Temperature Adjustment of Wireless Charging Pad

Abstract

The wireless charging device includes a controller, at least one coil disposed near a surface of the charging device and configured to transmit an electromagnetic field, and a first driver circuit configured to drive the transmit coil. The controller is configured to cause the driver circuit to provide a charging current to the transmit coil, decode a transmit power reduction request from modulation of the charging current, reduce the amplitude of the charging current in accordance with the transmit power reduction request when a temperature measured at the surface of the charging device is below a threshold temperature, and initiate a cooling sequence when the temperature measured at the surface of the charging device is equal to or greater than the threshold temperature. In one example, the transmit power reduction request can be provided by an ASK modulated signal superimposed on the charging current.

Description

Technical Field

[0001] Priority Claim This application claims the priority and benefit of Patent Application No. 17 / 087,610, filed with the United States Patent and Trademark Office on November 2, 2020, the entire content of which is incorporated herein by reference for all purposes as if fully set forth below.

[0002] The present invention generally relates to wireless charging of batteries including batteries of mobile computing devices, and more particularly to detection and improvement of overheating during charging.

Background Art

[0003] Wireless charging systems have been developed to enable certain types of devices to charge their internal batteries without using a physical charging connection. Devices that can utilize wireless charging include mobile devices and / or communication devices. With standard specifications such as the Qi standard defined by the Wireless Power Consortium, it is possible to wirelessly charge a device manufactured by a first supplier with a charger manufactured by a second supplier. The standards for wireless charging are optimized for devices with relatively simple configurations and tend to provide basic charging functions.

[0004] Improvements to wireless charging functionality are necessary to accommodate increasingly complex mobile devices and changing form factors. For example, there is a need for faster and lower-power detection technologies that can detect a charging device on the surface of a charging device, identify its position, or detect the removal or repositioning of a charging device during a wireless charging operation.

Brief Description of the Drawings

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[0006] The detailed description set forth below in connection with the appended drawings is intended to be a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be implemented. The detailed description includes specific details for providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that the concepts can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order not to obscure such concepts.

[0007] Next, particular aspects of the wireless charging system are presented with reference to various apparatuses and methods. These apparatuses and methods are described in the following detailed description and are illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or as software depends upon the particular application and design constraints imposed on the overall system.

[0008] For example, an element, any part of an element, or any combination of elements may be implemented in a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gate logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors of the processing system can execute software. Software is broadly construed to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, or hardware description language. The software may be resident on a processor-readable storage medium. The processor-readable storage medium, also referred to herein as a computer-readable medium, can include, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., compact disks (CDs), digital versatile disks (DVDs)), smart cards, flash memory devices (e.g., cards, sticks, key drives), near field communication (NFC) tokens, random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, removable disks, carrier waves, transmission lines, or any other medium suitable for storing or transmitting software. The computer-readable medium may be present within the processing system, external to the processing system, or distributed among multiple entities including the processing system. The computer-readable medium may be embodied in a computer program product.As an example, a computer program product can include a computer-readable medium within a packaging material. One of ordinary skill in the art will recognize the best method for implementing the described functionality presented throughout this disclosure in light of the particular application and overall design constraints imposed on the overall system.

[0009] Summary Certain aspects of the present disclosure relate to systems, devices, and methods applicable to wireless charging devices. A charging cell is composed of one or more induction coils to provide a charging surface for a charging device, enabling the charging device to wirelessly charge a plurality of chargeable devices via the charging surface. The position of a device to be charged can be detected via sensing techniques that associate the position of the device with changes in physical properties centered around a known position on the charging surface. Sensing of the position can be implemented using capacitive, resistive, inductive, contact, pressure, load, strain, and / or another suitable type of sensing.

[0010] In one aspect of the present disclosure, a device includes a power source for battery charging, a plurality of charging cells configured in a matrix, a first plurality of switches each configured to couple a row of coils within the matrix to a first terminal of the battery charging power source, and a second plurality of switches each configured to couple a column of coils within the matrix to a second terminal of the battery charging power source. Each charging cell of the plurality of charging cells can include one or more coils surrounding a power transmission area. The plurality of charging cells may be arranged adjacent to a charging surface of the charging device such that the power transmission areas of the charging cells among the plurality of charging cells do not overlap.

[0011] In some cases, this device may also be referred to as a charging surface. Electric power can be wirelessly transmitted to a power receiving device disposed at any location on the surface of the device. The device can have an arbitrarily defined size and / or shape and can be placed regardless of any individual placement that can be charged. Multiple devices can be charged simultaneously on a single charging surface. The device can track the movement of one or more devices across the charging surface. The specific concepts disclosed herein are equally applicable to a charging device having a single transmission coil or charging cell.

[0012] In various aspects of the present disclosure, a wireless charging device configured for multi-device charging can identify, calculate, or estimate a case where an over-temperature condition exists in one of a plurality of devices being charged simultaneously. The wireless charging device can take measures to lower the temperature in the power receiving device identified as having the over-temperature condition. The wireless charging device constitutes a driver circuit that drives a transmission coil disposed near the surface of the charging device, causes the driver circuit to supply a charging current to the transmission coil, decodes a reduction requirement for transmission power from the modulation of the charging current, and can determine whether an over-temperature condition exists or is indicated in the device being charged. The over-temperature condition can correspond to the temperature of the battery exceeding the maximum temperature defined by the rating, protocol, or designer. The over-temperature condition can be indicated when the temperature measured on the surface of the charging device exceeds a threshold temperature. The wireless charging device may reduce the amplitude of the charging current in response to a reduction requirement for transmission power when the temperature measured on the surface of the charging device is less than the threshold temperature. The wireless charging device can start a cooling sequence when the temperature measured on the surface of the charging device becomes equal to or higher than the threshold temperature.

[0013] Charging cell According to certain aspects disclosed herein, a charging surface is provided using charging cells within a charging device, and these charging cells are disposed adjacent to the charging surface. In one example, the charging cells are disposed in one or more layers of the charging surface according to a honeycomb package configuration. The charging cells can be implemented using one or more coils that can each induce a magnetic field along an axis substantially orthogonal to the charging surface adjacent to the coil. As used herein, a charging cell refers to a component having one or more coils configured to generate an electromagnetic field that is additive with respect to the fields generated by other coils within the charging cell and that is oriented along or in proximity to a common axis.

[0014] In some implementations, the charging cells include coils that are stacked along a common axis and / or that overlap to contribute to an induced magnetic field substantially orthogonal to the charging surface. In some embodiments, the charging cells are disposed within a defined portion of the charging surface and include coils that contribute to an induced magnetic field within a portion of the charging surface that is substantially orthogonal to the charging cells. In some implementations, the charging cells may be configurable by supplying an activation current to the coils included in the dynamically defined charging cells. For example, the charging device can include a stack of multiple coils disposed across the charging surface, and the charging device can detect the position of the device to be charged and select some combination of the stack of coils to provide a charging cell adjacent to the device to be charged. In one example, a charging cell can include or be characterized as a single coil. However, it should be understood that a charging cell can include multiple stacked coils and / or multiple adjacent coils or stacks of coils. As used herein, a coil may sometimes be referred to as a charging coil, a wireless charging coil, a transmitter coil, a transmission coil, a power transmission coil, a power transmitter coil, and the like.

