PATENT DOCUMENT

Publication Number: US-11916406-B1
Application Number: US-202217830722-A
Country: US
Kind Code: B1

Title: Techniques for wireless power systems power delivery

Abstract:
A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device may include a coil and wireless power transmitting circuitry coupled to the coil. The wireless power transmitting circuitry may include impulse response measurement circuitry that measures the inductance of the power transmitting coil and the quality factor of the power transmitting coil. The measured inductance and quality factor may subsequently be used to determine a position of the wireless power receiving device relative to the wireless power transmitting device. The determined position of the wireless power receiving device relative to the wireless power transmitting device may be used to estimate an expected power loss associated with the power transmitting coil. The power transfer operations may be adjusted based on expected and actual power losses.

Claims:
What is claimed is: 
     
       1. A wireless power transmitting device configured to transmit wireless power signals to a wireless power receiving coil in a wireless power receiving device, comprising:
 a coil configured to transmit the wireless power signals; 
 inverter circuitry coupled to the coil; and 
 control circuitry configured to:
 measure an inductance for the coil and a quality factor for the coil; 
 determine a position of the wireless power receiving device relative to the wireless power transmitting device based at least on the measured inductance and the measured quality factor; and 
 determine an expected power loss associated with the coil based at least on the determined position of the wireless power receiving device. 
 
 
     
     
       2. The wireless power transmitting device of  claim 1 , further comprising:
 a current sensor coupled to the coil, wherein the control circuitry is configured to:
 determine an actual power loss associated with the coil based at least on a current measured by the current sensor. 
 
 
     
     
       3. The wireless power transmitting device of  claim 2 , wherein the control circuitry is configured to:
 in accordance with determining that the expected power loss differs from the actual power loss by greater than a threshold magnitude, reduce a power level of the transmitted wireless power signals. 
 
     
     
       4. The wireless power transmitting device of  claim 2 , wherein the control circuitry is configured to:
 in accordance with determining that the expected power loss differs from the actual power loss by greater than a threshold magnitude, stop the coil from transmitting the wireless power signals. 
 
     
     
       5. The wireless power transmitting device of  claim 2 , wherein the control circuitry is configured to:
 in accordance with determining that the expected power loss differs from the actual power loss by less than a threshold magnitude, increase a power level of the transmitted wireless power signals. 
 
     
     
       6. The wireless power transmitting device of  claim 1 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a lateral misalignment between a first center of the wireless power receiving coil and a second center of the coil. 
     
     
       7. The wireless power transmitting device of  claim 1 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a lateral misalignment between the wireless power receiving coil and the coil. 
     
     
       8. The wireless power transmitting device of  claim 7 , wherein determining the lateral misalignment between the wireless power receiving coil and the coil comprises determining the lateral misalignment between the wireless power receiving coil and the coil using the measured quality factor. 
     
     
       9. The wireless power transmitting device of  claim 1 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a magnitude of a vertical gap between a first plane that includes the wireless power receiving coil and a second plane that includes the coil. 
     
     
       10. The wireless power transmitting device of  claim 9 , wherein determining the magnitude of the vertical gap between the first plane that includes the wireless power receiving coil and the second plane that includes the coil comprises determining the magnitude of the vertical gap between the first plane that includes the wireless power receiving coil and the second plane that includes the coil using the measured inductance. 
     
     
       11. The wireless power transmitting device of  claim 1 , wherein measuring the inductance for the coil and the quality factor for the coil comprises measuring the inductance for the coil and the quality factor for the coil using impulse response measurement circuitry. 
     
     
       12. A non-transitory computer-readable storage medium storing one or more programs configured to be executed by one or more processors of a wireless power transmitting device configured to transmit wireless power signals to a wireless power receiving coil in a wireless power receiving device, wherein the wireless power transmitting device comprises a coil configured to transmit the wireless power signals and inverter circuitry coupled to the coil, the one or more programs including instructions for:
 measuring an inductance for the coil and a quality factor for the coil; 
 determining a position of the wireless power receiving device relative to the wireless power transmitting device based at least on the measured inductance and the measured quality factor; and 
 determining an expected power loss associated with the coil based at least on the determined position of the wireless power receiving device. 
 
     
     
       13. The non-transitory computer-readable storage medium of  claim 12 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a lateral misalignment between the wireless power receiving coil and the coil. 
     
