Finder metal loss estimation

Abstract

A wireless power transfer device may include a coil coupled to a corresponding coil of a counterpart device to facilitate wireless power transfer; a power converter coupled to the coil; and a controller and communication circuitry that monitors one or more observable parameters associated with the wireless power transfer to detect the presence of a foreign matter other than the counterpart device, and controls the power converter in response to detecting a foreign matter. The controller and communication circuitry may perform foreign matter detection based on a power accounting that includes estimating friendly metal loss associated with the counterpart device. The controller and communication circuitry may receive, from the counterpart device, friendly metal loss modeling parameters associated with the counterpart device, the modeling parameters including one or more coefficients related to a wireless power transfer current and one or more coefficients related to a wireless power transfer voltage.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 376,228, filed on September 19, 2022, entitled “FRIENDLY METAL LOSS ESTIMATION,” which is incorporated herein by reference in its entirety for all purposes. Background Art

[0003] Wireless power transfer ("WPT"), such as inductive power transfer ("IPT"), can be used to provide power for charging various battery-powered electronic devices. One application where WPT usage is increasing is in the consumer electronics space surrounding devices such as mobile phones (i.e., smartphones) and their accessories (e.g., wireless earphones, smart watches, etc.), as well as tablets and other types of portable computers and their accessories (e.g., styluses, etc.). Such WPT systems may employ a foreign object detection ("FOD") system that is designed to identify conductive objects that are separated from the wireless power transmitter and the wireless power receiver, thereby regulating the transmitted wireless power to prevent unnecessary power delivery to such objects. Summary of the invention

[0004] Some FOD systems employ estimates of “friendly metal” losses, which are losses associated with the conductive components in the WPT equipment rather than the WPT system itself. Accurately estimating these friendly metal losses may be complicated by unknown parameters associated with the operating WPT system, such as the relative positions between WPT devices, differences between different WPT devices, etc. Therefore, it may be necessary to develop improved friendly metal loss estimation techniques for specific implementation in WPT FOD systems.

[0005] A wireless power transmission device may include: a coil coupled to a corresponding coil of a peer device to facilitate wireless power transmission; a power converter coupled to the coil; and a controller and communication circuitry, the controller and communication circuitry monitoring one or more observable parameters associated with the wireless power transmission to detect the presence of a foreign object other than the peer device, and controlling the power converter in response to detecting the foreign object. The controller and communication circuitry may perform foreign object detection based on power accounting, the power accounting including estimating a friendly metal loss associated with the peer device. The controller and communication circuitry may receive friendly metal loss modeling parameters associated with the peer device from the peer device, the modeling parameters including one or more coefficients associated with a wireless power transmission current and one or more coefficients associated with a wireless power transmission voltage. The modeling parameters may also include one or more coefficients associated with a wireless power transmission current and one or more coefficients associated with a wireless power transmission voltage under a first coupling factor, and one or more coefficients associated with a wireless power transmission current and one or more coefficients associated with a wireless power transmission voltage under a second coupling factor.

[0006] The wireless power transmission device may be a wireless power transmitter. The peer device may be a wireless power receiver. The power converter may be an inverter. The control circuit may control the power converter in response to detecting a foreign object by at least one of the following means: reducing or limiting the amount of power transmitted, interrupting power transmission, or providing an alert to a user. The controller and the communication circuit perform foreign object detection based on power accounting in the following manner: subtracting the power received by the wireless power receiver from the power transmitted by the wireless power transmitter to obtain a measured power loss; estimating the friendly metal loss using the received friendly metal loss modeling parameters; calculating the net foreign object loss by subtracting the estimated friendly metal loss from the measured power loss; and determining the presence of a foreign object if these net foreign object losses exceed a threshold.

[0007] Estimating the friendly metal loss using the received friendly metal loss modeling parameters may also include using a model that relates observable circuit parameters to the friendly metal loss, the model using the received friendly metal loss modeling parameters. The model may have the following form:

[0008] P FM =α FM (I Tx ) 2 +β FM +γ FM V in +δ FM

[0009] Among them, P FM is the estimated friendly metal loss, α FMis the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss. The model can have the following form:

[0010]

[0011] Among them, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for the high coupling condition, k is the coupling coefficient, and kth is the threshold coupling coefficient, which is the boundary between the low coupling condition and the high coupling condition.