[0015] FIG. 1 shows an example of a charging cell 100 that can be deployed and / or configured to provide a charging surface of a charging device. As described herein, the charging surface can include an array of charging cells 100 provided on one or more substrates 106. A circuit consisting of one or more integrated circuits (ICs) and / or discrete electronic components can be provided on the one or more substrates 106. This circuit can include drivers and switches used to control the current supplied to a coil used to transmit power to a power receiving device. This circuit can be configured as a processing circuit including one or more processors and / or one or more controllers configured to perform the specific functions disclosed herein. In some embodiments, part or all of the processing circuit may be provided outside the charging device. In some embodiments, a power source can be coupled to the charging device.

[0016] The charging cell 100 can be provided near the outer surface area of the charging device, and one or more devices can be placed thereon for charging. The charging device can include a plurality of instances of the charging cell 100. In one example, the charging cell 100 has a substantially hexagonal shape surrounding one or more coils 102 that can be constructed using a conductor, wiring, or circuit board trace capable of receiving a current sufficient to generate an electromagnetic field in the power transmission region 104. In various embodiments, some of the coils 102 may have a shape that is substantially polygonal, including the hexagonal charging cell 100 illustrated in FIG. 1. In other embodiments, coils 102 having other shapes are provided. The shape of the coil 102 can be determined at least in part by the capabilities or limitations of the manufacturing technology and / or to optimize the layout of the charging cells on a substrate 106 such as a printed circuit board. Each coil 102 can be implemented using a wire in a spiral configuration, a printed circuit board trace, and / or other connectors. Each charging cell 100 can span two or more layers separated by an insulator or substrate 106 such that the coils 102 of different layers are centered on a common axis 108.

[0017] FIG. 2 is a diagram showing an example of an arrangement 200 of charging cells 202 provided in a single layer of segments of a charging surface of a charging device that can be adapted according to certain aspects disclosed herein. The charging cells 202 are arranged according to a honeycomb packaging configuration. In this embodiment, the charging cells 202 are arranged end-to-end without overlapping. This arrangement can be provided without through-holes or wire wiring. Other arrangements are also possible, such as an arrangement where some of the charging cells 202 overlap. For example, wires consisting of two or more coils can be interleaved to some extent.

[0018] FIG. 3 is a diagram showing an example of the arrangement of charging cells from two viewpoints (e.g., top view 300 and side view) when multiple layers are stacked within a segment of a charging surface that can be adapted according to certain aspects disclosed herein. Layers of charging cells 302, 304, 306, 308 are provided within one segment of the charging surface. The charging cells within each layer of charging cells 302, 304, 306, 308 are arranged according to a honeycomb packaging configuration. In one embodiment, the layers of charging cells 302, 304, 306, 308 can be formed on a printed circuit board with four or more layers. The arrangement of the charging cells 100 can be selected to completely cover the assigned charging area adjacent to the illustrated segment.

[0019] FIG. 4 is a diagram showing the arrangement of power transmission regions provided on a charging surface 400 that employs multiple layers of charging cells configured according to certain aspects disclosed herein. The illustrated charging surface is composed of four layers of charging cells 402, 404, 406, 408. In FIG. 4, each power transmission region provided by the charging cells of the first layer of charging cells 402 is denoted as "L1", each power transmission region provided by the charging cells of the second layer of charging cells 404 is denoted as "L2", each power transmission region provided by the charging cells of the third layer of charging cells 406 is denoted as "L3", and each power transmission region provided by the charging cells of the fourth layer of charging cells 408 is denoted as "L4".

[0020] Wireless Transmitter FIG. 5 is a diagram showing a wireless transmitter 500 that can be provided in a charger base station. The controller 502 can receive a feedback signal that is filtered by the adjustment circuit 508 or processed in other ways. The controller can control the operation of the driver circuit 504 that supplies alternating current to the resonant circuit 506 including the capacitor 512 and the inductor 514. The resonant circuit 506 is also referred to herein as a tank circuit, an LC tank circuit, or an LC tank. The voltage 516 measured at the LC node 510 of the resonant circuit 506 is also referred to as the tank voltage.

[0021] The wireless transmitter 500 can be used by a charging device to determine whether a compatible device is placed on the charging surface during a detection procedure. For example, the charging device can identify that a compatible device is placed on the charging surface by transmitting an intermittent test signal (active or digital Ping) via the wireless transmitter 500, where the resonant circuit 506 can detect or receive an encoded signal when the compatible device responds to the test signal. The charging device can be configured to excite one or more coils in at least one charging cell when it receives a response signal defined by a standard, convention, manufacturer, or application. In some examples, the compatible device can respond to the Ping by communicating the received signal strength so that the charging device can find the optimal charging cell to use for charging the compatible device. The detection procedure enables the charging device to determine the charging settings to be used to charge the detected device. The charging settings can define one or more transmission coils or charging cells that receive a charging current when charging the detected device, the level of power transmitted to the detected device, the maximum and minimum levels of power transmitted to the detected device.

[0022] The passive ping technique can identify the presence of a power receiving coil proximate to a charging pad of a device adapted according to certain aspects disclosed herein using voltages and / or currents measured or observed at the LC node 510. Many conventional transmitters for wireless chargers are provided with circuitry to measure the voltage at the LC node 510 or the current within the LC network. These voltages and currents can be monitored for power regulation purposes or to support communication between devices. In the example shown in FIG. 5, the voltage at the LC node 510 is monitored, although it is contemplated that the current can be additionally or alternatively monitored to support a passive Ping where a short pulse is provided to the resonant circuit 506. The response of the resonant circuit 506 to the passive Ping (initial voltage V0) can be expressed as follows in terms of the voltage (V LC ) at the LC node 510. TIFF0007710753000001.tif12170

[0023] According to certain aspects disclosed herein, one or more coils within a charging cell can be selectively activated to provide an electromagnetic field optimal for charging a compatible device. In some embodiments, coils are assigned to charging cells, and some charging cells can overlap other charging cells. In the latter case, an optimal charging setting can be selected on a charging cell-by-charging cell basis. In other examples, the charging cells may be defined based on the placement of the device to be charged on the surface of the charging device. In such other examples, the combination of coils activated for each charging event can vary. In some implementations, the charging device can include a driver circuit that can select one or more cells and / or one or more predetermined charging cells to excite during a charging event.

