Wireless power system with foreign object detection

Abstract

A wireless power system has a wireless power transmission device and a wireless power receiving device. The wireless power transmission device emits a wireless power signal to the wireless power receiving device using a wireless power transmission coil. The wireless power transmission device determines whether an external object is present. The external object can be a foreign object such as a coin or a paperclip, or can be the wireless power receiving device. A quality factor measurement is used to detect the external object. Wireless communication is used to distinguish between the foreign object and the wireless power receiving device. For aging effects and temperature effects, a temperature measurement and a frequency-based and measured resistance-based compensation of the quality factor measurement can be used.

Description

[0001] This patent application claims priority to U.S. Patent Application No. 17 / 109793, filed December 2, 2020; U.S. Provisional Patent Application No. 62 / 943043, filed December 3, 2019; and U.S. Provisional Patent Application No. 63 / 012813, filed April 20, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates in general to power systems, and more specifically to wireless power systems for charging electronic devices. Background Technology

[0003] In a wireless charging system, a wireless power transmission device, such as a charging pad, wirelessly transmits power to a wireless power receiving device, such as a portable electronic device. The wireless power transmission device uses a wireless power transmission coil to transmit a wireless power signal to the wireless power receiving device. The wireless power receiving device has a coil and a rectifier circuit. The coil of the wireless power receiving device receives the AC wireless power signal from the wireless power transmission device. The rectifier circuit converts the received signal into DC power. Summary of the Invention

[0004] The goal is to obtain the amount of power received or not received by the wireless power receiving device from the wireless power transmitting device.

[0005] In some implementations, the wireless power transmission device determines whether an external object is present in the vicinity of the wireless power transmission coil. The external object can be a foreign object such as a button or paperclip, or it can be a wireless power receiving device. If an external object is detected, appropriate actions can be taken, such as relinquishing wireless power transmission.

[0006] In some implementations, quality factor measurements can be used to detect external objects. The current quality factor measurement is compared to a baseline quality number measurement to determine the presence of an external object. Wireless communication can be used to distinguish between external objects and wireless power receiving devices.

[0007] Quality factor measurements can be performed by: applying a pulse to the wireless power transmission coil and measuring the attenuation envelope associated with the pulse response in the coil; or by directly measuring the impedance of the wireless power transmission coil and determining the current quality factor from the measured impedance. For aging and temperature effects, quality factor measurements can be compensated for using temperature measurements and frequency- and coil resistance-based measurements. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of an exemplary wireless power system according to the implementation plan.

[0009] Figure 2 This is a circuit diagram of an exemplary wireless power system according to the implementation plan.

[0010] Figure 3 A graph is shown to illustrate the ability to analyze the pulse response of a wireless power transmission coil to measure the coil's quality factor according to the embodiment.

[0011] Figure 4 The circuit diagram of an exemplary wireless power transmitter according to the implementation scheme shows a circuit that can be used to perform quality factor measurement.

[0012] Figure 5 Formulas for determining parameters such as coil quality factor based on impedance measurements are shown according to the implementation scheme.

[0013] Figure 6 To illustrate a formula, according to the implementation scheme, that can be applied to current quality factor measurements to determine the compensated quality factor value.

[0014] Figure 7 and Figure 8 A diagram illustrating exemplary operations involved in using a wireless power system according to an implementation scheme.

[0015] Figure 9 A graph illustrating the pulse response of the wireless power transmission circuit according to the embodiment is provided.

[0016] Figure 10 This is a graph plotted according to the implementation scheme, where the change in quality factor is used as a function of coil resistance. Detailed Implementation

[0017] Wireless power systems include wireless power transmission devices, such as wireless charging pads. The wireless power transmission device wirelessly transmits power to a wireless power receiving device. The wireless power receiving device can be a device such as a wristwatch, cellular phone, tablet, laptop, or other electronic equipment. The wireless power receiving device uses the power from the wireless power transmission device to power the device and charge its internal battery.

[0018] One or more wireless power transmission coils are used to transmit wireless power from a wireless power transmission device to a wireless power receiving device. The wireless power receiving device has one or more wireless power receiving coils coupled to a rectifier circuit that converts the received wireless power signal into DC power.

[0019] If a foreign object, such as a paperclip, coin, or other metal object, is present near the wireless power transmission coil of a wireless power transmission device, there is a risk of eddy currents being generated in the foreign object, which can raise its temperature. To determine the presence of a foreign object, such as a paperclip or coin, the wireless power transmission device measures the quality factor of the wireless power transmission coil and determines whether the quality factor has been affected by the presence of the foreign object. By detecting the presence of a foreign object, appropriate actions can be taken (e.g., the wireless power transmission device can abort wireless power transmission whenever a foreign object is detected).

[0020] Figure 1 An exemplary wireless power system (wireless charging system) is shown. For example... Figure 1 As shown, the wireless power system 8 includes wireless power transmission devices (such as wireless power transmission device 12) and wireless power receiving devices (such as wireless power receiving device 24). Wireless power transmission device 12 includes control circuitry 16. Wireless power receiving device 24 includes control circuitry 30. The control circuitry in system 8, such as control circuitry 16 and control circuitry 30, is used to control the operation of system 8. This control circuitry may include processing circuitry associated with a microprocessor, power management unit, baseband processor, digital signal processor, microcontroller, and / or application-specific integrated circuit (ASIC) having processing circuitry. The processing circuitry implements desired control and communication characteristics in devices 12 and 24. For example, the processing circuitry may be used to select coils, determine power transmission levels, process sensor data and other data to detect intrusive objects and perform other tasks, process user input, handle negotiations between devices 12 and 24, transmit and receive in-band and out-of-band data, perform measurements, and otherwise control the operation of system 8.

[0021] The control circuitry in system 8 can be configured to perform operations within system 8 using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. Software code used to perform operations within system 8 is stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium) in the control circuitry 8. This software code may sometimes be referred to as software, data, program instructions, commands, or code. The non-transitory computer-readable storage medium may include non-volatile memory such as non-volatile random access memory (NVRAM), one or more hard disk drives (e.g., disk drives or solid-state drives), one or more removable flash drives, or other removable media. The software stored on the non-transitory computer-readable storage medium can be executed on the processing circuitry of control circuitry 16 and / or 30. The processing circuitry may include an application-specific integrated circuit (ASIC) with processing circuitry, one or more microprocessors, a central processing unit (CPU), or other processing circuitry.

[0022] The power delivery device 12 can be a standalone power adapter (e.g., a wireless charging pad or puck including power adapter circuitry), a wireless charging pad or puck coupled to a power adapter or other equipment via a cable, a portable device, equipment already integrated into furniture, vehicles, or other systems, a removable battery case, or other wireless power delivery equipment. The wireless power delivery device 12 is an exemplary configuration of a wireless charging pad, sometimes described herein as an example.

[0023] The power receiving device 24 may be a portable electronic device, such as a wristwatch, cell phone, laptop computer, tablet computer, accessories such as earphones, or other electronic equipment. The power transmitting device 12 may be coupled to a wall socket (e.g., an AC power source), may have a battery for supplying power, and / or may have another power source. The power transmitting device 12 may have an AC-DC power converter, such as an AC-DC power converter 14, for converting AC power from the wall socket or other power source into DC power. The DC power can be used to power the control circuitry 16. During operation, the controller in the control circuitry 16 uses the power transmitting circuitry 52 to transmit wireless power to the power receiving circuitry 54 of the device 24. The power transmitting circuitry 52 may have a switching circuit (e.g., an inverter circuitry 61 formed of transistors) that is turned on or off based on a control signal provided by the control circuitry 16 to form an AC current signal through one or more wireless power transmitting coils, such as wireless power transmitting coil 36. These coil drive signals cause coil 36 to transmit wireless power. Multiple coils 36 may be arranged as a planar coil array (e.g., in a configuration where device 12 is a wireless charging pad) or may be arranged to form a coil cluster (e.g., in a configuration where device 12 is a wireless charging stand). In some arrangements, device 12 (e.g., charging pad, charging stand, etc.) may have only a single coil. In other arrangements, the wireless charging device may have multiple coils (e.g., two or more coils, 5-10 coils, at least 10 coils, 10-30 coils, fewer than 35 coils, fewer than 25 coils, or other suitable number of coils).

