Patent Description:
Wireless power transfer is used in a variety of different applications, including battery charging for portable electronic devices, such as cell phones and handheld appliance (e.g., electric shavers and toothbrushes), and for higher-power applications, such as vehicle charging. Wireless power transfer techniques have also been employed to provide power to computing devices, such as servers.

<FIG> illustrates a DC/DC converter arrangement commonly used in conventional wireless power transfer systems. The system includes a transmitter circuit <NUM> configured to be coupled to a DC power source. The transmitter circuit <NUM> is a converter circuit including transistors Q1, Q2 and an output network including a capacitor Cr and inductors Lr, Lp. The transmitter circuit <NUM> is coupled to a primary winding of a transformer <NUM>. A receiver circuit <NUM> is coupled to a secondary winding of the transformer <NUM> and includes another converter circuit including a rectifier comprising diodes D1, D2, which develops an output voltage Vo across and output capacitor Cf. <FIG> illustrates a conventional split core arrangement used for the transformer <NUM>, including first and second separable coil assemblies 20a, 20b, including E-shaped magnetic cores 22a, 22b having first and second windings 24a, 24b on middle legs thereof. When providing wireless power transfer, the coil assemblies 20a, 20b are brought in close proximity to facilitate flux transfer between the cores 22a, 22b. Generally, efficiency of power transfer is dependent upon a distance d between the cores 22a, 22b.

<CIT> discloses an inductive charging coupler for use in an inductive charging system comprising a charge port into which the coupler is inserted. The charging coupler comprises a housing, and a magnetic core disposed in the housing. A primary winding is disposed around the magnetic core. A current conductor is coupled to the primary winding for coupling current thereto. The magnetic core has plastic-ferrite covers disposed on opposite sides thereof. The plastic-ferrite covers are typically bonded to exterior flat surfaces of the magnetic core. The plastic-ferrite covers protect the ferrite core while preserving the magnetic properties of the coupler when it is inserted in the charge port. The plastic-ferrite material exhibits both plastic and ferrite properties and covers and protects the magnetic core in the coupler.

<CIT> discloses a magnetic field transmitter which is positioned on a first side of a barrier and a magnetic field receiver which is positioned on a second side of the barrier opposite the first side comprises the steps of disposing at least one flux flow member in or adjacent the barrier at least partially between the transmitter and the receiver. The flux flow member comprises a magnetic permeability different from the magnetic permeability of the barrier.

<CIT> discloses an inductive coupling permiting bi-directional data and power to be transferred through the skin of an aircraft thereby avoiding pin connectors. The coupling comprises a sending unit which is detachably mounted to the skin exterior, and the pick-up unit is located on the interior skin surface in alignment with the sending unit.

<CIT> discloses a coil unit for the inductive transfer of electrical energy, comprising a coil and a flux guide unit for guiding a magnetic flux generated during operation of the coil, wherein the coil and/or the flux guide unit are surrounded by stray field screening, and a device for the inductive transfer of electrical energy between a fixed primary coil unit and a secondary coil unit mounted on a movable load. The invention solves the problem of providing a coil unit and a device for the inductive transfer of electrical energy that have a small and weak stray field, do not exceed the desired specifications for the maximum flux density outside the vehicle, and improve the efficiency of inductive energy transfer to the vehicle, comprising a coil unit in which the stray field screening is mounted at a lateral distance from the flux guide unit and the coil.

The present invention provides an apparatus according to claim <NUM>, a system according to claim <NUM> and a method as defined in claim <NUM>. Preferred embodiments are defined in dependent claims. The embodiments and/or examples of the following description which are not covered by the appended claims are considered as not being part of the present invention.

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. 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, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, 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.

