PATENT DOCUMENT

Publication Number: US-10608474-B2
Application Number: US-201815881336-A
Country: US
Kind Code: B2

Title: Wireless power system with power management

Abstract:
A wireless power receiving device may have wireless power receiving circuitry with a coil and rectifier. The wireless power receiving circuitry receives wireless power signals and uses the rectifier to supply a corresponding output. The output is characterized by a current, a voltage, and a power equal to a product of the current and voltage. The output of the rectifier is supplied to a direct-current-to-direct-current power regulator integrated circuit, which supplies direct-current power to a system load and battery. A controller integrated circuit directs the power regulator circuit to dither the current while monitoring for a peak in the power. If the power regulator circuit dithers the current satisfactorily, the wireless power receiving circuitry may be operated at the peak power. If the power regulator circuitry does not dither the current in response to being directed to dither the current, a wireless power transmission level may be reduced.

Claims:
What is claimed is: 
     
       1. A wireless power receiving device configured to receive wireless power signals transmitted from a wireless power transmitting device at a wireless power transmission level, comprising:
 wireless power receiving circuitry having a wireless power receiving coil, a rectifier coupled to the wireless power receiving coil, and regulator circuitry receiving a current and voltage from the rectifier, wherein a product of the current and voltage corresponds to a power; and 
 control circuitry configured to direct the regulator circuitry to adjust the current while monitoring for a peak in the power. 
 
     
     
       2. The wireless power receiving device of  claim 1  wherein the control circuitry is configured to:
 upon determining that the regulator has not adjusted the current as requested, send a request to the wireless power transmitting device to decrease the wireless power transmission level. 
 
     
     
       3. The wireless power receiving device of  claim 1  wherein the control circuitry is configured to operate the regulator circuitry at an operating point associated with the peak in the power. 
     
     
       4. The wireless power receiving device of  claim 1  wherein the control circuitry is further configured to:
 periodically adjust a target power value for the power; 
 compare the power to the target power value; and 
 send corresponding requests to the wireless power transmitting device that cause the wireless power transmitting device to adjust the wireless power transmission level to maintain the power at the target power value. 
 
     
     
       5. The wireless power receiving device of  claim 1  further comprising:
 measurement circuitry configured to measure the current and voltage. 
 
     
     
       6. The wireless power receiving device of  claim 1  wherein the control circuitry includes a controller integrated circuit coupled to the regulator circuitry. 
     
     
       7. The wireless power receiving device of  claim 6  wherein the regulator circuitry comprises a direct-current-to-direct-current power converter integrated circuit and wherein the rectifier forms part of a rectifier integrated circuit. 
     
     
       8. The wireless power receiving device of  claim 1  wherein the regulator circuitry comprises a direct-current-to-direct-current power converter integrated circuit, the wireless power receiving device further comprising a battery configured to receive power from the direct-current-to-direct-current power converter integrated circuit. 
     
     
       9. A wireless power receiving device, comprising:
 a coil; 
 a rectifier that receive wireless power signals using the coil and produces a corresponding output characterized by a current and voltage; 
 a regulator circuit that receives the output; and 
 control circuitry configured to identify a peak in a power value determined from a product of the current and the voltage by controlling the regulator circuit to adjust the output while the rectifier and coil receive the wireless power signals. 
 
     
     
       10. The wireless power receiving circuit of  claim 9  wherein the control circuitry is further configured to send wireless power transmission level adjustment requests to a wireless power transmitting device. 
     
     
       11. The wireless power receiving circuit of  claim 10  wherein the control circuitry is further configured to send the wireless power transmission level adjustment requests using in-band amplitude-shift-keying communications. 
     
     
       12. The wireless power receiving circuit of  claim 11  wherein the control circuitry is configured to identify the peak by controlling the regulator circuit to dither the current while the rectifier receives the wireless power signals. 
     
