PATENT DOCUMENT

Publication Number: US-10840007-B2
Application Number: US-201715658227-A
Country: US
Kind Code: B2

Title: Shielding for multi-coil wireless power transfer systems

Abstract:
A shield for redirecting magnetic field generated from a plurality of transmitter coils includes a ferromagnetic structure divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability, where the plurality of boundary regions are configured to resist a propagation of magnetic field from a first area of the ferromagnetic structure to a second area of the ferromagnetic structure, where the first area intercepts the magnetic field generated from at least one active transmitter coil of the plurality of transmitter coils.

Claims:
What is claimed is: 
     
       1. A shield for redirecting magnetic field generated from a plurality of transmitter coils, the shield comprising:
 a ferromagnetic structure divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability, wherein the plurality of boundary regions comprises:
 a first subset of boundary regions forming a border around at least a portion of a transmitter coil of the plurality of transmitter coils, the first subset is configured to resist a propagation of magnetic field from a first area within the border to a second area outside of the border, wherein the first area intercepts the magnetic field generated from the transmitter coil; and 
 a second subset of boundary regions intersecting at a center of the transmitter coil. 
 
 
     
     
       2. The shield of  claim 1 , wherein the plurality of boundary regions extend across the entire shield from edge to edge. 
     
     
       3. The shield of  claim 1 , wherein the plurality of boundary regions intersect one another at a plurality of points. 
     
     
       4. The shield of  claim 3 , wherein the plurality of points align with centers of respective transmitter coils. 
     
     
       5. The shield of  claim 1 , wherein the plurality of boundary regions comprise a continuous strip of the second material. 
     
     
       6. The shield of  claim 1 , wherein the plurality of boundary regions comprise a non-continuous strip of the second material. 
     
     
       7. The shield of  claim 1 , wherein the second material comprises a dielectric material. 
     
     
       8. The shield of  claim 1 , wherein the second material comprises a conductive material. 
     
     
       9. The shield of  claim 1 , wherein the second material comprises air. 
     
     
       10. The shield of  claim 1 , wherein the first area includes a first portion of segments, and the second area includes a second portion of segments. 
     
     
       11. The shield of  claim 10 , wherein the first area is a charging area that corresponds to an area of the shield that overlaps the at least one active transmitter coil, and the second area is a leakage area that overlaps at least one inactive transmitter coil of the plurality of transmitter coils. 
     
     
       12. A wireless power transmitting device to transmit magnetic field for wireless power transfer, the wireless power transmitting device comprising:
 a housing having a charging surface; 
 a plurality of transmitter coils disposed within the housing below the charging surface and configured to generate magnetic field during a charging event; and 
 a shield comprising a ferromagnetic structure to redirect at least a portion of the magnetic field generated by the plurality of transmitter coils during the charging event, wherein the ferromagnetic structure is divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability, and wherein the plurality of boundary regions comprises:
 a first subset of boundary regions forming a border around at least a portion of a transmitter coil of the plurality of transmitter coils, the first subset is configured to resist a propagation of magnetic field from a first area within the border to a second area outside of the border, wherein the first area intercepts the magnetic field generated from the transmitter coil; and 
 a second subset of boundary regions intersecting at a center of the transmitter coil. 
 
 
     
     
       13. The wireless power transmitting device of  claim 12 , wherein each boundary region is tangent to at least one of the transmitter coils and bisects at least one other of the transmitter coils. 
     
     
       14. The wireless power transmitting device of  claim 12 , further comprising a driver board disposed below the plurality of transmitter coils. 
     
     
       15. The wireless power transmitting device of  claim 14 , wherein the shield is disposed between the plurality of transmitter coils and the driver board so that the magnetic field is prevented from exposing on components mounted on the driver board. 
     
     
       16. The wireless power transmitting device of  claim 15 , wherein the shield comprises a top side and a bottom side so that the magnetic field enters and exits the shield into and out of the top side. 
     
     
       17. The wireless power transmitting device of  claim 12 , wherein the plurality of boundary regions intersect one another at a plurality of points. 
     
     
       18. The wireless power transmitting device of  claim 12 , wherein the first area intercepts the magnetic field generated from at least one active transmitter coil of the plurality of transmitter coils. 
     
