Foreign body detection and affinity metals

Abstract

The present disclosure provides systems, methods, and apparatus for object detection by a power transmitter (PTx) that supports both induction heating and wireless power transmission. The object detection assessment is based on measurements taken while the PTx is transmitting an object detection pulse (also called an object detection signal). Once the PTx determines that a power receiver (PRx) is present within the PTx's magnetic field, the PTx can compare the measurements to various thresholds to determine whether a foreign object is also present within the magnetic field. The various thresholds include a PRx threshold range. In some embodiments, the PRx threshold range enables the PTx to distinguish between foreign objects and PRx containing affinity metals that would otherwise be detected as foreign objects. In some embodiments, the object detection assessment is combined with a coupling coefficient measurement to simultaneously detect foreign objects and calculate the coupling coefficient between the PTx and the PRx.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to wireless power transfer and possibly foreign object detection techniques. [Background technology]

[0002] An electrical appliance (such as a kitchen countertop or hob) can support induction heating of an object (such as a cooking vessel or utensil). For example, a hob may include several "burner" positions on which a user can place the cooking vessel or utensil to be heated. Traditional hobs use an electric or gas heat source to heat the cooking vessel in contact with the heat source. Modern hobs that support induction heating can use an electromagnetic field (without a direct heat source) to heat the internal cooking vessel or utensil. The electromagnetic field may be generated by one or more coils (sometimes called induction coils). During induction heating, the electromagnetic field induces currents in the metal surface of the cooking vessel or utensil. The induced currents in the cooking vessel or utensil surface induce further currents (sometimes called eddy currents) within the cooking vessel, thereby providing heat throughout the cooking vessel.

[0003] Meanwhile, in another technical field, technologies enabling wireless power transmission have been developed. Wireless power transmission is sometimes referred to as contactless power transmission or contactless power transmission. Wireless power can be transmitted using inductive or resonant coupling between a power transmitter (sometimes referred to as a "wireless power transmitter") and a power receiver (sometimes referred to as a "wireless power receiver"). For example, a power transmitter can include one or more coils (called primary coils) that generate an electromagnetic field. The electromagnetic field can induce an electromotive force in the secondary coil of the power receiver when the secondary coil is placed in close proximity to the primary coil. In this configuration, the electromagnetic field can wirelessly transmit power to the secondary coil. Power receivers can be included in various types of devices, such as mobile devices, small electronic devices, computers, tablets, gadgets, electrical appliances (such as cordless blenders, kettles, and mixers), and some types of large electronic devices, among other examples.

[0004] Because induction heating and wireless power transmission share some common components and applications in the kitchen, it is desirable to provide a multifunction hob that supports both induction heating and wireless power transmission modes. Alternatively, a multifunction hob can support either induction heating of one type of object (such as a cooking vessel or appliance) and wireless power transmission to another type of object (such as an electrical appliance with a power receiver), depending on which type of object is present at a particular time. A third type of object (such as a key, coin, metal can, or aluminum foil, among other examples) is referred to as a metallic foreign object or foreign body. When a foreign object is present in an electromagnetic field, eddy currents can cause the foreign object to heat up. Therefore, a multifunction hob must accurately determine which type of object is present in the electromagnetic field, especially before the multifunction hob initiates induction heating or wireless power transmission. Summary of the Invention

[0005] The systems, methods, and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless power transmission by a power transmitter, the method including: receiving a communication from a power receiver present within a magnetic field of the power transmitter; obtaining measurements based on an object detection evaluation; and determining, based on the measurements, whether a foreign object is present in the magnetic field with the power receiver.

[0007] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless power transmission, the method including: receiving a communication from a power receiver present within a magnetic field of a power transmitter; obtaining measurements of low power transmission from the power transmitter during an object detection evaluation; and calculating a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver.

[0008] Another innovative aspect of the subject matter described in this disclosure can be embodied as an apparatus for wireless power transmission. The apparatus includes a communication unit configured to receive communications from a power receiver present within a magnetic field of a power transmitter. The apparatus includes a measurement unit configured to obtain measurements based on an object detection evaluation. The apparatus includes a control unit configured to determine whether a foreign object is present in the magnetic field with the power receiver based on the measurements.

[0009] Another innovative aspect of the subject matter described in this disclosure can be embodied as an apparatus for wireless power transmission. The apparatus includes a communication unit configured to receive communications from a power receiver present within a magnetic field of a power transmitter. The apparatus includes a measurement unit configured to obtain measurements of low power transmission from the power transmitter during object detection evaluation. The apparatus includes a control unit configured to calculate a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver. [Brief explanation of the drawings]

[0010] The details of one or more embodiments of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. It should be noted that the relative dimensions of the following figures may not be drawn to scale.

[0011] [Figure 1] FIG. 1 is a conceptual diagram illustrating an example multifunction hob and an example object. [Figure 2] FIG. 1 is a block diagram of an exemplary wireless power transfer system. [Figure 3] 1 is a flow diagram of an exemplary process for object detection evaluation. [Figure 4] FIG. 1 conceptually illustrates various ranges and measurements for object detection. [Figure 5] FIG. 1 conceptually illustrates measurements and ranges of a power receiver (PRx) with affinity metal. [Figure 6] FIG. 1 is a timing diagram showing a baseline scenario when PRx with affinity metals is repeatedly detected as foreign bodies. [Figure 7] FIG. 10 is a timing diagram illustrating an example scenario in which a reference value of a PRx with an affinity metal can be used for subsequent object detection evaluation. [Figure 8]FIG. 10 is a timing diagram illustrating an example scenario in which communication from a PRx with an affinity for metals can improve object detection evaluation results. [Figure 9] FIG. 1 is a block diagram of an exemplary power transmitter (PTx). [Figure 10] FIG. 10 is a block diagram of an example PRx that can disconnect the secondary coil with a switch during object detection evaluation using coupling coefficient measurements. [Figure 11] 1 is a flow diagram of an exemplary process according to some aspects of the present disclosure. [Figure 12] 1 is a flow diagram of an exemplary process according to some aspects of the present disclosure. [Figure 13] FIG. 1 is a block diagram of an exemplary apparatus for use in a multifunction hob.

[0012] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0013] A device (such as a multifunction hob) may support an induction heating mode (for use with some types of appliances) and a wireless power transmission mode (for use with other types of appliances). For example, in the induction heating mode, the device may support induction heating of an induction heating appliance (such as a cooking vessel or utensil). In the wireless power transmission (WPT) mode, the device may support wireless power transmission to a wireless power receiver (PRx). For brevity, this disclosure may refer to the device as a power transmitter (PTx) because it supports the wireless power transmission mode. Furthermore, while a multifunction hob may have multiple such PTxs, the concepts of this disclosure are described in relation to one PTx and can be extended to other PTxs in a multifunction hob. The disclosed PTx may differ from conventional PTxs in that it is configured to also support the induction heating mode when an appropriate induction heating appliance is placed in proximity to one or more coils of the PTx.

[0014] Because the PTx of the present disclosure supports both induction heating and wireless power transfer, it is desirable to detect different types of objects that may be placed in proximity to one or more coils of the PTx. Examples of a first type of object include a pot, pan, wok, or any cooking vessel or utensil for which induction heating mode is appropriate. All of these may be referred to as induction heating devices. Examples of a second type of object include a mobile device, small electronic device, computer, tablet, gadget, electrical appliance (such as a cordless blender, kettle, or mixer), or any type of equipment, including a PRx, for which wireless power transfer mode is appropriate. Another type of object that may be inadvertently present in the PTx's operating environment may be referred to as a foreign object. Non-limiting examples of foreign objects may include ferrous objects, metal cans, coins, metal spoons, keys, aluminum foil, or other conductive or ferrous objects that are not induction heating devices or PRxes. When a foreign object (FO) is in proximity to the PTx's magnetic field, the foreign object may interact with the magnetic field and be undesirably heated. Therefore, it is desirable to detect what type of object (induction heating device, PRx, or FO) is present in the PTx's operating environment.

[0015] Typically, the PTx performs an object detection assessment before initiating induction heating or wireless power transfer. The object detection assessment can be used to detect whether the object is an induction heating device, a PRx, or a foreign object. Thus, the object detection assessment may also be referred to as a foreign object detection procedure, a pot detection procedure, a pan detection procedure, a PRx detection procedure, a foreign object detection procedure, or other terms. As part of the object detection assessment, the PTx may apply a pulse to the primary coil or one or more object detection coils. The PTx measures measurements associated with the magnetic field generated by the pulse or associated with characteristics of the primary coil or one or more object detection coils. Examples of measurements (sometimes referred to as parameters) include, among other examples, voltage, current, impedance, quality factor, coupling coefficient, differential value (the difference between measurements at two coils, such as differential voltage, differential current, or differential impedance), or any type of parameter associated with the power transfer circuit. The measurements may also be referred to as object detection measurements, measurement parameters, or other similar terms. The object detection assessment includes comparing the measurements to one or more thresholds to determine the type of object in the operating environment. Thus, the object detection assessment can be used to detect the presence of an induction heating device, a PRx, or a foreign object. The PTx is configured to perform the object detection assessment before transitioning to the power transfer phase to ensure that no foreign object has been introduced into the operating environment.

[0016] In some cases, an electrical appliance may contain a PRx and an affinity metal. The affinity metal may include conductive materials within the device (such as knobs, metal shields, wires, microprocessors, or motors, among other examples) that are intentionally included to support the function or structure of the device. Due to the presence of the affinity metal, the PTx may perform an object detection evaluation that results in a foreign object detection (FOD) fault, even though the object is actually an electrical appliance with a PRx and an affinity metal. Typically, a user may clear the FOD fault by a user action, such as removing the electrical appliance from the operating environment and returning the electrical appliance to the operating environment.

