Friendly metal loss estimation for wireless power transmission

Abstract

To provide friendly metal loss estimation for wireless power transmission.SOLUTION: In a wireless power transmission system 100, a method for estimating friendly metal loss associated with wireless power transmission from a wireless power transmitter 110 to a wireless power receiver 120 includes obtaining an instruction of received power including a rectifier voltage and a rectifier current of the wireless power receiver, and calculating the friendly metal power loss based on the instruction of the rectifier voltage and the rectifier current of the wireless power receiver and one or more coefficients corresponding to baseline wireless power transmission between the wireless power transmitter and the wireless power receiver. Calculating the friendly metal power loss may use an equation having a certain form, where b is a coefficient related to the rectifier current, c is a coefficient related to the rectifier voltage, and a is a coefficient related to a transmitter current ITX.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] Wireless power transfer is used in a variety of electronic devices. For example, smartphones, tablet computers, smartwatches, wireless earbuds, styluses, and the like may employ wireless power transfer to facilitate charging of batteries within the devices. In some applications, higher levels of wireless power transfer may be desired, for example, to provide faster charging. Such higher power transfer levels may benefit from techniques for improving estimation of losses, including losses associated with "friendly metal" associated with wireless power transmitter and / or wireless power receiver devices. Summary of the Invention

[0002] The wireless power transmitter may include a wireless power transmission coil configured to magnetically couple to a wireless power transmission coil of the wireless power receiver to wirelessly transmit power to the wireless power receiver; an inverter configured to receive input power and generate an output that drives the wireless power transmission coil; and a controller and communication circuit coupled to the inverter and the wireless power transmission coil and controlling the inverter to adjust the wireless power transmission to the wireless power receiver, wherein the controller and communication circuit estimates friendly metal loss associated with the wireless power transmission to the wireless power receiver by: receiving from the wireless power receiver an indication of received power including a rectifier voltage and a rectifier current of the wireless power receiver associated with the wireless power transmission; calculating friendly metal power loss based on the received rectifier voltage and the received 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 adjusting the wireless power transmission to the wireless power receiver using the friendly metal power loss.

[0003] The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver may have been derived by performing a regression analysis on the received indications of received power including or derived from corresponding rectifier voltages and rectifier currents of another wireless power receiver associated with another wireless power transmission and the determined measured power loss values ​​derived therefrom to calculate the one or more coefficients. The one or more coefficients may include a first coefficient related to the rectifier current and a second coefficient related to the rectifier voltage.

[0004] To calculate the friendly metal power loss, an equation having the following form can be used:

number

[0005] The controller and communication circuitry can further receive one or more power loss scaling factors from the wireless power receiver and estimate the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, where the one or more power loss scaling factors are based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

[0006] The controller and communication circuitry can further receive one or more power loss scaling factors from the wireless power receiver and estimate the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, where the one or more power loss scaling factors are based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

[0007] A method performed by control circuitry of a wireless power transmitter or a wireless power receiver to estimate friendly metal loss associated with a wireless power transmission from a wireless power transmitter to a wireless power receiver may include obtaining an indication of received power including a rectifier voltage and a rectifier current of the wireless power receiver, calculating friendly metal power loss based on the indication of the 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 adjusting the wireless power transmission using the friendly metal power loss, where the rectifier voltage is the rectifier output voltage and the rectifier current is the rectifier output current, and calculating the friendly metal power loss uses an equation having the following form:

number

[0008] The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. The one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver may have been derived by performing a regression analysis on a received plurality of indications of received power and corresponding rectifier voltage and rectifier current of another wireless power receiver associated with another wireless power transmission, and a determined plurality of measured power loss values ​​derived therefrom, to calculate the one or more coefficients.

[0009] The method may further include receiving one or more power loss scaling factors from the wireless power receiver, and calculating the friendly metal power loss may be based on the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and the actual wireless power transmitter or wireless power receiver.

[0010] The wireless power transmitter may include a wireless power transmission coil configured to magnetically couple to a wireless power transmission coil of the wireless power receiver to wirelessly transmit power to the wireless power receiver, an inverter configured to receive input power and generate an output that drives the wireless power transmission coil, and a controller and communication circuit coupled to the inverter and the wireless power transmission coil and controlling the inverter to adjust the wireless power transmission to the wireless power receiver. The controller and communication circuit may estimate friendly metal loss associated with wireless power transmission to the wireless power receiver by receiving an indication of received power from the wireless power receiver, the indication including a rectifier voltage and a rectifier current of the wireless power receiver, calculating friendly metal power loss based on the rectifier voltage and the 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 adjusting the wireless power transmission to the wireless power receiver using the friendly metal power loss. The rectifier voltage may be a rectifier output voltage, and the rectifier current may be a rectifier output current. To calculate the friendly metal power loss, an equation having the following form can be used:

number

[0011] The one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and another wireless power receiver may have been derived by performing a regression analysis on the received plurality of indications of received power including or derived from a corresponding rectifier voltage and rectifier current of the other wireless power receiver associated with the other wireless power transmission and the determined plurality of measured power loss values ​​derived therefrom to calculate the one or more coefficients. The controller and communications circuitry may further receive one or more power loss scaling coefficients from the wireless power receiver and estimate the friendly metal loss by calculating the friendly metal power loss as a function of the one or more power loss scaling coefficients, the one or more power loss scaling coefficients being based on the pairing between the reference wireless power transmitter or wireless power receiver and the actual wireless power transmitter or wireless power receiver. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a simplified block diagram of a wireless power transfer system.

[0013] [Figure 2A] 1 illustrates various configurations of a wireless power transfer system. [Figure 2B] 1 illustrates various configurations of a wireless power transfer system. [Figure 2C] 1 illustrates various configurations of a wireless power transfer system.

[0014] [Figure 3] 1 shows a simplified flowchart of a foreign object detection technique based on power calculations.

[0015] [Figure 4] 1 shows a flowchart of the friendly metal loss estimation technique.

[0016] [Figure 5A] 1 shows a circuit model and related equations for a wireless power transfer system. [Figure 5B] 1 shows a circuit model and related equations for a wireless power transfer system.

[0017] [Figure 6] FIG. 1 is a circuit diagram of an exemplary wireless power system, according to one embodiment.

[0018] [Figure 7] 1 is a flowchart of exemplary operations associated with using a device in a wireless power system, according to an embodiment.

[0019] [Figure 8] 1 is a flowchart of exemplary operations associated with using a device in a wireless power system, according to an embodiment.

[0020] [Figure 9] 1 illustrates aspects of an ecosystem scaling configuration for a wireless power transfer system.

[0021] [Figure 10] 10 illustrates some combinations of monitorable parameters in a wireless power transfer system that can be used for friendly metal loss estimation. DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings in this disclosure represent structures and devices in block diagram form in order to avoid obscuring the present invention. In the interest of clarity, not all features of an actual implementation are described in this specification. Moreover, the language used in this specification has been chosen solely for purposes of readability and explanation, and not to limit or restrict the disclosed subject matter. Rather, the appended claims are intended for such purposes.

