PATENT DOCUMENT

Publication Number: US-10938252-B2
Application Number: US-202016869365-A
Country: US
Kind Code: B2

Title: Wireless charging system with temperature sensing

Abstract:
A wireless power transmitting device transmits wireless power signals to a wireless power receiving device. To detect foreign objects, the wireless power transmitting device has an array of temperature sensors. The array of temperature sensors may include temperature sensor components such as temperature sensitive thin-film resistors or other temperature sensitive components. A temperature sensor may have thin-film resistors formed on opposing sides of a substrate. The thin-film resistors may be formed from meandered metal traces to reduce eddy current formation during operation of the wireless power transmitting device. Signal paths coupling control circuitry on the wireless power transmitting device to the array of temperature sensors may be configured to extend along columns of the temperature sensors without running along each row of the temperature sensors, thereby reducing eddy currents from loops of signal routing lines. Some temperature sensors may have multiple components coupled to a common temperature sensing pad.

Claims:
What is claimed is: 
     
       1. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device that has a wireless power receiving coil, the wireless power transmitting device comprising:
 at least one coil; 
 wireless power transmitting circuitry coupled to the at least one coil to transmit wireless power signals to the wireless power receiving device; 
 an array of temperature sensors overlapping the at least one coil and extending across the charging surface; and 
 control circuitry configured to detect a foreign object on the charging surface based on temperature information gathered with the temperature sensors, wherein each temperature sensor in the array includes a substrate having opposing first and second sides, a first resistor formed on the first side of the substrate, and a second resistor formed on the second side of the substrate. 
 
     
     
       2. The wireless power transmitting device of  claim 1 , wherein the at least one coil comprises an array of coils. 
     
     
       3. The wireless power transmitting device of  claim 1 , wherein the first and second resistors include meandered metal traces. 
     
     
       4. The wireless power transmitting device of  claim 1 , wherein the temperature sensors comprise temperature sensitive resistors, wherein the temperature sensors are coupled into Wheatstone bridge circuits, and wherein each Wheatstone bridge circuit includes at least one temperature sensitive resistor. 
     
     
       5. The wireless power transmitting device of  claim 1 , wherein the temperature sensors comprise temperature sensitive resistors, wherein the temperature sensors are coupled into Wheatstone bridge circuits, wherein each Wheatstone bridge circuit includes at least two of the temperature sensitive resistors, and wherein a connection sense is reversed to the temperature sensitive resistors to substantially cancel magnetic flux coupling through the Wheatstone bridge circuit. 
     
     
       6. The wireless power transmitting device of  claim 1 , wherein the array of temperature sensors includes rows and columns of the temperature sensors. 
     
     
       7. The wireless power transmitting device of  claim 6 , further comprising signal lines formed with metal traces that provide temperature measurements to the control circuitry from the temperature sensors, wherein the signal lines extend parallel to a selected one of: (1) the rows and (2) the columns. 
     
     
       8. The wireless power transmitting device of  claim 1 , further comprising signal lines that electrically couple the control circuitry to the temperature sensors, wherein the signal lines extend along a first dimension of the array of temperature sensors without extending past multiple temperature sensors in the array of temperature sensors along a second dimension of the array of temperature sensors and wherein the second dimension is orthogonal to the first dimension of the array of temperature sensors. 
     
     
       9. The wireless power transmitting device of  claim 8 , wherein the array of temperature sensors includes a first set of temperature sensitive resistors and a second set of temperature sensitive resistors, wherein temperature sensitive resistors of the first set of temperature sensitive resistors are separated from the charging surface by a first thermal resistance and wherein temperature sensitive resistors of the second set of temperature sensitive resistors are separated from the charging surface by a second thermal resistance that is greater than the first thermal resistance. 
     
     
       10. The wireless power transmitting device of  claim 1 , wherein the array of temperature sensors includes a first set of temperature sensitive resistors and a second set of temperature sensitive resistors, wherein temperature sensitive resistors of the first set of temperature sensitive resistors are separated from the charging surface by a first thermal resistance and wherein temperature sensitive resistors of the second set of temperature sensitive resistors are separated from the charging surface by a second thermal resistance that is greater than the first thermal resistance. 
     