[0024] When an AC current passes through one or more coils 36, an alternating electromagnetic (e.g., magnetic) field (wireless power signal 44) is generated. This alternating electromagnetic field is received by one or more corresponding receiver coils, such as one or more coils 48 in a power receiving device 24. Device 24 may have a single coil 48, at least two coils 48, at least three coils 48, at least four coils 48, or other suitable number of coils 48. When the alternating electromagnetic field is received by a coil 48, a corresponding alternating current is induced in the coil 48. The AC signal used to transmit wireless power can have any suitable frequency (e.g., 100kHz-250kHz, etc.). A rectifier circuit, such as rectifier circuit 50 (which includes rectifier components, such as synchronously rectified metal-oxide-semiconductor transistors arranged in a bridge network), converts the AC signal (the received AC signal associated with the electromagnetic signal 44) received from one or more coils 48 into a DC voltage signal for powering device 24.

[0025] The DC voltage generated by rectifier circuit 50 (sometimes referred to as rectifier output voltage Vrect) can be used to charge batteries such as battery 58 and to power other components in device 24. For example, device 24 may include input-output device 56. Input-output device 56 may include input devices for acquiring user input and / or performing environmental measurements, and may include output devices for providing output to the user. For example, input-output device 56 may include a display for creating visual output, a speaker for presenting output as an audio signal, LED status indicators and other light-emitting components for emitting light to provide status information and / or other information to the user, tactile devices for generating vibrations and other tactile outputs, and / or other output devices. Input-output device 56 may also include sensors for acquiring input from the user and / or for measuring the surrounding environment of system 8. Exemplary sensors that may be included in input-output device 56 include three-dimensional sensors (e.g., three-dimensional image sensors such as structured light sensors that emit a light beam and use a two-dimensional digital image sensor to acquire image data for a three-dimensional image from the light spot generated when the light beam illuminates a target; binocular three-dimensional image sensors that use two or more cameras in a binocular imaging arrangement to acquire three-dimensional images; three-dimensional lidar (light detection and ranging) sensors; three-dimensional radio frequency sensors; or other sensors that acquire three-dimensional image data), cameras (e.g., infrared and / or visible light cameras with corresponding infrared and / or visible digital image sensors, and / or ultraviolet light cameras), gaze tracking sensors (e.g., gaze tracking systems based on image sensors and (if needed) on light sources emitting one or more light beams, wherein the image sensor is used to track the one or more light beams after the user's eye reflects the light beam), and touch sensors. Devices include: buttons, capacitive proximity sensors, light-based (optical) proximity sensors such as infrared proximity sensors, other proximity sensors, force sensors, sensors such as switch-based contact sensors, gas sensors, pressure sensors, humidity sensors, magnetic sensors, audio sensors (microphones), ambient light sensors, optical sensors for performing spectral and other measurements on a target object (e.g., by emitting light and measuring the reflected light), microphones for acquiring voice commands and other audio input, distance sensors, motion, position, and / or orientation sensors configured to acquire information about motion, position, and / or orientation (e.g., accelerometers, gyroscopes, compasses, and / or inertial measurement units including all of these sensors or a subset of these sensors), sensors such as buttons for detecting button press input, joysticks with sensors for detecting joystick movement, keyboards, and / or other sensors. Device 12 may have one or more input-output devices 70 (e.g., input devices and / or output devices of the type described in combination with input-output device 56).

[0026] Device 12 and / or device 24 can perform wireless communication using in-band or out-of-band communication. Device 12 may, for example, have a wireless transceiver circuit 40 that uses an antenna to wirelessly transmit out-of-band signals to device 24. The wireless transceiver circuit 40 can be used to wirelessly receive out-of-band signals from device 24 using an antenna. Device 24 may have a wireless transceiver circuit 46 that transmits out-of-band signals to device 12. The receiver circuit in wireless transceiver 46 can use an antenna to receive out-of-band signals from device 12. In-band transmission between devices 12 and 24 can be performed using coils 36 and 48. In one exemplary configuration, frequency shift keying (FSK) is used to transmit in-band data from device 12 to device 24, and amplitude shift keying (ASK) is used to transmit in-band data from device 24 to device 12. During these FSK and ASK transmissions, power can be wirelessly transferred from device 12 to device 24.

[0027] It is desirable that the power transmitting device 12 and the power receiving device 24 can communicate information such as received power and battery charging status to control wireless power delivery. However, the aforementioned technology can function without involving the transmission of personally identifiable information. Out of due care, it is important to note that, to some extent, if any specific implementation of this charging technology involves the use of personally identifiable information, the implementer should adhere to privacy policies and practices generally considered to meet or exceed industry or governmental requirements for protecting user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly explained to the user.

[0028] Control circuit 16 includes an external object measurement circuit 41, which can be used to detect the presence of an external object on the charging surface of the housing of device 12 (e.g., detecting an object on top of a charging pad, or, if necessary, detecting an object adjacent to the coupling surface of a charging dock). The housing of device 12 may have polymer walls, walls of other dielectrics, metal structures, fabric, and / or other housing wall structures encapsulating the coil 36 and other circuitry of device 12. The charging surface may be a flat outer surface of the upper housing wall of device 12 or an outer surface with other shapes (e.g., concave, convex, etc.). Circuit 41 can detect foreign objects such as coils, paperclips, and other metallic objects, and can detect the presence of a wireless power receiving device 24 (e.g., circuit 41 can detect the presence of one or more coils 48). During object detection and characterization operations, the external object measurement circuit 41 can be used to perform measurements on coil 36 and / or other coils (e.g., an optional foreign object detection coil in device 12) to determine the presence of any device 24 on device 12.

[0029] In an exemplary arrangement, the measurement circuit 41 of the control circuit 16 includes signal generator circuitry, such as a pulse generator that provides control signals to the inverter 61. These control signals cause the inverter 61 to generate pulses, such that the pulse response can be measured by the circuit 41 (e.g., by using a voltage sensor, an analog-to-digital converter configured to convert analog voltage measurements into digital voltage measurements, and / or other sensing circuitry). The measurement circuit may also have an AC source and other circuitry for performing measurements on the coil 36.

[0030] In some implementations, a quality factor measurement is performed on coil 36 to determine the presence of a foreign object. For example, direct impedance measurements and / or impulse responses can be analyzed to measure the quality factor (Q-factor) of coil 36. The Q-factor measurement of coil 36 (including a measurement of the change in the Q-factor value relative to a baseline value) can be performed at any suitable time, such as before transmitting wireless power from device 12 to device 24. If the Q-factor value deviates by more than a threshold amount and the object causing the Q-factor deflection does not respond to subsequent digital checks, device 12 can determine that a foreign object is present on coil 36 and can abandon wireless power transmission and / or take other appropriate actions (e.g., by transmitting power at a limited level below the level permitted in the presence of a detected foreign object, by stopping power transmission, etc.).

[0031] Figure 2 An exemplary circuit in system 8 is shown that allows measurement of the Q-factor (Q) of coil 36. Figure 2 The wireless power circuitry includes a wireless power transmission circuit 52 in the wireless power transmission device 12 and a wireless power receiving circuit 54 in the wireless power receiving device 24. During operation, the wireless power signal 44 is transmitted by the wireless power transmission circuit 52 and received by the wireless power receiving circuit 54. Figure 2 As shown, the wireless power transmission circuit 52 includes an inverter circuit 61.

[0032] Inverter circuit (inverter) 61 can be used to provide signals to coil 36. During wireless power transmission, the control circuit of device 12 provides a signal to control input 82 of inverter circuit 61, which causes inverter 61 to provide an AC drive signal to coil 36. Figure 2As shown, circuit components such as capacitor 70 may be coupled in series with coil 36. When an AC current signal is supplied to coil 36, a corresponding AC electromagnetic signal (wireless power signal 44) is transmitted to a nearby coil, such as the exemplary coil 48 in the wireless power receiving circuit 54. This induces a corresponding AC current signal in coil 48. Capacitors such as capacitor 72 may be coupled in series with coil 48. Rectifier 50 receives AC current from coil 48 and generates a corresponding DC power (e.g., DC voltage Vrect) at output terminal 76. This power can be used to power a load.

[0033] Device 12 may have measurement circuitry for monitoring signals on 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). Current source 92 and / or inverter 61 may also be used to supply signals to coil 36 during foreign object detection operations (e.g., enabling Q to be measured against coil 36). In some embodiments, Q-factor measurement is performed using a direct measurement of the impedance of coil 36 utilizing an AC current source. Q measurement can be performed in the presence and absence of wireless power receiving device 24 (e.g., periodic free-air Q measurement can be performed when device 24 is absent). By monitoring changes in Q relative to its free-air value, the presence of a foreign object can be detected and appropriate action taken.

