CN210123910U - Wireless power transmission apparatus - Google Patents

Abstract

One embodiment of the present invention relates to a wireless power transfer device. Disclosed is a wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising: a coil array; a wireless power transfer circuit coupled to the coil array to transfer a wireless power signal to the wireless power receiving device; a temperature sensor array overlapping the coil array and extending across the charging surface; and a control circuit configured to detect foreign matter on the charging surface based on temperature information collected with the temperature sensor.

Description

Wireless power transmission apparatus

This patent application claims priority from U.S. patent application No. 16/206,758 filed on 30.11.2018 and U.S. provisional patent application No. 62/726,124 filed on 31.8.2018, which are hereby incorporated by reference in their entirety.

Technical Field

The present disclosure relates generally to wireless systems, and more particularly to systems in which devices are charged wirelessly.

Background

In a wireless charging system, a wireless power transfer device, such as a device having a charging surface, wirelessly transfers power to another electronic device, such as a battery-powered portable electronic device. The portable electronic device receives the wirelessly transmitted power and uses the power to charge an internal battery and power components in the portable electronic device.

Performing wireless charging operations in a wireless charging system can be challenging. For example, it is challenging to ensure that foreign objects, such as coins, present on the charging surface are not inadvertently heated during a wireless charging operation.

SUMMERY OF THE UTILITY MODEL

The wireless power transmitting apparatus transmits a wireless power signal to the wireless power receiving apparatus. The wireless power receiving device has a rectifier and a wireless power receiving coil that receives a wireless power signal.

In some embodiments, the wireless power transfer device uses the coil layer to transfer the wireless power signal. A dielectric layer in a wireless power transmitting device defines a charging surface for receiving a wireless power receiving device. The dielectric layer overlaps the coil layer.

In some implementations, the temperature sensor layer is interposed between the coil layer and the dielectric layer. The temperature sensor may be configured to measure a heat flux through the charging surface.

Control circuitry in the wireless power transfer device uses temperature information from the temperature sensor to determine whether foreign matter, such as coins, is present on the charging surface. In response to detecting the foreign object, the control circuitry takes appropriate action, such as stopping transmission of the wireless power signal.

According to one embodiment, a wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising: a coil array; a wireless power transfer circuit coupled to the coil array to transfer a wireless power signal to the wireless power receiving device; a temperature sensor array overlapping the coil array and extending across the charging surface; and a control circuit configured to detect foreign matter on the charging surface based on temperature information collected with the temperature sensor.

According to one embodiment, the temperature sensor array is configured to measure heat flux through the charging surface.

According to one embodiment, the control circuit is configured to interrupt charging based on temperature difference information of the temperature sensor.

According to one embodiment, the temperature sensor array includes a first set of temperature sensing devices and a second set of temperature sensing devices, wherein the temperature sensing devices of the first set of temperature sensing devices are separated from the charging surface by a first thermal resistance, and wherein the temperature sensing devices of the second set of temperature sensing devices are separated from the charging surface by a second thermal resistance, the second thermal resistance being greater than the first thermal resistance.

According to one embodiment, the first set of temperature sensing devices has a first temperature sensing pad thermally coupled to a respective first temperature sensor component, wherein the second set of temperature sensing devices has a second temperature sensing pad thermally coupled to a respective second temperature sensor component, and wherein the wireless power transfer device comprises a dielectric layer between the first temperature sensing pad and the second temperature sensing pad.

According to one embodiment, the array of temperature sensors is configured to measure a first set of temperatures using the first set of temperature sensing devices and is configured to measure a second set of temperatures using the second set of temperature sensing devices.

According to one embodiment, the temperature information comprises the first set of temperatures, and wherein the control circuit is configured to detect the foreign object based on the first set of temperatures, and wherein the temperature information comprises the second set of temperatures, and wherein the control circuit is configured to detect the foreign object based on the first set of temperatures and the second set of temperatures.

According to one embodiment, the control circuitry is configured to determine, for each of the first set of temperature sensing devices, a corresponding surface temperature on the charging surface, wherein the temperature information comprises the surface temperature, and wherein the control circuitry is configured to detect the foreign object based on the surface temperature.

According to one embodiment, the control circuit is configured to predict a future surface temperature of the charging surface, and wherein the control circuit is configured to detect the foreign object based on the future surface temperature.

According to one embodiment, the control circuit is configured to determine a transfer function associated with the first and second sets of temperatures and the wireless power signal, and to detect the foreign object using the transfer function.

According to one embodiment, the control circuit is configured to determine the transfer function by amplitude modulation of the wireless power signal when the wireless power receiving device is not receiving the wireless power signal.

According to one embodiment, the control circuit is configured to determine the transfer function by measuring a coil current when the wireless power receiving device is receiving the wireless power signal.

According to one embodiment, the wireless power transfer device further comprises an additional temperature sensor layer overlapping the temperature sensor array, wherein the control circuitry is configured to create a temperature offset for a temperature sensing device in the temperature sensor array based on information from the additional temperature sensor layer.

According to one embodiment, the control circuit is configured to detect the foreign matter by comparing a rate of temperature change measured with a given one of the temperature sensors with a predetermined rate of temperature change threshold.

According to one embodiment, the control circuit is configured to interrupt charging by comparing the rate of change of temperature measured at two or more sensors to a pre-calculated set of acceptable rate of change patterns.

According to one embodiment, the wireless power transfer device further comprises a coil impedance measurement circuit or a transimpedance measurement circuit, wherein the control circuit is configured to acquire the temperature information in response to detecting a change in coil impedance in the coil array using the coil impedance measurement circuit.

According to one embodiment, the control circuit is configured to correct the temperature measurement with the temperature sensor by taking into account a portion of the temperature measurement due to wireless heating of a temperature sensor pad in the temperature sensor by the wireless power signal.

According to one embodiment, the control circuit is configured to apply a thermal hysteresis correction function to the temperature measurements from the temperature sensors to produce corresponding hysteresis corrected temperature measurements, and wherein the control circuit is configured to detect the foreign object based on the hysteresis corrected temperature measurements.

According to one embodiment, a wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising: a coil; a wireless power transfer circuit coupled to the coil to transfer a wireless power signal to the wireless power receiving device; a temperature sensor overlapping the coil and configured to acquire temperature information, wherein the temperature sensor includes a first temperature sensor pad configured to acquire a first temperature, a second temperature sensor pad configured to acquire a second temperature, and a dielectric layer between the first temperature sensor pad and the second temperature sensor pad; and a control circuit configured to detect foreign matter on the charging surface based on the temperature information collected with the temperature sensor.

According to one embodiment, a wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising: a dielectric layer forming the charging surface; a coil array in a coil layer; a wireless power transfer circuit coupled to the coil array to transfer a wireless power signal to the wireless power receiving device; a temperature sensor array interposed between the dielectric layer and the coil array, the temperature sensor array configured to measure heat flux through the charging surface; and a control circuit configured to detect foreign matter on the charging surface based on temperature information collected with the temperature sensor and configured to stop transmitting the wireless power signal to the wireless power receiving device in response to detecting the foreign matter, wherein the temperature sensor array includes a first set of temperature sensing devices and a second set of temperature sensing devices, wherein the temperature sensing devices of the first set of temperature sensing devices are separated from the charging surface by a first thermal resistance, and wherein the temperature sensing devices of the second set of temperature sensing devices are separated from the charging surface by a second thermal resistance, the second thermal resistance being greater than the first thermal resistance.

Drawings

Fig. 1 is a schematic diagram of an exemplary wireless charging system, according to one embodiment.

Fig. 2 is a top view of an exemplary wireless power transfer apparatus having an array of coils forming a wireless charging surface, according to one embodiment.