     
       19. The wireless power transmitting device of  claim 12 , wherein the second material comprises a dielectric material.

Description:
BACKGROUND 
     Electronic devices (e.g., mobile phones, media players, electronic watches, and the like) operate when there is charge stored in their batteries. Some electronic devices include a rechargeable battery that can be recharged by coupling the electronic device to a power source through a physical connection, such as through a charging cord. Using a charging cord to charge a battery in an electronic device, however, requires the electronic device to be physically tethered to a power outlet. Additionally, using a charging cord requires the mobile device to have a connector (e.g., a receptacle connector) configured to mate with a connector (e.g., a plug connector) of the charging cord. The receptacle connector typically includes a cavity in the electronic device that provides an avenue within which dust and moisture can intrude and damage the device. Furthermore, a user of the electronic device has to physically connect the charging cable to the receptacle connector in order to charge the battery. 
     To avoid such shortcomings, wireless charging devices have been developed to wirelessly charge electronic devices without the need for a charging cord. For example, some electronic devices can be recharged by merely resting on a charging surface of a wireless charging device. A transmitter coil disposed below the charging surface may produce a time-varying magnetic field that induces a current in a corresponding receiving coil in the electronic device. The induced current can be used by the electronic device to charge its internal battery. 
     Typical wireless charging devices only use a single transmitter coil to perform wireless power transfer. This requires the electronic device to be placed in a very specific position to effectuate power transfer, such as directly above the transmitter coil. Some wireless charging devices use multiple transmitter coils so that an electronic device can be charged over a broad charging surface area. These types of wireless charging devices often have a number of disadvantages. For instance, some wireless charging devices can leak magnetic field into areas of the charging surface where an electronic device is not positioned. This leakage causes heat generation and efficiency losses, which reduce the effectiveness of the wireless charging device. Furthermore, the leaked magnetic field can cause unintended interactions with other devices near or on the charging surface. 
     SUMMARY 
     Some embodiments of the disclosure provide shielding structures for a multi-coil wireless charging device that mitigate leakage of magnetic fields across its charging surface. In some embodiments, a shield can be divided into segments by boundary regions. The boundary regions can include material having a magnetic permeability that is lower than a magnetic permeability of the segments so that magnetic fields propagating through the shield will encounter resistance from the boundary regions. Resistance from the boundary regions reduce leakage of magnetic field across the charging surface, thereby minimizing power losses and enhancing power transfer efficiency. 
     In some embodiments, a wireless charging system includes a shield for redirecting magnetic field generated from a plurality of transmitter coils, the shield including a ferromagnetic structure divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability, wherein the plurality of boundary regions are configured to resist a propagation of magnetic field from a first area of the ferromagnetic structure to a second area of the ferromagnetic structure, wherein the first area intercepts the magnetic field generated from at least one active transmitter coil of the plurality of transmitter coils. 
     The plurality of boundary regions can extend across the entire shield from edge to edge. The plurality of boundary regions can intersect one another at a plurality of points. The plurality of points can align with centers of respective transmitter coils. The plurality of boundary regions can include a continuous strip of the second material. The plurality of boundary regions can include a non-continuous strip of the second material. In certain embodiments, the second material includes a dielectric material. In further embodiments, the second material comprises a conductive material. In some embodiments, the second material comprises air. The first area can include a first portion of segments, and the second area can include a second portion of segments. The first area can be a charging area that corresponds to an area of the shield that overlaps the at least one active transmitter coil, and the second area can be a leakage area that overlaps at least one inactive transmitter coil of the plurality of transmitter coils. 
     In some embodiments, a wireless power transmitting device to transmit magnetic field for wireless power transfer can include a housing having a charging surface, a plurality of transmitter coils disposed within the housing below the charging surface and configured to generate magnetic field during a charging event, and a shield comprising a ferromagnetic structure to redirect at least a portion of the magnetic field generated by the plurality of transmitter coils during the charging event, where the ferromagnetic structure is divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability. 
