Patent Description:
Wireless charging systems have been deployed to enable certain types of devices to charge internal batteries without the use of a physical charging connection. Devices that can take advantage of wireless charging include mobile processing and/or communication devices. Standards, such as the Qi standard defined by the Wireless Power Consortium enable devices manufactured by a first supplier to be wirelessly charged using a charger manufactured by a second supplier. Standards for wireless charging are optimized for relatively simple configurations of devices and tend to provide basic charging capabilities.

Improvements in wireless charging capabilities are required to support continually increasing complexity of mobile devices and changing form factors. For example, there is a need for improved charging techniques for multi-coil, multi-device charging pads.

The document <CIT> discloses a wireless charging device comprising a multi-coil surface and a processor for determining reconfiguration of the multiple switchable coils based on a difference between a measured parameter and a reference parameter retrieved from a look-up table. The coils are parts of resonant circuits that operate one at a time and not concurrently.

Several aspects of wireless charging systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawing by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements").

The software may reside on a processor-readable storage medium. A processor-readable storage medium, which may also be referred to herein as a computer-readable medium may include, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), Near Field Communications (NFC) token, random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, a carrier wave, a transmission line, and any other suitable medium for storing or transmitting software. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. Computer-readable medium may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

Certain aspects of the present disclosure relate to systems, apparatus and methods applicable to wireless charging devices that provide a free-positioning charging surface that has multiple transmitting coils or that can concurrently charge multiple receiving devices. In one aspect, a controller in the wireless charging device can locate a device to be charged and can configure one or more transmitting coils optimally positioned to deliver power to the receiving device. Charging cells may be provisioned or configured with one or more inductive transmitting coils and multiple charging cells may be arranged or configured to provide the charging surface. The location of a device to be charged may be detected through sensing techniques that associate location of the device to changes in a physical characteristic centered at a known location on the charging surface. In some examples, sensing of location may be implemented using capacitive, resistive, inductive, touch, pressure, load, strain, and/or another appropriate type of sensing.

Certain aspects disclosed herein relate to improved wireless charging techniques. Systems, apparatus and methods are disclosed that accommodate free placement of chargeable devices on a surface of a multi-coil wireless charging device. Certain aspects can improve the efficiency and capacity of wireless power transmission to a receiving device. In one example, a wireless charging apparatus has a battery charging power source, a plurality of charging cells configured in a matrix, a first plurality of switches in which each switch is configured to couple a row of coils in the matrix to a first terminal of the battery charging power source, and a second plurality of switches in which each switch is configured to couple a column of coils in the matrix to a second terminal of the battery charging power source. Each charging cell in the plurality of charging cells may include one or more coils surrounding a power transfer area. The plurality of charging cells may be arranged adjacent to a charging surface without overlap of power transfer areas of the charging cells in the plurality of charging cells.

In one aspect of the disclosure, an apparatus has a battery-charging power source and a plurality of charging cells, where a controller can select and couple each charging cell to the power source as needed or desired. Each charging cell in the plurality of charging cells may include one or more coils surrounding a power transfer area. The plurality of charging cells may be arranged adjacent to a charging surface without overlap of power transfer areas of the charging cells.

Certain aspects of the present disclosure relate to systems, apparatus and methods for wireless charging using stacked coils that can charge targeted devices presented to a charging device without a requirement to match a particular geometry or location within a charging surface of the charging device. Each coil may have a shape that is substantially polygonal. In one example, each coil may have a hexagonal shape. Each coil may be implemented using wires, printed circuit board traces and/or other connectors that are provided in a spiral. Each coil may span two or more layers separated by an insulator or substrate such that coils in different layers are centered around a common axis.

According to certain aspects disclosed herein, power can be wirelessly transferred to a receiving device located anywhere on a charging surface that can have an arbitrarily defined size or shape without regard to any discrete placement locations enabled for charging. Multiple devices can be simultaneously charged on a single charging surface. The charging surface may be manufactured using printed circuit board technology, at low cost and/or with a compact design.