Some embodiments of the inventive subject matter arise from a realization that improved performance in wireless power transfer systems may be achieved by using enclosures that are constructed from magnetically permeable materials that facilitate flux linkage between transfer components. In some embodiments, for example, an enclosure may be constructed all or in part from a magnetically permeable material, such as a plastic impregnated with iron particles or other magnetically permeable materials (e.g. dielectromagnetic materials, ferromagnetic composite materials, and the like). In some embodiments, a wall or other component of an enclosure used for wireless power transfer may be constructed from such materials. In further embodiments, such a component may be formed in situ by, for example, installing a magnetically permeable material into the enclosure wall or molding a magnetically permeable material into the enclosure wall to provide an enhanced magnetic flux transmission region. In still further embodiments, such materials may be inserted, molded, or otherwise installed between wireless power transfer coil assemblies to provide flux path enhancement.

<FIG> illustrates some components of a wireless power transfer system according to some embodiments. A coil assembly <NUM> includes a magnetic core <NUM> positioned adjacent a wall 310a of an enclosure <NUM>. A coil <NUM> is positioned on the magnetic core <NUM>. A main flux path <NUM> in the magnetic core <NUM> is associated with a current i in the coil <NUM> and is directed through the wall 310a. The main flux path <NUM> may be, for example, a main path of a flux induced by the current i produced when the coil <NUM> is driven by a wireless power transmitter circuit (e.g., an inverter). In some embodiments, the main flux path <NUM> may be of flux that induces the current i, with the flux being created by a current in a mating coil assembly (not shown) on an opposite side of the enclosure wall 310a.

As shown, the enclosure <NUM> may be constructed of a magnetically permeable material. For example, in some embodiments, substantially all of the enclosure <NUM> may be constructed from such a material. In other embodiments, only a portion of the enclosure <NUM>, such as all or part of the wall 310a, may be constructed of such a material. In some embodiments illustrated in <FIG>, a magnetically permeable material region <NUM> may be embedded in the wall 310a, and the magnetic core <NUM> of the coil assembly <NUM> may be positioned adjacent the magnetically permeable region <NUM>.

In some embodiments, the magnetically permeable material has a magnetic permeability substantially greater than the magnetic permeability of air (or materials of similar permeability) to provide an enhanced flux path through the enclosure wall. Examples of materials that may be used to form a magnetically permeable enclosure and/or region within such an enclosure include, but are not limited to, soft iron, carbonyl iron, iron powder, silicon steel, ferrite ceramic, and vitreous metal. Such materials may be cast, machined, extruded, or otherwise formed and/or bound in a polymer (e.g., plastic) or other supporting matrix. As explained below, these materials may be used to form a component of an enclosure (e.g., a wall) and/or used to form inserts, plugs or other structures that may be embedded in a wall of an enclosure. For ease of explanation, such enhanced permeability materials may be referred to herein as "magnetically permeable.

<FIG> illustrate examples of wireless power transfer applications for the apparatus illustrated in <FIG>. <FIG> illustrates the enclosure <NUM> positioned adjacent a second enclosure <NUM> housing a coil apparatus <NUM> including a magnetic core <NUM> and coil <NUM>, similar to the coil apparatus <NUM> of <FIG>. The housings <NUM>, <NUM> are arranged such that the magnetic cores <NUM>, <NUM> of the respective coil assemblies <NUM>, <NUM> are substantially aligned. Like the wall 310a of the enclosure <NUM>, the confronting wall 510a of the enclosure 510a may be constructed from an enhanced magnetic permeability material to support a main flux path through the walls 310a, 310b. One of the coil assemblies <NUM>, <NUM> may, for example, be coupled to a transmitter circuit, while the other of the coil assemblies may be coupled to a receiver circuit, such that wireless power transfer between the enclosures is provided. <FIG> shows a similar arrangement for the apparatus of <FIG>. In particular, wireless power transfer is provided between first coil assembly <NUM> and a second coil assembly <NUM> (including a core <NUM> and coil <NUM>) using magnetically permeable regions <NUM>, <NUM> embedded in walls 310a, 610a of respective enclosures. It will be understood that other arrangements may be used, e.g., a unit with an enclosure having a magnetically permeable wall as illustrated in <FIG> may be mated with a unit having an enclosure with a magnetically permeable insert or other embedded region as shown in <FIG>.

