and a second magnetic body <NUM>.

The first magnetic body <NUM> and the second magnetic body <NUM> may differ in magnetic permeability. The second magnetic body <NUM> may have a higher saturation magnetic flux density than the first magnetic body <NUM>. Here, the magnetic permeability may be expressed by the following Equation <NUM>.

Here, µ represents magnetic permeability, µ<NUM> represents magnetic permeability in a vacuum (or air), which is 4π x <NUM>-<NUM>, µs represents relative permeability, and the unit of each of µ, µ<NUM> and µs is [Henry/meter] (hereinafter referred to as H/m).

Referring to Equation <NUM>, the difference in magnetic permeability between the first magnetic body <NUM> and the second magnetic body <NUM> may mean that the first magnetic body <NUM> and the second magnetic body <NUM> have different values of relative permeability.

For example, the first magnetic body <NUM> may include ferrite, and the second magnetic body <NUM> may include a metal ribbon. Here, the relative permeability µs of the ferrite may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m, and the relative permeability µs of the metal ribbon may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m. For example, the ferrite may be Mn-Zn-based ferrite, and the metal ribbon may be a Fe-based nanocrystalline metal ribbon. The Fe-based nanocrystalline metal ribbon may be a nanocrystalline metal ribbon including Fe and Si.

Here, the nanocrystalline material is a material with a crystallite size of <NUM> to <NUM>.

The first magnetic body <NUM> may be manufactured by coating ferrite powder with a ceramic or polymer binder, insulating the ferrite powder coated with the ceramic or polymer binder, and molding the insulated ferrite powder coated with the ceramic or polymer binder at a high pressure. Alternatively, the first magnetic body <NUM> may be manufactured by stacking a plurality of ferrite sheets on one another, each of the sheets being formed by coating ferrite powder with a ceramic or polymer binder and insulating the ferrite powder coated with the ceramic or polymer binder. However, the disclosure is not limited to any particular method of forming the first magnetic body <NUM>.

Each of the first magnetic body <NUM> and the second magnetic body <NUM> may have a toroidal shape. The second magnetic body <NUM> may include at least one of an upper magnetic body <NUM> or a lower magnetic body <NUM>. The second magnetic body <NUM> is illustrated as including both the upper magnetic body <NUM> and the lower magnetic body <NUM> in <FIG>. However, the disclosure is not limited thereto. In another embodiment, the second magnetic body <NUM> may include only one of the upper magnetic body <NUM> and the lower magnetic body <NUM>.

The upper magnetic body <NUM> may be disposed on the top surface S1 of the first magnetic body <NUM>, and the lower magnetic body <NUM> may be disposed on the bottom surface S3 of the first magnetic body <NUM>.

The thickness of the second magnetic body <NUM> in the x-axis direction may be less than the thickness of the first magnetic body <NUM> in the x-axis direction. That is, the thickness of each of the upper magnetic body <NUM> and the lower magnetic body <NUM> in the x-axis direction may be less than the thickness of the first magnetic body <NUM> in the x-axis direction. The magnetic permeability of the magnetic core 400A may be adjusted by adjusting at least one of a ratio of the thickness of the upper magnetic body <NUM> to the thickness of the first magnetic body <NUM> or a ratio of the thickness of the lower magnetic body <NUM> to the thickness of the first magnetic body <NUM>. To this end, each of the upper magnetic body <NUM> and the lower magnetic body <NUM> may include a metal ribbon stacked in multiple layers.

The magnetic core 400A may further include a bobbin <NUM>. The bobbin <NUM> may further include an upper bobbin <NUM> and a lower bobbin <NUM>.

A method of forming the magnetic core 400A shown in <FIG> will be described below with reference to <FIG>. However, the disclosure is not limited thereto. That is, the magnetic core 400A shown in <FIG> may be manufactured in a manner different from that shown in <FIG>.

First, referring to <FIG>, the upper bobbin <NUM>, the upper magnetic body <NUM>, the first magnetic body <NUM>, the lower magnetic body <NUM> and the lower bobbin <NUM> are prepared.

Subsequently, referring to <FIG>, the lower magnetic body <NUM> is adhered to the bottom of the lower bobbin <NUM>, an adhesive is applied to each of the top surface S1 of the first magnetic body <NUM> and the bottom surface S3 of the first magnetic body <NUM>, the upper magnetic body <NUM> is adhered to the top surface S1 of the first magnetic body <NUM>, and the lower magnetic body <NUM> is adhered to the bottom surface S3 of the first magnetic body <NUM>. Here, the adhesive may be an adhesive including at least one of epoxy-based resin, acrylic resin, silicon-based resin, or varnish. The bonding of the second magnetic body <NUM> and <NUM> to the first magnetic body <NUM>, which is different from the second magnetic body <NUM> and <NUM>, using an adhesive may prevent deterioration in performance due to physical vibration.

Subsequently, referring to <FIG>, the lower bobbin <NUM>, to which the lower magnetic body <NUM> is adhered, and the first magnetic body <NUM> are assembled to each other.

Subsequently, referring to <FIG>, the upper bobbin <NUM> is assembled to the product shown in <FIG>.

As illustrated in <FIG>, the embodiment 400A of the magnetic core is configured such that the upper magnetic body <NUM> is disposed on the top surface S1 of the first magnetic body <NUM> and such that the lower magnetic body <NUM> is disposed on the bottom surface S3 of the first magnetic body <NUM>.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of another embodiment 400B of the magnetic core <NUM> shown in <FIG>.

Referring to <FIG>, the magnetic core 400B may be configured such that the upper magnetic body <NUM> is disposed on one portion of the side surface S2 and S4 of the first magnetic body <NUM> and on the top surface S1 of the first magnetic body <NUM> and such that the lower magnetic body <NUM> is disposed on the opposite portion of the side surface S2 and S4 of the first magnetic body <NUM> and on the bottom surface S3 of the first magnetic body <NUM>. The magnetic core 400B shown in <FIG> is the same as the magnetic core 400A shown in <FIG>, except that the upper magnetic body <NUM> is disposed so as to extend from the top surface S1 of the first magnetic body <NUM> to the side surface S2 and S4 of the first magnetic body <NUM> and that the lower magnetic body <NUM> is disposed so as to extend from the bottom surface S3 of the first magnetic body <NUM> to the side surface S2 and S4 of the first magnetic body <NUM>, and a duplicate explanation thereof will therefore be omitted.

With the above-described configuration, in which the magnetic core 400A and 400B includes the mutually different first and second magnetic bodies <NUM> and <NUM>, it is possible to remove noise over a wide frequency band.

In the case in which each of the first magnetic body and the second magnetic body, included in the magnetic core <NUM> shown in <FIG>, has a toroidal shape, the side surface of the first magnetic body, among the surfaces of the first magnetic body on which the second magnetic body is disposed, may be at least one of the outer circumferential surface or the inner circumferential surface of the first magnetic body. In this case, the second magnetic body included in the magnetic core <NUM> may be disposed on at least a portion of the top surface, the bottom surface, the inner circumferential surface or the outer circumferential surface of the first magnetic body. Still another embodiment of the magnetic core <NUM> will be described below with reference to the accompanying drawings.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still another embodiment 800A of the magnetic core <NUM> shown in <FIG>, and <FIG> are perspective views showing a process of forming the magnetic core 800A shown in <FIG>.

Referring to <FIG>, the magnetic core 800A may include a first magnetic body <NUM> and a second magnetic body <NUM>.

The first magnetic body <NUM> and the second magnetic body <NUM> may differ in magnetic permeability (or relative permeability), and the second magnetic body <NUM> may have a higher saturation magnetic flux density than the first magnetic body <NUM>.

The first magnetic body <NUM> may include ferrite, and the second magnetic body <NUM> may include a metal ribbon. Here, the metal ribbon may be a thin metal strip formed of a metal material, i.e. a long and thin strip-shaped metal sheet. However, the disclosure is not limited thereto.