Fig. 3 is a top view of a portion of an exemplary temperature sensor array extending across a wireless charging surface, according to one embodiment.

Fig. 4 is a cross-sectional side view of an exemplary wireless power transfer apparatus, in accordance with one embodiment.

FIG. 5 is a top view of an exemplary temperature sensor pad formed from metal traces with fingers separated by slots according to one embodiment.

Fig. 6 is a flow diagram of exemplary operations involved in detecting foreign matter using a temperature sensor, according to one embodiment.

Fig. 7 is a flow diagram of exemplary operations involved in determining whether foreign objects are present by comparing temperature measurements to thresholds, according to one embodiment.

Fig. 8 is a flow diagram of exemplary operations involved in determining whether foreign matter is present by comparing a charging surface temperature extrapolated from temperature measurements in a temperature sensor layer to a threshold, according to one embodiment.

Fig. 9 is a graph showing how an illustrative time-dependent temperature rise curve may be fitted to a series of temperature measurements to predict future surface temperatures, according to one embodiment.

Fig. 10 is a flowchart of exemplary operations involved in determining whether foreign matter is present by comparing a predicted future temperature to a threshold, according to one embodiment.

Fig. 11 is a graph of illustrative coil power over time signature types that may be obtained when control circuitry in a wireless power transfer device is performing amplitude modulation on a wireless power signal, according to one embodiment.

FIG. 12 is a graph of an exemplary temperature difference between two sensor layers as a function of time associated with the coil power over time feature of FIG. 11, in accordance with one embodiment.

FIG. 13 is a graph in which exemplary transfer functions associated with the coil power and temperature differential measurements of FIGS. 11 and 12 are plotted, according to one embodiment.

Fig. 14 is a flow diagram of exemplary operations involved in using transfer function information to determine whether a foreign object is present, according to one embodiment.

Fig. 15 is a flow diagram of exemplary operations involved in determining whether foreign matter is present by comparing a measured rate of temperature change to a threshold, according to one embodiment.

Fig. 16 is a flow diagram of exemplary operations involved in using a wireless power transfer apparatus according to one embodiment.

FIG. 17 is a flow diagram of exemplary operations involved in analyzing impedance measurements to determine whether a temperature measurement should be taken to detect foreign matter, according to one embodiment.

Fig. 18 is a flow diagram of exemplary steps involved in calibrating a temperature sensor circuit in a wireless power transfer apparatus according to one embodiment.

Fig. 19 is a graph illustrating how a calibration system may apply heat to a wireless power transfer device to acquire thermal hysteresis correction data, according to one embodiment.

Fig. 20 is a graph illustrating how temperature in a wireless power transfer apparatus according to one embodiment may vary in response to the exemplary applied heat of fig. 17.

Fig. 21 is a graph showing how temperature measurements in a wireless power transfer device may vary in response to the exemplary applied heat of fig. 17 after applying a time-dependent thermal hysteresis correction function to the temperature measurements, according to one embodiment.

Fig. 22 is a cross-sectional side view of an illustrative wireless power transfer device showing a temperature sensor configured to measure heat flux, in accordance with one embodiment.

Fig. 23 and 24 are additional cross-sectional side views of an exemplary wireless power transfer apparatus for measuring heat flux, in accordance with an embodiment.

Detailed Description

The wireless power system has a wireless power transmitting device that wirelessly transmits power to a wireless power receiving device. The wireless power transfer device is a device such as a wireless charging pad, wireless charging tray, wireless charging stand, or other wireless power transfer device. The wireless power transfer device has one or more coils for transferring wireless power to one or more wireless power receiving coils in the wireless power receiving device. A wireless power receiving device is a device such as a cellular phone, watch, media player, tablet, a pair of earplugs, remote control, laptop computer, other portable electronic device, or other wireless power receiving device.

During operation, the wireless power transfer device provides an alternating current drive signal to one or more wireless power transfer coils. This causes the coil to transmit an alternating electromagnetic signal (sometimes referred to as a wireless power signal) to one or more corresponding wireless power receiving coils in the wireless power receiving device. Rectifier circuitry in the wireless power receiving device converts the received wireless power signal to Direct Current (DC) power to power the wireless power receiving device.

An array of temperature sensors is included in the wireless power transfer device 10 to monitor the elevated temperature of the charging surface of the wireless power transfer device 10. Large temperature rises are generally undesirable because they may indicate the presence of undesirable foreign objects (such as coins) on the wireless power transfer device that intercept power during wireless power transfer operations.

An illustrative wireless power system (wireless charging system) is shown in fig. 1. As shown in fig. 1, the wireless power system 8 includes a wireless power transmitting device 12 and one or more wireless power receiving devices, such as wireless power receiving device 10. The device 12 may be a stand-alone device such as a wireless charging pad, may be built into furniture, or may be other wireless charging equipment. The device 10 is a portable electronic device such as a wristwatch, cellular telephone, tablet computer or other electronic device. An illustrative configuration in which device 12 is a pad or other device forming a wireless charging surface and in which device 10 is a portable electronic device that rests on the wireless charging surface during wireless power transfer operations is sometimes described herein as an example.

During operation of system 8, a user places one or more devices 10 on a charging surface of device 12. The power transfer device 12 is coupled to an ac power source, such as an ac power source 50 (e.g., a wall socket supplying line power or other mains power), has a battery for supplying power, such as a battery 38, and/or is coupled to another power source. A power converter, such as an alternating current-to-direct current (AC-DC) power converter 40, may convert power from a mains or other Alternating Current (AC) power source into Direct Current (DC) power for powering control circuitry 42 and other circuitry in device 12. During operation, the control circuitry 42 transmits an alternating electromagnetic signal 48 to the device 10 using the wireless power transmission circuitry 34 and the one or more coils 36 coupled to the circuitry 34, and thereby delivers wireless power to the wireless power receiving circuitry 46 of the device 10.

The power transfer circuit 34 has a switching circuit (e.g., a transistor in an inverter circuit) that is turned on and off based on a control signal provided by a control circuit 42 to generate an AC signal (drive signal) through the coil 36. When the AC signal passes through the coil 36, an alternating electromagnetic field (wireless power signal 48) is generated that is received by one or more corresponding coils 14 coupled to the wireless power receiving circuit 46 in the receiving device 10. When an alternating electromagnetic field is received by the coil 14, a corresponding alternating current and voltage is induced in the coil 14. Rectifier circuitry in circuit 46 converts AC signals (received alternating current and voltage associated with the wireless power signal) received from one or more coils 14 to DC voltage signals for powering device 10. The DC voltage is used to power components in the device 10, such as the display 52, touch sensor components and other sensors 54 (e.g., accelerometers, force sensors, temperature sensors, light sensors, pressure sensors, gas sensors, humidity sensors, magnetic sensors, etc.), wireless communication circuitry 56 for wirelessly communicating with corresponding wireless communication circuitry 58 in the control circuitry 42 of the wireless power transfer device 12 and/or other devices, audio components and other components (e.g., the input-output device 22 and/or the control circuitry 20) and for charging an internal battery (such as the battery 18) in the device 10.