In order to improve the reconfiguration of the multi-coil surface of the prior art, a wireless charging method is provided according to the independent claim <NUM> and a corresponding wireless charging device is provided according to the independent claim <NUM>. Certain aspects of the present disclosure relate to systems, apparatus and methods applicable to wireless charging devices that provide a free-positioning charging surface that has multiple transmitting coils or that can concurrently charge multiple receiving devices. In one aspect, a processing circuit coupled to the free-positioning charging surface can be configured to locate a device to be charged and can select and configure one or more transmitting coils that are optimally positioned to deliver power to the receiving device. Charging cells may be configured with one or more inductive transmitting coils and multiple charging cells may be arranged or configured to provide the charging surface. The location of a device to be charged may be detected through sensing techniques that associate location of the device to changes in a physical characteristic centered at a known location on the charging surface. In some examples, sensing of location may be implemented using capacitive, resistive, inductive, touch, pressure, load, strain, and/or another appropriate type of sensing.

According to certain aspects disclosed herein, a charging surface may be provided using charging cells that are deployed adjacent to the charging surface. In one example the charging cells are deployed in accordance with a honeycomb packaging configuration. A charging cell may be implemented using one or more coils that can each induce a magnetic field along an axis that is substantially orthogonal to the charging surface adjacent to the coil. In this disclosure, a charging cell may refer to an element having one or more coils where each coil is configured to produce an electromagnetic field that is additive with respect to the fields produced by other coils in the charging cell and directed along or proximate to a common axis. In this description, a coil in a charging cell may be referred to as a charging coil or a transmitting coil.

In some implementations, a charging cell includes coils that are stacked along a common axis. One or more coils may overlap such that they contribute to an induced magnetic field substantially orthogonal to the charging surface. In some examples, a charging cell includes coils that are arranged within a defined portion of the charging surface and that contribute to an induced magnetic field within the defined portion of the charging surface, the magnetic field contributing to a magnetic flux flowing substantially orthogonal to the charging surface. In some implementations, charging cells may be configurable by providing an activating current to coils that are included in a dynamically-defined charging cell. For example, a wireless charging device may include multiple stacks of coils deployed across a charging surface, and the wireless charging device may detect the location of a device to be charged and may select some combination of stacks of coils to provide a charging cell adjacent to the device to be charged. In some instances, a charging cell may include, or be characterized as a single coil. However, it should be appreciated that a charging cell may include multiple stacked coils and/or multiple adjacent coils or stacks of coils.

<FIG> illustrates an example of a charging cell <NUM> that may be deployed or configured to provide a charging surface in a wireless charging device. In this example, the charging cell <NUM> has a substantially hexagonal shape that encloses one or more coils <NUM> constructed using conductors, wires or circuit board traces that can receive a current sufficient to produce an electromagnetic field in a power transfer area <NUM>. In various implementations, some coils <NUM> may have a shape that is substantially polygonal, including the hexagonal charging cell <NUM> illustrated in <FIG>. Other implementations may include or use coils <NUM> that have other shapes. The shape of the coils <NUM> may be determined at least in part by the capabilities or limitations of fabrication technology, or to optimize layout of the charging cells on a substrate <NUM> such as a printed circuit board substrate. Each coil <NUM> may be implemented using wires, printed circuit board traces and/or other connectors in a spiral configuration. Each charging cell <NUM> may span two or more layers separated by an insulator or substrate <NUM> such that coils <NUM> in different layers are centered around a common axis <NUM>.

<FIG> illustrates an example of an arrangement <NUM> of charging cells <NUM> provided on a single layer of a segment or portion of a charging surface that may be adapted in accordance with certain aspects disclosed herein. The charging cells <NUM> are arranged according to a honeycomb packaging configuration. In this example, the charging cells <NUM> are arranged end-to-end without overlap. This arrangement can be provided without through-holes or wire interconnects. Other arrangements are possible, including arrangements in which some portion of the charging cells <NUM> overlap. For example, wires of two or more coils may be interleaved to some extent.

<FIG> illustrates an example of an arrangement of charging cells from two perspectives <NUM>, <NUM> when multiple layers are overlaid within a segment or portion of a charging surface that may be adapted in accordance with certain aspects disclosed herein. Layers of charging cells <NUM>, <NUM>, <NUM>, <NUM> are provided within the charging surface. The charging cells within each layer of charging cells <NUM>, <NUM>, <NUM>, <NUM> are arranged according to a honeycomb packaging configuration. In one example, the layers of charging cells <NUM>, <NUM>, <NUM>, <NUM> may be formed on a printed circuit board that has four or more layers. The arrangement of charging cells <NUM> can be selected to provide complete coverage of a designated charging area that is adjacent to the illustrated segment.

