PATENT DOCUMENT

Publication Number: US-10164469-B1
Application Number: US-201615265061-A
Country: US
Kind Code: B1

Title: Adaptive wireless power transfer system

Abstract:
Wireless power may be transferred using wireless power elements such as coil antennas for inductive wireless power transfer technology or patch antennas for capacitive wireless power transfer technology. These antennas in source equipment may couple in a near-field region to antennas implemented in target equipment. Wireless power may also be transferred from the source equipment to the target equipment using radiating antennas in their far-field regions. Wireless power transfer may be optimized by performing channel estimation operations. Foreign objects can be detected and located using sensors or by analyzing the quality of wireless channels. Optimum power transfer settings may be used to maximize wireless power transfer to a set of the antennas in the target equipment while minimizing power transfer to the foreign object.

Claims:
What is claimed is: 
     
       1. A system in which power is transferred wirelessly in the vicinity of a foreign object, comprising:
 source equipment having an array of source wireless power transfer elements and having source wireless power transfer circuitry; and 
 target equipment having an array of target wireless power transfer elements and having target wireless power transfer circuitry, wherein the source equipment and target equipment are configured to transfer power wirelessly from the source equipment to the target equipment using the array of source wireless power transfer elements, the source wireless power transfer circuitry, the array of target wireless power transfer elements, and the target wireless power transfer circuitry while aligning a wireless power null with the foreign object by using at least one of the target wireless power transfer elements to transmit wireless power signals while the source wireless power transfer elements are transmitting wireless power signals. 
 
     
     
       2. The system defined in  claim 1  further comprising:
 at least one sensor, wherein the source equipment and target equipment is configured to use the sensor to locate the foreign object. 
 
     
     
       3. The system defined in  claim 2  wherein the source equipment and target equipment are configured to transfer the power wirelessly from the source equipment to the target equipment using the array of source wireless power transfer elements, the source wireless power transfer circuitry, the array of target wireless power transfer elements, and the target wireless power transfer circuitry based at least partly on information from the sensor. 
     
     
       4. The system defined in  claim 3  wherein the source equipment and target equipment are configured to transfer the power wirelessly from the source equipment to the target equipment based at least partly on channel estimates performed using the source and target wireless power transfer circuitry and the source and target arrays of wireless power transfer elements. 
     
     
       5. The system defined in  claim 3  wherein the array of source wireless power transfer elements comprises an array of source coils, wherein the array of target wireless power transfer elements comprises an array of target coils, and wherein the source and target equipment are configured to transfer power wirelessly to the target equipment from the source equipment by directing wireless power towards a subset of target coils in the target equipment and away from the foreign object. 
     
     
       6. A method of transferring power wirelessly from source equipment having wireless power transfer circuitry and having an array of coils to at least one target coil in target equipment, comprising:
 performing channel estimation operations using the array of coils and the at least one target coil in the target equipment; 
 determining wireless power transfer settings to use in transmitting signals with the array of coils using the wireless power transfer circuitry based at least partly on the channel estimation operations; and 
 transmitting wireless power signals from the array of coils to the at least one target coil in the target equipment that is near-field coupled to the array of coils using the wireless power transfer settings, wherein performing the channel estimation operations using the array of coils and the at least one target coil in the target equipment comprises measuring a reflected impedance from the at least one target coil in the target equipment at each of the coils in the array of coils. 
 
     
     
       7. The method defined in  claim 6  wherein performing the channel estimation operations using the array of coils and the at least one target coil in the target equipment comprises receiving signals at each of the coils in the array of coils with the wireless power transfer circuitry while transmitting signals from transmitter circuitry coupled to the at least one target coil in the target equipment. 
     
     
       8. The method defined in  claim 7  wherein the at least one target coil in the target equipment comprises an array of target coils and wherein transmitting the wireless power signals comprises transmitting the wireless power signals from the array of coils in the source equipment to the array of target coils in the target equipment. 
     