According to some embodiments, an enclosure with enhanced magnetic permeability may be advantageously used in a wireless power transfer system with an EE-type split transformer arrangement. Referring to <FIG>, a first device <NUM> is configured to wirelessly provide power to a second device <NUM>. The first device <NUM> includes an enclosure <NUM> comprising at least one wall 711a formed of a material having a magnetic permeability greater than the magnetic permeability of air (or materials with comparable permeability, such as plastic or aluminum). A coil assembly <NUM> includes an E-shaped magnetic core <NUM> including first, second and third legs 713a, 713b, 713c. A coil <NUM> is arranged around the center leg 713c. The coil assembly <NUM> is positioned adjacent the wall 711a of the enclosure <NUM> such that ends of the legs 713a, 713b, 713c abut the wall 711a. A transmitter circuit <NUM> is electrically coupled to the coil <NUM> and is configured to generate a current through the coil <NUM>. The transmitter circuit <NUM> may, for example, have a converter circuit topology the same as or similar to that of the transmitter circuit <NUM> of <FIG>. It will be appreciated, however, that the transmitter circuit <NUM> may take any of a number of other forms. It will be appreciated that, in some embodiments, the transmitter circuit <NUM> may be contained by the enclosure <NUM> or may be located external to the enclosure <NUM>.

The second device <NUM> includes an enclosure <NUM> comprising at least one wall 721a formed of a material having a magnetic permeability greater than the magnetic permeability of air (e.g., the same material used in the first enclosure <NUM> a material with similar properties). A second coil assembly <NUM> includes an E-shaped magnetic core <NUM> including first, second and third legs 733a, 733b, 733c. A coil <NUM> is arranged around the center leg 723c. The coil assembly <NUM> is positioned adjacent the wall 721a of the enclosure <NUM> such that ends of the legs 723a, 723b, 723c abut the wall 721a and are aligned with the legs 713a, 713b, 713c of the first coil assembly <NUM>. A receiver circuit <NUM> is coupled to the second coil <NUM>, and provides power received via the coil <NUM> to a load <NUM>. The receiver circuit <NUM> may, for example, have a converter circuit topology the same as or similar to that of the receiver circuit <NUM> of <FIG>. It will be appreciated, however, that the receiver circuit <NUM> may take any of a number of other forms. It will be appreciated that, in some embodiments, the receiver circuit <NUM> may be contained by the enclosure <NUM> or may be located external to the enclosure <NUM>. It will be further understood that the load <NUM> may be contained in the enclosure <NUM> or externally located.

<FIG> illustrates a similar arrangement of first and second devices <NUM>, <NUM>, except that coil assemblies <NUM>, <NUM> are housed in respective enclosures <NUM>, <NUM> that have enhanced magnetic permeability regions embedded in opposing walls 811a, <NUM> between the coil assemblies <NUM>, <NUM>. In particular, the enclosure <NUM> includes first, second and third enhanced permeability regions 811b, 811c, 811d and the second enclosure <NUM> includes first, second, and third enhanced permeability regions 821b, 821c, 821d interposed between opposing legs 713a, 713b, 713c, 721a, 721b, 721c of the cores of the coil assemblies <NUM>, <NUM>. The rest of the enclosure walls, such as intervening regions in the enclosure walls separating the enhanced permeability regions 811b, 811c, 811d, 821b, 821c, 821d, may be formed of a less permeable material, which may reduce flux leakage through adjacent portions of the walls of the enclosures <NUM>, <NUM>.