[0034] In the first example of the Q-factor measurement arrangement, the control circuit of device 12 causes the inverter 61 to provide signal pulses to coil 36, and uses measurement circuitry such as voltage sensor 90 to measure the corresponding pulse response. Because... Figure 2 The resonance in the circuit applies a signal pulse to coil 36 to generate an envelope with attenuation (such as...). Figure 3 The oscillating signal with an attenuated envelope (94). The attenuated envelope has an attenuated envelope consisting of e -tπfr / Q Given the characteristics, where fr is the frequency of the oscillating signal, the value of Q can be determined by measuring fr and the attenuation envelope 94.

[0035] If necessary, an adjustable capacitor arrangement (e.g., a capacitor circuit with a switching circuit and multiple capacitors, which can be selectively switched for use under the control of control circuit 16 to adjust the capacitance value in the resonant circuit and thereby adjust the resonant frequency) can be used to achieve this. Figure 2 The capacitor 70. In an arrangement where the capacitor 70 has selectable values, when measuring the pulse response of the wireless power transmission circuit to determine Q (as in combination with...) Figure 3 As described, a first value (e.g., C1) can be used, and a second value (e.g., C2) can be used when the wireless power transmission circuit transmits the wireless power signal 44.

[0036] In the second exemplary Q-factor measurement arrangement, the value of Q is obtained from the direct measurement of the impedance of coil 36. Figure 4 for Figure 2 A circuit diagram of the wireless power transmission circuit and measurement circuit is provided, illustrating how the parasitic resistance R can be associated with the resonant circuit. In the case of the direct impedance measurement method, a small current is injected from current source 92 into coil 36 while voltage is measured using voltage sensor 90. The magnitude of the injected current can be low enough to allow current injection without the use of a high-power MOSFET. This current can be, for example, an alternating current (AC) current at a frequency such as 125 kHz, greater than 125 kHz, or less than 125 kHz, or other suitable frequency (e.g., a frequency that can be chosen regardless of the resonant frequency associated with the wireless power transmission circuit). The complex impedance of coil 36 is then determined at this frequency, and the value of Q is inverted from the angle θ of the measured impedance. Figure 5 The formula associated with this is shown: Q (the coil Q-factor) is determined from the perspective of complex impedance and by arbitrary values ​​of inductance L and resistance R (the real part of AC impedance), which can be calculated from direct impedance measurements. Figure 5 In the formula, I is the injected AC current, and V is the voltage obtained by voltage sensor 90.

[0037] The measurement circuitry 41 of device 12 can be calibrated during manufacturing. For example, the value of the Q-factor (Q0) measured at the initial stage of device 12 manufacturing (using a first exemplary Q-factor measurement arrangement, a second exemplary Q-factor measurement arrangement, and / or additional Q-factor measurement techniques) can be stored as a baseline value in device 12 for later use. If necessary, device-specific calibration operations can be performed so that each device 12 is individually calibrated using its corresponding individual baseline value for Q. When device 12 is operated in the field, device 12 can measure the current value of Q and compare this measured value of Q with the stored baseline value of Q0 from the factory. In this way, the amount of change in Q can be determined, indicating the presence of a foreign object or other external object on the charging surface of device 12.

[0038] If necessary, compensation techniques can be used to compensate for temperature effects, aging effects, and other effects that may induce drift in Q. Temperature variations can affect the parasitic resistance of components such as coil 36. The coil inductance L can also depend on temperature. Frequency variations and aging effects (e.g., mechanical wear) can also affect component values ​​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.

[0039] The values ​​of the baseline Q-factor Q0 and the resonant frequency ω(2πfr) measured during calibration (e.g., at the beginning of manufacturing) are given by Equations 1 and 2.

[0040] Q0=ω0L0 / R0(ω0) (1)

[0041] ω0=1 / (L0C) 1 / 2 (2)

[0042] The values ​​of Q and ω (as well as L and R) measured during operation (sometimes referred to as current Q, current ω, current L, and current R) are derived from equations 3, 4, 5, and 6, respectively. FO ω FO L FO and R FO Given.

[0043] Q FO =ω FO L FO / R FO (ω FO (3)

[0044] ω FO =1 / (L) F0 C) 1 / 2 (4)

[0045] L FO =L0+ΔL FO (5)

[0046] R FO =R0+ΔR FO (6)

[0047] During the compensation operation, the current temperature T of device 12 is measured using temperature sensor 60 of device 12 (see, for example, Figure 1 The change in temperature ΔT relative to temperature T0, measured during calibration measurements during manufacturing, is given by Equation 7.

[0048] ΔT=T-T0 (7)

[0049] Figure 6 The formula shows how to use the currently measured Q-factor based on one or more compensation factors. Figure 6 The function of Q' in the formula determines the compensated value of Q (e.g., the value of Qcomp).

[0050] The first example of a characteristic compensation factor involves frequency compensation. For example... Figure 6 As shown in the formula, Q' can be multiplied by a compensation factor (ω0 / ω) to compensate for the change in the resonant frequency during Q' measurement relative to the resonant frequency during Q0 measurement during manufacturing.

[0051] The second example of the indicative compensation factor involves the temperature dependence of inductance and resistance. For example... Figure 6 As shown in the formula, Q' can be multiplied by a compensation factor (1+κRΔT) / (1+κLΔT), where κR is the resistive temperature change coefficient and κL is the inductive temperature change coefficient. The values ​​of these temperature coefficients are influenced by the design of device 12 and, if necessary, can be determined empirically by performing measurements on one or more representative units of wireless power transmission device 12 during manufacturing.

[0052] The third example of the compensation factor involves the offset of the AC resistance RAC and DC resistance RDC of coil 36 relative to the baseline value. In this resistance compensation technique, the current value of the quality factor is compensated based on the compensated value of the overall (total) induction coil resistance associated with the wireless power transmission coil 36. Coil 36 is characterized in that the overall induction coil resistance value has a DC portion and an AC portion. During compensation operation, the control circuit 16 compensates for changes in the overall induction coil resistance by calculating the compensated value of the overall induction coil resistance from the sum of the baseline DC portion of the overall induction coil resistance measured at the initial time and the current AC portion of the overall coil resistance. This compensated overall induction coil resistance value is then used to compensate for the current quality factor using the compensated overall induction coil resistance.

[0053] like Figure 6 As shown in the formula, the resistance-based compensation factor is based on: the measured baseline DC resistance (R) obtained during calibration measurements during manufacturing. DC,0 The baseline AC resistance (R) obtained during calibration measurements during manufacturing. AC ); and the value of η, which is the AC resistance R varying according to the resonant frequency ω (e.g., 50 m-Ω per 100 kHz or other suitable value) obtained during calibration measurements during manufacturing. AC The coefficient of change. Parameter R meas Equal to the measured AC resistance R AC The measured DC resistance R DC The sum of .

[0054] exist Figure 6 In the examples, all three of these exemplary compensation factors have been applied to the measured Q' value (e.g., Qcomp is determined by compensating Q' based on frequency variation and the effects induced by frequency variation, and for the effects induced by temperature variation). In general, one or two of these compensation techniques and / or other compensation techniques can be used to calibrate Q factor measurements based on measured temperature, resonant frequency, and / or other variables.

[0055] As illustrated in the previous example, a compensated Q-factor value Qcomp can be generated based on measurements of temperature and frequency. This value can then be compared to a baseline value of Q measured during manufacturing and stored in device 12 for use in later comparisons. If necessary, compensation can be performed on the baseline Q-factor value to generate a compensated baseline Q, rather than on the field-measured value of Q. The method of performing compensation on the field-measured Q value instead of the baseline Q value is described herein as an example.

[0056] exist Figure 7 A flowchart illustrating an exemplary operation using System 8 to detect foreign objects is shown. In this embodiment, if a foreign object is detected, power transmission is suppressed. Alternatively, detected foreign objects can be simply flagged for use as additional information to determine an appropriate power transmission level during the power transmission phase. For example, in response to the detection of a foreign object, the maximum power level used during power transmission operation can be reduced to a predetermined level below the maximum power level.

[0057] During operation of block 100, device 12 measures the current value of Q using either a first exemplary Q-factor measurement arrangement (e.g., applying a pulse using inverter 61 and measuring Q from the envelope 94 of the pulse response) or a second exemplary Q-factor measurement arrangement (e.g., deriving Q from a direct impedance measurement of coil 36 performed by injecting current into coil 36 using AC current source 92). Measurements of Q using techniques such as these or other suitable Q-factor measurement techniques may sometimes be referred to as low-power verification (LPP) or analog verification operations.

