PATENT DOCUMENT

Publication Number: US-11605985-B2
Application Number: US-202016867460-A
Country: US
Kind Code: B2

Title: Wireless power system with object detection

Abstract:
A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device may be a wireless charging mat or other device with one or more wireless power transmitting coils for transmitting wireless power signals. The wireless power receiving device may be a portable electronic device with one or more wireless power receiving coils for receiving the transmitted wireless power signals. The wireless power transmitting device may have foreign object detection coils. Q-factor measurements may be made on the transmitting coil during wireless power transmission and/or voltage measurements may be made using the foreign object detection coils to detect whether a foreign object is present. The foreign object detection coils may include overlapping coils with different winding patterns to enhance foreign object detection coverage.

Claims:
What is claimed is: 
     
       1. A wireless power transmitting device for transmitting wireless power to a wireless power receiving device, comprising:
 wireless power transmitting circuitry including a wireless power transmitting coil configured to transmit wireless power signals; 
 a layer of magnetic material; 
 printed circuit with metal traces forming foreign object detection coils of at least first and second different winding patterns overlapping the wireless power transmitting coil, wherein the printed circuit is interposed between the wireless power transmitting coil and the layer of magnetic material; and 
 control circuitry configured to monitor for the presence of a foreign object using the foreign object detection coils. 
 
     
     
       2. The wireless power transmitting device of  claim 1  wherein the first winding pattern comprises a spiral winding pattern. 
     
     
       3. The wireless power transmitting device of  claim 2  wherein the second winding pattern comprises a figure eight winding pattern. 
     
     
       4. The wireless power transmitting device of  claim 1  wherein there are only four foreign object detection coils of the first winding pattern formed in a first layer. 
     
     
       5. The wireless power transmitting device of  claim 4  wherein there are only four foreign object detection coils of the second winding pattern formed in a second layer. 
     
     
       6. The wireless power transmitting device of  claim 5  wherein the first winding pattern comprises one or more spiral coil winding pattern(s) and wherein the second winding pattern comprises one or more figure eight winding pattern(s). 
     
     
       7. The wireless power transmitting device of  claim 6  wherein each of the foreign object detection coils has a ring-quarter-segment outline. 
     
     
       8. The wireless power transmitting device of  claim 7  wherein the foreign object detection coils of the first winding pattern overlap the foreign object detection coils of the second winding pattern. 
     
     
       9. The wireless power transmitting device of  claim 8  wherein the foreign object detection coils in the first layer overlap with the wireless power transmitting coil and do not overlap a central opening in the wireless power transmitting coil. 
     
     
       10. The wireless power transmitting device of  claim 1  wherein each of the foreign object detection coils of the first winding pattern in the first layer overlaps and shares a common shape with a respective one of the foreign object detection coils of the second winding pattern in the second layer. 
     
     
       11. The wireless power transmitting device of  claim 1  wherein:
 the foreign object detection coils of the first winding pattern are formed in a first layer and have a first orientation; and 
 the foreign object detection coils of the second winding pattern are formed in a second layer and have a second orientation different than the first orientation. 
 
     
     
       12. The wireless power transmitting device of  claim 11  wherein the foreign object detection coils further comprise foreign object detection coils formed in a third layer and foreign object detection coils formed in a fourth layer, wherein the foreign object detection coils in the first layer have a first shape, wherein the foreign object detection coils in the second layer have the first shape, wherein the foreign object detection coils in the third layer have a second shape different than the first shape, and wherein the foreign object detection coils in the fourth layer have the second shape. 
     
     
       13. The wireless power transmitting device of  claim 12  wherein the foreign object detection coils in the first, second, third, and fourth layers comprise 16 total foreign object detection coils. 
     
     
       14. The wireless power transmitting device of  claim 1  wherein the foreign object detection coils of the first winding pattern comprise wedge shaped coils and wherein the foreign object detection coils of the second winding pattern comprise ring segment shaped coils. 
     
     
       15. The wireless power transmitting device of  claim 1  wherein the foreign object detection coils of the first and second winding patterns comprise wedge shaped coils. 
     
