OBJECT DETECTION FOR WIRELESS POWER TRANSMISSION

Abstract

A wireless energy transmitter (WPT) may include wireless energy switching logic comprising a wireless WPT coil that transmits wireless energy signals; and control switching logic coupled to the WPT switching logic, which: measures a current value of a first function of the quality factor and resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and resonant frequency of the WPT coil while the WPT is coupled to a wireless energy receiver; determines a change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and resonant frequency of the WPT coil;Determines whether a foreign object is present if the change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and the resonance frequency exceeds a threshold in a magnetic state space.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

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

[0002] Electronic devices such as smartphones, tablet computers, smart watches, wireless headphones, pens, etc., can utilize wireless power transfer to facilitate charging of the devices' batteries. Therefore, it may be desirable to provide higher power transfer. However, these higher energy levels may require improved detection of other objects that may affect or be affected by the wireless power transfer. SUMMARY

[0003] A wireless energy transmitter may include wireless energy transmitter circuitry having a wireless energy transmitter coil that transmits wireless energy signals; and control circuitry coupled to the wireless energy transmitter that: measures a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmitter coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmitter coil while the wireless energy transmitter is coupled to a wireless energy receiver; determines a change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmitter coil;determines whether a foreign object is present if the change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and the resonant frequency exceeds a threshold in a magnetic state space. The first function of the quality factor and the resonant frequency may be the quality factor. The second function of the quality factor and the resonant frequency may be the resonant frequency. The threshold may include multiple linear thresholds.

[0004] A wireless energy transmitter may include wireless energy transmitting circuitry having a wireless energy transmitting coil that transmits wireless energy signals; and control circuitry coupled to the wireless energy transmitter that: measures a current value of a first function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmitting coil, a current value of a second function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmitting coil, and a third function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmitting coil while the wireless energy transmitter is connected to a wireless energy receiver;Determines a distance between the measured current values ​​of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmitting coil and a curve fit to corresponding baseline values; Determines whether a foreign object is present depending on a distance between the measured current values ​​of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient and the curve fit to the corresponding baseline values ​​in a magnetic state space that exceeds a threshold or falls between multiple thresholds.

[0005] The first, second, and third functions of the quality factor, resonant frequency, and coupling coefficient can be chosen to provide a linear curve fit in magnetic state space. The first function of the quality factor, resonant frequency, and coupling coefficient can be the coupling coefficient squared. The second function of the quality factor, resonant frequency, and coupling coefficient can be the resonant frequency squared, and the third function of the quality factor, resonant frequency, and coupling coefficient can be the inverse of the resonant frequency times the quality factor. The spacing can be an L1 spacing or an L2 spacing (or another suitable spacing).

[0006] The control logic may inhibit wireless power transmission in response to the detection of the foreign object. The control logic may transmit power at a level below a maximum power level in response to the detection of the foreign object.

[0007] The control circuitry may measure the current quality factor and resonant frequency of the wireless power transfer coil by: causing an inverter to provide one or more signal pulses to the wireless power transfer coil; using measurement circuitry to measure responses to the provided one or more signal pulses, wherein the responses include a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and determining the current quality factor and resonant frequency from the frequency of the ringing signal.

[0008] The control logic can characterize a foreign object as a moderate foreign object or a strong foreign object based on the distance between the measured current values ​​of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless power transmission coil and the curve fit to the corresponding baseline values. The control logic can prohibit wireless power transmission if it determines that the foreign object is a strong foreign object. Alternatively, the control logic can allow relatively low-power wireless power transmission if it determines that the foreign object is a moderate foreign object.

[0009] The corresponding baseline values ​​can be measured during the manufacture of the wireless energy transmitter. The corresponding baseline values ​​can be updated during operation of the wireless energy transmitter in the field. The control logic can determine the distance between the measured current values ​​of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil using scaling factors based on a specific transmitter-receiver coupling.

[0010] A method of operating a wireless energy transmitter having a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission coil may be performed by the wireless energy control circuitry and may include: measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmission coil to the corresponding baseline values;and detecting a foreign object based at least in part on comparing the measured current values ​​of the first and second functions of quality factor and resonant frequency with the corresponding baseline values.;

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

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

[0013] The first, second, and third functions of the quality factor, resonant frequency, and coupling coefficient can be chosen to provide a linear curve fit in the magnetic state space. The first function of the quality factor, resonant frequency, and coupling coefficient can be the coupling coefficient squared. The second function of the quality factor, resonant frequency, and coupling coefficient can be the resonant frequency squared. The third function of the quality factor, resonant frequency, and coupling coefficient can be the inverse of the resonant frequency times the quality factor.

[0014] The distance can be an L1 distance or an L2 distance (or any other suitable distance).

[0015] Measuring the quality factor and the resonant frequency of the wireless energy transmitter may include: causing an inverter to provide one or more signal pulses to the wireless energy transmission coil; using measurement circuitry to measure responses to the provided one or more signal pulses, wherein the responses include a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and determining the current quality factor from the frequency of the ringing signal.

[0016] The method may further include blocking wireless power transmission in response to detecting the foreign object. The method may further include transmitting power at a level below a maximum power level in response to detecting the foreign object.

[0017] The method may further include characterizing a foreign object as a moderate foreign object or a strong foreign object based on the distance between the measured current values ​​and the curve fit to the corresponding baseline values ​​in magnetic state space. The method may further include disabling wireless power transmission in response to determining that the foreign object is a strong foreign object. Alternatively, the method may include allowing wireless power transmission at a relatively low power level if the foreign object is determined to be a moderate foreign object.

[0018] The corresponding baseline values ​​can be measured during manufacture of the wireless energy transmitter. The corresponding baseline values ​​can be updated during operation of the wireless energy transmitter in the field. The method can further include scaling the corresponding baseline values ​​using scaling factors based on a specific transmitter-receiver coupling. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 illustrates a block diagram of a wireless power transmission system. Fig. Figure 2 illustrates a simplified schematic diagram of a wireless power transmission system. Fig. Figure 3 illustrates a graph showing the impulse response of a wireless power transmission coil, which can be analyzed to measure a quality factor value for the coil. Fig. Figure 4 is a simplified schematic diagram of a wireless energy transmitter with circuitry that can be used for quality factor measurement. Fig. Figure 5 shows equations that can be used to determine parameters such as the quality factor of a coil based on impedance measurements. Fig. Figure 6 illustrates an equation illustrating compensation factors that can be applied to a current quality factor measurement to determine a compensated quality factor value. Fig. 7 and Fig. 8 are diagrams illustrating how foreign objects are detected based on the measured quality factor in a wireless power transmission system. Fig. Figure 9 illustrates the principles of foreign object detection using Mated-Q and resonance frequency measurement. Fig. Figure 10 illustrates a flowchart for a Mated-Q method for detecting foreign objects. Fig. Figure 11 illustrates a sequence of Mated-Q measurements associated with an object brought into proximity of a paired wireless energy transmitter / receiver. Fig. 12 and Fig. 13 illustrate flowcharts for scaling the parameters of a wireless power transfer device. Fig. Figure 14 illustrates a process for scaling mated Q and resonance frequency parameters. Fig. Figure 15 illustrates a variable threshold for foreign object detection in Mated-Q. Fig. 16A-16B illustrate a multidimensional Mated-Q state space for deriving a linear threshold line for foreign object detection. Fig. Figures 17A-17D illustrate alternative distance metrics for multidimensional foreign object detection in Mated-Q. Fig. Figures 18A–18C illustrate the scaling of the ecosystem for a multidimensional Mated-Q foreign object detection system. Fig. Figure 19 illustrates determining the distance to a foreign object in a multidimensional Mated-Q foreign object detection system. Fig. Figure 20 illustrates the limitation of transmitted energy based on the distance of foreign objects in a multidimensional Mated-Q foreign object detection system. Fig. Figure 21 illustrates the principles of fall detection using a mated-Q and resonant frequency measurement. DETAILED DESCRIPTION

[0019] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings of this disclosure illustrate structures and devices in block diagram form for convenience. For clarity, this disclosure does not describe all features of an actual implementation. Furthermore, the language used in this disclosure was chosen for readability and instructional purposes and not to limit or circumscribe the disclosed subject matter. Rather, the appended claims are provided for that purpose.

[0020] Various embodiments of the disclosed concepts are illustrated by way of example and not limitation in the accompanying drawings, wherein like references indicate like elements. For simplicity and clarity of illustration, reference numerals have been repeated where appropriate throughout the several figures to indicate corresponding or analogous elements. Furthermore, numerous specific details are set forth in order to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures, and components have not been described in detail in order not to obscure the associated relevant function being described. References in this disclosure to "a," "a particular," or "another" embodiment do not necessarily refer to the same or different embodiment, and mean at least one.A given figure may be used to illustrate the features of more than one embodiment or more than one type of disclosure, and not all elements in the figure may be required for a given embodiment or type. A reference number, when provided in a given drawing, refers to the same element in all of the various drawings, although it may not be repeated in every drawing. The drawings are not to scale unless otherwise indicated, and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.

[0021] A wireless power system may include a wireless power transmission device, such as a wireless charging puck or mat. The wireless power transmission device may wirelessly transmit power to a wireless power reception device. The wireless power reception device may be a device such as a wristwatch, a mobile phone, a tablet computer, a laptop, or other electronic equipment. The wireless power reception device may use the power of the wireless power transmission device to power the device and / or charge an internal battery. The wireless power may be transferred from the wireless power transmission device to the wireless power reception device using one or more wireless power transmission coils.The wireless power receiving device may include one or more wireless power receiving coils connected to rectifier circuitry capable of converting received wireless power signals into direct current.

[0022] When a foreign object such as a paper clip, coin, or other metallic object is near the wireless power transfer coil of the wireless power transfer device, eddy current generation in the foreign object may increase the foreign object's temperature. To determine whether such a foreign object is near the wireless power transfer device, the wireless power transfer device may measure the quality factor (also referred to as the "Q factor" or "Q") of the wireless power transfer coil and determine whether the quality factor has been affected by the presence of a foreign object. In some cases, the Q factor measurement may be taken "in the open," meaning the transmitter is not paired with a receiver. In some cases, as explained in more detail below, the Q factor may be measured "paired," meaning the transmitter is paired with a receiving device.In both cases, detection of the presence of a foreign object may enable appropriate action to be taken (e.g., the wireless power transfer device may refrain from wireless power transfer operations or reduce the power transferred when a foreign object is detected).

[0023] An illustrative wireless energy system (wireless charging system) is shown in Fig. 1. The wireless power system 8 may include a wireless power transmitter 12 and a wireless power receiver 24. The wireless power transmitter 12 may include control circuitry 16. The wireless power receiver 24 may include control circuitry 30. The respective control circuitries may be used to control the operation of the wireless power system 8. This control circuitry may include processing circuitry associated with microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and / or application-specific integrated circuits having processing circuitry. The processing circuitry may implement desired control and communication features in the wireless power transmitters 12 and the wireless power receivers 24.The processing circuitry may be used, for example, in selecting coils, determining power transmission levels, processing sensor data and other data to detect foreign objects and perform other tasks, processing user input, handling negotiations between the wireless power transmitter 12 and the wireless power receiver 24, sending and receiving in-band and out-of-band data, taking measurements, and otherwise controlling the operation of the wireless power system 8.

[0024] The control circuitry 16, 30 in system 8 may be configured to perform operations using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. The software code for performing operations in system 8 may be stored on non-transitory, computer-readable storage (e.g., tangible computer-readable storage media) within the control circuitry. The software code may sometimes be referred to as software, data, program instructions, instructions, and / or code. The non-transitory, computer-readable storage media may include non-volatile memory such as non-volatile random access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid-state drives), one or more removable flash drives or other removable media, or the like.Software stored on the non-transitory computer-readable storage media may execute on the processing circuitry of the control circuitry 16 and / or 30. The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, a central processing unit (CPU), or other processing circuitry, including analog, digital, and / or hybrid circuitry.

[0025] The wireless power transmitter 12 may comprise a standalone power adapter (e.g., a wireless charging mat or charging puck including power adapter circuitry), a wireless charging mat or puck connected via a cable to a power adapter or other equipment, a portable device, equipment built into a piece of furniture, a vehicle, or other system, a removable battery case, or other wireless power transfer device. Illustrative configurations in which the wireless power transmitter 12 is a wireless charging mat are sometimes described herein as an example.

[0026] The wireless power receiver 24 may be a portable electronic device such as a watch, a mobile phone, a laptop, a tablet computer, an accessory such as an earbud, a stylus, or other electronic equipment. The wireless power transmitter 12 may be plugged into an electrical outlet (e.g., an AC power source), have a battery that supplies power, and / or have another power source. The wireless power transmitter 12 may include an alternating current (AC) to direct current (DC) power converter, such as the AC-DC power converter 14, to convert the AC power from a wall outlet or other power source to DC power. DC power may be used to power the control circuitry 16.During operation, a controller in the control circuitry 16 may use the power transfer circuitry 52 to wirelessly transfer power to the power receive circuitry 54 of the wireless power receiver 24. The power transfer circuitry 52 may include switching circuitry (e.g., inverter circuitry 61 formed of transistors) that is turned on and off based on control signals provided by the control circuitry 16 to generate AC signals through one or more wireless power transfer coils, such as the wireless power transfer coil(s) 36. These coil drive signals cause the coil(s) 36 to wirelessly transfer power. Multiple coils 36 may be arranged in a flat coil array (e.g., in device configurations where the device 12 is a wireless charging mat) or in the form of a coil cluster (e.g.,In device configurations where device 12 is a wireless charging puck, the wireless energy transmitter 12 may be arranged in a single coil. In other arrangements, a wireless energy transmitter may have multiple coils.

[0027] When the alternating currents flow through one or more coils 36, alternating electromagnetic (e.g., magnetic) fields (wireless power signals 44) are generated, which are received by one or more corresponding receiver coils, such as one or more coils 48 in the wireless power receiver 24. The wireless power receiver 24 may include a single coil 48 or any other suitable number of coils 48. When the alternating electromagnetic fields are received by the coil(s) 48, corresponding alternating currents are induced in the coil(s) 48. The alternating current signals used for wireless power transmission 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.).Rectifier circuitry such as rectifier circuitry 50, which includes rectifier components such as metal oxide semiconductor transistors arranged in a bridge network with synchronous rectification, converts received AC signals (received AC signals in conjunction with electromagnetic signals 44) from one or more coils 48 into DC signals for powering wireless energy receiver 24.