[0058] During the operation of box 102, the value of the change in Q (e.g., the Q-factor deflection value Qdefl) can be determined. During the operation of box 102, compensation techniques (such as combining...) can be applied. Figure 6 The compensation technique described can be used to compensate for the measured value of Q, or it can compensate for the baseline value of Q (Q0) stored in device 12 during manufacturing. For example, the value of Qdefl can be calculated using Formula 8.

[0059] Qdefl=(Q0-Qcomp) / Q0=1-(Qcomp / Q0) (8)

[0060] In the example of Equation 8, Qdefl is calculated at least in part based on the difference between the compensated measured Q (Qcomp) and the baseline Q (Q0) and the ratio between Qcomp and Q0. In the case of Equation 8, if the current value of Q decreases by 5% relative to the baseline Q0, Qdefl will be 5%. Generally, Qdefl can be based solely on the difference between the measured Q and the baseline Q, solely on the ratio between the measured Q and the baseline Q, or both the difference between the measured Q and the baseline Q and the ratio between the measured Q and the baseline Q, and / or on other functions of the measured Q and the baseline Q. (See also: [link to Equation 8]). Figure 6 The compensation technique described herein can compensate for the measured value of Q used to calculate Qdefl in response to temperature, frequency and aging effects, and / or can compensate for the baseline value of Q in response to temperature, frequency and aging effects.

[0061] During operation at block 103, the control circuitry of device 12 determines whether Q has stabilized. If Q changes rapidly (e.g., due to an external object moving across the charging surface of device 12 as measurement is performed), the value of Qdefl is not yet sufficiently stable, and operation can return to block 100. A new measurement of Q can then be obtained during operation at block 100. A new Q measurement can be obtained in this manner every 0.1 seconds (or at another suitable sampling rate) as long as Q is not yet stable. Once the continuous change in the value of Qdefl is less than a predetermined threshold amount (e.g., 1%), Q can be considered sufficiently stable to allow analysis of the value of Qdefl to determine the presence of a foreign object, and operation can proceed to block 104.

[0062] During the operation at box 104, device 12 compares the value of Qdefl with a predetermined threshold TH (e.g., 3% or other suitable value). If Qdefl does not exceed the threshold (e.g., if the measured value of Q has not decreased by more than 3% relative to the baseline Q), device 12 can determine that no external object exists (e.g., no wireless power receiving device 24 exists, and no coin or other foreign object exists). The measurement operation can then continue at box 100. However, if it is determined during the operation at box 104 that Qdefl exceeds the threshold, device 12 can determine that the measured Q has decreased by more than the threshold amount relative to the baseline Q0 (e.g., Q is at least 3% lower than Q0), and therefore some type of external object exists (a foreign object such as a coin or either wireless power receiving device 24). The operation then proceeds to box 106 to distinguish between these two possibilities.

[0063] During the operation of block 106, device 12 may attempt to communicate wirelessly with wireless power receiving device 24. For example, device 12 may use in-band communication to transmit a wireless digital request. The wireless digital request is used to request device 24 to wirelessly transmit a corresponding digital response to device 12 to confirm its presence by using in-band communication. This digital communication request process may sometimes be referred to as digital verification. During the operation of block 108, device 12 determines whether it has received a response to the digital verification from device 24 to indicate the presence of device 24.

[0064] If device 24 is present on the charging surface of device 12, device 24 will respond to the digital verification using a wireless digital response. This response may include information such as a digital identifier corresponding to the type of device 24 present. In response to the presence of a cellular phone, watch, or other wireless power receiving device 24 during operation of block 108, device 12 will transmit a wireless power signal 44 to device 24 (e.g., during operation of block 110).

[0065] If device 24 is not present on the charging surface of device 12, device 12 will not receive any acknowledgment from device 24. In response to determining that device 24 is not present during operation at block 108, device 12 can conclude that a foreign object is present at the charging surface of device 12, and operation can proceed to block 112.

[0066] During box 112, device 12 monitors Q to determine when a present foreign object has been removed. Specifically, Q is measured during operation in box 114, as described in conjunction with the Q measurement in box 100. The value of Qdefl is calculated at box 116. Operation in box 118 involves comparing Qdefl with a threshold TH or another threshold. If the foreign object remains present, Qdefl will remain at a value exceeding the threshold, and additional measurements can be performed at box 114. However, if the foreign object is removed, processing returns to box 100, allowing device 12 to determine the presence of device 24, and if present, to begin transmitting wireless power to device 24.

[0067] When determining Qdefl, device 12 performs a comparison of the measured Q with a baseline value of Q acquired during manufacturing and stored in device 12 for future use. Temperature variations, frequency variations, coil resistance variations, and other variations can affect the Q baseline, so the Q baseline can be continuously updated if necessary. In the illustrative arrangement, the Q baseline is updated using a filter based on the newly measured Q reading each time it is determined that no external object is present at the charging surface of device 12. For example, each time device 12 determines that Qdefl is not greater than a threshold during operation of block 104, device 12 can conclude that no external object is present and no wireless power transmission device is present on the charging surface. Therefore, device 12 can conclude that the most recent measurement of Q from block 100 is actually an updated value that can be used at least partially to update the Q baseline (e.g., the current Q value that can be used as filter input).

[0068] In the case of this implementation scheme, Figure 7 At point P1 in the flowchart, the updated value of the Q baseline can be stored in device 12 each time Qdefl is determined to be no greater than the threshold TH. When updating the Q baseline, the current value of Q (measured during the most recent access box 100) can be incorporated into the Q baseline using a suitable filtering scheme (e.g., using a weighted historical average, using an averaging scheme with de-emphasized noise data, or other filtering arrangements). By using current measurement data to update the Q baseline in this way, the impact of aging on the baseline Q value can be reduced.

[0069] In the exemplary configuration, device 12 uses a low-pass filter to update the Q baseline using the measured current value of Q. Let q[n] be the effective Q deflection sample. An example of a low-pass filter for Q is a single-pole filter (see, for example, Equation 9), where α∈[0,1] and close to 1.

[0070] Q filt [n]=αQ filt [nl]+(1-α)Q defl [n]Q filt [0] = 0 (9)

[0071] Another example is the sliding window average given in Formula 10.

[0072]

[0073] As these examples illustrate, there are several possible arrangements for incorporating current Q measurement data from block 100 into the baseline Q value retained in device 12 and subsequently used to calculate Qdefl. In these update operations, control circuitry 16 uses filtering operations to periodically update the baseline quality factor based on historical current quality factor measurements, thereby ensuring that the value of the baseline quality factor is adjusted for aging effects and other effects that may cause the quality factor measurement to drift over time.

[0074] Updating the baseline Q value at point P1 involves performing an independent filtering operation at box 100 after each Q measurement. If necessary, the number of filtering operations per unit time can be reduced by performing the filtering operation at point P2 instead of point P1 (and thus reducing the number of times the updated Q baseline value is calculated and stored in device 12 per unit time). In this type of arrangement, the Q value measured during the operation of box 100 is stored (cached) by control circuitry 16 each time point P1 is reached (e.g., each time it is determined that no foreign object is present). If the operation of box 104 determines that the latest Q value exceeds the threshold TH, processing proceeds to box 106 to perform a digital verification. During the operation of box 108, control circuitry 16 determines: a) corresponding to the digital verification, whether a response has not yet been received (in this case, a foreign object is present and processing proceeds to box 112); or b) whether a wireless digital response has been received from device 24. At this point (e.g., point P2), device 12 is aware that device 24 has just been placed on the charging surface of device 12. Before initiating power transfer at box 110, device 12 retrieves the last value of Q cached at point P1 (and this value represents a Q factor measurement when there are no foreign objects or other external objects on device 12) and uses the retrieved current value of Q to update the value of the Q baseline.

[0075] In this method, the filtering operation for updating the Q baseline is performed only when it is determined that the wireless power receiving device is newly present (and there are no external objects). When no external object is present, the filtering operation is performed using the most recently obtained Q value (e.g., the Q value cached at point P1 with no external object present). A Q value storage operation still occurs each time point P1 is reached, but the calculation of the updated baseline Q value using the filter is performed at a lower frequency (e.g., only when point P2 is reached). Updating the baseline Q value only when it is determined that there is no wireless power receiving device and no external object ensures that the baseline quality factor value is adjusted for aging effects and other effects that may cause the quality factor measurement to drift over time, but without involving the same number of independent filtering operations as when the filtering operation is performed at point P1.