<FIG> illustrates the arrangement of power transfer areas provided in a charging surface <NUM> that employs multiple layers of charging cells configured in accordance with certain aspects disclosed herein. The illustrated charging surface is constructed from four layers of charging cells <NUM>, <NUM>, <NUM>, <NUM>. In <FIG>, each power transfer area provided by a charging cell in the first layer of charging cells <NUM> is marked "L1", each power transfer area provided by a charging cell in the second layer of charging cells <NUM> is marked "L2", each power transfer area provided by a charging cell in the third layer of charging cells <NUM> is marked "L3", and each power transfer area provided by a charging cell in the fourth layer of charging cells <NUM> is marked "L4".

<FIG> illustrates an example of a wireless transmitter <NUM> that can be provided in a base station of a wireless charging device. A base station in a wireless charging device may include one or more processing circuits used to control operations of the wireless charging device. A controller <NUM> may receive a feedback signal filtered or otherwise processed by a filter circuit <NUM>. The controller may control the operation of a driver circuit <NUM> that provides an alternating current to a resonant circuit <NUM>. In some examples, the controller <NUM> may generate a digital frequency reference signal used to control the frequency of the alternating current output by the driver circuit <NUM>. In some instances, the digital frequency reference signal may be generated using a programmable counter or the like. In some examples, the driver circuit <NUM> includes a power inverter circuit and one or more power amplifiers that cooperate to generate the alternating current from a direct current source or input. In some examples, the digital frequency reference signal may be generated by the driver circuit <NUM> or by another circuit. The resonant circuit <NUM> includes a capacitor <NUM> and inductor <NUM>. The inductor <NUM> may represent or include one or more transmitting coils in a charging cell that produced a magnetic flux responsive to the alternating current. The resonant circuit <NUM> may also be referred to herein as a tank circuit, LC tank circuit, or LC tank, and the voltage <NUM> measured at an LC node <NUM> of the resonant circuit <NUM> may be referred to as the tank voltage.

Passive ping techniques may use the voltage and/or current measured or observed at the LC node <NUM> to identify the presence of a receiving coil in proximity to the charging pad of a device adapted in accordance with certain aspects disclosed herein. Some conventional wireless charging devices include circuits that measure voltage at the LC node <NUM> of the resonant circuit <NUM> or the current in the resonant circuit <NUM>. These voltages and currents may be monitored for power regulation purposes and/or to support communication between devices. According to certain aspects of this disclosure, voltage at the LC node <NUM> in the wireless transmitter <NUM> illustrated in <FIG> may be monitored to support passive ping techniques that can detect presence of a chargeable device or other object based on response of the resonant circuit <NUM> to a short burst of energy (the ping) transmitted through the resonant circuit <NUM>.

A passive ping discovery technique may be used to provide fast, low-power discovery. A passive ping may be produced by driving a network that includes the resonant circuit <NUM> with a fast pulse that includes a small amount of energy. The fast pulse excites the resonant circuit <NUM> and causes the network to oscillate at its natural resonant frequency until the injected energy decays and is dissipated. The response of a resonant circuit <NUM> to a fast pulse may be determined in part by the resonant frequency of the resonant LC circuit. A response of the resonant circuit <NUM> to a passive ping that has initial voltage = V<NUM> may be represented by the voltage VLC observed at the LC node <NUM>, such that: <MAT>.

The resonant circuit <NUM> may be monitored when the controller <NUM> or another processor is using digital pings to detect presence of objects. A digital ping is produced by driving the resonant circuit <NUM> for a period of time. The resonant circuit <NUM> is a tuned network that includes a transmitting coil of the wireless charging device. A receiving device may modulate the voltage or current observed in the resonant circuit <NUM> by modifying the impedance presented by its power receiving circuit in accordance with signaling state of a modulating signal. The controller <NUM> or other processor then waits for a data modulated response that indicates that a receiving device is nearby.