     
       14. The non-transitory computer-readable storage medium of  claim 12 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a magnitude of a vertical gap between a first plane that includes the wireless power receiving coil and a second plane that includes the coil. 
     
     
       15. The non-transitory computer-readable storage medium of  claim 12 , wherein measuring the inductance for the coil and the quality factor for the coil comprises measuring the inductance for the coil and the quality factor for the coil using impulse response measurement circuitry. 
     
     
       16. The non-transitory computer-readable storage medium of  claim 12 , wherein the wireless power transmitting device further comprises a current sensor coupled to the coil and wherein the one or more programs further include instructions for:
 determining an actual power loss associated with the coil based at least on a current measured by the current sensor; and 
 in accordance with determining that the expected power loss differs from the actual power loss by greater than a threshold magnitude, reducing a power level of the transmitted wireless power signals. 
 
     
     
       17. A method of operating a wireless power transmitting device configured to transmit wireless power signals to a wireless power receiving coil in a wireless power receiving device, wherein the wireless power transmitting device comprises a coil configured to transmit the wireless power signals and inverter circuitry coupled to the coil, the method comprising:
 measuring an inductance for the coil and a quality factor for the coil; 
 determining a position of the wireless power receiving device relative to the wireless power transmitting device based at least on the measured inductance and the measured quality factor; and 
 determining an expected power loss associated with the coil based at least on the determined position of the wireless power receiving device. 
 
     
     
       18. The method of  claim 17 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a lateral misalignment between the wireless power receiving coil and the coil. 
     
     
       19. The method of  claim 17 , wherein determining the position of the wireless power receiving device relative to the wireless power transmitting device comprises determining a magnitude of a vertical gap between a first plane that includes the wireless power receiving coil and a second plane that includes the coil. 
     
     
       20. The method of  claim 17 , wherein the wireless power transmitting device further comprises a current sensor coupled to the coil, the method further comprising:
 determining an actual power loss associated with the coil based at least on a current measured by the current sensor; and 
 in accordance with determining that the expected power loss differs from the actual power loss by greater than a threshold magnitude, reducing a power level of the transmitted wireless power signals.