Here, the relative permeability µs of the ferrite may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m, and exemplarily may be <NUM>,<NUM>/m, and the relative permeability µs of the metal ribbon may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m, exemplarily from <NUM>,<NUM>/m to <NUM>,<NUM>/m. For example, the ferrite may be Mn-Zn-based ferrite, and the metal ribbon may be a Fe-based nanocrystalline metal ribbon. The Fe-based nanocrystalline metal ribbon may be a nanocrystalline metal ribbon including Fe and Si.

As illustrated in <FIG>, each of the first magnetic body <NUM> and the second magnetic body <NUM> may have a toroidal shape. In this case, the second magnetic body <NUM> may include an outer magnetic body <NUM> and an inner magnetic body <NUM>. The outer magnetic body <NUM> may be disposed on the outer circumferential surface S2 of the first magnetic body <NUM>, and the inner magnetic body <NUM> may be disposed on the inner circumferential surface S4 of the first magnetic body <NUM>.

The thickness TO of the first magnetic body <NUM> in the diameter direction thereof (e.g. the y-axis direction or the z-axis direction) may be greater than the thickness of the second magnetic body <NUM>. That is, the thickness TO of the first magnetic body <NUM> in the y-axis direction (or the z-axis direction) may be greater than the thickness T1O and T1I of each of the outer magnetic body <NUM> and the inner magnetic body <NUM> in the y-axis direction (or the z-axis direction). The magnetic permeability of the magnetic core 800A may be adjusted by adjusting at least one of a ratio of the thickness T1O of the outer magnetic body <NUM> to the thickness TO of the first magnetic body <NUM> or a ratio of the thickness T1I of the inner magnetic body <NUM> to the thickness TO of the first magnetic body <NUM>.

A method of forming the magnetic core 800A shown in <FIG> will be described below with reference to <FIG>. However, the disclosure is not limited thereto. That is, the magnetic core 800A shown in <FIG> may be manufactured in a manner different from that shown in <FIG>.

First, referring to <FIG>, a process of winding the outer magnetic body <NUM>, which is a metal ribbon, around the outer circumferential surface S2 of the toroidal-shaped first magnetic body <NUM> is performed. Here, the winding process may include not only a process of winding a wire, i.e. an annular-shaped conductive wire having a diameter, around the surface of any object but also a process of winding a long and thin strip-shaped metal sheet, such as a metal ribbon, around the surface of any object.

Subsequently, referring to <FIG>, the inner magnetic body <NUM>, which is a metal ribbon that has been wound in a toroidal shape in advance, is inserted into the hollow region in the first magnetic body <NUM>. The inner magnetic body <NUM>, which has been wound in advance, may be expanded so as to fit the size of the inner circumferential surface S4 of the first magnetic body <NUM>.

The outer circumferential surface S2 of the first magnetic body <NUM> and the outer magnetic body <NUM> may be adhered to each other using an adhesive, and the inner circumferential surface S4 of the first magnetic body <NUM> and the inner magnetic body <NUM> may be adhered to each other using an adhesive. Here, the adhesive may be an adhesive including at least one of epoxy-based resin, acrylic resin, silicon-based resin, or varnish. The bonding of the mutually different magnetic bodies to each other using an adhesive may prevent deterioration in performance due to physical vibration.

At this time, at least one of the number of windings, the thickness T1O of the outer magnetic body <NUM> or the thickness T1I of the inner magnetic body <NUM> may be adjusted in order to obtain a desired magnetic permeability.

Each of the outer and inner magnetic bodies <NUM> and <NUM>, as illustrated in <FIG>, may include a metal ribbon that is wound multiple turns and is stacked in multiple layers. The thickness T1O and T1I and magnetic permeability of each of the outer and inner magnetic bodies <NUM> and <NUM> may be varied depending on the number of layers in which the metal ribbon is stacked. The noise removal performance of an EMI filter, to which the magnetic core 800A is applied, may be varied depending on the magnetic permeability of the magnetic core 800A. That is, the larger the thicknesses T1O and T1I of the outer and inner magnetic bodies <NUM> and <NUM>, the higher the noise removal performance. Based on this principle, the number of layers in which the metal ribbon is stacked may be adjusted such that the thicknesses T1O and T1I of the outer and inner magnetic bodies <NUM> and <NUM>, which are disposed on a region around which the coil <NUM> is wound, are greater than the thicknesses T1O and T1I of the outer and inner magnetic bodies <NUM> and <NUM>, which are disposed on a region around which the coil <NUM> is not wound.

The number of layers of the metal ribbon may be adjusted by the number of windings, the starting point of winding and the ending point of winding. As illustrated in <FIG>, when the outer magnetic body <NUM>, which is a metal ribbon, is wound one turn from the starting point of winding around the outer circumferential surface S2 of the first magnetic body <NUM>, the outer magnetic body <NUM> may include a one-layered metal ribbon.

Alternatively, when the outer magnetic body <NUM> is wound two turns from the starting point of winding, the outer magnetic body <NUM> may include a two-layered metal ribbon. When the starting point of winding and the ending point of winding do not coincide with each other, for example, when the outer magnetic body <NUM> is wound one and a half turns from the starting point of winding, the outer magnetic body <NUM> includes a region in which a metal ribbon is stacked in a single layer and a region in which a metal ribbon is stacked in two layers.

Alternatively, when the outer magnetic body <NUM> is wound two and a half turns from the starting point of winding, the outer magnetic body <NUM> includes a region in which a metal ribbon is stacked in two layers and a region in which a metal ribbon is stacked in three layers. In this case, if the coil <NUM> is disposed on a region in which the number of layers in which a metal ribbon is stacked is larger, the noise removal performance of an EMI filter to which the magnetic core 800A according to the embodiment is applied may be further improved.

For example, in the case in which the magnetic core 800A has a toroidal shape and in which the first coil <NUM> and the second coil <NUM> are wound opposite each other around the magnetic core 800A, the first coil <NUM> may be disposed on a region in which the number of stacked layers of the outer magnetic body <NUM>, which is disposed on the outer circumferential surface S2 of the first magnetic body <NUM>, is relatively large, and the second coil <NUM> may be disposed on a region in which the number of stacked layers of the inner magnetic body <NUM>, which is disposed on the inner circumferential surface S4 of the first magnetic body <NUM>, is relatively large. Accordingly, each of the first coil <NUM> and the second coil <NUM> may be disposed on a region in which the number of stacked layers of a respective one of the outer and inner magnetic bodies <NUM> and <NUM> is relatively large, but may not be disposed on a region in which the number of stacked layers of a respective one of the outer and inner magnetic bodies <NUM> and <NUM> is relatively small, thereby achieving improved noise removal performance.

The outer magnetic body <NUM> and the inner magnetic body <NUM> may be formed of the same material as each other or may be formed of different materials from each other. The thicknesses T1O and T1I of the outer magnetic body <NUM> and the inner magnetic body <NUM> may be the same as each other or may be different from each other. However, the disclosure is not limited thereto. The outer magnetic body <NUM> and the inner magnetic body <NUM> may have different materials, different values of magnetic permeability, and/or different thicknesses T1O and T1I. Therefore, the magnetic permeability of the magnetic core 800A may have a wide range of values.

For example, in <FIG>, the outer magnetic body <NUM> and the inner magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Further, the thickness ratio (T1O:TO) between the outer magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, preferably from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the outer magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Still further, the thickness ratio (T1I:TO) between the inner magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the inner magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still an embodiment 800B of the magnetic core <NUM> shown in <FIG> that may be employed in embodiments of the present invention.

Referring to <FIG>, in embodiments of the invention, the width (or the height h1) of the first magnetic body <NUM> in the x-axis direction is greater than the width (or the height h2) of the outer and/or inner magnetic body <NUM> and <NUM> in the x-axis direction. To this end, in the process shown in <FIG>, a metal ribbon having a width h2 less than the width h1 of the first magnetic body <NUM> is wound to form the second magnetic body <NUM>.