The wireless power transfer device 12 includes communication means for establishing communication with the device 10. Such communication may include determining that device 10 is an acceptable device for receiving power, and negotiating to determine a desired power transmission rate and the actual power accepted by device 10. The wireless power transfer device 12 includes measurement circuitry 59 that uses the coil 36 and/or other circuitry to measure characteristics of electronics and other objects that overlap the coil 36. For example, measurement circuitry 59 may include impulse response measurement circuitry (sometimes referred to as inductance measurement circuitry and/or Q-factor measurement circuitry) and/or other measurement circuitry coupled to coils 36 to measure the inductance L and the quality factor Q of each coil 36. During the impulse response measurement, control circuitry 42 instructs circuitry 59 to provide one or more excitation pulses (pulses) to each coil 36. The pulse may be, for example, a square wave pulse of duration 1 mus. Longer or shorter pulses may be applied if desired. The resulting resonant response (oscillation) of coil 36 and the resonant circuit in device 12 including coil 36 is then measured by circuit 59 to determine L and Q. Using measurements such as these, the control circuitry 42 may monitor one or more of the coils 36 (e.g., each coil 36 in the coil array 36 in the device 12) for the presence of an external object, such as one of the devices 10 that may be compatible with wireless power transfer (sometimes referred to herein as a wireless power receiving device) or an incompatible object such as a coin or paperclip (sometimes referred to herein as foreign object). Foreign matter is also detected based on temperature information, such as temperature sensor measurements made using the temperature sensor 57. In some embodiments, only temperature information or impedance information is used to detect foreign matter. In other embodiments, the control circuit 42 uses both temperature information and impedance information to detect foreign objects.

Devices 12 and 10 include control circuits 42 and 20. Control circuits 42 and 20 include storage and processing circuits such as microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application specific integrated circuits with processing circuits. The control circuits 42 and 20 are configured to execute instructions for implementing desired control and communication features in the system 8. For example, control circuits 42 and/or 20 may be used to determine power transfer levels, process sensor data (such as temperature sensor data), process user inputs, process information from receive circuit 46, determine when to start and stop wireless charging operations using information from circuits 34 and/or 46 (such as signal measurements on output circuits in circuit 34 and other information from circuits 34 and/or 46), adjust charging parameters (such as charging frequency, coil assignments in a multi-coil array, and wireless power transfer levels), and perform other control functions. Control circuits 42 and 20 may be configured to support wireless communication between devices 12 and 10 (e.g., control circuit 20 may include wireless communication circuitry such as circuitry 56, and control circuit 42 may include wireless communication circuitry such as circuitry 58). Control circuitry 42 and/or 20 may be configured to perform these operations using hardware (e.g., dedicated hardware or circuitry) and/or software (e.g., code running on hardware of system 8). The software code for performing these operations is stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium). The software code may sometimes be referred to as software, data, program instructions, or code. The non-transitory computer-readable storage medium may include non-volatile memory such as non-volatile random access memory (NVRAM), one or more hard disk drives (e.g., magnetic disk drives or solid state drives), one or more removable flash drives or other removable media, other computer-readable media, or a combination of these or other storage devices. Software stored on a non-transitory computer readable storage medium may be executed on the processing circuitry of control circuitry 42 and/or 20. The processing circuitry may include an application specific integrated circuit having processing circuitry, one or more microprocessors, or other processing circuitry.

Device 12 and/or device 10 may communicate wirelessly during operation of system 8. The devices 10 and 12 may have, for example, in the control circuits 42 and 20 (see, e.g., wireless communication circuits such as circuits 58 and 56 of fig. 1) wireless transceiver circuitry that allows signals to be wirelessly transmitted between the devices 10 and 12 (e.g., using an antenna separate from the coils 36 and 14 to transmit and receive unidirectional or bidirectional wireless signals, using the coils 36 and 14 to transmit and receive unidirectional or bidirectional wireless signals, etc.). In some embodiments, devices 12 and 10 may communicate the amount of power transmitted and the amount of power received and the presence of other losses, referred to as Power Counts (PCs). Other losses may include eddy currents or other acceptable power losses in the housing, or they may include losses caused by foreign body heating.

With one exemplary configuration, the wireless transmission device 12 is a wireless charging pad or other wireless power transmission device that includes an array of coils 36 that are configured to provide wireless power through a wireless charging surface. An arrangement of this type is shown in figure 2. In the example of fig. 2, the device 12 has an array of coils 36 lying in parallel X-Y planes. The coil 36 of the device 12 is covered by a planar dielectric layer. The outermost surface of the dielectric layer forms a charging surface 60. The lateral dimensions (X and Y dimensions) of the array of coils 36 in the device 36 may be 1 to 1000cm, 5 to 50cm, greater than 5cm, greater than 20cm, less than 200cm, less than 75cm, or other suitable dimensions. The coils 36 may overlap or may be arranged in a non-overlapping configuration. The coils 36 may be placed in a rectangular array having rows and columns and/or may be tiled using a hexagonal tiling pattern or other pattern.

As shown in the example of fig. 2, external objects such as external object 62 and object 64 may overlap with one or more coils 36. In some cases, the objects 62 and 64 will be portable electronic devices 10. In other cases, one or more of the objects 62 and 64 will be incompatible foreign objects (e.g., foreign objects such as metal coins or other conductive objects). It is also possible that a foreign object and a wireless power receiving device overlap the same coil or coils 36. During operation, the system 8 automatically detects whether an object located on the surface 60 corresponds to a wireless power receiving device 10 to which wireless power should be provided or whether foreign objects to which wireless power should not be provided. In an exemplary embodiment, impedance monitoring circuitry and/or temperature measurement circuitry (such as temperature sensor 57) in measurement circuitry 59 is used to detect when foreign matter is present and/or when undesirable heating of foreign matter occurs. Upon detection of the foreign object, the system 8 automatically takes appropriate action, such as reducing and/or interrupting wireless power transmission.

When wireless power from the coil 36 is transferred, currents may be induced in foreign objects on the charging surface 60 that cause these objects to heat. In order to monitor an undesired temperature rise type associated with heating of foreign matter on the charging surface 60, the temperature sensors 57 may be formed in an array form on the entire charging surface 60, as shown in fig. 3. The temperature sensors 57 can be arranged in an array having N rows and M columns (e.g., where N and/or M are at least 1, at least 2, at least 5, at least 10, at least 20, at least 35, at least 60, at least 100, at least 200, at least 400, less than 1000, less than 450, less than 210, less than 125, less than 70, less than 50, less than 40, or other suitable values). The temperature sensors may be organized into rectangles with rounded corners or other suitable shapes (e.g., shapes that match the contour of the charging surface 60). The temperature sensor 57 overlaps with a dielectric layer on top of the wireless power transfer device 12 and is interposed between the coil 36 and the dielectric layer, which forms the charging surface 60.

Fig. 4 shows a cross-sectional side view of the wireless power transfer device 12. As shown in FIG. 4, device 12 has a housing, such as housing 70. In some embodiments, wireless power transmission through housing 70 is not desired, and housing 70 is formed of a metallic material. In some embodiments, housing 70 is formed from metal, polymer, glass, or other material.

A printed circuit 72 is placed over the housing 70. Printed circuit 72 includes integrated circuits (e.g., control circuit 42), temperature sensors (e.g., sensors that measure the change in resistance of a material as a function of temperature), and other circuits (e.g., integrated circuits, signal paths, etc.) for device 12. The temperature sensor in the printed circuit 72 is used during a calibration operation of the temperature sensor 57.

A magnetic shield layer 74 is formed over the printed circuit 72 and is configured to shield the circuitry in the printed circuit 72 from the magnetic field from the coil 36. A layer of ferrite or other magnetic material is used to form the magnetic shield layer 74.

The coils 36 are placed in one or more coil layers 76.

An electron shield layer 78 is formed over the coil layer 76 and includes a conductive layer for electrically isolating the coil 36 from circuitry in upper layers of the device 12.

The temperature sensor array 57 is formed in a layer between the shield layer 78 and the adhesive layer 92, and in some embodiments includes upper temperature sensor pads, such as upper temperature sensor pad 90, and lower temperature sensor pads, such as lower temperature sensor pad 84. There may be a different number of pads 90 and pads 84 or the number of pads 90 and pads 84 may be equal. Arrangements in which the number of pads 90 and pads 84 is equal are sometimes described herein as an example. Adhesive layer 92 (a polymer layer such as polycarbonate layer 94) and an elastomeric polymer layer (such as silicone layer 96) and/or other dielectric material layers form a dielectric layer on top of device 12 that overlaps sensor 57. The outermost surface of the dielectric layer (e.g., the top surface of layer 96) defines charging surface 60.

