Patent Application
20160141097
The present disclosure relates generally to wireless power transfer, and more particularly to wireless charging of a rechargeable battery used for powering a portable device.
Wireless charging allows a battery coupled to a portable device to be charged without the use of conventional electrical connectors, which allows a user a more flexible means for recharging a battery. A similar technology uses inductive charging where a primary coil is located in a charging station, typically in a spindle, and a secondary coil is located in the device in which the battery to be charged is located. Inductive charging is considered to be “close coupled” because of the necessity to align the device with the charger, without any freedom to move the device from the charging position or place the device in a different position relative to the charging station.
Wireless charging, which employs magnetic resonance, however, is “loosely coupled” because there is only a general area in which to place a device, rather than a specific position relative to a wireless charger. This allows additional devices to be charged simultaneously by the wireless charger, without particular regard for the positioning of any of the devices so long as they are located within a charging area of the wireless charger. A typical wireless charger includes a charging coil that is wound in a generally planar orientation in a charging surface of the wireless charger. Devices to be used with a wireless charger, or battery packs used to power devices, contain a receiving coil that is also typically planar wound. The charging coil is excited with a charging power signal, which produces a charging field in the vicinity of the charging coil. The charging field is a time varying magnetic field that is coupled to the receiving coil, which is used to produce a direct current (DC) charging current and/or voltage.
However, given that both the charging coil and the receiving coil are typically planar or substantially planar wound coils, the most efficient charging occurs when the planes of the charging and receiving coils are substantially aligned within the charging area. Deviation from being parallel aligned reduces the efficiency of energy transfer from the charging coil to the receiving coil. In some cases when the charging coil and a receiving coil are oriented normal (orthogonal) to each other (i.e. their respective planes are at 90 degrees) the amount of energy transfer can drop to zero. Users of such devices may not have knowledge of the location and orientation of a receiving coil with respect to a given device in which the receiving coil is disposed (or in the battery pack powering the device). This can lead to users placing the device in the charging area of a wireless charger in an orientation that is sub-optimal for charging efficiency, or even resulting in no charging occurring.
Accordingly, there is a need for an arrangement that is orientation-independent to assure efficient charging in a wireless charger for different orientations of a device in a charging area of a wireless charger.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
Embodiments include a charging circuit for receiving a wireless charging signal including a receiving coil having a plurality of windings. The receiving coil is a multi-plane receiving coil having a first planar section and a second planar section that is contiguous with the first planar section and oriented at an angle with respect to the first planar section. Each winding of the plurality of windings has a first portion of the winding in the first planar section and a second portion of the winding in the second planar section. In some embodiments ferromagnetic material is layered with the planar coil, wherein a first section of the ferromagnetic material is layered with the first planar section of the receiving coil and a second section of the ferromagnetic material is layered with the second planar section of the receiving coil.
The charging field of a charging coil induces an alternating current (AC) signal 108 across the terminals of the receiving coil 102. A resonance control circuit 110 assures efficient matching between the receiving coil 102 and an AC to DC circuit 114. The output of the resonance control circuit 110 is a matched AC signal 112. The AC to DC circuit 114 converts the matched AC signal 112 to a DC level 116, which can be either a DC current or a DC voltage. The DC level 116 is unregulated, so its magnitude may drift slowly over time, based on the strength of the charging field that is coupled to the receiving coil 102. The DC level 116 is provided to a charge control circuit 118, which includes a regulator circuit 120 and a controller 122. The regulator circuit 120 can be controlled to output a regulated DC level for charging a rechargeable battery 126. The controller 122 controls the regulator circuit 120 to output a desired DC level. For example, the regulator circuit 120 can regulate current through the battery 126 at a constant level, assuming sufficient electrical energy is received by the receiving coil 102.
In some embodiments the receiving coil 102, resonance control circuit 110, AC to DC circuit 114, and the charge control circuit can be disposed in a portable device that is powered by a detachable battery pack in which the battery 126 is located. A detachable battery pack can be connected to a portable device using a connector 124 (e.g. contacts). In some embodiments the device in which the receiving coil 102, resonance control circuit 110, AC to DC circuit 114, the charge control circuit, and the battery are located is a detachable battery pack.
