Patent Description:
Inductor coils can generate heat, and in certain situations this heat needs to be extracted in order to cool the inductor coil.

<CIT> describes an assembly of a reactor as the induction machine which includes the coil and the pair of E-shaped cores and arranged opposite and a reactor which includes the heat dissipating member has the pair of E-shaped cores and arranged in contact with the heat dissipating members respectively, and is provided with a projection portion having a shape conforming with an outer circumferential surface of a coil portion on a side of a surface of the heat dissipating member which comes into contact with the pair of E-shaped cores.

<CIT> describes an inductance component comprising a core type inductance component body having cores, bobbins, and coils including air gaps, and a heat sink for heat dissipation arranged in a close contact with the body, a counterbore portion for receiving a part of outer peripheral surfaces of the coils is formed in a surface of the heat sink. The inductance component body is disposed so that a part of the outer peripheral surfaces of the coils is in a close contact with the counterbore portion through an insulative heat dissipation sheet in a state where the cores are in a close contact with the surface of the heat sink.

<CIT> describes that an inductor includes a magnetizable core with a winding axis and at least one winding, the winding is formed by a conductor which at least partly surrounds the winding axis of the core, and the winding is formed in one layer and a cross section of the conductor is rectangular, in particular square.

<CIT> describes a reactor which uses a reactor core in which J-shaped iron cores are oppositely disposed in a ring shape. It is described that in the ring shape, an axial outer circumferential part of a first coil wound around a first gap and an axial outer circumferential part of a second coil wound around a second gap overlap each other in an axial direction. It is described that regarding four holding stay parts disposed at four corners of the reactor, the rigidity of the holding stay parts close to the first gap and the second gap is lower than the rigidity of the holding stay parts far from the first gap and the second gap.

<CIT> describes that a circuit assembly includes: a circuit board; an inductor that is disposed on the circuit board, and that includes a coil including a winding portion made by winding a winding wire, and a core member; and a heat dissipation plate that is disposed on the opposite side of the surface of the circuit board on which the inductor is disposed, wherein a through hole is provided in a region of the circuit board that corresponds to the inductor, and a receiving protrusion that penetrates the through hole and protrudes to a surface side of the circuit board on which the inductor is disposed, and that is in heat transfer contact with the coil and the core member is provided in a region that corresponds to the through hole in the heat dissipation plate.

<CIT> describes a heat-sink-mounted inductor that is provided with: a core; a coil wound around the core; and a heat sink which is made of a magnetic material and which is disposed directly or indirectly in contact with the coil so as to release heat from the core and the coil to outside. It is described that the heat sink has at least one opening that connects the coil side-facing surface thereof and the surface opposite thereto, and that reduces the heat generated by electromagnetic induction of the heat sink.

<CIT> describes that an inductor comprises a ferromagnetic or ferrimagnetic core with a reluctance gap, a plurality of conductive windings disposed about the ferromagnetic or ferrimagnetic core, and a spacer. It is described that the spacer separates the conductive windings from the ferromagnetic or ferrimagnetic core in the immediate vicinity of the reluctance gap, such that the conductive windings are substantially unaffected by fringing flux from the reluctance gap.

Current solutions rely on a mechanical housing that encapsulates the entire inductor using some form of epoxy compound. This is beneficial over using natural convection because the thermal conductivity of air is approx. whereas cost effective epoxies that are applicable for potting inductors range at 1W/m. k which is effectively over <NUM> times better with regards to thermal performance. This has obvious benefits at first sight but it also has some significant disadvantages that are not necessarily taken into consideration when looking at the process as a whole. Ferrite materials saturate more readily at the higher temperatures from <NUM> to <NUM>, and a <NUM>% reduction in saturation levels is observed even with high grade materials such as 3C96. Complete encapsulation also provides a better path for the ferrite material, and consequently maximum saturation current levels are reduced. Materials in both the potting compound and the mechanical housing, to fully encapsulate the inductor, add extra cost. The price of each individual part is significantly increased due to the extra materials required. Following encapsulation the footprint of the component is increased to allow for potting material and housing. Potentially you have the issue of induced eddy currents in the housing itself, if the case is manufactured too tight or close to the ferrite.

It would be advantageous to have improved inductor coil and method of cooling an inductor coil.

Claim <NUM> defines an inductor coil. Claim <NUM> defines an inductor coil. Claim <NUM> defines a method of cooling an inductor coil. Claim <NUM> defines a method of cooling an inductor coil. The invention and its scope of protection is defined by these independent claims. The following aspects and examples of the disclosure provide the skilled person with examples of how technical subject matters can be combined.