[0012] A method for performing foreign object detection in a wireless power transmission system including a wireless power transmitter and a wireless power receiver may be performed by the control and communication circuit of the wireless power transmitter or the wireless power receiver and may include: subtracting the power received by the wireless power receiver from the power transmitted by the wireless power transmitter to obtain a measured power loss; estimating friendly metal loss, including using friendly metal loss modeling parameters received from a peer wireless power transmission device; calculating a net foreign object loss by subtracting the estimated friendly metal loss from the measured power loss; and determining the presence of a foreign object if these net foreign object losses exceed a threshold.

[0013] The method may also include applying mitigation measures if foreign matter is present. The mitigation measures may include at least one of: reducing or limiting the amount of power transmitted, interrupting the power transmission, or providing an alert to the user. The method may be performed by the control and communication circuit of the wireless power transmitter, and the counterpart wireless power transmission device may be the wireless power receiver. These friendly metal loss modeling parameters may include one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a first coupling factor, and one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a second coupling factor.

[0014] These friendly metal loss modeling parameters can correspond to a model of the following form:

[0015] P FM =α FM (I TX ) 2 +β FM +γ FM Vin +δ FM

[0016] Among them, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss. These friendly metal loss modeling parameters can correspond to a model of the following form:

[0017]

[0018] Among them, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for the high coupling condition, k is the coupling coefficient, and kth is the threshold coupling coefficient, which is the boundary between the low coupling condition and the high coupling condition.

[0019] A method for estimating friendly metal loss in a wireless power transmission system including a wireless power transmitter and a wireless power receiver may be performed by a control and communication circuit of the wireless power transmitter or the wireless power receiver and may include: measuring one or more observable parameters of the wireless power transmission system; obtaining a friendly metal loss parameter from a corresponding wireless power transmission device; and estimating the friendly metal loss using a model that relates the friendly metal loss to the measured observable parameters and the received friendly metal loss parameter. The observable parameters may include at least a current of the wireless power transmission system and a voltage of the wireless power transmission system.

[0020] The method may be performed by the control and communication circuit of the wireless power transmitter, and the peer wireless power transmission device may be the wireless power receiver. The current of the wireless power transmission system may be a transmitting coil current, and the voltage of the wireless power transmission system may be an inverter voltage. The friendly metal loss modeling parameters may include one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a first coupling factor, and one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a second coupling factor.

[0021] These friendly metal loss modeling parameters can correspond to a model of the following form:

[0022] PFM =α FM (I TX ) 2 +β FM +γ FM V in +δ FM

[0023] Among them, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss. These friendly metal loss modeling parameters correspond to a model of the following form:

[0024]

[0025] Among them, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for the high coupling condition, k is the coupling coefficient, and kth is the threshold coupling coefficient, which is the boundary between the low coupling condition and the high coupling condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A block diagram of a wireless power transfer system is illustrated.

[0027] FIG. 2A to FIG. 2C Various configurations of wireless power transfer systems are illustrated.

[0028] Figure 3 A simplified flow chart of the power accounting based foreign object detection technique is depicted.

[0029] Figure 4 A flow chart illustrating the friendly metal loss estimation technique. DETAILED DESCRIPTION

[0030] 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.

[0031] Various embodiments of the disclosed concepts are illustrated by way of example, and are not limited to individual drawings, in which similar reference numerals indicate similar elements. For simplicity and clear illustration, 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 the drawings, the reference numerals refer to the same element throughout several drawings, but they 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.

[0032] Figure 1 A 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 can receive input power, which is converted by an inverter 114 into an AC voltage having specific voltage and frequency characteristics. The inverter 114 can be controlled by a controller / communication module 116, which operates as further described below. In various embodiments, the inverter controller and the communication module can be implemented in a common system (such as a system based on a microprocessor, a microcontroller, etc.). In other embodiments, the inverter controller can be implemented by a separate controller module and a communication module with a communication device therebetween. The inverter 114 can be constructed 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., MOSFET, IGBT, etc. manufactured using silicon, silicon carbide, or gallium nitride devices).