     
       16. The wireless power transmitting device of  claim 1  wherein the foreign object detection coils of the first and second winding patterns comprise ring segment shaped coils. 
     
     
       17. A wireless power transmitting device for transmitting wireless power to a wireless power receiving device, comprising:
 wireless power transmitting circuitry including a wireless power transmitting coil configured to transmit wireless power signals; 
 a layer of magnetic material; and 
 printed circuit with metal traces forming a spiral-winding foreign object detection coil with a spiral winding pattern and a figure-eight-winding foreign object detection coil with a figure-eight winding pattern, wherein the printed circuit is interposed between the wireless power transmitting coil and the layer of magnetic material. 
 
     
     
       18. The wireless power transmitting device of  claim 17  wherein the printed circuit is interposed between the wireless power transmitting coil and the layer of magnetic material to reduce sensitivity to misalignment of the wireless power receiving device with respect to the wireless power transmitting coil.

Description:
This application claims the benefit of provisional patent application No. 62/889,162, filed Aug. 20, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to power systems, and, more particularly, to wireless power systems for charging electronic devices. 
     BACKGROUND 
     In a wireless charging system, a wireless power transmitting device such as a charging mat wirelessly transmits power to a wireless power receiving device such as a portable electronic device. The portable electronic device has a coil and rectifier circuitry. The coil of the portable electronic device receives alternating-current wireless power signals from the wireless charging mat. The rectifier circuitry converts the received signals into direct-current power. To ensure satisfactory operation, the wireless charging system may have circuitry to detect foreign objects. 
     SUMMARY 
     A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device may be a wireless charging mat or other device with one or more wireless power transmitting coils for transmitting wireless power signals. The wireless power receiving device may be a portable electronic device with one or more wireless power receiving coils for receiving the transmitted wireless power signals. 
     The wireless power transmitting device has foreign object detection coils of one or more winding types. Q-factor measurements may be made on a transmitting coil during wireless power transmission and/or magnetic field measurements may be made using the foreign object detection coils to detect whether a foreign object is present. 
     The foreign object detection coils may include overlapping coils of different types. For example, the foreign object detection coils may include a first set of coils with spiral windings and second set of coils with figure-eight windings. By overlapping the first coils and second coils, foreign object detection accuracy can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative wireless power system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG.  2    is a graph of an illustrative wireless power transmitter signal in accordance with an embodiment. 
         FIG.  3    is a circuit diagram showing illustrative measurement circuitry in a wireless power transmitter in accordance with an embodiment. 
         FIGS.  4 ,  5 ,  6 , and  7    are diagrams of illustrative wireless power transmitter coils and foreign object detection coils in accordance with an embodiment. 
         FIG.  8    is a cross-sectional side view of an illustrative wireless power system in accordance with an embodiment. 
         FIG.  9    is a diagram of an illustrative foreign object detection coil with a spiral winding in accordance with an embodiment. 
         FIG.  10    is a diagram of an illustrative foreign object detection coil with a figure eight winding forming a pair of subcoils with respective clockwise and counterclockwise winding senses in accordance with an embodiment. 
         FIG.  11    is a cross-sectional side view of a portion of an illustrative wireless power transmitting coil and overlapping subcoils in a foreign object detection coil in accordance with an embodiment. 
         FIG.  12    is a graph showing potential output readings from overlapping spiral and figure eight foreign object detection coils as a function of foreign object location in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system includes a wireless power transmitting device such as a wireless charging mat. The wireless power transmitting device wirelessly transmits power to a wireless power receiving device such as a wristwatch, cellular telephone, tablet computer, laptop computer, or other electronic equipment. The wireless power receiving device uses power from the wireless power transmitting device for powering the device and for charging an internal battery. 