Referring to <FIG>, the outer magnetic body <NUM> is not disposed on the boundary between the top surface S1 and the outer circumferential surface S2 of the first magnetic body <NUM> and the boundary between the bottom surface S3 and the outer circumferential surface S2 of the first magnetic body <NUM>. The inner magnetic body <NUM> is not disposed on the boundary between the top surface S1 and the inner circumferential surface S4 of the first magnetic body <NUM> and the boundary between the bottom surface S3 and the inner circumferential surface S4 of the first magnetic body <NUM>. However, the disclosure is not limited thereto. The second magnetic body <NUM> is not disposed on at least one of the boundary between the top surface S1 and the outer circumferential surface S2 of the first magnetic body <NUM>, the boundary between the top surface S1 and the inner circumferential surface S4 of the first magnetic body <NUM>, the boundary between the bottom surface S3 and the outer circumferential surface S2 of the first magnetic body <NUM>, or the boundary between the bottom surface S3 and the inner circumferential surface S4 of the first magnetic body <NUM>.

As illustrated in <FIG>, in embodiments of the invention, in which the second magnetic body <NUM> is disposed on the surface of the first magnetic body <NUM>, the second magnetic body <NUM> and <NUM> may be prevented from cracking along at least one of the boundary between the top surface S1 and the outer circumferential surface S2 of the first magnetic body <NUM>, the boundary between the bottom surface S3 and the outer circumferential surface S2 of the first magnetic body <NUM>, the boundary between the top surface S1 and the inner circumferential surface S4 of the first magnetic body <NUM>, or the boundary between the bottom surface S3 and the inner circumferential surface S4 of the first magnetic body <NUM>.

Further, the thickness ratio (T1O:TO) between the outer magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the outer magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still another embodiment 800C of the magnetic core <NUM> shown in <FIG>.

In the case of the magnetic core 800A and 800B shown in <FIG>, the second magnetic body <NUM> includes the outer magnetic body <NUM> and the inner magnetic body <NUM>, which are respectively disposed on the outer circumferential surface S2 and the inner circumferential surface S4 of the first magnetic body <NUM>. Unlike this, according to still another embodiment, as illustrated in <FIG>, the magnetic core 800C may include the outer magnetic body <NUM>, but may not include the inner magnetic body <NUM>. The magnetic core 800C shown in <FIG> is the same as the magnetic core 800A shown in <FIG>, except that the inner magnetic body <NUM> is not included, and a duplicate explanation thereof will therefore be omitted.

For example, in <FIG>, the outer magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still another embodiment 800D of the magnetic core <NUM> shown in <FIG>.

In the case of the magnetic core 800A and 800B shown in <FIG>, the second magnetic body <NUM> includes the outer magnetic body <NUM> and the inner magnetic body <NUM>, which are respectively disposed on the outer circumferential surface S2 and the inner circumferential surface S4 of the first magnetic body <NUM>. Unlike this, according to still another embodiment, as illustrated in <FIG>, the magnetic core 800D may include the inner magnetic body <NUM>, but may not include the outer magnetic body <NUM>. The magnetic core 800D shown in <FIG> is the same as the magnetic core 800A shown in <FIG>, except that the outer magnetic body <NUM> is not included, and a duplicate explanation thereof will therefore be omitted.

For example, in <FIG>, the inner magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Further, the thickness ratio (T1I:TO) between the inner magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the inner magnetic body <NUM> may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still another embodiment 800E of the magnetic core <NUM> shown in <FIG>.

In the case of the magnetic core 800A and 800B shown in <FIG>, the second magnetic body <NUM> is disposed on the outer circumferential surface S2 and the inner circumferential surface S4 of the first magnetic body <NUM>, but is not disposed on the top surface S1 or the bottom surface S3 of the first magnetic body <NUM>. Unlike this, according to still another embodiment, as illustrated in <FIG>, the magnetic core 800E may be configured such that the second magnetic body <NUM> is disposed not only on the outer circumferential surface S2 and the inner circumferential surface S4 of the first magnetic body <NUM> but also on the top surface S1 and the bottom surface S3 of the first magnetic body <NUM>. Except for this difference, the magnetic core 800E shown in <FIG> is the same as the magnetic core 800A shown in <FIG>, and a duplicate explanation thereof will therefore be omitted.

For example, in <FIG>, the second magnetic body <NUM>, which is disposed on the outer circumferential surface S2 and the inner circumferential surface S4, may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Further, the thickness ratio (T1O:TO) between the second magnetic body <NUM> disposed on the outer circumferential surface S2 and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the second magnetic body <NUM> disposed on the outer circumferential surface S2 may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Still further, the thickness ratio (T1I:TO) between the second magnetic body <NUM> disposed on the inner circumferential surface S4 and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the second magnetic body <NUM> disposed on the inner circumferential surface S4 may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns.

Still further, the second magnetic body may be disposed on each of the top surface S1 and the bottom surface S3 of the first magnetic body in the manner of being stacked in a number within the range from <NUM> layers to <NUM> layers, preferably from <NUM> layers to <NUM> layers, so as to have the same thickness as the second magnetic body disposed on the outer circumferential surface S2 or the inner circumferential surface S4 of the first magnetic body.

With the above-described configuration, in which the magnetic core 800A to 800E includes the mutually different first and second magnetic bodies <NUM> and <NUM> having different values of magnetic permeability, it is possible to remove noise over a wide frequency band.

In particular, compared to a toroidal-shaped magnetic core that is formed only of Mn-Zn-based ferrite, the magnetic core 400A, 400B, and 800A to 800E according to the embodiment is capable of effectively removing high-frequency noise by preventing concentration of the magnetic flux on the surface thereof and is capable of being applied to high-power products due to the low degree of internal saturation.

Further, the performance of the magnetic core 400A, 400B, and 800A to 800E may be adjusted by adjusting at least one of the magnetic permeability or the volume ratio of at least one of the first magnetic body <NUM> and <NUM> or the second magnetic body <NUM> and <NUM>.

<FIG> are, respectively, a coupled perspective view and a partial cross-sectional view of still another embodiment <NUM> of the magnetic core <NUM> shown in <FIG>.

Referring to <FIG>, the magnetic core <NUM> may include a first magnetic body <NUM> and a second magnetic body <NUM>.

The first magnetic body <NUM> and the second magnetic body <NUM> may differ in magnetic permeability. The second magnetic body <NUM> may have a higher saturation magnetic flux density than the first magnetic body <NUM>.

The first magnetic body <NUM> may have a toroidal shape, and the second magnetic body <NUM> may be disposed on a region in the surface of the first magnetic body <NUM>, around which the coil <NUM> is wound. For example, in the case in which the coil <NUM> includes a first coil <NUM> wound around the magnetic core <NUM> and a second coil <NUM> wound so as to be opposite the first coil <NUM>, the second magnetic body <NUM> may be disposed so as to cover the top surface S1, the outer circumferential surface S2, the bottom surface S3 and the inner circumferential surface S4 of the first magnetic body <NUM> in each of the regions around which the first coil <NUM> and the second coil <NUM> are wound.

The thickness of the second magnetic body <NUM> may be less than the thickness of the first magnetic body <NUM> in at least one of the z-axis direction or the x-axis direction. The magnetic permeability of the magnetic core <NUM> may be adjusted by adjusting a ratio of the thickness of the second magnetic body <NUM> to the thickness of the first magnetic body <NUM>. To this end, the second magnetic body <NUM> may include a metal ribbon stacked in multiple layers.

For example, in <FIG>, the second magnetic body <NUM>, which is disposed on the outer circumferential surface S2 and the inner circumferential surface S4, may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns. Alternatively, the second magnetic body <NUM> may be disposed so as to be stacked in a number within the range from <NUM> layers to <NUM> layers, preferably from <NUM> layers to <NUM> layers.

Further, the thickness ratio (T1O:TO) between the second magnetic body <NUM> disposed on the outer circumferential surface S2 and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the second magnetic body <NUM> disposed on the outer circumferential surface S2 may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns. Alternatively, the second magnetic body <NUM> disposed on the outer circumferential surface S2 may be stacked in a number within the range from <NUM> layers to <NUM> layers, preferably from <NUM> layers to <NUM> layers.

