PATENT DOCUMENT

Publication Number: US-11165273-B2
Application Number: US-201916422750-A
Country: US
Kind Code: B2

Title: Wireless charging systems for electronic devices

Abstract:
Embodiments describe a portable electronic device that includes a housing having an interface surface and an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar. The portable electronic device further includes charging circuitry coupled to the inductor coil and configured to operate the inductor coil to wirelessly receive power and wirelessly transmit power, control circuitry coupled to the charging circuitry and configured to instruct the charging circuitry to operate the inductor coil to wirelessly receive power and to wirelessly transmit power, and a device detection coil coupled to the control circuitry and configured to detect the presence of an external device on the charging surface, the device detection coil is configured to operate at a different frequency from the inductor coil.

Claims:
What is claimed is: 
     
       1. A portable electronic device, comprising:
 a housing having an interface surface; 
 an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar; 
 charging circuitry coupled to the inductor coil and configured to operate the inductor coil to wirelessly receive power and wirelessly transmit power; 
 control circuitry coupled to the charging circuitry and configured to instruct the charging circuitry to operate the inductor coil to wirelessly receive power and to wirelessly transmit power; and 
 a device detection coil coupled to the control circuitry and configured to detect a presence of an external device on the interface surface, wherein the device detection coil is configured to operate at a different frequency from the inductor coil and is constructed of a wire having a narrower trace width than the conductive wire of the inductor coil. 
 
     
     
       2. The portable electronic device of  claim 1 , wherein the conductive wire of the inductor coil is formed of a plurality of sub-wires arranged in a single plane. 
     
     
       3. The portable electronic device of  claim 1 , further comprising an electromagnetic shield disposed between the inductor coil and the interface surface and comprising a substrate layer and a conductive layer attached to the substrate layer, the electromagnetic shield being configured to intercept electric field while allowing magnetic flux to pass through. 
     
     
       4. The portable electronic device of  claim 3 , wherein the inductor coil and the device detection coil are attached to the electromagnetic shield. 
     
     
       5. The portable electronic device of  claim 3 , wherein an outer profile of the device detection coil is the same as an outer profile of the electromagnetic shield, and wherein the device detection coil is positioned at an outer perimeter of the electromagnetic shield. 
     
     
       6. The portable electronic device of  claim 1 , wherein the inductor coil has a first outer profile and the device detection coil has a second outer profile different from the inductor coil. 
     
     
       7. The portable electronic device of  claim 1 , wherein the device detection coil is disposed outside of an outer perimeter of the inductor coil. 
     
     
       8. The portable electronic device of  claim 1 , wherein the device detection coil is formed of a patterned conductive trace on a substrate, and the inductor coil is formed of a stranded coil. 
     
     
       9. The portable electronic device of  claim 1 , further comprising a magnetic material disposed between adjacent turns of the plurality of turns of the conductive wire of the inductor coil. 
     
     
       10. The portable electronic device of  claim 9 , wherein the conductive wire of the inductor coil is formed of a plurality of sub-wires arranged in a single plane, and wherein the magnetic material is further disposed between adjacent sub-wires of each turn of conductive wire. 
     
     
       11. A portable electronic device, comprising:
 a housing having an interface surface; 
 an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar; 
 an electromagnetic shield disposed between the inductor coil and the interface surface, the electromagnetic shield comprising a substrate layer and a conductive layer attached to the substrate layer and configured to intercept electric fields while allowing magnetic flux to pass through; 
 an interconnection component comprising a first contact pad and a second contact pad positioned at a coupling end of the interconnection component; the first contact pad configured to couple with the electromagnetic shield, and the second contact pad configured to couple with the inductor coil; and 
 a device detection coil configured to detect the presence of an external device on the interface surface, wherein the device detection coil is configured to operate at a different frequency from the inductor coil and is constructed of a wire having a narrower trace width than the conductive wire of the inductor coil. 
 
     
     
       12. The portable electronic device of  claim 11 , further comprising charging circuitry disposed within the housing and coupled to the inductor coil, wherein the charging circuitry is configured to receive current from the inductor coil. 
     
     
       13. The portable electronic device of  claim 12 , wherein the interconnection component comprises a flexible circuit and is configured to ground the electromagnetic shield and couple the inductor coil to the charging circuitry. 
     
     
       14. The portable electronic device of  claim 11 , wherein the interconnection component is a flexible circuit board. 
     
     
       15. The portable electronic device of  claim 11 , wherein the coupling end is positioned at a center of the inductor coil such that the electromagnetic shield and the inductor coil both terminate at the center of the inductor coil. 
     
     
       16. The portable electronic device of  claim 11 , wherein the conductive wire of the inductor coil comprises a stranded coil, each strand having a cross-sectional profile in the shape of a square, circle, or rectangle. 
     
     
       17. A wireless charging system, comprising:
 a wireless charging device comprising a transmitter coil; and 
 a portable electronic device configured to receive power from the wireless charging device, wherein the portable electronic device comprises:
 a housing having an interface surface; 
 an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar; 
 charging circuitry coupled to the inductor coil and configured to operate the inductor coil to wirelessly receive power and wirelessly transmit power; 
 control circuitry coupled to the charging circuitry and configured to instruct the charging circuitry to operate the inductor coil to wirelessly receive power and to wirelessly transmit power; and 
 a device detection coil coupled to the control circuitry and configured to detect a presence of an external device on the interface surface, wherein the device detection coil is configured to operate at a different frequency from the inductor coil and is constructed of a wire having a narrower trace width than the conductive wire of the inductor coil. 
 
 
     
     
       18. The wireless charging system of  claim 17 , further comprising an electromagnetic shield disposed between the inductor coil and the interface surface and comprising a substrate layer and a conductive layer attached to the substrate layer, the electromagnetic shield being configured to intercept electric field while allowing magnetic flux to pass through.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/676,419, filed on May 25, 2018, U.S. Provisional Patent Application No. 62/720,001, filed on Aug. 20, 2018, and U.S. Provisional Patent Application No. 62/834,323, filed on Apr. 15, 2019, the disclosures of which are hereby incorporated by reference in their entirety and for all purposes. 
    