During normal charging operation, the wireless power receiving device 10 rests in a position 98 on the charging surface 60. However, in some cases, foreign objects such as coins or paperclips may be present in the location 98 and may be heated by the wireless power signal emitted by the coil 36. The control circuit 42 uses the temperature sensor 57 to detect undesired heating. When undesired heating is detected, the control circuit 42 takes appropriate action, such as stopping wireless power transfer with the coil 36, thereby preventing foreign matter on the charging surface 60 from becoming overheated.

In some embodiments, such as the illustrative arrangement of fig. 4, the temperature sensor 57 has a temperature sensing device configured to measure the heat flux through the charging surface 60. The sensors 57 may, for example, include a first set of temperature sensing devices spaced apart from the charging surface 60 by a first thermal resistance and a second set of temperature sensing devices spaced apart from the charging surface 60 by a second thermal resistance greater than the first thermal resistance. In this type of arrangement, a first temperature sensing device may react relatively quickly to changes at the charging surface 60, while a second temperature sensing device may react more slowly and thus may be considered a reference temperature sensing device (e.g., a temperature sensing device that measures the ambient temperature of the device 12). Using differential measurements with data from the first and second sets of temperature sensing devices allows the heat flux through the charging surface 60 to be estimated.

The temperature sensing device used in temperature sensor 57 may be based on a thermistor (e.g., a resistive temperature sensing device type sometimes based on a temperature sensitive ceramic or metal oxide), a resistive thermometer (e.g., a resistive temperature sensing device type sometimes formed of a metal temperature sensing element, such as an element formed of platinum, nickel, or other metal and which may be formed of a thin film resistor if desired), a thermocouple, a semiconductor temperature sensing device, or other temperature sensor component.

In the example of fig. 4, the temperature sensor 57 includes a temperature sensing device having a temperature sensor component 82 (e.g., a thermistor, resistance thermometer, etc.) and an associated metal pad thermally coupled to the temperature sensor component. In each temperature sensor 57, for example, the first temperature sensing device may include a first temperature sensor component 82 thermally coupled to a lower metal trace forming a lower temperature sensor pad 84 and a second temperature sensor component 82 thermally coupled to an upper metal trace forming an upper temperature sensor pad 90 using a metal via 86. This allows the first temperature sensing device to measure the temperature at the lower temperature sensor pad 84 and the second temperature sensing device to measure the temperature at the upper temperature sensor pad 90. If desired, the second temperature sensor component can be directly coupled to the upper temperature sensor pad 90 (see, e.g., exemplary temperature sensor component 82'). Pads 84 and 90 are supported on opposite upper and lower surfaces of a dielectric layer, such as a printed circuit substrate 88. Adhesive 80 is used to attach printed circuit substrate 88 to layer 78. Air surrounds the temperature sensor component 82. The pads 84 and/or 90 may have any suitable shape (rectangular, hexagonal, square, circular, shapes with straight and/or curved sides, triangular, etc.). In one exemplary configuration, the pads 84 and 90 have elongated fingers separated by interposed slots, as shown by the exemplary pads PD of fig. 5. The presence of slots SL between fingers FG in pad PD helps to prevent eddy currents and undesirable heating of the temperature sensor pad during transmission of electromagnetic signals from coil 36. Any residual heating of the temperature sensor pad due to wireless power signal transmission is taken into account by the control circuitry 42 (e.g., by calibrating the temperature information to correct the temperature reading for the effect of the wireless power signal on the temperature of the pad).

Because the temperature sensing pad 90 is closer to the surface 60 than the pad 84, the structure between the pad 90 and the surface 60 has a lower thermal resistance than the structure between the pad 84 and the surface 60. This allows for a temperature difference measurement (temperature gradient measurement) and thus a measurement of the heat flux through the surface 60. The temperature sensing device of fig. 4 uses temperature sensing pads (metal pads), but some or all of these pads may be omitted and/or other structures may be used to allow the temperature sensor 57 to make heat flux measurements. Furthermore, the number of pads (pads 90) associated with the lower thermal resistance sensing devices need not be the same as the number of pads (pads 84) associated with the higher thermal resistance sensing devices. For example, there may be fewer pads 84 than pads 90.

During operation of the device 12, the coil 36 generates a wireless power signal that is transmitted to the device 10. In some cases, foreign matter such as coins are present on the charging surface 60. To determine whether the charging has caused a temperature rise in coins or other foreign matter on the charging surface 60, the control circuit 42 uses the temperature sensor 57 to gather temperature information.

As shown in fig. 4, the charging surface 60 is characterized by a temperature Tsurface. The upper temperature sensor pad 90 in the metal trace layer formed between the adhesive layer 92 and the temperature sensor printed circuit substrate 88 is characterized by a temperature Ttop, and the lower temperature sensor pad 90 in the metal trace layer formed between the adhesive layer 80 and the substrate 88 is characterized by a temperature Tbottom. During operation, the control circuit 42 uses temperature information (such as information about known or calculated values of Tsurface, Ttop, and/or Tbottom) and/or other information from the temperature sensor 57 to determine whether foreign objects are present on the charging surface 60 (e.g., by determining whether the heat flux through the surface 60 is greater than a predetermined threshold amount, by determining whether the measured temperature is too high, and/or by otherwise processing the temperature data).

Fig. 6 shows a flow diagram of illustrative operations involved in using temperature information during operation of device 12. During operation of block 100, control circuitry 42 collects information from temperature sensor array 57 in device 12 during and/or after transmission of wireless power using coil 36. Specifically, the temperature Ttop and Tbottom of each of the temperature sensors 57 in the temperature sensor array is measured using the temperature sensor component 82, and this temperature information is analyzed using a data processing operation to determine whether heated foreign matter is present on the surface 60. If no foreign object is detected, the device 12 may continue to transmit wireless power to the device 10 and the control circuitry 42 may continue to use the sensor 57 for temperature measurements. In response to detecting a foreign object on the surface 60 (e.g., because the temperature exceeds a predetermined threshold), the control circuitry 42 takes appropriate action during the operations of block 102. Examples of actions that may be taken at block 102 include stopping wireless power transfer, reducing the amount of power wirelessly transferred, turning off a subset of one or more coils 36 (e.g., one or more coils that overlap with a detected foreign object) such that the subset of coils stops wireless power transfer, sounding an alarm (e.g., using an output device in device 12 to sound a visual and/or audio alert to a user indicating the presence of a foreign object on charging surface 60), and/or wirelessly sending an alarm message to device 10 or other device. Operations may then loop back to block 100, if appropriate.

The temperature measurements may be converted into information regarding the presence or absence of foreign matter on the surface 60 during block 100 using any suitable processing technique. In some embodiments, device 12 may communicate with device 10 to establish the temperature or power consumption of the subsystem. Charging may be interrupted if the device 10 or other charging device does not adequately account for the surface temperature estimate. Charging may be interrupted if the device 10 does not adequately account for the estimated rate of temperature rise. In some embodiments, if the estimated surface temperature rises before the wireless power transfer coil is activated, device 12 may wait for the temperature to stabilize before charging begins. In some embodiments, if charging has been interrupted by a thermal event, device 12 may wait for an electromagnetic change before attempting to resume power transfer.