Description:
This application claims priority to U.S. provisional patent application No. 63/245,052, filed Sep. 16, 2021, 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 transmits wireless power to a wireless power receiving device. The wireless power transmitting device uses a wireless power transmitting coil to transmit wireless power signals to the wireless power receiving device. The wireless power receiving device has a coil and rectifier circuitry. The coil of the wireless power receiving device receives alternating-current wireless power signals from the wireless power transmitting device. The rectifier circuitry converts the received signals into direct-current power. 
     SUMMARY 
     A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device may include a coil and wireless power transmitting circuitry coupled to the coil. The wireless power transmitting circuitry may be configured to transmit wireless power signals with the coil. The wireless power receiving device may include a coil that is configured to receive wireless power signals from the wireless power transmitting device and rectifier circuitry that is configured to convert the wireless power signals to direct current power. 
     The wireless power transmitting circuitry may include impulse response measurement circuitry that measures the inductance of the power transmitting coil and the quality factor of the power transmitting coil. The measured inductance and quality factor may subsequently be used to determine a position of the wireless power receiving device relative to the wireless power transmitting device. 
     The determined position of the wireless power receiving device relative to the wireless power transmitting device may be used to estimate an expected power loss associated with the power transmitting coil. The expected power loss may be compared to an actual power loss that is determined using power loss accounting. If the difference between the expected power loss and the actual power loss is greater than a threshold magnitude, the power transfer rate may be reduced, or power transfer may be ceased entirely. If the difference between the expected power loss and the actual power loss is less than a threshold magnitude, the power transfer rate may be increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative wireless power system in accordance with an embodiment. 
         FIG.  2    is a circuit diagram of an illustrative wireless power system in accordance with an embodiment. 
         FIG.  3    is a graph of an illustrative impulse response to an applied impulse signal in a wireless charging system in accordance with an embodiment. 
         FIG.  4 A  is a top view of an illustrative wireless power system with lateral misalignment between a wireless power receiving coil and a corresponding wireless power transmitting coil in accordance with an embodiment. 
         FIG.  4 B  is a cross-sectional side view of an illustrative wireless power system with a vertical gap between a wireless power receiving coil and a corresponding wireless power transmitting coil in accordance with an embodiment. 
         FIG.  5    is a flowchart of illustrative operations performed by a wireless power transmitting device that determines a position of a wireless power receiving device and estimates power loss based at least on the position of the wireless power receiving device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system includes a wireless power transmitting device. The wireless power transmitting device wirelessly transmits power to a wireless power receiving device. The wireless power transmitting device may be a charging puck, a charging mat, a portable electronic device with power transmitting capabilities, a removable battery case with power transmitting capabilities, or other power transmitter. The wireless power receiving device may be a device such as a cellular telephone, tablet computer, laptop computer, removable battery case, electronic device accessory, wearable such as a wrist watch, or other electronic equipment. The wireless power receiving device uses power from the wireless power transmitting device for powering the receiving device and for charging an internal battery. 
     Wireless power is transmitted from the wireless power transmitting device to the wireless power receiving device by using an inverter in the wireless power transmitting device to drive current through one or more wireless power transmitting coils. 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 (sometimes called a 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 processing user input, handling negotiations between devices  12  and  24 , sending and receiving in-band and out-of-band data, making measurements, estimating power losses, determining power transmission levels, and otherwise controlling the operation of system  8 . 
     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  and other data 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. 
     Power receiving device  24  may be a portable electronic device such as a cellular telephone, a laptop computer, a tablet computer, a wearable such as an earbud or wrist watch, a wirelessly charged removable battery case for an electronic device, 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 coil(s)  36 . These coil drive signals cause coil(s)  36  to transmit wireless power. Multiple 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, portable electronic device such as a cellular telephone, etc.) may have only a single wireless power transmission coil. In other arrangements, a wireless charging device may have multiple coils (e.g., two or more coils, 2-4 coils, 5-10 coils, at least 10 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 . The AC signals that are used in transmitting wireless power may have any suitable frequency (e.g., 100-400 kHz, etc.). 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 . Input-output devices  56  may include input devices for gathering user input and/or making environmental measurements and may include output devices for providing a user with output. As an example, input-output devices  56  may include a display, speaker, camera, touch sensor, ambient light sensor, and other devices for gathering user input, making sensor measurements, and/or providing user with output. Device  12  may include input-output devices  69  (e.g., any of the input-output devices described in connection with input-output devices  56 ). 