    
     BACKGROUND 
     Portable electronic devices (e.g., mobile phones, media players, electronic watches, and the like) operate when there is charge stored in their batteries. Some portable electronic devices include a rechargeable battery that can be recharged by coupling the portable electronic device to a power source through a physical connection, such as through a charging cord. Using a charging cord to charge a battery in a portable electronic device, however, requires the portable electronic device to be physically tethered to a power outlet. Additionally, using a charging cord requires the mobile device to have a connector, typically a receptacle connector, configured to mate with a connector, typically a plug connector, of the charging cord. The receptacle connector typically includes a cavity in the portable electronic device that provides an avenue within which dust and moisture can intrude and damage the device. Furthermore, a user of the portable electronic device has to physically connect the charging cable to the receptacle connector in order to charge the battery. 
     To avoid such shortcomings, wireless charging devices have been developed to wirelessly charge portable electronic devices without the need for a charging cord. For example, some portable electronic devices can be recharged by merely resting the device on a charging surface of a wireless charging device. A transmitter coil disposed below the charging surface may produce a time-varying magnetic flux that induces a current in a corresponding receiving coil in the portable electronic device. The induced current can be used by the portable electronic device to charge its internal battery. The receiving coil in the portable electronic device can only receive power from the wireless charging device. 
     SUMMARY 
     Some embodiments of the disclosure provide a portable electronic device that includes a hybrid wireless charging system. The hybrid wireless charging system is configured to not only receive charge from a wireless charging device, but also transmit charge to a secondary electronic device. In some embodiments, the hybrid charging system can include a hybrid receiver/transmitter coil and one or more alignment mechanisms to assist in alignment with the secondary electronic device. By incorporating a hybrid charging system in a portable electronic device, it improves functionality of the electronic device and helps the portable electronic device achieve efficient power transfer with a secondary electronic device. 
     In some embodiments, a portable electronic device includes a housing having an interface surface and an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar. The device can further include charging circuitry coupled to the inductor coil and configured to operate the inductor coil to wirelessly receive power and wirelessly transmit power, control circuitry coupled to the charging circuitry and configured to instruct the charging circuitry to operate the inductor coil to wirelessly receive power and to wirelessly transmit power, and a device detection coil coupled to the control circuitry and configured to detect a presence of an external device on the interface surface, the device detection coil is configured to operate at a different frequency from the inductor coil. 
     The device detection coil can be constructed of a wire having a narrower trace width than the conductive wire used to form the inductor coil. The conductive wire can be formed of a plurality of sub-wires arranged in a single plane. The device can further include an electromagnetic shield disposed between the inductor coil and the interface surface and comprising a substrate layer and a conductive layer attached to the substrate layer, where the electromagnetic shield can be configured to intercept electric field while allowing magnetic flux to pass through. The inductor coil and the device detection coil can be attached to the electromagnetic shield. An outer profile of the device detection coil can be the same as an outer profile of the electromagnetic shield. The device detection coil can be positioned at an outer perimeter of the electromagnetic shield. The inductor coil can have a first outer profile and the device detection coil can have a second outer profile different from the inductor coil. The device detection coil can be disposed outside of an outer perimeter of the inductor coil. The device detection coil can be formed of a patterned conductive trace on a substrate, and the inductor coil can be formed of a stranded coil. The device can further include a magnetic material disposed between adjacent turns of the plurality of turns of the conductive wire. The conductive wire can be formed of a plurality of sub-wires arranged in a single plane, and the magnetic material can be further disposed between adjacent sub-wires of each turn of conductive wire. 
     In certain embodiments, a portable electronic device includes a housing having an interface surface, an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar, and an electromagnetic shield disposed between the inductor coil and the interface surface. The electromagnetic shield can include a substrate layer and a conductive layer attached to the substrate layer and be configured to intercept electric fields while allowing magnetic flux to pass through. The device can further include an interconnection component comprising a first contact pad and a second contact pad positioned at a coupling end of the interconnection component, where the first contact pad can be configured to couple with the electromagnetic shield, and the second contact pad can be configured to couple with the inductor coil. The device can also include a device detection coil configured to detect the presence of an external device on the charging surface, where the device detection coil is configured to operate at a different frequency from the inductor coil. 
     The device can further include charging circuitry disposed within the housing and coupled to the inductor coil, the charging circuitry can be configured to receive current from the inductor coil. The interconnection component can include a flexible circuit and be configured to ground the electromagnetic shield and couple the inductor coil to the charging circuitry. The interconnection component can be a flexible circuit board. The coupling end can be positioned at a center of the inductor coil such that the electromagnetic shield and the inductor coil both terminate at the center of the inductor coil. The conductive wire can be formed of a stranded coil, each strand having a cross-sectional profile in the shape of a square, circle, or rectangle. 
     In some embodiments, a wireless charging system includes a wireless charging device comprising a transmitter coil and a portable electronic device configured to receive power from the wireless charging device. The portable electronic device can include a housing having an interface surface, and an inductor coil disposed within the housing and comprising a conductive wire wound in a plurality of turns about a center point and in increasing radii such that the inductor coil is substantially planar. The device can further include charging circuitry coupled to the inductor coil and configured to operate the inductor coil to wirelessly receive power and wirelessly transmit power, control circuitry coupled to the charging circuitry and configured to instruct the charging circuitry to operate the inductor coil to wirelessly receive power and to wirelessly transmit power, and a device detection coil coupled to the control circuitry and configured to detect a presence of an external device on the interface surface, where the device detection coil is configured to operate at a different frequency from the inductor coil. 
     The system can further include an electromagnetic shield disposed between the inductor coil and the interface surface and comprising a substrate layer and a conductive layer attached to the substrate layer, the electromagnetic shield being configured to intercept electric field while allowing magnetic flux to pass through. The device detection coil can be constructed of a wire having a narrower trace width than the conductive wire used to form the inductor coil. 
     A better understanding of the nature and advantages of embodiments of the present invention may be gained with reference to the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an exemplary portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 2A  is a simplified diagram illustrating electrical interactions experienced by an exemplary hybrid wireless charging system as it is receiving power from a wireless charging device, according to some embodiments of the present disclosure. 
         FIG. 2B  is a simplified diagram illustrating electrical interactions experienced by the exemplary wireless charging system as it is transmitting power to a secondary device, according to some embodiments of the present disclosure. 
         FIG. 2C  is a simplified diagram illustrating electrical interactions experienced by the exemplary wireless charging system as it is transmitting power to a secondary device that is resting on its side, according to some embodiments of the present disclosure. 
         FIG. 3A  is a simplified diagram illustrating an exploded view of a portable electronic device including a hybrid receiver/transmitter coil formed as a flexible printed circuit (FPC) coil, according to some embodiments of the disclosure. 
         FIG. 3B  is a simplified diagram illustrating an exemplary attachment assembly composed of a sheet of single-sided adhesive and double-sided adhesives positioned at edges of a hybrid receiver/transmitter coil in an overlapping arrangement, according to some embodiments of the present disclosure. 
         FIG. 3C  is a simplified diagram illustrating an exemplary attachment assembly where double-sided adhesives are crescent-shaped and do not overlap with edges of the hybrid receiver/transmitter coil, according to some embodiments of the present disclosure. 
         FIGS. 4A-4J  are simplified diagrams illustrating different hybrid receiver/transmitter coil constructions that are suitable for receiving power and transmitting power, according to some embodiments of the present disclosure. 
         FIG. 5  is a simplified cross-sectional view of a portion of a wireless power receiving/transmitting module including a hybrid receiver/transmitter coil formed as a FPC and positioned within a housing of a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 6A  is a simplified diagram illustrating an exemplary hybrid wireless charging system that includes a hybrid receiver/transmitter coil and a device detection coil in an interwound configuration, according to some embodiments of the present disclosure. 
         FIG. 6B  is a simplified diagram illustrating an exemplary hybrid wireless charging system including a device detection coil in an outer-wound configuration, according to some embodiments of the present disclosure. 
         FIG. 6C  is a simplified diagram illustrating an exemplary hybrid wireless charging system including a device detection coil in an inner-wound configuration, according to some embodiments of the present disclosure. 
         FIG. 7  is a simplified diagram illustrating an exploded view of a portable electronic device including a hybrid receiver/transmitter coil formed as a stranded coil, according to some embodiments of the disclosure. 
         FIG. 8A  is a simplified diagram illustrating a top-down view of an electromagnetic shield and a hybrid receiver/transmitter coil, according to some embodiments of the present disclosure. 
         FIG. 8B  is a simplified diagram illustrating a cross-sectional view of a strand of the conductive wire as shown by the cut line illustrated in  FIG. 8A , according to some embodiments of the present disclosure. 
         FIG. 8C  is a simplified diagram illustrating a close-up top-down view of a portion of an electromagnetic shield, according to some embodiments of the present disclosure. 
         FIG. 8D  is a simplified diagram illustrating an exemplary pattern having three transmitter coils, according to some embodiments of the present disclosure. 
         FIG. 8E  is a simplified diagram illustrating an exemplary transmitter coil arrangement configured in a rosette pattern, according to some embodiments of the present disclosure. 
         FIGS. 8F-8H  are simplified diagrams illustrating the different layers of a transmitter coil arrangement configured in a rosette pattern, according to some embodiments of the present disclosure. 
         FIG. 9A  is a simplified diagram illustrating an exploded view of another exemplary wireless power receiving/transmitting module having a stranded hybrid receiver/transmitter coil for a portable electronic device, according to some embodiments of the present disclosure. 