[0076] In addition to periodically updating the baseline value of Q (at point P1 or point P2), control circuitry 16 can also periodically update the value of the threshold TH used during the comparison operation of block 104 (e.g., an adjustable threshold TH can be used instead of a fixed, predetermined value). For example, the value of TH can be updated based on historical Q factor measurements or other measurements (e.g., Q factor measurements cached at point P1 when no external object is present). This filtering operation to update the value of TH can be performed at point P2 (e.g., when it is determined that no external object is present) using measurements (such as one or more cached Q factor measurements when no wireless power receiving device or external object is present).

[0077] If needed, the value of Qdefl can be compared with several different thresholds (e.g., to determine whether a small or large foreign object is present). Device 12 can then take different actions depending on whether a small or large foreign object is present. For example, if a small foreign object is detected in the presence of a wireless power receiving device, wireless power can be transmitted at a limited power level, but can be completely abandoned in the presence of a large foreign object.

[0078] For example, consider Figure 8 The figure illustrates the operation of device 12 in a system with multiple foreign object detection thresholds. Figure 8 In the example, system 8 has a lower first threshold THair (e.g., 3% or any other suitable value such as less than or greater than 3%) and a higher second threshold THfo (e.g., 6%, a value higher or lower than 6%, or any other suitable value higher than the first threshold). Device 12 operates in states 120, 122, 124, and 126. Transitions between these states are made according to transition rule 128. The values ​​of thresholds THair and THfo can be appropriately adjusted to distinguish between moderately foreign objects (e.g., objects with relatively little metal and / or moderately conductive metal) and strongly foreign objects (e.g., objects with more metal and / or greater conductive metal). In the case of a strongly foreign object, power will be suppressed until free air is observed. However, by setting the thresholds high enough, implementations can easily avoid using the "strongly foreign object" state.

[0079] like Figure 8As shown, in block 122, device 12 compares Qdefl with a first threshold and a second threshold, and determines that Qdefl is lower than the first threshold. In this scenario, device 12 can determine that there is no foreign object, and therefore can set the power transmission level of the wireless power signal 44 to a relatively high power level (power level 2). Power can then be wirelessly transmitted from device 12 to device 24 during the power transmission operation in block 126.

[0080] In block 120, the presence of an intrusive object has been determined because Qdefl is greater than a first threshold. It has also been determined that Qdefl is less than a second threshold. Therefore, device 12 can conclude that although an intrusive object is present, it is not a large one. Therefore, during the operation of block 126, device 12 can continue to wirelessly transmit power to device 24. Because the power is transmitted to device 24 in the presence of a small intrusive object, the power is reduced by the wirelessly transmitted level (e.g., the maximum level) to a relatively low power level (e.g., power level 1, which is less than power level 2). This helps prevent the small intrusive object from overheating.

[0081] In box 124, a large foreign object has been identified because Qdefl is greater than the second threshold. In this case, device 12 does not transmit wireless power.

[0082] The following sections further describe the aforementioned implementation scheme.

[0083] This section describes an accurate, wireless power transfer foreign object pre-detection (FOD) technique that can be used to detect foreign objects placed on device 10 (e.g., a PTx pad, sometimes referred to as PTx) before device 24 (e.g., a portable device or other power receiving device sometimes referred to as PRx) arrives.

[0084] This technology addresses several challenges:

[0085] 1. Modified-Q Foreign Object Detection (FOD) has difficulty distinguishing and handling foreign objects (FO).

[0086] The alignment offset between PRx and PTx. This is because the baseline Q is calculated as the average of mated-Q at five predetermined (e.g., five) different locations, rather than stored as a function of locations that are not easily determined at runtime. There are other potential challenges with mated-Q:

[0087] a. It relies on a reference measurement of Q taken at 100 kHz. Frequency may vary within the system. Since inductance L is a function of frequency, this frequency difference compared to the calibrated Qref can cause deviations in the measured Q during operation.

[0088] b. It does not take into account capacitor ESR, PCB trace resistance, and FET Rds(on) resistance when using non-COG capacitors.

[0089] c. It does not take into account temperature drift or frequency drift.

[0090] d. For TPR measurement reference Q, the reference Q may have a deflection on Q that differs from that of other transmitters.

[0091] exist Figure 7 The diagram illustrates the general procedure for an open-air Q test that conveys the general concept. During the startup phase (box 100), PTx uses a simulated inspection to detect objects placed on the pad. The inspection is used to measure the deflection to Q, defined as:

[0092]

[0093] Where Q0 is the calibrated value of open-air Q measured during manufacturing and verified by simulation during operation (see, for example, Q deflection calculation at box 102 and operation while waiting for Q to stabilize at box 103). Note that if FO is absent, ΔQ≈0, but it is usually not exactly zero due to effects such as temperature drift. Component aging can also cause ΔQ≠0.

[0094] When an object is placed on the pad, Q deflects by a certain amount. If ΔQ (sometimes called Qdefl) exceeds a threshold, an object is detected. In some implementations, the absolute value (|ΔQ|) is compared to a threshold (box 104) to indicate the presence of an extremely high-Q receiver placed on the PTx pad. To determine whether the object is an FO or a receiver, a response from a digital verification is awaited (box 106). If the digital verification is confirmed, the system can continue negotiation. If not confirmed, the object is assumed to be an FO, and power transfer is blocked until the FO is removed from the pad and ΔQ≈0 is obtained again.

[0095] There are many methods for measuring Q, such as:

[0096] 1. Perform a frequency scan to find the resonant frequency, and then calculate Q as the ratio of the slot voltage to the inverter voltage at the resonant frequency.

[0097] 2. Use an LCR meter directly connected to the coil at a specific frequency to measure specific L and Q.

[0098] Q measurement can also be performed in other ways.

[0099] As a first example, Q can be estimated from the decay of the oscillating response. In this method, an energy pulse is injected into the coil and the decay of the oscillating response is measured, such as... Figure 3 As shown. Then Q is estimated from the attenuation envelope.

[0100] Estimating Q requires accurate sampling of the waveform peaks to obtain their envelope. To eliminate the effect of DC offset, based on attenuation estimation, it is recommended to measure the envelope amplitude as the peak-to-valley difference, such as... Figure 9 As shown.

[0101] That is, definition

[0102]

[0103] So

[0104]

[0105] Where N is the distance between the second sample and the first sample (in terms of the number of peaks (N=1 indicates that the peaks are adjacent)).

[0106] This method is affected by frequency drift (mainly due to changes caused by the presence of FO).

[0107] As a second example, Q is calculated from coil impedance measurements. In this method, as... Figure 4 As shown, coil Q is directly measured at a fixed frequency. This method has the advantage of eliminating frequency drift from the Q measurement, but it requires preventing high voltage at the positive coil node.

[0108] Inject AC current I into the coil and measure the complex voltage:

[0109] V=(jωL+R)I (14)

[0110] The angle between V and I is

[0111]

[0112] therefore,

[0113]

[0114] The phase angle between V and I can be determined by comparing their peak or zero-crossing offsets or by taking the dot product of the waveforms.

[0115] The presence of FO causes offsets of L and R by ΔL and ΔR, respectively, and:

[0116]

[0117]

[0118] This offset causes a change in Q.

[0119]

[0120] This produces a measurable Q-deflection.

[0121]

[0122] Due to the frequency drift caused by FO, there may be an enhancement of Q deflection. In addition to measuring Q, the frequency of the oscillatory response can also be measured accurately. Through (17c), FO also deflects the oscillatory response. We can use this fact to enhance the deflection of Q:

[0123]

[0124] This results in enhanced Q deflection in the presence of predominantly iron-free FO, which leads to a decrease in L.

[0125]

[0126] When ΔL FO When <0, the result of formula (21) is greater than the result of (19).

[0127] This enhanced Q deflection is not applicable to the second example method for Q measurements operating at a fixed frequency.

[0128] The value of Q can be compensated for drift. In some implementations, there is a possibility of improving the Q deflection measurement. The Q deflection in Equation (11) is intended to compare the runtime measurement of Q with the manufacturing calibration measurement of Q. During runtime, in addition to the presence of FO, effects such as temperature and frequency drift can cause Q deflection. Compensating for these effects improves the reliability of open-air Q testing.

[0129] The DC and AC resistors can be separated. When measuring Q, various drift effects occur in the DC portion of the resistor, while the resistor itself is unaffected by the presence of FO. The DC resistance includes resistance from the PCB traces, capacitor ESR, and inverter FET resistance. If we separate the DC resistance from the overall resistance, we can use the DC resistance calibrated during manufacturing and remove...