     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. 
     Control circuitry  16  has measurement circuitry  41 . Measurement circuitry  41  may include voltage measurement circuitry (e.g., for measuring one or more voltages in device  12  such as a coil voltage associated with a wireless power transmitting coil) and/or current measurement circuitry (e.g., for measuring one or more currents such as a wireless power transmitting coil current). Measurement circuitry  41  may be used, as an example, to determine an inductance and quality factor of coil  36 . 
     Control circuitry  30  has measurement circuitry  43 . Measurement circuitry  43  may include voltage measurement circuitry (e.g., for measuring one or more voltages in device  24  such as a coil voltage associated with a wireless power transmitting coil and/or a rectifier output voltage) and/or current measurement circuitry (e.g., for measuring one or more currents such as wireless power receiving coil current and/or rectifier output current). 
       FIG.  2    shows illustrative wireless power circuitry in system  8  in an illustrative scenario in which a wireless power transmitting device has been paired with a wireless power receiving device. The wireless power circuitry of  FIG.  2    includes wireless power transmitting circuitry  52  in wireless power transmitting device  12  and wireless power receiving circuitry  54  in wireless power receiving device  24 . During operation, wireless power signals  44  are transmitted by wireless power transmitting circuitry  52  and are received by wireless power receiving circuitry  54 . The configuration of  FIG.  2    includes a single transmitting coil  36  and a single receiving coil  48  (as an example). 
     As shown in  FIG.  2   , wireless power transmitting circuitry  52  includes inverter circuitry  61 . Inverter circuitry (inverter)  61  may be used to provide signals to coil  36 . During wireless power transmission, the control circuitry  16  of device  12  supplies signals to control input  82  of inverter  61  that cause inverter  61  to supply alternating-current drive signals to coil  36 . Circuit components such as capacitor  70  may be coupled in series with coil  36  as shown in  FIG.  2   . Measurement circuitry  41  in device  12  may make measurements on operating currents and voltages in device  12 . For example, current sensor  41 B may be used to measure the coil current through coil  36 . In other implementations, voltage across capacitor  70  is measured and current through the coil is inferred from that measurement. 
     As shown in  FIG.  2   , measurement circuitry  41  in device  12  may also include impulse response measurement circuitry  41 A. Impulse response measurement circuitry  41 A may be coupled to node N in wireless power transmitting circuitry  52 . Control circuitry  16  may use impulse response measurement circuitry  41 A to make measurements on the inductance (L) of coil  36  and quality factor (Q) of coil  36 . 
     When alternating-current current signals are supplied to coil  36 , corresponding alternating-current electromagnetic signals (wireless power signals  44 ) are transmitted to nearby coils such as illustrative coil  48  in wireless power receiving circuitry  54 . This induces a corresponding alternating-current (AC) current signal in coil  48 . Capacitors such as capacitors  72  may be coupled in series with coil  48 . Rectifier  50  receives the AC current from coil  48  and produces corresponding direct-current power (e.g., direct-current voltage Vrect) at output terminals  76 . This power may be used to power a load. Measurement circuitry  43  in device  24  may make measurements on operating currents and voltages in device  24 . For example, voltage sensor  43 A may measure Vrect (the output voltage of rectifier  50 ) or a voltage sensor may measure the coil voltage on coil  48 . Current sensor  43 B may measure the rectifier output current of rectifier  50  or a current sensor may measure the current of coil  48 . 
     If desired, some of the devices in wireless power system  8  may have both the ability to transmit wireless power signals and to receive wireless power signals. A cellular telephone or other portable electronic device may, as an example, have a single coil that can be used to receive wireless power signals from a charging puck or other wireless power transmitting device and that can also be used to transmit wireless power to another wireless power device (e.g., another cellular telephone, an accessory device, etc.). A device that can both transmit and receive wireless power may have all of the components of wireless power transmitting device  12  and all the components of wireless power receiving device  24  (e.g., power transmitting circuitry  52  and power receiving circuitry  54  are included in a single device). However, the functionality of the wireless power transmission and the wireless power reception is the same as described in connection with  FIGS.  1  and  2   . Therefore, although the examples herein will focus on a scenario where a dedicated wireless power transmitting device transfers charge to a dedicated wireless power receiving device, it should be understood that a device that both transmits and receives wireless power may be substituted for one or both devices. 
     During impulse response measurements, circuitry  16  uses impulse response measurement circuitry  41 A (sometimes referred to as inductance measurement circuitry and/or quality factor measurement circuitry) to perform measurements of inductance L and quality factor Q. Control circuitry  16  may obtain measurements with circuitry  41 A at regular intervals, in response to manual input, in response to wirelessly received commands, in response to information from one or more sensors within device  12 , etc. 
