PATENT DOCUMENT

Publication Number: US-10725515-B2
Application Number: US-201816127046-A
Country: US
Kind Code: B2

Title: Inductive interconnection system

Abstract:
Embodiments describe a receiving element that includes a ferromagnetic structure axially symmetrical around a central axis disposed along a length of the ferromagnetic structure. The ferromagnetic structure includes a groove region defining two end regions on opposing sides of the groove region, where the groove region has a smaller length than the two end regions. The receiving element also includes an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions.

Claims:
What is claimed is: 
     
       1. A stylus for inputting data into a host electronic device, the stylus comprising:
 an elongated housing having first and second opposing ends and a housing wall extending along a length of the housing in between the first and second ends and including a charging region extending along at least a portion of a length of the housing; 
 an interfacing end that tapers to a tip and is coupled to the first end of the housing; 
 a wireless power receiving element disposed within the housing at a location adjacent to the charging region, the wireless power receiving element comprising:
 a shield having a plurality of sidewalls and a back wall extending between the sidewalls to form a cavity; 
 a ferromagnetic structure disposed within the cavity and having a groove region extending along a first axis of the ferromagnetic structure between first and second end regions on opposing sides of the groove region, each of the first and second end regions protruding past the groove region in a mirrored relationship with each other along second and third axes, respectively, perpendicular to the first axis, and each of the first and second end regions having an interface surface at its distal end facing the charging region and a back surface opposite the distal end; 
 an inductor coil disposed within the cavity and wound about the groove region of the ferromagnetic structure in between the first and second end regions; 
 a spacer coupling the ferromagnetic structure to the shield, the spacer including first and second portions disposed between the shield and the back surface of the first and second end regions of the ferromagnetic structure, respectively, wherein the spacer has a thickness that creates a gap between the inductor coil and the shield electrically isolating the inductor coil from the shield. 
 
 
     
     
       2. The receiving element of  claim 1 , wherein the shield comprises four sidewalls coupled to the back wall to form a five-sided box that defines the cavity, and wherein the interface surfaces face toward outside of the cavity. 
     
     
       3. The receiving element of  claim 1 , wherein the shield includes one or more extensions that extend from one or more sidewalls of the shield in a direction parallel to a plane in which the back wall is oriented. 
     
     
       4. The stylus of  claim 1  wherein the first portion and the second portion of the spacer are two separate components. 
     
     
       5. An inductive interconnection system, comprising:
 a first electronic device including a wireless power transmitting element comprising:
 a transmitting ferromagnetic structure having a transmitting groove region defining two transmitting end regions disposed on opposing sides of the transmitting groove region; and 
 a transmitting inductor coil wound about the transmitting groove region of the transmitting ferromagnetic structure and in between the two transmitting end regions, the transmitting inductor coil configured to generate time-varying magnetic flux through the transmitting ferromagnetic structure; and 
 
 an electronic stylus including: (i) an elongated housing having first and second opposing ends and a housing wall extending along a length of the housing in between the first and second ends, wherein the housing wall includes opposing interior and exterior surfaces, the interior surface defining a cavity within the housing and the exterior surface defining an outer perimeter of the stylus; (ii) an interfacing end that tapers to a tip and is coupled to the first end of the housing; and (iii) a wireless power receiving element disposed within the housing and comprising:
 a receiving ferromagnetic structure having a groove region defining first and second end regions on opposing sides of the groove region, each end region comprising respective interface surfaces, wherein the groove region has a smaller length than the two end regions; 
 a receiving inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions; 
 a shield comprising a plurality of sidewalls and a back wall that form a cavity within which the receiving ferromagnetic structure and receiving inductor coil are positioned; and 
 a spacer coupling the receiving ferromagnetic structure to the shield, the spacer including first and second portions disposed between the shield and a back surface of the first and second end regions of the receiving ferromagnetic structure opposite the respective interface surfaces, wherein the spacer has a thickness that creates a gap between the receiving inductor coil and the shield electrically isolating the receiver inductor coil from the shield. 
 
 
     
     
       6. The inductive interconnection system of  claim 5 , wherein the transmitting end regions each include respective transmitting interfacing surfaces that face toward the receiving element, and wherein the transmitting end regions each include respective receiving interfacing surfaces that face toward the transmitting element. 
     
     
       7. The inductive interconnection system of  claim 6 , wherein the transmitting interfacing surfaces face toward at least a portion of the receiving interfacing surfaces. 
     
     
       8. The inductive interconnection system of  claim 6 , wherein the transmitting ferromagnetic structure further comprises sidewalls positioned between the groove region and the two end regions that extend a distance equal to or greater than a thickness of the inductor coil. 
     
     
       9. The inductive interconnection system of  claim 5 , wherein the shield comprises four sidewalls coupled to the back wall to form a five-sided box that defines the cavity. 
     
     
       10. A stylus for inputting data into a host device, the stylus comprising:
 an elongated housing comprising a wall having a flat region extending along at least a portion of a length of the housing; 
 power receiving circuitry disposed within the housing; 
 a wireless power receiving element disposed within the housing and coupled to the power receiving circuitry, the wireless power receiving element comprising:
 a ferromagnetic structure having a groove region extending between first and second end regions disposed on opposing sides of the groove region, each of the first and second end regions comprising respective interface surfaces spaced apart from and facing the flat region of the elongated housing, wherein the groove region has a smaller length than the two end regions; 
 an inductor coil wound about the groove region of the ferromagnetic structure and in between the first and second end regions, wherein the length of the groove region is a dimension that extends along a direction perpendicular to an axis of the inductor coil; 
 a shield comprising a plurality of sidewalls and a back wall extending there between, the shield forming a cavity within which the ferromagnetic structure and inductor coil are positioned; and 
 a first spacer positioned between the first end of the ferromagnetic structure and the shield to attach the first end of the ferromagnetic structure to the shield and a second spacer positioned between the second end of the ferromagnetic structure and the shield to attach the second end of the ferromagnetic structure to the shield, wherein each of the first and second spacers contacts at least two different surfaces of the ferromagnetic structure and the first and second spacers create a gap between the inductor coil and the shield electrically isolating the inductor coil from the shield; and 
 
 an operating system coupled to the power receiving circuitry and the receiving element, and configured to operate the power receiving circuitry and the receiving element to receive power from the host device. 
 
     
     
       11. The stylus of  claim 10 , wherein each of the first and second spacers is positioned behind a respective interface surface of the first and second end regions of the ferromagnetic structure. 
     
     
       12. The stylus of  claim 11 , wherein each of the first and second spacers comprises one or more retainers that wrap around parts of the ferromagnetic structure. 
     
     
       13. The stylus of  claim 12 , wherein the one or more retainers wraps around portions side surfaces of the ferromagnetic structure. 
     
     
       14. The stylus of  claim 10 , wherein the shield comprises four sidewalls coupled to the back wall to form a five-sided box that defines the cavity. 
     
     
       15. The stylus of  claim 10 , wherein the end regions are configured to direct propagation of magnetic flux toward a transmitting element. 
     
     
       16. The stylus of  claim 10 , further comprising an interfacing end that is configured to make contact with the host device to input data into the host device. 
     
     
       17. The stylus of  claim 16 , wherein the interfacing end has a structure that tapers to a tip. 
     
     
       18. The stylus of  claim 10  further comprising a circuit board disposed within the housing an having at least one integrated circuit mounted on the circuit board at a location between the shield and the a portion of the housing wall opposite the flat region. 
     
     
       19. The stylus of  claim 10  wherein the flat region of the housing wall includes first and second edges running along a length of the housing and the housing wall further includes a curved region extending along a length of the housing and defining a perimeter of the housing from the first edge of the flat region to the second edge of the flat region. 
     
     
       20. The stylus of  claim 10  further comprising a support frame disposed within the housing and extending along at least a portion of the housing length, the support frame having a C-shaped cross-section such that the support frame is positioned against an inner periphery of the curved wall of the housing with an opening of the support frame facing flat region of the wall.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/565,460, filed on Sep. 29, 2017 and U.S. Provisional Patent Application No. 62/565,471, filed on Sep. 29, 2017, and is related to the concurrently filed and commonly assigned U.S. Non-Provisional patent application Ser. No. 16/127,072, filed Sep. 10, 2018, entitled “Attachment Devices for Inductive Interconnection Systems”, the disclosures of which are herein incorporated by reference in their entirety and for all purposes. 
    
