FOREIGN OBJECT DETECTION IN A WIRELESS POWER TRANSFER SYSTEM

This disclosure provides systems, methods and apparatuses for foreign object detection (FOD) in a wireless power transfer (WPT) system. An FOD protocol can be coordinated with different operating phases of the WPT system, such as an idle phase, a configuration phase, a connected phase, and a power transfer phase. An FOD assessment unit may perform foreign object detection assessments as part of each operating phase. The FOD protocol may include an initial idle phase foreign object detection assessment in the idle phase to handle a scenario in which a Power Receiver is placed on the Power Transmitter before the Power Transmitter has been turned on. The FOD assessment unit may adjust offset values used during each FOD assessment to improve accuracy of foreign object detection. The offset values may be adapted to accommodate movement of the Power Receiver after the initial idle phase foreign object detection assessment.

TECHNICAL FIELD

This disclosure relates generally to wireless power. More specifically, this application relates to foreign object detection in a wireless power transfer system.

DESCRIPTION OF RELATED TECHNOLOGY

Technology has been developed to enable the wireless transmission of power from a Power Transmitter (sometimes also referred to as a “wireless power transmission apparatus”) to a Power Receiver (sometimes also referred to as a “wireless power reception apparatus”). A Power Receiver may be included in various types of devices, such as mobile devices, small electronic devices, computers, tablets, gadgets, appliances (such as cordless blenders, kettles, or mixers), and some types of larger electronic devices, among other examples. Wireless power transmission may be referred to as a contactless power transmission or a non-contact power transmission. The wireless power may be transferred using inductive coupling or resonant coupling between the Power Transmitter and the Power Receiver. For example, the Power Transmitter may include a primary coil that produces an electromagnetic field. The electromagnetic field may induce an electromotive force in a secondary coil of the Power Receiver when the secondary coil is placed in proximity to the primary coil. In this configuration, the electromagnetic field may wirelessly transfer power to the secondary coil.

In a wireless power transfer system, when a foreign metal object (such as a key, a coin, a metallic can, or aluminum foil, among other examples) is in proximity of the electromagnetic field, the foreign metal object may be undesirably heated up due to eddy currents. This may result in safety hazards, such as fire safety hazards. Furthermore, the efficiency of wireless power transfer process may be inadvertently affected or disrupted. Traditional techniques for detecting foreign objects in a wireless power transfer system may be inadequate or ineffective to prevent such safety hazards.

SUMMARY

The systems, methods, and apparatuses of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosure can be implemented as method for foreign object detection (FOD) in a wireless power transfer (WPT) system. The method may include initializing an FOD assessment unit prior to or as part of an idle phase in response to a user input to turn on a Power Transmitter. Initializing the FOD assessment unit may include setting an FOD flag to a first value to represent that an initial idle phase foreign object detection assessment has not yet been performed. The method may include indicating an FOD fault status if the Power Transmitter transitions from the idle phase to a different operating phase when the FOD flag is set to the first value.

Another innovative aspect of the subject matter described in this disclosure can be implemented as system for FOD. The system may include a Power Transmitter configured to initialize an FOD assessment unit prior to or as part of an idle phase in response to a user input to turn on the Power Transmitter. Initializing the FOD assessment unit may include setting an FOD flag to a first value to represent that an initial idle phase foreign object detection assessment has not yet been performed. The system may include the FOD assessment unit being configured to indicate an FOD fault status if the Power Transmitter transitions from the idle phase to a different operating phase when the FOD flag is set to the first value.

DETAILED DESCRIPTION

A wireless power transfer (WPT) system may include a wireless power transmission apparatus and a wireless power reception apparatus. The wireless power transmission apparatus may include a Power Transmitter (sometimes referred to as a “PTx”). The wireless power transmission apparatus may include other elements; however, the terms “wireless power transmission apparatus” and “Power Transmitter” may be used, interchangeably, to represent all or part of an apparatus of the WPT system that transfers power to a wireless power reception apparatus via inductive or resonant coupling of an oscillating electromagnetic field. The wireless power reception apparatus may include a Power Receiver (sometimes referred to as a “PRx”). The wireless power reception apparatus may include other elements; however, the terms “wireless power reception apparatus” and “Power Receiver” may be used, interchangeably, to represent all or part of an apparatus of the WPT system that receives power via the inductive or resonant coupling of the oscillating electromagnetic field. An interface surface may demark a space between the Power Transmitter and the Power Receiver.

Occasionally, a foreign object (sometimes referred to as a foreign metal object) may be in proximity of the electromagnetic field, such as in or near the interface surface. A foreign object may be any object that is electrically conductive or have detectable magnetic permeability and that is not part of a WPT system but is inadvertently present in an operative environment of the WPT system. Non-limiting examples of foreign objects may include a ferrous object, a metallic can, a coin, a metal spoon, a key, aluminum foil, or other electrically conductive or ferrous objects. When a foreign object is in proximity of the electromagnetic field, the foreign object may interact with the electromagnetic field—which can negatively impact the wireless power transfer or cause the foreign object to become undesirably heated up.

The WPT system may include a foreign object detection system (sometimes also referred to as a “detection apparatus”). The detection apparatus may include a plurality of detection coils used to obtain or generate values (also referred to as “detection values” or “FOD values”) for a foreign object detection (FOD) assessment. Each detection value may represent a comparison of current, voltage, impedance, or other electrical characteristic between two coils of a coil pair. For example, the detection value may be a differential current, differential voltage, or any value that indicates a difference in impedance associated with a pair of detection coils. As part of an FOD assessment, an FOD assessment unit may measure a detection value for each pair of detection coils while those detection coils are actively or passively excited with electrical energy. For example, the detection apparatus may include sensors or other circuitry to measure or obtain the detection values and send the detection values to the FOD assessment unit. The FOD assessment unit may be part of the Power Transmitter (such as implemented in a controller of the Power Transmitter), part of the detection apparatus (such as a control unit of the detection apparatus), part of an appliance (such as a processor of the appliance) that contains the Power Transmitter and the detection apparatus, or as an external processor, among other examples. The FOD assessment unit may compare a detection value to a detection threshold to determine whether a metal object is near one of the detection coils in a coil pair. In some types of foreign object detection assessments, the FOD assessment unit may determine whether the detection value crossing detection threshold is due to a foreign object or a Power Receiver movement based on how many coil pairs indicate the presence of the metal object. The metal object may be determined to be a foreign object when fewer coil pairs (such as less than a threshold quantity) have detected the presence of the metal object. Conversely, the FOD assessment unit may determine that the metal object is a Power Receiver when more coil pairs (such as more than the threshold quantity) have detected the presence of the metal object.

A WPT system operates in different phases, such as an idle phase, a configuration phase, a connected phase, and a power transfer phase. A technical specification may define how the Power Transmitter and Power Receiver can transition between the operating phases. For example, the Power Transmitter typically begins in the idle phase after being turned on. Turning on the Power Transmitter refers to powering a controller, communication unit, driver, or other components of the Power Transmitter except for the primary coil. The primary coil is only energized in the power transfer phase after a communication to do so between a Power Receiver and the Power Transmitter. When a Power Receiver is placed on the interface surface, a pinging of the Power Transmitter's communication coil detects the presence of Power Receiver. A handshaking process happens between the Power Transmitter and the Power Receiver. Based on the successful handshaking, the Power Transmitter transitions from the idle phase to the configuration phase. The Power Transmitter and Power Receiver communicate regarding transitions from the configuration phase to the connected phase and power transfer phase. Traditional foreign object detection techniques are related to the power transfer phase without regard to unique scenarios that can happen in specific operating phases such as the idle phase.

This disclosure provides systems, methods and apparatuses for foreign object detection in a wireless power transfer system that operates in different operating phases. The type of foreign object detection assessment performed at any particular time may depend on the operating phase of the Power Transmitter. Thus, the FOD assessment unit may follow a protocol (sometimes referred to as an “FOD protocol”) that defines how FOD assessments are performed in relation to various operating phases. For example, the FOD protocol may include an initial idle phase foreign object detection assessment to detect for foreign objects and mitigate a scenario in which a Power Receiver is placed on the Power Transmitter before the Power Transmitter has been turned on. The FOD protocol may include subsequent foreign object detection assessments (such as pre-power foreign object detection assessments and during-power foreign object detection assessments) as the Power Transmitter transitions to other operating phases towards the power transfer phase. The Power Transmitter (in coordination with the FOD assessment unit) may prevent the WPT system from producing wireless power in the event that a foreign object is introduced before or during each operating phase.

Each foreign object detection assessment may be based on a comparison of detection values with a detection threshold, and in some operating phases, the foreign object detection assessment is further based on a comparison of how many coil pairs indicate the presence of a metal object. In accordance with aspects of this disclosure, the FOD assessment unit may adjust the detection values using offset values to improve accuracy of foreign object detection in the WPT system. The offset values are added to (or subtracted from) corresponding ones of the detection values to compensate for system changes, such as a discrepancy in the detection coils, movement of a Power Receiver, or presences of non-foreign objects (sometimes referred to as “friendly objects” or “friendly metals”) in the WPT system, among other examples.

In some implementations, the FOD assessment unit may be configured to perform an initial idle phase foreign object detection assessment to detect for a foreign object when a Power Transmitter is first turned on or initialized. The Power Transmitter may cause the FOD assessment unit to perform an initial idle phase foreign object detection assessment soon after the Power Transmitter is first turned on and in relation to the idle phase. For an initial idle phase foreign object detection assessment, the offset values (referred to as “initial offset values”) are based on “calibration values” that may be predetermined. For example, the calibration values may be previously measured (referred to as “calibration” or being “calibrated”) at a moment when the interface surface is known to be free of Power Receivers and foreign objects, such as when the Power Transmitter is installed or serviced. The calibration values may be stored in the non-volatile memory of the Power Transmitter such that they remain available for the FOD assessment unit when the Power Transmitter is first turned on. As part of an FOD initialization, the FOD assessment unit determines the plurality of offset values (as “initial offset values”) based on the calibration values obtained from the non-volatile memory. As described further herein, the initial idle phase foreign object detection assessment may use a different criteria for detecting foreign objects compared to the other operating phases in which a Power Receiver is already present in the interface surface. In the event that a Power Receiver is already present when the Power Transmitter is turned on, the initial idle phase foreign object detection assessment may prevent the Power Transmitter from transmitting wireless power until an FOD fault status can be cleared. In the event that a Power Receiver is not present when the Power Transmitter is turned on, the initial idle phase foreign object detection assessment may successfully determine whether foreign objects are present or not.