     
       11. The wireless power transmitting device of  claim 1 , wherein the control circuitry is further configured to:
 responsive to detecting a foreign object on the charging surface, at least partially reduce power to the at least one coil. 
 
     
     
       12. The wireless power transmitting device of  claim 1 , wherein the at least one coil comprises first and second coils and wherein the control circuitry is further configured to:
 responsive to detecting a foreign object on the charging surface, at least partially reduce power to the first coil while maintaining power to the second coil. 
 
     
     
       13. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device that has a wireless power receiving coil, the wireless power transmitting device comprising:
 at least one coil; 
 wireless power transmitting circuitry coupled to the at least one coil to transmit wireless power signals to the wireless power receiving device; and 
 an array of temperature sensors overlapping the at least one coil and extending across the charging surface, wherein the temperature sensors each include a metal pad thermally coupled to multiple temperature sensor components. 
 
     
     
       14. The wireless power transmitting device of  claim 13 , wherein the at least one coil comprises an array of coils. 
     
     
       15. The wireless power transmitting device of  claim 14 , wherein the temperature sensor components include resistive temperature sensors. 
     
     
       16. The wireless power transmitting device of  claim 14 , wherein the resistive temperature sensors include meandered metal traces forming temperature sensitive resistors. 
     
     
       17. The wireless power transmitting device of  claim 14 , wherein the array of temperature sensors has first and second orthogonal dimensions and wherein the wireless power transmitting device further comprises:
 control circuitry configured to detect a foreign object on the charging surface based on temperature information gathered with the temperature sensors; and 
 parallel signal lines that extend between the control circuitry and the temperature sensor components along the first dimension. 
 
     
     
       18. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device that has a wireless power receiving coil, the wireless power transmitting device comprising:
 at least one coil; 
 wireless power transmitting circuitry coupled to the at least one coil to transmit wireless power signals to the wireless power receiving device; 
 an array of temperature sensors, wherein the array of temperature sensors includes a first set of temperature sensor components and a second set of temperature sensor components, wherein the first set of temperature sensor components are separated from the charging surface by a first thermal resistance and wherein the second set of temperature sensor components are separated from the charging surface by a second thermal resistance greater than the first thermal resistance; 
 signal lines; and 
 control circuitry configured to detect a foreign object on the charging surface based on temperature information gathered using the array of temperature sensors and provided to the control circuitry using the signal lines, wherein the signal lines extend along a first dimension of the array of temperature sensors without extending past multiple temperature sensors in the array of temperature sensors along a second dimension of the array of temperature sensors that is orthogonal to the first dimension of the array of temperature sensors. 
 
     
     
       19. The wireless power transmitting device of  claim 18 , wherein the temperature sensors comprise thermistors. 
     
     
       20. The wireless power transmitting device of  claim 19 , wherein the at least one coil comprises an array of coils and wherein the array of temperature sensors overlaps the array of coils. 
     
     
       21. The wireless power transmitting device of  claim 18 , wherein the temperature sensors comprise thin-film resistors. 
     
     
       22. The wireless power transmitting device of  claim 21 , wherein the thin-film resistors comprise meandered metal traces. 
     
     
       23. The wireless power transmitting device of  claim 18 , wherein the temperature sensor components comprise thermistors.

Description:
This application is a continuation of International Application PCT/US2019/41470, with an international filing date of Jul. 11, 2019, which claims priority to U.S. patent application Ser. No. 16/204,847, filed on Nov. 29, 2018, which claims the benefit of provisional patent application No. 62/726,072, filed Aug. 31, 2018, which are hereby incorporated by reference herein in their entireties. 
    