[0028] The DC voltage generated by the rectifier circuit 50 (sometimes referred to as the rectifier output voltage V rect(referred to as "battery pack 58") may be used to charge a battery, such as battery pack 58, and to power other components in 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 sensing user input and / or performing environmental measurements, and may include output devices for providing output to a user. Input / output devices 56 may include, for example, a display for visual output, a speaker for outputting audio signals, light-emitting diodes for status indication and other light-emitting components for emitting light that provides status and / or other information to the user, haptic devices for generating vibrations and other haptic outputs, and / or other output devices.The input / output devices 56 may also include sensors to capture inputs from a user and / or to take measurements in the environment of the wireless power system 8. Illustrative sensors that may be included in the input / output devices 56 include three-dimensional sensors (e.g., three-dimensional image sensors such as structured light sensors that emit light beams and use two-dimensional digital image sensors to collect image data for three-dimensional images from points of light created when a target is illuminated by the light beams, binocular three-dimensional image sensors that collect three-dimensional images using two or more cameras in a binocular array, three-dimensional lidar (light detection and ranging) sensors, three-dimensional radio frequency sensors, or other sensors that capture three-dimensional data), cameras (e.g.,Infrared and / or visible cameras with corresponding infrared and / or visible digital image sensors and / or ultraviolet light cameras), gaze tracking sensors (e.g., a gaze tracking system based on an image sensor and, if desired, a light source emitting one or more light beams that are tracked using the image sensor after being reflected from a user's eyes), touch sensors, buttons, capacitive proximity sensors, light-based (optical) proximity sensors such as infrared proximity sensors, other proximity sensors, force sensors, sensors such as contact sensors based on switches, gas sensors, pressure sensors, humidity sensors, magnetic sensors, audio sensors (microphones), ambient light sensors, optical sensors for performing spectral and other measurements on target objects (e.g.,by emitting light and measuring the reflected light), microphones for capturing voice commands and other audio inputs, proximity sensors, motion, position, and / or orientation sensors configured to capture information about motion, position, and / or orientation (e.g., accelerometers, gyroscopes, compasses, and / or inertial measurement units that include all or a subset of one or two of these sensors), sensors such as buttons that detect keystroke inputs, joysticks with sensors that detect joystick movements, keyboards, and / or other sensors. The wireless energy transmitter 12 may include one or more input / output devices 68 (e.g., input devices and / or output devices of the type described in connection with the input / output devices 56).

[0029] The wireless power transmitter 12 and / or the wireless power receiver 24 can communicate wirelessly via in-band or out-of-band communication. For example, the wireless power transmitter 12 can include wireless transmit / receive circuitry 40 that wirelessly transmits out-of-band signals to the wireless power receiver 24 via an antenna. The wireless transmit / receive circuitry 40 can be used to receive wireless out-of-band signals from the wireless power receiver 24 using the antenna. The wireless power receiver 24 can include wireless transmit / receive circuitry 46 that transmits out-of-band signals to the device 12. The receive circuitry in the wireless transceiver 46 can use an antenna to receive out-of-band signals from the wireless power transmitter 12. In-band transmissions between the wireless energy transmitter 12 and the wireless energy receiver 24 may be performed using the coils 36 and 48.In one illustrative configuration, frequency shift keying (FSK) of one or more parameters of the wirelessly transmitted energy (e.g., voltage, current, etc.) may be used to transmit in-band data from the wireless energy transmitter 12 to the wireless energy receiver 24, and amplitude shift keying (ASK) of one or more parameters of the wirelessly transmitted energy (e.g., voltage, current, etc.) may be used to transmit in-band data from the wireless energy receiver 24 to the wireless energy transmitter 12. Energy may be transmitted wirelessly from the wireless energy transmitter 12 to the wireless energy receiver 24 during these FSK and ASK transmissions.

[0030] It may be desirable for the wireless power transmitter 12 and the 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 technology described above does not need to involve the transmission of personally identifiable information to function. As a precaution, to the extent an implementation of this charging technology involves the use of personally identifiable information, implementers should adhere to privacy policies and practices that are generally recognized as meeting or exceeding industry or regulatory requirements for preserving user privacy.In particular, personally identifiable information should be managed and handled in a manner that minimizes the risks of accidental or unauthorized access or use, and the nature of any authorized use should be clearly communicated to users.

[0031] The control circuitry 16 may include external object detection circuitry 41 that can detect whether external objects (including, but not limited to, "foreign objects") are on or near the charging surface of the wireless energy transmitter 12 housing (e.g., to detect objects on the surface or near a charging mat or puck). The wireless energy transmitter 12 housing may include polymer walls, walls made of another dielectric material, metal structures, fabric, and / or other housing wall structures that enclose the coils 36 and other circuitry of the wireless energy transmitter 12. The charging surface may be a flat outer surface of the top housing wall of the wireless energy transmitter 12 or an outer surface having other shapes (e.g., concave, convex, etc.).The circuitry 41 can detect foreign objects such as coins, paper clips, and other metallic objects, and can determine the presence of a wireless energy receiver 24 (e.g., the circuitry 41 can detect the presence of one or more wireless energy receiving coils 48). During object detection and characterization, the external object measurement circuitry 41 can be used to perform measurements on the coils 36 and / or other coils, such as optional additional foreign object detection coils, in the wireless energy transmitter 12 to determine whether wireless energy receivers 24 and / or foreign objects are present on or near the wireless energy transmitter 12.

[0032] In one illustrative arrangement, the measurement circuitry 41 of the control circuitry 16 may include signal generator circuitry, such as a pulse generator, that may provide control signals to the inverter 61. These control signals may cause the inverter 61 to generate pulses so that the impulse responses may be measured by the circuitry 41 (e.g., using a voltage sensor, an analog-to-digital converter configured to convert analog voltage measurements to digital voltage measurements, and / or other sensing circuitry). The measurement circuitry 41 may also include AC power sources and / or other circuitry for performing measurements on the coil 36.

[0033] In some embodiments, quality factor measurements may be taken on coil 36 to determine whether a foreign object is present. These quality factor measurements may include measurements of various observables of the wireless power system and need not be limited to the Q-factor. Such factors may include, but are not limited to, the resonant frequency, the coupling factor, self-induction, and combinations of these and other observables. The Q-factor measurements are exemplary for the present description, but measurements of other observables may be substituted unless the context clearly dictates otherwise. For example, direct impedance measurements and / or impulse responses may be analyzed to perform quality factor (Q-factor) measurements on coil 36.Measurements of the Q-factor of coil 36 (including measurements of changes in the Q-factor value from a baseline value) may be made at any suitable time, for example, prior to transmitting wireless power from wireless power transmitter 12 to wireless power receiver 24. This may include measurements “in the open,” meaning that no wireless power receiver 24 is present, and / or measurements in a “paired” state, meaning that a wireless power receiver 24 is present and paired with wireless power transmitter 12.If the Q-factor value deviates by more than a threshold value outdoors (resulting in a Q-factor "deflection") and the object causing the Q-factor deflection does not respond to a subsequent digital ping or other attempts to establish communication, the wireless energy transmitter 12 may conclude that a foreign object is on the coil 36 and refrain from wireless energy transmission and / or take other appropriate action (e.g., by transmitting energy at a restricted level lower than the level permitted without detection of the foreign object, by stopping energy transmission, etc.). In the paired case, Q-factor measurements can be used to detect the introduction of a foreign object during or after initiating wireless energy transmission.Such an event can also result in either the wireless power transmission being interrupted and / or the power being reduced to a limited level, as described above. In general, Q-factor measurements can be performed using the same hardware and methodology whether in open-air or pairing mode, and the control techniques implemented by the respective control circuitry can be configured to respond appropriately to Q-factor (or resonant frequency) excursions based on thresholds and logic appropriate for the respective regimes.

[0034] Fig. Figure 2 shows illustrative circuitry in the wireless energy transfer system 8 that enables measurements of the Q factor of the coil 36. The wireless energy transfer circuitry of Fig. 2 may include wireless power transmission circuitry 52 in the wireless power transmitter 12 and wireless power reception circuitry 54 in the wireless power receiver 24. During operation, wireless power signals 44 may be transmitted by the power transmission circuitry 52 and received by the wireless power reception circuitry 54. As shown in Fig. 2, the wireless power transfer circuitry 52 may include inverter circuitry 61.

[0035] The inverter circuitry 61 can be used to provide signals to the coil 36. During wireless power transmission, the control circuitry of the wireless power transmitter 12 can provide signals to the control input 82 of the inverter circuitry 61, causing the inverter 61 to provide alternating current (AC) signals to the coil 36. Circuit components such as the capacitor 70 can be connected in series with the coil 36, as shown in Fig. 2. When alternating current (AC) signals are supplied to coil 36, corresponding electromagnetic alternating current signals (wireless power signals 44) may be transmitted to nearby coils, such as the illustrative coil 48 in the wireless power receiving circuitry 54, which may induce a corresponding AC signal in coil 48. Capacitors, such as capacitors 72, may be coupled in series with coil 48. Rectifier 50 may receive the AC current from coil 48 and convert corresponding power (e.g., DC voltage V rect ) at the output terminals 76. This power can be used to power a load.

[0036] The wireless power transmitter 12 may include measurement circuitry for monitoring the signals at the coil 36. This circuitry 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.). The current source 92 and / or the inverter 61 may also be used to supply signals to the coil 36 during foreign object detection (e.g., so that Q for the coil 36 can be measured). In some embodiments, the Q-factor measurement may be performed by directly measuring the impedance of the coil 36 with an AC power source. The Q measurements may be performed in the presence of the wireless power receiving device 24 (“mated-Q measurements”) and / or in the absence of wireless power receiving devices (“outdoor” measurements).In some applications or embodiments, periodic Q measurements may be performed outdoors when no wireless power receiver 24 is present, and / or periodic mated Q measurements may be performed when a wireless power receiver 24 is present. By monitoring changes in Q (whether outdoors or in pairing), the presence of a foreign object may be detected and appropriate action taken.

[0037] In a first illustrative arrangement for Q-factor measurement, the control circuitry of device 12 may cause inverter 61 to provide signal pulses to coil 36 and measurement circuitry such as voltage sensor 90 to measure the corresponding pulse responses. Due to the resonance in the circuit of Fig. 2, the application of a signal pulse to the coil 36 generates a ringing signal with a decay envelope such as that shown in Fig. 3 illustrated decay envelope 94. The decay envelope may have a decay envelope defined by e eπfrQt is given, where f r is the frequency of the ringing signal. By measuring f r and the decay envelope 94, the value of Q can be determined. An equivalent approach, which is computationally simpler, can be achieved by sampling the waveform peaks to obtain the waveform envelope. That is, to define: Vi=Vi+−Vi−,i=1,2 then Q=πNln(V1V2) where N is the distance (in terms of the number of peaks) between the second samples and the first samples (e.g. = 1 means that the peaks are adjacent).

[0038] If desired, the capacitor 70 can be Fig. 2 may be implemented using an adjustable capacitor arrangement, such as a capacitor circuit with switching logic and a plurality of capacitors that can be selectively operated under the control of the control circuitry 16 to adjust the capacitance value in the resonant circuit and thereby adjust the resonant frequency. In arrangements in which the capacitor 70 has a selectable or otherwise controllable value, a first value (e.g., C1) may be used when measuring the impulse response of the wireless energy transfer circuitry to determine Q (as described in connection with Fig. 3), and a second value (e.g., C2) may be used when the wireless power transfer circuitry transmits wireless power signals 44. In other embodiments, a single capacitance value may be used for both operations.

[0039] In a second illustrative arrangement for Q-factor measurement, the value of Q can be obtained by directly measuring the impedance of the coil 36. Fig. Figure 4 is a circuit diagram of the wireless power transfer circuitry and the measurement circuitry of Fig. 2, which shows how a parasitic resistor R may be connected to the resonant circuit. In direct impedance measurement, a small current can be injected from current source 92 into coil 36, while the voltage can be measured with voltage sensor 90. The magnitude of the injected current can be so small that the current can be injected without using large-power field-effect transistors. The current can be, for example, an alternating current (AC) with a frequency chosen to optimize the ability to distinguish a foreign object based on the design of the LC tank. In some cases, this may be a frequency of 125 kHz. However, depending on the design, a higher or lower frequency may be used. For example, another design might have a range of 150-300 kHz, although any suitable frequency could be used.In any case, this frequency can be chosen independently of the resonant frequency of the wireless power transmission circuit. The complex impedance of coil 36 can then be determined at this frequency, and the value of Q can be derived from the angle θ of the measured impedance. Fig. Figure 5 shows equations for determining Q (Q factor of the coil) from the angle of the complex impedance and optional values ​​for the inductance L and the resistance R (the real part of the AC impedance), which can be calculated from the direct impedance measurement. In the equations of Fig. 5, I is the injected alternating current and V is the resulting voltage measured by the voltage sensor 90.

[0040] The measurement circuitry 41 of the device 12 may be calibrated during manufacturing. For example, the value of the Q-factor (Q0) measured at an initial time when the device 12 is manufactured (using the first illustrative Q-factor measurement arrangement, the second illustrative Q-factor measurement arrangement, and / or additional Q-factor measurement techniques) may be stored in the device 12 as a baseline value for later use. Likewise, calibration may be performed for other observables to be measured, such as the resonant frequency and the like. If desired, device-specific calibration operations may be performed so that each device 12 is individually calibrated with a corresponding individual baseline value of Q.When operating in the field, the device 12 can measure the current value of Q and compare this measured value of Q with the factory-stored baseline value of Q0. In this way, the magnitude of the change in Q or other observables can be determined, which is an indication of whether a foreign object or other external object is in the vicinity of the wireless energy transmitter 12.

[0041] If desired, compensation techniques can be used to compensate for the effects of temperature, aging, and other effects that may cause deviation in Q or other measured parameters. For the following calibration example, a specific Q compensation technique is discussed, although other compensation techniques may be applied, and compensation for measurands other than Q (such as resonant frequency, coupling factor, etc.) may also be used. Temperature variations can affect the parasitic resistance of components such as coil 36. Coil inductance L may also depend on temperature. Frequency changes and aging effects (e.g., mechanical wear) can affect the values ​​of the components and, therefore, the measured value of Q.Compensating for these effects when comparing Q to Q0 can help improve the accuracy of foreign object detection measurements.

[0042] The value of the baseline Q-factor Q0 and the value of the resonance frequency ω0, e.g., 2πf r measured during calibration (e.g., at an initial time during manufacturing) can be given by equations 3 and 4. Q0=ω0L0 / R0 ω0=1 / L0C where R0 increases with ω0 due to the skin effect. The values ​​of Q and ω (and of L and R) measured at runtime (sometimes referred to as current Q, current ω, current L and current R) are given by Q FO , ω FO , L FO and R FO (where R FO is also a function of frequency) of equations 5, 6, 7 and 8. QFO=ωFOLFO / RFO ωFO=1 / LFOC LFO=L0+ΔLFO RFO=R0+ΔRFO

[0043] During the compensation processes, the current temperature T of the wireless energy transmitter 12 can be measured with the temperature sensor 60 of the wireless energy transmitter 12 (see e.g. Fig. 1). The change in temperature ΔT compared to the temperature T0 measured during calibration measurements during production is given by Equation 9. ΔT=T−T0

[0044] The equation of Fig. 6 shows how a compensated value of Q (e.g. the value of Qcomp) as a function of the currently measured Q-factor (Q' in the equation of Fig. 6) can be determined based on one or more compensation factors.