With one illustrative arrangement shown in the flowchart of fig. 7, during operation of block 104, control circuitry 42 of device 12 collects measurements of Ttop and Tbottom from upper and lower temperature sensor pads in each temperature sensor 57 of the temperature sensor array and compares these temperature measurements to predetermined thresholds. If either of the Ttop or Tbottom values exceed the predetermined temperature threshold, device 12 takes appropriate action at block 102 of FIG. 6. Otherwise, operation continues at block 104 while wireless power is transmitted by the coil 36.

With another illustrative arrangement shown in the flow chart of fig. 8, the control circuit 42 uses an array of temperature sensors 57 to collect Ttop and measurements of Ttop. For each temperature sensor, the value of Tsurface may then be estimated using equation 1, where the value of the constant k is determined from previous calibration measurements made on the device 12 or calculated from the material properties and design of the device 12.

Tsurface ＝ Ttop + k (Ttop – Tbottom) (1)

Once the value of Tsurface is extrapolated for each temperature sensor 57 in the array of temperature sensors covering surface 60, control circuitry 42 compares each extrapolated value of Tsurface to a predetermined surface temperature threshold Tsurface. In response to determining that any of the extrapolated values of Tsurfface exceed Tsurfface, appropriate action is taken at block 102 of FIG. 6.

Fig. 9 is a graph showing how the temperature rise measured by using the temperature sensor 57 is predicted as a function of time for Tsurface in the future. During the calibration operation, the expected temperature Tsurface rise is measured under different operating conditions. A series of temperature rise curves is then identified which characterize the surface temperature Tsurface as a function of different heating conditions. During operation, temperature measurements (e.g., extrapolated Tsurface values) are measured over a period of time using sensor 57. In the example of FIG. 9, four measurements 108 of Tsurface are taken during time period 116. The time period 116 may be, for example, 5 seconds or other suitable amount of time. The predicted future surface temperature Tsurface 'is determined by fitting a time-dependent surface temperature rise curve, such as curve 110, to the measurements 108 and by extending the fitted curve to the future time period 108 (e.g., 15 seconds) as shown by curve portion 110'.

An exemplary operation involved with using this type of surface temperature prediction technique is shown in fig. 10. During operation of block 120, the control circuit 42 collects temperature measurements Ttop and Tbottom from sensors 57 in a sensor array that overlaps the charging surface 60. Temperature measurements are collected over a first time period (e.g., period 116 of fig. 9). Using the curve-fitting arrangement of fig. 9, the control circuit 42 predicts a future temperature Tsurface' on the charging surface 60 at the completion of a second time period (e.g., time period 118 of fig. 9, which may be longer than time period 116). The predicted surface temperature value Tsurface' for the entire charging surface 60 is then compared to a predetermined threshold temperature. If any of the predicted surface temperatures exceed the threshold, appropriate action is taken at block 102 of FIG. 6. In some embodiments, the pre-treatment is from a set of patterns or curves of the apparatus 10 and corresponding temperature differences, rates of change of temperature differences, and rates of change of temperature under various conditions. The control circuitry of the device 10 compares the current sensor information to the pre-processed pattern or profile and interrupts charging if the sensor information is sufficiently different from an acceptable pattern.

Transfer function techniques may be used to characterize the thermal behavior of foreign matter on charging surface 60, if desired.

For example, consider the illustrative methods of fig. 11, 12, and 13. As shown in fig. 11, the amount of power P transmitted from the coil 36 may be modulated (e.g., amplitude modulated) by the control circuit 42 as a function of time. As shown in fig. 12, this results in a corresponding time-varying response in the measured temperature difference Δ T (e.g., the temperature difference Δ T is equal to Ttop-Tbottom and proportional to the heat flux flowing through the temperature sensor layer). The control circuit 42 modulates the power P with different frequencies so that the transfer function Δ T/P can be characterized.

The wireless power receiving device 12 may not receive the wireless power signal generated by the coil 36 during the amplitude modulation process. The modulation function for the power P is a square wave in the example of fig. 11, but other types of time-varying power characteristics may be used to modulate the wireless transmission power P if desired.

The transfer function (Δ T/P) is associated with the first and second temperatures measured using the temperature sensors (e.g., the temperature difference Δ T for each temperature sensor 57) and the amplitude modulated wireless power signal. As shown in fig. 13, a corresponding transfer function curve (Δ T/P in logarithmic scale) may be plotted as a function of modulation frequency, and the bandwidth (e.g., 3dB bandwidth or other transfer function bandwidth) of each of these curves may be determined and compared to a threshold to determine whether a foreign object is present.

In the example of fig. 13, transfer function 124 corresponds to a larger object, such as wireless power-receiving device 10, and is characterized by a transfer function bandwidth BWL that is less than a predetermined threshold, while transfer function 122 corresponds to a smaller object, such as a coin or other foreign object, and is characterized by a transfer function bandwidth BWH that exceeds a predetermined threshold. Transfer function techniques such as these may be used during wireless power transfer, if desired. For example, when wireless power-receiving device 10 is receiving a wireless power signal, device 12 may obtain a transfer function (e.g., determine a transfer function during normal charging operation by measuring a coil current of coil 36 without charging device 12 pulsing the wireless power signal).

An illustrative operation associated with using a transfer function technique to detect foreign objects is shown in fig. 14. As shown in fig. 14, during operation of block 126, control circuitry 42 determines a transfer function associated with the temperature information (e.g., Δ T) collected by temperature sensor 57 and the wireless power signal generated by coil 36 (during amplitude modulation of the wireless power signal when device 12 is not being charged or during normal charging of device 12). The control circuit 42 then calculates the transfer function bandwidth of the transfer function. The transfer function bandwidth is compared to a predetermined transfer function bandwidth threshold. In response to determining that the transfer function bandwidth exceeds the predetermined transfer function bandwidth, control circuit 42 concludes that foreign objects are present on charging surface 60 and takes appropriate action at block 102 of fig. 6.

If desired, the control circuit 42 may determine whether foreign objects are present on the surface 60 by measuring the rate of change of temperature measured using the sensor 57. This type of method is shown in the flow chart of fig. 15. During operation of block 134, the control circuit 42 collects temperature measurements (e.g., Ttop and/or Tbottom) using the temperature sensor 57. A series of two or more measurements are taken over a period of time to determine the rate of change RC of the temperature Ttop and/or the rate of change of the temperature Tbottom. The rate of temperature change RC is then compared to a predetermined threshold RCTH. If the rate of change is greater than the threshold, then a foreign object is deemed to be present and appropriate action is taken at block 102 of FIG. 6. For another example, control circuitry 42 may determine whether foreign objects are present on surface 60 by measuring the rate of change of the temperature difference measured using sensor 57. During operation of block 134, the control circuit 42 collects temperature measurements (e.g., Ttop and/or Tbottom) using the temperature sensor 57. A series of two or more measurements are taken over a period of time to determine a rate of change of the difference between the temperature Ttop and the temperature Tbottom. The rate of change of the temperature difference is then compared to a predetermined threshold. If the rate of change is greater than the threshold, then a foreign object is deemed to be present and appropriate action is taken at block 102 of FIG. 6. In another example, a linear combination of the rate of change of the temperature difference of two sensors is combined with the rate of change of the absolute temperature of the other sensor and the result is compared to a predetermined threshold and if the threshold is exceeded, appropriate action is taken (e.g., interrupting the charging).

Fig. 16 shows an example of using Power Counts (PC), coil inductance changes, and mutual inductance changes as a means to avoid accidental, undesirable overheating of foreign objects. When power is supplied to the charging pad 12 and the charging pad is active, the coil modulation pulse is used to scan the appropriate device 10, and the device 10 responds by modulating the load on its receive coil 14. A series of temperature scans of the thermal measurement array are made each time a change in the number or placement of devices 10 is detected on the wireless power transmitting device 12 and wireless power is requested by at least one device 10. These changes, such as triggering a subsequent temperature scan, can be detected using Electromagnetic (EM) measurements (e.g., by evaluating the pattern of coil currents caused by the coil modulation pulses). Alternatively and/or in conjunction with using electromagnetic measurements, the system 8 may use power tracking and power counting techniques to detect changes on the transmitting device 12 that trigger thermal measurements.