[0033] The inverter 114 can deliver the generated AC voltage to the transmitter coil 112. In addition to allowing magnetic coupling to the wireless coil of the receiver, Figure 1The illustrated transmitter coil block 112 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 metal 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.

[0034] The PTx controller / communication module 116 may monitor the transmitter coil and use the information derived therefrom to control the inverter 114 to suit a given situation. For example, the controller / communication module may be configured to operate the inverter 114 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) applied by the PRx on the magnetic link to receive information, and may command the inverter to modulate the delivered power by manipulating various parameters of the generated voltage (such as voltage, frequency, etc.) to transmit information to the PRx. In some embodiments, the controller / communication module may be configured to employ frequency shift keying (FSK) communication to convey 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.

[0035] 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 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.

[0036] The PTx device 110 may optionally include other systems and components, such as a separate communication ("comms") 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.

[0037] 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 1 The illustrated receiver coil block 122 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 metal 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.

[0038] 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).

[0039] The PRx controller / communication module 126 may monitor the receiver coil and use the 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 transmit information to the PTx device to effectively control the power delivered to the receiver. This information may be transmitted via the power transmission coil (i.e., in-band communication) or may be transmitted 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 transmit the 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 convey 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.

[0040] 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 and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuits.

[0041] The PRx device 120 may optionally include other systems and components, such as a communication module 128. In some embodiments, the communication module 128 may communicate with a corresponding module in the PTx via a power transmission coil. In other embodiments, the communication module 128 may communicate with a corresponding module or tag using a separate physical channel 138.

[0042] Many variations and enhancements of the wireless power transmission system 100 described above are possible, and the following teachings apply to any of such variations and enhancements.

[0043] Wireless power transmission as described above depends on the degree of electromagnetic coupling between PTx and PRx. For example, in an inductive charging system, the transmitter coil 112 and the receiver coil 122 can be considered as loosely coupled transformers. Therefore, the relative position of PTx and PRx can affect the degree of magnetic coupling between PTx and PRx, which in turn can affect the power transmission capability of the system. Figure 2A A simplified diagram of a PTx (110)-PRx (120) system is shown. The two devices are shown in a plan view (upper portion of the figure) and an edge cross-sectional view (lower portion of the figure). The PTx device 110 includes a transmitter coil 112, and the PRx device 120 includes a receiver coil 122. In some embodiments, the PTx device 110 can be a wireless charging plate, pad, or stand (or other wireless power transmission device), and the PRx device 120 can be a mobile phone, tablet computer, smart watch (or other wireless power receiver device). Although the respective devices are depicted as having a generally rectangular shape with a generally circular charging coil, it should be understood that other configurations are possible.

[0044] Figure 2B The "optimal" alignment of PTx 110 and PRx 120 is shown. Figure 2B In the embodiment of the present invention, the device (more specifically, its wireless power transfer coil) is aligned horizontally (as depicted in the plan view), vertically aligned, and as close as possible (as shown in the cross-sectional view). In this context, horizontal and vertical are used only as terms of convenience, and the actual orientation of the system may vary, and the following description applies to systems in any such orientation, although "horizontal" and "vertical" will continue to be used for clarity of context. Figure 2C The devices are shown 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 radial displacement can be caused by any number of things, such as slightly misaligning the phone relative to the charging pad. In addition, there is 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 also be caused by any number of things, such as a phone enclosed in a housing or cover. The cross-sectional view also shows a lateral / radial displacement. It should be understood that in some cases, there may be only radial displacement or only vertical displacement.

[0045] The above-mentioned offset can reduce the degree of magnetic coupling between the PTx and PRx devices. The reduced magnetic coupling can limit the amount of power that can be delivered from the PTx 110 to the PRx 120. More specifically, the reduced coupling between the PTx 110 and the PRx 120 reduces the portion of the power transmitted from the PTx 110 that is received by the PRx 120. In addition, the reduced degree of magnetic coupling between the PTx 110 and the PRx 120 can be at least partially addressed by retuning the receiver (or transmitter) circuit accordingly. For example, one or more tuning capacitors can be included between the inverter 114 and the transmitter coil 112 in the PTx circuit. Similarly, one or more tuning capacitors can be included between the rectifier 124 and the receiver coil 122 in the PRx circuit. The function of these respective capacitors is to tune the circuit by adjusting the resonant frequency of the respective circuit, and these capacitors 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 specific design operating mode of the circuit. To this end, a plurality of selectable capacitors may be provided on the PTx 110 and / or PRx 120, and appropriate tuning capacitances may be selected by the respective devices based on coupling factor estimates derived from various observable circuit parameters (such as voltage, current, etc.).