    
     FIELD 
     This relates generally to wireless systems, and, more particularly, to systems in which devices are wirelessly charged. 
     BACKGROUND 
     In a wireless charging system, a wireless power transmitting device such as a device with a charging surface wirelessly transmits power to another electronic device such as a battery-powered, portable electronic device. The portable electronic device receives the wirelessly transmitted power and uses this power to charge an internal battery and to power components in the portable electronic device. Foreign objects in proximity to a wireless power receiving device can intercept power intended for the wireless power receiving device. It is desirable to reduce power transfer to foreign objects during wireless charging operations. 
     SUMMARY 
     A wireless power transmitting device transmits wireless power signals to a wireless power receiving device. To detect foreign objects, the wireless power transmitting device has an array of temperature sensors. Control circuitry in the device is configured to detect a foreign object on a charging surface of the device based on temperature information gathered with the temperature sensors. Appropriate action such as the halting of wireless charging operations is then taken. 
     The array of temperature sensors may include temperature sensor components such as temperature sensitive thin-film resistors or other temperature sensitive components. A temperature sensor may have thin-film resistors formed on opposing sides of a substrate. The thin-film resistors may be formed from spiral metal traces to reduce eddy current formation during operation of the wireless power transmitting device. Signal paths coupling control circuitry on the wireless power transmitting device to the array of temperature sensors may be configured to extend along columns of the temperature sensors without running along each row of the temperature sensors, thereby reducing eddy currents from loops of signal routing lines. 
     Some temperature sensors may have multiple components coupled to a common temperature sensing pad. The control circuitry may average readings from multiple components in a single temperature sensor to reduce the impact of lateral temperature gradients on temperature measurements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system in accordance with embodiments. 
         FIG. 2  is a top view of an illustrative wireless power transmitting device with an array of coils that forms a wireless charging surface in accordance with an embodiment. 
         FIG. 3  is a top view of a portion of an illustrative temperature sensor array extending across the wireless charging surface in accordance with an embodiment. 
         FIGS. 4, 5, 6, 7, and 8  are cross-sectional side views of illustrative wireless power transmitting devices with temperature sensing circuitry in accordance with embodiments. 
         FIG. 9  is a top view of an illustrative spiral metal trace in a thin-film resistive temperature sensor in accordance with an embodiment. 
         FIG. 10  is a side view of illustrative metal traces in a thin-film resistive temperature sensor in accordance with an embodiment. 
         FIG. 11  is a circuit diagram of an illustrative temperature sensor with temperature sensor components such as temperature sensitive thin-film resistors or other temperature sensor components in a bridge circuit in accordance with an embodiment. 
         FIG. 12  is a diagram of an illustrative temperature sensor array in accordance with an embodiment. 
         FIGS. 13 and 14  are diagrams of illustrative signal line patterns that may be used in electrically coupling temperature sensor components to control circuitry while avoiding eddy currents in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system has a wireless power transmitting device that transmits power wirelessly to a wireless power receiving device. The wireless power transmitting device is a device such as a wireless charging mat, wireless charging puck, wireless charging stand, wireless charging table, or other wireless power transmitting equipment. The wireless power transmitting device has one or more coils that are used in transmitting wireless power to one or more wireless power receiving coils in the wireless power receiving device. The wireless power receiving device is a device such as a cellular telephone, watch, media player, tablet computer, pair of earbuds, remote control, laptop computer, other portable electronic device, or other wireless power receiving equipment. 
     During operation, the wireless power transmitting device supplies alternating-current drive signals to one or more wireless power transmitting coils. This causes the coils to transmit alternating-current electromagnetic signals (sometimes referred to as wireless power signals) to one or more corresponding wireless power receiving coils in the wireless power receiving device. Rectifier circuitry in the wireless power receiving device converts received wireless power signals into direct-current (DC) power for the wireless power receiving device. 