Still further, the thickness ratio (T1I:TO) between the second magnetic body <NUM> disposed on the inner circumferential surface S4 and the first magnetic body <NUM> in the diameter direction (e.g. the y-axis direction or the z-axis direction) of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto. In this case, the second magnetic body <NUM> disposed on the inner circumferential surface S4 may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns. Alternatively, the second magnetic body <NUM> disposed on the outer circumferential surface S2 may be stacked in a number within the range from <NUM> layers to <NUM> layers, preferably from <NUM> layers to <NUM> layers.

With the above-described configuration, in which the second magnetic body <NUM>, <NUM> and <NUM>, which is different from the first magnetic body <NUM>, <NUM> and <NUM>, is disposed on at least a portion of the surface of the first magnetic body <NUM>, <NUM> and <NUM>, it is possible to improve the noise removal performance of the magnetic core 400A, 400B, 800A to 800E and <NUM>.

<FIG> is a graph showing a skin effect theory, wherein the horizontal axis represents a frequency f and the vertical axis represents a depth δ of the skin.

<FIG> is a graph showing a magnetic flux depending on a depth δ of the skin of a ferrite material, and <FIG> is a graph showing a magnetic flux depending on a depth δ of the skin of a ferrite material and a metal ribbon material. In each graph, the horizontal axis represents a depth δ of the skin, and the vertical axis represents magnetic flux Bm.

<FIG> are graphs showing magnetic permeability µ and inductance L of a ferrite material and a metal ribbon material. In each graph, the horizontal axis represents a frequency f. The vertical axis in the graph shown in <FIG> represents magnetic permeability µ, and the vertical axis in the graph shown in <FIG> represents inductance L.

Referring to <FIG> and the following Equation <NUM>, as the relative permeability µs of a material is higher and as the frequency f is higher, the value of the depth δ of the skin is reduced, and the magnetic flux Bm is therefore concentrated on the surface of a material.

Referring to <FIG>, as the depth δ of the skin is smaller, a higher magnetic flux Bm is applied. Because the saturation magnetic flux density of a ferrite material is <NUM>. 47T, in the case in which the magnetic core includes only the first magnetic body <NUM>, <NUM> and <NUM>, which is a ferrite core, if the magnetic flux Bm is greater than <NUM>. 47T, the magnetic core is saturated, which may deteriorate the noise removal performance.

Referring to <FIG>, in the case in which a material, e.g. a metal ribbon material, which has a higher saturation magnetic flux density than a ferrite material, is used as the second magnetic body <NUM>, <NUM> and <NUM> and is disposed on the surface of the first magnetic body <NUM>, <NUM> and <NUM>, which is a ferrite material, the magnetic core is capable of enduring a high magnetic flux Bm at a small depth δ of the skin, whereby the noise removal performance is maintained. With the configuration in which the second magnetic body <NUM>, <NUM> and <NUM>, which has a higher saturation magnetic flux density than the first magnetic body <NUM>, <NUM> and <NUM>, is disposed on at least a portion of the surface of the first magnetic body <NUM>, <NUM> and <NUM>, it is possible to increase the effective cross-sectional area of the magnetic core 400A, 400B, 800A to 800E and <NUM> at a high frequency.

Referring to <FIG>, the magnetic core 400A, 400B, 800A to 800E and <NUM>, which includes the first magnetic body <NUM>, <NUM> and <NUM> formed of a ferrite material and the second magnetic body <NUM>, <NUM> and <NUM> formed of a metal ribbon material, which have different values of magnetic permeability for respective frequencies f, exhibits high inductance in a predetermined frequency range and therefore achieves high noise removal performance.

Hereinafter, the magnetic cores according to a comparative example and embodiments will be compared and described below with reference to the accompanying drawings.

<FIG> illustrates top views and cross-sectional views of the comparative example and Embodiments <NUM> to <NUM> of the magnetic core.

In <FIG>, the comparative example has a configuration in which the magnetic core includes the first magnetic body <NUM> but does not include the second magnetic body <NUM>, <NUM> and <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body <NUM> includes only the outer magnetic body <NUM>, which is disposed on the outer circumferential surface of the first magnetic body <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body <NUM> includes only the inner magnetic body <NUM>, which is disposed on the inner circumferential surface of the first magnetic body <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body <NUM> includes the outer magnetic body <NUM> and the inner magnetic body <NUM>, which are respectively disposed on the outer circumferential surface and the inner circumferential surface of the first magnetic body <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body includes the upper magnetic body <NUM> and the lower magnetic body <NUM>, which are respectively disposed on the top surface and the bottom surface of the first magnetic body <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body <NUM> is disposed so as to cover the outer circumferential surface, the inner circumferential surface, the top surface and the bottom surface of the first magnetic body <NUM>. Embodiment <NUM>, for example, as illustrated in <FIG>, has a configuration in which the second magnetic body <NUM> is disposed on a region of the first magnetic body <NUM>, around which the coil <NUM> is wound.

<FIG> is a graph showing the noise removal performance of the comparative example and Embodiments <NUM> to <NUM>, wherein the horizontal axis represents a thickness of a different material, which is a thickness of the second magnetic body <NUM>, <NUM> and <NUM>, which is different from the first magnetic body <NUM>, <NUM> and <NUM>, i.e. a thickness from the center of the magnetic core in the y-axis or z-axis direction, and the vertical axis represents additional attenuation.

<FIG> show leakage inductance Lk and inductance L for each θ in Embodiment <NUM>, respectively, <FIG> shows the noise reduction effect in a differential mode of the comparative example and Embodiment <NUM> shown in <FIG>, and <FIG> shows the noise reduction effect in a common mode of the comparative example and Embodiment <NUM> shown in <FIG>.

Referring to <FIG>, in the comparative example and Embodiments <NUM> to <NUM>, the first magnetic body <NUM>, <NUM> and <NUM> has an inner diameter ID of <NUM>, an outer diameter OD of <NUM>, and a height HI of <NUM>, and a toroidal-shaped Mn-Zn-based ferrite core is used as the first magnetic body. Further, in Embodiments <NUM> to <NUM>, a Fe-Si-based metal ribbon is used as the second magnetic body <NUM>, <NUM> and <NUM> in such a manner that a metal ribbon having a thickness of <NUM> ± <NUM> is wound or stacked. The metal ribbon may be wound in the range from <NUM> turns to <NUM> turns, preferably from <NUM> turns to <NUM> turns, or may be stacked in a number within the range from <NUM> layers to <NUM> layers, preferably from <NUM> layers to <NUM> layers.

The noise removal performance of the comparative example and Embodiments <NUM> to <NUM> was simulated under the conditions of <NUM> windings of a coil around the magnetic core and the application of current of <NUM> A (ampere) and power of <NUM> W. Referring to <FIG>, it is confirmed that Embodiment <NUM>, in which the second magnetic body <NUM> is disposed on the entire surface of the first magnetic body <NUM>, achieves the highest noise removal performance and that the larger the area occupied by the second magnetic body, the higher the noise removal performance.

Comparing Embodiments <NUM> to <NUM>, Embodiment <NUM> is configured such that the second magnetic core <NUM> is disposed only outside the first magnetic core <NUM>, Embodiment <NUM> is configured such that the second magnetic core <NUM> is disposed only inside the first magnetic core <NUM>, and Embodiment <NUM> is configured such that the second magnetic core <NUM> (<NUM> and <NUM>) is disposed inside and outside the first magnetic core <NUM>. It is confirmed that the degree of attenuation of Embodiment <NUM> is improved by about <NUM>% compared to that of Embodiments <NUM> and <NUM>. Further, Embodiments <NUM> and <NUM> are capable of achieving improved noise removal performance with the same thickness in the diameter direction (e.g. the y-axis direction or the z-axis direction). That is, it is possible to achieve improved noise removal performance with the same size.

Still further, referring to <FIG>, showing Embodiment <NUM>, and <FIG>, as the value of θ decreases, the exposed area of the first magnetic body increases, whereby the leakage inductance Lk increases and the inductance decreases. On the other hand, as the value of θ increases, the exposed area of the first magnetic body decreases, whereby the leakage inductance Lk decreases and the inductance L increases, leading to an improvement in noise removal performance.

