PATENT DOCUMENT

Publication Number: US-10594170-B2
Application Number: US-201815882651-A
Country: US
Kind Code: B2

Title: Wireless power system with interference avoidance

Abstract:
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 at a wireless power transmission frequency. Wireless power signals at the wireless power transmission frequency can create interference with a sensitive electrical component in the wireless power receiving device when the wireless power transmission frequency lies in a sensitive frequency band associated with the component. Measurement circuitry in the wireless power receiving device can measure the wireless power transmission frequency. In response to determining that the wireless power transmission frequency lies in a sensitive frequency band, the wireless power receiving device may send an in-band wireless power level adjustment request to the wireless power transmitting device. The request causes a frequency adjustment that moves the wireless power transmission frequency out of the sensitive band.

Claims:
What is claimed is: 
     
       1. A wireless power receiving device configured to receive wireless power signals transmitted from a wireless power transmitting device, the wireless power receiving device comprising:
 wireless power receiving circuitry having a wireless power receiving coil and rectifier circuitry coupled to the wireless power receiving coil; 
 wireless power transmission frequency measurement circuitry configured to measure the frequency of a wireless power signal received at the wireless power receiving coil; 
 an electrical component that is sensitive to wireless transmission at a sensitive frequency band; and 
 control circuitry configured to:
 determine whether the frequency of the wireless power signal received at the wireless power receiving coil overlaps the sensitive frequency band; and 
 upon determining that the frequency of the wireless power signal received at the wireless power receiving coil overlaps the sensitive frequency band, send a wireless power level adjustment request to the wireless power transmitting device. 
 
 
     
     
       2. The wireless power transmitting device of  claim 1  wherein the control circuitry is configured to determine whether the wireless power level adjustment request includes a request for an increase or for a decrease in wireless power transmission from the wireless power transmitting device. 
     
     
       3. The wireless power transmitting device of  claim 1  wherein the wireless power level adjustment request is associated with a request for an amount of wireless power level change and wherein the control circuitry is configured to determine the amount of wireless power level change based at least partly on a size of the sensitive frequency band. 
     
     
       4. The wireless power transmitting device of  claim 1  wherein the wireless power level adjustment request is associated with a request for an amount of wireless power level change and wherein the control circuitry is configured to determine the amount of wireless power level change based at least partly on the frequency of the wireless power signal received at the wireless power receiving coil. 
     
     
       5. The wireless power receiving device of  claim 1  wherein the control circuitry is configured to at least temporarily disable sending of wireless power adjustment requests in response to determining that the wireless power level adjustment request resulted in no change in the wireless power transmission frequency. 
     
     
       6. The wireless power receiving device of  claim 5 , wherein the control circuitry is configured to cause a change in operation of the electrical component, in response to determining that the wireless power level adjustment request resulted in no change in the frequency of the wireless power signal received at the wireless power receiving coil. 
     
     
       7. The wireless power receiving device of  claim 1  wherein the electrical component comprises a display. 
     
     
       8. The wireless power receiving device of  claim 1  wherein the electrical component comprises a touch sensor. 
     
     
       9. The wireless power receiving device of  claim 1  wherein the electrical component comprises an image sensor. 
     
     
       10. The wireless power receiving device of  claim 1  wherein the electrical component comprises a force sensor. 
     
     
       11. The wireless power receiving device of  claim 1  wherein the control circuitry comprises in-band transmitter circuitry configured to send the wireless power level adjustment request to the wireless power transmitting device. 
     
     
       12. The wireless power receiving device of  claim 11  wherein the in-band transmitter circuitry comprises an amplitude-shift-keying in-band transmitter. 
     
     
       13. A wireless power receiving device, comprising:
 wireless power receiving circuitry configured to receive wireless power signals at a wireless power transmission frequency; and 
 control circuitry configured to transmit a wireless power transmission level adjustment request based on determining that the wireless power transmission frequency lies in a sensitive frequency band. 
 
     
     
       14. The wireless power receiving device of  claim 13  wherein the control circuitry comprises an amplitude-shift-keying transmitter configured to send the wireless power transmission level adjustment request. 
     
     
       15. The wireless power receiving device of  claim 13  further comprising a display, wherein the sensitive frequency band is associated with interference between the wireless power signals at a wireless power transmission frequency in the sensitive frequency band and operation of the display. 
     
     
       16. The wireless power receiving device of  claim 13  further comprising a touch sensor, wherein the sensitive frequency band is associated with interference between the wireless power signals at a wireless power transmission frequency in the sensitive frequency band and touch detection by the touch sensor. 
     
     
       17. The wireless power receiving device of  claim 13  further comprising a sensor, wherein the sensitive frequency band is associated with interference between the wireless power signals at a wireless power transmission frequency in the sensitive frequency band and operation of the sensor. 
     