After the initial idle phase foreign object detection assessment, the FOD assessment unit may perform subsequent foreign object detection assessments, such as in other operating phases. In the other operating phases, FOD assessment unit may adapt the plurality of offset values to account for system changes detected. Adaptation (sometimes also referred to as “recalibration”) enables the FOD assessment unit to update the plurality of the offset values (for use in a subsequent foreign object detection assessment) to account for the system changes (such as movement of a Power Receiver) when a Power Receiver is detected and no foreign object is present. The updated offset values (sometimes also referred to as “adapted offset values”) may be stored in a volatile memory such that they can be used while the Power Transmitter is on and are removed when the Power Transmitter is turned off. Each time the Power Transmitter is turned off and then on, the plurality of offset values are reset to the calibrated values. Adaptation happens after the FOD assessment unit detects a Power Receiver that is present on the interface surface, such as in the configuration phase, connected phase, or power transfer phase. The FOD assessment unit may carry out adaptation in the other operating phases to compensate for the presence or movement of the Power Receiver and when no foreign object is detected.

For each foreign object detection assessment, the FOD assessment unit may indicate a fault status (sometimes referred to as an “FOD fault”) when a foreign object has been detected. A Power Transmitter or Power Receiver may control operations at different phases based on the fault status. This disclosure includes several examples of FOD fault handling that can be used when the FOD assessment unit determines an FOD fault, depending on the current phase of the WPT system. For example, an FOD fault may be indicated by a user interface of the Power Transmitter, the Power Receiver, or both. In some implementations, the FOD assessment unit may communicate a message to the Power Receiver, the Power Transmitter, a processor of the appliance that includes either the Power Transmitter or the Power Receiver, or any combination thereof. In some implementations, a user interaction (such as via a user interface of the PRx or PTx) can be used to override or clear an FOD fault. Alternatively, or additionally, an FOD fault status may be cleared by user intervention to remove the foreign object and the PRx from the operative environment of the WPT system.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Foreign object detection can be accurately performed at different operating phases of a WPT system. For example, the FOD assessment unit may properly indicate an FOD fault when a foreign object is detected. And the FOD assessment unit may properly adjust the detection values to account for movement of a Power Receiver when no foreign object is present. Using the techniques in this disclosure, a WPT system can coordinate the FOD procedures and the operating phases. Furthermore, in some implementations, the FOD procedures can address some common user errors such as placement of a Power Receiver on the Power Transmitter before the WPT has an opportunity to check for foreign objects. Thus, the implementations of this disclosure can provide additional safety and reliability of wireless power transfer systems.

The following description is directed to certain implementations for the purposes of describing innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in any means, apparatus, system, or method for wireless power transfer.

FIG.1shows a block diagram of an example wireless power transfer system100. The wireless power transfer system may include a Power Transmitter102and a Power Receiver118. The Power Transmitter102may include one or more primary coils110that transmit wireless energy (as a wireless power signal) to one or more corresponding secondary coils120in the Power Receiver118. A primary coil refers to a source of wireless energy (such as inductive or magnetic resonant energy producing an electromagnetic field) in the Power Transmitter. The primary coil110may be associated with a power signal generator106. The primary coil110may be a wire coil which transmits wireless power (which also may be referred to as wireless energy or a wireless power signal). Together, the power signal generator and the primary coil may generate a primary magnetic field during wireless power transfer. The power signal generator106may include components (not shown) to provide power to the primary coil110causing the primary coil110to produce the wireless power signal. For example, the power signal generator106may include one or more switches, drivers, series capacitors, rectifiers or other components. The Power Transmitter102also may include a transmission controller108(sometimes also referred to as a PTX controller) that controls the components of the power signal generator106. For example, the transmission controller108may determine an operating point (such as voltage or current) and control the power signal generator106according to the operating point.

In some implementations, the power signal generator106, the transmission controller108and other components (not shown) may be collectively referred to as a power transmitter circuit. Some or all of the power transmitter circuit may be embodied as an integrated circuit (IC) that implements features of this disclosure for controlling and transmitting wireless power to one or more Power Receivers. The transmission controller108may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC) or any other suitable electronic device.

A power source112may provide power to the power transmitter circuit in the Power Transmitter102. The power source112may convert alternating current (AC) power to direct current (DC) power. For example, the power source112may include a converter that receives an AC power from an external power supply (such as a supply mains) and converts the AC power to a DC power used by the power signal generator106.

In some implementations, a first communication unit142may be coupled to the components of the power signal generator106or the primary coil110to send or receive communications via the wireless power signal. The first communication unit142may include logic for controlling one or more switches and other components that cause transmission and reception of wireless signals via the wireless power signal. For example, the first communication unit142may include modulators or demodulators that convert information to modulated signals added to the wireless power signal. In one example, the first communication unit142may convert data from the transmission controller108into a frequency shift key (FSK) modulated signal that is combined with the wireless power signal for a communication from the Power Transmitter102to the Power Receiver118. In another example, the first communication unit142may sense load modulated amplitude shift key (ASK) signals from the power signal generator106or the primary coil110and demodulate the ASK signals to obtain data that the first communication unit142provides to the transmission controller108.

In some implementations, the Power Transmitter102may include a wireless communication interface114. The wireless communication interface114may be connected to a first communication coil116(which may be a coil or a loop antenna). The wireless communication interface114may include logic for controlling one or more switches and other components that cause transmission and reception of wireless communication signals via the first communication coil116. In some implementations, the wireless communication interface114may support short range radio frequency communication (such as Bluetooth™) or Near-Field Communication (NFC). NFC is a technology by which data transfer occurs on a carrier frequency of 13.56 MHz. The wireless communication unit114also may support any suitable communication protocol.

The transmission controller108may detect the presence or proximity of a Power Receiver118using a variety of techniques. In some implementations, the presence or proximity of the Power Receiver118may be detected based on a load change in response to a periodic low power signal generated by the power signal generator106and the primary coil110. In some implementations, the presence or proximity of the Power Receiver118may happen during a periodic pinging process of the wireless communication interface114in the Power Transmitter102.

The transmission controller108may control characteristics of wireless power that the Power Transmitter102provides to the Power Receiver118. After detecting the Power Receiver118, the transmission controller108may receive information from a Power Receiver118. For example, the transmission controller108may receive the information during a hand shaking process with the Power Receiver118. The information may include information about the Power Receiver118(such as a power rating, load states, the manufacturer, the model, or parameters of the receiver when operating on a standard transmitter, among other examples). The transmission controller108may use this information to determine at least one operating control parameter (such as frequency, duty cycle, voltage, etc.) for wireless power it provides to the Power Receiver118. To configure the wireless power, the transmission controller108may modify the frequency, duty cycle, voltage or any other suitable characteristic of the power signal generator106.

The Power Receiver118may include a secondary coil120, a rectifier126, and a receiver controller128. The secondary coil120may receive the wireless energy via the electromagnetic field. When the secondary coil120is aligned to the primary coil110, the secondary coil120may generate an induced voltage based on a received wireless power signal from the primary coil110. A capacitor (not shown) and a switch (not shown) may be in series between the secondary coil120and the rectifier126. The rectifier126may rectify the induced voltage and provide the induced voltage to a load130. In some implementations, the load130may be external to the Power Receiver118and coupled via electrical lines from the rectifier126. In some implementations, the rectifier126may be absent and the induced voltage in the secondary coil120may be fed to the elements in series to the secondary coil120and the load130.

A receiver controller128may be connected to the rectifier126and a second communication unit152. The second communication unit152may be coupled to the components of the secondary coil120or the rectifier126to send or receive communications via the wireless power signal. The second communication unit152may include logic for controlling one or more switches and other components that cause transmission and reception of communication signals via the wireless power signals. For example, the second communication unit152may include modulators or demodulators that convert information to ASK or FSK modulated signals. In one example, the second communication unit152may convert data from the receiver controller128into an ASK modulated signal that used to load modulate the wireless power signal for a communication from the Power Receiver118to the Power Transmitter102. In another example, the second communication unit152may sense FSK signals in the wireless power signal at the secondary coil120or the rectifier126and demodulate the FSK signals to obtain data that the second communication unit152provides to the receiver controller128.

In some implementations, the Power Receiver118may include a wireless communication interface132. The wireless communication interface132may contain modulation and demodulation circuits to wirelessly communicate via a second communication coil134(which may be a coil or a loop antenna). Thus, the receiver controller128may wirelessly communicate with the transmission controller108via the wireless communication interface132and the wireless communication interface114using NFC communications or Bluetooth.

In some traditional wireless power systems, a primary coil can transfer wireless energy to a secondary coil up to a rating predetermined by a wireless standard. For example, a low power wireless power signal may convey 5 Watts (5 W), 9 W, 12 W, or 15 W. A low power wireless power system may deliver up to 15 Watts of energy which is suitable for many electronic devices. Higher power wireless systems are being developed to support wireless power transmission to appliances or devices that require more power. For example, a high-power cordless kitchen transmitter may deliver power as high as 2.2 kW.

An interface surface180(sometimes also referred to as an “interface space”) may demark a space between the Power Transmitter and the Power Receiver. For example, the interface surface may include a surface of the Power Transmitter on which the Power Receiver may be placed. A distance between the primary coil110and the secondary coil120may include a thickness of a surface in the interface surface. During wireless power transfer, the primary coil110may induce a magnetic field (referred to as the primary magnetic field) through the interface surface and into an operative environment in which the secondary coil is placed. Thus, the “operative environment” is defined by the primary magnetic field in the system, where the primary magnetic field of a primary coil110is detectably present and can detectably interact with the secondary coil or a foreign object190(shown as FO190).

When a foreign object190is present in the operative environment of the WPT system, the foreign object190may experience an increase in temperature due to interaction with the magnetic field. Therefore, when a foreign object is detected, the Power Transmitter may discontinue generating the primary magnetic field or otherwise prevent the Power Transmitter from transferring sufficient amounts of energy in the foreign object to cause the foreign object to heat beyond a safe level. A WPT system may include a detection apparatus (sometimes also referred to as a foreign object detection mat or “FOD mat”). In some implementations, the detection apparatus may be integrated or coupled with the Power Transmitter102or the interface surface180.

FIG.2shows a block diagram of an example wireless power transfer system200with a detection apparatus for foreign object detection. The wireless power transfer system200includes a Power Transmitter102(with a primary coil110), an interface surface180, and a Power Receiver118(with a secondary coil120) as described with reference toFIG.1. For brevity, other components of the Power Transmitter102and the Power Receiver118are not shown inFIG.2. A detection apparatus (such as the FOD mat150shown inFIG.2, or variations thereof) may include a plurality of detection coils170capable of detecting the presence of a foreign object in accordance with some aspects of this disclosure. In some implementations, the detection apparatus may include an FOD mat150and the detection coils may be constructed into or onto the FOD mat150. Although not shown inFIG.2, in some implementations, the FOD mat may extend for a full area of the interface surface. Alternatively, the FOD mat (and the quantity or configuration of the detection coils therein) may be sized based on a technical specification that defines the sizes of the primary coil110, the secondary coil120, or both. While the example inFIG.2shows the detection apparatus deployed as a FOD mat150in or on a surface, in some implementations the detection apparatus may be deployed on or in any surface or construction in the space between the primary coil110and secondary coil120.