     A temperature sensor array is included in the wireless power transmitting device  10  to monitor for elevated temperatures on a charging surface of wireless power transmitting device  10 . Temperature rises exceeding expected device operating responses can be indicative of the presence of undesired foreign objects, such as coins, on the wireless power transmitting device that are intercepting power during wireless power transmission operations. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  8  includes wireless power transmitting device  12  and one or more wireless power receiving devices such as wireless power receiving device  10 . Device  12  may be a stand-alone device such as a wireless charging mat, may be built into furniture, or may be other wireless charging equipment. Device  10  is a portable electronic device such as a wristwatch, a cellular telephone, a tablet computer, or other electronic equipment. Illustrative configurations in which device  12  is a mat or other equipment that forms 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 are sometimes be described herein as examples. 
     During operation of system  8 , a user places one or more devices  10  on the charging surface of device  12 . Power transmitting device  12  is coupled to a source of alternating-current voltage such as alternating-current power source  50  (e.g., a wall outlet that supplies line power or other source of mains electricity), has a battery such as battery  38  for supplying power, and/or is coupled to another source of power. A power converter such as alternating-current-to-direct current (AC-DC) power converter  40  can convert power from a mains power source or other alternating-current (AC) power source into direct-current (DC) power that is used to power control circuitry  42  and other circuitry in device  12 . During operation, control circuitry  42  uses wireless power transmitting circuitry  34  and one or more coil(s)  36  coupled to circuitry  34  to transmit alternating-current electromagnetic signals  48  to device  10  and thereby convey wireless power to wireless power receiving circuitry  46  of device  10 . 
     Power transmitting circuitry  34  has switching circuitry (e.g., transistors in an inverter circuit) that are turned on and off based on control signals provided by control circuitry  42  to create AC signals (drive signals) through coil(s)  36 . As the AC signals pass through coil(s)  36 , alternating-current electromagnetic fields (wireless power signals  48 ) are produced that are received by corresponding coil(s)  14  coupled to wireless power receiving circuitry  46  in receiving device  10 . When the alternating-current electromagnetic fields are received by coil  14 , corresponding alternating-current currents and voltages are induced in coil  14 . Rectifier circuitry in circuitry  46  converts received AC signals (received alternating-current currents and voltages associated with wireless power signals) from coil(s)  14  into DC voltage signals for powering device  10 . The DC voltages are used in powering components in device  10  such as display  52 , touch sensor components and other sensors  54  (e.g., accelerometers, force sensors, temperature sensors, light sensors, pressure sensors, gas sensors, moisture sensors, magnetic sensors, etc.), wireless communications circuits  56  for communicating wirelessly with corresponding wireless communications circuitry  58  in control circuitry  42  of wireless power transmitting device  12  and/or other equipment, audio components, and other components (e.g., input-output devices  22  and/or control circuitry  20 ) and are used in charging an internal battery in device  10  such as battery  18 . 
     Wireless power transmitting device includes measurement circuitry  59  that uses coils  36  and/or other circuitry to measure the characteristics of electronic devices and other object overlapping coils  36 . As an 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 make measurements of inductance L and quality factor Q for each of coils  36 , and mutual inductance M of pairs of coils  36 . During impulse response measurements, control circuitry  42  directs circuitry  59  to supply one or more excitation pulses (impulses) to each coil  36 . The impulses may be, for example, square wave pulses of 1 μs in duration. Longer or shorter pulses may be applied, if desired. The resulting resonant response (ringing) of coil  36  and resonant circuitry in device  12  that includes coil  36  is then measured by circuitry  59  to determine L, M, and Q. Using measurements such as these, control circuitry  42  can monitor one or more of coils  36  (e.g., each coil  36  in an array of coils  36  in device  12 ) for the presence of an external object such as one of devices  10  that is potentially compatible for 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 a foreign object). Foreign objects are also detected based on temperature information such as temperature sensor measurements made using temperature sensors  57 . In some embodiments, foreign objects are detected using temperature information or impedance information alone. In other embodiments, control circuitry  42  uses both temperature information and impedance information in detecting foreign objects. 