    
     BACKGROUND 
     Portable electronic devices, such as tablets, smart phones, and the like, have become ubiquitous in modern day life. The functionality and utility provided by these portable electronic devices enhance the life of a user by simplifying tasks, improving productivity, and providing entertainment. Some portable devices, however, are difficult to interact with because several input methods are simply not provided. For instance, the small form factor of some portable electronic devices result in devices that do not have a physical keyboard, making typing cumbersome. Additionally, portable electronic devices have a display screen which is not a suitable surface on which the user can write with a typical writing utensil, e.g., a pen or pencil. 
     Accordingly, accessory devices have been developed to complement the use of these portable electronic devices to enhance user experience by filling in these gaps in usability. For instance, portable keyboards have been developed to connect with these portable electronic devices to provide a physical keyboard on which a user can type by pressing keys. Furthermore, electronic writing devices, e.g., styluses, smart pencils, and the like, have been designed to act as a writing utensil for these portable electronic devices. 
     In some cases, these accessory devices operate by utilizing power from a host device, such as the portable electronic device. The power from the host device can be provided to the accessory devices during use or at an earlier time when the accessory devices are storing power in one or more locally stored batteries only to be used at a later time. Often, these accessory devices couple to the host device through one or more exposed electrical contacts. Using exposed electrical contacts to charge a battery in an accessory device, however, requires the host device and accessory device to have exposed electrical contacts. The exposed contacts can be formed of a plug-and-socket type connection mechanism that results in one or more openings in both the host and accessory devices. This can provide an avenue within which dust and moisture can intrude and damage the devices. Furthermore, the plug-and-socket type of connections require the host and accessory device to be physically connected together, thereby limiting the ease at which the accessory device can be charged by the host device. 
     SUMMARY 
     Some embodiments of the disclosure provide an inductive interconnection system that enables wireless power transfer between a host device and an accessory device. The inductive interconnection system enables the accessory device to receive power from the host device in various rotational orientations. This eases the way in which the accessory device can receive power from the host device. 
     In some embodiments, a receiving element includes a ferromagnetic structure having a groove region defining two end regions on opposing sides of the groove region, where each end region including respective interface surfaces, and the groove region has a smaller length than the two end regions. The receiving element can further include an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions, where the length of the groove region is a dimension that extends along a direction perpendicular to the axis of the inductor coil. The receiving element can also include a shield comprising a plurality of sidewalls and a back wall that form a cavity within which the ferromagnetic structure and inductor coil are positioned, and a spacer positioned between the ferromagnetic structure and the shield to attach the ferromagnetic structure to the shield. 
     In some additional embodiments, an inductive interconnection system includes a transmitting element and a receiving element. The transmitting element includes a transmitting ferromagnetic structure having a transmitting groove region defining two transmitting end regions disposed on opposing sides of the transmitting groove region, and a transmitting inductor coil wound about the transmitting groove region of the transmitting ferromagnetic structure and in between the two transmitting end regions, the transmitting inductor coil configured to generate time-varying magnetic flux through the transmitting ferromagnetic structure. The receiving element can include a ferromagnetic structure having a groove region defining two end regions on opposing sides of the groove region, each end region comprising respective interface surfaces, wherein the groove region has a smaller length than the two end regions. The receiving element can further include an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions, a shield comprising a plurality of sidewalls and a back wall that form a cavity within which the ferromagnetic structure and inductor coil are positioned, and a spacer positioned between the ferromagnetic structure and the shield to attach the ferromagnetic structure to the shield. 
     In certain embodiments, a stylus for inputting data into a host device includes a housing comprising a curved portion and a flat portion, power receiving circuitry disposed within the housing, a receiving element disposed within the housing and coupled to the power receiving circuitry, and an operating system coupled to the power receiving circuitry and the receiving element, and configured to operate the power receiving circuitry and the receiving element to receive power from the host device. The receiving element includes a ferromagnetic structure having a groove region defining two end regions on opposing sides of the groove region, where each end region includes respective interface surfaces, and the groove region has a smaller length than the two end regions. The receiving element can further include an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions, where the length of the groove region is a dimension that extends along a direction perpendicular to the axis of the inductor coil. The receiving element can also include a shield comprising a plurality of sidewalls and a back wall that form a cavity within which the ferromagnetic structure and inductor coil are positioned, and a spacer positioned between the ferromagnetic structure and the shield to attach the ferromagnetic structure to the shield. 
     In some embodiments, an alignment device includes a center magnet having poles arranged in a vertical orientation, first and second strengthening magnets disposed on opposite ends of the center magnet, where the first and second strengthening magnets having poles arranged in a horizontal orientation, and first and second ferromagnetic structures disposed on outer ends of corresponding first and second strengthening magnets such that the first strengthening magnet is disposed between the first ferromagnetic structure and the center magnet, and the second strengthening magnet is disposed between the second ferromagnetic structure and the center magnet. 
     In some additional embodiments, an alignment device including a center ferromagnetic structure; first and second magnets disposed on opposite ends of the center ferromagnetic structure, the first and second magnets having polar ends that are arranged in a horizontal orientation, and first and second side ferromagnetic structures disposed on ends of the first and second magnets such that the first magnet is disposed between the first side ferromagnetic structure and the center ferromagnetic structure, and the second magnet is disposed between the second side ferromagnetic structure and the center ferromagnetic structure. 
     In certain embodiments, a portable electronic device includes a housing, a battery disposed within the housing, a display disposed within the housing and configured to perform user interface functions, a processor disposed within the housing and coupled to the display and configured to command the display to perform the user interface functions, a transmitting element disposed within the housing, and power transmitting circuitry coupled to the processor and the battery, wherein the power transmitting circuitry is configured to route power from the battery to the transmitting element. The transmitting element includes a center magnet having poles arranged in a vertical orientation, first and second strengthening magnets disposed on opposite ends of the center magnet, the first and second strengthening magnets having poles arranged in a horizontal orientation, and first and second ferromagnetic structures disposed on outer ends of corresponding first and second strengthening magnets such that the first strengthening magnet is disposed between the first ferromagnetic structure and the center magnet, and the second strengthening magnet is disposed between the second ferromagnetic structure and the center magnet. 
     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 wireless charging system having an inductive interconnection system, according to some embodiments of the present disclosure. 
         FIGS. 2A-2C  illustrate different perspective views of an exemplary transmitting element, according to some embodiments of the present disclosure. 
         FIG. 3A  illustrates a top-down view of an exemplary host device having two transmitting elements, according to some embodiments of the present disclosure. 
         FIG. 3B  illustrates a perspective view of a portion of the host device shown in  FIG. 3A  where the transmitting element is incorporated in a housing and some surfaces of the transmitting element are exposed, according to some embodiments of the present disclosure. 
         FIG. 3C  illustrates a perspective view of a cross-section of the illustration shown in  FIG. 3B  along the illustrated cut-line, according to some embodiments of the present disclosure. 
         FIG. 4  illustrates an exemplary receiving element configured to receive power from a transmitting element when it is positioned at any point along a limited angular rotation, according to some embodiments of the present disclosure. 
         FIG. 5  illustrates exemplary magnetic interactions between a transmitting element and a receiving element in an inductive interconnection system during wireless power transfer, according to some embodiments of the present disclosure. 
         FIG. 6  is a simplified perspective view diagram of an exemplary accessory device, according to some embodiments of the present disclosure. 
         FIG. 7A  is a simplified cross-sectional diagram of an accessory device at a point across a receiver coil of a receiver element, according to some embodiments of the present disclosure. 
         FIG. 7B  is a simplified cross-sectional diagram of accessory device at a point across an interface surface of a receiver element, according to some embodiments of the present disclosure. 
         FIG. 8A  is a simplified top-down view of an exemplary wireless charging system, according to some embodiments of the present disclosure. 
         FIG. 8B  is a simplified cross-sectional view of an exemplary wireless charging system, according to some embodiments of the present disclosure 
         FIG. 9  is an exploded view diagram of an exemplary receiving assembly, according to some embodiments of the present disclosure. 
         FIG. 10  is an exploded view diagram of an exemplary transmitting assembly, according to some embodiments of the present disclosure. 
         FIG. 11A  illustrates a perspective view of an inductive interconnection system where a transmitting element is positioned at an angle with respect to a receiving element, according to some embodiments of the present disclosure. 
         FIG. 11B  illustrates a cross-sectional view along the dotted cut line through the inductive interconnection system shown in of  FIG. 6A , according to some embodiments of the present disclosure. 
         FIG. 11C  is a graph illustrating a degree of power transfer efficiency between transmitting and receiving elements with respect to varying both separation distance and rotational angle, according to some embodiments of the present disclosure. 
         FIG. 12A  is a perspective view illustrating an elongated receiving element, according to some embodiments of the present disclosure. 
         FIG. 12B  illustrates an exemplary inductive interconnection system including an elongated receiving element, according to some embodiments of the present disclosure. 
         FIGS. 13A-13C  illustrate perspective and plan views of an exemplary transmitting element capable of receiving power from any position across a 360° of angular rotation, according to some embodiments of the present disclosure. 
         FIG. 14A  illustrates a perspective view of an inductive interconnection system whose receiving element is moving into position to receive power from a transmitting element, according to some embodiments of the present disclosure. 
         FIG. 14B  illustrates an inductive interconnection system when a receiving element is aligned with a transmitting element to receive power, according to some embodiments of the present disclosure. 
         FIG. 14C  illustrates a cross-sectional view of an inductive interconnection system showing exemplary magnetic interactions between a transmitting element and a receiving element during wireless power transfer, according to some embodiments of the present disclosure. 
         FIG. 15  is a simplified illustration of an exemplary host alignment device for a host device having a single center magnet, according to some embodiments of the present disclosure. 
         FIG. 16  is a simplified illustration of an exemplary host alignment device having a center magnet and two strengthening magnets, according to some embodiments of the present disclosure. 
         FIG. 17A  illustrates an exemplary accessory alignment device that can be attracted to a host alignment device at any point along a complete 360° angular rotation, according to some embodiments of the present disclosure. 
         FIG. 17B  illustrates an exemplary perspective view of an alignment system including an accessory alignment device and a host alignment device, according to some embodiments of the present disclosure. 
         FIG. 18  is a graph illustrating a force profile between accessory and host alignment devices without chamfered edges. 
         FIG. 19  is a graph illustrating a force profile between accessory and host alignment device with chamfered edges, according to some embodiments of the present disclosure. 
         FIG. 20  illustrates an exemplary host device aligned with an exemplary accessory device configured to receive charge at any point along a complete 360° angular rotation, according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the disclosure describe an inductive interconnection system for a wireless charging system that enables wireless power transfer between a host device and an accessory device. The inductive interconnection system can include a transmitting element and a receiving element configured to receive wireless power from the transmitting element. The transmitting element can be housed within the host device, and the receiving element can be housed within the accessory device so that the accessory device can receive power from the host device. In some embodiments, the transmitting and receiving elements each include a ferromagnetic structure and an inductive coil wound about at least a portion of the ferromagnetic structure. During wireless power transfer, the transmitting element can generate time-varying magnetic flux that can induce a corresponding current in the receiving element to charge the accessory device. The configuration of the transmitting and receiving elements can enable the accessory device to receive power from the host device in various rotational orientations, as will be discussed in further detail herein. Accordingly, the inductive interconnection system significantly improves the ease at which the accessory device can receiver power from the host device. 
     I. Wireless Charging System 