     
       9. The method defined in  claim 8  further comprising transmitting signals from at least one of the target coils in the array of target coils in the target equipment while transmitting the wireless power signals from the array of coils in the source equipment to the array of target coils in the target equipment. 
     
     
       10. The method defined in  claim 9  further comprising:
 determining the location of a foreign object, wherein transmitting the wireless power signals from the array of coils comprises transmitting the wireless power signals from the array of coils based at least partly on the location of the foreign object. 
 
     
     
       11. The method defined in  claim 10  wherein the source equipment includes at least one sensor and control circuitry and wherein determining the location of the foreign object comprises:
 using the control circuitry and the sensor to determine the location of the foreign object. 
 
     
     
       12. A method of transferring power wirelessly from source equipment having wireless power transfer circuitry and having an array of coils to at least one target coil in target equipment, comprising:
 performing channel estimation operations using the array of coils and the at least one target coil in the target equipment; 
 determining wireless power transfer settings to use in transmitting signals with the array of coils using the wireless power transfer circuitry based at least partly on the channel estimation operations; 
 transmitting wireless power signals from the array of coils to the at least one target coil in the target equipment that is near-field coupled to the array of coils using the wireless power transfer settings; and 
 determining where a foreign object od located using the source equipment, wherein transmitting the wireless power signals from the array of coils comprises transmitting the wireless power signals from the array of coils based at least partly on where the foreign object is located. 
 
     
     
       13. A method of transferring power wirelessly from source equipment having wireless power transfer circuitry and having an array of coils to at least one target coil in target equipment, comprising:
 performing channel estimation operations using the array of coils and the at least one target coil in the target equipment; 
 determining wireless power transfer settings to use in transmitting signals with the array of coils using the wireless power transfer circuitry based at least partly on the channel estimation operations; and 
 transmitting wireless power signals from the array of coils to the at least one target coil in the target equipment that is near-field coupled to the array of coils using the wireless power transfer settings, wherein the target equipment comprises a vehicle and wherein transmitting the wireless power signals comprises transmitting the wireless power signals to the target coil in the vehicle. 
 
     
     
       14. A system for wirelessly transmitting power from a wireless power unit to a vehicle having at least one target antenna, comprising:
 an array of antennas that are near-field coupled to the at least one target antenna; 
 at least one sensor configured to detect foreign objects; and 
 wireless power transfer circuitry configured to transfer power wirelessly to the target antenna using the array of antennas based at least partly on information from the sensor about the foreign object. 
 
     
     
       15. The system defined in  claim 14  wherein the array of antennas comprises an array of coils. 
     
     
       16. The system defined in  claim 15  further comprising control circuitry configured to use the information from the sensor to determine where the foreign object is located, wherein the control circuitry is configured to halt wireless power transfer with the wireless power transfer circuitry based at least partly on the information. 
     
     
       17. The system defined in  claim 14  wherein the at least one target antenna comprises one of an array of target antennas, wherein the system further comprises a transmitter coupled to a given one of the target antennas in the array of target antennas, and wherein the transmitter transmits signals through the given one of the target antennas while the wireless power transfer circuitry transfers power wirelessly to the vehicle. 
     
     
       18. The system defined in  claim 17  wherein the transmitter is configured to transmit signals through the given one of the target antennas in the array of target antennas while the wireless power transfer circuitry transfers power wirelessly to the vehicle based at least partly on where the foreign object is located. 
     