According to certain aspects disclosed herein, coils in one or more charging cells may be selectively activated to provide an optimal electromagnetic field for charging a compatible device. In some instances, coils may be assigned to charging cells, and some charging cells may overlap other charging cells. The optimal charging configuration may be selected at the charging cell level. In some examples, a charging configuration may include charging cells in a charging surface that are determined to be aligned with or located close to the device to be charged. A controller may activate a single coil or a combination of coils based on the charging configuration which in turn is based on detection of location of the device to be charged. In some implementations, a wireless charging device may have a driver circuit that can selectively activate one or more transmitting coils or one or more predefined charging cells during a charging event.

<FIG> illustrates a first topology <NUM> that supports matrix multiplexed switching for use in a wireless charging device adapted in accordance with certain aspects disclosed herein. The wireless charging device may select one or more charging cells <NUM> to charge a receiving device. Charging cells <NUM> that are not in use can be disconnected from current flow. A relatively large number of charging cells <NUM> may be used in the honeycomb packaging configuration illustrated in <FIG> and <FIG>, requiring a corresponding number of switches. According to certain aspects disclosed herein, the charging cells <NUM> may be logically arranged in a matrix <NUM> having multiple cells connected to two or more switches that enable specific cells to be powered. In the illustrated topology <NUM>, a two-dimensional matrix <NUM> is provided, where the dimensions may be represented by X and Y coordinates. Each of a first set of switches <NUM> is configured to selectively couple a first terminal of each cell in a column of cells to a first terminal of a voltage or current source <NUM> that provides current to activate coils in one or more charging cells during wireless charging. Each of a second set of switches <NUM> is configured to selectively couple a second terminal of each cell in a row of cells to a second terminal of the voltage or current source <NUM>. A charging cell is active when both terminals of the cell are coupled to the voltage or current source <NUM>.

The use of a matrix <NUM> can significantly reduce the number of switching components needed to operate a network of tuned LC circuits. For example, N individually connected cells require at least N switches, whereas a two-dimensional matrix <NUM> having N cells can be operated with √N switches. The use of a matrix <NUM> can produce significant cost savings and reduce circuit and/or layout complexity. In one example, a <NUM>-cell implementation can be implemented in a 3x3 matrix <NUM> using <NUM> switches, saving <NUM> switches. In another example, a <NUM>-cell implementation can be implemented in a 4x4 matrix <NUM> using <NUM> switches, saving <NUM> switches.

During operation, at least <NUM> switches are closed to actively couple one coil or charging cell to the voltage or current source <NUM>. Multiple switches can be closed at once in order to facilitate connection of multiple coils or charging cells to the voltage or current source <NUM>. Multiple switches may be closed, for example, to enable modes of operation that drive multiple transmitting coils when transferring power to a receiving device.

<FIG> illustrates a second topology <NUM> in which each individual coil or charging cell is directly driven by a driver circuit <NUM> in accordance with certain aspects disclosed herein. The driver circuit <NUM> may be configured to select one or more coils or charging cells <NUM> from a group of coils <NUM> to charge a receiving device. It will be appreciated that the concepts disclosed here in relation to charging cells <NUM> may be applied to selective activation of individual coils or stacks of coils. Charging cells <NUM> that are not in use receive no current flow. A relatively large number of charging cells <NUM> may be in use and a switching matrix may be employed to drive individual coils or groups of coils. In one example, a first switching matrix may configure connections that define a charging cell or group of coils to be used during a charging event and a second switching matrix may be used to activate the charging cell and/or group of selected coils.

Certain aspects disclosed herein relate to tuned networks that include one or more capacitors and one or more inductors. Tuned networks may be employed in charging systems in which a base station is electromagnetically coupled to a receiving device. Networks may be tuned to optimize power transfer, to enable communication between a base station and a receiving device or to enable the base station to detect presence of a receiving device. Some wireless charging devices and power supplies are designed to maintain a constant setpoint, where the setpoint may define a level of power, current or voltage.

