EP4693353A2

EP4693353A2 - Transformer

Info

Publication number: EP4693353A2
Application number: EP24785179.3A
Authority: EP
Inventors: In Seong Sohn; Jung Eun Lee; Sung San Kim
Original assignee: LG Innotek Co Ltd
Current assignee: LG Innotek Co Ltd
Priority date: 2023-04-05
Filing date: 2024-04-02
Publication date: 2026-02-11
Also published as: WO2024210474A2; WO2024210474A3; CN121002596A; KR20240149146A

Abstract

A transformer of an embodiment comprises: a core portion including an upper core and a lower core disposed in a first direction opposite to the upper core; a bobbin portion disposed at least partially within the core portion; and a coil portion including a primary coil and a secondary coil disposed at least partially on the bobbin portion, wherein the core portion forms a receiving space with the bobbin portion to receive the coil portion, and the primary coil and the secondary coil are disposed in a second direction intersecting the first direction in the receiving space and are disposed to overlap each other in the first direction on the outside of the receiving space.

Description

[Technical Field]

Embodiments relate to a transformer.

[Background Art]

Various coil components, such as transformers or line filters, are mounted in power supply units of electronic devices.
A transformer may be included in an electronic device for various purposes. For example, a transformer may be used to perform a function of transferring energy from one circuit to another circuit. In addition, a transformer may also be used to perform a function of changing the magnitude of voltage, such as stepping up or stepping down voltage. Further, because a transformer provides only inductive coupling between a primary winding and a secondary winding without directly forming a DC path, the transformer may also be used to block direct current while passing alternating current or to electrically isolate two circuits.
In such a transformer, a primary coil and a secondary coil need to be disposed horizontally in order to secure leakage inductance. However, when the primary coil and the secondary coil are disposed horizontally in a slim-type transformer, the overall area of the transformer increases, and improvement is therefore required. In addition, low leakage inductance of the transformer is not necessarily desirable, whereas in an LLC circuit, very low leakage inductance is required for high-frequency operation.

[Disclosure]

[Technical Problem]

Embodiments provide a transformer having reduced leakage inductance.

[Technical Solution]

A transformer according to an embodiment may include a core unit including an upper core and a lower core disposed opposite the upper core in a first direction, a bobbin unit at least partially disposed within the core unit, and a coil unit including a primary coil and secondary coils, each being at least partially disposed on the bobbin unit. The core unit may define an accommodation space together with the bobbin unit to accommodate the coil unit, and the primary coil and the secondary coils may be disposed in the accommodation space in a second direction intersecting the first direction and may overlap each other in the first direction in an area outside the accommodation space.
In an example, the bobbin unit may include a core area overlapping the core unit in the first direction, the core area defining the accommodation space together with the upper core and the lower core, a first non-core area extending from the core area in a third direction intersecting both the first direction and the second direction, and a second non-core area extending from the core area to be opposite the first non-core area.
In an example, the primary coil and the secondary coils may be disposed in the core area in the second direction and may be disposed in at least one of the first or second non-core area so as to at least partially overlap each other in the first direction.
In an example, the primary coil may include a first inner portion disposed in the core area and a first outer portion disposed in the first non-core area, and each of the secondary coils may include second inner portions disposed in the core area, a second outer portion disposed in the second non-core area and including an end portion of each of the secondary coils, and a plurality of third outer portions disposed in the first non-core area to interconnect the second inner portions.
In an example, the plurality of third outer portions may include an upper third outer portion extending from one of the second inner portions to be disposed above the first outer portion and a lower third outer portion extending from the remaining one of the second inner portions to be disposed below the first outer portion, and the first outer portion may at least partially overlap the upper third outer portion and the lower third outer portion in the first direction.
In an example, the first non-core area of the bobbin unit may include a receiving recess formed to allow the first outer portion of the primary coil to be received therein, an upper seating recess formed to allow the upper third outer portion to be seated therein, the upper seating recess being disposed above the receiving recess, and a lower seating recess formed to allow the lower third outer portion to be seated therein, the lower seating recess being disposed below the receiving recess.
In an example, a first height from a reference surface of the first non-core area to the top surface of the upper third outer portion of each of the secondary coils may be less than or equal to a second height from the reference surface to the top surface of the core unit.
In an example, a first distance from the bottom surface of the lower third outer portion to the top surface of the upper third outer portion may be less than or equal to a second distance from the bottom surface of the lower core to the top surface of the upper core.
In an example, the first non-core area may include first guide recesses protruding in the third direction from one side of the first non-core area adjacent to the core unit, the first guide recesses being spaced apart from each other in the first direction to receive one end of each of the secondary coils and second guide recesses protruding in the third direction from the opposite side of the first non-core area adjacent to the core unit, the second guide recesses being spaced apart from each other in the first direction to receive the other end of each of the secondary coils.
In an example, the first guide recesses may have shapes guiding one end of one of the pair of secondary coils to extend to the upper seating recess and guiding one end of the other of the pair of secondary coils to extend to the lower seating recess, and the second guide recesses may have shapes guiding the other end of the one of the secondary coils to extend to the upper seating recess and guiding the other end of the other of the secondary coils to extend to the lower seating recess.
In an example, the first direction and the second direction may be perpendicular to each other, and the second direction and the third direction may be perpendicular to each other.