[0045] A first illustrative compensation factor includes frequency compensation. As shown in the equation in Fig. As shown in Figure 6, Q' can be multiplied by the compensation factor (ω0 / ω) to compensate for changes in the resonant frequency when measuring Q' compared to the resonant frequency when measuring Q0 in production. A second illustrative compensation factor relates to the temperature dependence of inductance and resistance. As shown in the equation in Fig. 6, Q' can be calculated with the compensation factor (1+κ R ΔT) / (1+κ L ΔT), where κ R the ohmic temperature change coefficient and κ Lis the inductive temperature change coefficient. The values ​​of these temperature coefficients can be influenced by the design of the wireless energy transmitter 12 and can, if desired, be determined empirically by taking measurements on one or more representative units of the wireless energy transmitter 12 during manufacture. A third illustrative compensation factor involves compensating for shifts in the AC resistance R AC the coil 36 and the DC resistance R DCof coil 36 compared to the baseline values. With this resistance compensation technique, the current value of the quality factor can be compensated based on a compensated value of the total (total) inductive coil resistance of the wireless power transmission coil 36. The coil 36 can be characterized by a total inductive coil resistance value that includes DC and AC portions. During compensation operations, the control circuitry 16 can compensate for changes in the total inductive coil resistance by calculating a compensated value of the total inductive coil resistance from a 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 resistance of the inductor can then be used to compensate for the power quality factor using the compensated total resistance of the inductor. As shown in the equation in . Fig. 6, the resistance-based compensation factor can be calculated based on the measured baseline DC resistance (R DC,0 ), obtained from the calibration measurements during manufacturing, the baseline AC resistance (R AC ), obtained during calibration measurements during manufacture, and the value of η, which is the coefficient of variation of the alternating current resistance R AC depending on changes in the resonance frequency ω (e.g., 50 m-Ω per 100 kHz or another suitable value) obtained from calibration measurements during production. The parameter R meas is equal to the sum of the measured alternating current resistance R ACand the measured DC resistance R DC .

[0046] In the example of Fig. 6, all three of these illustrative compensation factors were applied to the measured Q' value (e.g., Qcomp was determined by compensating Q' based on changes in frequency and frequency-related effects, as well as for temperature-related effects). Generally, one or two of these compensation techniques may be used and / or other compensation techniques may be used to calibrate Q-factor measurements based on measured temperature, resonant frequency, and / or other variables. As set forth in the example above, a compensated Q-factor value Qcomp may be generated based on measurements of temperature and frequency. This value may then be compared to a baseline Q value measured during manufacturing and stored in the device 12 for use during later comparisons.If desired, compensation operations may be performed on the base Q-factor value to produce a compensated base Q, rather than performing compensation operations on the field-measured value of Q. Approaches in which compensation operations are performed on a field-measured Q value rather than a base Q value are described herein as an example.

[0047] Fig. Figure 7 shows an illustrative flowchart for detecting foreign objects using the wireless power transmission system 8. In this embodiment, the power supply may be interrupted when a foreign object is detected. It is also possible to simply flag the detection of the foreign object for use as additional information in determining appropriate power supply levels during the power supply phase. For example, the maximum power level used during power delivery may be reduced to a predetermined level below the maximum power level in response to the detection of the foreign object.

[0048] During the operations of block 100, the wireless energy transmitter 12 may measure a current value of Q using the first illustrative Q-factor measurement arrangement (e.g., using the inverter 61 to apply a pulse and measure Q from the impulse response envelope 94) or the second illustrative Q-factor measurement arrangement (e.g., where Q is derived from a direct impedance measurement of the coil 36 performed by injecting current into the coil 36 using the AC power source 92). Measuring Q using techniques such as these or other suitable Q-factor measurement techniques may sometimes be referred to as a low-power ping (LPP) or analog ping operation.

[0049] During the operations of block 102, the value of the change in Q (e.g., Q-factor deflection value Q defl) can be determined. During the operations of block 102, compensation techniques such as those associated with Fig. 6 can be applied to compensate for the measured value of Q or the baseline value of Q (ie, Q0) stored in the wireless energy transmitter 12 during manufacture. The value of Q defl can be calculated, for example, using equation 10. Qdefl=Q0−QcompQ0=1−QcompQ0

[0050] In the example of equation 10, Q defl at least partly due to a difference between the compensated measured Q (ie Q comp ) and the baseline Q (ie Q0) and at least partly on a relationship between Q comp and Q0. Using equation 10, if the current value of Q decreases by 5% from the baseline value Q0, Q defl 5%. In general, Q deflonly based on the difference between the measured Q and the baseline value Q, can only be based on the ratio between the measured Q and the baseline value Q (e.g. Q defl =Q comp / Q0), can be based on the difference between the measured and the baseline value Q as well as on the ratio between the measured Q and the baseline value Q and / or can be based on other functions of the measured Q and the baseline value Q. The measured values ​​of Q and / or the baseline value of Q used to calculate Q defl can be compensated for temperature, frequency and / or aging effects, as described in conjunction with the compensation techniques of Fig. 6. (As explained in more detail below, the frequency deflection can be calculated in the same way.)

[0051] During the operations in block 103, the control logic of the wireless energy transmitter 12 may determine whether Q has settled. If Q changes rapidly (e.g., due to the movement of an external object across the charging surface of the wireless energy transmitter 12 while the measurements are being taken), the value of Q defl may not stabilize sufficiently, and the process may return to block 100. During the operations of block 100, a new measurement of Q can then be obtained. As long as Q has not settled, you can obtain a new Q measurement every 0.1 s (or at another suitable sampling rate) in this way. Once the successive values ​​of Q defl by less than a predetermined threshold (e.g. 1%), it can be assumed that Q has settled sufficiently to allow an analysis of the value of Q deflto determine if a foreign object is present, and operation may continue with block 104.

[0052] During the operations in block 104, the wireless energy transmitter 12 may determine the value of Q defl with a given threshold value TH (e.g. 3% or another suitable value). If Q defl does not exceed the threshold (e.g., if the measured value of Q has not decreased by more than 3% compared to the baseline value Q), the wireless energy transmitter 12 may conclude that no external object is present (e.g., the wireless energy receiving device 24 is not present, and no foreign objects are present). The measurement operations may then continue at block 100. However, if it is determined during the operations in block 104 that Q deflexceeds the threshold, device 12 may conclude that the measured Q has changed by more than the threshold compared to baseline Q0 (e.g., Q is at least 3% lower than Q0) and that, therefore, an external object of some kind is present (either a foreign object or a wireless energy receiving device 24). Operations may then proceed to block 106 to distinguish between these two possibilities.

[0053] During the operations in 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 use in-band communications to transmit a wireless digital request. The wireless digital request may be used to request the wireless power receiver 24 to confirm its presence by wirelessly transmitting a corresponding digital response to the wireless power transmitter 12 via in-band communications. This process of requesting digital communication may sometimes be referred to as a digital ping. During the operations in block 108, the wireless power transmitter 12 may determine whether it has received a response to the digital ping from the wireless power receiver 24 to indicate that a wireless power receiver is present.

[0054] If the wireless energy receiver 24 is located on the charging surface of the wireless energy transmitter 12, the wireless energy receiver 24 will receive the digital ping with a wireless digital response. This response may include information such as a digital identifier corresponding to the type of wireless energy receiver 24 present, etc. In response to determining during the operations of block 108 that a cellular phone, wristwatch, or other wireless energy receiver 24 is present, the wireless energy transmitter 12 may transmit wireless energy signals 44 to the device 24 (e.g., during the operations of block 110). Subsequent Mated-Q measurements may also be performed during this time, as described in more detail below.If there is no wireless energy receiver 24 on the charging surface of the wireless energy transmitter 12, the wireless energy transmitter 12 will not receive an acknowledgment from the wireless energy receiver 24. If it is determined during the operations in block 108 that there is no wireless energy receiver 24, the wireless energy transmitter 12 may conclude that a foreign object is present (which caused the measured Q deflection), and operations may continue with block 112.

[0055] During block 112, the wireless energy transmitter 12 may monitor Q to determine when the present foreign object has been removed. In particular, Q may be measured during the operations of block 114, as described in connection with the Q measurements of block 100. The value of Q defl can be calculated in block 116. The operations in block 118 can include the comparison of Q deflwith the threshold TH or another threshold. If the foreign object is still present, Q defl at a value that exceeds the threshold, and further measurements may be taken in block 114. However, if the foreign object is removed, the process returns to block 100 so that the wireless power transmitter 12 can determine whether a wireless power receiver 24 is present and, if so, can begin delivering wireless power to the wireless power receiver 24.

[0056] When determining Q deflThe wireless energy transmitter 12 may perform comparisons of the measured Q with the baseline value of Q obtained during manufacturing and stored in the wireless energy transmitter 12 for future use. Temperature changes, frequency changes, changes in coil resistance, and other changes may affect Q0, so Q0 may be continuously updated if desired. In one illustrative arrangement, a filter is used to update the Q baseline based on a newly measured Q value each time it is determined that no external objects are present at the charging surface of the wireless energy transmitter 12. For example, each time the wireless energy transmitter 12 determines that Q deflis not greater than the threshold, determine that no foreign objects and no wireless power transmission devices are present. Accordingly, the wireless power transmitter 12 may conclude that the last measurement of Q from block 100 is an updated outdoor Q value that can be used, at least in part, to update Q0 (e.g., a current Q value that can be used as a filter input).

[0057] In this embodiment, therefore, each time it is determined that Q defl is not greater than the threshold TH, an updated value of Q0 in the wireless energy transmitter 12 at point P1 of the flow chart of Fig. 7. When updating Q0, the current value of Q (measured during the last visit in block 100) can be integrated into Q0 using a suitable filtering scheme (e.g., using a weighted historical average, using an averaging scheme that suppresses noisy data, or another filtering arrangement). By updating Q0 in this way with current measurement data, the effects of aging on the baseline value of Q can be reduced.

[0058] In an illustrative configuration, the wireless energy transmitter 12 can update Q0 with the current value of the measured Q using a low-pass filter. Let q[n] be a valid Q-deflection sample. An example of a low-pass filter for Q is a single-pole filter (see, e.g., Equation 11) where α ∈ [0,1] and close to 1. Qfilt[n]=αQfilt[n−1]+(1−α)Qdefl[n],Qfilt[0]=0

[0059] Another example is the moving window average given in Equation 12. Qfilt[n]={∑m=0nQdefl[m]nfu¨rn <M∑m=n−MnQdefl[m]Mfu¨r N≥M

[0060] As these examples show, there are several ways to incorporate the current Q measurement data from block 100 into the baseline value Q, which is stored in the wireless energy transmitter 12 and subsequently used to calculate Q defl is used. During these update operations, the control logic 16 may periodically update the baseline quality factor by performing a filtering operation based on a history of current quality factor measurements, thus ensuring that the value of the baseline quality factor is adjusted for aging and other effects that could cause the quality factor measurements to drift over time.

[0061] Updating the baseline value Q at point P1 may include performing a separate filtering operation after each measurement of Q in block 100. If desired, the number of filtering operations per unit time (and therefore the number of times an updated value of the Q baseline is calculated and stored in the device 12 per unit time) may be reduced by performing filtering operations at point P2 instead of P1. With this type of arrangement, the values ​​of Q measured during the operations of block 100 may be stored by the control logic 16 each time point P1 is reached (e.g., each time it is determined that no foreign object is present). If the operations in block 104 determine that the last Q value exceeds the threshold TH, processing may continue to block 106, where a digital ping is performed.During the operations in block 108, the control circuitry 16 may determine whether (a) no response to the digital ping was received (in which case, a foreign object is present, and processing continues with block 112); or whether (b) a wireless digital response was received from the device 24. At this point (e.g., at point P2), the wireless power transmitter 12 may know that the wireless power receiver 24 was just placed on the charging surface of the wireless power transmitter 12. Before initiating power delivery in block 110, the wireless power transmitter 12 may retrieve the last value of Q that was cached at point P1 (and which represents a Q-factor measurement when no foreign object or other external object is present on the device 12) and use this retrieved current value of Q to update the value of the Q baseline.

[0062] With this approach, filtering to update the baseline Q value can only be performed when it is determined that a wireless energy receiver 24 is newly present (and no foreign object is present). The filtering process can be performed on the last obtained Q value when no external object was present (e.g., the Q value without an external object, which was cached at point P1). Each time point P1 is reached, the Q value must still be stored, but the calculation of the updated baseline Q value using the filter can be performed less frequently (e.g., only when P2 is reached).Updating the baseline Q value only when it has been determined that no wireless energy receiving device and no foreign object are present ensures that the baseline quality factor value is adjusted for aging and other effects that could cause the quality factor measurements to drift over time, but does not require as many separate filtering operations as if the filtering operations were performed at point P1.

[0063] In addition to periodically updating the baseline value of Q (either at point P1 or at point P2, as examples), the control logic 16 may periodically update the value of the threshold TH used during the comparison operations of block 104 (e.g., an adjustable threshold TH may be used instead of a fixed value). For example, low-pass filtering or other filtering 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 taken when no external object was present and buffered at point P1). This filtering operation to update the value of TH may be performed at point P2 (e.g.,when it is determined that no foreign object is present), using measurements such as one or more cached Q-factor measurements taken when no wireless energy receiving device or foreign object was present.

[0064] If desired, the value of Q deflcompared with several different threshold values ​​(e.g., to determine whether a small or large foreign object is present). Device 12 may then perform 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, while the wireless power receiving device may be omitted entirely if a large foreign object is present. In this context, "small" or "large" may refer to the physical size and / or other physical characteristics of the device that correlate with the degree of heating such a foreign object is expected to generate at various wireless power transfer levels.