     
       13. The wireless power receiving circuit of  claim 12  wherein the control circuitry is configured to send a request to the wireless power transmitting device to decrease a wireless power transmission level upon determining that dithering of the current has failed. 
     
     
       14. The wireless power receiving device of  claim 13  wherein the control circuitry is configured to operate the regulator circuitry at an operating point associated with the peak in the power upon determining that the dithering of the current has not failed. 
     
     
       15. The wireless power receiving device of  claim 14  wherein the control circuitry is further configured to:
 periodically adjust a target power value for the power value; and 
 send requests to the wireless power transmitting device that cause the wireless power transmitting device to adjust the wireless power transmission level to maintain the power value at the target power value. 
 
     
     
       16. The wireless power receiving device of  claim 9  further comprising a battery configured to receive power from the regulator circuit. 
     
     
       17. The wireless power receiving device of  claim 16  wherein the regulator circuit comprises a direct-current-to-direct-current power converter integrated circuit. 
     
     
       18. A wireless power receiving device configured to receive wireless power signals transmitted from a wireless power transmitting device, comprising:
 wireless power receiving circuitry having a wireless power receiving coil, a rectifier coupled to the wireless power receiving coil, and a direct-current-to-direct-current power regulator integrated circuit receiving an output from the rectifier, wherein the output is characterized by a current, a voltage, and a power equal to a product of the current and the voltage; and 
 control circuitry configured to direct the direct-current-to-direct-current power regulator integrated circuit to adjust the current up and down while monitoring for a peak in the power. 
 
     
     
       19. The wireless power receiving device of  claim 18  wherein the wireless power transmitting device is configured to transmit the wireless power signals at a wireless power transmission level and wherein the control circuitry is configured to:
 send a request to the wireless power transmitting device to decrease the wireless power transmission level upon determining that the direct-current-to-direct-current power regulator integrated circuit failed to adjust the current up and down as directed by the control circuitry. 
 
     
     
       20. The wireless power receiving device of  claim 19  wherein the control circuitry is configured to:
 operate the direct-current-to-direct-current power regulator integrated circuit at an operating point associated with the peak in the power when the direct-current-to-direct-current power regulator integrated circuit adjusts the current up and down as directed by the control circuitry.