[0130] The effect of DC resistor drift. Specifically, let

[0131] R = R DC (T)+R coil，AC (T,ω) (22)

[0132] We have already pointed out that RDC is temperature sensitive, and R coil，AC For temperature and frequency

[0133] sensitive.

[0134] Using (22), Q can be written as

[0135]

[0136] The total resistance can also be determined by simulating and verifying the oscillation response (or by impedance measurement):

[0137]

[0138]

[0139] R coil，AC =RR DC (24c)

[0140] When we measure DC resistance, we can store its value RDC, 0 at manufacturing time, and then calculate Q at runtime:

[0141]

[0142] This effectively eliminates DC drift from Q measurements, at the cost of additional measurement error in resistance.

[0143] As indicated in (22), the coil RAC can be a function of frequency.

[0144] R coil，AC (ω)≈R coil，AC，0 (1+ηΔω) (26)

[0145] in It is the change in frequency compared to the frequency measured at manufacturing time, and η is the slope of the drift. Let,

[0146]

[0147] Then further compensation can be made for RAC frequency drift (25), as follows:

[0148]

[0149] If the PTx design specifies this, then frequency compensation for L can also be applied.

[0150]

[0151] As indicated in (22), the coil RAC can be a function of temperature.

[0152] R coil，AC ≈R coil，AC，0 (1+κ R ΔT) (30)

[0153] Where ΔT = T - T0 is the temperature change compared to the temperature at which the device was calibrated during manufacturing, and κR is the temperature coefficient of coil resistance. Assuming PTx has a device for measuring the coil temperature, Q can be further compensated for temperature T as follows:

[0154]

[0155]

[0156] Combining (20), (28) and (32), we obtain the following options to improve Q accuracy.

[0157] Q Measurement Method 1

[0158]

[0159] Q Measurement Method 2

[0160]

[0161] Finally, we replace (11) with

[0162]

[0163] The sensitivity of Q deflection to FO can also be plotted [using, for example, formula (21)] for a specific PTx implementation. For example, assuming ΔLFO = 0 and ΔRFO = 22 mΩ, we can see how ΔQ is relative to FO. Figure 10 The resistance of the coil in the coil changes.

[0164] Figure 10 The instruction states that to achieve a 15% Q deflection, the PTx AC resistance should not exceed 125Ω. If Q can be measured more accurately, the PTx can have a higher AC resistance.

[0165] According to an embodiment, a wireless power transmission device is provided, comprising: a wireless power transmission circuit having a wireless power transmission coil configured to transmit a wireless power signal; and a control circuit coupled to the wireless power transmission circuit and configured to: measure a current quality factor of the wireless power transmission coil; compare the current quality factor with a baseline quality factor; and determine the presence of an intrusive object based at least in part on determining whether the current quality factor is lower than the baseline quality factor by at least a threshold amount.

[0166] According to another embodiment, the control circuit is configured to: wirelessly transmit a wireless digital request from a wireless power receiving device requesting a corresponding wireless digital response in response to determining that the current quality factor is lower than the baseline quality factor by at least a threshold amount; and determine the presence of an intrusive object in response to not receiving a wireless digital response from the wireless power receiving device corresponding to the wireless digital request.

[0167] According to another embodiment, the control circuit is configured to compare the current quality factor with the baseline quality factor at least in part by calculating the difference between the current quality factor and the baseline quality factor.

[0168] According to another embodiment, the control circuit is configured to compare the current quality factor with the baseline quality factor at least in part by calculating the ratio between the current quality factor and the baseline quality factor.

[0169] According to another embodiment, the control circuit is configured to measure a baseline quality factor at an initial time and to save the measured baseline quality factor for later comparison with the current quality factor.

[0170] According to another implementation, the control circuit is configured to periodically update the baseline quality factor based on historical measurements using filtering operations.

[0171] According to another embodiment, the control circuit is configured to perform a filtering operation when it is determined that a wireless power receiving device is present and no external object is present, and is configured to perform the filtering operation using the current quality factor value measured when no wireless power receiving device is present and no external object is present.

[0172] According to another embodiment, the control circuit is configured to periodically update the baseline quality factor based on a quality factor measurement performed after an initial time using a filtering operation.

[0173] According to another embodiment, the threshold amount includes a predetermined threshold amount.

[0174] According to another implementation, the control circuit is configured to update the threshold value using a filtering operation based on historical measurements.

[0175] According to another embodiment, the control circuit is configured to perform a filtering operation to update the threshold value when it is determined that a wireless power receiving device is present and no external object is present, and is configured to perform the filtering operation using the current quality factor value measured when no wireless power receiving device is present and no external object is present.

[0176] According to another implementation, the control circuit is configured to periodically update the threshold value based on the quality factor measurement using a filtering operation.

[0177] According to another embodiment, a baseline quality factor is measured at a first frequency, a current quality factor is measured at a second frequency, and a control circuit is configured to compensate for the current quality factor measurement for changes in the second frequency relative to the first frequency.

[0178] According to another embodiment, the wireless power transmission coil has a frequency-dependent induction coil resistance, and the control circuit is configured to compensate for the current quality factor measurement in response to changes in the induction coil resistance due to frequency variations.

[0179] According to another embodiment, the wireless power transmission device includes a temperature sensor configured to measure temperature, and a control circuit configured to compensate for the current quality factor measurement based on the temperature.

[0180] According to another embodiment, the wireless power transmission coil has an overall induction coil resistance with DC and AC portions, and the control circuit is configured to compensate for variations in the overall induction coil resistance by: determining a compensated value for the overall induction coil resistance from the sum of the baseline DC portion of the overall induction coil resistance and the current AC portion of the overall coil resistance; and using the compensated overall induction coil resistance to compensate for the current quality factor.

[0181] According to another embodiment, the baseline DC portion is measured at the initial time, and the currently measured AC portion of the overall coil resistance is measured after the initial time.

[0182] According to another embodiment, the control circuit is configured to measure the current quality factor by one of the following: a) applying a pulse to the wireless power transmission coil and measuring the attenuation envelope associated with the oscillation signal generated in the wireless power transmission coil due to the applied pulse; and b) using an AC source coupled to the wireless power transmission coil to measure the impedance of the wireless power transmission coil and determining the current quality factor from the measured impedance.

[0183] According to an embodiment, a wireless power transmission device is provided, comprising: a wireless power transmission circuit having a wireless power transmission coil configured to transmit a wireless power signal; and a control circuit coupled to the wireless power transmission coil and configured to: measure the quality factor of the wireless power transmission coil by applying a pulse to the wireless power transmission coil and measuring an attenuation envelope associated with an oscillation signal generated in the wireless power transmission coil due to the applied pulse; compensate for frequency-induced variations in the measured quality factor; compare the compensated measured quality factor with a baseline quality factor; and determine the presence of an intrusive object based at least in part on determining that the measured quality factor is at least a threshold amount lower than the baseline quality factor.

[0184] According to an embodiment, a wireless power transmission device is provided, comprising: a wireless power transmission circuit having a wireless power transmission coil configured to transmit a wireless power signal; and a control circuit coupled to the wireless power transmission coil and configured to: measure the impedance of the wireless power transmission coil by using an alternating current source coupled to the wireless power transmission coil and determine a quality factor from the measured impedance; measure the quality factor of the wireless power transmission coil; compare the measured quality factor with a baseline quality factor; and determine the presence of an intrusive object based at least in part on determining that the measured quality factor is at least a threshold amount lower than the baseline quality factor.

[0185] According to an embodiment, a wireless power transmission device is provided, comprising: a wireless power transmission circuit having a wireless power transmission coil configured to transmit a wireless power signal; and a control circuit coupled to the wireless power transmission circuit and configured to: measure a current quality factor of the wireless power transmission coil; compare the current quality factor with a baseline quality factor; determine the presence of an intruder based at least in part on comparing the difference between the current quality factor and the baseline quality factor with at least one threshold; wirelessly transmit a wireless power signal at a first power level using the wireless power transmission circuit in response to determining that no intruder exists; and wirelessly transmit a wireless power signal at a second power level below the first power level using the wireless power transmission circuit in response to determining that an intruder exists.

[0186] According to another embodiment, at least one threshold includes a first threshold and a second threshold, and the control circuit is configured to: determine that no foreign object exists in response to determining that the difference between the current quality factor and the baseline quality factor is lower than the first threshold; determine that a moderate foreign object exists in response to determining that the difference between the current quality factor and the baseline quality factor is between the first threshold and the second threshold; and determine that a strong foreign object exists in response to determining that the difference between the current quality factor and the baseline quality factor is higher than the second threshold.