         FIGS. 9B-9C  are simplified diagrams illustrating pads on a coupling end of an interconnection component for a power receiving/transmitting module, according to some embodiments of the present disclosure. 
         FIGS. 10A-10D  are simplified diagrams illustrating different alignment mechanisms for hybrid wireless charging systems, according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosure describe a hybrid wireless charging system for a portable electronic device. The hybrid wireless charging system can include a hybrid receiver/transmitter coil that can be operated to receive power as well as transmit power. For instance, the hybrid receiver/transmitter coil can be coupled to hybrid charging circuitry that can operate the hybrid receiver/transmitter coil to receive power when the portable electronic device is positioned on a charging surface of a wireless charging device. The hybrid charging circuitry can also operate the hybrid receiver/transmitter coil to transmit power when a secondary electronic device is positioned on a charging surface of the portable electronic device. According to some embodiments of the present disclosure, the hybrid receiver/transmitter coil can be designed to be efficient in both receiving power as well as transmitting power, which will be discussed in further detail herein. In some embodiments, the hybrid wireless charging system can further include alignment mechanisms to help align the secondary electronic device to the hybrid receiver/transmitter coil of the portable electronic device. The alignment mechanism can be a passive alignment mechanism, or an active alignment mechanism. 
     Accordingly, the portable electronic device can wirelessly receive power from a wireless charging device, as well as wirelessly transmit power to a secondary electronic device, thereby increasing the functionality and versatility of the portable electronic device. Aspects and features of embodiments of such a portable electronic device are discussed in further detail herein. 
     I. Portable Electronic Device 
     A portable electronic device is an electronic device that can operate without being coupled to a power grid by running on its own locally stored electrical power. The portable electronic device can be specifically designed to perform various functions for a user. In some embodiments, electronic device  100  is a consumer electronic device, such as a smart phone, tablet, laptop, and the like. 
       FIG. 1  is a block diagram illustrating an exemplary portable electronic device  100 , an exemplary power supplying apparatus  119  for coupling with device  100  to charge device  100 , and an exemplary secondary electronic device  124  for receiving power from portable electronic device  100  according to some embodiments of the present disclosure. Device  100  includes a computing system  102  coupled to a memory bank  104 . Computing system  102  can include control circuitry configured to execute instructions stored in memory bank  104  for performing a plurality of functions for operating device  100 . The control circuitry can include one or more suitable computing devices, such as microprocessors, computer processing units (CPUs), graphics processing units (GPUs), field programmable gate arrays (FPGAs), and the like. 
     Computing system  102  can also be coupled to a user interface system  106 , a communication system  108 , and a sensor system  110  for enabling electronic device  100  to perform one or more functions. For instance, user interface system  106  can include a display, speaker, microphone, actuator for enabling haptic feedback, and one or more input devices such as a button, switch, capacitive screen for enabling the display to be touch sensitive, and the like. Communication system  108  can include wireless telecommunication components, Bluetooth components, and/or wireless fidelity (WiFi) components for enabling device  100  to make phone calls, interact with wireless accessories, and access the Internet. Sensor system  110  can include light sensors, accelerometers, gyroscopes, temperature sensors, and any other type of sensor that can measure a parameter of an external entity and/or environment. 
     All of these electrical components require a power source to operate. Accordingly, electronic device  100  also includes a battery  112  for discharging stored energy to power the electrical components of device  100 . To replenish the energy discharged to power the electrical components, electronic device  100  includes a hybrid wireless charging system  118 . Hybrid wireless charging system  118  can include hybrid charging circuitry  114  and hybrid receiver/transmitter coil  116  for receiving power from a wireless charging device  120  coupled to an external power source  122 . Wireless charging device  120  can include a transmitter coil for generating a time-varying magnetic flux capable of generating a corresponding current in hybrid receiver/transmitter coil  116 . The generated current can be utilized by hybrid charging circuitry  114  to charge battery  112 . According to some embodiments of the present disclosure, hybrid wireless charging system  118  can also transmit power to secondary electronic device  124 . Details of such a hybrid wireless charging system is discussed in further detail herein. 
     II. Hybrid Wireless Charging System 
     Embodiments of the disclosure describe a hybrid wireless charging system that can both wirelessly receive power as well as wirelessly transmit power.  FIGS. 2A and 2B  illustrate an exemplary hybrid wireless charging system during wireless power transfer. Specifically,  FIG. 2A  illustrates the electrical interactions experienced by an exemplary hybrid wireless charging system as it is receiving power from a wireless charging device, and  FIG. 2B  illustrates the electrical interactions experienced by the exemplary wireless charging system as it is transmitting power to a secondary device, according to some embodiments of the present disclosure. 
     With reference to  FIG. 2A , a portable electronic device  204  is positioned on a charging surface  212  of a wireless charging device  202 . Portable electronic device  204  can include a hybrid wireless charging system  207  that has a hybrid receiver/transmitter coil  208  and hybrid charging circuitry  205 ; and wireless charging device  202  can include a transmitter coil  206 . Hybrid receiver/transmitter coil  208  can be an inductor coil that can interact with and/or generate time-varying magnetic flux. Portable electronic device  204  can be a consumer electronic device, such as a smart phone, tablet, and the like. Wireless charging device  202  can be any suitable device configured to generate time-varying magnetic field to induce a corresponding current in a receiving device. For instance, wireless charging device  202  can be a wireless charging mat, puck, docking station, and the like. Portable electronic device  204  may rest on the wireless charging device  202  at charging surface  212  to enable power transfer. 
     During wireless power transfer from wireless charging device  202  to portable electronic device  204 , hybrid wireless charging system  207  can operate to receive power from wireless charging device  202 . For instance, hybrid charging circuitry  205  can operate hybrid receiving coil  208  as a receiving coil to receive power by interacting with time-varying magnetic flux  210  generated by transmitter coil  206 . Hybrid charging circuitry  205  can correspond with hybrid charging circuitry  114  in  FIG. 1 . Interaction with time-varying magnetic flux  210  results in an inducement of current in hybrid receiver/transmitter coil  208 , which can be used by hybrid charging circuitry  205  to charge an internal battery of portable electronic device  204 . As shown in  FIG. 2A , portable electronic device  204  can rest on charging surface  212  of wireless charging device  202 . In some embodiments, an interface surface  220  of portable electronic device  204  makes contact with charging surface  212  during wireless power transfer. Thus, portable electronic device  204  can receive power through interface surface  220 . Interface surface  220  can be an external surface of a housing of portable electronic device  204 . 
     According to some embodiments of the present disclosure, hybrid wireless charging system  207  can also operate to transmit power to a secondary device. For instance, with reference to  FIG. 2B , a secondary electronic device  214  can be positioned on a charging surface of portable electronic device  204  to receive charge from portable electronic device  204 . In some embodiments, interface surface  220  is the charging surface upon which secondary electronic device  214  can receive power from portable electronic device  204 . Thus, portable electronic device  204  can receive power as well as transfer power through the same surface, i.e., interface surface  220 . 
     Secondary electronic device  214  can be an electronic device that can operate without being coupled to a power grid by running on its own locally stored electrical power. For instance, secondary electronic device  214  can be an accessory that operates with portable electronic device  204 , such as a smart watch, smart phone, wireless earbuds, a case for the wireless earbuds, and the like, or it can be any other portable electronic device such as a tablet, laptop, and the like. Secondary electronic device  214  can include a secondary receiving coil  216  for receiving power during wireless power transfer. 
     During wireless power transfer from portable electronic device  204  to secondary electronic device  214 , hybrid wireless charging system  207  can operate to transmit power to secondary electronic device  214 . For instance, hybrid charging circuitry  205  can operate hybrid receiving coil  208  as a transmitter coil to generate a time-varying magnetic flux  218  to interact with secondary receiver coil  216 . In some embodiments, hybrid charging circuitry  205  can drive current through hybrid receiver/transmitter coil  208  and cause hybrid receiver/transmitter coil  208  to generate time-varying magnetic flux  218  that can induce a corresponding current in secondary receiver coil  216 . Current induced in secondary receiver coil  216  can be used by secondary electronic device  214  to charge its battery. In some embodiments, hybrid wireless charging system  207  can also include an alignment mechanism to help align secondary receiver coil  216  with hybrid receiver/transmitter coil  208 , as will be discussed further herein. 
     In some embodiments, hybrid wireless charging system  207  can also operate to transmit power to the secondary device even when it is resting on its side. In such instances, horizontal magnetic flux generated by hybrid wireless charging system  207  can be received by the secondary device. For instance, with reference to  FIG. 2C , secondary electronic device  214  can be positioned on its side on the charging surface of portable electronic device  204 . Hybrid receiver/transmitter coil  208  can be configured to generate flux up to a certain distance away from interface surface  220  so that horizontal components of magnetic flux  218  can be received by secondary receiver coil  216 . In some embodiments, secondary receiver coil  216  can be wound around a ferromagnetic structure (not shown) to direct flux through coil  216  to improve power transfer efficiency. 
     Given that hybrid receiver/transmitter coil  208  can operate to receive power as well as transmit power, hybrid charging circuitry  205  can include circuitry suitable for enabling these operations. As an example, hybrid charging circuitry  205  can include power receiving circuitry that can receive induced current from hybrid receiver/transmitter coil  208  and convert the received power (typically alternating current (AC) power) to usable power (e.g., direct current (DC) power). Hybrid charging circuitry can also include power transmitting circuitry that can drive current into hybrid receiver/transmitter coil  208  and cause hybrid receiver/transmitter coil  208  to generate time-varying magnetic flux. In some embodiments, hybrid charging circuitry  205  can also include a switching mechanism for coupling hybrid receiver/transmitter coil  208  to either the power receiving circuitry or the power transmitting circuitry, but not both at the same time, to operate hybrid receiver/transmitter coil  208  accordingly. For instance, hybrid charging circuitry  205  can include a multiplexer for coupling hybrid receiver/transmitter coil  208  to either the power receiving circuitry or the power transmitting circuitry. The switching mechanism can be coupled between hybrid receiver/transmitter coil  208  and both the power receiving circuitry and the power transmitting circuitry. 
     III. Architecture and Construction of Hybrid Wireless Charging Systems 