[Advantageous Effects]

The transformer according to the embodiment may have a reduced size in a horizontal direction and reduced leakage inductance, and imbalance and DCR of secondary coils may be improved.
The effects achievable through the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood by those skilled in the art from the following description.

[Description of Drawings]

FIG. 1A is a top perspective view of a transformer according to an embodiment.
FIG. 1B is a bottom perspective view of the transformer according to the embodiment.
FIG. 2A is a coupled plan view of the transformer shown in FIGs. 1A and 1B.
FIG. 2B is a coupled top perspective view of the transformer shown in FIGs. 1A and 1B.
FIG. 2C is a coupled bottom perspective view of the transformer shown in FIGs. 1A and 1B.
FIG. 2D is a coupled front view of the transformer shown in FIGs. 1A and 1B.
FIG. 2E is an enlarged view of portion "A" in FIG. 2D.
FIG. 3A is a perspective view of the transformer shown in FIG. 2C, with an upper core removed.
FIG. 3B is a plan view of the transformer shown in FIG. 3A.
FIG. 3C is a coupled plan view of only a coil unit and a bobbin unit in the transformer shown in FIG. 3A.
FIG. 3D is a coupled bottom view of only the coil unit and the bobbin unit in the transformer shown in FIG. 3A.
FIG. 4 is a perspective view of the transformer shown in FIG. 3A, with a primary coil removed.
FIG. 5A is a cross-sectional view taken along line I-I' in FIG. 3C.
FIG. 5B is a right side view of the transformer shown in FIG. 3C when viewed in the -x-axis direction.

[Best Mode]