[0065] For example, the diagram in Fig. 8 illustrates the operation of the wireless energy transmitter 12 in a system with multiple thresholds for the detection of foreign objects. In the example of Fig. 8, the wireless energy transmission system 8 may have a lower first threshold value TH Luft (e.g. 3% or another appropriate value such as a value below 3% or a value above 3%) and a higher second threshold TH FO (e.g., 6%, a value above or below 6%, or another suitable value above the first threshold). The wireless energy transmitter 12 can operate in states 120, 122, 124, and 126. Transitions between these states can occur according to transition rules 128. The values ​​of the thresholds TH Luft and TH FOcan be adjusted accordingly to distinguish a moderate foreign object (e.g., an object with a relatively small amount of metal and / or metal with moderate conductivity) from a strong foreign object (e.g., an object with more metal and / or metal with higher conductivity). These "moderate" and "strong" foreign objects can correspond to the "small" and "large" foreign objects described above. Wireless power transmission can be interrupted in the case of a strong foreign object until clear air is seen. However, by setting the threshold high enough, implementations can decide to avoid using the "strong foreign object" state.

[0066] As in Fig. 8, the wireless energy transmitter 12 in block 122 Q defl with the first and second threshold values ​​and determine that Q deflis lower than the first threshold. In this scenario, the wireless power transmitter 12 may conclude that no foreign object is present and may therefore adjust the power output for the wireless power signals 44 to a relatively higher power level (power level 2). The power may then be wirelessly transmitted from the wireless power transmitter 12 to the wireless power receiver 24, while the power delivery occurs in block 126.

[0067] In block 120, it may have been determined that a foreign object is present because Q defl is greater than the first threshold. It may also have been determined that Q deflis smaller than the second threshold. From this, the wireless energy transmitter 12 can conclude that although a foreign object is present, it is not a large or strong foreign object. The wireless energy transmitter 12 can therefore wirelessly deliver power to the wireless energy receiver 24 during the operations in block 126. Because power is supplied to the wireless energy receiver 24 in the presence of a small or moderate foreign object, the level at which power is wirelessly transmitted (e.g., the maximum power level) can be reduced to a relatively lower power level (e.g., power level 1, which is less than power level 2). This can help prevent or limit the heating of the small / moderate foreign object. In block 124, it can detect that a large or strong foreign object is present because Q deflis greater than the second threshold. In this situation, the wireless energy transmitter 12 may forego wireless energy transmission.

[0068] The embodiment described above is merely exemplary, and other control logic may be implemented, including multiple thresholds, multiple power levels, and variations in whether wireless power transmission is limited or completely prevented in response to the respective thresholds. Furthermore, further details regarding Q measurement techniques, compensation techniques, accuracy improvements for such measurements, and the like are described in Applicant's U.S. patent application Ser. No. 18 / 327,721, entitled "Wireless Power Systems with Foreign Object Detection," filed June 1, 2023, which is hereby incorporated by reference in its entirety.

[0069] As previously mentioned, the detection of foreign objects in a wireless power transfer system can also be based on Mated-Q measurements, either separately from or in conjunction with outdoor Q measurements, as described above. In general, the operating principles of Mated-Q measurements are as described above. That is, when the wireless power transmitter 12 is coupled to a wireless power receiver 24, the corresponding control circuitry 16, the measurement circuitry 41, and the power transfer circuitry 52 can be configured to provide a signal that enables the measurement of the coupled Q factor (or other magnetic parameters), as described above. This signal can be in the form of an impulse response and a ringdown, as described above in Fig. 2-3. Additionally or alternatively, this measurement may be based at least in part on a complex impedance measurement, as described above in the Fig. 4-5. The resulting Q-deflection or other magnetic parameters can be used in conjunction with a measurement of the system resonance frequency to detect foreign objects. The system resonance frequency can be derived from the pulse-based measurement of the Q-deflection, which is carried out as described with reference to Fig. 2-3. More specifically, the resonant frequency is both a factor (together with the Q factor) that characterizes the ringdown envelope 94 and can be measured directly by reference to the ringing waveform. Alternatively, the resonant frequency of the system can be determined by circuit logic such as that used for measuring complex impedances, as described with reference to Fig. 4-5, for example, by sweeping the frequency of the applied waveform to identify a peak associated with the resonant frequency.

[0070] For a particular wireless energy transmitter 12, one or more pairs of baseline values ​​for mated Q and resonant frequencies may be obtained, each pair corresponding to one or more reference receivers 24, e.g., during manufacture of the wireless energy transmitter 12. Such one or more baseline pairs of mated Q and resonant values ​​may be compared to mated Q and resonant frequency measurements taken during operation to detect a foreign object that may be brought into proximity of the wireless power transmission system 8 during operation. In some cases, the number of potential wireless energy receivers 24 may be so large that measuring and storing pairs of values ​​for each possible transmitter / receiver combination becomes unwieldy.In such cases, the principles of ecosystem scaling described in more detail below can be used to make the situation more manageable by storing fewer baseline pairs and providing a mechanism for calculating modified baseline pairs that correspond to the respective sender-receiver combination.

[0071] The baseline values ​​or modified baseline values ​​can be compared with the measured values ​​in a two-dimensional space in which the presence and absence of a foreign object are sufficiently separated. Such a space can be considered a magnetic state space in which normal operation (in which no foreign object is present) and a scenario in which a foreign object is present and can be heated if it remains undetected are sufficiently separated to be distinguishable. An example of such a space is shown in Fig. 9 via the diagram 900. The diagram 900 plots a first observation that is a function of the resonant frequency and the Q-factor (x(f,Q), e.g., measured excursion of the resonant frequency) on the x-axis against a second observation that is a function of the resonant frequency and the Q-factor (y(f,Q), e.g., measured excursion of the counter frequency on the y-axis). The measured excursion of the resonant frequency may be the difference between a measured resonant frequency during operation and a baseline resonant frequency (optionally modified by ecosystem scaling calculations, as described in more detail below). The measured excursion may be the difference between a measured excursion value during operation and a baseline Q-factor (optionally modified by ecosystem scaling calculations, as described in more detail below).Generally, when no foreign object is present, the values ​​for the Mated-Q and resonant frequency deflection (or the deflection of other magnetic parameters, as described above) appear in the 905 range. Generally, when a foreign object is present, the values ​​for the Mated-Q and resonant frequency deflection appear in the 903 range. Fig. 9 is based on an fQ space. In an f 2 , 1 / fQ space, as described below with reference to Fig. As described in Figure 17A, the relative position between the areas corresponding to the presence or absence of a foreign object could be reversed. Thus, the relative position between these areas can vary depending on the selected functions.

[0072] The separation between these two areas, i.e. no foreign object or foreign object present, can be demarcated by a curve 901. The curve 901 can be a linear function of the form: A0+A1f+A2Q=0 where f and Q are the system resonant frequency and the Q value, and A0, A1, and A2 are coefficients that can be extracted using suitable statistical methods. For example, in at least some embodiments, logistic regression may be used. In a more general sense, the resonant frequency f and the quality factor Q can be replaced by corresponding functions of f and Q. Equation 13a thus becomes: A0+A1x(f,Q)+A2y(f,Q) where x(f,Q) is a first function of the resonant frequency and the quality factor, and y(f,Q) is a second function of the resonant frequency and the quality factor. For example, x(f,Q) could be the resonant frequency f and y(f,Q) could be the quality factor Q, which would yield Equation 13a provided above. Alternatively, in an exemplary embodiment, x(f,Q) could be f 2 (resonance frequency squared) and y(f,Q) 1(f⋅Q) (the inverse of resonance frequency times quality factor). Consequently, the determination of whether a foreign object is present or not can be made by detecting a change in the position of the first function-based and the second function-based measurements in a suitable state space.

[0073] Fig. 10 illustrates a flowchart of a foreign object detection method 1000 using Mated-Q measurements as described above. Starting at block 1007, the system may optionally perform a Q-based outdoor foreign object detection routine as described above. In response, the system may initiate the transmission of energy (block 1009) at an appropriate level, as also described above. The exact operation of the outdoor Q portion of the foreign object detection method 1000 may vary depending on the embodiment and / or may be omitted entirely in some embodiments if desired. The Mated-Q portion of the foreign object detection method 1000 begins at block 1011, where Mated-Q and the resonant frequency are measured as described above. Then, at block 1013, the system may (e.g.,The control circuitry 16 of the wireless energy transmitter 12 may determine whether a foreign object is present by comparing the measured Mated-Q and resonant frequency as described above. For example, the processing circuitry may compare the measured Mated-Q and resonant frequency values ​​to reference values ​​stored in the device and determine whether the associated deflection falls within range 905 (. Fig. 9) the magnetic state space (in which no foreign object is present) or the area 903 ( Fig. 9) (in which a foreign object is present). If it is determined that no foreign object is present, the process may proceed to block 1014, which allows the continuation or resumption of wireless power transmission at a relatively higher power level. Control may return to block 1011 so that mated-Q and resonant frequency measurements may be taken periodically at desired intervals during the power transmission process initiated in block 1009, enabling ongoing / continuous mated-Q foreign object detection.

[0074] Alternatively, if a foreign object is detected in block 1013, the processing circuitry may determine whether the detected foreign object is a "moderate" or "small" foreign object, or a "strong" or "large" foreign object, as described above. Additionally, more than two levels of foreign object classification may be provided. Generally, a moderate / small foreign object is one that allows wireless power transmission at a limited or lower energy level without causing excessive heating (e.g., above a threshold) of the foreign object. Similarly, a strong / large foreign object is one that may require interrupting wireless power transmission to prevent excessive heating.What constitutes an elevated level of heating, and thus defines the classification of a foreign object as moderate / small or severe / large (or further gradations), may vary from one application or embodiment to the next. However, it may be desirable for the Mated-Q and / or resonant frequency excursions to differ sufficiently between these classes to allow the processing circuitry (e.g., the control circuitry 16 of the wireless energy transmitter 12) to perform an analysis. Based on this classification, if it is determined in block 1015 that the detected foreign object is a small / moderate foreign object, the energy transfer may be reduced in block 1017, and control may return to block 1011, allowing continuous / periodic detection of foreign objects in Mated-Q.If the foreign object is subsequently removed, the power transfer may resume at the higher level (block 1014). Alternatively, if the foreign object remains, the flow will again proceed along the path 1015-1017-1011 described above. Another alternative is that if it is determined in block 1015 that the detected foreign object is not a moderate / small foreign object, but rather a strong / large foreign object, control transfers to block 1019, where the wireless power transfer is suspended or prevented. Control then returns to block 1007 to resume the power transfer once the open-air ping process has determined that no foreign object is present. If the open-air ping functionality 1007 is omitted in a particular embodiment or application, control may return to the path that leads to the initiation of the wireless power transfer (e.g.,Block 1009).

[0075] The above description is only one example of Mated-Q-based foreign object detection and wireless power control. Various modifications of such an arrangement are possible. For example, the classification of a detected foreign object as moderate / small or strong / large could be omitted entirely, and the detection of a foreign object in the mating-Q phase could lead to the interruption / prevention of wireless power transmission. Likewise, there could be multiple foreign object classifications, each with a different reduced energy limit. As already mentioned, the foreign object detection algorithm for outdoor Q measurement could also be omitted or modified from the example described above. Numerous other variations and permutations are possible.

[0076] Fig. Figure 11 illustrates a sequence of Mated-Q measurements related to settling / rest detection that can be used for foreign object detection. The sequence is represented as a graph 1100 of measured deflections (on the vertical axis) versus time (on the horizontal axis), where each deflection measurement represents a point. The deflection is the difference between the measured Mated-Q value at that time and the reference Mated-Q value stored in a device, such as a wireless energy transmitter 12. The initial reference value can be programmed into the unit during manufacture and can be updated periodically, as described elsewhere herein.

[0077] An initial sequence 1121 of zero Q-deflection values ​​corresponds to the situation where no object, neither a foreign object nor a wireless energy receiver, is present. These intervals may provide an opportunity to update the stored reference values, as described elsewhere herein. Starting at approximately 2 seconds in the example graph 1100, the Q-deflection value begins to increase, but does not have a constant value over a sequence of samples 1123. This corresponds to the time an object, which may be a wireless energy transmitter or a foreign object, is brought into proximity with the transmitter. During this interval, it may be desirable for the processing system, e.g., the processing circuitry 16 or the wireless energy transmitter 12, to do nothing until the Q-deflection values ​​stabilize.Nevertheless, in some situations, such as very large Q deflections, it may be desirable to take more rapid action to reduce or prevent energy transfer. In either case, the processing circuitry can apply appropriate averaging or filtering to the Q deflection values ​​to determine whether the system has reached a stable point of equilibrium. Such a steady state may be indicated when a sequence of measured Q deflection values ​​shows no change, as with samples 1125. Samples 1125 indicate that the system has stabilized at a Q deflection of approximately 0.5 (although other Q values ​​are also possible). This stabilized Q deflection value (and the associated resonant frequency value) can then be used to perform the Q-related foreign object detection described above.In some cases, the sequence of Mated Q measurements (instead of displacement), resonant frequency measurements, or resonant frequency displacement can be used to determine whether the system has reached a steady-state operating condition when an object is brought into proximity. In some applications, measurements of the system's resonant frequency and / or resonant frequency displacement can provide a better estimate of when the system stabilizes than Mated Q / displacement sampling.

[0078] As previously mentioned, the use of Mated-Q measurements for foreign object detection can be based on Mated-Q and resonant frequency measurements, which may be different for each possible wireless energy transmitter and wireless energy receiver pair. In some cases, multiple such baseline values ​​may be determined during manufacturing, for example, and stored in a wireless energy transmitter as described above. However, as the number of possible transmitter-receiver pairs increases, this can quickly become impractical. For example, it may be desirable to provide one or more baseline value pairs for each transmitter based on one or more "reference" or "golden" receiver pairs. Each receiver can then be characterized relative to one or more of the reference / golden receivers and provided with its own stored values ​​according to this characterization.For example, this could be implemented as a plurality of scaling factors relative to the reference / gold receiver(s). A wireless power receiver could then provide its scaling factors to the wireless power transmitter, which could then calculate appropriate baseline values ​​for mated Q and resonant frequency based on the stored reference values ​​and the scaling factors. Example techniques for scaling the loss measurement are described in applicant's U.S. patent application 17 / 681,363, entitled "Wireless Power Systems with Shared Inductive Loss Scaling Factors," filed on February 25, 2022, and incorporated by reference. Fig. 2, Fig. 12 and Fig. 13 is fully incorporated into this document.

[0079] As described above, Fig. 2 shows the wireless power switching logic of the wireless power transmission system 8 in a scenario in which a wireless power transmitter has been paired with a wireless power receiver. The wireless power switching logic of Fig. 2 includes wireless power transmission circuitry 52 in the wireless power transmitter 12 and wireless power reception circuitry 54 in the wireless power receiver 24. During operation, wireless power signals 44 are transmitted by the wireless power transmission circuitry 52 and received by the wireless power reception circuitry 54. The configuration of Fig. 2 includes a single transmit coil 36 and a single receive coil 48 (for example).