[0023] Various embodiments of the disclosed concepts are illustrated in the accompanying drawings, by way of example, and not by way of limitation, wherein like reference numerals indicate like elements. For simplicity and clarity of illustration, where considered appropriate, reference numerals have been repeated among different drawings to indicate corresponding and / or similar elements. Additionally, numerous specific details have been described to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the relevant associated functionality being described. References to "an," "one," or "another" embodiment in the present disclosure do not necessarily refer to the same or different embodiments, but rather to at least one. A given drawing may be used to illustrate multiple embodiments or multiple species of the present disclosure, and not all elements in the drawing may be required for a given embodiment or species. A reference numeral, if provided in a given drawing, may refer to the same element throughout the drawings, but may not be repeated in all drawings. The drawings are not to scale unless otherwise indicated and the proportions of certain parts may be exaggerated to better show the details and features of the present disclosure. Wireless Power Transfer

[0024] FIG. 1 shows a simplified block diagram of a wireless power transfer system 100. The wireless power transfer system includes a power transmitter (PTx) 110 that transmits power wirelessly to a power receiver (PRx) 120, such as via inductive coupling 130. The power transmitter 110 can receive input power, which is converted by an inverter 114 to an AC voltage having specific voltage and frequency characteristics. The inverter 114 can be controlled by a controller / communications module 116, which operates as described further below. In various embodiments, the inverter controller and communications module can be implemented in a common system, such as a system based on a microprocessor, microcontroller, or the like. In other embodiments, the inverter controller can be implemented by a separate controller module and communications module having means for communication therebetween. The inverter 114 can be configured using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and can be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc., fabricated using silicon, silicon carbide, or gallium nitride devices).

[0025] The inverter 114 can deliver the generated AC voltage to the transmit coil 112. In addition to the wireless coil that enables magnetic coupling to the receiver, the transmit coil block 112 shown in FIG. 1 may include tuning circuit components, 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 or different operating frequencies. The wireless coil itself can be configured in a variety of different ways. In some embodiments, the wireless coil can be formed as a winding of wire wrapped around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are possible and can be used in conjunction with the various embodiments described herein. The wireless transmit coil can also include a core of a magnetically permeable material (e.g., ferrite) configured to affect the magnetic flux pattern of the coil in a manner suitable for a particular application. The teachings herein can be applied in conjunction with any of a wide variety of transmit coil arrangements suitable for a given application. In some contexts, the transmit coil 112 can be described as a transmit coil or transmitter coil. In some embodiments, devices may be capable of bidirectional operation, i.e., transmitting or receiving wireless power, and thus the wireless power transmission coil of such devices may be capable of transmitting or receiving power depending on the mode of operation.

[0026] The PTx controller / communications module 116 can monitor the transmission coil and use information derived therefrom to control the inverter 114 appropriately for a given situation. For example, the controller / communications module can be configured to operate the inverter 114 at a given frequency or output voltage depending on a particular application. In some embodiments, the controller / communications module can be configured to receive information from the PRx device and control the inverter 114 accordingly. This information can be received via the power transmission coil (i.e., in-band communication) or via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communications module 116 can detect and decode signals (such as voltage, frequency, or load variations) imposed on the magnetic link by the PRx to receive the information, and can instruct the inverter to modulate the delivered power by manipulating various parameters (such as voltage, frequency, etc.) of the generated voltage to transmit the information to the PRx. In some embodiments, the controller / communications module may be configured to communicate data to the PRx employing frequency shift keying (FSK) communications, in which the frequency of the inverter signal is modulated. The controller / communications 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 / communications module 126 may be configured to vary the current drawn at the receiver side to manipulate the waveform seen on the Tx coil to deliver information from the PRx to the PTx. For out-of-band communications, additional modules may be provided to enable communication between the PTx and PRx, such as WiFi, Bluetooth, or other wireless links, or any other suitable communications channel.

[0027] As mentioned above, the controller / communications module 116 may be a single module, for example, provided on a single integrated circuit, or may be constructed from multiple modules / devices provided on different integrated circuits, or a combination of integrated circuits and discrete circuits with analog, digital, and / or programmable components that may be field programmable or updatable. The teachings herein are not limited to any particular arrangement of controller / communications circuitry.

[0028] The PTx device 110 may optionally include other systems and components, such as a separate communications module 118. In some embodiments, the communications module 118 can communicate with a corresponding module tag in the PTx via the power transfer coil. In other embodiments, the communications module 118 can communicate with a corresponding module using a separate physical channel 138.

[0029] As mentioned above, the wireless power transmission system also includes a wireless power receiver (PRx) 120. The wireless power receiver may include a transmit coil 122 that may be magnetically coupled (130) to the transmit coil 112. Similar to the transmit coil 112 described above, the transmit coil block 122 shown in FIG. 1 may include tuning circuit components, such as additional inductors and capacitors, to facilitate transmitter operation under different conditions, such as different degrees of magnetic coupling to the receiver or different operating frequencies. The wireless coil itself may be configured in a variety of different ways. In some embodiments, the wireless coil may be formed as a winding of wire wound around a suitable bobbin. In other embodiments, the wireless coil may be formed as a trace on a printed circuit board. Other arrangements are possible and may be used in conjunction with the various embodiments described herein. The wireless transmit coil may also include a core of a magnetically permeable material (e.g., ferrite) configured to affect the coil's magnetic flux pattern in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a wide variety of transmit coil arrangements suitable for a given application. In some contexts, the transmit coil 122 may be described as a receive coil or a receiver coil. In some embodiments, devices may be capable of bidirectional operation, i.e., transmitting or receiving wireless power, and thus the wireless power transmission coil of such devices may be capable of transmitting or receiving power depending on the mode of operation.

[0030] The transmit coil 122 outputs an AC voltage induced therein by magnetic induction through the transmit coil 112. This output AC voltage may be provided to a rectifier 124, which provides DC output power to one or more loads associated with the PRx device. The rectifier 124 may be controlled by a controller / communications module 126, which operates as described further below. In various embodiments, the rectifier controller and communications module may be implemented in a common system, such as a system based on a microprocessor, microcontroller, or the like. In other embodiments, the rectifier controller may be implemented by a separate controller module and communications module having means of communication therebetween. The rectifier 124 may be configured 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., fabricated using silicon, silicon carbide, or gallium nitride devices).

[0031] The PTx controller / communications module 126 can monitor the transmit coil and use information derived therefrom to appropriately control the rectifier 124 depending on given circumstances. For example, the controller / communications module can be configured to operate the rectifier 124 to provide a given output voltage depending on a particular application. In some embodiments, the controller / communications module can be configured to transmit information to the PTx device to effectively control the power delivered to the receiver. This information can be received and transmitted via the power transmit coil (i.e., in-band communication) or can be transmitted via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communications module 126 can transmit information to the PTx, for example, by modulating the load current or other electrical parameters of the received power. In some embodiments, the controller / communications module 126 can be configured to detect and decode signals (such as voltage, frequency, or load variations) applied by the PTx to the magnetic link in order to receive information from the PTx. In some embodiments, the controller / communications module 126 may be configured to receive frequency shift keying (FSK) communications, in which the frequency of the inverter signal is modulated to communicate data to the PRx. The controller / communications 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 / communications module 126 may be configured to vary the current drawn at the receiver to manipulate the waveform seen on the Tx coil to deliver information from the PRx to the PTx. For out-of-band communications, additional modules may be provided to enable communication between the PTx and PRx, such as WiFi, Bluetooth, or other wireless links, or any other suitable communications channel.

[0032] As mentioned above, the controller / communications module 126 may be a single module, for example, provided on a single integrated circuit, or may be constructed from multiple modules / devices provided on different integrated circuits, or a combination of integrated circuits and discrete circuits with analog, digital, and / or programmable components that may be field programmable or updatable. The teachings herein are not limited to any particular arrangement of controller / communications circuitry. The PRx device 120 may optionally include other systems and components, such as a communications (“comms”) module 128. In some embodiments, the communications module 128 can communicate with a corresponding module in the PTx via a power transfer coil. In other embodiments, the communications module 128 can communicate with a corresponding module or tag using a separate physical channel 138.

