Patent Description:
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, typically a receptacle connector, configured to mate with a connector, typically a plug connector, of the charging cord. The receptacle connector typically includes a cavity in the 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 the device on a charging surface of a wireless charging device. A transmitter coil disposed below the charging surface may produce a time-varying magnetic flux that induces a current in a corresponding receiving coil in the electronic device. The induced current can be used by the electronic device to charge its internal battery.

Some existing wireless charging devices and electronic devices configured for wireless charging have a number of disadvantages. For instance, some wireless charging devices generate an unintended voltage on a receiving coil. The unintended voltage can create noise in the electronic device within which the receiving coil is housed. The noise can cause disturbance of sensitive electronic components in the electronic device, such as touch-sensitive components like a touch-sensitive display. Additionally, the electronic devices also generate an unintended voltage on a transmitter coil in a wireless charging device. The unintended voltage can cause inefficiencies in wireless power transfer.

Document <CIT> relates to a method for manufacturing a receiving antenna for a wireless charger and a receiving antenna for a wireless charger manufactured using the same.

Document <CIT> relates to an inductive module.

Document <CIT> relates to wireless power transfer.

Document <CIT> relates to reducing the impact of an inductive energy transfer system on a touch sensing device.

Document <CIT> relates to a device, a system, and a method for transmitting electric power and information.

Document <CIT> relates to a contactless power transmission device, and a power supply device and power receiving device used therein.

Document <CIT> relates to a leakage preventing device of electromagnetic waves.

Especially, <CIT> and <CIT> disclose that the device comprises an electromagnetic shield provided with diametrically opposed gaps.

Some embodiments of the disclosure provide shielding components for a wireless charging system to avoid the generation of detrimental voltages on a receiver coil and/or a transmitter coil of a wireless charging system during wireless power transfer. In some aspects, a transmitter shield and a receiver shield are implemented in a wireless charging system to intercept electric fields generated between the transmitter coil and the receiver coil during wireless power transfer. By intercepting the electric fields, detrimental voltages are prevented from being generated on the receiver coil by the transmitter coil, and vice versa, during wireless power transfer.

The invention provides wireless charging systems and electronic devices according to the independent claims. Further embodiments are provided in the dependent claims. The configurations disclosed in the following description which are not covered by the appended claims are useful for illustrating and understanding the invention.

A wireless charging system according to the present invention is defined in independent claim <NUM>.

The transmitter shield and receiver shield can each be grounded to discharge voltage generated by the electric field. The transmitter shield can be positioned along the direction of the magnetic flux. The transmitter shield can be formed of a conductive material. In some embodiments, the conductive material can be NiV. The transmitter shield can have a thickness between <NUM>-<NUM>.

A wireless charging device configured to generate magnetic flux to perform wireless power transfer can include a driver board; a plurality of transmitter coils disposed above the driver board and configured to generate the magnetic flux upward; an electromagnetic shield disposed above the plurality of transmitter coils, and configured to be transparent to magnetic flux and opaque to electric fields, the electromagnetic shield including: a substrate comprising a stiff material; and a conductive layer disposed on a bottom surface of the substrate; and an adhesive layer disposed between the plurality of transmitter coils and the electromagnetic shield, the adhesive layer configured to attach the electromagnetic shield to the plurality of transmitter coils.

The electromagnetic shield can further include conductive traces embedded within the conductive layer. The traces can be grounded. The traces can be positioned perpendicular to coils of wire of the plurality of transmitter coils. The conductive material can be NiV. The conductive material can have a thickness between <NUM> to <NUM>. The wireless charging device can further include a ferrite layer disposed between the driver board and the plurality of transmitter coils.

Additionally, a electronic device according to the present invention is defined in independent claim <NUM>.

The transmitter coil can include a coil of wire and an insulating material attached to the coil of wire. The insulating material can be PI. The electromagnetic shield can include a conductive layer. The conductive layer can be formed of silver. The electromagnetic shield can have a thickness between <NUM> and <NUM>. The conductive adhesive layer can be conductive pressure sensitive adhesive, CPSA.

A better understanding of the nature and advantages of embodiments of the present invention as defined in the dependent claims, may be gained with reference to die following detailed description and die accompanying drawings.

During wireless power transfer in a wireless charging system, numerous electrical interactions can occur between a transmitter coil and a receiver coil in the wireless charging system. Some of the electrical interactions are intended interactions between the transmitter and receiver coil, while other electrical interactions are unintended interactions that can cause inefficiencies in power transfer and create issues in the electronic device. For example, <FIG> is a simplified diagram illustrating electrical interactions between a transmitter coil <NUM> and a receiver coil <NUM> of an exemplary wireless charging system <NUM> during wireless power transfer. Transmitter coil <NUM> may be disposed within a wireless charging device, such as a wireless charging mat, and receiver coil <NUM> may be disposed within a consumer electronic device, such as a smart phone, smart watch, tablet, laptop, and the like. The electronic device may rest on the wireless charging device at interface <NUM> to enable power transfer.