With the illustrative power tracking embodiment, after a satisfactory thermal scan with the temperature sensor 57, the system 8 is placed in a known state (baseline power tracking state) at regular intervals (e.g., by the control circuitry 42 and/or 20) and the wireless power transfer efficiency between the device 12 and the device 10 is recorded and tracked during these baseline power tracking periods. This establishes a set of baseline efficiencies. Closed loop power transfer operation may be suspended during the baseline power tracking state, if desired. In response to detecting a sufficient change in the power transfer efficiency value during the baseline power tracking state relative to a previously recorded power transfer efficiency value (e.g., a change in detected efficiency that exceeds a predetermined threshold amount, etc.), a new thermal measurement by the temperature sensor 57 may be triggered.

With the exemplary power counting technique, dynamic modeling may be used to detect trigger events. The temperature sensor 57 is periodically scanned to search for an excessively high temperature. After each satisfactory scan, the system 8 is placed in a known state and a baseline model building operation (closed-loop or open-loop) is performed. During the model build operation, the control circuitry in system 8 builds a power count regression model to predict power losses. After the model is built, the control circuit continuously uses the model to predict losses (e.g., using a power counting scheme). If the measured loss detected is higher than the model predicted loss (e.g., if the loss measured by the power count exceeds the loss predicted by the power count model by more than a predetermined threshold amount), a new thermal measurement using the sensor 57 may be triggered. If desired, the closed loop power transfer operation may be performed during model build and while the model is used to predict wear.

In general, any suitable technique may be used to trigger additional thermal measurements using the temperature sensor 57. The above examples such as impedance change detection using electromagnetic measurements and measurement of thermal changes using sensor 57 (e.g., power tracking, power counting using a regression model, etc.) are illustrative.

In one embodiment, the transmission device 12 continues to monitor the communication and temperature of the temperature sensor 57 when the temperature measured by the thermal array formed by the temperature sensor 57 is above a threshold. When the temperature no longer rises at a rate above the threshold, a power counting algorithm is used to estimate the configured power efficiency. If the estimated expected charging efficiency is above the threshold for certain coil combinations, power transfer begins at a rate R0. The temperature of the sensors 57 in the array covering the charging surface 60 is monitored. For each pair of sensors at the top and bottom, the following calculations are performed: tave + B Δ T + Cd (Δ T)/dt > M, where Tave is the average temperature of the top and bottom sensors, (Δ T) is the temperature difference between each pair of top and bottom sensors, d (Δ T)/dt is the rate of change of the temperature difference (Δ T), B, C and M are suitably selected constants determined by measuring a plurality of similar charging devices 10. If the inequality is true, charging is interrupted and the device 12 waits for a change in power count, mutual inductance, or self inductance. If the inequality is false and there is no electromagnetic change, then charging is started or continued and another set of temperature measurements is taken. As long as the thermal test passes, the cycle of temperature measurement, electromagnetic monitoring and charging continues, and device 10 continues to request charging power.

Fig. 17 shows how coil impedance change measurements can be used to determine whether foreign objects are present. During operation of block 136, control circuitry 42 measures the impedance (e.g., inductance) associated with each coil 36 using impedance measurement circuitry 59. If an impedance change is measured in any of the coils 36 (e.g., if a newly measured impedance value differs from a previous impedance value by more than a threshold amount), the control circuit 42 may infer that there is an increased likelihood of foreign objects being present on the charging surface 60. Accordingly, the control circuit 42 performs temperature-based foreign object detection measurement and analysis during operation of block 138 (e.g., using an arrangement of the type described in connection with fig. 7-15). By performing temperature measurements only when foreign objects are suspected due to measured coil impedance variations, the number of temperature measurements performed by the apparatus 12 may be reduced. The operations of block 136 may be performed in addition to temperature measurement, may be performed in place of temperature measurement, and/or may be omitted.

To improve the accuracy of temperature-based foreign object detection, the temperature sensor circuitry in the device 12 may be calibrated. The operations associated with the calibration apparatus 12 are illustrated in fig. 18. During operation of block 128, a heated probe in the test fixture is placed adjacent to the charging surface 60 (e.g., over a particular temperature sensor or set of temperature sensors). The temperature rise measured by temperature sensor 57 for the known heat applied with the probe is then determined so that the value of k in equation (1) can be determined and stored in device 12 along with other suitable calibration data.

Another type of calibration operation performed on the device 12 involves a temperature sensor component 82 (e.g., a thermistor, resistance thermometer, etc.). The temperature sensor component 82 drifts due to aging and other effects. The calculation of Δ T may not be as accurate as possible if the component associated with the upper temperature sensor pad drifts relative to the component associated with the corresponding lower temperature sensor pad. To compensate for component drift, once per day or at other suitable times when device 12 is in a steady state, control circuit 42 measures Ttop and Tbottom using each temperature sensor 57. The control circuit also uses additional temperature sensor components (e.g., additional thermistors or additional resistance thermometers) in the printed circuit 72 to measure the temperature Tpc of the corresponding lower portion of the device 12 (e.g., in the printed circuit 72). Based on the measured values of Ttop and Tpc at each sensor location, the control circuit 42 interpolates to determine an appropriate value of Tbottom at that sensor location, and applies a correction offset to a thermistor, resistance thermometer, or other temperature sensor component associated with the temperature Tbottom at that sensor location to calibrate the bottom temperature sensor component at that sensor location. Calibration data for this offset is stored in the memory of the control circuit 42 for all temperature sensors 57 for use during subsequent measurements.

The apparatus 12 may also be calibrated to account for heating due to operation of the coil 36 (separation and separate heating from foreign objects when the coil 36 is in operation). For example, when each coil 36 is driven with a modulated current I (and thus a modulated power P, as described in connection with fig. 11), temperature measurements may be collected from each of the temperature sensors 57. The transfer function H ═ DeltaT/I is then calculated²As a function of the modulation frequency. The apparatus 12 is calibrated by determining a correspondence H between each coil and each of the temperature sensors 57. This information is stored in the device 12. Later, when calculating any of the temperature-based values in the foreign object detection methods of fig. 8-13, the collected temperature data (e.g., the values of Ttop and Tbottom from the temperature sensor component 82) is corrected by using the information about the transfer function H to determine which portions of these temperatures are due to coil-induced heating (separate from coil-induced heating of the object on the surface 60). A portion of the temperature value due to heating by the coil may be subtracted from the temperature sensor component output data to produce corrected Ttop and Tbottom data (e.g., to correct the Ttop and Tbottom values for direct wireless heating of the temperature sensor pad during wireless power signal transmission). Temperature sensor component drift may also be compensated for when generating values of Ttop and Tbottom, if desired, as described in connection with the use of temperature sensor components in the printed circuit 72.

Another technique that may be used to ensure that the temperature measurements for foreign object detection are accurate is illustrated in conjunction with the graphs of fig. 19, 20, and 21. Fig. 19 is a graph of exemplary temperature steps produced by a heated probe in a test fixture. When this sudden temperature step is applied to the charging surface 60, the temperatures Ttop and Tbottom (collectively TA in fig. 20) rise at a slower rate, as shown by the exemplary curve of fig. 20. The delay in the measured temperature rise TA of fig. 20 compared to the sudden step of applying the temperature TF of fig. 19 is due to thermal hysteresis associated with heating the material layer between the charging surface 60 and the temperature sensor 57. This lag may be compensated for by applying a thermal lag correction function to the time-dependent measurement of temperature TA (e.g., the time-dependent measurement of Ttop and/or the time-dependent measurement of Tbottom), resulting in a corresponding lag-corrected temperature measurement, such as lag-corrected temperature measurement TC of fig. 21.