Description:
This application claims the benefit of provisional patent application No. 62/552,990, filed Aug. 31, 2017, 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 charging mat wirelessly transmits power to a portable electronic device that is placed on the mat. The portable electronic device has a receiving coil and rectifier circuitry for receiving wireless alternating-current (AC) power from a coil in the wireless charging mat that is overlapped by the receiving coil. The rectifier converts the received AC power into direct-current (DC) power. 
     SUMMARY 
     A wireless power system may use a wireless power transmitting device to transmit wireless power to a wireless power receiving device. The wireless power transmitting device may transmit wireless power signals at a wireless power transmission level. Wireless power receiving circuitry in the wireless power receiving device may be used to receive the wireless power signals. 
     The wireless power receiving circuitry may have a coil and a rectifier. The wireless power receiving circuitry receives the wireless power signals and produces a corresponding current and voltage at the output of the rectifier. The power at the output of the rectifier is equal to the product of the current and the voltage at the output of the rectifier. The voltage at the output of the rectifier is supplied to a direct-current-to-direct-current power regulator integrated circuit, which supplies a corresponding regulated voltage to a system load and battery. 
     During operation, a controller integrated circuit directs the power regulator circuit to dither the current while monitoring the power to detect a peak in the power. If the power regulator circuit dithers the current satisfactorily, the wireless power receiving circuitry may be operated at the peak power. If the power regulator circuitry does not dither the current in response to being directed to dither the current, the wireless power transmission level may be reduced. For example, the wireless power receiver may send an in-band amplitude-shift-keying request to the wireless power transmitting device that directs the wireless power transmitting device to reduce the wireless power transmission level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG. 2  is a circuit diagram of illustrative wireless power transmitting circuitry and illustrative wireless power receiving circuitry in accordance with an embodiment. 
         FIG. 3  is a top view of an illustrative wireless power transmitting device in accordance with an embodiment. 
         FIG. 4  is a top view of an illustrative lower layer of eight coils for the wireless power transmitting device of  FIG. 3  in accordance with an embodiment. 
         FIG. 5  is a top view of an illustrative middle layer of seven coils for the wireless power transmitting device of  FIG. 3  in accordance with an embodiment. 
         FIG. 6  is a top view of an illustrative upper layer of seven coils for the wireless power transmitting device of  FIG. 3  in accordance with an embodiment. 
         FIG. 7  is a diagram of illustrative circuitry in a wireless power receiving device in accordance with an embodiment. 
         FIG. 8  is a graph of an illustrative voltage versus current characteristic for a wireless charging system in accordance with an embodiment. 
         FIG. 9  is a graph of an illustrative power versus current characteristic for a wireless charging system in accordance with an embodiment. 
         FIG. 10  is a diagram of illustrative operations involved in using a wireless charging system in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system has 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. 
     The wireless power transmitting device has wireless power transmitting coils arranged under a charging surface. During operation, the wireless power transmitting coils are used to transmit wireless power signals that are received by a wireless power receiving coil in the wireless power receiving device. Wireless power signals are transmitted at a wireless power transmission frequency such as a frequency of about 128 kHz, frequencies in a range between 100 kHz and 200 kHz, or other suitable frequency. 
     To ensure that the amount of power that is transmitted between the wireless power transmitting device and the wireless power receiving device is satisfactory, power transmission may be regulated dynamically. For example, a wireless power receiving device may periodically send wireless power level adjustment requests to the wireless power transmitting device. These requests may direct the wireless power transmitting device to increase or decrease the amount of wireless power being transmitted. The wireless power receiving device may also make internal adjustments to search for satisfactory operating conditions. 
     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 includes 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 determining power transmission levels, processing sensor data, processing user input, handling communications between devices  12  and  24  (e.g., sending and receiving in-band and out-of-band data), selecting wireless power transmitting coils, and otherwise controlling the operation of system  8 . If desired, control circuitry in system  8  may be used to authorize components to use power and ensure that components do not exceed maximum allowable power consumption levels. 