     During the impulse response measurements, control circuitry  16  directs inverter  61  to supply one or more excitation pulses (impulses) to coil  36 , so that the inductance L and capacitance of capacitor  70  in the wireless power transmitting circuitry  52  that includes that coil  36  form a resonant circuit. The impulses may be, for example, square wave pulses of 1 μs in duration. Longer or shorter pulses and/or pulses of other shapes may be applied, if desired. The resonant circuit resonates at a frequency near to the normal wireless charging frequency of coil  36  (e.g., about 120 kHz, 50-300 kHz, about 240 kHz, 100-500 kHz, more than 75 kHz, less than 400 kHz, or other suitable wireless charging frequency) or may resonate at other frequencies. 
     The impulse response (e.g., the voltage V(N) at node N) to the applied pulse(s) is as shown in  FIG.  3   . A voltage sensor in impulse response measurement circuitry  41 A may measure the voltage at node N after the excitation pulses are applied to coil  36 . The frequency of the impulse response signal of  FIG.  3    is proportional to 1/sqrt(LC), where L is the inductance of coil  36  and C is the capacitance of capacitor  70 . Therefore, L can be obtained from the known value of C and the measured frequency of the impulse response signal. Q may be derived from L and the measured decay of the impulse response signal. As shown in  FIG.  3   , if signal V(N) decays slowly, Q is high (e.g., HQ) and if signal V(N) decays more rapidly, Q is low (e.g., SQ). Measurement of the decay envelope of V(N) and frequency of V(N) of the impulse response signal of  FIG.  3    with circuitry  41 A will therefore allow control circuitry  16  to determine Q and L. 
     The values of quality factor and/or inductance determined by the impulse response measurement circuitry may be used to estimate the coupling coefficient (k) between the power transmitting coil  36  and the power receiving coil  48 . Information received from the wireless power receiving device (e.g., through in-band communication or out-of-band communication) may also be used to estimate the coupling coefficient if desired. 
     The inductance and quality factor determined by impulse response measurement circuitry  41 A, as well as the estimated coupling coefficient, may be used to determine the position of power receiving device  24  relative to power transmitting device  12 .  FIG.  4 A  is a top view of an illustrative wireless power system  8  showing how transmitting coil  36  may be laterally misaligned relative to receiver coil  48 . For optimal power transfer efficiency, it is desirable for the centers of coil  48  and  36  to be vertically aligned (e.g., aligned in the Z-direction). However, in some cases coils  48  and  36  may not be perfectly aligned when the power receiving device  24  is placed on the power transmitting device  12  (e.g., the centers of coils  36  and  48  may not overlap). As shown in  FIG.  4 A , receiver coil  48  may be shifted within the XY-plane relative to transmitter coil  36  by distance  84 . Because the magnitude of distance  84  impacts the properties of the wireless power transfer operations, it may be desirable for the wireless power system to know the magnitude of distance  84 . Distance  84  may be determined at least based on the inductance and quality factor determined by impulse measurement response circuitry  41 A. The estimated coupling coefficient may also be used to determine the magnitude of distance  84 . 
     Coil  36  may be formed within a plane that is parallel to the XY-plane. Coil  48  may also be formed within a plane that is parallel to the XY-plane. The lateral misalignment  84  may refer to the offset between coils  36  and  48  (e.g., the centers of the coils) in a direction that is parallel to the planes of coils  36  and  48 . 
     In addition to a lateral misalignment parallel to the XY-plane, receiving coil  48  may be separated from the power transmitting coil  36  by a variable gap height.  FIG.  4 B  is a cross-sectional side view of an illustrative wireless power system  8  showing how transmitting coil  36  may be separated from receiver coil  48  by gap  86 . For optimal power transfer efficiency, it is desirable for power receiving device  24  to be placed directly on power transmitting device  12 . In other words, a surface  92  (e.g., a rear surface) of power receiving device  24  directly contacts the charging surface  90  of power transmitting device  12 . In this arrangement, gap  86  (sometimes referred to as vertical gap  86  or distance  86 ) between coils  36  and  48  is at a minimum, resulting in a maximum power transfer efficiency. 
     However, in some cases distance  86  may be increased by the presence of an accessory such as a removable case  88  that is coupled to the power receiving device. When accessory  88  is coupled to power receiving device  24 , the accessory  88  is interposed between the power receiving device and the power transmitting device when the power receiving device is placed on charging surface  90 . The thickness of accessory  88  therefore increases the gap  86  between coils  36  and  48 . Because the magnitude of distance  86  impacts the properties of the wireless power transfer operations, it may be desirable for the wireless power system to know the magnitude of distance  86 . Distance  86  may be determined at least based on the inductance and quality factor determined by impulse measurement response circuitry  41 A. The estimated coupling coefficient may also be used to determine the magnitude of distance  86 . 
     Coil  36  may be formed within a first plane that is parallel to the XY-plane. Coil  48  may also be formed within a second plane that is parallel to the XY-plane. The gap  86  may refer to the distance between the first plane and the second plane in a direction that is orthogonal to the first and second planes. In other words, gap  86  defines the separation in the vertical direction (Z-direction) between the first and second planes. 