[0080] As in Fig. 2, the wireless power transfer circuitry 52 may include inverter circuitry 61. The inverter circuitry 61 may be used to provide signals to the coil 36. During wireless power transfer, the control circuitry of the wireless power transmitter 12 may provide signals to the control input 82 of the inverter 61, causing the inverter 61 to provide AC signals to the coil 36. Circuit components such as the capacitor 70 may be connected in series with the coil 36, as shown in Fig. 2. The measurement circuitry 41 in the wireless power transmitter 12 can make measurements of the operating currents and voltages in the wireless power transmitter 12. For example, a voltage sensor 41A can be used to measure the coil voltage across the coil 36, and a current sensor 41B can be used to measure the coil current through the coil 36. In other implementations, the voltage across the capacitor 70 can be measured, and the current through the coil is derived from this measurement.

[0081] When alternating current signals are applied to coil 36, corresponding electromagnetic alternating current signals (wireless power signals 44) can be transmitted to nearby coils, such as the illustrative coil 48 in the wireless power transfer circuitry 54. This can induce a corresponding alternating current (AC) signal in coil 48. Capacitors, such as capacitors 72, can be coupled in series with coil 48. Rectifier 50 can receive the alternating current from coil 48 and convert corresponding power (e.g., DC voltage V rect ) at the output terminals 76. This power can be used to supply power to a load. The measurement circuitry 43 in the device 24 can make measurements of the operating currents and voltages of the device 24. For example, the voltage sensor 43A V rect(the output voltage of the rectifier 50) or a voltage sensor can measure the coil voltage of the coil 48. The current sensor 43B can measure the rectifier output current of the rectifier 50, or a current sensor can measure the current of the coil 48.

[0082] The measurements performed by measurement circuitry 41 and 43 can be processed to extract magnetic loss characteristics (e.g., coefficients or other parameters that characterize the level of power loss in the wireless power transmitter 12 and the wireless power receiver 24, and that depend on the magnetic properties of the transmitter and receiver). These measurements can be stored in each device and exchanged between the devices so that the wireless power transmitter 12 (and, if desired, the wireless power receiver 24) can use this information to accurately estimate the power loss from any foreign objects that may be present and / or other related parameters, such as a Mated Q measurement and / or a Mated resonant frequency measurement.

[0083] If desired, these measurements can be used to estimate how well the transmitter and receiver are able to transmit wireless power. For example, these measurements can be used to estimate a magnetic coupling coefficient K, the efficiency of wireless power transfer, the estimated power loss from foreign objects, and / or other properties of the paired transmitter-receiver pair. In addition to, or instead of, estimating the power loss from foreign objects to determine whether a foreign object is present and therefore whether to proceed with wireless power transfer, the system can use this information (e.g.,The system may use the estimated power dissipation of the foreign object and / or related coupling and / or efficiency information to determine whether to display a confirmation message to the system user to inform them that the wireless power transfer is proceeding properly (e.g., to inform the user that this process has not been thwarted by the presence of a poor coupling due to the presence of a foreign object, possible misalignment, or other factors). Example confirmation messages include an audible output such as a chime and / or a visual output on the wireless power receiver 24.

[0084] In general, any suitable information may be exchanged between the devices in System 8, and this information may be used in any suitable manner. Illustrated is the exchange of measurements as performed using measurement logic 41 and 43, and the use of this information to determine whether a foreign object is present.

[0085] After the measurements with the circuit logic 41 and 43, the amount of energy potentially absorbed by a foreign object in the system 10 can be determined using equation 14. PFO=POUT−PIN−PLOSSTX−PLOSSRX

[0086] In equation 14, P FO for the amount of energy absorbed by a foreign object present (if any). P OUT stands for the output energy (e.g. the output energy of the rectifier 50), P IN stands for the input energy (e.g. the input energy of coil 36), PLOSSTX represents the power loss attributable to the wireless energy transmitter 12 and P LOSSRX represents the power loss attributable to the wireless energy receiver 24. The values ​​of P OUT and P IN can be measured (e.g., using circuit logic 41 and 43). Mathematical models can be used to derive functional expressions for P LOSSTX and P LOSSRX and these expressions can be evaluated against measured operating parameters, such as the measurements taken with the circuit logic 41 and 43. For example, in one illustrative embodiment, P LOSSTX and P LOSSRX can be calculated using equations 15a and 16a respectively. PLOSSTX=b⋅RAIRTX⋅(ITX)2 PLOSSRX=m⋅RAIRRX⋅(IRX)2+α⋅(IRX)2+αDC

[0087] In equations 15a and 16a, I TX for the transmitter current (e.g. coil current) and IRX for the receiver current (e.g., rectifier output current or, in some embodiments, receiver coil current). The values ​​of R AIRTX and R AIRRX represent measured AC coil resistances for coils 36 and 48, respectively. The values ​​of b, m, α and α DC are model parameters (sometimes referring to magnetic energy loss coefficients) that characterize the performance of the coupled pair of wireless energy transmitter and wireless energy receiver in the wireless energy transmission system 8. The energy losses of the transmitter P LOSSTX In the model of equation 15a, these losses are exclusively due to the energy losses of the transmitter coil. The energy loss of the receiver P LOSSRXhas a first component due to the energy losses of the receiver coil (the first term of equation 16a), and a second component (composed of the last two terms of equation 16a) representing friendly metal losses (e.g., losses due to eddy currents induced in the receiver during energy transfer). The parameter b is sometimes referred to as the transmitter coil loss parameter or coefficient. The parameter m can also be referred to as the receiver coil loss parameter or coefficient, and the parameters α and α DC can also be referred to as loss parameters or loss coefficients for friendly metal. The parameters b, m, α and α DCdepend on the magnetic interactions between the wireless energy transmitter 12 and the wireless energy receiver 24 when coupled, and may therefore sometimes be referred to as magnetic loss parameters or magnetic loss coefficients.

[0088] In an ecosystem where a user has multiple different models of wireless power transmitting devices (e.g., different models of wireless power transmitter 12) and multiple different models of wireless power receiving devices 24 (e.g., different models of both devices), the magnetic power loss parameters may vary depending on which wireless power transmitter and wireless power receiver are paired. For example, when a Model I transmitter and a Model J receiver are paired, the amount of power loss in each device will be different from that experienced when pairing these devices with other devices.

[0089] To account for these fluctuations and thereby ensure an accurate estimation of the energy loss from foreign objects in Equation 14, scaling factors for the magnetic energy loss parameters (sometimes referred to as scaling factors for the magnetic energy loss coefficient) can be used. In particular, the models P LOSSTX and P LOSSRX Equations 15a and 16a, which may be inaccurate in ecosystems with several different transmitter and receiver models, are replaced by equations 15b and 16b, respectively. PLOSSTX=gb⋅bR⋅RAIRTX⋅(ITX)2 PLOSSRX=gm⋅mR⋅RAIRRX⋅(IRX)2+gα⋅αR⋅(IRX)2+gα⋅αR⋅(IRX)2+gαDC⋅αRDC

[0090] In equation 15b, the transmitter coil loss parameter b from equation 15a was replaced by a reference transmitter coil loss value b R(sometimes referred to as the transmitter coil loss coefficient), which is associated with the transmitter loss measured when a reference transmitter is coupled to a reference receiver. This value can then be scaled with the scaling factor g b In equation 16b, the transmitter coil loss parameter m can be replaced by m R (sometimes called the transmitter coil loss coefficient), which is associated with the measured transmitter coil loss when a reference receiver and a transmitter are coupled. This value can then be scaled with the scaling factor g m In equation 16b, the parameters for the friendly metal losses α and α DC by the parameters for the friendly metal losses (coefficients) α R and α RDCobtained from measurements with reference to a reference transmitter and a reference receiver. The reference parameters for the loss of friendly metal can be calculated using the appropriate scaling factors g α and g αDC By using scaling factors when calculating P LOSSTX (see e.g. equation 15b) and P LOSSRX (see e.g. equation 16b), equation 14 can be evaluated satisfactorily, regardless of which models of transmitter and receiver are paired.

[0091] Illustrative procedures for using test transmitters and receivers to determine their scaling parameters are shown in flowchart 1200 in Fig. 12. The Fig. The operations described in Figure 12 can be performed at design time, and the resulting scaling factors can be stored in production units. Illustrative operations for using the scaling parameters in the wireless power transfer system 8 are shown in Fig. 13. The processes in Fig. 13 can be performed at runtime (e.g., when transmitter and receiver are paired in preparation for the transmission of wireless energy between transmitter and receiver). In the examples of Fig. 12 and Fig. 13, it can be assumed that the scaling factors for a particular model of transmitter (e.g., a Model I transmitter) and a particular model of receiver (e.g., a Model J receiver) were obtained from measurements on a reference device and are subsequently used when pairing a Model I transmitter with a Model J receiver. In general, this process can be assumed to be performed for numerous models of transmitters (e.g., models other than Model I) and for numerous models of receivers (e.g., models other than Model J). Furthermore, in general, any of the various models of transmitters that have been characterized can be paired by a user with any of the various models of receivers that have been characterized. This is because not all users have the same transmitter model and not all users have the same receiver model.In this example, a user pairs during the operations in . Fig. 13 a type I transmitter with a type J receiver.

[0092] The procedures for measuring the scaling factors for the magnetic energy losses of a Model I transmitter and a Model J receiver are described in Fig. 12. During the operations in block 1290, a wireless power receiver is paired (physically or via a simulated pairing such as a finite element analysis simulation pairing) with a wireless power transmitter as a reference. Physical reference devices may be obtained from a central source or constructed by various device manufacturers according to a universally distributed reference design. Once connected, the wireless power transmitter and wireless power receiver may begin transferring power. In particular, during the operations in block 1290, the wireless power transmitter may transmit wireless power signals to the wireless power receiver while internal operating parameters (e.g., currents and voltages of the transmitter and receiver) are measured and stored. From these measurements, the reference magnetic loss parameters may be extracted (e.g.,the values ​​of the magnetic reference loss parameters b. R , m R , α R and α RDC can be obtained). In scenarios where pairing simulations are used instead of measurements on physically paired devices, finite element analysis simulation can be used to determine the LQC (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.

[0093] After the parameters for the magnetic reference losses have been determined (either through physical measurements or simulations), a Model J power receiver may be paired with a wireless power transmitter with reference to the reference. While these devices are being paired in a simulation, or while these devices are being physically paired and wireless power is being transmitted from the reference wireless power transmitter to the Model J receiver, loss parameter measurements for the Model J receiver may be obtained. In particular, during the operations of block 1292, the loss parameters (coefficients) of the Model J b RJ , m RJ , α RJ and α RJDCThe "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 operates with a wireless energy transmitter under reference. The scaling factor g b (Equation 15b) for the Model J receiver can then be calculated using Equation 17 (below) and stored in all Model J wireless power receiving devices (e.g., during manufacturing or later through an update). gb=bRJ / bR

[0094] During the operations in block 1294, a Model I wireless energy transmitter may be paired with a wireless energy receiver by reference. Energy may be transmitted wirelessly while the operating parameters of the wireless energy transmitter (e.g., currents and voltages) are measured. From these measurements or simulations, the magnetic loss parameters mIR , b IR , α IR and α IRDC for the transmitter model I. Using equations 18, 19 and 20, the scaling factors g m , g α and g αDC for the Model I transmitter. gm=mIR / mR gα=αIR / αR gαDC=αIRDC / αRDC

[0095] The scaling factors for the Model I transmitter can then be saved in all Model I transmitters (e.g. during production or later through an update).

[0096] Illustrative processes for using the scaling factors for a Model I transmitter and a Model J receiver in a scenario where a Model I transmitter and a Model J receiver are paired by a user are shown in the flowchart in Fig. 13. During the events in Fig. 13, a user with a Model J receiver and a Model I transmitter who wishes to wirelessly transfer power from the Model I transmitter to the Model J couples the Model I transmitter and the Model J receiver during the operations in block 1301 (e.g., by magnetically coupling a Model I wireless power transmitter (e.g., a wireless charging puck, as just one example) with a Model J wireless power receiver (e.g., a cellular phone, as just one example). During the operations in block 1302, the Model I transmitter and the Model J receiver may exchange information such as their preprogrammed scaling factors (e.g., using low-power in-band or other wireless communication) and begin transferring power. For example, the Model J receiver may use the value of the scaling factor gm obtained from the Model J measurements with the reference transmitter in block 1292 of Fig. 12 to the Model I transmitter. The Model I transmitter can transmit the values ​​of the scaling factors g m , g α and g αDC , which are derived from the measurements of Model I with the reference receiver in block 1294 of the Fig. 12 to the Model J receiver. During the wireless power transfer from the Model I wireless power transmitter to the Model J power receiver, the measurement circuitry 41 in the wireless power transmitter and the measurement circuitry 43 in the wireless power receiver can measure the operating parameters of the transmitter and receiver (e.g., coil currents and voltages, 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 radio communication). The information measured by the circuitry 41 and 43 can be used in conjunction with the exchanged scaling factors to calculate P LOSSRX and P LOSSTX using equations 15b and 16b.

[0097] For example, during the operations of block 1304, the Model J receiver may measure the rectifier current and the rectifier voltage (their product P OUT is) and the measurements in conjunction with the scaling factors g m , g α and g αDC received from the Model I transmitter during the operations of block 1202 to evaluate equation 16b and thereby determine P LOSSRX The scaling factors received by the Model I transmitter can provide the receiver J with information about the expected operating characteristics of the Model I transmitter with respect to the losses of the receiver coil and the friendly metal.

[0098] As an example, consider the receiver coil loss. If the receiver J were paired with a wireless energy transmitter under reference, the value of the scaling factor g mbe one. The receiver J could then use the first term in equation 16b to determine the loss of the receiver coil (the loss of the receiver coil is m R · R AIRRX · (I RX ) 2 , where the values ​​of m R , R AIRRX and the receiver current I RX known to the receiver J. In the present situation, however, the receiver J is not paired with a wireless energy receiver, but with the transmitter I. The transmitter I could have been previously determined to cause lower energy losses in paired receivers than the reference transmitter, so that the value of g m , which the transmitter I passed to the receiver of the Model J during block 1302, may be (as an example) 0.9. When the Model J receiver evaluates equation 16b with the received scaling factor of 0.9 from the Model I transmitter, the Model J receiver estimates a slightly lower value of P LOSSRX(due to the presence of the Model I transmitter, which is known to cause smaller amounts of receiver coil losses than the wireless energy transmitter.) As this example shows, the magnetic loss parameters used by the receiver J to calculate P LOSSRX used, be scaled appropriately using scaling factors received from the Model I transmitter to reflect the presence of a Model I transmitter instead of a wireless energy transmitter, thereby increasing the accuracy with which the value of P LOSSRX can be estimated, is improved.