<FIG> are views respectively showing the noise removal performance in a differential mode and the noise removal performance in a common mode, obtained by connecting the comparative example and Embodiment <NUM> of the magnetic core to a power board and measuring a magnetic field.

Referring to <FIG>, compared to the comparative example, a degree of internal saturation of Embodiment <NUM> of the magnetic core decreases. Therefore, it is confirmed that the magnetic core according to the embodiment of the disclosure is suitable for high-power products.

Referring to <FIG>, as the frequency becomes higher, the area efficiency of the comparative example is lowered due to the saturation of the surface of the magnetic core, whereas Embodiment <NUM> of the magnetic core has an improved area efficiency because the surface of the magnetic core is not saturated due to the second magnetic body <NUM> (<NUM> and <NUM>) disposed on the surface of the first magnetic body <NUM>, and consequently has an improved noise removal effect at a high frequency.

Hereinafter, the characteristics of inductors including the comparative example and Embodiment <NUM> of the magnetic core, which are shown in <FIG>, will be compared and described below with reference to the accompanying drawings. Embodiment <NUM> of the magnetic core shown in <FIG> may have the configuration of the magnetic core 800A illustrated in <FIG>. However, the disclosure is not limited thereto. The inductor, which will be described below, is capable of being applied to any inductor that includes a magnetic core having an outer magnetic body and an inner magnetic body.

First, the characteristics of the inductor according to the comparative example in a differential mode will be described below.

<FIG> is a view showing the magnetic-field characteristics of a general inductor in a differential mode, wherein reference numerals B11 to B16 represent magnetic fields of a first coil <NUM> and reference numerals B21 to B26 represent magnetic fields of a second coil <NUM>.

The inductor shown in <FIG> may include a magnetic core <NUM> and first and second coils <NUM> and <NUM>. In the case in which the inductor shown in <FIG> is the inductor according to the comparative example, the magnetic core <NUM> includes only a first magnetic body. The first magnetic body of the magnetic core <NUM>, which is included in the inductor according to the comparative example, may correspond to the first magnetic body <NUM>, <NUM> and <NUM> shown in <FIG>. The first and second coils <NUM> and <NUM> shown in <FIG> are the same as the first and second coils <NUM> and <NUM> shown in <FIG>, and a duplicate explanation thereof will therefore be omitted.

Referring to <FIG>, most of the magnetic field that is induced in the inductor according to the comparative example by the current applied to the first and second coils <NUM> and <NUM> of the inductor from the outside (hereinafter referred to as "applied current") needs to be cancelled. The magnetic field B13 of the first coil <NUM> and the magnetic field B23 of the second coil <NUM> may have the same magnitude at an upper side of the inductor, and may therefore cancel each other out. Further, the magnetic field B14 of the first coil <NUM> and the magnetic field B24 of the second coil <NUM> may have the same magnitude at a lower side of the inductor, and may therefore cancel each other out. However, the magnetic field B11 of the first coil <NUM> may have a larger magnitude than the magnetic field B21 of the second coil <NUM> at a left side of the inductor, around which the first coil <NUM> is wound, and the magnetic field B22 of the second coil <NUM> may have a larger magnitude than the magnetic field B12 of the first coil <NUM> at a right side of the inductor, around which the second coil <NUM> is wound. As such, in the case of the inductor according to the comparative example, the magnetic fields are not actually cancelled out. Further, when high current is applied, the saturation area of the magnetic body by the magnetic fields increases, which may deteriorate performance. However, compared to the magnetic-field characteristics in a common mode to be described later, the inductor according to the comparative example may store relatively high energy due to the higher degree of cancellation of the magnetic fields.

<FIG> shows the configuration of the inductor shown in <FIG>, in which the inductor is divided into three sections SE1, SE2 and SE3.

<FIG> show the magnetic permeability (or relative permeability) of the first, second and third sections SE1, SE2 and SE3, respectively, at a certain time point in a differential mode of the inductor according to the comparative example. Here, the magnetic permeability may be expressed by the above Equation <NUM>, and has a value obtained under the condition of relative permeability µs of <NUM>,<NUM>/m.

In <FIG>, reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a mode in which low power is applied to the inductor (hereinafter referred to as a "low-power mode"), and reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a mode in which high power is applied to the inductor (hereinafter referred to as a "high-power mode"). In <FIG>, the horizontal axis represents a position in the radial (r) direction of the inductor. In <FIG> and <FIG>, "r=<NUM>" represents the center of the annular-shaped inductor.

Referring to <FIG>, in any of the sections, the magnetic permeability of the first magnetic body of the magnetic core <NUM> has a minimum value at the inner edge r1 and the outer edge r2 of the magnetic core <NUM> and has a maximum value at the center rc of the magnetic core <NUM>. This phenomenon occurs identically both in the high-power mode <NUM>, <NUM> and <NUM> and in the low-power mode <NUM>, <NUM> and <NUM>.

<FIG> is a graph showing an average magnetic permeability on the y-z plane in a differential mode of the inductor according to the comparative example, wherein the horizontal axis represents a position in the radial (r) direction of the inductor and the vertical axis represents an average magnetic permeability on the y-z plane. In <FIG>, reference numeral <NUM> represents an average magnetic permeability in a low-power mode, and reference numeral <NUM> represents an average magnetic permeability in a high-power mode.

<FIG> is a graph showing an average magnetic permeability in a differential mode of the inductor according to the comparative example, wherein the horizontal axis represents current and the vertical axis represents an average magnetic permeability.

<FIG> shows a result obtained through line integration of the magnetic permeability, which is obtained at every time point, as illustrated in <FIG>, in the circumferential direction of the inductor and structural average and time average of the line integration value when the frequency of the applied current (hereinafter referred to as an "applied frequency") is in the range from <NUM> to <NUM>. <FIG> shows a result obtained through volume integration of the result value shown in <FIG> and time average of the volume integration value.

Referring to <FIG>, as the current increases in a differential mode, the average magnetic permeability of the inductor according to the comparative example decreases. When the applied current is IC1, the inductor according to the comparative example reaches a partially saturated PS state in which the inductor loses <NUM>% of the function thereof, and as the current continuously increases, the inductor reaches a completely saturated CS state in which the inductor loses <NUM>% of the function thereof.

Next, the characteristics of the inductor according to the comparative example in a common mode will be described below.

<FIG> is a view showing the magnetic-field characteristics of a general inductor in a common mode, wherein reference numerals B11 to B16 represent magnetic fields of a first coil <NUM> and reference numerals B21 to B26 represent magnetic fields of a second coil <NUM>.

The inductor shown in <FIG> may include a magnetic core <NUM> and first and second coils <NUM> and <NUM>. In the inductor according to the comparative example shown in <FIG>, the magnetic core <NUM> includes only a first magnetic body. The first magnetic body of the magnetic core <NUM>, which is included in the inductor according to the comparative example, may correspond to the first magnetic body <NUM>, <NUM> and <NUM> shown in <FIG>. The first and second coils <NUM> and <NUM> shown in <FIG> are the same as the first and second coils <NUM> and <NUM> shown in <FIG>, and a duplicate explanation thereof will therefore be omitted.

Referring to <FIG>, the magnetic field B13 of the first coil <NUM> and the magnetic field B23 of the second coil <NUM> are added to each other at an upper side of the inductor, the magnetic field B14 of the first coil <NUM> and the magnetic field B24 of the second coil <NUM> are added to each other at a lower side of the inductor, the magnetic field B11 of the first coil <NUM> is added to the magnetic field B21 of the second coil <NUM> at a left side of the inductor, around which the first coil <NUM> is wound, and the magnetic field B22 of the second coil <NUM> is added to the magnetic field B12 of the first coil <NUM> at a right side of the inductor, around which the second coil <NUM> is wound. As such, the magnetic fields induced in the inductor by the applied current applied to the first and second coils <NUM> and <NUM> of the inductor according to the comparative example from the outside are not cancelled, but the magnetic fields are mostly added to each other, whereby the magnetic permeability may be easily saturated when noise is introduced (i.e. when reverse current is introduced). The function may be maintained when reflected current is equal to or less than <NUM>/<NUM> of power consumption.