       FIG.  5    is a flowchart of illustrative operations for operating a wireless power transmitting device. The operations of  FIG.  5    may be performed by, for example, control circuitry  16  within power transmitting device  12 . During the operations of block  102 , measurement circuitry  41  such as impulse response measurement circuitry  41 A in  FIG.  2    may be used to measure the inductance and quality factor of coil  36 . As previously described in connection with  FIGS.  2  and  3   , measurement of the decay envelope and frequency of an impulse response signal may be measured using circuitry  41 A to determine inductance (L) and quality factor (Q). Also during the operations of block  102 , the control circuitry in power transmitting device  12  may estimate the coupling coefficient (k) using the information (e.g., measured inductance and/or quality factor) from impulse response measurement circuitry  41 A. 
     Next, during the operations of block  104 , control circuitry  16  may determine a position of the wireless power receiving device  24  relative to the wireless power transmitting device  12 . Control circuitry  16  may determine the position of wireless power receiving device  24  relative to power transmitting device  12  using the inductance measured during block  102 , the quality factor measured during block  102 , and/or the estimated coupling coefficient. 
     The position of power receiving device  24  relative to power transmitting device  12  may be characterized using one or more coordinates (e.g., x, y, and z coordinates). For example, a (0, 0) position for the (x, y) coordinates of wireless power receiving device  24  may be defined as the point where coils  36  and  48  have no lateral misalignment (e.g., the centers of coils  36  and  48  overlap in the Z-direction in  FIG.  4 A ). 
     The minimum vertical gap  86  between the coils may be greater than 0 (due to the thickness of the charging surface of the power transmitting device and/or the thickness of the rear housing wall of the power receiving device). The determined magnitude of the vertical gap may therefore be characterized in the z-coordinate in absolute terms (e.g., the actual distance between coils  36  and  48 ) or relative to the minimum distance (e.g., where the minimum distance is characterized as a vertical gap of 0 and larger distances are characterized as a vertical gap of actual distance minus minimum distance). 
     For example, the minimum distance  86  between coils  36  and  48  (e.g., when device  24  is placed directly on device  12 ) may be 3 millimeters. If a 2 millimeter thick accessory is interposed between devices  12  and  24 , the vertical gap may be characterized as 5 millimeters (in absolute terms) or 2 millimeters (relative to the minimum gap). Either convention is suitable for characterizing the position of the power receiving device. 
     The aforementioned example of using the center of coils  36  and  48  as a reference point for characterizing the coil position is merely illustrative. In some arrangements, coil  36  and/or  48  may have a non-circular arrangement. In general, any desired point of wireless power transmitting device  12  and/or wireless power receiving device  24  may be used to characterize the position of wireless power receiving device  24  relative to wireless power transmitting device  12 . 
     Moreover, the aforementioned example of using (x, y, z) coordinates to characterize the position of wireless power receiving device  24  relative to wireless power transmitting device  12  is merely illustrative. In another possible arrangement, the magnitude of lateral misalignment  84  may be used to characterize receiver position (e.g., without specifying the direction of the misalignment). The magnitude of the misalignment may be the key factor that determines the impact of the misalignment on wireless power transfer operations. Therefore, the direction of the misalignment vector may be omitted from the position characterization. In other words, a receiver coil  48  that is shifted by 2 millimeters in the positive X-direction may have a similar wireless charging performance to a receiver coil that is shifted by 2 millimeters in the negative X-direction. In both of these examples, the lateral misalignment can be represented simply using the magnitude 2 millimeters. This type of characterization of position may be represented using (r, z), where r is the magnitude of lateral misalignment and z is the magnitude of separation in the vertical direction (Z-direction). 
     An algorithm may be used to determine the position of the wireless power receiving device based on inductance and quality factor. In general, the vertical position of the wireless power receiving device may have a strong correlation with the measured coil inductance. Therefore, control circuitry  16  may determine the magnitude of the vertical gap based on the measured coil inductance. In general, the lateral misalignment of the wireless power receiving device may have a strong correlation with the measured coil quality factor. Therefore, control circuitry  16  may determine the lateral misalignment of the wireless power receiving device based on the measured coil quality factor. 
     In addition to using the measured inductance and quality factor to determine the position of the power receiving device, control circuitry  16  may use information from the wireless power receiving device. For example, each wireless power receiving device  24  may have expected inductance and quality factor values (and, optionally, coupling coefficients) for power transmitting coil  36  at a (0, 0, 0) position (e.g., without misalignment). This anchor point (known inductance, quality factor, and/or coupling coefficient values at a known position) may be used by control circuitry  16  to tune/scale an algorithm that determines the receiver position based on inductance and quality factor. Additional anchor points may be used to further improve the accuracy of control circuitry  16  in determining position based on inductance and quality factor. For example, each wireless power receiving device may have additional known inductance and quality factor values for power transmitting coil  36  at various misalignment positions (e.g., (0, 0, 1), (0, 0, 2), (1, 0, 0), etc.). 
