Power transfer accounting for wireless power transfer

Abstract

The invention relates to power transfer accounting for wireless power transfer. A transmitter and / or receiver in a wireless power transfer system for predicting power loss to account for the presence or absence of foreign matter.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the rights to co-pending U.S. Provisional Patent Application 63 / 583,001, filed on September 15, 2023, entitled “Power Transfer Accounting for Wireless Power Transfer”; U.S. Provisional Patent Application 63 / 550,248, filed on February 6, 2024, entitled “Power Transfer Accounting for Wireless Power Transfer”; U.S. Patent Application 18 / 617,080, filed on March 26, 2024, entitled “Power Transfer Accounting for Wireless Power Transfer”; U.S. Patent Application 18 / 617,103, filed on March 26, 2024, entitled “Power Transfer Accounting for Wireless Power Transfer”; U.S. Provisional Patent Application 63 / 644,096, filed on May 8, 2024, entitled “Power Transfer Accounting forWireless Power Transfer”; U.S. Provisional Patent Application 63 / 644,096, filed on July 16, 2024, entitled “Power Transfer Accounting for Wireless Power Transfer”; and the benefit of priority of U.S. patent application 18 / 787,485, filed on July 29, 2024, entitled “Power Transfer Accounting for Wireless Power Transfer”; each of which is incorporated herein by reference. Background Art

[0003] Wireless power transfer is becoming increasingly popular in a variety of electronic devices. For example, many electronic devices, such as smartphones, tablets, smart watches, wireless headphones, styluses, etc., may employ wireless power transfer to facilitate charging of batteries within the device. In some applications, higher levels of wireless power transfer may be required, such as to provide faster charging speeds. Such higher power transfer levels may benefit from techniques for detecting the presence of foreign objects within the electromagnetic field associated with wireless power transfer. Summary of the invention

[0004] A method performed by a control circuit of a wireless power transmitter for detecting foreign objects affected by an electromagnetic field associated with a wireless power transfer from the wireless power transmitter to a wireless power receiver, the method may include: receiving a receiver power indication associated with the wireless power transfer from the wireless power receiver, the indication including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver; determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication with a transmitter power measured by the wireless power transmitter; calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the indication including or derived from a corresponding rectifier voltage or rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transfer between the wireless power transmitter and the wireless power receiver; and determining the presence of a foreign object when the measured power loss exceeds the predicted power loss by more than a threshold.

[0005] The received received power indication may be the rectifier voltage and the rectifier current, and the method may further include calculating the receiver power based on the rectifier voltage and the rectifier current. The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The transmitter power may be calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current.

[0006] The method may also include calculating the one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by: receiving multiple indications of receiver power from the wireless power receiver, the multiple indications of receiver power including or derived from a corresponding rectifier voltage and a rectifier current of the wireless power receiver associated with the wireless power transmission; determining multiple measured power loss values ​​by comparing the receiver power indication with a corresponding transmitter power measured by the wireless power transmitter, the multiple measured power loss values ​​each corresponding to one of the multiple received power level indications associated with the wireless power transmission; and performing a regression analysis on the multiple indications of received receiver power and the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients.

[0007] Receiving multiple indications of receiver power from the wireless power receiver may include receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission. The three or more operating points may include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power. The multiple indications at three or more operating points may include multiple samples at each of the three or more operating points. The multiple samples at each of the three or more operating points may include 25 or more samples at each of the three or more operating points.

[0008] The one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current. The predicted power loss may have the following form:

[0009]

[0010] Wherein α is the first coefficient associated with the rectifier voltage, and β is the second coefficient associated with the rectifier current. Performing the regression analysis on the received multiple indications of receiver power associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients may also include performing a baselining process, the baselining process including determining that the multiple indications of receiver power are linearly independent. The baselining process may also include determining that the multiple indications of receiver power are located in a two-dimensional plane.

[0011] Performing the regression analysis on multiple indications of received receiver power and corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer and the determined multiple measured power loss values ​​to calculate the one or more coefficients may include: calculating a first plurality of coefficients corresponding to an initial operating cycle having a wireless power transfer level below a first threshold, wherein the absence of foreign matter is indicated by another foreign matter detection technique; calculating a second plurality of coefficients corresponding to a baseline capture cycle having a wireless power transfer level above the first threshold; and comparing the first plurality of coefficients and the second plurality of coefficients to determine whether foreign matter was introduced during the baseline capture cycle.

[0012] The method may also include mitigating the presence of the foreign object by reducing the power level of the wireless power transmission or suspending the wireless power transmission in the presence of the foreign object.

[0013] A method performed by a control circuit of a wireless power transmitter for calculating one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and a wireless power receiver for detecting foreign objects affected by an electromagnetic field associated with a wireless power transmission from the wireless power transmitter to the wireless power receiver, the method may include: receiving multiple indications of receiver power levels from the wireless power receiver, the multiple indications of receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission; determining multiple measured power loss values ​​by comparing the receiver power indication with a corresponding transmitter power measured by the wireless power transmitter, the multiple measured power loss values ​​each corresponding to one of the multiple indications of the receiver power associated with the wireless power transmission; and performing a regression analysis on the multiple indications of the received receiver power including or derived from the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients.

[0014] The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The transmitter power may be calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current. The one or more coefficients may include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0015] Receiving multiple indications of receiver power from the wireless power receiver may include receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission. The three or more operating points may include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power. The multiple indications at three or more operating points may include multiple samples at each of the three or more operating points. The multiple samples at each of the three or more operating points may include 25 or more samples at each of the three or more operating points.

[0016] The method may further include calculating a predicted power loss based on the corresponding rectifier voltage and rectifier current and the one or more coefficients, wherein the predicted power loss has the following form:

[0017]

[0018] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

[0019] Performing the regression analysis on a plurality of indications of received receiver power and corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission and a plurality of determined measured power loss values ​​to calculate the one or more coefficients may also include performing a baselining process, the baselining process including determining that the plurality of received power level indications are linearly independent. The baselining process may include determining that the plurality of received power level indications are located in a two-dimensional plane.

[0020] A wireless power transmitter may include: a wireless power transmitter coil, which is configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver; an inverter, which is configured to receive input power and generate an output to drive the wireless power transmitter coil; and a controller and communication circuit, which are coupled to the inverter and the wireless power transmitter coil, and the controller and communication circuit control the inverter to regulate the wireless power transfer to the wireless power receiver. The controller and communication circuitry may include logic or programming that detects foreign objects affected by electromagnetic fields associated with a wireless power transfer to the wireless power receiver by: receiving a receiver power indication associated with the wireless power transfer from the wireless power receiver, the indication including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver; determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication with a transmitter power measured by the wireless power transmitter; calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the indication including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transfer between the wireless power transmitter and the wireless power receiver; and determining the presence of a foreign object when the measured power loss exceeds the predicted power loss by more than a threshold.

[0021] The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The transmitter power may be calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current. The controller and communication circuit may also include logic or programming that calculates one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by: receiving multiple indications of receiver power from the wireless power receiver, the multiple indications of receiver power including or derived from the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission; determining multiple measured power loss values ​​by comparing the receiver power indication with the corresponding transmitted wireless power level measured by the wireless power transmitter, the multiple measured power loss values ​​each corresponding to one of the multiple indications of the receiver power associated with the wireless power transmission; and performing regression analysis on the multiple indications of the received receiver power including or derived from the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients.

[0022] Receiving multiple indications of receiver power from the wireless power receiver may include receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission. The three or more operating points may include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power. The multiple indications at three or more operating points may include multiple samples at each of the three or more operating points. The multiple samples at each of the three or more operating points may include 25 or more samples at each of the three or more operating points.

[0023] The one or more coefficients may include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current. The predicted power loss may have the following form:

[0024]

[0025] Wherein α is the first coefficient associated with the rectifier voltage, and β is the second coefficient associated with the rectifier current. Performing the regression analysis on multiple indications of received receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission and multiple determined measured power loss values ​​to calculate the one or more coefficients may include performing a baselining process, the baselining process including determining that the multiple indications of receiver power are linearly independent. The baselining process may also include determining that the multiple indications of receiver power are located in a two-dimensional plane.

[0026] The controller and communication circuitry also include logic or programming to mitigate the presence of a foreign object by reducing the power level of the wireless power transfer or pausing the wireless power transfer if the foreign object is present.