     
       19. The system defined in  claim 14  further comprising control circuitry configured to perform channel estimation operations using the array of antennas and the at least one target antenna in the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/233,880, filed Sep. 28, 2015, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to power transfer systems and, more particularly, to systems that transfer power wirelessly. 
     It is often desirable to transfer power between a source of power and equipment that requires power. In some systems, a user must manually plug a power cable into equipment that requires power. In other systems, power cables can be eliminated by transferring power wirelessly. 
     Challenges may arise in using wireless power transfer systems effectively. Alignment issues and other issues may make wireless power transfer systems cumbersome and inefficient. 
     It would therefore be desirable to be able to provide improved systems for transferring power wirelessly to equipment that uses power. 
     SUMMARY 
     Equipment that contains a source of power such as a wireless power transfer unit or other source equipment may transfer power wirelessly to target equipment. The wireless power transfer unit may contain an array of wireless power transfer elements. The target equipment may be a vehicle or other equipment that includes a corresponding array of wireless power transfer elements. 
     The wireless power transfer elements (sometimes referred to as antennas, wireless power transmitter elements when transmitting wireless power, and wireless power receiver elements when receiving wireless power) may be coil antennas or other antennas that support inductive wireless power transfer, may be capacitor plates that support capacitively coupled wireless power transfer, may be antennas that support far-field wireless power transfer, or may be any other type of antenna structure. During wireless power transfer operations, the antennas in the source equipment may transfer power to the antennas in the target equipment using near-field coupling or far-field signal propagation. This allows wireless power to be transferred from the source equipment to the target equipment. 
     Wireless power transfer may be optimized by controlling the signals supplied to the wireless power transfer elements. For example, the signal strengths of the wireless power signals supplied to different wireless power transfer elements can be controlled to direct a beam of wireless power signals towards an appropriate set of the wireless power transfer elements in the target equipment. The optimum settings to use in supplying signals to the wireless power transfer elements (e.g., signal strengths for each of the antennas in an array of antennas) may be determined by performing channel estimation measurements. During channel estimation, the characteristics of signal propagation between transmitter and receiver such as power decay with distance, scattering, and fading may be determined. Channel estimation may be performed by gathering information at a wireless power receiver associated with one antenna while transmitting information with the wireless power transmitter associated with another antenna. Channel estimation may also be performed by making impedance measurements while transferring power between antennas. 
     Channel estimation information may be used to control beamforming operations with the antennas during inductive wireless power transfer. Foreign objects can also be detected and located using sensors. Using channel estimation information and foreign object location information, optimum power transfer settings may be identified and used to maximize wireless power transfer to a set of the antennas in the target equipment while minimizing power transfer to a foreign object. 
     In some situations, one or more transmitters in the target equipment may transmit signals through one or more of the antennas in the target equipment while power is being wirelessly transferred from the antennas in the source equipment to remaining antennas in the target equipment. This type of arrangement may help optimize wireless power transfer (e.g., by minimizing power transfer to with foreign objects while maximizing power transfer to target antennas). 
     Further features will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a wireless power transfer system in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry of the type that may be used in equipment that transmits wireless power and equipment that receives wireless power in accordance with an embodiment. 
         FIG. 3  is a diagram of illustrative power transfer equipment that may be used in transferring power wirelessly in accordance with embodiments. 
         FIG. 4  is a diagram showing illustrative circuitry that may be used in a system of the type shown in  FIG. 3  in accordance with an embodiment. 