     Wireless power is transmitted from the wireless power transmitting device to the wireless power receiving device using one or more wireless power transmitting coils to charge a battery in the wireless power receiving device and/or to power other load circuitry. The wireless power receiving device has one or more wireless power receiving coils coupled to rectifier circuitry that converts received wireless power signals into direct-current power. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG.  1   . As shown in  FIG.  1   , wireless power system  8  includes a wireless power transmitting device such as wireless power transmitting device  12  and includes a wireless power receiving device such as wireless power receiving device  24 . Wireless power transmitting device  12  includes control circuitry  16 . Wireless power receiving device  24  includes control circuitry  30 . Control circuitry in system  8  such as control circuitry  16  and control circuitry  30  is used in controlling the operation of system  8 . This control circuitry may include processing circuitry associated with microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. The processing circuitry implements desired control and communications features in devices  12  and  24 . For example, the processing circuitry may be used in selecting coils, determining power transmission levels, processing sensor data and other data to detect foreign objects and perform other tasks, processing user input, handling negotiations between devices  12  and  24 , sending and receiving in-band and out-of-band data, making measurements, and otherwise controlling the operation of system  8 . In an illustrative configuration, the processing circuitry of device  12  uses foreign object detection coils to monitor for the presence of foreign objects such as coins, paper clips, credit cards, etc. and takes appropriate action (e.g., halting power transmission) in response to detecting that a foreign object is present. 
     Control circuitry in system  8  may be configured to perform operations in system  8  using hardware (e.g., dedicated hardware or circuitry), firmware and/or software. Software code for performing operations in system  8  is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) in control circuitry  8 . 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, or the like. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry  16  and/or  30 . The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, a central processing unit (CPU) or other processing circuitry. 
     Power transmitting device  12  may be a stand-alone power adapter (e.g., a wireless charging mat or charging puck that includes power adapter circuitry), may be a wireless charging mat or puck that is coupled to a power adapter or other equipment by a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, may be a removable battery case, or may be other wireless power transfer equipment. Illustrative configurations in which wireless power transmitting device  12  is a wireless charging mat are sometimes described herein as an example. 
     Power receiving device  24  may be a portable electronic device such as a wristwatch, a cellular telephone, a laptop computer, a tablet computer, an accessory such as an earbud, or other electronic equipment. Power transmitting device  12  may be coupled to a wall outlet (e.g., an alternating current power source), may have a battery for supplying power, and/or may have another source of power. Power transmitting device  12  may have an alternating-current (AC) to direct-current (DC) power converter such as AC-DC power converter  14  for converting AC power from a wall outlet or other power source into DC power. DC power may be used to power control circuitry  16 . During operation, a controller in control circuitry  16  uses power transmitting circuitry  52  to transmit wireless power to power receiving circuitry  54  of device  24 . Power transmitting circuitry  52  may have switching circuitry (e.g., inverter circuitry  61  formed from transistors) that is turned on and off based on control signals provided by control circuitry  16  to create AC current signals through one or more wireless power transmitting coils such as wireless power transmitting coils  36 . These coil drive signals cause coil(s)  36  to transmit wireless power. Coils  36  may be arranged in a planar coil array (e.g., in configurations in which device  12  is a wireless charging mat) or may be arranged to form a cluster of coils (e.g., in configurations in which device  12  is a wireless charging puck). In some arrangements, device  12  (e.g., a charging mat, puck, etc.) may have only a single coil. In other arrangements, a wireless charging device may have multiple coils (e.g., two or more coils, 5-10 coils, at least 10 coils, 10-30 coils, fewer than 35 coils, fewer than 25 coils, or other suitable number of coils). 