In general, any suitable calibration technique may be used to correct the temperature measurements made by the temperature sensor 57, such as drift compensation techniques, compensation techniques that account for the temperature rise caused by the coils in the temperature sensor 57 separately from foreign object-induced heating, and thermal hysteresis correction techniques (e.g., the like).

If desired, the temperature sensor for the device 12 may have a temperature sensing device arranged differently than the exemplary arrangement of FIG. 4. For example, consider the arrangement of fig. 22. The device 12 of fig. 22 has an array of temperature sensors 57 configured to make temperature measurements. The structure 155 includes the coil 36 (e.g., a coil located below and overlapping the temperature sensor) and associated structures, such as polymer layers, metal layers, ferrite layers, and/or other structures for forming the housing and other structures of the device 12. The upper portion of structure 155 forms charging surface 60. Structure 140 may overlap with a temperature sensing component, such as component 82F, and structure 142 may overlap with a temperature sensing component, such as component 82A. Structures 140 and 142 may include air gaps, polymer structures, metal structures (e.g., optional temperature sensor metal pads and/or vias), and/or other structures. The thermal conductivity of the structure 140 and the portion of the structure 155 interposed between the temperature sensing component 82F and the charging surface 60 is greater than the thermal conductivity of the structure 142 and the portion of the structure 155 interposed between the temperature sensing component 82A and the charging surface 60. Therefore, there is a thermal resistance between the temperature sensing part 82A and the charging surface 60 that is greater than the thermal resistance between the temperature sensing part 82F and the charging surface 60. Thus, the thermal sensing device formed by components 82F and 82A responds differently to heated objects on surface 60. The thermal resistance between surface 60 and component 82A is greater than the thermal resistance between surface 60 and component 82F, so component 82F tends to react quickly, while component 82A is used to measure the ambient temperature inside device 12. When a heated object is present on the device 12 and the surface 60 is heated, a temperature gradient (from high to low) will be established between the surface 60 and the interior of the device 12 and this gradient (and hence the heat flux flowing through the surface 60) can be measured using the temperature difference sensing arrangement of fig. 22 or other heat flux measurement arrangement.

Figure 23 shows how the array of temperature sensors 57 in device 12 may have two different sets of temperature sensing devices. Temperature sensing device 57F may be formed closer to charging surface 60 than temperature sensing device 57A and/or the structure between device 57F and surface 60 may have a lower thermal resistance than the structure between device 57A and surface 60, allowing heat flux to be measured (e.g., by measuring a temperature gradient using these sensor groups). The number of devices 57F in the first set of devices and devices 57A in the second set of devices need not be the same. For example, as shown in fig. 23, there may be more devices 57F than devices 57A (e.g., to reduce complexity without sacrificing a desired amount of lateral temperature measurement resolution). Thus, each temperature sensor 57 includes a respective one of the devices 57F, but multiple sensors 57 share a given one of the devices 57A. In the illustrative arrangement of fig. 24, each temperature sensor 57 includes a respective sensing device 57F and a respective sensing device 57A. Other configurations having different numbers of temperature sensing devices in the first and second sets of temperature sensing devices may be used if desired.

According to one embodiment, a wireless power transfer device is provided having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device including a coil array, wireless power transfer circuitry coupled to the coil array to transfer a wireless power signal to the wireless power receiving device, a temperature sensor array overlapping the coil array and extending across the charging surface, and control circuitry configured to detect foreign objects on the charging surface based on temperature information collected with the temperature sensor.

According to another embodiment, the temperature sensor array is configured to measure heat flux through the charging surface.

According to another embodiment, the control circuit is configured to interrupt charging based on temperature difference information of the temperature sensor.

According to another embodiment, the temperature sensor array includes a first set of temperature sensing devices separated from the charging surface by a first thermal resistance and a second set of temperature sensing devices separated from the charging surface by a second thermal resistance greater than the first thermal resistance.

According to another embodiment, the first set of temperature sensing devices has a first temperature sensing pad thermally coupled to a corresponding first temperature sensor component, the second set of temperature sensing devices has a second temperature sensing pad thermally coupled to a corresponding second temperature sensor component, and the wireless power transfer device includes a dielectric layer between the first temperature sensing pad and the second temperature sensing pad.

According to another embodiment, the array of temperature sensors is configured to measure a first set of temperatures using a first set of temperature sensing devices and is configured to measure a second set of temperatures using a second set of temperature sensing devices.

According to another embodiment, the temperature information includes a first set of temperatures, and the control circuit is configured to detect the foreign object based on the first set of temperatures.

According to another embodiment, the temperature information includes a second set of temperatures, and the control circuit is configured to detect the foreign object based on the first temperature and the second set of temperatures.

According to another embodiment, the control circuit is configured to determine, for each of the first set of temperature sensing devices, a corresponding surface temperature at the charging surface, the temperature information including the surface temperature, and the control circuit is configured to detect the foreign object based on the surface temperature.

According to another embodiment, the control circuit is configured to predict a future surface temperature of the charging surface, and the control circuit is configured to detect the foreign object based on the future surface temperature.

According to another embodiment, the control circuit is configured to determine a transfer function associated with the first and second sets of temperatures and the wireless power signal, and to detect the foreign object using the transfer function.

According to another embodiment, the control circuit is configured to determine the transfer function by amplitude modulation of the wireless power signal when the wireless power receiving device is not receiving the wireless power signal.

According to another embodiment, the control circuit is configured to determine the transfer function by measuring a coil current while the wireless power receiving device is receiving the wireless power signal.

According to another embodiment, the wireless power transfer device includes an additional temperature sensor layer overlapping the temperature sensor array, the control circuit configured to create a temperature offset for the temperature sensing devices in the temperature sensor array based on information from the additional temperature sensor layer.

According to another embodiment, the control circuit is configured to detect the foreign object by comparing a rate of temperature change measured with a given one of the temperature sensors with a predetermined rate of temperature change threshold.

According to another embodiment, the control circuit is configured to interrupt charging by comparing the rate of change of temperature measured at the two or more sensors to a pre-calculated set of acceptable rate of change patterns.

According to another embodiment, the control circuitry is configured to interrupt charging by comparing the rate of change of temperature measured at the two or more sensors to a pre-calculated set of acceptable rate of change patterns, wherein the acceptable patterns are based on wireless communication with the wireless power receiving device.

According to another embodiment, a wireless power transfer device includes coil impedance or transimpedance measurement circuitry, the control circuitry configured to acquire temperature information in response to detecting a change in coil impedance in the coil array using the coil impedance measurement circuitry.

According to another embodiment, the control circuit is configured to correct the temperature measurement with the temperature sensor by taking into account a portion of the temperature measurement due to wireless heating of the temperature sensor pad in the temperature sensor by the wireless power signal.

According to another embodiment, the control circuit is configured to apply a thermal hysteresis correction function to the temperature measurements from the temperature sensor to produce corresponding hysteresis corrected temperature measurements, and the control circuit is configured to detect the foreign object based on the hysteresis corrected temperature measurements.

According to one embodiment, a wireless power transfer device is provided having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device including a coil, a wireless power transfer circuit coupled to the coil to transfer a wireless power signal to the wireless power receiving device, a temperature sensor overlapping the coil and configured to collect temperature information, and a control circuit configured to detect a foreign object on the charging surface based on the temperature information collected with the temperature sensor, the temperature sensor including a first temperature sensor pad configured to collect a first temperature, a second temperature sensor pad configured to collect a second temperature, a dielectric layer between the first temperature sensor pad and the second temperature sensor pad.