Transmitter coil <NUM> and receiver coil <NUM> can be positioned substantially concentric to one another to enable efficient power transfer by means of magnetic induction. During wireless power transfer, transmitter coil <NUM> can generate time-varying magnetic flux <NUM>, which can propagate through both device housings at interface <NUM> and be received by receiver coil <NUM>. Time-varying magnetic flux <NUM> interacts with receiver coil <NUM> to generate a corresponding current in receiver coil <NUM>. The generated current can be used to charge a battery for operating the electronic device.

In addition to time-varying magnetic flux <NUM>, however, electric fields <NUM> and <NUM> can be unintentionally generated between transmitter and receiver coils <NUM> and <NUM> during wireless power transfer. For instance, when transmitter coil <NUM> generates magnetic flux <NUM>, a large voltage difference can exist between transmitter coil <NUM> and receive coil <NUM>. The voltage on transmitter coil <NUM> in some cases can be larger than the voltage on receiver coil <NUM>, thereby orienting some electric fields <NUM> toward receiver coil <NUM> and causing unintended voltage to be generated in receiver coil <NUM>. In some additional cases, voltage existing on receiver coil <NUM> may also orient some electric fields <NUM> toward transmitter coil <NUM> and cause detrimental voltage to be generated on transmitter coil <NUM>. Detrimental voltages generated on receiver coil <NUM> may disturb and/or disrupt the operation of sensitive components disposed proximate to receiver coil <NUM>, such as touch-sensitive devices like a touch-sensitive display. And, detrimental voltages generated on transmitter coil <NUM> may cause inefficiencies in power transfer.

Disclosed herein is a wireless charging system that mitigates the unintentional generation of detrimental voltage on a receiver and/or a transmitter coil during wireless power transfer. One or more electromagnetic shielding components will be incorporated in the wireless charging system to prevent electric fields from generating detrimental voltages on the receiver and/or transmitter coils, while allowing time-varying magnetic flux to freely propagate between the transmitter and receiver coils to perform wireless power transfer.

A transmitter shield can be implemented in a wireless charging device to prevent detrimental voltage from being generated on a receiver coil in an electronic device. The transmitter shield can be positioned in the wireless charging device to intercept electric fields generated by the transmitter coil to prevent the electric fields from exposing on the receiver coil. As a result, the intercepted electric fields may generate voltage on the transmitter shield instead of on the receiver coil. This voltage can then be discharged by routing the voltage to ground, thereby disposing of the detrimental voltage and preventing it from affecting sensitive electronic components in the electronic device. In addition to the transmitter shield, a receiver shield can also be implemented in the wireless charging system to prevent detrimental voltage from being generated on the transmitter coil in the wireless charging device. Similar to the transmitter shield, the receiver shield can also be positioned in the electronic device to intercept electric fields generated by the receiver coil so that the electric fields are not exposed to the transmitter coil. Voltage generated in die receiver shield can be discharged to ground to prevent detrimental voltage from being generated on the transmitter coil. Aspects and features of embodiments of such a wireless charging system are discussed in further detail herein.

<FIG> is a simplified diagram illustrating an exemplary wireless charging system <NUM> including a transmitter shield <NUM> and a receiver shield <NUM>. Transmitter shield <NUM> may be positioned in front of transmitter coil <NUM> so that magnetic flux <NUM> is directed toward transmitter shield <NUM>. For instance, transmitter shield <NUM> is positioned between transmitter coil <NUM> and receiver coil <NUM> during wireless power transfer so that magnetic flux <NUM> first passes through transmitter shield <NUM> before reaching receiver coil <NUM>. Transmitter shield <NUM> can be positioned between interface <NUM> and transmitter coil <NUM> when an electronic device rests on the wireless charging device to perform wireless power transfer. Accordingly, transmitter shield <NUM> and transmitter coil <NUM> can both be positioned within the wireless charging device. Transmitter shield <NUM> can be substantially transparent to magnetic flux <NUM> so that a substantial percentage of magnetic flux <NUM> generated by transmitter coil <NUM> is received by receiver <NUM>.

While transmitter shield <NUM> can be substantially transparent to magnetic flux <NUM>, transmitter shield <NUM> can, on the other hand, be substantially opaque to electric field <NUM> such that electric field <NUM> is substantially blocked by transmitter shield <NUM>. This prevents electric field <NUM> from exposing on receiver coil <NUM> and generating an detrimental voltage on receiver coil <NUM>. Because transmitter shield <NUM> substantially blocks electric field <NUM> before it can reach receiver coil <NUM>, electric field <NUM> may generate voltage on transmitter shield <NUM> instead of receiver coil <NUM>. The amount of voltage generated on transmitter shield <NUM> may correspond to the amount of voltage that would have been generated on transmitter coil <NUM> had transmitter shield <NUM> not been present.