Certain aspects of this disclosure provide techniques usable in a wireless charging device to maintain or sustain performance of circuits that employ tuned circuits. <FIG> illustrates a wireless transmitting circuit <NUM> provided in a base station of a wireless charging device, where the wireless transmitting circuit <NUM> can couple a driver <NUM> to one or more coils 812a, 812b, 812c in a resonant circuit <NUM> during charging and/or detection operations. In one example, each coil 812a, 812b, 812c corresponds to transmitting coil activated by a charging configuration. In another example, each coil 812a, 812b, 812c represents one charging cell selected to transmit power by a charging configuration. The illustrated example shows three coils 812a, 812b, 812c although it will be appreciated that a much larger number of coils may be selected or affected by a charging configuration. The coils 812a, 812b, 812c coupled to the driver <NUM> may be selected to provide a charging configuration optimized to facilitate delivery of power to the location of a receiving device placed on a charging surface. In the illustrated example, the resonant circuit <NUM> is configured by a set of switches 814a, 814b, 814c that enables each coil 812a, 812b, 812c to be selectively coupled to a source of charging current <NUM> provided by the driver <NUM> through a capacitor <NUM>. The impedance of the resonant circuit <NUM> is defined by a capacitor <NUM> that has a nominal capacitance (Cres), and the combination of coupled coils 812a, 812b, 812c. In the illustrated example, each of the coils 812a, 812b, 812c has a nominal inductance (Lres). The impedance of the resonant circuit <NUM> varies with the number of coils 812a, 812b, 812c coupled to the driver <NUM>. Accordingly, a resonant circuit <NUM> that is tuned when it includes the capacitor <NUM> and one or more coils 812a, 812b, 812c is detuned when the number of coils 812a, 812b, 812c is changed.

In certain aspects of this disclosure, table-based dynamic tuning can be used when the configuration of the resonant circuit <NUM> is changed. The resonant frequency of a tuned resonant circuit <NUM> may change when additional inductors are switched into the resonant circuit <NUM>. Power transmission level or efficiency for the wireless transmitting circuit <NUM> may be optimized when the frequency of the charging current <NUM> is tuned to match the resonant frequency of the resonant circuit <NUM>, and optimization may be maintained by retuning the frequency of the charging current <NUM> after the frequency of the resonant circuit <NUM> has been changed. A setpoint associated with the wireless transmitting circuit <NUM> may be maintained by adjusting the frequency of the charging current <NUM> to obtain a desired or specified level of power, current and/or voltage.

The frequency of the charging current <NUM> may be referred to herein as an operating point. The operating point may be selected through a lookup table that relates frequency to the number, type and/or identity of coils included in the resonant circuit <NUM>. In one example, the lookup table may relate frequency to known values of inductance associated with the individual coils included in the resonant circuit <NUM>. The use of a lookup table may maintain near-constant output from the supply from the wireless transmitting circuit <NUM>. For example, the lookup table may provide information that permits the controller <NUM> or another processor to change the frequency of the charging current <NUM> provided by the driver <NUM> concurrently with changes in coil configuration.

The diagram <NUM> in <FIG> illustrates impedance characteristics <NUM>, <NUM> for two configurations of the resonant circuit <NUM>, where the configurations include different numbers of coils 812a, 812b, 812c. The resonant circuit <NUM> may be designed with a setpoint that is obtained when the resonant circuit <NUM> has a nominal or optimal impedance <NUM>. The impedance characteristics <NUM>, <NUM> illustrate that impedance is a function of frequency of the charging current <NUM> and also varies with resonant frequency. When the configuration of the resonant circuit <NUM> changes, the controller <NUM> may change the frequency of the charging current <NUM> to obtain the nominal or optimal impedance <NUM>. In implementations where a finite or limited number of configurations of the resonant circuit <NUM> are available, a look-up table can be used to define a frequency of the charging current <NUM> for each configuration of the resonant circuit <NUM>. The frequencies recorded in the table may be obtained during initial configuration at the time of device assembly or manufacture, and/or can be updated or calibrated during operation of the wireless transmitting circuit <NUM>. The lookup table based approach can be used to enable fast and low-overhead tuning between operating points <NUM>, <NUM>.