     A wireless charging system includes an electronic transmitting device that transmits power and an electronic receiving device that receives power from the electronic transmitting device. According to some disclosures herein, the electronic transmitting device can be a host device, e.g., a tablet, smart hone, and any other portable consumer electronic device, that is capable of performing various functions for a user; and, the electronic receiving device can be an accessory device, e.g., a portable keyboard, stylus, smart pencil, wireless earphones, and any other suitable electronic device, that can enhance the function of the host device. 
       FIG. 1  is a block diagram illustrating an exemplary wireless charging system  100  having an inductive interconnection system  105 , according to some embodiments of the present disclosure. Wireless charging system  100  include a host device  101  and an accessory device  103  that is configured to receive power transmitted from host device  101 . In some embodiments, host device  101  includes a computing system  102  coupled to a memory bank  104 . Computing system  102  can execute instructions stored in memory bank  104  for performing a plurality of functions for operating device  101 . Computing system  102  can be 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 , communication system  108 , and a sensor system  110  for enabling host device  101  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  101  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. 
     Host device  101  can also include a battery  112 . Battery  112  can be any suitable energy storage device, such as a lithium ion battery, capable of storing energy and discharging stored energy. The discharged energy can be used to power the electrical components of device  101 . 
     In some embodiments, battery  112  can also be discharged to transmit power to accessory device  103 . For instance, battery  112  can discharge energy to power transmitting circuitry  114 , which can in turn drive a current through transmitting element  116 . Driving current through transmitting element  116  can cause it to generate time-varying magnetic flux  128  that can propagate out of host device  101 . Flux  128  can interact with receiving element  118  and cause a corresponding current to be generated in receiving element  118 . This induced current can then be received by power receiving circuitry  120 , which can convert the received power (e.g., alternating current (AC) power) into usable power (e.g., direct current (DC) power). The usable power can then be provided to battery  122  for storage or to operating system  119  for operating accessory device  103 . 
     According to some embodiments of the present disclosure, transmitting element  116  and receiving element  118  together can be a part of an inductive interconnection system  105 . As will be discussed further herein, inductive interconnection system  105  can be configured such that accessory device  103  can receive power from host device  101  when it is positioned in various rotational orientations. In some embodiments, inductive interconnection system  105  can also include a pair of alignment devices: a host alignment device  124  and an accessory alignment device  126 . Host alignment device  124  can attract accessory alignment device  126  so that when they are fully attracted to each other, transmitting element  116  is aligned with receiving element  118  to ensure efficient power transfer between the two elements. Details of the inductive interconnection system  105  will be discussed further herein. 
     II. Inductive Interconnection System 
     As mentioned above, an interconnection system for a wireless charging system can include a transmitting element in a host device and a receiving element in an accessory device. The transmitting element can be configured to generate time-varying magnetic flux that can induce a corresponding current in the receiving element. The current can be converted to usable power and either stored as energy in the accessory device, or immediately used to operate the accessory device. According to some embodiments of the present disclosure, the transmitting and receiving elements each include a ferromagnetic structure and an inductor coil, as will be discussed further herein. 
     A. Transmitting Element 
       FIGS. 2A-2C  illustrate different perspective views of an exemplary transmitting element  200 , according to some embodiments of the present disclosure. Specifically,  FIG. 2A  illustrates a perspective view of transmitting element  200 ,  FIG. 2B  illustrates a top-down view of transmitting element  200 , and  FIG. 2C  illustrates a side-view of transmitting element  200 , according to some embodiments of the present disclosure. 
     With reference to  FIG. 2A , transmitting element  200  can include a coil  202  and a ferromagnetic structure  204 . Coil  202  can be a conductive strand of wire that is wound about a portion of ferromagnetic structure  204 . When wound, coil  202  forms an inductor coil that can generate time-varying magnetic flux when current is driven through coil  202 . Ferromagnetic structure  204  can be a structure that can redirect the propagation of magnetic flux. For instance, ferromagnetic structure  204  can be formed of a magnetic material including ferrite, such as MnZn. Because the magnetic properties of ferromagnetic structure  204  can redirect the magnetic flux generated by coil  202  through its body, ferromagnetic structure  204  can be configured to guide the magnetic flux toward certain directions based upon its structural design. For instance, ferromagnetic structure  204  can include interfacing surfaces  206  and  208  that are positioned past a side surface of a groove region  212  of ferromagnetic structure  204  to guide the magnetic flux toward a certain direction. A better illustration of the structural configuration of transmitting element  200  is the top-down view shown in  FIG. 2B . 
     As shown in  FIG. 2B , transmitting element  200  can include a groove region  212  defining two end regions  214  and  216  positioned on opposing sides of groove region  212 . Coil  202  can be wound around groove region  212  and between (but not around) end regions  214  and  216 . As mentioned herein, transmitting element  200  can include two interfacing surfaces  206  and  208 . Interfacing surfaces  206  and  208  can be respective surfaces of end regions  214  and  216  that are positioned in the same plane. End regions  214  and  216  can protrude past a surface  210  of groove region  212  toward direction D such that the plane in which end regions  214  and  216  are positioned is disposed a distance Y 1,TX  away from a plane in which surface  210  resides. As can be noticed in  FIG. 2B , surface  210  is hidden behind coil  202  but is represented by a dashed line for clarity. In some embodiments, surface  210  can be connected to interfacing surfaces  206  and  208  by sidewalls  218   a  and  218   b . Thus, sidewalls  218   a  and  218   b  can be disposed between groove region  212  and end regions  214  and  216 . Sidewalls  218   a  and  218   b  can extend a distance Y 1,TX , which can be selected to be any suitable distance equal to or greater than a thickness of coil  202 . For instance, Y 1,TX  can be between 0.5 and 1.5 mm, such as 1 mm in a particular embodiment. As can be seen in  FIG. 2B , the overall structure of transmitting element  200  can have a strong resemblance to the letter “U” of the English alphabet. 
     In some embodiments, transmitting element  200  can have an overall width X TX  and an overall length Y TX . As shown in  FIG. 2B , width X TX  and length Y TX  can be a dimension of transmitting element  200  that extends in a direction that is perpendicular to the axis of coil  202 . Additionally, end regions  214  and  216  can have a width X 1,TX . Dimensions X TX , Y TX , and X 1,TX  can be selected to achieve a certain degree of inductive coupling between transmitting element  200  and a receiving element, while resulting in an overall size that can fit within space constraints of a housing for a host device. In some instances, widths X TX  and X 1,TX  are selected to be equal to the corresponding widths of the receiving element for efficient power transfer. Width X TX  can range between 10 mm and 20 mm, width X 1,TX  can range between 3 mm and 4 mm, and length Y TX  can range between 3 mm and 4 mm. In some embodiments, groove region  212  can have a length  220  that is defined by the difference between length Y 1,TX  and Y TX . Thus, length  220  of groove region  212  can be less than length Y TX  in particular embodiments. Accordingly, groove region  212  can have a smaller length than end regions  214  and  216 . 
     Furthermore, as shown in the side-view perspective of transmitting element  200  in  FIG. 2C , transmitting element  200  can also have a height Z TX . In some embodiments, height Z TX  is also selected to achieve a certain degree of inductive coupling between transmitting element  200  and a receiving element, while resulting in an overall size that can fit within space constraints of a housing for a host device. Z TX  can range between 3 and 4 mm. As can be further seen in  FIG. 2C , transmitting element  200  can have a cross-sectional profile that is in the shape of a rectangle. It is to be appreciated however that the rectangular cross-sectional profile of transmitting element  200  in  FIG. 2C  is merely exemplary and that other embodiments can have different profile shapes. For instance, some embodiments can have profiles that are substantially square, circular, ovular, triangular, trapezoidal, and the like. 
     It is to be appreciated that end regions  214  and  216  can protrude in any desired direction. The embodiment illustrated in  FIG. 2B  shows that end regions  214  and  216  can protrude toward direction D. In some embodiments, direction D is a direction that points toward a receiving element so that magnetic fields generated by coil  202  are redirected toward the receiving element by ferromagnetic structure  204 , as will be discussed further herein with respect to  FIG. 5 . 
       FIGS. 3A-3C  illustrate a transmitting element incorporated into a host device, according to some embodiments of the present disclosure. Specifically,  FIG. 3A  illustrates a top-down view of an exemplary host device  300  having two transmitting elements, according to some embodiments of the present disclosure. Host device  300  can be a variety of different electronic devices including, for example, a tablet computer, a smart phone, a laptop computer, among others. 
     With reference to  FIG. 3A , a host device  300  can include a housing  302  and one or more transmitting elements disposed within housing  302 . For example, host device  300  can include two transmitting elements: a first transmitting element  304  and a second transmitting element  306 . First and second transmitting elements  304  and  306  can be positioned proximate to outer surfaces of housing  302  so that they can be positioned as close as possible to an external device, such as an accessory device that contacts an outer surface of housing  302  to wirelessly receive power from host device  300 . In some embodiments, first and second transmitting elements  304  and  306  can be located at opposite sides of housing  302 . For instance, first transmitting element  304  can be located at a left side  308  of housing  302 , and second transmitting element  306  can be located at a right side  310  of housing  302 . Being positioned at left and right sides  308  and  310  of housing  302  enables host device  300  to transmit power to an accessory device on the left and right sides of housing  302 . 
     Although  FIG. 3A  illustrates host device  300  as having two transmitting elements  304  and  306 , embodiments are not limited to such configurations. Additional or alternative embodiments can have more or less than two transmitting elements. For instance, some embodiments can have four transmitting elements, one located on each of the four sides of host device  300 , or three transmitting elements located on left, right, and top sides of host device  300 . Furthermore,  FIG. 3A  illustrates two transmitting elements located only at sides of housing  302 . Embodiments, however, are not so limited. Some embodiments can have a transmitting element positioned proximate to a face of host device  300  so that an accessory device can receive power from host device  300  by resting on the face of host device  300 . 
       FIG. 3B  illustrates a perspective view of a portion  312  of host device  300  shown in  FIG. 3A  where transmitting element  304  is incorporated in housing  302  and some surfaces of transmitting element  304  are exposed, according to some embodiments of the present disclosure. As shown, transmitting element  304  is positioned within housing  302  but proximate to an outer surface  314  of housing  302 . According to some embodiments of the present disclosure, interfacing surfaces  316  and  318  of transmitting element  304  can face outward, away from outer surface  314 , so that magnetic flux generated by transmitter coil  320  of transmitting element  304  can be directed outward toward a receiving element, as will be discussed further herein. 
     To have a better understanding of how transmitting element  304  is incorporated in housing  302 ,  FIG. 3C  illustrates a perspective view of a cross-section of the illustration shown in  FIG. 3B  along the illustrated cut-line. Transmitting element  304  can be fixed in housing  302  by a bracket  322  that is secured to housing  302 . Bracket  322  can be any suitable structure formed of a stiff material, such as stainless steel, and can be secured to housing  302  in any suitable way, such as with an adhesive  324  or a mechanical fastener (not shown). When secured, bracket  322  can press transmitting element  304  against housing  302  to fix it in place with the help of an adhesive material  324 . Bracket  322  can include an opening  323  into which transmitter coil  320  can extend to minimize the amount of space occupied by the entire module. Interfacing surfaces  316  and  318  of ferromagnetic structure  326  can face outward and be covered by a radio frequency (RF) window  328 . RF window  328  can be formed of a material that is transparent to magnetic flux while also providing a degree of protection against physical damage, such as ceramic, sapphire, and the like. 
     A. Receiving Element 
     As discussed herein, the structural design of the ferromagnetic structure of a transmitting element enables it to directionally transmit power to a receiving element by way of its protruded interfacing surfaces. Similarly, a receiving element can include a ferromagnetic structure that is specifically designed to receive the time-varying magnetic flux propagating out of the interfacing surfaces of the transmitting element when the receiving element is positioned across from the transmitting element. 
     In some embodiments, the construction of a receiving element can be substantially similar to the construction of a transmitting element form which it receives wireless power. For instance,  FIG. 4  illustrates an exemplary receiving element  400  configured to receive power from a transmitting element when it is positioned directly across from the transmitting element, according to some embodiments of the present disclosure. In certain embodiments, receiving element  400  can be substantially similar to a transmitting element, like transmitting element  200  in  FIG. 2A . Thus, receiving element  400  can include a coil  402  wound about a groove region  410  of ferromagnetic structure  404 . End regions  414  and  416  can be positioned on opposing sides of groove region  410  and protrude past a side surface of ferromagnetic structure  404 . End regions  414  and  416  can also include interfacing surfaces  406  and  408  through which magnetic flux can enter into and be redirected through ferromagnetic structure  404  to induce a corresponding current in coil  402  during wireless power transfer. In some embodiments, coil  402  is formed of approximately 85 turns in a dual-layer configuration, meaning two layers of turns: a first layer of turns that winds between interfacing surfaces  406  and  408 , and a second layer of turns that winds on top of the first layer and between interfacing surfaces  406  and  408 . 
