Patent Application
20200258671
The inventive subject matter relates to electric circuit components and, more particularly, to inductors.
Wide bandgap power semiconductors have enabled high frequency switching operations of power electronic devices. These high switching frequencies can create high frequency ripple currents that need to be controlled (minimized, attenuated, reduced). Power inductors are frequently used to reduce these ripple currents. One challenge frequently encountered by high-frequency filter inductors with high power ratings is high losses. As a result, the core and winding temperatures can be very high.
A very common inductor topology is a toroid core with evenly distributed winding turns. The core is usually made of powdered materials with distributed gaps to store energy. Other magnetic materials and air gaps can also be used. The conductor can be round wires or Litz wires. Recently, vertical winding using flat wire has been used to reduce winding temperature, reduce skin effect, reduce turn-to-turn stray capacitance, and improve electromagnetic compatibility. But the core temperature can still be high when using such inductors in high-frequency, high-power applications.
There are several solutions to reduce core temperature. One solution is to use larger cores to reduce magnetic flux density, but this can increase inductor cost. A second solution is to use low-loss powder cores, but these cores often have low saturation flux density and low DC bias performance and tend to be more expensive, so the result again can be a larger and more expensive core. A third solution is the use of advanced cooling configurations, but this solution may require more cooling power and cooling space.
Some embodiments of the inventive subject matter provide an inductor including a plurality of stacked core parts having aligned central openings, at least one spacer separating the core parts from one another, a winding comprising a plurality of turns wound around the stack core parts through central openings of the core parts. In some embodiments, the at least one spacer may include respective groups of spacers disposed between respective pairs of the core parts. In some embodiments, the spacers may be disc-shaped. In further embodiments, the at least one spacer may include a plurality of spacers disposed between first and second ones of the core parts and radially distributed in a circular pattern aligned with the first and second core parts.
In some embodiments, the inductor may further include a plug spacer disposed between a major surface of one of the core parts and the winding and configured to deflect an air flow through the central openings of the core parts. The plug spacer may include a disc having a plurality of slots therein that receive respective turns of the winding.
In further embodiments, the at least one spacer may include a plurality of spacers, each of which includes a first portion disposed in a gap between adjacent ones of core parts and a second portion extending from the first portion and disposed between adjacent turns of the winding. The spacers may include a thermally conductive and electrically insulating material. Each spacer may further include a third portion extending from the first portion and having at least a portion disposed in central openings of the adjacent core parts.
Some embodiments provide an inductor including a first core part, a second core part having a central opening aligned with a central opening of the first core part, a winding wound around the first and second core parts through the central openings thereof, and a plurality of spacers disposed between the first and second core parts and radially distributed in a circular pattern aligned with the first and second core parts. The spacers may be disposed at openings between adjacent turns of the windings. Each of the spacers may include a portion that extends between adjacent turns of the winding.
Still further embodiments provide an inductor including a first core part, a second core part having a central opening aligned with a central opening of the first core part, a winding wound around the first and second core parts and through the central openings thereof, a plurality of spacers disposed between the first and second core parts, and a plug spacer disposed between a major surface of the first core part and the winding and configured to deflect an air flow through the central openings of the first and second core parts. The plug spacer may include a disc having a plurality of slots therein that receive respective turns of the winding.
Specific exemplary embodiments of the inventive subject matter now will be described with reference to the accompanying drawings. This inventive subject matter may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. In the drawings, like numbers refer to like items. It will be understood that when an item is referred to as being “connected” or “coupled” to another item, it can be directly connected or coupled to the other item or intervening items may be present. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, items, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, items, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In some embodiments, an inductor is designed with concentric toroidal core parts stacking together having gaps between each other supported by smaller spacers, and with vertical winding using flat conducting strip disposed in a helical coil configuration of circular shape. The gaps between toroidal magnetics core parts provides additional heat transfer areas and cooling channels that can substantially reduce the core temperature especially for high-frequency high-power applications. Some embodiments provide cooling configurations that can reduce both winding and core temperature. It will be appreciated that such advantages may also be achieved using core parts that have other shapes, such as rectangular or elliptical core parts with central openings or windows through which windings pass.
Some embodiments of the inventive concept can reduce the core temperature without increasing the core size, cost, and may require much less cooling power as compared to similar designs. This can be done by dividing the core into two or more toroidal parts in parallel, with spacers in between the toroidal parts.
The core parts 120 can be made of powder materials with distributed gaps to control the magnetic permeability. They can also be made of other materials like ferrites, or amorphous materials with discrete gaps (normal to the circumferential direction to control the magnetic permeability), or next generation materials like nanocrystalline magnetics with tunable permeability. Spacers 130 can be made of any material, since they are not directly in the magnetic flux path. The spacers 130 can also be made of a dielectric non-magnetic material with a relative permeability close to that of air, to concentrate the magnetic flux in the core and minimize stray and/or leakage flux and minimize additional losses in the spacers due to eddy currents and core losses. The spacers 130 are shown as small round discs, but the spacers 130 may also be larger and non-circular with a perimeter ridge or fin and made of a high thermal conductivity material to increase the heat transfer area. The winding 110 can be made of copper, aluminum, or other conductors, which may have various different shapes, such as round wires, flat (ribbon-like) wires, Litz wires, etc. It can have one turn, and as many turns as allowed by the core window size. The turns of the winding 110 are uniformly distributed circumferentially around the toroid shaped core parts 120. With no discrete gap in the core, the magnetic flux is confined within the core. As a result, the inductor has minimal stray flux. The winding 110 has little parasitic capacitance. It also has large heat transfer area and fin-type configuration, which reduces winding temperature and allows high current-density designs. Although toroidal core parts 120 are shown, it will be appreciated that some embodiments may use core parts with other shapes, such as rectangular or elliptical core parts with similar core windows through which windings may pass.
Such a design can be suitable for both natural convection and forced convection cooling conditions. Natural convection cooling can be used for designs which have relatively low heat losses. For this case, the inductor 100 can be positioned either horizontally or vertically or with any angle in between, depending on the loss distribution between the winding and the core parts. For example, if the winding loss is the primary loss, then a horizontal positioning (axis of winding 110 oriented upward) can be used; if the core loss is high, then a vertical positioning (axis of winding 110 oriented sideways) can be used.
Forced convection cooling can be used for designs with relatively high heat losses. Fans can be used to blow air toward the inductor. This inductor design can accommodate multiple cooling scenarios. A few of the scenarios will be described here with reference to
In a first scenario, the air flow direction is parallel to toroidal core parts 220. Spacers between the toroidal core parts 220 should be small to reduce or minimize blockage of air flow. The winding 210 with flat wire creates inlet and outlet passages for cooling air to flow through the airgaps 250 between the toroidal core parts 220 and cool the core. The cooling air enters the air gaps 250 via the openings between turns of the winding 210 on the upwind side of the winding 210, and then exits the air gaps 250 through openings in the winding 210 around the toroidal core parts 220. It may be desirable to duct the air through the air gaps 250 and make it exit at a leeward side of the inductor 200. Flow shields 240 can be placed at the sides of the toroidal core parts 220, as shown. This shields 240 can be, for example, tapes that block the flow path; they can also be made of structurally strong materials which not only block the flow path, but also provide mechanical support. As shown in
According to embodiments illustrates in
The drawings and specification, there have been disclosed exemplary embodiments of the inventive subject matter. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter being defined by the following claims.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/803,069 entitled “High-Frequency High-Power Inductors with Low-Temperature Winding and Cores,” filed Feb. 9, 2019 and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62803069 | Feb 2019 | US |