     As the AC currents pass through one or more coils  36 , alternating-current electromagnetic (e.g., magnetic) fields (wireless power signals  44 ) are produced that are received by one or more corresponding receiver coils such as coil(s)  48  in power receiving device  24 . Device  24  may have a single coil  48 , at least two coils  48 , at least three coils  48 , at least four coils  48 , or other suitable number of coils  48 . When the alternating-current electromagnetic fields are received by coil(s)  48 , corresponding alternating-current currents are induced in coil(s)  48 . Rectifier circuitry such as rectifier circuitry  50 , which contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network, converts received AC signals (received alternating-current signals associated with electromagnetic signals  44 ) from one or more coils  48  into DC voltage signals for powering device  24 . 
     The DC voltage produced by rectifier circuitry  50  (sometime referred to as rectifier output voltage Vrect) can be used in charging a battery such as battery  58  and can be used in powering other components in device  24 . For example, device  24  may include input-output devices  56  such as a display, touch sensor, communications circuits, audio components, sensors, light-emitting diode status indicators, other light-emitting and light detecting components, and other components and these components (which form a load for device  24 ) may be powered by the DC voltages produced by rectifier circuitry  50  (and/or DC voltages produced by battery  58 ). 
     Device  12  and/or device  24  may communicate wirelessly using in-band or out-of-band communications. Device  12  may, for example, have wireless transceiver circuitry  40  that wirelessly transmits out-of-band signals to device  24  using an antenna. Wireless transceiver circuitry  40  may be used to wirelessly receive out-of-band signals from device  24  using the antenna. Device  24  may have wireless transceiver circuitry  46  that transmits out-of-band signals to device  12 . Receiver circuitry in wireless transceiver  46  may use an antenna to receive out-of-band signals from device  12 . In-band transmissions between devices  12  and  24  may be performed using coils  36  and  48 . With one illustrative configuration, frequency-shift keying (FSK) is used to convey in-band data from device  12  to device  24  and amplitude-shift keying (ASK) is used to convey in-band data from device  24  to device  12 . Power may be conveyed wirelessly from device  12  to device  24  during these FSK and ASK transmissions. 
     It is desirable for power transmitting device  12  and power receiving device  24  to be able to communicate information such as received power, states of charge, and so forth, to control wireless power transfer. However, the above-described technology need not involve the transmission of personally identifiable information in order to function. Out of an abundance of caution, it is noted that to the extent that any implementation of this charging technology involves the use of personally identifiable information, implementers should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     Control circuitry  16  has external object measurement circuitry  41  that may be used to detect external objects on the charging surface of device  12  (e.g., on the top of a charging mat or, if desired, to detect objects adjacent to the coupling surface of a charging puck). Circuitry  41  can detect foreign objects such as coils, paper clips, and other metallic objects and can detect the presence of wireless power receiving devices  24  (e.g., circuitry  41  can detect the presence of one or more coils  48 ). During object detection and characterization operations, external object measurement circuitry  41  can be used to make measurements on coils  36  and/or on foreign object detection coils  70  to determine whether any devices  24  are present on device  12 . 
     In an illustrative arrangement, measurement circuitry  41  of control circuitry  16  contains signal generator circuitry (e.g., oscillator circuitry for generating AC probe signals at one or more probe frequencies, a pulse generator that can create impulses so that impulse responses can be measured to gather inductance information, Q-factor information, etc.) and signal detection circuitry (e.g., filters, analog-to-digital converters, impulse response measurement circuits, etc.). In some configurations, Q-factor measurements and other measurements may be made during wireless power transfer operations. Switching circuitry in device  12  may be used to switch desired coils into use during wireless power transmission and/or foreign object detection operations. 
     Measurement circuitry  43  in control circuitry  30  and/or measurement circuitry  41  in control circuitry  16  may be used in making current and voltage measurements. Based on this information or other information, control circuitry  30  can configure rectifier circuitry  50  to help enhance wireless power reception by coils  48 . 