[0187] According to another embodiment, the control circuit is configured to transmit a wireless power signal at a first wireless power level in response to determining that no foreign object exists by determining that the difference between the current quality factor and the baseline quality factor is less than a first threshold.

[0188] According to another embodiment, the control circuit is configured to transmit a wireless power signal at a second wireless power level in response to determining the presence of a moderately foreign object.

[0189] According to another embodiment, the control circuit is configured to abandon the use of the wireless power transmission circuit to transmit wireless power signals in response to determining the presence of a strong external object.

[0190] According to another embodiment, a baseline quality factor is measured at a first frequency, a current quality factor is measured at a second frequency, and a control circuit is configured to compensate for the current quality factor measurement for changes in the second frequency relative to the first frequency.

[0191] According to another embodiment, the wireless power transmission coil has a frequency-dependent induction coil resistance, and the control circuit is configured to compensate for the current quality factor measurement in response to changes in the induction coil resistance due to frequency variations.

[0192] According to another embodiment, the wireless power transmission device includes a temperature sensor configured to measure temperature, and a control circuit configured to compensate for the current quality factor measurement based on the temperature.

[0193] The foregoing description is merely illustrative and various modifications can be made to the described implementation scheme. The described implementation scheme can be implemented independently or in any combination.

Claims

1. A wireless power transmitter, comprising: A wireless power transmission circuit, wherein the wireless power transmission circuit has a wireless power transmission coil for transmitting wireless power signals; and Control circuit, the control circuit being coupled to the wireless power transmission circuit, the control circuit: Measure the current quality factor of the wireless power transmission coil; Determine the change between the measured current quality factor and the baseline quality factor; In response to the change between the measured current quality factor and the baseline quality factor being less than a threshold, the current quality factor of the wireless power transmission coil is measured again and the change between the measured current quality factor and the baseline quality factor is determined. In response to the change between the measured current quality factor and the baseline quality factor being greater than the threshold, an attempt is made to initiate digital communication with the wireless power receiver; as well as In response to initiating digital communication with the wireless power receiver and transmitting wireless power to the wireless power receiver, the baseline quality factor is updated based on one or more recently measured current quality factors. The control circuit measures the current quality factor of the wireless power transmission coil by: This causes the inverter to provide one or more signal pulses to the wireless power transmitter coil; The response to the one or more signal pulses provided is measured using a measurement circuit, wherein the response includes an oscillating signal having a decaying envelope characterized by the frequency of the oscillating signal and the current quality factor; as well as The current quality factor is determined based on the frequency of the oscillation signal.

2. The wireless power transmitter of claim 1, wherein the change between the measured current quality factor and the baseline quality factor includes the ratio of the measured current quality factor to the baseline quality factor.

3. The wireless power transmitter of claim 1, wherein the change between the measured current quality factor and the baseline quality factor includes the difference between the measured current quality factor and the baseline quality factor.

4. The wireless power transmitter of claim 1, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: The peak-to-valley difference of the oscillation signal in the first period is compared with the peak-to-valley difference of the oscillation signal in subsequent periods.

5. The wireless power transmitter of claim 1, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for temperature effects.

6. The wireless power transmitter of claim 5, wherein temperature effect compensation includes temperature effect compensation on coil resistance.

7. The wireless power transmitter of claim 5, wherein temperature compensation includes compensation for temperature effects on coil inductance.

8. The wireless power transmitter of claim 1, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for frequency effects.

9. The wireless power transmitter of claim 8, wherein compensating for frequency effects includes compensating for changes in the resonant frequency.

10. The wireless power transmitter of claim 1, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensating for the effects of aging.

11. The wireless power transmitter of claim 10, wherein compensating for aging effects comprises: Update the baseline quality factor.

12. The wireless power transmitter of claim 1, wherein the control circuit measures the current quality factor of the wireless power transmission coil by: The complex impedance of the wireless power transmission coil is measured using a measurement circuit; and The current quality factor is determined based on the phase angle of the complex impedance.

13. The wireless power transmitter of claim 1, wherein the control circuit is further configured to: In response to determining that the change between the measured current quality factor and the baseline quality factor exceeds the threshold, the control circuit determines that an external object exists; In response to determining that the change between the measured current quality factor and the baseline quality factor does not exceed the threshold, the control circuit determines that no foreign object exists; and The control circuit updates the baseline quality factor based on one or more recently measured current quality factors only when there are no external objects present.

14. The wireless power transmitter according to claim 13, wherein: In response to determining the presence of the foreign object, the control circuit suppresses power transmission; and In response to determining that no foreign object exists, the control circuit allows power transfer.

15. The wireless power transmitter of claim 1, wherein the threshold comprises a first threshold and a second threshold higher than the first threshold, and wherein: In response to determining that the change between the measured current quality factor and the baseline quality factor exceeds the second threshold, the control circuit determines that an unacceptable power loss from an external object is possible; In response to determining that the change between the measured current quality factor and the baseline quality factor exceeds the first threshold but does not exceed the second threshold, the control circuit determines that an acceptable power loss from an external object is possible; In response to determining that the change between the measured current quality factor and the baseline quality factor does not exceed the first threshold, the control circuit determines that no external object power loss is expected; as well as The control circuit updates the baseline quality factor based on one or more recently measured current quality factors only when there are no external objects present.

16. The wireless power transmitter according to claim 15, wherein: In response to the possibility that unacceptable power loss from an external object is determined, the control circuit suppresses power transfer; In response to the possibility of determining acceptable power loss from an external object, the control circuitry allows power transmission at a relatively low power level; and In response to determining that there is no expected power loss from external objects, the control circuitry allows power transmission at a relatively high power level.

17. The wireless power transmitter of claim 1, wherein the control circuit measures the current quality factor of the wireless power transmission coil by: The complex impedance of the wireless power transmission coil is measured using a measurement circuit; and The current quality factor is determined based on the phase angle of the complex impedance.

18. A method of operating a wireless power transmitter, the wireless power transmitter having a wireless power transmission circuit and a control circuit, the wireless power transmission circuit including a wireless power transmission coil for transmitting wireless power signals, the control circuit being coupled to the wireless power transmission circuit, the method being performed by the wireless power control circuit, and the method comprising: Measure the current quality factor of the wireless power transmission coil; Determine the change between the measured current quality factor and the baseline quality factor; In response to the change between the measured current quality factor and the baseline quality factor being less than a threshold, the current quality factor of the wireless power transmission coil is measured again and the change between the measured current quality factor and the baseline quality factor is determined. In response to the change between the measured current quality factor and the baseline quality factor being greater than the threshold, an attempt is made to initiate digital communication with the wireless power receiver; as well as In response to initiating digital communication with the wireless power receiver and transmitting wireless power to the wireless power receiver, the baseline quality factor is updated based on one or more recently measured current quality factors. Measuring the current quality factor of the wireless power transmission coil also includes: This causes the inverter to provide one or more signal pulses to the wireless power transmitter coil; The response to the provided one or more signal pulses is measured using a measurement circuit, wherein the response includes an oscillating signal having a decaying envelope characterized by the frequency of the oscillating signal and the current quality factor; and The current quality factor is determined based on the frequency of the oscillation signal.

19. The method of claim 18, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: The peak-to-valley difference of the oscillation signal in the first period is compared with the peak-to-valley difference of the oscillation signal in subsequent periods.

20. The method of claim 18, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: Compensation for temperature effects.

21. The method of claim 18, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: Compensation for frequency effects.

22. The method of claim 18, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: Compensating for the effects of aging.

23. The method of claim 18, further comprising: The complex impedance of the wireless power transmission coil is measured using a measuring circuit. as well as The current quality factor is determined based on the phase angle of the complex impedance.

24. The method of claim 18, further comprising: In response to determining that the change between the current quality factor and the baseline quality factor exceeds the threshold, it is determined that an external object exists; In response to determining that the change between the current quality factor and the baseline quality factor does not exceed the threshold, it is determined that there is no foreign object; as well as The baseline quality factor is updated based on one or more recently measured current quality factors only when no external object exists.

25. The method of claim 24, further comprising: In response to determining the presence of the foreign object, power transmission is suppressed; as well as Power transfer is permitted in response to the determination that no foreign object exists.

26. The method of claim 18, wherein the threshold comprises a first threshold and a second threshold higher than the first threshold, and wherein the method further comprises: In response to determining that the change between the current quality factor and the baseline quality factor exceeds the second threshold, it is possible to determine an unacceptable power loss from an external object; In response to determining that the change between the current quality factor and the baseline quality factor exceeds the threshold but does not exceed the second threshold, it is possible to determine an acceptable foreign object power loss; In response to determining that the change between the current quality factor and the baseline quality factor does not exceed the first threshold, it is determined that no external object power loss is expected; as well as The baseline quality factor is updated based on one or more recently measured current quality factors only when no external object exists.