According to certain aspects of the disclosure, the resonant circuit <NUM> may be continuously tuned in some implementations. <FIG> illustrates a continuously-tunable wireless transmitter <NUM> provided in a base station of the wireless charging device, and the diagram <NUM> in <FIG> illustrates impedance characteristics <NUM>, <NUM> corresponding to two different configurations of the resonant circuit <NUM> and/or for a configuration of the resonant circuit <NUM> affected by differences in location of a power receiving device coupled to the resonant circuit <NUM>. In <FIG>, the resonant circuit <NUM> is transitioning <NUM> from a first operating point <NUM> to a second operating point <NUM>. The transition between operating points <NUM>, <NUM> may be caused by a change in the number of coils 812a, 812b, 812c activated in the resonant circuit <NUM> and/or by a repositioning of the receiving device that affects the electromagnetic coupling between the resonant circuit <NUM> and the receiving device.

The continuously-tunable wireless transmitter <NUM> includes the elements of the wireless transmitting circuit <NUM> in <FIG> with an additional feedback loop <NUM>. In one example, the feedback loop <NUM> operates as a current sense feedback loop that enables the driver <NUM> or controller <NUM> to monitor power transfers as indicated by the current flow through the resonant circuit <NUM>. The driver <NUM> or controller <NUM> may adjust the operating point <NUM>, <NUM> to track changes in impedance of the resonant circuit <NUM>. In one example, changes in the impedance of the resonant circuit <NUM> are tracked by incrementally adjusting the frequency of the charging current <NUM>.

The driver <NUM> or controller <NUM> may include or implement a proportional-integral-derivative (PID) tuning. PID tuning can be implemented using a control loop that includes the current sense feedback <NUM>. The driver <NUM> or controller <NUM> may continuously calculate an error value as the difference between a desired setpoint for the current flow in the resonant circuit <NUM> and the measured current flow in the resonant circuit <NUM>, as indicated by the current sense feedback <NUM>. The driver <NUM> or controller <NUM> may apply a correction calculated as some combination of proportional, integral, and derivative values (referred to as P, I, and D values respectively).

PID-based dynamic tuning can be implemented as a PID loop enabled after and/or during a change in configuration of the resonant circuit <NUM>. A sufficiently fast PID loop can be free-running and changes can be applied without added delay. In some instances, the PID loop implemented by the driver <NUM> or controller <NUM> may not be able to respond with sufficient speed to changes in configuration of the resonant circuit <NUM>, and a transitional period may be added to gradually change the configuration from one operating point to another. In one example, a delay may be introduced using pulse-width modulation applied to switches 814a, 814b, 814c or through a switch 814a, 814b, 814c that transitions though a linear mode of operation.

<FIG> illustrates an example of a PID control circuit <NUM>. A defined setpoint <NUM> and the current sense feedback <NUM> are received and combined to obtain an error value <NUM> that is provided to the PID processor <NUM>. The PID processor <NUM> generates a control signal <NUM> that controls a frequency generator <NUM> used to provide the charging current <NUM>. The timing diagram <NUM> illustrates a graduated transition in frequency of the charging current <NUM> when the driver <NUM> or controller <NUM> is unable to respond with sufficient speed to changes in configuration of the resonant circuit <NUM>. It will be appreciated that other control circuits and/or algorithms may be used including, for example, systems that employ controllers based on Prandtl-Ishlinskii (PI) hysteresis, etc. The type of control loop used is selected based on system requirements or specifications.

<FIG> is a flowchart <NUM> illustrating one example of a method for operating a wireless charging device. The method may be performed by a controller provided in a wireless charging apparatus. At block <NUM>, the controller may provide a charging current to a first charging coil in a surface of the wireless charging device. At block <NUM>, the controller may determine that an impedance of a resonant circuit has varied from a threshold or setpoint impedance. The resonant circuit may include the first charging coil. At block <NUM>, the controller may restore the threshold or setpoint impedance by modifying the frequency of the charging current.

In certain implementations, the controller may couple a second charging coil to the resonant circuit. The controller may provide the charging current to the second charging coil. The coupling of the second charging coil may modify the impedance of the resonant circuit. The controller may use a lookup table to determine the frequency of the charging current to be used after the second charging coil is coupled to the resonant circuit.