     The structural construction of a hybrid receiver/transmitter coil can be arranged so that it is substantially effective at both receiving and transmitting power. Furthermore, the assembly of the hybrid receiver/transmitter coil within a portable electronic device can be specifically designed to complement the receiving and transmitting capabilities of the hybrid receiver/transmitter coil. In some embodiments, the hybrid receiver/transmitter coil can be formed in a variety of ways. For instance, the hybrid receiver/transmitter coil can be formed of a conductive winding of material arranged in a plurality of turns wound about a center point and in increasing radii such that the hybrid receiver/transmitter coil is substantially planar. The conductive winding can be formed as a flexible printed circuit (FPC) coil or as a stranded coil, as will be discussed further herein. 
     A. Flexible Printed Circuit Coil 
       FIG. 3A  illustrates an exploded view of a portable electronic device  300  including a hybrid receiver/transmitter coil  305  formed as a FPC coil, according to some embodiments of the disclosure. Portable electronic device  300  can include a top housing  326  and a housing  325  that can mate to define an interior cavity. As shown in  FIG. 3A , portable electronic device  300  can include at least three separate shields: an electromagnetic shield  306 , a ferromagnetic shield  310 , and a thermal shield  315  along with an adhesive component  320  that attaches wireless power receiving/transmitting module  301  to housing  325 . 
     Electromagnetic shield  306  can be positioned in front of hybrid receiver/transmitter coil  305  so that magnetic flux first passes through electromagnetic shield  306  before reaching hybrid receiver/transmitter coil  305  when hybrid receiver/transmitter coil  305  operates as a receiver coil, or so that magnetic flux is directed toward electromagnetic shield  306  when hybrid receiver/transmitter coil  305  operates as a transmitter coil. For instance, electromagnetic shield  306  can be positioned between hybrid receiver/transmitter coil  305  and housing  325 . In some embodiments, electromagnetic shield  306  can be a shielding layer that is substantially transparent to magnetic flux so that a large percentage of magnetic flux can pass through it, but also be substantially opaque to electric field such that electric field generated by hybrid receiver/transmitter coil  305  or a transmitter coil in a wireless charging device during operation is substantially blocked by it. Voltage generated in electromagnetic shield  306  by blocking the electric fields can be discharged to ground. Blocking electric fields mitigates noise stemming from a buildup of voltage on hybrid receiver/transmitter coil  305 . In some embodiments, electromagnetic shield  306  is formed of any material suitable for blocking electric fields while allowing electromagnetic fields to pass through, such as a thin layer of silver. 
     Ferromagnetic shield  310  can be positioned between hybrid receiver/transmitter coil  305  and thermal shield  315 . In some embodiments, ferromagnetic shield  310  acts as a magnetic field shield for redirecting magnetic flux to get higher coupling with a transmitter coil in a wireless charging device, which can result in improved charging efficiency. Ferromagnetic shield  310  can also redirect magnetic flux to prevent stray flux from interfering with sensitive internal components within portable electronic device  300 . 
     Thermal shield  315  can include a graphite or similar layer that provides thermal isolation between wireless power receiving/transmitting module  301  and the battery and other components of portable electronic device  300  in which the wireless power receiving/transmitting module  301  is incorporated. Thermal shield  315  can also include a copper layer that is tied to ground and contributes to the thermal shielding while also capturing stray flux. 
     Adhesive component  320  can be a single sheet of an adhesive material, such as pressure sensitive adhesive (PSA), that attaches wireless power receiving/transmitting module  301  to housing  325 . In some embodiments, wireless power receiving/transmitting module  301  is attached to housing  325  within a cutout area  330  sized and shaped to receive the wireless power receiving/transmitting module  301 , thereby saving space within the electronic device to minimize the thickness of portable electronic device  300 . Instead of being attached to housing  325  with a single sheet of adhesive material, wireless power receiving/transmitting module  301  can be attached to housing  325  with an attachment assembly that is composed of more than one sheet of adhesive material, as discussed herein with respect to  FIGS. 3B and 3C . 
       FIG. 3B  illustrates an exemplary attachment assembly  332  composed of a sheet of single-sided adhesive  336  and double-sided adhesives  334   a  and  334   b  positioned at edges of hybrid receiver/transmitter coil  305  in an overlapping arrangement, according to some embodiments of the present disclosure. Double-sided adhesives  334   a  and  334   b  can be formed of PSA to attach thermal shield  315  to housing  325 . Single-sided adhesive  336  can be attached to housing  325  and act as an anti-splinter film in case of a breakage event. In particular embodiments, single-sided adhesive  336  may not be coupled to portable electronic device  300  so that ferromagnetic shield  310  and hybrid receiver/transmitter coil  305  are decoupled from housing  325 . By decoupling ferromagnetic shield  310  and hybrid receiver/transmitter coil  305  from housing  325 , vibrations caused by time-varying magnetic fields generated during wireless power transfer may not be transferred to housing  325 , thereby minimizing acoustic coupling between ferromagnetic shield  310  and hybrid receiver/transmitter coil  305  from housing  325 . In some embodiments, single-sided adhesive  336  is formed of polyimide. As shown in  FIG. 3B , double-sided adhesives  334   a  and  334   b  can be positioned around the perimeter of hybrid receiver/transmitter coil  305 . In some instances, double-sided adhesives  334   a  and  334   b  can overlap edges of hybrid receiver/transmitter coil  305 , as indicated by the relative position of the dotted profile of hybrid receiver/transmitter coil  305 . 
     Although  FIG. 3B  illustrates attachment assembly  340  as having double-sided adhesives  334   a  and  334   b  positioned around the perimeter of hybrid receiver/transmitter coil  305  in such a way that overlaps with edges of hybrid receiver/transmitter coil  305 , embodiments are not so limited. Other attachment assemblies have double-sided adhesives that do not overlap with edges of hybrid receiver/transmitter coil  305 .  FIG. 3C  illustrates an exemplary attachment assembly  338  where double-sided adhesives  340   a - d  are crescent-shaped and do not overlap with edges of hybrid receiver/transmitter coil  305 , according to some embodiments of the present disclosure. Double-sided adhesives  340   a - d  are shaped as a crescent to conform to the outer profile of hybrid receiver/transmitter coil  305 . Double-sided adhesives  340   a - d  attach ferromagnetic shield  310  to housing  325  without overlapping with hybrid receiver/transmitter coil  305 . In some embodiments, single-sided adhesive  336  can have a shape that corresponds with the shape of hybrid receiver/transmitter coil  305 . For instance, single-sided adhesive  336  can be substantially circular. 
     With reference back to  FIG. 3A , hybrid receiver/transmitter coil  305  can be disposed between electromagnetic shield  306  and ferromagnetic shield  310 . In some embodiments, hybrid receiver/transmitter coil  305  can be operated to generate time-varying magnetic flux to transmit power to a secondary device. The generated time-varying magnetic flux can pass through electromagnetic shield  306  to charge the secondary device but be redirected by ferromagnetic shield  310  to prevent stray magnetic flux from interference with other components in portable electronic device  300 . Hybrid receiver/transmitter coil  305  can also be operated to receive power from time-varying magnetic flux generated by a transmitter coil in a wireless charging device. The time-varying magnetic flux can first pass through electromagnetic shield  306  before exposing on hybrid receiver/transmitter coil  305  and be redirected by ferromagnetic shield  310  to get higher coupling with the transmitter coil. 
       FIGS. 4A-4E  illustrate simplified diagrams of different hybrid receiver/transmitter coil constructions that are suitable for receiving power and transmitting power, according to some embodiments.  FIG. 4A  illustrates an exemplary hybrid receiver/transmitter coil  400  configured as a spirally wound FPC coil, according to some embodiments of the present disclosure. Coil  400  can wind from an inner diameter to an outer diameter in a spiral configuration such that the overall shape is similar to a planar inductor coil that is formed of a plurality of turns of patterned wire on a flexible substrate. A termination end positioned in the inner diameter of coil  400  can be routed to an outer diameter bay way of a conductive trace  402 . Accordingly, charging circuitry, such as hybrid charging circuitry  114  in  FIG. 1 , can couple with coil  400  at one edge location  404  to operate coil  400  to transmit or receive power. 
     The cross-sectional width of the wire used to form coil  400  and the gap between adjacent turns of coil  400  can be specifically tuned to achieve a sufficient degree of efficiency during charging. For instance, each turn of wire in coil  400  can have a cross-section that is a single structure having a certain width and can be separated from adjacent turns by a certain distance. This is better shown in  FIGS. 4G-4H .  FIG. 4G  is a close-up top-down illustration of a portion  460  of coil  400 , according to some embodiments of the present disclosure. As shown, coil  400  can include a plurality of turns including first and second turns  462  and  464  that form part of a spirally wound planar coil that begins from a first termination end  466  and winds outward in a planar configuration until a second termination end (not shown in  FIG. 4G  but can be seen in  FIG. 4A  where the coil ends at the outer perimeter of coil  400 ).  FIG. 4H  is a cross-sectional view of turns  462  and  464  of coil  400 , according to some embodiments of the present disclosure. Each turn can be a single structure with a certain width  468  separated from an adjacent turn by a separation distance  469  that are both tailored to achieve a target direct current resistance (DCR) and alternating current resistance (ACR) that is within design specifications to achieve efficient wireless power transfer. For instance, each turn can have a width  468  between 0.7 to 0.9 mm, particularly approximately 0.8 mm in some embodiments. And, each turn can be separated from adjacent turns by a separation distance  469  of between 0.25 to 0.45, particularly around 0.34 mm in some embodiments. This configuration can result in a cross-sectional area per turn of between 0.05 to 0.06 mm 2 , such as approximately 0.056 mm 2  in some embodiments 
     While each turn can be a single structure in some instances, embodiments are not limited to such configurations. Other embodiments can have more structures per turn. For instance,  FIG. 4B  is a top-down view of an exemplary hybrid receiver/transmitter coil  450  configured as a spirally wound FPC coil where each turn includes two structures, according to some embodiments of the present disclosure. Each pair of structures can be electrically coupled together such that the pair of structures functions as a single conductive path for a turn of wire. In order for the pair of structures to be coupled together, the pair of structures can be coupled together at each termination end of the wire. This can be better understood with reference to  FIGS. 4I-4J   FIG. 4I  is a close-up top-down illustration of a portion  470  of coil  450  in  FIG. 4B , according to some embodiments of the present disclosure. As shown, coil  450  can include a plurality of turns including first and second turns  472  and  474  that form part of a spirally wound planar coil that begins from a first termination end  476  and winds outward in a planar configuration until a second termination end (not shown in  FIG. 4I  but can be seen in  FIG. 4B  where the coil ends at the outer perimeter of coil  450 ). 