[0027] A wireless power transmitter may include: a wireless power transmitter coil, which is configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver; an inverter, which is configured to receive input power and generate an output to drive the wireless power transmitter coil; and a controller and communication circuit, which are coupled to the inverter and the wireless power transmitter coil, and the controller and communication circuit control the inverter to regulate the wireless power transfer to the wireless power receiver. The controller and communication circuitry may include logic or programming that calculates one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by: receiving multiple indications of receiver power from the wireless power receiver, the multiple indications of receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission; determining multiple measured power loss values ​​by comparing the receiver power indications with corresponding transmitted wireless power levels measured by the wireless power transmitter, the multiple measured power loss values ​​each corresponding to one of the multiple indications of receiver power associated with the wireless power transmission; and performing a regression analysis on the received multiple indications of receiver power including or derived from the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients.

[0028] The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The transmitter power may be calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current. The one or more coefficients may include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0029] Receiving multiple indications of receiver power from the wireless power receiver may include receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission. The three or more operating points may include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power. The multiple indications at three or more operating points may include multiple samples at each of the three or more operating points. The multiple samples at each of the three or more operating points may include 25 or more samples at each of the three or more operating points.

[0030] The controller and communication circuitry may also include logic or programming that calculates a predicted power loss based on the corresponding rectifier voltage and rectifier current and the one or more coefficients, and wherein the predicted power loss has the form:

[0031]

[0032] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current. Performing the regression analysis on multiple indications of received receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission and multiple determined measured power loss values ​​to calculate the one or more coefficients may include performing a baselining process, the baselining process including determining that the multiple received power level indications are linearly independent. The baselining process may also include determining that the multiple received power level indications are located in a two-dimensional plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A simplified block diagram of a wireless power transfer system is illustrated.

[0034] Figure 2 Illustrated is a graph of power measurements that may be used to detect foreign objects using power loss measurements in a wireless power transfer system.

[0035] Figure 3 A flow chart illustrating a portion of a power-losing foreign object detection technique used in a wireless power transfer system.

[0036] Figure 4 Graph illustrating power measurements at various stages of the power loss foreign object detection technique.

[0037] Figure 5A graph illustrating power measurements of the power loss foreign object detection technique at different temperatures.

[0038] Figure 6 A flow chart illustrating a temperature compensation technique for power loss foreign object detection technology.

[0039] Figure 7 A flow chart illustrating a power loss foreign object detection technique used in a wireless power transfer system.

[0040] Figure 8 Illustrate a graph of power measurements and estimated losses used in the power loss foreign object detection technique.

[0041] Fig. 9 A flow chart illustrating an alternative power loss foreign object detection technique for use in a wireless power transfer system. DETAILED DESCRIPTION

[0042] In the following description, for the purpose of explanation, many specific details are set forth in order to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings in the drawings of the present disclosure represent structures and devices in block diagram form for simplicity. For the sake of clarity, not all features of actual implementations are described in the present disclosure. In addition, the language used in the present disclosure is selected for readability and instructional purposes and has not been selected to describe or limit the disclosed subject matter. Instead, the attached claims are intended for this purpose.

[0043] Various embodiments of the disclosed concepts are described by way of example, and are not limited to individual drawings, in which similar reference numerals indicate similar elements. For simplicity and clarity of description, reference numerals are repeated in different drawings to indicate corresponding or similar elements, where appropriate. In addition, many specific details are shown in order to provide a full understanding of the specific implementation described herein. In other cases, methods, procedures, and components are not described in detail to avoid blurring the related functions described. Mentioning "one", "a kind of" or "another" embodiment in this disclosure is not necessarily the same or different embodiments, and this means at least one. A given drawing may be used to illustrate more than one embodiment or more than one type of features of the present disclosure, and all elements in the drawings may not be required for a given embodiment or type. When provided in a given drawing, the reference numeral refers to the same element throughout several drawings, but it may not be repeated in each drawing. Unless otherwise specified, the drawings are not drawn to scale, and the proportions of certain components may be enlarged to better illustrate the details and features of the present disclosure.

[0044] Figure 1A simplified block diagram of a wireless power transmission system 100 is illustrated. The wireless power transmission system includes a power transmitter (PTx) 110 that wirelessly transmits power to a power receiver (PRx) 120, such as via an inductive coupling 130. The power transmitter 110 may receive input power converted by an inverter 114 into an AC voltage having specific voltage and frequency characteristics. The inverter 114 may be controlled by a controller / communication module 116, which operates as further described below. In various embodiments, the inverter controller and the communication module may be implemented in a common system (such as a system based on a microprocessor, a microcontroller, etc.). In other embodiments, the inverter controller may be implemented by a separate controller module and a communication module having a communication device therebetween. The inverter 114 may be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc. manufactured using silicon, silicon carbide, or gallium nitride devices).

[0045] Inverter 114 can deliver the generated AC voltage to transmitter coil 112. In addition to allowing magnetic coupling to the wireless coil of the receiver, Figure 1 The transmitter coil block 112 shown may include tuning circuits (such as additional inductors and capacitors) that facilitate operation of the transmitter under different conditions (such as different degrees of magnetic coupling to the receiver, different operating frequencies, etc.). The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil can be formed as a winding of wire around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless transmitter coil may also include a magnetically permeable material (e.g., ferrite) core that is configured to affect the flux pattern of the coil in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a variety of transmitter coil arrangements suitable for a given application.

[0046] The PTx controller / communication module 116 may monitor the transmitter coil and use information derived therefrom to control the inverter 114 to suit a given situation. For example, the controller / communication module may be configured to cause the inverter 114 to operate at a given frequency or output voltage depending on the particular application. In some embodiments, the controller / communication module may be configured to receive information from the PRx device and control the inverter 114 accordingly. This information may be received via the power transmission coil (i.e., in-band communication) or may be received via a separate communication channel (not shown, i.e., out-of-band communication). For in-band communication, the controller / communication module 116 may detect and decode signals (such as voltage, frequency, or load changes) imposed on the magnetic link by the PRx to receive information, and may instruct the inverter to modulate the delivered power by manipulating various parameters of the generated voltage (such as voltage, frequency, etc.) to send information to the PRx. In some embodiments, the controller / communication module may be configured to employ frequency shift keying (FSK) communication to transmit data to the PRx, in which the frequency of the inverter signal is modulated. The controller / communication module 116 may be configured to detect amplitude shift keying (ASK) communications or load modulation based communications from the PRx. In either case, the controller / communication module 126 may be configured to vary the current drawn on the receiver side to manipulate the waveform seen on the Tx coil, thereby delivering information from the PRx to the PTx. For out-of-band communications, additional modules may be provided that allow communication between the PTx and PRx, such as WiFi, Bluetooth, or other radio links, or any other suitable communication channel.

[0047] As described above, the controller / communication module 116 can be a single module, for example, disposed on a single integrated circuit, or can be constructed from a plurality of modules / devices disposed on different integrated circuits or a combination of integrated circuits and discrete circuits having analog components and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuits.

[0048] The PTx device 110 may optionally include other systems and components, such as a separate communication module 118. In some embodiments, the communication module 118 may communicate with a corresponding module tag in the PRx via a power transfer coil. In other embodiments, the communication module 118 may communicate with a corresponding module using a separate physical channel 138.

[0049] As mentioned above, the wireless power transfer system also includes a wireless power receiver (PRx) 120. The wireless power receiver may include a receiver coil 122 that may be magnetically coupled 130 to the transmitter coil 112. As discussed above, the transmitter coil 112, Figure 1The receiver coil block 122 shown may include tuning circuits (such as additional inductors and capacitors) that facilitate operation of the transmitter under different conditions (such as different degrees of magnetic coupling to the receiver, different operating frequencies, etc.). The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil can be formed as a winding of wire around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless receiver coil may also include a magnetically permeable material (e.g., ferrite) core that is configured to affect the flux pattern of the coil in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a variety of receiver coil arrangements suitable for a given application.

[0050] The receiver coil 122 outputs an AC voltage induced therein by magnetic induction via the transmitter coil 112. The output AC voltage may be provided to a rectifier 124, which provides a DC output power to one or more loads associated with the PRx device. The rectifier 124 may be controlled by a controller / communication module 126, which operates as further described below. In various embodiments, the rectifier controller and the communication module may be implemented in a common system (such as a system based on a microprocessor, a microcontroller, etc.). In other embodiments, the rectifier controller may be implemented by a separate controller module and a communication module with a communication device therebetween. The rectifier 124 may be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc. manufactured using silicon, silicon carbide, or gallium nitride devices).