27. The method of claim 26, further comprising: In response to the possibility of unacceptable power loss from foreign objects, power transmission is suppressed; In response to the determination that acceptable power loss from foreign objects is possible, power transmission at a relatively low power level is permitted; and In response to the determination that there is no expected power loss from external objects, power transmission at a relatively high power level is permitted.

28. A wireless power transmitter, comprising: A wireless power transmission circuit, wherein the wireless power transmission circuit has a wireless power transmission coil for transmitting wireless power signals; and Control circuit, the control circuit being coupled to the wireless power transmission circuit, the control circuit: The current quality factor of the wireless power transmission coil is measured using the following procedure: This causes the inverter to provide one or more signal pulses to the wireless power transmitter coil; The response to the one or more signal pulses provided is measured using a measurement circuit, wherein the response includes an oscillating signal having a decaying envelope characterized by the frequency of the oscillating signal and the current quality factor; as well as The current quality factor is determined based on the frequency of the oscillation signal; Determine the change between the measured current quality factor and the baseline quality factor; In response to the change between the measured current quality factor and the baseline quality factor exceeding a threshold, an attempt is made to initiate digital communication with the wireless power receiver; as well as Foreign objects are detected based at least in part on the measured change between the current quality factor and the baseline quality factor, and on the response from the wireless power receiver to an attempt to initiate digital communication, or the absence of such a response from the wireless power receiver.

29. The wireless power transmitter of claim 28, wherein the control circuit suppresses wireless power transmission in response to the detection of the foreign object.

30. The wireless power transmitter of claim 28, wherein in response to detecting the foreign object, the control circuit transmits power at a level below the maximum power level.

31. The wireless power transmitter of claim 28, wherein the control circuitry compares the change between the current quality factor and the baseline quality factor with a plurality of thresholds to detect the foreign object.

32. The wireless power transmitter of claim 31, wherein the plurality of thresholds includes a first threshold and a second threshold higher than the first threshold, and wherein the control circuitry further includes: In response to determining that the change between the current quality factor and the baseline quality factor exceeds the second threshold, a possible unacceptable power loss from foreign objects is indicated, and wireless power transmission is suppressed; In response to determining that the change between the current quality factor and the baseline quality factor exceeds the first threshold but does not exceed the second threshold, a possible acceptable power loss due to foreign objects is indicated, allowing wireless transmission at a relatively low power level; and In response to determining that the change between the current quality factor and the baseline quality factor does not exceed the first threshold, it indicates that there is no power loss due to external objects, allowing wireless power transmission at a relatively high power level.

33. The wireless power transmitter of claim 28, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: The peak-to-valley difference of the oscillation signal in the first period is compared with the peak-to-valley difference of the oscillation signal in subsequent periods.

34. The wireless power transmitter of claim 28, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for temperature effects.

35. The wireless power transmitter of claim 34, wherein temperature compensation includes compensating for temperature effects on coil resistance.

36. The wireless power transmitter of claim 34, wherein temperature compensation includes compensation for temperature effects on coil inductance.

37. The wireless power transmitter of claim 28, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for frequency effects.

38. The wireless power transmitter of claim 37, wherein compensating for frequency effects includes compensating for changes in the resonant frequency.

39. The wireless power transmitter of claim 28, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensating for the effects of aging.

40. The wireless power transmitter of claim 39, wherein compensating for aging effects comprises: Update the baseline quality factor.

41. The wireless power transmitter of claim 28, wherein the change between the measured current quality factor and the baseline quality factor includes the ratio of the measured current quality factor to the baseline quality factor.

42. The wireless power transmitter of claim 28, wherein the change between the measured current quality factor and the baseline quality factor includes the difference between the measured current quality factor and the baseline quality factor.

43. The wireless power transmitter of claim 28, wherein the baseline quality factor is measured during the manufacture of the wireless power transmitter.

44. The wireless power transmitter of claim 28, wherein the baseline quality factor is updated during field operation of the wireless power transmitter.

45. A wireless power transmitter, comprising: A wireless power transmission circuit, wherein the wireless power transmission circuit has a wireless power transmission coil for transmitting wireless power signals; and A control circuit, coupled to the wireless power transmission coil, and the control circuit: The current quality factor of the wireless power transmission coil is measured using the following procedure: This causes the inverter to provide one or more signal pulses to the wireless power transmitter coil; The response to the one or more signal pulses provided is measured using a measurement circuit, wherein the response includes an oscillating signal having a decaying envelope characterized by the frequency of the oscillating signal and the current quality factor; as well as The current quality factor is determined based on the frequency of the oscillation signal; Determine the change between the measured current quality factor and the baseline quality factor; In response to the change between the measured current quality factor and the baseline quality factor exceeding a threshold, an attempt is made to initiate digital communication with the wireless power receiver; as well as In response to initiating digital communication with the wireless power receiver, power transfer with the wireless power receiver is initiated.

46. ​​The wireless power transmitter of claim 45, wherein the control circuit suppresses wireless power transmission in response to determining the presence of an intrusive object.

47. The wireless power transmitter of claim 45, wherein in response to determining the presence of an intrusive object, the control circuit initiates power transmission at a level below the maximum power level.

48. The wireless power transmitter of claim 45, wherein the threshold includes a first threshold and a second threshold higher than the first threshold, and wherein the control circuitry includes: In response to determining that the change between the current quality factor and the baseline quality factor exceeds the second threshold, a possible unacceptable power loss from foreign objects is indicated, and wireless power transmission is suppressed; In response to determining that the change between the current quality factor and the baseline quality factor exceeds the first threshold but does not exceed the second threshold, a possible acceptable power loss due to foreign objects is indicated, allowing wireless transmission at a relatively low power level; and In response to determining that the change between the current quality factor and the baseline quality factor does not exceed the first threshold, it indicates that there is no power loss due to external objects, allowing wireless power transmission at a relatively high power level.

49. The wireless power transmitter of claim 45, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: The peak-to-valley difference of the oscillation signal in the first period is compared with the peak-to-valley difference of the oscillation signal in subsequent periods.

50. The wireless power transmitter of claim 45, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for temperature effects.

51. The wireless power transmitter of claim 45, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensation for frequency effects.

52. The wireless power transmitter of claim 45, wherein determining the current quality factor based on the frequency of the oscillation signal comprises: Compensating for the effects of aging.

53. The wireless power transmitter of claim 45, wherein the baseline quality factor is measured during the manufacture of the wireless power transmitter.

54. The wireless power transmitter of claim 45, wherein the baseline quality factor is updated during field operation of the wireless power transmitter.

55. A method of operating a wireless power transmitter, the wireless power transmitter having a wireless power transmission circuit and a control circuit, the wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal, the control circuit being coupled to the wireless power transmission circuit, the method being performed by the wireless power control circuit, and the method comprising: The current quality factor of the wireless power transmission coil is measured using the following procedure: This causes the inverter to provide one or more signal pulses to the wireless power transmitter coil; The response to the one or more signal pulses provided is measured using a measurement circuit, wherein the response includes an oscillating signal having a decaying envelope characterized by the frequency of the oscillating signal and the current quality factor; as well as The current quality factor is determined based on the frequency of the oscillation signal; The measured current quality factor is compared with the baseline quality factor; as well as Foreign objects are detected, at least in part, based on the comparison between the measured current quality factor and the baseline quality factor.

56. The method of claim 55, further comprising: In response to the comparison between the measured current quality factor and the baseline quality factor, an attempt is made to initiate digital communication with the wireless power receiver; The determination of the presence of the foreign object is based at least in part on the response from the wireless power receiver to the attempt to initiate digital communication or the absence of a response from the wireless power receiver to the attempt to initiate digital communication.

57. The method of claim 55, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: The peak-to-valley difference of the oscillation signal in the first period is compared with the peak-to-valley difference of the oscillation signal in subsequent periods.

58. The method of claim 55, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: Compensation for temperature effects.

59. The method of claim 57, wherein determining the current quality factor based on the frequency of the oscillating signal comprises: Compensating for the effects of aging.

60. The method of claim 55, further comprising: In response to the detection of the foreign object, wireless power transmission is suppressed.

61. The method of claim 55, further comprising: In response to the detection of the foreign object, power is transmitted at a level lower than the maximum power level.

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