[0046] In a wireless power transmission system, it may be necessary to detect the presence of "foreign objects". For example, objects (such as coins, keys, paper clips, etc.) that are close to the wireless power transmission coil may receive a portion of the power sent by the PTx 110, which not only limits the power available to the PRx 120, but may also cause induced eddy currents in the foreign object. Wireless power transmission systems can use a variety of foreign object detection ("FOD") technologies. One type of FOD technology is based on power accounting. The basic principle of power accounting is as follows: the power sent by the PTx110 minus the power received by the PRx 120 is the "lost" power. This lost power can be considered to flow to one of the following three places. Part of the power may be absorbed by the so-called "friendly metal" of the PTx 110. Part of the power may be absorbed by the friendly metal of the PRx 120. Part of the power may be absorbed by foreign objects. In this context, "friendly metal" refers to the metal or other conductive structure that constitutes the PTx and PRx. The metal or other conductive structure can be a frame or housing part, an internal circuit element, a magnet, etc. These elements are designated as friendly metals because they are known and taken into account in the design of wireless power transfer systems. Losses not associated with friendly metals can be assumed to be associated with foreign objects.

[0047] Figure 3A simplified flow chart of a foreign object detection technique 330 based on power accounting is depicted. Starting from box 331a, the PTx 110 calculates the power transmitted by the PTx. This can be achieved by multiplying the output voltage of the inverter 114 by the current flowing through the transmitting coil 112. Accordingly, box 331b calculates the power received by the PRx 120. This can be achieved by multiplying the current flowing through the receiver coil 122 by the output voltage of the rectifier 124. In some applications, it may be difficult to make these measurements on the PRx side. In such cases, the received power can be calculated as the power output (rather than input) of the PRx 120 plus the estimated losses of the PRx 120 and its associated coil 122. Additionally or alternatively, power measurements or estimates on the PTx side can be used to perform power estimation. These PTx-side measurements can be based on the DC input power of the PTx 110, or AC measurements of the output of the inverter 114. In summary, the power transmitted by PTx 110 or the power received by PRx 120 can be estimated by directly measuring the current flowing through the corresponding wireless power transmission coil (112 / 122), or indirectly using the input DC current of the transmitter or the output DC current of the receiver. The corresponding voltage and current can be monitored by sensors coupled to the corresponding controller circuits located in the controller and communication modules 116 (for PTx 110) and 126 (for PRx 120). The specific implementation of such measurement systems is well known to those skilled in the art and will not be described in detail here.

[0048] In block 332b, PRx 120 may communicate the received power value to PTx 110, which receives the power value as shown in block 332a. This discussion assumes that foreign object detection is performed by PTx 110, such as by circuitry located in controller / communication module 126. However, in some applications, the foreign object detection process may be run on PRx 120, in which case PTx 110 may send its measured power value to PRx 120. In either case, this may be done via in-band communication (involving modulation of the transmitted wireless power, such as voltage, current, frequency, phase, etc.) or out-of-band communication using a separate communication module 118 / 128 and a separate communication channel 138, which may be near field communication (NFC), Bluetooth communication, WiFi communication, etc., as described above. Alternatively, instead of sending calculated power values, the devices may send basic measurements (e.g., voltage and current measurements) that allow the peer devices to calculate their respective powers.

[0049] In either case, in block 333, the PTx (or PRx, if it is performing foreign object detection) may calculate the measured power loss as the difference between the transmit power and the receive power. As described above, this measured power loss may include two components: friendly metal loss (associated with PTx 110 or PRx 120) and foreign object loss. Thus, in block 334, the PTx (or PRx, if it is performing foreign object detection) estimates the friendly metal loss. Exemplary friendly metal loss estimation techniques are described below in conjunction with Figure 4 For a more detailed discussion. For the purposes of this discussion, the estimation of friendly metal losses can be viewed as being based on the calculation of observable circuit parameters (voltage, current, coupling factors, etc.) and predetermined parameters relating these observable circuit parameters to the losses incurred. These parameters can be part of a model that can be derived analytically or empirically during the design of a particular wireless power transfer device. These model parameters can be stored in a memory associated with a controller of a corresponding wireless power transfer device and used by that device to estimate its friendly metal losses, or provided to a peer device to allow that device to estimate its peer's friendly metal losses.