The receiving coil 208 includes a first planar section 209, here oriented vertically, and a second planar section 210, here oriented horizontally, coplanar with the charging coil 202, forming an “L” shape. The receiving coil 208 includes a plurality of windings (successive loops around a center point) which have a portion of each winding/loop on the first planar section 209 and a portion of the winding/loop on the second planar section 210. Thus, individual winding loops traverse portions of both the first and second planar sections 209, 210 of the receiving coil 208.
The multi-plane receiving coil 208 is disposed in the device 206, and can be, for example, formed using a flexible circuit board that is bent to form the two different planes. In some embodiments the receiving coil 208 can be formed by plating conductor material on the interior surfaces of a polymeric housing of the device 206. The two different planes can thus be oriented at 90 degrees with respect to each other. For example, the first planar section 209 can be located along an inside back surface of the device 206, while the second planar section 210 can be located along the inside of a bottom surface of the device 206. By orienting the receiving coil in multiple planes it can be more effective at receiving energy from the charging coil 202 when the device 206 is placed in the wireless charger in different orientations, and at different locations on top of the charging coil. Thus, there is less variation in energy transfer based on the location of the device 206 on charging coil 202, which can allow additional devices to be placed on the charging coil 202.
When used with a wireless charger having a charging surface with a transmitting charging coil underneath, the ferromagnetic material 308 greatly enhances the ability of the receiving coil structure 300 to receive energy from the charging field in a way that greatly diminishes the dependence on location with respect to the charging coil, as well as orientation. If a device with only a single plane receiving coil is placed on a horizontally oriented charging coil, the receiving coil must also be horizontally oriented, and if the device is located at the periphery of the charging coil, the coupling efficiency is substantially diminished. By using a multi-plane receiving coil, the device in which the receiving coil is located can not only be oriented in multiple orientations, but the location with respect to the charging coil has much less effect on the coupling efficiency between the charging coil and the receiving coil.
A ferromagnetic material layer 416 is placed in intimate proximity with the receiving coil, as indicated by arrow 422, to increase the coupling efficiency between the receiving coil 402 and the charging coil. The ferromagnetic material has a first section 418 that is layered with the first planar section 404 of the receiving coil 402, and a second section 420 that is layered with the second planar portion 406 of the receiving coil 402. While the first and second sections 418, 420 of the ferromagnetic material can be separate, they must be magnetically coupled so as to allow magnetic flux to freely traverse between. Forming the ferromagnetic material 416 as a unitary L-shaped member eliminates the issue of magnetically coupling individual sections, however. In some embodiments, where the receiving coil 402 is formed by metallization on the inside surfaces of a polymeric device housing, a thin dielectric insulator layer may be placed between the receiving coil 402 and the ferromagnetic material 416. In some embodiments the ferromagnetic material can be formed into the polymeric device housing using molding techniques to conform to the shape of the receiving coil. Likewise, in some embodiments, the conductor material forming the receiving coil can be insert molded into the housing material as well, or instead of the ferromagnetic material.
In testing it has been found that when a single plane receiving coil is used, and the device in which the single plane receiving coil is disposed is oriented such that the receiving coil plane is perpendicular to that of the charging surface/charging coil, the coupling efficiency drops to near zero. As the device is tilted from the vertical to the horizontal, the coupling efficiency increase to being close to 100% when the receiving coil and the charging coil planes are parallel and the receiving coil and the charging coil are in close proximity in the center of the charging coil. However, even when horizontally oriented to be in parallel planes, when the device is moved to an edge of the charging coil, the coupling efficiency decreases substantially. When a multi-plane charging coil structure is used, however, the coupling efficiency can be maintained to over 80% at the edges of the charging coil. Furthermore, using only a single plane coil with a ferromagnetic material does not substantially improve coupling when the single plane coil structure is oriented to be anti-parallel to the plane of the charging coil. Hence, a multi-plane coil solves the problem of miss-oriented devices with respect to a charging coil, and when only single charging coil is present, the presence of the ferromagnetic material allows increased coupling in the planar section that is not parallel with the charging coil.
The various embodiments provide the benefit of increasing the coupling efficiency between a charging coil of a wireless charger and a receiving coil in a device to be charged by the wireless charger. By using a multi-plane receiving coil the device can be oriented in multiple orientations with respect to the charging coil without substantially reducing the coupling efficiency. Furthermore, the use of a receiving coil structure in accordance with the various embodiments eliminates the loss of coupling efficiency when positioned near the periphery of the charging coil as occurs with single plane receiving coils.
In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors (or “processing devices”) such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.
Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