[0033] Many variations and extensions of the wireless power transmission system 100 described above are possible, and the following teachings are applicable to any such variations and extensions. Improved Friendly Metal Loss Estimation

[0034] In some applications, it may be desirable to increase the rate of power transfer from a wireless power transmitter to a wireless power receiver. One approach to achieving this may be the use of a magnetic power profile (“MPP”), such as that described in the Qi 2.0 specification published by the Wireless Power Consortium (“WPC”). The MPP may use magnets to provide improved alignment between the wireless power transmission coils of the wireless power transmitter and the wireless power receiver. This improved alignment may be one aspect of facilitating higher levels of power transfer. Another aspect of achieving higher levels of power transfer may include improved techniques for foreign object detection and associated losses. In some cases, the presence of a foreign object near the wireless power transmitter and / or receiver may absorb power and result in undesired heating of the foreign object. Mitigating these effects may be based on power loss calculation (“PLA”) techniques, which may use a comparison of the power transmitted by the wireless power transmitter and the power received by the wireless power receiver to determine the power loss associated with wireless power transfer.

[0035] By modeling the expected loss for a given wireless power transfer level, the presence of a foreign object may be inferred if the actual loss experienced exceeds the expected loss by a certain threshold amount. The expected loss may arise from a variety of sources, including losses associated with the circuitry of the wireless power transmitter and / or receiver, "friendly metal" within the housing or other structure of the wireless power transmitter and / or receiver, etc. If the actual loss experienced (e.g., measured) exceeds a level expected based on modeling, mitigation techniques may be employed, such as reducing or stopping power transfer, providing an audio or visual indication (or other feedback) to the user, etc. Introducing friendly metal loss estimation

[0036] Exemplary friendly metal loss modeling and estimation techniques are described in Applicant's co-pending U.S. patent application Ser. No. 18 / 166,839, entitled "Friendly Metal Loss Estimation," filed February 9, 2023, which is incorporated by reference in its entirety, certain teachings of which are reproduced below.

[0037] Wireless power transfer as described above depends on the degree of electromagnetic coupling between the PTx and PRx. For example, in an inductive charging system, the transmission coil 112 and the transmission coil 122 can be considered loosely coupled transformers. Therefore, the relative positions of the PTx and PRx can affect the degree of magnetic coupling between the PTx and PRx, which can affect the power transfer capability of the system. FIG. 2A shows a simplified diagram of a PTx (110)-PRx (120) system. Both devices are shown in a plan view (top of the figure) and a cross-sectional view (bottom of the figure). The PTx device 110 includes a transfer coil 112, and the PRx device 120 includes a transfer coil 122. In some embodiments, the PTx device 110 may be a wireless charging pad, mat, or stand (or other wireless power transmission device), and the PRx device 120 may be a mobile phone, tablet computer, smartwatch (or other wireless power receiver device). Although each device is shown as being generally rectangular in shape with a generally circular charging coil, it should be understood that other configurations are possible.

[0038] FIG. 2B shows the PTx 110 and PRx 120 in “optimal” alignment. In FIG. 2B, the devices, and more specifically, their wireless power transmission coils, are aligned horizontally (as shown in the plan view) and vertically (as shown in the cross-sectional view), as close to each other as possible. In this context, horizontal and vertical are used merely as terms of convenience; the true orientation of the system may vary, and the following description is applicable to a system in any such orientation; however, “horizontal” and “vertical” continue to be used to clarify the context. FIG. 2C shows the devices with a slight misalignment. More specifically, there is a radial displacement “r,” which can be understood by noting that the centers of coils 112 and 122 no longer coincide in the plan view. Such a radial displacement could be caused by several things, such as, for example, a slight misplacement of the phone relative to the charging pad. Additionally, there is also a vertical displacement “z,” which can be understood by noting the separation between the PTx device 110 and the PRx device 120 in the cross-sectional view. This vertical displacement can be caused by any number of things, such as a phone housed in a case or cover. The cross-sectional view also shows lateral / radial displacement. It will be understood that in some situations there may be only radial displacement or only vertical displacement.

[0039] The above-mentioned offset can reduce the degree of magnetic coupling between the PTx and PRx devices. This reduced magnetic coupling can limit the amount of power that can be delivered from the PTx 110 to the PRx 120. More specifically, reduced coupling between the PTx 110 and the PRx 120 reduces the proportion of power transmitted from the PTx 110 that is received by the PRx 120. Furthermore, the reduced degree of magnetic coupling between the PTx 110 and the PRx 120 can be addressed, at least in part, by retuning the receiver (or transmitter) circuitry accordingly. For example, one or more tuning capacitors may be included in the PTx circuit between the inverter 114 and the transmit coil 112. Similarly, one or more tuning capacitors may be included in the PRx circuit between the rectifier 124 and the transmit coil 122. The function of each of these capacitors is to tune the circuit by adjusting the resonant frequency of the respective circuit, and they may include, for example, a series resonant capacitor in series with the respective coil or a parallel resonant capacitor in parallel with the respective coil, depending on the particular designed operating mode of the circuit. To this end, multiple selectable capacitors may be provided in either or both of the PTx 110 and PRx 120, with the appropriate tuning capacitance being selected by the individual device based on an estimate of the coupling coefficient derived from various observable circuit parameters such as voltage, current, etc.

[0040] In wireless power transfer systems, it may be desirable to detect the presence of "foreign objects." For example, objects such as coins, keys, or paper clips near the wireless power transfer coil can receive a portion of the power transmitted by the PTx 110, which can limit the power available to the PRx 120 and induce eddy currents in the foreign object. Wireless power transfer systems can employ various foreign object detection ("FOD") techniques. One group of FOD techniques is based on power accounting. The basic principle of power calculation is that the power transmitted by the PTx 110 minus the power received by the PRx 120 is the "lost" power. This lost power can be considered to fall into one of three places: Some power can be absorbed by so-called "friendly metal" of the PTx 110; some power can be absorbed by friendly metal of the PRx 120; and some power can be absorbed by foreign objects. "Friendly metal" in this context refers to the metal or other conductive structures that make up the PTx and PRx. These may be frame or case parts, internal circuit elements, magnets, etc. These elements are designated as friendly metals because their presence is known and considered in the design of wireless power transfer systems. Losses not associated with friendly metals may be assumed to be associated with foreign objects.

[0041] FIG. 3 shows a simplified flowchart of a power calculation-based foreign object detection technique 330. Starting at block 331a, the PTx 110 calculates the power transmitted by the PTx. This can be accomplished by multiplying the output voltage of the inverter 114 by the current through the transmit coil 112. In some implementations, the power considered transmitted by the PTx is the output voltage times the current minus the losses in the transmit coil. Furthermore, it is the output-side value that needs to be used. Sometimes, these values, such as the output RMS current, which is AC, can be more difficult to measure. Alternatively, the input voltage (and / or current) can be used, but then inverter and / or coil losses can be subtracted to improve accuracy. Correspondingly, block 331b calculates the power received by the PRx 120. In some implementations, this is accomplished by multiplying the current through the transmit coil 122 by the input voltage of the rectifier 124. In some applications, it can be difficult to make these measurements on the AC side of the PRx rectifier. Alternatively, the received power may be calculated as the power from (rather than to) the rectifier of the PRx 120 plus estimated losses in the rectifier and coil 122. Additionally or alternatively, PTx-side power measurements or power estimates may be used for power estimation. These PTx-side measurements may be based on DC input power to the PTx 110 or AC measurements of the output of the inverter 114. In summary, the power transmitted by the PTx 110 or the power received by the PRx 120 may be estimated by directly measuring the current flowing through the respective wireless power transmission coils (112 / 122) or indirectly using the DC current entering the transmitter or leaving the receiver. The respective voltages and currents may be monitored by sensors coupled to separate controller circuits located in the controller and communications modules 116 (for the PTx 110) and 126 (for the PRx 120). Implementations of such measurement systems are known to those skilled in the art and therefore will not be repeated here.