[0050] Once the friendly metal loss is estimated / determined (box 334), the device performing foreign object detection may calculate a net foreign object loss (box 335), which may be the difference between the calculated measured power loss (box 333) and the estimated friendly metal loss (box 334). The net foreign object loss may then be compared to a net loss threshold (box 336). If the net foreign object loss is less than the threshold, it may be inferred that no foreign object is present (box 338) and no mitigation measures are required. Alternatively, if the net foreign object loss is greater than the threshold (box 336), it may be inferred that a foreign object is present (box 337) and some mitigation measures may be taken. Such mitigation measures may include reducing or limiting the amount of power transmitted, interrupting power transmission, providing an alert to a user (such as an audiovisual alert), etc.

[0051] In high-performance wireless power transfer systems, even relatively low levels of foreign object losses may be significant, so it is desirable to be able to detect such losses at levels that may be slightly lower than friendly metal losses. Therefore, it is desirable to ensure the accuracy of the estimated friendly metal losses. For example, if the estimated friendly metal losses are higher than the actual friendly metal losses, unnecessary induced eddy currents may be generated in the foreign object. Alternatively, if the estimated friendly metal losses are lower than the actual friendly metal losses, the system may unnecessarily take mitigation measures, such as the mitigation measures described above. However, these mitigation measures may result in a poor user experience, such as slower charging or complete interruption of charging, false user interface messages, etc. In addition, all of these problems may become more apparent as typical wireless power levels increase from relatively low levels (e.g., around 5W) to relatively high levels (e.g., 20W or more).

[0052] One way to estimate the friendly metal loss is as a function of the current flowing through the PTx transmit coil 112. The friendly metal loss can be measured as a linear function of the square of the transmit coil current, i.e.:

[0053] P FM =α FM (I TX ) 2 +β FM

[0054] Among them, P FM is the estimated friendly metal loss, α FM is the first coefficient, β FM is the second coefficient. As mentioned above, these coefficients can be derived analytically or empirically, for example, based on TX 2 The friendly metal loss can also be I RX and I TX with I RX ; however, these relationships can be combined as functions of ITX. However, the model can be further optimized in two ways. First, a more accurate estimate of the friendly metal losses can be obtained by modeling the losses as a function of voltage rather than just current. Second, the friendly metal loss model can be modified to account for different coupling factors.

[0055] Regarding the first optimization, in addition to the sending coil current I TX In addition, the DC input voltage V in can also be included to improve the friendly metal loss model. (As an alternative, the inverter output voltage or other suitable voltage can also be used. Therefore, the estimated friendly metal loss can be expressed as:

[0056] PFM =α FM (I TX ) 2 +β FM +γ FM V in +δ FM

[0057] Among them, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is a fourth coefficient related to voltage loss. As mentioned above, these coefficients can be derived analytically or empirically, for example, based on the two independent variables I TX 2 (sending coil current squared) and V in (inverter input voltage, or other suitable voltage, if applicable). This optimization can significantly improve the accuracy of friendly metal loss estimation.

[0058] Regarding the second optimization, 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 factor k between PTx 110 and PRx 120 is above a threshold; a second set of coupling coefficients may be used for low coupling conditions, where the coupling factor k between PTx 110 and PRx 120 is below the threshold. Therefore, if both the first optimization and the second optimization are adopted, the estimated friendly metal loss may be expressed as:

[0059]

[0060] Among them, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for the high coupling condition, k is the coupling coefficient, and kth is the threshold coupling coefficient, which is the boundary between the low coupling condition and the high coupling condition. In some applications, additional higher order terms (e.g., V in 2 、V in 3 etc.) or lower order terms (e.g., I TX), with appropriate coefficients. Although defined in terms of low and high coupling conditions, some implementations may use more than two coupling conditions and appropriate coefficients, such as a three-level system with low, medium, and high coupling levels and associated coefficients, or a greater number of coupling conditions and a corresponding number of coefficients.