Voltage generated on transmitter shield <NUM> can be removed so that the voltage does not permanently remain on transmitter shield <NUM>. As an example, voltage on transmitter shield <NUM> can be discharged to ground. Thus, transmitter shield <NUM> can be coupled to a ground connection <NUM> to allow voltage on transmitter shield <NUM> to be discharged to ground. Ground connection <NUM> can be a ground ring or any other suitable conductive structure coupled to ground that can remove voltage from transmitter shield <NUM>.

Similar to transmitter shield <NUM>, a receiver shield <NUM> may also be implemented in wireless charging system <NUM> to prevent detrimental voltage from being generated on transmitter coil <NUM> from electric field <NUM> generated by receiver coil <NUM>. Receiver shield <NUM> may be positioned in front of receiver coil <NUM> so that magnetic flux <NUM> first passes through receiver shield <NUM> before exposing on receiver coil <NUM>. Receiver shield <NUM> is positioned within a housing of an electronic device within which receiver coil <NUM> is also disposed. Thus, receiver shield <NUM> can be positioned between interface <NUM> and receiver coil <NUM> when the electronic device rests on a wireless charging device to perform wireless power transfer.

Similar to transmitter shield <NUM>, receiver shield <NUM> can be substantially transparent to magnetic flux <NUM> so that a substantial percentage of magnetic flux <NUM> generated by transmitter coil <NUM> passes through receiver shield <NUM> and is received by receiver <NUM>, while receiver shield <NUM> can be substantially opaque to electric field <NUM> such that electric field <NUM> is substantially blocked by receiver shield <NUM>. This prevents electric field <NUM> from being exposed to transmitter coil <NUM> and generating an detrimental voltage on transmitter coil <NUM> while enabling wireless power transfer. Like transmitter shield <NUM>, receiver shield <NUM> may also be grounded so that voltage generated by electric field <NUM> may be discharged to a ground connection <NUM>. Ground connection <NUM> may be a structure similar to ground connection <NUM>, or it may be the same structure as ground connection <NUM>.

By incorporating transmitter and receiver shield <NUM> and <NUM> into wireless charging system <NUM>, the wireless charging device and the electronic device within which transmitter and receiver shields <NUM> and <NUM> are implemented are exposing their grounds to each other. This mutes any ground noise caused by the electrical interactions between transmitter and receiver coils <NUM> and <NUM>.

As can be appreciated by disclosures herein, transmitter shield <NUM> and receiver shield <NUM> are shielding structures that are able to block the passage of electric fields, yet allow the passage of magnetic flux. These shielding structures may include materials and thicknesses that are suitable for providing such electrical characteristics and functions. Details of the materials that can be used to form transmitter shields and receiver shields are discussed in further detail herein.

An electromagnetic shield, e.g., transmitter shield <NUM> and/or receiver shield <NUM>, can be formed of a material having properties that enable magnetic flux to pass through but prevent electric fields from passing through. In a first example, an electromagnetic shield can be formed of a non-conductive material. Non-conductive materials naturally allow magnetic flux to pass through but prevents electric fields from passing through. In a second example, transmitter shield <NUM> can be formed of a conductive material that has a plurality of apertures. The conductive nature of the material allows voltage to be discharged to ground and the apertures provide avenues through which magnetic flux may tunnel to expose on transmitter shield <NUM>. In a third example, transmitter shield <NUM> can be formed of a very thin conductive material that allows magnetic flux to pass through but prevents electric fields from passing through. The thickness of the conductive material can be thin enough to allow passage of magnetic flux and have low enough resistance to allow voltage to travel through the conductive material in an efficient manner. Materials of various conductive properties and thicknesses are discussed in <FIG> herein.

<FIG> is a graph <NUM> representing a measure of mutual inductance achieved between a transmitter coil and a receiver coil when a shielding layer, e.g., any one of transmitter shield <NUM> or receiver shield <NUM>, is disposed between the transmitter and receiver coils during wireless power transfer. The y-axis represents die percentage of mutual inductance attained between the transmitter and receiver coil increasing upward where <NUM>% indicates that all of the magnetic flux generated by the transmitter coil is received by the receiver coil. The x-axis represents thickness of the shielding layer in a logarithmic scale ranging from <NUM>. 0E-<NUM> to <NUM>. 0E-<NUM> in millimeters increasing to the right.

