Object detection for wireless power transfer

Abstract

To provide object detection for wireless power transfer.SOLUTION: A wireless power transmitter (WPT) may include a WPT circuit including a radio WPT coil which transmits a wireless power signal, and a control circuit which is connected to the WPT circuit. While the WPT is connected to a wireless power receiver, the control circuit measures a current value of a first function of a quality coefficient and a resonant frequency of the wireless power transmitter coil and a current value of a second function of a quality coefficient and a resonant frequency of the WPT coil, determines a change between the measured current values of the first function and the second function of the quality coefficient and the resonant frequency of the WPT coil and corresponding baseline values, and determines whether a foreign substance is present in accordance with the change, exceeding a threshold value in a magnetic state space, between the measured current values of the first function and the second function of the quality coefficient and the resonant frequency and the corresponding baseline values.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 581,318, entitled "Mated-Q Object Detection for High Power Wireless Power Transfer," filed September 8, 2023, U.S. Provisional Application No. 63 / 605,047, entitled "Object Detection for Wireless Power Transfer," filed December 1, 2023, U.S. Patent Application No. 18 / 612,886, entitled "Mated-Q Object Detection for High Power Wireless Power Transfer," filed March 21, 2024, U.S. Patent Application No. 18 / 612,892, entitled "Object Detection for Wireless Power Transfer," filed March 21, 2024, and U.S. Patent Application No. 18 / 612,904, entitled "Object Detection for Wireless Power Transfer," filed March 21, 2024, each of which is incorporated by reference in its entirety herein. [Background technology]

[0002] Electronic devices such as smartphones, tablet computers, smart watches, wireless earbuds, styluses, and the like may employ wireless power transmission to facilitate charging of batteries within the devices. As a result, it may be desirable to provide increased levels of power transmission. However, such higher power levels may create a need for improved detection of other objects that may affect or be affected by the wireless power transmission. Summary of the Invention

[0003] The wireless power transmitter may include a wireless power transmission circuit having a wireless power transmission coil for transmitting a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, the control circuit measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmission coil and a current value of a second function of a quality factor and a resonant frequency of the wireless power transmission coil while the wireless power transmitter is coupled to the wireless power receiver, determining a change between the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless power transmission coil and a corresponding baseline value, and determining whether a foreign object is present in response to a change between the measured current values ​​of the first and second functions of the quality factor and the resonant frequency and a corresponding baseline value that exceeds a threshold in the magnetic state space. The first function of the quality factor and the resonant frequency may be a quality factor. The second function of the quality factor and the resonant frequency may be a resonant frequency. The threshold may include a plurality of linear thresholds.

[0004] The wireless power transmitter may include a wireless power transmission circuit having a wireless power transmission coil that transmits a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, wherein the control circuit measures, while the wireless power transmitter is coupled to the wireless power receiver, a current value of a first function of a quality factor, a resonant frequency, and a coupling coefficient of the wireless power transmission coil, a current value of a second function of the quality factor, the resonant frequency, and a coupling coefficient of the wireless power transmission coil, and a current value of a third function of the quality factor, the resonant frequency, and a coupling coefficient of the wireless power transmission coil, determines a distance between the measured current values ​​of the first function, the second function, and the third function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless power transmission coil and a curve fit to a corresponding baseline value, and determines whether a foreign object is present as a function of a distance between the measured current values ​​of the first function, the second function, and the third function of the quality factor, the resonant frequency, and the coupling coefficient and a curve fit to a corresponding baseline value in a magnetic state space that exceeds a threshold value or falls between a plurality of threshold values.

[0005] The first, second and third functions of the quality factor, resonant frequency and coupling coefficient may be selected to provide a linear curve fit in the magnetic state space. The first function of the quality factor, resonant frequency and coupling coefficient may be the square of the coupling coefficient. The second function of the quality factor, resonant frequency and coupling coefficient may be the square of the resonant frequency, and the third function of the quality factor, resonant frequency and coupling coefficient may be the inverse of the resonant frequency multiplied by the quality factor. The distance may be the L1 distance or the L2 distance (or any other suitable distance).

[0006] The control circuitry can inhibit wireless power transmission in response to detecting a foreign object. The control circuitry can transmit power at a level less than a maximum power level in response to detecting a foreign object.

[0007] The control circuit may measure the current quality factor and resonant frequency of the wireless power transmitting coil by causing the inverter to provide one or more signal pulses to the wireless power transmitter coil, measuring a response to the provided one or more signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by the frequency of the ringing signal and the current quality factor, and determining the current quality factor and resonant frequency from the frequency of the ringing signal.

[0008] The control circuitry may characterize the foreign object as a medium foreign object or a strong foreign object based on distances between the measured current values ​​of the first, second, and third functions of the quality factor, resonant frequency, and coupling coefficient of the wireless power transmitting coil and the curve fits to the corresponding baseline values. The control circuitry may inhibit wireless power transmission in response to determining that the foreign object is a strong foreign object. Alternatively, the control circuitry may enable wireless power transmission at a relatively lower power level in response to determining that the foreign object is a medium foreign object.

[0009] The corresponding baseline values ​​can be measured during manufacturing of the wireless power transmitter. The corresponding baseline values ​​can be updated during field operation of the wireless power transmitter. The control circuit can determine a distance between the measured current values ​​of the first, second, and third functions of the quality factor, resonant frequency, and coupling factor of the wireless power transmitting coil using a scale factor based on the particular transmitter-receiver pairing.

[0010] A method of operating a wireless power transmitter including a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal and a control circuit coupled to the wireless power transmission circuit can be performed by the wireless power control circuit and includes measuring, while the wireless power transmitter is coupled to a wireless power receiver, a current value of a first function of a quality factor and a resonant frequency of the wireless power transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless power transmission coil, comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless power transmission coil with corresponding baseline values, and detecting a foreign object based at least in part on the comparison of the measured current values ​​of the first and second functions of the quality factor and the resonant frequency with the corresponding baseline values.

[0011] The first function of the quality factor and the resonant frequency can be a quality factor. The second function of the quality factor and the resonant frequency can be a resonant frequency. Comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency to the corresponding baseline values ​​can include determining whether a difference between the measured current values ​​and the corresponding baseline values ​​exceeds a threshold value including a plurality of linear threshold values.

[0012] A method of operating a wireless power transmitter including a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, can be performed by the wireless power control circuit, and includes measuring, while the wireless power transmitter is coupled to a wireless power receiver, a current value of a first function of a quality factor, a resonant frequency, and a coupling coefficient of the wireless power transmission coil, a current value of a second function of a quality factor, a resonant frequency, and a coupling coefficient of the wireless power transmission coil, and a current value of a third function of a quality factor, a resonant frequency, and a coupling coefficient of the wireless power transmission coil; comparing the current measured values ​​of the first, second, and third functions of the quality factor, resonant frequency, and coupling coefficient of the wireless power transmitting coil to the corresponding baseline values ​​by determining a distance between the current measured values ​​of the first, second, and third functions of the frequency, and the coupling coefficient and a curve fit to the corresponding baseline values ​​in the magnetic state space; and detecting a foreign object based at least in part on a distance between the current measured values ​​of the first, second, and third functions of the quality factor, resonant frequency, and coupling coefficient and a curve fit to the corresponding baseline values ​​in the magnetic state space that exceeds a threshold value.

[0013] The first, second and third functions of the quality factor, resonant frequency and coupling coefficient may be selected to provide a linear curve fit in the magnetic state space. The first function of the quality factor, resonant frequency and coupling coefficient may be the square of the coupling coefficient. The second function of the quality factor, resonant frequency and coupling coefficient may be the square of the resonant frequency. The third function of the quality factor, resonant frequency and coupling coefficient may be the inverse of the resonant frequency multiplied by the quality factor. The distance may be the L1 distance or the L2 distance (or any other suitable distance).

[0014] Measuring a current quality factor and resonant frequency of wireless power transmission may include causing an inverter to provide one or more signal pulses to the wireless power transmitter coil, measuring a response to the provided one or more signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by a frequency of the ringing signal and the current quality factor, and determining the current quality factor from the frequency of the ringing signal.

[0015] The method can further include inhibiting wireless power transmission in response to detecting the foreign object.The method can further include transmitting power at a level less than a maximum power level in response to detecting the foreign object.

[0016] The method may further include characterizing the foreign object as a medium foreign object or a strong foreign object based on a distance between the measured current value and a curve fit to a corresponding baseline value in the magnetic state space. The method may further include inhibiting wireless power transmission in response to determining that the foreign object is a strong foreign object. Alternatively, the method may include enabling wireless power transmission at a relatively lower power level in response to determining that the foreign object is a medium foreign object.

[0017] The corresponding baseline value may be measured during manufacturing of the wireless power transmitter. The corresponding baseline value may be updated during field operation of the wireless power transmitter. The method may further include scaling the corresponding baseline value using a scale factor based on the particular transmitter-receiver pairing. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows a block diagram of a wireless power transmission system.

[0019] [Diagram 2] FIG. 1 shows a simplified schematic diagram of a wireless power transfer system.

[0020] [Diagram 3] 1 shows a graph illustrating the impulse response of a wireless power transmitting coil that can be analyzed to determine a quality factor value of the coil.

[0021] [Figure 4] FIG. 1 is a simplified schematic diagram of a wireless power transmitter showing circuitry that may be used to perform quality factor measurements.

[0022] [Diagram 5] Equations are presented that can be used to determine parameters such as the coil quality factor based on impedance measurements.

[0023] [Figure 6] 1 is an equation showing a compensation factor that can be applied to a current quality factor measurement to determine a compensated quality factor value.

[0024] [Figure 7] FIG. 1 illustrates an exemplary foreign object detection operation based on a measured quality factor in a wireless power transfer system. [Figure 8] FIG. 1 illustrates an exemplary foreign object detection operation based on a measured quality factor in a wireless power transfer system.

[0025] [Figure 9] The principles for foreign object detection using combined Q and resonant frequency measurements are presented.

[0026] [Figure 10] 1 shows a flow chart of a combined Q foreign object detection method.

[0027] [Figure 11] 13 shows a sequence of combined Q measurements in a situation where an object is brought close to a combined wireless power transmitter / receiver pair.

[0028] [Figure 12] 1 shows a flowchart of a wireless power transfer device parameter scaling operation. [Figure 13] 1 shows a flowchart of a wireless power transfer device parameter scaling operation.

[0029] [Figure 14] A process for scaling the combination Q and resonant frequency parameters is shown.

[0030] [Figure 15] 13 shows a variable threshold for combined Q foreign object detection.

[0031] [Figure 16A] We present a multidimensional combinatorial Q-state space for deriving a linear threshold line for foreign object detection. [Figure 16B] We present a multidimensional combinatorial Q-state space for deriving a linear threshold line for foreign object detection.

[0032] [Figure 17A] We present an alternative distance metric for multidimensional combinatorial Q foreign object detection. [Figure 17B] We present an alternative distance metric for multidimensional combinatorial Q foreign object detection. [Figure 17C] We present an alternative distance metric for multidimensional combinatorial Q foreign object detection. [Figure 17D] We present an alternative distance metric for multidimensional combinatorial Q foreign object detection.

[0033] [Figure 18A] We present ecosystem scaling of the multidimensional combinatorial Q foreign object detection system. [Figure 18B] We present ecosystem scaling of the multidimensional combinatorial Q foreign object detection system. [Figure 18C] We present ecosystem scaling of the multidimensional combinatorial Q foreign object detection system.

[0034] [Figure 19] 1 illustrates the determination of distance to a foreign object in a multi-dimensional combination Q foreign object detection system.

[0035] [Figure 20] We present a method to limit the transmit power based on the foreign object distance in a multi-dimensional combined Q foreign object detection system.

[0036] [Figure 21] The principle of case detection using combined Q and resonant frequency measurements is presented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] In the following description, for the sake of convenience, numerous specific details are set forth to enhance the understanding of the disclosed concepts. As part of this description, some drawings in the present disclosure represent structures and devices in block diagram form for simplicity. In the interest of clarity, not all features of an actual implementation are described herein. Moreover, the language used in this specification has been selected solely for purposes of readability and explanation, and not to limit or restrict the disclosed subject matter. Rather, the appended claims are intended for such purposes.

[0038] Various embodiments of the disclosed concepts are illustrated in the accompanying drawings, by way of example and not by way of limitation, in which like reference numerals refer to like elements. For simplicity and clarity of illustration, where considered appropriate, reference numerals have been repeated in different drawings to indicate corresponding and / or similar elements. In other instances, numerous specific details have been described to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the relevant associated functionality being described. References to "an", "one", or "another" embodiment in the present disclosure are not necessarily to the same or different embodiments, but rather to at least one. A given drawing is used to illustrate multiple embodiments of the present disclosure or multiple species of the present disclosure, and not all elements in the drawing may be required in a given embodiment or species. A reference numeral, when provided in a given drawing, refers to the same element throughout several drawings, but may not be repeated in all drawings. The drawings are not to scale unless otherwise indicated and the proportions of certain parts may be exaggerated to better show the details and features of the present disclosure.

[0039] The wireless power system may include a wireless power transmitting device, such as a wireless charging pack or mat. The wireless power transmitting device may wirelessly transmit power to a wireless power receiving device. The wireless power receiving device may be a device such as a watch, a mobile phone, a tablet computer, a laptop computer, or other electronic device. The wireless power receiving device may use power from the wireless power transmitting device to power the device and / or charge an internal battery. Wireless power may be transmitted from the wireless power transmitting device to the wireless power receiving device using one or more wireless power transmitting coils. The wireless power receiving device may have one or more wireless power receiving coils coupled to a rectifier circuit that may convert a received wireless power signal to DC power.