       FIG. 5  illustrates exemplary magnetic interactions between transmitting element  200  and receiving element  400  in an inductive interconnection system  500  during wireless power transfer, according to some embodiments of the present disclosure. In this embodiment, transmitting element  200  and receiving element  400  are substantially similar in construction, as discussed herein with respect to  FIG. 4 . Furthermore, transmitting element  200  is shown as being housed within housing  302 . 
     During wireless power transfer, coil  202  can generate a plethora of time-varying magnetic flux  502  that can propagate in many different directions. According to some embodiments of the present disclosure, a substantial majority of magnetic flux is redirected by ferromagnetic structure  204  so that the flux exits or enters through interfacing surfaces  208  and  206 . As mentioned herein, the shape of ferromagnetic structure  204  can direct the flux toward a certain direction by way of the protruding portions, which in this case is toward receiving element  400 . Accordingly, a concentration of magnetic flux  502  can exist in regions  504  between corresponding interfacing surfaces of ferromagnetic structures  204  and  404 . 
     Depending on the direction of current flowing through coil  202 , a substantial amount of magnetic flux  502  generated by coil  202  can first flow out of interfacing surface  208  and into interfacing surface  408  of ferromagnetic structure  404 , which can then propagate through ferromagnetic structure  404  and exit out of interfacing surface  406  so that magnetic flux  502  can enter back into ferromagnetic structure  204  through interfacing surface  206 . The resulting flow magnetic flux forms a magnetic loop  506  that induces a current in coil  402  that can be used to provide power to an accessory device within which receiving element  400  is disposed. It is to be appreciated that although magnetic loop  506  is shown in a clockwise direction, magnetic loop  506  can also propagate in a counter-clockwise direction when current is flowing through coil  202  in an opposite direction. 
     Although  FIG. 5  illustrates transmitting element  200  as transmitting power to receiving element  400 , embodiments are not so limited. Other embodiments can reverse the transfer of power such that transmitting element  200  receives power from receiving element  400 . As an example, current can be driven into coil  402  of receiving element  400  such that coil  402  generates time-varying magnetic flux. The generated time-varying magnetic flux can be redirected by ferromagnetic structure  404 , which can be received by ferromagnetic structure  204 . The received magnetic flux in ferromagnetic structure  204  can induce a corresponding current in coil  202 , which can be used to provide power to a host device within which transmitting element  200  is disposed. 
     As can be understood in  FIG. 5 , the orientation of receiving element  400  with respect to transmitting element  200  can substantially affect the efficiency at which power is transferred in inductive interconnection system  500 . In some embodiments, optimal power transfer is achieved when transmitting element  200  is aligned with receiving element  400 , and when the two elements are oriented such that interfacing surfaces  406  and  408  of ferromagnetic structure  404  are facing toward corresponding interfacing surfaces  206  and  208  of ferromagnetic structure  204 . Furthermore, optimal power transfer can be achieved when the separation distance  426  between transmitting and receiving elements  200  and  400  is minimized. 
     According to some embodiments of the present disclosure, receiving element  400  can be incorporated within an accessory device to enable wireless power transfer between a host device, e.g., host device  300  in  FIG. 3 , and the accessory device.  FIG. 6  is a simplified perspective view diagram of an exemplary accessory device  600 , according to some embodiments of the present disclosure. As shown in  FIG. 6 , accessory device  600  can be any suitable electronic device having an operating system, power receiving circuitry, and a battery, such as accessory device  103  in  FIG. 1 . Accessory device  600  can be operated to input data into a host device. As an example, accessory device  600  can be a stylus or a smart pencil that a user can use to make contact with the host device to input data into the host device. Accordingly, in some embodiments, accessory device  600  can include a housing  602  having a back end  606  and an interfacing end  604  opposite of back end  606  that is configured to make contact with the host device. For instance, interfacing end  604  can have a structure that tapers to a tip to mimic the tip of a conventional writing utensil, such as a pencil or pen. 
     In some embodiments, housing  602  of accessory device  600  can include a curved surface portion  608  and a flat portion  610  that both extend between at least a portion of interfacing end  604  and back end  606  of housing  602 . Flat portion  610  can include a receiving surface  611 , against which a housing for a host device can be positioned to effectuate wireless power transfer, as will be discussed herein with respect to  FIGS. 7A-7B and 8A . According to some embodiments, accessory device  600  can include a receiving element  612  disposed within and adjacent to flat portion  610  of housing  602 . Receiving element  612  can have the same form and function as receiving element  400  discussed herein with respect to  FIGS. 4 and 5 . Thus, receiving element  612  can include a ferromagnetic structure  605  having interfacing surfaces  614  and  616 , and a receiver coil  618  wound about a groove region (not shown, but similar to groove region  410  of receiving element  400  in  FIG. 4 ) of ferromagnetic structure  605 . In some embodiments, interfacing surfaces  614  and  616  can face toward flat portion  610  of housing  602  so that accessory device  600  can wirelessly receive power by interacting with magnetic flux propagating from a transmitting element through flat portion  610 . The cross sectional profile of housing  602  can resemble an upper case letter “D”, as better illustrated in  FIGS. 7A and 7B . 
       FIGS. 7A and 7B  illustrate cross-sectional views of accessory device  600  at different locations, according to some embodiments of the present disclosure. Specifically,  FIG. 7A  is a simplified cross-sectional diagram  700  of accessory device  600  at a point across receiver coil  618  of receiving element  612 , and  FIG. 7B  is a simplified cross-sectional diagram of accessory device  600  at a point across interface surface  616  of receiving element  612 , according to some embodiments of the present disclosure. 
     As shown in  FIG. 7A , housing  602  includes curved portion  608  and flat portion  610  that extend along a length (i.e., parallel to the center axis) of housing  602 . Curved and flat portions  608  and  610  can form a monolithic structure that can enclose one or more electrical components within it, such as receiving element  612 , as discussed herein with respect to  FIG. 6 . In addition to receiving element  612 , housing  602  can also enclose various other components such as, but not limited to, a shield  702 , a support frame  704 , one or more electrical components  715 , and a driver board  717  upon which component  715  is mounted. Shield  702  can be formed of any material suitable for blocking magnetic flux propagating around receiving element  612  from being exposed on electrical component(s)  715  within housing opening  710  of housing  602 . For instance, shield  702  can be formed of copper. Electrical component(s)  715  can be any suitable electronic device for operating accessory device  600  and/or receiver coil  618 . For instance, electrical component(s)  715  can be a microcontroller, field programmable logic array (FPGA), application specific integrated circuit (ASIC), and the like. Electrical component(s)  715  can be electrically coupled to receiver coil  618  of receiving element  612  to receive wireless power, such as by receiving current from receiver coil  618  induced by a magnetic flux generated by a transmitter element. 
     In some embodiments, shield  702  is constructed and positioned in a way that enhances the blockage of magnetic flux. For instance, shield  702  can include an inner bottom surface  714  and inner side surfaces  716  and  718  that form a cavity within which receiving element  612  is disposed so that shield  702  is positioned around five sides of receiving element  612 . A perspective view of shield  702  is shown in  FIG. 9 , which will be discussed further herein. By being positioned around five sides of receiving element  612 , shield  702  can enhance its ability to block magnetic flux from propagating into opening  710  and/or outside of accessory device  600 . In some embodiments, shield  702  can include outer side surfaces  720  and  722  and outer back surface  724 . Outer sides surfaces  720  and  722  can conform to the profile of support frame  704  and thus have a curved profile, while outer back surface  724  can be substantially flat to provide space, e.g., housing opening  710 , within which components, e.g., electrical component(s)  715 , of accessory device  600  can be positioned. In some embodiments, the thickness of shield  702  is greater for regions between inner side surfaces  716  and  718  and respective outer side surfaces  720  and  722 , as shown in  FIG. 7A . The thicker parts of shield  702  can provide a more structurally robust shielding component, as well as provide additional structural protection for receiving element  612 . In particular embodiments, outer back surface  724  is positioned along a center vertical line  712  that divides the accessory device into two halves. In such embodiments, shield  702  is positioned within regions of one half of the accessory device. 
     Support frame  704  can be any suitable structure capable of providing structural support for housing  602  and protection for the internal components of accessory device  600  from mechanical stress. In certain embodiments, support frame  704  is positioned against an inner surface of housing  602  and extends along an area of the inner surface except for regions between receiving element  612  and flat portion  610  of housing  602 , as shown in  FIG. 7A . Support frame  704  can be formed of any suitable stiff material, such as aluminum, steel, and the like. 
     In some embodiments, a gap  706  can exist between receiving element  612  and inner side surfaces  716  and  718  and bottom surface  714  of shield  702 . Gap  706  can be vacant space that helps to electrically isolate receiver coil  618  from shield  702  to ensure optimal operating efficiency of receiver coil  618 . If gap  706  is too small, receiver coil  618  may be too close to shield  702 , thereby decreasing the efficiency at which receiver coil  618  can operate. In some embodiments, gap  706  is between 0.2 and 0.4 mm, particularly 0.3 mm in certain embodiments. Receiving element  612  can be physically coupled to shield  702  to minimize susceptibility to mechanical strain. For instance, receiving element  612  can be coupled to shield  702  by one or more spacers  726 , as shown in  FIG. 7B . Spacers  726  can be directly attached to ferromagnetic structure  605  of receiving element  612  and inner bottom surface  714  and at least a portion of both inner side surfaces  716  and  718  of shield  702 . In some embodiments, spacers  726  are positioned against surfaces of ferromagnetic structure  605  opposite of interface surfaces  614  and  616 . Thus, spacers  726  can be positioned on opposite sides of receiver coil  618 . Any suitable adhesive, such as pressure sensitive adhesive (PSA), can be used to attach spacer  726  between ferromagnetic structure  605  and shield  702 . Utilizing spacers  726  can fix receiving element  612  in space to prevent it from shifting around during use. In some embodiments, spacer  726  is designed to have a thickness suitable for positioning receiving element  612  a certain distance away from shield  702  to ensure electrical isolation of receiver coil  618  and shield  702 . For example, spacer  726  can have a thickness between 0.5 and 0.7 mm, particularly approximately 0.6 mm in some instances. 
     It is to be appreciated that even though  FIGS. 6 and 7A-7B  illustrate an accessory device as having a housing that includes only one flat region, embodiments are not so limited. Other embodiments can have more flat regions around housing, such as two, three, or even six. Furthermore, an accessory device may not have any curved regions in its housing. Instead, the housing can be formed of a plurality of flat regions so that the cross-sectional profile is in a geometrical shape, such as a triangle, square, rectangle, pentagon, hexagon, and the like. It is to be appreciated that any suitable cross sectional profile can be used without departing from the spirit and scope of the present disclosure. 
     During the operation of a wireless charging system, as discussed herein with respect to  FIG. 5 , a transmitting element can be positioned near a receiving element to effectuate wireless power transfer by generating magnetic flux, which can interact with the receiving element to induce a current in the receiving element to charge a battery of an accessory device. An example of a wireless charging system including accessory device  600  is shown in  FIGS. 8A-8B . 
       FIG. 8A  is a simplified top-down view of an exemplary wireless charging system  800 , according to some embodiments of the present disclosure; and,  FIG. 8B  is a simplified cross-sectional view of exemplary wireless charging system  800 , according to some embodiments of the present disclosure. System  800  includes an accessory device, e.g., accessory device  600 , as discussed herein with respect to  FIGS. 6 and 7A-7B , and a host device, e.g., host device  300  discussed herein with respect to  FIGS. 3A-3C , to which accessory device  600  is coupled to receive power wirelessly. For brevity, reference numerals used in  FIGS. 3A-3C, 6, and 7A-7B  are used in  FIG. 8  to indicate their correlation, and thus details of such components can be referenced in the respective figures. Furthermore, for clarity and ease of understanding, housing  602  and shield  702  of accessory device  600  are drawn with dotted lines while housing  302  of host device  300  is drawn with solid lines, and portions of respective housings are transparent so the internal components of the devices can be seen. 
     As shown, accessory device  600  is positioned against host device  300  to allow wireless power transfer. When positioned, receiving surface  611  of accessory device  600  can be in contact, or in close proximity to, outer surface  314  of host device  300 ; and, both receiving element  612  and transmitting element  304  can be positioned so that interface surfaces  614  and  616  of receiving element  612  face toward interface surfaces  316  and  318  of transmitting element  304  to concentrate the propagation of magnetic flux between them, which is discussed herein with respect to wireless charging system  500  in  FIG. 5 . That way, magnetic flux generated by transmitter coil  320  can be redirected by ferromagnetic structure  326  toward ferromagnetic structure  605 , and then induce a corresponding current in receiver coil  618  by propagating through ferromagnetic structure  605 . 