It should be noted that the following described aspects and examples of the invention apply also to the inductor coils and to the methods of cooling inductor coils.

In a first aspect, there is provided an inductor coil as defined on claim <NUM>.

In an example, the first material and/or structural characteristic comprises a magnetic permeability and the second material and/or structural characteristic comprises a magnetic permeability greater than the magnetic permeability of the first part of the heat sink.

In an example, the first material and/or structural characteristic comprises a resistance or resistivity and the second material and/or structural characteristic comprises a resistance or resistivity less than the resistance or resistivity of the first part of the heat sink.

In an example, a circumferential resistance of the first part of the heat sink is greater than a radial resistance of the first part of the heat sink, and the circumferential resistance of the first part of the heat sink is greater than a radial resistance of the second part of the heat sink and is greater than a circumferential resistance of the second part of the heat sink.

In an example, the first material and/or structural characteristic comprises a conductivity or conductance and the second material and/or structural characteristic comprises a conductivity or conductance less than the resistance or resistivity of the first part of the heat sink.

In an example, a circumferential conductance of the first part of the heat sink is less than a radial conductance of the first part of the heat sink, and the circumferential conductance of the first part of the heat sink is less than a radial conductance of the second part of the heat sink and is less than a circumferential conductance of the second part of the heat sink.

In an example, the heat sink is formed from a single piece, wherein the first structural characteristic of the first part is different to the second structural characteristic of the second part.

In an example, the first part of the heat sink has a thickness in an axial direction of the core that is less than a thickness of the second part of the heat sink in the axial direction of the core.

In an example, the first part of the heat sink comprises a plurality of slots or grooves.

In an example, the plurality of slots or grooves extend to the inner surface of the first part of the heat sink.

In an example, the plurality of slots or grooves extend to a boundary between the first part of the heat sink and the second part of the heat sink.

In an example, the plurality of slots or grooves each have a longitudinal axis that intersects with a central axis of the core.

In an example, the second part of the heat sink is configured to connect to a printed circuit board.

In an example, the heat sink comprises at least one third part located on at opposite side of the second part of the heat sink to the first part of the heat sink. The at least one third part of the heat sink is configured to transfer heat away from the second part of the heat sink.

In an example, a third part of the at least one third part the heat sink comprises a finned structured.

In an example, a third part of the at least one third part the heat sink comprises a connection terminal.

In an example, the connection terminal comprises the finned structure.

In an example, the connection terminal comprises a thick copper wire.

In an example, the second part of the heat sink comprises one or more pins configured for mechanical alignment with a printed circuit board and/or for mechanical fixation to the printed circuit board.

In an example, the first part and second part of the heat sink extend substantially in a direction perpendicular to a central axis of the core.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap in the core. The first part of the length of conductor is wound around the core and the gap in the core. An inner part of the conductor of two or more turns of the conductor located around the core is spaced from a central axis of the core by at least one first distance. An inner part of the conductor of one or more turns of the conductor located around the gap in the core is spaced from the central axis by at least one second distance greater than the at least one first distance.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap in the core. A spacer is located in the gap in the core to form a gap around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the first component and an outer surface of the second component that form the core.

In an example, a dimension of the portion of the spacer adjacent to the outer surface of the first component and the outer surface of the second component in the direction of the central axis is greater than a dimension of the gap in the core in the direction of the central axis.

In an example, the outer surface of the portion of the spacer is configured to contact the one or more turns of conductor located around the gap in the core.

In an example, the spacer comprises a non-conductive material.

In an example, the spacer comprises a central hole configured to be located around the central axis.

In a second aspect, there is provided an inductor coil as defined in claim <NUM>.

In an example, the heat sink comprises at least one third part located on an opposite side of the second part of the heat sink to the first part of the heat sink. The at least one third part of the heat sink is configured to transfer heat away from the second part of the heat sink.

In an example, the core of the second component is spaced from the first component to form a gap between the core and the first component. The first part of the length of conductor is wound around the core and the gap between the core and the first component. An inner part of the conductor of two or more turns of the conductor located around the core are spaced from a central axis of the core by at least one first distance. An inner part of the conductor of one or more turns of the conductor located around the gap between the core and the first component is spaced from the central axis by at least one second distance greater than the at least one first distance.

In an example, the core of the second component is spaced from the first component to form a gap between the core and the first component. A spacer is located in the gap between the core and the first component to form a gap around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the core of the second component.

In an example, a dimension of the portion of the spacer adjacent to the outer surface of the core of the second component in the direction of the central axis is greater than a dimension of the gap between the core and the first component in the direction of the central axis.