     Wireless power receiving device  24  may indicate one or more anchor points to power transmitting device  12  using in-band communication or out-of-band communication. Alternatively, wireless power receiving device  24  may indicate its device type to power transmitting device  12  (e.g., using in-band communication or out-of-band communication). Power transmitting device  12  may have one or more anchor points stored in memory associated with various device types. For example, a first wireless power receiving device may indicate that it is a wrist watch device and a second wireless power receiving device may indicate that it is a cellular telephone. Power transmitting device  12  has one or more anchor points stored for the wrist watch device that are used to tune the position-determining algorithm when the power receiving device is indicated as a wrist watch device. Power transmitting device  12  also has one or more anchor points stored for the cellular telephone that are instead used to tune the position-determining algorithm when the power receiving device is indicated as a cellular telephone. 
     Next, during the operations of block  106 , control circuitry  16  may determine an expected power loss associated with power transmitting coil  36  based on the position of the wireless power receiving device determined in block  104 . Power loss refers to the amount of power that is lost during power transfer operations between coil  36  and  48 . Some amount of power loss may be expected in wireless power system  8 . However, the magnitude of the expected power loss may vary depending on the position of the wireless power receiving device  24  relative to wireless power transmitting device  12 . 
     Therefore, the position of the wireless power transmitting device  24  determined in block  104  may be used to obtain a higher accuracy estimate of the expected power loss in block  106  (than if the position information was unknown). In addition to using the position from block  104 , control circuitry  16  may determine an expected power loss in block  106  based on current information for the power transmitting coil  36 . For example, current sensor  41 B in  FIG.  2    may be used to monitor the current of coil  36  during power transfer operations. A characterization of the current such as the root mean square current may be used in addition to receiver position to determine the expected power loss. 
     In addition to using the position information and coil current information to determine expected power loss, control circuitry  16  may also receive information from power receiving device  24  that is used to estimate expected power loss. For example, power receiving device  24  may transmit rectifier voltage (e.g., from sensor  43 A in  FIG.  2   ), rectifier current (e.g., from sensor  43 B in  FIG.  2   ), or other information regarding power receiving circuitry  54  to device  12  (e.g., using in-band communication or out-of-band communication). Control circuitry  16  may use the information from the power receiving device  24  when determining the expected power loss. 
     Next, during the operations of block  108 , control circuitry  16  may perform power loss accounting to determine an actual power loss for the power transmitting coil  36 . During power loss accounting, control circuitry  16  in device  12  may receive information from device  24  (e.g., via in-band communication or out-of-band communication) indicating the amount of power that device  24  is wirelessly receiving. Device  24  may indicate to device  12  an amount of power that device  24  is receiving or may indicate other characterizations of device  24  that device  12  then uses to derive the amount of power that device  24  is receiving. The information received by control circuitry  16  that characterizes the amount of power that device  24  is receiving may be referred to as received power information. 
     In addition to having the received power information from device  24 , device  12  may also know how much power is actually being transmitted by coil  36 . Control circuitry  16  in wireless power transmitting device  12  may determine the actual transmitted power based on the magnitude of the signal being used to drive coil  36  from inverter  61 , based on the coil current measured by sensor  41 B (e.g., the root mean square current of coil  36 ), and/or using other information regarding wireless power transmitting circuitry  52 . 
     Ultimately, control circuitry  16  may compare the transmitted power (as determined using information regarding wireless power transmitting circuitry  52 ) to the received power (as indicated by wireless power receiving circuitry  54 ) to determine an actual power loss for coil  36 . As a specific example, the transmitted power for coil  36  may be 5.0 W and the received power for coil  48  in device  24  may be 4.5 W. In this case, there is 0.5 W of power loss associated with the power transmitted by coil  36 . 
     During the operations of block  110 , control circuitry  16  may take suitable action based on a difference between the expected power loss (from block  106 ) and the actual power loss (from block  108 ). The actual power loss being greater than the expected power loss (by more than a threshold amount) may, for example, indicate the presence of a foreign metal object between the wireless power transmitting device  12  and the wireless power receiving device  24 . If a foreign metal object is present between the wireless power transmitting device  12  and the wireless power receiving device  24 , control circuitry  16  may cease power transfer operations (e.g., stop transmitting wireless power signals) or reduce the rate of power transfer. 
     In some embodiments, when power transfer operations are ceased or reduced (e.g., because a foreign metal object is determined to likely be present), control circuitry  16  may generate an alert to notify the user. The alert may be, for example, a visual indication displayed on power receiving device  24  or an auditory output emitted by power receiving device  24 . For example, power transmitting device  12  may convey the alert to power receiving device  24  using in-band communication. Power receiving device  24  may then display a visual indication using a display, emit an auditory output using a speaker, or convey a tactile output using a haptic output device. Power receiving device  24  may convey these outputs using appropriate components, such as input-output devices  56  which may be display and/or audio components. Alternatively, or additionally, power transmitting device  12  may use one or more of input-output components  69  (e.g., a display, audio, or haptic component) to convey the alert to the user. 