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. The examples, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. It is to be understood that the present disclosure covers all modifications, equivalents, and alternatives falling within the scope and spirit of the present disclosure.
While ordinal numbers including "second," "first," etc. may be used to describe various components, they are not intended to limit the components. These expressions are used only to distinguish one component from another component. For example, a second element could be termed a first element, and, similarly, a first element could be termed a second element, without departing from the scope of the present disclosure. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can 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" or "directly coupled" to another element, 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. In addition, 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 clarity and convenience of explanation, and may not accurately reflect the actual size.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments of the disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the term "include" or "have", when used herein, specifies the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.
Unless otherwise defined, all terms used herein, which include technical or scientific terms, have the same meanings as those generally appreciated by those skilled in the art. The terms, such as ones defined in common dictionaries, should be interpreted as having the same meanings as terms in the context of pertinent technology, and should not be interpreted as having ideal or excessively formal meanings unless clearly defined in the specification.
Hereinafter, a transformer according to an embodiment will be described in detail with reference to the accompanying drawings. The same or equivalent elements are denoted by the same reference numerals even when they are depicted in different drawings, and redundant descriptions thereof will be omitted. In addition, a transformer according to an embodiment will be described using the Cartesian coordinate system, but may also be described using other coordinate systems. In the Cartesian coordinate system, the x-axis, the y-axis, and the z-axis shown in each drawing are perpendicular to each other, but the embodiments are not limited thereto. The x-axis, the y-axis, and the z-axis may intersect each other obliquely. Hereinafter, for convenience of description, the z-axis direction will be referred to as a "first direction," the y-axis direction will be referred to as a "second direction," and the x-axis direction will be referred to as a "third direction."
FIG. 1A is a top perspective view of a transformer according to an embodiment, and FIG. 1B is a bottom perspective view of the transformer according to the embodiment, rotated 180° from the state shown in FIG. 1A.
FIG. 2A is a coupled plan view of the transformer shown in FIGs. 1A and 1B, FIG. 2B is a coupled top perspective view of the transformer shown in FIGs. 1A and 1B, FIG. 2C is a coupled bottom perspective view of the transformer shown in FIGs. 1A and 1B, rotated 180° from the state shown in FIG. 2C, FIG. 2D is a coupled front view of the transformer shown in FIGs. 1A and 1B, and FIG. 2E is an enlarged view of portion "A" in FIG. 2D.
In addition, FIG. 3A is a perspective view of the transformer shown in FIG. 2C, with an upper core 110 removed, FIG. 3B is a plan view of the transformer shown in FIG. 3A, FIG. 3C is a coupled plan view of only a coil unit 200 and a bobbin unit 300 in the transformer shown in FIG. 3A, and FIG. 3D is a coupled bottom view of only the coil unit 200 and the bobbin unit 300 in the transformer shown in FIG. 3A, rotated 180° from the state shown in FIG. 3C.
FIG. 4 is a perspective view of the transformer shown in FIG. 3A, with a primary coil 210 removed.
For convenience of description, illustration of a secondary coil 220 is omitted in FIG. 4.
The transformer according to the embodiment may include a core unit 100, a coil unit 200, and a bobbin unit 300.
The core unit 110 may have the characteristics of a magnetic circuit and thus may act as a path for magnetic flux. The core unit 100 may include an upper core 110 and a lower core 120. The upper core 110 and the lower core 120 may be separated in the first direction. The upper core 110 and the lower core 120 may be coupled to form the core unit 100. That is, the lower core 120 may be disposed opposite the upper core 110 in the first direction. In this case, the upper core 110 may be defined as a core that is located farthest from an upper surface of a circuit board in the first direction, and the lower core 120 may be defined as a core that is located closest to the upper surface of the circuit board in the first direction. The upper core 110 and the lower core 120 may have shapes symmetrical or asymmetrical with respect to each other in the vertical direction, i.e., the z-axis direction. However, for convenience of explanation, the following description will be given on the assumption that the upper core 110 and the lower core 120 have shapes symmetrical to each other in the vertical direction.