In certain implementations, the controller may decouple a second charging coil from the resonant circuit. Decoupling the second charging coil may modify the impedance of the resonant circuit. The controller may use a lookup table to determine the frequency of the charging current to be used after the second charging coil is decoupled from the resonant circuit.

In one example, the impedance of the resonant circuit is modified by a change in location of a receiving device on the surface of the wireless charging device.

In certain implementations, the controller may detect a change in a monitored current that flows in the resonant circuit, and may determine that the impedance of the resonant circuit has varied based on the change in the monitored current. The controller may receive a feedback signal representative of the change in the monitored current, and may control the frequency of the charging current using the feedback signal. Controlling the frequency of the charging current may include incrementally adjusting the frequency of the charging current until the impedance of the resonant circuit matches the threshold or setpoint impedance. Controlling the frequency of the charging current may include delaying modification of the frequency of the charging current.

<FIG> illustrates an example of a hardware implementation for an apparatus <NUM> that may be incorporated in a wireless charging device or in a receiving device that enables a battery to be wirelessly charged. In some examples, the apparatus <NUM> may perform one or more functions disclosed herein. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements as disclosed herein may be implemented using a processing circuit <NUM>. The processing circuit <NUM> may include one or more processors <NUM> that are controlled by some combination of hardware and software modules. Examples of processors <NUM> include microprocessors, microcontrollers, digital signal processors (DSPs), SoCs, ASICs, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, sequencers, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. The one or more processors <NUM> may include specialized processors that perform specific functions, and that may be configured, augmented or controlled by one of the software modules <NUM>. The one or more processors <NUM> may be configured through a combination of software modules <NUM> loaded during initialization, and further configured by loading or unloading one or more software modules <NUM> during operation.

In the illustrated example, the processing circuit <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing circuit <NUM> and the overall design constraints. The bus <NUM> links together various circuits including the one or more processors <NUM>, and storage <NUM>. Storage <NUM> may include memory devices and mass storage devices, and may be referred to herein as computer-readable media and/or processor-readable media. The storage <NUM> may include transitory storage media and/or non-transitory storage media.

The bus <NUM> may also link various other circuits such as timing sources, timers, peripherals, voltage regulators, and power management circuits. A bus interface <NUM> may provide an interface between the bus <NUM> and one or more transceivers <NUM>. In one example, a transceiver <NUM> may be provided to enable the apparatus <NUM> to communicate with a charging or receiving device in accordance with a standards-defined protocol. Depending upon the nature of the apparatus <NUM>, a user interface <NUM> (e.g., keypad, display, speaker, microphone, joystick) may also be provided, and may be communicatively coupled to the bus <NUM> directly or through the bus interface <NUM>.

One or more processors <NUM> in the processing circuit <NUM> may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, algorithms, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside in computer-readable form in the storage <NUM> or in an external computer-readable medium. The external computer-readable medium and/or storage <NUM> may include a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a "flash drive," a card, a stick, or a key drive), RAM, ROM, a programmable read-only memory (PROM), an erasable PROM (EPROM) including EEPROM, a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium and/or storage <NUM> may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. Computer-readable medium and/or the storage <NUM> may reside in the processing circuit <NUM>, in the processor <NUM>, external to the processing circuit <NUM>, or be distributed across multiple entities including the processing circuit <NUM>. The computer-readable medium and/or storage <NUM> may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

The storage <NUM> may maintain and/or organize software in loadable code segments, modules, applications, programs, etc., some or all of which may be referred to herein as software modules <NUM>. Each of the software modules <NUM> may include instructions and data that, when installed or loaded on the processing circuit <NUM> and executed by the one or more processors <NUM>, contribute to a run-time image <NUM> that controls the operation of the one or more processors <NUM>. When executed, certain instructions may cause the processing circuit <NUM> to perform functions in accordance with certain methods, algorithms and processes described herein.

Some of the software modules <NUM> may be loaded during initialization of the processing circuit <NUM>, and these software modules <NUM> may configure the processing circuit <NUM> to enable performance of the various functions disclosed herein. For example, some software modules <NUM> may configure internal devices and/or logic circuits <NUM> of the processor <NUM>, and may manage access to external devices such as a transceiver <NUM>, the bus interface <NUM>, the user interface <NUM>, timers, mathematical coprocessors, and so on. The software modules <NUM> may include a control program and/or an operating system that interacts with interrupt handlers and device drivers, and that controls access to various resources provided by the processing circuit <NUM>. The resources may include memory, processing time, access to a transceiver <NUM>, the user interface <NUM>, and so on.