     If the difference between the expected power loss and the actual power loss is high (e.g., greater than a first threshold), the power transfer rate may be reduced (and optionally ceased entirely). If the difference between the expected power loss and the actual power loss is low (e.g., lower than the first threshold), the power transfer rate may be increased or the power transfer operations may continue at the same rate. As a specific example, control circuitry  16  may use wireless power transmitting circuitry  52  in device  12  to transmit wireless power at 15 W to power receiving device  24 . If the difference between the expected power loss and the actual power loss is greater than the first threshold, the power transfer is ceased. If the difference between the expected power loss and the actual power loss is less than the first threshold, the power transfer may continue at 15 W or the power transfer rate may be increased to a second, higher rate (e.g., 20 W, 25 W, 30 W, etc.). The increased power transfer rate may be higher than the initial power transfer rate by at least 3 W, at least 5 W, at least 10 W, at least 15 W, etc. The higher power transfer rate may be greater than 15 W, greater than 20 W, greater than 25 W, greater than 30 W, etc. 
     Control circuitry  16  may compare the difference between the expected power loss and the actual power loss to one or more thresholds during the operations of block  110 . For example, a first threshold may be used to determine whether or not to cease power transfer. A second, lower threshold may be used to determine whether or not to increase the power transfer rate. For example, the first threshold may be 1.0 W and the second threshold may be 0.5 W. If the difference between the expected power loss and the actual power loss is greater than 1.0 W, power transfer operations may be ceased. If the difference between the expected power loss and the actual power loss is between 0.5 W and 1.0 W, power transfer operations may continue at the same rate. If difference between the expected power loss and the actual power loss is less than 0.5 W, the power transfer rate may be increased. The specific examples of thresholds used herein are merely illustrative. In general, any desired number of thresholds may be used and each threshold may have any desired magnitude. 
     Additional thresholds may be used to form more power loss zones, with each power loss zone corresponding to an acceptable maximum power transfer rate. For example, a first maximum power transfer rate may be used when the difference between expected power loss and actual power loss has a first magnitude, a second maximum power transfer rate (greater than the first maximum power transfer rate) may be used when the difference between expected power loss and actual power loss has a second magnitude (less than the first magnitude), a third maximum power transfer rate (greater than the second maximum power transfer rate) may be used when the difference between expected power loss and actual power loss has a third magnitude (less than the second magnitude), a fourth maximum power transfer rate (greater than the third maximum power transfer rate) may be used when the difference between expected power loss and actual power loss has a fourth magnitude (less than the third magnitude), and a fifth maximum power transfer rate (greater than the fourth maximum power transfer rate) may be used when the difference between expected power loss and actual power loss has a fifth magnitude (less than the fourth magnitude). In general, a lower difference between expected power loss and actual power loss may correlate to a greater maximum power transfer rate for the wireless power system. 
     It should be noted that, at the beginning of the operations of block  102 , power transmitting device  12  may be inductively coupled to power receiving device  24 . Power transmitting device  12  may transfer wireless power to power receiving device  24  at a given wireless power transfer rate before the operations of block  102 . In this case, the power transfer operations may be paused for the inductance and quality factor measurements of block  102 . Alternatively, the measurements of block  102  may be performed after power receiving device  24  is placed on power transmitting device  12  but before devices  12  and  24  enter a dedicated power transfer phase. 
     The example in  FIG.  5    of using the determined power loss of block  106  in a comparison with power loss determined using power loss accounting is merely illustrative. In general, control circuitry  16  determining the position of the wireless power receiving device relative to the wireless power transmitting device (based on inductance and quality factor) may have numerous advantages/applications. In addition to being used to estimate power loss (as in block  106 ), the position determined in block  104  may be used to adjust settings in wireless power transmitting circuitry  52  to enhance wireless power transfer operations. 
     Similarly, control circuitry  16  determining the expected power loss associated with the power transmitting coil in block  106  may have numerous advantages/applications in addition to determining the difference between the expected and actual power loss and taking suitable action as in block  110 . The expected power loss determined in block  106  may be used to adjust settings in wireless power transmitting circuitry  52  to enhance wireless power transfer operations. 
     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: 20220602
Publication Date: 20240227
Grant Date: 20240227
Priority Date: 20210916
Inventors: MALAN, Wynand
WANG, WENWEI
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 90014876