     
       18. The wireless power receiving device of  claim 17  wherein the sensor comprises an image sensor. 
     
     
       19. The wireless power receiving device of  claim 17  wherein the sensor comprises a force sensor. 
     
     
       20. The wireless power receiving device of  claim 13  wherein the wireless power receiving circuitry comprises a wireless power receiving coil and rectifier circuitry coupled to the wireless power receiving coil. 
     
     
       21. The wireless power receiving device of  claim 13  further comprising:
 wireless power transmission frequency measurement circuitry configured to detect a frequency of wireless power signals at the wireless power receiving coil. 
 
     
     
       22. A wireless power receiving device configured to receive wireless power signals transmitted from a wireless power transmitting device at a wireless power transmission frequency, comprising:
 wireless power receiving circuitry configured to receive the wireless power signals, the wireless power receiving circuitry comprising a wireless power receiving coil; 
 circuitry configured to detect wireless power signals of the wireless power transmission frequency at the wireless power receiving coil; 
 control circuitry configured to:
 determine whether the measured wireless power transmission frequency lies within a sensitive frequency band; and 
 upon determining that the measured wireless power transmission frequency lies within the sensitive frequency band, sending a wireless power level adjustment request to the wireless power transmitting device that causes the wireless power transmitting device to adjust a power level associated with the wireless power signals and that causes the wireless power transmitting device to adjust the wireless power transmission frequency out of the sensitive frequency band. 
 
 
     
     
       23. The wireless power receiving device of  claim 22  further comprising:
 an electrical component subject to interference in the presence of wireless power signals in the sensitive frequency band. 
 
     
     
       24. The wireless power receiving device of  claim 23  wherein the electrical component comprises a component selected from the group consisting of: a display, a touch sensor, and an image sensor.

Description:
This application claims the benefit of provisional patent application No. 62/551,711, filed on Aug. 29, 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 the wireless power at a wireless power transmission frequency. Wireless power signals at the wireless power transmission frequency can create interference when the wireless power transmission frequency lies in a sensitive frequency band associated with the sensitive electrical component. The sensitive electrical component may be, for example, an image sensor, a touch sensor, a force sensor, or a display. 
     Measurement circuitry in the wireless power receiving device can measure the wireless power transmission frequency. In response to determining that the wireless power transmission frequency lies in a sensitive frequency band, the wireless power receiving device may send an in-band wireless power level adjustment request to the wireless power transmitting device. The request directs the wireless power transmitting device to adjust a wireless power transmission level associated with the transmitted wireless power and indirectly causes the wireless power transmitting device to adjust the frequency of the wireless power signals to avoid the sensitive frequency band. 
    
    
     