[0099] During the operations in block 1306, the Model I transmitter may make measurements of the measured transmit coil current I TX , the known values ​​of b R and R AIRTX and the scaling factor g received from the wireless energy transmitter b when evaluating equation 15b to determine P LOSSTX to be estimated. The scaling factor gb reflects how Model J receivers affect receiver coil loss in transmitters paired with Model J receivers instead of a reference wireless power receiver. For example, Model J receivers may tend to cause paired transmitters to have higher receiver coil losses than a reference-class wireless power receiver. As a result, the value of the scaling factor g b that the Model I transmitter receives from the Model J receiver should be 1.1 (for example). When evaluating Equation 15b, this increased scaling factor helps Transmitter I account for the fact that the Model I transmitter is coupled to a Model J receiver and should therefore expect larger receiver coil losses than if it were coupled to a wireless power receiver.

[0100] During the operations in block 1307, the value of P calculated in block 1304 may LOSSRXto the paired transmitter. During the operations in block 1308, the wireless power transmission system 8 (e.g., the wireless power transmitter 12 and / or the associated control circuitry 16) may determine the value of P FO using equation 14 (e.g., an estimate of the energy loss of the foreign object can be made, if any). By accurately estimating P LOSSTX using the scale factor information received from the Model J receiver and by receiving the estimated value of P LOSSRX From the Model J receiver, the Model I transmitter can receive both P LOSSTX as well as P LOSSRX for equation 14. The value of P IN The wireless energy transmitter receives the product of the current of the transmitting coil (I TX ) and the voltage of the measuring circuit 41. The value of P OUTThe wireless energy transmitter can be obtained by multiplying the product of the rectifier output current I RX and the rectifier output voltage received by the measuring logic 43 or P OUT from the wireless energy receiver.

[0101] After determining the value of P FO During the operations of block 1308, the transmitter P FO with a threshold value for energy loss (TH). The wireless energy transfer system 8 can then take appropriate measures. For example, if it is determined that P FO is less than TH, it can be concluded that no foreign object is present and the energy transfer can continue normally (e.g., so that energy can be transferred to charge the battery 58). In response to determining that P FOgreater than TH, the transfer of energy can be restricted. Examples of energy transfer restrictions that can be implemented include foregoing all energy transfer operations (e.g., disabling wireless energy transfer) and / or stopping energy transfer if it is already in progress, limiting the maximum amount of energy that can be transferred (e.g., to a predetermined, relatively low energy level below the normal maximum energy transfer capabilities of the wireless energy transfer system), and / or issuing a visual, audible, and / or vibrating alarm to a user. If desired, warnings for a user (e.g.,Warnings and / or other informational content informing the user that power transfer operations are not proceeding normally because a foreign object has been detected) may be displayed via output devices in the wireless power transmitter 12 and / or the wireless power receiver 24. For example, the control logic of the wireless power transmitter 12 may wirelessly communicate with the control logic of the wireless power receiver 24 to output a visual warning displayed on a display of the wireless power receiver 24.

[0102] The exchange of scaling parameters between different wireless power transfer devices described above can be considered "ecosystem scaling," as it expands the "ecosystem" of devices that can cooperate to provide wireless power transfer and foreign object detection. Such ecosystem scaling can be extended to the Mated-Q foreign object detection described above.

[0103] The basic process for performing ecosystem scaling for Mated-Q includes four steps 1431-1434, which are described in Fig. 14. (As used in the specification, the term "step" refers only to the respective operations performed and is not intended to lead to a "step-plus-function" interpretation of claims that refer to elements of steps 1431-1434, unless such claims expressly use the phrase "step for xyz"). In steps 1431-1433, new coefficients are extracted. In step 1 (1431): a golden (reference) wireless energy transmitter (denoted GTx) may be paired with a golden (reference) wireless energy receiver (denoted GRx), and the Mated-Q threshold (e.g., line 901, Fig. 9) can be extracted: A0,gg+A1,ggx(f,Q)+A2,ggy(f,Q)=0

[0104] The extracted threshold coefficients A 0,gg ; A 1,gg , A 2,ggcan be stored in the GTx firmware. In step 2 (1432): A new wireless energy transmitter (PTx) can be paired with GRx and the threshold value can be extracted: A0,tg+A1,tgx(f,Q)+A2,tgy(f,Q)=0

[0105] The threshold coefficients A 0,tg ; A 1,tg , A 2,tg can be stored in the PTx firmware.

[0106] In step 3 (1433): A new wireless energy receiver (PRx) can be paired with GTx and the threshold can be extracted: A0,gr+A1,grx(f,Q)+A2,gry(f,Q)=0

[0107] An additional step can be performed here to extract the “scaling” of the threshold coefficients: g0=A0,gr−A0,gg g1=A1,grA1,gg g2=A2,grA2,gg

[0108] The coefficients g0, g1, and g2 are the "scaling coefficients" and can be stored in the PRx firmware. It's worth noting that g1 and g2 are defined as the ratio between the threshold coefficients in step 3 and step 1, while the scaling of the DC term g0 is defined as a difference. The reason for this is explained below.

[0109] Step 4 (1434): Up to this point, both the new PTx and the PRx have a set of coefficients in their respective firmware. The threshold coefficients A 0,tg , A 1,tg , A 2,tg are stored in the PTx, and the scaling coefficients g0, g1, and g2 are stored in the PRx. When the PTx and PRx meet in the field, the new detection threshold can be defined as follows: (g0+A0,tg)+g1A1,tgx(f,Q)+g2A2,tgy(f,Q)=0

[0110] The technique described above eliminates the need to extract new threshold coefficients for each PTx and PRx combination. Instead, the new coefficients come from the previous coefficients extracted against a "golden" or reference pair.

[0111] As described above, the Mated-Q technique(s) can be used to detect foreign objects (FOs) in the vicinity of a wireless power transmission system (including a wireless power transmitter and a wireless power receiver). The physical quantities, for example, the resonant frequency (f), the quality factor (Q), and the coupling coefficient (K) of the coupled system (PTx coupled to PRx), can be measured using a low-power ping (LPP), for example, as described above in Fig. 7. Foreign objects can be detected in an fQ space, i.e., a space with resonant frequency on one axis and quality factor on another axis. One approach may be to use a linear threshold to separate the two classes: without FO (Rx only or Rx with casing or cover) and with FO (both with and without casing or cover). (As described here, “casing,” “cover,” and “casing / cover” refer to an object associated with the PRx device, for example, a casing or cover used in conjunction with a mobile phone.) To determine the threshold, a linear classifier can be trained on a given dataset using a linear support vector machine (SVM). Other classifiers may also be used, and the trained classifier can be compared with the method described above. Fig. 1, possibly together with suitable software running on that hardware. However, due to the non-linear alignment of the clusters formed by PRx at different locations (denoted by R and z), the linear classifier may be less than ideal in certain scenarios. Multiple linear thresholds can be used to achieve more effective separation, the so-called split-threshold approach, as described in Fig. 15 illustrates.

[0112] In particular, Fig. 15 different clusters of frequency deflections versus Q deflection measurements. Parameters other than frequency deflection and Q deflection can also be used, so the axes can correspond to different functions of f and Q, as described above with respect to Fig. 9. These changes are described in more detail below. However, in the example of Fig. 15, clusters 1505a-1505f correspond to various scenarios or configurations in which only one receiver is present. Clusters 1503a-1503c correspond to various scenarios or configurations in which a foreign object is present. Curve 1501a-1501b shows a multiple linear threshold curve as described in the previous paragraph. This generally corresponds to the curve described above with reference to Fig. 9 described arrangement.

[0113] A potential disadvantage of a multi-threshold system can be an increased number of parameters required to describe the shared thresholds. The nonlinear separation can also pose challenges for ecosystem scaling (e.g., because the thresholds may depend on the training state space). To overcome these challenges, an approach described below can be used that relies on a reduced state space (Rx only, i.e., no foreign object) while improving classification accuracy. Using this technique, the physical quantities resonance frequency f, quality factor Q, and coupling coefficient K can be mapped into a different space where the Rx-only clusters are naturally aligned with each other. The parameters for the line (representing the Rx-only cluster) can be calculated using linear regression.When a foreign object is coupled to the coupled system, the data deviates from this line and can thus be detected. A clear separation of the four categories: Rx only, Rx+case / cover, Rx+FO, Rx+FO+case / cover, can be demonstrated based on the distance from this line. Since the classifier does not need to be trained on data from foreign objects, it can work for all foreign objects (ferrous and non-ferrous), as long as separation occurs when the foreign object is placed within the detection boundary (e.g., within 23-24 mm in some applications).

[0114] To transform the physical quantities f, Q, and K into new observables that exhibit a linear dependence, we need to model the theoretical correlation between them. The paired resonant frequency is given by the condition where the system has an imaginary input impedance of zero from the Tx, Im(Z in) = 0. The input impedance results from the Tx impedance, Z Tx , and the reflected impedance of Rx, Z ref : Zin=ZTx+Zref

[0115] The Tx impedance, Z Tx , is ZTx=RTx'+jωLTx+1jωCTx where RTx'=RTx+Rdson1+Rdson2+Rdcm1b. The reflected impedance of Rx, Z ref , is Zref=−Zm2ZRx wherein Zm=RM+jωLM RM=KrRTxRRx LM=KiLTxLRx ZRx=RRx+jωLRx+1jωCtot

[0116] The combination of Eqs. (28) - (34), the imaginary input impedance, Im(Z in ), can be calculated as follows: Im(Zin)=(ω2LM2−RM2)ωCtot(1−ω2LRxCtot)−2ω3LMCtot2RMRRx(1−ω2LRxCtot)2+ω2Ctot2RRx2+ωLTx−1ωCTx

[0117] To simplify the calculation, note that ω can be in the range of ten to the sixth power, C tot in the range of ten to the power of -9, L Min the range of ten to the power of -5, R M , R Rx can be in the range of ten to the power of 0. Then the imaginary part of the input impedance can be simplified as: Im(Zin)=ω3LM2Ctot+ωLTx−1ωCTx

[0118] Under the condition that Im(Z in ) = 0, at the paired resonance frequency, ω gepaart can be solved as: ωpaired=−1+1+4Ki2LRxCtotωTx22Ki2LRxCtot where the coupling coefficient K i is defined as: Ki=LMLTxLRx

[0119] And the natural resonance frequency of Tx is defined as: ωTx=1LTxCTx

[0120] The relationship between ω gepaart and ω Tx can be determined as follows: ωpairedωTx=−1+1+2xx where x=2Ki2LRxCtot. Based on the range of values, x is the range from ten to the power of -2. Using the Taylor series expansion at x=0, it can be simplified as follows: ωpairedωTx≈1−x4

[0121] Therefore, ω gepaart slightly lower than ω Tx .

[0122] Then the connected inductance L gepaart defined as: Lpaired=1ωpaired2CTx=14π2f2CTx

[0123] Based on (39) and (42), L¡paired≈LTx

[0124] Therefore, Ki2≈LMLpairedLRx=4π2LMCTxLRxfpaired2

[0125] In addition, the quality factor of the paired system is: Qpaired=2πfpairedLpairedRpaired where R gepaart is the paired resistance. Rpaired=12πCTx⋅1fpairedQpaired

[0126] Alternatively, R gepaart by the real part of the input impedance Re(Z in) which at ω gepaart is evaluated. According to Eqs. (1-1) - (1-7), we obtain: Re(Zin)=(ω2LM2−RM2)ω2Ctot2RRx+2ω2LMCtotRM(1−ω2LRxCtot)(1−ω2LRxCtot)2+ω2Ctot2RRx2+RTx'

[0127] With similar assumptions as for Im(Z in ), at the paired frequency, it can be simplified as: Re(Zin)paired=RTx'+8π2CtotLMRMfpaired2,

[0128] Following Eqs. (44), (46) and (48), Ki2,fpaired2, and 1 / f gepaart- Q gepaart- ) show a linear dependence for the paired system.

[0129] As described above, due to the linear dependence fpaired2, 1 / (f gepaart Q gepaart ) and K 2 to transform the fQC space for foreign object detection. In practice, we use fdef2, 1 / (f def Q def ), Kdef2 as observations to reduce the influence of part-to-part variation, where: fdef=fmeas / fcal, Qdef=Qmeas / Qcal. Kdef=Kmeas / Kcal.

[0130] In Eqs. (49)-(51), "meas" represents the measured quantities at runtime (based on the actual Tx-Rx coupling), and "cal" represents the calibration of the Tx module at the factory / during manufacturing (this value can be stored in a memory of the transmitting device as described above). Using such calibration can reduce the influence of part-to-part variations caused by manufacturing tolerances, etc.

[0131] With reference to diagram 1600a in Fig. 16A, by fitting the pure Rx clusters 1605a-1605e using linear regression (line 1601), the L2 distance of various measured points in the other clusters 1603a-1603c (foreign object), 1607a-1607b (receiver and casing / cover), and 1609a-1609b (receiver, casing / cover, and foreign object) to the line in the transformed fQC space may indicate the presence of a single receiver, a receiver and casing / cover, a receiver and a foreign object, or a receiver, casing / cover, and a foreign object. (Note that in the illustrated example, cluster 1603b, corresponding to measurements related to the presence of a receiver and a foreign object, and cluster 1609a, corresponding to measurements related to the presence of a receiver, a housing / cover, and a foreign object, overlap, although this may not be the case in all cases.As shown in histogram 1600b of . Fig. 16B illustrates, the Rx Only (1605), Rx+Chassis / Cover (1607), Rx+FO (1603), and Rx+FO+Chassis / Cover (1609) categories may be separated based on the L2 distance to the regression line 1601. In the illustrated example, a threshold of 0.125 for the L2 distance may be used to effectively separate the non-foreign object cases from the foreign object cases. In the illustrated example, there is overlap between the "Chassis / Cover Absent" and "Chassis / Cover Present" measurements, although this does not affect the determination of whether a foreign object is present. Furthermore, the specific threshold provided above is only exemplary. Depending on the specific physical characteristics and configurations of a particular implementation, a different threshold may be required.This threshold (or another suitable threshold based on the specifics of a particular application) can be programmed into a classifier implemented with a suitable combination of hardware and software as described above.

[0132] Such a classifier can offer at least two advantages: (1) No training with the FO data is required. After distributing the first two categories (Rx-only 1605 and Rx+case / cover 1607), the threshold for foreign object detection can be set based on their maximum distance from the line. Anything beyond the threshold is checked against FO. Therefore, the technique can be used for any type of FO. (2) Such a classifier can be insensitive to the state space. Since the clusters in the "Rx-only" category (1605a-1605e) are aligned, the linear regression converges to a fixed value as long as the state space is large enough.