In one example, the apparatus <NUM> includes or operates as a wireless charging apparatus that has a battery charging power source coupled to a charging circuit, a plurality of charging cells and a controller, which may be included in one or more processors <NUM>. The plurality of charging cells may be configured to provide a charging surface. At least one coil may be configured to direct an electromagnetic field through a charge transfer area of each charging cell.

The controller may be configured to provide a charging current to a first charging coil in a surface of the wireless charging device, determine that an impedance of a resonant circuit has varied from a threshold or setpoint impedance, and restore the threshold or setpoint impedance by modifying frequency of the charging current. The resonant circuit may include the first charging coil.

In certain examples, the controller may couple a second charging coil to the resonant circuit, and provide the charging current to the second charging coil. The coupling of the second charging coil may modify the impedance of the resonant circuit. The controller may use a lookup table to determine the frequency of the charging current to be used after the second charging coil is coupled to the resonant circuit.

In certain examples, the controller may decouple a second charging coil from the resonant circuit. Decoupling the second charging coil may modify the impedance of the resonant circuit. The controller may use a lookup table to determine the frequency of the charging current to be used after the second charging coil is decoupled from the resonant circuit.

In certain examples, the controller may detect a change in a monitored current that flows in the resonant circuit, and may determine that the impedance of the resonant circuit has varied based on the change in the monitored current. The controller may receive a feedback signal representative of the change in the monitored current, and may control the frequency of the charging current using the feedback signal. Controlling the frequency of the charging current may include incrementally adjusting the frequency of the charging current until the impedance of the resonant circuit matches the threshold or setpoint impedance. Controlling the frequency of the charging current may include delaying modification of the frequency of the charging current.

In some examples, the storage <NUM> maintains instructions and information where the instructions are configured to cause the controller to provide a charging current to a first charging coil in a surface of the wireless charging device, determine that an impedance of a resonant circuit has varied from a threshold or setpoint impedance, and restore the threshold or setpoint impedance by modifying frequency of the charging current. The resonant circuit may include the first charging coil.

In some examples, the instructions are configured to cause the controller to couple a second charging coil to the resonant circuit, and provide the charging current to the second charging coil. The coupling of the second charging coil may modify the impedance of the resonant circuit. The instructions may be configured to cause the controller to use a lookup table to determine the frequency of the charging current to be used after the second charging coil is coupled to the resonant circuit.

In some examples, the instructions are configured to cause the controller to decouple a second charging coil from the resonant circuit. Decoupling the second charging coil may modify the impedance of the resonant circuit. The controller may use a lookup table to determine the frequency of the charging current to be used after the second charging coil is decoupled from the resonant circuit.

In some examples, the instructions are configured to cause the controller to detect a change in a monitored current that flows in the resonant circuit, and determine that the impedance of the resonant circuit has varied based on the change in the monitored current. The controller may receive a feedback signal representative of the change in the monitored current, and may control the frequency of the charging current using the feedback signal. Controlling the frequency of the charging current may include incrementally adjusting the frequency of the charging current until the impedance of the resonant circuit matches the threshold or setpoint impedance. Controlling the frequency of the charging current may include delaying modification of the frequency of the charging current.

Claim 1:
A method for operating a wireless charging device (<NUM>, <NUM>, <NUM>), comprising:
providing a charging current to a first charging coil (812a) in a surface (<NUM>) of the wireless charging device;
determining that an impedance of a resonant circuit (<NUM>) has varied from a threshold or setpoint impedance, wherein the resonant circuit includes the first charging coil; and
restoring the threshold or setpoint impedance by modifying frequency of the charging current;
coupling a second charging coil (812b) to the resonant circuit; characterised by,
providing the charging current to the second charging coil and the first charging coil, wherein coupling the second charging coil modifies the impedance of the resonant circuit; and
using a lookup table to determine the frequency of the charging current to be used after the second charging coil is coupled to the resonant circuit.