The inductor shown in <FIG>, like the inductor shown in <FIG>, may be divided into three sections SE1, SE2 and SE3.

<FIG> show the magnetic permeability (or relative permeability) of the first, second and third sections SE1, SE2 and SE3, respectively, at a certain time point in a common mode of the inductor according to the comparative example. Here, the magnetic permeability may be expressed by the above Equation <NUM>, and has a value obtained under the condition of relative permeability µs of <NUM>,<NUM>/m.

In <FIG>, reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a low-power mode, and reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a high-power mode. In <FIG>, the horizontal axis represents a position in the radial (r) direction of the inductor. In <FIG>, "r=<NUM>" represents the center of the annular-shaped inductor.

Referring to <FIG>, in each of the low-power mode <NUM>, <NUM> and <NUM> and the high-power mode <NUM>, <NUM> and <NUM>, the magnetic permeability of the magnetic core <NUM> gradually increases from the inner edge r1 of the magnetic core <NUM> to the outer edge r2 thereof in any of the sections.

<FIG> is a graph showing an average magnetic permeability on the y-z plane in a common mode of the inductor according to the comparative example, wherein the horizontal axis represents a position in the radial (r) direction of the inductor and the vertical axis represents an average magnetic permeability on the y-z plane. In <FIG>, reference numeral <NUM> represents an average magnetic permeability in a low-power mode, and reference numeral <NUM> represents an average magnetic permeability in a high-power mode.

<FIG> is a graph showing an average magnetic permeability in a common mode of the inductor according to the comparative example, wherein the horizontal axis represents current and the vertical axis represents an average magnetic permeability.

<FIG> shows a result obtained through line integration of the magnetic permeability, which is obtained at every time point, as illustrated in <FIG>, in the circumferential direction of the inductor and structural average and time average of the line integration value. <FIG> shows a result obtained through volume integration of the result value shown in <FIG> and time average of the volume integration value.

Referring to <FIG>, as the current increases in a common mode, the average magnetic permeability of the inductor according to the comparative example decreases. When the applied current is IC2, the inductor according to the comparative example reaches a partially saturated PS state in which the inductor loses <NUM>% of the function thereof, and as the applied current continuously increases, the inductor reaches a completely saturated CS state in which the inductor loses <NUM>% of the function thereof. Referring to <FIG>, it is confirmed that the partial saturation is realized earlier at a lower current in the common mode CM than in the differential mode DM.

In the state in which the applied current to be used in the inductor according to the comparative example is applied in a differential manner (i.e. in the state in which the function of the magnetic body is lowered), when reverse current noise of a power factor correction circuit and reverse current noise due to switching for driving a transformer are introduced in the manner of a high-frequency (e.g. <NUM> to <NUM>) common mode and when high-frequency noise (e.g. <NUM> to <NUM>) due to other communication circuits is introduced, the noise reduction function may be lowered. The function of the inductor according to the comparative example may be greatly lowered when reverse current is introduced due to impedance mismatch between an EMI filter to be described later and the power factor correction circuit.

Next, the characteristics of Embodiment <NUM> of the inductor in a differential mode will be described below.

Embodiment <NUM> of the inductor, as shown in <FIG>, includes first and second coils <NUM> and <NUM> and a magnetic core <NUM>. The magnetic core <NUM>, as illustrated in <FIG>, may include a first magnetic body <NUM> and a second magnetic body <NUM>, and the second magnetic body <NUM> may include an outer magnetic body <NUM> and an inner magnetic body <NUM>.

Like the inductor according to the comparative example, Embodiment <NUM> of the inductor, as shown in <FIG>, may be divided into three sections.

<FIG> show the magnetic permeability (or relative permeability) of the first, second and third sections SE1, SE2 and SE3, respectively, at a certain time point in a differential mode of Embodiment <NUM> of the inductor. Here, the magnetic permeability may be expressed by the above Equation <NUM>.

In <FIG>, reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a low-power mode, and reference numerals <NUM>, <NUM> and <NUM> represent magnetic permeability in a high-power mode. In <FIG>, the horizontal axis represents a position in the radial (r) direction of the inductor.

Referring to <FIG>, when the applied frequency of the current applied to the first and second coils <NUM> and <NUM> is less than a critical frequency, in any of the sections in a low-power mode, the relative permeability (hereinafter referred to as a "first relative permeability") of the first magnetic body <NUM>, which is located at the center rc of a magnetic sheet, is less than the relative permeability (hereinafter referred to as a "second relative permeability") of the outer magnetic body <NUM>, which is located at the outer portion r2 of the magnetic sheet, and is less than the relative permeability (hereinafter referred to as a "third relative permeability") of the inner magnetic body <NUM>, which is located at the inner portion r1 of the magnetic sheet. Alternatively, the relative permeability of the magnetic bodies, which are located at the inner portion r1, the outer portion r2 and the center rc of the magnetic sheet, may be constant.

On the other hand, when the frequency of the current applied to the first and second coils <NUM> and <NUM> is equal to or greater than the critical frequency, unlike the phenomenon shown in <FIG>, each of the second relative permeability and the third relative permeability becomes less than the first relative permeability in any of the sections in a low-power mode. In Embodiment <NUM> of the inductor, the magnetic permeability <NUM>, <NUM> and <NUM> in a high-power mode are contrary to the magnetic permeability <NUM>, <NUM> and <NUM> in a low-power mode.

Here, the critical frequency is a frequency at which the magnetic permeability is reversed due to a reduction in the second and third relative permeability of the second magnetic body <NUM> (i.e. a reduction in the induction amount due to loss of eddy current), which is embodied as a nanoribbon, at a high frequency.

The above-described critical frequency may increase as the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> decreases. This is because a reduction in the induction amount due to loss of eddy current decreases as the thickness T10 and T1I of the second magnetic body <NUM>, which is embodied as a nanoribbon, decreases.

For example, the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is in the range from <NUM> ± <NUM> (<NUM> ± <NUM> and <NUM> turns) to <NUM> ± <NUM> (<NUM> ± <NUM> and <NUM> turns), the critical frequency may range from <NUM> to <NUM>. For example, when the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is <NUM> ± <NUM> and when the number n of turns of each of the first and second coils <NUM> and <NUM> is <NUM>, the critical frequency is <NUM>. When the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is <NUM> ± <NUM> and when the number n of turns of each of the first and second coils <NUM> and <NUM> is <NUM>, the critical frequency may increase to <NUM> to <NUM>, for example, <NUM>.

The inductance LDM of Embodiment <NUM> of the inductor in a differential mode may be expressed by the following Equation <NUM>.

Here, LCM represents inductance of Embodiment <NUM> of the inductor in a common mode and is expressed by the following Equation <NUM>, and M represents a mutual inductance.

<FIG> is a graph showing an average magnetic permeability on the y-z plane in a differential mode of Embodiment <NUM> of the inductor, wherein the horizontal axis represents a position in the radial (r) direction of the inductor and the vertical axis represents an average magnetic permeability on the y-z plane. In <FIG>, reference numeral <NUM> represents an average magnetic permeability in a low-power mode, and reference numeral <NUM> represents an average magnetic permeability in a high-power mode.

<FIG> is a graph showing an average magnetic permeability in a differential mode of Embodiment <NUM> of the inductor, wherein the horizontal axis represents current and the vertical axis represents an average magnetic permeability.

<FIG> shows a result obtained through line integration of the magnetic permeability, which is obtained at every time point, as illustrated in <FIG>, in the circumferential direction of the inductor and structural average and time average of the line integration value when the frequency of the current applied to the inductor is in the range from <NUM> to <NUM>. <FIG> shows a result obtained through volume integration of the result value shown in <FIG> and time average of the volume integration value.