[0042] At block 332b, the PRx 120 may communicate the received power value to the PTx 110, as shown in block 332a. This description assumes that foreign object detection is performed by the PTx 110, e.g., by circuitry located within the controller / communications module 126. However, in some applications, the foreign object detection process may be performed on the PRx 120, in which case the PTx 110 may transmit its measured power value to the PRx 120. In either case, this may be done by either in-band communication (including modulation of the wireless power, such as transmitted voltage, current, frequency, phase, etc.) or out-of-band communication using a separate communications module 118 / 128 and a separate communications channel 138, which may be near field communication (NFC), Bluetooth communication, Wi-Fi communication, etc., as described above. Alternatively, rather than transmitting a calculated power value, a device may transmit underlying measurements (e.g., voltage and current measurements) that allow the other device to calculate the individual power.

[0043] In either case, in block 333, the PTx (or PRx, if performing foreign object detection) may calculate the measured power loss as the difference between the transmitted power and the received power. As described above, this measured power loss may include two components: friendly metal loss (associated with either the PTx 110 or the PRx 120) and foreign object loss. Thus, in block 334, the PTx (or PRx, if performing foreign object detection) estimates the friendly metal loss. Exemplary friendly metal loss estimation techniques are described in more detail below with respect to FIG. 4. For purposes of this description, estimating friendly metal loss may be considered a calculation based on observable circuit parameters (such as voltage, current, coupling coefficient, etc.) and predetermined parameters relating these observable circuit parameters to the resulting losses. These parameters may be part of a model that may be derived analytically or empirically during the design of a particular wireless power transfer device. These model parameters may either be stored in a memory associated with the controller of an individual wireless power transmission device and used by that device to estimate its friendly metal loss, or provided to a mating device to enable that device to estimate its mating friendly metal loss.

[0044] Once the friendly metal loss is estimated / determined (block 334), the device performing foreign object detection can calculate the net foreign object loss (block 335), which may be the difference between the calculated measured power loss (block 333) and the estimated friendly metal loss (block 334). The net foreign object loss can then be compared to a net loss threshold (block 336). If the net foreign object loss is less than the threshold, it can be inferred that a foreign object is not present (block 338) and no mitigation is required. Alternatively, if the net foreign object loss is greater than the threshold (block 336), it can be inferred that a foreign object is present (block 337) and some mitigation can be employed. Such mitigation can include reducing or limiting the amount of power transmitted, interrupting power transmission, providing an alert to the user, such as an audiovisual alert, etc.

[0045] In a high-performance wireless power transfer system, even relatively small levels of foreign object loss can be significant, and therefore it is desirable to be able to detect such loss at levels somewhat lower than the friendly metal loss. Therefore, accuracy of the estimated friendly metal loss is desirable. For example, if the estimated friendly metal loss is higher than the actual friendly metal loss, there may be undesirable eddy currents induced in the foreign object. Alternatively, if the estimated friendly metal loss is lower than the actual friendly metal loss, the system may unnecessarily apply mitigations such as those described above. However, these mitigations may present an undesirable user experience, such as slower or completely interrupted charging, spurious user interface messages, etc. Furthermore, all of these issues may become more pronounced as typical wireless power levels increase from relatively low levels (e.g., 5 W) to relatively high levels (e.g., 20 W or higher).

[0046] One way to estimate friendly metal loss is as a function of the current through the PTx transmit coil 112. Friendly metal loss can be measured as a linear function of the square of the transmit coil current.

number

[0047] Regarding the first improvement, the transmitting coil current I TX In addition, the inverter's DC input voltage V in The friendly metal loss model can be improved by including: Alternatively, the inverter output voltage or any other suitable voltage can be used. The estimated friendly metal loss is therefore given by:

number

[0048] For the second refinement, different model coefficients may be provided for different coupling conditions. For example, a first set of coupling coefficients may be used for high coupling conditions where the coupling coefficient k between the PTx 110 and the PRx 120 is above a threshold, and a second set of coupling coefficients may be used for low coupling conditions where the coupling coefficient k between the PTx 110 and the PRx 120 is below the threshold. Thus, when both the first refinement and the second refinement are used, the estimated friendly metal loss may be given by:

number

number

number

[0049] Such an arrangement may leverage existing logic and functionality in the control circuitry of a wireless power transmitter (or receiver). For example, as noted above, some wireless power transmission devices may include controller circuitry that measures several circuit parameters (e.g., voltage and current) and estimates the coupling coefficient k based on these values. The controller circuitry may then select a tuning capacitor (or capacitors) to provide appropriate tuning for the circuit for such coupling coefficient. This same calculation may then be used to select appropriate coefficients for the friendly metal loss estimation model.

[0050] 4 shows a flowchart of a friendly metal loss estimation technique 440. Starting at block 441, the FOD system may measure observable parameters of the wireless power transfer system. These measurements may be performed by the PTx 110, if the PTx 110 implements the FOD system, or by the PRx 120, if the PRx 120 implements the FOD system. These observable parameters may include wireless power transfer voltage, current, phase shift, frequency, impedance, etc., as well as parameters that may be derived therefrom, such as power consumption, efficiency, coupling coefficient, etc. A device implementing an FOD system may perform these measurements using appropriate sensors in combination with the device's control circuitry, as described above.

[0051] In block 442b, the FOD system implemented by the PTx 110 may receive friendly metal parameters from the PRx 120 (block 442a). If the FOD system is implemented by the PRx 120, the opposite may be true. This communication may occur using either in-band or out-of-band communication, as described above. The transmitted friendly metal parameters may include model coefficients as described above, including model parameters for current, voltage, and coupling coefficients. In one embodiment, the PRx may transmit a list of parameters including current and voltage parameters for a first coupling coefficient and current and voltage parameters for a second coupling coefficient. For a wireless power transfer system capable of operating at different power transfer frequencies, it may be appropriate to include different parameters for the different operating frequencies. In some applications, the communication may occur according to a predetermined industry standard, such as the Qi standard for wireless power transfer / charging promulgated by the Wireless Power Consortium (WPC).

[0052] In block 443, the FOD system may estimate friendly metal loss from the observables obtained in block 441 and the parameters received from the counterpart device. The FOD system may also have friendly metal loss model parameters associated with it, which may correspond to different coupling coefficients and / or operating frequencies of the received friendly metal loss model parameters received from the counterpart device. Then, in block 444, the estimated friendly metal loss may be provided to an FOD system, such as that described above with respect to FIG. 3, for foreign object detection.

[0053] Below we describe an improved MPP power loss calculation (MPLA) technique that can be used to further improve the accuracy of expected loss estimation. MPLA, defined in the Qi v2.0 specification, is a method for calculating friendly metal losses (P FM) modeling is assumed. To improve accuracy, a new model of friendly metal losses is proposed to take into account the fluctuations of the rectified voltage and current. Further friendly metal loss explanations

[0054] MPLA power loss estimation begins by estimating the power delivered to the foreign object by estimating the difference between the power transmitted by the wireless power transmitter and the power received by the wireless power receiver. In at least some embodiments, this comparison can be performed by a controller circuit located in the wireless power transmitter, while in some embodiments, this comparison may be performed by a controller circuit located in the wireless power receiver. In either case, the comparison can be expressed by the following equation:

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[0055] In some applications, various improvements to wireless power transmission can be achieved by varying the rectifier voltage VRECT, i.e., the output voltage of the rectifier 124 in the wireless power receiver. (See, for example, 124 in FIG. 1.) In such cases, the rectified voltage and current (V RECT and I RECT To account for the variability of the FMloss It may be desirable to extend the friendly metal loss:

number

number

[0056] 5A and 5B show the derivation of the above model. More specifically, FIG. 5A shows an equivalent circuit 500 that can be used to model a wireless power transfer system. In the equivalent circuit 500, the inverter input voltage is represented by a voltage source Vin, and the load on the wireless power receiver is represented by a resistor R L The wireless power transmitter current i TX is the capacitance C, which represents the tuning capacitance of the wireless power transmitter. TX , a resistance R representing the conduction losses associated with the wireless power transmitter circuit CONN_TX , and the resistance R, which represents the loss in the wireless power transmission coil of the wireless power transmitter. COIL_TX , a resistance R representing friendly metal losses associated with metal or other conductive structures within the wireless power transmitter. FM_TX , and an inductance L representing the leakage inductance of the wireless power transmission coil of the wireless power transmitter. TX_LK The wireless power transmitter current i TX is then the magnetizing current i M and receiver current i RX The magnetizing current i M is the inductance L that represents the magnetization effect of the wireless power transmission coil. M and resistor R M The receiver current i RX is the inductance L, which represents the leakage inductance of the wireless power transmission coil of the wireless power receiver. RX_LK , R, which represents the friendly metal losses associated with metal or other conductive structures in the wireless power receiver. FM_RX, R, which represents the loss in the wireless power transmission coil of the wireless power receiver. COIL_RX , a resistance R representing the conduction losses associated with the wireless power receiver circuit CONN_RX , and a capacitance C representing the tuning capacitance of the wireless power receiver. RX Rather than specific physical devices, the circuit elements described above may represent such devices and / or may be lumped parameters that represent or model multiple physical components or structures.

[0057] 5A, equation 501 describes the interrelationships between the various circuit elements and parameters of equivalent circuit model 500. These equations can be combined to generate equation 502. Then, with further reference to FIG. 5B, the equations can be further manipulated to generate equation 503, which is:

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[0058] The above explanation is based on the square of the transmitter current

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[0059] Rectifier voltage VRECT and rectifier current I RECT Further aspects of power loss accounting, including losses due to friendly metal, from this perspective are described in Applicant's co-pending U.S. patent application Ser. No. 18 / 617,103, entitled "Power Transfer Accounting for Wireless Power Transfer," filed Mar. 26, 2024, and incorporated by reference in its entirety.

[0060] Ecosystem Scaling

[0061] The accuracy of friendly metal loss estimation may vary depending on different possible wireless power transmitter and wireless power receiver pairings. In some implementations, baseline values ​​and / or adjustments (e.g., scaling factors, offsets, etc.) may be determined for various pairs of wireless power transmitters and wireless power receivers, e.g., at the time of manufacture, and stored in one or more of the wireless power transmitter and power receiver devices. However, as the number of potential transmitter-receiver pairs becomes large, this may quickly become impractical. Therefore, it may be desirable to provide one or more baseline value pairs for each transmitter based on one or more “reference” or “golden” receiver pairings. Each receiver may then be characterized relative to one or more of the reference / golden receivers and provided with its own stored values ​​corresponding to such characterization. For example, this may be implemented as different scaling factors for the reference / golden receivers. The wireless power receiver can then provide the scale factor to the wireless power transmitter, which can then adjust its friendly metal estimate based on the stored reference value and scaling factor that accounts for differences in the magnetic parameters of the particular wireless power transmission device, such as the inductance (L) of the wireless power transmission coil, the quality factor (Q) of the coil, etc.

[0062] Exemplary techniques for loss measurement scaling are described in the applicant's U.S. patent application Ser. No. 17 / 681,363, entitled "Wireless Power Systems with Shared Inducive Loss Scaling Factors," filed February 25, 2022, the entirety of which is incorporated herein by reference, and specific teachings thereof are reproduced below.

[0063] To accurately estimate foreign object power loss values, various potential sources of power loss in a wireless power system must be considered. Some power losses exhibited by the power transmitter and receiver are unrelated to the magnetic properties of the transmitter and receiver (e.g., switching losses, losses dependent on the drain-source resistance of field-effect transistors in inverters and rectifiers, etc.). Losses such as these can be accounted for by characterizing the relevant device components (e.g., by ascertaining the drain-source resistance of the transistors using measurements made during manufacturing and / or other testing).

[0064] Transmitters and receivers also exhibit power losses that depend on the inductive properties of the transmitter and receiver (e.g., losses that depend on the magnetic properties of the coupled transmitter and receiver, sometimes referred to as coupling-dependent losses, inductive losses, magnetic losses, etc.). Examples of power losses that depend on the magnetic properties of the transmitter and receiver include 1) coil losses that depend on the alternating current (AC) resistance of the coupled transmission coils, 2) friendly metal losses (e.g., power losses due to eddy currents induced in the metal housing of a receiving device), and 3) foreign object losses that occur when a foreign object is present between the transmitter and receiver. These power losses that depend on the magnetic properties of the transmitter and receiver can be characterized in terms of LQK magnetic parameters, where L refers to the inductance of the transmission coil, Q refers to the quality factor of the coil, and K refers to the magnetic coupling of the coil.

[0065] In a wireless power ecosystem with many different transmitters and receivers, each pairing between a given one of the transmitters and a given one of the receivers will result in a potentially different set of magnetic properties, thereby posing a challenge to accurate assessment of power loss, which depends on the magnetic properties of the coupled transmitter-receiver pair. To facilitate accurate transmitter and receiver power loss estimation, measurements between various models of transmitters and receivers and reference units (e.g., reference transmitters and reference receivers) can be used to determine magnetic power loss parameters associated with the transmitters and receivers. Characterization information from measurements made with the reference transmitter and / or reference receiver can be stored for each different model of device and subsequently used to help ensure that accurate power loss estimation is performed when a specific model transmitter is paired with a specific model receiver.

[0066] 6 shows an example wireless power circuit within a wireless power transmission system 608 in an example scenario in which a wireless power transmitting device is paired with a wireless power receiving device. In some examples, the system 608 implements the design of the wireless power transmission system 100 described above with reference to FIG. 1. The wireless power circuit of FIG. 6 includes a wireless power transmitting circuit 652 within the wireless power transmitting device 612 and a wireless power receiving circuit 654 within the wireless power receiving device 624. In operation, a wireless power signal 644 is transmitted by the wireless power transmitting circuit 652 and received by the wireless power receiving circuit 654. The configuration of FIG. 6 includes (by way of example) a single transmit coil 636 and a single transmit coil 648. In other implementations, the voltage on the capacitor 670 is measured, and from that measurement, the current through the coil is inferred.

[0067] As shown in FIG. 6 , the wireless power transmission circuit 652 includes an inverter circuit 661. The inverter circuit (inverter) 661 may be used to provide a signal to the coil 636. During wireless power transmission, a control circuit in the device 612 provides a signal to a control input 682 of the inverter 661, causing the inverter 661 to provide an AC drive signal to the coil 636. A circuit component, such as a capacitor 670, may be coupled in series with the coil 636 as shown in FIG. 6 . A measurement circuit 641 in the device 612 may perform measurements related to operating currents and operating voltages in the device 612. For example, a voltage sensor 641A may be used to measure the coil voltage on the coil 636, and a current sensor 641B may be used to measure the coil current through the coil 636.

[0068] When an alternating current signal is supplied to coil 636, a corresponding alternating current electromagnetic signal (wireless power signal 644) is transmitted to a nearby coil, such as exemplary coil 648 in wireless power receiver circuit 654. This induces a corresponding alternating current (AC) current signal in coil 648. A capacitor, such as capacitor 672, may be coupled in series with coil 648. Rectifier 650 receives the AC current from coil 648 and generates corresponding DC power (e.g., DC voltage Vrect) at output terminal 676. This power may be used to power a load. Measurement circuit 643 in device 624 may perform measurements related to operating currents and voltages within device 624. For example, voltage sensor 643A may measure Vrect (the output voltage of rectifier 650), or a voltage sensor may measure the coil voltage on coil 648. Current sensor 643B may measure the rectifier output current of rectifier 650, or a current sensor may measure the current in coil 648.

