Planar magnetics with integrated cooling

Details Planar magnetics with integrated cooling Planar magnetics with integrated cooling

1999-11-16

2001-08-21

Gellner, Michael L. (Department: 2832)

Inductor devices

Coil or coil turn supports or spacers

Printed circuit-type coil

C336S059000, C336S060000

Reexamination Certificate

active

06278353

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to planar magnetic devices and, more particularly, to planar magnetic devices having integrated cooling.
BACKGROUND OF THE INVENTION
Traditionally, magnetic devices have been fabricated by wrapping a conductor (e.g., a wire) around a core material (e.g., ferrite) that has a relatively high magnetic permeability. Recently, with the miniaturization of many electrical products, the need for compact magnetic devices has arisen. One specific compact magnetic device is a planar magnetic (PM) transformer. The PM transformer uses interconnected planar layers of electrical conductors, rather than relatively bulky wire, disposed around magnetic core material to create primary and secondary windings. PM transformers are typically used in applications such as switching power supplies that are commonly found in many consumer and industrial products.
As is the case in many electrical applications, power dissipation that generates heat in the windings and the core is a consideration when using PM devices. Excessive heat caused by such power dissipation can damage the PM device itself as well as other components or circuitry located proximate thereto. This heat is typically dissipated through the use of a heat sink attached to the outside of the PM transformer. PM transformers are advantageous in that they provide a relatively large and planar surface area to which a heat sink may be fastened. However, even if a PM transformer is fitted with the best heat sink available, the PM transformer will still generate heat that cannot be dissipated without excessive internal heating of the PM transformer because the heat sink can only reduce the external surface temperatures of the PM transformer. Accordingly, the current, and therefore the power, that may be handled by a given PM transformer having a heat sink will be reduced from the power that the same PM transformer could handle given a more effective technique of extracting heat from the device.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a planar magnetic device includes a planar conductive winding and a planar cooling element separate from the planar conductive winding having a passage therethrough to accommodate a flow of a coolant, the planar cooling element being disposed adjacent the planar conductive winding.
The planar cooling element includes first and second cooling layers wherein one of the cooling layers includes a relieved portion having an outer periphery and forming a channel that is capable of accommodating the coolant. The planar cooling element may further include a third cooling layer having an aperture therein, the third cooling layer being disposed between the first and second cooling layers, wherein the aperture has an outer periphery substantially coincident with the outer periphery of the relieved portion.
The first and second cooling layers may each include relieved portions having coincident outer peripheries that form the channel that is capable of accommodating the coolant.
The planar conductive winding has a first footprint and the planar cooling element has a second footprint and wherein the second footprint substantially includes the first footprint. The planar conductive winding and the planar cooling element are fabricated of copper and may have a dielectric insulator disposed between the planar conductive winding and the planar cooling element. The dielectric insulator may be polyimide, aramid or ceramic.
The first and second cooling layers may be bonded together by a diffusion bonding process or by a brazing process or by adhesive. Alternatively, the first and second cooling layers may be clamped together.
According to a further aspect of the present invention, a planar cooling device for use in a planar transformer includes first and second cooling layers wherein one of the first and second cooling layers includes a relieved portion having an outer periphery and forming a channel that is capable of accommodating a coolant.


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Prior Art Multisource Technology Corporation Brochure, p. 2, Feb. 1, 1992.
Ben-Yaakov, The Benefits of Planar Magnetics in HF Power Conversion, pp. 1-7, 1996.

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