     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), digital signal processing circuits, baseband processors, power management units with processing circuitry, microcontrollers, and other processing circuitry. 
     Power transmitting device  12  may be a stand-alone power adapter (e.g., a wireless charging mat that includes power adapter circuitry), may be a wireless charging mat that receives power from a power adapter or other equipment using a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, or may be other wireless power transfer equipment. Illustrative configurations in which wireless power transmitting device  12  is a wireless charging mat may sometimes be 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, or other electronic equipment. Power transmitting device  12  may receive power from a wall outlet (e.g., alternating current), may have a battery for supplying power, and/or may have another source of power. Power transmitting device  12  may have an AC-DC power converter such as 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  may use 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  60  formed from transistors) that is turned on and off at an alternating-current wireless power transmission frequency based on control signals provided by control circuitry  16 . This creates AC current signals through one or more coils  42 . Coils  42  may be arranged in a planar coil array (e.g., in configurations in which device  12  is a wireless charging mat). 
     As AC currents pass through one or more coils  42 , alternating-current electromagnetic fields (signals  44 ) are produced that are received by one or more corresponding coils such as coil  48  in power receiving device  24 . When the alternating-current electromagnetic fields are received by coil  48 , corresponding alternating-current currents are induced in coil  48 . Rectifier circuitry such as rectifier  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 coil  48  into DC voltage signals for powering device  24 . 
     The DC voltages produced by rectifier  50  can be used in powering 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, and other components and these components may be powered by the DC voltages produced by rectifier  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 . 
     Wireless transceiver circuitry  40  uses one or more coils  42  to transmit in-band signals to wireless transceiver circuitry  46  that are received by wireless transceiver circuitry  46  using coil  48 . Any suitable modulation scheme may be used to support in-band communications between device  12  and device  24 . In some configurations, 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 is conveyed wirelessly from device  12  to device  24  during these FSK and ASK transmissions. 
     During wireless power transmission operations, circuitry  52  supplies AC drive signals to one or more coils  42  at a given power transmission frequency. The power transmission frequency may be, for example, a predetermined frequency of about 128 kHz, at least 80 kHz, at least 100 kHz, less than 500 kHz, less than 300 kHz, less than 200 kHz, 100-200 kHz, 50-200 kHz, 100-200 kHz, or other suitable wireless power frequency. In some configurations device  12  varies the power transmission frequency during operation. 
     In configurations that support FSK in-band communications, wireless transceiver circuitry  40  uses FSK modulation to modulate the power transmission frequency of the driving AC signals that device  12  is using to transmit wireless power and thereby modulates the frequency of signals  44 . In device  24 , coil  48  is used to receive signals  44 . Power receiving circuitry  54  uses the received signals on coil  48  and rectifier  50  to produce DC power. At the same time, wireless transceiver circuitry  46  uses FSK demodulation to extract the transmitted in-band data from signals  44 . This approach allows FSK data (e.g., FSK data packets) to be transmitted in-band from device  12  to device  24  with coils  42  and  48  while power is simultaneously being wirelessly conveyed from device  12  to device  24  using coils  42  and  48 . 
     In configurations that support ASK in-band communications wireless transceiver circuitry  46  transmits in-band data to device  12  by using a switch (e.g., one or more transistors in transceiver  46  that are connected to coil  48 ) to modulate the impedance of power receiving circuitry  54  (e.g., coil  48 ). This, in turn, modulates the amplitude of signal  44  and the amplitude of the AC signal passing through coil(s)  42 . Wireless transceiver circuitry  40  monitors the amplitude of the AC signal passing through coil(s)  42  and, using ASK demodulation, extracts the transmitted in-band data from these signals that was transmitted by wireless transceiver circuitry  46 . The use of ASK communications allows ASK data bits (e.g., ASK data packets) to be transmitted in-band from device  24  to device  12  with coils  48  and  42  while power is simultaneously being wirelessly conveyed from device  12  to device  24  using coils  42  and  48 . 