     Each boundary region can be tangent to at least one of the transmitter coils and can bisect at least one other of the transmitter coils. The wireless power transmitting device can further include a driver board disposed below the plurality of transmitter coils. The shield can be disposed between the plurality of transmitter coils and the driver board so that the magnetic field is prevented from exposing on components mounted on the driver board. The shield can include a top side and a bottom side so that the magnetic field enters and exits the shield into and out of the top side. The plurality of boundary regions can be configured to resist a propagation of magnetic field from a first area of the shield to a second area of the shield. The plurality of boundary regions can intersect one another at a plurality of points, where the plurality of points can align with centers of respective transmitter coils. The first area can intercept the magnetic field generated from at least one active transmitter coil of the plurality of transmitter coils. The second material can include a dielectric material. 
     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 simplified diagram illustrating a wireless charging device configured to perform wireless power transfer. 
         FIG. 2  is a simplified diagram illustrating an exemplary transmitter coil arrangement within a wireless charging device. 
         FIG. 3A  is a simplified diagram illustrating a simplified cross-sectional view of an electronic device resting on a wireless charging device and the electrical interactions between them during wireless power transfer. 
         FIG. 3B  is a simplified diagram illustrating a simplified top-down view of  FIG. 3A . 
         FIG. 4A  is a simplified diagram illustrating a simplified cross-sectional view of an electronic device resting on a wireless charging device with a segmented shield and the electrical interactions between them during wireless power transfer, according to some embodiments of the present disclosure. 
         FIG. 4B  is a simplified diagram illustrating a simplified top-down view of  FIG. 4A , according to some embodiments of the present disclosure. 
         FIG. 5A  is a simplified diagram illustrating an exemplary segmented shield having a plurality of boundary regions in a first configuration that divide the segmented shield into segments, according to some embodiments of the present disclosure. 
         FIG. 5B  is a simplified diagram illustrating an exemplary segmented shield having a plurality of boundary regions in a second configuration that divide the segmented shield into segments, according to some embodiments of the present disclosure 
         FIG. 6A  is a simplified diagram illustrating a multi-coil array superimposed over the segmented shield shown in  FIG. 5B , according to some embodiments of the present disclosure. 
         FIG. 6B  is a simplified diagram illustrating a zoomed-in top-down view of transmitter coils in the multi-coil array of  FIG. 6A  superimposed over the segmented shield shown in  FIG. 5B , according to some embodiments of the present disclosure 
         FIG. 7A  is a simplified diagram illustrating an exemplary segmented shield that has boundary regions that are configured with bridging structures between segments, according to some embodiments of the present disclosure. 
         FIG. 7B  is a simplified diagram illustrating an exemplary segmented shield having an outer profile that corresponds to the outer profile of a multi-coil array configured in the transmitter coil arrangement shown in  FIG. 2 , according to some embodiments of the present disclosure 
         FIG. 8  is a simplified diagram illustrating a simplified, exploded view of an exemplary wireless charging device having a segmented shield, according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosure describe a shield for a multi-coil wireless charging device that mitigates leakage of magnetic fields across its charging surface. The shield can be housed in an enclosure along with multiple transmitter coils, which are configured to generate time-varying magnetic fields capable of inducing current in a receiver of an electronic device or of a docking station with which the electronic device is coupled. The transmitter coils can be arranged in a manner that enables the multi-coil wireless charging device to provide power to the electronic device positioned anywhere within a broad charging surface. For instance, when the electronic device is placed on only a portion of the charging surface, magnetic fields from the wireless charging device can be confined to areas of the charging surface immediately surrounding the electronic device without leaking to other areas of the charging surface where the electronic device is not positioned. According to embodiments, the shield substantially reduces the leakage of magnetic fields across the charging surface, thereby resulting in improved power transfer efficiency and reduced power losses. Aspects of multi-coil wireless charging devices and shields are discussed in detail further herein. 
     I. Multi-Coil Wireless Charging Device 
       FIG. 1  illustrates a wireless charging device  100  configured to perform wireless power transfer. Wireless charging device  100  can include a charging surface  102  upon which an electronic device  106  having a wireless power receiver can be placed to wirelessly charge its battery. In some embodiments, charging surface  102  may be a region of a top surface  104  of wireless charging device  100  that spans across a vast majority, if not the entire area, of top surface  104 . Time-varying magnetic fields generated by wireless charging device  100  can propagate through regions of top surface  104  within charging surface  102  and form a continuous region within which devices can wirelessly receive power. Time-varying magnetic fields can be generated by multiple transmitter coils embedded within wireless charging device  100 . For instance, wireless charging device  100  can include a transmitter coil arrangement as shown in  FIG. 2 . 
       FIG. 2  illustrates an exemplary transmitter coil arrangement  200  within wireless charging device  100 . The illustration of  FIG. 2  shows wireless charging device  100  with top surface  104  removed so that the embedded transmitter coil arrangement  200  may be seen. Transmitter coil arrangement  200  can include multiple arrays of transmitter coils arranged in different layers and in a non-concentric fashion so that when all of the transmitter coils are operating, an array of magnetic fields can be generated across charging surface  102 . 