         FIG. 5  is a flow chart of illustrative steps involved transferring power wirelessly in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It may be desirable to transfer power wirelessly from a first piece of equipment to a second piece of equipment. The first piece of equipment may be, for example, a stationary or mobile wireless power transfer unit (sometimes referred to as source equipment, a wireless power source, a wireless power transfer system, or a source device). The second piece of equipment, which may sometimes be referred to as target electronic equipment or a target device, may be a computer or other electronic device, may be an electric vehicle or other mobile electronic equipment, may be an appliance, may be lighting or other stationary electronic equipment, or may be any other suitable electronic equipment. The power that is wirelessly transferred to the target equipment may be used to recharge a battery in the target equipment or to power other circuitry in the target equipment. Configurations in which the target equipment is an electric vehicle and in which power is provided wirelessly from a wireless power transfer unit to the vehicle to recharge a battery in the vehicle may sometimes be described herein as an example. 
     An illustrative system that includes target equipment and source equipment for providing power to the target equipment is shown in  FIG. 1 . As shown in  FIG. 1 , source equipment  10 A may rest on a surface such as surface  36 . Surface  36  may be the floor of a garage or other suitable surface. Source equipment  10 A may include wheels, a motor, and control circuitry for moving equipment  10 A to a desired location on surface  36  (e.g., to a position under target equipment  10 B that allows equipment  10 A and  10 B to be aligned with each other) or source equipment  10 A may be stationary equipment such as a wireless charging pad (mat) resting on surface  26 . 
     Source equipment  10 A and target equipment  10 B may each contain one or more antennas or other wireless power transfer elements such as elements  12 A in equipment  10 A and elements  12 B in target equipment  10 B. Wireless power may be transferred between equipment  10 A and  10 B using inductive techniques, capacitively coupled capacitor plates, near-field coupled antennas operating at microwave frequencies or other frequencies, or other wireless power transfer techniques. For example, wireless power transfer elements  12 A and  12 B may be inductively coupled (near-field coupled) coil antennas (e.g., coils such as loop antennas with multiple turns) or may be capacitor electrodes that are capacitively near-field coupled. When current is applied through a loop in the source equipment, a magnetic field is produced that induces a corresponding current in the loop of the target equipment. Electric fields may be produced using capacitor electrodes. Other types of wireless power transfer elements such as radiating antenna elements (operating in a far-field region) may be used, if desired. 
     Elements  12 A and/or  12 B may form arrays of elements. Power and, if desired, communications signals may be transmitted and/or received by elements  12 A and  12 B of the arrays. Near-field wireless or far-field signals can be emitted and/or received, so array-based systems of the type shown in  FIG. 1  may sometimes be referred to as near-field or far-field multiple-input-multiple-output wireless power transfer systems. By controlling the signals supplied to the elements of the arrays, beamforming operations may be performed (i.e., wireless power can be steered in a desired direction), allowing power transfer efficiency to be enhanced in real time without needing to physically move equipment  10 A and  10 B after initial alignment. Wireless power nulls (areas characterized by minimums in wireless power) can also be steered using beamforming operations to ensure that more power than desired is not directed towards foreign objects. 
     A schematic diagram of illustrative circuitry  20  that may be provided in source equipment  10 A and/or target equipment  10 B is shown in  FIG. 2 . As shown in  FIG. 2 , circuitry  20  may include control circuitry  38 . Control circuitry  38  may include microprocessors, memory (e.g., volatile and nonvolatile storage), application-specific integrated circuits, and other storage and processing circuitry. Code that is implemented on control circuitry  38  may be used in implementing control processes for equipment  10 A and  10 B. These control processes may be used in analyzing sensor data and other input (e.g., to identify the location of any foreign objects in the vicinity of equipment  10 A and  10 B) and in controlling each of the signals being transmitted and received with the respective elements  12 A and  12 B of the arrays. Signal adjustments such as these may be made by control circuitry  38  in real time to adjust the location of maximum energy distribution (signal strength maximums) and minimum energy distribution (nulls). For example, signal adjustments may be used to ensure that wireless power transfer operations between elements  12 A and  12 B are being performed efficiently by source wireless power transfer circuitry  60  and other source circuitry  20  in source equipment  10 A and by target wireless power transfer circuitry  60  and other target circuitry  20  while this circuitry aligns nulls with any foreign objects that are detected in the vicinity of equipment  10 A and  10 B. 