[0017] A PRx may remain within its operating environment but occasionally transition into and out of the power transmission phase. For example, the PRx may be located within an electrical appliance that is occasionally turned on or off by user action, or the PRx may be programmed to receive wireless power according to a schedule. The PTx may perform a new object detection evaluation before each transition into the power transmission phase. However, due to the presence of metals that are compatible with the PRx, the PTx may incorrectly detect the PRx and the metals as foreign objects and trigger an FOD fault before each transition into the power transmission phase. This can be frustrating for end users, especially if an FOD fault is repeatedly triggered for the same PRx each time the PRx requests the PTx to transition into the power transmission phase, requiring user interaction with each FOD fault.

[0018] The present disclosure provides systems, methods, and devices for object detection adapted to a PRx having an affinity metal. The present disclosure includes several aspects of object detection that can minimize or eliminate user interaction for object detection evaluation of the same PRx having an affinity metal. In some aspects, the PTx can determine whether a foreign object is present in the magnetic field with the PRx based on a comparison of a measurement value with one or more threshold ranges. For example, the PRx threshold range can be based on a reference value for the PRx containing an affinity metal. Alternatively or additionally, the reference value or PRx threshold range can be based on a previous measurement value from a previous object detection evaluation in which the object was identified as a PRx having an affinity metal. If the PTx determines that a foreign object is not present in the magnetic field with the PTx, the PTx can store the previous measurement value as the reference value for the PRx or update the PRx threshold range. Movement of the PRx can change the measurement value. If the PTx detects that a new measurement value for the PRx is due to movement of the PRx rather than FO, the PTx can store the new measurement value as the reference value for the PRx.

[0019] In some embodiments, the PRx can communicate a reference value or range of expected values ​​to the PTx during the pre-power transfer phase, where the reference value or range of expected values ​​is based on the results of an object detection evaluation in a test environment when the PRx is placed on a standard test PTx and no foreign objects are present. The PTx can determine the PRx threshold range based on the reference value. Alternatively or additionally, the PRx can communicate an instruction (sometimes referred to as an affinity metal instruction) to notify the PTx that the PRx has an affinity metal, thereby causing the PTx to adjust the PRx threshold range.

[0020] In some embodiments, the PRx can communicate its identity in association with the reference value, expected range of measurements, or affinity metal indication. The PTx can store its identity in association with the PRx's reference value, expected range of measurements, or affinity metal indication.

[0021] In some embodiments, object detection assessment can be combined with coupling coefficient measurement. The coupling coefficient (sometimes referred to as the K-factor) refers to a metric that indicates the alignment of the primary coil of the PTx and the secondary coil of the PRx. The coupling coefficient is calculated based on the ratio of the voltage applied to the primary coil to the voltage measured at the secondary coil. In some embodiments, the same pulse (sometimes referred to as the object detection pulse) used for object detection assessment can also be used simultaneously for coupling coefficient measurement. In some implementations, the same measurement (of a first parameter) can be used for object detection assessment and coupling coefficient measurement. In some implementations, the PTX can obtain a first measurement (of a first parameter) and a second measurement (of a second parameter) during the same object detection assessment. The PTx can use the first measurement (e.g., voltage) to calculate the coupling coefficient, while using the second measurement (e.g., impedance or Q factor) to detect a foreign object or the PRx. The object detection assessment can include the PTx transmitting an energy pulse through the primary coil. The pulse of energy can have a measured or configured voltage referred to as a transmit voltage. In some cases, the PTx may measure the coil current or coil impedance of the primary coil during the object detection pulse. Meanwhile, during the pulse, the PRx may measure the voltage induced in the secondary coil of the PRx as a result of the pulse. For example, the PRx may measure the voltage (sometimes referred to as the received voltage or the induced voltage) while the power receiving circuit switch is electrically open to obtain an accurate voltage measurement and / or to protect other components of the PRx. The PRx may communicate the received voltage value to the PTx after the pulse. The PTx may calculate a coupling coefficient based at least in part on the ratio of the received voltage value to the transmitted voltage value relative to the voltage of the pulse at the PTx side. During the pulse, the PTx may take the same measurement of a first parameter (e.g., voltage) or a different measurement of a second parameter (e.g., current, impedance, quality factor, or other parameter) and use that measurement for object detection evaluation.

[0022] Certain implementations of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages: A PTx can use the techniques of the present disclosure to more accurately detect various types of objects, such as induction heating equipment, electrical appliances with a PTx and an affinity metal, or foreign objects. In some cases, a PRx with an affinity metal can use the techniques of the present disclosure to assist the PTx in detecting the PRx with little or no user interaction. The PTx can use historical information from one or more previous object detection evaluations to reduce the occurrence of false-positive FO detections, thereby improving the usability of the PTx and user satisfaction. In some cases, the combination of object detection evaluations and coupling coefficient measurements can improve the overall operation of the wireless power system.

[0023] FIG. 1 is a conceptual diagram 100 illustrating an example multifunction hob 110 and an example object. The multifunction hob 110 can include several locations 104 for placing objects. At least one of the locations 104 can include a PTx 120 that supports induction heating or wireless power transfer to an object when an appropriate object is placed in a location associated with the PTx 120. FIG. 1 shows the PTx 120 in one of the locations 104. It should be understood that the multifunction hob 110 can include a PTx in two or more (or even all) of the locations 104. In such a scenario, each of the locations 104 that includes a PTx can operate according to the embodiments described herein with reference to the PTx 120. The multifunction hob 110 can include a first user interface 140 having inputs (such as knobs, buttons, or touchscreen sensors) for receiving user input or presenting instructions to a user of the multifunction hob 110. In some embodiments, the multifunction hob 110 may be referred to as a hob, a countertop, a stove, or other terms referring to a kitchen appliance. Additionally, while the examples described in this disclosure refer to a multifunction hob, aspects of the present disclosure may be used with other types of appliances that support both induction heating and wireless power transmission. In some embodiments, the multifunction hob may be portable in nature and may include a single PTx. For example, a portable multifunction hob may include a battery or allow for an external power source to power the PTx. In some embodiments, a portable multifunction hob (with one or more PTx) may be suitable for camping.

[0024] The PTx 120 may include a primary coil. For simplicity, this disclosure will refer to one or more primary coils as primary coil 130, although it should be understood that some implementations of the PTx 120 may include two or more primary coils 130. The primary coil 130 is configured to generate a magnetic field for transmitting wireless energy to objects within the magnetic field of the primary coil 130. In some implementations, the primary coil 130 may be a wire coil coupled to a driver that applies power to the primary coil 130 during either an induction heating operation or a wireless power transfer operation.

[0025] The multifunction hob 110 may provide at least one PTx 120 that can support either induction heating or wireless power transfer, depending on which type of object is in proximity to the primary coil 130. The primary coil 130 may be referred to as an induction coil, particularly when the PTx 120 is used in an induction heating mode. Additionally or alternatively, the primary coil 130 may be referred to as a power transfer coil, particularly when the PTx 120 is used in a wireless power transfer mode. For brevity, this disclosure may use the terms "device" and "PTx" interchangeably to collectively refer to devices that support both induction heating and wireless power transfer modes.

[0026] 1 also shows examples 150 of various types of objects that may be placed within the magnetic field of the primary coil 130. In a first example 160, the object may be an induction heating device 165. In a second example 170, the object may be a wireless power receiver (PRx) 175. In a third example 180, the object may be a foreign object 190.

[0027] Referring to the first example 160, the induction heating device 165 may be a cooking vessel, utensil, or any other device intended to be heated using induction heating. During induction heating, the primary coil 130 may generate a magnetic field for transferring energy that conducts eddy currents in the ferrous or semi-ferrous surface of the induction heating device 165. The eddy currents conducted in the ferrous or semi-ferrous components of the induction heating device 165 heat the induction heating device 165, thereby heating food or other materials placed within the induction heating device 165.

[0028] Referring to the second example 170, the device may include a PRx 175 having one or more receiving coils (sometimes referred to as secondary coils). The PRx 175 may also have a rectifier for collecting power from the magnetic field and using that power to operate various other components of the device in which the PRx 175 is located. The PRx 175 and the PTx 120 may operate according to technical standard specifications that define a communication protocol for controlling the amount of power transmitted by the magnetic field. The PTx 120 and the PRx 175, when both are present, may form a wireless power transmission system.

[0029] It is clear that induction heating is not the same as wireless power transfer. The purpose of induction heating is to transfer energy that creates eddy currents within the induction heating device 165, but such eddy currents are undesirable in the PRx 175. The purpose of wireless power transfer is to transfer energy that creates an electromagnetic potential in a secondary coil that can be harvested to power components of the device, including the PRx 175.

[0030] Referring to a third example 180, a foreign object 190 (sometimes referred to as a metallic foreign object) may be present in the operating environment of the primary coil 130. The FO 190 may be any object that is conductive or magnetically permeable and is not intended for use as an induction heating device 165 or a PRx 175. When the FO 190 is present in the operating environment of the primary coil 130 and the primary coil 130 is generating a magnetic field, the FO 190 may be undesirably heated. If the FO 190 is heated by either induction heating or wireless power transmission, there is a possibility of fire, damage to the PTx 120, or harm to the user. Therefore, when the FO 190 is detected, the PTx 120 may discontinue generating the primary magnetic field or otherwise prevent the PTx 120 from transmitting a sufficient amount of energy to the FO 190 to heat it beyond safe levels.