[0061] Such an arrangement may utilize logic and functionality already present in the control circuitry of a wireless power transmitter (or receiver). For example, as described above, some wireless power transfer devices may include a controller circuit that measures certain circuit parameters (e.g., voltage and current) and estimates a coupling factor k based on these values. The controller circuit may then select one (or more) tuning capacitors to provide appropriate tuning for the circuit for such coupling factor. The same calculations may also be used to select appropriate coefficients for the friendly metal loss estimation model.

[0062] Figure 4 A flow chart of a friendly metal loss estimation technique 440 is illustrated. Beginning at box 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., and parameters that may be derived therefrom, such as power consumption, efficiency, coupling coefficient, etc. As described above, a device implementing the FOD system may perform these measurements using appropriate sensors in conjunction with the control circuitry of the device.

[0063] In box 442b, the FOD system implemented by PTx 110 may receive friendly metal parameters from PRx 120 (box 442a). If the FOD system is implemented by PRx 120, the situation may be reversed. The communication may be performed using in-band or out-of-band communication, as described above. The friendly metal parameters sent may include model coefficients as described above, including model parameters related to current, voltage, and coupling factors. In one embodiment, PRx may transmit a parameter list including current and voltage parameters for a first coupling coefficient and current and voltage parameters for a second coupling coefficient. For wireless power transmission systems that can operate at different power transmission frequencies, it may be appropriate to include different parameters for different operating frequencies. In some applications, communication may be performed according to a predetermined industry standard, such as the Qi standard for wireless power transmission / charging published by the Wireless Power Consortium organization.

[0064] In block 443, the FOD system may estimate the friendly metal loss based on the observable values ​​obtained in block 441 and the parameters received from the peer device. The FOD system may also have friendly metal loss modeling parameters associated with it, which may correspond to different coupling factors and / or operating frequencies of the received friendly metal loss modeling parameters received from the peer device. Then, in block 444, the estimated friendly metal loss may be provided to the FOD system, such as described above with respect to Figure 3 A system for foreign object detection is described.

[0065] The foregoing describes an exemplary embodiment of a wireless power transmission system capable of transmitting 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 sent in the 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.

[0066] Risks can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, data de-identification can be used to protect the privacy of users. For example, a device identifier can be partially masked to convey the power characteristics of a device without uniquely identifying the device. De-identification can be facilitated by removing identifiers, controlling the amount or specificity of stored data (e.g., collecting location data at a city level rather than an address level), controlling how data is stored (e.g., aggregating data across users), and / or other methods such as differential privacy, where appropriate. Robust encryption can also be used to reduce the likelihood that communications between inductively coupled devices can be spoofed.

Claims

1. A wireless power transmission device, comprising: a wireless power transfer coil coupled to a corresponding coil of a peer wireless power transfer device to facilitate wireless power transfer; a power converter coupled to the wireless power transfer coil; and a controller and communication circuitry that monitors one or more observable parameters associated with the wireless power transfer to detect the presence of a foreign object that is not the peer wireless power transfer device, and controls the power converter in response to detecting the foreign object; wherein: The controller and communication circuitry perform foreign object detection based on power accounting, the power accounting including estimating friendly metal losses associated with the peer wireless power transfer device; and The controller and the communication circuit receive friendly metal loss modeling parameters associated with the counterpart wireless power transmission device from the counterpart wireless power transmission device, the modeling parameters including one or more coefficients related to wireless power transmission current and one or more coefficients related to wireless power transmission voltage.

2. The wireless power transmission device according to claim 1, wherein the modeling parameters include one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a first coupling factor, and one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a second coupling factor.

3. The wireless power transmission device according to claim 1, wherein the wireless power transmission device is a wireless power transmitter, the counterpart wireless power transmission device is a wireless power receiver, the power converter is an inverter, and the controller and the communication circuit control the power converter in response to detecting the foreign object in at least one of the following ways: reducing or limiting the amount of power transmitted, interrupting power transmission, or providing an alert to a user.