[0040] When a foreign object such as a paper clip, coin, or other metal object is present near the wireless power transmission coil of a wireless power transmission device, eddy currents are generated in the foreign object, which may increase the temperature of the foreign object. To determine whether such a foreign object is present in the vicinity of the wireless power transmission device, the wireless power transmission device may measure the quality factor (also known as "Q-factor" or "Q") of the wireless power transmission coil and determine whether the quality factor has been affected by the presence of the foreign object. In some cases, the Q-factor may be measured in "open air," meaning that the transmitter is not coupled to the receiver. In some cases, as described in more detail below, the Q-factor may be measured as "combined," meaning that the transmitter is coupled to the receiver device. In either / both cases, detecting whether a foreign object is present may allow appropriate action to be taken (e.g., the wireless power transmission device may cease wireless power transmission operation or reduce the transmitted power level whenever a foreign object is detected).

[0041] An exemplary wireless power system (wireless charging system) is shown in FIG. 1. The wireless power system 8 can include a wireless power transmitter 12 and a wireless power receiver 24. The wireless power transmitter 12 can include a control circuit 16. The wireless power receiver 24 can include a control circuit 30. Each control circuit can be used to control the operation of the wireless power system 8. The control circuit can include a processing circuit associated with a microprocessor, a power management unit, a baseband processor, a digital signal processor, a microcontroller, and / or an application specific integrated circuit having processing circuitry. The processing circuit can implement desired control and communication functions in the wireless power transmitter 12 and the wireless power receiver 24. For example, the processing circuit can be used in selecting coils, determining power transmission levels, processing sensor data and other data to detect foreign objects and perform other tasks, processing user inputs, handling negotiation between the wireless power transmitter 12 and the wireless power receiver 24, transmitting and receiving in-band and out-of-band data, performing measurements, and otherwise controlling the operation of the wireless power system 8.

[0042] The control circuitry 16, 30 in the system 8 may be configured to perform operations using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. Software code for performing operations in the system 8 may be stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium) in the control circuitry. The software code may be referred to as software, data, program instructions, instructions, and / or code. The non-transitory computer-readable storage medium may include non-volatile memory such as a 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, etc. The software stored on the non-transitory computer-readable storage medium may be executed on the processing circuitry of the control circuitry 16 and / or the control circuitry 30. The processing circuitry may include an application specific integrated circuit having processing circuitry, one or more microprocessors, a Central Processing Unit (CPU), or other processing circuitry including analog, digital, and / or hybrid circuitry.

[0043] The wireless power transmitter 12 may be a stand-alone power adapter (e.g., a wireless charging mat or charging pack that includes a power adapter circuit), a wireless charging mat or pack that is coupled to a power adapter or other device by a cable, a portable device, a device that is integrated into furniture, a vehicle, or other system, a removable battery case, or other wireless power transmission device. An exemplary configuration in which the wireless power transmitter 12 is a wireless charging mat is sometimes described herein as an example.

[0044] The wireless power receiver 24 may be a portable electronic device, such as a wristwatch, a mobile phone, a laptop computer, a tablet computer, an accessory such as an earphone, a stylus, or other electronic device. The wireless power transmitter 12 may be connected to a wall outlet (e.g., an AC power source), may have a battery to provide power, and / or may have another power source. The wireless power transmitter 12 may have an AC-DC power converter, such as an AC-DC power converter 14, to convert AC power from a wall outlet or other power source to direct current (DC) power. The DC power may be used to power the control circuit 16. In operation, a controller in the control circuit 16 may transmit wireless power to the power receiving circuit 54 of the wireless power receiver 24 using the power transmitting circuit 52. The power transmitting circuit 52 may have a switching circuit (e.g., an inverter circuit 61 formed from transistors) that is turned on and off based on a control signal provided by the control circuit 16 to generate an AC current signal through one or more wireless power transmitting coils, such as the wireless power transmitting coil(s) 36. These coil drive signals cause the coil(s) 36 to transmit wireless power. The multiple coils 36 may be arranged in a planar coil array (e.g., in a configuration where the device 12 is a wireless charging mat) or may be arranged to form a cluster of coils (e.g., in a configuration where the device 12 is a wireless charging pack). In some configurations, the wireless power transmitter 12 (e.g., a charging mat, pack, etc.) may have only a single coil. In other configurations, the wireless power transmitter may have multiple coils.

[0045] When an AC current flows through one or more coils 36, an alternating electromagnetic field (e.g., magnetic field) (wireless power signal 44) is generated that is received by one or more corresponding receiving coils, such as coil(s) 48 in the wireless power receiver 24. The wireless power receiver 24 may have a single coil 48 or any other suitable number of coils 48. When the AC electromagnetic field is received by the coil(s) 48, a corresponding alternating current is induced in the coil(s) 48. The AC signal used in transmitting wireless power may have any suitable frequency (e.g., 100-250 kHz, 128 kHz, 326 kHz, 360 kHz, 300-400 kHz, 1.7-1.8 MHz, 6.78 MHz, etc.). A rectifier circuit, such as rectifier circuit 50, including rectifier components, such as synchronous rectifier metal oxide semiconductor transistors arranged in a bridge network, converts the received AC signal (the received alternating signal associated with the electromagnetic signal 44) from the one or more coils 48 to a DC voltage signal for powering the wireless power receiver 24.

[0046] The DC voltage generated by the rectifier circuit 50 (rectifier output voltage V rect, which may be referred to as a power supply, may be used to charge batteries, such as battery 58, and may be used to power other components within wireless power receiver 24. For example, wireless power receiver 24 may include input / output devices 56. Input / output devices 56 may include input devices for collecting user input and / or making environmental measurements, and may include output devices for providing output to a user. By way of example, input / output devices 56 may include displays for generating visual output, speakers for providing output as audio signals, light emitting components for emitting light emitting diode status indicator lights and other light that provide status and / or other information to a user, haptic devices for generating vibrations and other tactile output, and / or other output devices. Input / output devices 56 may also include sensors for collecting input from a user and / or making measurements of the surroundings of wireless power system 8.Exemplary sensors that may be included in the input / output device 56 include three-dimensional sensors (e.g., a three-dimensional image sensor such as a structured light sensor that emits a light beam and uses a two-dimensional digital image sensor to collect image data for a three-dimensional image from a light spot that is generated when a target is illuminated by the light beam, a binocular three-dimensional image sensor that collects a three-dimensional image using two or more cameras in a binocular imaging configuration, a three-dimensional LIDAR (light detection and ranging) sensor, a three-dimensional radio frequency sensor, or other sensor that collects three-dimensional image data), cameras (e.g., infrared and / or visible cameras with corresponding infrared and / or visible digital image sensors, and / or ultraviolet cameras), eye-tracking sensors (e.g., eye-tracking systems based on image sensors and, if desired, light sources that emit one or more light beams that are reflected from the user's eyes and then tracked using an image sensor), optical sensors such as touch sensors, buttons, capacitive proximity sensors, infrared proximity sensors, etc. The sensors may include sensors such as a proximity sensor based (optical), other proximity sensors, force sensors, switch-based contact sensors, gas sensors, pressure sensors, humidity sensors, magnetic sensors, audio sensors (microphones), ambient light sensors, optical sensors for making spectral measurements and other measurements about a target object (e.g., by emitting light and measuring reflected light), microphones for collecting voice commands and other audio input, distance sensors, motion, position, and / or orientation sensors configured to collect information about the motion, position, and / or orientation (e.g., an inertial measurement unit including an accelerometer, gyroscope, compass, and / or all of these sensors or one or two subsets of these sensors), sensors such as a button to detect button press inputs, a joystick with sensors to detect joystick movement, a keyboard, and / or other sensors. The wireless power transmitter 12 may have one or more input / output devices 68 (e.g., input devices and / or output devices of the types described in connection with the input / output devices 56).

[0047] The wireless power transmitter 12 and / or the wireless power receiver 24 can communicate wirelessly using in-band or out-of-band communication. The wireless power transmitter 12 can have a wireless transceiver circuit 40 that wirelessly transmits out-of-band signals to the wireless power receiver 24 using, for example, an antenna. The wireless transceiver circuit 40 can be used to wirelessly receive the out-of-band signals from the wireless power receiver 24 using an antenna. The wireless power receiver 24 can have a wireless transceiver circuit 46 that transmits the out-of-band signals to the device 12. A receiver circuit within the wireless transceiver 46 can receive the out-of-band signals from the wireless power transmitter 12 using an antenna. The in-band transmission between the wireless power transmitter 12 and the wireless power receiver 24 can be performed using the coils 36 and 48. In one exemplary configuration, in-band data can be delivered from the wireless power transmitter 12 to the wireless power receiver 24 using frequency shift keying (FSK) of one or more parameters of the wirelessly transmitted power (e.g., voltage, current, etc.), and in-band data can be delivered from the wireless power receiver 24 to the wireless power transmitter 12 using amplitude shift keying (ASK) of one or more parameters of the wirelessly transmitted power (e.g., voltage, current, etc.). Power can be delivered wirelessly from the wireless power transmitter 12 to the wireless power receiver 24 during these FSK and ASK transmissions.

[0048] It may be desirable for the wireless power transmitter 12 and wireless power receiver 24 to be able to communicate information such as received power, other power level estimates, etc., to control wireless power transmission. However, the above-described technology does not need to involve the transmission of personally identifiable information to function. As a matter of prudence, it is noted that to the extent any implementation of this charging technology involves the use of personally identifiable information, implementers should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. In particular, personal information data should be managed and handled in a manner that minimizes the risk of unintended or unauthorized access or use, and the nature of authorized use should be clearly indicated to the user.

[0049] The control circuitry 16 may include an external object measurement circuitry 41 that may be used to detect whether an external object (including, but not limited to, a "foreign object") is present on or near a charging surface of the housing of the wireless power transmitter 12 (e.g., to detect an object on or adjacent to a charging mat or puck). The housing of the wireless power transmitter 12 may have polymer walls, walls of other dielectric materials, metal structures, fabric, and / or other housing wall structures that surround the coil 36 and other circuitry of the wireless power transmitter 12. The charging surface may be a flat exterior surface of the upper housing wall of the wireless power transmitter 12, or an exterior surface having another shape (e.g., concave, convex, etc.). The circuitry 41 may detect foreign objects such as coils, paper clips, and other metal objects, and may detect the presence of the wireless power receiver 24 (e.g., the circuitry 41 may detect the presence of one or more wireless power receiving coils 48). During object detection and characterization operations, the external object measurement circuitry 41 can be used to measure the coil 36 and / or other coils, such as optional additional foreign object detection coils, within the wireless power transmitter 12 to determine whether the wireless power receiver 24 and / or a foreign object is present on or near the wireless power transmitter 12.

[0050] In an exemplary configuration, measurement circuitry 41 of control circuit 16 may include signal generator circuitry, such as a pulse generator, that may provide control signals to inverter 61. These control signals may cause inverter 61 to generate impulses such that an impulse response may be measured by circuitry 41 (e.g., by using a voltage sensor, an analog-to-digital converter configured to convert analog voltage measurements to digital voltage measurements, and / or other sensing circuitry). Measurement circuitry 41 may also include an AC power source and / or other circuitry for making measurements on coil 36.

[0051] In some embodiments, quality factor measurements can be made on the coil 36 to determine if a foreign object is present. These quality factor measurements can include measurements of various observables of the wireless power system and need not be limited to Q-factor. Such factors can include, but are not limited to, resonant frequency, coupling coefficient, self-inductance, and combinations of these and other observables. In the description herein, Q-factor measurements are exemplary, but measurements of other observables can be substituted unless the context clearly dictates otherwise. For example, direct impedance measurements and / or impulse responses can be analyzed to make quality factor (Q-factor) measurements of the coil 36. Measurements of the Q-factor of the coil 36 (including measurements of changes in Q-factor from a baseline value) can be made at any appropriate time, such as before transmitting wireless power from the wireless power transmitter 12 to the wireless power receiver 24. This can include measurements made in the "open air," meaning that the wireless power receiver 24 is not present, and / or in a "combined" state, meaning that the wireless power receiver 24 is present and coupled to the wireless power transmitter 12. In the open air case, if the Q-factor deviates beyond a threshold amount (causing a "deviation" in the Q-factor) and the object causing the Q-factor deviation does not respond to subsequent digital pings or other attempts to establish communication, the wireless power transmitter 12 may conclude that a foreign object is present on the coil 36 and may cease wireless power transmission and / or take other appropriate action (e.g., by transmitting power at a limited level below the level permitted in the absence of a foreign object detected, by ceasing power transmission, etc.). In the combined case, the combined Q-factor measurement may be used to detect the introduction of a foreign object during or after the initiation of wireless power transmission. Such an event may similarly cause either throttling of wireless power transmission and / or reduction of power levels to limited levels, as described above.In general, Q-factor measurements, whether open-air or combined, can be performed using the same hardware and methods, and the control techniques implemented by the respective control circuits can be configured to respond appropriately to Q-factor (or resonant frequency) deviations based on thresholds and logic appropriate for each regime.

[0052] 2 illustrates an example circuit within the wireless power transmission system 8 that enables measurement of the Q-factor of the coil 36. The wireless power circuit of FIG. 2 may include a wireless power transmission circuit 52 within the wireless power transmitter 12 and a wireless power receiving circuit 54 within the wireless power receiver 24. In operation, a wireless power signal 44 may be transmitted by the wireless power transmission circuit 52 and received by the wireless power receiving circuit 54. As shown in FIG. 2, the wireless power transmission circuit 52 may include an inverter circuit 61.

[0053] An inverter circuit (inverter) 61 may be used to provide a signal to the coil 36. During wireless power transmission, a control circuit of the wireless power transmitter 12 may provide a signal to a control input 82 of the inverter circuit 61 that causes the inverter 61 to provide an alternating current (AC) drive signal to the coil 36. A circuit component, such as a capacitor 70, may be coupled in series with the coil 36 as shown in FIG. 2. When an alternating current (AC) current signal is provided to the coil 36, a corresponding alternating current electromagnetic signal (wireless power signal 44) may be transmitted to a nearby coil, such as the exemplary coil 48 in the wireless power receiving circuit 54, and may induce a corresponding AC current signal in the coil 48. A capacitor, such as capacitor 72, may be coupled in series with the coil 48. The rectifier 50 may receive the AC current from the coil 48 and produce a corresponding DC power (e.g., a DC voltage V rect ) can be generated. This power can be used to power a load.