A first outer leg portion 111 may be disposed on one side of the upper core 110 in the second direction. The first outer leg portion 111 may protrude downward, i.e., in the first direction, and may extend in the third direction. In addition, a second outer leg portion 112 may be disposed on the opposite side of the upper core 110 in the second direction. The second outer leg portion 112 may protrude downward, i.e., in the first direction, and may extend in the third direction. In addition, an intermediate leg portion 113 may be disposed between the first outer leg portion 111 and the second outer leg portion 112. The intermediate leg portion 113 may protrude downward, i.e., in the first direction, and may extend in the third direction. The first outer leg portion 111, the second outer leg portion 112, and the intermediate leg portion 113 may be disposed parallel to each other. In addition, the first outer leg portion 111, the second outer leg portion 112, and the intermediate leg portion 113 may have the same width or different widths in the second direction.
Meanwhile, the lower core 120 may also include a first outer leg portion 121, a second outer leg portion 122, and an intermediate leg portion 123, which are disposed opposite those of the upper core 110. For example, the intermediate leg portions 113 and 123 may have a rectangular planar shape, or may have an elliptical planar shape, as shown in the drawings. However, the embodiments are not limited to any specific shape of the intermediate leg portions 113 and 123.
The core unit 100 may further include a first space 130 and a second space 140. The first space 130 may be defined between the first outer leg portions 111 and 121 and the intermediate leg portions 113 and 123, and may accommodate a portion of the coil unit 200 and a portion of the bobbin unit 300, which will be described later. The second space 140 may be defined between the second outer leg portions 112 and 122 and the intermediate leg portions 113 and 123, and may accommodate the portion of the coil unit 200 and the portion of the bobbin unit 300 that are formed on the opposite side in the y-axis direction, which will be described later. Accordingly, the first space 130 and the second space 140 may be defined to correspond to the thicknesses and widths of the two opposite portions of the coil unit 200 and the two opposite portions of the bobbin unit 300 accommodated therein. The inductance of the core unit 100 may be controlled by adjusting the sizes of the first space 130 and the second space 140, and heat generation of the transformer may be controlled according to the number of first spaces 130 and the number of second spaces 140. The core unit 100 may include a magnetic material, for example, iron or ferrite. However, the disclosure is not limited thereto.
The coil unit 200 may include a primary coil 210 and a secondary coil 220.
A portion of the primary coil 210 may be disposed within the core unit 100, and the opposite portion of the primary coil 210 may be disposed outside the core unit 100. The primary coil 210 may have a wound or planar shape. However, the embodiments are not limited to any specific shape of the primary coil 210. As such, at least a portion of the primary coil 210 may be accommodated in the first space 130 and the second space 140.
The primary coil 210 may secure withstand voltages of the individual components of the transformer by employing an insulation-enhanced wire. When a magnetic component such as a transformer is developed, individual components require specific withstand voltages. In general, required withstand voltage is higher than or equal to a certain multiple of the operating voltage of the corresponding component. Accordingly, in the case of a component in which a conventional UTSC wire is wound, an insulation distance for satisfying withstand voltage is generated, thereby securing withstand voltage.
An insulation-enhanced wire may be applied to the primary coil 210. That is, all wires of the primary coil may be coated with an insulating synthetic resin, such as epoxy. The application of the insulation-enhanced wire may increase the overall strength of the winding form, and may also increase the overall rigidity of the transformer.