The WPT system may include an FOD assessment unit155. In some implementations, the FOD assessment unit155may be part of the Power Transmitter102(as shown inFIG.2). In some other implementations, the FOD assessment unit155may located elsewhere in the WPT system (such as in the detection apparatus, an FOD control unit (not shown), or as part of an appliance (not shown) that houses the Power Transmitter102, among other examples. The FOD assessment unit155may be configured to detect a foreign object190in proximity to the detection coils170based on detection values, described further herein. In some implementations, the FOD assessment unit155may disable or enable the wireless power transfer operations of the Power Transmitter102based on an FOD assessment result. The FOD assessment result may indicate whether the FOD assessment unit155detects the foreign object190in proximity to the detection coils170or not. In some implementations, the FOD assessment unit155may communicate the FOD assessment result with the Power Receiver118to cause the Power Receiver118to enable or disable the wireless power transfer operations of the Power Receiver118based on the FOD assessment result. In some implementations, when the FOD assessment result is that a foreign object is detected, the FOD assessment result may be referred to as an FOD fault signal. Although only one FOD mat150is shown inFIG.2, in some implementations, two or more FOD mats may be deployed in a WPT system. For example, the FOD assessment unit155may perform foreign object detection using FOD mats (not shown) located in relation to different primary coils of different Power Transmitters in a stove top or other wireless power appliance. Alternatively, or additionally, one FOD mat may be located in association with the Power Transmitter and another FOD mat may be located in association with the Power Receiver. Each of the FOD mats may be connected to the same or different foreign object assessment units (performing the functions described with reference to the FOD assessment unit155ofFIG.2).

The technique by which an FOD assessment unit155communicates an FOD assessment result with the Power Transmitter102or the Power Receiver118may vary. In some implementations, the FOD assessment unit155is implemented in a transmission controller (not shown) of the Power Transmitter102and may provide the FOD assessment result as information processed by the transmission controller. In some other implementations, the FOD assessment unit155may have a wired communication link (not shown) to the transmission controller of the Power Transmitter102. In some implementations, the FOD assessment unit155may communicate by a wireless communication link (not shown) with the Power Transmitter102or the Power Receiver118, or both. In implementations in which the FOD assessment unit155are not integrated in a transmission controller of the Power Transmitter102, the transmission controller may manage the timing of FOD assessments performed by the FOD assessment unit155. For example, the transmission controller may cause the FOD assessment unit155to perform FOD assessments during various operating phases of the WPT system. In some implementations, when the Power Transmitter102triggers FOD assessments, the Power Transmitter102may provide the FOD assessment unit155with an indicator of the current operating phase of the Power Transmitter or may indicate which type of FOD assessment for the FOD assessment unit155to perform. In some implementations, the FOD assessment unit155may communicate an FOD assessment result to the Power Transmitter102or the Power Receiver118using a memory storage unit, a pin line or other control signal without a need for a communication protocol. In some implementations, the FOD assessment unit155may be collocated or implemented as software within a controller of the Power Transmitter102or the Power Receiver118.

The FOD mat150may be a flexible mat, a conformable mat, a rigid mat or a plug and play mat, a standalone mat, or combinations thereof. A substrate of the FOD mat150may be made of electrically insulating material. In some implementations, the FOD mat150may further include a mechanical wear resistant material to withstand movement of the Power Receiver over it (such as when the Power Receiver118is a large appliance). In some implementations, the FOD mat150may further be designed for outdoor application and designed to withstand temperature, humidity and may be resistant to water ingress. The detection coils170may be disposed on a substrate of the FOD mat150or may be embedded in the substrate of the FOD mat150for user safety and aesthetics. In some other embodiments, the detection coils170may be printed, molded, woven, or additively manufactured on the substrate of the FOD mat150.

The detection coils170may be operated in pairs. The FOD assessment unit155may obtain the detection values (such as differential voltages, differential currents, or differential impedances, among other examples) associated with multiple coil pairs. Typically, a Power Receiver118is large enough that it will simultaneously span multiple coil pairs. Conversely, a foreign object190may be smaller than the Power Receiver118. A foreign object190may span only one coil or may span two coils belonging to adjacent coil pairs. By comparing differences in the detection values in a pair of the detection coils, the FOD assessment unit155can detect the presence of a foreign object in the vicinity of the coil pair. For example, a first detection coil171and a second detection coil172may form a coil pair. The foreign object190near the first detection coil171may cause the detection values for the first detection coil171and the second detection coil172to differ. A detection apparatus (such as FOD mat150) may have several such coil pairs and the FOD assessment unit155may compare respective detection values for the coils in each coil pair.

In an implementation that uses active excitation, the FOD assessment unit155may cause a driver (not shown) to excite the first detection coil171and the second detection coil172using a high frequency (higher than a frequency typically used for the primary magnetic field, such as 200 kHz or higher, as an example). The coil pair may be coupled in a parallel circuit to a driver that concurrently excites the detection coils of the coil pair. When present, the foreign object may cause the first detection coil171to experience a different impedance or current flow compared to the second detection coil172(where no foreign object is present). By comparing the current drawn through the first detection coil171and the second detection coil172, the FOD assessment unit155may determine that the foreign object is present near the first detection coil171or the second detection coil172. The difference in current drawn by a coil pair may be referred to as a differential current.

In an implementation that uses passive excitation, the FOD assessment unit155may observe voltages that are induced in detection coils based on the magnetic field produced by the primary coil110. The detection coils in a coil pair may be connected in series and terminated by a known impedance. When the primary coil110is excited by the Power Transmitter102, the magnetic field produced by the primary coil110may induce voltages in the detection coils of a coil pair. In the absence of a foreign object, the voltages in the detection coils may be uniform and effectively cancel out. Conversely, when a foreign object is present, the voltages in the detection coils are non-uniform and results in a differential voltage that can be measured. The differential voltage is an example of a detection value that can be adjusted using the offset values in various implementations of this disclosure.

Thus, the techniques of this disclosure can be used with detection apparatuses that use active excitation or passive excitation. For brevity, many of the examples in this disclosure are based on active excitation, but the same or similar concepts apply to a detection apparatus that uses passive excitation.

FIG.3shows a block diagram300of an example detection apparatus in which a detection value is based on a comparison of coil circuits associated with a pair of detection coils.FIG.3shows a coil pair comprising a first detection coil171and a second detection coil172. The coil pair is connected in parallel to a driver305. Thus, when one of the detection coils in the coil pair is excited, so is the other detection coil. A driver305may be operatively coupled to the coil pair (the first detection coil171and the second detection coil172in this example). The driver305may be configured to concurrently excite the detection coils171and172of the coil pair using an alternating current signal through coil circuits311and312. For example, a first coil circuit311may include a path for electric current from the driver305through the first detection coil171and a second coil circuit312may include a path for electric current from the driver305through the second detection coil172.

A sensing apparatus (not shown) or FOD assessment unit (not shown) may obtain a detection value350associated with the coil pair. For example, the detection value350may be a differential current, a differential voltage, or a differential impedance, among other examples. The detection value350represents a comparison of how electric current is conducted differently when comparing the first detection coil171and the second detection coil172. For example, the detection value350may be a differential current representing a difference between a first current (referenced as “A” inFIG.2) passing through the first coil circuit311and a second current (referenced as “B” inFIG.2) passing through the second coil circuit312.

The detection value350may be adjusted using offset values in accordance with the techniques of this disclosure. In some implementations, the impedance values of the first detection coil171and the second detection coil172may be the same or similar when a foreign object190is not present. However, when the foreign object190is present, the foreign object190may cause a change in impedance to one of the detection coils171and172such that the first detection coil171has a first impedance value and second detection coil172has a second impedance value. The difference in impedance may cause an amount of current drawn through the coil circuits311and312to differ. A differential current may refer to a comparison of the current drawn through the coil circuits311and312. When the foreign object190is not present and the impedance of the detection coils171and172are same or similar, the amount of current drawn through the coil circuits311and312may be same or similar. Therefore, the detection value350may be a low value indicating little or no difference. Conversely, when the foreign object190is present near one of the first detection coil171, the impedance of that first detection coil171will change causing the detection value350to indicate a higher difference in the current drawn through the coil circuits311and312.

An FOD assessment unit (not shown) can obtain detection values (such as detection value350) from multiple coil pairs of detection coils. The FOD assessment unit may distinguish between a movement of the Power Receiver versus introduction of a foreign object based on how many coil pairs have a change in detection values. For example, when the detection values for a threshold quantity of multiple coil pairs indicate a change in differential currents or differential voltages, the FOD assessment unit may determine that such changes are due to a movement of the Power Receiver. When the detection value for one or two coil pairs (or below a threshold quantity) indicates a change in differential current or differential voltage, the FOD assessment unit may determine that such change is due to the introduction of a foreign object. In such instances, the FOD assessment unit may send an FOD assessment result that indicates an FOD fault condition. In some implementations, the FOD assessment unit may modify or offset the detection values for multiple coil pairs in response to determining that a movement of the Power Receiver has occurred. Thus, for a subsequent comparison of the detection values, the FOD assessment unit can adjust the detection values to account for the previous movement of the Power Receiver within the magnetic field of the WPT system. Thus, the accuracy of a subsequent FOD assessment can be improved by accounting for the normal impedance impact of the Power Receiver while still providing an accurate technique for detecting a foreign object.

FIG.4shows a chart400with example magnitudes of detection values. For example,FIG.4pictorially illustrates example magnitudes of differential currents350A and350B (as examples of the differential current350ofFIG.3) and how the differential current may can be used to determine whether a foreign object is present. When no foreign object is present (shown at graph411), a magnitude of the differential current350A may be lower than a detection threshold420. When a foreign object is present (shown at graph412), the magnitude of the differential current350B may be above the detection threshold420. The detection threshold420may be a configurable parameter based on a desired sensitivity of the FOD assessment unit.

In the example shown inFIG.4, a foreign object is detected when the differential current is above a detection threshold. In some implementations, the foreign object is detected based on an amount of change in the differential current. For example, the differential current may be higher during a baseline state and then decrease below a threshold amount when the foreign object is detected. The differential current may become greater or may become lesser (compared to a previous measurement or a baseline measurement) when a foreign object is present. Thus, in some implementations, the amount of change in differential current can indicate the presence of a foreign object. A change in the amount of the differential current may be compared with a detection threshold to determine whether the change is based on the introduction of a foreign object.