[0051] The PRx controller / communication module 126 may monitor the receiver coil and use information derived therefrom to control the rectifier 124 to suit a given situation. For example, the controller / communication module may be configured to cause the rectifier 124 to provide a given output voltage depending on the particular application. In some embodiments, the controller / communication module may be configured to send information to the PTx device to effectively control the power delivered to the receiver. This information may be sent via the power delivery coil (i.e., in-band communication) or may be sent via a separate communication channel (not shown, i.e., out-of-band communication). For in-band communication, the controller / communication module 126 may, for example, modulate the load current or other electrical parameters of the received power to send information to the PTx. In some embodiments, the controller / communication module 126 may be configured to detect and decode signals (such as voltage, frequency, or load changes) imposed on the magnetic link by the PTx to receive information from the PTx. In some embodiments, the controller / communication module 126 may be configured to receive frequency shift keying (FSK) communications in which the frequency of the inverter signal has been modulated to transmit data to the PRx. The controller / communication module 126 may be configured to generate amplitude shift keying (ASK) communications or load modulation based communications from the PRx. In either case, the controller / communication module 126 may be configured to vary the current drawn on the receiver side to manipulate the waveform seen on the Tx coil, thereby delivering information from the PRx to the PTx. For out-of-band communications, additional modules may be provided that allow communication between the PTx and PRx, such as WiFi, Bluetooth, or other radio links, or any other suitable communication channel.

[0052] As described above, the controller / communication module 126 can be a single module, for example, disposed on a single integrated circuit, or can be constructed from multiple modules / devices disposed on different integrated circuits or a combination of integrated circuits and discrete circuits having analog components and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuits. The PRx device 120 may optionally include other systems and components, such as a communication ("communication") module 128. In some embodiments, the communication module 128 can communicate with a corresponding module in the PTx via a power transfer coil. In other embodiments, the communication module 128 can communicate with a corresponding module or tag using a separate physical channel 138.

[0053] Many variations and enhancements of the wireless power transfer system 100 described above are possible, and the following teachings apply to any of such variations and enhancements.

[0054] In a wireless power transmission system, it may be necessary to detect the presence of conductive foreign objects within the range of influence of the wireless power transmission magnetic field, for example, to mitigate the undesirable heating effect of such foreign objects. There are many techniques that can be used to perform such foreign object detection. One class of such techniques can be based on power accounting. In the power accounting technique, the wireless power transmitter can receive a communication from the wireless power receiver indicating the amount of power that the wireless power receiver has received. The receiver can calculate its received power by various techniques, for example, monitoring its rectifier voltage and coil current, etc. The received power can be obtained by calculating the product of these values. The receiver can transmit the value back to the wireless power transmitter using in-band or out-of-band communication, as described above. In some cases, such communications may take the form specified by an industrial standard such as the Qi wireless power transmission standard issued by the Wireless Charging Alliance or by a proprietary protocol. The wireless power transmitter can compare the received power value of the wireless power receiver with the amount of power transmitted by the wireless power transmitter. The wireless power transmitter can calculate the value in various ways, for example, the value can be the product of the inverter output voltage and the wireless power transmission coil current.

[0055] The difference between the power transmitted by the wireless power transmitter and the power received by the wireless power receiver is the power loss. The power loss may include losses associated with the so-called "friendly metals" of the wireless power transmitter and receiver and any losses associated with potential foreign objects. Various techniques may be used to enable friendly metal losses to be taken into account. For example, the wireless power receiver may provide the wireless power transmitter with information programmed into the wireless power receiver at the time of manufacture, so that the wireless power transmitter can estimate the losses associated with the friendly metals of the wireless power receiver. Similarly, the wireless power transmitter may be programmed with information that enables it to estimate its own friendly metal losses at the time of manufacture. In some cases, additional calibration mechanisms may be provided so that the friendly metal loss estimation parameters of the wireless power receiver and / or wireless power transmitter can be updated over time. In any case, once the friendly metal loss is taken into account, it can be assumed that any remaining losses are associated with the presence of foreign objects. If the foreign object loss exceeds a threshold (which may be a predetermined static threshold or a dynamic threshold), the wireless power transmission may be reduced or suppressed to prevent the undesirable heating effect of the foreign object.

[0056] An exemplary foreign object detection technique based on power accounting is described in U.S. Provisional Patent Application No. 63 / 581,318 filed by the applicant on September 8, 2023, which is incorporated herein by reference along with all references incorporated into the application. Such techniques may be used with the additional foreign object detection techniques described below.

[0057] Figure 2Graphs 240 and 245 of power measurements that can be used to detect foreign objects using power loss measurements in a wireless power transfer system are illustrated. The upper graph 240 illustrates a series of wireless power receiver power measurements 241a-241d and 243a-243e obtained over a period of time starting from the start of wireless power transfer. As shown in the graph 240, the power level may start at a level of 0W and initially ramp up to a first value (power measurement 241a) such as 15W during an initial operating cycle 242. Assuming that no foreign objects are detected during this initial operating cycle 242, the received power level may continue to increase to an even higher (second) power level corresponding to the power measurement 241d, for example, 28W during the baseline recording period 247. This higher second power level value may correspond to the maximum power cap 244. Subsequently, operational received power measurements 243a-243e may be made during an incremental power loss activity time period 249 (which may include or overlap with a baseline recording time period 247) to be used with a determined baseline value as explained in more detail below to determine if a foreign object is present. These power measurements 243a-243e may show a decrease in power over time, for example, when a battery being charged by the wireless power receiver approaches a fully charged state and the charging rate is reduced accordingly, or when power is reduced, for example, to regulate battery temperature.

[0058] Figure 2 The lower graph 245 illustrates power loss measurements 246a–246d (from a baseline recording period to determine a baseline loss, sometimes referred to as a baseline phase) and 248a–248e (from a higher level power transmission duty cycle where incremental power loss measurements are obtained and compared to the baseline value). These power loss measurements 246a–246d and 248a–248e correspond to the wireless power reception measurements 241a–241d and 243a–243e discussed above, respectively. The power loss measurements 246a–246d and 248a–248e can be obtained by the wireless power transmitter according to the general principles and techniques described above and in other patent applications of the applicant cited above. For example, the power loss measurement can be obtained by comparing the wireless power receiver received power with the wireless power transmitter transmitted power. The embodiments of the power loss states described herein further optimize the power loss measurements to inherently account for associated friendly metal losses, as described in more detail herein. Thus, each wireless power receiver power measurement 241a - 241d and 243a - 243e may have an associated or corresponding power loss measurement 246a - 246d and 248a - 248e.

[0059] During the initial operating period 242, foreign object detection may be performed by techniques described in the applications incorporated by reference above, which provide indication and protection against the introduction of foreign objects during the initial operating period 242. Once a first threshold power level for the initial operating state is reached (e.g., 15W received power measurement 241a), a power loss state 249 may begin from a baseline recording period 247. During this baseline recording period, the transmit power may be further increased to a second, higher (e.g., maximum) power level for which the PTx and PRx systems are designed. Figure 2 In the example of , the wireless power system is designed to operate below 30W, as indicated by the received power measurement 241d. Although 28W and 30W are used as the upper end of the higher power operating state in the illustrated example, other power levels for this boundary may also be used. At these threshold power levels and at one or more intermittent power levels corresponding to the received power measurements 241b, 241c, a baseline power loss value can be calculated so that for each received power measurement 241a-241d, there is a corresponding power loss value 246a-246d obtained by the wireless power transmitter. Once the maximum power cap 244 is reached (corresponding to the power measurement 241d and the power loss baseline value 246d), the baseline state is completed. The measured baseline value can be as described below with respect to Figure 3 and Figure 4 The invention is described in more detail for obtaining information, such as coefficients, which can be further used for foreign object detection. More specifically, such coefficients can be used to predict the power loss for a given received power measurement from a wireless power receiver. If the actual power loss determined by the wireless power transmitter exceeds the predicted power loss based on the received power measurement (i.e., the power loss) by more than a predetermined threshold, it can be assumed that a foreign object is present and mitigation steps (such as reducing, suspending and / or stopping the wireless power transmission) can be taken. For example, the power can be reduced to the first threshold level described above, for example, 15W. Reference Figure 7 and Fig. 9 The technology is further described. Additionally, the PRx device may request a rebaseline and / or the PTx device may initiate a rebaseline based on any detected change in operating conditions. Such a rebaseline may include restoring to a first threshold level as an initial step. For example, a PRx may request a rebaseline when retuning its resonant circuit for power transfer and / or data communication optimization.

[0060] Implementation 1: According to P RECT 2 Measured value determination P LOSS

[0061] Figure 3 A flow chart 300 illustrating coefficient determination for a power loss foreign object detection technique used in a wireless power transfer system. Figure 4A graph 400 of power measurements during various stages of a power loss foreign object detection technique is illustrated. These two graphs will be interpreted together to describe the process of determining coefficients for a power loss foreign object detection technique. Figure 4 The square of the received power measurement from the wireless power receiver on the x-axis is shown. and the power loss (P LOSS ) is a graph 400. These two parameters show a linear relationship, which can be described by the following equation:

[0062]

[0063] Where α0 and α1 are fitting coefficients that can be determined by performing a linear regression analysis, as described below. Alternatively, during power transfer, the PLOSS value can be calculated using the following formula:

[0064] P LOSS =α0+α1P RECT

[0065] (P LOSS : Equation 1b) P LOSS This calculation may be performed when the wireless power receiver is in an incremental power loss active phase (e.g., Figure 2 In stage 249) of the present invention, the rectifier voltage (V RECT ) target.