       FIG.  2    is a graph showing an illustrative wireless power transmitting signal during wireless power transmission. Wireless power transmitting coil signal  72  (e.g., coil voltage) is characterized by an alternating-current waveform that is established by inverter  61  as inverter  61  drives a wireless power transmission coil. In the example of  FIG.  2   , this waveform is a square wave. Other types of alternating-current (AC) waveforms may be supplied, if desired. The frequency of the AC drive signal may be 10 kHz to 1 MHz, at least 50 kHz, less than 300 kHz, or other suitable frequency. 
     As shown in  FIG.  2   , ringing  74  may be induced in wireless power transmitting coil signal  72  (e.g., ringing resulting from each square wave cycle of the AC drive signal and/or ringing resulting from impulses applied separately to the wireless power transmitting coil by control circuitry  16  during wireless power transmission). Using analog-to-digital converter circuitry, peak detection circuitry, envelope detection circuitry, and/or other measurement circuitry  41  in control circuitry  16 , the magnitude and frequency of the ringing component of the wireless power transmitting coil signal and decay envelope  76  can be measured, thereby allowing coil parameters such as inductance L and Q factor to be measured. When no foreign object is present, the decay envelope may have a shape of the type shown by illustrative decay envelope  76  (as an example). When a foreign object is present, a damped response (see, e.g., damped envelope  76 ′) may be exhibited. 
       FIG.  3    is a circuit diagram of an illustrative transmitting coil circuit. As shown in  FIG.  3   , measurement circuitry  41  may have a voltage sensor that is configured to measure signal  72  (including the ringing portion of signal  72 ) on wireless power transmitting coil  36 . The components of  FIG.  3    (e.g., coil  36  and capacitor C) form a parallel resonant circuit which is tuned to a measurable frequency (e.g., a frequency of at least 0.2 MHz, at least 0.5 MHz, about 1 MHz, less than 2 MHz, less than 1.5 MHz, or other suitable frequency). Capacitor C may be used to reduce the frequency of ringing  74 . The value of capacitor C may be at least 0.2 nF, at least 2 nF, 22 nF, less than 200 nF, less than 400 nF, or other suitable value. In the absence of capacitor C, the frequency of ringing  74  may be tens of MHz, which can pose measurement challenges. In the presence of capacitor C, which is coupled across coil  36 , the frequency of ringing  74  may be reduced (e.g., to hundreds of kHz, 1 MHz, or other suitable frequency), thereby facilitating measurement of ringing  74  with measurement circuitry  41 . 
     During operation, control circuitry  16  can use measurement circuitry  41  to measure coil characteristics such as Q factor (e.g., by measuring decay envelope  76 ) to determine whether a foreign object is present on coil  36 . In the presence of foreign object s (e.g., metallic objects), wireless power signals will induce eddy currents in the foreign object that will create lowered values of Q factor. In response to detecting that the measured value of Q is less than a predetermined threshold (or using other suitable detection criteria), control circuitry  16  can conclude that a foreign object is likely present and can take appropriate action (e.g., by notifying a user of system  8 , by halting wireless power transmission, by reducing the amount of power being transmitted to a relatively low level, etc.). The analysis of the ringing signal can take place during power transmission operations, so power transmission need not be interrupted to detect foreign objects. 
     If desired, control circuitry  16  can detect foreign objects using foreign object detection coils  70 . Coils  70  may be arranged to fully or partially overlap one or more of coils  36 .  FIGS.  4 ,  5 ,  6 , and  7    show how coils  70  may include four overlapping layers of coils that are configured to provide foreign object detection for an overlapped transmitting coil  36 . In the example of  FIGS.  4  and  5   , coils  70  form segments of a ring. The layout of coils  70  differs between  FIG.  4    and to enhance detection sensitivity. In the example of  FIGS.  6  and  7   , coils  70  have the shape of circular sectors (e.g., wedges). The patterns of coils  70  in  FIGS.  6  and  7    differ from each other and differ from the coil patterns of coils  70  in  FIGS.  4  and  5    to create sensitivity in different areas and thereby enhance foreign object detection coverage. There are four layers of coils  70  and 16 coils  70  in total in the illustrative configuration of  FIGS.  4 ,  5 ,  6   , and  7 . In general, there may be one layer of coils  70 , at least two layers of coils  70 , at least three layers of coils  70 , at least four layers of coils  70 , or other suitable number of foreign object detection coil layers. Coils  70  may be formed from signal lines such as metal traces on flexible printed circuit substrates and/or other substrates, metal wires, or other signal paths. In some configurations, coils  70  may include spiral coils and/or figure eight coils. 