[0024] The charging device can define a charging setting based at least in part on information received from the device to be charged. The device to be charged can communicate its ID and the required power transmission level by modulating the current received by power transmission from the charging device. The device to be charged can modulate the received current by changing the load applied to the power receiving coil. The change in load is reflected to the charging device through electromagnetic coupling, and this can capture the modulation signal by measuring the tank voltage and current flowing through the transmission coil. As an example, amplitude shift keying (ASK) modulation can be used to encode information in the tank voltage.

[0025] FIG. 6 is a diagram illustrating an example of a processing circuit 600 that can be configured to receive and decode an ASK modulation signal. The processing circuit 600 includes a processor 602 that can be coupled to a memory device 604 and / or a register that can store a message transmitted using the ASK modulation signal 612 and / or a message decoded from the received ASK modulation signal 612. The processing circuit 600 includes an ASK decoder 606 that can be implemented using hardware, software, or some combination of hardware and software. The ASK decoder 606 can use a clock signal received from a clock generation or recovery circuit 608 to control the timing of the transmitted ASK modulation signal 612 and to control the sampling and decoding of the received ASK modulation signal 612.

[0026] FIG. 7 shows examples of encoding schemes 700, 720 that can be adapted to digitally encode messages exchanged between a power receiver and a power transmitter. In a first example, a differential binary phase encoding scheme 700 encodes binary bits in the phase of a data signal 704. In the illustrated example, each bit of a data byte 706 is encoded in a corresponding cycle 708 of an encoder clock signal 702. The value of each bit is encoded by the presence or absence (phase change) of a transition 710 in the data signal 704 during the corresponding cycle 708.

[0027] In a second example, power supply 724 is encoded using a power signal amplitude encoding scheme 720. In the illustrated example, the binary bits of data byte 726 are encoded at the level of power supply 724. Each bit of data byte 726 is encoded in a corresponding cycle 728 of encoder clock signal 722. The value of each bit is encoded by the voltage level of power supply 724 relative to the nominal 100% voltage level 730 of power supply 724 during the corresponding cycle 708.

[0028] Selective coil excitation According to certain aspects disclosed herein, the transmission coils within one or more charging cells can be selectively activated to provide an electromagnetic field optimal for charging a compatible device. In some embodiments, transmission coils are assigned to charging cells, and some charging cells may overlap other charging cells. In the latter case, an optimal charging setting can be selected on a per charging cell basis. In other examples, the charging cells may be defined based on the placement of the device to be charged on the surface of the charging device. In such other examples, the combination of coils activated for each charging event may vary. In some implementations, the charging device may include a driver circuit capable of selecting one or more cells and / or one or more predetermined charging cells to excite during a charging event.

[0029] FIG. 8 shows an example of a topology 800 in which each coil or charging cell is individually and / or directly driven by a driver circuit 802, in accordance with certain aspects disclosed herein. The driver circuit 802 can be configured to select one or more coils or charging cells 100 from a coil group 804 to charge a power receiving device. It should be understood that the concepts disclosed herein in connection with the charging cell 100 can be applied to the selective excitation of individual coils or coil stacks. No current flows through the charging cells 100 that are not in use. A relatively large number of charging cells 100 can be used, and a switching matrix can be employed to drive individual coils or coil groups. In one example, a first switching matrix can configure connections that define the charging cells or coil groups used during a charging event, and a second switching matrix can be used to excite the charging cells and / or selected coil groups.

[0030] In some implementation examples, a matrix switching method may be adopted to select a charging cell 100 for charging a power receiving device from a coil group 804. In the honeycomb packaging configuration shown in FIGS. 2 and 3, a relatively large number of charging cells 100 can be used, and at least some of the charging cells 100 can be logically arranged or connected in a switching matrix. By using a switching matrix, the number of switching components required to operate a network of tuned LC circuits can be significantly reduced. For example, N individually connected cells require at least N switches, but a two-dimensional matrix with N cells can be operated with √N switches. In one example, a 9-cell implementation example can be implemented in a 3x3 matrix using 6 switches, saving 3 switches. In another example, a 16-cell implementation can be implemented in a 4x4 matrix using 8 switches, saving 8 switches. During operation, at least two switches are closed to actively couple one coil to a wireless transmitter and / or receiver circuit. Multiple switches can be closed at once to facilitate connection of multiple coils to a wireless transmitter and / or receiver circuit. For example, when transferring power to a power receiving device by closing multiple switches, an operation mode of driving multiple transmission coils can be enabled.

[0031] Temperature Regulation of a Multi-Device-Compatible Multi-Coil Wireless Charger Batteries used in mobile communication devices are prone to heat generation when large currents flow or when they are charged with large currents. Batteries installed in devices may overheat when the heat sinks and heat dissipation capabilities of the devices are limited. For example, the batteries of mobile communication devices are often placed in a small space close to the battery volume where the airflow is restricted. When the airflow is restricted, the dissipation of heat due to the losses during charging and discharging of the battery is inhibited, and the area near the battery or the entire mobile communication device may become hot. In order to prevent battery damage and prevent the runaway of chemical reactions leading to explosion and combustion of battery components, control of heat generation, accumulation, and dissipation is necessary. Certain industry groups have defined and published standards and protocols for managing the operation of batteries by protecting them from overheating. For example, the Japan Electronics and Information Technology Industries Association (JEITA) has defined the operating limits of lithium-ion batteries. Lithium-ion batteries are widely used in portable electronic devices due to their high energy density, and the JEITA guidelines and procedures aim to prevent the ignition of lithium-ion batteries.

[0032] JEITA defines operating conditions that affect lithium-ion batteries used at high temperatures. As an example, pulse current charging technology is used to improve the lifespan, charging speed, charging capacity, discharge capacity, and temperature control of lithium-ion batteries. JEITA defines a duty cycle in the range of 20% - 80%.

[0033] Certain aspects of the present disclosure provide techniques, circuits, and methods for monitoring, limiting, and / or controlling over-temperature events in a rechargeable device during battery charging, including when the charging device is a multi-device, multi-coil wireless charger. By changing the charging settings defined for or by the wireless charger to limit and improve overheating events, the imposition of an inefficient charging duty cycle can be avoided when operating the rechargeable device in accordance with the JEITA protocol.

[0034] Wireless chargers typically do not recognize the temperature or charging state of the battery of the device to be charged. The device to be charged can request a reduction in charging power or stop charging until cooling is complete in order to monitor the battery temperature and address temperature issues. The request for reduction of charging power or stop of charging by the device to be charged can be made for various reasons other than temperature-related reasons. For example, a reduction in charging power may be requested when the battery of the device to be charged reaches or approaches full capacity. Therefore, the request for a change in charging power is a less reliable indicator for distinguishing whether the request is based on the charging state of the battery or the temperature state of the battery when the charging device does not know the charging state of the battery of the device to be charged.