       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 graph of an illustrative relationship between wireless power transmission level and wireless power transmission frequency for a wireless power transmitting device in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative operations involved in transmitting wireless power in a wireless power system while avoiding sensitive frequency bands associated with electrical components in a wireless power receiving device 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. In some examples, a wireless power receiving device periodically sends wireless power level adjustment requests to the wireless power transmitting device. These requests direct the wireless power transmitting device to increase or decrease the amount of wireless power being transmitted. In some examples, the wireless power transmitting device changes the wireless power transmission frequency as part of adjusting the wireless power transmission level in the wireless power system. In some embodiments, a wireless power receiving device leverages this ability to affect the wireless power transmission frequency via wireless power adjustment level requests to help avoid undesired interference between the wireless power signals and sensitive circuitry in the wireless power receiving device. 
     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, force 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 embodiments, 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 power transmission frequency based on the power requirements of device  24 . In some configurations, the device  12  transmits power at a fixed power transmission frequency, or a frequency that is at least nominally fixed in that device  12  would not change power transmission frequency in response to receiver power requirements. 
     In embodiments 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 embodiments 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 one coil, at least 2 coils, at least 3 coils, at least 5 coils, at least 7 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 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 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 having seven coils for wireless power transmitting device  12  of  FIG. 3 . In this example, the lower layer has 8 coils, the middle layer has 7 coils, and the upper layer 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. 
     Device  24  may contain circuitry that is sensitive to radio-frequency signal interference. This circuitry may include, for example, input-output devices  56  such as a display, a touch sensor (e.g., a two-dimensional capacitive touch sensor) overlapping the display, a radio (e.g., an amplitude modulation radio), a force sensor, digital image sensors (e.g., infrared and/or visible light image sensors for components such as cameras, etc.), and/or other sensitive circuitry. During wireless power transmission, the wireless power signals  44  that are transmitted to device  24  can directly interfere with the sensitive circuitry and/or can interfere with the sensitive circuitry by generating interfering signal harmonics. For example, some touch sensors do not sense touches properly when subjected to radio interference and some force sensors do not sense force input properly when subjected to radio interference. For example, some displays do not display frames consistently (e.g., images appear wavy) when subjected to radio interference. 
     To prevent disruption to the operation of device  24  as wireless power signals are being transmitted by device  10 , device  24  can be characterized using testing equipment (e.g., during manufacturing). The testing equipment can supply signals  44  over a range of potential operating frequencies while the performance of radio-frequency-interference-sensitive components in device  24  is monitored. Frequency bands in which undesired interference effects are detected can be identified. Information on these frequency bands (which may sometimes be referred to as disallowed frequency bands, sensitive frequency bands, interference-producing frequency bands, etc.) such as start and end frequencies for the frequency bands may be stored in memory in device  24 . During wireless power transfer operations, device  24  can measure the wireless power transmitting frequency in use, can compare this measured frequency to the stored sensitive frequency bands, and can take action to avoid use (or at least to avoid prolonged use) of wireless power signals with frequencies in the sensitive frequency bands. 
     In systems in which the frequency of power transmitting circuitry  52  can be adjusted in response to frequency adjustment commands from device  24 , device  24  can send frequency adjustment commands to device  12  whenever power is being transmitted at a wireless power transmission frequency that falls within a sensitive frequency band. In some configurations, however, device  12  may not support the use of frequency adjustment commands. 
     To prevent interference in scenarios in which device  12  does not support frequency adjustment commands, device  24  can transmit power adjustment commands to device  12  that indirectly cause device  24  to adjust its wireless power transmission frequency. 
     Consider, as an example, the scenario illustrated in  FIG. 7 . In  FIG. 7 , the output power P of an illustrative wireless power transmitting device such as device  12  has been plotted as a function of wireless power transmission frequency f (curve  80 ). Illustrative sensitive frequency bands associated with an illustrative wireless power receiving device (e.g., sensitive frequency band  84  extending from frequency fa to frequency fb and sensitive frequency band  82  extending from frequency fc to frequency fd) are also plotted in  FIG. 7 . When device  12  transmits wireless power at a frequency f that lies outside of bands  84  and  82  (and within permitted frequency range f 1  to f 2 , which may be, for example, 100 kHz to 200 kHz or other suitable permitted frequency range), device  24  operates within design tolerances, for example, in its ability to sense input and provide output. However, when device  12  transmits wireless power at a frequency f that lies within one of sensitive bends  84  and  82 , the transmitted wireless power signals interfere with the operation of device  12 . For example, images displayed on a display in device  24  will contain undesired visual artifacts, touch sensor or force sensor measurements will contain excessive noise, the reception of wireless communications signals (e.g., cellular or WiFi) will be adversely affected, and/or sensitive components such as digital image sensors will not be able to capture satisfactory images. 
     During operation, wireless power receiving device  24  may require varying amounts of wireless power. When an increase in power is desired, wireless power receiving device  24  transmits a wireless power adjustment request (e.g., a wireless power adjustment command) that requests and thereby causes device  12  to increase its transmitted power level. Device  24  can issue wireless power adjustment requests that cause device  12  to decrease the amount of wireless power being transmitted when device  24  desires to receive less power from device  12 . Device  12  may satisfy these power adjustment requests by using control circuitry  16  to adjust the drive signals provided to the inverter circuitry in device  12  and thereby adjust the properties of wireless power signals  44 . Notably, device  12  adjusts the wireless power transmission frequency f that is associated with the drive signals for inverter circuitry  60  and that is associated with wireless power signals  44  in accordance with curve  80 . In exemplary curve  80 , when less power is required, frequency f is adjusted upwards. When more power is required, frequency f can be lowered. 