     Termination end  476  can include a bridging portion  482  that couples the two structures together for each turn. That way, while each turn is formed of two structures, both can act as a single conductive path through which current flows. Bridging portion  482  can be a portion of the patterned wire that forms each turn such that the wire and the bridging portion  482  a part of a monolithic structure. That is, coil  450  can be a patterned, deposited coil that is a planar coil that winds radially outward from a central axis in a planar fashion, where each turn of coil  450  includes two structures that are coupled together physically and electrically via bridging portions. In some embodiments, bridging portion  482  is positioned at the termination ends of coil  450 , i.e., at the points where the monolithic structure of coil  450  physically ends. Thus, coil  450  can have two bridging portions, bridging portion  482  positioned within an inner diameter of coil  450 , and an outer bridging portion (not shown, but can be seen in  FIG. 4F ) positioned at an outer edge of coil  450 . 
       FIG. 4J  is a cross-sectional view of turns  472  and  474  of coil  450 , according to some embodiments of the present disclosure. Each turn can include two structures: first structure  475  and second structure  477 . Each structure can have a rectangular cross-sectional profile as shown in  FIG. 4J , or any other suitable profile such as a square, circular, ovular, or trapezoidal profile. The rectangular profile can efficiently utilize the space available for each turn of wire. Both first and second structures  475  and  477  can be electrically coupled together by bridging portion  482  shown in  FIG. 4I . Each structure  475  and  477  of each turn  472  and  474  of wire can have a certain width  478  and  480  and be separated by a structure separation distance  473 , and each turn can be separated from an adjacent turn by a turn separation distance  479 , all of which can be tailored to achieve a target DCR and ACR that is within design specifications to achieve efficient wireless power transfer. For instance, each turn can have a width  468  between 0.35 to 0.45 mm, particularly approximately 0.41 mm in some embodiments. And, each turn can be separated from adjacent turns by separation distance  469  of between 0.1 to 0.2, particularly around 0.16 mm in some embodiments. Each turn of coil  450  can also have a substantially similar cross sectional area per turn to coil  400 , which can be between 0.05 to 0.06 mm 2 , such as approximately 0.057 mm 2  in some embodiments. Utilizing two or more separate structures instead of one can achieve better charging efficiency while having substantially the same DCR as a coil with only one structure per turn (e.g., coil  400 ). 
     In some embodiments, coil  400  is a single-layered spirally wound coil; however, other embodiments are not so limited. In some instances, coil  400  can be a dual-layered spirally wound coil. For example, the entirety of coil  400  can be dual-layered so that each turn shown in  FIG. 4A  represents two layers of coils. Having additional layers throughout the entirety of coil  400  can increase the strength of magnetic field generated by coil  400 , as well as increase the ability of coil  400  to receive power from a time-varying magnetic field. 
     Although  FIG. 4A  illustrates coil  400  as being either entirely single-layered, or dual-layered, embodiments are not so limited. Some coils can have portions of turns that are single-layered and some turns that are dual-layered. For instance,  FIG. 4B  illustrates exemplary hybrid receiver/transmitter coil  410  configured as a spirally wound coil that includes a single-layered portion  412  and a dual-layered portion  414 , according to some embodiments of the present disclosure. Having different portions with different numbers of layers can alter the strength profile of time-varying magnetic flux generated by hybrid transmitter coil  410 . For instance, magnetic flux generated by regions of single-layered portion  412  may not be as strong as magnetic flux generated by regions of dual-layered portion  414 . The size of each region may be configured to correspond with sizes of receiver coils in different secondary electronic devices to maximize efficiency of power transfer to those secondary electronic devices. Additionally, the size of each region may be configured to correspond with sizes of transmitter coils in different wireless charging devices to maximize efficiency of power transfer from those wireless charging devices. 
       FIG. 4C  illustrates an exemplary hybrid receiver/transmitter coil  420  arranged in a bimodal configuration, according to some embodiments of the present disclosure. In a bimodal configuration, hybrid receiver/transmitter coil  420  can include more than one inductor coil. For instance, hybrid receiver/transmitter coil  420  can include a first coil  422  and a second coil  424  interwound within a region of first coil  422  in a concentric manner, as shown in  FIG. 4C . Each coil can be operated independently from one another so that first coil  422  can operate to transmit power while second coil  424  is turned off, and vice versa. In some embodiments, first coil  422  and second coil  424  of hybrid receiver/transmitter coil  420  can each be optimized for different charging scenarios or different secondary electronic devices. For instance, first coil  422  can be optimized to transmit power to (or receive power from) devices that operate at a first frequency or have a receiver coil of a first size corresponding to the size of first coil  422 ; and, second coil  424  can be optimized to transmit power to (or receive power from) devices that operate at a second frequency or have a receiver coil of a second size corresponding to the size of second coil  424 . The inner termination end of first coil  422  can couple to charging circuitry through conductive trace  402 , while its outer termination end can couple with charging circuitry without the need for an additional conductive trace. However, both termination ends of second coil  424  can couple with charging circuitry through conductive traces  426  and  428 . Accordingly, charging circuitry, such as hybrid charging circuitry  114  in  FIG. 1 , can couple with hybrid receiver/transmitter coil  420  at one edge location  404  to operate both coils  422  and  424  of hybrid receiver/transmitter coil  420  to transmit or receive power. 
       FIG. 4D  illustrates an exemplary hybrid receiver/transmitter coil  430  arranged in a symmetrical coil configuration, according to some embodiments of the present disclosure. Hybrid receiver/transmitter coil  430  can begin and end at edge location  404  and have crossing-over portions  432  and  434  that allow hybrid receiver/transmitter coil  430  to be symmetrical across a vertical and horizontal axis. The symmetrical profile results in a decrease in capacitive coupling between hybrid receiver/transmitter coil  430  and a transmitter coil form which it receives power during wireless power transfer, or a receiver coil to which it transmits power. 
       FIG. 4E  illustrates an exemplary hybrid receiver/transmitter coil  440  arranged in an offset coil configuration, according to some embodiments of the present disclosure. In the offset coil configuration, hybrid receiver/transmitter coil  440  can include two inductor coils: a first inductor coil  442  and a second inductor coil  444 . Unlike hybrid receiver/transmitter coil  420  in  FIG. 4C , both coils  442  and  444  are not concentric. Rather, second inductor coil  444  is offset from the central axis of first inductor coil  442 . Offsetting second inductor coil  444  from the center of first inductor coil  442  allows second inductor coil  444  to provide magnetic flux propagating in the horizontal direction across the center of hybrid receiver/transmitter coil  440 . This allows secondary electronic devices that are configured to receive horizontal magnetic flux to receive power from second inductor coil  444  even though it is positioned at the center of (i.e., aligned with) hybrid receiver/transmitter coil  440 . In some embodiments, first inductor coil  442  can be configured to receive and/or transmit power, while second inductor coil  444  is configured to only transmit power. In some embodiments, second inductor coil  444  can couple to charging circuitry through conductive trances  446  and  448 , where conductive trace  448  is coupled to conductive trace  402 . Thus, conductive trace  402  can be used to couple both first and second inductor coils  442  and  444  to charging circuitry. 
     As shown in  FIG. 4E , first and second inductor coils  442  and  444  can be formed of different sizes. For instance, the inner and outer diameters of second inductor coil  444  can be smaller than the inner and outer diameters of first inductor coil  442 . Furthermore, second inductor coil  444  can be formed of a winding of conductive material that has a different thickness and width than a winding of conductive material of first inductor coil  442 . The different sizes and thicknesses can be configured to correspond with receiver coils of a secondary electronic device to which hybrid receiver/transmitter coil  440  transmits power, and with transmitter coils of a wireless charging device from which hybrid receiver/transmitter coil  440  receives power. It is to be appreciated that while coils  400 ,  410 ,  420 ,  430 ,  440 , and  450  are exemplary hybrid receiver/transmitter coils, other embodiments can utilize these coils as strictly receiver coils or strictly transmitter coils and that embodiments are not limited to hybrid receiver/transmitter coils only. 
     Reference is now made to  FIG. 5 , which is a simplified cross-sectional view of a portion of a wireless power receiving/transmitting module  500  including a hybrid receiver/transmitter coil  508  formed as a FPC and positioned within a housing of a portable electronic device, according to some embodiments of the present disclosure. Wireless power receiving/transmitting module  500  can include, for example, wireless power receiving/transmitting module  301  shown in  FIG. 3A . As shown in  FIG. 5 , the portable electronic device can include a glass plate  502  having a layer of ink  504  coated on the inside surface of glass plate  502 . Glass plate  502  can be attached to a housing of the portable electronic device to form a back surface of the portable electronic device. In some embodiments ink layer  504  has low electrical conductivity and the color of the ink layer can be chosen to match other exterior surfaces of the portable electronic device. 
     As shown, wireless power receiving/transmitting module  500  can include three separate shields including an electromagnetic shield  514 , a ferromagnetic shield  510 , and a thermal shield  512 . Electromagnetic shield  514  can be representative of electromagnetic shield  306  shown in  FIG. 3A ; ferromagnetic shield  510  can be representative of ferromagnetic shield  310  and thermal shield  512  can be representative of thermal shield  315 . An adhesive  506 , such as a pressure sensitive adhesive, can attach module  500  to ink-coated glass layer  502 / 504  and act as an anti-splinter film in case of a breakage event. 
     Ferromagnetic shield  510  includes a relatively thick layer of ferrite material  522  sandwiched between a thin adhesive layer  520  and a thin thermoplastic polymer layer  524 , such as a PolyEthylene Terephthalate film. Adhesive layer  520  and thermoplastic polymer layer  524  provide a carrier for ferrite layer  522  that contains the ferrite and prevents minor cracks, burrs or other imperfections at the ferrite surface from coming into contact with other components of the wireless power receiving/transmitting module. Ferromagnetic shield  510  is positioned within wireless power receiving/transmitting module  500  on the opposite side of conductive coil  518  as electromagnetic shield  514 . 
     Thermal shield  512  can include a thermal layer  528  adhered to a conductive layer  526  by a thin conductive adhesive (not shown). Thermal layer  528  provides thermal isolation between wireless power receiving/transmitting module  500  and various components of the portable electronic device. Conductive layer  526  provides additional thermal shielding and can be coupled to ground to capture stray flux and prevent such flux from interfering with the display (not shown) or other components of the portable electronic device. 