     Devices  12  and  10  include control circuitry  42  and  20 . Control circuitry  42  and  20  includes storage and processing circuitry such as microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. Control circuitry  42  and  20  is configured to execute instructions for implementing desired control and communications features in system  8 . For example, control circuitry  42  and/or  20  may be used in determining power transmission levels, processing sensor data such as temperature sensor data, processing user input, processing information from receiving circuitry  46 , using information from circuitry  34  and/or  46  such as signal measurements on output circuitry in circuitry  34  and other information from circuitry  34  and/or  46  to determine when to start and stop wireless charging operations, adjusting charging parameters such as charging frequencies, coil assignments in a multi-coil array, and wireless power transmission levels, and performing other control functions. Control circuitry  42  and  20  may be configured to support wireless communications between devices  12  and  10  (e.g., control circuitry  20  may include wireless communications circuitry such as circuitry  56  and control circuitry  42  may include wireless communications 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 that runs on the hardware of system  8 ). Software code for performing these operations is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media). The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid state drives), one or more removable flash drives or other removable media, other computer readable media, or combinations of these computer readable media or other storage. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry  42  and/or  20 . The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, or other processing circuitry. 
     Device  12  and/or device  10  may communicate wirelessly during operation of system  8 . Devices  10  and  12  may, for example, have wireless transceiver circuitry in control circuitry  42  and  20  (see, e.g., wireless communications circuitry such as circuitry  58  and  56  of  FIG. 1 ) that allows wireless transmission of signals between devices  10  and  12  (e.g., using antennas that are separate from coils  36  and  14  to transmit and receive unidirectional or bidirectional wireless signals, using coils  36  and  14  to transmit and receive unidirectional or bidirectional wireless signals, etc.). In some embodiments, device  12  communicates wirelessly with devices  10  to establish the characteristics of devices  10  and receive power at devices  10 . The coil information and wirelessly received information is used to account for power transmitted, power received, and wireless power transfer efficiency and losses, referred to as power counting (PC). Some losses would be characterized as expected, for example, eddy currents in metallic components, and in other cases, losses may be due to foreign objects. In some embodiments, power counting is used to distinguish circumstances where losses are low enough, or efficiency high enough, for charging to proceed, or to be inhibited if potentially significant foreign objects are inferred to be present. 
     With one illustrative configuration, wireless transmitting device  12  is a wireless charging mat or other wireless power transmitting equipment that has an array of coils  36  that supply wireless power over a wireless charging surface. This type of arrangement is shown in  FIG. 2 . In the example of  FIG. 2 , device  12  has an array of coils  36  that lie in parallel X-Y planes. Coils  36  of device  12  are covered by one or more planar dielectric layers each of which may include one or more layers of material. The outermost surface of the dielectric layer(s) forms charging surface  60 . The lateral dimensions (X and Y dimensions) of the array of coils  36  in device  12  may be 1-1000 cm, 5-50 cm, more than 5 cm, more than 20 cm, less than 200 cm, less than 75 cm, or other suitable size. Coils  36  may overlap or may be arranged in a non-overlapping configuration. Coils  36  can be placed in a rectangular array having rows and columns and/or may be tiled using a hexagonal tile pattern or other pattern. 
     As shown in the example of  FIG. 2 , external objects such as external object  62  and object  64  may overlap one or more coils  36 . In some situations, objects  62  and  64  will be portable electronic devices  10 . In other situations, one or more of objects  62  and  64  will be incompatible external objects (e.g., foreign objects such as metallic coins or other conductive objects). Situations may also arise in which foreign objects and wireless power receiving devices magnetically coupled to the same coil or coils  36 . During operation, system  8  automatically detects whether objects located on surface  60  correspond to wireless power receiving devices  10 , to which wireless power should be provided, or foreign objects, to which wireless power should not be coupled. In an illustrative embodiment, impedance monitoring circuitry in measurement circuitry  59  and/or temperature measurement circuitry such as temperature sensors  57  is used in detecting when foreign objects are present and/or when undesired heating of foreign objects is taking place. Upon detection of a foreign object, system  8  automatically takes suitable action such as reducing and/or halting wireless power transmission. 
     When wireless power from coils  36  is being transmitted, currents may be induced in foreign objects on charging surface  60  that cause these objects to heat. To monitor for undesired temperature rises of the type associated with heating of foreign objects on charging surface  60 , temperature sensors  57  may be formed in an array across charging surface  60 , as shown in  FIG. 3 . 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, fewer than 1000, fewer than 450, fewer than 210, fewer than 125, fewer than 70, fewer than 50, fewer than 40, or other suitable values. Temperature sensors  57  may be organized in a rectangle with rounded corners or other suitable shape (e.g., a shape that matches the outline of charging surface  60 ). Temperature sensors  57  are overlapped by the layer of dielectric on the top of wireless power transmitting device  12  that forms charging surface  60  and are interposed between coils  36  and the layer of dielectric. 