[0133] In practice, each cluster may have a certain volume in the transformed fQC space. As the FO radius (defined as the distance between the FO center and the Tx center) increases, the last two categories (Rx + FO and Rx + FO + case / cover) may eventually overlap with the first two categories (Rx only and Rx + case / cover). The maximum FO radius without an intersection can be defined as the detection limit. In an exemplary embodiment, the detection limit can be between 23 mm and 24 mm. Note that the detection limit is not the same as the critical radius. The detection limit is the FO distance at which an FO can be reliably detected. The critical radius is determined by the tolerance of the FO temperature increase and therefore increases with the delivered energy level. Therefore, it may be desirable for the detection limit to be larger than the critical radius.

[0134] The measurement of the distance between a data point and the linear regression line can be optimized to increase the range between the categories with and without a foreign object. In particular, as shown in diagram 1700a in 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 shortest distance to the line, can be selected for the measurement. These distances are exemplary, and other distances can also be used. As shown in histogram 1700b of Fig. 17B, ​​the L2 distance can provide a small margin between the cases with and without a foreign object (for the example system shown). Conversely, the L1 distance can provide better margins, as shown in histogram plot 1700c of Fig. 17C corresponding to the L1 distance and histogram plot 1700d of Fig. 17D is shown.

[0135] The newly mapped state space (e.g. the f2, 1 / (fQ), K state space described above) can also be mapped to the state space described above with reference to Fig. 12-14. Such use of ecosystem scaling is described below with reference to Fig. 18A-18C. For any Tx-Rx pair, whether golden or generic, the Rx-only clusters 1805a-1805f will always be aligned in the transformed fQC space 1800a. For simplicity, the transformed observables can be renamed x, y, and z. The linear equation for the alignment of the Rx-only clusters 1805a-1805f can then be written as follows: x=k1z+b1 y=k2z+b2

[0136] Similar to the ecosystem scaling described above, scaling coefficients for a generic Tx and Rx can be calculated with reference to a golden (reference) Tx and Rx, with these scaling coefficients being applied to the parameters defining the fitting line 1601a.

[0137] As in Fig. 18A-18C, an exemplary scaled fitting line 1801b is very similar to the calculated line given by the linear regression of the data set (1801a). Therefore, as can be seen from the comparison of Fig. 18B-18C, the histogram 1800c with respect to the scaled fitting line 1801b ( Fig. 18A) close to the histogram 1800b, which corresponds to the actual line 1801a ( Fig. 18A). The accuracy of the scaled fit line means that reasonable accuracy in foreign object detection can be expected when applying the ecosystem scaling principles described below. In many cases, the threshold does not need to be changed at all.

[0138] In at least some applications, the Mated-Q measurements described here can provide information not only about the presence of a foreign object, but also about the location of the foreign object. This information could be used to estimate the potential losses of foreign objects at given P rect and V rect values. Furthermore, as described above, the position of the foreign object can influence the distance between the measured data points and the linear regression fit line.

[0139] As shown in diagram 1900 of Fig. As illustrated in Figure 19, the L2 distance (vertical axis) between the data point and the linear regression line decreases with the FO radius, i.e., the distance to the foreign object. This is true for each group of measurements, i.e., receiver-only measurements, shown in curve 1905, receiver plus enclosure / cover measurements, shown in curve 1907, receiver and foreign object measurements, shown in curve 1903, and receiver plus enclosure / cover plus foreign object measurements, shown in curve 1909. The error bars represent the standard deviation of each category. Since the FO radius is directly related to the FO loss, the distance can be used to adjust the transmitter power level accordingly. The table below provides example estimates of the FO radius at which the power dissipated in the foreign object reaches 800 mW, which range from 20 mm to 30 mm.The first column of the table lists example energy levels (for each row). The second column lists the estimated FO radius when Tx and Rx are coupled with a radial offset of zero and a z-axis / vertical offset of 2 mm, and the third column lists the estimated FO radius when Tx and Rx are coupled with a radial offset of 2 mm and a z-axis / vertical offset of 2.2 mm. P rect FO-Radius (800 mW) Rx-Position: R = 0, z = 2 FO-Radius (800 mW) Rx-Position: R = 2, z = 2,2 5 W - (innerhalb von etwa 20 mm) - (innerhalb von etwa 20 mm) 15 W Etwa 20,4 mm Etwa 21,5 mm 25 W Etwa 22,1 mm Etwa 23,6 mm 50 W Etwa 24,6 mm Etwa 25,8 mm

[0140] By combining the relationship between L2 distance and RFO and the relationship between FO loss and RFO, an acceptable energy level can be estimated as a function of L2 distance. Therefore, instead of completely shutting off energy transmission when a foreign object is detected, a multi-stage energy adjustment strategy can be used. An example of such a multi-stage energy level adjustment is shown in Fig. Figure 20 illustrates: (1) If the L2 spacing is within 0.12, full power (e.g., a power level of 50 W) can be delivered; (2) If the L2 spacing is between 0.12 and 0.22, the power should be set to a first intermediate power level (e.g., 25 W); (3) If the spacing is between 0.22 and 0.35, the power should be set to a second intermediate power level (e.g., 15 W); (4) If the L2 spacing is greater than 0.35, the power should be set to a low power level (e.g., 5 W). These power levels are exemplary and may be useful in various embodiments, but the respective L2 spacings and power levels may be suitable for a particular application.

[0141] As already mentioned, Fig. 20 shows the various energy levels in the form of concentric cylinders centered on the fit line through the Rx-only data points 2005. Received data points plus the housing / cover 2007 are also shown. The inner cylinder 2010 corresponds to the highest energy level described above (e.g., 50 W). The next cylinder 2011 corresponds to the first intermediate energy level (e.g., 25 W). The next cylinder 2012 corresponds to the second intermediate energy level (e.g., 15 W). The outer cylinder 2013 corresponds to the low energy level (e.g., 5 W). If the measured operating point has an L2 distance from the linear regression fit line 2001 that exceeds the example thresholds described above, the transmit power can be limited to the specified values ​​(and corresponding to the concentric cylinders).

[0142] In other embodiments, whether used separately or in combination with features of the embodiments described above, the Mated-Q measurement spaces (including, without limitation, the magnetic parameters described above) may also be used to detect the presence of a housing, cover, or similar device enclosing or protecting the wireless energy receiver, thus providing some z-axis separation between the wireless energy transmitter (PTx) and the wireless energy receiver (PRx). In this context, the z-axis refers to a direction perpendicular to the plane of the respective coils. In this case, the measurements and determinations of the various circuit parameters may be performed using any suitable technique, including the techniques described above.The resulting data point groups can be plotted in a state space based on the measured parameters as described above.

[0143] Fig. Figure 21 illustrates an example state-space diagram 2100. The illustrated state space is based on the changes in the quality factor (Q) and the resonant frequency (f), plotted on the vertical and horizontal axes, respectively. However, any other suitable state space with other parameter combinations, such as the linearized parameters described above, may be used. Fig. Figure 21 also illustrates data points 2105a-2105f, which correspond only to the Mated-Q measurements of a receiving device. As previously mentioned, these Mated-Q measurements may include any combination of the above-mentioned parameters, which may be directly measured and / or calculated by the processing system based on measured parameters. Each of the clusters 2105a-2105f corresponds to a different distance between the receiver and the transmitter, in the illustrated example, 0 mm, 1 mm, 2 mm, 2.2 mm, 3 mm, and 3.2 mm, respectively. Fig. 21 also illustrates data points 2107a-2107d, which correspond to a receiver having a housing or other cover or device disposed between the wireless energy transmitter (PTx) and the wireless energy receiver (PRx).

[0144] Similar to the techniques described above, the system can calculate a threshold that allows the system to detect a z-axial / vertical separation between the wireless energy transmitter and the wireless energy receiver, such as a separation caused by the presence of a housing, cover, or other similar object. However, such a separation does not have to be caused by the presence of an additional object. In any case, the detection of such a z-axis / vertical separation can be used by the PTx device to reduce energy to mitigate electromagnetic interference with other devices. The process can be broadly similar to that described above in Fig. 10, but instead of detecting a foreign object, the presence of a housing or cover and / or the z-axial / vertical separation between PTx and PRx is detected.

[0145] To achieve such detection, the threshold may be defined by a curve 2101. The curve 2101 may be a linear function of the form: β0+β1f+Aβ2Q=0 where f and Q are the system resonant frequency and the Q value, respectively, and β0, β1, and β2 are coefficients that can be extracted using suitable statistical methods. For example, in at least some embodiments, logistic regression may be used. In a more general sense, the resonant frequency f and the quality factor Q can be replaced by corresponding functions of f and Q. Equation 54 thus becomes: β0+β1x(f,Q)+β2y(f,Q) where x(f,Q) is a first function of the resonant frequency and the quality factor, and y(f,Q) is a second function of the resonant frequency and the quality factor. For example, x(f,Q) could be the resonant frequency f and y(f,Q) could be the quality factor Q, which would yield Equation 54 provided above. Alternatively, in an exemplary embodiment, x(f,Q) could be f 2 (resonance frequency squared) and y(f,Q) to 1(f⋅Q) (the inverse of resonant frequency times quality factor). Consequently, the determination of whether or not a housing or z-axis / vertical separation exists can be made by detecting a change in the position of the first-function-based and second-function-based measurements in a suitable state space.

[0146] It can be observed that the slope of the threshold line 2101 is negative compared to the slope of the foreign object detection line from the above examples. Therefore, if both foreign object detection and z-axis / vertical separation / case detection are performed, separate thresholds can be used for each detection, even though both detections (and the associated regression or other statistical analyses) may be based on the same measurements / data points. In the example described with reference to Fig. 1, it is determined 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 the Fig. 9-10. In other respects, the measurements, analyses, decisions, etc., performed by the processing systems of the respective devices may be largely similar.

[0147] Additional points: 1. Wireless energy transmitter, comprising: wireless power transmission circuitry comprising a wireless power transmission coil that transmits wireless power signals; and Control circuitry coupled to the wireless power transfer circuitry that: measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy 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 energy transmission coil and the corresponding baseline values; determines whether a foreign object is present when the change between the measured current values ​​of the first and second functions of the quality factor and the resonance frequency and the corresponding baseline values ​​in a magnetic state space exceeds a threshold. 2. A wireless energy transmitter according to item 1, wherein the control logic blocks the wireless energy transmission in response to the detection of the foreign object. 3. A wireless energy transmitter according to item 1, wherein the control circuitry transmits energy at a level below a maximum energy level in response to detection of the foreign object. 4. Wireless energy transmitter according to item 1, wherein the control circuitry measures a current quality factor and the resonant frequency of the wireless energy transmission coil by: Causing an inverter to provide one or more signal pulses to the wireless power transmission coil; Using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and Determine the current quality factor and resonance frequency from the frequency of the ringing signal. 5. Wireless energy transmitter according to item 1, wherein the control logic: characterizes a foreign object as a moderate foreign object or a strong foreign object based on the change between the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transfer coil and the corresponding baseline values; and blocks wireless energy transmission if it is determined that the foreign object is a strong foreign object; or enables wireless energy transmission at a relatively low energy level when the foreign object is determined to be a moderate foreign object. 6. Wireless energy transmitter according to item 1, wherein the corresponding baseline values ​​are measured during manufacture of the wireless energy transmitter. 7. Wireless energy transmitter according to item 1, with the corresponding baseline values ​​updated during operation of the wireless energy transmitter in the field. 8. The wireless energy transmitter of item 1, wherein the control circuitry determines the change between the measured current values ​​of the first and second quality factor functions and the resonant frequency of the wireless energy transmission coil using scaling factors based on a particular transmitter-receiver pairing. 9. A method for operating a wireless energy transmitter having wireless energy transmission circuitry comprising a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission circuitry, the method being performed by the control circuitry and comprising: Measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; Comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmission coil with the corresponding baseline values; and Detecting a foreign object based at least in part on comparing the measured current values ​​of the first and second functions of quality factor and resonance frequency with the corresponding baseline values. 10. Procedure according to point 9, whereby: the comparison of the measured current values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmission coil with the corresponding baseline values ​​includes the analysis of a change between the measured current values ​​and the corresponding baseline values ​​in a magnetic state space; and detecting the foreign object based at least in part on comparing the measured current values ​​of the first and second functions of the quality factor and the resonant frequency with the corresponding baseline values ​​comprises determining whether the change between the measured current values ​​and the corresponding baseline values ​​in the magnetic state space exceeds a threshold. 11. The method of item 9, further comprising measuring the current quality factor and the resonant frequency of the wireless energy transfer coil by: Causing an inverter to provide one or more signal pulses to the wireless power transmission coil; Using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and Determine the current quality factor from the frequency of the ring signal. 12. The method of item 9, further comprising blocking the wireless power transmission in response to the detection of the foreign object. 13. The method of item 9, further comprising transmitting energy at a level below a maximum energy level in response to detection of the foreign object. 14. Procedure according to point 9, further comprising: Characterizing a foreign object as a moderate foreign object or a strong foreign object based on a change between the measured current values ​​and the corresponding baseline values ​​in a magnetic state space; and Blocking the wireless power transmission in response to determining that the foreign object is a strong foreign object; or Enabling wireless power transmission at a relatively low power level in response to determining that the foreign object is a moderate foreign object. 15. The method of item 9, wherein the corresponding baseline values ​​are measured during manufacture of the wireless energy transmitter. 16. Procedure according to item 9, whereby the corresponding baseline values ​​are updated during operation of the wireless energy transmitter in the field. 17. The method of item 9, further comprising scaling the respective baseline values ​​using scaling factors based on a particular transmitter-receiver pairing. 18. Wireless energy transmitter, comprising: wireless power transmission circuitry comprising a wireless power transmission coil that transmits wireless power signals; and control circuitry coupled to the wireless power transfer circuitry, including: Means for measuring the current values ​​of two or more observables related to the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; and Means for detecting a foreign object based on the measured current values ​​of two or more observables related to the quality factor and the resonant frequency of the wireless power transmission coil, which are measured while the wireless power transmitter is coupled to a wireless power receiver. 19. A wireless energy transmitter according to item 18, wherein the control circuitry further comprises: Means for characterizing a foreign object as a moderate foreign object or a strong foreign object based on the measured current values ​​of two or more observables related to the quality factor and the resonant frequency of the wireless energy transmission coil measured while the wireless energy transmitter is coupled to a wireless energy receiver; wherein the control circuitry: blocks wireless energy transmission if it is determined that the foreign object is a strong foreign object; or enables wireless energy transmission at a relatively low energy level when the foreign object is determined to be a moderate foreign object.