FIG.5shows a block diagram of an example detection apparatus500in which a detection value is based on a voltage induced by a differential current. The example detection apparatus may include detection coils arranged in pairs as described herein. For example, the example detection apparatus may include a pair of detection coils171and172(referred to as a coil pair) as described with reference toFIG.3. The detection apparatus may include a driver (not shown) configured to concurrently excite the coil pair during an FOD period. The presence (or lack thereof) of the foreign object190may cause a differential current in the coil circuits311and312.FIG.5provides one example of a differential current sensing apparatus that can be used to measure the differential current. The differential current sensing apparatus may include a magnetic core510and a differential current sensing circuit501, which work in combination to provide a voltage which can be measured to obtain a detection value545.

When the currents on the coil circuits311and312are passed through a magnetic core510, the difference in current generates a flux linkage in the magnetic core. The coil circuits311and312are passed through the magnetic core in opposite directions so that an equal current in the coil circuits311and312will generate a smaller flux linkage while differences in the current of the coil circuits311and312generate a greater flux linkage. The flux linkage in the magnetic core510may induce a corresponding electrical signal in a sensor coil520wound around the magnetic core510. This induced electrical signal, under conditions of the magnetic core510not magnetically saturated, has an induced voltage522that is dependent on (such as related to or proportional to) the difference between current in the coil circuits311and312and is representative of a measure of the differential current between the coil pair of detection coils171and172.

The differential current sensing circuit501also may include a rectifier530that receives and rectifies the induced electrical voltage signal to generate a DC voltage545(referred to as detection value545). An optional filter540may filter the detection voltage before sending the detection voltage to the control unit155. In one example, the filter540is configured to filter out high frequency components from the measurement.

An FOD assessment unit155may be configured to generate a foreign object detection assessment result580(FOD result) indicating the result of the foreign object detection assessment using the detection value545. In some implementations, the FOD assessment unit155may include a comparator560configured to compare an absolute value of the detection value with a detection threshold565. Based on the comparison of the detection value with the detection threshold565, the FOD assessment unit155may provide an FOD assessment result580or other control signal to a component of the WPT system (such as a Power Transmitter or a Power Receiver). For example, when the absolute value of the detection value is greater than the detection threshold565, the FOD assessment unit155may provide an FOD assessment result580that indicates a foreign object is present. Alternatively, the detection value in the presence of foreign object may be lower than the detection value when the foreign object is absent. Thus, in some implementations, a change in the absolute value of the detection voltage (from a previous or baseline measurement to the present measurement) may be compared with a delta threshold and a foreign object may be detected when the amount of change is greater than the delta threshold. The FOD assessment unit155may include a component (referred to as an absolute value unit or ABS555) to generate the absolute value (referred to as the magnitude) of the detection value545.

In some implementations, the FOD assessment unit155also may include an adjustment unit550configured to add or subtract offset values (sometimes referred to as an “offset” for brevity) to corresponding ones of the detection voltage. For example, the offset value may be based on a normal difference in impedance of the coil pair of detection coils171and172or may be based on results of a previous foreign object detection assessment. In some implementations, the initial offset value may be determined during or after manufacturing of the detection coils171and172. Alternatively, or additionally, the initial offset value may be determined by the FOD assessment unit155or test equipment (not shown) during a baseline measurement of the detection apparatus when no foreign object is present. For example, the initial offset value may account for minor differences in impedance caused by other components of an FOD mat, a Power Transmitter, or a Power Receiver, depending on where the detection apparatus is installed. During a calibration of the FOD assessment unit155, calibration values may be measured and stored for use as the initial offset values. During an initial idle phase foreign object detection assessment, the initial offset value (for each detection value) will be subtracted from the actual detection value and passed on to ABS555. The comparator560may compare the absolute value generated by the ABS555with the detection threshold565to generate the FOD result580.

In the idle phase, an initial idle phase foreign object detection assessment utilizes a plurality of offset values, referred to as initial offset values, which are based on the calibration values. In the other operating phases, a Power Receiver is present in the interface surface. The FOD assessment unit155may adapt the plurality of offset values to account for detection of a movement of the Power Receiver on the interface surface when no foreign object is present. For example, the detection value may be used as an updated offset value associated with that coil pair for use in a subsequent foreign object detection assessment (such as in the configuration phase, connected phase, or power transfer phase). The updated offset value may reflect the change in impedance that is attributed to movement of the Power Receiver. In the subsequent foreign object detection assessment, the updated offset value is used by the adjustment unit550to adjust the detection value545.

FIG.6shows a diagram600of a plurality of detection coils in an example detection apparatus. Four coil pairs are shown. A first coil pair comprises first and second detection coils171and172. A second coil pair comprises third and fourth detection coils173and174. A third coil pair comprises fifth and sixth detection coils175and176. A fourth coil pair comprises seventh and eighth detection coils177and178. It should be apparent that the example ofFIG.6is provided for pedagogical purposes and a detection apparatus may have any variety of coil pairs. For brevity, the detection coils171,172,173,174,175,176,177and178are referred to as L1, L2, L3, L4, L5, L6, L7and L8, respectively.

During a foreign object detection assessment, one or more coil pairs may be actively or passively excited such that a detection value can be obtained for each coil pair. In some implementations, the coil pairs may be excited in a sequential pattern so that its related detection value may be measured absent from interference of the other coil pairs. In some implementations, two or more coil pairs having non-adjacent detection coils may be excited and measured concurrently.

FIG.6also shows an example in which a foreign object190is located in proximity to coil L3. When the coil pair of coils L3and L4are excited, those detection coils will draw different currents and the detection value may be indicative that the foreign object is located near one of those coils.

FIG.7shows a diagram of multiple coil pairs capable of distinguishing between movement of a Power Receiver or presence of a foreign object. The layout ofFIG.7utilizes the example configuration of multiple coil pairs described with reference toFIG.6. A primary coil (not shown) may be positioned centered and underneath the detection zones covered by coils L1-L8. A first example701illustrates a secondary coil (shown by a single circle, for brevity) that moves from a first position710to a second position720over the array of detection coils. Because the secondary coil includes metallic and ferrite components, the secondary coil may cause a change in impedance of the detection coils. Thus, when the detection values of the coil pairs are measured, the secondary coil itself may cause a disparity in the detection values associated with some coil pairs. However, because the secondary coil is relatively large compared to the size of the detection coils, multiple coil pairs will measure the change in detection value. By comparison, a second example702illustrates a foreign object190introduced in the operating environment of the WPT system. The foreign object is relatively small compared to the size of the detection coils. Thus, perhaps only one or two coil pairs may measure a change in detection value due to the introduction of the foreign object. In some implementations, the size of the detection coils L1-L8(and their sub coils) may be selected based on a standardized size (or sizes) of a secondary coil that conforms to a technical specification. Similarly, the size of the detection coils L1-L8may be selected based on a potential size of foreign objects that are likely to be introduced into the operating environment. For example, a detection apparatus for use in a kitchen WPT system may include detection coils that are sized appropriately to detect a spoon, fork, coin, key, tin can, or metal plate, among other examples. A detection apparatus for use in an EV WPT system may include detection coils that are sized appropriately to detect a wrench, aluminum can, gas tank, washer, nut, or screw, among other examples. A detection apparatus for use in a desktop WPT system may include detection coils that are sized appropriately to detect foreign object (such as a pen, keys, computer component, ring, or thumb drive, among other examples).

FIG.8shows example charts800comparing detection values of coil pairs due to movement of a Power Receiver versus presence of a foreign object. In a first example810, an FOD assessment unit (such as the FOD assessment unit155described with reference to any of the Figures herein) may establish a baseline representation of the detection voltages (having been adjusted by initial offset values based on calibration values). For example, in the idle phase, the FOD assessment unit may add initial offset values to the detection values for each coil pair based on calibration values. The detection values811,812,813and814may represent measurements of the differential currents (or differential voltages) of multiple coil pairs. The FOD assessment unit may determine that no foreign object is present based on the detection values (having been adjusted by the initial offset values). For example, the FOD assessment unit may compare each detection value with a detection threshold and determine, for each coil pair, that no foreign object is present. Alternatively, or additionally, the detection FOD assessment unit may compare an amount of change for each detection value with a delta threshold and determine that no foreign object is present when the amount of change is below the delta threshold. In other operating phases, in which a Power Receiver is present, and no foreign object is detected, the FOD assessment unit may adapt the plurality of offset values based on changes in impedance caused by movement of the Power Receiver. In the other operating phases, the updated offset values may be used to adjust the detection values for the coil pairs during a subsequent foreign object detection assessment.

In a second example820(such as a subsequent foreign object detection assessment), the Power Receiver may have moved from a previous location associated with a previous assessment. That movement may cause a change in the detection values for the coil pairs. For example, the detection values821,822,823and824may represent measurements of the differential currents (or differential voltages) of multiple coil pairs during the subsequent foreign object detection assessment. In the second example, the detection values822,823and824corresponding do the second, third, and fourth coil pair has changed. The changes in the detection values822,823, and824are circled at826,827, and828, respectively, for the benefit of this description. Although illustrated as a decrease in detection values (circled at826,827, and828) for pedagogical purposes, in some implementations the change may be an increase in detection values. Regardless of whether the change is an increase or a decrease, the FOD assessment unit may determine how many coil pairs have had a change in detection value that is more than a delta threshold. The FOD assessment unit may determine that the changes are due to movement of the Power Receiver because more than a threshold quantity of coil pairs have had a change in their respective detection values. The threshold quantity may be a configurable parameter or may be predetermined. In some implementations, a change in three or more coil pairs may be deemed to be due to a movement of the Power Receiver during wireless power transfer. Once the FOD assessment unit has determined that a change in the detection values is due to a movement of the Power Receiver, the FOD assessment unit may adapt the offset values to account for a new position of the Power Receiver. In some implementations, the offset values may be adapted whenever the result of a foreign object detection assessment is determined to be based on a movement of the Power Receiver.

In a third example830, a foreign object may be introduced into the operating environment during wireless power transfer. The detection values831,832,833and834may represent measurements of the differential currents (or differential voltages) of multiple coil pairs. In the third example, the detection value832of the second coil pair has changed. The change in the detection value832is circled at836for the benefit of this description. Because the quantity of coil pairs having a change in detection value is less than a threshold quantity, the FOD assessment unit may determine that the change is due to a foreign object introduced in proximity to the detection coils of the second coil pair. The FOD assessment unit may send an FOD fault signal or control signal to the WPT system to indicate that a foreign object may be present.

FIG.9shows a block diagram900of an example foreign object detection assessment in which detection values are adjusted based on offset values. The block diagram900may describe features of an FOD assessment unit (such as any of the FOD assessment units described herein, including FOD assessment unit155). At some point prior to a foreign object detection assessment (such as during an installation or servicing of the Power Transmitter), a calibration process905may be performed to determine calibration values910. The calibration values910represent a baseline measurement of impedance differences among the coil pairs at a moment when no foreign objects or Power Receivers are present in the interface surface. The calibration values910may be stored in a non-volatile memory associated with the FOD assessment unit so that they remain even when the Power Transmitter and FOD assessment unit are turned off. When the Power Transmitter is turned on, the FOD assessment unit undergoes an FOD initialization920in which the calibration values910are retrieved from the non-volatile memory and used as initial offset values for the corresponding adjustment units921,922,923, and924.