In an example, the outer surface of the portion of the spacer is configured to contact the one or more turns of conductor located around the gap between the core and the first component.

In a third aspect, there is provided a method of cooling an inductor coil as defined in claim <NUM>.

In an example, the method comprises connecting the second part of the heat sink to a printed circuit board.

In an example, the heat sink comprises at least one third part located on at opposite side of the second part of the heat sink to the first part of the heat sink. The method comprises transferring heat away from the second part of the heat sink via the at least one third part of the heat sink.

In an example, the second part of the heat sink comprises one or more pins. The method comprises mechanically aligning the one or more pins with a printed circuit board and/or mechanically fixing the one or more pins to the printed circuit board.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap in the core. The first part of the length of conductor is wound around the core and the gap in the core. An inner part of the conductor of two or more turns of the conductor located around the core is/are spaced from a central axis of the core by at least one first distance. The method comprises spacing an inner part of the conductor of one or more turns of the conductor located around the gap in the core from the central axis by at least one second distance greater than the at least one first distance.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap in the core. The method comprises locating a spacer in the gap in the core to form a gap around the core, wherein an outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the first component and an outer surface of the second component that form the core.

In an example, the method comprises contacting the outer surface of the portion of the spacer with the one or more turns of conductor located around the gap in the core.

In a fourth aspect, there is provided a method of cooling an inductor coil as defined in claim <NUM>.

In an example, the second part of the heat sink comprises one or more pins and wherein the method comprises mechanically aligning the one or more pins with a printed circuit board and/or mechanically fixing the one or more pins to the printed circuit board.

In an example, the core of the second component is spaced from the first component to form a gap between the core and the first component. The first part of the length of conductor is wound around the core and the gap between the core and the first component. An inner part of the conductor of two or more turns of the conductor located around the core are spaced from a central axis of the core by at least one first distance. The method comprises spacing an inner part of the conductor of one or more turns of the conductor located around the gap between the core and the first component from the central axis by at least one second distance greater than the at least one first distance.

In an example, the core of the second component is spaced from the first component to form a gap between the core and the first component. The method comprises locating a spacer in the gap between the core and the first component to form a gap around the core, wherein an outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the core of the second component.

In an example, the method comprises contacting the outer surface of the portion of the spacer with the one or more turns of conductor located around the gap between the core and the first component.

<FIG> relate to inductor coils and methods of cooling inductor coils.

In an example, an inductor coil comprises a first component <NUM>, a second component <NUM>, a length of conductor <NUM>, and a heat sink <NUM>. The first component is located adjacent to the second component. A core <NUM> is formed from the first component and the second component. A first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor. The heat sink comprises a thermally conductive material. The heat sink comprises a first part <NUM>, <NUM> and a second part. The first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic. An inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor.

Thus, an inductor coil with a core formed from two componenents has a heat sink <NUM> with a first part <NUM> that is acting as a thermal transfer element or material, that thermally conducts heat from the coil <NUM> while reducing eddy currents from being generated. It is to be noted that the first and second parts <NUM>, <NUM> of the heat sink <NUM> can be combined into a single part, but the characteristics and technical benefits of the first thermal transfer element <NUM> remain the same.

In an example, the heat sink <NUM> is formed from a single piece, wherein the first structural characteristic of the first part <NUM> is different to the second structural characteristic of the second part <NUM>.

In an example, the first part <NUM> of the heat sink has a thickness in an axial direction of the core that is less than a thickness of the second part of the heat sink in the axial direction of the core.

In an example, the first part <NUM> of the heat sink comprises a plurality of slots or grooves.

In an example, the second part of the heat sink is configured to connect to a printed circuit board <NUM>.

In an example, the heat sink comprises at least one third part(<NUM>, <NUM> located on at opposite side of the second part of the heat sink to the first part of the heat sink. The at least one third part of the heat sink is configured to transfer heat away from the second part of the heat sink.

In an example, a third part of the at least one third part the heat sink comprises a finned structured <NUM>.

In an example, a third part of the at least one third part the heat sink comprises a connection terminal <NUM>.

In an example, the second part of the heat sink comprises one or more pins configured for mechanical alignment with a printed circuit board <NUM> and/or for mechanical fixation to the printed circuit board.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap <NUM> in the core. The first part of the length of conductor is wound around the core and the gap in the core. An inner part of the conductor of two or more turns of the conductor located around the core are spaced from a central axis of the core by at least one first distance. An inner part of the conductor of one or more turns of the conductor located around the gap in the core is spaced from the central axis by at least one second distance greater than the at least one first distance.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap <NUM> in the core. A spacer <NUM> is located in the gap in the core to form a gap <NUM> around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the first component and an outer surface of the second component that form the core.