Referring to <FIG>, as the applied current increases in a differential mode, the average magnetic permeability of Embodiment <NUM> of the inductor decreases. When the applied current is IC3, Embodiment <NUM> of the inductor reaches a partially saturated PS state in which the inductor loses <NUM>% of the function thereof, and as the current continuously increases, the inductor reaches a completely saturated CS state in which the inductor loses <NUM>% of the function thereof. Referring to <FIG>, in a differential mode, the current (hereinafter referred to as "partial saturation current") at which the inductor according to the comparative example DM is partially saturated is IC1, and the partial saturation current of Embodiment <NUM> E3D of the inductor is IC3, which is greater than IC1. As such, in a differential mode, Embodiment <NUM> reaches a partially saturated state at a higher current value IC3 than the comparative example. Referring to <FIG>, in the case in which the number n of turns of each of the first and second coils <NUM> and <NUM> is in the range from <NUM> to <NUM>, when the average magnetic permeability reaches a value corresponding to the partial saturation in a differential mode, the applied current IC3 may range from <NUM> A to <NUM> A.

That is, in a differential mode, a reduction in the magnetic permeability in Embodiment <NUM> due to an increase in the applied current (i.e. an increase in the magnitude of the magnetic field) is lower than that in the comparative example. This is because Example <NUM> of the inductor includes the first magnetic body <NUM>, which may be embodied as ferrite, and the second magnetic body <NUM> (<NUM> and <NUM>), which may be embodied as a nanoribbon having a higher magnetic permeability and a higher saturation magnetic flux density than the first magnetic body <NUM>, and because the thickness TO of the first magnetic body <NUM> is greater than each of the thickness T1I of the inner magnetic body <NUM> and the thickness T10 of the outer magnetic body <NUM>, based on a fact that magnetic energy is mainly concentrated on a material having a higher magnetic permeability. For example, when the number of turns of winding around each of the outer magnetic body <NUM> and the inner magnetic body <NUM> is in the range from <NUM> to <NUM>, each of the thickness ratio (T10:TO) between the outer magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction of the first magnetic body <NUM> and the thickness ratio (T1I:TO) between the inner magnetic body <NUM> and the first magnetic body <NUM> in the diameter direction of the first magnetic body <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>, preferably from <NUM>:<NUM> to <NUM>:<NUM>. However, the disclosure is not limited thereto.

Therefore, compared to the comparative example, a reduction in the magnetic permeability in Embodiment <NUM> due to an increase in the current or an increase in the number of windings may be further prevented.

Next, the characteristics of Embodiment <NUM> of the inductor in a common mode will be described below.

<FIG> show the magnetic permeability (or relative permeability) of the first, second and third sections SE1, SE2 and SE3, respectively, at a certain time point in a common mode of Embodiment <NUM> of the inductor. Here, the magnetic permeability may be expressed by the above Equation <NUM>.

Like the differential mode, referring to <FIG>, in a low-power mode of a common mode, when the applied frequency of the applied current applied to the first and second coils <NUM> and <NUM> is less than a critical frequency, in any of the sections in a low-power mode, the first relative permeability of the first magnetic body <NUM>, which is located at the center rc of the magnetic core, is less than the second relative permeability of the outer magnetic body <NUM>, which is located at the outer portion r2 of the magnetic core, and is less than the third relative permeability of the inner magnetic body <NUM>, which is located at the inner portion r1 of the magnetic core. On the other hand, when the frequency of the current applied to the first and second coils <NUM> and <NUM> is equal to or greater than the critical frequency, unlike the phenomenon shown in <FIG>, each of the second relative permeability and the third relative permeability becomes less than the first relative permeability in any of the sections in a low-power mode.

In Embodiment <NUM> of the inductor, the magnetic permeability <NUM>, <NUM> and <NUM> in a high-power mode gradually increases from the point r1 where the inner magnetic body <NUM> is located to the point r2 where the outer magnetic body <NUM> is located.

Like the differential mode, as the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> decreases, the above-described critical frequency may increase. For example, when the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is in the range from <NUM> ± <NUM> (<NUM> ± <NUM> and <NUM> turns) to <NUM> ± <NUM> (<NUM> ± <NUM> and <NUM> turns), the critical frequency may range from <NUM> to <NUM>. For example, when the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is <NUM> ± <NUM>, the critical frequency may be <NUM>.

The inductance LCM of Embodiment <NUM> of the inductor in a common mode may be expressed by the following Equation <NUM>.

Here, α represents a coefficient, µ<NUM> represents the first relative permeability of the first magnetic body <NUM>, µ<NUM> represents the second relative permeability of the outer magnetic body <NUM>, µ<NUM> represents the third relative permeability of the inner magnetic body <NUM>, S<NUM> represents the cross-sectional area of the first magnetic body <NUM>, S<NUM> represents the cross-sectional area of the outer magnetic body <NUM>, and S<NUM> represents the cross-sectional area of the inner magnetic body <NUM>. Referring to <FIG>, each of S<NUM>, S<NUM> and S<NUM> may correspond to the cross-sectional area on the z-x plane. Referring to <FIG>, LE<NUM> is a circumferential length of the first magnetic body <NUM> about the center thereof, LE<NUM> is a circumferential length of the outer magnetic body <NUM> about the center thereof, LE<NUM> is a circumferential length of the inner magnetic body <NUM> about the center thereof, and n is the number of turns of each of the first and second coils <NUM> and <NUM>.

Further, each of the first, second and third relative permeability µ<NUM>, µ<NUM> and µ<NUM> may vary depending on the applied frequency of the current applied to the inductor. When the number n of windings of each of the first and second coils <NUM> and <NUM> is <NUM> and when the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> is <NUM> ± <NUM> (<NUM> ± <NUM> and <NUM> turns), the first relative permeability µ<NUM> may be <NUM>,<NUM>/m, and each of the second and third relative permeability µ<NUM> and µ<NUM> may range from <NUM>/m to <NUM>,<NUM>/m. For example, when the above-described critical frequency is <NUM>, the first, second and third relative permeability µ<NUM>, µ<NUM> and µ<NUM> for each applied frequency may be as follows.

When the applied frequency is <NUM>, the first relative permeability µ<NUM> may be <NUM>,<NUM>/m, and each of the second and third relative permeability µ<NUM> and µ<NUM> may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m.

Alternatively, when the applied frequency is <NUM>, the first relative permeability µ<NUM> may be <NUM>,<NUM>/m, and each of the second and third relative permeability µ<NUM> and µ<NUM> may range from <NUM>,<NUM>/m to <NUM>,<NUM>/m.

<FIG> is a graph showing an average magnetic permeability on the y-z plane in a common mode of Embodiment <NUM> of the inductor, wherein the horizontal axis represents a position in the radial (r) direction of the inductor and the vertical axis represents an average magnetic permeability on the y-z plane. In <FIG>, reference numeral <NUM> represents an average magnetic permeability in a low-power mode, and reference numeral <NUM> represents an average magnetic permeability in a high-power mode.

<FIG> is a graph showing an average magnetic permeability in a common mode of Embodiment <NUM> of the inductor, wherein the horizontal axis represents current and the vertical axis represents an average magnetic permeability.

Referring to <FIG>, as the applied current increases in a common mode, the average magnetic permeability of Embodiment <NUM> of the inductor decreases. When the applied current is IC4, Embodiment <NUM> of the inductor reaches a partially saturated PS state in which the inductor loses <NUM>% of the function thereof, and as the applied current continuously increases, the inductor reaches a completely saturated CS state in which the inductor loses <NUM>% of the function thereof. Referring to <FIG>, in a common mode, the partial saturation current of the inductor according to the comparative example CM is IC2, and the partial saturation current of Embodiment <NUM> E3C of the inductor is IC4, which is greater than IC2. As such, in a common mode, Embodiment <NUM> reaches a partially saturated state at a higher current value IC4 than the comparative example. That is, in a common mode, a reduction in the magnetic permeability in Embodiment <NUM> due to an increase in the applied current (i.e. an increase in the magnitude of the magnetic field) is lower than that in the comparative example.

Referring to <FIG>, in the case in which the number n of turns of each of the first and second coils <NUM> and <NUM> is in the range from <NUM> to <NUM>, the partial saturation current IC4 may range from <NUM> A to <NUM> A in a common mode.