       FIG.  8    is a cross-sectional side view of system  8 . In the illustrative configuration of  FIG.  8   , device  12  has a single wireless power transmitting coil  36  that overlaps flexible printed circuit  78 . A layer of magnetic material such as ferrite layer  80  may be overlapped by coil  36  and flexible printed circuit  78 . Foreign object detection coils  70  are formed from metal traces in flexible printed circuit  78 . Flexible printed circuit  78  is interposed between coil  36  and the layer of magnetic material (e.g., layer  80 ). Misalignment of wireless power receiving device  24  creates unbalance between detection coil voltages, which can, in some situations, mimic the appearance of a foreign object. By placing printed circuit  78  below coil(s)  36 , printed circuit  78  and coils  70  are interposed between wireless power transmitting coil  36  and ferrite layer  80  to reduce sensitivity to misalignment of wireless power receiving device  24  with respect to wireless power transmitting coil  36 . 
     The circuitry of device  12  may be formed from components  82  mounted to printed circuit  84 . Connector  86  electrically couples the circuitry on printed circuit  84  to foreign object detection coils  70  in printed circuit  78 . Wires (e.g., lengths of Litz wire) electrically couple inverter  61  to respective terminals of coil  36 . 
     Foreign objects such as foreign object  90  may be located above coil  36  (e.g., at a distance R from the center of coil  36 ). Control circuitry  16  uses foreign object detection coils  70  to measure magnetic fields B to monitor for the presence of objects such as object  90 . 
     To enhance detection sensitivity, foreign object detection coils  70  may include coils of different winding types. For example, some of coils  70  may have spiral winding patterns and some of coils  70  may have figure eight winding patterns. Each type of coil may exhibit different peaks and valleys in sensitivity to foreign objects, so by overlapping coils with different types of winding patterns, blind spots can be avoided. 
       FIG.  9    is an illustrative foreign object detection coil with a spiral winding. Conductive path (line)  92  of the winding of illustrative coil  70  of  FIG.  9    has a spiral shape that fits within a desired coil outline. Coil  70  of  FIG.  9    has the shape of a ring quarter segment. Distance (radius) R is associated with the distance from the center of coil  36 . Wedge shaped coil shapes and other coil outlines may be used, if desired. Terminals  94  are coupled electrically to control circuitry  16  (e.g., measurement circuitry  41 ). During operation, changes in voltage (ΔV) across terminals  94  are monitored by circuitry  41  to determine if foreign object  90  is present. There may be any suitable number of turns in the spiral coil winding of  FIG.  9    (e.g., at least one, at least two, at least three, at least five, at least 10, fewer than 20, etc.). 
       FIG.  10    is an illustrative foreign object detection coil with a figure eight winding. Conductive path (line)  96  of illustrative coil  70  of  FIG.  10    has an outline with the shape of a ring quarter segment (as an example). The use of a common shape for coil  70  of  FIG.  10    and coil  70  of  FIG.  9    (e.g., matching coil outlines) allows coil  70  of  FIG.  10    to overlap and match the outline of coil  70  of  FIG.  9   . Other shapes may be used, if desired (e.g., other shapes such as the wedge shapes of  FIG.  6    or other shapes that match the shape of an overlapped spiral coil). 
     Conductive path  96  is coupled to measurement circuitry  41  by terminals  98 . A first portion of coil  70  of  FIG.  10    forms a first subcoil C 1  with a first winding sense (e.g., clockwise), whereas a second portion of coil  70  of  FIG.  10    forms a second subcoil C 2  with a second winding sense (e.g., a clockwise winding sense). Because subcoils C 1  and C 2  have opposite winding senses, coil  70  of  FIG.  10    tends to be sensitive to perturbations in lateral magnetic fields. This sensitivity is complementary to the sensitivity of coil  70  of  FIG.  9   , so by using both coil  70  of  FIG.  9    and coil  70  of  FIG.  10   , foreign object detection blind spots are avoided. Coils C 1  and/or C 2  may each have a single turn (as shown in  FIG.  10   ) and/or coil C 1  and/or coil C 2  may have two or more turns. 
       FIG.  11    is a diagram showing how coil  36  may produce lateral magnetic fields B 1 , B 1 ′, B 2 , and B 2 ′ during wireless power transmission. Figure-eight coil  70  has first subcoil C 1  and second subcoil C 2  in areas that overlap respective portions of coil  36  (e.g., coil  70  may have a quarter ring segment shape of the type shown in  FIGS.  4  and  5   ). The behavior of the magnetic fields associated with coil  36  during operation depends on whether foreign object  90  is present. In the absence of object  90 , coils  36  produce magnetic fields B 1  and B 2 . Magnetic field B 1  has a first portion that passes upwardly through coil C 1  and a second portion that passes downwardly through coil C 2 . This induces two voltage contributions that add constructively to produce a resulting ΔV value at the terminals of coil  70 . Magnetic field B 2  passes through coil C 1  but not through coil C 2 , so magnetic field B 2  contributes less to the induced voltage ΔV in this example. 