[0054] The wireless power transmitter 12 may have a measurement circuit for monitoring the signal on the coil 36. This circuit may include, for example, a voltage sensor 90 (e.g., a voltage sensing circuit coupled to and / or formed as part of an analog-to-digital converter, etc.). A current source 92 and / or an inverter 61 may also be used to provide a signal to the coil 36 during a foreign object detection operation (e.g., so that the Q can be measured for the coil 36). In some embodiments, a Q factor measurement may be made using a direct measurement of the impedance of the coil 36 by an AC current source. A measurement of Q may be made when the wireless power receiving device 24 is present (a "combined Q measurement") and / or when the wireless power receiving device is not present (an "open air" measurement). In some applications or embodiments, periodic open air Q measurements may be made when the wireless power receiver 24 is not present and / or periodic combined Q measurements may be made when the wireless power receiver 24 is present. By monitoring the change in Q (open air or combined), the presence of a foreign object may be detected and appropriate action may be taken.

[0055] In a first exemplary Q-factor measurement configuration, the control circuitry of the device 12 can cause the inverter 61 to provide a signal pulse to the coil 36, and a measurement circuit, such as a voltage sensor 90, is used to measure a corresponding impulse response. Due to resonance in the circuit of FIG. 2, application of the signal pulse to the coil 36 produces a ringing signal having a decaying envelope, such as the decaying envelope 94 shown in FIG. 3. The decaying envelope can be

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[0056] If desired, the capacitor 70 of Fig. 2 can be implemented using an adjustable capacitor configuration, such as a capacitor circuit having a switching circuit and multiple capacitors that can be selectively switched under the control of the control circuit 16 to adjust the capacitance value in the resonant circuit and thereby the resonant frequency. In a configuration in which the capacitor 70 has a selectable or otherwise controllable value, a first value (e.g., C1) can be used when the impulse response of the wireless power transmission circuit is being measured to determine the Q (as described in connection with Fig. 3), and a second value (e.g., C2) can be used when the wireless power transmission circuit is transmitting the wireless power signal 44. In other embodiments, a single capacitance value can be used for both operations.

[0057] In a second exemplary Q-factor measurement configuration, the value of Q can be obtained from a direct measurement of the impedance of the coil 36. FIG. 4 is a circuit diagram of the wireless power transmission circuit and measurement circuit of FIG. 2, showing how a parasitic resistance R can be associated with the resonant circuit. In the direct impedance measurement approach, a small current can be injected into the coil 36 from a current source 92, and a voltage measurement can be made using a voltage sensor 90. The magnitude of the injected current can be low enough to allow the current to be injected without the use of large power field effect transistors. The current can be an alternating current (AC) current, for example, at a frequency selected to optimize the ability to identify the presence of a foreign object based on an LC tank design. In some cases, this can be a frequency of 125 kHz. However, depending on the design, higher or lower frequencies can be used. For example, another design can have a range of 150 to 300 kHz, but any suitable frequency can be used. In either case, this frequency can be selected independently of the resonant frequency associated with the wireless power transmission circuit. The complex impedance of the coil 36 can then be determined at this frequency, and the value of Q can be inferred from the angle θ of the measured impedance. 5 shows the equations related to the determination of Q (coil Q factor) from the angle of the complex impedance and any values ​​of inductance L and resistance R (the real part of the AC impedance) that can be calculated from direct impedance measurements. In the equations of FIG. 5, I is the injected AC current and V is the resulting voltage measured by voltage sensor 90.

[0058] The measurement circuitry 41 of the device 12 can be calibrated during manufacturing. For example, the Q-factor (Q0) measured at an initial time when the device 12 is being manufactured (using the first exemplary Q-factor measurement configuration, the second exemplary Q-factor measurement configuration, and / or additional Q-factor measurement techniques) can be stored in the device 12 as a baseline value for later use. Similarly, calibration can be performed for other observables to be measured, such as resonant frequency, etc. If desired, device-specific calibration operations can be performed such that each device 12 is individually calibrated with a corresponding individual baseline value of Q. When the device 12 is operated in the field, the device 12 can measure a current value of Q and compare this measured value of Q to a stored baseline value of Q0 from the factory. In this manner, an amount of change in Q or other observables that indicates whether a foreign object or other external object is present in the vicinity of the wireless power transmitter 12 can be determined.

[0059] If necessary, compensation techniques can be used to compensate for temperature, aging effects, and other effects that may induce drift in Q or other measured parameters. In the calibration examples below, a particular Q compensation technique is described, but other compensation techniques may be applied, and compensation for measured observables other than Q-factor (such as resonant frequency, coupling coefficient, etc.) may also be used. Temperature variations may affect the parasitic resistance of components such as the coil 36. The coil inductance L may also be temperature dependent. Frequency changes and aging effects (e.g., mechanical wear) may affect component values ​​and therefore the measured value of Q. Compensating for these effects when comparing Q to Q0 can help increase the accuracy of foreign object detection measurements.

[0060] The value of the baseline Q factor Q0 and the value of the resonant frequency ω0, i.e., 2πf r may be measured during calibration (e.g., an initial time during manufacturing) and given by Equations 3 and 4:

number

number

[0061] During the compensation operation, the current temperature T of the wireless power transmitter 12 can be measured using the temperature sensor 60 of the wireless power transmitter 12 (see, for example, FIG. 1). The temperature change ΔT from the temperature T measured during the calibration measurement during manufacturing is given by Equation 9:

number

[0062] A first exemplary compensation factor includes frequency compensation. As shown in the equation of FIG. 6, Q′ can be multiplied by a compensation factor (ω0 / ω) to compensate for the change in the measured resonant frequency of Q′ relative to the measured resonant frequency of Q0 at manufacturing. A second exemplary compensation factor relates to the temperature dependence of inductance and resistance. As shown in the equation of FIG. 6, Q′ can be multiplied by a compensation factor (1+κ R ΔT) / (1+κ L ΔT), where κ R is the resistive temperature coefficient, and κ Lis the inductive temperature change coefficient. The values ​​of these temperature coefficients may be affected by the design of the wireless power transmitter 12 and, if desired, may be determined empirically by performing measurements on one or more representative units of the wireless power transmitter 12 during manufacturing. A third exemplary compensation coefficient is the change in the AC resistance R of the coil 36 from a baseline value. AC and the DC resistance R of the coil 36 DC With this resistance compensation technique, the current value of the quality factor may be compensated based on a compensated value of the total (total) inductive coil resistance associated with the wireless power transmitting coil 36. The coil 36 may be characterized by a total inductive coil resistance value having a DC portion and an AC portion. During the compensation operation, the control circuit 16 may compensate for the change in the total inductive coil resistance by calculating a compensation value for the total inductive coil resistance from the sum of a baseline DC portion of the total inductive coil resistance measured at an initial time and the current AC portion of the total coil resistance. This compensated total inductive coil resistance value may then be used in compensating the current quality factor using the compensated total inductive coil resistance. As shown in the equation of FIG. 6, the resistance-based compensation coefficient is calculated by multiplying the measured baseline DC resistance (R DC,0 ), the baseline AC resistance (R AC ), and the AC resistance R as a function of the change in resonant frequency ω (e.g., 50 m-Ω per 100 kHz or other suitable value) obtained during calibration measurements during production. AC The parameter R can be based on the value of η, which is the coefficient of change of meas is the measured AC resistance R AC and the measured DC resistance R DC It is equal to the sum of.

[0063] In the example of FIG. 6, all three of these exemplary compensation factors are applied to the measured Q' value (e.g., Qcomp is determined by compensating Q' based on the change in frequency and the effects caused by the change in frequency, and based on the effects caused by the change in temperature). In general, one or two of these compensation techniques may be used, and / or other compensation techniques may be used, to calibrate the Q-factor measurement based on the measured temperature, resonant frequency, and / or other variables. As described in the previous example, a compensated Q-factor Qcomp may be generated based on the temperature and frequency measurements. This value may then be compared to a baseline value of Q measured during manufacturing and stored in the device 12 for use during later comparisons. If desired, rather than performing a compensation operation on a field measurement of Q, a compensation operation may be performed on a baseline Q-factor to generate a compensated baseline Q. An approach in which a compensation operation is performed on a field measured Q-factor rather than on a baseline Q-factor is described herein as an example.

[0064] A flow chart of an exemplary operation for detecting a foreign object using the wireless power transmission system 8 is shown in FIG. 7. In this embodiment, power delivery may be inhibited if a foreign object is detected. It is also possible to simply flag the detection of a foreign object for use as additional information in determining an appropriate power delivery level during the power delivery phase. As an example, the maximum power level used during a power delivery operation may be reduced to a predetermined level lower than the maximum power level in response to the detection of the presence of a foreign object.

[0065] During the operation of block 100, the wireless power transmitter 12 can measure the current value of Q using a first exemplary Q-factor measurement configuration (e.g., applying an impulse using the inverter 61 and measuring Q from the envelope 94 of the impulse response) or using a second exemplary Q-factor measurement configuration (e.g., deriving Q from a direct impedance measurement of the coil 36 performed by injecting current into the coil 36 using an AC current source 92). Measuring Q using techniques such as these or other suitable Q-factor measurement techniques is sometimes referred to as a low power ping (LPP) or analog ping operation.

[0066] During the operation of block 102, the value of the change in Q (e.g., the Q-factor deviation value Q defl During the operation of block 102, a compensation technique, such as the compensation technique described in connection with FIG. 6, may be applied to compensate for a measured value of Q or a baseline value of Q (i.e., Q0) stored in the wireless power transmitter 12 during manufacturing. Q defl The value of can be calculated using, as an example, Equation 10:

number

[0067] During the operation of block 103, the control circuitry of the wireless power transmitter 12 can determine whether Q has stabilized. If Q is changing rapidly (e.g., due to the movement of an external object across the charging surface of the wireless power transmitter 12 while the measurement is being taken), then Q defl The value of Q may not be sufficiently stable, and operations may return to block 100. A new measurement of Q may then be obtained during the operation of block 100. As long as Q is not stable, a new measurement of Q may be obtained in this manner every 0.1 seconds (or at another suitable sampling rate). defl When successive values ​​of change by less than a predetermined threshold amount (e.g., 1%), Q is used to determine whether a foreign object is present. defl may be deemed sufficiently stable to allow analysis of the value of , and operation may proceed to block 104.

[0068] During the operation of block 104, the wireless power transmitter 12 defl The value of Q can be compared to a predetermined threshold value TH (e.g., 3% or other suitable value). defl If Q does not exceed the threshold (e.g., the measured Q is not reduced by more than 3% relative to the baseline Q), the wireless power transmitter 12 may conclude that no external object is present (e.g., no wireless power receiving device 24 is present and no foreign object is present). The measurement operation may then continue in block 100. However, if Q deflIf Q is determined to exceed the threshold, then the device 12 may conclude that the measured Q has changed relative to the baseline Q0 by more than a threshold amount (e.g., Q is at least 3% lower than Q0) and therefore some type of external object is present (either a foreign object or a wireless power receiving device 24). Operation may then proceed to block 106 to distinguish between these two possibilities.

[0069] During the operation of block 106, the wireless power transmitter 12 may attempt to wirelessly communicate with the wireless power receiver 24. As an example, the device 12 may transmit a wireless digital request using in-band communication. The wireless digital request may be used to request that the wireless power receiver 24 acknowledge its presence by wirelessly transmitting a corresponding digital response to the wireless power transmitter 12 using in-band communication. This digital communication request process may also be referred to as a digital ping. During the operation of block 108, the wireless power transmitter 12 may determine whether a response to the digital ping is received from the wireless power receiver 24 to indicate the presence of the wireless power receiver.

[0070] If a wireless power receiver 24 is present on the charging surface of the wireless power transmitter 12, the wireless power receiver 24 responds to the digital ping with a wireless digital response. The response may include information such as a digital identifier corresponding to the type of wireless power receiver 24 present. In response to determining during the operation of block 108 that a mobile phone, watch, or other wireless power receiver 24 is present, the wireless power transmitter 12 may transmit a wireless power signal 44 to the device 24 (e.g., during the operation of block 110). Subsequent combined Q measurements may be performed during this period as well, as described in more detail below. Alternatively, if a wireless power receiver 24 is not present on the charging surface of the wireless power transmitter 12, the wireless power transmitter 12 does not receive any acknowledgement from the wireless power receiver 24. In response to determining during the operation of block 108 that a wireless power receiver 24 is not present, the wireless power transmitter 12 may conclude that a foreign object is present (causing the measured Q deviation), and operation may proceed to block 112.

[0071] During block 112, the wireless power transmitter 12 may monitor Q to determine when a foreign object present has been removed. In particular, Q may be measured during the operation of block 114 as described in connection with the Q measurement of block 100. Q defl The value of Q can be calculated in block 116. The operation of block 118 calculates Q defl The method may include comparing Q to a threshold value TH or another threshold value. If the foreign object remains present, Q defl remains above the threshold and additional measurements may be performed at block 114. If, however, the foreign object has been removed, processing returns to block 100 and the wireless power transmitter 12 may determine whether a wireless power receiver 24 is present and, if so, may begin providing wireless power to the wireless power receiver 24.

[0072] Q deflIn determining Q, the wireless power transmitter 12 may perform a comparison of the measured Q to a baseline value of Q obtained during manufacturing and stored in the wireless power transmitter 12 for future use. Temperature changes, frequency changes, coil resistance changes, and other changes may affect Q, and thus, Q may be continually updated, if desired. In an exemplary configuration, a filter is used in updating the Q baseline based on a newly measured Q reading each time it is determined that no foreign object is present on the charging surface of the wireless power transmitter 12. For example, the wireless power transmitter 12 may, during the operation of block 104, compare the measured Q to a baseline value of Q. defl Each time the wireless power transmitter 12 determines that Q is not greater than the threshold, the wireless power transmitter 12 may conclude that no foreign object or wireless power transmitting device is present. Thus, the wireless power transmitter 12 may conclude that the most recent measurement of Q from block 100 is, in effect, an updated open-air Q value (e.g., a current Q value that may be used as a filter input) that may be used at least in part in updating Q0.