     A cross-sectional side view of wireless power transmitting device  12  is shown in  FIG. 4 . Device  12  of  FIG. 4  has an array of temperature sensors  57  configured to make temperature measurements. Structures  155  include polymer layers, metal layers, ferrite layers, and/or other structures for forming a housing and other structures for device  12 . Upper portion  155 T of structures  155  forms charging surface  60 . Lower portion  155 L of structures  155  includes coils  36 . Structures  140  may overlap temperature sensing components such as temperature sensing component  82 F and structures  142  may overlap temperature sensing components such as temperature sensing component  82 A. Structures  140  and  142 , which may include polymer layers, air gaps, metal layers, and/or other materials, can have different thermal resistances, so that differential temperature measurements may be made to gather information on heat flux through charging surface  60 . Temperature sensing components  82 F and  82 A may be arranged adjacent to each other as shown in the example of  FIG. 4  or may, if desired, overlap each other (e.g., some or all of component  82 F may be interposed between charging surface  60  and component  82 A). 
     The temperature sensing components in device  12  (e.g., components such as components  82 F and  82 A) may be thermistors (e.g., resistive temperature sensing devices of the type that are sometimes based on temperature sensitive ceramics or metal oxides), resistance thermometers (e.g., resistive temperature sensing devices of the type that are sometimes formed from metal temperature sensing elements such as elements formed from platinum, nickel, or other metals and which may, if desired, be formed from thin-film resistors), thermocouples, semiconductor temperature sensing devices such as semiconductor diodes, or other temperature sensor components. Illustrative configurations in which temperature sensors  57  are formed using temperature sensor components such as resistance thermometers formed from thin-film temperature-sensing resistors are sometimes described herein as an example. 
     If desired, temperature sensors  57  may each include a single temperature sensing component (e.g., to form an array of sensors that monitor for elevated temperatures). In the illustrative embodiment of  FIG. 4 , each temperature sensor  57  includes first and second temperature sensing components that are used in measuring temperature gradients and heat flux through charging surface  60 . There is a single one of components  82 F and a single one of components  82 A in each illustrative temperature sensor  57  of  FIG. 4 . Arrangements in which device  12  includes an array of temperature sensors  57  having first and second sets of temperature sensing components and in which some of the second set of temperature sensing components are shared by more than one of the first set of temperature sensing components may also be used. For example, each sensor  57  may include a respective one of components  82 F and each of components  82 A may be shared by multiple sensors  57 . 
     By including temperature sensing components in device  12  such as components  82 F and  82 A that are thermally coupled to charging surface  60  with different amounts of thermal resistance, differential (gradient) temperature measurements and heat flux measurements can be made. The temperature sensing components may overlap each other and/or may be formed adjacent to each other. In the illustrative configuration of  FIG. 4 , temperature sensors  57  each include a first temperature sensing component  82 F and a second temperature sensing component  82 A, that is adjacent to temperature sensing component  82 F. There may be more than one of components  82 F and/or more than one of components  82 A in each sensor  57 , if desired. 
     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 structures  140  and the portion of structures  155  interposed between temperature sensing component  82 F and charging surface  60  is greater than the thermal conductivity of structures  142  and the portions of structures  155  interposed between temperature sensing components  82 A. As a result, there is a greater thermal resistance between temperature sensing component  82 A and charging surface  60  than between temperature sensing component  82 F and charging surface  60 . Components  82 F and  82 A therefore respond differently to a heated object on surface  60 . There is more thermal resistance between surface  60  and component  82 A than between surface  60  and component  82 F, so component  82 F tends to react quickly while component  82 A serves to measure the ambient temperature of the interior of device  12 . When a heated object is present on device  12  and surface  60  is heated, there will be a temperature gradient (high-to-low) established between surface  60  and the interior of device  12  and this gradient (and therefore the heat flux flowing through surface  60 ) can be measured using the differential temperature sensing arrangement of  FIG. 4  or other heat flux measurement arrangements. 