In the example scenario described with reference toFIG.9, the FOD assessment unit may be configured to receive detection values911,912,913, and914associated with first, second, third, and fourth coil pairs, respectively. For example, the detection values may be a differential voltage, differential current, or differential impedance describing a difference in the energy flowing through the detection coils of a coil pair that are actively or passively excited. Each of the detection values may be obtained using sensing circuits associated with the coil pairs. The detection values911,912,913, and914may be adjusted using adjustment units921,922,923, and924, respectively. Each adjustment unit921,922,923, and924may adjust a corresponding detection values911,912,913, and914by adding or subtracting a corresponding offset value. In the initial idle phase foreign object detection assessment, the offset values (referred to, collectively, as offset values970) may be based on the initial offset values obtained during FOD initialization920. After the detection values911,912,913, and914have been adjusted by adjustment units921,922,923, and924, respectively, ABS's951,952,953, and954, respectively, may generate the absolute values (magnitudes) of the adjusted detection values. A comparator960may compare each adjusted detection value with a detection threshold965to determine whether a foreign object is located near a detection coil of a particular coil pair. In some implementations, such as for an initial idle phase foreign object detection, if any one of the detection values is above the detection threshold, the comparator may send an FOD result980indicating an FOD fault signal. In a foreign object detection assessment in other operating phases, the comparator may determine a quantity of the adjusted detection values that are above the detection threshold965. For example, the comparator may determine a change count indicating how many of the adjusted detection values (corresponding to respective coil pairs) are above the detection threshold965. If the change count is above a threshold quantity967, the comparator may determine that the changes are due to a movement of the Power Receiver. In this situation, the FOD assessment unit may perform an adaptation990to adapt the offset values970for use with a subsequent foreign object detection assessment. Alternatively, if the change count is below the threshold quantity967, the FOD assessment unit may determine that the FOD result980should indicate presence of a foreign object. For the initial idle phase foreign object detection assessment, the threshold quantity967may be disabled, or otherwise set to a high value, such that no change count will be interpreted as a movement of a Power Receiver. In the idle phase, when at least one of the adjusted detection values is above the detection threshold965, the FOD result980may indicate an FOD fault status. In other operating phases, the threshold quantity967may be a configurable value (such as 3 or 4) so that when multiple ones of the adjusted detection values are above the detection threshold965, the FOD assessment unit may determine that the FOD result980should indicate no foreign object present and may perform the adaptation990to update the offset values970for use in a subsequent foreign object detection assessment.

The FOD result980may include a first state that indicates no foreign object detected and a second state that indicates a foreign object has been detected. In some implementations, when the FOD result980indicates a foreign object is detected, the FOD result980may also be referred to as an FOD fault status signal, an FOD fault indication, or term to indicate an FOD fault to the Power Transmitter or Power Receiver). In some implementations, the FOD fault indication will result in the Power Transmitter stopping or reducing the power to the Power Receiver. In some implementations, the FOD fault indication may be presented via a user interface associated with either the Power Transmitter or the Power Receiver.

FIG.10shows a state diagram1000of various operating phases of a WPT system. The state diagram1000illustrates the operating phases in which the WPT system may operate. When a Power Receiver is placed within an interface surface of a Power Transmitter, the two start to communicate with the aim to configure and control the power transfer. There can be four operating phases associated with the WPT system: an idle phase1010(sometimes also referred to as a ping phase), a configuration phase1020, a connected phase1030, and a power transfer phase1040. A technical specification may define how the Power Transmitter and Power Receiver can transition between the operating phases. For example, the WPT system typically begins in the idle phase1010, and can transition from the idle phase1010to the configuration phase1020. From the configuration phase1020, the WPT system can transition to the connected phase1030. From the connected phase1030, the WPT system can transition to the power transfer phase1040. Furthermore, the WPT system can transition back to the idle phase1010from any of the other phases (the configuration phase1020, the connected phase1030, or the power transfer phase1040), such as when a Power Receiver is removed from the interface surface. Each of the operating phases are briefly described herein for reference.

In the idle phase1010(ping phase), the Power Transmitter tries to establish communications with a Power Receiver. The Power Receiver may be just placed on the interface surface or may not be present during this operating phase. The Power Transmitter may attempt to communicate or detect the presence of the Power Receiver. For example, the Power Transmitter may use an analog ping, out-of-band communication (such as NFC), a digital ping, or any combination thereof, to determine that a compatible Power Receiver is present. Once the WPT system determines that a Power Receiver is present (such as by confirming NFC communication), the WPT system may transition to the configuration phase1020.

In the configuration phase1020, the Power Receiver may send basic identification and configuration data to the Power Transmitter. For example, the Power Transmitter may retrieve static configuration information from the Power Receiver via the NFC communication. The Power Transmitter and the Power Receiver may use this information to verify that they both use compatible versions of a technical specification or protocol for wireless power transfer. The Power Transmitter and Power Receiver may communicate basic settings or communicate regarding their respective capabilities. From the configuration phase1020, the WPT system may transition to the connected phase1030.

In the connected phase1030, the Power Transmitter and the Power Receiver may exchange further communications to negotiate the parameters that govern the power transfer phase. After negotiating the parameters, the Power Transmitter may be prepared to transfer wireless power and the Power Receiver may be prepared to receive the wireless power. However, the Power Transmitter may wait for a request or command from the Power Receiver before transitioning to the power transfer phase1040. This may be useful, for example, when a cordless appliance (such as a blender, toaster, mixer, or microwave, among other examples) is configured for use pending a user interaction. The user may initiate the power transfer phase1040by a user interface of the Power Receiver, which in turn communicates to the Power Transmitter to transition to the power transfer phase1040.

In the power transfer phase1040, the Power Transmitter may transfer wireless power to the Power Receiver. Typically, the Power Transmitter will periodically perform a foreign object detection assessment during the power transfer phase1040. In some, the Power Transmitter may perform a foreign object detection assessment to ensure that no foreign objects are present before transitioning from the connected phase1030to the power transfer phase1040. The Power Transmitter also may perform periodic foreign object detection assessments during the power transfer phase1040.

The idle phase1010, the configuration phase1020, and the connected phase1030may be collectively referred to as pre-power phases1002, while the power transfer phase1040may be referred to as a during-power phase1004. Traditional implementations of WPT systems typically describe foreign object detection assessments in the during-power phase1004. However, such implementations may be inadequate to detect and properly handle issues that can arise by the presence of a foreign object in the pre-power phases1002. Furthermore, even when a foreign object detection assessment is performed during one of the pre-power phases1002(such as the idle phase1010), traditional WPT systems do not contemplate how the foreign object detection assessments are coordinated among the various operation phases as the Power Transmitter transitions between them.

FIG.11shows an overview diagram1100of foreign object detection assessments in relationship to the various operating phases of a WPT system. The overview diagram1100includes the idle phase1010, the configuration phase1020, the connected phase1030, and the power transfer phase1040, as described with reference toFIG.10. In accordance with this disclosure, foreign object detection assessments (shown as idle phase FOD assessment1110, pre-power FOD assessments1120and1130, and during-power FOD assessment1140) can be performed in association with multiple (or all) of the operating phases1010,1020,1030, and1040. In some implementations, the foreign object detection assessments may be a precondition before transitioning to a next operating phase. When a foreign object is detected during any of the foreign object detection assessments, an FOD assessment unit may indicate an FOD fault. This application describes various FOD fault handling1180options, some of which may depend on which operating phase the WPT system was performing when the foreign object is detected.

In some implementations, the FOD assessment unit may perform a foreign object detection initialization1108after the Power Transmitter is turned on (shown at block1106) and before (or as part of) the idle phase1010. In some implementations, the Power Transmitter may initialize the FOD assessment unit to prompt an idle phase FOD assessment. During the FOD initialization1108, the FOD assessment may obtain the calibration values (such as from a non-volatile memory) and load them as initial offset values in the FOD assessment unit settings for an initial idle phase foreign object detection assessment1110. In some implementations, foreign object detection initialization1108may include setting a status indicator (referred to as an FOD flag) to maintain a status regarding whether the initial idle phase foreign object detection assessment has been performed. For example, the FOD assessment unit may “set” the FOD flag to a first value (such as “1” or “true”) may represent that the initial idle phase foreign object detection assessment (after powering on the Power Transmitter) has not yet been performed. Conversely, the FOD assessment unit may “clear” the FOD flag by resetting it to a second value (such as “0” or “false”) to represent that the initial idle phase foreign object detection assessment (after powering on the Power Transmitter) has been performed. The example first and second values for the FOD flag are provided here as non-limiting examples. The FOD flag (in addition to the FOD fault status) may control how the WPT system transitions between the various operating phases.

In relationship to the idle phase1010(particularly before a Power Receiver is placed in the interface surface of the Power Transmitter), the FOD assessment unit may perform an idle phase FOD assessment1110. For an idle phase FOD assessment1110, the FOD assessment unit may indicate an FOD fault status when any one or more of the detection values (having been adjusted by the initial offset values associated with calibration values stored in a non-volatile memory) are above the detection threshold. Thus, the idle phase FOD assessment1110may differ from FOD assessments in other operating phases (such as the pre-power FOD assessments1120and1130or the during-power FOD assessment1140) in that the idle phase FOD assessment1110does not attempt to account for movement of a Power Receiver and a lower threshold quantity of detection value comparisons will trigger an FOD fault status. If a foreign object is detected (at block1112), the FOD assessment unit may indicate an FOD fault status (shown at block1175) and proceed to one of several FOD fault handling options1180, as described further with reference toFIG.14. Alternatively, if no foreign object is detected (at block1112), the FOD assessment unit may clear the FOD fault status (and also may clear the FOD flag that was set during the FOD initialization) such that the WPT system may continue operating in the idle phase1010or transition to the configuration phase1020when a Power Receiver is placed on the interface surface. As a reminder, the FOD flag is used by the FOD assessment unit to store and indicate whether the initial idle phase foreign object detection assessment has been performed after the Power Transmitter has been turned on. The FOD flag is set during the FOD initialization (in relation to the Power Transmitter being turned on) and is cleared once the initial idle phase foreign object detection assessment has been performed.