[0031] FIG. 2 shows a block diagram of an exemplary wireless power transmission system 200. The wireless power transmission system may include a PTx 120 and a PRx 175 as described with reference to FIG. 1. The PTx 120 may include one or more primary coils 130 configured to transmit wireless energy (as a wireless power signal) to one or more corresponding secondary coils 220 in the PRx 175. A primary coil refers to a wireless energy source (such as induction or magnetic resonance energy that generates an electromagnetic field) in a power transmitter. The primary coil 130 may be associated with a power driver 206. The primary coil 130 may be a wire coil that transmits wireless power (also referred to as wireless energy or a wireless power signal). The power driver and primary coil together can generate a primary magnetic field during wireless power transmission. The power driver 206 may include components (not shown) that provide power to the primary coil 130, causing the primary coil 130 to generate the wireless power signal. For example, the power driver 206 may include one or more switches, drivers, series capacitors, rectifiers, or other components. The PTx 120 may also include a transmission controller 208 (sometimes referred to as a PTX controller, or for brevity as a controller) that controls components of the power driver 206. For example, the transmission controller 208 may determine an operating point (such as a voltage or current) and control the power driver 206 according to the operating point.

[0032] In some implementations, the power driver 206, the transmission controller 208, and 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 the present disclosure for controlling and transmitting wireless power to one or more power receivers. The transmission controller 208 may be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application specific integrated circuit (ASIC), or any other suitable electronic device.

[0033] The power supply 212 can provide power to the power transmitter circuitry within the PTx 120. The power supply 212 can convert alternating current (AC) power to direct current (DC) power. For example, the power supply 212 can include a converter that receives AC power from an external power source (such as a power mains) and converts the AC power to DC power used by the power driver 206.

[0034] In some implementations, the first communication unit 242 can be coupled to components of the power driver 206 or the primary coil 130 to send or receive communications via wireless power signals. The first communication unit 242 can include logic for controlling one or more switches and other components that cause the transmission and reception of wireless signals via wireless power signals. For example, the first communication unit 242 can include a modulator or demodulator that converts information added to the wireless power signal into a modulated signal. In one example, the first communication unit 242 can convert data from the transmission controller 208 into a frequency shift key (FSK) modulated signal that is combined with the wireless power signal for communication from the PTx 120 to the PRx 175. In another example, the first communication unit 242 can sense a load-modulated amplitude shift key (ASK) signal from the power driver 206 or the primary coil 130 and demodulate the ASK signal to obtain the data that the first communication unit 242 provides to the transmission controller 208.

[0035] In some embodiments, the PTx 120 may include a wireless communication interface 214. The wireless communication interface 214 may be connected to a first communication coil 216 (which may be a coil or a loop antenna). The wireless communication interface 214 may include logic to control one or more switches and other components that cause wireless communication signals to be transmitted and received via the first communication coil 216. In some embodiments, the wireless communication interface 214 may support short-range radio frequency communication (such as Bluetooth™) or near field communication (NFC). NFC is a technology that transmits data at a carrier frequency of 13.56 MHz. The wireless communication unit 214 may also support any suitable communication protocol.

[0036] The transmission controller 208 can detect the presence or proximity of the PRx 175 using various techniques. In some implementations, the presence or proximity of the PRx 175 can be detected based on a change in load in response to a periodic low-power signal generated by the power driver 206 and the primary coil 130. In some implementations, the presence or proximity of the PRx 175 can occur during a periodic ping process of the wireless communication interface 214 within the PTx 120. When the PRx 175 is placed on the interface surface of the PTx 120, a ping of the wireless communication interface 214 via the first communication coil 216 may result in a response communication from the PRx 175. The ping and response communication can form part of a handshake process involving two-way communication between the PTx 120 and the PRx 175. Based on a successful handshake, the transmission controller 208 can determine that the PRx 175 has been detected. As described herein, the PTx 120 can perform an object detection assessment that can detect the presence of an induction heating device (not shown), the PRx 175, or the FO 190. The PTx 120 can perform object detection evaluations at various times, which may be before and / or after the periodic low power signal or periodic ping process of a conventional wireless power system.

[0037] The transmission controller 208 can control the characteristics of the wireless power that the PTx 120 provides to the PRx 175. After detecting the PRx 175, the transmission controller 208 can receive information from the PRx 175. For example, the transmission controller 208 can receive information during a handshake process with the PRx 175. This information can include information about the PRx 175 (such as the power rating, load status, manufacturer, model, or receiver parameters when operating with a standard transmitter, among other examples). The transmission controller 208 can use this information to determine at least one operating control parameter (e.g., frequency, duty cycle, voltage, etc.) for the wireless power it provides to the PRx 175. To configure the wireless power, the transmission controller 208 can vary the frequency, duty cycle, voltage, or any other suitable characteristic of the power driver 206.

[0038] The PRx 175 may include a secondary coil 220, a rectifier 226, and a receiver controller 228. The secondary coil 220 may receive wireless energy via an electromagnetic field. When the secondary coil 220 is aligned with the primary coil 130, the secondary coil 220 may generate an induced voltage based on the wireless power signal received from the primary coil 130. A capacitor (not shown) and a switch (not shown) may be in series between the secondary coil 220 and the rectifier 226. The rectifier 226 may rectify the induced voltage and provide it to a load 230. In some embodiments, the load 230 may be external to the PRx 175 and coupled via a wire from the rectifier 226. In some embodiments, the rectifier 226 may not be present, and the induced voltage in the secondary coil 220 may be provided to an element in series with the secondary coil 220 and the load 230.

[0039] The receiver controller 228 may be connected to the rectifier 226 and the second communication unit 252. The second communication unit 252 may be coupled to components of the secondary coil 220 or the rectifier 226 to transmit and receive communications via the wireless power signal. The second communication unit 252 may include logic to control one or more switches and other components that cause communication signals to be transmitted and received via the wireless power signal. For example, the second communication unit 252 may include a modulator or demodulator that converts information into an ASK modulated signal or an FSK modulated signal. In one example, the second communication unit 252 can convert data from the receiver controller 228 into an ASK modulated signal that is used to load modulate the wireless power signal for communication from the PRx 175 to the PTx 120. In another example, the second communication unit 252 can sense the FSK signal in the wireless power signal at the secondary coil 220 or the rectifier 226 and demodulate the FSK signal to obtain the data that the second communication unit 252 provides to the receiver controller 228.

[0040] In some embodiments, the PRx 175 may include a wireless communication interface 232. The wireless communication interface 232 may include a modulation circuit and a demodulation circuit for wireless communication via a second communication coil 234 (which may be a coil or a loop antenna). Thus, the receiver controller 228 may wirelessly communicate with the transmission controller 208 via the wireless communication interface 232 and the wireless communication interface 214 using NFC communication or Bluetooth.

[0041] The interface surface 280 (sometimes referred to as the "interface space") can define the space between the power transmitter and the power receiver. For example, the interface surface can include a surface of the power transmitter on which the power receiver can be disposed. The distance between the primary coil 130 and the secondary coil 220 can include a thickness of the surface at the interface surface. During wireless power transmission, the primary coil 130 can induce a magnetic field (referred to as the primary magnetic field) through the interface surface into the operating environment in which the secondary coil is disposed. Thus, the "operating environment" is defined by the primary magnetic field within the system in which the primary magnetic field of the primary coil 130 detectably exists and can detectably interact with the secondary coil or foreign object 190 (denoted as FO 190).

[0042] If a foreign object 190 is present in the operating environment of the WPT system, the foreign object 190 may experience an increase in temperature due to interaction with the magnetic field. Thus, when a foreign object is detected, the PTx 120 ceases generating the primary magnetic field or otherwise prevents the PTx 120 from transmitting to the foreign object 190 an amount of energy that would cause the foreign object 190 to heat above safe levels.

[0043] The PTx 120 may also include an object detection unit 290. In some embodiments, the object detection unit 290 may be referred to as a pot / pan detection unit, a PRx detection unit, or a FO detection unit. In some embodiments, the object detection unit 290 may be integrated into the transmission controller 208. For example, the object detection unit 290 may be co-located within the transmission controller 208 or implemented as software. Alternatively or additionally, the object detection unit 290 may be implemented as a separate system for the PTx 120 or as a multi-function hob that includes the PTx 120. For example, the multi-function hob may include an object detection mat at any one of multiple PTx locations configured to detect induction heating equipment, a PRx, or foreign objects.

[0044] The object detection unit 290 may be configured to detect objects within the operating environment of the PTx 120 based on measurements obtained in association with object detection pulses. The object detection pulses may be generated by the power driver 206 or a different driver (not shown). The object detection unit 290 may cause an object detection pulse to be transmitted through the primary coil 120 or one or more object detection coils (not shown) as part of an object detection evaluation. The object detection unit 290 may take measurements while the pulses are being transmitted. The object detection unit 290 may provide the measurements to the transmission controller 208 so that the transmission controller 208 can compare the measurements to one or more thresholds to detect various types of objects. Alternatively, the object detection unit 290 may perform a comparison of the measurements to one or more thresholds and provide the results of the object detection evaluation to the transmission controller 208.

[0045] Figure 3 shows a flow diagram of an exemplary process 300 for object detection evaluation. The operations of process 300 may be performed by a controller or object detection unit of the PTx, such as transmission controller 208 or object detection unit 290 described with reference to Figure 2. In some implementations, process 300 may be implemented by a controller included in or part of a processor of the multifunction fob.