     As shown in  FIG. 5 , wireless power receiving/transmitting module  500  can also include a hybrid receiver/transmitter coil  508  that can be operated to receive or transmit power, according to some embodiments of the present disclosure. Hybrid receiver/transmitter coil  508  can include a flexible dielectric base layer  516 , such as a polyimide layer. In some embodiments, electromagnetic shield  514  can be formed directly on one side of polyimide layer  516  and a conductive coil  518  can be formed directly on the opposing side. Having electromagnetic shield  514  and conductive coil  518  formed directly on opposing sides of base layer  516  allows a single carrier layer to be used for both the receiver shield and receiver coil and thus enables the overall thickness of wireless power receiving/transmitting module  500  to be reduced. To further reduce thickness, some embodiments of the disclosure do not include a coverlay or other type of protective layer over the flex as is used for traditional flex circuits to encapsulate and protect the circuits formed on the flex. Instead, some embodiments of the disclosure plate the conductive coil  518  with an electroless nickel plating process followed by and a thin layer of immersion gold that protects the nickel from oxidation. 
     In some embodiments, conductive coil  518  can be formed of a single length of patterned conductive trace that is wound into a plurality of turns including turns  518   a  and  518   b.  The conductive trace can be wound about a center point and in increasing radii such that the resulting coil is substantially planar. As further shown in  FIG. 5 , each turn is separated by a gap  532  that separates adjacent turns  518   a  and  518   b  of conductive coil  518 . Often times, the coil width-to-gap ratio in conventional receiver coils is selected to maximize the size of the receiver coil and to achieve the greatest wire width that the receiver can fit in its allotted space. According to some embodiments, however, the coil width-to-gap ratio is not selected to maximize the size of conductive coil  518  or to achieve the greatest wire width. Rather, the coil width-to-gap ratio can be tailored to maximize efficiency according to an operating frequency used during wireless power transfer. Higher operating frequencies tend to work better with coils having smaller wire widths. Thus, in some embodiments, the wire width-to-gap ratio can vary between 60:40 to 80:20, particularly 70:30 in some instances for an operating frequency of approximately 130 kHz. In some embodiments, gaps  532  can be filled with a magnetic material  530  to help induce magnetic flux to propagate through hybrid receiver/transmitter coil  508 . Magnetic material  530  can be a ferrite material formed of a glue-based material that has magnetic properties for redirecting magnetic flux through conductive coil  518 . In some instances, magnetic material  530  completely fills the space between adjacent turns  518   a  and  518   b  of conductive coil  518  and between ferrite layer  522  and electromagnetic shield  514 , as shown in  FIG. 5 . Although conductive coil  518  is shown to have a single cross-sectional structure, it is to be appreciated that other embodiments can have conductive coil  518  formed to include multiple cross-sectional structures, as discussed herein with respect to  FIG. 4J . In such instances, magnetic material  530  can also fill in regions between the structures of each turn, such as within the gap created by the structure separation distance, e.g., structure separation distance  473  in  FIG. 4J . 
     As mentioned herein, a hybrid receiver/transmitter coil in a portable electronic device can not only receive power, but also transmit power. Power can be transmitted to a secondary electronic device when the secondary electronic device is placed against a charging surface of the portable electronic device. Often times however, a secondary electronic device is not positioned anywhere near a charging surface of the portable electronic device. Thus, the hybrid receiver/transmitter coil should not be generating magnetic flux for transmitting power. In some embodiments of the present disclosure, a device detection coil can be implemented in the hybrid wireless charging system, as will be discussed herein with respect to  FIGS. 6A-6C . 
       FIGS. 6A-6C  illustrate different exemplary hybrid wireless charging systems that include hybrid receiver/transmitter coils and device detection coils for detecting the presence of an electronic device positioned to receive power from the hybrid receiver/transmitter coil, according to some embodiments of the present disclosure. The exemplary hybrid receiver/transmitter coils shown in  FIGS. 6A-6C  are constructed as FPC coils. 
       FIG. 6A  illustrates an exemplary hybrid wireless charging system  600  that includes a hybrid receiver/transmitter coil  602  and a device detection coil  604  in an interwound configuration, according to some embodiments of the present disclosure. Hybrid receiver/transmitter coil  602  can be formed of a conductive coil that is a single length of patterned conductive trace wound into a plurality of turns. The wire can be wound about a center point and in increasing radii such that the resulting coil is substantially planar. As shown in  FIG. 6A , the interwound configuration is arranged such that device detection coil  604  is wound within a portion of hybrid receiver/transmitter coil  602 . For instance, device detection coil  604  can be wound in gaps between adjacent turns of conductive traces of hybrid receiver/transmitter coil  602 . Device detection coil  604  can be interwound within any portion of hybrid receiver/transmitter coil  602 . As an example, device detection coil  604  can be interwound near the outer edge  608  of hybrid receiver/transmitter coil  602  as shown in  FIG. 6A . Alternatively, device detection coil  604  can be interwound near the inner edge  606  of hybrid receiver/transmitter coil  602 , or within hybrid receiver/transmitter coil  602  away from either the outer edge  608  or inner edge  606 . 
     Although  FIG. 6A  illustrates device detection coil  604  in an interwound configuration, embodiments are not limited to such configurations. For instance, a device detection coil can be wound around an outer edge of a hybrid receiver/transmitter coil or within an inner edge of a hybrid receiver/transmitter coil, as shown in  FIGS. 6B and 6C .  FIG. 6B  illustrates an exemplary hybrid wireless charging system  610  including a device detection coil  612  in an outer-wound configuration, according to some embodiments of the present disclosure. In the outer-wound configuration, device detection coil  612  can be wound around an outer edge  614  of hybrid receiver/transmitter coil  602 .  FIG. 6C  illustrates an exemplary hybrid wireless charging system  610  including a device detection coil  622  in an inner-wound configuration, according to some embodiments of the present disclosure. In the inner-wound configuration, device detection coil  622  can be wound outside of and proximate to an inner edge  624  of hybrid receiver/transmitter coil  602   
     Device detection coils  604 ,  612 , and  622  can operate independently from hybrid receiver/transmitter coil  602  to detect the presence of an external device on a charging surface of a portable electronic device within which hybrid receiver/transmitter coil  602  is housed. For instance, detection coils  604 ,  612  and  622  can turn on to perform device detection while hybrid receiver/transmitter coil  602  is turned off and not generating time-varying magnetic flux. In addition to detecting the presence of an external device, device detection coils  604 ,  612 , and  622  can also detect the presence of sensitive radio frequency identification (RFID) components, such as credit cards, that are sensitive to magnetic fields that are positioned on a charging surface of the portable electronic device. In such cases, if a sensitive RFID component is detected, the portable electronic device may be configured to ensure that hybrid receiver/transmitter coil  602  is not turned on so that it does not generate strong magnetic fields that are capable of erasing the credit card. 
     In some embodiments, device detection coils  604 ,  612 , and  622  can operate at a different frequency than hybrid receiver/transmitter coil  602 . As an example, device detection coils  604 ,  612 , and  622  can operate at a higher frequency than hybrid receiver/transmitter coil  602 . In addition to the difference in operating frequency, device detection coils  604 ,  612 , and  622  can also be constructed differently than hybrid receiver/transmitter coil  602 . In some embodiments, device detection coils  604 ,  612 , and  622  have a narrower trace width than hybrid receiver/transmitter coil  602 . The narrower width can allow device detection coils  604 ,  612 , and  622  to operate at higher frequencies than hybrid receiver/transmitter coil  602 . 
     According to some embodiments, control circuitry in a computing system, e.g., computing system  102  in  FIG. 1 , can be configured to operate hybrid receiver/transmitter coil  602  based on a detection signal from any of device detection coils  604 ,  612 , and  622 . For instance, device detection coils  604 ,  612 , and  622  can generate a detection signal when an external device is detected to be positioned on a charging surface. The detection signal can be received by control circuitry, which can then use this information to turn on hybrid receiver/transmitter coil  602 . In some embodiments, once a detection signal is received, control circuitry can determine whether the external device is a device that is suitable for providing power (e.g., a wireless charging device), or a device that is suitable for receiving power (e.g., a secondary electronic device). This determination can be made through communication with the external device, such as through Bluetooth communication or through power-modulating communication between the two coils. If it is determined that the external device is a wireless charging device, then the control circuitry can activate the switching mechanism to couple hybrid receiver/transmitter coil  602  to the power receiving circuitry to operate hybrid receiver/transmitter coil  602  to receive power. However, if it is determined that the external device is a secondary electronic device, then the control circuitry can activate the switching mechanism to couple hybrid receiver/transmitter coil  602  to the power transmitting circuitry to operate hybrid receiver/transmitter coil  602  to transmit power. 
     B. Stranded Coil 
     Although a hybrid receiver/transmitter coil can be formed as a FPC coil, embodiments are not limited to such configurations. Rather, some embodiments can include hybrid charging systems that have a hybrid receiver/transmitter coil formed as a stranded coil.  FIG. 7  illustrates an exploded view of a portable electronic device  700  including a hybrid receiver/transmitter coil  705  formed as a stranded coil, according to some embodiments of the disclosure. Portable electronic device  700  can include a top housing  726  and a bottom housing  725  that can mate to define an interior cavity. As shown in  FIG. 7 , portable electronic device  700  can include at least three separate shields: an electromagnetic shield  706 , a ferromagnetic shield  710 , and a thermal shield  715  along with an adhesive component  720  that attaches wireless power receiving/transmitting module  701  to housing  725 . The three shields and the adhesive component function and are positioned in a way that is substantially similar to the corresponding components discussed herein with respect to  FIGS. 3A-3C . Detail of those operations, functionalities, configurations, and positions can be referenced in  FIG. 3A  and are not discussed herein with respect to  FIG. 7  for brevity. Unlike wireless power receiving/transmitting module  301  in  FIG. 3A-3C , electromagnetic shield  706  and adhesive component  720  can include a center opening corresponding to an inner diameter of hybrid receiver/transmitter coil  705 . 
     In some embodiments, unlike FPC coils whose device detection coil is formed as part of the same FPC as the hybrid receiver/transmitter coil, device detection coils for hybrid wireless charging systems can be implemented with the electromagnetic shield. As shown in  FIG. 7 , wireless power receiving/transmitting module  701  can include a device detection coil  708  that is positioned around a perimeter of electromagnetic shield  706 . Further details with respect to stranded hybrid receiver/transmitter coil  705  and device detection coil  708  are discussed herein with respect to  FIGS. 8A-8C . 
       FIG. 8A  is a top-down view of electromagnetic shield  706  and a hybrid receiver/transmitter coil  705 , according to some embodiments of the present disclosure. As shown, electromagnetic shield  706  is semi-transparent and superimposed over hybrid receiver/transmitter coil  705  so that the relative positioning and configurations of hybrid receiver/transmitter coil  705  and electromagnetic shield  706  can be observed. Hybrid receiver/transmitter coil  705  can be formed of a conductive coil that is a single length of conductive wire wound into a plurality of turns between a first termination end  802  and a second termination end  804 . First termination end  802  can be positioned within an inner diameter of hybrid receiver/transmitter coil  705 , and second termination end  804  can be positioned outside an outer diameter of hybrid receiver/transmitter coil  705 . The wire can be wound about a center point and in increasing radii such that the resulting coil is substantially planar. In some embodiments, the wire is formed of a plurality of sub-wires configured in various ways, as further discussed herein with respect to  FIG. 8B . 