Various curves are plotted against graph <NUM> as shown in <FIG>. The various curves represent different conductive materials having different conductivities in terms of percentage of the conductivity of copper (i.e., % IACS, or percentage of the International Annealed Copper Standard). For instance, graph <NUM> may include curves representing materials having conductivities of <NUM>% IACS, <NUM>% IACS, <NUM>% IACS, <NUM>% IACS, <NUM>% IACS, <NUM>% IACS, and <NUM>% IACS at a specific frequency of <NUM>. Materials having higher conductivity, i.e., higher % IACS, means those materials are better at accommodating the movement of electric charge. The various curves can provide guidance on selecting material of a certain conductivity and thickness to allow a high percentage of mutual inductance between the transmitter and receiver coil. As shown, each curve represents an achievable mutual inductance between the transmitter and receiver coils based on its thickness for different materials having different conductivities. For instance, a transmitter shield formed of a material having a conductivity of <NUM>% IACS may allow a mutual inductance of <NUM>% when its thickness is approximately <NUM>. In another example, a transmitter shield formed of a material having a conductivity of <NUM>% IACS may allow a mutual inductance of <NUM>% when its thickness is less than approximately <NUM>. Thus, as can be understood by graph <NUM>, materials having higher conductivity can decrease the mutual inductance between the transmitter and receiver coil, but this decrease in mutual inductance may be compensated by decreasing the thickness of the shield. Allowing higher mutual inductance means that the wireless charging system is transferring power more efficiently and that the shield has less negative impact on wireless power transfer.

In addition to conductivity and mutual inductance, the resistivity of a material may also be considered when determining a suitable material for forming the shield. This is because the material cannot be so resistive that it is too difficult to route voltage on the shield to ground. <FIG> is a graph <NUM> representing an alternating current resistance (ACR) of a material based on its thickness. The ACR of a material represents the amount of resistance a material has when an alternating current (AC) voltage is applied. The y-axis represents the amount of resistance of a material in units of ohms increasing upward, and the x-axis represents thickness of die shielding layer in a logarithmic scale in millimeters increasing to the right.

Similar to graph <NUM> in <FIG>, various curves are plotted against graph <NUM>. The various curves may be curves for conductive materials having different conductivity in terms of % IACS. As shown in <FIG>, the curves represent materials having the same conductivities as those shown in graph <NUM> of <FIG> for ease of reference and cross comparison. The various curves can provide guidance on selecting material of a certain resistance and thickness to form a shield that can enable the efficient discharge of accumulated voltage from an electric field without generating excessive heat. In <FIG>, each curve may represent an amount of resistance based on its thickness for different materials having different conductivities. For instance, a transmitter shield formed of a material having a conductivity of <NUM>% IACS may have a resistance of approximately <NUM> ohms when its thickness is approximately <NUM>. In another example, a transmitter shield formed of a material having a conductivity of <NUM>% IACS may have a resistance of approximately <NUM> ohms when its thickness is approximately <NUM>. Thus, as can be understood by graph <NUM>, the ACR of a material can increase as thickness increases, but the ACR can be decreased by using materials with lower conductivity. Having higher resistance means that it is more difficult to discharge voltage accumulated on the shield. Moving voltage through a material having high resistance results in the dissipation of energy in the form of heat, which can decrease efficiency and cause damage to electrical components in excessive degrees.

A transmitter shield and/or a receiver shield can be formed of a material that allows high mutual inductance of between <NUM>-<NUM>% and a mutual ACR of less than <NUM> ohms with a desired thickness determined by device design constraints. Thus, an exemplary material that can be used to form a transmitter shield can include nickel vanadium (NiV) with a thickness ranging between <NUM> to <NUM>. Preferably, the transmitter shield is formed of NiV with a thickness of approximately <NUM>. An preferred material that can be used to form a receiver shield can include silver with a thickness ranging between <NUM> and <NUM>. The receiver shield is formed of silver with a thickness of approximately <NUM>.

Although the shields may be formed of a conductive material, other materials having similar properties can be used instead. For instance, a material including carbon may be used to form the electromagnetic shields. In an example, the transmitter shield may include carbon ink, such as N6X carbon ink. Such an ink can be easily customized to achieve the electrical properties desired to allow passage of magnetic flux while preventing passage of electric fields. As shown in <FIG>, carbon ink is represented by a vertical line. This is because the thickness of carbon ink is dictated by the process with which the carbon ink is deposited. For instance, typical printing processes can print carbon ink in thicknesses of approximately <NUM>.

As mentioned herein, a transmitter shield can be included in a wireless charging device, such as a wireless charging mat, and a receiver shield can be included in an electronic device configured to rest on the wireless charging device to wirelessly receiver power from the wireless charging mat. <FIG> illustrates an exploded view of an exemplary wireless charging system <NUM> including a wireless charging device <NUM> and an electronic device <NUM>, each having electromagnetic shielding. Wireless charging device <NUM> can generate time-varying magnetic flux to induce a corresponding current in electronic device <NUM> for performing wireless power transfer.