[0073] Therefore, in this embodiment, Q defl Each time it is determined that Q is not greater than the threshold TH, an updated value of Q0 may be stored in the wireless power transmitter 12 at point P1 of the flowchart of Figure 7. In updating Q0, the current value of Q (measured during the most recent visit to block 100) may be incorporated into Q0 using an appropriate filtering scheme (e.g., using a weighted historical average, using an averaging scheme that de-emphasizes noisy data, or using other filtering configurations). Updating Q0 with the current measurement data in this manner may reduce the effects of aging on the baseline Q value.

[0074] In an exemplary configuration, the wireless power transmitter 12 can use a low-pass filter to update Q0 with the current value of the measured Q. Let q[n] be a valid Q deviation sample. One example of a low-pass filter for Q is a one-pole filter (see, e.g., Equation 11), where α∈[0,1] and is close to 1.

number

number

[0075] Updating the baseline Q value at point P1 may include performing a separate filtering operation following each measurement of Q in block 100. If desired, the number of filtering operations per unit time (and therefore the number of times per unit time that an updated value of the Q baseline is calculated and stored in device 12) may be reduced by performing a filtering operation at point P2 instead of P1. In this type of configuration, the value of Q measured during the operation of block 100 may be stored (cached) by control circuitry 16 each time point P1 is reached (e.g., each time it is determined that no foreign object is present). If the operation of block 104 determines that the latest Q value exceeds threshold TH, processing may proceed to block 106, where a digital ping is performed. During the operation of block 108, control circuitry 16 may determine whether (a) a response corresponding to the digital ping has not been received (in which case a foreign object is present and processing proceeds to block 112), or (b) a wireless digital response has been received from device 24. At this point (e.g., at point P2), the wireless power transmitter 12 may know that the wireless power receiver 24 has just been placed on the charging surface of the wireless power transmitter 12. Before initiating power delivery at block 110, the wireless power transmitter 12 may retrieve the last value of Q that was cached at point P1 (representing a Q-factor measurement when no foreign objects or other external objects are present on the device 12) and may use this retrieved current value of Q to update the value of the Q baseline.

[0076] In this approach, the filtering operation used to update the value of the Q baseline may be performed only when the wireless power receiver 24 is determined to be newly present (and foreign object is not present). The filtering operation may be performed using the most recently obtained value of Q when no foreign object was present (e.g., the foreign object-free value of Q cached at point P1). There is still a Q value storage operation each time point P1 is reached, but the calculation of an updated baseline Q value using the filter may be performed less frequently (e.g., only when P2 is reached). Updating the baseline Q factor only when it is determined that no wireless power receiving device is present and no foreign object is present ensures that the baseline quality factor value is adjusted for aging and other effects that may cause quality factor measurements to drift over time, but does not involve as many separate filtering operations as when the filtering operation is performed at point P1.

[0077] In addition to periodically updating the baseline value of Q (e.g., at either point P1 or point P2), the control circuit 16 may periodically update the value of the threshold TH used during the comparison operation of block 104 (e.g., an adjustable threshold TH may be used rather than a fixed, predetermined value). For example, a low-pass filtering operation or other filtering operation may be used to update the value of TH based on a history of Q-factor measurements or other measurements (e.g., Q-factor measurements made when no external object was present and cached at point P1). This filtering operation to update the value of TH may be performed at point P2 (e.g., upon determining that no foreign object is present) using measurements such as one or more cached Q-factor measurements made when no wireless power receiving device or foreign object was present.

[0078] If desired, Q deflThe value of may be compared to multiple different thresholds (e.g., to determine whether a small or large foreign object is present). The device 12 may then take different actions depending on whether a small or large foreign object is present. For example, wireless power may be transmitted at a limited power level if a small foreign object is detected in the presence of a wireless power receiving device, but may be discontinued entirely in the presence of a large foreign object. In this context, small or large may refer to the physical size and / or other physical characteristics of the device that correlate to the level of heating that such a foreign object may be expected to experience at various wireless power transmission levels.

[0079] As an example, consider the diagram of Figure 8, which illustrates the operation of a wireless power transmitter 12 in a system with multiple foreign object detection thresholds. In the example of Figure 8, the wireless power transmission system 8 operates with a first lower threshold TH air (e.g., 3%, or any other suitable value, such as a value less than 3% or a value greater than 3%), and a higher second threshold TH FO (e.g., 6%, a value greater than or less than 6%, or any other suitable value greater than the first threshold). The wireless power transmitter 12 can operate in states 120, 122, 124, and 126. Transitions between these states can occur according to transition rules 128. The threshold TH air and T.H. FO The value of can be appropriately tuned to distinguish medium foreign objects (e.g., objects with relatively small amounts of metal and / or medium conductivity metal) from strong foreign objects (e.g., objects with more metal and / or greater conductivity metal). These "medium" and "strong" foreign objects may correspond to the "small" and "large" foreign objects described above. Wireless power transmission may be inhibited in the case of a strong foreign object until free air is visible. However, by setting the threshold high enough, an implementation may choose to avoid using the "strong foreign object" state.

[0080] As shown in FIG. 8, in block 122, the wireless power transmitter 12 deflcan be compared to first and second thresholds, Q defl is lower than the first threshold. In this scenario, the wireless power transmitter 12 may conclude that no foreign object is present and, therefore, may set the power delivery level of the wireless power signal 44 to a relatively high power level (power level 2). Power may then be transmitted wirelessly from the wireless power transmitter 12 to the wireless power receiver 24 during the power delivery operation of block 126.

[0081] In block 120, Q defl Since Q is greater than the first threshold, it may be determined that a foreign object is present. defl It may also have been determined that Q is less than the second threshold. As a result, the wireless power transmitter 12 may conclude that a foreign object is present, but that it is not a large or strong foreign object. Thus, the wireless power transmitter 12 may proceed to wirelessly provide power to the wireless power receiver 24 during operation of block 126. Since power is being provided to the wireless power receiver 24 in the presence of a small or medium foreign object, the level at which power is wirelessly transmitted (i.e., the maximum power level) may be reduced to a relatively low power level (e.g., power level 1, which is less than power level 2). This may help prevent or limit heating of the small / medium foreign object. In block 124, Q defl is greater than the second threshold, it can be detected that a large or strong foreign object is present. In this situation, the wireless power transmitter 12 can cease wireless power transmission.

[0082] The above-described embodiments are merely exemplary, and different control logic may be implemented, including multiple thresholds, multiple power levels, and variations in whether wireless power transmission is limited or completely suppressed depending on the respective thresholds. In addition, further details of Q measurement techniques, compensation methods, accuracy improvements for such measurements, etc. are described in applicant's U.S. patent application Ser. No. 18 / 327,721, entitled "Wireless Power Systems with Foreign Object Detection," filed Jun. 1, 2023, which is incorporated herein by reference in its entirety.

[0083] As mentioned above, foreign object detection in a wireless power transmission system can also be based on combined Q measurements, either separately from or together with the open-air Q measurements as described above. At a high level, the operating principle of combined Q measurements is as described above. That is, when a wireless power transmitter 12 is coupled to a wireless power receiver 24, the corresponding control circuit 16, measurement circuit 41, and power transmission circuit 52 may be configured to provide a signal that allows measurement of the combined Q factor (or other magnetic parameter(s) as described above). This signal may be in the form of an impulse response and ring-down, as described above with respect to Figs. 2-3. Additionally or alternatively, this measurement may be based at least in part on a complex impedance measurement, as described above with respect to Figs. 4-5. The Q deviation or other magnetic parameter thus obtained may be used in conjunction with a measurement of the system resonant frequency for foreign object detection. The system resonant frequency may be derived from an impulse-based measurement of the Q deviation, performed as described with reference to Figs. 2-3. More specifically, the resonant frequency is a coefficient that characterizes the ring-down envelope 94 (along with the Q-factor) and / or can be measured directly by reference to the ringing waveform. Alternatively, the system resonant frequency may be determined by circuitry such as those used for complex impedance measurements as described with reference to Figures 4-5, for example by sweeping the frequency of an applied waveform and identifying a peak associated with the resonant frequency.

[0084] For a given wireless power transmitter 12, one or more baseline combined Q value and resonant frequency value pairs, each pair corresponding to one or more reference receivers 24, may be obtained, for example, during manufacturing of the wireless power transmitter 12. Such one or more baseline combined Q value and resonant frequency value pairs may be compared to combined Q and resonant frequency measurements made during operation to detect foreign objects that may be brought near the wireless power transmission system 8 during operation. In some cases, the number of potential wireless power receivers 24 may be such that it is difficult to measure and store a pair of values ​​for every possible transmitter / receiver combination. In such cases, ecosystem scaling principles, described in more detail below, may be employed to make the situation more tractable by storing fewer baseline value pairs and providing a mechanism for the calculation of modified baseline value pairs corresponding to a particular transmitter-receiver combination.

[0085] The baseline or modified baseline values ​​can be compared to measurements in a two-dimensional space where the presence and absence of foreign objects are sufficiently separated. Such a space can be thought of as a magnetic state space where normal operation (no foreign object present) is sufficiently separated to be distinguishable from a scenario where heating may occur if a foreign object is present and not detected. An example of such a space is shown in FIG. 9 by plot 900. Plot 900 plots a first observable (x(f,Q), e.g., measured resonant frequency deviation) that is a function of resonant frequency and Q-factor on the x-axis versus a second observable (y(f,Q), e.g., measured combined Q deviation) that is a function of resonant frequency and Q-factor on the y-axis. The measured resonant frequency deviation can be the difference between a measured resonant frequency during operation and a baseline resonant frequency (optionally corrected by ecosystem scaling calculations as described in more detail below). The measured combined Q deviation can be the difference between a measured combined Q value during operation and a baseline Q-factor (optionally corrected by ecosystem scaling calculations as described in more detail below). When no foreign object is present, the combined Q and resonant frequency deviation values ​​(or deviations of other magnetic parameters as described above) generally appear in region 905. When a foreign object is present, the combined Q and resonant frequency deviation values ​​generally appear in region 903. FIG. 9 is based on the fQ space. 2 , 1 / fQ space, the relative positions between the regions corresponding to the presence and absence of a foreign object may be inverted, as will be described below with reference to Fig. 17A, and therefore the relative positions between these regions may vary depending on the function selected.

[0086] The separation between these two regions, i.e., no foreign object present or foreign object present, can be depicted by a curve 901. Curve 901 may be a linear function of the following form:

number

number

[0087] FIG. 10 shows a flow chart of a foreign object detection method 1000 using combined Q measurements as described above. Beginning at block 1007, the system may optionally execute an open-air Q based foreign object detection routine as described above. In response, the system may begin power transmission at an appropriate level (block 1009), as described above. The exact operation of the open-air Q portion of the combined Q foreign object detection method 1000 may vary depending on the particular implementation, and / or may be omitted entirely, as desired, in some embodiments. The combined Q portion of the foreign object detection method 1000 begins at block 1011, where the combined Q and resonant frequency are measured as described above. Then, at block 1013, the system (e.g., the control circuitry 16 of the wireless power transmitter 12) may determine whether a foreign object is present by comparing the measured combined Q to the resonant frequency, as described above. For example, the processing circuitry may compare the measured combined Q and resonant frequency values ​​to reference values ​​stored in the device and determine whether the associated deviation corresponds to region 905 (FIG. 9) (no foreign object present) or region 903 (FIG. 9) (foreign object present) of the magnetic state space. If it is determined that no foreign object is present, the process may proceed to block 1014, allowing wireless power transfer to continue or resume at a relatively high power level. Control may return to block 1011, allowing combined Q and resonant frequency measurements to be made periodically at desired intervals during the power transfer operation initiated in block 1009, allowing ongoing / continuous combined Q foreign object detection.

[0088] Alternatively, if a foreign object is determined to be present in block 1013, the processing circuitry may determine whether the detected foreign object is a "medium" or "small" foreign object, or a "strong" or "large" foreign object, as described above. Additionally, more than two tiers of foreign object classification may be provided. In general, a medium / small foreign object is one that may allow wireless power transmission at a limited or lower power level without increasing the heating level of the foreign object (e.g., exceeding a threshold). Similarly, a strong / large foreign object is one that may require the suppression or suspension of wireless power transmission to prevent elevated levels of heating. What constitutes an elevated level of heating and thus defines the classification of a foreign object as medium / small or strong / large (or further tiers) may vary from application to application or embodiment. However, it may be desirable for the combined Q and / or resonant frequency deviation to be sufficiently different between such classes to allow for easy analysis by the processing circuitry (e.g., the control circuit 16 of the wireless power transmitter 12). Based on this classification, if the detected foreign object is determined to be a small / medium foreign object in block 1015, the power transfer level can be reduced in block 1017 and control can return to block 1011 to allow continuous / periodic combined Q foreign object detection. If the foreign object is subsequently removed, power transfer can resume at a higher level (block 1014). Alternatively, if the foreign object remains, flow again proceeds along the same 1015-1017-1011 path described above. As yet another alternative, if the detected foreign object is determined to be not a medium / small foreign object in block 1015 and thus a strong / large foreign object, control proceeds to block 1019 and wireless power transfer is suspended or inhibited. Then, once the open air ping process determines that the foreign object is no longer present, control returns to block 1007 for resumption of power transfer. If the open air ping function 1007 is omitted from a particular embodiment or application, control can return to any path that results in the initiation of wireless power transfer (e.g., block 1009).

[0089] The foregoing description is only one example of a combined Q-based foreign object detection and wireless power transfer control technique based thereon. Various modifications to such a configuration are possible. For example, classification of detected foreign objects as medium / small or strong / large can be omitted entirely, and detection of any foreign object in the combined Q phase can result in suspension / suppression of wireless power transfer. Similarly, there may be multiple classifications of foreign objects, each with different reduced power limits. Also, as noted above, the initial open-air Q-measurement foreign object detection algorithm can be omitted or modified from the above-described example. Numerous other variations and permutations are possible.