In an example, a dimension of the portion of the spacer adjacent to the outer surface of the first component and the outer surface of the second component in the direction of the central axis is greater than a dimension of the gap <NUM> in the core in the direction of the central axis.

In an example, the spacer comprises a central hole <NUM> configured to be located around the central axis.

In an example an inductor coil comprises a first component <NUM>, a second component <NUM>, a length of conductor <NUM>, and a heat sink <NUM>. The first component is located adjacent to the second component. A core <NUM> is formed from the second component. A first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor. The heat sink comprises a thermally conductive material. The heat sink comprises a first part <NUM>, <NUM> and a second part. The first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic. An inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor.

Thus, an inductor coil with a core formed from one componenet has a heat sink <NUM> with a first part <NUM> that is acting as a thermal transfer element or material, that thermally conducts heat from the coil <NUM> while reducing eddy currents from being generated. It is to be noted that the first and second parts <NUM>, <NUM> of the heat sink <NUM> can be combined into a single part, but the characteristics and technical benefits of the first thermal transfer element <NUM> remain the same.

In an example, the heat sink comprises at least one third part <NUM>, <NUM> located on at opposite side of the second part of the heat sink to the first part of the heat sink. The at least one third part of the heat sink is configured to transfer heat away from the second part of the heat sink.

In an example, the core of the second component is spaced from the first component to form a gap <NUM> between the core and the first component. The first part of the length of conductor is wound around the core and the gap between the core and the first component. An inner part of the conductor of two or more turns of the conductor located around the core are spaced from a central axis of the core by at least one first distance. An inner part of the conductor of one or more turns of the conductor located around the gap between the core and the first component is spaced from the central axis by at least one second distance greater than the at least one first distance.

In an example, the core of the second component is spaced from the first component to form a gap <NUM> between the core and the first component. A spacer <NUM> is located in the gap between the core and the first component to form a gap <NUM> around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the core of the second component.

In an example, a dimension of the portion of the spacer adjacent to the outer surface of the core of the second component in the direction of the central axis is greater than a dimension of the gap <NUM> between the core and the first component in the direction of the central axis.

In an example, an inductor coil comprises a first component <NUM>, a second component <NUM>, and a length of conductor <NUM>. The first component is located adjacent to the second component. A core <NUM> is formed from the first component and the second component. A first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor. An exemplar method of cooling the inductor coil comprises:.

In an example, the method comprises connecting the second part of the heat sink to a printed circuit board <NUM>.

In an example, the heat sink comprises at least one third part <NUM>, <NUM> located on at opposite side of the second part of the heat sink to the first part of the heat sink. The method comprises transferring heat away from the second part of the heat sink via the at least one third part of the heat sink.

In an example, the second part of the heat sink comprises one or more pins. The method comprises mechanically aligning the one or more pins with a printed circuit board <NUM> and/or mechanically fixing the one or more pins to the printed circuit board.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap <NUM> in the core. The first part of the length of conductor is wound around the core and the gap in the core. An inner part of the conductor of two or more turns of the conductor located around the core is/are spaced from a central axis of the core by at least one first distance. The method comprises spacing an inner part of the conductor of one or more turns of the conductor located around the gap in the core from the central axis by at least one second distance greater than the at least one first distance.

In an example, a core portion of the first component is spaced from a core portion of the second component to form a gap <NUM> in the core. The method comprises locating a spacer <NUM> in the gap in the core to form a gap <NUM> around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the first component and an outer surface of the second component that form the core.

In an example, an inductor coil comprises a first component <NUM>, a second component <NUM>, and a length of conductor <NUM>. The first component is located adjacent to the second component. A core <NUM> is formed from the second component. A first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor. An exemplar method of cooling the inductor coil comprises:.

In an example, the core of the second component is spaced from the first component to form a gap <NUM> between the core and the first component. The first part of the length of conductor is wound around the core and the gap between the core and the first component. An inner part of the conductor of two or more turns of the conductor located around the core are spaced from a central axis of the core by at least one first distance. The method comprises spacing an inner part of the conductor of one or more turns of the conductor located around the gap between the core and the first component from the central axis by at least one second distance greater than the at least one first distance.

In an example, the core of the second component is spaced from the first component to form a gap <NUM> between the core and the first component. The method comprises locating a spacer <NUM> in the gap between the core and the first component to form a gap <NUM> around the core. An outer surface of a portion of the spacer is located a distance from a central axis of the core that is greater than a distance from the central axis to an outer surface of the core of the second component.