<FIG> illustrates a graph of simulated coupling coefficient performance as function of enclosure relative permeability for a system using an enclosure wall with enhanced permeability along the lines illustrated in <FIG>. As can be seen, coupling improves as the relatively permeability of the enclosure increases above <NUM> to about <NUM>, peaking at a value of about <NUM>. As the permeability of the enclosure increases, however, the coupling coefficient begins to decline, falling below the coupling coefficient for an air gap when the permeability of the enclosure reaches about <NUM>. It is believe that this degradation in coupling with further increased permeability may be caused by increased flux leakage through portions of the wall of the enclosure lateral to the main flux path. Such flux leakage may be reduced in embodiments along the lines illustrated in <FIG>, due to the presence of relatively low permeability material between the enhanced permeability regions 811a, 811b, 811c, 821a, 821b, 821c.

Enhanced-permeability regions for enclosure walls along the lines discussed above may be formed in any of a number of different ways. For example, such regions may take the form of plugs, inserts, plates, molded regions, and the like embedded in enclosure walls. Such regions may be formed from a variety of materials, including, but not limited to, soft iron, carbonyl iron, iron powder, silicon steel, ferrite ceramic, and vitreous metal. Such materials may include dielectromagnetic materials, such as ferromagnetic composite materials described, for example, in <NPL>). Such materials may be cast, machined, molded, or otherwise formed.

<FIG> illustrate an example of such a region, in particular, an enhanced-permeability insert <NUM> that is configured to be installed in an opening, recess or other similar feature in an enclosure wall <NUM>. As shown, the insert <NUM> may be installed prior to placement of a wireless power transfer coil assembly <NUM>. The insert <NUM> may be held in place using, for example, retaining hardware (e.g., clip, clamp or the like), adhesives, or other fastening techniques and/or may be held in place by hardware that holds the coil assembly <NUM> against the enclosure wall <NUM>.

According to further embodiments, an enhanced-permeability region may be formed in situ using a moldable enhanced-permeability material, such as plastic resin or similar material containing magnetic particles, such as iron powder. As shown in <FIG>, such a material <NUM> may be deposited in a recess <NUM> or similar feature in an enclosure wall <NUM>. The material <NUM> may, for example, be manually distributed or pressed into place by a coil assembly <NUM> to form an enhanced permeability region <NUM>' in the enclosure wall <NUM>.

Still further embodiments may employ such a material in other arrangements. Referring to <FIG>, a coil assembly <NUM> may include a coil <NUM> arranged on a magnetic (e.g., ferrite) core <NUM>. As shown in <FIG>, two such coil assemblies <NUM> may be arranged in an opposed adjacent relationship. Flux linkage between the cores <NUM> may be enhanced by providing a magnetically permeable material <NUM>, such as the dielectromagnetic composite materials described above, between the coil assemblies <NUM>. As shown in <FIG>, such an arrangement may be used for wireless power transfer between first and second devices having respective enclosure walls <NUM>, <NUM>. The magnetically permeable material <NUM> may be, for example, a dielectromagnetic composite resin or gel that is applied in a factory on at an installation site. In some embodiments, the magnetically permeable material <NUM> may be a preformed sheet, disc, gasket or similar structure attached to one of the device and/or inserted between the coil assemblies <NUM> during assembly or installation.

<FIG> illustrate a similar use for a structure including interlocking coil assemblies <NUM>, <NUM>. The coil assemblies <NUM>, <NUM> include interlocking cores <NUM>, <NUM> having respective coils <NUM>, <NUM> arranged thereon. A magnetically permeable material <NUM> along the lines discussed above may be placed or formed between the mated coil assemblies <NUM>, <NUM>. As shown in <FIG>, such an arrangement may be used for wireless power transfer between devices having respective enclosure walls <NUM>, <NUM>.