[0090] 11 shows a sequence of combined Q measurements associated with stationary / quiet detection that may be used for foreign object detection. The sequence is shown as a plot 1100 of measured combined Q deviation (on the vertical axis) versus time (on the horizontal axis), with each combined Q measurement being a point. The combined Q deviation is the difference between the measured combined Q value at that moment and a reference combined Q value stored in the device, e.g., wireless power transmitter 12. The initial reference value may be programmed into the unit at the time of manufacture or may be updated periodically as described elsewhere herein.

[0091] An initial sequence 1121 of zero Q deviation values ​​corresponds to a situation where no object is present, either a foreign object or a wireless power receiver. These intervals may provide an opportunity to update stored reference values, as described elsewhere herein. Beginning at approximately 2 seconds in the exemplary plot 1100, the Q deviation values ​​begin to increase but do not have a steady value over a series of samples 1123. This corresponds to a time when an object, which may be a wireless power receiver or a foreign object, is being brought close to the transmitter. During this interval, it may be desirable for the processing system, e.g., control circuit 16 or wireless power transmitter 12, to do nothing until the Q deviation readings stabilize. Nevertheless, in some situations, e.g., very large Q deviations, it may be desirable to take action more quickly to reduce or inhibit power transmission. In either case, the processing circuit may apply appropriate averaging or filtering to the Q deviation values ​​to determine whether the system has reached a stable steady state point. Such a steady state may be indicated when the sequence of measured Q deviation values ​​shows no change, such as sample 1125. Sample 1125 shows that the system has stabilized at a Q deviation value of about 0.5 (other Q values ​​are possible as well). This stabilized Q deviation value (and its associated resonant frequency value) can then be used to perform combined Q foreign object detection as described above. In some cases, a sequence of combined Q measurements (rather than deviation), resonant frequency measurements, or resonant frequency deviations can be used to detect whether the system has reached a steady state of operation when an object is brought nearby. Indeed, in some applications, resonant frequency measurements and / or resonant frequency deviations may provide a better estimate of when the system has stabilized than the combined Q value / deviation samples.

[0092] As mentioned above, the use of combined Q measurements for foreign object detection may depend on baseline combined Q and resonant frequency measurements, which may be different for each potential wireless power transmitter and wireless power receiver pair. In some cases, multiple such baseline values ​​may be determined, for example, at the time of manufacture and stored in the wireless power transmitter as described above. However, as the number of potential transmitter / receiver pairs becomes large, this may quickly become infeasible. Therefore, it may be desirable to provide one or more baseline value pairs for each transmitter based on one or more "reference" or "golden" receiver pairings. Each receiver may then be characterized against one or more of the reference / golden receivers and provided with its own stored values ​​corresponding to such characterization. For example, this may be implemented as various scaling factors against the reference / golden receivers. The wireless power receiver may then provide its scaling factors to the wireless power transmitter, which may then calculate the appropriate baseline combined Q factor and resonant frequency value based on the stored reference values ​​and scaling factors. Exemplary techniques for loss measurement scaling are described in the applicant's U.S. patent application Ser. No. 17 / 681,363, entitled "Wireless Power Systems with Shared Inducive Loss Scaling Factors," filed Feb. 25, 2022, which is incorporated by reference in its entirety and summarized below with reference to Figures 2, 12, and 13.

[0093] As mentioned above, Figure 2 illustrates an example wireless power circuit in a wireless power transmission system 8 in an example scenario where a wireless power transmitter is paired with a wireless power receiver. The wireless power circuit of Figure 2 includes a wireless power transmit circuit 52 in the wireless power transmitter 12 and a wireless power receive circuit 54 in the wireless power receiver 24. In operation, a wireless power signal 44 is transmitted by the wireless power transmit circuit 52 and received by the wireless power receive circuit 54. The configuration of Figure 2 includes (by way of example) a single transmit coil 36 and a single receive coil 48.

[0094] As shown in FIG. 2, the wireless power transmission circuit 52 may include an inverter circuit 61. The inverter circuit (inverter) 61 may be used to provide a signal to the coil 36. During wireless power transmission, a control circuit of the wireless power transmitter 12 may provide a signal to a control input 82 of the inverter 61 that causes the inverter 61 to provide an AC drive signal to the coil 36. A circuit component such as a capacitor 70 may be coupled in series with the coil 36 as shown in FIG. 2. The measurement circuit 41 in the wireless power transmitter 12 may perform measurements related to operating currents and voltages in the wireless power transmitter 12. For example, a voltage sensor 41A may be used to measure a coil voltage on the coil 36, and a current sensor 41B may be used to measure a coil current through the coil 36. In other implementations, the voltage on the capacitor 70 may be measured, and from that measurement, the current through the coil may be inferred.

[0095] When an alternating current signal is provided to the coil 36, a corresponding alternating electromagnetic signal (wireless power signal 44) may be transmitted to a nearby coil, such as exemplary coil 48 in the wireless power receiving circuit 54. This may induce a corresponding alternating current (AC) current signal in the coil 48. A capacitor, such as capacitor 72, may be coupled in series with the coil 48. The rectifier 50 may receive the AC current from the coil 48 and produce a corresponding DC power (e.g., a DC voltage V rect ) can be generated. This power can be used to power a load. Measurement circuitry 43 in device 24 can make measurements related to operating currents and voltages in device 24. For example, voltage sensor 43A can measure V rect The current sensor 43B may measure the rectifier output current of the rectifier 50, or the current sensor may measure the current in the coil 48.

[0096] The measurements made by measurement circuitry 41 and measurement circuitry 43 may be processed to extract magnetic loss characteristics (e.g., coefficients or other parameters that characterize the amount of power loss in the wireless power transmitter 12 and wireless power receiver 24 and that depend on the magnetic properties of the transmitter and receiver). These measurements may be stored within each device or exchanged between devices so that the wireless power transmitter 12 (and, if desired, the wireless power receiver 24) can use this information in accurately estimating any foreign object power losses that may be present and / or other related parameters, such as a combined Q measurement and / or a combined resonant frequency measurement.

[0097] If desired, these measurements may be used to estimate how well the transmitter and receiver can transmit wireless power. For example, these measurements may be used to estimate the magnetic coupling coefficient K, the wireless power transmission efficiency, the estimated foreign object power loss, and / or other attributes of the combined transmitter-receiver pair. In addition to or instead of estimating the foreign object power loss to determine whether a foreign object is present and therefore whether to proceed with wireless power transmission, the system may use this information (e.g., the estimated foreign object power loss and / or associated coupling and / or efficiency information) to determine whether to present a confirmation message to a user of the system informing the user that wireless power transmission is proceeding properly (e.g., informing the user that the process was not impeded by the presence of a foreign object, possible misalignment, or poor coupling due to other factors). Exemplary confirmation messages include an audio output, such as a chime, and / or a visual output presented on the wireless power receiver 24.

[0098] In general, any suitable information may be exchanged between devices in system 8, and this information may be used in any suitable manner. The exchange of measurements such as those obtained using measurement circuitry 41 and measurement circuitry 43, and the use of this information in determining whether a foreign object is present, is exemplary.

[0099] Following measurements using circuits 41 and 43, the amount of power potentially absorbed by a foreign object in system 10 can be determined using Equation 14.

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[0100] In Equation 14, P FO represents the amount of power absorbed by foreign objects present (if any). P OUT represents the output power (e.g., the output power of the rectifier 50), and P IN represents the input power (e.g., the input power to the coil 36), and P LOSSTX represents the power loss caused by the wireless power transmitter 12, and PL OSSRX represents the power loss due to the wireless power receiver 24. OUT and P IN The value of P can be measured (for example, using circuits 41 and 43). Using a mathematical model, LOSSTX and P LOSSRX A functional representation of P may be generated, which may be evaluated using measured operating parameters, such as measurements obtained using circuit 41 and circuit 43. For example, in one exemplary modeling embodiment, P LOSSTX and P LOSSRX can be calculated using Equations 15a and 16a, respectively.

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[0101] In formulas 15a and 16a, I TX represents the transmitter current (e.g., coil current), and I RX R represents the receiver current (e.g., the rectifier output current, or in some embodiments, the receiver coil current). AIRTX and R AIRRX The values ​​of b, m, α and α represent the AC coil resistances measured for coil 36 and coil 48, respectively. DCThe value of is a model parameter (sometimes called the magnetic power loss coefficient) that characterizes the performance of a coupled wireless power transmitter and wireless power receiver pair in the wireless power transmission system 8. LOSSTX is due only to the transmitter coil power losses in the model of Equation 15a. The receiver power losses P LOSSRX has a first component due to receiver coil power losses (first term in Eq. 16a) and a second component (consisting of the last two terms in Eq. 16a) that represents friendly metal losses (e.g., losses due to eddy currents induced in the receiver when power is being transmitted). Parameter b may be referred to as a transmitter coil loss parameter or coefficient. Parameter m may be referred to as a receiver coil loss parameter or coefficient, and parameters α and α DC may be called the friendly metal loss parameter or friendly metal loss factor. The parameters b, m, α and α DC depends on the magnetic interaction between the wireless power transmitter 12 and the wireless power receiver 24 when coupled, and may therefore be referred to as a magnetic loss parameter or magnetic loss coefficient.

[0102] In an ecosystem where there are multiple different models of wireless power transmitting devices (e.g., different models of wireless power transmitters 12) and multiple different models of wireless power receiving devices 24 (e.g., different models of either device) available to users, the magnetic loss parameters may vary depending on which particular wireless power transmitter and wireless power receiver are paired together. As an example, when a model I transmitter and a model J receiver are paired, the amount of power loss in each device is different than the amount of power loss experienced when these devices are paired with different devices.

[0103] To account for these variations and thereby ensure accurate estimation of the foreign object power loss in Equation 14, a magnetic power loss parameter scaling factor (sometimes referred to as a magnetic power loss coefficient scaling factor) may be used. In particular, the P in Equations 15a and 16a, which may be inaccurate in an ecosystem with multiple different transmitter and receiver models, LOSSTX and P LOSSRX can be replaced by Equation 15b and Equation 16b, respectively.

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[0104] In Equation 15b, the transmitter coil loss parameter b from Equation 15a is converted to a reference transmitter coil loss value b that is related to the transmitter loss measured when the reference transmitter is coupled to a reference receiver. R (sometimes called the transmitter coil loss factor). This value is then scaled by a scaling factor g b In Equation 16b, the receiver coil loss parameter m is related to the receiver coil loss measured when the reference receiver and reference transmitter are coupled, m R (sometimes called the receiver coil loss factor). This value can then be replaced by the scaling factor g m In Equation 16b, the friendly metal loss parameters α and α DC is the reference friendly metal loss parameter (coefficient) α extracted using measurements made at the reference transmitter and the reference receiver. R and α RDC The reference friendly metal loss parameters can be replaced by the respective scaling factors g α and g αDC It can be scaled by P LOSSTX (See, for example, Equation 15b) and P LOSSRX(see, for example, Equation 16b), Equation 14 can be evaluated satisfactorily regardless of which model of transmitter and receiver are paired with each other.

[0105] Exemplary operations involved in using measuring transmitters and receivers to determine their scaling parameters are shown in flow chart 1200 of FIG. 12. The operations of FIG. 12 may be performed at design time, and the resulting scaling coefficients may be stored in a production unit. Exemplary operations involved in using scaling parameters in wireless power transmission system 8 are shown in FIG. 13. The operations of FIG. 13 may be performed at run time (e.g., when a transmitter and receiver are paired in preparation for transmitting wireless power between them). In the examples of FIG. 12 and FIG. 13, it may be assumed that scaling coefficients for a particular model transmitter (e.g., a Model I transmitter) and a particular model receiver (e.g., a Model J receiver) have been obtained using reference device measurements and are then used when the Model I transmitter is paired with the Model J receiver. In general, it may be expected that this process will be performed for multiple models of transmitters (e.g., models other than Model I) and multiple models of receivers (e.g., models other than Model J). Furthermore, any of the various models of characterized transmitters may generally be paired by a user with any of the various models of characterized receivers. This is because not all users have the same model transmitter and not all users have the same model receiver. In this example, an exemplary user pairs a Model I transmitter with a Model J receiver during operation of FIG.

[0106] The operations involved in measuring the magnetic power loss parameter scaling factors of a model I transmitter and a model J receiver are illustrated in FIG. 12. During the operation of block 1290, a reference wireless power receiver is paired with a reference wireless power transmitter (physically or by simulated pairing, such as finite element analysis simulation pairing). The physical reference device may be obtained from a centralized source or may be built by different device manufacturers according to a globally disseminated reference design. Once paired, the reference wireless power transmitter and the reference wireless power receiver may begin transmitting power. In particular, during the operation of block 1290, the reference wireless power transmitter may transmit a wireless power signal to the reference wireless power receiver while internal operating parameters (e.g., transmitter and receiver currents and voltages) are measured and stored. From these measurements, a reference magnetic loss parameter may be extracted (e.g., a reference magnetic loss parameter b R , m R , α R , and α RDC In scenarios where pairing simulation is used instead of measurements on physically paired devices, finite element analysis simulations can be used to determine the LQK (inductance, Q-factor, and coupling coefficient) of the coupled transmitter-receiver pair, and then circuit simulations can be used to determine the expected currents and voltages. These simulated currents and voltages can then be used to determine the magnetic loss parameters.

[0107] After determining the reference magnetic loss parameters (either by physical measurement or simulation), the model J receiver can be paired with the reference wireless power transmitter. The model J receiver loss parameter measurements can be obtained while the devices are paired in a simulation, or while the devices are physically paired and wireless power is transmitted from the reference wireless power transmitter to the model J receiver. In particular, during the operation of block 1292, the model J loss parameters (coefficients) b RJ , mRJ , α RJ , and α RJDC The "J" in each of these parameters and the R (for "reference") in each of these parameters indicate that the loss parameters are specific to a scenario in which a model J receiver is operating with a reference wireless power transmitter. The scaling factor g b (Equation 15b) can be calculated using Equation 17 (below) and stored in all model J wireless power receiving devices (eg, during manufacturing or with a later update).