     During wireless power transfer, shield  702  can prevent stray flux from exposing onto other internal components within accessory device  600  or from exiting out of housing  602 . Similarly, host device  300  can also include a shield  802  to prevent stray flux from exposing onto other internal components within host device  300  or from exiting out of housing  302 . Shield  802  can be a sheet of copper, or any other suitable material for blocking magnetic flux, that extends behind transmitting element  304 , e.g., on a side of transmitting element  304  opposite of the side where transparent window  328  is positioned. In some embodiments, shield  802  can extend beyond the farthest left and right edges of transmitting element  304  to enhance the shielding capabilities of shield  802 . 
     In some embodiments, flat portion  610  of housing  602  can be transparent to magnetic flux such that magnetic flux can freely pass through its structure, while also providing a degree of protection against physical damage. For instance, flat portion  610  can be formed of a material such as ceramic, sapphire, and the like. In some embodiments, the entire flat portion  610  can be transparent to magnetic flux, or only a part of the flat portion  610  that is disposed along the path of magnetic flux propagation, such as parts of flat portion  610  that are covering interface surfaces  614  and  616  or parts of flat portion  610  that are positioned directly across from RF window  328 , can be transparent to magnetic flux. That way, magnetic flux generated by transmitting element  304  can freely travel through RF window  328  and flat portion  610  of housing  602  to be received by receiving element  612  to effectuate wireless power transfer. 
     In some embodiments, the relative dimensions of transmitting element  304  and receiving element  612  can be adjusted to improve alignment tolerances so that accessory device  600  can still receive power from host device  300  when accessory device  600  is not exactly aligned with host device  300 , e.g., when the respective horizontal axes of transmitting element  304  and receiving element  612  do not overlap with one another. For instance, as shown in  FIG. 8B , height Z TX  of transmitting element  304  can be shorter than a height Z RX  of receiving element  612 . By having a greater height Z RX , receiving element  612  can shift a few millimeters upward or downward and still be suitably positioned to receive power from transmitting element  304  without suffering a significant decrease in power transfer efficiency. 
       FIGS. 9 and 10  are exploded view diagrams of receiving and transmitting assemblies  900  and  1000  to better illustrate the different components that form the receiving and transmitting elements. Specifically,  FIG. 9  is an exploded view diagram of receiving assembly  900  including receiving element  612 , and  FIG. 10  is an exploded view diagram of an exemplary transmitting assembly  1000  including transmitting element  304 . 
     As shown in  FIG. 9 , receiving assembly  900  can include receiving element  612 , shield  702 , and spacer  726 . Receiving element  612  can include ferromagnetic structure  605  and receiver coil  618  as discussed herein with respect to  FIG. 6 . These components are also discussed in more detail with respect to corresponding components  404  and  402  in  FIG. 4 . Shield  702  can block magnetic flux from propagating to other internal components of accessory device  600  as well as block magnetic flux from exiting accessory device  600 , and spacer  726  can fix receiving element  612  in position and prevent receiver coil  618  from being too close to shield  702 , as discussed herein with respect to  FIG. 7B . Shield  702  can be a five-sided box formed of four sidewalls and a back wall that forms a cavity  910  within which receiving element  612  and spacer  726  can be disposed. When disposed in cavity  910 , interface surfaces  614  and  616  of receiving element  612  can face toward outside of cavity  910 . In some instances, shield  702  can include two extensions  912  and  914  to provide more surface area with which to attach to an anchor point within housing  602  of accessory device  600 . Extensions  912  and  914  can extend from respective sidewalls of shield  702  in a direction parallel to a plane in which the back wall is oriented. Extensions  912  and  914  can be secured to an anchor point to prevent shield  702  from shifting and becoming loose. In addition, shield  702  can also include an opening  916  near the back side of shield  702 . Opening  916  can provide a passage way through which wires can thread. For example, wire  918  that forms receiver coil  618  can enter and exit cavity  910  of shield  702  through opening  916 . That way, wire  918  can make electrical connection with a driver board (not shown) or any other driving component configured to operate receiver coil  618  during wireless power transfer. 
     In some embodiments, spacer  726  can be formed of two separate parts: a first part  902  and a second part  904 . Each part  902  and  904  can be attached to and positioned behind a respective portion of ferromagnetic structure  605 . For instance, first part  902  can be positioned behind interface surface  614  and second part  904  can be positioned behind interface surface  616 . Spacer  726  is made up of two parts so that receiver coil  618  can be positioned between first and second parts  902  and  904  of spacer  726 . In some embodiments, each part  902  and  904  can include a retainer that overlaps parts of ferromagnetic structure  605 . As an example, first part  902  can include individual retainers  906   a - c  coupled to a back retainer  907  and second part  904  can include individual retainers  908   a - c  coupled to a back retainer  909 . Individual retainers  906   a - c  and back retainer  907  can form a monolithic structure, and the same can be said for retainers  908   a - c  and back retainer  909 . Each retainer can overlap respective portions of top, bottom, and side surfaces of ferromagnetic structure  605  to increase the amount of surface area parts  902  and  904  are in contact with ferromagnetic structure  605 . This increase in surface area creates a stronger coupling between spacer  726  and ferromagnetic structure  605  so that spacer  726  can better fix receiving element  612  in place and prevent it from detaching and becoming loose when experiencing drop events. Although  FIG. 9  illustrates retainers  906   a - c  and  908   a - c  as individual, separate extensions of respective back retainers  908  and  908 , embodiments are not limited to such embodiments. In some instances, instead of having multiple individual retainers, each part  902  and  904  can have a single retainer that wraps around three consecutive sides of ferromagnetic structure  605  in an uninterrupted manner. 
     With reference to  FIG. 10 , transmitting assembly  1000  can include transmitting element  304 , spacer  1002 , and a stiffener  1004 . Transmitting element  304  can include ferromagnetic structure  326  and transmitter coil  320  as discussed herein with respect to  FIGS. 3A-3C . These components are also discussed in more detail with respect to corresponding components  204  and  202  in  FIGS. 2A-2C . Stiffener  1004  can be a hard component that provides structural support for transmitting element  304  and provide a structure upon which transmitting element  304  can be mounted. In some embodiments, stiffener  1004  is a plate that is formed of a stiff material, such as, but not limited to, FR4. Spacer  1002  can be formed of two parts: a first part  1006  and a second part  1008 , that can be positioned on either end of transmitter coil  320 . Spacer  1002  can couple ferromagnetic structure  326  to stiffener  1004  so that transmitting element  304  is substantially fixed in place. In some embodiments, transmitting element  304  is attached to stiffener  1004  so that interface surfaces  316  and  318  are facing in a direction that is perpendicular to the direction in which stiffener  1004  is facing. That way, interface surfaces  316  and  318  can be positioned to direct magnetic flux to a receiving element, as shown and discussed herein with respect to  FIGS. 3B-3C and 5 . Wire  1010  that is used to form transmitter coil  320  can be coupled to a connector  1007  containing contact pads  1008   a - b . Each termination end of transmitter coil  320  can make contact with a respective contact pad so that wire  1010  can make electrical connection with a driver board (not shown) or any other driving component configured to operate transmitter coil  320  during wireless power transfer. 
     Although the wireless charging systems discussed herein with respect to  FIGS. 5 and 8A  have the transmitting and receiving elements positioned so that the respective interface surfaces are directly facing one another for wireless power transfer, embodiments are not limited to such alignment constraints. Rather, some embodiments herein enable wireless charging even though transmitting and receiving elements are not directly facing one another. For instance, the receiving element can be specifically designed to receive the time-varying magnetic flux propagating out of the interfacing surfaces in various rotatable orientations. As an example, the receiving element can have a design that enables power transfer at any point along a limited angular rotation and another design that enables power transfer at any point along a complete 360° angular rotation, as will be discussed further herein. 
     1. Receiving Element Enabling Limited Angular Rotation 
     The transmitting element in a host device can transmit power to a receiving element by way of the interfacing surfaces of its ferromagnetic structure. According to some embodiments of the present disclosure, the receiving element can be specifically designed to receive the time-varying magnetic flux propagating out of the interfacing surfaces so that the receiving element can still receive power from the transmitting element when it is positioned at any point along a limited angular rotation. 
     According to some embodiments of the present disclosure, the concentration of magnetic flux between interfacing surfaces of transmitting and receiving elements  200  and  400  (discussed herein with respect to  FIGS. 2A-2C and 4 ) enables sufficient power transfer even when separation distance  426  is increased due to an adjustment of an angular orientation of transmitting element  200  with respect to receiving element  400 .  FIG. 11A  illustrates a perspective view of an inductive interconnection system  1100  where a transmitting element  1102  is positioned at an angle with respect to a receiving element  1104 , according to some embodiments of the present disclosure. Transmitting and receiving elements  1102  are similar in function and construction as transmitting and receiving elements  200  and  400  discussed herein with respect to  FIGS. 2A-2C and 4 . Thus, detailed descriptions of such elements can be referenced in those figures and are not discussed here for brevity. 
     As shown, transmitting element  1102  is disposed within housing  1108  of a host device and is positioned proximate to receiving element  1104  that is disposed within housing  1106  of an accessory device. In some instances, housing  1108  can be rotated a certain degree such that housing  1108  is tilted with respect to housing  1106  as shown in  FIG. 11B . This can occur, for example, when the host device is a tablet and the accessory device is a keyboard accessory and that the tablet is tilted so that the screen is angled upward toward a user&#39;s face. 
       FIG. 11B  illustrates a cross-sectional view along the dotted cut line through inductive interconnection system  1100  shown in of  FIG. 11A , according to some embodiments of the present disclosure. When housing  1108  is rotated at an angle  1109  with respect to housing  1106  around pivot point  1112 , respective transmitting and receiving elements  1102  and  1104  are correspondingly rotated along angle  1109 . Accordingly, transmitting element  1102  can be disposed a rotational separation distance  1110  away from receiving element  1104 . The rotation causes a greater net separation between transmitting and receiving element  1102  and  1104  than if no rotation is present. Thus, in some instances, rotational separation distance  1110  can be greater than separation distance  508  discussed herein with respect to  FIG. 5  even though the distance between the very bottom corner of transmitting element  1102  and receiving element  1104  may be substantially the same as distance  508 . The degree of inductive coupling between transmitting and receiving elements can thus depend on at least two factors: separation distance and rotational angle, as shown in  FIG. 11C . 
       FIG. 11C  is a graph  1101  illustrating a degree of power transfer efficiency between transmitting and receiving elements with respect to varying both separation distance and rotational angle. Graph  1101  has a y-axis representing a degree of power transfer efficiency in percentages increasing upwards, and an x-axis representing a degree of separation distance in millimeters increasing to the right. Three plots are shown in graph  1101 , each representing a different degree of angular rotation: plot  1120  representing a 0° angular rotation, plot  1122  representing a 20° angular rotation, and plot  1124  representing a 45° angular rotation. 
     As shown in graph  1101 , percentage of power transfer efficiency decreases as separation distance increases. Graph  1101  further shows that as angular rotation increases, power transfer efficiency decreases further across all separation distances. Thus, the losses of inductive coupling caused by angular rotation adds to the losses of inductive coupling caused by separation distance. However, it is to be appreciated that embodiments herein can still enable sufficient power transfer even with a degree of angular rotation. For instance, if the power transfer efficiency threshold for sufficient wireless power transfer between a transmitting element and a receiving element is 20% power transfer efficiency, then successful power transfer can still be achieved by an inductive interconnection system whose separation distance is less than 5.5 mm and whose angular rotation is less than 45°. These limits however are merely exemplary and that they can change depending on desired power transfer efficiency. 
     Disclosures aforementioned herein discuss angular rotation around a single pivot point, e.g., pivot point  1112  in  FIG. 11B ; however, embodiments are not limited to configurations that can only pivot round one pivot point. Some embodiments can pivot across any point along an elongated receiving element, as discussed herein with respect to  FIGS. 12A and 12B . 
       FIG. 12A  is a perspective view illustrating an elongated receiving element  1200 , according to some embodiments of the present disclosure. In some embodiments, elongated receiving element  1200  can have substantial similarities to transmitting element  200  discussed herein with respect to  FIG. 2A . For example, elongated receiving element  1200  can include a ferromagnetic structure  1204  and a coil  1202  wound about a central portion  1212  of ferromagnetic structure  1204 . Ferromagnetic structure can also include end regions  1214  and  1216  that protrude past a side surface (not shown, but positioned similarly to surface  210  in  FIG. 2A ) and have interfacing surfaces  1206  and  1208 . Thus, when elongated receiving element  1200  is observed from direction  1220 , the observed structure is substantially similar to receiving element  400  in  FIG. 4 , which is substantially similar to transmitting element  200  of  FIG. 2A . However, elongated receiving element  1200  can include a substantially greater height  1218  than height Z TX  of transmitting element  200  in  FIG. 2A . In some embodiments, height  1218  is greater than the widths of central portion  1212  and end regions  1214  and  1216  combined. The greater height allows a receiving element to receive power from any point along height  1218 , thereby providing a larger area at which receiving element can be positioned to receive charge. 