[0046] In some implementations, the steps of process 300 can begin after the PTx detects or receives an indication that a PRx or induction heating device is present near the PTx. For example, the PTx can receive wireless communications or read an NFC tag, either of which can indicate the presence of a PRx or induction heating device. Alternatively, the controller can periodically execute process 300 to detect objects and determine the type of object. In such a scenario, not all steps of 300 are performed.

[0047] In block 310, the controller causes a power driver or other component to generate an object detection pulse, which may be a low-power signal transmitted by the primary coil or one or more detection coils.

[0048] In block 320, the controller obtains a measurement value associated with the object detection pulse. For example, the controller may obtain the measurement value from a voltage sensor, current sensor, impedance sensor, or other measurement unit connected to the primary coil or one or more detection coils. In some implementations, the measurement value may be a measured parameter (e.g., coil impedance, coil current, or coil voltage) of the primary coil or at the output of the power driver. Alternatively, the measurement value may be the difference between measured parameters in two or more detection coils, such that the measurement value represents a differential impedance, differential current, or differential voltage. In the example of FIG. 3, the measurement value indicates the presence of an object within the magnetic field of the PTx. For example, the object may be detected based on a measurement value that differs from a steady-state measurement value in which no object is present.

[0049] In block 330, the controller compares the measurement to threshold ranges. In some implementations, one or more of the threshold ranges may be predefined or preconfigured in the controller's memory. In the example of FIG. 3 , a first range represents the range of expected measurements for the induction heating device, a second range represents the range of expected measurements for the PRx, and a third range represents the range of expected measurements for a foreign object. If the measurement is within the first range, the flow chart proceeds to block 340. If the measurement is within the second range, the flow chart proceeds to block 350. If the measurement is within the third range, the flow chart proceeds to block 360. If the measurement is not within any of the first, second, or third ranges, the controller can default to block 360 or resume object detection evaluation.

[0050] If the measurement is within the first range, the controller may determine that the object is an induction heating appliance, such as a pot or pan, at block 340. The controller may proceed to an induction heating mode of operation.

[0051] If the measurement is within the second range, the controller may determine that the object is an appliance that includes a PRx, at block 350. The controller may proceed to a wireless power transfer mode of operation.

[0052] If the measurement is within a third range, the controller may determine that the object is a foreign object at block 360. The controller may indicate a foreign object detection (FOD) fault, such as via a user interface associated with the PTx.

[0053] The operation described with reference to Figure 3 allows the PTx to detect various types of objects using object detection pulses. As will be further explained with reference to Figures 4 and 5, the various ranges of measurements can produce unpredictable or inaccurate results without the techniques of this disclosure.

[0054] In some implementations, the PTx can perform blocks 310, 320, 330, 340, and 360 as part of the pan detection evaluation. The PTx can detect the presence of the PRx using alternative techniques, such as communication from the PRx. For example, in block 345, the PTx can detect the PRx using a communication handshake that includes a ping using the NFC coil and a response from the PRx. In this scenario, once the communication handshake is achieved, the PTx can skip the pan detection evaluation and proceed directly to block 350 and wireless power transfer mode. In wireless power transfer mode, the PTx can use an object detection evaluation (in this case, referred to as a foreign object detection evaluation) to determine whether a foreign object is present with the PRx. The foreign object detection evaluation includes an object detection pulse (similar to block 310), taking a measurement (similar to block 320), and comparing the measurement to a second range and / or a third range (similar to block 330). In some implementations, the measurement in the foreign object detection evaluation can be based on a coupling coefficient measurement. Foreign object detection evaluation is typically performed during the connection phase of the power transfer protocol executed by the PTx and PRx, during which the secondary coil of the PRx is disconnected from the rest of the PRx circuit and the load using a series switch.

[0055] FIG. 4 is a diagram 400 conceptually illustrating various ranges and measurements for object detection. A scale 440 can represent various measurements that may be obtained during an object detection evaluation. A first range 410 may be associated with an induction heating device. A second range 420 may be associated with a foreign object and may be referred to as the FO threshold range. A third range 430 may be associated with a wireless power receiver and may be referred to as the PRx threshold range. Depending on where the measurement falls within the scale 440, the measurement may be within the first range 410, the second range 420, or the third range. For example, a first measurement 412 obtained when an induction heating device is present falls within the first range 410. A second measurement 414 obtained when a foreign object is present falls within the second range 420. A third measurement 416 obtained when a wireless power receiver (or an appliance including a PRx) is present falls within the third range 430.

[0056] As described herein, a PRx (or an appliance containing a PRx) may have affinity metals that may shift the range of expected measurements closer to or overlapping with the second range 420 associated with foreign matter.

[0057] FIG. 5 is a diagram 500 conceptually illustrating measurements and ranges of a PRx having an affinity metal. In FIG. 5, a first range 410 and a second range 420 are shown on a scale 440, as described with reference to FIG. 4. However, a third range 530 indicates the range of measurements that may be expected for a PRx having an affinity metal. As shown in FIG. 5, there may be an overlapping range 550 of values ​​that fall within the second range 420 and the third range 530. Furthermore, the measurement 518 may be for a foreign object or a PRx. Using the techniques of the present disclosure, the PTx (or controller) can determine whether the measurement 518 is for a PRx having an affinity metal or a foreign object.

[0058] FIG. 6 is a timing diagram 600 illustrating a baseline scenario when a PRx with an affinity metal is repeatedly detected as a foreign object. As previously discussed, object detection pulses can also be used for FOD when the presence of a valid PRx is identified using a communication handshake. Timing diagram 600 illustrates communication 601 from a PRx to a PTx as part of the communication handshake. Timing diagram 600 illustrates the PTx 120 performing a first object detection evaluation 610 (sometimes referred to as a foreign object detection evaluation) in the presence of a PRx 175. The first object detection evaluation 610 may occur before the PTx 120 proceeds to wireless power transfer mode. Alternatively or additionally, the first object detection evaluation 610 may occur during the connection phase before the PTx 120 transitions to the power transfer phase.

[0059] In the example of FIG. 6 , the PRx 175 has an affinity for metals that may cause the PRx 175 to be erroneously detected as a foreign object. For example, the measurement value of the first object detection evaluation 610 may fall within the overlapping range of values ​​550 described with reference to FIG. 5 . Because the measurement value falls within the overlapping range of values, the first object detection evaluation 610 may result in an FOD fault. The first FOD fault process 612 may include a user interaction, such as removing the PRx 175 from the interface surface and placing it back on the PTx 120. Alternatively or additionally, the first FOD fault process 612 may include a user interface, button, or other action. The user interaction may be designed to inform the PTx 120 that the object detected by the first object detection evaluation 610 is actually the PRx 175 and not a foreign object. After the first FOD fault process 612, the PTx 120 may proceed with other operations, such as transferring power in a wireless power transfer operating mode.

[0060] The PRx 175 may then request the PTx 120 to transition to the connected mode and remain in that state until the next power transfer phase. In some cases, the PRx 175 may periodically request a transition to the power transfer phase or the connected phase, resulting in multiple subsequent object detection evaluations to detect the presence of an FOD. For simplicity, FIG. 6 shows only one subsequent object detection evaluation (second object detection evaluation 620). In a baseline scenario, the second object detection evaluation 620 results in another FOD fault, requiring second FOD fault processing 622. The second FOD fault processing 622 may also include user interaction. Due to repeated FOD faults, the operator of the PRx 175 may need to perform multiple user interactions, potentially causing frustration or dissatisfaction.

[0061] FIG. 7 is a timing diagram 700 illustrating an exemplary scenario in which a reference value of a PRx having an affinity for metals may be used in a subsequent object detection evaluation. Similar to FIG. 6, the timing diagram 700 illustrates communication 701 from the PRx to the PTx as part of a communication handshake. The timing diagram 700 also illustrates the PTx 120 performing a first (foreign) object detection evaluation 610 in which the PRx 175 is present. However, FIG. 7 differs from FIG. 6 in that following the first FOD fault processing 612, the PTx 120 may store the reference value of the PRx 175 (shown in block 714). For example, the reference value may be a measurement of the first object detection evaluation 610. In some implementations, the reference value may be stored in association with an identification (ID) of the PRx 175, such as an ID in a communication from the PRx 175 to the PTx 120 (not shown).

[0062] 7, the PTx 120 may perform a subsequent object detection evaluation (second foreign object detection evaluation 720). The PTx 120 may compare the measurement of the second object detection evaluation 720 to the reference value 714. If the measurement of the second object detection evaluation 720 is within a threshold range of the reference value 714, the PTx 120 may determine that the detected object is the previously detected PRx 175.

[0063] In some implementations, measurements may change as the PRx 175 moves within the PTx 120's operating environment. Similarly, measurements may change as a result of temperature drift or other identifiable changes that affect measurements without the introduction of a foreign object. The PTx 120 may determine that a change in measurement is due to movement, temperature drift, or other identifiable changes associated with the PRx 175, rather than the introduction of a foreign object. For example, a change in receiver alignment may be determined based on a change in measurements from the power receiver in response to a foreign object detection pulse applied at the power transmitter. If the measurement changes and the PTx 120 determines that an FO has not been introduced, the PTx 120 stores the changed measurement as an updated reference value for the PRx 175 and may use this updated measurement in subsequent object detection evaluations (not shown).