The secondary coil 220 may be disposed along the outer periphery of the primary coil 210 in the winding direction of the primary coil 210. At least a portion of the secondary coil 220 may be accommodated in the first space 130 and the second space 140 together with the primary coil 210. The secondary coil 220 may be formed by winding a plurality of secondary wires in a single layer or multiple layers.
Meanwhile, the bobbin unit 300 may be a part to which the core unit 100 and the coil unit 200 are coupled. The bobbin unit 300 may include a first non-core area NCA1 (or a first end portion) disposed on one side thereof, a second non-core area NCA2 (or a second end portion) disposed on the opposite side thereof in the third direction, and a core area CA disposed between the first non-core area NCA1 and the second non-core area NCA2.
At least a portion of the primary coil 210 and at least a portion of the secondary coil 220 may be disposed on the bobbin unit 300.
In the bobbin unit 300, the core area CA is defined as an area that overlaps the core unit 100 in the vertical direction, i.e., the first direction. As such, at least a portion of the bobbin unit 300 may be disposed within the core unit 100. That is, the core unit 100 may be disposed in the core area CA of the bobbin unit 300. The upper core 110 and the lower core 120 of the core unit 100 may define an accommodation space together with the core area CA of the bobbin unit 300. At least a portion of the coil unit 200 may be accommodated in the accommodation space defined in this manner.
In the bobbin unit 300, the first and second non-core areas NCA1 and NCA2 are defined as areas that do not overlap the core unit 100 in the vertical direction, and more specifically, as areas that extend in the third direction, which is one of the horizontal directions, from the core area CA and are disposed on opposite sides in the third direction with the core area CA interposed therebetween. That is, the first non-core area NCA1 is an area extending in the third direction from the core area CA, and the second non-core area NCA2 is an area extending from the core area CA so as to be opposite the first non-core area NCA1.
Accordingly, in the bobbin unit 300, the area other than the first non-core area NCA1 and the second non-core area NCA2 may be understood as the core area CA.
The bobbin unit 300 may include terminal portions OL1 and OL2 disposed in the first non-core area NCA1 and the second non-core area NCA2, respectively. The first terminal portion OL1 may be a portion in which an end portion of the primary coil 210 is disposed, and may have a groove shape that accommodates and holds the end portion of the primary coil 210. For example, the first terminal portion OL1 may include three terminal portions OL11, OL12, and OL13. However, the embodiments are not limited to any specific number or shape of the first terminal portion OL1.
In addition, the second terminal portion OL2 may be a portion in which an end portion of the secondary coil 220 is disposed, and may have a groove shape that accommodates and holds the end portion of the secondary coil 220. For example, the second terminal portion OL2 may include four terminal portions OL21, OL22, OL23, and OL24. However, the embodiments are not limited to any specific number or shape of the second terminal portion OL2.
The primary coil 210 described above may include a first inner portion IP1 and a first outer portion OP1. A portion of the primary coil 210 that is disposed in the core area CA is referred to as the first inner portion IP1, and a portion of the primary coil 210 that is disposed in the first non-core area NCA1 is referred to as the first outer portion OP1.
The secondary coil 220 may include a second inner portion IP2 and second and third outer portions OP2 and OP3. A portion of the secondary coil 220 that is disposed in the core area CA is referred to as the second inner portion IP2, and a portion of the secondary coil 220 that is disposed in the second non-core area NCA2 is referred to as the second outer portion OP2. An end portion of the secondary coil 220 belongs to the second outer portion OP2. In addition, a portion of the secondary coil 220 that is disposed in the first non-core area NCA1 is referred to as the third outer portion OP3. The third outer portion OP3 serves to interconnect sections of the second inner portion IP2 that are spaced apart from each other with the first inner portion IP1 interposed therebetween.