     For instance,  FIG. 12B  illustrates an exemplary inductive interconnection system  1201  including elongated receiving element  1200 , according to some embodiments of the present disclosure. Elongated receiving element  1200  can wirelessly receive a sufficient amount of power from transmitting element  1222  when transmitting element  1222  is positioned along any point across height  1218 . As an example, elongated receiving element  1200  can receive power from transmitting element  1222  when it is positioned at any one of points  1224 ,  1226 , and  1228 . 
     2. Receiving Element Enabling 360° Rotation 
     As discussed with respect to the aforementioned figures, a receiving element can be configured to receive power from a transmitting element in a limited range of angular rotation. However, as will be discussed further herein with the following figures, a receiving element can be configured to receive power from a transmitting element at any point along a complete 360° range of angular rotation, according to some embodiments of the present disclosure. Accordingly, an accessory device within which the receiving element is disposed can receive power from a host device regardless of how the receiving element is rotated along its axis. This enables the accessory device to be easily placed against the host device to receive power, thereby substantially enhancing user experience. 
       FIGS. 13A-13C  illustrate perspective and plan views of an exemplary receiving element  1300  capable of receiving power from any position across a 360° of angular rotation, according to some embodiments of the present disclosure. Specifically,  FIG. 13A  illustrates a perspective view of receiving element  1300 ,  FIG. 13B  illustrates a top-down view of receiving element  1300 , and  FIG. 13C  illustrates a side-view of receiving element  1300 , according to some embodiments of the present disclosure. 
     With reference to  FIG. 13A , receiving element  1300  can include a coil  1302  and a ferromagnetic structure  1304 . Coil  1302  can be a conductive strand of wire that is wound about a portion of ferromagnetic structure  1304 . When wound, coil  1302  forms an inductor coil that can generate time-vary magnetic flux when current is driven through coil  1302 . Ferromagnetic structure  1304  can be a structure that can redirect the propagation of magnetic flux. For instance, ferromagnetic structure  1304  can be formed of a magnetic material including ferrite, such as MnZn. 
     Because the magnetic properties of ferromagnetic structure  1304  can redirect the magnetic flux generated by coil  1302  through its body, ferromagnetic structure  1304  can be configured to guide the magnetic flux toward all directions in a 360° manner based upon its structural design. For instance, unlike the rectangular block-like structure of receiving element  400  in  FIG. 4A , receiving element  1300  can be substantially cylindrical in form. In some embodiments, receiving element  1300  can be symmetrical about a central axis  209  disposed along a length of ferromagnetic structure  1304 . A channel  1311  can be positioned along central axis  209  and provide vacant space through which objects, such as wires, cables, and the like, can tunnel. Receiving element  1300  can include interfacing surfaces  1306  and  1308  that are positioned past an outer surface of a groove region of ferromagnetic structure  1304 . A better illustration of the structural configuration of receiving element  1300  is shown in the top-down view of  FIG. 13B . 
     As shown in  FIG. 13B , receiving element  1300  can include a groove region  1312  defining two end regions  1314  and  1316  positioned on opposing sides of groove region  1312 . Coil  1302  can be wound around groove region  1312  and between (but not around) end regions  1314  and  1316 . As mentioned herein, receiving element  1300  can include two interfacing surfaces  1306  and  1308 , which can be respective surfaces of end regions  1314  and  1316  that are positioned the same distance away from central axis  1309 . Interfacing surfaces  1306  and  1308  can be axially symmetrical around central axis  1309  so that it is substantially annular in shape. End regions  1314  and  1316  can protrude past a surface  1310  of groove region  1312  such that interfacing surfaces  1306  and  1308  are disposed a distance Y 1,RX  away from surface  1310 . As can be noticed in  FIG. 13B , surface  1310  is hidden behind coil  1302  but is represented by a dashed line for clarity. In some embodiments, surface  1310  can be connected to interfacing surfaces  1306  and  1308  by sidewalls  1318   a  and  1318   b . Thus, sidewalls  1318   a  and  1318   b  can be disposed between groove region  1312  and end regions  1314  and  1316 . Sidewalls  1318   a  and  1318   b  can extend a distance Y 1,RX , which can be selected to be any suitable distance greater than or equal to a thickness of coil  1302 . For instance, Y 1,RX  can be between 0.5 and 1.5 mm, such as 1 mm in a particular embodiment. In some embodiments, end regions  1314  and  1316  can be in the shape of flanges that flare outward from central axis  1309 . As can be seen in  FIG. 13B , the overall structure of receiving element  1300  can have a strong resemblance to the structure of a bobbin. 
     In some embodiments, receiving element  1300  can have an overall width X RX  and an overall diameter d RX . Additionally, end regions  1314  and  1316  can have a width X 1,RX . Dimensions X RX , Y RX , and X 1,RX  can be selected according to design. For instance, dimensions X RX , Y RX , and X 1,RX  can be selected to achieve a certain degree of inductive coupling between receiving element  1300  and a transmitting element, while resulting in an overall size that can fit within space constraints of a housing for an accessory device. In some instances, widths X RX  and X 1,RX  are selected to be equal to the corresponding widths of the transmitting element for efficient power transfer. Width X RX  can range between 10 mm and 80 mm, width X 1,RX  can range between 3 mm and 4 mm, and length Y RX  can range between 3 mm and 4 mm. 
     Furthermore, as shown in the side-view perspective of receiving element  1300  in  FIG. 13C , receiving element  1300  can also have a length d RX  and a radial thickness y RX . Length d RX  can also be defined as the diameter of receiving element  1300 . In some embodiments, length d RX  and radial thickness y RX  are also selected to achieve a certain degree of inductive coupling between receiving element  1300  and a receiving element, while resulting in an overall size that can fit within space constraints of a housing for an accessory device. In particular embodiments, d RX  can range between 7 and 8 mm, and radial thickness y RX  can range between 3 and 4 mm. In some embodiments, radial thickness y RX  can be equal to the overall length Y TX  of the transmitter coil from which it receives power, an example of which can be referenced in  FIG. 2A . In some further embodiments, groove region  1312  in  FIG. 13B  can have a length  1320  that is defined by the difference between length Y 1,RX  and d RX . Thus, length  1320  of groove region  1312  can be less than length d RX  in particular embodiments. Accordingly, groove region  1312  can have a smaller length than end regions  1316  and  1316 . 
     It is to be appreciated that end regions  1314  and  1316  can protrude away from, and in an orientation perpendicular to, central axis  1309 , and around the entire circumference of receiving element  1300 . Thus, end regions  1314  and  1316  can protrude continuously around central axis  1309 . According to embodiments of the present disclosure, this enables receiving element  1300  to receive power from a transmitting element in any rotational orientation around central axis  1309 , as will be discussed further herein with respect to  FIGS. 14A-14C . 
       FIG. 14A  illustrates a perspective view of an inductive interconnection system  1400  whose receiving element  1300  is moving into position to receive power from transmitting element  200 , according to some embodiments of the present disclosure. As mentioned herein with respect to  FIG. 2A , transmitting element  200  can include coil  202  wound about a central portion of ferromagnetic structure  204 , which has interfacing surfaces  206  and  208 . To receive power, receiving element  1300  can be moved toward and into alignment with transmitting element  200  such that interfacing surfaces  1306  and  1308  of receiving element  1300  are positioned proximate to respective interfacing surfaces  206  and  208  of transmitting element  200 . 
       FIG. 14B  illustrates inductive interconnection system  1400  when receiving element  1300  is aligned with transmitting element  200  to receive power, according to some embodiments of the present disclosure. Transmitting element  200  is shown as being housed within housing  302 , as discussed herein with respect to  FIG. 3 , which can be a housing for any suitable portable electronic device (e.g., a tablet computer, a smart phone, a laptop computer, and the like). When aligned, coil  202  can generate time-varying magnetic flux that can induce a corresponding current in coil  1302  regardless of how receiving element  1300  is rotated along rotational pathway  1401  around central axis  1309 . This is because receiving element  1300  is axially symmetrical around central axis  1309  so that no matter how receiving element  1300  is rotated around central axis  1309 , the electrical interactions between it and transmitting element  200  are not impacted and can continue to transfer power. A better illustration of this concept is shown in  FIG. 14C . 
       FIG. 14C  illustrates a cross-sectional view of inductive interconnection system  1400  showing exemplary magnetic interactions between transmitting element  200  and receiving element  1300  during wireless power transfer, according to some embodiments of the present disclosure. Transmitting element  200  is shown as being housed within housing  302 . As can be appreciated by the illustration shown in  FIG. 14C , central axis  1309  can divide receiving element  1300  in two halves: a first half  1410  and a second half  1412 . First half  1410  positioned closest to transmitting element  200  can have a cross section that is substantially similar to receiving element  400  in  FIGS. 4 and 5 . Thus, the electrical interactions during wireless power transfer are substantially similar. For instance, during wireless power transfer, coil  202  can generate a plethora of time-varying magnetic flux  1402 , a substantial portion of which can be redirected by ferromagnetic structure  204  so that the flux exits or enters through interfacing surfaces  208  and  206  and enters or exits ferromagnetic structure  1304  through interfacing surfaces  1306  and  1308 . Thus, a concentration of magnetic flux  1402  can exist in regions  1404  between corresponding interfacing surfaces/rings of ferromagnetic structures  204  and  1304 . In some embodiments, surfaces of interfacing surfaces  1306  and  1308  are parallel to central axis  1309 . 
     Furthermore, depending on the direction of current flowing through coil  202 , a substantial amount of magnetic flux  1402  generated by coil  202  can first flow out of interfacing surface  208  and into interfacing surface  1308  of ferromagnetic structure  1304 , which can then propagate through ferromagnetic structure  1304  and exit out of interfacing surface  1306  so that magnetic flux  1402  can enter back into ferromagnetic structure  204  through interfacing surface  206 . The resulting flow magnetic flux forms a magnetic loop  1406  that induces a current in coil  1302  that can be used to provide power to an accessory device within which receiving element  1300  is disposed. Although magnetic loop  1406  is shown in a clockwise direction, magnetic loop  1406  can also propagate in a counter-clockwise direction when current is flowing through coil  202  in an opposite direction. It is to be appreciated that because receiving element  1300  is symmetrical around central axis  1309 , second half  1412  can be identical to first half  1410  but just arranged in a mirror image of first half  1410 . Thus, if receiving element  1300  is rotated round central axis  1309 , the half closest to transmitting element  200  will be identical to first half  1410  as shown in  FIG. 14C  and have the same electrical interactions. As such, receiving element  1300  can receive power regardless of how it is rotated around central axis  1309 , thereby substantially increasing the ease at which receiving element  1300  can receive power from transmitting element  200 . 
     Although  FIG. 14C  illustrates transmitting element  200  as transmitting power to receiving element  1300 , embodiments are not so limited. Other embodiments can reverse the transfer of power such that transmitting element  200  receives power from receiving element  1300 . As an example, current can be driven into coil  1302  of receiving element  1300  such that coil  1302  generates time-varying magnetic flux. The generated time-varying magnetic flux can be redirected by ferromagnetic structure  1304 , which can be received by ferromagnetic structure  1304 . The received magnetic flux in ferromagnetic structure  1304  can induce a corresponding current in coil  1302 , which can be used to provide power to a host device within which transmitting element  200  is disposed. 
     III. Alignment Devices for Inductive Interconnection Systems 
     As can be understood by the disclosures herein, efficient power transfer is achieved when a receiving element in an accessory device is aligned with a transmitting element in a host device. To achieve alignment between the two elements, one or more alignment devices can be implemented. However, when the receiving element is substantially symmetrical about its central axis, e.g., receiving element  1300  in  FIG. 13A , and housed within a housing of an accessory device that is also substantially symmetrical about its central axis, e.g., a stylus, smart pencil, and the like, then the alignment device for the accessory device may also need to be able to align the receiving element with the transmitting element in any degree of angular rotation. According to some embodiments of the present disclosure, one or more alignment devices can be implemented in the host device and the accessory device to enable the accessory device to align with the host device at any point along a complete 360° range of angular rotation. 
       FIG. 15  is a simplified illustration of an exemplary host alignment device  1500  for a host device having a single center magnet  1502 , according to some embodiments of the present disclosure. Host alignment device  1500  can be housed within the host device to align an accessory device to the host device by aligning to an accessory alignment device in the accessory device. Center magnet  1502  can be any suitable permanent magnet, such as a neodymium magnet. Host alignment device  1500  can have an interfacing surface  1504  that is directed toward the accessory alignment device to attract the accessory alignment device, as will be discussed further herein. In some embodiments, center magnet  1502  can be arranged such that its magnetic poles are positioned vertically, meaning that its north and south pole are positioned along a vertical axis. For instance, as shown in  FIG. 15 , center magnet  1502  can have a north pole positioned at interfacing surface  1504  so that magnetic flux  1505  is directed outward to attract an accessory alignment device that has a corresponding south pole. 