Wireless charging mat <NUM> can include a housing formed of two shells: a first shell <NUM> and a second shell <NUM>. First shell <NUM> can mate with second shell <NUM> to form an interior cavity within which internal components may be positioned. First and second shells <NUM> and <NUM> can also include notches 508a and 508b, respectively, that form an opening within the housing when first and second shells <NUM> and <NUM> are mated. An electrical connector <NUM>, such as a receptacle connector, can be positioned within the opening so that wireless charging mat <NUM> can receive power from an external power source through a cable connected to electrical connector <NUM>. The electrical connector <NUM> 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 the wireless charging mat <NUM> to provide power for wireless power transfer.

The interior cavity formed between mated first and second shells <NUM> and <NUM> can include components that generate the magnetic flux for performing the wireless charging of electronic device <NUM>. As an example, an array of transmitter coils <NUM> coupled to a driver board <NUM> can be housed within the inner cavity. Transmitter coils <NUM> can be operated to generate time-varying magnetic flux that propagate above the top surface of first shell <NUM> to induce a current in receiver coil <NUM> in electronic device <NUM>. Driver board <NUM> can be a printed circuit board (PCB) configured to route signals and power for operating transmitter coils <NUM>.

In addition to transmitter coils <NUM> and driver board <NUM>, wireless charging device <NUM> includes a transmitter shield <NUM>. Transmitter shield <NUM> is configured to allow passage of magnetic flux and to prevent passage of electric fields, as discussed herein with respect to transmitter shield <NUM> in <FIG>. Accordingly, transmitter shield <NUM> can be positioned within wireless charging device <NUM> in a suitable location for blocking electric field from exposing on a receiver coil <NUM> in electronic device <NUM>. For example, transmitter shield <NUM> can be positioned in the direction of magnetic flux flow, such as between transmitter coils <NUM> and first shell <NUM>.

First shell <NUM> includes a charging surface <NUM> upon which electronic device <NUM> having receiver coil <NUM> may be placed to receive power from wireless charging mat <NUM>. Charging surface <NUM> can be a generally planar region of a top surface of shell <NUM> where magnetic flux generated by transmitter coils <NUM> is present to induce a current in receiver coil <NUM> for charging an internal battery of electronic device <NUM>. Electronic device <NUM> may merely rest on charging surface <NUM> to receive power from wireless charging device <NUM>. The interface (e.g., interface <NUM> in <FIG>) where electronic device <NUM> makes contact with wireless charging device <NUM> can be a plane where respective housings of electronic device <NUM> and wireless charging device <NUM> make contact with each other. Magnetic flux generated by wireless charging device <NUM> can be shielded from internal components in electronic device <NUM> by a ferrite plate <NUM> Ferrite plate <NUM> is positioned above receiver coil <NUM> so that magnetic flux is first exposed to receiver coil <NUM> before being blocked by ferrite plate <NUM>.

Electronic device <NUM> can include atop housing <NUM> and a bottom housing <NUM> that can mate to form an inner cavity that houses internal components, such as receiver coil <NUM> and ferrite plate <NUM>. Electronic device <NUM> can also include an electromagnetic shield within its inner cavity. For example, electronic device <NUM> can include a receiver shield <NUM> that can be configured to allow magnetic flux generated by transmitter coils <NUM> to be received by receiver coil <NUM> but prevent electric fields from receiver coil <NUM> from exposing on transmitter coils <NUM>, as discussed herein with respect to receiver shield <NUM> in <FIG>. Receiver shield <NUM> can be positioned within electronic device <NUM> in a suitable location for blocking electric field from exposing on transmitter coils <NUM> in wireless charging device <NUM>. For example, receiver shield <NUM> can be positioned between receiver coils <NUM> and bottom housing <NUM>. In this position, the magnetic flux first passes through receiver shield <NUM> before exposing on receiver coil <NUM>.

Implementing transmitter shield <NUM> and receiver shield <NUM> allows mutual inductance to exist between transmitter coils <NUM> and receiver coil <NUM>, but prevents detrimental voltages from being generated in transmitter coils <NUM> and receiver coil <NUM>. Preventing these voltages from being generated improves the operation of both wireless charging device <NUM> and electronic device by avoiding electrical disturbances.

The transmitter shield and receiver shield can each be formed to have a specific structure suitable for implementation in a wireless charging system for performing wireless power transfer without generating detrimental voltages on the transmitter and receiver coils. Details of the structure of transmitter and receiver shields will be discussed further herein.

<FIG> illustrates a top-down view of an exemplary transmitter shield <NUM>. Transmitter shield <NUM> can be housed in a wireless charging device, such as a wireless charging mat, e.g., wireless charging mat <NUM> having transmitter shield <NUM> in <FIG>. Transmitter shield <NUM> can have dimensions that correspond to the dimensions of the wireless charging device. For instance, transmitter shield <NUM> can be in the shape of a rectangle having a width W and a length L that correspond to the width and length of the wireless charging device. Although transmitter shield <NUM> can be in the shape of a rectangle, it is to be appreciated that transmitter shields can have any other shape that corresponds to a wireless charging device, such as a square, rectangle, hexagon, triangle, and the like. A notch <NUM> may be formed at an edge of transmitter shield <NUM> to provide space for other components in a wireless charging mat, such as a receptacle connector for making connection with an external cable to receive power from an external source.