     Control circuitry  16  has external object measurement circuitry  41  (sometimes referred to as foreign object detection circuitry or external object detection circuitry) that detects external objects on a charging surface associated with device  12 . 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 . Control circuitry  30  has measurement circuitry  43 . Measurement circuitry  41  and  43  may be used in making inductance measurements (e.g., measurements of the inductances of coils  42  and  48 ), input and output voltage measurements (e.g., a rectifier output voltage, and inverter input voltage, etc.), current measurements, capacitance measurements, frequency measurements (e.g., measurements of the frequency of wireless power signals), and/or other measurements on the circuitry of system  8 . Illustrative circuitry of the type that may be used for forming power transmitting circuitry  52  and power receiving circuitry  54  of  FIG. 1  is shown in  FIG. 2 . 
     As shown in  FIG. 2 , power transmitting circuitry  52  may include drive circuitry such as inverters  60  that supply drive signals at the wireless power transmission frequency to respective wireless power transmitter resonant circuits. Each wireless power transmitter resonant circuit may include a wireless power transmitting coil  42  and capacitor  70 . Rectifier  50  in wireless power receiving circuitry  54  receives wireless power signals using a wireless power receiver resonant circuit that includes capacitor  74  and wireless power receiving coil  48 . 
     Inverters  60  have metal-oxide-semiconductor transistors or other suitable transistors that are modulated by AC control signals from control circuitry  16  ( FIG. 1 ) that are received on respective control signal inputs  62 . The attributes of each AC control signal (e.g., duty cycle, frequency, etc.) may be adjusted by control circuitry  16  dynamically during power transmission to control the amount of power being transmitted by power transmitting coils  42 . 
     When transmitting wireless power, control circuitry  16  ( FIG. 1 ) selects one or more appropriate coils  42  to use in transmitting signals  44  to coil  48  (e.g., control circuitry  16  supplies control signals to the inputs  62  of the inverters  60  that are to drive the selected coils to produce signals  44 ). Coil  48  and capacitor  74  form a resonant circuit in circuitry  54  that receives signals  44 . Receiver  50  rectifies the received signals and provides direct-current output power at output  68 . 
     A top view of an illustrative configuration for device  12  in which device  12  has an array of coils  42  is shown in  FIG. 3 . Device  12  may, in general, have any suitable number of coils  42  (e.g., 22 coils, at least 5 coils, at least 10 coils, at least 15 coils, fewer than 30 coils, fewer than 50 coils, etc.). Coils  42  may be arranged in rows and columns and may or may not partially overlap each other. In the example of  FIG. 3 , coils  42  partially overlap each other and arranged in three layers. 
     Device  12  may have a housing  78  (e.g., a housing formed from plastic or other materials) that forms a planar housing surface that covers coils  42  (sometimes referred to as a charging surface). One or more wireless power receiving devices such as device  24  may be positioned on the charging surface to receive wireless power from coils  42 . Coils  42  may be circular or may have other suitable shapes (e.g., coils  42  may be square, may have hexagonal shapes, may have other shapes having rotational symmetry, etc.). In the illustrative configuration of  FIG. 3 , coils  42  are circular and are formed from multiple wire turns (e.g., multiple turns formed from metal traces, bare wire, insulated wire, wire monofilaments, multifilament wire, etc.). 
       FIGS. 4, 5, and 6  are diagrams of illustrative layers of coils  42  in a wireless power transmitting device such as a charging mat having 22 coils in three layers. 
       FIG. 4  is a top view of an illustrative configuration for a lower layer  84  having eight coils  42  in wireless power transmitting device  12  of  FIG. 3 .  FIG. 5  is a top view of an illustrative configuration for a middle layer  82  having seven coils  42  for wireless power transmitting device  12  of  FIG. 3 .  FIG. 6  is a top view of an illustrative configuration for an upper layer  80  having seven coils for wireless power transmitting device  12  of  FIG. 3 . In this example, lower layer  84  has 8 coils, middle layer  82  has 7 coils, and upper layer  80  has 7 coils. In general, each layer may have any suitable number of coils (e.g., at least 2 coils, at least 5 coils, fewer than 9 coils, fewer than 14 coils, 6-9 coils, etc.). Device  12  may have one layer of coils  42 , at least two layers of coils  42 , at least three layers of coils  42 , at least four layers of coils  42 , fewer than five layers of coils  42 , 4-6 layers of coils, etc. Configurations in which device  12  has only a single coil  42  may also be used. 
       FIG. 7  is a circuit diagram of illustrative wireless power circuitry for device  24 . In the example of  FIG. 7 , wireless power receiving circuitry  45  includes rectifier circuitry (e.g., rectifier  50 ) that is implemented in integrated circuit  90 . Integrated circuit  90  may also include control circuitry such as control circuit  96  to facilitate communications with other circuitry in device  24 . Rectifier  50  of integrated circuit supplies an output to integrated circuit  92 . The output is characterized by a current, a voltage, and a power equal to the product of the current and voltage. 