The secondary coil 220 may include a pair of coils 222 and 224. In this case, one end portion and the other end portion of one 222 of the pair of secondary coils 220 are disposed in the 2-2^nd and 2-4^th terminal portions OL22 and OL24, respectively, and have planar shapes surrounding the outer periphery of the primary coil 210. One end portion and the other end portion of the other 224 of the pair of secondary coils 220 are disposed in the 2-1^st and 2-3^rd terminal portions OL21 and OL23, respectively, and have planar shapes surrounding the outer periphery of the primary coil 210.
According to the embodiment, the primary coil 210 and the secondary coil 220 may be disposed in the horizontal direction, i.e., the second direction, within the accommodation space defined by the bobbin unit 300 and the core unit 100 so as not to overlap each other in the vertical direction, i.e., the first direction, but may overlap each other in the vertical direction, i.e., the first direction, in an area outside the accommodation space. An example of this configuration will now be described in detail with reference to FIGs. 1A to 4. However, the embodiments are not limited thereto.
That is, in the transformer according to the embodiment, the primary coil 210 and the secondary coil 220 may be disposed in the horizontal direction so as not to overlap each other in the vertical direction, i.e., the first direction, in the core area CA of the bobbin unit 300, but may be disposed to overlap each other in the vertical direction, i.e., the first direction, in at least one of the first non-core area NCA1 or the second non-core area NCA2. Given this configuration, the transformer of the embodiment may also be applied to a transformer having a configuration different from that shown in FIGs. 1A to 4.
FIG. 5A is a cross-sectional view taken along line I-I' in FIG. 3C, and FIG. 5B is a right side view of the transformer shown in FIG. 3C when viewed in the -x-axis direction.
Referring to FIG. 5A, the primary coil 210 and the secondary coils 220 (222 and 224) may be disposed in the horizontal direction so as not to overlap each other in the vertical direction, i.e., the first direction, in the core area CA. On the other hand, the primary coil 210 and the secondary coils 220 (222 and 224) may be disposed to overlap each other in the vertical direction, i.e., the first direction, in at least one of the first non-core area NCA1 or the second non-core area NCA2, e.g., in the first non-core area NCA1.
That is, the third outer portion OP3 of one 224 of the pair of secondary coils 220 (222 and 224) extends from the second inner portion IP2 to be disposed above the first outer portion OP1 of the primary coil 210, and is hereinafter referred to as an "upper third outer portion." The third outer portion OP3 of the other 222 of the pair of secondary coils 220 (222 and 224) extends from the second inner portion IP2 to be disposed below the first outer portion OP1 of the primary coil 210, and is hereinafter referred to as a "lower third outer portion." As such, according to the embodiment, at least part of the first outer portion OP1 of the primary coil 210 may be disposed to overlap the upper third outer portion and the lower third outer portion in the vertical direction, i.e., the first direction.
In order to allow the secondary coils 220 to be vertically stacked above and below the primary coil 210 in the first non-core area NCA1, the first non-core area NCA1 of the bobbin unit 300 may include a receiving recess RH, an upper seating recess RHU, and a lower seating recess RHL, as shown in FIG. 2D. In this case, the receiving recess RH is not visible, but is indicated by a dotted line for ease of understanding.
The receiving recess RH may be a recess in which the first outer portion OL1 of the primary coil 210 is received. The upper seating recess RHU may receive the upper third outer portion OL3 seated therein and may be disposed above the receiving recess RH, and the lower seating recess RHL may receive the lower third outer portion OL3 seated therein and may be disposed below the receiving recess RH.
In addition, the first non-core area NCA1 of the bobbin unit 300 may include first and second guide recesses GH1 and GH2.
The first guide recesses GH1 protrude in the third direction, i.e., the x-axis direction, from one side of the first non-core area NCA1 of the bobbin unit 300 that is adjacent to the core unit 100 and are spaced apart from each other in the vertical direction, i.e., the z-axis direction, to receive one end of each of the secondary coils 220 (222 and 224). The second guide recesses GH2 protrude in the third direction from the opposite side of the first non-core area NCA1 of the bobbin unit 300 that is adjacent to the core unit 100 and are spaced apart from each other in the vertical direction, i.e., the z-axis direction, to receive the other end of each of the secondary coils 220 (222 and 224).