     Illustrative embodiments for temperature sensors  57  in  FIG. 12  are shown in  FIGS. 5, 6 , and  7 . In the example of  FIG. 5 , component  82 A is thermally coupled to temperature sensor pad  162  and component  82 F is thermally coupled to temperature sensing pad  160  through via  164 . Via  164  may be a thermally conductive structure formed from metal and may pass through dielectric substrate  163  (e.g., a printed circuit substrate). Pads  160  and  162  may be formed from metal traces on opposing sides of substrate  163  (as an example). Fingers and other structures may be formed in pads  160  and  162  to reduce eddy currents when wireless power signals are being transmitted to device  10  by coils  36 . Because via  164  thermally couples component  82 F to a pad such as pad  160  that is closer to surface  60  than pad  162 , component  82 F will tend to react more quickly to changes in temperature at surface  60 , whereas component  82 A will tend to measure internal (e.g., ambient) temperatures in device  12 . 
     In the example of  FIG. 6 , component  82 F is overlapped by metal structures  166  and component  82 A is overlapped by air-filled cavity  168 . Air is more thermally resistive than metal, so the thermal resistance between component  82 A and surface  60  is greater than the thermal resistance between component  82 F and surface  60 . 
     In the example of  FIG. 7 , components  82 A and  82 F overlap each other. Component  82 F is closer to surface  60  than component  82 A. As a result, component  82 A is thermally coupled to surface  60  by a greater thermal resistance than component  82 F. 
     Additional embodiments of device  12  may have different configurations for temperature sensing components  82 F and  82 A. As described above, for example, there need not be equal numbers of components  82 F and  82 A in the array of temperature sensors  57  in device  12 . There may be, for example, a larger number of components  82 F than components  82 A. 
       FIG. 8  is a cross-sectional side view of a portion of device  12  showing how each temperature sensor  57  may, if desired, include multiple temperature sensing components coupled to a common temperature sensor pad. In the illustrative embodiment of  FIG. 8 , there are two temperature sensor components  82 F- 1  and  82 F- 1  located at different horizontal locations across a shared temperature sensor pad  160 . Temperature sensor component  82 F- 1  is thermally coupled to a left-hand portion of pad  160  through a left-hand via  164  and temperature sensor component  82 F- 2  is thermally coupled to a right-hand portion of pad  160  through a right-hand via  164 . During operation, control circuitry  42  can average the temperature sensor readings gathered with sensor components  82 F- 1  and  82 F- 2  or may otherwise process these signals to help reduce measurement inaccuracies due to lateral thermal gradients. In general, any suitable number of temperature sensing components  82 F (e.g., one, at least two, at least three, at least four, etc.) may be coupled to the upper thermal pad or other structures in each temperature sensor  57  and any suitable number of temperature sensing components  82 A (e.g., one, at least two, at least three, at least four, etc.) may be coupled to the lower thermal pad or other structures in each temperature sensor  57 . 
     Components  82 A and  82 F may, if desired, be formed from thin-film resistive sensors. A metal trace pattern of the type that may be used for a thin-film resistive sensor is shown in  FIG. 9 . As shown in  FIG. 9 , the metal trace pattern of  FIG. 9  may include a first portion  170  that forms signal traces  172  and a second portion that forms a thin-film resistive (temperature sensing component  82 ). The traces  172  that form component  82  may be coupled at end point  174 . A meandered pattern which retraces along its own path or other suitable layout may be used for traces  172  in component  82  to help reduce magnetic field coupling with the wireless power signals being transmitted by coils  36 . Portion  170  may form interconnect lines that couple component  82  to an integrated circuit and/or other processing circuitry (e.g., control circuitry  42 ). During operation, control circuitry  42  may measure the resistance of component  82 . 
     Metal traces such as traces  172  of  FIG. 9  may be formed on one or both sides of a printed circuit substrate or other dielectric substrate. A passivation layer of inorganic and/or organic material may cover traces  172 . To provide component  82  with a desired change of resistance with temperature, traces  172  may be formed from a metal such as platinum, nickel, or other metal (e.g. an elemental metal).  FIG. 10  is a cross-sectional side view of an illustrative double-sided printed circuit board substrate (substrate  173 ). Temperature sensor component  82  of  FIG. 10  has a first temperature sensing portion (temperature sensor component)  82 T formed from a retraced spiral portion of metal traces  172 T on the upper surface of substrate  173  and has a second temperature sensing portion (temperature sensor component)  82 B formed from a retraced spiral portion of metal traces  172 B on the opposing lower surface of substrate  173 . Portion  170 T of traces  172 T electrically couples temperature sensing portion  82 T to control circuitry  42  and portion  170 B of traces  172 B electrically couples temperature sensing portion  82 B to control circuitry  42 . 