[0066] For example, from Figure 4 Starting from region 456, the region may correspond to Figure 2 , the wireless power transmitter may receive from the wireless power receiver a plurality of received power values ​​measured by the wireless power receiver, the plurality of received power values ​​corresponding to the x-axis coordinates of data points 457a–457c. The wireless power transmitter may determine a power loss associated with each of these data points, the power loss corresponding to the y-axis coordinates of data points 457a–457c. In one embodiment, the wireless power transmitter may then calculate coefficients α′0 and α′1 using a linear regression analysis on points 457a–457c. Although three points are illustrated, the actual calculation may use a different number of points depending on the granularity used to capture the desired data, which may vary depending on the requirements of a particular implementation.

[0067] Then, in the Figure 2 The baseline recording period depicted in Figure 247 Figure 4In region 458, the wireless power transmitter may receive from the wireless power receiver an additional plurality of received power values ​​measured by the wireless power receiver, the additional plurality of received power values ​​corresponding to the x-axis coordinates of data points 459a–459d. The wireless power transmitter may determine a power loss associated with each of these data points, the power loss corresponding to the y-axis coordinates of data points 459a–459d. In one embodiment, the wireless power transmitter may then calculate coefficients α″0 and α″1 using linear regression analysis on points 459a–459d. Although four points are illustrated, actual calculations may use a different number of points depending on the granularity used to capture the desired data, which may vary depending on the requirements of a particular implementation. Calculations of coefficients α′0 and α′1 and coefficients α″0 and α″1 correspond to Figure 3 Blocks 351 and 352 of flowchart 300 are shown.

[0068] As described above, during the initial working cycle 242 ( Figure 4 During the region 456 of the baseline capture period 247 ( Figure 4 If no foreign matter is introduced during the region 458 of the incremental power loss state, a comparison can be made between the coefficients α′0 and α′1 and α″0 and α″1. For example, the values ​​of α′0 and α″0 can be compared, and the values ​​of α′1 and α″1 can be compared, and if these values ​​are within acceptable tolerances, it can be assumed that the baseline capture period 247 ( Figure 4 Another possible comparison could be to use the coefficients α′0 and α′1 and the P corresponding to data point 459d. RECT Value calculation P LOSS value, and compare the calculated value with the determined P LOSS The value is compared to the actual y coordinate of data point 459d. If the value is within an appropriate tolerance that can be calculated according to the requirements of the specific implementation, it can be assumed that the baseline capture period 247 ( Figure 4 The foregoing two examples are merely illustrative of various ways in which the corresponding coefficients may be compared to determine whether a foreign object was inserted during the baseline capture period 242. Figure 3 353 of flowchart 300 in FIG.

[0069] If it is determined that a foreign object was introduced during the baseline capture period (in block 353), the wireless power transfer may be limited to a relatively low value, e.g., a first value of 15 W, as depicted in block 354. While in the illustrated example, 15 W is used as the upper end of the lower power operating state, other power levels for this boundary may also be employed. Otherwise, if it is determined that no foreign object was introduced during the baseline capture period (in block 353), all captured data points, e.g., during the initial operating period 242 ( Figure 4 and the data points 457a-457c captured during the baseline capture period 247 ( Figure 4 Data points 459a-459d captured during the region 458 of FIG. 45A may be used to recalculate coefficients α0 and α1. Alternatively, a subset of the total number of data points may be used if desired or appropriate for a given application.

[0070] In at least some applications, temperature can affect the relationship between the wireless power received and reported by the wireless power receiver and the losses measured by the wireless power transmitter. For example, particularly when operating at higher transmission power levels, an increase in transmission power can result in increased losses, which can otherwise affect the coefficients calculated as described above. Figure 5 A graph 500 is shown illustrating power measurements of a power loss foreign object detection technique at different temperatures. More specifically, the graph 500 shows the power measurements at elevated temperatures T0, T1, T2 fitted to the same The graph 500 and the curves 561, 562, and 563 illustrate that as the temperature increases, the same Values ​​with higher P LOSS value.

[0071] These coefficients, particularly the α1 coefficient, can be updated as a function of temperature using power loss measurements obtained at different temperatures. In implementation, the actual operating temperature may not be known because there are various components with different thermal masses and other heat transfer characteristics in both the wireless power transmitter and the wireless power receiver. However, as a general principle, the temperature will increase during operation until a thermal steady state is finally reached some time after the power transfer level reaches its own steady state. Therefore, the coefficients can be updated periodically (i.e., at different times) until they stabilize at the steady-state operating temperature of the wireless power transmitter / wireless power receiver system.

[0072] Figure 6 A flow chart 600 is shown illustrating a temperature compensation technique for a power loss foreign object detection technique. The temperature compensation technique may optionally be combined with the above-described Figure 3 and Figure 4Beginning at block 664, the fitting coefficients may be determined at a temperature corresponding to a first (possibly unknown) temperature Temp. n The first time n The coefficient calculation can be referred to above. Figures 2 to 4 Then, after a period of time has passed, in block 665, it may be determined whether a foreign object exists. This determination may be made by using the predicted P calculated using the coefficients determined in block 664. LOSS Value and according to P RECT The current value of the measured P LOSS If foreign matter is detected in block 665, the power may be reduced (block 666). Otherwise, if no foreign matter is present, the new coefficient may be set at a value corresponding to the temperature Temp. n+1 (may also be unknown) Time n+1 These coefficients may then be used to update the baseline (block 668) by replacing the previously calculated coefficients from block 664 with the updated coefficients calculated in block 667. The process may then be repeated, with additional foreign object detections (block 665) and subsequent coefficient updates (block 667) occurring after another period of time. This enables the baseline value to be updated to account for temperature increases associated with continued operation at a higher power level as well as temperature decreases, e.g., associated with operation at a reduced / lower power level, such as Figure 2 In some cases, the baseline update (block 668) may be skipped if the changes in the calculated coefficients are relatively small and / or the time interval between recalculations can be increased (or decreased in the case of relatively large differences in coefficients).

[0073] Figure 7 Flowchart 700 illustrates a power loss foreign object detection technique used in a wireless power transmission system. Beginning at block 771, a wireless power transmitter may receive data indicating a received power level from a wireless power receiver. The wireless power receiver may monitor various voltages and / or currents, such as those described above with reference to Figure 1The voltage or current associated with the wireless power receiving coil and / or rectifier determines the received power level. In some embodiments, the received power (also described herein as "receiver power") can be determined (approximately) by the receiver multiplying the rectifier output voltage and the rectifier output current. Although this is the rectifier output power, the rectifier output voltage and the rectifier output current are DC quantities, which can simplify the measurement and calculation of related values. In other embodiments, the rectifier input voltage and current or other suitable voltages and / or currents can be used as needed. In some embodiments, the wireless power receiver can transmit the calculated receiver power to the wireless power transmitter. In other embodiments, the wireless power receiver can convert basic measurements such as voltage and current to the wireless power transmitter. The transmission of receiver power information can utilize in-band or out-of-band communication as described above.

[0074] In block 772, the wireless power transmitter may determine P corresponding to the received wireless power value, for example, by subtracting the receiver power from the transmitter's own transmitter power measurement. LOSS In some embodiments, the transmitter power can be determined (approximately) by the transmitter multiplying the inverter input voltage and the inverter input current. Although this is the inverter input power, the fact that the inverter input voltage and the inverter input current are DC quantities can simplify the measurement and calculation of related values. In other embodiments, the inverter output voltage and current or other suitable voltages and / or currents can be used to determine the transmitter power as needed.

[0075] In block 773, the wireless power transmitter may use the Figures 2 to 4 The procedure described calculates the predicted P based on the fit coefficients obtained during the baseline measurement phase. LOSS These coefficients may also optionally be used similarly to the above Figures 5 and 6 The temperature compensation is performed by the process described above or other suitable processes. LOSS Determination and prediction of P LOSS The calculations can be performed in any order or simultaneously.