     Input-output devices  40  may be used in gathering input from a user and/or making measurements on the environment surrounding equipment  10 A and  10 B and/or may be used in supplying output to a user and/or equipment in the vicinity of equipment  10 A and  10 B. Control circuitry  38  may process the information obtained by input-output devices  40  and may provide input-output devices  40  with output. 
     Input-output devices  40  may include user input-output devices  50 . Devices  50  may include buttons, touch sensors, track pads, keyboards, and other components for receiving input from a user. Sensors  42  may be used in gathering information in connection with alignment operations (e.g., information associated with aligning equipment  10 A and equipment  10 B), information associated with detecting foreign objects and determining the location of foreign objects, and/or receiving user input. Sensors  42  may include light-based sensors for detecting ambient light, light-based proximity sensors for detecting objects in the vicinity of equipment  10 A and  10 B, magnetic sensors, temperature sensors, lidar sensors, radar sensors, accelerometers and other position and/or motion sensors, acoustic sensors, gas sensors, humidity sensors, cameras (e.g., visible, infrared, and/or ultraviolet image sensors), compasses, and other sensors. Audio components  44  may include speakers and other components for producing audio output and acoustic sensors such as microphones for gathering input from a user (e.g., voice commands) and/or for measuring ambient sounds. Displays  46  may include touch screens and/or displays that are insensitive to touch. Light-emitting diodes, lamps, lasers, and other light-emitting devices  48  may be used to provide a user with output and/or may be used as part of a sensor system (e.g., a system that identifies the location of equipment  10 A, equipment  10 B, or other objects). 
     Circuitry  20  may include wireless communications circuitry such as wireless communications circuitry  70 . Wireless communications circuitry  70  may be used to transmit and/or receive radio-frequency wireless signals (e.g., Bluetooth® signals, WiFi® signals, other wireless signals, etc.), light-based wireless signals, and/or other wireless signals. Data may also be communicated over wired paths. Wireless communications circuitry  70  and wireless power transfer circuitry  60  may use wireless power transfer elements such as elements  12 A and  12 B and other antennas  72  and in transmitting and receiving wireless signals. For example, wireless communications circuitry  70  may use antenna such as inverted-F antennas, monopole antennas, loop antennas, patch antennas, dipole antennas, planar inverted-F antennas, slot antennas, and other antennas in transmitting and receiving wireless communications signals at radio-frequencies (e.g., at frequencies of 700 MHz to 5 GHz, at wireless local area network frequencies such as 2.4 GHz or 5 GHz, at frequencies below 700 MHz or above 5 GHz, or at other suitable frequencies). In some configurations, circuitry  70  and/or  60  may transmit and/or receive near field signals (e.g., near field wireless power transfer signals at frequencies below 5 GHz, below 1 GHz, below 100 MHz, below 1 MHz, below 100 kHz, above 1 kHz, or other suitable frequencies). 
     Equipment  10 A may include some or all of circuitry  20  of  FIG. 2  or other suitable circuitry, equipment  10 B may include some or all of circuitry  20  of  FIG. 2  or other suitable circuitry, or both equipment  10 A and equipment  10 B may include some or all of circuitry  20  or other suitable circuitry. 
     By controlling the signals provided to the wireless power transfer elements, the location and concentration of power associated with wirelessly transmitted power may be controlled. Optimal charging conditions may be determined based on sensor measurements, may be based on channel estimation measurements (e.g., measurements in which wireless signal paths between different combinations of elements  12 A and  12 B are evaluated), may be based on the known locations of receiving elements (e.g., some or all of elements  12 B in target equipment  10 B), and may be based on the location of any detected foreign objects (i.e., external objects to which it is not desired to couple power during wireless power transfer operations). 