     According to some embodiments, center magnet  1502  can be positioned between two ferromagnetic structures  1506  and  1508 . Ferromagnetic structures  1506  and  1508  are not permanent magnets, but are structures formed of ferromagnetic material through which magnetic flux is allowed to propagate. As an example, ferromagnetic structures  1506  and  1508  can be formed of ferritic stainless steel, iron, nickel, cobalt, or any other suitable material. In some embodiments, ferromagnetic structures  1506  and  1508  have widths  1510  and  1512  that are larger than a width  1514  of center magnet  1502 . Having wider ferromagnetic structures  1506  and  1508  can allow magnetic flux to propagate farther away from center magnet  1502  so that magnetic flux is not concentrated in regions immediately beside center magnet  1502 , thereby smoothing the force profile as an accessory alignment device is moved in that region, as will be discussed further herein with respect to  FIGS. 18-19 . 
     With further reference to  FIG. 15 , host alignment device  1500  can also include chamfered regions  1516  and  1518  positioned at the interfaces of center magnet  1502  and both ferromagnetic structures  1506  and  1508 . In some embodiments, chamfered regions  1516  and  1518  are sloped surfaces that form a V-shape where the lowest end of the sloped surfaces are positioned at the interface between center magnet  1502  and both ferromagnetic structures  1506  and  1508 . Chamfered regions  1516  and  1518  can enlarge the separation distance between the top corners of center magnet  1502  and both ferromagnetic structures  1506  and  1508  to decrease the strength of the magnetic flux at chamfered regions  1516  and  1518  as well as minimize magnetic flux leakage due to a high concentration of magnetic flux that would exist at those regions if no chamfering existed. By decreasing the magnetic flux strength of chamfered regions  1516  and  1518 , the force profile exerted on an accessory alignment device as it moves into alignment with host alignment device  1500  can be smoothed, as will be discussed further herein. Furthermore, by minimizing magnetic flux leakage at chamfered regions  1516  and  1518 , magnetically sensitive devices can be brought close to host alignment device  1500  without suffering from a negative interaction. For instance, minimizing magnetic flux leakage can prevent a credit card from being demagnetized when it is inadvertently brought close to host alignment device  1500 . 
     In some embodiments, host alignment device  1500  can include outer chamfered edges  1520  and  1522  for further smoothing the force profile exerted on an accessory alignment device. For instance, outer chamfered edges  1520  and  1522  can slope downwards away from center magnet  1502  so that as an accessory alignment device moves toward center magnet  1502 , the attractive force on the accessory alignment device gradually builds up. If outer chamfered edges  1520  and  1522  did not exist, then magnetic flux propagating out of ferromagnetic structures  1506  and  1508  may dramatically begin attracting the accessory alignment device as it moves close to ferromagnetic structures  1506  and  1508 . According to some embodiments of the present disclosure, one or more strengthening magnets can be implemented in a host alignment device to enhance the strength of magnetic attraction with an accessory alignment device, as discussed herein with respect to  FIG. 16 . 
       FIG. 16  is a simplified illustration of an exemplary host alignment device  1600  for a host device having a center magnet  1602  and two strengthening magnets  1604  and  1606 , according to some embodiments of the present disclosure. Host alignment device  1500  can be housed within the host device to align an accessory device to the host device by aligning to an accessory alignment device in the accessory device. Alignment device  1600  can have an interfacing surface  1608  that is directed toward the accessory alignment device to attract the accessory alignment device, as will be discussed further herein. Similar to center magnet  1502 , center magnet  1602  can be arranged such that its magnetic poles are positioned vertically, meaning that its north and south poles are positioned along a vertical axis. For instance, as shown in  FIG. 16 , center magnet  1602  can have a north pole positioned at interfacing surface  1608  so that magnetic flux  1605  is directed outward to attract an accessory alignment device that has a corresponding south pole. 
     However, unlike host alignment device  1500 , host alignment device  1600  can include two strengthening magnets  1604  and  1606  on opposite sides of center magnet  1602 . 
     Strengthening magnets  1604  and  1606  can be arranged such that their magnetic poles are positioned along a horizontal axis. Further, the orientation of the magnetic poles of strengthening magnets  1604  and  1606  can be arranged such that their magnetic flux aggregates and strengthens the magnetic flux generated by center magnet  1602 . For instance, if center magnet is arranged such that its north pole is upwards and its south pole is downwards, strengthening magnet  1604  is arranged such that its north pole is on the right and its south pole is on the left, and strengthening magnet  1606  is arranged such that its north pole is on the left and its south pole is on the right. Accordingly, magnetic flux from strengthening magnets  1604  and  1606  can first propagate toward center magnet  1602  and then aggregate with magnetic flux generated by center magnet  1602  to provide a strengthened magnetic flux  1605  propagating upward toward an accessory alignment device. In some embodiments, strengthening magnets  1604  and  1606  have polarities that are opposite from each other so that magnetic flux from both magnets are either directed toward center magnet  1602  or away from center magnet  1602 . Accordingly, the poles of strengthening magnets that are positioned beside center magnet  1602  can be the same pole as the pole of center magnet  1602  that is oriented upward in the direction of an accessory alignment device. 
     According to some embodiments, center magnet  1602  and strengthening magnets  1604  and  1606  are positioned between two ferromagnetic structures  1607  and  1609 . For instance, strengthening magnet  1604  can be positioned between ferromagnetic structure  1607  and center magnet  1602 , and strengthening magnet  1606  can be positioned between ferromagnetic structure  1609  and center magnet  1602 . Ferromagnetic structures  1607  and  1609  can be substantially similar to ferromagnetic structures  1506  and  1508  in  FIG. 15  in form and function. Thus, ferromagnetic structures  1607  and  1609  are structures formed of ferromagnetic material through which magnetic flux is allowed to propagate, and have widths  161160  and  1612  that are larger than a width  1614  of center magnet  1602 . Having wider ferromagnetic structures  1607  and  1609  can allow magnetic flux to propagate farther away from strengthening magnets  1604  and  1606  so that magnetic flux is not concentrated in regions immediately beside strengthening magnets  1604  and  1606 , thereby smoothing the force profile as an accessory alignment device is moved in that region, as will be discussed further herein with respect to  FIGS. 18-19 . 
     With further reference to  FIG. 16 , host alignment device  1600  can also include chamfered regions  1616  and  1618  positioned at the interfaces of center magnet  1502  and both strengthening magnets  1604  and  1606 . Similar to chamfered regions  1516  and  1518 , chamfered regions  1616  and  1618  can decrease the strength of the magnetic flux at chamfered regions  1616  and  1618  as well as minimize magnetic flux leakage due to a high concentration of magnetic flux that would exist at those regions if no chamfering existed. Thus, the force profile exerted on an accessory alignment device as it moves into alignment with host alignment device  1500  can be smoothed, as will be discussed further herein. And, magnetically sensitive devices can be brought close to host alignment device  1600  without suffering from a negative interaction, as discussed herein with respect to  FIG. 15 . 
       FIGS. 15 and 16  illustrate center magnets  1502  and  1602  has having a north pole oriented upward and a south pole oriented downward; however, it is to be appreciated that embodiments are not limited to such configurations. Some embodiments can have center magnets  1502  and  1602  arranged in opposite polarities. In such instances, strengthening magnets  1604  and  1606  can also be arranged in opposite polarities. 
     Although host alignment device  1600  is not shown as having outer chamfered edges, like outer chamfered edges  1520  and  1522  in  FIG. 15 , it is to be appreciated that host alignment device  1600  can include outer chamfered edges in some embodiments for further smoothing the force profile exerted on an accessory alignment device. 
     According to some embodiments of the present disclosure, an accessory alignment device can be configured to be attracted to the center magnet of a host alignment device at any point along a complete 360° angular rotation.  FIG. 17A  illustrates an exemplary accessory alignment device  1700  that can be attracted to a host alignment device at any point along a complete 360° angular rotation, according to some embodiments of the present disclosure. Accessory alignment device  1700  can include a pair of magnets  1702  and  1704  positioned between a center ferromagnetic structure  1706  and two side ferromagnetic structures  1028  and  1710 . For instance, magnet  1702  can be positioned between center ferromagnetic structure  1706  and side ferromagnetic structure  1708 , and magnet  1704  can be positioned between center ferromagnetic structure  1706  and side ferromagnetic structure  1710 . Magnets  1702  and  1704  can be any suitable permanent magnets, e.g., neodymium magnets, and ferromagnetic structures  1706 ,  1708 , and  1710  can be formed of any suitable ferromagnetic material, e.g., ferritic stainless steel, iron, nickel, cobalt, or any other suitable material. 
     Magnetic poles of magnets  1702  and  1704  can be arranged horizontally and oriented such that both of their magnetic flux propagate toward or away from center ferromagnetic structure  1706 . Accordingly, their magnetic flux can aggregate and strengthen in center ferromagnetic structure  1706  and then propagate outward in all radial directions  1714  away from (or towards depending on polarity) its central axis  1712 . For instance, magnets  1702  and  1704  can have their south poles oriented toward center ferromagnetic structure  1706  such that magnetic flux propagates toward central axis  1712  from all radial directions  1714 . In some embodiments, accessory alignment device  1700  has a substantially cylindrical shape so that its structure is axially symmetrical with respect to central axis  1712 . Thus, accessory alignment device  1700  can be attracted to any magnet having a north pole in any degree of rotation around its central axis  1712 , as better shown in  FIG. 17B . 
       FIG. 17B  illustrates an exemplary perspective view of an alignment system  1701  including an accessory alignment device (e.g., accessory alignment device  1700 ) and a host alignment device (e.g., host alignment device  1600 ), according to some embodiments of the present disclosure. As shown in  FIG. 17B , accessory alignment device  1700  is being attracted to host alignment device  1600 . When accessory alignment device  1700  is brought close to host alignment device  1600 , forces generated by complementary magnetic fluxes draw them toward alignment. For ease of understanding, the magnetic polarities discussed herein with respect to  FIGS. 16 and 17A  are also applied to  FIG. 17B . During alignment, host alignment device  1600  has a strong north polarity at its interfacing surface  1608  that attracts the south polarity of center ferromagnetic structure  1706  of accessory alignment device  1700 . The substantially axially symmetrical structure of accessory alignment device  1700  enables it to be attracted to host alignment device  1600  in any degree of rotation  1716  around its central axis  1712 . In some embodiments, a channel  1711  can be positioned along central axis  1712  and provide vacant space through which objects, such as wires, cables, and the like, can tunnel. 
     As mentioned herein, accessory alignment device  1700  further includes side ferromagnetic structures  1708  and  1710 . Side ferromagnetic structures  1708  and  1710  can help spread out the propagation of magnetic flux so that there is not a high concentration of magnetic flux at the interface between magnets  1702  and  1704 . The spreading of magnetic flux by ferromagnetic structures  1708 ,  1710 ,  1607 , and  1609  in conjunction with the chamfered edges  1616  and  1618  helps smooth the force profile of an attraction force between devices  1700  and  1600  such that the user feels a smooth attraction between them. 
       FIGS. 18 and 19  are graphs illustrating exemplary force profiles between accessory and host alignment devices. Specifically,  FIG. 18  is a graph illustrating a force profile  1802  between accessory and host alignment devices without chamfered edges (e.g., chamfered edges  1616  and  1618  in  FIG. 17B ), and  FIG. 19  is a graph illustrating a force profile  1902  between accessory and host alignment devices with chamfered edges, according to some embodiments of the present disclosure. Both graphs have an x-axis representing a distance between the center of an accessory alignment device and the center of a host alignment device where 0 represents alignment. Both graphs also have a y-axis representing a degree of force where positive values indicate a repelling force and negative values indicate an attractive force. 
     As shown in  FIG. 18 , without the chamfered edges, force profile  1802  can include peaks  1804  and  1806  of high repelling forces experienced by a user. These peaks can be positioned at the interfaces between a center magnet (e.g.,  1602  in  FIGS. 16 and 17B ) and both strengthening magnets (e.g.,  1604  and  1606  in  FIGS. 16 and 17B ). Thus, the user will feel strong resistance as accessory alignment device  1700  moves toward the aligned position before feeling a strong attractive force as the two devices are aligned. In contrast, force profile  1902  as shown in  FIG. 19  does not have peaks  1804  and  1806  but instead has flat regions  1904  and  1906  where the peaks would be if the host alignment device did not have chamfered edges. The chamfered edges reduce the concentration of magnetic flux at that area so a strong repelling force does not exist to repel the accessory alignment device at those locations. As a result of having chamfered regions, the force profile is substantially smoother, thereby resulting a better user feel. 
       FIG. 20  illustrates an exemplary wireless charging system where a host device  2000  is aligned with an exemplary accessory device  2002  configured to receive charge at any point along a complete 360° angular rotation, and/or an exemplary accessory device  2003  whose housing includes a flat portion that makes contact with host device  2000 , according to some embodiments of the present disclosure. Host device  2000  can include host alignment devices  2004 - 2007  and transmitting elements  2008 - 2009 . Each host alignment device  2004 - 2007  can be configured as host alignment device  1600  discussed herein with respect to  FIG. 16 . Further, each transmitting element  2008 - 2009  can be configured as transmitting element  200  discussed herein with respect to  FIG. 2A . Host alignment devices  2004 - 2007  and transmitting elements  2008 - 2009  can be housed within housing  2001  of host device  2000 . 