     Device  24  can use measurement circuitry  43  to measure the frequency f of the wireless power signals that are being received by wireless power receiving circuitry  54 . Whenever frequency f overlaps a sensitive frequency band such as band  84  and band  82  of  FIG. 7 , device  24  can use ASK in-band communications and/or other wireless communications to transmit a wireless power level adjustment request to device  12 . The wireless power level adjustment request directs device  12  to adjust the amount of wireless power being transmitted and indirectly causes the wireless power transmission frequency to be adjusted out of the sensitive band. If, as an example, it is determined that wireless power signals are being transmitted at a frequency associated with operating point  86  in sensitive band  82 , device  24  can transmit a wireless power adjustment request to device  12  that requests that device  24  increase its wireless power transmission level. In response, device  12  may transition from transmitting wireless power at the power and frequency associated with point  86  to a higher power (and therefore lower frequency) associated with operating point  88 . The wireless power transmission frequency at operating point  88  is a safe frequency that is outside sensitive frequency band  82 , so interference with the operation of components of device  24  is avoided. 
       FIG. 8  is a flow chart of illustrative operations associated with operating system  8  while preventing undesired interference between the wireless power signal transmitted by device  12  and the operation of sensitive components in device  24 . 
     During the operations of block  90 , device  12  transmits wireless power signals  44  at wireless power transmission frequency f and power P. Wireless power receiving device  24  receives the transmitted signals using power receiving circuitry  54  while using measurement circuitry  43  or other suitable circuitry in device  24  to measure the frequency associated with the transmitted wireless power signals. The frequency f may be compared to the known (stored) sensitive frequency bands (e.g., bands  82  and  84  in the example of  FIG. 7 ). So long as the frequency f of the wireless power signals lies outside of the sensitive bands, wireless power can be transmitted normally. During these normal operations, device  24  may occasionally issue wireless power level adjustment commands according to the time-varying power needs of device  24 . Due to adjustments made by device  12  and/or changes made by device  12  in response to normal wireless power level adjustment commands received from device  24 , the wireless power transmitting frequency f may move into a sensitive frequency band. 
     When operation in a sensitive frequency band is detected by device  24  (e.g., by wireless-power-transmission-frequency measurement circuitry such as circuitry  43 ), device  24  may take corrective action. In some examples, during the operations of block  92 , device  24  may determine whether the wireless power transmission frequency should be adjusted up or down. Device  24  may, as an example, determine that the wireless power transmission frequency should be moved towards the closest edge of the sensitive band. As an example, the wireless power frequency may be lowered to avoid operating in band  82  in scenarios in which the operating frequency for device  12  lies within band  82  close to lower frequency fc and may be raised to avoid operating in band  82  in scenarios in which the operating frequency for device  12  lies within band  82  close to upper frequency fd. In some examples, device  24  determines that the last frequency change was a change in a particular up or down direction, and again moves the frequency in the same direction. 
     During the operations of block  94 , device  24  may determine how much the wireless power level P should be adjusted in the power level adjustment request (e.g., device  24  may determine a desired value of power level adjustment ΔP) and may supply a corresponding wireless power adjustment request to device  12  (e.g., using in-band communications such as ASK data transmission between device  24  and device  12 ). The value of ΔP may be determined by computing a fixed fraction (e.g., 10%, 1-15%, 0.01-2%, at least 0.5%, at least 2%, less than 7%, less than 1.5%, or other suitable amount) of the current wireless power level P, may be based on the size of the sensitive frequency band in which the wireless power transmission frequency lies (e.g., so that larger bands results in larger ΔP values), and/or may be based on other suitable criteria (e.g., the wireless power transmission frequency, the distance of the wireless power transmission frequency to the closest sensitive band edge, etc.). Device  24  may also use its wireless power transmission frequency monitoring circuitry to measure the change in wireless power transmission frequency that results from the requested change in wireless power transmission level. 
     In response to determining that the wireless power transmission frequency has changed, but still lies within a sensitive frequency band, the operations of blocks  92  and  94  can be repeated to make sure that the wireless power transmission frequency is moved out of the sensitive band. 
     In response to determining that the wireless power transmission frequency has changed and no longer lies within a sensitive frequency band, operations may loop back to block  90  (normal operation). 
     In response to determining that the wireless power transmission frequency did not change in response to a given power adjustment request sent to device  12  or more than a predetermined number of power adjustment requests send to device  12 , device  24  may, if desired disable frequency avoidance operations (e.g., block  96 ) for a predetermined period of time, until device  24  pairs with a new wireless power transmitting device, and/or until other criteria have been satisfied. This may help avoid unnecessary power adjustments in systems in which power adjustments are determined to not readily result in frequency adjustments of the type associated with curve  80  of  FIG. 7 . In some configurations, device  24  may, if desired, change the direction of power adjustments (and therefore the direction of frequency adjustments) that are being made in response to determining that attempts to avoid a sensitive band are not succeeding. This allows avoidance of a sensitive band in situations in which the current frequency is at an edge of an allowed frequency band of device  24  and is therefore unable to be further adjusted in the current direction. In some embodiments, device  24  may additionally or alternatively cause a change in operation of a sensitive electrical component in response to determining that the wireless power transmission frequency did not change in response to the power adjustment request sent to device  12 . For example, a display frame rate may be adjusted, an image sensor frame rate may be adjusted, a touch sensor or force sensor clock may be adjusted, wireless communications frequencies being used to handle a communications session may be adjusted, or other changes may be made. 
     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: 20180129
Publication Date: 20200317
Grant Date: 20200317
Priority Date: 20170829
Inventors: FALKENBURG, DAVID R.
TOLVA, CORTLAND S.
WALKER, JAMES R.
SCHAEVITZ, SAMUEL B.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65437878