[0035] In one aspect of the present disclosure, the temperature measured on the surface of the charging device (which may also be referred to as a "charging pad") can be used to determine the likely reason for a request to change the charging power. In one example, a request for a reduction in charging power when the surface temperature of the charging device is within the nominal value or a preset range may indicate that the battery in the device to be charged is at or near full capacity. In another example, a request for a reduction in charging power when the surface temperature of the charging device exceeds the nominal maximum temperature or is outside a preset temperature range may indicate that the battery in the device to be charged is at a high temperature.

[0036] Figures 9 and 10 show configurations 900, 1000, 1020 of a multi-device wireless charging device that can be equipped to measure temperature according to certain aspects of the present disclosure. Figure 9 is a two-dimensional view of configuration 900 of the wireless charging device, in which temperature sensors 9041 - 9046 and 9061 - 9064 are deployed around an array of charging cells (LP1 - LP18) provided on the surface 902 of the wireless charging device. The combination of the horizontal temperature sensors 9041 - 9046 and the vertical temperature sensors 9061 - 9064 may enable an estimated or calculated mapping of the temperature across the surface 902 of the wireless charging device. The temperature sensors 9041 - 9046, 9061 - 9064 can include thermocouples or other temperature measuring devices.

[0037] In other examples, the temperature sensors may be provided at the center of each charging cell or between each pair of charging cells. FIG. 10 shows cross-sectional views of different configurations 1000, 1020 of temperature sensors 10081 - 10083 and 10281 - 10283 provided in alignment with corresponding charging cells 10041 - 10043 in the vertical direction. The temperature sensors 10081 - 10083 and 10281 - 10283 can include thermocouples or other temperature measuring devices. The temperature sensors 10081 - 10083, 10281 - 1028 3は are embedded in, attached to, or otherwise thermally conducted to the heat conduction layers 1006, 1026 located on or near the surface 902 of the wireless charging device.

[0038] The heat conduction layers 1006, 1026 can further function as electrical insulation or can provide, enhance, or configure the electromagnetic characteristics of the surface 902 of the wireless charging device. In the first configuration 1000, the heat conduction layer 1006 is provided above or near the surface 902 of the wireless charging device and under the charging cells 10041 - 10043. In the second configuration 1020, the heat conduction layer 1026 is provided in the upper layer of the charging cells 10041 - 10043. In other configurations (not shown), the temperature sensors may be provided in the same layer as the charging cells and may be arranged at the center of each charging cell or between the charging cells. The wireless charging device can be configured to consider the surface temperature when determining whether a power transmission reduction requirement indicates that a battery temperature problem has been detected by the device to be charged.

[0039] In some implementation examples, temperature sensors 9041-9046, 9061-9064, 10081-10083 and 10281-10283 can be calibrated using an instrumented rechargeable device. In one example, the instrumented rechargeable device is placed on the surface 902 of a wireless charging device over one or more rechargeable cells 10041-10043. The measured internal temperature obtained by the instrumented rechargeable device is compared and correlated with the simultaneous measured surface temperature captured by temperature sensors 9041-9046, 9061-9064 or 10081-10083 to provide information usable by the controller 1002 of the wireless charging device to estimate the internal temperature of the rechargeable device during normal operation. In one example, the wireless charging device can be configured to include a look-up table that can create an index using the surface temperature of the wireless charging device to obtain an estimated value of the internal temperature of the device being charged during normal operation.

[0040] According to certain aspects of the present disclosure, the wireless charging device can determine that a device being charged is cooling based on a combination of information including the pad or surface temperature and the power draw request. The wireless charging device can assist in cooling by reducing the charging power to a minimum level while monitoring the temperature change measured at the surface of the wireless charging device to estimate or infer that a temperature change has occurred within the device being charged. The wireless charging device may end the charging if the temperature does not decrease at a sufficient rate. After ending the charging of a device being cooled, the wireless charging device can reduce or end the charging of one or more other devices if the temperature does not decrease at a sufficient rate.

[0041] Graph 1100 of FIG. 11 is a diagram showing a cooling process managed by a wireless charging device according to a particular aspect of the present disclosure. The graph includes a curve representing the battery temperature 1102 measured or estimated by the device during charging, which may have some correspondence or correlation with the temperature measured at the surface of the wireless charging device. The wireless charging device can estimate the internal temperature of the device being charged based on the temperature measured at the surface of the wireless charging device.

[0042] Initially, the battery temperature 1102 rises until it reaches the high temperature limit 1130 at the first point in time 1104. The high temperature limit 1130 may correspond to the maximum temperature defined for the battery of the device to be charged. Depending on the protocol or industry standard, the charging power may be limited when the maximum temperature is reached. The device to be charged issues a request to change the transmitted power, thereby reducing the power transmission rate. In one example, the device to be charged can issue a request to cause power transmission to conform to a duty cycle defined by a protocol or standard for charging a hot battery. Imposing restrictions on charging by the duty cycle may reduce the efficiency of charging and temperature reduction.

[0043] In one aspect, the wireless charging device can associate a request to change the transmitted power with an over-temperature event when the temperature measured at the surface of the wireless charging device indicates that the battery temperature 1102 of the device to be charged exceeds the threshold temperature level and reaches or is within the range of the high temperature limit 1130. The wireless charging device can enter the cooling mode 1120 when it is determined that an over-temperature event has occurred. The cooling mode 1120 can continue until the measured or estimated battery temperature 1102 reaches the low temperature threshold 1132. Multiple phases or stages can be defined for the cooling mode 1120.

[0044] The first stage 1122 of the cooling mode 1120 starts after the temperature limit is triggered or after the high temperature limit 1130 is reached. In the first stage 1122, the wireless charging device can reduce the transmitted power to the lowest level that does not trigger or cause disconnection from the device to be charged. The lowest level of the transmitted power is associated with the lowest level of the dissipated power of the device to be charged, and a decrease in the measured or estimated battery temperature 1102 can be expected. The cooling mode 1120 can define a limited duration, and the battery temperature 1102 can be expected to decrease to the level of the low temperature threshold 1132 within the duration of the cooling mode 1120. The thermal gradient of the battery temperature 1102 can be monitored to determine whether the battery temperature 1102 is likely to fall below the low temperature threshold 1132 during the cooling mode 1120. In the illustrated example, the rate of change of the battery temperature 1102 varies and can be characterized by a plurality of temperature gradients 1106, 1108, 1110. The temperature gradients 1106, 1108, 1110 can be calculated based on the difference in the battery temperature 1102 measured or estimated over a period defined by a specified timer interval.

[0045] The first temperature gradient 1106 is consistent with the likelihood that the battery temperature 1102 will reach the low temperature threshold 1132 while the cooling mode 1120 is active. The rate of change of the battery temperature 1102 decreases, as shown by the two subsequent temperature gradients 1108 and 1110 and the leveling off to the zero gradient 1112. Thus, in the illustrated example, it is clear that the measured or estimated battery temperature 1102 does not reach the low temperature threshold 1132 while the cooling mode 1120 is active. In this example, the first stage 1122 ends and the second stage 1124 begins.