     In the presence of a magnetic foreign object such as a paper clip formed from magnetic steel or another object formed from magnetic material (e.g., foreign object  90  of  FIG.  11   ), magnetic fields are perturbed. In the example of  FIG.  11   , magnetic field B 1  may follow the path of magnetic field B 1 ′ of  FIG.  11    in the presence of foreign object  90 , which induces a voltage similar to that induced in the absence of foreign object  90 . On the other hand, magnetic field B 2  now follows the path of magnetic field B 2 ′ of  FIG.  11    because the magnetic material of foreign object  90  of  FIG.  11    forms a bridge. As a result, magnetic field B 2 ′ passes upwardly through coil C 1  and downwardly through coil C 2  and therefore induces more voltage ΔV than magnetic field B 2 . Using measurement circuitry  41 , circuitry  16  measures the difference in the value of ΔV resulting from the presence of object  90 , thereby detecting when object  90  is present. 
       FIG.  12    is a graph illustrating the response (ΔV 1 ) of a spiral foreign object detection coil (e.g., coil  70  of  FIG.  9   ) and the response (ΔV 2 ) of an overlapping figure eight coil having the same outline when a foreign object such as a magnetic foreign object is located at distance R from the center of coil  36 . As shown by the graph, the spiral coil may exhibit a minimum sensitivity to the presence of foreign objects at distance XM. At this location, the figure eight coil has a maximum in sensitivity, so the responses of the coils with different winding patterns are complementary and detection blind spots are avoided. As this example demonstrates, the use of overlapping detection coils  70  helps device  12  detect magnetic foreign objects. 
     In the presence of a non-magnetic foreign object, the foreign object may perturb magnetic fields differently. In particular, instead of forming a bridge for magnetic fields as with a magnetic foreign object, a non-magnetic foreign object may tend to block magnetic flux. As a result, induced voltages in coils  70  for coils such as spiral and figure-eight shape coils will tend to be reduced relative to other coils in the group with no foreign object present. When flux is blocked in one part of the transmitter it is increased (net flux is still the same) through other sections (detection coils) whose voltages in this case are increased. But in the presence of a magnetic foreign object, flux is perturbed only around close proximity to the foreign object since it is bridged rather than blocked. 
     In the example of  FIGS.  9 ,  10 ,  11 , and  12   , foreign object detection coils  70  include a first set of coils of a first type (e.g., a set of four or more spiral coils) and a second set of coils of a second type that is different than the first type (e.g., a set of four or more figure eight coils). These coils may have quarter-ring-segment shapes or other suitable shapes. Other types of coil  70  and/or other coil shapes may be used, if desired. The outlines of coils  70  may overlap completely or partly with each other and may overlap completely or partly with the windings of coil  36 . The illustrative quarter ring segment coils  70  of  FIGS.  4  and  5    completely overlap the windings of coil  36  (e.g., none of the windings of coils  70  fall outside of the footprint of coil  36 ), whereas the illustrative wedge shaped coils  70  of  FIGS.  6  and  7    partially overlap the windings of coil  36  and partially overlap the empty center of ring-shaped coil  36 . Coils  70  may include only one layer of coils (e.g., the coil layer of  FIG.  4   ), may include only two layers of coils (e.g., a first layer with the pattern of  FIG.  4    and spiral windings and a second layer with the pattern of  FIG.  4    and matching figure-eight windings), may include three or more layers of coils, may include coil layers with different coil shapes and/or orientations (see, e.g., the layers of  FIGS.  4 ,  5 ,  6 , and  7   ), and/or may include other arrangements of coils. 
     The foregoing is merely 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: 20200505
Publication Date: 20230314
Grant Date: 20230314
Priority Date: 20190820
Inventors: RUSSELL, ANTOIN J.
SJOEROOS, JUKKA-PEKKA J.
MOUSSAOUI, ZAKI
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0029", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01V3/101", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01V3/101", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01V3/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/366", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01V3/104", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F5/003", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01V3/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01V3/104", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01V3/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 74646464