The first guide recesses GH1 have shapes that guide one 224 of the pair of secondary coils 222 and 224 such that one end thereof extends to the upper seating recess RHU and guide the other 222 of the pair of secondary coils 222 and 224 such that one end thereof extends to the lower seating recess RHL.
The second guide recesses GH2 have shapes that guide one 224 of the pair of secondary coils 222 and 224 such that the other end thereof extends to the upper seating recess RHU and guide the other 222 of the pair of secondary coils 222 and 224 such that the other end thereof extends to the lower seating recess RHL.
As such, a portion of each of the pair of secondary coils 222 and 224 may be wound in a manner of being flipped once by means of the first and second guide recesses GH1 and GH2. However, the embodiments are not limited thereto.
In addition, the first and second guide recesses GH1 and GH2 may also serve to support the secondary coils 224 and 222.
According to the embodiment, as shown in FIG. 5B, a first height H1 from a reference surface RS of the first non-core area NCA1 to a top surface of the upper third outer portion of the secondary coil 224 may be less than or equal to a second height H2 from the reference surface RS to a top surface 100T of the core unit 100.
For example, the reference surface RS may be a top surface 300T of the bobbin unit 300 in the first non-core area NCA1, as shown in the drawings.
Alternatively, a first distance D1 from a bottom surface 222BS of the lower third outer portion 222 to a top surface 224TS of the upper third outer portion 224 may be less than or equal to a second distance T5 from a bottom surface 120BS of the lower core 120 to the top surface 100T of the upper core 110.
For example, a sum of a thickness T1 of the first outer portion OP1 of the primary coil 210, a thickness T2 of the upper third outer portion OP3 of the secondary coil 224, a thickness T3 of the lower third outer portion OP3 of the secondary coil 222, and a thickness T4 of the first non-core area NCA1 of the bobbin unit 300 may be less than or equal to the thickness T5 of the core unit 100.
Hereinafter, a transformer of a comparative example and the transformer of the embodiment will be compared with each other.
Unlike the embodiment, in the transformer according to the comparative example, the primary coil 210 and the secondary coils 220 are disposed in the horizontal direction so as not to overlap each other in the vertical direction both in the core area CA and in the first non-core area NCA1 of the bobbin unit 300. Accordingly, the transformer according to the comparative example may increase in size in the horizontal direction. A separation distance between the secondary coils 220 disposed in the first non-core area NCA1 and the core unit 100 may increase, and a separation distance between the primary coil 210 and the secondary coils 220 disposed in the first non-core area NCA1 may increase. As a result, leakage inductance may increase.
In contrast, according to the embodiment, the secondary coils 224 and 222 are disposed above and below the primary coil 210 so as to vertically overlap the primary coil 210 in the first non-core area NCA1 of the bobbin unit 300. Accordingly, the transformer according to the embodiment may decrease in size in the horizontal direction compared to the comparative example. In addition, a separation distance between the secondary coils 220 disposed in the first non-core area NCA1 and the core unit 100 in the third direction may decrease compared to the comparative example, and a separation distance between the primary coil 210 and the secondary coils 220 disposed in the first non-core area NCA1 may decrease compared to the comparative example. As a result, leakage inductance may be reduced.
As an experimental example, it is assumed in both the comparative example and the embodiment that the length by which the primary coil 210 protrudes from the core unit 100 in the third direction is 0.6 mm, the winding width of the primary coil 210 is 8.4 mm, and the turn ratio of the transformer and the shape of the core unit 100 are fixed. In this case, in the transformer according to the comparative example, a distance from the core unit 100 to the outermost edge of the secondary coils 220 in the third direction is 18 mm, and in the transformer according to the embodiment, a distance from the core unit 100 to the outermost edge of the secondary coils 220 (222 and 224) in the third direction is 2.9 mm. Under these conditions, leakage inductance Lk of each of the comparative example and the embodiment may be obtained as follows. [Table 1]