A flexible or formable flux linking material may also be used to improve flux linkage between the EE-type coil assemblies discussed above with reference to <FIG> and <FIG>. Referring to <FIG>, first and second E-shaped coil assemblies <NUM> may be joined by magnetic material regions <NUM>, which may be fabricated from a formable dielectromagnetic material during factory fabrication or site installation. As shown in <FIG>, such an arrangement may be used for wireless power transfer between first and second devices having respective enclosures <NUM>, <NUM>. As shown in <FIG>, magnetic coil assemblies <NUM> may be arranged in enclosures having magnetically permeable walls <NUM>, <NUM> or walls <NUM>, <NUM> having magnetically permeable regions <NUM>, <NUM> embedded therein. A magnetically permeable material <NUM>, <NUM> may be inserted or formed between the walls <NUM>, <NUM>, <NUM>, <NUM> at the location of the coil assemblies <NUM>. The magnetically permeable material <NUM>, <NUM> may be inserted or formed when the devices are fabricated and/or may be installed when the devices are installed.

The flux enhancement structures described above may be used in a variety of different applications. For example, <FIG> illustrates a server rack architecture wherein a server rack <NUM> includes a wireless power receiver unit <NUM> that provides <NUM> volt power to buses that run vertically in the rack <NUM>. A wireless power transmitter unit <NUM> is configured to mate with the receiver unit <NUM>. Enclosures of the transmitter unit <NUM> and the receiver unit <NUM> may contain complementary coil assemblies along lines discussed above, and the enclosures may incorporate magnetically permeable wall features (e.g., magnetically permeable walls, walls with magnetically permeable subregions, inserts or the like) as described above. For example, as shown in <FIG>, a transmitter unit <NUM>' may include an enclosure <NUM> having multiple coil assemblies 2312a, 2312b, 2312c positioned or otherwise positioned adjacent a wall 2311a formed of a magnetically permeable material and, similarly, a receiver unit <NUM>' may include an enclosure <NUM> having multiple coil assemblies 2322a, 2322b, 2322c positioned adjacent a wall 2321a formed of a similar magnetically permeable material. The multiple coil assemblies may be used to provide a desired power transfer capacity, e.g., the coils may be coupled to paralleled receiver and/or transmitter circuits to provide a desired capacity.

Some embodiments may also use formable magnetically permeable material along the lines discussed above with reference to <FIG>. For example, <FIG> shows a transmitter unit <NUM>" including an enclosure <NUM> containing multiple coil assemblies 2412a, 2412b, 2412c positioned at a wall of the enclosure <NUM>. A receiver unit <NUM>" includes an enclosure <NUM> containing multiple coil assemblies 2422a, 2422b, 2422c positioned at a wall of the enclosure <NUM>. Magnetically permeable material regions <NUM>, e.g., regions formed from formable dielectromagnetic materials, may be disposed between the coil assemblies 2412a, 2412b, 2412c, 2422a, 2422b, 2422c to concentrate flux therebetween. It will be appreciated that the arrangements shown in <FIG> and <FIG> are provide for purposes of illustrations, and that a wide variety of other arrangements of coil assemblies and magnetically permeable features may be used in other embodiments.

Claim 1:
An apparatus comprising:
an enclosure (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to be installed in an equipment rack and comprising a wall (310a, 510a, 610a, 711a, 821a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, 2311a, 2321a, <NUM>);
a coil assembly (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, 2312a, 2312b, 2312c, 2322a, 2322b, 2322c, 2412a, 2412b, 2412c, 2422a, 2422b, 2422c) in the enclosure and comprising a magnetic core (<NUM>, <NUM>, <NUM>, <NUM>) and a coil (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) disposed on the magnetic core, the magnetic core positioned adjacent the wall such that a main flux path (<NUM>) in the magnetic core is through at least one portion of the wall having a magnetic permeability greater than air; and
a wireless power receiver circuit in the enclosure, wherein the wireless power receiver circuit is coupled to the coil and configured to be connected to at least one load (<NUM>) in the equipment rack;
characterized in that
the at least one portion of the wall comprises a region (<NUM>, <NUM>, 811b, 811c, 811d, 821b, 821c, 821d, <NUM>', <NUM>, <NUM>, <NUM>, <NUM>) with a first magnetic permeability embedded in another wall component having a second magnetic permeability less than the first magnetic permeability, and wherein the magnetic core is positioned adjacent the region such that the main flux path is directed through the region.