[0064] FIG. 8 is a timing diagram 800 illustrating an example scenario in which communication with friendly metals from the PRx can improve object detection evaluation results. Similar to FIGS. 6 and 7, timing diagram 800 illustrates operations related to the PTx 120 and PRx 175. The PTx 120 detects the PRx 175 through PRx-to-PTx communication 801 as part of a communication handshake. FIG. 8 differs from FIGS. 6 and 7 in that the PRx 175 is configured to communicate communication 802 to the PTx 120. Communications 801 and 802 may be short-range, high-frequency communications (e.g., using NFC). Communications 801 and 802 may be active or passive transmissions. Passive transmissions may include an NFC tag integrated into or attached to the PRx 175 that is readable by the NFC interface of the PTx 120. Communication 802 may be an NFC Data Exchange Format (NDEF) message. Communication 802 may include a reference measurement, a range of expected measurements, or an indication of a friendly metal.

[0065] In one example, communication 802 includes a baseline measurement taken by a standard power transmitter performing a test object detection evaluation in which the PRx 175 is present without a foreign object. In block 805, the PTx 120 may store this baseline measurement as a baseline value for the PRx 175. During each of object detection evaluations 810 and 820, the PTx 120 may determine that the detected object is the PRx 175 without an FOD if the measurement is within a PRx threshold range of the baseline value (stored in block 805). Thus, the PTx 120 may refrain from triggering an FOD fault, preventing the need for FOD fault processing.

[0066] In another example, communication 802 includes a range of expected measurements of the PRx 175. For example, the range of expected measurements may indicate an acceptable measurement threshold for an object detection evaluation that should result in the detection of the PRx 175 and not a foreign object. In block 805, the PTx 120 may store the range of expected measurements and determine a PRx threshold range based on the range of expected measurements. During each of object detection evaluations 810 and 820, the PTx 120 may determine that the detected object is the PRx 175 if the measurement is within the range of expected measurements (stored in block 805). Alternatively, in block 805, the PTx 120 may calculate a reference value based on the range of expected measurements and store the reference value.

[0067] The range may be in any of a variety of formats, including an offset value, a minimum value, a maximum value, minimum and maximum values, or a scalar factor, among other examples. Referring to Figures 3-5, the range of expected measurement values ​​may be a third range 430 or 530. If the range of expected measurement values ​​overlaps with the second range 420, the PTx 120 may override the second range 420 for the overlap range 550 and treat any measurement values ​​within the overlap range 500 as being within the third range 530 (the range of expected measurement values), thereby detecting the object as a PRx rather than a foreign object.

[0068] In yet another example, communication 802 includes an indication of an affinity metal. For example, the indication of an affinity metal may be a value or bit that informs the PTx 120 that the PRx 175 has an affinity metal. The PTx 120 may store the indication of the affinity metal in block 805. During each of object detection evaluations 810 and 820, the PTx 120 may determine that the detected object is the PRx 175 if it receives an indication of an affinity metal from the PRx 175 in communication 802. For example, the PTx 120 may disable measurements that would otherwise be associated with a foreign object.

[0069] In another exemplary method, when a PRx 175 is placed on a PTx 120 for the first time, the PRx can indicate the presence of an affinity metal 802. The PTx stores information 805. During the very first object evaluation (Object Detection Evaluation 810), the PTx 120 stores the measurement value along with the PRx's ID in its non-volatile memory. During a subsequent object detection evaluation (Object Detection Evaluation 820, etc.), either during the initial placement of the PRx 175 on the PTx 120 or during subsequent placements, the PTx 120 checks whether the measurement value is within the PRx threshold range of the stored measurement value corresponding to that PRx 175. If the measurement value is outside the PRx threshold range, the PTx 120 triggers an FOD action. The FOD action can prompt a user action to confirm that no FOD is present. If the user action confirms that no FOD is present, the PTx 120 updates the stored measurement value corresponding to the PRx 175 in its non-volatile memory. This value can be replaced, or the value range can be updated.

[0070] FIG. 9 shows a block diagram of an exemplary PTx 120. The PTx 120 may include a power supply 212, a power driver 206, a transmission controller 208, a primary coil 130, a wireless communication interface 214, and a first communication coil 216, as described with reference to FIG. 2. The power driver 206 is shown as a half-bridge circuit that converts DC power from the power supply 212 into an AC signal that is applied to the primary coil 130. Although not shown in FIG. 8, the power supply 212 may include a conversion unit that converts AC mains power to DC power for the power supply 212. Furthermore, the power driver 206 may be any type of power conversion circuit capable of providing an AC signal to the primary coil 130. For example, the power driver 206 may include a half-bridge circuit with a parallel capacitor, as shown in FIG. 8. Alternatively, the power driver 206 may include a full-bridge circuit.

[0071] The transmission controller 208 can cause the PTx 120 to transmit an object detection pulse through the primary coil 130. In some implementations, the object detection pulse may be referred to as a ping signal or a “pan detection” signal. When an induction heating device is placed near the primary coil 130, the PTx 120 (or an object detection unit therein) can measure a change in a measurement (e.g., impedance) to detect whether the induction heating device is placed over the primary coil 130. If the measurement is within a predetermined range (e.g., an acceptable limit), the PTx 120 changes operation from a ping mode to an induction-based heating mode, which uses induction to transfer energy. Thus, the induction heating device can be detected based on the impedance provided by the pan / appliance. In the case of a power receiver (such as those described herein), one or more switches can cause the impedance of the secondary coil to fall outside acceptable limits. For example, a series switch can cause the impedance measured by the PTx 120 to be higher than acceptable limits.

[0072] In some implementations, once a power receiver is detected (e.g., via a communication handshake), an object detection pulse can be used to not only detect the presence of an FO with the power receiver but also simultaneously determine the coupling coefficient of the power receiver. The coupling coefficient (sometimes referred to as k-factor) can be an indicator of how well the secondary coil and primary coil can transmit wireless power. For example, the k-factor can be a measure of the potential magnetic flux coupling of wireless power transmission between the primary coil and the secondary coil. In some implementations, the k-factor can depend, among other things, on the number of turns in the primary coil (n1), the number of turns in the secondary coil (n2), the voltage transmitted by the primary coil (v1), and the voltage induced in the secondary coil during the measurement period (v2). The voltage v1 can also be referred to as the transmit voltage, and the voltage v2 can also be referred to as the receive voltage. The k-factor can be calculated as follows (Equation 1):

number

[0073] FIG. 10 shows a block diagram of an example PRx 175 capable of disconnecting the secondary coil with a switch during object detection evaluation via coupling coefficient measurements. Components of the PRx 175 may include similarly numbered components to those of the PRx 175 described with reference to FIG. 2 . FIG. 10 illustrates the switch 1050 as a switch in series with one branch of the secondary coil 220. However, in some implementations, the switch 1050 may be any type of switch that prevents or minimizes current from passing through the secondary coil 220 when the switch 1050 is in a first position. In FIG. 10 , the first position of the switch 1050 is an open position such that the circuit including the secondary coil 220 does not conduct current. The PRx 175 may also include a voltage sensor 1020 coupled to the secondary coil 220. During object detection evaluation, the receiver controller 228 can cause the switch 1050 to disconnect the secondary coil 220 from the power receiving circuit (e.g., the rectifier 226 and the load 230). During the power transfer phase, the receiver controller 228 can cause the switch 1050 to connect the secondary coil 220 to the power receiving circuit.

[0074] The switch 1050 may be used to disconnect the secondary coil 220 from the power receiving circuit (e.g., the rectifier 226, the load 230, or both) when an object detection evaluation is performed. The object detection evaluation may include any of the operations described herein, such as the object detection evaluation described with reference to Figures 3-8. The object detection evaluation may be performed during a foreign object detection (FOD) period, a k-factor measurement period, or both.

[0075] In FIG. 10 , the object detection evaluation (performed as a foreign object detection evaluation) is combined with the coupling coefficient measurement. As part of the foreign object detection evaluation by an active PRx receiver during the connection phase, the PTx (not shown) can transmit an object detection pulse. In some implementations, the object detection pulse may be transmitted using a known or predetermined voltage (v1) and frequency (fp). The PTx can determine the presence of an FO based on measurements (voltage, current, impedance, or quality factor) used to detect the FO. Simultaneously, the voltage sensor 1020 may enable the receiver controller 228 to measure the received voltage (v2) of the secondary coil 220 induced by the object detection pulse. The receiver controller 228 can communicate a message to the PTx via the wireless communication interface 232. The message may include a received voltage value based on the measured v2. The PTx can use the received voltage value to determine a coupling coefficient (k factor). The k factor may be used by the PTx to determine the operating point of the wireless power signal that the PTx transmits during the power transfer phase. For example, the operating point may be based on a calculation that considers the ratio of v1 to v2. Therefore, the same object detection pulse is used to measure the coupling coefficient as well as to detect the presence of an FO.

[0076] 11 shows a flow diagram of an example process 1100 according to some aspects of the present disclosure. In some implementations, one or more process blocks of FIG. 11 may be performed by a PTx, such as the PTx 120 described herein. Alternatively, one or more process blocks of FIG. 11 may be performed by a controller or object detection unit of the PTx. For simplicity, the process blocks are described as being performed by the PTx.