Transmitter shield <NUM> may be coupled to ground at its edges <NUM> to discharge any voltage on transmitter shield <NUM>. Voltage existing near the inner regions of transmitter shield <NUM> may have to travel to edges <NUM> by traversing across a large portion of transmitter shield <NUM>, which may cause difficulties in routing the voltage to ground, e.g., by creating larger resistances. Thus, one or more conductive traces <NUM> may be embedded within transmitter shield <NUM> to assist with discharging voltage to ground. The low resistivity and high conductivity of traces <NUM> provides an avenue through which voltage can quickly travel to edges <NUM>. Accordingly, transmitter shield <NUM> may be able to quickly discharge voltage to ground.

Transmitter shield <NUM> can have dimensions that are suitable for shielding an array of transmitter coils disposed within the wireless charging device. For example, <FIG> illustrates an exemplary wireless charging device <NUM> including transmitter shield <NUM> positioned over an array of transmitter coils <NUM>. Transmitter coils <NUM> may be similar in function and form to transmitter coils <NUM> in <FIG>. Upper layers of wireless charging device <NUM> are not illustrated so that transmitter shield <NUM> and transmitter coils <NUM> can be seen. Additionally, transmitter coils <NUM> are illustrated with dotted lines to indicate that transmitter coils are disposed below transmitter shield <NUM>. Showing transmitter coils <NUM> helps to understand their relative position with respect to transmitter shield <NUM>.

As shown in <FIG>, transmitter shield <NUM> is large enough to cover the entire array of transmitter coils <NUM> so that each transmitter coil is shielded by transmitter shield <NUM>. During operation, each transmitter coil <NUM> may generate magnetic flux that pass through transmitter shield <NUM> to induce a current on a receiver coil. Electric fields generated by the large voltage difference between a transmitter coil and a receiver coil may generate voltage in transmitter shield <NUM> around each transmitter coil. The generated voltage may flow across transmitter shield <NUM> to edges <NUM> and be discharged to ground.

As mentioned above, conductive traces <NUM> can be embedded in transmitter shield <NUM> to expedite the discharging of generated voltage on transmitter shield <NUM>. Conductive trances <NUM> can be positioned over respective transmitter coils to route these voltages to ground at edges <NUM>. Additionally, conductive traces <NUM> can be positioned orthogonal to the windings of each transmitter coil <NUM> to minimize current generation in conductive traces <NUM> during operation of transmitter coils <NUM>. This current can be generated by electrical interaction between conductive traces <NUM> and magnetic flux generated by transmitter coils <NUM>. The induced current may impede the ability to discharge voltage on transmitter shield <NUM>. Thus, arranging conductive traces <NUM> orthogonal to the winding of transmitter coils <NUM> may minimize this induced current.

Transmitter shield <NUM> can be formed of a structure that includes more than one layer of material. <FIG> is a simplified diagram illustrating a cross section <NUM> of a transmitter shield and transmitter coils for a wireless charging device Specifically, <FIG> illustrates a cross-section of exemplary transmitter coil <NUM> and transmitter shield <NUM> shown in <FIG>. Transmitter shield <NUM> may be disposed above transmitter coils <NUM> so that magnetic flux generated by transmitter coils <NUM> may flow upward through transmitter shield <NUM> toward an interface surface <NUM>. Interface surface <NUM> may be a top surface of a housing of the wireless charging device, such as charging surface <NUM> in <FIG>, that makes contact with a housing of an electrical device to perform wireless charging. Transmitter coils <NUM> can each be encapsulated by a protective layer such as coil encapsulating layer <NUM>. Encapsulating layer <NUM> can be formed of any suitable non-conductive material for protecting transmitter coils <NUM>, such as polyimide (PI).

Transmitter shield <NUM> can include a conductive layer <NUM> for performing the electrical functions of transmitter shield <NUM>. For instance, conductive layer <NUM> can be a layer of conductive material having properties that allow magnetic flux to pass through transmitter shield <NUM> but prevent electric fields from passing through transmitter shield <NUM>, such as any of the conductive materials discussed herein with respect to <FIG>. The conductive layer <NUM> can be formed of NiV having a thickness of approximately <NUM>.

As mentioned herein, transmitter shield <NUM> can include conductive traces <NUM> for expediting the discharge of accumulated voltage from electric fields. As shown in <FIG>, conductive traces <NUM> can be embedded within conductive layer <NUM> so that voltage existing in conductive layer <NUM> can flow into conductive traces <NUM> and be quickly routed to edges of transmitter shield <NUM> and discharged to ground.