[0046] In the second stage 1124, the wireless charging device ends the power transmission to the device to be charged. Since there is no transmitted power, the energy dissipation generated by charging disappears, and a decrease 1114 in the battery temperature 1102 is expected unless there are other heat sources. The thermal gradient of the battery temperature 1102 can be monitored to determine whether the battery temperature 1102 may fall below the low temperature threshold 1132 within a preset maximum cooling period during the cooling mode 1120. The preset maximum cool-down time can be defined based on standards, protocols, or information identifying the type and capabilities of the device to be charged. The preset maximum cool-down time may be specified by the charging settings defined for the device to be charged. In the illustrated example, the rate of change of the battery temperature 1102 is constant or has a gradient indicating that the battery temperature 1102 is unlikely to fall below the low temperature threshold 1132. Here, the second stage 1124 ends and the third stage 1126 begins.

[0047] In the third stage 1126, the power level transmitted to one or more neighboring devices by the wireless charging device is reduced or terminated. In the third stage 1126, cooling is forced across multiple devices, and the temperature measured in the charging cells involved in charging the neighboring devices can also be monitored. In some implementations, thermal cut-off or thermal limitation can be globally applied across the surface 902 of the wireless charging device to cool all devices, thereby cooling the charging system including the wireless charging device and all devices placed on the surface 902 of the wireless charging device. The temperature gradient of the battery temperature 1102 can be monitored to determine whether the battery temperature 1102 may fall below the low temperature threshold 1132 during the cooling mode 1120. In the illustrated example, a decrease 1116 in the battery temperature 1102 occurs.

[0048] FIG. 12 is a flowchart 1200 showing a first example of a method for managing thermal cooling in a device being charged by a multi-coil wireless charging system. This method is executed by a controller 1002 within the multi-coil wireless charging system. The multi-coil wireless charging system may be capable of charging multiple chargeable devices simultaneously. At block 1202, the controller 1002 can detect the presence of a power receiving device disposed on or near the surface 902 of the multi-coil wireless charging system. The controller 1002 can interrogate and / or negotiate with the power receiving device to generate a charging setting. The controller 1002 can then cause a charging current to be supplied to one or more transmission coils of the multi-coil wireless charging system according to the charging setting.

[0049] At block 1204, the controller 1002 can determine whether the power receiving device has reached a temperature limit. This temperature limit may be related to the temperature of a battery being charged in the power receiving device. The temperature limit can be determined to have been reached based on the temperature measured at the surface of the multi-coil wireless charging system. If the controller 1002 determines that the temperature limit has not been reached, charging continues at block 1202. If the controller 1002 determines that the temperature limit has been reached, the controller 1002 can interpret a power reduction request from the power receiving device as an indication that the power receiving device is attempting to lower its temperature, and the controller 1002 can proceed to block 1206.

[0050] In one example, the controller 1002 can determine, at block 1206, whether the requested power level is below the minimum power level defined by the charging setting, protocol, or system configuration. If the requested power level is greater than or equal to the minimum power level, charging can continue at the requested lower power level at block 1202. If the requested power level is less than the minimum power level, the controller 1002 can determine that the power receiving device is attempting cooling and can enter a cooling mode at block 1208. The power receiving device may request a power level lower than the minimum power level to execute a duty cycle defined by the protocol.

[0051] In some embodiments, the controller 1002 may also respond to a request to change the transmitted power received from the power receiving device when the temperature limit has not been reached, and one or more requests regarding the charging power level.

[0052] Example of a processing circuit FIG. 13 is a diagram illustrating an example of a hardware implementation of an apparatus 1300 that can be incorporated into a charging device or a power receiving device that enables wireless charging of a battery. In some examples, the apparatus 1300 can perform one or more functions disclosed herein. According to various aspects of the present disclosure, an element, any portion of an element, or any combination of elements disclosed herein can be implemented using a processing circuit 1302. The processing circuit 1302 can include one or more processors 1304 controlled by a certain combination of hardware modules and software modules. Examples of the processor 1304 include a microprocessor, a microcontroller, a digital signal processor (DSP), a system-on-chip (SoC), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, a sequencer, gate logic, discrete hardware circuits, and other suitable hardware configured to perform various functionalities described throughout the present disclosure. The one or more processors 1304 can include dedicated processors for performing specific functions and can be configured, enhanced, or controlled by one of the software modules 1316. The one or more processors 1304 may be configured through a combination of software modules 1316 loaded during initialization and may be further configured by loading or unloading one or more software modules 1316 during operation.

[0053] In the illustrated example, the processing circuit 1302 can be implemented in a bus architecture generally denoted by a bus 1310. The bus 1310 can include any number of interconnecting buses and bridges depending on the specific application of the processing circuit 1302 and overall design constraints. The bus 1310 links various circuits including one or more processors 1304 and a storage 1306. The storage 1306 can include a memory device and a mass storage device and is also referred to herein as a computer-readable medium and / or a processor-readable medium. The storage 1306 can include a temporary storage medium and / or a non-temporary storage medium.

[0054] Bus 1310 may link various other circuits such as a timing source, a timer, peripheral devices, a voltage regulator, and a power management circuit. Bus interface 1308 can provide an interface between bus 1310 and one or more transceivers 1312. In one example, a transceiver 1312 can be provided so that device 1300 can communicate with a charging device or a power receiving device according to a standard defined protocol. Also, depending on the nature of device 1300, a user interface 1318 (e.g., a keypad, a display, a speaker, a microphone, a joystick) may be provided and can be communicatively coupled directly to bus 1310 or via bus interface 1308.

[0055] Processor 1304 can be responsible for the management of bus 1310 and overall processing including the execution of software stored in a computer-readable medium including storage 1306. In this regard, processing circuit 1302 including processor 1304 can be used to implement any of the methods, functions, and techniques disclosed herein. Storage 1306 can be used to store data to be operated on by processor 1304 during the execution of software, and the software can be configured to execute any one of the methods disclosed herein.

[0056] One or more processors 1304 of the processing circuit 1302 can execute software. Software is broadly interpreted as meaning instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, algorithms, etc., regardless of whether it is called software, firmware, middleware, microcode, or a hardware description language. The software may be present in the storage 1306 in a computer-readable form or may be present on an external computer-readable medium. The external computer-readable medium and / or the storage 1306 may include a non-transitory computer-readable medium. Non-transitory computer-readable media can include, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., compact discs (CDs), digital versatile discs (DVDs)), smart cards, flash memory devices (e.g., "flash drives", cards, sticks, key drives), RAM, ROM, programmable read-only memory (PROM), erasable PROM (EPROM) including electrically erasable PROM (EEPROM), registers, removable disks, and any other suitable medium for storing software and / or instructions that can be accessed and read by a computer. Also, the computer-readable medium and / or the storage 1306 can include, for example, carrier waves, transmission lines, and any other suitable medium for transmitting software and / or instructions that can be accessed and read by a computer. The computer-readable medium and / or the storage 1306 may be present within the processing circuit 1302, within the processor 1304, external to the processing circuit 1302, or distributed among multiple entities including the processing circuit 1302. The computer-readable medium and / or the storage 1306 may be embodied in a computer program product.As an example, a computer program product can include a computer-readable medium within a packaging material. Those skilled in the art will recognize the best way to implement the described functionality presented throughout this disclosure, depending on the particular application and overall design constraints imposed on the overall system.