     An illustrative wireless power transfer arrangement is shown in  FIG. 3 . As shown in  FIG. 3 , source equipment  10 A may have circuitry  80 A (e.g., wireless power transfer circuitry and, if desired, wireless communications circuitry) coupled to a single power transfer element  12 A or an array of power transfer elements  12 A. Target equipment  10 B may have circuitry  80 B (e.g., wireless power transfer circuitry and, if desired, wireless communications circuitry) coupled to a single power transfer element  12 B or an array of power transfer elements  12 B. Elements  12 A and  12 B may be, for example, coil antennas and may be inductively coupled to support near-field inductive charging of a battery within equipment  12 B from power supplied by equipment  12 A, may be capacitor electrode that are capacitively coupled to support wireless charging of the battery, or may be far-field antenna elements that transfer power wirelessly to support wireless charging of the battery. 
     When using an array of antennas or other collection of wireless power transfer elements, it is possible to adjust the signals transmitted by each element to create a desired power transfer beam (e.g., the phase and magnitude and/or other signal properties of the signal associated with each of the elements may be controlled to direct power transfer to a desired target location and away from other locations). As an example, circuitry  80 A may provide an appropriate set of signals to the array of elements  12 A in equipment  10 A to shape the signals that are emitted by elements  12 A in a desired pattern that overlaps the array of elements  12 B (or a desired subset of these elements) in equipment  10 B. By using near-field field shaping or far-field beamforming principals in this way, wireless power can be efficiently transferred between antenna elements  12 A and an appropriate set of antenna elements  12 B, even in scenarios in which equipment  10 A and  10 B is not precisely aligned. 
     When equipment  10 A and/or  10 B detects a foreign object such as foreign object  82 , it can use near-field shaping or far-field beamforming to place a global or local signal strength minimum (null) over the foreign object. In some examples, equipment  10 A and/or  10 B uses sensors  42  or other circuitry  20  to detect foreign objects. In this way, equipment  10 A and/or  10 B can maintain the field strength at the foreign object is at a desired level during wireless power transfer operations. The process of identifying optimum wireless power transfer setting for equipment  10 A and  10 B may involve satisfying criteria related to efficient power transfer while satisfying criteria related to avoiding excess signal strength in the vicinity of foreign objects such as object  82 . 
     In some scenarios, all of elements  12 A are used for signal transmission and all of elements  12 B are used for signal reception (e.g., to convert the received wireless signals into direct current power for use in equipment  10 B). In other scenarios, one or more of elements  12 B may be used to transmit signals while elements  12 A are transmitting signals to element  12 B as part of a wireless power transfer process. The signals produced by the one or more transmitting elements  12 B help equipment  10 A and  10 B produce a desired field pattern. With this type of arrangement, one or more of elements  12 B in target equipment  10 B may be used to transmit signals at the same time that other elements  12 B in target equipment  10 B are receiving wirelessly transmitted power. The overall beamforming operation that is performed by using elements  12 A and one or more of elements  12 B as transmitters may be able to direct power to a desired subset of elements  12 B while avoiding foreign objects more satisfactorily than if all of elements  12 B were only used as receivers. 
     In the illustrative example of  FIG. 3 , wireless power transmission circuitry in circuitry  80 A and  80 B is transmitting wireless power signals using all of elements  12 A in equipment  10 A and using element  12 B″ in equipment  10 B. This creates a near-field or far-field pattern (depending on the technology used) that is concentrated in maximum power region  86  and that has a minimum in null region  84 . Wireless power transfer elements  12 B′ are being used to receive power for equipment  10 B. Because maximum power region  86  overlaps elements  12 B′, power can be efficiently transferred from elements  12 A of equipment  10 A to elements  12 B′ of equipment  10 B. Because null region  84  overlaps foreign object  82 , foreign object  82  will not be exposed to unnecessarily elevated signal strengths (i.e., potential disruption to wireless power transfer operations from the presence of conductive materials or other structures in object  82  will be reduced). 