Conductive layer <NUM> can be attached to a support structure configured to provide structural support for conductive layer <NUM>. As an example, conductive layer <NUM> can be attached to substrate <NUM>. Substrate <NUM> can be a base structure upon which conductive layer <NUM> may be deposited or laminated. Substrate <NUM> can be formed of a stiff material having a minimum thickness for surviving the deposition or lamination of conductive layer <NUM>. For instance, substrate <NUM> may be formed of polyethylene terephthalate (PET) having a thickness ranging between <NUM> to <NUM>, particularly <NUM>. Thus, substrate <NUM> can provide structural support for conductive layer <NUM>.

An adhesive layer <NUM> fixes conductive layer <NUM> over transmitter coils <NUM> so that conductive layer <NUM> is positioned to intercept electrical fields associated with transmitter coils <NUM> during wireless power transfer to prevent detrimental voltage from being generated on the receiver coil. Since transmitter coils <NUM> may not extend across the entire bottom surface of conductive layer <NUM>, adhesive layer <NUM> may not have to extend across the entire bottom surface of conductive layer <NUM> either. Instead, adhesive layer <NUM> can just extend far enough to sufficiently couple transmitter coils <NUM> conductive layer <NUM>. Adhesive layer <NUM> does not extend across the entire bottom surface of conductive layer <NUM>, thereby reducing manufacturing cost. Adhesive layer <NUM> can be formed of any suitable non-conductive adhesive material. For example, adhesive layer <NUM> can be formed of pressure sensitive adhesive (PSA).

<FIG> illustrates a top-down view of an exemplary receiver shield <NUM>, according to embodiments of the present disclosure. Receiver shield <NUM> can be housed in an electronic device, such as a smart phone, smart watch, tablet, laptop, and the like, e.g., electronic device <NUM> having shield <NUM> in <FIG>. Receiver shield <NUM> can have dimensions that correspond to the dimensions of a receiver coil. For instance, receiver shield <NUM> can be generally circular in shape, or any other shape that corresponds to a receiver coil, such as a square, rectangle, hexagon, triangle, and the like. Receiver shield <NUM> has a gap <NUM> to provide an area where a connection to ground can be routed for discharging voltage generated on receiver shield <NUM>. Additionally, gap <NUM> can provide space for other components of the electronic device, such as connection terminals for a receiver coil, as will be discussed further herein.

Connection to ground can be established at an end <NUM> of receiver shield <NUM> closest to the top of gap <NUM> so that voltage generated on receiver shield <NUM> can be discharged to ground. While providing a connection to ground at end <NUM> helps discharge voltage on receiver shield <NUM>, The performance of receiver shield <NUM> is improved by including a cut <NUM> in receiver shield <NUM> positioned opposite of gap <NUM> to electrically separate receiver shield <NUM> into two halves: first half <NUM> and second half <NUM>. A connection to ground can be provided at end <NUM> closes to the bottom of gap <NUM> so that both halves <NUM> and <NUM> can be coupled to ground to discharge any voltage generated in receiver shield <NUM>. Without cut <NUM> in receiver shield <NUM>, the potential difference between ends <NUM> and <NUM> may be based on the voltage captured by the entire surface area of receiver shield <NUM>. This can cause a large potential difference to build up between ends <NUM> and <NUM>, and can be difficult to discharge to ground. By including cut <NUM>, the potential difference can be substantially decreased, such as by a half, thereby making it easier to discharge the voltage to ground.

Receiver shield <NUM> can have dimensions that are suitable for shielding a receiver coil disposed within the electronic device. For example, <FIG> illustrates a top-down view of an exemplary receiver system <NUM> for an electronic device. Receiver system <NUM> can include receiver shield <NUM>, a ferrite plate <NUM>, and a receiver coil <NUM> positioned between receiver shield <NUM> and ferrite plate <NUM>. Receiver coil <NUM> is illustrated with dotted lines to indicate that transmitter coils are disposed behind receiver shield <NUM> as shown from the top-down perspective of <FIG>. Showing receiver coil <NUM> helps to understand its relative position with respect to receiver shield <NUM>.

As shown in <FIG>, receiver shield <NUM> is large enough to cover the entire receiver coil <NUM> so that receiver coil <NUM> is completely shielded by receiver shield <NUM>. Receiver coil <NUM> can have a flat, disc-like shape formed of a winding of coil that is wound from an inner diameter to an outer diameter. Likewise, receiver shield <NUM> can also have a disk-like shape that has a corresponding inner and outer diameter. During operation, an electric field from receiver coil <NUM> can generate a voltage in receiver shield <NUM>. The generated voltage may flow across receiver shield <NUM> to at least one of ends <NUM> and <NUM> and be discharged to ground.