According to another embodiment, a temperature sensor includes a via through a dielectric layer and a first temperature sensor component thermally coupled directly to a first temperature sensor pad and a second temperature sensor component thermally coupled to a second temperature sensor pad through the via.

According to another embodiment, the dielectric layer includes a printed circuit substrate, the first temperature sensor pad is formed from a first metal trace having first fingers separated by first slots on a first surface of the printed circuit substrate, and the second temperature sensor pad is formed from a second metal trace having second fingers separated by second slots on an opposite second surface of the printed circuit substrate.

According to one embodiment, a wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil is provided that includes a dielectric layer forming the charging surface, a coil array in the coil layer, wireless power transfer circuitry coupled to the coil array to transfer a wireless power signal to the wireless power receiving device, and a temperature sensor array interposed between the dielectric layer and the coil array configured to measure heat flux through the charging surface.

According to another embodiment, a wireless power transfer device includes a control circuit configured to detect foreign objects on a charging surface based on temperature information collected with a temperature sensor and configured to stop transferring a wireless power signal to a wireless power receiving device in response to detecting the foreign objects, the temperature sensor array including a first set of temperature sensing devices separated from the charging surface by a first thermal resistance and a second set of temperature sensing devices separated from the charging surface by a second thermal resistance, the second thermal resistance being greater than the first thermal resistance.

According to another embodiment, a wireless power transfer device includes a control circuit configured to detect foreign objects on a charging surface based on temperature measurements acquired with a temperature sensor and to trigger use of the temperature sensor array based on (1) electromagnetic impedance measurements on a coil and (2) thermal changes detected using information from the temperature sensor array.

The foregoing is illustrative and various modifications may be made to the embodiments. The foregoing embodiments may be implemented independently or in any combination.

Claims (20)

1. A wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising:

a coil array;

a wireless power transfer circuit coupled to the coil array to transfer a wireless power signal to the wireless power receiving device;

a temperature sensor array overlapping the coil array and extending across the charging surface; and

a control circuit configured to detect foreign matter on the charging surface based on temperature information collected with the temperature sensor.

2. The wireless power transfer apparatus of claim 1, wherein the array of temperature sensors is configured to measure heat flux through the charging surface.

3. The wireless power transfer apparatus of claim 1, wherein the control circuit is configured to interrupt charging based on temperature difference information of the temperature sensor.

4. The wireless power transfer apparatus of claim 1, wherein the array of temperature sensors comprises a first set of temperature sensing devices and a second set of temperature sensing devices, wherein the temperature sensing devices of the first set of temperature sensing devices are separated from the charging surface by a first thermal resistance, and wherein the temperature sensing devices of the second set of temperature sensing devices are separated from the charging surface by a second thermal resistance, the second thermal resistance being greater than the first thermal resistance.

5. The wireless power transfer apparatus of claim 4, wherein the first set of temperature sensing devices has a first temperature sensing pad thermally coupled to a respective first temperature sensor component, wherein the second set of temperature sensing devices has a second temperature sensing pad thermally coupled to a respective second temperature sensor component, and wherein the wireless power transfer apparatus comprises a dielectric layer between the first temperature sensing pad and the second temperature sensing pad.

6. The wireless power transfer device of claim 4, wherein the array of temperature sensors is configured to measure a first set of temperatures using the first set of temperature sensing devices and is configured to measure a second set of temperatures using the second set of temperature sensing devices.

7. The wireless power transfer apparatus of claim 6, wherein the temperature information comprises the first set of temperatures, and wherein the control circuit is configured to detect the foreign object based on the first set of temperatures, and wherein the temperature information comprises the second set of temperatures, and wherein the control circuit is configured to detect the foreign object based on the first set of temperatures and the second set of temperatures.

8. The wireless power transfer apparatus of claim 6, wherein the control circuit is configured to determine, for each of the first set of temperature sensing devices, a corresponding surface temperature on the charging surface, wherein the temperature information includes the surface temperature, and wherein the control circuit is configured to detect the foreign object based on the surface temperature.

9. The wireless power transfer apparatus of claim 6, wherein the control circuit is configured to predict a future surface temperature of the charging surface, and wherein the control circuit is configured to detect the foreign object based on the future surface temperature.

10. The wireless power transfer apparatus of claim 6, wherein the control circuit is configured to determine transfer functions associated with the first and second sets of temperatures and the wireless power signal, and to detect the foreign object using the transfer functions.

11. The wireless power transfer apparatus of claim 10 wherein the control circuit is configured to determine the transfer function by amplitude modulation of the wireless power signal when the wireless power receiving apparatus is not receiving the wireless power signal.

12. The wireless power transfer apparatus of claim 10 wherein the control circuit is configured to determine the transfer function by measuring a coil current when the wireless power receiving apparatus is receiving the wireless power signal.

13. The wireless power transfer device of claim 1, further comprising an additional temperature sensor layer overlapping the temperature sensor array, wherein the control circuit is configured to create a temperature offset for a temperature sensing device in the temperature sensor array based on information from the additional temperature sensor layer.

14. The wireless power transfer apparatus of claim 1, wherein the control circuit is configured to detect the foreign object by comparing a rate of temperature change measured with a given one of the temperature sensors to a predetermined rate of temperature change threshold.

15. The wireless power transfer apparatus of claim 1, wherein the control circuit is configured to interrupt charging by comparing a rate of change of temperature measured at two or more sensors to a pre-calculated set of acceptable rate of change patterns.

16. The wireless power transfer apparatus of claim 1 further comprising a coil impedance measurement circuit or a transimpedance measurement circuit, wherein the control circuit is configured to acquire the temperature information in response to detecting a change in coil impedance in the coil array using the coil impedance measurement circuit.

17. The wireless power transfer apparatus of claim 1, wherein the control circuit is configured to correct the temperature measurement with the temperature sensor by considering a portion of the temperature measurement due to wireless heating of a temperature sensor pad in the temperature sensor by the wireless power signal.

18. The wireless power transfer apparatus of claim 1, wherein the control circuit is configured to apply a thermal hysteresis correction function to the temperature measurement from the temperature sensor to produce a corresponding hysteresis corrected temperature measurement, and wherein the control circuit is configured to detect the foreign object based on the hysteresis corrected temperature measurement.

19. A wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising:

a coil;

a wireless power transfer circuit coupled to the coil to transfer a wireless power signal to the wireless power receiving device;

a temperature sensor overlapping the coil and configured to acquire temperature information, wherein the temperature sensor includes a first temperature sensor pad configured to acquire a first temperature, a second temperature sensor pad configured to acquire a second temperature, and a dielectric layer between the first temperature sensor pad and the second temperature sensor pad; and

a control circuit configured to detect foreign matter on the charging surface based on the temperature information collected with the temperature sensor.

20. A wireless power transfer device having a charging surface configured to receive a wireless power receiving device having a wireless power receiving coil, the wireless power transfer device comprising:

a dielectric layer forming the charging surface;

a coil array in a coil layer;

a wireless power transfer circuit coupled to the coil array to transfer a wireless power signal to the wireless power receiving device;

a temperature sensor array interposed between the dielectric layer and the coil array, the temperature sensor array configured to measure heat flux through the charging surface; and

a control circuit configured to detect foreign matter on the charging surface based on temperature information collected with the temperature sensor and configured to stop transmitting the wireless power signal to the wireless power receiving device in response to detecting the foreign matter, wherein the temperature sensor array comprises a first set of temperature sensing devices and a second set of temperature sensing devices, wherein the temperature sensing devices of the first set of temperature sensing devices are separated from the charging surface by a first thermal resistance, and wherein the temperature sensing devices of the second set of temperature sensing devices are separated from the charging surface by a second thermal resistance, the second thermal resistance being greater than the first thermal resistance.

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