[0148] Further additional points: 1. Wireless energy transmitter, comprising: wireless energy transfer circuitry comprising a wireless energy transfer coil that transmits wireless energy signals; and control circuitry coupled to the wireless energy transfer circuitry is the: measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; determines a change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmitting coil; determining a z-axis separation distance between the wireless energy transmitter and the wireless energy receiver that is responsive to the change between the measured current values ​​and the corresponding baseline values ​​of the first and second functions of the quality factor and the resonant frequency exceeding a threshold in a magnetic state space. 2. A wireless energy transmitter according to item 1, wherein the z-axis separation distance includes the presence of a housing or cover on the wireless energy receiver. 3. Wireless energy transmitter according to point 1, wherein: the first function of the quality factor and the resonance frequency is the quality factor; the second function of quality factor and resonance frequency is the resonance frequency; and the threshold comprises several linear thresholds. 4. Wireless energy transmitter, comprising: wireless power transmission circuitry comprising a wireless power transmission coil that transmits wireless power signals; and Control circuitry coupled to the wireless power transfer circuitry that: measures a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil, a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil, and a third function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is connected to a wireless energy receiver; 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 energy transfer coil and a curve fit to corresponding baseline values ​​in a magnetic state space; determining a z-axis separation distance between the wireless energy transmitter and the wireless energy receiver responsive to the distance between the measured current values ​​of the first, second, and third functions of the quality factor and the resonant frequency and the curve fit to the corresponding baseline values ​​in the magnetic state space exceeding a threshold. 5. A wireless energy transmitter according to item 4, wherein the z-axis separation distance includes the presence of a housing or cover on the wireless energy receiver. 6. A wireless energy transmitter according to item 4, wherein the first, second and third functions of the quality factor and the resonant frequency are selected to provide a linear curve fit in the magnetic state space. 7. A wireless energy transmitter according to item 6, wherein the first function of the quality factor and the resonant frequency is the coupling coefficient squared, the second function of the quality factor and the resonant frequency is the resonant frequency squared, and the third function of the quality factor and the resonant frequency is the inverse of the resonant frequency times the quality factor. 8. Wireless energy transmitter according to point 4, where the distance is a Pythagorean distance. 9. Wireless energy transmitter according to item 4, where the distance is an L1 distance. 10. Wireless energy transmitter according to item 4, where the distance is an L2 distance. 11. A wireless energy transmitter according to item 4, wherein the control circuitry transmits energy at a level below a maximum energy level when the Z-axis separation distance exceeds the threshold or when an enclosure is present. 12. The wireless energy transmitter of item 4, wherein the control circuitry measures a current quality factor and the resonant frequency of the wireless energy transmission coil by: causing an inverter to provide one or more signal pulses to the wireless energy transmission coil; using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and determining the current quality factor and the resonant frequency from the frequency of the ringing signal. 13. Wireless energy transmitter according to item 4, with the corresponding baseline values ​​measured during manufacture of the wireless energy transmitter. 14. Wireless energy transmitter according to item 4, with the corresponding baseline values ​​updated during operation of the wireless energy transmitter in the field. 15. The wireless energy transmitter of item 4, wherein the control logic determines the distance between the measured current values ​​of the first, second, and third quality factor functions and the resonant frequency of the wireless energy transmission coil using scaling factors based on a particular transmitter-receiver pairing. 16. A method for operating a wireless energy transmitter having wireless energy transmission circuitry comprising a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission circuitry, the method being performed by the control circuitry and comprising: Measuring a current value of a first function of the quality factor and the 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 while the wireless power transmitter is coupled to a wireless power receiver; 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 to the corresponding baseline values; and determining a z-axis separation distance between the wireless power transmitter and the wireless power receiver 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 to the corresponding baseline values. 17. The method of item 16, wherein the z-axis separation distance includes the presence of a housing or cover on the wireless energy receiver. 18. Procedure according to point 16, whereby: the first function of the quality factor and the resonance frequency is the quality factor; and the second function of the quality factor and the resonance frequency is the resonance frequency. 19. A method for operating a wireless energy transmitter having wireless energy transmission circuitry comprising a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission circuitry, the method being performed by the control circuitry and comprising: Measuring a current value of a first function of the quality factor and the resonant frequency of the wireless power transmission coil, a current value of a second function of the quality factor and the resonant frequency of the wireless power transmission coil, and a current value of a third function of the quality factor and the resonant frequency of the wireless power transmission coil while the wireless power transmitter is coupled to a wireless power receiver; Comparing the measured current values ​​of the first, second, and third functions of the quality factor and the resonant frequency of the wireless power transmission coil to 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 transmission coil and a curve fit to corresponding baseline values ​​in a magnetic state space;and; Determining a z-axis separation distance between the wireless energy transmitter and the wireless energy receiver based at least in part on the distance between the measured current values ​​of the first, second, and third functions of the quality factor and the resonant frequency and the curve fit to the corresponding baseline values ​​in the magnetic state space that exceed a threshold. 20. The method of item 19, wherein the z-axis separation distance includes the presence of a housing or cover on the wireless energy receiver. 21. The method of item 19, wherein the first, second and third functions of the quality factor and the resonant frequency are chosen to provide a linear curve fit in the magnetic state space. 22. The method of item 21, wherein the first function of the quality factor and the resonant frequency is the coupling coefficient squared, the second function of the quality factor and the resonant frequency is the resonant frequency squared, and the third function of the quality factor and the resonant frequency is the inverse of the resonant frequency times the quality factor. 23. Method according to item 19, where the distance is a Pythagorean distance. 24. Method according to item 19, wherein the distance is an L1 distance. 25. The method of item 19, wherein the distance is an L2 distance. 26. The method of item 19, further comprising measuring the current quality factor and the resonant frequency of the wireless energy transmission coil by: Causing an inverter to supply the wireless energy transmission coil with or provide multiple signal pulses; Using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and Determine the current quality factor from the frequency of the ring signal. 27. The method of item 19, further comprising transmitting energy at a level below a maximum energy level in response to detecting that the z-axis separation distance exceeds the threshold or the presence of a housing. 28. The method of item 19, wherein the corresponding baseline values ​​are measured during manufacture of the wireless energy transmitter. 29. The procedure according to item 19, whereby the corresponding baseline values ​​are updated during operation of the wireless energy transmitter in the field. 30. The method of item 19, further comprising scaling the respective baseline values ​​using scaling factors based on a particular transmitter-receiver pairing.

[0149] The features and embodiments described above relate to the use of the Q-factor and associated magnetic property measurements for object detection in wireless power transmission systems. Such arrangements can be used in a variety of applications, but are particularly advantageous when used in conjunction with electronic devices such as mobile phones, tablet computers, laptops or notebooks, and accessories such as wireless headphones, pens, etc. While numerous specific features and various embodiments have been described, it is to be understood that the various features and embodiments may be used in various combinations in a particular implementation, provided they are not mutually exclusive.Therefore, the various embodiments described above are provided for illustrative purposes only and should not be construed as limiting the scope of the disclosure. Various modifications and changes may be made to the principles and embodiments contained herein without departing from the scope of the disclosure and without departing from the scope of the claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 581,318

[0001] US 63 / 605,047

[0001] US 18 / 612,886

[0001] US 18 / 612,892

[0001] US 18 / 612,904

[0001] US 18 / 327,721

[0068] US 17 / 681,363

[0078] Cited non-patent literature

[0000] Wireless Power Systems with Foreign Object Detection”, which was released on June 1, 2023

[0068] Wireless Power Systems with Shared Inducive Loss Scaling Factors”, published on February 25, 2022

[0078]

Claims

[1] Wireless energy transmitter comprising: wireless power transmission circuitry comprising a wireless power transmission coil that transmits wireless power signals; and Control circuitry coupled to the wireless power transfer circuitry that: measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; determines a change between the measured current values and the corresponding baseline values of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmitting coil; determines whether a foreign object is present if the change between the measured current values and the corresponding baseline values of the first and second functions of the quality factor and the resonance frequency exceeds a threshold value in a magnetic state space. [2] A wireless energy transmitter according to claim 1, wherein: the first function of the quality factor and the resonance frequency is the quality factor; the second function of the quality factor and the resonance frequency is the resonance frequency; and the threshold comprises several linear thresholds. [3] Wireless energy transmitter comprising: wireless energy transfer circuitry with a wireless energy transfer coil, which transmits wireless power signals; and control circuitry coupled to the wireless power transmission circuitry which: a current value of a first function of the quality factor, the resonance frequency and the coupling coefficient of the wireless energy transmission coil, a current value of a second function of the quality factor, the resonance frequency and the coupling coefficient of the wireless energy transmission coil and a current value of a third function of the quality factor, the resonant frequency and the coupling coefficient of the wireless energy transmission coil, while the wireless energy transmitter is coupled to a wireless energy receiver; a distance between the measured current values of the first, second and third functions of the quality factor, the resonance frequency and the coupling coefficient of the wireless energy transmitting coil and a curve fit to corresponding baseline values; determines whether a foreign object is present depending on a distance between the measured current values of the first, second and third functions of the quality factor, the resonance frequency and the coupling coefficient and the curve fitting to the corresponding baseline values in a magnetic state space exceeding a threshold or falling between several thresholds. [4] A wireless energy transmitter according to claim 3, wherein the first, second and third functions of the quality factor, the resonant frequency and the coupling coefficient are selected to provide a linear curve fit in the magnetic state space. [5] The wireless energy transmitter of claim 4, wherein the first function of the quality factor, the resonant frequency, and the coupling coefficient is the coupling coefficient squared, the second function of the quality factor, the resonant frequency, and the coupling coefficient is the resonant frequency squared, and the third function of the quality factor, the resonant frequency, and the coupling coefficient is the inverse of the resonant frequency times the quality factor. [6] The wireless power transmitter of claim 3, wherein the distance is an L1 distance. [7] The wireless energy transmitter of claim 3, wherein the distance is an L2 distance. [8] The wireless power transmitter of claim 3, wherein the control logic disables wireless power transmission in response to detection of the foreign object. [9] The wireless energy transmitter of claim 3, wherein the control circuitry transmits energy at a level below a maximum energy level in response to detecting the foreign object. [10] The wireless energy transmitter of claim 3, wherein the control logic measures a current quality factor and the resonant frequency of the wireless energy transmission coil by: Causing an inverter to provide one or more signal pulses to the wireless power transmission coil; Using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and Determine the current quality factor and resonance frequency from the frequency of the ringing signal. [11] A wireless energy transmitter according to claim 3, wherein the control circuitry: characterizes a foreign object as a moderate foreign object or a strong foreign object based on the distance between the measured current values of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transfer coil and the curve fit to the corresponding baseline values; and blocks wireless energy transmission if it is determined that the foreign object is a strong foreign object; or enables wireless energy transmission at a relatively low energy level when the foreign object is determined to be a moderate foreign object. [12] The wireless energy transmitter of claim 3, wherein the respective baseline values are measured during manufacture of the wireless energy transmitter. [13] The wireless energy transmitter of claim 3, wherein the respective baseline values are updated during operation of the wireless energy transmitter in the field. [14] The wireless power transmitter of claim 3, wherein the control logic determines the distance between the measured current values of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless power transmission coil using scaling factors based on a particular transmitter-receiver pairing. [15] A method for operating a wireless energy transmitter having wireless energy transmission circuitry comprising a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission circuitry, the method being performed by the control circuitry and comprising: Measuring a current value of a first function of the quality factor and the resonant frequency of the wireless energy transmission coil and a current value of a second function of the quality factor and the resonant frequency of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; Comparing the measured current values of the first and second functions of the quality factor and the resonant frequency of the wireless energy transmission coil with the corresponding baseline values; and Detecting a foreign object based at least in part on comparing the measured current values of the first and second functions of the quality factor and the resonant frequency with the corresponding baseline values. [16] The method of claim 15, wherein: the first function of the quality factor and the resonance frequency is the quality factor; the second function of the quality factor and the resonance frequency is the resonance frequency; and comparing the measured current values of the first and second functions of the quality factor and the resonance frequency with the corresponding baseline values comprises determining whether a difference between the measured current values and the corresponding baseline values exceeds a threshold comprising a plurality of linear thresholds. [17] A method of operating a wireless energy transmitter having wireless energy transmission circuitry comprising a wireless energy transmission coil configured to transmit wireless energy signals and control circuitry coupled to the wireless energy transmission circuitry, the method being performed by the control circuitry and comprising: Measuring a current value of a first function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil, a current value of a second function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil, and a current value of a third function of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil while the wireless energy transmitter is coupled to a wireless energy receiver; Comparing the measured current values of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil with corresponding baseline values by determining a distance between the measured current values of the first, second, and third functions of the quality factor, the resonant frequency, and the coupling coefficient of the wireless energy transmission coil and a curve fit to corresponding baseline values in a magnetic state space; and Detecting a foreign object based at least in part on a distance between the measured current values of the first, second and third functions of the quality factor, the resonant frequency and the coupling coefficient and the curve fit to the corresponding baseline values in the magnetic state space that exceeds a threshold. [18] The method of claim 17, wherein the first, second and third functions of the quality factor, the resonant frequency and the coupling coefficient are chosen to provide a linear curve fit in the magnetic state space. [19] The method of claim 18, wherein the first function of the quality factor, the resonant frequency and the coupling coefficient is the coupling coefficient squared, the second function of the quality factor, the resonant frequency and the coupling coefficient is the resonant frequency squared, and the third function of the quality factor, the resonant frequency and the coupling coefficient is the inverse of the resonant frequency times the quality factor. [20] The method of claim 17, wherein the distance is an L1 distance. [21] The method of claim 17, wherein the distance is an L2 distance. [22] The method of claim 17, further comprising measuring the current quality factor and the resonant frequency of the wireless energy transfer coil by: Causing an inverter to provide one or more signal pulses to the wireless power transmission coil; Using measurement circuitry to measure responses to the provided one or more signal pulses, the responses including a ringing signal having a decay envelope characterized by a frequency of the ringing signal and the present quality factor; and Determine the current quality factor from the frequency of the ring signal. [23] The method of claim 17, further comprising disabling wireless power transmission in response to detection of the foreign object. [24] The method of claim 17, further comprising transmitting energy at a level below a maximum energy level in response to detection of the foreign object. [25] The method of claim 17, further comprising: Characterizing a foreign object as a moderate foreign object or a strong foreign object based on the distance between the measured current values and the curve fit to the corresponding baseline values in the magnetic state space; and Blocking the wireless power transmission in response to determining that the foreign object is a strong foreign object; or Enabling wireless power transmission at a relatively low power level in response to determining that the foreign object is a moderate foreign object. [26] The method of claim 17, wherein the respective baseline values are measured during manufacture of the wireless energy transmitter. [27] The method of claim 17, wherein the respective baseline values are updated during operation of the wireless energy transmitter in the field. [28] The method of claim 17, further comprising scaling the respective baseline values using scaling factors based on a particular transmitter-receiver pairing.

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