Thus, a new heat sink technology has been developed that in specific embodiments utilizes a optimises the heat transfer from the windings of an inductor coil to a medium such as a printed circuit board or extended heat sink. Furthermore, eddy currents are reduced or inhibited from being generated in the thermally conductive heatsink when exposed to alternating currents associated with typical applications as switch mode converters, and consequently less heat is initially generated that then needs to be transferred by the heat sink.

Specific embodiments are now described, where reference is again made to <FIG>.

<FIG> shows a cross-section through a detailed specific embodiment of an inductor coil, prior to the heat sink being placed in contact with turns of the conductor. A first component part <NUM> of a ferrite material is shown at the top. This has a base portion, and a cylindrical core portion extending downwards. Outer limb portions extend downwards and are spaced from the core portion and within which turns of a conductor <NUM> in the form of a multi-strand wire can be located. Here six turns are shown, but there can be more or less turns than this. A second component part <NUM> again of a ferrite material is shown at the bottom. This again has a base portion, and a cylindrical core portion <NUM> extending upwards, and outer limb portions that extend upwards and spaced from the core portion and within which turns of the conductor <NUM> can be located. The core portions of the of the first component part of the second component part form a core <NUM>. A centre <NUM> in the core is shown between the two component parts, with a centre gap has a dimension <NUM> that can for example be <NUM>, but can be greater than or less than this. As discussed, six turns of the multi-strand wire (or Litz wire) are shown would around the core and the gap in the core, but there can be less than or more than this. In addition to a gap <NUM> being provided between the cores, a gap <NUM> is formed around this central gap and the wire turns do not encroach into this gap <NUM>, and as shown wire turns have been deformed to keep them out of this gap <NUM>. Thus <FIG> illustrates that the cross section for each turn is kept the same, but under compression free space is created to avoid the gap created by the ferrite. The central gap <NUM> is the area in which non-conductive material spacer <NUM> can be placed that forms the gap <NUM>, discussed in more detail below.

<FIG> shows a cross-section through a detailed specific embodiment of an inductor coil, again prior to the heat sink being placed in contact with turns of the conductor. A first component part <NUM> of a ferrite material is shown at the top. This has a base portion. A second component part <NUM> again of a ferrite material shown at the bottom. This again has a base portion, and has a cylindrical core <NUM> extending upwards. Outer limb portions extend upwards and are spaced from the core, within which turns of a conductor <NUM> in the form of a multi-strand wire can be located. The core <NUM> is spaced from the base portion of the first component part to form a gap <NUM> in the core. Six turns of the multi-strand wire are shown wound around the core and the gap in the core, but there can be less than or more than this. In addition to a gap <NUM> being provided between the core and the first component part, a gap <NUM> is formed effectively in the core between the core and the first component part, and the wire turns do not encroach into this gap <NUM>, and as shown wire turns have been deformed to keep them out of this gap <NUM>. Thus again <FIG> illustrates that the cross section for each turn is kept the same, but under compression free space is created to avoid the gap created by the ferrite. The top gap <NUM> is the area in which non-conductive material spacer <NUM> can be placed that forms the gap <NUM>, discussed in more detail below.

<FIG> shows a detailed specific embodiment of an inductor coil, for example as shown in <FIG> that has a central gap <NUM> in the core, the conductor <NUM> is not shown and the heat sink is also not shown. The first component part <NUM> and the second component part <NUM> are shown separated from one another, and the spacer <NUM> is shown that also has a central hole <NUM>. As shown there is a space <NUM> in both the first and second component parts for windings of the conductor <NUM> in the form of a multi-strand wire. Thus this figure illustrates a non-conductive insert (spacer <NUM>) that extends over the pole length. This can be used with and without the hole in the centre <NUM> of the non-conductive part. This can be added during the compression or after the compression of the wires to ensure that the wires do not enter the fringing field after compression.

<FIG> shows a representative cross-section through an inductor coil, showing a through the outer limbs of a first component part12 or a second component part <NUM>, showing top surface of core <NUM> of one of the <NUM> component parts. With a cross-section through the centre of the gap spacer <NUM> the outer limbs of the first or second component part or actually also not actually been cut through but are the top surface. The turns of the wire of the conductor <NUM> can be pushed sideways by the spacer <NUM>, and/ or the turns of the wire can be deformed by the spacer <NUM> in the region of central gap <NUM> to keep the turns of the wire conductor <NUM> out of the fringing field. Thus the ring spacer <NUM> can be used to either compress the conductive wire <NUM> or to allow the bundle or strand to jump over the space containing the fringing field, and the wire could form a bump <NUM> outside of the core shape where space <NUM> may be free for the wire to enter. Thus the spacer <NUM> by keeping the terms of the wire conductor out of the fringing field, produces heat production, improves thermal stability, and less heat is generated that has to be transferred by the heat sink.