[0076] In block 774, the wireless power transmitter may determine the determined P LOSS The value (i.e., the transmitted power value measured by the wireless power transmitter minus the received power value reported by the wireless power receiver) exceeds the predicted P LOSSThe value (calculated using the baseline model) reaches a threshold. The threshold may be static or dynamic and may be predetermined and / or calculated or periodically updated as desired. In any case, if the difference between the measured power loss and the predicted power loss is greater than such a threshold, it may be inferred that a foreign object is present and mitigation steps may be taken (box 775). Such mitigation steps may include reducing the output power to a lower level selected to reduce or eliminate the possibility of undesirable heating effects of such foreign objects, or may include completely interrupting or stopping the wireless power transmission. Otherwise, if the difference between the measured power loss and the predicted power loss does not exceed the threshold, it may be inferred that no foreign object is present (box 776), or if foreign object is present, the temperature effect on the foreign object will remain within acceptable limits, and therefore, wireless power transmission may continue at the current level, with the process repeated as necessary (illustrated by returning to box 771).

[0077] Implementation 2: According to V RECT 2 / I RECT 2 Measured value determination P LOSS

[0078] In the above example, the expected power loss of the wireless power transmission system is based on the rectifier power (ie, ) estimate, with fitting coefficients to estimate the expected power loss derived from the regression analysis. In some embodiments, variations of this technique may be employed. As an example, the estimated loss may be calculated based on one or more other parameters such as PTx inverter input voltage (Vin) output current (Itx), PRx rectifier output voltage (Vrect), receiver current (Irect), etc. One or more of these variables may be used in a regression analysis as described above to obtain coefficients that can be used to obtain system power loss. Such regression analysis may be based on linear regression as described above, or on other regression models such as exponential, logarithmic, polynomial, etc. In addition, since the power in an electrical system is proportional to the square of the current and / or the square of the voltage, the squares of the various parameters described above may be used as part of the estimation routine. Such a regression model may optionally include a bias term (e.g., a DC term), which may be a constant such as the α0 term described above.

[0079] In some embodiments, such as using Figure 8 As shown in the graph 800, the system loss can be calculated based on the PRx rectifier voltage (V rect ) and the square of the rectifier current (I rect ). In other words, the loss can be estimated by:

[0080]

[0081] Where α and β are regression fit coefficients calculated using the above technique. System losses can be derived from the multiple V rect and I rect Baselining points 877a, 877b, ..., 877c are estimated as follows with respect to Fig. 9 More specifically, three or more baselining points (such as four, five or more baselining points) enable the baselining techniques described below to be used. A wireless power receiver or wireless power transmitter may calculate P loss function coefficients and / or perform a baseline check as described in more detail below. These baseline points can be used to calculate the P loss The regression coefficients α and β of the function define plane 878. Similarly, for any V rect / I rect Value, P loss The function can be used to calculate the predicted power loss 879, which will be located on the calculated plane. These calculated P loss The value is used during power transfer, as described in more detail below.

[0082] To confirm the validity of the baselined points, an optional baselined process may be performed by the wireless power receiver and / or the wireless power transmitter, and more specifically by one or more processors included in the control and communication circuitry of such devices. Baselining may optionally include two (or more) steps.

[0083] In a first step, the baselining points 877a, 877b, ..., 877c may be checked to determine that the baselining points define a plane; in other words, the baselining points are sufficiently non-collinear to define a single plane, rather than an infinite number of planes. This check may be performed in a variety of ways. In one embodiment, the baselining points 877a, 877b, ..., 877c may be checked to determine that the baselining points define a plane; in other words, the baselining points are sufficiently non-collinear to define a single plane, rather than an infinite number of planes. rect and I rect The measurement value construction matrix A is as follows:

[0084]

[0085] Where V rect,n and I rect,n is the corresponding rectifier voltage / current pair. It can be seen that three or more baseline points can be used to determine the regression coefficients. The determinant of this matrix is ​​multiplied by its transpose, that is,

[0086] |A T A|

[0087] is an indication of whether the points are collinear. More specifically, if the determinant is 0, the baselined points are collinear, while a non-zero value indicates that the baselined points are not collinear. To ensure a sufficient degree of nonlinearity, the determinant may be scaled by the number of points and compared to a threshold to determine whether the points have sufficient non-collinearity to make the baselining valid. In other words, the condition:

[0088]

[0089] This may indicate that the baselining is effective.Other algorithms may alternatively be used to determine that the baselining points are sufficiently non-collinear (ie, sufficiently linearly independent) to define a suitable predicted loss plane.

[0090] A second baselining check may be performed to confirm that the baselining points fit on a sufficiently flat plane (i.e., a two-dimensional plane), rather than a parabola or other higher order surface. In other words, it is desirable that the baselining points fit (within reasonable limits) on a plane that is exactly two-dimensional. One way to check this is to confirm that the compensated power loss P loss The maximum absolute value minus the corresponding and The term does not exceed the maximum fitting error, in other words:

[0091]

[0092] This may be an indication that the plane defined by the calculated regression coefficients is sufficiently planar. This adjustment can be used to eliminate the power loss on the Tx side (e.g., C TX The change of the loss contribution of the tuning capacitor) or the change of the power loss of the PTx coil is eliminated, which occurs when some other parameter or some other parameters are changed. More details of the example calculations.

[0093] During power transfer, ΔP loss The value can be calculated by the following formula:

[0094] ΔP loss =(P Ptx -P Prx )-P loss

[0095] (ΔP loss : Equation 3a)

[0096] Where P Ptx is the transmitter power, P Prx is the receiver, and P lossAs mentioned above, the transmitter power can be determined or estimated using the inverter input voltage and current in DC quantities or any other suitable PTx voltage and / or current values. Similarly, the receiver power can be determined or estimated using the rectifier output voltage and current in DC quantities or any other suitable PRx voltage and / or current values. Sometimes, P Ptx Call it P in , P Prx Call it P rect The use of voltage and / or current values ​​does not exclude the use or transfer of power values ​​from PRx to PTx. If the ΔP loss If the value is greater than a threshold, then it is inferred that a foreign object is present and mitigation may be performed as described above. Alternatively, during power transfer, a method may be used that takes into account the transmitter I 2 The incremental Ploss value is calculated from the equation for R loss, such as the following:

[0097]

[0098] Fig. 9 is a flow chart 900 of an alternative power loss foreign object detection technique that introduces a V rect and I rect The modified model of wireless power transmission system is used as described above. In box 981, the wireless power transmitter (PTx) may calculate the transmitter power as described above. Similarly, in box 982, the wireless power receiver (PRx) may calculate the receiver power in a similar manner (also as described above). Alternatively, the PRx device may report its relevant voltage and / or current directly to the PTx instead of calculating the receiver power. The Ptx may then perform the power calculation itself. The reporting may be performed over the wireless power link between the PTx and the PRx, for example, using in-band communication such as ASK to transmit one or more data packets including relevant voltage and current information. In box 983, the PRx may provide the calculated received power (and / or the relevant voltage and current parameters for calculating the power) to the PTx device, which receives such data in box 984. In box 985, the PTx device may, for example, calculate the power based on the square of the rectifier voltage. and the square of the rectifier current and calculates the estimated system loss using the coefficients calculated previously as described above. Additionally, in block 985, PTx may calculate ΔP loss , as described in the preceding paragraphs (Equation 3a or Equation 3b). In some embodiments, block 985 may also include the above reference Figure 8 The one or more baselining steps described.

[0099] In block 986, the calculated ΔP lossThe value can be compared to a threshold value to determine if a foreign object is present. loss If the threshold is exceeded, the presence of a foreign object may be inferred (block 987), and mitigation steps such as limiting, reducing, pausing, and / or stopping power delivery may be performed. For example, the power may be reduced to the first threshold level described above, e.g., 15W. Otherwise, if the calculated ΔP loss If the threshold is not exceeded, then it may be inferred that no foreign object is present (block 988) and the power level may be allowed to be increased.

[0100] Implementation 3: According to V RECT 2 / I RECT 2 Determination of ΔP from measured values LOSS Another aspect of

[0101] Similar to the above embodiment, ΔP is calculated LOSS This may include measuring the total system loss at a single instance and comparing it to a baseline value. LOSS It can be simply defined by calculating the difference between the transmitted power and the received power. Therefore:

[0102] P LOSS =P INV -P RECT

[0103] Where P LOSS is the power loss, P INV is the transmitted power (i.e., inverter power), and P RECT is the received power (i.e., rectifier power). In addition, The power loss can be adjusted by eliminating the power loss in the PTx coil or eliminating the change in the power loss of the PTx coil, which occurs when one or more parameters change. This adjustment can be used to eliminate the Tx side (e.g., C TX The change in the loss contribution of the tuning capacitor). Therefore:

[0104]

[0105] in is the power loss to be compensated, P LOSS Calculated as above, R circuit,tx is the resistance of the transmitter circuit, and I TX is the emitter side current. During operation, R circuit,tx Includes selected C TX Add the ESR (internal resistance, i.e., equivalent or effective series resistance) of any switch. In at least some cases, Can be calculated more easily than other power loss accounting techniques, depending on extensive simulation and measurement to determine the power used to calculate the foreign body power P FO The fitting of

[0106] As mentioned above Figure 8Briefly described, according to V RECT 2 and I RECT 2 Determination of ΔP from measured values LOSS A baselining process may be included. One purpose of this baselining process may be to record the loss curves and and This relationship can be modeled as Figure 8 More specifically, during the initial power transfer phase, by collecting various V RECT and P RECT Baselining may be performed at three or more points (including four, five or more baselining points) of the power value. As one example, the baselining may occur at a relatively low power level (e.g., less than 15 W), although any suitable low power level may be selected, including levels greater than or less than 15 W. When the initial ramp up power (and V RECT and / or RECT ), each V RECT / I RECT The power level may be slightly paused at the power level to collect and / or calculate stable data. This may have the effect of slowing down the initial power ramp, which in turn may increase the charging time, so collecting fewer data points may be preferred. In at least some simulated embodiments, three data points have been found to provide sufficient margin to predict the remainder of the plane. However, a greater number of points may be used if desired.