[0069] The measurements made by measurement circuitry 641 and measurement circuitry 643 may be processed to extract magnetic loss characteristics (e.g., coefficients or other parameters that characterize the amount of power loss in device 612 and device 624 and that depend on the magnetic properties of the transmitter and receiver). These measurements may be stored within each device and exchanged between devices so that device 612 (and, if desired, device 624) can use this information to accurately estimate the operating conditions, power losses, and other characteristics of the wireless power transfer system.

[0070] For example, these measurements can be used to estimate how well the transmitter and receiver can transfer wireless power and, therefore, whether to notify the user that the wireless power transfer operation is proceeding normally. As another example, these measurements can be used to estimate the magnetic coupling coefficient K, the wireless power transfer efficiency, the estimated foreign object power loss, and / or other attributes of the coupled transmitter-receiver pair. In addition to, or instead of, estimating the foreign object power loss to determine whether a foreign object is present and, therefore, whether to proceed with wireless power transfer, the system 608 can use this information (e.g., the estimated foreign object power loss and / or associated coupling and / or efficiency information) to determine whether to present a confirmation message to the user of the system 608 informing the user that the wireless power transmission is proceeding properly (e.g., informing the user that the process was not disrupted by the presence of a foreign object, possible misalignment, or the presence of insufficient coupling due to other factors). Exemplary confirmation messages include an audio output, such as a chime, and / or a visual output presented on the device 624 to reassure the user that the charging operation is proceeding normally.

[0071] Consider an example in which the amount of power potentially absorbed by a foreign object in system 10, following measurements by circuits 641 and 643, is determined using the following equation:

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[0072] Exemplary operations involved in measuring a wireless power transmitter and receiver to determine their scaling parameters are shown in the flowchart of FIG. 7. The operations of FIG. 7 are performed at design time, and the resulting scaling coefficients are stored in a manufacturing unit. Exemplary operations involved in using scaling parameters in system 608 are shown in FIG. 8. The operations of FIG. 8 are performed at run time (e.g., when a transmitter and receiver are paired in preparation for transmitting wireless power between them). In the examples of FIGS. 7 and 8, it is assumed that scaling coefficients for a particular model transmitter (e.g., a Model I transmitter) and a particular model receiver (e.g., a Model J receiver) have been obtained using reference device measurements and are then used when the Model I transmitter is paired with the Model J receiver. In general, it is expected that this process will be performed for multiple models of transmitters (models other than Model I) and multiple models of receivers (models other than Model J). Furthermore, any of a variety of different models of characterized transmitters can generally be paired by a user with any of a variety of different models of characterized receivers. This is because not all users own the same model transmitter, and not all users own the same model receiver. In this example, an exemplary user pairs a Model I transmitter with a Model J receiver during the operation of FIG.

[0073] The operations involved in measuring the magnetic power loss parameter scaling factors for a Model I transmitter and a Model J receiver are shown in FIG. 7. During the operation of block 790, a reference wireless power receiving device is paired with a reference wireless power transmitting device (physically or by simulated pairing, such as finite element analysis simulation pairing). The physical reference device may be obtained from a centralized source or may be built by a different device manufacturer according to a globally distributed reference design. Once paired, the reference transmitter and reference receiver may begin transmitting power. Specifically, during the operation of block 790, the reference transmitter may transmit a wireless power signal to the reference receiver while internal operating parameters (e.g., transmitter and receiver current and voltage) are measured and stored. From these measurements, reference magnetic loss parameters are extracted (e.g., values ​​of the reference magnetic loss parameters bR, mR, αR, and αRDC are obtained). In scenarios where pairing simulations are used instead of measurements on physically paired devices, finite element analysis simulations are used to determine the LQK of the coupled transmitter-receiver pair, and then circuit simulations are used to determine the expected currents and voltages. These simulated currents and voltages can then be used to determine the magnetic loss parameters.

[0074] After determining the reference magnetic loss parameters (either by physical measurement or simulation), the model J receiver is paired with the reference transmitter. Loss parameter measurements of the model J receiver can be obtained while the devices are paired in a simulation, or while the devices are physically paired and wireless power is transmitted from the reference transmitter to the model J receiver. Specifically, during the operation of block 792, the model J loss parameters (coefficients) bRj, mRj, αRj, and αRjDC are obtained. The “J” in each of these parameters and the R (for “reference”) in each of these parameters indicate that the loss parameters are specific to the scenario in which the model J receiver is operating with the reference transmitter. The model J receiver scaling coefficient gb (Equation 7b) can then be calculated using Equation 9 and stored in all model J wireless power receiving devices (e.g., during manufacturing or using a later update).

number

[0075] During the operation of block 794, a Model I transmitter is paired with a reference receiver. Power is transmitted wirelessly while transmitter operating parameters (e.g., current and voltage) are measured. From these measurements or simulations, the magnetic loss parameters m, b, α, and α are obtained for the Model I transmitter. Equations 10, 11, and 12 are then used to calculate the scaling factors g, g, and g for the Model I transmitter.

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[0076] Exemplary operations involved in the use of scaling factors for a Model I transmitter and a Model J receiver in a scenario in which the Model I transmitter and the Model J receiver are paired by a user are shown in the flowchart of Figure 8. During the operations of Figure 8, a user having a Model J receiver and a Model I transmitter who desires to wirelessly transfer power from the Model I transmitter to the Model J mobile phone pairs the Model I transmitter and the Model J receiver during the operations of block 800 (e.g., by magnetically attaching a Model I charging pack to a Model J mobile phone, by way of example only).

[0077] During the operation of block 802, the Model I transmitter and Model J receiver exchange information such as their scaling factors and transfer power (e.g., using low-power in-band or other wireless communications). For example, the Model J receiver transmits to the Model I transmitter the value of the scaling factor g obtained from Model J measurements using the reference transmitter in block 792 of FIG. 7. The Model I transmitter transmits to the Model J receiver the values ​​of the scaling factors g, g, and g obtained from Model I measurements using the reference receiver in block 794 of FIG. 7.

[0078] During wireless power transfer from the Model I transmitter to the Model J receiver, measurement circuitry 641 in the transmitter and measurement circuitry 643 in the receiver can measure operating parameters of the transmitter and receiver (e.g., coil current and voltage, rectifier output voltage and current, etc.). Current and voltage measurements can be exchanged between the transmitter and receiver (e.g., using in-band wireless communications) if desired. The information measured by circuitry 641 and circuitry 643 can be used in conjunction with exchanged scaling factors to calculate PLOSSRX and PLOSSTX using Equations 7b and 8b.

[0079] During the operation of block 804, for example, the Model J receiver may measure the rectifier current and rectifier voltage (the product of which is P) and use the measurements in conjunction with the scaling factors g, g, and g received from the Model I transmitter during the operation of block 802 to evaluate Equation 8b, thereby estimating PLOSSRX. The scaling factors received from the Model I transmitter provide the receiver J with information about the expected operating characteristics of the Model I transmitter with respect to receiver transmit coil losses and friendly metal losses.