[0077] In block 1110, the PTx receives a communication from a power receiver present within the magnetic field of the power transmitter. The communication may be part of a communication handshake indicating the presence of the power receiver. In block 1120, the PTx obtains a measurement based on an object detection evaluation. In block 1130, the PTx determines whether a foreign object is present within the magnetic field along with the power receiver based on the measurement. For example, the PTx may determine that a foreign object is not present if the measurement is outside a foreign object (FO) threshold range for the foreign object. Alternatively or additionally, the PTx may determine that a foreign object is not present if the measurement is within a power receiver (PRx) threshold range based on a reference measurement of the PRx. In some embodiments, the FO threshold range may be similar to the third range described with reference to FIGS. 3-4. In some embodiments, the PRx threshold range may be similar to the second range described with reference to FIGS. 3-4. In some embodiments, the PRx threshold range may be based on a previous object detection evaluation or a communication from the power receiver, as described with reference to FIGS. 7-8.

[0078] Although Figure 11 illustrates example blocks of process 1100, in some implementations, process 1100 may include additional, fewer, different, or differently arranged blocks compared to those illustrated in Figure 11. Additionally or alternatively, two or more of the blocks of process 1100 may be performed in parallel.

[0079] 12 illustrates a flow diagram of an exemplary process 1200 according to some aspects of the present disclosure. In some implementations, one or more processing blocks of FIG. 12 may be performed by a PTx, such as the PTx 120 described herein. Alternatively, one or more process blocks of FIG. 12 may be performed by a controller or object detection unit of the PTx. For simplicity, the process blocks are described as being performed by the PTx.

[0080] In block 1210, the PTx receives a communication from a power receiver present within the magnetic field of the power transmitter. In block 1220, the PTx obtains a measurement of low power transmission from the PTx during object detection evaluation. In block 1230, the PTx calculates a coupling coefficient between the PTx and the PRx based on the measurement, the coupling coefficient representing the alignment of the primary coil of the PTx and the secondary coil of the PRx.

[0081] Although Figure 12 illustrates example blocks of process 1200, in some implementations, process 1200 may include additional, fewer, different, or differently arranged blocks compared to those illustrated in Figure 12. Additionally or alternatively, two or more of the blocks of process 1200 may be performed in parallel.

[0082] FIG. 13 shows a block diagram of an exemplary device 1300 for use in a multifunction hob. In some implementations, the device 1300 may be part of a PTx, such as any of the PTxs described herein. In some implementations, the device 1300 may be implemented as part of a multifunction hob including one or more PTxs capable of operating in induction heating mode and wireless power transfer mode. The device 1300 may include a processor 1302 (possibly including multiple processors, multiple cores, multiple nodes, or multithreading implementations, etc.). The device 1300 may also include memory 1306. The memory 1306 may be system memory or any one or more of the possible implementations of a computer-readable medium described herein. The device 1300 may also include a bus 1311 (e.g., PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.).

[0083] The device 1300 may include one or more controllers (e.g., controller 1362) configured to manage object detection evaluation. The object detection evaluation may be performed by an object detection unit (not shown). Alternatively, the controller 1362 may implement the object detection unit. In some implementations, the controller 1362 may be distributed within the processor 1302, the memory 1306, and the bus 1311. The controller 1362 may perform some or all of the operations described herein.

[0084] The memory 1306 may include computer instructions executable by the processor 1302 to perform the functions of the embodiments described with reference to Figures 1-12. Any of these functions may be implemented partially (or entirely) in hardware or in the processor 1302. For example, the functions may be implemented in an application specific integrated circuit, logic implemented in the processor 1302, a co-processor on a peripheral device or card, etc. Furthermore, an implementation may include fewer or additional components not shown in Figure 13. The processor 1302, the memory 1306, and the controller 1362 may be coupled to a bus 1311. Although the memory 1306 is shown as being coupled to the bus 1311, it may also be coupled to the processor 1302.

[0085] The diagrams, operations, and components described herein are examples intended to aid in understanding exemplary implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some different operations.

[0086] 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 acquired from practice of the aspects. Although aspects of the present disclosure have been described with reference to various examples, any combination of aspects from any example is within the scope of the present disclosure. The examples of the present disclosure are provided for educational purposes. Alternatively, or in addition to other examples described herein, examples include any combination of the following implementation options (listed as clauses for clarity):

[0087] Terms Clause 1. A method for wireless power transmission by a power transmitter, the method comprising: receiving a communication from a power receiver present within a magnetic field of the power transmitter; obtaining a measurement based on an object detection evaluation; and determining, based on the measurement, whether a foreign object is present within the magnetic field with the power receiver.

[0088] Clause 2. The method of clause 1, wherein determining whether a foreign object is present includes at least one of determining that a foreign object is not present if the measurement value is outside a foreign object (FO) threshold range for the foreign object, or determining that a foreign object is not present if the measurement value is within a power receiver (PRx) threshold range based on a reference measurement value for PRx.

[0089] Clause 3. The method of clause 2, wherein determining whether a foreign object is present further includes at least one of determining that a foreign object is present if the measurement value is outside a PRx threshold range or determining that a foreign object is present if the measurement value is within a FO threshold range.

[0090] Clause 4. The method of any one of clauses 2 to 3, wherein the PRx threshold range and the FO threshold range overlap each other, and the measurement is compared to the PRx threshold range before comparing the measurement to the FO threshold range.

[0091] Clause 5. The method of any one of clauses 2 to 4, further comprising determining the PRx threshold range based on a fixed offset of the power receiver reference value.

[0092] Clause 6. The method of any one of clauses 2 to 5, further comprising determining the PRx threshold range based on a previous measurement of a previous object detection evaluation in which the power transmitter confirmed that no foreign object was present within the magnetic field together with the power receiver.

[0093] Clause 7 The method of clause 6, further comprising: detecting a user action after a previous object detection evaluation when the previous object detection evaluation is within the FO threshold range, the user action indicating that no foreign object is present in the magnetic field; storing the previous measurement value as a reference value for the power receiver; and updating the PRx threshold range based on the reference value.

[0094] Clause 8. The method of clause 6, further comprising: if the previous object detection evaluation is within the FO threshold range, receiving a communication from the power receiver after the previous object detection evaluation indicating that no foreign object is present in the magnetic field; storing the previous measurement value as a reference value for the power receiver; and updating the PRx threshold range based on the reference value.

[0095] Clause 9. The method of any one of clauses 2 to 8, further comprising receiving a communication from the power receiver indicating a PRx threshold range for the power receiver, the PRx threshold range being measured in a test environment when the power receiver is placed on a standard power transmitter with no foreign objects present.

[0096] Clause 10. The method of any one of clauses 2 to 9, further comprising receiving a communication from the power receiver indicating a reference value for the power receiver, and determining a PRx threshold range based on the reference value.

[0097] Clause 11. The method of clause 10, wherein the reference values ​​include reference measurements taken in a test environment when the power receiver is placed on a standard power transmitter.

[0098] Clause 12. The method of any one of clauses 2 to 11, further comprising receiving a communication from the power receiver indicating that the power receiver includes an affinity metal, and determining a PRx threshold range based on predetermined measurements of the power receiver including the affinity metal.

[0099] Clause 13. The method of any one of clauses 2 to 12, further comprising receiving a communication from the power receiver indicating a range of expected measurement values ​​for the power receiver, and determining a PRx threshold range based on the range of expected measurement values.

[0100] Clause 14. The method of any one of clauses 2 to 13, further comprising obtaining the PRx threshold range, or a reference value indicative of the PRx threshold range, or both, from a data field of an out-of-band communication received by the power transmitter from the power receiver.

[0101] Clause 15. The method of clause 14, wherein the out-of-band communication is a Near Field Communication (NFC) Data Exchange Format (NDEF) message.

[0102] Clause 16. The method of any one of clauses 1 to 11, further comprising enabling a wireless power transmission mode of the power transmitter when a foreign object is not present with the power receiver, and disabling the wireless power transmission mode of the power transmitter when a foreign object is present with the power receiver.

[0103] Clause 17. The method of any one of clauses 2 to 16, further comprising calculating a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver.

[0104] Clause 18. The method of any one of clauses 1 to 17, wherein the measured value is at least one value selected from the group consisting of coil voltage or differential voltage of two or more detection coils of a coil pair, coil current or differential current of two or more detection coils of a coil pair, coil impedance or differential impedance of two or more detection coils of a coil pair, a quality factor calculated as part of the object detection assessment, and energy loss of low power transmission in the primary coil of the power transmitter.

[0105] Clause 19. A method for wireless power transmission, comprising: receiving a communication from a power receiver present within a magnetic field of the power transmitter; obtaining a first measurement of a first parameter of low power transmission from the power transmitter during an object detection assessment; and calculating a coupling coefficient between the power transmitter and the power receiver based on the first measurement, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver.

[0106] Clause 20. The method of clause 19, further comprising determining whether a foreign object is present in the magnetic field along with the power receiver based on at least one of the first measurement or a second measurement of a second parameter obtained during the object detection evaluation.

[0107] Clause 21 The method of clause 20, wherein determining whether a foreign object is present includes at least one of determining that a foreign object is not present if the first measurement value or the second measurement value is outside a foreign object (FO) threshold range for the foreign object, or determining that a foreign object is not present if the first measurement value or the second measurement value is within a power receiver (PRx) threshold range based on a reference measurement value of PRx.

[0108] Clause 22. The method of any one of clauses 19 to 21, wherein obtaining the measurements includes transmitting a low power signal while a power receiving circuit of the power receiver is disabled, the low power signal having a first voltage on the primary coil, receiving a communication from the power receiver indicating a second voltage on the power receiving circuit caused by the low power signal, and calculating a coupling coefficient based at least in part on a ratio of the second voltage to the first voltage.