     Electronic device  106  can be any suitable device configured to receive power from wireless charging device  100 . For example, electronic device  106  can be a portable electronic device (e.g., a mobile phone, a media player, an electronic watch, and the like), a docking station, or an accessory electronic device, each having a receiver coil configured to receive power when exposed to magnetic fields produced by wireless charging device  100 . When electronic device  106  in  FIG. 1 , is placed on charging surface  102  of wireless charging device  100 , time-varying magnetic fields generated by the transmitter coils can induce a corresponding current in a receiver coil of device  106 , as shown in  FIG. 3A . 
       FIG. 3A  illustrates a simplified cross-sectional view of electronic device  106  resting on wireless charging device  100  and the electrical interactions between receiver coil  302  and a transmitter coil  300 - 1  during wireless power transfer. Transmitter coil  300 - 1  can be one transmitter coil of a plurality of transmitter coils, such as N number of transmitter coils where transmitter coil  300 -N is the N th  transmitter coil. Transmitter coils  300 - 1  to  300 -N can be organized as transmitter coil arrangement  200  shown in  FIG. 2 . 
     During wireless power transfer, transmitter coil  300 - 1  can generate time-varying magnetic field  304 , which can propagate through both device housings and be received by receiver coil  302 . Time-varying magnetic field  304  interacts with receiver coil  302  to generate a corresponding current in receiver coil  302 . The generated current can be used to charge a battery for operating electronic device  106 . 
     Although magnetic field  304  can flow towards receiver coil  302 , magnetic field  304  can also flow towards other components, e.g., components  308 ,  310 ,  312 , and  314 , within wireless charging device  100 , such as control microprocessors, power electronics, and the like. Exposing components  308 ,  310 ,  312 , and  314  to magnetic field  304  can disturb and compromise the performance of those components. Thus, a shield  306  can be implemented between transmitter coils  300 - 1  through  300 -N and components  308 ,  310 ,  312 , and  314 , as shown in  FIG. 3A . Shield  306  can be formed of a material that has a high magnetic permeability, such as ferrite. Shield  306  can thus redirect magnetic field  304  to prevent exposure upon components  308 ,  310 ,  312 , and  314 . Redirection of magnetic field  304  occurs because of the high magnetic permeability of shield  306  when compared to air. Accordingly, magnetic field  304  may prefer to flow into shield  306  instead of flowing out of it. In some instances, magnetic field  304  flows into and out of a first side of shield  306  (i.e., the top side of shield  306  as shown in  FIG. 3A ) instead of flowing through it and exiting out of a second side of shield  306  (i.e., the bottom side of shield  306  as shown in  FIG. 3A ). Thus, components  308 ,  310 ,  312 , and  314  receive minimal, if any, exposure to magnetic field  304 . 
     Typical shields, such as shield  306  in  FIG. 3A , are structures formed of a continuous piece of ferromagnetic material. The continuous construction of shield  306  means that its structure is formed of ferromagnetic material throughout its entire build, without any regions of non-ferromagnetic material. For instance, portions of the shield that directly overlap transmitter coils are continuous in construction and do not have regions of non-ferromagnetic material. While this construction effectively shields the magnetic field, its continuous structure also allows magnetic field to propagate across itself and leak out in areas where an electronic device is not positioned. For instance, as shown in  FIG. 3A , leaking magnetic field  307  can propagate along shield  306  all the way to an area of shield  306  where electronic device  106  is not positioned. Another perspective of the leakage area is shown in  FIG. 3B . 
       FIG. 3B  illustrates a top-down view of magnetic field leakage when electronic device  106  is positioned on wireless charging device  100  for wireless power transfer. Electronic device  106  can receive power from wireless charging device  100  by merely resting on charging surface  102  of wireless charging device  100 . During wireless power transfer, magnetic field  304  is generated by transmitter coil  300 - 1  and received by receiver coil  302  in electronic device  106 , as discussed herein with respect to  FIG. 3A . Magnetic field  304  may propagate around the immediate areas surrounding electronic device  106 , which is shown as charging area  320 . Charging area  320  can also be defined by an area of shield  306  that intercepts magnetic field generated by transmitter coil  300 - 1 . However, given the continuous construction of shield  306 , magnetic field  307  can propagate along a length of shield  306  and leak to areas where electronic device  106  is not positioned, such as leakage area  322 . It is to be appreciated that charging area  320  and leakage area  322  correspond to areas of shield  306  as well as wireless charging device  100  because a substantial portion of their structures correspond/overlap with each other. Thus, charging area  320  and leakage area  322  are not specific to either shield  306  or wireless charging device  100 , but apply to both shield  306  and wireless charging device  100 . 
     This leaked magnetic field can dissipate energy in the form of heat, thereby decreasing the power transfer efficiency of wireless charging device  100 . Furthermore, the leaked magnetic field can disturb other electronic devices that are placed on charging surface  102  but not intended and/or not configured to receive charge from wireless charging device  100 . This unintended interaction with the leaked magnetic field can damage components in the other electronic devices, such as a radio frequency chip. 