[0080] As an example, consider the receiver transmit coil loss. When receiver J is paired with a reference transmitter, the value of the scaling factor gm is 1.0. The receiver then uses the first term of Equation 8b to calculate the receiver transmit coil loss (the receiver transmit coil loss is 1.0 * mR * RAIRRX * (IRX)2), where the values ​​of mR, RAIRRX, and receiver current IRX are known to the receiver. However, in this situation, receiver J is not paired with the reference transmitter, but instead is paired with transmitter I. Transmitter I may have previously been determined to induce lower coil loss in the coupled receiver than the reference transmitter, and therefore the value of gm that transmitter I passed to the model J receiver during block 802 may be 0.9 (as one example). When the model J receiver evaluates equation 8b using the scaling factor value of 0.9 received from the model I transmitter, the model J receiver accurately estimates a somewhat reduced value of PLOSSRX (due to the presence of the model I transmitter, which is known to induce a lower amount of receiver transmit coil loss than the reference transmitter). As this example demonstrates, by using the scaling factor received from the model I transmitter, the magnetic loss parameters used by the receiver to calculate PLOSSRX can be appropriately scaled to reflect the presence of the model I transmitter instead of the reference transmitter, thereby increasing the accuracy of estimating the value of PLOSSRX.

[0081] During the operation of block 806, the model I transmitter estimates PLOSSTX using the measured transmitter transmit coil current ITX, the known values ​​of bR and RAIRTX, and the scaling factor gb received from the receiver during the evaluation in Equation 7b. The scaling factor gb reflects how the model J receiver is expected to affect the transmitter transmit coil loss in a transmitter paired with the model J receiver instead of the reference receiver. As an example, a model J receiver may tend to cause a paired transmitter to exhibit higher transmitter transmit coil loss than the reference receiver. As a result, the value of the scaling factor gb that the model I transmitter receives from the model J receiver may be 1.1 (as an example). When evaluating Equation 7b, the increased scaling factor helps transmitter I account for the fact that the model I transmitter is coupled to a model J receiver and therefore should expect greater transmitter transmit coil loss than if it were coupled to a reference receiver.

[0082] During operation of block 807, the value of PLOSSRX calculated in block 804 can be transmitted to the paired transmitter. During operation of block 808, the system 608 evaluates the value of PFO (e.g., an estimate of foreign object power loss, if any) using Equation 6. By accurately estimating PLOSSTX using the scaling factor information received from the model J receiver and receiving an estimated value of PLOSSRX from the model J receiver, the model I transmitter will have both PLOSSTX and PLOSSRX per Equation 6. The value of P can be obtained by the transmitter by calculating the product of the transmitter transmit coil current (ITX) and the voltage from measurement circuit 641. The value of P can be obtained by the transmitter by calculating the product of the rectifier output current IRX and the rectifier output voltage received from measurement circuit 643, or by receiving POUT from the receiver.

[0083] After determining the value of PFO during the operation of block 808, the transmitter may compare the PFO to a threshold power loss value (TH) (block 810). Suitable action may then be taken by the system 608. For example, in response to determining that the PFO is less than TH, it may be concluded that no foreign object is present and that the power transfer operation may proceed normally (e.g., so that power can be transferred to charge the battery 658). In response to determining that the PFO is greater than TH, the power transfer operation may be limited. Examples of power transfer limitations that may be implemented include canceling all power transfer operations and / or stopping power transfer if already in progress, limiting the maximum amount of power that may be transferred (e.g., to a relatively low, predetermined power level that is below the normal maximum power transfer capability of the system 608), and / or issuing a visual, audible, and / or vibration alert to the user. If desired, an alert to the user (e.g., a warning and / or other informational content informing the user that a power transfer operation is not proceeding normally because a foreign object has been detected) may be presented using output devices within device 612 and / or device 624. For example, control circuitry within device 612 may wirelessly communicate with control circuitry within device 624 to issue a visual alert that is presented on a display within device 624. Further Ecosystem Scaling Explained

[0084] In an ecosystem where there are multiple different models of wireless power transmitting devices and multiple different models of wireless power receiving devices available to users (e.g., different models of either device), the electrical and / or magnetic loss parameters may vary depending on which particular wireless power transmitter and wireless power receiver are paired together. As an example, when a Model I transmitter and a Model J receiver are paired, the amount of power loss in each device will be different from the amount of power loss experienced when these devices are paired with different devices.

[0085] To account for these variations and thereby ensure accurate estimation of friendly metal, foreign object, and / or other losses, scaling factors for electric and magnetic power loss parameters (sometimes referred to as power loss coefficient scaling factors) can be used. By using such scaling factors to calculate various parameters, loss equations can be well estimated regardless of what models are paired with each other between the transmitter and receiver. The above-described exchange of scaling parameters between various wireless power transmission devices can be thought of as providing “ecosystem scaling” in that it expands the “ecosystem” of devices that can cooperate to provide wireless power transfer and foreign object detection. Such ecosystem scaling can be extended to the context-friendly metal loss estimation described above.

[0086] Techniques for performing ecosystem scaling for friendly metal loss estimation may include various aspects shown in FIG. 9. Starting with diagram 901 of FIG. 9, on the wireless power transmitter (PTx) side, various gain coefficients g may be calculated for various parameters based on pairings between a "promising" or "reference" wireless power transmitter GTx and wireless power receiver GRx and an actual wireless power transmitter PTx and wireless power receiver PRx. More specifically, a scaling factor or proportionality constant (a) may be used to scale the measurement GG between the prospective transmitter or reference transmitter GTx and the prospective receiver or reference receiver GRx to correspond to the measurement GR between the prospective transmitter GTx and the actual receiver PRx. Similarly, a scaling or proportionality constant (b) may be used to scale the measurement TR, such as between the actual wireless power transmitter PTx and the actual wireless power receiver PRx, as between the actual power transmitter PTx and the prospective wireless power receiver GRx. Thus, as shown in the equation below diagram 901, the wireless power transmitter transmit coil g coil,TX The gain for may be calculated into a value that may be stored in the wireless power transmitter.

[0087] As shown in diagram 902 of FIG. 9 , scaling of a wireless power receiver can proceed similarly. More specifically, various gain coefficients g can be calculated for various parameters based on pairings between a "promising" or "reference" wireless power transmitter GTx and wireless power receiver GRx and an actual wireless power transmitter PTx and wireless power receiver PRx. More specifically, a scaling factor or proportionality constant (a) can be used to scale the measurement GG between the prospective or reference transmitter GTx and the prospective or reference receiver GRx to correspond to the measurement TG between the prospective receiver GRx and the actual transmitter PTx. Similarly, a scaling or proportionality constant (b) can be used to scale the measurement TR, such as between the actual wireless power transmitter PTx and the actual wireless power receiver PRx, as between the actual power receiver PRx and the prospective wireless power transmitter GTx. Thus, as shown in the equation below in FIG. 902, the wireless power receiver transmit coil g coil,RX The gain for the transmitter current (g) can be calculated into a value that can be provided to the wireless power receiver and / or stored in the wireless power transmitter. Similarly, the gain parameter for ecosystem scaling can be calculated into a value that can be provided to the wireless power receiver and / or stored in the wireless power transmitter. FM,ITX ), rectifier current (g FM,IRECT ), and rectifier voltage (g FM,VRECT ), the coefficients described above for friendly metal loss estimation can be calculated similarly. These gain parameters for ecosystem scaling can be calculated by and remain on the wireless power transmitter, but in some embodiments may also be calculated by and / or provided to the wireless power receiver.

[0088] 10 shows a table 1000 illustrating some combinations of monitorable parameters in a wireless power transfer system that can be used for friendly metal loss estimation. The parameters that can be used include DC model parameters (DC), transmitter current (squared) ITX, 2 , rectifier current (squared) IRECT 2, inverter input voltage (Vin), and rectifier voltage (squared) VRECT 2 The above discussion focused on the combination shown in row 1041 of table 1000, using the square of the transmitter current, the square of the rectifier current, and the square of the rectifier voltage. However, the inventors have experimented with models incorporating two to four of the variables in various combinations, as shown in rows 1042-1051, and observed different accuracies for the various models, depending on the particular implementation. Thus, in a given implementation, it may be desirable to use one or more models incorporating different combinations of such variables, as appropriate for a given application. In either case, a model equation can be selected, and corresponding coefficients can be adapted based on power transfer measurements as described above and in the incorporated applications.