<FIG> is a representation of a horizontal cross section through an inductor coil, with a heat sink <NUM>. The heatsink has a first part <NUM> that has a series of grooves or slots and this first part is in contact and thermally bonded with the wire turnings and is in contact with a second part of the heat sink, that is itself in contact with the ferrite material of the first component <NUM> and/or the second component <NUM>. The first part <NUM> of the heat sink <NUM> can be considered to be an eddy heat sink, in that the slots or grooves reduce the volume of magnetic permeable material adjacent to the wire turnings, and the eddy reduction heatsink <NUM> reduces eddy current flow within the thermally conductive heatsink, and therefore less heat is generated.

<FIG> is a representation of a horizontal cross section through an inductor coil, with a heat sink <NUM>. The heatsink has a first part <NUM> that is in contact and thermally bonded with the wire turnings and is in contact with a second part of the heat sink, that is itself in contact with the ferrite material of the first component <NUM> and/or the second component <NUM>. The first part <NUM> of the heat sink <NUM> is thinner than the second part of the heat sink, and can again be considered to be an eddy heat sink, in that being thin the volume of magnetic permeable material adjacent to the wire turnings is reduced, and the eddy reduction heatsink <NUM> reduces eddy current flow within the thermally conductive heatsink, and therefore less heat is generated. It is to be noted that the first part of the heat sink <NUM> described with respect to <FIG> that has grooves and slots can also be the heat sink <NUM> that is thinner than the second part of the heat sink as described with respect to <FIG>. Thus in <FIG> the heatsink touches the ferrite material but uses a thermally conductive pad or material to provide a thermal conductive path but reducing eddy current generation by creating a low magnetics permeable space, and in this embodiment the second part of the heat sink is shown in contact with a printed circuit board (PCB) <NUM>.

<FIG> is an illustration of an inductor coil and heatsink of the same nature as shown in <FIG>, but with the option of the heatsink having a third part <NUM> for improved heat transmission to ambient via the screw terminals on the heatsink or press fit of the pins or via a finned structure for heat transmission to ambient.

<FIG> is an illustration of an inductor coil and heatsink of the same nature as shown in <FIG> (and is of a form as shown in <FIG>), but with the embodiment of the eddy space as a combinational heat reduction part and an improved thermal path from the novel heatsink solution. Here the third part of the heat sink is in the form of a connection terminal <NUM> that is a thick copper wire, and that helps to transfer heat away from the inductor coil.

<FIG> is an illustration of how screw terminals from heatsink base can be used to mount the inductor coil and heat sink to a printed circuit board in which the thermal path is transferred from the copper on the printed circuit board to mounting holes to a mechanical enclosure. In <FIG> "A" represents how PCB mounting holes can be utilised, where copper is connected to a ground plane and inductor coil heatsink so that the thermal path from the copper to the mechanical housing is improved, and where "B" represents holes for screwing the inductor coil base and heatsink to the PCB for an additional thermal path from the inductor coil, where copper resist can be removed to improve the heat transfer to the printed circuit board.

<FIG> shows an inductor coil comprising a first part <NUM> and second part <NUM>, which are combined forming a magnetic flux cage with a core <NUM> and a length of conductor <NUM> forming a coil and a heat sink, or in other words heat transfer element <NUM>, connected at least thermally to the winding of a length of conductor <NUM> on a part of the conductor's <NUM> outer surface. The heat transfer element comprises a heat transmitting area <NUM> and a heat sink area <NUM> and the energy is transmitted from heat transmitting area <NUM> to the heat sink area <NUM>. The heat sink area <NUM> may be a part of the element <NUM> designed to work as a cooling body. The heat sink are may also be a mounting plate, which is designed to create a good thermal contact to a heat sink. The material of the heat transfer element or heat sink element <NUM> may be aluminum. The heat transmitting area is in detail designed to transmit heat preferably in a radial direction away from the coil conductor <NUM> by modifications of the material structure on a sub millimeter scale. The modifications in the heat transmitting area <NUM> may be thin slots or laminations, which locally comprise thermally conductive layers which are extended in a radial direction but less extended in a circumferential direction related to the central axis of the core <NUM>. The heat sink area <NUM> of the element <NUM> may be structured or coated in order to improve head transfer to the environment or to a cooling device. With the help of this arrangement the heat which is created in the length of conductor <NUM> is at least partially transferred through the heat transfer area of element <NUM> and transmitted to the heat sink area <NUM>.