     During operation, rectifier output current I and rectifier output voltage V are received by integrated circuit  92 , which implements a direct-current-to-direct-current (DC-DC) power converter such as a buck converter (sometimes referred to as a voltage regulator or regulator circuit). Regulator integrated circuit  92  receives unregulated voltage V at its input and supplies a regulated voltage output. The output of the DC-DC converter of integrated circuit  92  is supplied to system load  100  (e.g., a display, application processor, sensors, input-output components, communications circuitry, etc.) and is supplied to battery  58  to charge battery  58 . 
     Control circuitry such as controller  94  may be used in controlling the operation of integrated circuits  90  and  92 . Controller  94  may be formed using an integrated circuit that is separate from integrated circuits  90  and  92  and/or the circuitry of integrated circuits  90 ,  92 , and/or  94  may be implemented using one integrated circuit, two integrated circuits, or more than three integrated circuits. The example of  FIG. 7  is merely illustrative. 
     During operation, rectifier  50  may receive AC wireless power signals from coil  48  and may supply corresponding DC output power (I, V) to regulator integrated circuit  92 . The voltage V may, as an example, range between 4 V and 12 V or other suitable voltage range. The output of regulator integrated circuit  92  may be regulated to 4 V (as an example). 
     The amount of power delivered by coil  48  and rectifier  50  (e.g., the product of I and V) may vary in accordance with the IV characteristic of  FIG. 8  and the power-versus-current characteristic of  FIG. 9 . Curves  102 ,  104 , and  106  of  FIG. 8  represent the IV characteristics of coil  48  and rectifier  50  under various different power delivery scenarios. Curve  102  corresponds to the IV characteristic when wireless power transmitting device  12  is transmitting a first amount of power, curve  104  corresponds to the IV characteristic when wireless power transmitting device  12  is transmitting a second amount of power that is less than the first amount of power, and curve  106  is an illustrative IV characteristic associated with a scenario in which wireless power transmitting device  12  is transmitting a third amount of power that is less than the first and second amounts of power. 
     Power versus current curve  110  of  FIG. 9  corresponds to the IV characteristic and wireless power transmission scenario of curve  102  of  FIG. 8 , power versus current curve  112  of  FIG. 9  corresponds to the IV characteristic and wireless power transmission scenario of curve  104  of  FIG. 8 , and power versus current curve  114  of  FIG. 9  corresponds to the IV characteristic and wireless power transmission scenario of curve  106  of  FIG. 8 . An illustrative operating point associated with operation of system  8  in a scenario in which device  12  is transmitting the first amount of power is shown by point  108  on curve  102  and point  116  on curve  110 . 
     During operation, device  24  may require varying amounts of power. For example, if battery  58  is uncharged and the temperature of device  24  is low (e.g., room temperature), device  24  may be capable of accepting a first amount of power (e.g., 4.5 W). If, however, battery  58  is at an elevated temperature (e.g., above 35° C. where battery charging is not permitted) and/or battery  58  is full, device  24  may only be capable of accepting a second amount of power (e.g., 2 W) that is less than the first amount of power. 
     To ensure that an appropriate amount of power is transmitted from device  12  to device  24 , device  24  can implement a target power control loop (sometimes referred to as a receiver power loop) in which device  24  periodically uses ASK in-band communications or other suitable wireless communications to send wireless power transmission level adjustment requests to dynamically adjust a target power delivery value (e.g., the amount of wireless power transmitted by device  12  to device  24 ). These adjustments to the amount of wireless power transmission (e.g., adjustments to a target amount of delivered power Ptarget) may be made dynamically during operation of device  24 . 
     At each different target power level, device  12  may adjust the operation of wireless power transmitting circuitry  52  to ensure that wireless power Ptarget is satisfactorily delivered. For example, if the amount of power delivered is below Ptarget, device  12  can adjust the duty cycle and/or other attributes of the wireless power signal (e.g., wireless power transmission frequency, etc.) being used by circuitry  52  to ensure that the power delivered rises to Ptarget. 