[0057] Storage 1306 can maintain and / or organize software, such as loadable code segments, modules, applications, programs, etc., also referred to herein as software modules 1316. Each of the software modules 1316 can include instructions and data that, when installed or loaded into the processing circuit 1302 and executed by one or more processors 1304, contribute to a runtime image 1314 that controls the operation of the one or more processors 1304. Certain instructions, when executed, can cause the processing circuit 1302 to perform functions according to the particular methods, algorithms, and processes described herein.

[0058] Some of the software modules 1316 may be loaded during the initialization of the processing circuit 1302, and these software modules 1316 can configure the processing circuit 1302 to enable the execution of the various functions disclosed herein. For example, some of the software modules 1316 can configure the internal devices and / or logic circuits 1322 of the processor 1304 and can manage access to external devices such as the transceiver 1312, the bus interface 1308, the user interface 1318, timers, numeric co-processors, etc. The software modules 1316 can include control programs and / or operating systems that interact with interrupt handlers and device drivers to control access to the various resources provided by the processing circuit 1302. Resources can include memory, processing time, access to the transceiver 1312, the user interface 1318, etc.

[0059] One or more processors 1304 of the processing circuit 1302 are multifunctional, whereby some of the software modules 1316 are loaded and configured to execute different functions or different instances of the same function. Further, the one or more processors 1304 may be adapted to manage background tasks that are initiated in response to inputs from, for example, the user interface 1318, the transceiver 1312, and the device driver. To support the execution of multiple functions, the one or more processors 1304 may be configured to provide a multitasking environment, whereby each of the multiple functions is implemented as a set of tasks provided by the one or more processors 1304 as needed. In one example, the multitasking environment may be implemented using a time-sharing program 1320 that transfers control of the processor 1304 between different tasks, whereby each task returns control of the one or more processors 1304 to the time-sharing program 1320 in response to the completion of an outstanding operation and / or an input such as an interrupt. When a task has control of the one or more processors 1304, the processing circuit is effectively specialized for the purpose addressed by the functions associated with the control task. The time-sharing program 1320 can include an operating system, a main loop that transfers control in a round-robin fashion, a function that assigns control of the one or more processors 1304 according to the priority of the functions, and / or an interrupt-driven main loop that responds to external events by providing control of the one or more processors 1304 to the processing function.

[0060] In one embodiment, the apparatus 1300 includes, or operates as, a wireless charging device having a battery charging power source coupled to a charging circuit, a plurality of charging cells, one or more driver circuits (see, e.g., FIGS. 5 and 8), and a controller that may be included in one or more processors 1304. The one or more driver circuits may be configured to decode an ASK modulated message from a tank voltage or current flowing through the transmission coil. 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 region of each charging cell. The one or more driver circuits may include a first driver circuit configured to drive a transmission coil disposed near the surface of the charging device. The controller may be configured to cause the driver circuit to supply a charging current to the transmission coil, decode a transmission power reduction request from a modulation of the charging current, reduce an amplitude of the charging current in accordance with the transmission power reduction request when a temperature measured at the surface of the charging device is less than a threshold temperature, and initiate a cooling sequence when the temperature measured at the surface of the charging device is greater than or equal to the threshold temperature. In one example, the transmission power reduction request may be provided as an ASK modulation signal superimposed on the charging current.

[0061] In one example, one or more sensors may be thermally coupled to the charging surface of the apparatus 1300 and configured to provide periodic temperature measurements of at least a portion of the surface of the charging device. The threshold temperature level may be obtained from a prior calibration performed during a charging procedure. When the temperature measured at the surface of the charging device is greater than or equal to the threshold temperature, it may indicate that the internal temperature of the device being charged is exceeding a temperature limit.

[0062] In some examples, the threshold voltage level is stored in a look-up table. The look-up table may include threshold temperatures for each of a plurality of device types. The controller may further be configured to provide a minimum transmission power in response to a lower transmission power requirement when starting a cooling sequence. The controller may further identify a gradient of a time series of temperature measurements taken at the surface of the charging device, and may be configured to terminate the charging current when the gradient of the time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature during a defined cooling period for the device being charged.

[0063] In some embodiments, the controller may further identify a gradient of a time series of temperature measurements taken at the surface of the charging device, and may be configured to reduce the output of one or more driver circuits of the charging device when the gradient of the time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature during a defined cooling period for the device being charged.

[0064] In some embodiments, the controller may further identify a first gradient of a first time series of temperature measurements taken at the surface of the charging device, and may be configured to terminate the charging current when the first gradient of the first time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature defined for the device being charged during a first cooling period. After terminating the charging current, the controller may further identify a second gradient of a second time series of temperature measurements taken at the surface of the charging device, and may be configured to reduce the power output of one or more other driver circuits of the charging device when the second gradient of the second time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature defined for the device being charged during a second cooling period.

[0065] In certain embodiments, storage 1306 holds instructions and information, and the instructions cause one or more processors 1304 to drive a transmission coil located near the surface of the charging device in a driver circuit, supply a charging current from the driver circuit to the transmission coil, decode a transmission power reduction request from the modulation of the charging current, reduce the amplitude of the charging current according to the transmission power reduction request when the temperature measured at the surface of the charging device is less than a threshold temperature, and start a cooling sequence when the temperature measured at the surface of the charging device is greater than or equal to the threshold temperature.

[0066] In some embodiments, the instructions can be configured to receive, obtain, or acquire temperature measurements from one or more sensors thermally coupled to the surface of the charging device. The value of the threshold temperature can be obtained from a prior calibration performed during the charging procedure. When the temperature measured at the surface of the charging device is greater than or equal to the threshold temperature, it may indicate that the internal temperature of the device being charged exceeds the temperature limit.

[0067] In some examples, the threshold voltage level is held in a look-up table. The look-up table can include threshold temperatures for each of a plurality of device types. The instructions can be configured to provide a minimum transmission power in response to a lower transmission power request when starting a cooling sequence. The instructions can identify the gradient of a time series of temperature measurements taken at the surface of the charging device, and can be configured to terminate the charging current when the gradient of the time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature during a defined cooling period for the device being charged. The instructions can identify the gradient of a time series of temperature measurements taken at the surface of the charging device, and can be configured to reduce the output of one or more driver circuits of the charging device when the gradient of the time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature during a defined cooling period for the device being charged.