     In the example of  FIG. 3 , an optimum wireless power transfer scenario is illustrated in which all of elements  12 A and element  12 B″ are being used to produce a field pattern with an elevated field strength in region  86  overlapping elements  12 B′ in target equipment  10  and a reduced (e.g., null) field strength in null region  84  overlapping foreign object  82 . Other optimum wireless power transmission scenarios may involve different patterns of transmitting and receiving wireless power transfer elements. As an example, wireless power can be concentrated in a region such as region  86  that overlaps all of receiving elements  12 B, wireless power can be minimized in region  84  even if maximum power region  86  does not coincide with elements  12 B, wireless power can be patterned by transmitting signals with a subset of elements  12 A, wireless power can be patterned by using two or more of elements  12 B to transmit signals while transmitting wireless power with elements  12 A during wireless transfer operations, multiple null regions  84  may be produced and each aligned with a respective foreign object  82 , and/or other wireless power transfer arrangements may be used. The configuration of  FIG. 3  is merely illustrative. 
     Illustrative circuitry  80 A and  80 B that may be used in equipment  10 A and  10 B is shown in  FIG. 4 . As shown in  FIG. 4 , equipment  10 A may include wireless communications transceiver circuitry  90 A coupled to antenna  92 A and equipment  10 B may include wireless communications transceiver  90 B coupled to antenna  92 B. Transceiver circuitry  90 A and  90 B may operate at frequencies in cellular telephone communications bands, wireless local area network communications bands, or other communications bands. Equipment  10 A and  10 B may communicate using a wireless link established using circuitry  90 A and  90 B. 
     Circuitry  80 A and  80 B may also include wireless power transceiver circuitry  98 A and  98 B, respectively. Switching circuitry such as switch  94 A may be used to selectively couple wireless power transmitter  100 A or wireless power receiver  102 A of circuitry  98 A to element  12 A. There may be multiple elements  12 A in equipment  10 A, each with a respective wireless power circuit  98 A and switching circuit  94 A. Switching circuitry such as switch  94 B may be used to selectively couple wireless power transmitter  100 B or wireless power receiver  102 B in wireless power circuitry  98 B to element  12 A. There may be multiple elements  12 B in equipment  10 B, each with a respective wireless power circuit  98 B and switching circuit  94 B. 
     Channel estimation operations may be performed using circuitry  80 A and  80 B. With one illustrative approach, all transmitters  100 A and  100 B and all receivers  102 A and  102 B are turned off. Each transmitter and receiver is then turned on systematically until signal transmission across the channel associated with each possible transmitter-receiver pair (or at least a representative selection of these pairs) has been measured. Signals received at the receivers can be transmitted back to the equipment of the transmitters using transmitters in circuits  98 A and  98 B or using transceiver circuitry such as transceiver circuitry  90 A and  90 B. If desired, channel estimation can also be performed using a passive receiver arrangement. With this approach, each receiver acts passively and does not measure or communicate channel information to the equipment of the transmitter. Instead, the transmitter circuitry is used to measure near-field channel parameters for beamforming by measuring the reflected impedance that each of the receivers imposes on each of the transmitters. Based on these channel measurements or any other suitable channel estimation measurements, and, if desired, information on the location of any foreign objects, optimal settings for circuitry  80 A and  80 B can be obtained and used for power transfer operations. 
     Illustrative operations associated with using near-field beamforming techniques to optimize wireless power transfer between equipment  10 A and  10 B is shown in  FIG. 5 . Operations  110  may take place concurrently. During the operations of blocks  120  and  122 , equipment  10 A and/or  10 B may monitor for foreign objects and take appropriate action. During the operations of blocks  112 ,  114 , and  116 , equipment  10 A and/or  10 B may be configured to transfer power effectively without directing excess power towards the foreign objects. 
     At block  120 , equipment  10 A and/or  10 B may use sensors  42  and other circuitry  20  to monitor for the presence of foreign objects. If no foreign objects are detected, processing can loop back to block  120  for additional monitoring. If foreign objects are detected, appropriate action can be taken during block  122 . Examples of action that may be taken when foreign objects are detected include issuing an audible or visible alert, transmitting a wireless message to a user of the wireless power transfer system, halting the transfer of wireless power until a user can inspect and manually restart the system, reducing the amount of power that is being wirelessly transferred (e.g., placing the system in a low power mode), or otherwise adjusting power transfer operations, issuing alerts and other messages, etc. The location of each foreign object that is detected during the operations of block  120  may, if desired, be supplied to equipment  10 A and/or  10 B (e.g. wirelessly, through internal connections, etc.). 