     To ensure that device  24  is operating efficiently, control circuitry  30  (e.g., controller  94 ) may adjust integrated circuit (regulator)  92  to adjust the current I while computing the output power P (P=I*V) of rectifier  59 . Current I may be adjusted by adjusting a current limit value (sometimes referred to as Ilim) associated with the current flowing into integrated circuit  92  from integrated circuit  90 . By adjusting integrated circuit  92  so that the current flowing into integrated circuit  92  goes up and down in magnitude (dithering the current), resulting variations in P can be observed and the current associated with the peak (maximum) P value can be identified and used. In this way, device  24  may continually hunt for peak power conditions (operating point  116  of  FIG. 9 ) to enhance efficiency. 
     Controller  94  can monitor the response of integrated circuit  92  to the commands provided from controller  94  to dither current I. In some circumstances, current dithering operations may fail. For example, integrated circuit  92  may be configured to prevent the value of V from falling below the voltage of battery  58 . If an attempted dithering of current I runs against this limit, dithering will fail (e.g., integrated circuit  92  will not dither the current as requested by controller  94  and may, if desired, set a flag bit accordingly within its memory that controller  94  can detect). When a failure of current dithering is detected, device  24  can conclude that excess power is being transmitted from device  12  (e.g., the operating point of device  24  is to the left of illustrative maximum efficiency operating point  116  on curve  110  of  FIG. 9 ), and can therefore send device  12  a request to decrease the wireless power transmission level. This lowers the power-versus-current curve (e.g., to curve  114  of  FIG. 9 ) and allows dithering (and peak power searching) to resume. 
       FIG. 10  shows illustrative control loops that may be implemented in system  8  to perform these operations. 
     During the operation of current limit loop  118 , controller  94  may direct integrated circuit  92  to dither current I (e.g., by adjusting him up and down about its present operating point). As current I is dithered, power P (e.g., I*V) may be measured and monitored for a peak power. Current I and voltage V (and P) may be measured using measurement circuitry  43  (e.g., current and voltage sensors in wireless power receiver circuitry such as integrated circuits  90  and/or  92 ). The operating current setting (e.g., the value of current I) may be updated to the current associated with the identified peak power operating point. To ensure that the identified peak power operating point is valid (e.g., to confirm that a peak power has been satisfactorily reached), controller  94  may check to determine whether dithering operations are being performed satisfactorily without failing. Dithering operations can take place at any suitable frequency (e.g., 5 Hz). If desired, other operational settings may be dithered instead of or in addition to dithering current I. For example, the duty cycle of field-effect transistors in the regulator circuitry of integrated circuit  92  may be adjusted to dither the load imposed by integrated circuit  92  (and/or I and/or V). 
     During the operations of transmit power loop  120 , wireless power level adjustment requests are periodically sent to device  12  (e.g., at 0.5 Hz or other suitable frequency), so that a desired target wireless power level Ptarget is maintained. If, for example, control circuitry  30  determines that the level of wireless power being transmitted from device  12  is too low, control circuitry  30  may send an in-band ASK request(s) to device  12  to direct device  12  to increase its wireless power transmission level to Ptarget. 
     During the operation receiver power control loop  122 , device  24  may periodically make adjustments to Ptarget. If as an example, control circuitry  30  determines that wireless power transmitting device  12  has high power capabilities, control circuitry  30  may request that device  12  transmit 7.5 W of power to device  24  (e.g., Ptarget may be set to 7.5 W). As another example, during camera operations with a camera in input-output devices  56 , there may be a potential for wireless power interference with wireless power signals transmitted from device  12 , so control circuitry  30  can direct wireless power transmitting device  12  to reduce the power level of the wireless power signals transmitted to device  24  (e.g., Ptarget may be set to 1 W). The operations of loop  122  may be performed at any suitable frequency (e.g., 0.5 Hz, less than 0.5 Hz, or more than 0.5 Hz). 
     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: 20180126
Publication Date: 20200331
Grant Date: 20200331
Priority Date: 20170831
Inventors: SCHAEVITZ, SAMUEL B.
TOLVA, CORTLAND S.
WALKER, JAMES R.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04L27/14", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L27/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L27/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/248", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L27/14", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/0081", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L27/14", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L27/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/248", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65437813