<FIG> shows an embodiment without a magnetic flux cage. Then the magnetic field is creating magnetic fields which are even more penetrating the heat transfer element. These magnetic fields would create strong heat production based on eddy current effects in case of high alternating current frequencies in the heat transfer element if this element would have a high electrical conductivity in the heat transmitting area <NUM>. Accordingly, the eddy current power density is reduced by use of an anisotropic or reduced electrical conductivity in the heat transmitting area, partial volume <NUM>, which is close to the windings of the coil <NUM>.

<FIG> shows a similar embodiment without heat transfer area <NUM>. Here the heat is transferred to an external heat sink, which is mounted thermally conductive to the heat transfer element <NUM>. The material <NUM> may be a metal alloy. The heat transfer element <NUM> may comprise two locally different chemical element mixtures in the alloy in order to reduce electrical conductivity in the heat transfer area <NUM> compared to the conductivity in the heat sink area <NUM> or <NUM> (see <FIG> as well). In many cases the electrical and thermal conductivity of the material <NUM> behave similarly, then thermal conductivity is high when electrical conductivity is low.

<FIG> shows an embodiment with a heat transfer element <NUM> between the heat transfer or heat sink element <NUM> and the coil conductor <NUM>. The material of the heat transfer element <NUM> is different from the material <NUM> of the heat sink element <NUM>. The heat transfer element <NUM> may be made from heat transfer material, which has a high thermal conductivity compared with other polymers but a very low electrical conductivity like an insulation material. The benefit of this embodiment is that the heat which is produced in the high power coil <NUM> can be transmitted through the transfer element <NUM> to the transfer and heat sink element <NUM> but only little eddy current losses are created in the transfer element <NUM> due to its low electrical conductivity. Both the thermal and the electrical conductivity of the material <NUM> may be high and nevertheless the eddy current losses will be low. The same kind of heat transfer element <NUM> can the heat transfer area <NUM> in embodiments which are shown in <FIG>, <FIG>. The preferred heat transfer material is thermally conductive but electrically insulating material, which may consist of a silicone type material like SILPAD by Henkel material or other polymers or mixtures from polymers with particles.

<FIG> shows an example with a regular winding, which has no freedom of the eddy current creating space around the gap <NUM>. The cross-sectional view AB shows how the thermal contact is made between transmitting element <NUM> and coil conductor <NUM> and heat sink element <NUM>.

<FIG> shows views of an exemplar heatsink. This heatsink is made from a single piece of extruded aluminium. Features on the first part and second part, of the single piece, have differences in structural characteristics as discussed above. The slots within the aluminium change the average electrical resistance of the volume of material by breaking up the circulating eddy currents. The second part, which is away from the current field, can be a solid structure as eddy losses here are low and optimal thermal transfer can be achieved. Slots within the aluminium will be filled with thermal epoxy, this thermal epoxy will also bridge any gap between the first part with slots and the coil itself as thermal epoxy is <NUM> times more effective than air in most cases. Mounting techniques can consist of thermal transfer through PCB to case through thermal vias and mounting holes, removing and solder resist transfer from aluminium to copper and thermal via and PCB mounting holes to transfer to case. Other methods such as PCB cut-outs to allow the aluminium heatsink to pass through the PCB to mount directly on the casing or larger heatsink that is also providing heatsinking for any switching MOSFETS or power electronics.

In one example the thermal conductivity of the heat transmitting area <NUM> is providing an anisotropic thermal conductivity in a sub millimeter scale. Anisotropic means that the thermal conductivity is high due to the local structure and local material properties but the thermal conductivity is low at least in the circumferential direction according to the central axis of core <NUM> or in other words the thermal conductivity in the heat transfer region is low more or less tangential to the surface of the coil <NUM> but high in the radial direction. The low tangential thermal conductivity is achieved by a selection of radial laminate structure with laminated thin layers of conductive material with radial plane direction and little tangential thickness or small slots in radial direction which are filled with air or polymer or oil. The majority of the heat transfer element <NUM> is a good thermal conductor with an isotropic thermal conductivity.