     Thus, according to some embodiments of the present disclosure, a segmented shield structure is designed to mitigate leakage of magnetic field to areas of the shield where magnetic field is not needed or intended to exist. As will be discussed in more detail further herein, the segmented shield has boundary regions of low permeability that can confine magnetic fields to a charging area, e.g., charging area  320 , where an electronic device is receiving charge, and mitigate leakage of magnetic field to areas outside of the charging area, e.g., leakage area  322 . 
     II. Wireless Charging Device With Shielding 
     Embodiments of the disclosure describe a wireless charging device that has a segmented shield for mitigating leakage of magnetic field across its charging surface. The segmented shield can be formed of a ferromagnetic structure that includes regions of low magnetic permeability. These regions can hinder the propagation of magnetic field across the shield to mitigate leakage of the magnetic field to areas outside of a charging area. 
       FIG. 4A  illustrates a simplified cross-sectional view of electronic device  106  resting on a wireless charging device  400  that includes a segmented shield  406 . Wireless charging device  400  is substantially similar to wireless charging device  100  in  FIG. 3A , but different in that wireless charging device  400  includes segmented shield  406  that has boundary regions of low magnetic permeability, according to embodiments of the present disclosure. Thus, the other components shared between wireless charging device  100  and  400  will not be discussed here, and that such details can be referenced in the discussion with respect to  FIG. 3A . 
     During wireless power transfer, transmitter coil  400 - 1  can generate time-varying magnetic field  404 , which can propagate through both device housings and be received by receiver coil  302 . Time-varying magnetic field  404  interacts with receiver coil  302  to generate a corresponding current in receiver coil  302 . The generated current can be used to charge a battery for operating electronic device  106 . 
     As aforementioned herein, segmented shield  406  can be implemented between transmitter coils  400 - 1  through  400 -N and components  408 ,  410 ,  412 , and  414 , as shown in  FIG. 4A , to redirect magnetic field  404  to prevent exposure upon components  408 ,  410 ,  412 , and  414 . Redirection of magnetic field  404  occurs because of the high magnetic permeability of segmented shield  406  when compared to air. Accordingly, magnetic field  404  may prefer to flow into segmented shield  406  instead of flowing out of it. In some instances, magnetic field  404  flows into and out of a first side of segmented shield  406  (i.e., the top side of segmented shield  406  as shown in  FIG. 4A ) instead of flowing through it and exiting out of a second side of segmented shield  406  (i.e., the bottom side of segmented shield  406  as shown in  FIG. 4A ). Thus, components  408 ,  410 ,  412 , and  414  receive minimal, if any, exposure to magnetic field  404 . 
     According to some embodiments of the present disclosure, unlike shield  306  in  FIG. 3A , segmented shield  406  can be a structure that is divided into segments by a plurality of boundary regions. For instance, segmented shield  406  can include a boundary region  404  that divides segmented shield  406  into segments  416  and  418 . Boundary region  404  can be configured to have low magnetic permeability which allows it to resist and/or obstruct the propagation of magnetic field through certain areas of segmented shield  406 . Thus, boundary region  404  can substantially confine magnetic fields generated during wireless power transfer to certain areas of segmented shield  406  and wireless charging device  400 . As an example, confined magnetic field  407  can be confined by boundary region  404  so that magnetic field  407  exits out of segmented shield  406  at or near boundary region  404  before it can propagate across the entire segmented shield  406 . By resisting and/or obstructing the propagation of magnetic field across segmented shield  406 , magnetic fields generated during wireless power transfer can be confined to areas of segmented shield  406  and wireless charging device  400  that immediately surround electronic device  106 , thereby minimizing leakage of magnetic fields and enhancing power efficiency. 
     Another perspective of this concept is shown in  FIG. 4B , which illustrates a top-down view of  FIG. 4A . By incorporating boundary region  404 , magnetic field can be substantially confined to charging area  320 , and substantially resisted from leaking to areas outside of charging area  320 . For instance, boundary region  404  can confine magnetic fields to propagate within only segment  416  and substantially resist propagation of the magnetic fields to segment  418 . Accordingly, segmented shield  406  can mitigate leakage of magnetic field such that a leakage area (e.g., leakage area  322  in  FIG. 3B ) is not created during wireless power transfer. 
     As shown in  FIG. 4B , boundary region  404  can have a length that is greater than its width so that boundary region  404  has an elongated profile. In some embodiments, boundary region  404  has a length that is a multitude times greater than its width so that boundary region  404  has a build similar to a stripe. Boundary region  404  can extend across at least a portion of segmented shield  406 . For instance, boundary region  404  can extend across segmented shield  406  from edge to edge. Furthermore, even though boundary region  404  is shown as a straight line, embodiments are not so limited. Boundary regions in other embodiments can be curved or angled, or be configured to form a polygon. Additionally, boundary regions in other embodiments can be formed of a perforated line so that when viewed generally, boundary region is elongated like a stripe, but when viewed narrowly, boundary region is formed of a plurality of small dots or non-elongated regions of low magnetic permeability that are arranged in a line. 