     The temperature sensors of device  12  may include resistance measurement circuits for measuring resistance changes in temperature sensitive thin-film resistors.  FIG. 11  is a circuit diagram showing an illustrative Wheatstone bridge circuit that may be used in measuring resistance changes in portions  82 T and  82 B. Wheatstone bridge  190  may be supplied with direct-current (DC) and/or alternating current (AC) drive (supply) signals across terminals  180  and  182  by control circuitry  42  while control circuitry  42  measures resulting output signals across output terminals  186 . The use of this type of resistance measurement circuit may help reduce common mode noise (e.g., resistance changes in portions  170  of traces  172 )). In some embodiments, there is a residual magnetic flux coupling from power transmission coils to circuits including the temperature sensitive resistors. In some embodiments, the temperature sensors are coupled into Wheatstone bridge circuits where the connection sense is reversed to the temperature sensitive resistors to substantially cancel magnetic flux coupling through the circuit when a differential measurement is made of a pair of coils. Other resistance measurement circuits may be used, if desired. 
     An illustrative embodiment for an array of temperature sensors  57  is shown in  FIG. 12 .  FIG. 12  shows how sensors  57  may, if desired, be arranged in rows R 1 , R 2 , R 3 , . . . RN and orthogonal columns C 1 , C 2 , . . . CN across charging surface  60 . Control circuitry  42  may measure the resistances of each of the temperature sensor components  82  such as temperature sensing components  82 F and  82 A in sensors  57 . In some embodiments, each temperature sensor component is coupled to circuitry  42  with its own signal path. In other embodiments, rows, columns, and/or other sets of the temperature sensing components may use shared signal paths. As an example, the first terminal of each sensor component in a given row may be coupled to a shared drive line and the second terminal of each sensor component in a given column may be coupled to a shared sense line. In this type of embodiment, different rows may be driven with different alternating current signals so that sensing circuitry in control circuitry  42  can identify the row associated with each received signal on a given column. 
     To help reduce eddy currents, current loops in the interconnect paths used in coupling control circuitry  42  to sensors  57  may be reduced by reducing or eliminating grid shaped interconnect paths formed from orthogonal signal lines. A first illustrative signal line pattern that may be used for coupling metal traces  172  to sensors  57  is shown in  FIG. 13 . In this type of arrangement, metal traces extend from control circuitry  42  vertically along respective columns of sensors  57  (and sensor components  82  associated with sensors  57 ). The first terminal of each sensor component in each row may be coupled to a different respective vertically extending interconnect path (vertical traces  172 ′) and the second terminal of each sensor in each row may be coupled to a shared vertically extending (and therefore parallel) interconnect path (vertical trace  172 ″). No signal lines need extend past multiple columns of sensors (e.g., there need be no interconnect paths running perpendicular to the vertical traces). A second illustrative interconnect pattern for the sensor array is shown in  FIG. 14 . In the  FIG. 14  embodiment, first traces  172 ′ and second traces  172 ′ extend from control circuitry  42  vertically along respective columns of sensors  57  (and sensor components  82  associated with sensors  57 ). Each trace  172 ′ is coupled to a respective sensor  57  (e.g., a respective temperature sensor component  82  in that sensor  57 ) and each trace  172 ″ is coupled to a respective sensor  57  (and component  82 ). For example, in each column, each component  82  may have a set of dedicated metal traces that run vertically to that component. 
     In the examples of  FIGS. 13 and 14 , the signal paths formed from metal traces  172  extend primarily along a single lateral dimension. For example, at least 70%, at least 90%, at least 95%, or other suitable portion of the signal paths (by length) may extend vertically (or, if desired, may extend along another lateral dimension such as horizontally). No signal paths need extend past multiple sensors in the direction orthogonal to this single lateral dimension. This helps reduce conductive signal path loops and reduces magnetic field coupling between the signal paths and coils  36 . As a result, induced electromagnetic force due to changing magnetic flux through the sensor circuit has a reduced effect on the temperature measurement circuitry, and eddy currents in the signal paths due to the transmitted wireless power signals will be reduced and associated heating of the signal paths will be reduced. 
     The foregoing is illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20200507
Publication Date: 20210302
Grant Date: 20210302
Priority Date: 20180831
Inventors: Smith, J. Stephen
SETH, SIDDHARTH
ADAMS, DOUGLAS J.
CRETELLA, MICHAEL A.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01C3/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0044", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0044", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C7/008", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C3/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01C7/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C7/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01K1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C7/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C13/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01C7/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01C7/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 68766101