[0109] Clause 23. An apparatus for wireless power transmission, comprising: a communication unit configured to receive communications from a power receiver present within the magnetic field of the power transmitter; a measurement unit configured to obtain measurements based on an object detection assessment; and a control unit configured to determine whether a foreign object is present within the magnetic field of the power receiver based on the measurements.

[0110] Clause 24. The apparatus of clause 23, wherein the control unit is configured to determine that a foreign object is not present if the measurement value is outside a foreign object (FO) threshold range for the foreign object, or to determine that a foreign object is not present if the measurement value is within a power receiver (PRx) threshold range based on a reference measurement value of PRx.

[0111] Clause 25. The apparatus of clause 24, wherein the control unit is configured to determine that a foreign object is present if the measurement value is outside the PRx threshold range or to determine that a foreign object is present if the measurement value is within the FO threshold range.

[0112] Clause 26. An apparatus as described in any one of clauses 24 to 25, wherein the PRx threshold range and the FO threshold range overlap each other, and wherein the control unit is configured to compare the measurement value with the PRx threshold range before comparing the measurement value with the FO threshold range.

[0113] Clause 27. The apparatus of any one of clauses 24 to 26, wherein the control unit is configured to determine the PRx threshold range based on a fixed offset of the power receiver reference value.

[0114] Clause 28. An apparatus as described in any one of clauses 24 to 27, wherein the control unit is configured to determine the PRx threshold range based on previous measurements of a previous object detection evaluation in which the power transmitter confirmed that no foreign object was present within the magnetic field together with the power receiver.

[0115] Clause 29 The apparatus of clause 28, wherein the control unit is configured to detect a user action after a previous object detection evaluation when the previous object detection evaluation is within the FO threshold range, the user action indicating that no foreign object is present in the magnetic field, store the previous measurement value as a reference value for the power receiver, and update the PRx threshold range based on the reference value.

[0116] Clause 30. The apparatus of clause 28, wherein the communication unit is configured to receive a communication from the power receiver after a previous object detection evaluation indicating that no foreign object is present in the magnetic field if the previous object detection evaluation is within the FO threshold range, and the control unit is configured to store the previous measurement as a reference value for the power receiver and update the PRx threshold range based on the reference value.

[0117] Clause 31. Apparatus as described in any one of clauses 24 to 30, wherein the communication unit is configured to receive a communication from the power receiver indicating a PRx threshold range of the power receiver, the PRx threshold range being measured in a test environment when the power receiver is placed on a standard power transmitter with no foreign objects present.

[0118] Clause 32. An apparatus as described in any one of clauses 24 to 31, wherein the communication unit is configured to receive a communication from the power receiver indicating a reference value of the power receiver, and the control unit is configured to determine a PRx threshold range based on the reference value.

[0119] Clause 33. The apparatus of clause 31, wherein the reference values ​​include reference measurements taken in a test environment when the power receiver is placed on a standard power transmitter.

[0120] Clause 34. An apparatus as described in any one of clauses 24 to 33, wherein the communication unit is configured to receive a communication from the power receiver indicating that the power receiver includes an affinity metal, and the control unit is configured to determine a PRx threshold range based on predetermined measurements of the power receiver including the affinity metal.

[0121] Clause 35. An apparatus as described in any one of clauses 24 to 34, wherein the communication unit is configured to receive a communication from the power receiver indicating a range of expected measurement values ​​for the power receiver, and the control unit is configured to determine a PRx threshold range based on the range of expected measurement values.

[0122] Clause 36. The apparatus of any one of clauses 24 to 35, wherein the control unit is configured to obtain the PRx threshold range, or a reference value indicative of the PRx threshold range, or both, from a data field of an out-of-band communication received by the power transmitter from the power receiver.

[0123] Clause 37. The apparatus of clause 36, wherein the out-of-band communication is a Near Field Communication (NFC) Data Exchange Format (NDEF) message.

[0124] Clause 38. An apparatus as described in any one of clauses 23 to 33, wherein the control unit is configured to enable a wireless power transmission mode of the power transmitter when a foreign object is not present with the power receiver, and to disable a wireless power transmission mode of the power transmitter when a foreign object is present with the power receiver.

[0125] Clause 39. An apparatus as described in any one of clauses 24 to 38, wherein the control unit is configured to calculate a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing the alignment of the primary coil of the power transmitter and the secondary coil of the power receiver.

[0126] Clause 40. The apparatus of any one of clauses 23 to 39, wherein the measurement is at least one value selected from the group consisting of coil voltage or differential voltage of two or more detection coils of a coil pair, coil current or differential current of two or more detection coils of a coil pair, coil impedance or differential impedance of two or more detection coils of a coil pair, a quality factor calculated as part of the object detection assessment, and energy loss of low power transmission in the primary coil of the power transmitter.

[0127] Clause 41 An apparatus for wireless power transmission, comprising: a communication unit configured to receive communications from a power receiver present within a magnetic field of the power transmitter; and a measurement unit configured to obtain a first measurement value of a first parameter of low power transmission from the power transmitter during an object detection assessment, wherein the control unit is configured to calculate a coupling coefficient between the power transmitter and the power receiver based on the first measurement value, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver.

[0128] Clause 42. The apparatus of clause 41, wherein the control unit is configured to determine whether a foreign object is present in the magnetic field together with the power receiver based on at least one of the first measurement value or the second measurement value of the second parameter obtained during the object detection evaluation.

[0129] Clause 43. The apparatus of clause 42, wherein the control unit is configured to determine that a foreign object is not present if the first measurement or the second measurement is outside a foreign object (FO) threshold range for the foreign object, or to determine that a foreign object is not present if the first measurement or the second measurement is within a power receiver (PRx) threshold range based on a reference measurement of PRx.

[0130] Clause 44 An apparatus as described in any one of clauses 41 to 43, wherein the control unit is configured to cause the primary coil or the detection coil to transmit a low power signal while a power receiving circuit of the power receiver is disabled, the low power signal having a first voltage in the primary coil, the communication unit is configured to receive a communication from the power receiver indicating a second voltage in the power receiving circuit caused by the low power signal, and the control unit is configured to calculate a coupling coefficient based at least in part on a ratio of the second voltage to the first voltage.

[0131] Another innovative aspect of the subject matter described in this disclosure can be embodied as an apparatus that can include a modem and at least one processor communicatively coupled to the at least one modem. The processor can be configured in conjunction with the modem to perform any one of the foregoing methods or features described herein.

[0132] Another innovative aspect of the subject matter described in this disclosure can be implemented as a computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform any one of the above methods or features described herein.

[0133] Another innovative aspect of the subject matter described in this disclosure can be embodied as a system having means for performing any one of the above methods or features described herein.

[0134] As used herein, phrases referring to "at least one of" or "one or more of" a list of items refer 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 and b combinations, a and c combinations, b and c combinations, and a, b, and c combinations.

[0135] The various illustrative components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in connection with the embodiments disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware, or software, including the structures disclosed herein and their structural equivalents. The interchangeability of hardware, firmware, and software is generally described in terms of functionality and illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the particular application and design constraints imposed on the overall system.

[0136] The hardware and data processing equipment used to implement the various exemplary components, logic, logic blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed using general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices (PLDs), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration. In some implementations, specific processes, operations, and methods may be performed by circuitry specific to a given function.

[0137] As noted above, some aspects of the subject matter described herein can be implemented as software. For example, various functions of the 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 may 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 device, including components of a device 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, or any other medium usable for storing program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0138] Various modifications to the embodiments described in this disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the present disclosure. Thus, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the present disclosure, the principles, and novel features disclosed herein.

[0139] Furthermore, various features described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Thus, while features may be described above as acting in a particular combination and may even initially be claimed as such, one or more features from a claimed combination can, in some cases, be deleted from the combination, and the claimed combination can be directed to a subcombination or a variation of the subcombination.

[0140] Similarly, although operations are shown in the figures in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown, or in any sequential order, or that all of the operations shown be performed, to achieve desirable results. Furthermore, the figures may generally depict one or more exemplary processes in the form of a flow chart or diagram. However, other operations not shown may be incorporated into the generally depicted exemplary process. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the depicted operations. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged in multiple software products.

Claims

1. 1. A method for wireless power transmission by a power transmitter, comprising: receiving a communication from a power receiver present within a magnetic field of the power transmitter; obtaining measurements based on the object detection assessment; determining whether a foreign object is present in the magnetic field with the power receiver based on the measurements; A method comprising:

2. determining whether the foreign object is present, determining that the foreign object is not present if the measurement is outside a foreign object (FO) threshold range for the foreign object; or determining that the foreign object is not present if the measurement is within a power receiver (PRx) threshold range based on a reference measurement of the PRx; The method of claim 1 , comprising at least one of:

3. determining whether the foreign object is present, determining that the foreign object is present if the measurement value is outside the PRx threshold range; or determining that the foreign object is present when the measured value is within the FO threshold range; The method of claim 2 , further comprising at least one of:

4. 4. The method of claim 2, wherein the PRx threshold range and the FO threshold range overlap, and the measurement is compared to the PRx threshold range before comparing the measurement to the FO threshold range.