     Boundary region  404  can be configured to have a magnetic permeability that is lower than the magnetic permeability of segments  416  and  418 . For instance, boundary region  404  can be an air gap. In such instances, each segment  416  and  418  can be individually fixed in position, such as with an adhesive or with one or more bridging structures that attach neighboring segments with one another, as will be discussed further herein. 
     In some additional and alternative embodiments, boundary region  404  can be formed of a diamagnetic material that has non-conductive properties and structural rigidity, unlike an air gap. For instance, boundary region  404  can be formed of a dielectric material that has a high dielectric breakdown voltage such as epoxy resin, polytetrafluoroethylene (PTFE), high density polyethylene (HDPE), and the like. The type of material used to form boundary region  404  can also have properties that minimize interference during device operation, such as materials with low radio frequency (RF) loss (which include the materials listed herein). By using a material that has structural rigidity, segmented shield  400  can have a structural composition like a solid continuous shield structure, but have electrical properties reflective of a segmented structure. 
     Furthermore, boundary region  404  can be formed of a diamagnetic material that has conductive properties. As an example, boundary region  404  can be formed of copper, or any other conductive material that has a relative permeability of at least −1.0. 
     A. Boundary Region Configurations 
     Although  FIGS. 4A and 4B  illustrate segmented shield  406  as having only one boundary region, segmented shield  406  can include a plurality of boundary regions, according to some embodiments of the present disclosure. For instance,  FIG. 5A  illustrates an exemplary segmented shield  500  having a plurality of boundary regions  502   a - d  that divide segmented shield  500  into segments  506   a - h . Boundary regions  502   a - c  can be vertically oriented, and boundary region  502   d  can be horizontally oriented to divide segmented shield  500  into a plurality of rectangular segments  506   a - h . During wireless power transfer, boundary regions  502   a - d  can substantially mitigate propagation of magnetic field across segmented shield  500 , and thus help confine magnetic field to certain areas of segmented shield  500 . In some embodiments, magnetic field can be substantially confined within segment  506   b , or the magnetic field can be confined within segments  506   b  and  506   c  if active transmitter coil(s) are overlapped by both segments  506   b  and  506   c  such that the transmitter coil(s) emit magnetic field in segments  506   b  and  506   c . Although boundary regions  502   a - d  are shown as solid lines, it is to be appreciated that boundary regions  502   a - d  have a width dimension. 
     The degree at which boundary regions  502   a - d  resist the propagation of magnetic fields across its region can vary depending on their widths. Wider boundary regions have larger effective resistances against propagation of magnetic field. Conversely, narrower boundary regions have smaller resistances. However, adjusting the width can affect the total inductance of the multi-coil array. For instance, wider boundary regions decrease the total inductance, while narrower boundary regions increase the total inductance. Thus, the width of boundary regions  502   a - d  can be tuned specifically to the amount of resistance and inductance desired. In some embodiments, the width of boundary regions  502   a - d  can range between 1 and 5 mm. 
     The configuration shown in  FIG. 5A  is merely exemplary and not intended to be limiting. That is, other embodiments can have more or less boundary regions that divide a segmented shield into more or less than the number shown in  FIG. 5A . Furthermore, boundary regions do not have to be oriented in strictly vertical and horizontal orientations; rather, boundary regions can be oriented in any configuration. For example,  FIG. 5B  illustrates an exemplary segmented shield  501  divided into segments  512  by boundary regions  510  that include diagonally oriented boundary regions. Letter designations are not assigned in  FIG. 5B  for clarity purposes given the large number of boundary regions and segments. Boundary regions  510  can include diagonal and horizontal boundary regions that form triangular segments  512 . In some embodiments, each boundary region can extend across the entire segmented shield  501  from edge to edge. It is to be appreciated that the configuration of boundary regions, segments, and boundary region orientations can vary by design. For instance, the configuration can be designed according to an array of transmitter coils positioned adjacent to the segmented shield. As an example, boundary regions  510  can be configured according to a multi-coil array of transmitter coils, as will be discussed in further detail herein. 
       FIG. 6A  illustrates a multi-coil array  600  superimposed over segmented shield  501 , according to some embodiments of the present disclosure. Multi-coil array  600  can be arranged to maximize a charging surface of a wireless charging device, as discussed herein with respect to  FIG. 2 . Boundary regions  510  can be positioned to confine magnetic fields generated by one or more transmitter coils so that if some transmitter coils are activated in only one area of the wireless charging device, magnetic fields do not substantially leak across to other areas of the charging surface, as discussed herein with respect to  FIGS. 4A and 4B . The configuration of the boundary regions are discussed in further detail in  FIG. 6B . 