The FOD assessment unit is capable of handling various scenarios, such as a first scenario when no Power Receiver is placed on the interface surface before the Power Transmitter is turned on and a second scenario when a Power Receiver is placed on the interface surface before the Power Transmitter is turned on. In both scenarios, the FOD assessment unit may use the initial offset values (based on calibration values) for idle phase FOD assessments. In an idle phase FOD assessment1110, the FOD assessment unit may indicate an FOD fault status indication when it detects a disparity above a detection threshold in at least one of the detection values for any coil pair. In the scenario when a Power Receiver is placed on the interface surface before the Power Transmitter is turned on, the FOD assessment unit will not clear the FOD flag set during the FOD initialization and will indicate an FOD fault status which can either be cleared by user action (such as using a switch or user interface) or by the user removing the Power Receiver (and foreign object, if present) for a brief period of time and returning the Power Receiver after the FOD assessment unit has performed the initial idle phase foreign object detection assessment.

Recall that the idle-phase FOD assessment1110may use initial offset values based on calibration values stored in a non-volatile memory. The FOD assessment unit may perform foreign object detection assessments1120,1130,1140(and corresponding blocks1122,1132,1142) in relation to the configuration phase1020, the connected phase1030, and the power transfer phase1040, respectively. In each operating phase other than the idle phase, a Power Receiver is present and the FOD assessment unit may determine whether a foreign object is present based on a criteria that can distinguish between foreign objects and system changes, such as a movement of the Power Receiver. For example, movement of the Power Receiver may be detected when multiple adjusted detection values have changed (in comparison to a detection threshold). Conversely, a foreign object may be detected when one (or less than a threshold quantity) of adjusted detection values have changed (in comparison to a detection threshold). When the FOD assessment unit determines there is no foreign object present, the FOD assessment unit may adapt the offset values to account for the system changes. After the adaptation, the updated offset values may be used in a subsequent foreign object detection assessment, including those associated with a later operating phase of the WPT system. In some implementations, the updated offset values (based on adaptation for present system changes unrelated to the presence of a foreign object) may be maintained in a volatile memory associated with the FOD assessment unit.

FIG.12shows a detailed diagram1200of foreign object detection assessments in relationship to the various operating phases of a WPT system. Elements inFIG.12having the same reference numeral as those inFIG.11describe like features. At block1106, the Power Transmitter may be turned on. For example, this may include activating a stovetop or hob that has one or more Power Transmitters integrated therein. When the Power Transmitter is turned on, the Power Transmitter may initialize an FOD assessment unit. The Power Transmitter may initialize the FOD assessment unit before beginning, or during, an idle phase. At block1108, the FOD assessment unit may set an FOD flag (indicating that the initial idle phase foreign object detection assessment has not yet been performed) and an FOD fault status. For example, the FOD flag may be set to a first value (such as “1”) to indicate that the initial idle phase foreign object detection assessment has not yet been performed. Once the initial idle phase foreign object detection assessment has been performed, the FOD flag may be cleared or set to a second value (such as “0”) to indicate such. Furthermore, at block1108, the FOD assessment unit may obtain calibration values and use them to set initial offset values for the initial idle phase foreign object detection assessment.

At block1210(in the idle phase), the Power Transmitter may perform an NFC ping to determine whether a Power Receiver is present. If a Power Receiver is present and at least partially powered, the Power Transmitter's NFC ping will result in a communication from the Power Receiver to the Power Transmitter. Otherwise, if the Power Receiver is not present or does not have its communication interface enabled, the Power Transmitter will not receive a communication in response to the NFC ping. At block1212, if the Power Transmitter receives a response to the NFC ping, the Power Transmitter may transition to the configuration phase at block1220. Note that, in one scenario, a user may have placed the Power Receiver on the Power Transmitter before turning on the Power Transmitter. Thus, in this scenario, it is possible that the Power Transmitter will transition to the configuration phase before an initial idle phase foreign object detection assessment is performed. As described further in detail below, the process described with reference toFIG.12can accommodate this scenario by not clearing the FOD flag and by triggering an FOD fault status, thereby preventing an inaccurate foreign object detection assessment and potentially dangerous outcome.

Continuing briefly with the idle phase, at block1212, if the Power Transmitter does not receive a ping response, the process may continue to block1110. At block1110, the FOD assessment unit may perform an idle phase FOD assessment (such as described with reference toFIG.13). At block1112, the FOD assessment unit may check the result of the idle phase FOD assessment1110to determine if a foreign object has been detected. Note that, in the idle phase, a Power Receiver that did not respond to the NFC ping would also be treated as a foreign object until after the FOD assessment unit has performed an initial idle phase foreign object detection assessment and the Power Transmitter has received a ping response from the Power Receiver. If the FOD assessment unit determines that a foreign object is detected, the process continues to block1215in which the FOD flag is set. From block1215, the process may return to block1210to continue looping in the idle phase until a Power Receiver's NFC ping response is detected. Alternatively, in some implementations (such as when the Power Transmitter or appliance thereof has a user interface), the process may proceed to block1175in which the FOD assessment unit indicates an FOD fault status.

In block1112, if a foreign object is not detected, the process continues to block1214. In block1214, the FOD assessment unit may clear the FOD flag to indicate that the initial idle phase foreign object detection assessment has been performed and no foreign object has been detected. From blocks1214and1215, the process returns to block1210to again ping for the presence of a Power Receiver and remain in the idle phase until such time that the Power Transmitter receives a ping response from a Power Receiver. After any of the idle phase FOD assessments, if the FOD flag had been previously set and the foreign object is removed by the user, the process would ultimately include block1214in which the FOD flag is cleared.

At some point the Power Transmitter may receive a response to the NFC ping. From block1212, the process may continue to block1220(also representing a change from the idle phase to the configuration phase). In block1220, the Power Transmitter may receive configuration information from the Power Receiver. At block1222, the Power Transmitter (or the FOD assessment unit) may check the FOD flag. If the FOD flag is set to a first value (such as “1”) indicating that the initial idle phase foreign object detection assessment has not been performed or a foreign object was not cleared before the placement of the Power Receiver, the process may continue to block1175. At block1175, the FOD assessment unit may indicate an FOD fault status. This scenario happens, for example, when a Power Receiver has been placed on the Power Transmitter before the initial idle phase foreign object detection assessment has been performed (such as before the Power Transmitter is turned on) or when a foreign object has been detected in the idle phase and not yet removed to cause the FOD assessment unit to clear the FOD flag. Because the FOD assessment unit cannot confirm that no foreign object is present, the FOD flag and FOD fault status would prevent the Power Transmitter from continuing operation until an idle phase foreign object detection assessment can be performed and the FOD assessment unit can confirm that no foreign object is present. As described further herein, the FOD fault handling1180may include the user removing the Power Receiver briefly so that the Power Transmitter can return to the idle phase (block1210) and perform another idle phase FOD assessment at block1110in the idle phase. For example, the FOD fault handling1180may include the user removing the foreign object or Power Receiver so that the idle phase FOD assessment1110can verify that the interface surface is clear of all foreign objects and Power Receiver.

In block1222, if the FOD flag is cleared (or otherwise indicates that the idle phase foreign object detection assessment has confirmed there are no foreign objects present before placement of the Power Receiver), the process may continue to block1221. In block1221, the FOD assessment unit may perform an adaptation to recalibrate the offset values. The FOD assessment unit may take new measurements of the detection values and store them as adapted offset values. Thus, the adapted offset values take into account the presence of the Power Receiver in the interface surface.

At block1120, the FOD assessment unit may perform another foreign object detection assessment, this time with the Power Receiver placed over the Power Transmitter. This operation at block1120may be used to verify that no foreign object has been introduced and also to adapt the offset values that can be used in subsequent foreign object detection assessments for taking care of impedance changes on account of movement of the Power Receiver on the interface surface. At block1122(in the configuration phase), if a foreign object is detected, the process may continue to block1175to indicate an FOD fault status and cease the configuration operating phase. Otherwise, at block1122, if no foreign object is detected, the process may continue to block1230. In some implementations, the FOD assessment unit may adapt the offset values (not shown) to account for the system changes, such as movement of the Power Receiver. After the adaptation, the updated offset values may be used in a subsequent foreign object detection assessment, including those associated with a later operating phase of the WPT system.

At block1230, the Power Transmitter may determine whether the Power Receiver is ready for operation. When the Power Receiver is operated, it is ready to receive the wireless power transfer. Typically, a user interface on the Power Receiver may control whether the Power Receiver is ready for operation, such as when a user presses a button to activate the Power Receiver. If the Power Receiver is not ready for operation, the process may continue to block1130. At block1130, the FOD assessment unit may perform a foreign object detection assessment and at block1132, the FOD assessment unit may determine whether the result of the foreign object detection assessment indicates a foreign object is detected or not. If a foreign object is detected, the process continues to block1175. If no foreign object is detected, the process continues to block1231. At block1231, the FOD assessment unit may adapt the offset values to account for the system changes. For example, if the FOD assessment unit detects a movement of the Power Receiver (such as based on a count of adjusted detection values being above a threshold quantity), the FOD assessment unit may perform an adaptation to adapt the offset values for use in a subsequent foreign object detection assessment. Note that blocks1230,1130,1132and1231may form a loop such that the FOD assessment unit can periodically or continuously monitor for a foreign object introduced into the operative environment of the Power Transmitter while the Power Transmitter is in the connected phase and the Power Receiver is not being operated. When the Power Receiver is ready for operation, the Power Receiver may communicate a message to the Power Transmitter to request a transition from the connected phase to the power transfer phase. At block1230, when the Power Receiver is ready for operation (as indicated by the aforementioned message), the Power Transmitter may transition to the power transfer phase at block1240.

At block1240, the Power Transmitter may begin power transfer by energizing a primary coil of the Power Transmitter and generating an electromagnetic field to transfer power to the Power Receiver. During the power transfer phase, the Power Transmitter may periodically confirm that the Power Receiver is being operated (shown at block1242) and the FOD assessment unit may periodically perform foreign object detection assessments (shown at block1140). At any time that the Power Receiver is no longer being operated (as determined in block1242), the process may continue to block1280. At block1280, the Power Transmitter may determine whether the Power Receiver is still present. If so, the Power Transmitter may transition back to the connected phase at block1230. If the Power Receiver has been removed, the Power Transmitter may transition back to the idle phase at block1210. During the power transfer phase, the FOD assessment unit may periodically perform foreign object detection assessments (shown at block1140). This enables the WPT system to react to an introduction of a foreign object in the operative environment. At block1142, when the FOD assessment unit determines that no foreign object is present, the process proceed to block1241to adapt the offset values to account for system changes, if any. From block1241, the process may return to block1240to continue the wireless power transfer. At block1142, when a foreign objected is detected, the process may continue to block1244. At block1244, the Power Transmitter may end or limit the wireless power transfer. From block1244, the process may continue to block1175to indicate an FOD fault status.