[0107] As an example, three baseline data points may be selected as the span V RECT and P RECT Three equally spaced points of the target range, for example:

[0108] ●In 1 point (e.g., point 877a; Figure 8 )

[0109] ●In 1 point (e.g., point 877b; Figure 8 )

[0110] ●In 1 point (for example, point 877c; Figure 8 )

[0111] Requires P RECT and V RECTThe coefficients α and β are calculated at least three points of the grid, as defined above in Equation 2. In one embodiment, 25 samples may be taken at each location to average out any additional system noise. However, other numbers of samples ranging from 1 to 50, 100, or even more samples may be taken at each point. Once a sample is taken at a given point, validity may be verified by confirming that the applicable power loss taking into account the foreign object power threshold is still within bounds.

[0112] In at least some embodiments, the PTx device can take these three points and fit the α and β coefficients to the following equation (which corresponds to Equation 2, described above).

[0113]

[0114] More specifically, during the baselining phase, PRx may send back to PTx the RECT 、V RECT and I RECT PRx may also control the point at which baselining is performed. Ptx may be responsible for calculating the linear fit. These packets may be processed similarly to the MPLA (Magnetic Power Loss Accounting) packets as described in the Qi 2 specification published by the Wireless Power Consortium, since PTx / PRx synchronization is required. The α and β coefficients may be calculated using a series of sums (e.g., from PTx). To obtain the calculation results, the following two sums are used, where, for simplicity, P LOSS_COMPENSATED Abbreviated as P LC :

[0115]

[0116] And using two equations and two unknowns, we can solve for α and β, namely:

[0117]

[0118] as well as

[0119]

[0120] These values ​​then need to be verified to be valid. The various checking algorithms are described in more detail below.

[0121] The linear baselining check and fit error check described below can be used to ensure that the fit is in good condition. The linear baselining check can be performed by checking how close the data is to a singularity. The following equation (similar to the equation described above for Embodiment 2) can define this process. As described above, the linear baselining check can be performed according to V rect and I rect The measurement value construction matrix A is as follows:

[0122]

[0123] Where V rect,n and I rect,n is the corresponding rectifier voltage / current pair. It can be seen that the regression coefficients can be determined using three or more baseline points (such as four, five or more baseline points). The determinant of this matrix is ​​multiplied by its transpose, that is,

[0124] |A T A|

[0125] is an indication of whether the points are collinear.

[0126] More specifically, if the determinant is 0, the baselining points are collinear, while a non-zero value indicates that the baselining points are not collinear. The matrix ATA is given by:

[0127]

[0128] Therefore, the determinant is given by:

[0129]

[0130] To ensure a sufficient degree of nonlinearity, the determinant can be scaled by the number of points and compared to a threshold to determine whether the points have sufficient non-collinearity to make the baselining valid. In other words, the exemplary condition

[0131]

[0132] This may indicate that the baselining is effective.Other algorithms may alternatively be used to determine that the baselining points are sufficiently non-collinear (ie, sufficiently linearly independent) to define a suitable predicted loss plane.

[0133] A second baselining check may be performed to confirm that the baselining points fit on a sufficiently flat plane (i.e., a two-dimensional plane), rather than a parabola or other higher order surface. In other words, it is desirable that the baselining points fit on a plane that is exactly two-dimensional within reasonable limits. Therefore, after calculating the α and β coefficients, the maximum fit error may be calculated to confirm that the baselining is good. One way to check this is to confirm that the compensated power loss P loss_compensated The maximum absolute value minus the corresponding and The term does not exceed the maximum fitting error, in other words:

[0134]

[0135] This is the P that will be measured LOSS_COMPENSATEDThe predicted losses are calculated point by point. As described above, if the maximum error exceeds a predetermined threshold, the fit is invalid and the system may revert to using other power loss accounting schemes (e.g., MPLA) and / or limiting power (e.g., to 15W).

[0136] P LOSS This may be evaluated (e.g., by PTx) upon receipt of its complementary packet (e.g., from PRx), and if this threshold is exceeded, the system may limit power, e.g., by reverting to a 15W operating mode. LOSS It can be given by the following formula:

[0137]

[0138] This equation is essentially the same as equation 3a discussed above with respect to embodiment 2. A grace period is given for lost packets, such as 8 seconds. Afterwards, the system can be restarted to provide a complete startup process. Otherwise, once baselining is complete and the rectified power exceeds the low power threshold (e.g., 15W), ΔP LOSS =When the rectified power remains below a certain threshold (e.g., 10 W), the system may switch back to the alternative scheme (e.g., MPLA) (although other thresholds may be used). Considering ΔP below 10 W (or other suitable threshold) caused by different operating conditions such as phase modulation on the PTx side LOSS The accuracy will be reduced, which may be desirable.

[0139] In the foregoing description, it has been contemplated that the foreign object detection techniques described herein will be performed by a wireless power transmitter, and more specifically, by appropriately programmed or configured control circuitry of the wireless power transmitter, which control circuitry may, for example, be described above with respect to Figure 1 However, all or part of the functions may also be performed by a wireless power receiver with appropriately programmed control circuitry. Such an arrangement may require slightly different control flows and communications, but is still similar in construction and operation to the systems and methods described herein.

[0140] Additional items:

[0141] Item 1. A method performed by a control circuit of a wireless power transmitter for detecting a foreign object affected by an electromagnetic field associated with wireless power transmission from the wireless power transmitter to a wireless power receiver, the method comprising:

[0142] receiving, from the wireless power receiver, a receiver power indication associated with the wireless power transfer, the receiver power indication comprising or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver;

[0143] determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication to a transmitter power measured by the wireless power transmitter; calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the receiver power indication including or derived from a corresponding rectifier voltage or rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transfer between the wireless power transmitter and the wireless power receiver; and

[0144] The presence of a foreign object is determined in the event that the measured power loss exceeds the predicted power loss by more than a threshold value.

[0145] Item 2. A method according to Item 1, wherein the received received power indication is the rectifier voltage and the rectifier current, and the method also includes calculating the receiver power based on the rectifier voltage and the rectifier current.

[0146] Item 3. The method of Item 1, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

[0147] Item 4. A method according to Item 1, wherein the transmitter power is calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current.

[0148] Item 5. The method according to Item 1, further comprising calculating the one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by:

[0149] receiving, from the wireless power receiver, a plurality of indications of receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer;

[0150] determining a plurality of measured power loss values ​​by comparing a receiver power indication with a corresponding transmitter power measured by the wireless power transmitter, the plurality of measured power loss values ​​each corresponding to a received power level indication of the plurality of received power level indications associated with the wireless power transfer; and

[0151] A regression analysis is performed on corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer and a plurality of indications of received receiver power and the determined plurality of measured power loss values ​​to calculate the one or more coefficients.

[0152] Item 6. A method according to Item 5, wherein receiving multiple indications of receiver power from the wireless power receiver includes receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission.

[0153] Item 7. A method according to Item 6, wherein the three or more operating points include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power.

[0154] Item 8. The method of Item 6, wherein the plurality of indications at three or more operating points comprises a plurality of samples at each of the three or more operating points.

[0155] Item 9. The method of Item 8, wherein the plurality of samples at each of the three or more operating points comprises 25 or more samples at each of the three or more operating points.

[0156] Item 10. The method of Item 5, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0157] Item 11. The method of Item 10, wherein the predicted power loss has the following form:

[0158]

[0159] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

[0160] Item 12. A method according to Item 5, wherein performing the regression analysis on multiple indications of received receiver power associated with the wireless power transmission and the determined multiple measured power loss values ​​to calculate the one or more coefficients also includes performing a baselining process, wherein the baselining process includes determining that the multiple indications of receiver power are linearly independent.