       FIG. 6B  illustrates a zoomed-in top-down view of transmitter coils  602   a - d  in multi-coil array  600  superimposed over segmented shield  501  having boundary regions  510  that include boundary regions  604   a - l , according to some embodiments of the present disclosure. Other transmitter coils are faded and drawn with dotted lines to indicate their location without detracting from the focus on transmitter coils  602   a - d  and boundary regions  604   a - l , which are drawn with solid lines. 
     As shown in  FIG. 6B , boundary regions  604   a - l  can be arranged so that each boundary region is positioned tangential to at least one transmitter coil while also positioned through the center of at least one other transmitter coil. For instance, boundary region  604   c  is positioned tangential to transmitter coils  602   b  and  602   d  while also positioned through the center of transmitter coils  602   a  and  602   c . All boundary regions of a segmented shield can be arranged in this manner so that as a whole, each transmitter coil is bisected by one or more boundary regions and has one or more other boundary regions that are tangential to it. As an example, transmitter coil  602   a  is bisected by boundary regions  604   c ,  604   f , and  604   j , and has boundary regions  604   i ,  604   d ,  604   g ,  604   k ,  604   b , and  604   e  (recited in a clockwise fashion) that are positioned tangential to it. The nature of this configuration results in a segmented shield design where bisecting boundary regions intersect at the center of each transmitter coil, and tangential boundary regions are positioned around each transmitter coil and effectively form a perimeter around each transmitter coil. 
     This arrangement is designed to maximize resistance against propagation of magnetic field between transmitter coils (i.e., mitigate leakage), but minimize interference with the magnetic field generated within each transmitter coil (i.e., maximize inductance of the transmitter coils). As mentioned herein, bisecting boundary regions intersect at the center of a transmitter coil. Given that an active transmitter coil generates a magnetic field that emanates radially to/from the center of the active transmitter coil, bisecting boundary regions are positioned parallel to the propagation of generated magnetic fields. Accordingly, bisecting magnetic fields do not significantly interfere with the generated magnetic fields. On the other hand, tangential boundary regions are positioned substantially perpendicular to the radial direction of generated magnetic fields. Thus, tangential boundary regions can substantially interfere and resist the propagation of magnetic field across the tangential boundary regions. As a result, the tangential boundary regions can effectively form a perimeter of low magnetic permeability to confine the generated magnetic field to areas immediately surrounding the active transmitter coil, thereby forming a charging area over the active transmitter coil. For instance, if continuing with the example with respect to transmitter coil  602   a , bisecting boundary regions  604   c ,  604   f , and  604   j  are positioned parallel to magnetic field generated by transmitter coil  602   a , and tangential boundary regions  604   i ,  604   d ,  604   g ,  604   k ,  604   b , and  604   e  are positioned perpendicular to the magnetic field generated by transmitter coil  602   a . The charging area is then defined as a hexagonal shape formed by the tangential boundary regions surrounding transmitter coil  602   a.    
     A charging area is not limited to the area over one transmitter coil; rather, the size and shape of the charging area is defined by the number and arrangement of active transmitter coils. Larger groups of active transmitter coils result in a larger charging areas that correspond to the size and shape of the arrangement of the active transmitter coils. For instance, if transmitter coils  602   a  and  602   b  are active, then the charging area can be defined by boundary regions  604   i ,  604   d ,  604   g ,  604   l ,  604   a , and  604   e  (recited in clockwise order). Thus, when transmitter coils  602   a  and  602   b  are active during wireless power transfer, magnetic fields generated by transmitter coils  602   a  and  602   b  can be substantially confined within that charging area, and magnetic field can be substantially prevented from leaking out of that charging area, thereby avoiding excessive heating from leaked magnetic fields and resulting in a loss of power efficiency. 
     It is to be appreciated that the image shown in  FIG. 6B  shows transmitter coils superimposed over boundary regions  604   a - l . Thus, descriptions regarding intersection and the like are not intended to mean that the boundary regions and the transmitter coils are actually in physical contact with one another. Rather, the discussion pertains to their position relative to one another. One skilled in the art understands that the transmitter coils and the boundary regions of the segmented shield are positioned in separate layers of a wireless charging device. Furthermore, although not specifically labeled for clarity purposes, segments of shield  500  are understood to be the areas delineated by boundary regions  604   a - l . For instance, segments of shield  500  in  FIG. 6B  have a triangular shape and are oriented such that six triangular segments are positioned over each transmitter coil. 
     As shown in  FIGS. 4B, 5A -B, and  6 A-B, boundary regions can be configured to have low magnetic permeability continuously across its entire length. However, such embodiments are not intended to be limiting, and that other embodiments can have boundary regions that do not have low magnetic permeability continuously across its entire length. For instance, forming a boundary region with an air gap can result in a segment that is freely movable unless it is fixed to a static structure. Thus, in some embodiments, segments can be fixed in place by configuring the boundary regions with one or more bridging structures as shown in  FIG. 7A . 