In one example the electrical conductivity of the heat transmitting area <NUM> is providing an anisotropic electrical conductivity in a sub millimeter scale. Anisotropic means that the electrical conductivity is high due to the local structure and local material properties but the electrical conductivity is low at least in the circumferential direction according to the central axis of core <NUM> or in other words the electrical conductivity in the heat transfer region is low more or less tangential to the surface of the coil <NUM> but high in the more or less radial direction. The low tangential electrical conductivity is achieved by a selection of radial laminate structure with laminated thin layers of conductive material with radial plane direction and little tangential thickness or small slots in radial direction which are filled with air or polymer or oil. The majority of the heat transfer element <NUM> is a good electrical conductor with an isotropic electrical conductivity. The material of Element <NUM> may be an aluminum alloy.

Reference is made above to Eddy current generation, with the following providing some relevant details.

The formula for eddy losses is a function of; <MAT>.

Where, ρ is the resistivity of the material, B is magnetic field strength, d is thickness of material, and f is frequency.

With respect to the inductor coil and heat sink described above, f the frequency can be considered to be constant in all innovation applications. However, B the magnetic field, does change between <NUM> and <NUM>. However, due to the requirement to have thermal transfer between <NUM> and <NUM> of the heat sink <NUM> a change in the thickness d or ρ is provided to achieve this. Regarding the resistivity ρi of the material. If the first part <NUM> and second part <NUM> of the heat sink <NUM> are made from extruded aluminum, the thickness d can be changed as the resistivity of the aluminum will remain constant if both parts are made from the same material. However, by reducing the d term between the parts, you are introducing a medium of higher electrical resistance in between to break down the eddy fields.

This holds true for laminate or slotted aluminum as you are adding air (potentially filled with thermal epoxy) or Baclac for gluing laminate which both have higher electrical resistance.

Adding a thermal SIL-pad add a layer of high electrical resistance thermal transfer layer to the aluminum. To add enough distance to reduce the B field sufficiently the thickness of the SIL-Pad would need to be large and fairly poor for thermal transfer but could be an embodiment of use.

Thus, an inductor coil and heatsink have been developed where a heatsink of thermally conductive material is connected to a coil of a plurality of turns of electrically conductive material of the inductor. The heatsink is connected to the coil via a thermally conductive path that reduces eddy field generation through a difference in structure and/or material within the field generating area.

A reduction in volume can for example be achieved via a thermal conductive pad, where the thickness of the pad creates a thermal path to the heatsink but introduces a reduced volume.

A reduction in volume of material can be achieved alternatively or additionally through removal of material in slots or grooves that reduces circulating eddy currents.

Furthermore, the heatsink can have screw terminals for mechanical fixing, and pins for mechanical alignment and mechanical fixing to a medium such as a printed circuit board. The screw terminals can screw into an a heatsink with fin features, in which heat transfer to ambient is improved.

Additionally, it is to be noted that inductor coils can be provided with a gap in the core, either centrally between to ferrite components or next to one of the ferrite components. The gap can be important in inductor design, because it can be used with respect to the control of magnetic resistance in magnetic circuit. However, now eddy currents in the windings of the coil are prevented because the wire is kept away from this central gap, via a nonconductive spacer placed in the gap that is wider than the core. The nonconductive spacer helps to keep the conductor out of the eddy current space, and reduces heat generation.

The following relates to examples not covered by the appended claims, that provide specific details on a number of possible arrangements of the inductor coils, and specific details on a number of possible ways of cooling the inductor coils.

Claim 1:
An inductor coil, comprising:
- a first component (<NUM>);
- a second component (<NUM>);
- a length of conductor (<NUM>);
- a heat sink (<NUM>);
wherein, the first component is located adjacent to the second component;
wherein, a core (<NUM>) is formed from cylindrical portions of the first component and the second component;
wherein, a first part of the length of conductor is wound around at least the core to form a plurality of turns of conductor;
wherein, the heat sink comprises a thermally conductive material;
wherein, the heat sink comprises a first part (<NUM>, <NUM>) and a second part;
wherein, the first part of the heat sink has a first material and/or structural characteristic and the second part of the heat sink has a second material and/or structural characteristic different to the first material and/or structural characteristic; and
wherein, an inner surface of the first part of the heat sink is in contact with an outer surface of a part of the plurality of turns of conductor;
wherein the first material and/or structural characteristic comprises a resistance or resistivity and the second material and/or structural characteristic comprises a resistance or resistivity less than the resistance or resistivity of the first part of the heat sink; and
characterized in that a circumferential resistance of the first part of the heat sink is greater than a radial resistance of the first part of the heat sink, and wherein the circumferential resistance of the first part of the heat sink is greater than a radial resistance of the second part of the heat sink and is greater than a circumferential resistance of the second part of the heat sink.