4. The wireless power transmission device of claim 3, wherein the controller and the communication circuit perform foreign object detection based on power accounting in the following manner: subtracting power received by the wireless power receiver from power transmitted by the wireless power transmitter to obtain a measured power loss; estimating friendly metal loss using the received friendly metal loss modeling parameters; calculating the net foreign object loss by subtracting the estimated friendly metal loss from the measured power loss; and If the net foreign object loss exceeds a threshold, it is determined that the foreign object is present.

5. The wireless power transmission device of claim 4, wherein estimating the friendly metal loss using the received friendly metal loss modeling parameters further comprises using a model relating observable circuit parameters to the friendly metal loss, the model using the received friendly metal loss modeling parameters.

6. The wireless power transmission device according to claim 5, wherein the model has the following form: P FM =a FM (I TX ) 2 +b FM +g FM V in +d FM in, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss.

7. The wireless power transmission device according to claim 5, wherein the model has the following form: in, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for high coupling conditions, k is the coupling coefficient, and k th is a threshold coupling coefficient, and the threshold coupling coefficient is a boundary between the low coupling condition and the high coupling condition.

8. A method for detecting foreign objects in a wireless power transmission system including a wireless power transmitter and a wireless power receiver, the method being performed by a control and communication circuit of the wireless power transmitter or the wireless power receiver, the method comprising: subtracting power received by the wireless power receiver from power transmitted by the wireless power transmitter to obtain a measured power loss; estimating a friendly metal loss, including using a friendly metal loss modeling parameter received from a peer wireless power transfer device; calculating the net foreign object loss by subtracting the estimated friendly metal loss from the measured power loss; and If the net foreign object loss exceeds a threshold, it is determined that foreign matter is present.

9. The method of claim 8, further comprising applying mitigation measures if the foreign matter is present.

10. The method of claim 9, wherein the mitigation action comprises at least one of reducing or limiting the amount of power transferred, interrupting power transfer, or providing an alert to a user. 11 . The method according to claim 8 , wherein the method is performed by a control and communication circuit of the wireless power transmitter, and the counterpart wireless power transmission device is the wireless power receiver.

12. The method of claim 8, wherein the friendly metal loss modeling parameters include one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a first coupling factor, and one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a second coupling factor.

13. The method of claim 11, wherein the friendly metal loss modeling parameters correspond to a model of the following form: P FM =a FM (I TX ) 2 +b FM +g FM V in +d FM in, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss.

14. The method of claim 11, wherein the friendly metal loss modeling parameters correspond to a model of the following form: in, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for high coupling conditions, k is the coupling coefficient, and k th is a threshold coupling coefficient, and the threshold coupling coefficient is a boundary between the low coupling condition and the high coupling condition.

15. A method for estimating friendly metal loss in a wireless power transmission system including a wireless power transmitter and a wireless power receiver, the method being performed by a control and communication circuit of the wireless power transmitter or the wireless power receiver, the method comprising: measuring one or more observable parameters of the wireless power transfer system; Obtaining friendly metal loss parameters from a corresponding wireless power transmission device; Friendly metal loss is estimated using a model that relates friendly metal loss to measured observable parameters and received friendly metal loss parameters. 16 . The method according to claim 15 , wherein the observable parameters include at least a current of the wireless power transmission system and a voltage of the wireless power transmission system.

17. The method of claim 16, wherein the friendly metal loss modeling parameters include one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a first coupling factor, and one or more coefficients related to the wireless power transmission current and one or more coefficients related to the wireless power transmission voltage under a second coupling factor.

18. The method of claim 16, wherein the friendly metal loss modeling parameters correspond to a model of the form: P FM =a FM (I TX ) 2 +b FM +g FM V in +d FM in, P FM is the estimated friendly metal loss, α FM is the first coefficient related to the transmitting coil current, β FM is the second coefficient related to current loss, γ FM is the third coefficient related to the inverter voltage, and δ FM is the fourth coefficient related to voltage loss.

19. The method of claim 16, wherein the friendly metal loss modeling parameters correspond to a model of the form: in, P FM is the estimated friendly metal loss, and are the model coefficients for low coupling conditions, and is the model coefficient for high coupling conditions, k is the coupling coefficient, and k th is a threshold coupling coefficient, and the threshold coupling coefficient is a boundary between the low coupling condition and the high coupling condition.

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