[0161] Item 13. A method according to Item 12, wherein the baselining process also includes determining that multiple indications of the receiver power are located in a two-dimensional plane.

[0162] Item 14. The method of Item 12, performing the regression analysis on a plurality of indications of corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and received receiver power and a plurality of determined measured power loss values ​​to calculate one or more coefficients, comprising:

[0163] calculating a first plurality of coefficients corresponding to an initial duty cycle having a wireless power transfer level below a first threshold, wherein the absence of a foreign object is indicated by another foreign object detection technique;

[0164] calculating a second plurality of coefficients corresponding to baseline capture periods having wireless power transfer levels above the first threshold; and

[0165] The first and second pluralities of coefficients are compared to determine whether foreign matter was introduced during the baseline capture period.

[0166] Item 15. The method according to Item 1 further includes: in the presence of foreign matter, reducing the power level of the wireless power transmission or suspending the wireless power transmission to mitigate the presence of the foreign matter.

[0167] Item 16. A method performed by a control circuit of a wireless power transmitter for calculating one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and a wireless power receiver for detecting a foreign object affected by an electromagnetic field associated with wireless power transmission from the wireless power transmitter to the wireless power receiver, the method comprising:

[0168] receiving, from the wireless power receiver, a plurality of indications of receiver power levels, the plurality of indications of receiver power levels comprising or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer;

[0169] determining a plurality of measured power loss values ​​by comparing the receiver power indication to a corresponding transmitter power measured by the wireless power transmitter, the plurality of measured power loss values ​​each corresponding to one of a plurality of indications of the receiver power associated with the wireless power transfer; and

[0170] The regression analysis is performed on a plurality of indications of received receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer and a plurality of determined measured power loss values ​​to calculate the one or more coefficients.

[0171] Item 17. The method of Item 16, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

[0172] Item 18. A method according to Item 16, wherein the transmitter power is calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current.

[0173] Item 19. A method according to Item 16, wherein receiving multiple indications of receiver power from the wireless power receiver includes receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission.

[0174] Item 20. A method according to Item 19, wherein the three or more operating points include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power.

[0175] Item 21. The method of Item 19, wherein the plurality of indications at three or more operating points comprises a plurality of samples at each of the three or more operating points.

[0176] Item 22. A method according to Item 21, wherein the plurality of samples at each of the three or more operating points includes 25 or more samples at each of the three or more operating points.

[0177] Item 23. A method according to Item 16, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0178] Item 24. The method of Item 23, further comprising calculating a predicted power loss based on the corresponding rectifier voltage and rectifier current and the one or more coefficients, wherein the predicted power loss has the following form:

[0179]

[0180] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

[0181] Item 25. A method according to Item 16, wherein the regression analysis is performed on the corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transmission and multiple indications of the received receiver power and the determined multiple measured power loss values ​​to calculate one or more coefficients, and may also include performing a baselining process, the baselining process including determining that the multiple received power level indications are linearly independent.

[0182] Item 26. A method according to Item 25, wherein the baselining process includes determining that the multiple received power level indications are located in a two-dimensional plane.

[0183] Item 27. A wireless power transmitter, the wireless power transmitter comprising:

[0184] a wireless power transmitter coil configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver;

[0185] an inverter configured to receive input power and generate an output that drives the wireless power transmitter coil; and

[0186] a controller and communication circuitry coupled to the inverter and the wireless power transmitter coil, the controller and communication circuitry controlling the inverter to regulate wireless power transfer to the wireless power receiver, wherein the controller and communication circuitry includes logic or programming that detects the wireless power transfer to the wireless power receiver by:

[0187] Foreign objects affected by electromagnetic fields associated with wireless power transmission from wireless power receivers:

[0188] receiving, from the wireless power receiver, a receiver power indication associated with the wireless power transfer, the receiver power indication comprising or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver;

[0189] determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication to a transmitter power measured by the wireless power transmitter;

[0190] calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the receiver power indication including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver; and

[0191] The presence of a foreign object is determined in the event that the measured power loss exceeds the predicted power loss by more than a threshold value.

[0192] Item 28. A wireless power transmitter according to Item 27, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

[0193] Item 29. A wireless power transmitter according to Item 27, wherein the transmitter power is calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current.

[0194] Item 30. The wireless power transmitter of Item 27, wherein the controller and communication circuitry further comprises logic or programming that calculates the one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by:

[0195] receiving, from the wireless power receiver, a plurality of indications of receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer;

[0196] determining a plurality of measured power loss values, each corresponding to one of a plurality of indications of the receiver power associated with the wireless power transfer, by comparing the receiver power indication to a corresponding transmit wireless power level measured by the wireless power transmitter; and

[0197] The regression analysis is performed on a plurality of indications of received receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer and a plurality of determined measured power loss values ​​to calculate the one or more coefficients.

[0198] Item 31. A wireless power transmitter according to Item 30, wherein receiving multiple indications of receiver power from the wireless power receiver includes receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission.

[0199] Item 32. A wireless power transmitter according to Item 31, wherein the three or more operating points include an operating point at minimum rectifier voltage and maximum receiver power, an operating point at nominal rectifier voltage and nominal receiver power, and an operating point at maximum rectifier voltage and minimum receiver power.

[0200] Item 33. A wireless power transmitter according to Item 31, wherein the multiple indications at three or more operating points include multiple samples at each of the three or more operating points.

[0201] Item 34. A wireless power transmitter according to Item 33, wherein the multiple samples at each of the three or more operating points include 25 or more samples at each of the three or more operating points.

[0202] Item 35. A wireless power transmitter according to Item 27, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0203] Item 36. The wireless power transmitter of Item 35, wherein the predicted power loss has the following form:

[0204]

[0205] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

[0206] Item 37. A wireless power transmitter according to Item 27, wherein the regression analysis is performed on multiple indications of received receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission and multiple determined measured power loss values ​​to calculate the one or more coefficients, including performing a baselining process, the baselining process including determining that the multiple indications of receiver power are linearly independent.

[0207] Item 38. A wireless power transmitter according to Item 37, wherein the baselining process also includes determining that multiple indications of the receiver power are located in a two-dimensional plane.

[0208] Item 39. A wireless power transmitter according to Item 27, wherein the controller and communication circuit also include logic or programming that mitigates the presence of foreign matter by reducing the power level of the wireless power transmission or pausing the wireless power transmission if foreign matter is present.

[0209] Item 40. A wireless power transmitter, the wireless power transmitter comprising:

[0210] a wireless power transmitter coil configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver;

[0211] an inverter configured to receive input power and generate an output that drives the wireless power transmitter coil; and

[0212] a controller and communication circuitry coupled to the inverter and the wireless power transmitter coil, the controller and communication circuitry controlling the inverter to regulate wireless power transmission to the wireless power receiver, wherein the controller and communication circuitry includes logic or programming that calculates a corresponding baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by:

[0213] One or more coefficients:

[0214] receiving, from the wireless power receiver, a plurality of indications of receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer;

[0215] determining a plurality of measured power loss values, each corresponding to one of a plurality of indications of the receiver power associated with the wireless power transfer, by comparing the receiver power indication to a corresponding transmit wireless power level measured by the wireless power transmitter; and

[0216] performing the regression analysis on a plurality of indications of received receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer and a plurality of determined measured power loss values,

[0217] to calculate the one or more coefficients.

[0218] Item 41. A wireless power transmitter according to Item 40, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

[0219] Item 42. A wireless power transmitter according to Item 40, wherein the transmitter power is calculated by the wireless power transmitter by multiplying the inverter input voltage by the inverter input current.

[0220] Item 43. A wireless power transmitter according to Item 40, wherein receiving multiple indications of receiver power from the wireless power receiver includes receiving the multiple indications at three or more operating points, the multiple indications including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission.

[0221] Item 44. A wireless power transmitter according to Item 43, wherein the three or more operating points include an operating point at minimum rectifier voltage and maximum receiver power, an operating point at nominal rectifier voltage and nominal receiver power, and an operating point at maximum rectifier voltage and minimum receiver power.

[0222] Item 45. A wireless power transmitter according to Item 43, wherein the multiple indications at three or more operating points include multiple samples at each of the three or more operating points.

[0223] Item 46. A wireless power transmitter according to Item 45, wherein the multiple samples at each of the three or more operating points include 25 or more samples at each of the three or more operating points.

[0224] Item 47. A wireless power transmitter according to Item 40, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

[0225] Item 48. The wireless power transmitter of Item 47, wherein the controller and communication circuitry further comprises logic or programming that calculates a predicted power loss based on the corresponding rectifier voltage and rectifier current and the one or more coefficients, and wherein the predicted power loss has the following form:

[0226]

[0227] Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

[0228] Item 49. A wireless power transmitter according to Item 40, wherein the regression analysis is performed on multiple indications of received receiver power including or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transmission and multiple determined measured power loss values ​​to calculate the one or more coefficients, including performing a baselining process, the baselining process including determining that the multiple indications of receiver power are linearly independent.