     To ensure that power is transferred efficiently, channel estimation operations may be performed at block  112 . For example, equipment  10 A and  10 B may cycle through each of the transmitters and receivers associated with equipment  10 A and  10 B, turning on each possible transmitter-receiver pair and making a corresponding channel measurement. The transmitters and receivers that are used in making the channel measurements may be the same transmitters and receivers used in transferring power wirelessly or may be low-power transmitters and/or receivers that are switched into use with switching circuitry  94 A and  94 B. Channel measurements may also be made by measuring reflected impedances that the receiver circuitry imposes on the transmitter circuitry (e.g., by measuring the impedances associated with conveying signals using different pairs of near-field coupled coil antennas and/or sets of coil antennas). During channel estimation, the characteristics of signal propagation between each of the transmitters and receivers associated with equipment  10 A and  10 B may be determined (e.g., power decay with distance, scattering, and fading). With one illustrative technique, a training sequence approach may be used in estimating channel state information. A known training sequence may be transmitted and the training sequence and received signal information from the receivers may be used in estimating channel parameters. 
     Channel estimation data from the operations of block  112  and foreign object location information from block  120  may be used in determining optimum wireless power transfer settings at block  114 . Wireless power transfer settings may involve settings for transmitters in equipment  10 A and, if desired, one or more transmitters in equipment  10 B (e.g., to help locate nulls over foreign objects). Control circuitry in equipment  10 A and/or equipment  10 B may be used in identifying optimum settings. 
     At block  116 , power can be transferred wirelessly from equipment  10 A to equipment  10 B using the optimum settings identified at step  114 . For example, wireless power circuitry in equipment  10 A can provide signals to elements  12 A that are wirelessly transmitted via near-field inductive coupling, near-field capacitive coupling, or far-field radiation to some or all of elements  12 B in equipment  10 B. One or more of elements  12 B may optionally be used to transmit signals while power is being transferred from elements  12 A to the remainder of elements  12 B (e.g., to help align nulls or other areas of low power over foreign objects and/or to enhance power transfer efficiency). For example, when one or more target elements  12 B are desired for use in null formation, one or more of switches  94 B can be configured to couple one or more respective wireless transmitters  100 B to one or more respective elements  12 B to transmit wireless power. At other times, when, for example, a foreign object moves out of the vicinity of equipment  10 A and  10 B, switches  94 B can be reconfigured so that the same elements  12 B are coupled to wireless power receivers  102 B. In this configuration, wireless power may be received by these target elements  12 B. The operations of block  112 ,  114 , and  116  can be performed continuously (e.g., in a loop) during operation of equipment  10 A and  10 B. 
     Operations  110  may be performed by control circuitry  38  in equipment  10 A and/or  10 B. During operation, this control circuitry (which may sometimes be referred to as processing circuitry, processing and storage, computing equipment, a computer, etc.) may be configured to perform the method of  FIG. 5  (e.g., using dedicated hardware and/or using software code running on hardware in equipment  10 A and/or  10 B such as control circuitry  38 ). The software code for performing these methods, which may sometimes be referred to as program instructions, code, data, instructions, or software, may be stored on non-transitory (tangible) computer readable storage media in control circuitry  38  in equipment  10 A and/or  10 B such as read-only memory, random-access memory, hard drive storage, flash drive storage, removable storage medium, or other computer-readable media and may be executed on processing circuitry such as microprocessors and/or application-specific integrated circuits with processing circuits in control circuitry  38 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20160914
Publication Date: 20181225
Grant Date: 20181225
Priority Date: 20150928
Inventors: JADIDIAN, Jouya
CABRAL, STEVEN W.
PATHAK, VANEET
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/60", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 64692392