[0068] In some embodiments, the instruction identifies a first gradient of a first time series of temperature measurements taken at the surface of the charging device, and when the first gradient of the first time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature defined for the device being charged during a first cooling period, the charging current is terminated. Also, after terminating the charging current, a second gradient of a second time series of temperature measurements taken at the surface of the charging device is identified, and when the second gradient of the second time series of temperature measurements indicates that the surface of the charging device remains above a restart temperature defined for the device being charged during a second cooling period, the power output of one or more other drive circuits of the charging device is configured to be reduced.

[0069] FIG. 14 is a flowchart 1400 showing a method of operating a charging device according to a particular aspect of the present disclosure. This method can be executed using a controller within the charging device. In block 1402, the controller can configure a driver circuit to drive a transmission coil disposed near the surface of the charging device. In block 1404, the controller can cause the driver circuit to supply a charging current to the transmission coil. In block 1406, the controller can decode a transmission power reduction request from the modulation of the charging current. In block 1408, the controller can determine whether an overtemperature condition exists or is indicated in the device being charged. The overtemperature condition can correspond to the temperature of the battery exceeding a maximum temperature defined by a rating, protocol, or designer. The overtemperature condition can be indicated when the temperature measured at the surface of the charging device exceeds a threshold temperature. In one embodiment, in block 1410, when the temperature measured at the surface of the charging device is less than the threshold temperature, the controller can reduce the amplitude of the charging current in response to the transmission power reduction request. In another embodiment, in block 1412, when the temperature measured at the surface of the charging device becomes greater than or equal to the threshold temperature, the controller can initiate a cooling sequence.

[0070] In some embodiments, the controller can receive temperature measurements from one or more sensors thermally coupled to the surface of the charging device. The sensors are thermally coupled to the surface of the charging device, for example, when embedded in the surface of the charging device or fixed or attached using, for example, a thermally conductive adhesive. In some examples, the value of the threshold temperature can be obtained from a prior calibration performed during the charging procedure. In some examples, when the temperature measured at the surface of the charging device is above the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds the temperature limit.

[0071] In a particular example, the threshold voltage level is held in a look-up table. The look-up table can include threshold voltage levels for each of a plurality of device types. In a particular example, the cooling sequence can be initiated by providing a minimum transmission power in response to a reduced transmission power requirement. A time-series gradient of the temperature measurements taken at the surface of the charging device can be determined, estimated, or calculated. The charging current can be terminated when the time-series gradient of the temperature measurements indicates that the surface of the charging device remains above the restart temperature defined for the device to be charged during the cooling period. When the time-series gradient of the temperature measurements indicates that the surface of the charging device remains above the restart temperature defined for the device to be charged during the cooling period, the power output of one or more other driver circuits within the charging device can be reduced.

[0072] In a specific example, a first gradient of a first time series of temperature measurement values measured on the surface of the charging device can be determined. The charging current can be terminated when the first gradient of the first time series of temperature measurement values indicates that the surface of the charging device remains above the restart temperature defined for the device to be charged during a first cooling period. The first cooling period can be defined by a standard, protocol, or system designer. After terminating the charging current, a second gradient of a second time series of temperature measurement values measured on the surface of the charging device can be determined, estimated, or calculated. If the second gradient of the second time series of temperature measurement values indicates that the surface of the charging device remains above the restart temperature defined for the device to be charged during a second cooling period, the power output of one or more other driver circuits within the charging device can be reduced.

[0073] Some embodiments are described in the following numbered clauses. 1. A method of operating a charging device, comprising: configuring a driver circuit to drive a transmission coil disposed near the surface of the charging device; supplying a charging current to the transmission coil by the driver circuit; decoding a transmission power reduction request from modulation of the charging current; reducing an amplitude of the charging current according to the transmission power reduction request when a temperature measured on the surface of the charging device is less than a threshold temperature; and starting a cooling sequence when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature.

[0074] 2. The method according to item 1, further comprising receiving temperature measurement values from one or more sensors thermally coupled to the surface of the charging device.

[0075] 3. The method according to item 1 or item 2, wherein the threshold temperature is set based on a prior calibration performed during a charging procedure.

[0076] 4. The method according to any one of items 1 to 3, wherein when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds a temperature limit.

[0077] 5. The method according to any one of items 1 to 4, wherein the threshold temperature is defined by a look-up table.

[0078] 6. The method according to item 5, wherein the look-up table includes threshold temperatures for each of a plurality of device types.

[0079] 7. The method according to any one of items 1 to 6, wherein the step of starting the cooling sequence includes providing a minimum transmission power in response to the transmission power reduction request.

[0080] 8. The method according to item 7, further including the steps of identifying a gradient of a time series of temperature measurement values measured on the surface of the charging device, and terminating the charging current when the gradient of the time series of the temperature measurement values indicates that the surface of the charging device remains at or above a restart temperature during a defined cooling period for the device to be charged.

[0081] 9. The method according to item 7 or 8, further including the steps of identifying a gradient of a time series of temperature measurement values measured on the surface of the charging device, and reducing the power output of one or more other driver circuits within the charging device when the gradient of the time series of the temperature measurement values indicates that the surface of the charging device remains at or above a restart temperature.

[0082] 10. The method according to any one of items 7 to 9, wherein when the temperature measured on the surface of the charging device is equal to or higher than the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds the temperature limit.

[0083] 11. A charging device, comprising: a driver circuit configured to drive a transmission coil disposed near the surface of the charging device; and a controller configured to cause the driver circuit to supply a charging current to the transmission coil, decode a transmission power reduction request from modulation of the charging current, reduce the amplitude of the charging current according to the transmission power reduction request when the temperature measured on the surface of the charging device is less than a threshold temperature, and start a cooling sequence when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature.

[0084] 12. The charging device according to item 11, further comprising one or more sensors thermally conductively coupled to the surface of the charging device and configured to provide periodic temperature measurements of at least a portion of the surface of the charging device.

[0085] 13. The charging device according to item 11 or 12, wherein the threshold temperature is set based on a prior calibration performed during a charging procedure.

[0086] 14. The charging device according to any one of items 11 to 13, wherein when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds a temperature limit.

[0087] 15. The charging device according to any one of claims 11 to 15, wherein the threshold temperature is defined in a look-up table.

[0088] 16. The charging device according to item 15, wherein the look-up table includes threshold temperatures for each of a plurality of device types.

[0089] 17. The charging device according to any one of items 11 to 16, wherein the controller is further configured to provide a minimum transmission power in response to a lower transmission power request when starting a cooling sequence.

[0090] 18. The controller further specifies a gradient of a time series of temperature measurement values measured on the surface of the charging device, and when the gradient of the time series of the temperature measurement values indicates that the surface of the charging device remains at or above the restart temperature during a cooling period defined for the device to be charged, the charging current is configured to be terminated. The charging device according to item 17.

[0091] 19. The controller further specifies a gradient of a time series of temperature measurement values measured on the surface of the charging device, and when the gradient of the time series of the temperature measurement values indicates that the surface of the charging device remains at or above the restart temperature during a cooling period defined for the device to be charged, the output of one or more driver circuits of the charging device is configured to be reduced. The charging device according to item 17 or 18.