[0229] Item 50. A wireless power transmitter according to Item 49, wherein the baselining process also includes determining that the multiple received power level indications are located in a two-dimensional plane.

[0230] Various features and embodiments regarding foreign object detection in a wireless power transmission system are described above. Such an arrangement can be used in a variety of applications, but can be particularly advantageous when used with electronic devices such as mobile phones, tablet computers, laptops or notebook computers and accessories such as wireless headphones, styluses, etc. In addition, although many specific features and various embodiments have been described, it should be understood that the various features and embodiments may be combined in different ways in a particular embodiment unless otherwise specified as mutually exclusive. Therefore, the various embodiments described above are provided by way of example only and should not be construed as limiting the scope of the present disclosure. Various modifications and changes may be made to the principles and embodiments herein without departing from the scope of the present disclosure and without departing from the scope of the claims.

[0231] The foregoing describes an exemplary embodiment of a wireless power transmission system capable of conveying certain information between a PTx and a PRx in the system. The present disclosure contemplates that this information transfer improves the ability of devices to provide wireless power signals to each other in an efficient manner to facilitate battery charging, such as by sharing the power handling capabilities of the devices with each other. Entities implementing the present technology should be careful to ensure compliance with established privacy policies and / or privacy practices to the extent that any sensitive information is used in a particular implementation. In particular, such entities will be expected to implement and consistently apply privacy practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Implementers should inform users where personally identifiable information is expected to be transmitted in a wireless power transmission system, and allow users to "opt-in" or "opt-out" participation. For example, if a power transmitter is configured to poll for sensitive information from a power receiver, such information may be presented to the user when the user places the device onto the power transmitter.

Claims

1. A method performed by a control circuit of a wireless power transmitter for detecting a foreign object affected by an electromagnetic field associated with wireless power transfer from the wireless power transmitter to a wireless power receiver, the method comprising: receiving, from the wireless power receiver, a receiver power indication associated with the wireless power transfer, the receiver power indication comprising or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver; determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication to a transmitter power measured by the wireless power transmitter; calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the receiver power indication including or derived from a corresponding rectifier voltage or rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver; as well as The presence of a foreign object is determined in the event that the measured power loss exceeds the predicted power loss by more than a threshold value. 2 . The method of claim 1 , wherein the received receiver power indication is the rectifier voltage and the rectifier current, and the method further comprises calculating the receiver power based on the rectifier voltage and the rectifier current. 3 . The method of claim 1 , wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current. 4 . The method of claim 1 , wherein the transmitter power is calculated by the wireless power transmitter by multiplying an inverter input voltage by an inverter input current.

5. The method of claim 1 , further comprising calculating the one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by: receiving, from the wireless power receiver, a plurality of indications of receiver power, the plurality of indications of receiver power comprising or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer; determining a plurality of measured power loss values ​​by comparing a receiver power indication with a corresponding transmitter power measured by the wireless power transmitter, the plurality of measured power loss values ​​each corresponding to a received power level indication of the plurality of received power level indications associated with the wireless power transfer; as well as A regression analysis is performed on corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer and a plurality of indications of received receiver power and the determined plurality of measured power loss values ​​to calculate the one or more coefficients.

6. The method of claim 5, wherein receiving from the wireless power receiver multiple indications of receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer comprises receiving the multiple indications at three or more operating points.

7. The method of claim 6, wherein the three or more operating points include an operating point at a minimum rectifier voltage and a maximum receiver power, an operating point at a nominal rectifier voltage and a nominal receiver power, and an operating point at a maximum rectifier voltage and a minimum receiver power. 8 . The method of claim 6 , wherein the plurality of indications at three or more operating points comprises a plurality of samples at each of the three or more operating points. 9 . The method of claim 8 , wherein the plurality of samples at each of the three or more operating points comprises 25 or more samples at each of the three or more operating points.

10. The method of claim 5, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

11. The method of claim 10, wherein the predicted power loss has the following form: Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

12. The method of claim 5, wherein the regression analysis is performed on multiple indications of received receiver power associated with the wireless power transmission and multiple determined measured power loss values ​​to calculate the one or more coefficients, and further comprises performing a baselining process, the baselining process comprising determining that the multiple indications of receiver power are linearly independent.

13. The method of claim 12, wherein the baselining process further comprises determining that the plurality of indications of receiver power lie in a two-dimensional plane.

14. The method of claim 12, wherein performing the regression analysis on a plurality of indications of corresponding rectifier voltages and rectifier currents of the wireless power receiver and received receiver power associated with the wireless power transfer and the determined plurality of measured power loss values ​​to calculate the one or more coefficients comprises: calculating a first plurality of coefficients corresponding to an initial duty cycle having a wireless power transmission level below a first threshold in which another foreign object detection technique indicates that no foreign object is present; calculating a second plurality of coefficients corresponding to baseline capture periods having a wireless power transfer level above the first threshold; as well as The first and second pluralities of coefficients are compared to determine whether foreign matter was introduced during the baseline capture period.

15. The method according to claim 1, further comprising: If foreign matter is present, the presence of the foreign matter is mitigated by reducing the power level of the wireless power transfer or suspending the wireless power transfer.

16. A method performed by a control circuit of a wireless power transmitter for calculating one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and a wireless power receiver for detecting a foreign object affected by an electromagnetic field associated with wireless power transfer from the wireless power transmitter to the wireless power receiver, the method comprising: receiving, from the wireless power receiver, a plurality of indications of receiver power levels, the plurality of indications of receiver power levels comprising or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer; determining a plurality of measured power loss values ​​by comparing the receiver power indication to a corresponding transmitter power measured by the wireless power transmitter, the plurality of measured power loss values ​​each corresponding to one of a plurality of indications of the receiver power associated with the wireless power transfer; as well as The regression analysis is performed on a plurality of indications of received receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer and a plurality of determined measured power loss values ​​to calculate the one or more coefficients.

17. The method of claim 16, wherein the one or more coefficients include a first coefficient related to the rectifier voltage and a second coefficient related to the rectifier current.

18. The method of claim 17, further comprising calculating a predicted power loss based on the corresponding rectifier voltage and rectifier current and the one or more coefficients, wherein the predicted power loss has the following form: Wherein α is a first coefficient related to the rectifier voltage, and β is a second coefficient related to the rectifier current.

19. A wireless power transmitter, the wireless power transmitter comprising: a wireless power transmitter coil configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver; an inverter configured to receive input power and generate an output that drives the wireless power transmitter coil; as well as a controller and communication circuitry coupled to the inverter and the wireless power transmitter coil, the controller and communication circuitry controlling the inverter to regulate wireless power transfer to the wireless power receiver, wherein the controller and communication circuitry includes logic or programming to detect a foreign object affected by an electromagnetic field associated with wireless power transfer to the wireless power receiver by: receiving, from the wireless power receiver, a receiver power indication associated with the wireless power transfer, the receiver power indication comprising or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver; determining a measured power loss associated with the wireless power transfer by comparing the receiver power indication to a transmitter power measured by the wireless power transmitter; calculating a predicted power loss based on the receiver power indication associated with the wireless power transfer, the receiver power indication including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver; as well as The presence of a foreign object is determined in the event that the measured power loss exceeds the predicted power loss by more than a threshold value.

20. A wireless power transmitter, comprising: a wireless power transmitter coil configured to magnetically couple to a wireless power receiver coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver; an inverter configured to receive input power and generate an output that drives the wireless power transmitter coil; as well as a controller and communication circuitry coupled to the inverter and the wireless power transmitter coil, the controller and communication circuitry controlling the inverter to regulate wireless power transmission to the wireless power receiver, wherein the controller and communication circuitry includes logic or programming that calculates one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver by: receiving, from the wireless power receiver, a plurality of indications of receiver power, the plurality of indications of receiver power comprising or derived from corresponding rectifier voltages and rectifier currents of the wireless power receiver associated with the wireless power transfer; determining a plurality of measured power loss values ​​by comparing the receiver power indication to a corresponding transmit wireless power level measured by the wireless power transmitter, the plurality of measured power loss values ​​each corresponding to one of a plurality of indications of the receiver power associated with the wireless power transfer; as well as The regression analysis is performed on a plurality of indications of received receiver power including or derived from a corresponding rectifier voltage and rectifier current of the wireless power receiver associated with the wireless power transfer and a plurality of determined measured power loss values ​​to calculate the one or more coefficients.

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