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[0108] During the operation of block 1294, the Model I transmitter may be paired with a reference wireless power receiver. Power may be transmitted wirelessly while the wireless power transmitter operating parameters (e.g., current and voltage) are measured. From these measurements or simulations, the magnetic loss parameter m of the Model I transmitter may be determined. IR , b IR , α IR , and α IRDC Then, using equations 18, 19, and 20, the scaling factor g m , g α , and g αDC can be calculated.

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[0109] Exemplary operations involved in the use of scaling factors for a model I transmitter and a model J receiver in a scenario in which the model I transmitter and the model J receiver are paired by a user are illustrated in the flow chart of FIG. 13. During the operations of FIG. 13, a user having a model J receiver and a model I transmitter who desires to wirelessly transfer power from the model I transmitter to a model J pairs the model I transmitter and the model J receiver during the operations of block 1301 (e.g., by magnetically coupling the model I wireless power transmitter (e.g., by way of example only, a wireless charging pack) to the model J wireless power receiver (e.g., by way of example only, a mobile phone). During the operations of block 1302, the model I transmitter and the model J receiver can exchange information such as their preprogrammed scaling factors (e.g., using low power in-band communications or other wireless communications) and transfer power. For example, the model J receiver can transmit to the model I transmitter a value of the scaling factor g obtained from a model J measurement with a reference transmitter in block 1292 of FIG. 12. The Model I transmitter is configured to use the scaling factor g obtained from the Model I measurement using the reference receiver in block 1294 of FIG. m , g α , and g αDC , and transmits a value of P to the model J receiver. During the wireless transfer of power from the model I transmitter to the model J receiver, measurement circuitry 41 in the wireless power transmitter and measurement circuitry 43 in the wireless power receiver can measure operating parameters of the transmitter and receiver (e.g., coil current and voltage, rectifier output voltage and current, etc.). Current and voltage measurements can be exchanged between the wireless power transmitter and wireless power receiver, if desired (e.g., using in-band wireless communication). The information measured by circuits 41 and 43 can be calculated using Equations 15b and 16b to calculate P LOSSRX and P LOSSTX This can be used in conjunction with the exchanged scaling factors to compute

[0110] During the operation of block 1304, for example, a model J receiver calculates the rectifier current and the rectifier voltage (the product of which is P OUT) received from the Model I transmitter during operation of block 1202. m , g α , and g αDC Using the measurements in conjunction with, we evaluate Equation 16b, thereby LOSSRX The scaling coefficients received from the Model I transmitter can provide receiver J with information about the expected operating characteristics of the Model I transmitter with respect to receiver coil losses and friendly metal losses.

[0111] As an example, consider receiver coil losses. When a receiver J is paired with a reference wireless power transmitter, the scaling factor g m The value of is 1. The receiver J can then determine the receiver coil loss using the first term of Equation 16b (the receiver coil loss is m R ·R AIRRx ·(I RX ) 2 and m R , R AIRRX , and the receiver current I RX The value of g is known to receiver J. However, in this situation, receiver J is not paired with the reference wireless power transmitter, but instead is paired with transmitter I. Since transmitter I may have been pre-determined to induce lower coil losses in the paired receiver than the reference transmitter, the g that transmitter I passed to the model J receiver during block 1302 may be m The value of P may be 0.9 (as an example). When the Model J receiver evaluates Equation 16b using the scaling factor value of 0.9 received from the Model I transmitter, the Model J receiver evaluates Equation 16b with a somewhat reduced P (due to the presence of the Model I transmitter, which is known to induce less receiver coil loss than the reference wireless power transmitter). LOSSRX As this example demonstrates, by using the scaling coefficients received from the model I transmitter, receiver J accurately estimates the value of P LOSSRXThe magnetic loss parameters used to calculate P can be appropriately scaled to reflect the presence of a Model I transmitter in place of the reference wireless power transmitter, thereby LOSSRX This allows for improved accuracy in estimating the value of

[0112] During the operation of block 1306, the Model I transmitter generates a measured transmitter coil current I TX Measurement value of b R and R AIRTX , as well as the scaling factor g received from the wireless power receiver during the evaluation in Equation 15b. b Using P LOSSTX The scaling factor g can be estimated. b reflects how a model J receiver is expected to affect the transmitter coil loss in a transmitter paired with the model J receiver instead of the reference wireless power receiver. As an example, a model J receiver may tend to cause the paired transmitter to account for a higher transmitter coil loss than the reference wireless power receiver. As a result, the scaling factor g that a model I transmitter receives from a model J receiver b The value of may be 1.1 (as an example). When evaluating Equation 15b, the increased scaling factor helps transmitter I account for the fact that it is coupled to a model J receiver and therefore should expect larger transmitter coil losses than if it were coupled to a reference wireless power receiver.

[0113] During the operation of block 1307, P calculated in block 1304 LOSSRX During the operation of block 1308, the wireless power transfer system 8 (e.g., the wireless power transmitter 12 and / or associated control circuitry 16) may transmit the value of P FO The value of P can be evaluated (e.g., if there is foreign object power loss, an estimate of the foreign object power loss can be made). Using the scaling factor information received from the Model J receiver, LOSSTX Accurately estimate and transmit P from the Model J receiver. LOSSRXBy receiving an estimate of P, the Model I transmitter can calculate P for Equation 14. LOSSTX and P LOSSRX It is possible to have both. IN The value of is determined by the transmitter coil current (I TX ) and the voltage from the measurement circuit 41. OUT The value of is the receiver coil current I RX and the rectifier output voltage received from the measurement circuit 43, or by calculating P OUT The information can be obtained by receiving the

[0114] During the operation of block 1308, FO After determining the value of P FO can be compared to a threshold power loss value (TH). Appropriate action can then be taken by the wireless power transfer system 8. For example, P FO In response to determining that P is less than TH, it may be concluded that no foreign object is present and may allow the power transfer operation to proceed normally (e.g., to transfer power to charge the battery 58). FOIn response to determining that T is greater than TH, the power transfer operation may be limited. Examples of power transfer limitations that may be implemented include canceling all power transfer operations (i.e., inhibiting wireless power transfer) and / or stopping power transfer if already in progress, limiting the maximum amount of power that may be transferred (e.g., to a relatively low, predetermined power level that is below the normal maximum power transfer capability of the wireless power transfer system), and / or issuing a visual, audio, and / or vibration alert to the user. If desired, an alert to the user (e.g., a warning and / or other informational content informing the user that a power transfer operation is not proceeding normally because a foreign object has been detected) may be presented using an output device within the wireless power transmitter 12 and / or wireless power receiver 24. For example, control circuitry within the wireless power transmitter 12 may wirelessly communicate with control circuitry within the wireless power receiver 24 to issue a visual alert that is presented on a display within the wireless power receiver 24.

[0115] The above-described exchange of scaling parameters between various wireless power transmission devices may be thought of as providing "ecosystem scaling" in that it expands the "ecosystem" of devices that can cooperate to provide wireless power transmission and foreign object detection. Such ecosystem scaling may be extended to the context of combined Q foreign object detection, as described above.

[0116] The basic procedure for performing combined Q ecosystem scaling includes four steps 1431-1434 shown in FIG. 14. (As used herein, a "step" refers simply to a respective operation that is performed and is not intended to invoke a "step-plus-function" interpretation of any claim that refers to elements of steps 1431-1434, unless the phrase "step for xyz" is explicitly used in such claim.) Steps 1431-1433 include extraction of new coefficients. In step 1 (1431), a promising (reference) wireless power transmitter (denoted as GTx) may be combined with a promising (reference) wireless power receiver (denoted as GRx), and a combined Q threshold (e.g., line 901 in FIG. 9) may be extracted as follows:

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[0117] In step 3 (1433), a new wireless power receiver (denoted PRx) may be paired with GTx, and a threshold value may be extracted as follows:

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[0118] Step 4 (1434): Up to this point, both the new PTx and PRx have a set of coefficients in their respective firmware. 0,tg , A 1,tg , A 2,tg is stored in PTx, and the scaling coefficients g0, g1, and g2 are stored in PRx. When PTx and PRx are coincident within a field, a new detection threshold can be defined as follows:

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[0119] As explained above, the combined Q technique can be used to detect foreign objects (FO) in the vicinity of a wireless power transmission system (including a wireless power transmitter and a wireless power receiver). Physical quantities, such as the resonant frequency (f), quality factor (Q), and coupling factor (K) of the combined system (PTx coupled to PRx), can be measured using low power ping (LPP), for example, as described above with respect to FIG. 7. Foreign objects can be detected in the fQ space, i.e., the space with the resonant frequency on one axis and the quality factor on another axis. One approach can be to use a linear threshold to separate two classes: no FO (only Rx or Rx with case or cover) and with FO (both with and without case or cover). (As described herein, "case," "cover," and "case / cover" refer to an object associated with a PRx device, for example, as a case or cover used in connection with a mobile phone. To obtain the thresholds, a linear support vector machine (SVM) can be used to train a linear classifier with a given dataset. Other classifier implementations can also be used, and the trained classifier can potentially be implemented using the hardware described above with respect to FIG. 1, along with suitable software running on that hardware. However, due to the non-linear alignment of clusters formed by PRx at different locations (characterized by R and z), a linear classifier may not be ideal in some scenarios. Multiple linear thresholds can be used to generate a more effective separation, known as a split threshold approach, as shown in FIG. 15.

[0120] More specifically, Fig. 15 shows various clusters of frequency deviation versus Q deviation measurements. Parameters other than frequency deviation and Q deviation can be used and therefore the axes can correspond to various functions of f and Q, as introduced above with respect to Fig. 9. Such modifications are described in more detail below. Nevertheless, in the example of Fig. 15, clusters 1505a-1505f correspond to different scenarios or configurations where only a receiver is present. Clusters 1503a, 1503c correspond to different scenarios or configurations where a foreign object is present. Curves 1501a-1501b show multiple linear threshold curves as described in the previous paragraph. This generally corresponds to the configurations described above with reference to Fig. 9.

[0121] One potential drawback of a multi-threshold system may be the increased number of parameters required to describe the split threshold(s). Nonlinear separation may also pose challenges to ecosystem scaling (e.g., since the thresholds may depend on the training state space). To address these challenges, the technique described below based on a reduced state space (Rx only, i.e., no foreign objects) can be used while improving classification accuracy. This technique can use mapping the physical quantities: resonant frequency f, quality factor Q, and coupling factor K to a different space where Rx-only clusters naturally align with each other. The parameters of the line (representing the Rx-only cluster) can be calculated by linear regression. When a foreign object is coupled to the combined system, the data will deviate from this line and can therefore be detected. A clear separation of the four categories: Rx only, Rx+case / cover, Rx+FO, Rx+FO+case / cover can be demonstrated by taking the distance to the line. The classifier does not require training with foreign object data and can therefore work for any foreign object (ferrous and non-ferrous) as long as there is separation when the foreign object is located within the detection limits (e.g., within 23-24 mm in some applications).

[0122] In order to map the physical quantities f, Q, and K to new observables that exhibit linear dependences, it is necessary to model the theoretical correlation between them. The combined resonant frequency is determined when the system experiences zero imaginary input impedance Im(Z in The input impedance is given by the condition that indicates that Z = 0. Tx and the reflected impedance from Rx, Z ref is given by:

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[0123] To simplify the calculations, ω can be in the range of 10^6, and C tot can be in the range of 10-9, and L M can be in the range of 10-5, and R M , R Rx Observe that can be in the range of 0 to the power of 10. Then, the imaginary part of the input impedance can be simplified to:

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[0124] ω 組み合わせ and ω Tx The ratio of

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[0125] Next, the combined inductance L 組み合わせ is defined as follows:

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[0126] Furthermore, the quality factor of the combined system is:

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[0127] As mentioned above, due to the linear dependency, in order to transform the fQK space for foreign object detection, 2 組み合わせ , 1 / (f 組み合わせ Q 組み合わせ ), and K 2 In practice, to reduce the effect of part-to-part variation, f 2 def , 1 / (fdef Q def ), K 2 We use as our observables, where

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[0128] In equations (49)-(51), "meas" represents a quantity measured at run time (based on the actual Tx to Rx coupling) and "cal" represents a calibration of the Tx module at factory / manufacturing (this value can be stored in the memory of the transmitter device as described above). Using such a calibration can reduce the effects of part-to-part variations due to manufacturing tolerances etc.

[0129] Referring to plot 1600a in FIG. 16A, by fitting the Rx only cluster 1605a-1605e using a linear regression (line 1601), the L2 distances of various measurement points in the other clusters 1603a-1603c (foreign object), 1607a-1607b (receiver and case / cover), and 1609a-1609b (receiver, case / cover, and foreign object) to a line in the transformed fQK space can indicate the presence of receiver only, receiver and case / cover, receiver and foreign object, or receiver, case / cover, and foreign object. (Note that cluster 1603b, corresponding to measurements associated with the presence of a receiver and a foreign object, and cluster 1609a, corresponding to measurements associated with the presence of a receiver, case / cover, and foreign object, overlap in the illustrated example, but this is not the case in all cases. As shown in histogram plot 1600b in FIG. 16B, the categories of Rx only (1605), Rx+case / cover (1607), Rx+FO (1603), and Rx+FO+case / cover (1609) can be separated based on the L2 distance from regression line 1601. In the illustrated example, A threshold of 0.125 can be used to effectively separate non-foreign object cases from foreign object cases. In the illustrated example, there is overlap between the case / cover absent and case / cover present measurements, but this does not affect the determination of whether a foreign object is present. Additionally, the particular threshold given above is merely exemplary. Depending on the particular physical characteristics and configuration of a given implementation, a different threshold may be required. This threshold (or any suitable threshold based on the details of a given application) may be programmed into a classifier implemented using any suitable combination of hardware and software as described above.

[0130] Such a classifier may have at least two advantages: (1) it does not require training with FO data. Once the distributions of the first two categories (Rx only 1605 and Rx+cases / covers 1607) are determined, the foreign object detection threshold can be set by the maximum distance to the line. Anything above the threshold is considered with the FO. Thus, this technique can be performed for any type of FO. (2) such a classifier may be insensitive to the state space. Since the clusters in the Rx only category (1605a 1605e) are aligned, the linear regression will converge to a fixed value as long as the state space is large enough.