At block1175, the WPT system (such as the FOD assessment unit, the Power Transmitter, or the Power Receiver, among other examples) may indicate the FOD fault status. For example, the FOD fault status may be presented via a user interface associated with the Power Transmitter, the Power Receiver, or both. In some implementations, the FOD fault status may include a communication from the Power Transmitter to the Power Receiver (or vice versa) to communicate that an FOD fault status has been indicated. At block1180, there may be a multitude of ways to clear an FOD fault status, such as those described with reference toFIG.14. For example, the user may remove the foreign object. In another example, the user may remove the Power Receiver to enable the FOD assessment unit to perform an idle phase foreign object detection assessment in the idle phase using the initial offset values before returning the Power Receiver. In some implementations, a user interface may enable a manual override to reset the FOD fault status or to force an adaptation of the offset values to account for metals present in the operative environment and known to the user to be safe for use in the operative environment. Furthermore, a user interface may enable a manual initiation of a calibration procedure to measure new calibration values to be stored in a non-volatile memory for use the next time the Power Transmitter is turned on.

FIG.13shows a process1300for a foreign object detection assessment. At block1310, a FOD assessment unit may assess detection values for each coil pair of the detection coils. For example, at block1312, the FOD assessment unit may obtain a detection value (such as a differential current or differential voltage). At block1314, the FOD assessment unit may adjust the detection value using an offset value for that coil pair. In the idle phase, the offset value may be an initial offset value based on a calibration value. In the other operating phases, the offset value may be an adapted offset value based on a previous foreign object detection assessment. At block1316, the FOD assessment unit may compare the adjusted detection value (or an absolute value of the adjusted detection value) to a detection threshold. At block1318, if the adjusted detection value is above the detection threshold, the process may continue to block1322. At block1322, the FOD assessment unit may determine that a metal object (perhaps a foreign object or the Power Receiver) has been detected. At block1322, the FOD assessment unit may add the coil pair to a count of coil pairs that have detected a metal object. The count of coil pairs is reset for each foreign object detection assessment and represents a count of coil pairs impacted by the presence of a metal object during a particular iteration of the foreign object detection assessment. The process may continue to block1324, where the FOD assessment unit continues to assess a next coil pair in the same manner as described with reference to block1310. At block1318, when the adjusted detection value is not above the detection threshold, the FOD assessment unit may determine that the coil pair is not affected by a metal object and the process continues to block1324to assess a next coil pair. After assessing multiple coil pairs at bock1310, the process may continue to block1330.

At block1330, in some implementations the FOD assessment unit may determine whether a magnitude of any adjusted detection value is above a safety limit. If so, the process may continue to block1350where the FOD assessment unit may generate an FOD result indicating that a foreign object has been detected. Alternatively, or additionally, the FOD assessment unit may cause a user interface to request user feedback whether to continue with the FOD assessment. The safety limit provides a mechanism to detect a faulty coil pair, sensor, or a foreign object that may be present near one coil pair, even if multiple coil pairs have also registered the presence of a Power Receiver. For example, the safety limit may be higher than the detection threshold in block1318. If none of magnitudes of the adjusted detection values are above the safety limit, the process may continue to block1340.

At block1340, the FOD assessment unit may determine whether the count of coil pairs with metal detection (as accumulated at block1322) is above a threshold quantity. In some implementations, the threshold quantity may depend on the operating phase the Power Transmitter. For example, in the idle phase, when the Power Receive is absent, a single coil pair or even if all coil pairs have metal detection, the FOD assessment unit will trigger an FOD fault status and the process will proceed to block1350. In the configuration phase, connected phase, or power transfer phase, the threshold quantity may be set such that three or more coil pairs having metal detection may be interpreted as being due to movement of the Power Receiver.

Returning to block1340, if the count is below the threshold quantity, the process continues to block1350. As a reminder, at block1350, the FOD assessment unit may generate an FOD result indicating a foreign object has been detected. By way of example, at block1340, in the configuration phase, connected phase, or power transfer phase, if only one or two coil pairs has detected a metal object (and the threshold quantity is three coil pairs), the FOD assessment unit may infer that that coil pair has detected a foreign metal object. Alternatively, in the configuration phase, connected phase, or power transfer phase, if multiple coil pairs (above the threshold quantity, such as three) have detected a change in the adjusted detection values, the FOD assessment unit may infer that such change is due to a movement of the Power Receiver. At block1340, if the count of coil pairs with metal detection is above the threshold quantity, the process may continue to block1360. At block1360, the FOD assessment unit may perform an adaption in which the FOD assessment unit updates the offset values to account for the movement of the Power Receiver. Thereafter, the updated offset values may be used for a subsequent foreign object detection assessment. At block1370, the FOD assessment unit may generate an FOD result indicating that no foreign object has been detected.

FIG.14shows example operations1400for FOD fault handling. The example operations1400are provided as options, some of which may be omitted in various implementations. At block1410, a Power Transmitter may indicate the FOD fault, such as via a user interface associated with the Power Transmitter. At block1420, the Power Transmitter (or the FOD assessment unit) may communicate the FOD fault status to the Power Receiver. In turn, the Power Receiver may indicate the FOD fault, such as via a user interface associated with the Power Receiver.

In some implementations, a user interaction (such as via a user interface associated with the Power Transmitter or the Power Receiver) may cause the WPT system to override the FOD fault. At block1430, when a user interaction overrides the FOD fault, the process may continue to block1440. Otherwise, the process may continue to another FOD fault handling option, such as at block1470. At block1440, based on a user override, the FOD assessment unit may perform an adaptation in which the FOD assessment unit updates the offset values based on the existing detection values. At block1450, the FOD assessment unit may clear the FOD fault status. At block1460, the FOD assessment unit may reset the FOD flag. From there, the Power Transmitter may return (via reference “B”) to block1120ofFIG.12. In some implementations, with the user override, the Power Transmitter may return to block1221or block1230ofFIG.12and proceed subsequently to the connected phase.

In some implementations, the FOD fault status may be cleared by removing the Power Receiver from the interface surface. At block1470, when the Power Receiver is removed from the interface surface, the WPT system may revert to the idle phase. At block1452, the FOD assessment unit may clear the FOD fault status. At block1462, the FOD assessment unit may clear or reset the FOD flag. From there, the Power Transmitter may return (via reference “A”) to block1210ofFIG.12and the idle phase.

FIG.15shows a flowchart diagram of an example process1500for detecting a foreign object in accordance with some implementations. The operations of the process1500may be implemented by an FOD assessment unit as described herein. For example, the operations of process1500may be implemented by a FOD assessment unit described with reference toFIGS.2-14. In some implementations, the FOD assessment unit may be included in, or part of, a transmission controller of a Power Transmitter. Alternatively, the operations of process1500may be performed by a Power Transmitter, a Power Receiver, or another component of the WPT system. For brevity, the operations of process1500are described as performed by an apparatus.

At block1510, the apparatus may initialize an FOD assessment unit prior to or as part of an idle phase in response to a user input to turn on a Power Transmitter. Initializing the FOD assessment unit may include setting an FOD flag to a first value to represent that an initial idle phase foreign object detection assessment has not yet been performed.

At block1520, the apparatus may indicate an FOD fault status if the Power Transmitter transitions from the idle phase to a different operating phase when the FOD flag is set to the first value.

FIG.16shows a block diagram of an example apparatus1600for use in wireless power transfer system. In some implementations, the apparatus1600may be a detection apparatus, such as any of the detection apparatuses described herein. In some implementations, the apparatus1600may be an FOD assessment unit, such as any of the FOD assessment units described herein. The apparatus1600can include a processor1602(possibly including multiple processors, multiple cores, multiple nodes, or implementing multi-threading, etc.). The apparatus1600also can include a memory1606. The memory1606may be system memory or any one or more of the possible realizations of computer-readable media described herein. The apparatus1600also can include a bus1611(such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.).

The apparatus1600may include one or more controller(s)1662configured to manage excitation of multiple detection coils (such as a coil array1664). In some implementations, the controller(s)1662can be distributed within the processor1602, the memory1606, and the bus1611. The controller(s)1662may perform some or all of the operations described herein. For example, the controller(s)1662may implement the features of a driver controller described herein.

The memory1606can include computer instructions executable by the processor1602to implement the functionality of the implementations described with reference toFIGS.1-15. Any one of these functionalities may be partially (or entirely) implemented in hardware or on the processor1602. For example, the functionality may be implemented with an application specific integrated circuit, in logic implemented in the processor1602, in a co-processor on a peripheral device or card, etc. Further, realizations may include fewer or additional components not illustrated inFIG.16. The processor1602, the memory1606, and the controller(s)1662may be coupled to the bus1611. Although illustrated as being coupled to the bus1611, the memory1606may be coupled to the processor1602.

The figures, operations, and components described herein are examples meant to aid in understanding example implementations and should not be used to limit the potential implementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently.

The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. While the aspects of the disclosure have been described in terms of various examples, any combination of aspects from any of the examples is also within the scope of the disclosure. The examples in this disclosure are provided for pedagogical purposes. Alternatively, or in addition to the other examples described herein, examples include any combination of the following implementation options (enumerated as clauses for clarity).

CLAUSES

Clause 1. A method for foreign object detection (FOD) in a wireless power transfer (WPT) system, including: initializing an FOD assessment unit prior to or as part of an idle phase in response to a user input to turn on a Power Transmitter, where initializing the FOD assessment unit includes setting an FOD flag to a first value to represent that an initial idle phase foreign object detection assessment has not yet been performed; and indicating an FOD fault status if the Power Transmitter transitions from the idle phase to a different operating phase when the FOD flag is set to the first value.

Clause 2. The method of clause 1, further including: performing the initial idle phase foreign object detection assessment when the Power Transmitter is in the idle phase; and setting the FOD flag to a second value when a result of the initial idle phase foreign object detection assessment indicates that no foreign object is detected; and indicating the FOD fault status when the result of the initial idle phase foreign object detection assessment indicates that a foreign object is detected.

Clause 3. The method of clause 1, further including: determining that the Power Transmitter has transitioned from the idle phase to the different operating phase based on presence of a Power Receiver before the initial idle phase foreign object detection assessment has been performed, said determining based, at least in part, on the FOD flag being set to the first value when the Power Transmitter transitions from the idle phase to the different operating phase.

Clause 4. The method of clause 3, further including: indicating the FOD fault status to prompt a removal of the Power Receiver from an interface surface associated with the Power Transmitter.

Clause 5. The method of any one of clauses 1-4, where the initial idle phase foreign object detection assessment is unique compared to a pre-power foreign object detection assessment and a during-power foreign object detection assessment associated with different respective operating phases.

Clause 6. The method of any one of clauses 1-5, where performing the initial idle phase foreign object detection assessment includes: obtaining a plurality of detection values, each detection value indicating a disparity between detection coils in a respective pair of detection coils; adjusting one or more of the plurality of detection values by adding or subtracting corresponding ones of a plurality of offset values, where the plurality of offset values are initial offset values based on a calibration of the FOD assessment unit; comparing each of the plurality of detection values to a detection threshold; and determining that a foreign object is detected when at least one of the plurality of detection values is above the detection threshold.