5. determining the PRx threshold range based on a fixed offset of the power receiver reference value; The method of any one of claims 2 to 4, further comprising:

6. determining the PRx threshold range based on previous measurements of a previous object detection evaluation in which the power transmitter confirmed that the foreign object was not present within the magnetic field with the power receiver; The method of any one of claims 2 to 5, further comprising:

7. detecting a user action after the previous object detection evaluation if the previous object detection evaluation is within the FO threshold range, the user action indicating that a foreign object is not present within the magnetic field; storing the previous measurements as a reference value for the power receiver; updating the PRx threshold range based on the reference value; The method of claim 6 further comprising:

8. receiving a communication from the power receiver after the previous object detection evaluation indicating that no foreign object is present within the magnetic field if the previous object detection evaluation is within the FO threshold range; storing the previous measurement as the reference value of the power receiver; updating the PRx threshold range based on the reference value; The method of claim 6 further comprising:

9. receiving a communication from the power receiver indicating the PRx threshold range of the power receiver, the PRx threshold range being measured in a test environment when the power receiver was placed on a standard power transmitter with no foreign objects present; 9. The method of claim 2, further comprising:

10. receiving a communication from the power receiver indicating a reference value for the power receiver; determining the PRx threshold range based on the reference value; 10. The method of claim 2, further comprising:

11. The method of claim 10 , wherein the reference values ​​comprise reference measurements taken in a test environment when the power receiver is placed on a standard power transmitter.

12. receiving a communication from the power receiver indicating that the power receiver includes an affinity metal; determining the PRx threshold range based on predetermined measurements of a power receiver including an affinity metal; 12. The method of claim 2, further comprising:

13. receiving a communication from the power receiver indicating a range of expected measurements for the power receiver; determining the PRx threshold range based on the range of expected measurements; 13. The method of any one of claims 2 to 12, further comprising:

14. obtaining the PRx threshold range, or a reference value indicative of the PRx threshold range, or both, from a data field of an out-of-band communication received by the power transmitter from the power receiver; 14. The method of any one of claims 2 to 13, further comprising:

15. The method of claim 14 , wherein the out-of-band communication is a Near Field Communication (NFC) Data Exchange Format (NDEF) message.

16. enabling a wireless power transmission mode of the power transmitter when the foreign object is not present with the power receiver; disabling the wireless power transmission mode of the power transmitter when the foreign object is present with the power receiver; 12. The method of claim 1, further comprising:

17. calculating a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver; 17. The method of any one of claims 2 to 16, further comprising:

18. The measurement value is coil voltage or differential voltage of two or more detection coils of a coil pair; coil current or differential current of the two or more detection coils of the coil pair; coil impedance or differential impedance of the two or more detection coils of the coil pair; a quality factor calculated as part of said object detection evaluation; and Low power transmission energy loss of the primary coil of the power transmitter; 18. The method of claim 1, wherein the value is at least one value selected from the group consisting of:

19. receiving a communication from a power receiver present within a magnetic field of the power transmitter; obtaining a first measurement of a first parameter of low power transmission from the power transmitter during object detection evaluation; calculating a coupling coefficient between the power transmitter and the power receiver based on the first measurement, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver; A method for wireless power transmission, comprising:

20. the first measurement value, or a second measurement of a second parameter obtained during the object detection evaluation; determining whether a foreign object is present with the power receiver in the magnetic field based on at least one of:

20. The method of claim 19, further comprising:

21. determining whether the foreign object is present, determining that the foreign object is not present if the first measurement or the second measurement is outside a foreign object (FO) threshold range for the foreign object; or determining that the foreign object is not present if the first measurement or the second measurement is within a power receiver (PRx) threshold range based on a reference measurement of the PRx; 21. The method of claim 20, comprising at least one of:

22. obtaining the measurements, transmitting the low power signal while a power receiving circuit of the power receiver is disabled, the low power signal having a first voltage on the primary coil; receiving a communication from the power receiver indicating a second voltage in the power receiving circuit caused by the low power signal; calculating the coupling coefficient based at least in part on a ratio of a second voltage to the first voltage; 22. The method of any one of claims 19 to 21, comprising:

23. a communication unit configured to receive communications from a power receiver present within a magnetic field of the power transmitter; a measurement unit configured to obtain measurements based on the object detection evaluation; a control unit configured to determine whether a foreign object is present in the magnetic field together with the power receiver based on the measurements; An apparatus for wireless power transmission comprising:

24. The control unit determining that the foreign object is not present if the measurement is outside a foreign object (FO) threshold range for the foreign object; or determining that the foreign object is not present if the measurement is within a power receiver (PRx) threshold range based on a reference measurement of the PRx; 24. The apparatus of claim 23, configured to:

25. The control unit determining that the foreign object is present if the measurement value is outside the PRx threshold range; or determining that the foreign object is present when the measurement value is within the FO threshold range; 25. The apparatus of claim 24, configured to:

26. 26. The apparatus of claim 24, wherein the PRx threshold range and the FO threshold range overlap, and the control unit is configured to compare the measurement value with the PRx threshold range before comparing the measurement value with the FO threshold range.

27. The control unit determining the PRx threshold range based on a fixed offset of the power receiver reference value; 27. An apparatus according to any one of claims 24 to 26, configured to:

28. The control unit determining the PRx threshold range based on previous measurements of a previous object detection evaluation in which the power transmitter confirmed that the foreign object was not present within the magnetic field with the power receiver; 28. An apparatus according to any one of claims 24 to 27, configured to:

29. The control unit detecting a user action after the previous object detection evaluation if the previous object detection evaluation is within the FO threshold range, the user action indicating the absence of a foreign object within the magnetic field; storing the previous measurements as a reference value for the power receiver; updating the PRx threshold range based on the reference value; 29. The device of claim 28, configured to:

30. the communication unit is configured to receive a communication from the power receiver after the previous object detection evaluation indicating that no foreign object is present in the magnetic field if the previous object detection evaluation is within the FO threshold range; The control unit storing the previous measurement as the reference value for the power receiver; updating the PRx threshold range based on the reference value; It is configured as follows:

29. The apparatus of claim 28.

31. the communication unit is configured to receive a communication from the power receiver indicating the PRx threshold range of the power receiver, the PRx threshold range being measured in a test environment when the power receiver is placed on a standard power transmitter with no foreign objects present; 31. Apparatus according to any one of claims 24 to 30.

32. the communication unit is configured to receive a communication from the power receiver indicating a reference value of the power receiver; the control unit is configured to determine the PRx threshold range based on the reference value; 32. Apparatus according to any one of claims 24 to 31.

33. 32. The apparatus of claim 31, wherein the reference values ​​comprise reference measurements taken in a test environment when the power receiver is placed on a standard power transmitter.

34. the communication unit is configured to receive a communication from the power receiver indicating that the power receiver includes an affinity metal; the control unit is configured to determine the PRx threshold range based on predetermined measurements of a power receiver including an affinity metal; 34. Apparatus according to any one of claims 24 to 33.

35. the communication unit is configured to receive a communication from the power receiver indicating a range of expected measurements for the power receiver; the control unit is configured to determine the PRx threshold range based on the range of expected measurements.

35. Apparatus according to any one of claims 24 to 34.

36. 36. The apparatus of claim 24, wherein the control unit is configured to obtain the PRx threshold range, or a reference value indicative of the PRx threshold range, or both, from a data field of an out-of-band communication received by the power transmitter from the power receiver.

37. 37. The device of claim 36, wherein the out-of-band communication is a Near Field Communication (NFC) Data Exchange Format (NDEF) message.

38. The control unit enabling a wireless power transmission mode of the power transmitter when the foreign object is not present with the power receiver; Disabling the wireless power transmission mode of the power transmitter when the foreign object is present with the power receiver.

34. Apparatus according to any one of claims 23 to 33, configured to:

39. The control unit calculating a coupling coefficient between the power transmitter and the power receiver based on the measurements, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver; 39. Apparatus according to any one of claims 24 to 38, configured to:

40. The measurement value is coil voltage or differential voltage of two or more detection coils of a coil pair; current in a coil or a differential current in the two or more detection coils of the coil pair; coil impedance or differential impedance of the two or more detection coils of the coil pair; a quality factor calculated as part of the object detection evaluation t; and Low power transmission energy loss of the primary coil of the power transmitter; 40. The apparatus of any one of claims 23 to 39, wherein the at least one value is selected from the group consisting of:

41. a communication unit configured to receive communications from a power receiver present within a magnetic field of the power transmitter; a measurement unit configured to obtain a first measurement of a first parameter of the low power transmission from the power transmitter during object detection evaluation; a control unit configured to calculate a coupling coefficient between the power transmitter and the power receiver based on the first measurement, the coupling coefficient representing an alignment of a primary coil of the power transmitter and a secondary coil of the power receiver; A device for wireless power transmission.

42. The control unit the first measurement value, or a second measurement of a second parameter obtained during the object detection evaluation; determining whether a foreign object is present in the magnetic field together with the power receiver based on at least one of:

42. The apparatus of claim 41, configured to:

43. The control unit determining that the foreign object is not present if the first measurement or the second measurement is outside a foreign object (FO) threshold range for the foreign object; or determining that the foreign object is not present if the first measurement or the second measurement is within a power receiver (PRx) threshold range based on a reference measurement of the PRx; 43. The apparatus of claim 42, configured to:

44. the control unit is configured to cause a primary coil or a detection coil to transmit the low-power signal while a power receiving circuit of the power receiver is disabled, the low-power signal having a first voltage in the primary coil; the communication unit is configured to receive a communication from the power receiver indicating a second voltage in the power receiving circuit caused by the low power signal; the control unit is configured to calculate the coupling coefficient based at least in part on a ratio of a second voltage to the first voltage.

44. Apparatus according to any one of claims 41 to 43.

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