Gap (mm) Comparative Example Embodiment

L Lk L Lk

200 206.4 44.5 209.8 39.6

250 171.1 41.4 173.7 37.2

300 146.5 39.2 148.8 35.2

350 128.5 37.2 130.6 33.5

400 114.8 35.4 116.6 32.0
Here, the gap represents a separation distance between the intermediate legs 113 and 123 in the first direction, and L represents inductance.
Referring to Table 1 above, it can be seen that the leakage inductance Lk in the embodiment is reduced by approximately 10% compared to the comparative example.
In addition, in the embodiment, as shown in FIG. 5B, the sum of the thicknesses T1 to T4 is less than or equal to the thickness T5 of the core unit 100. Accordingly, even when the primary coil 210 and the secondary coils 222 and 224 are vertically stacked in the first non-core area NCA1, the thickness of the transformer does not increase. Furthermore, imbalance among the secondary coils 222 and 224 and the coil resistance value thereof, i.e., direct current resistance (DCR), may be improved.
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 detail 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 as defined by the appended claims.

[Mode for Disclosure]

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

[Industrial Applicability]

The transformer according to the embodiment may be used in a power supply unit of an electronic device or the like.

Claims

A transformer, comprising:
a core unit including an upper core and a lower core disposed opposite the upper core in a first direction;

a bobbin unit at least partially disposed within the core unit; and

a coil unit including a primary coil and secondary coils, each being at least partially disposed on the bobbin unit,

wherein the core unit defines an accommodation space together with the bobbin unit to accommodate the coil unit, and

wherein the primary coil and the secondary coils are disposed in the accommodation space in a second direction intersecting the first direction and overlap each other in the first direction in an area outside the accommodation space.
The transformer according to claim 1, wherein the bobbin unit includes:
a core area overlapping the core unit in the first direction, the core area defining the accommodation space together with the upper core and the lower core; and

a first non-core area extending from the core area in a third direction intersecting both the first direction and the second direction and a second non-core area extending from the core area to be opposite the first non-core area.
The transformer according to claim 2, wherein the primary coil and the secondary coils are disposed in the core area in the second direction and are disposed in at least one of the first or second non-core area so as to at least partially overlap each other in the first direction.
The transformer according to claim 3, wherein the primary coil includes:
a first inner portion disposed in the core area; and

a first outer portion disposed in the first non-core area, and

wherein each of the secondary coils includes:
second inner portions disposed in the core area;

a second outer portion disposed in the second non-core area, the second outer portion including an end portion of each of the secondary coils; and

a plurality of third outer portions disposed in the first non-core area to interconnect the second inner portions.
The transformer according to claim 4, wherein the plurality of third outer portions includes:
an upper third outer portion extending from one of the second inner portions to be disposed above the first outer portion; and

a lower third outer portion extending from a remaining one of the second inner portions to be disposed below the first outer portion, and

wherein the first outer portion at least partially overlaps the upper third outer portion and the lower third outer portion in the first direction.
The transformer according to claim 5, wherein the first non-core area of the bobbin unit includes:
a receiving recess formed to allow the first outer portion of the primary coil to be received therein;

an upper seating recess formed to allow the upper third outer portion to be seated therein, the upper seating recess being disposed above the receiving recess; and

a lower seating recess formed to allow the lower third outer portion to be seated therein, the lower seating recess being disposed below the receiving recess.
The transformer according to claim 5, wherein a first height from a reference surface of the first non-core area to a top surface of the upper third outer portion of each of the secondary coils is less than or equal to a second height from the reference surface to a top surface of the core unit.
The transformer according to claim 5, wherein a first distance from a bottom surface of the lower third outer portion to a top surface of the upper third outer portion is less than or equal to a second distance from a bottom surface of the lower core to a top surface of the upper core.
The transformer according to claim 6, wherein the first non-core area includes:
first guide recesses protruding in the third direction from one side of the first non-core area adjacent to the core unit, the first guide recesses being spaced apart from one end of each of the secondary coils in the first direction to receive the one end of each of the secondary coils; and

second guide recesses protruding in the third direction from an opposite side of the first non-core area adjacent to the core unit, the second guide recesses being spaced apart from an opposite end of each of the secondary coils in the first direction to receive the opposite end of each of the secondary coils.
The transformer according to claim 9, wherein the first guide recesses have shapes guiding one end of one of the pair of secondary coils to extend to the upper seating recess and guiding one end of a remaining one of the pair of secondary coils to extend to the lower seating recess, and
wherein the second guide recesses have shapes guiding an opposite end of the one of the secondary coils to extend to the upper seating recess and guiding an opposite end of the remaining one of the secondary coils to extend to the lower seating recess.