Clause 7. The method of clause 6, where initializing the FOD assessment unit further includes: obtaining the calibration values from a non-volatile memory; and determining the initial offset values based on the calibration values.

Clause 8. The method of clause 7, further including: determining the calibration values as part of a manufacturing, installation or servicing of the Power Transmitter; and storing the calibration values in the non-volatile memory.

Clause 9. The method of any one of clauses 1-8, further including: setting the FOD flag to a second value when a result of the initial idle phase foreign object detection assessment indicates that no foreign object is detected; determining that the Power Transmitter has transitioned from the idle phase to a configuration phase in response to a communication handshake between the Power Transmitter and a Power Receiver; and adapting a plurality of offset values for use in a pre-power foreign object detection assessment.

Clause 10. The method of clause 9, where adapting the FOD assessment unit includes: obtaining a plurality of detection values, each detection value indicating a disparity between detection coils in a respective pair of detection coils, and updating the plurality of offset values based on the plurality of detection values; and storing the plurality of offset values in a volatile memory of the Power Transmitter for use in a subsequent foreign object detection assessment.

Clause 11. The method of any one of clauses 1-10, further including: performing a plurality of foreign object detection assessments at more than one operating phase of the Power Transmitter, the plurality of FOD assessments including at least a pre-power foreign object detection assessment performed in a configuration phase or a connected phase.

Clause 12. The method of clause 11, where the pre-power foreign object detection assessment includes: obtaining updated values for the plurality of detection values; adjusting one or more of the plurality of detection values by adding or subtracting corresponding ones of the plurality of offset values; comparing each of the plurality of detection values to a detection threshold; determining a count of how many of the plurality of detection values are above the detection threshold; and indicating that a result of the pre-power foreign object detection assessment is that a foreign object is detected when the count is less than a threshold quantity.

Clause 13. The method of clause 12, where the pre-power foreign object detection assessment further includes: indicating that the result of the pre-power foreign object detection assessment is that a foreign object is detected when a magnitude of any one of the plurality of detection values is above a limit.

Clause 14. The method of clause 12, where the pre-power foreign object detection assessment further includes: indicating that the result of the pre-power foreign object detection assessment is that no foreign object is detected when the count is zero or when the count is greater than or equal to the threshold quantity.

Clause 15. The method of any one of clauses 12-14, further including: determining that a Power Receiver has moved when the count is greater than or equal to the threshold quantity; and adapting the plurality of offset values in to generate an updated plurality of offset values based on the plurality of detection values in response to a determination that the Power Receiver has moved such that the updated plurality of offset values are usable in a subsequent foreign object detection assessment.

Clause 16. The method of clause 15, further including: storing the updated plurality of offset values in a volatile memory such that the updated plurality of offset values is maintained while the Power Transmitter is turned on and the updated plurality of offset values are discarded when the Power Transmitter is turned off.

Clause 17. The method of any one of clauses 1-16, where indicating the FOD fault status includes at least one of: causing a user interface to present an indication of the FOD fault status, where the user interface is at the Power Transmitter, an appliance that houses the Power Transmitter, or a Power Receiver placed on an interface surface of the Power Transmitter, or communicating an indication of the FOD fault status via a communication interface associated with the Power Transmitter.

Clause 18. The method of any one of clauses 1-17, further including: receiving an indication of a user interaction to override the FOD fault status; setting the FOD flag to the second value; and clearing the FOD fault status.

Clause 19. The method of clause 18, further including: adapting the plurality of offset values for a subsequent foreign object detection assessment in response to said receiving the indication to override the FOD fault status.

Clause 20. The method of clause 19, further including: transitioning to the idle phase once the Power Receiver is removed from the interface surface; and performing the initial idle phase foreign object detection assessment when the Power Transmitter is in the idle phase.

Clause 21. A system for foreign object detection (FOD), including: a Power Transmitter configured to initialize an FOD assessment unit prior to or as part of an idle phase in response to a user input to turn on a Power Transmitter, where initializing the FOD assessment unit includes setting an FOD flag to a first value to represent that an initial idle phase foreign object detection assessment has not yet been performed; and the FOD assessment unit configured to indicate an FOD fault status if the Power Transmitter transitions from the idle phase to a different operating phase when the FOD flag is set to the first value.

Clause 22. The system of clause 21, where the FOD assessment unit is further configured to: perform the initial idle phase foreign object detection assessment when the Power Transmitter is in the idle phase; and set the FOD flag to a second value when a result of the initial idle phase foreign object detection assessment indicates that no foreign object is detected; and indicate the FOD fault status when the result of the initial idle phase foreign object detection assessment indicates that a foreign object is detected.

Clause 23. The system of clause 21, where the FOD assessment unit is configured to determine that the Power Transmitter has transitioned from the idle phase to the different operating phase based on presence of a Power Receiver before the initial idle phase foreign object detection assessment has been performed, said determining based, at least in part, on the FOD flag being set to the first value when the Power Transmitter transitions from the idle phase to the different operating phase.

Clause 24. The system of clause 23, where the FOD assessment unit is configured to indicate the FOD fault status to prompt a removal of the Power Receiver from an interface surface associated with the Power Transmitter.

Clause 25. The system of any one of clauses 21-24, where the initial idle phase foreign object detection assessment is unique compared to a pre-power foreign object detection assessment and a during-power foreign object detection assessment associated with different respective operating phases.

Clause 26. The system of any one of clauses 21-25, where, during the idle phase, the FOD assessment unit is configured to: obtain a plurality of detection values, each detection value indicating a disparity between detection coils in a respective pair of detection coils; adjust one or more of the plurality of detection values by adding or subtracting corresponding ones of a plurality of offset values, where the plurality of offset values are initial offset values based on a calibration of the FOD assessment unit; compare each of the plurality of detection values to a detection threshold; and determine that a foreign object is detected when at least one of the plurality of detection values is above the detection threshold.

Clause 27. The system of clause 26, further including: the non-volatile memory configured to store the calibration values, and where the FOD assessment unit is configured to determine the initial offset values based on the calibration values.

Clause 28. The system of any one of clauses 21-27, where the FOD assessment unit is configured to: set the FOD flag to a second value when a result of the initial idle phase foreign object detection assessment indicates that no foreign object is detected; determine that the Power Transmitter has transitioned from the idle phase to a configuration phase in response to a communication handshake between the Power Transmitter and a Power Receiver; and adapt a plurality of offset values for use in a pre-power foreign object detection assessment.

Clause 29. The system of clause 28, where the FOD assessment unit is further configured to: obtain a plurality of detection values, each detection value indicating a disparity between detection coils in a respective pair of detection coils, and update the plurality of offset values based on the plurality of detection values; and store the plurality of offset values in a volatile memory of the Power Transmitter for use in a subsequent foreign object detection assessment.

Clause 30. The system of any one of clauses 21-29, where the FOD assessment unit is configured to perform a plurality of foreign object detection assessments at more than one operating phase of the Power Transmitter, the plurality of FOD assessments including at least a pre-power foreign object detection assessment performed in a configuration phase or a connected phase.

Clause 31. The system of clause 30, where the FOD assessment unit being configured to perform the pre-power foreign object detection assessment includes the FOD assessment unit being configured to: obtain updated values for the plurality of detection values; adjust one or more of the plurality of detection values by adding or subtracting corresponding ones of the plurality of offset values; compare each of the plurality of detection values to a detection threshold; determine a count of how many of the plurality of detection values are above the detection threshold; and indicate that a result of the pre-power foreign object detection assessment is that a foreign object is detected when the count is less than a threshold quantity.

Clause 32. The system of clause 31, where the FOD assessment unit being configured to perform the pre-power foreign object detection assessment includes the FOD assessment unit being configured to: indicate that the result of the pre-power foreign object detection assessment is that a foreign object is detected when a magnitude of any one of the plurality of detection values is above a limit.

Clause 33. The system of clause 31, where the FOD assessment unit being configured to perform the pre-power foreign object detection assessment includes the FOD assessment unit being configured to: indicate that the result of the pre-power foreign object detection assessment is that no foreign object is detected when the count is zero or when the count is greater than or equal to the threshold quantity.

Clause 34. The system of any one of clauses 31-33, where the FOD assessment unit is further configured to: determine that a Power Receiver has moved when the count is greater than or equal to the threshold quantity; and adapt the plurality of offset values in to generate an updated plurality of offset values based on the plurality of detection values in response to a determination that the Power Receiver has moved such that the updated plurality of offset values are usable in a subsequent foreign object detection assessment.

Clause 35. The system of clause 34, where the FOD assessment unit is further configured to: store the updated plurality of offset values in a volatile memory such that the updated plurality of offset values is maintained while the Power Transmitter is turned on and the updated plurality of offset values are discarded when the Power Transmitter is turned off.

Clause 36. The system of any one of clauses 21-35, where the FOD assessment unit being configured to indicate the FOD fault status includes the FOD assessment unit being configured perform to at least one operation of: causing a user interface to present an indication of the FOD fault status, where the user interface is at the Power Transmitter, an appliance that houses the Power Transmitter, or a Power Receiver placed on an interface surface of the Power Transmitter, or communicating an indication of the FOD fault status via a communication interface associated with the Power Transmitter.

Clause 37. The system of any one of clauses 21-36, where the FOD assessment unit is further configured to: receive an indication of a user interaction to override the FOD fault status; set the FOD flag to the second value; and clear the FOD fault status.

Clause 38. The system of clause 37, where the FOD assessment unit is further configured to adapt the plurality of offset values for a subsequent foreign object detection assessment in response to said receiving the indication to override the FOD fault status.

Clause 39. The system of clause 38, where the Power Transmitter is configured to transition to the idle phase once the Power Receiver is removed from the interface surface; and where the FOD assessment unit is configured to perform the initial idle phase foreign object detection assessment when the Power Transmitter is in the idle phase.

Another innovative aspect of the subject matter described in this disclosure can be implemented as an apparatus. The apparatus may include a modem and at least one processor communicatively coupled with the at least one modem. The processor, in conjunction with the modem, may be configured to perform any one of the above-mentioned methods or features described herein.

Another innovative aspect of the subject matter described in this disclosure can be implemented as a computer-readable medium having stored therein instructions which, when executed by a processor, causes the processor to perform any one of the above-mentioned methods or features described herein.

Another innovative aspect of the subject matter described in this disclosure can be implemented as a system having means for implementing any one of the above-mentioned methods or features described herein.

As used herein, a phrase referring to “at least one of” or “one or more of” a list of items refers to any combination of those items, including single members. For example, “at least one of: a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

As described above, in some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process or algorithm disclosed herein can be implemented as one or more modules of one or more computer programs. Such computer programs can include non-transitory processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by, or to control the operation of, a data processing apparatus including the components of the devices described herein. By way of example, and not limitation, such storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.