[0131] In reality, each cluster may have some volume in the transformed fQK space. As the FO radius (defined as the distance between the FO center and the Tx center) increases, the latter two categories (Rx+FO and Rx+FO+case / cover) may eventually intersect with the first two categories (Rx only and Rx+case / cover). The maximum FO radius without intersections may be defined as the detection limit. In an exemplary embodiment, the detection limit may be 23mm to 24mm. Note that the detection limit is not the same as the critical radius. The detection limit is the FO distance at which the FO can be reliably detected. The critical radius is given by the tolerance of the FO temperature rise and therefore increases with the delivered power level. Therefore, it may be preferable for the detection limit to be larger than the critical radius.

[0132] The distance measurement between the data points and the linear regression line can be optimized to increase the margin between the foreign object and no foreign object categories. Specifically, as shown in plot 1700a of FIG. 17A, the L1 distance, i.e., the sum of the distances to the regression line 1701 in the x, y, and z directions, or the L2 distance, i.e., the distance closest to the line, can be selected for measurement. These distances are exemplary, and other distance measurements can also be used. As shown in histogram plot 1700b of FIG. 17B, the L2 distance may provide little margin between the foreign object and no foreign object cases (for the exemplary system shown). Conversely, the L1 distance may provide a better margin, as shown in histogram plot 1700c of FIG. 17C corresponding to the L1 distance and histogram plot 1700d of FIG. 17D.

[0133] The remapped state space (e.g., the f2,1 / (fQ), K state space described above) can also be used with the ecosystem scaling principles described above with reference to Figures 12-14. Such use of ecosystem scaling is described in more detail below with reference to Figures 18A-18C. For any one Tx-Rx pair, whether promising or general, the Rx-only clusters 1805a, 1805f are always aligned in the transformed fQK space 1800a. For simplicity, the transformed observables can be renamed x, y, and z. The linear equations that align the Rx-only clusters 1805a, 1805f can be written as follows:

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[0134] As shown in Figures 18A-18C, the exemplary scaled fitted line 1801b is very similar to the calculated line given by linear regression of the data set (1801a). Thus, as can be seen from a comparison of Figures 18B and 18C, the histogram 1800c for the scaled fitted line 1801b (Figure 18A) is close to the histogram 1800b associated with the actual line 1801a (Figure 18A). The accuracy of the scaled fitted line means that a suitable level of foreign object detection accuracy can be expected when using the ecosystem scaling principles described below. Indeed, in many cases, the threshold value does not need to be changed.

[0135] In at least some applications, combined Q measurements as described herein can provide information not only about the presence of a foreign object, but also about where the foreign object is located. Such information can be used to estimate the Q of a given P rect and V rect This can be used to estimate potential foreign object losses for a given value. Also, as mentioned above, foreign object position can affect the separation between the measured data points and the linear regression fit line.

[0136] As shown in plot 1900 of FIG. 19, the L2 distance between the data points and the linear regression line (vertical axis) decreases with FO radius, i.e., distance to the foreign object. This is true for each group of measurements: receiver only measurements shown in curve 1905, receiver + case / cover measurements shown in curve 1907, receiver and foreign object measurements shown in curve 1903, and receiver + case / cover + foreign object measurements shown in curve 1909. The error bars represent the standard deviation for each category. Since the FO radius is directly related to the FO loss, the distance can be used to adjust the transmitter output power level accordingly. The table below lists exemplary estimates of the FO radius at which the power dissipated in the foreign object reaches 800 mW, which is in the range of 20 mm to 30 mm. The first column of the table lists exemplary power levels (for each row). The second column lists the estimated FO radii having Tx and Rx combined with a radial offset of 0 and a z-axis / vertical offset of 2 mm, and the third column lists the estimated FO radii having Tx and Rx combined with a radial offset of 2 mm and a z-axis / vertical offset of 2.2 mm. [Table 1]

[0137] By combining the L2 distance vs. RFO relationship with the FO loss vs. RFO relationship, the allowable power level can be estimated as a function of the L2 distance. Thus, instead of completely shutting down the power transmission when a foreign object is detected, a multi-level power adjustment strategy can be adopted. An example of such a multi-level power level adaptation is shown in FIG. 20, which shows that (1) if the L2 distance is within 0.12, full power (e.g., a power level of 50 W) can be delivered, (2) if the L2 distance is between 0.12 and 0.22, the power should be adjusted to a first intermediate power level (e.g., 25 W), (3) if the distance is between 0.22 and 0.35, the power should be adjusted to a second intermediate power level (e.g., 15 W), and (4) otherwise, if the L2 distance is greater than 0.35, the power should be adjusted to a low power level (e.g., 5 W). While these power levels are exemplary and may be useful in various embodiments, the particular L2 distance and power levels may be adapted as appropriate for a given application.

[0138] As discussed above, FIG. 20 illustrates various power levels by concentric cylinders centered on a fit line passing through the Rx only data points 2005. Also shown are receiver+case / cover data points 2007. The inner cylinder 2010 corresponds to the highest power level discussed above (e.g., 50W). The next cylinder 2011 corresponds to a first intermediate power level (e.g., 25W). The next cylinder 2012 corresponds to a second intermediate power level (e.g., 15W). The outer cylinder 2013 corresponds to a low power level (e.g., 5W). As explained above, if the measured operating point has an L2 distance from the linear regression fit line 2001 that exceeds the exemplary thresholds discussed above, the transmit power may be limited to a specified (and concentric cylinder) level.

[0139] In other embodiments, either separately or in combination with the features of the above-mentioned embodiments, the combined Q-measurement state space (including but not limited to any of the magnetic parameters described above) may also be used to detect the presence of a case, cover, or other similar device that encloses or protects the wireless power receiver, thus providing some degree of z-axis separation between the wireless power transmitter (PTx) and the wireless power receiver (PRx). In this context, the z-axis refers to a direction perpendicular to the plane of the respective coils. In such cases, the measurement and determination of the various circuit parameters may be made according to any suitable technique, including those described above. The resulting group of data points may be plotted in the state space based on the parameters measured as described above.

[0140] FIG. 21 illustrates an exemplary state space plot 2100. The illustrated state space is based on the changes in quality factor (Q) and resonant frequency (f) plotted on the vertical and horizontal axes, respectively. However, any suitable state space using other combinations of parameters, such as the linearized parameters discussed above, may also be used. FIG. 21 also illustrates data points 2105a-2105f corresponding to combined Q measurements of the receiver device only. As discussed above, these combined Q measurements may include any combination of the parameters discussed above that may be directly measured and / or calculated by the processing system based on the measured parameters. Each of the clusters 2105a-2105f corresponds to a different distance between the receiver and the transmitter, which in the illustrated example are 0 mm, 1 mm, 2 mm, 2.2 mm, 3 mm, and 3.2 mm, respectively. Also illustrated in FIG. 21 are data points 2107a, 2107d corresponding to a receiver having a case or other cover or protection device interposed between the wireless power transmitter (PTx) and the wireless power receiver (PRx).

[0141] Similar to the techniques described above, a threshold value can be calculated by the system to enable the system to detect z-axis / vertical separation between the wireless power transmitter and the wireless power receiver, such as separation caused by the presence of a case, cover, or other similar object. However, such separation need not be caused by the presence of an additional object. In either case, detection of such z-axis / vertical separation can be used by the PTx device to reduce power to mitigate electromagnetic interference with other devices. The process can be generally similar to that described above with respect to FIG. 10, but rather than detecting a foreign object, what is being detected is the presence of a case or cover and / or the z-axis / vertical separation between the PTx and the PRx.

[0142] To achieve such detection, the threshold can be defined by a curve 2101. The curve 2101 can be a linear function of the following form:

number

number

[0143] It can be observed that the slope of the threshold line 2101 is negative relative to the slope of the foreign object detection line given in the example above. Thus, when performing both foreign object detection and z-axis / vertical separation / case detection, separate thresholds may be used for each detection, but both detections (and their associated regression or other statistical analyses) may be based on the same measurements / data points. In the example shown with respect to FIG. 1, the determination is whether there is a z-axis / vertical separation between PRx and PTx, as opposed to whether a foreign object is present as described above with reference to FIGS. 9-10. In other respects, the measurements, analyses, decisions, etc. performed by the processing systems of each device may be broadly similar.

[0144] Additional items: 1. A wireless power transmitter comprising: a wireless power transmitting circuit having a wireless power transmitting coil for transmitting a wireless power signal; a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: While the wireless power transmitter is coupled to the wireless power receiver, measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil; determining a change between the measured current values ​​of the first and second functions of a quality factor and a resonant frequency of the wireless power transmitting coil and corresponding baseline values; and a wireless power transmitter that determines whether a foreign object is present in response to a change between measured current values ​​of first and second functions of a quality factor and a resonant frequency and corresponding baseline values ​​in a magnetic state space that exceed a threshold value. 2. The wireless power transmitter according to item 1, wherein the control circuit suppresses wireless power transmission in response to detecting a foreign object. 3. The wireless power transmitter of item 1, wherein the control circuit transmits power at a level less than a maximum power level in response to detecting a foreign object. 4. The control circuit determines the current quality factor and resonant frequency of the wireless power transmitting coil; causing an inverter to provide one or more signal pulses to a wireless power transmit coil; measuring a response to the one or more provided signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by a frequency and a current quality factor of the ringing signal; 2. The wireless power transmitter of claim 1, wherein the measurement is performed by determining a current quality factor and a resonant frequency from the frequency of the ringing signal. 5. The control circuit is characterizing the foreign object as a medium foreign object or a strong foreign object based on a change between the measured current values ​​of the first function and the second function of the quality factor and the resonant frequency of the wireless power transmitting coil and corresponding baseline values; In response to determining that the foreign object is a strong foreign object, suppressing wireless power transmission, or 2. The wireless power transmitter of item 1, which enables wireless power transmission at a relatively lower power level in response to determining that the foreign object is a medium foreign object. 6. The wireless power transmitter of item 1, wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter. 7. The wireless power transmitter of item 1, wherein the corresponding baseline value is updated during field operation of the wireless power transmitter. 8. The wireless power transmitter of item 1, wherein the control circuit determines the change between measured current values ​​of the first and second functions of the quality factor and resonant frequency of the wireless power transmitting coil using a scale factor based on the particular transmitter-receiver pairing. 9. A method of operating a wireless power transmitter having a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, the method being performed by the control circuit; Measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil while the wireless power transmitter is coupled to the wireless power receiver; comparing the measured current values ​​of the first and second functions of a quality factor and a resonant frequency of the wireless power transmitting coil with corresponding baseline values; detecting a foreign object based at least in part on a comparison of the measured current values ​​of the first and second functions of the quality factor and the resonant frequency to corresponding baseline values; A method comprising: 10. Comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless power transmitting coil with the corresponding baseline values ​​includes analyzing a change between the measured current values ​​and the corresponding baseline values ​​in a magnetic state space; 10. The method of claim 9, wherein detecting a foreign object based at least in part on a comparison of the measured current values ​​of the first and second functions of the quality factor and the resonant frequency to corresponding baseline values ​​includes determining whether a change between the measured current values ​​and the corresponding baseline values ​​in magnetic state space exceeds a threshold value. 11. The current quality factor and resonant frequency of the wireless power transmitting coil are causing an inverter to provide one or more signal pulses to a wireless power transmit coil; measuring a response to the one or more provided signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by a frequency and a current quality factor of the ringing signal; 10. The method of claim 9, further comprising measuring by: determining a current quality factor from a frequency of the ringing signal. 12. The method of claim 9, further comprising inhibiting wireless power transmission in response to detecting a foreign object. 13. The method of claim 9, further comprising transmitting power at a level less than the maximum power level in response to detecting a foreign object. 14. Characterizing the foreign object as a medium foreign object or a strong foreign object based on the change between the measured current value and a corresponding baseline value in the magnetic state space; Suppressing wireless power transmission in response to determining that the foreign object is a strong foreign object; or 10. The method of claim 9, further comprising: in response to determining that the foreign object is a medium foreign object, enabling wireless power transmission at a relatively lower power level. 15. The method of item 9, wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter. 16. The method of item 9, wherein the corresponding baseline value is updated during field operation of the wireless power transmitter. 17. The method of claim 9, further comprising scaling a corresponding baseline value using a scale factor based on a particular transmitter-receiver pairing. 18. A wireless power transmitter comprising: a wireless power transmitting circuit having a wireless power transmitting coil for transmitting a wireless power signal; a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: means for measuring current values ​​of two or more observables related to a quality factor and a resonant frequency of a wireless power transmitting coil while the wireless power transmitter is coupled to the wireless power receiver; and means for detecting a foreign object based on measured current values ​​of two or more observables relating to a quality factor and a resonant frequency of a wireless power transmitting coil measured while the wireless power transmitter is coupled to a wireless power receiver. 19. The control circuit is The wireless power transmitter further comprises a means for characterizing the foreign object as a medium foreign object or a strong foreign object based on measured current values ​​of two or more observables related to a quality factor and a resonant frequency of the wireless power transmitting coil measured while the wireless power transmitter is coupled to the wireless power receiver, the control circuit comprising: In response to determining that the foreign object is a strong foreign object, suppressing wireless power transmission, or 20. The wireless power transmitter of item 18, wherein in response to determining that the foreign object is a medium foreign object, the wireless power transmitter enables wireless power transmission at a relatively lower power level.