Connection terminals <NUM> can be positioned in gap <NUM> of receiver shield <NUM>. Connection terminals <NUM> can provide electrical routes through which current induced in receiver coil <NUM> can be routed to provide power to charge a battery in the electronic device. Additionally, connection terminals <NUM> can include ground lines for routing voltage in receiver shield <NUM> to ground. For instance, receiver shield <NUM> can include a single ground line for routing voltage from the entire receiver shield <NUM> to ground (e.g., in instances where cut <NUM> is not present), or it can include two ground lines, one for routing voltage from first half <NUM> of receiver shield <NUM> to ground, and another for routing voltage from a second half <NUM> of receiver shield <NUM> to ground. Each ground line can be positioned close to the respective end for which it discharges voltage to ground. For example, the ground line for grounding first half <NUM> can be positioned close to end <NUM>, while the ground line for grounding second half <NUM> can be positioned close to end <NUM>.

Ferrite plate <NUM> can be positioned on a side of receiver coil <NUM> opposite of the side on which receiver shield <NUM> is positioned. Ferrite plate <NUM> can prevent magnetic flux and electrical fields from disturbing sensitive electrical components within the electronic device. Ferrite plate <NUM> can be formed of any suitable ferromagnetic material. To better understand the structural layering of receiver system <NUM>, a cross-sectional view of receiver system <NUM> is shown in <FIG>.

<FIG> is a simplified diagram illustrating a cross section <NUM> of receiver system <NUM>. Receiver system <NUM> can include receiver shield <NUM> coupled to receiver coil <NUM>, which is coupled to ferrite plate <NUM>. Receiver coil <NUM> can be positioned below ferrite plate <NUM> so that ferrite plate <NUM> can protect sensitive electrical components from magnetic flux and electrical fields generated during wireless power transfer. Receiver shield <NUM> may be disposed below receiver coil <NUM> so that magnetic flux generated by a transmitter may flow upward from interface surface <NUM> through receiver shield <NUM> before being received by receiver coil <NUM>. Interface surface <NUM> may be a bottom surface of a housing of the electronic device that makes contact with a charging surface of a wireless charging device for performing wireless charging. Receiver coil <NUM> can be encapsulated by a protective layer, such as coil encapsulating layer <NUM>. Encapsulating layer <NUM> can be formed of any suitable non-conductive material for protecting receiver coil <NUM>, such as polyimide (PI).

Receiver shield <NUM> can be formed of a layer of conductive material that can perform the electrical functions of a receiver shield discussed herein. For instance, receiver shield <NUM> can be a layer of conductive material having properties that allow magnetic flux to pass through receiver shield <NUM> but prevent electric fields from passing through receiver shield <NUM>, such as any of the conductive materials discussed herein with respect to <FIG>. Receiver shield <NUM> can be formed of silver, such as silver flake, having a thickness of approximately <NUM>.

Receiver shield <NUM> is coupled to receiver coil <NUM> by an adhesive layer <NUM>. Adhesive layer <NUM> may fix receiver shield <NUM> underneath receiver coil <NUM> so that receiver shield <NUM> is positioned to intercept electrical fields associated with receiver shield <NUM> during wireless power transfer to prevent detrimental voltage from being generated on the transmitter coil. Adhesive layer <NUM> can be configured to route voltage to ground by coupling with a connection terminal, such as connection terminal <NUM> in <FIG>. Thus, adhesive layer <NUM> is formed of any suitable conductive adhesive material. For example, adhesive layer <NUM> can be formed of conductive pressure sensitive adhesive (CPSA).

Receiver shield <NUM> can be covered by a protective layer <NUM>. Protective layer <NUM> can be positioned below receiver shield <NUM> to cover any exposed surfaces and prevent receiver shield <NUM> from oxidizing. Protective layer can be formed of any suitable dielectric material.

Claim 1:
A wireless charging system (<NUM>, <NUM>), comprising:
a transmitter coil (<NUM>) configured to generate a magnetic flux;
a receiver coil (<NUM>, <NUM>) positioned coaxial with the transmitter coil (<NUM>) to receive the generated magnetic flux, wherein electrical interaction between the transmitter coil (<NUM>) and the receiver coil (<NUM>, <NUM>) generates electric fields;
a transmitter shield (<NUM>, <NUM>) positioned between the transmitter coil (<NUM>) and the receiver coil (<NUM>, <NUM>) to intercept some of the electric fields directed away from the transmitter coil (<NUM>) and allow the magnetic flux to pass through the transmitter shield (<NUM>, <NUM>); and
a receiver shield (<NUM>, <NUM>) positioned between the transmitter shield (<NUM>, <NUM>) and the receiver coil (<NUM>, <NUM>) to intercept some of the electric fields directed away from the receiver coil (<NUM>, <NUM>) and allow the magnetic flux to pass through the receiver shield (<NUM>, <NUM>), the receiver shield defining a gap (<NUM>) being adapted to provide space for other components of the system and a cut (<NUM>) positioned opposite to and separate from the gap, the gap and the cut each extending completely through the receiver shield from an inner diameter of the receiver shield to an outer diameter of the receiver shield, to electrically separate the receiver shield into a first half (<NUM>) and a second half (<NUM>).