[0089] Various features and embodiments relating to improving friendly metal loss estimation to improve wireless power transfer in wireless power transfer systems have been described above. Such configurations may be used in a variety of applications, but may be particularly advantageous when used with electronic devices such as mobile phones, tablet computers, laptop or notebook computers, and accessories such as wireless headphones, styluses, etc. Furthermore, while numerous specific features and various embodiments have been described, it should be understood that the various features and embodiments may be combined in various permutations in a particular implementation, unless otherwise stated as mutually exclusive. Thus, the various embodiments described above are provided by way of example only and should not be construed as constituting the scope of the present disclosure. Various modifications and variations can 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.

[0090] The above describes an exemplary embodiment of a wireless power transmission system capable of transmitting certain information between PTxs and PRxs in the system. The present disclosure contemplates that the passing of this information improves the ability of devices to provide wireless power signals to each other in an efficient manner that facilitates battery charging, such as by sharing device ecosystem scaling parameters with each other. Entities implementing the present technology should take care to ensure that well-established privacy policies and / or practices are adhered to, to the extent that any sensitive information is used in a particular implementation. Specifically, such entities would be expected to implement and consistently apply privacy practices generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Implementers should inform users of where personally identifiable information is expected to be transmitted in the wireless power transmission system and allow users to “opt in” or “opt out” of participation. For example, such information may be presented to users when they place a device on a power transmitter if the power transmitter is configured to poll for sensitive information from power receivers.

Claims

1. 1. A wireless power transmitter, comprising: a wireless power transmission coil configured to be magnetically coupled to a wireless power transmission coil of a wireless power receiver and to wirelessly transmit power to the wireless power receiver; an inverter configured to receive input power and generate an output that drives the wireless power transfer coil; a controller and communication circuit coupled to the inverter and the wireless power transmission coil, the controller and communication circuit controlling the inverter to regulate wireless power transmission to the wireless power receiver, the controller and communication circuit controlling a friendly metal loss associated with wireless power transmission to the wireless power receiver by: receiving, from the wireless power receiver, an indication of received power including a rectifier voltage and a rectifier current of the wireless power receiver associated with the wireless power transmission; calculating a friendly metal power loss based on the received rectifier voltage and the received 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 adjusting wireless power transmission to the wireless power receiver using the friendly metal power loss.

2. 2. The wireless power transmitter of claim 1, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

3. The controller and communication circuitry may further configure the one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver to:

10. The wireless power transmitter of claim 1, configured to derive the one or more coefficients by performing a regression analysis on a plurality of received indications of received power including or derived from corresponding rectifier voltages and rectifier currents of another wireless power receiver associated with another wireless power transmission and a plurality of determined measured power loss values ​​derived therefrom to calculate the one or more coefficients.

4. The wireless power transmitter of claim 3 , wherein the one or more coefficients include a first coefficient for the rectifier current and a second coefficient for the rectifier voltage.

5. Calculating the friendly metal power loss uses an equation having the following form: [Equation 1] where b is the first coefficient related to the rectifier current, c is the second coefficient related to the rectifier voltage, a is a coefficient related to the transmitter current, and I TX 5. The wireless power transmitter of claim 4, wherein: is the transmitter current.

6. 6. The wireless power transmitter of claim 5, wherein the controller and communication circuitry further receives one or more power loss scaling factors from the wireless power receiver and estimates the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

7. Calculating the friendly metal power loss uses an equation having the following form: [Equation 2] where b is a first coefficient related to the rectifier current, c is a second coefficient related to the rectifier voltage, a is a coefficient related to the transmitter current, and I TX 10. The wireless power transmitter of claim 1, wherein: is the transmitter current.

8. 8. The wireless power transmitter of claim 7, wherein the controller and communication circuitry further receives one or more power loss scaling factors from the wireless power receiver and estimates the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

9. 2. The wireless power transmitter of claim 1, wherein the controller and communication circuitry further receives one or more power loss scaling factors from the wireless power receiver and estimates the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

10. 1. A method performed by control circuitry of a wireless power transmitter or a wireless power receiver to estimate friendly metal losses associated with wireless power transmission from the wireless power transmitter to the wireless power receiver, the method comprising: obtaining an indication of received power including a rectifier voltage and a rectifier current of the wireless power receiver; calculating a friendly metal power loss based on the indication of a rectifier voltage and a 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 adjusting wireless power transmission using the friendly metal power loss; the rectifier voltage is a rectifier output voltage, and the rectifier current is a rectifier output current; Calculating the friendly metal power loss uses an equation having the following form: [Equation 3] where b is a first coefficient related to the rectifier current, c is a second coefficient related to the rectifier voltage, a is a coefficient related to the transmitter current, and I TX is the transmitter current.

11. The method of claim 10 , wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

12. The one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and the wireless power receiver are:

11. The method of claim 10, wherein the one or more coefficients are derived by performing a regression analysis on a received plurality of indications of received power and corresponding rectifier voltage and rectifier current of another wireless power receiver associated with another wireless power transmission, and a determined plurality of measured power loss values ​​derived therefrom, to calculate the one or more coefficients.

13. 13. The method of claim 12, further comprising receiving one or more power loss scaling factors from the wireless power receiver, wherein calculating the friendly metal power loss is based on the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

14. 11. The method of claim 10, further comprising receiving one or more power loss scaling factors from the wireless power receiver, wherein calculating the friendly metal power loss is based on the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

15. 1. A wireless power transmitter, comprising: a wireless power transmission coil configured to be magnetically coupled to a wireless power transmission coil of a wireless power receiver and to wirelessly transmit power to the wireless power receiver; an inverter configured to receive input power and generate an output that drives the wireless power transfer coil; a controller and communication circuit coupled to the inverter and the wireless power transmission coil, the controller and communication circuit controlling the inverter to regulate wireless power transmission to the wireless power receiver, the controller and communication circuit controlling a friendly metal loss associated with wireless power transmission to the wireless power receiver by: receiving an indication of received power from the wireless power receiver, the indication including a rectifier voltage and a rectifier current of the wireless power receiver; calculating a friendly metal power loss based on the 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 adjusting wireless power transmission to the wireless power receiver using the friendly metal power loss; the rectifier voltage is a rectifier output voltage, and the rectifier current is a rectifier output current; Calculating the friendly metal power loss uses an equation having the following form: [Equation 4] where b is a first coefficient related to the rectifier current, c is a second coefficient related to the rectifier voltage, a is a coefficient related to the transmitter current, and I TX is the transmitter current,

16. The one or more coefficients corresponding to the baseline wireless power transmission between the wireless power transmitter and another wireless power receiver are:

16. The wireless power transmitter of claim 15, wherein the one or more coefficients are derived by performing a regression analysis on a plurality of received indications of received power including or derived from corresponding rectifier voltages and rectifier currents of another wireless power receiver associated with another wireless power transmission and a plurality of determined measured power loss values ​​derived therefrom to calculate the one or more coefficients.

17. 17. The wireless power transmitter of claim 16, wherein the controller and communication circuitry further receives one or more power loss scaling factors from the wireless power receiver and estimates the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

18. 16. The wireless power transmitter of claim 15, wherein the controller and communication circuitry further receives one or more power loss scaling factors from the wireless power receiver and estimates the friendly metal loss by calculating the friendly metal power loss according to the one or more power loss scaling factors, the one or more power loss scaling factors being based on a pairing between a reference wireless power transmitter or wireless power receiver and an actual wireless power transmitter or wireless power receiver.

19. 16. The wireless power transmitter of claim 15, wherein the rectifier voltage is a rectifier output voltage and the rectifier current is a rectifier output current.

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