[0092] 20. The controller further specifies a first gradient of a first time series of temperature measurement values measured on the surface of the charging device, and when the first gradient of the temperature measurement values of the first time series indicates that the surface of the charging device remains at or above the restart temperature defined for the device to be charged during a first cooling period, the charging current is terminated. Further, a second gradient of a second time series of temperature measurement values measured on the surface of the charging device after the charging current is terminated is specified, and when the second gradient of the second time series of temperature measurement values indicates that the surface of the charging device remains at or above the restart temperature defined for the device to be charged during a second cooling period, the power output of one or more other drive circuits of the charging device is configured to be reduced. The charging device according to any one of items 17 to 19.

[0093] The foregoing description has been provided to enable those skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. For this reason, the claims are not intended to be limited to the aspects shown herein, but rather the full scope consistent with the claim language is to be recognized, and references to singular elements are not intended to mean "sole" unless expressly stated otherwise, but rather "one or more." Unless expressly stated otherwise, the term "some" refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those skilled in the art are expressly incorporated herein by reference and are intended to be included within the claims. Further, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is expressly recited in the claims. Claim elements should not be construed under 35 U.S.C. § 112, paragraph 6, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the phrase "step for."

Claims

1. A method for operating a charging device, comprising: configuring a driver circuit to drive a transmission coil disposed near the surface of the charging device, wherein the charging device is a multi-device multi-coil wireless charger; causing the driver circuit to supply a charging current to the transmission coil; decoding a request for reducing transmission power from modulation of the charging current, wherein the request is encoded by a device charged with a signal superimposed on the charging current; acquiring a measured value of the temperature on the surface of the charging device after receiving the request for reducing transmission power; reducing the transmission power by reducing the amplitude of the charging current in accordance with the request for reducing transmission power when the temperature measured on the surface of the charging device is less than a threshold temperature; starting a cooling sequence when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature, the step of starting the cooling sequence including providing a minimum transmission power.

2. The method according to claim 1, further comprising receiving a measured value of the temperature from one or more sensors thermally coupled to the surface of the charging device.

3. The method according to claim 1, wherein the threshold temperature is set based on a prior calibration performed during a charging procedure.

4. The method according to claim 1, wherein when the temperature measured on the surface of the charging device is greater than or equal to the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds a temperature limit.

5. The method according to claim 1, wherein the threshold temperature is defined in a look-up table.

6. The method according to claim 5, wherein the look-up table includes threshold temperatures for each of a plurality of device types.

7. The method according to claim 1, wherein the step of starting the cooling sequence includes defining a limited duration of the cooling sequence.

8. Further, identifying a gradient of a time series of measured values of the temperature measured on the surface of the charging device; The method according to claim 7, further comprising the step of terminating the charging current when the gradient of the time series of the measured temperature values indicates that the surface of the charging device remains above a low temperature threshold value that should be reached during the limited duration of the cooling sequence.

9. The step of identifying the gradient of the time series of the measured temperature values measured at the surface of the charging device; The method according to claim 7, further comprising the step of reducing the power output of one or more other driver circuits within the charging device when the gradient of the time series of the measured temperature values indicates that the surface of the charging device remains above a low temperature threshold value that should be reached during the limited duration of the cooling sequence.

10. Furthermore, the step of identifying a first gradient of a first time series of measured temperature values measured at the surface of the charging device; The step of terminating the charging current when the first gradient of the measured temperature values of the first time series indicates that the surface of the charging device remains above a low temperature threshold value that should be reached during a first cooling period; The step of identifying a second gradient of a second time series of measured temperature values measured at the surface of the charging device after terminating the charging current; The method according to claim 7, further comprising the step of reducing the power output of one or more other driver circuits of the charging device when the second gradient of the second time series of measured temperature values indicates that the surface of the charging device remains above the low temperature threshold value that should be reached during a second cooling period for the device to be charged.

11. A charging device, comprising: A driver circuit configured to drive a transmission coil disposed near the surface of the charging device, wherein the charging device is a multi-device multi-coil wireless charger; A controller, to the driver circuit: Supply a charging current to the transmission coil; Decode a request for reducing transmission power from the modulation of the charging current, wherein the request is encoded by a device charged with a signal superimposed on the charging current; After receiving the request for reducing transmission power, obtain a measured temperature value at the surface of the charging device; Reduce the transmission power by reducing the amplitude of the charging current according to the request for reducing transmission power when the temperature measured at the surface of the charging device is less than a threshold temperature. When the temperature measured on the surface of the charging device is equal to or higher than the threshold temperature, starting a cooling sequence, which includes starting the cooling sequence to provide the minimum transmission power. A charging device, comprising a controller configured to cause the above to be implemented.

12. The charging device according to claim 11, further comprising one or more sensors thermally conductively coupled to the surface of the charging device and configured to provide measured values of periodic temperatures of at least a part of the surface of the charging device.

13. The charging device according to claim 11, wherein the threshold temperature is set based on a prior calibration performed during a charging procedure.

14. The charging device according to claim 11, wherein when the temperature measured on the surface of the charging device is equal to or higher than the threshold temperature, it indicates that the internal temperature of the device to be charged exceeds a temperature limit.

15. The charging device according to claim 11, wherein the threshold temperature is defined in a look-up table.

16. The charging device according to claim 15, wherein the look-up table includes threshold temperatures for each of a plurality of device types.

17. The charging device according to claim 11, wherein the controller is further configured to provide a limited duration of the cooling sequence.

18. The charging device according to claim 17, wherein the controller is further configured to identify a temporal gradient of measured values of the temperature measured on the surface of the charging device, and when the temporal gradient of the measured values of the temperature indicates that the surface of the charging device remains above a low temperature threshold to be reached during the limited duration of the cooling sequence, configured to terminate the charging current.

19. The controller is further configured to identify a temporal gradient of measured values of the temperature measured on the surface of the charging device. The charging device according to claim 17, wherein when the temporal gradient of the measured values of the temperature indicates that the surface of the charging device remains above a low temperature threshold to be reached during the limited duration of the cooling sequence, configured to reduce the output of one or more driver circuits of the charging device.

20. The controller is further configured to identify a first gradient of a first time series of measured values of the temperature measured on the surface of the charging device. When the first gradient of the measured value of the temperature in the first time series remains equal to or higher than the low temperature threshold that the surface of the charging device should reach during the first cooling period, the charging current is terminated. After terminating the charging current, a second gradient of a second time series of the measured value of the temperature measured at the surface of the charging device is specified, and when the second gradient of the second time series of the measured value of the temperature indicates that the surface of the charging device remains equal to or higher than the low temperature threshold that should be reached during the second cooling period for the device to be charged, the charging device according to claim 17, which is configured to reduce the power output of one or more other driver circuits of the charging device.

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