     As further shown in  FIG. 20 , accessory device  2002  can include accessory alignment devices  2010 - 2011  and receiving element  2012 . Each accessory alignment device  2010 - 2011  can be configured as accessory alignment device  1700  discussed herein with respect to  FIG. 17A . Further, receiving element  2012  can be configured as receiving element  1300  discussed herein with respect to  FIG. 13A . Accessory alignment devices  2010 - 2011  and receiving element  2020  can be housed within housing  2013  of accessory device  2002 . According to some embodiments of the present disclosure, housing  2013  can be axially symmetrical with respect to a central axis  2014  (e.g., substantially cylindrical), and able to receive power from host device  2000  by having its receiving element  2012  interact with time-varying magnetic flux generated by transmitting element  2009 . Accessory device  2002  can achieve alignment with host device  2000  to receive power by having its accessory alignment devices  2010  and  2011  interact with respective host alignment devices  2005  and  2007 . By being able to align with and receive power from host device  2000  in any degree of angular rotation around central axis  2014 , the ease at which accessory device  2002  receives power is substantially improved. 
     Host device  2000  can additionally or alternatively be configured to wirelessly charge accessory device  2003 . Accessory device  2003  can be an accessory device that includes a receiving element  2020  that can receive charge when it is positioned across from a transmitting element as discussed herein with respect to  FIGS. 5 and 8A-8B . Thus, receiving element  2020  can be configured as receiving element  400  in  FIG. 4  and receiving element  612  in  FIGS. 6, 7A-7B, 8A-8B, and 9 . In such embodiments, accessory device  2003  can include a housing that has a flat portion that makes contact with host device  2000  to enable wireless power transfer, as discussed herein with respect to  FIGS. 6, 7A-7B, and 8A-8B . In addition to receiving element  2020 , accessory device  2003  can also include accessory alignment devices  2022  and  2024 . Because accessory device  2003  may not be able to receive charge at any point along a complete 360° angular rotation, alignment devices  2022  and  2024  may not need to be configured to be cylindrical, such as alignment devices  2010  and  2011 . Instead, accessory alignment devices  2022  and  2024  can be substantially rectangular and can be positioned against one side of accessory device  2003  instead of having to extend around the entire housing, as is necessary for alignment devices  2010  and  2011 . Accessory alignment devices  2022  and  2024 , however, can still be configured to have the same magnetic structure as alignment devices  2010  and  2011 , meaning accessory alignment devices  2022  and  2024  can include a pair of magnets positioned between a center ferromagnetic structure and two side ferromagnetic structures, as discussed herein with respect to  FIGS. 17A-17B  for magnetically attracting to, and aligning with, respective host alignment devices  2004  and  2006 . 
     Host device  2000  can be any suitable portable electronic device having at least one of a computing system, communication system, sensor system, memory bank, user interface system, battery, and power transmitting circuitry, such as host device  101  discussed herein with respect to  FIG. 1 . In some embodiments, host device  2000  is a tablet computer, laptop computer, smart phone, or any other suitable device. Additionally, accessory device  2002  can be any suitable electronic device having an operating system, power receiving circuitry, and a battery, such as accessory device  103  in  FIG. 1 . Accessory device  2002  can be operated to input data into host device  2000 . As an example, accessory device  2002  can be a stylus or a smart pencil that a user can use to make contact with host device  101  to input data into host device  101 . Accordingly, in some embodiments, accessory device  2002  can include an interfacing end  2016  that is configured to make contact with housing  2001  of host device  2000 . For instance, interfacing end  2016  can have a structure that tapers to a tip to mimic the tip of a conventional writing utensil, such as a pencil or pen. 
     Although  FIG. 20  illustrates host device  2000  as having four host alignment devices  2004 - 2007  and two transmitting elements  2008 - 2009 , embodiment are not so limited. Other embodiments can have more or less host alignment devices and transmitting elements. Furthermore, embodiments are not limited to configurations where host alignment devices  2004 - 2007  and transmitting elements  2008 - 2009  are positioned either side of host device  2000 . It is to be appreciated that host alignment devices  2004 - 2007  and transmitting elements  2008 - 2009  can be positioned in any suitable location that enables power transfer with accessory device  2002 , such as a top and/or bottom edges of host device  2000 . 
     In addition to the embodiments discussed above, the following embodiments are also envisioned herein. In particular embodiments, a receiving element can include a ferromagnetic structure axially symmetrical around a central axis disposed along a length of the ferromagnetic structure. The ferromagnetic structure can include a groove region defining two end regions on opposing sides of the groove region, where the groove region has a smaller length than the two end regions. The receiving element can also include an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions. 
     The receiving element, in some cases, can further include a channel disposed along the central axis. The ferromagnetic structure can be in the shape of a cylinder. The end regions can be configured to direct propagation of magnetic flux toward a transmitting element. In some embodiments, the ferromagnetic structure further includes sidewalls that extend a distance equal to or greater than a thickness of the inductor coil. The sidewalls can be positioned between the groove region and the two end regions. 
     In additional embodiments, an inductive interconnection system includes a transmitting element and a receiving element. The transmitting element can include a transmitting ferromagnetic structure having a transmitting groove region defining two transmitting end regions disposed on opposing sides of the transmitting groove region, where the transmitting groove region has a smaller length than the two transmitting end regions. The transmitting element can also include a transmitting inductor coil wound about the transmitting groove region of the transmitting ferromagnetic structure and in between the two transmitting end regions. The transmitting inductor coil can be configured to generate time-varying magnetic flux through the transmitting ferromagnetic structure. The receiving element can include a receiving ferromagnetic structure axially symmetrical around a central axis disposed along a length of the receiving ferromagnetic structure. The receiving ferromagnetic structure can include a receiving groove region defining two receiving end regions on opposing sides of the receiving groove region, where the receiving groove region has a smaller length than the two receiving end regions. The receiving element can also include a receiving inductor coil wound about the receiving groove region of the receiving ferromagnetic structure and in between the two receiving end regions. The receiving inductor coil can be configured to receive a current induced by the time-varying magnetic flux. 
     The transmitting end regions can each include respective transmitting interfacing surfaces that face toward the receiving element, where the receiving end regions each include respective receiving interfacing surfaces that face toward the transmitting element. The transmitting interfacing surfaces can face toward at least a portion of the receiving interfacing surfaces. The receiving interfacing surfaces can be axially symmetrical around the central axis. The receiving ferromagnetic structure can further include a channel disposed along the central axis. The receiving ferromagnetic structure can be in the shape of a cylinder. 
     In some further embodiments, a stylus for inputting data into a host device can include a cylindrical housing, power receiving circuitry disposed within the cylindrical housing, a receiving element disposed within the cylindrical housing and coupled to the power receiving circuitry, and an operating system coupled to the power receiving circuitry and the receiving element, and configured to operate the power receiving circuitry and the receiving element to receive power from the host device. The receiving element can include a ferromagnetic structure axially symmetrical around a central axis disposed along a length of the ferromagnetic structure, the ferromagnetic structure comprising a groove region defining two end regions on opposing sides of the groove region, where the groove region has a smaller length than the two end regions, and an inductor coil wound about the groove region of the ferromagnetic structure and in between the two end regions. 
     The ferromagnetic structure can further include a channel disposed along the central axis. The ferromagnetic structure can be in the shape of a cylinder. The end regions can be configured to direct propagation of magnetic flux toward a transmitting element. The ferromagnetic structure can further include sidewalls that extend a distance equal to or greater than a thickness of the inductor coil. The sidewalls can be positioned between the groove region and the two end regions. The stylus can further include an interfacing end that is configured to make contact with the host device to input data into the host device. The interfacing end can have a structure that tapers to a tip. 
     In some embodiments, an alignment device includes a center magnet having poles arranged in a vertical orientation, first and second strengthening magnets disposed on opposite ends of the center magnet, the first and second strengthening magnets having poles arranged in a horizontal orientation, and first and second ferromagnetic structures disposed on outer ends of corresponding first and second strengthening magnets such that the first strengthening magnet is disposed between the first ferromagnetic structure and the center magnet, and the second strengthening magnet is disposed between the second ferromagnetic structure and the center magnet. 
     The first and second strengthening magnets can be opposite in polarity. The first and second ferromagnetic structures can each have a first width and the center magnet can have a second width less than the first width. The alignment device can further include chamfered regions disposed at interfaces between the center magnet and the first and second strengthening magnets. The chamfered regions can be formed of sloped surfaces in V-shapes where lowest ends of the sloped surfaces are positioned at interfaces between the center magnet and the first and second strengthening magnets. The alignment device can further include outer chamfered edges positioned at outer ends of the alignment device farthest away from the center magnet, where the outer chamfered edges are formed of sloped surfaces sloping downwards away from the center magnet. In some instances, the center magnet can include an interfacing surface having a first polarity, the first strengthening magnet having a second polarity oriented towards the right side, and the second strengthening magnet having a third polarity oriented towards the left side, where the first, second, and third polarities are the same polarity. 
     In some additional embodiments, an alignment device includes a center ferromagnetic structure; first and second magnets disposed on opposite ends of the center ferromagnetic structure, the first and second magnets having polar ends that are arranged in a horizontal orientation; and first and second side ferromagnetic structures disposed on ends of the first and second magnets such that the first magnet is disposed between the first side ferromagnetic structure and the center ferromagnetic structure, and the second magnet is disposed between the second side ferromagnetic structure and the center ferromagnetic structure. 
     The first and second magnets can be opposite in polarity. The alignment device can be axially symmetrical around a central axis disposed along a length of the alignment device. The alignment device can further include a channel disposed along the central axis. The alignment device can be substantially cylindrical. 
     In some further embodiments, a portable electronic device includes a housing, a battery disposed within the housing, a display disposed within the housing and configured to perform user interface functions, a processor disposed within the housing and coupled to the display and configured to command the display to perform the user interface functions, a transmitting element disposed within the housing, and power transmitting circuitry coupled to the processor and the battery, where the power transmitting circuitry is configured to route power from the battery to the transmitting element. The transmitting element can include a center magnet having poles arranged in a vertical orientation, first and second strengthening magnets disposed on opposite ends of the center magnet, the first and second strengthening magnets having poles arranged in a horizontal orientation; and first and second ferromagnetic structures disposed on outer ends of corresponding first and second strengthening magnets such that the first strengthening magnet is disposed between the first ferromagnetic structure and the center magnet, and the second strengthening magnet is disposed between the second ferromagnetic structure and the center magnet. 
     The first and second strengthening magnets can be opposite in polarity. The first and second ferromagnetic structures can each have a first width and the center magnet can have a second width less than the first width. The transmitting element can further include chamfered regions disposed at interfaces between the center magnet and the first and second strengthening magnets. The chamfered regions can be formed of sloped surfaces in V-shapes where lowest ends of the sloped surfaces are positioned at interfaces between the center magnet and the first and second strengthening magnets. The transmitting element can further include outer chamfered edges positioned at outer ends of the alignment device farthest away from the center magnet, where the outer chamfered edges are formed of sloped surfaces sloping downwards away from the center magnet. In some cases, the center magnet can include an interfacing surface having a first polarity, the first strengthening magnet can have a second polarity oriented towards the right side, and the second strengthening magnet can have a third polarity oriented towards the left side, where the first, second, and third polarities are the same polarity. The portable electronic device can be a tablet. 
     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: 20180910
Publication Date: 20200728
Grant Date: 20200728
Priority Date: 20170929
Inventors: MARSHALL, BLAKE R.
OW, FLORENCE W.
RUSCHER, JOEL N.
TAN, LIQUAN
ZIMMERMAN, AIDAN N.
NASIRI MAHALATI, REZA
ZHU, HAO
Ji, Qigen
SAMPATH, Madhusudanan Keezhveedi
LIU, NAN
SCRITZKY, ROBERT
LISI, GIANPAOLO
Assignee: APPLE INC
CPC Classifications: [{"code": "H01F7/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F27/306", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1683", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0247", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/363", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/306", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0044", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1698", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1635", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/038", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1669", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/166", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1632", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2200/1632", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F7/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F27/365", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/266", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1635", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/362", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65897523