[0145] Further additions: 1. A wireless power transmitter comprising: a wireless power transmitting circuit having a wireless power transmitting coil for transmitting a wireless power signal; a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: While the wireless power transmitter is coupled to the wireless power receiver, measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil; determining a change between the measured current values ​​of the first and second functions of a quality factor and a resonant frequency of the wireless power transmitting coil and corresponding baseline values; A wireless power transmitter that determines a z-axis separation distance between the wireless power transmitter and the wireless power receiver in response to a change between measured current values ​​of a first and second function of a quality factor and a resonant frequency and corresponding baseline values ​​that exceed a threshold value in a magnetic state space. 2. The wireless power transmitter of item 1, wherein the z-axis separation distance includes the presence of a case or cover over the wireless power receiver. 3. The first function of quality factor and resonant frequency is the quality factor, A second function of the quality factor and the resonant frequency is the resonant frequency, 2. The wireless power transmitter of item 1, wherein the threshold value includes a plurality of linear threshold values. 4. A wireless power transmitter comprising: a wireless power transmitting circuit having a wireless power transmitting coil for transmitting a wireless power signal; a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: While the wireless power transmitter is coupled to the wireless power receiver, measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil, a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil, and a third function of a quality factor and a resonant frequency of the wireless power transmitting coil; determining a distance between the measured current values ​​of the first function, the second function, and the third function of the quality factor and the resonant frequency of the wireless power transmitting coil and a curve fit to corresponding baseline values ​​in the magnetic state space; and determining a z-axis separation distance between the wireless power transmitter and the wireless power receiver in response to a distance between the measured current values ​​of the first, second, and third functions of the quality factor and the resonant frequency and a curve fit to corresponding baseline values ​​in the magnetic state space that exceed a threshold value. 5. The wireless power transmitter according to item 4, wherein the z-axis separation distance includes the presence of any case or cover on the wireless power receiver. 6. The wireless power transmitter of item 4, wherein the first function, the second function, and the third function of the quality factor and the resonant frequency are selected to provide a linear curve fit in the magnetic state space. 7. A wireless power transmitter as described in item 6, wherein a first function of the quality factor and the resonant frequency is the square of the coupling coefficient, a second function of the quality factor and the resonant frequency is the square of the resonant frequency, and a third function of the quality factor and the resonant frequency is the inverse of the resonant frequency multiplied by the quality factor. 8. The wireless power transmitter according to item 4, wherein the distance is a Pythagorean distance. 9. The wireless power transmitter according to item 4, wherein the distance is an L1 distance. 10. The wireless power transmitter according to item 4, wherein the distance is an L2 distance. 11. The wireless power transmitter of item 4, wherein the control circuit transmits power at a level less than the maximum power level in response to detecting a z-axis separation distance above a threshold or the presence of a case. 12. The control circuit determines the current quality factor and resonant frequency of the wireless power transmitting coil; causing an inverter to provide one or more signal pulses to a wireless power transmit coil; measuring a response to the one or more provided signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by a frequency and a current quality factor of the ringing signal; 5. The wireless power transmitter of claim 4, wherein the measurement is performed by determining a current quality factor and a resonant frequency from the frequency of the ringing signal. 13. The wireless power transmitter of item 4, wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter. 14. The wireless power transmitter of item 4, wherein the corresponding baseline value is updated during field operation of the wireless power transmitter. 15. The wireless power transmitter of item 4, wherein the control circuit determines the distance between the measured current values ​​of the first, second and third functions of the quality factor and resonant frequency of the wireless power transmitting coil using a scale factor based on the particular transmitter-receiver pairing. 16. A method of operating a wireless power transmitter having a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, the method being performed by the control circuit; Measuring a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil while the wireless power transmitter is coupled to the wireless power receiver; comparing the measured current values ​​of the first and second functions of a quality factor and a resonant frequency of the wireless power transmitting coil with corresponding baseline values; determining a z-axis separation distance between the wireless power transmitter and the wireless power receiver based at least in part on a comparison of the measured current values ​​of the first and second functions of the quality factor and the resonant frequency to corresponding baseline values; Including, method. 17. The method of claim 16, wherein the z-axis separation distance includes the presence of a case or cover on the wireless power receiver. 18. The first function of quality factor and resonant frequency is the quality factor, Item 17. The method of item 16, wherein the second function of the quality factor and the resonant frequency is the resonant frequency. 19. A method of operating a wireless power transmitter having a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, the method being performed by the control circuit; Measuring, while the wireless power transmitter is coupled to the wireless power receiver, a current value of a first function of a quality factor and a resonant frequency of the wireless power transmitting coil, a current value of a second function of a quality factor and a resonant frequency of the wireless power transmitting coil, and a current value of a third function of a quality factor and a resonant frequency of the wireless power transmitting coil; comparing the measured current values ​​of the first, second and third functions of the quality factor and the resonant frequency of the wireless power transmitting coil to the corresponding baseline values ​​by determining a distance between the measured current values ​​of the first, second and third functions of the quality factor and the resonant frequency of the wireless power transmitting coil and the corresponding baseline values ​​in a magnetic state space; determining a z-axis separation distance between the wireless power transmitter and the wireless power receiver based at least in part on a distance between the measured current values ​​of the first, second, and third functions of the quality factor and the resonant frequency and a curve fit to corresponding baseline values ​​in the magnetic state space that exceed a threshold; A method comprising: 20. The method of claim 19, wherein the z-axis separation distance includes the presence of a case or cover on the wireless power receiver. 21. The method of claim 19, wherein the first, second, and third functions of quality factor and resonant frequency are selected to provide a linear curve fit in magnetic state space. 22. The method according to item 21, wherein the first function of the quality factor and the resonant frequency is the square of the coupling coefficient, the second function of the quality factor and the resonant frequency is the square of the resonant frequency, and the third function of the quality factor and the resonant frequency is the inverse of the resonant frequency multiplied by the quality factor. 23. The method according to item 19, wherein the distance is the Pythagorean distance. 24. The method according to item 19, wherein the distance is the L1 distance. 25. The method according to item 19, wherein the distance is the L2 distance. 26. The current quality factor and resonant frequency of the wireless power transmitting coil are causing an inverter to provide one or more signal pulses to a wireless power transmit coil; measuring a response to the one or more provided signal pulses using a measurement circuit, the response including a ringing signal having a decaying envelope characterized by a frequency and a current quality factor of the ringing signal; 20. The method of claim 19, further comprising measuring by: determining a current quality factor from a frequency of the ringing signal. 27. The method of claim 19, further comprising transmitting power at a level less than the maximum power level in response to detecting a z-axis separation distance exceeding a threshold or the presence of a case. 28. The method of item 19, wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter. 29. The method of item 19, wherein the corresponding baseline value is updated during field operation of the wireless power transmitter. 30. The method of claim 19, further comprising scaling the corresponding baseline value using a scale factor based on the particular transmitter-receiver pairing.

[0146] Various features and embodiments relating to the use of combined Q-factors and related magnetic property measurements for object detection in wireless power transfer systems have been described above. Such configurations may be used in a variety of applications, but may be particularly advantageous when used with electronic devices such as mobile phones, tablet computers, laptop or notebook computers, and accessories such as wireless headphones, styluses, etc. In addition, although a number of specific features and various embodiments have been described, it should be understood that the various features and embodiments may be combined in various permutations in a particular implementation, unless otherwise specified as mutually exclusive. Thus, the various embodiments described above are provided by way of example only and should not be construed as constituting the scope of the present disclosure. Various modifications and variations may be made to the principles and embodiments herein without departing from the scope of the present disclosure and without departing from the scope of the claims.

Claims

1. 1. A wireless power transmitter, comprising: a wireless power transmitting circuit having a wireless power transmitting coil for transmitting a wireless power signal; a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: determining a current value of a first function of one or both of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of one or both of a quality factor and a resonant frequency of the wireless power transmitting coil while the wireless power transmitter is coupled to a wireless power receiver; comparing the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency of the wireless power transmitting coil with curve fits to corresponding baseline values ​​in a magnetic state space having axes defined by the first and second functions of one or both of the quality factor and resonant frequency; determining that no foreign object is present if the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency are on a first side of the curve; or determining that a foreign object is present if the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency are on a second side of the curve that is different from the first side of the curve; The wireless power transmitter, wherein the control circuit inhibits wireless power transmission or transmits power at a level less than a maximum power level in response to determining that the foreign object is present.

2. 2. The wireless power transmitter of claim 1, wherein the first and second functions of one or both of quality factor and resonant frequency are selected to provide a linear curve fit in the magnetic state space.

3. 3. The wireless power transmitter of claim 2, wherein the first function of the quality factor and / or resonant frequency is a square of the resonant frequency, and the second function of the quality factor and / or resonant frequency is the reciprocal of the resonant frequency multiplied by the quality factor.

4. The control circuit calculates the current quality factor and the resonant frequency of the wireless power transmitting coil by: causing an inverter to provide one or more signal pulses to the wireless power transmitting coil; measuring a response to the provided one or more signal pulses using a measurement circuit, the response including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the current quality factor; and determining the current quality factor and resonant frequency from the frequency of the ringing signal.

5. The control circuit characterizing a foreign object as a medium foreign object or a strong foreign object based on a distance between the measured current values ​​of first and second functions of one or both of the quality factor and resonant frequency of the wireless power transmitting coil and the curve fits to the corresponding baseline values; suppressing wireless power transmission in response to determining that the foreign object is a strong foreign object; or The wireless power transmitter of claim 1 , wherein the wireless power transmitter enables wireless power transmission at a relatively lower power level in response to determining that the foreign object is a medium foreign object.

6. The wireless power transmitter of claim 5 , wherein the distance is an L1 distance.

7. The wireless power transmitter of claim 5 , wherein the distance is an L2 distance.

8. The wireless power transmitter of claim 1 , wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter.

9. The wireless power transmitter of claim 1 , wherein the corresponding baseline value is updated during field operation of the wireless power transmitter.

10. The wireless power transmitter of claim 1 , wherein the control circuit scales the baseline value using a scaling factor based on a particular transmitter-receiver pairing.

11. 1. A method of operating a wireless power transmitter having a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, and a control circuit coupled to the wireless power transmission circuit, the method being performed by the control circuit: determining a current value of a first function of one or both of a quality factor and a resonant frequency of the wireless power transmitting coil and a current value of a second function of one or both of a quality factor and a resonant frequency of the wireless power transmitting coil while the wireless power transmitter is coupled to a wireless power receiver; comparing the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency of the wireless power transmitting coil with curve fits to corresponding baseline values ​​in a magnetic state space having axes defined by the first and second functions of one or both of the quality factor and resonant frequency; determining that no foreign object is present if the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency are on a first side of the curve; or determining that a foreign object is present if the determined current values ​​of the first and second functions of one or both of the quality factor and resonant frequency are on a second side of the curve that is different from the first side of the curve; In response to determining that the foreign object is present, inhibiting wireless power transmission or transmitting power at a level less than a maximum power level; A method comprising:

12. The method of claim 11 , wherein the first and second functions of one or both of quality factor and resonant frequency are selected to provide a linear curve fit in the magnetic state space.

13. 13. The method of claim 12, wherein the first function of the quality factor and / or resonant frequency is the square of the resonant frequency, and the second function of the quality factor and / or resonant frequency is the reciprocal of the resonant frequency multiplied by the quality factor.

14. The current quality factor and resonant frequency of the wireless power transmitting coil are causing an inverter to provide one or more signal pulses to the wireless power transmitting coil; measuring a response to the provided one or more signal pulses using a measurement circuit, the response including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the current quality factor; and determining the current quality factor from the frequency of the ringing signal.

15. characterizing a foreign object as a medium foreign object or a strong foreign object based on a distance between the measured current value and the curve fit to the corresponding baseline value in the magnetic state space; suppressing wireless power transmission in response to determining that the foreign object is a strong foreign object; or In response to determining that the foreign object is a medium foreign object, enabling wireless power transmission at a relatively lower power level; The method of claim 11 further comprising:

16. The method of claim 15, wherein the distance is the L1 distance.

17. The method of claim 15, wherein the distance is the L2 distance.

18. The method of claim 11 , wherein the corresponding baseline value is measured during manufacturing of the wireless power transmitter.

19. The method of claim 11 , wherein the corresponding baseline value is updated during field operation of the wireless power transmitter.

20. The method of claim 11 , further comprising scaling the corresponding baseline value using a scaling factor based on a particular transmitter-receiver pairing.

21. The wireless power transmitter of claim 1 , wherein the first function of one or both of the quality factor and the resonant frequency is a frequency deviation.

22. 2. The wireless power transmitter of claim 1, wherein the second function of one or both of the quality factor and the resonant frequency is 1 / (fdef*Qdef).

23. The wireless power transmitter of claim 10 , wherein the scaling factor is received from the wireless power receiver via the wireless power transmit coil.

24. The method of claim 11 , wherein the first function of one or both of the quality factor and the resonant frequency is a frequency deviation.

25. 12. The method of claim 11, wherein the quality factor and the second function of one or both of the resonant frequency and the quality factor is 1 / (fdef*Qdef).

26. 21. The method of claim 20, wherein the scaling factor is received from the wireless power receiver via the wireless power transmit coil.

27. A wireless power transmission circuit having a wireless power transmission coil for transmitting a wireless power signal; and a control circuit coupled to the wireless power transmission circuit, the control circuit comprising: and a control circuit configured to detect foreign objects by determining a point in a magnetic state space defined by a first axis corresponding to a first function of one or both of a quality factor and a resonant frequency, and a second axis corresponding to a second function of one or both of the quality factor and the resonant frequency, wherein the control circuit comprises: calculating a first coordinate of the point in the magnetic state space as a current value of a first function of one or both of the quality factor and resonant frequency of the wireless power transmitting coil with a wireless power transmitter coupled to a wireless power receiver; calculating a second coordinate of the point in the magnetic state space as a current value of a second function of one or both of the quality factor and resonant frequency of the wireless power transmitting coil with a wireless power transmitter coupled to a wireless power receiver; determining the point in the magnetic state space by comparing the determined point with a curve in the magnetic state space fitted to corresponding baseline values ​​of a first function and a second function of one or both of the quality factor and resonant frequency of the wireless power transmitting coil, thereby determining that a foreign object is present; the control circuit determines that a foreign object is not present in response to the determined point being on a first side of the curve; The control circuit determines that a foreign object is present in response to the determined point being on a second side of the curve that is different from the first side of the curve.

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