       FIG. 8B  illustrates cross-sectional views of different configurations of the conductive wire as shown by the cut line illustrated in  FIG. 8A . Specifically,  FIG. 8B  illustrates three non-limiting configurations: a first configuration A, a second configuration B, and a third configuration C. The conductive wire can include a plurality of sub-wires arranged in a single plane. Thus, each turn of wire in hybrid receiver/transmitter coil  705  can include a plurality of sub-wires. Forming the wire with a plurality of sub-wires allows the hybrid receiver/transmitter coil  705  to have a large number of turns, thereby enhancing the performance of hybrid receiver/transmitter coil  705 . 
     According to configuration A, coil  705  can be formed of plurality of turns of wire, each turn of wire can include a plurality of sub-wires  806  that have a circular cross-sectional shape. In some embodiments, each turn of wire can include twelve sub-wires with circular-cross sectional shape that are coplanar with one another. Embodiments, however, are not limited to coils having sub-wires of circular cross-sectional shape. For instance, according to configuration B, each turn of coil  705  can include a plurality of sub-wires  807  that have a square-like cross-sectional shape. This enables sub-wires  807  to better utilize the space between sub-wires  807  to maximize the cross-sectional area of the wire for each turn. In such embodiments, each turn of wire can include twelve sub-wires with square-like cross-sectional shape that are coplanar with one another. And according to configuration C, each turn of coil  705  can include a plurality of sub-wires  807  that have a rectangular cross-sectional shape. In such embodiments, each turn of wire can include six sub-wires with rectangular cross-sectional shape that are coplanar with one another. It is to be appreciated that the number of sub-wires are not limited to what is shown in  FIG. 8B  and that other embodiments can have more or less than the number of sub-wires shown in  FIG. 8B . 
     With reference back to  FIG. 8A , electromagnetic shield  706  can be a sheet of material capable of blocking the propagation of electric filed while allowing the propagation of magnetic field through its structure, For instance, electromagnetic shield  706  can include a layer of silver laminated against a layer of polyethylene terephthalate (PET), which can function as a support structure for the layer of silver. According to some embodiments of the present disclosure, device detection coil  708  can be attached to electromagnetic shield  706 . As an example, device detection coil  708  can be a patterned conductive trace formed around an outer perimeter of electromagnetic shield  706  and attached to a side of electromagnetic shield  706  on which hybrid receiver/transmitter coil  705  is also attached. In some instances, the outer profile of device detection coil  708  can correspond to the outer profile of electromagnetic shield  706 . For example, the outer profile of electromagnetic shield  706  is substantially square-like with rounded corners, as shown in  FIG. 8A . Accordingly, the outer profile of device detection coil  708  can also have a square-like shape with rounded corners. In certain embodiments, the outer profile of device detection coil  708  can be different from the outer profile of hybrid receiver/transmitter coil  705 , which can be substantially circular. Configuring device detection coil  708  around hybrid receiver/transmitter coil  705  enables device detection coil  708  to determine whether a secondary device is positioned to receive power from hybrid receiver/transmitter coil  705 . A close-up view of device detection coil  708  patterned on electromagnetic shield  706  is shown in  FIG. 8C . 
       FIG. 8C  illustrates a close-up top-down view of a portion of electromagnetic shield  706 , according to some embodiments of the present disclosure. As shown, device detection coil  708  can be patterned proximate to an outer edge  808  of electromagnetic shield  706 . In some embodiments, device detection coil  708  is patterned proximate to outer edge  808  so that it is positioned outside of an outer perimeter of hybrid receiver/transmitter coil  705 . Configuring device detection coil  708  around hybrid receiver/transmitter coil  705  enables device detection coil  708  to determine whether a secondary device overlaps with any region of the entire surface of hybrid receiver/transmitter coil  705 . In some embodiments, the patterned conductive trace width for device detection coil  708  is narrower than the stranded coil width of hybrid receiver/transmitter coil  705 . Similar to device detection coils  604 ,  612 , and  622  discussed herein with respect to  FIGS. 6A-6B , device detection coil  708  can operate at a different frequency than hybrid receiver/transmitter coil  705  to detect the presence of secondary electronic devices and/or sensitive RFID components. 
     Although the embodiments discussed herein with respect to  FIGS. 7 and 8A-8C  only include one stranded coil, embodiments are not limited to such embodiments. Some embodiments can include more than one stranded coil arranged in a specific pattern to generate an array of magnetic fluxes that forms a continuous charging surface upon which an electronic device can be charged. The continuous charging surface allows an electronic device to be efficiently charged at any location within a broad region of the charging surface. 
       FIG. 8D  an exemplary pattern  810  having three inductive coils: first inductive coil  812 , second inductive coil  814 , and third inductive coil  816 , according to some embodiments of the present disclosure. Each inductive coil can be a hybrid receiver/transmitter coil that can receive wireless power by interacting with magnetic fields or transmit wireless power by generating magnetic fields as discussed herein. Furthermore, each inductive coil can operate individually, meaning each inductive coil can be activated without activating the other inductive coils; and each inductive coil can provide power at the same frequency, phase, and amplitude. First, second, and third inductive coils  812 ,  814 , and  816  can be arranged in three separate layers, thereby forming a inductive coil stack. For example, first inductive coil  812  can be positioned in a first layer, second inductive coil  814  can be positioned in a second layer above the first layer, and third inductive coil  816  can be positioned in a third layer above the first and second layers. Each inductive coil can be formed of a single layer of wire that is wound from an outer radius to an inner radius so that it forms a flat, ring-like shape, as discussed herein with respect to  FIG. 7 . 
     In some embodiments, first, second, and third inductive coils  812 ,  814 , and  816  can each include a central termination zone. A central termination zone can be a region at the center of each inductive coil that is reserved for interfacing with an interconnection layer, such as a printed circuit board (PCB). As shown in  FIG. 8D , first, second, and third inductive coils  812 ,  814 , and  816  can have central termination zones  826 ,  828 , and  830 , respectively. Central termination zones  826 ,  828 , and  830  can be regions at the center of each inductive coil reserved for interfacing with the interconnection layer. Accordingly, first, second, and third inductive coils  812 ,  814 , and  816  can be positioned in locations where their respective central termination zones can interface with the interconnection layer without being blocked by a neighboring inductive coil. For instance, central termination zone  826  of inductive coil  812  is laterally positioned outside of the outer diameter of inductive coil  814  and  816 . The same can be said for central termination zones  828  and  830 . Accordingly, central termination zones  826 ,  828 , and  830  can extend through the inductive coil stack without intersecting another inductive coil. In some embodiments, central termination zones  826 ,  828 , and  830  may be positioned equally spaced apart from one another such that the central termination zones  826 ,  828 , and  830  form an equilateral triangle  832 . 
     In certain embodiments, pattern  810  can be expanded upon to form other patterns for different shapes and sizes of wireless charging mats. One of such patterns is a rosette pattern, which may be suitable for substantially circular wireless charging regions. The rosette pattern can be a pattern where the inductive coils are arranged in an overlapping arrangement such that different coils in the plurality of coils are on different planes and are non-concentric with each other. In an expanded base pattern, one or more inductive coil layers can include more than one inductive coil. 
       FIG. 4  illustrates an exemplary inductive coil arrangement  840  configured in a rosette pattern, according to some embodiments of the present disclosure. Inductive coil arrangement  840  can include three separate inductive coil layers where one or more of those layers include multiple inductive coils. For example, a first inductive coil layer can include inductive coils  842   a - c,  a second inductive coil layer can include inductive coils  844   a - c,  and a third inductive coil layer can include inductive coil  846 . Each inductive coil in inductive coil arrangement  840  can have an opening defined by an inner diameter of the inductive coil, where each opening includes a termination zone  858  (i.e. central portion) that is not overlapping any portion of an adjacent inductive coil. Additionally, the inductive coils are arranged such that no two coils in the plurality of coils are concentric with each other. 
     The base pattern may be pervasive throughout the rosette pattern such that every group of three inductive coils, one in each inductive coil layer, that are closest together is arranged in the base pattern. For instance, inductive coils  842   a,    844   a,  and  846  are arranged in the base pattern. Likewise, inductive coils  842   a,    844   b,  and  846  are arranged in the base pattern, inductive coils  844   b,    842   c,  and  846  are arranged in the base pattern, and so on and so forth. By arranging inductive coil arrangement  840  according to the base pattern, inductive coil arrangement  840  can create a continuous charging region within which an electronic device can charge in any location. 
     To better understand the arrangement of an expanded base pattern,  FIGS. 8F-8H  illustrate the different layers of inductive coil arrangement  840 . Specifically,  FIG. 8F  illustrates the first layer including inductive coils  842   a - c,    FIG. 8G  illustrates the second layer including inductive coils  844   a - c,  and  FIG. 5H  illustrates the third layer including inductive coil  846 . According to embodiments, inductive coils in the same layer can be equally spaced apart so that the generated magnetic fields can be arranged in an evenly spaced grid pattern. For example, inductive coils  842   a - c  and  844   a - c  can be spaced apart by a distance D 1 . The distance D 1  may be selected to be wide enough for parts of inductive coils in other layers to fit within it for stacking purposes, as will be discussed further herein. In other embodiments, the distance D 1  may be selected to be wide enough so that adjacent inductive coils do not make contact with each other. For instance, distance D 1  may be less than 3 mm. In a particular embodiment, distance D 1  is less than 1 mm. 
     The center of each inductive coil in the same layer can be separated by a distance D 2 . Distance D 2  can affect the uniformity of magnetic flux across the charging surface. Larger distances D 2  result in lower magnetic flux uniformity across the charging surface, whereas smaller distances D 2  result in higher magnetic flux uniformity across the charging surface. In some embodiments, distance D 2  is selected to be the smallest distance that allows for a suitable distance D 1  between inductive coils while taking into consideration the outer diameter of each inductive coil. In additional embodiments, distance D 2  is the same for all adjacent inductive coils in the same layer. Thus, groups of three inductive coils (e.g., inductive coils  842   a - c  and  844   a - c  in each of the first and second layers, respectively) can be arranged according to the end points of an equilateral triangle  862 . 