       FIG. 7A  illustrates an exemplary segmented shield  700  that has boundary regions  702  that are configured with bridging structures  704  between segments  706 , according to some embodiments of the present disclosure. These bridging structures can be extensions of segments  706  that bridge with neighboring segments to connect them together. Since bridging structures  704  are extensions of segments  706 , bridging structures  704  can be formed of the material as segments  706 , which is formed of a material having high magnetic permeability. Accordingly, instead of being a continuous strip, boundary regions  702  can be a dashed strip that includes sections of low magnetic permeability and high magnetic permeability. It is to be appreciated that boundary regions  702  do not have to include air as the low magnetic permeability component. Rather, the dashed strip configuration can apply to other types of boundary regions, such as boundary regions formed with a dielectric material or a conductive material discussed herein. 
     As shown in  FIGS. 3B, 4B, 5A -B,  6 A, and  7 A, the outer profile of a segmented shield can correspond to the outer profile of a wireless charging device; however, embodiments are not so limited. As an example, some embodiment can have outer borders that follow the profile of a multi-coil array, as shown in  FIG. 7B , which illustrates an exemplary segmented shield  701  having an outer profile that corresponds to the outer profile of a multi-coil array configured in the transmitter coil arrangement discussed herein with respect to  FIG. 2 , according to some embodiments of the present disclosure. Forming a segmented shield this way can reduce the amount of ferrite needed to manufacture segmented shield  701 . Reducing the amount of ferrite used to form the shield can save cost. 
     III. Wireless Charging Device With Segmented Shielding 
       FIG. 8  illustrates a simplified, exploded view of an exemplary wireless charging device  800  having a segmented shield  812 , according to some embodiments of the present disclosure. Wireless charging device  800  can include a housing formed of two shells: a first shell  802  and a second shell  804 . First shell  802  can mate with second shell  804  to form an interior cavity within which internal components may be positioned. First and second shells  802  and  804  can also include notches  806   a  and  806   b , respectively, that form an opening within the housing when first and second shells  802  and  804  are mated. An electrical connector  808 , such as a receptacle connector, can be positioned within the opening so that wireless charging device  800  can receive power from an external power source through a cable connected to electrical connector  808 . In some embodiments, electrical connector  808  may include a plurality of contact pins and a plurality of terminals electrically coupled to the contact pins so that power can be routed from the external power source to driver board  810  to provide power for wireless power transfer. 
     The interior cavity formed between mated first and second shells  802  and  804  can include components that generate the magnetic field for performing the wireless charging of an electronic device. As an example, an array of transmitter coils  810  can be housed within the inner cavity. Transmitter coils  810  can be operated to generate time-varying magnetic fields that propagate above the top surface of top shell  802  during wireless power transfer. The arrangement of transmitter coils  810  can form a charging surface  816  on to shell  802  within which an electronic device can be placed to receive power from wireless charging device  800 . The electronic device can be placed in any area of the charging surface to receive power. 
     In addition to transmitter coils  810 , wireless charging device  800  can also include a segmented shield  812  according to some embodiments of the present disclosure. Segmented shield  812  can be configured to prevent exposure of magnetic field upon electrical components within wireless charging device  800  and mitigate leakage of magnetic field across it structure, as discussed herein with respect to  FIGS. 4A-B . Accordingly, segmented shield  812  can be positioned within wireless charging device  800  in a suitable location for blocking magnetic field from exposing on components within wireless charging device  800 . For example, segmented shield  812  can be positioned between transmitter coils  810  and a driver board  814  that houses the components within wireless charging device  800 . 
     Implementing segmented shield  812  prevents magnetic field from exposing on sensitive electronic components with wireless charging device  800  and mitigates leakage of magnetic field across charging surface  816  to areas where no electronic device is positioned on charging surface  816 . Preventing leakage of magnetic fields can minimize unnecessary device heating and power losses, thereby enhancing power transfer efficiency. 
     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: 20170724
Publication Date: 20201117
Grant Date: 20201117
Priority Date: 20170724
Inventors: JADIDIAN, Jouya
PATHAK, VANEET
SCHAUER, MARTIN
LAM, CHEUNG-WEI
KASAR, DARSHAN R.
GRAHAM, Christopher S.
RADCHENKO, ANDRO
Assignee: APPLE INC
CPC Classifications: [{"code": "H01F27/2885", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/402", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F27/366", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/366", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/70", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F27/365", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/2885", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65023119