In the differential mode and the common mode, as the number n of turns increases, the partial saturation current IC3 and IC4 may decrease in inverse proportion to the square n<NUM> of the number n of turns. For example, when the number n of turns is <NUM>, the partial saturation current IC3 in the differential mode may be about <NUM> A, and the partial saturation current IC4 in the common mode may be about <NUM> A. However, if the number n of turns is increased to <NUM>, i.e. <NUM> times, the partial saturation current IC3 and IC4 may be reduced to <NUM>/<NUM>. That is, the partial saturation current IC3 may be reduced to <NUM> A, and the partial saturation current IC4 may be reduced to <NUM> A.

Since Embodiment <NUM> of the inductor includes the second magnetic body <NUM>, which is different from the first magnetic body <NUM>, Embodiment <NUM> is capable of receiving high power in a differential mode. Further, since the second magnetic body <NUM> included in the magnetic core of Embodiment <NUM> of the inductor has a high saturation magnetic flux density and since the saturation magnetic flux density is maintained at a high frequency, some energy may be stored in the second magnetic body <NUM> even when reverse current is introduced. Therefore, even when a common mode is performed such that reverse current of <NUM> mA or lower is generated, it is possible to remove noise, thereby securing the stability of the circuit with respect to reverse current.

In Embodiment <NUM> of the inductor, the characteristics thereof in a common mode are similar to those in a differential mode. However, when reverse current (reflection) due to circuit impedance mismatch is introduced in a common mode, Embodiment <NUM> may convert the introduced reverse current into magnetic energy and may store the magnetic energy in the outer magnetic body <NUM> and the inner magnetic body <NUM>. Therefore, when Embodiment <NUM> of the inductor is applied to an EMI filter to be described later, it is possible to remove noise and to prevent reverse current from being introduced into a power source.

A circuit, in which the inductor according to the embodiment is mainly utilized, may be configured to receive differential-type home AC current having a level of <NUM> V to <NUM> V and a frequency of <NUM> to <NUM> as main energy and may include a rectifier diode connected to a rear end thereof in the form of a Wheatstone bridge. In this case, the main energy has a low frequency and the noise source has a low power level, whereby it is possible to obtain the above-descried effects of the embodiment.

Meanwhile, the inductor according to the embodiment described above may be included in a line filter. For example, the line filter may be a line filter for noise reduction that is applied to an AC-to-DC converter.

<FIG> is an embodiment of an EMI filter including the inductor according to the embodiment.

Referring to <FIG>, an EMI filter <NUM> may include a plurality of X-capacitors Cx, a plurality of Y-capacitors Cy, and inductors L.

The X-capacitors Cx are respectively disposed between a first terminal P1 of a live line LIVE and a third terminal P3 of a neutral line NEUTRAL and between a second terminal P2 of the live line LIVE and a fourth terminal P4 of the neutral line NEUTRAL.

The plurality of Y-capacitors Cy may be disposed in series between the second terminal P2 of the live line LIVE and the fourth terminal P4 of the neutral line NEUTRAL.

The inductors L may be disposed between the first terminal P1 and the second terminal P2 of the live line LIVE and between the third terminal P3 and the fourth terminal P4 of the neutral line NEUTRAL. Here, each of the inductors L may be the inductor <NUM> according to the embodiment described above.

When common-mode noise is introduced, the EMI filter <NUM> removes the common-mode noise due to combined impedance characteristics of primary inductance and the Y-capacitors Cy. Here, the primary inductance of the live line LIVE may be obtained by measuring the inductance between the first terminal P1 and the second terminal P2 in the state of opening the third and fourth terminals P3 and P4, and the primary inductance of the neutral line NEUTRAL may be obtained by measuring the inductance between the third terminal P3 and the fourth terminal P4 in the state of opening the first and second terminals P1 and P2.

When differential-mode noise is introduced, the EMI filter <NUM> removes the differential-mode noise due to combined impedance characteristics of leakage inductance and the X-capacitors Cx. Here, the leakage inductance of the live line LIVE may be obtained by measuring the inductance between the first terminal P1 and the second terminal P2 in the short-circuit state of the third and fourth terminals P3 and P4, and the leakage inductance of the neutral line NEUTRAL may be obtained by measuring the inductance between the third terminal P3 and the fourth terminal P4 in the short-circuit state of the first and second terminals P1 and P2.

The inductor of the EMI filter <NUM> according to the embodiment may be the inductor according to Embodiment <NUM> described above. When the thickness T10 and T1I of each of the outer and inner magnetic bodies <NUM> and <NUM> of the second magnetic body <NUM> is <NUM> (<NUM> ± <NUM> and <NUM> turns), the EMI performance may be further improved as the number n of turns of each of the first and second coils <NUM> and <NUM> increases. For example, because saturation occurs when the number n of turns is greater than <NUM>, the most excellent EMI characteristics may be obtained when the number n of turns is <NUM>.

Further, in order to remove common-mode noise, the inductance LCM in a common mode, which is expressed by the above Equation <NUM>, needs to be large, and in order to remove differential-mode noise, the inductance LDM in a differential mode, which is expressed by the above Equation <NUM>, needs to be large. Therefore, the inductor according to the embodiment may include the first and second magnetic bodies <NUM> and <NUM>, which have S<NUM>, S<NUM>, S<NUM>, LE<NUM>, LE<NUM> and LE<NUM> determined based on the above principle. That is, since the relative permeability is not varied even when the number n of turns is varied, it is possible to maintain the inductance at a constant level by adjusting a ratio (S<NUM>/LE<NUM>, S<NUM>/LE<NUM> and S<NUM>/LE<NUM>) of the cross-sectional area to the circumferential length.

The contents of the above-described embodiments may be applied to other embodiments as long as they are not incompatible with one another.

While the present disclosure has been particularly shown and described with reference to exemplary embodiments thereof, these embodiments are only proposed for illustrative purposes and do not restrict the present disclosure, and it will be apparent to those skilled in the art that various changes in form and details may be made without departing from the essential characteristics of the embodiments set forth herein. For example, respective configurations set forth in the embodiments may be modified and applied. Further, differences in such modifications and applications should be construed as falling within the scope of the present disclosure. It is noted that the invention is only defined and limited by the appended claims.

Various embodiments have been described in the best mode for carrying out the disclosure.

Claim 1:
A power board, comprising:
a board;
a circuit portion formed on the board; and
an EMI filter (<NUM>) configured to be electrically connected to the circuit portion,
wherein the EMI filter comprises:
an inductor (<NUM>) comprising:
a magnetic core (<NUM>); and
a plurality of coils (<NUM>, <NUM>) wound around the magnetic core; and
a capacitor,
wherein the magnetic core (800B) comprises:
a first magnetic body (<NUM>) having a toroidal shape, the first magnetic body comprising ferrite;
a second magnetic body (<NUM>) disposed on an inner side of the first magnetic body; and
a third magnetic body (<NUM>) disposed on an outer side of the first magnetic body,
the second magnetic body (<NUM>) and the third magnetic body (<NUM>) comprising a metal ribbon,
wherein
the second magnetic body (<NUM>) is formed in multiple layers in a diameter direction of the first magnetic body (<NUM>) on an inner circumferential surface of the first magnetic body,
the third magnetic body (<NUM>) is formed in multiple layers in the diameter direction on an outer circumferential surface of the first magnetic body (<NUM>),
a thickness of the first magnetic body (<NUM>) is greater than a thickness of the second magnetic body (<NUM>) in the diameter direction,
a thickness of the third magnetic body (<NUM>) is less than the thickness of the first magnetic body (<NUM>) in the diameter direction, and
in each of a differential mode and a common mode of the inductor, when low power is applied to the inductor and a frequency of a current applied to the inductor (800B) is less than a critical frequency, a relative permeability of each of the second and third magnetic bodies (<NUM>, <NUM>) is higher than a relative permeability of the first magnetic body (<NUM>),
wherein, in each of a differential mode and a common mode of the inductor, when high power is applied to the inductor and the frequency of the current applied to the inductor is less than the critical frequency, the relative permeability of the second magnetic body (<NUM>) is lower than the relative permeability of the first magnetic body (<NUM>),
wherein the height of the at least one of the second or third magnetic body in a direction perpendicular to the diameter direction is less than the height of the first magnetic body in the direction perpendicular to the diameter direction to expose at least one part of a surface of the first magnetic body (<NUM>).