       FIG. 9A  illustrates an exploded view of another exemplary wireless power receiving/transmitting module  901  having a stranded hybrid receiver/transmitter coil  902  for a portable electronic device, according to some embodiments of the present disclosure. Like module  701 , power receiving/transmitting module  901  can include three separate shields: an electromagnetic shield  904 , a ferromagnetic shield  906 , and a thermal shield  908  along with an adhesive component  910  that attaches wireless power receiving/transmitting module  901  to the housing of the portable electronic device. The three shields and the adhesive component function and are positioned in a way that is substantially similar to the corresponding components discussed herein with respect to  FIGS. 3A-3C . Unlike wireless power receiving/transmitting module  701  in  FIG. 7 , electromagnetic shield  904  can have an outer diameter that substantially matches the outer diameter of hybrid receiver/transmitter coil  902 , and adhesive component  910  can include four portions that are structured and function similar to double-sided adhesives  340   a - b  in  FIG. 3C  to attach ferromagnetic shield  906  to the housing of the portable electronic device without overlapping with hybrid receiver/transmitter coil  902 . Electromagnetic shield  904  can be a separate structure that is bonded to a surface of coil  902  with an adhesive (not shown). Ferromagnetic shield  906  can be formed of any suitable ferromagnetic material, such as a nickel zinc ferrite material or a nanocrystalline foil. The nanocrystalline foil can be formed of multiple layers of nanocrystalline material separated by adhesive layers. 
     In some embodiments, power receiving/transmitting module  901  is coupled to an interconnection component  914  for enabling operation of coil  902  and the grounding of electromagnetic shield  904 . Interconnection component  914  can be a flexible circuit board that has a coupling end  916  whose z-height can fit within the z-height of module  901 . Accordingly, thermal shield  908  can have a cutout region  917  that follows a portion of interconnection component  914 , where cutout region  917  extends from the center of module  901  to an edge of module  901  to provide space within which interconnection component  914  can be positioned. Furthermore, ferromagnetic shield  906  and electromagnetic shield  904  can also have cutout regions  907  and  905 , respectively, that can provide space within which coupling end  916  can be positioned without substantially impacting the z-height of module  901 . In particular embodiments, coupling end  916  of interconnection component  914  is positioned at the center and/or within the inner diameter of hybrid receiver/transmitter coil  902  (i.e., at the center of power receiving/transmitting module  901 ) so that coil  902  can have one termination end that is coupled to coupling end  916  at the center of module  901 , and electromagnetic shield  904  can terminate at the center of module  901  on coupling end  916  for coupling to ground. 
     In some embodiments, coupling end  916  of interconnection component  914  can include two or more pads for coupling with hybrid receiver/transmitter coil  902  and electromagnetic shield  904 .  FIG. 9B  is a magnified top-down view of coupling end  916  of interconnection component  914 , according to some embodiments of the present disclosure. As shown, coupling end  916  can include two pads: a first contact pad  922  and a second contact pad  924  that are positioned adjacent to each other at coupling end  916 . First contact pad  922  can be coupled to electromagnetic shield  904  to couple electromagnetic shield  904  to ground, and second contact pad  924  can be coupled to coil  902  to enable operation of coil  902 . In some embodiments, second contact pad  924  is tilted to a certain degree with respect to first contact pad  922  so that each contact pad can be better oriented to couple with the respective shield and coil connections. An adhesive  923  can attach an end of electromagnetic shield  904  to interconnection component  914 . In some embodiments, adhesive  923  can be coated over the entire surface of first contact pad  922  as shown in  FIG. 9B , or can include two portions  926  and  928  that are coated over portions of first contact pad  922  as shown in  FIG. 9C . Portion  926  can cover a portion of a center of first contact pad  922 , and portion  928  can cover a portion of the outer edges of first contact pad  922  such that portion  928  is U-shaped. 
     C. Alignment Mechanisms for Hybrid Wireless Charging Systems 
     As mentioned herein, a hybrid receiver/transmitter coil can not only receive power, but also transmit power. To transmit power, a receiver coil in a secondary electronic device often needs to be aligned with the hybrid receiver/transmitter coil in the portable electronic device to maximize power transfer efficiency. Thus, hybrid wireless charging systems according to some embodiments of the present disclosure can include one or more alignment mechanisms. The alignment mechanisms can assist in aligning a receiver coil in a secondary device with a hybrid receiver/transmitter coil in a portable electronic device. For instance, in some embodiments, the alignment mechanism can be passive magnetic devices that attract corresponding magnets positioned in a secondary electronic device to align the receiver coil with the hybrid receiver/transmitter coil. Alternatively, the alignment mechanism can be active proximity detection devices that determine the relative location of a receiver coil with respect to the hybrid receiver/transmitter coil, as will be discussed further herein. 
       FIGS. 10A-10D  illustrate different alignment mechanisms for hybrid wireless charging systems, according to some embodiments of the present disclosure. In some embodiments, the alignment mechanisms can be disposed between housing  325 / 725  (see  FIGS. 3A and 7 ) and adhesive layer  320 /attachment assembly  332  and  338  (see  FIGS. 3A-3C ). The alignment mechanisms illustrated in  FIGS. 10A-10D  are shown superimposed over an attachment assembly including single sided adhesive  336  and double-sided adhesives  334   a  and  334   b,  along with hybrid receiver/transmitter coil  305  disposed under adhesives  336 ,  334   a,  and  334   b.  Adhesives  336 ,  334   a,  and  334   b  are discussed in detail herein with respect to  FIGS. 3B and 3C  and are not repeated for brevity. 
     According to some embodiments of the present disclosure, the alignment mechanism can be a passive alignment mechanism that includes one or more permanent magnets. For instance,  FIG. 10A  illustrates an exemplary alignment mechanism formed of magnets  1002   a - d  positioned at corners of a square configuration, according to some embodiments of the present disclosure. Magnets  1002   a - d  can be configured as rounded rectangular shapes, or any other suitable shape such as circular, square, trapezoidal, and ovular shapes. In some other embodiments, different configurations of magnets can be used. For instance,  FIG. 10B  illustrates an exemplary alignment mechanism formed of paired magnets  1004   a - d  positioned at corners of a square configuration, according to some embodiments of the present disclosure. Each paired magnet  1004   a - d  can include at least two magnets positioned beside one another in the configuration shown in  FIG. 10B .  FIGS. 10A and 10B  illustrate alignment mechanisms formed of four magnets positioned in a square configuration, however other embodiments can have different numbers of magnets and be positioned differently. For instance, some embodiments can have more or less than four magnets and be positioned around a perimeter of single-sided adhesive  336  or on only two sides of single-sided adhesive  336 . 
     Although  FIGS. 10A and 10B  illustrate alignment mechanisms formed of a plurality of magnets positioned in a square configuration, embodiments are not limited to such configurations. In some embodiments, the alignment mechanism can be formed of a perimeter magnet as shown in  FIG. 10C .  FIG. 10C  illustrates an exemplary alignment mechanism formed of a perimeter magnet  1006 , according to some embodiments of the present disclosure. Perimeter magnet  1006  can be a ring-like structure that has a rounded rectangle profile, as shown in  FIG. 10C . Perimeter magnet  1006  can have a profile that is substantially similar to the outer profile of single-sided adhesive  336  or adhesive layer  320 / 720 . 
       FIG. 10D  illustrates an exemplary alignment mechanism formed of an arrangement of proximity detection coils  1008   a - d,  according to some embodiments of the present disclosure. Each proximity detection coil  1008   a - d  can be formed of a coil of wire that can be actively used to detect the position of an external device. For instance, proximity detection coil  1008   a  can be operated to detect whether an external device is positioned proximate to coil  1008   a.  If coil  1008   a  detects that an external device is positioned proximate to coil  1008   a,  then a computing system, such as computing system  102  in  FIG. 1  can determine that a secondary device is misaligned because it is positioned near the top left position of hybrid receiver/transmitter coil  305 . In some embodiments, sufficient alignment can be detected by computing system  102  when all proximity detection coils  1008   a - d  detect that an external device is proximately positioned. 
     According to some embodiments, proximity detection coils  1008   a - d  can be used to aid a user in achieving alignment between hybrid receiver/transmitter coil  305  and a receiver coil in a secondary electronic device. In such embodiments, computing system  102  can use proximity detection coils  1008   a - d  to determine a position of the secondary electronic device by determining which detection coils  1008   a - d  are detecting the proximity of the secondary electronic device. If only detection coil  1008   a  is detecting the proximity of the secondary electronic device, then computing system  102  can determine that the two coils are misaligned. 
     In some embodiments, computing system  102  can be configured to notify the user that hybrid receiver/transmitter coil  305  is misaligned with the receiver coil in the secondary electronic device. The notification can be performed by operating a light-emitting diode (LED) observable by the user. As an example, the LED can emit a red color when the coils are misaligned, and a green color when the coils are aligned; or, the LED can “breathe” by gradually pulsing light at a frequency corresponding to a degree of alignment between the two coils. For instance, the LED can pulse at a higher frequency when the two coils are closer to alignment and a lower frequency when the two coils are farther from alignment. 
     In addition to merely notifying the user of alignment/misalignment, computing system  102  can also aid the user to move the secondary device toward alignment. For instance, computing system  102  can output an instruction on a display to aid the user in moving the secondary electronic device toward alignment. Following the example above, if only coil  1008   a  is detecting proximity of the secondary electronic device, then computing system  102  can instruct the user to move the secondary electronic device in a bottom-right direction. Once all four device detection coils  1008   a - d  detect proximity of the secondary electronic device, computing system  102  can output an instruction on the display to stop moving the secondary electronic device because the two coils are aligned. 
     Although  FIG. 10D  illustrates device detection coils  1008   a - d  as circular in shape, embodiments are not so limited. Other embodiments can have device detection coils that have profiles in the shape of rectangles, squares, triangles, or any other geometric shapes. Furthermore, embodiments do not necessarily require four detection coils arranged in a square configuration as shown in  FIG. 10D . Other embodiments can have more or less device detection coils arranged in other configurations. 
     Although the invention has been described with respect to specific embodiments, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.

Metadata:
Filing Date: 20190524
Publication Date: 20211102
Grant Date: 20211102
Priority Date: 20180525
Inventors: GRAHAM, Christopher S.
LARSSON, KARL RUBEN F.
HAUG, Grant S.
Oro, Aaron A.
POPE, BENJAMIN J.
LEE, SHERRY
TAN, TANG YEW
DINH, RICHARD HUNG MINH
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/0042", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F27/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/342", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0042", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/2871", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 68615312