Wireless power transmitter, wireless power receiver, and methods of operation thereof

Abstract

The present disclosure provides a wireless power transmitter, a wireless power receiver, and methods of operating the same. In one embodiment, a method of operating a wireless power transmitter can include receiving, from a wireless power receiver, a request to perform recalibration of a first type of foreign object detection (FOD) in response to the wireless power receiver attempting to change an electromagnetic parameter provided by the wireless power transmitter; performing a second type of FOD to generate a FOD result in response to receiving the request; stopping or limiting wireless power transmission and / or communicating the FOD result to the wireless power receiver when the FOD result indicates that a foreign object is present or likely to be present; and performing the recalibration and continuing the wireless power transmission when the FOD result indicates that a foreign object is not present or likely to be not present.

Description

TECHNICAL FIELD

[0001] The technology described herein relates to wireless power transfer, detection of foreign objects, and transition between different levels of power transfer. BACKGROUND

[0002] Wireless Power Transfer Systems (WPTS) are increasingly popular as a convenient way to provide power without wires or connectors. WPTSs that are currently under development in the industry can be divided into two broad categories: Magnetic Induction (MI) systems and Magnetic Resonance (MR) systems. Both types of systems include a wireless power transmitter and a wireless power receiver. Inductive WPTSs typically use frequency variation as a power flow control mechanism, operating over a range of frequencies in the hundreds of kilohertz assigned for this purpose. MR WPTSs typically operate at a single resonant frequency, using input voltage regulation to regulate the output power. In some applications, MR WPTSs operate at a frequency of 6.78 MHz. SUMMARY

[0003] The present invention provides a wireless power transmitter, a wireless power receiver, and methods of operating the same. The impact of foreign objects can be mitigated through a second type of foreign object detection.

[0004] A method of operating a wireless power transmitter according to the present invention includes: in response to a wireless power receiver attempting to change an electromagnetic parameter provided by the wireless power transmitter, receiving from the wireless power receiver a request to perform recalibration of a first type of foreign object detection (FOD); in response to receiving the request, performing a second type of FOD to produce a FOD result; when the FOD result indicates that a foreign object is present or likely to be present, stopping or limiting wireless power transfer, and / or communicating the FOD result to the wireless power receiver; and when the FOD result indicates that a foreign object is not present or likely to be present, performing the recalibration and continuing the wireless power transfer.

[0005] A wireless power transmitter is provided that includes circuitry configured to, in response to a wireless power receiver attempting to change an electromagnetic parameter provided by the wireless power transmitter, receive a request from the wireless power receiver for a recalibration of a first type of foreign object detection to be performed, in response to receiving the request, perform a second type of foreign object detection to produce a foreign object detection result, when the foreign object detection result indicates that a foreign object is present or likely to be present, stop or limit wireless power transmission, and / or communicate the foreign object detection result to the wireless power receiver, and when the foreign object detection result indicates that a foreign object is not present or likely to be not present, perform the recalibration and continue the wireless power transmission.

[0006] A method of operating a wireless power receiver is provided that includes, when attempting to change an electromagnetic parameter provided by a wireless power transmitter, sending a request to the wireless power transmitter for a recalibration of a first type of foreign object detection to be performed, receiving a second type of foreign object detection result from the wireless power transmitter, when the foreign object detection result indicates that a foreign object is present or likely to be present, changing one or more wireless power transmission parameters, limiting wireless power transmission, or stopping the wireless power transmission, and when the foreign object detection result indicates that a foreign object is not present or likely to be not present, continuing the wireless power transmission and performing the recalibration of the first type of foreign object detection.

[0007] A wireless power receiver is provided that includes circuitry configured to, when attempting to change an electromagnetic parameter provided by a wireless power transmitter, send a request to the wireless power transmitter for a recalibration of a first type of foreign object detection to be performed, receive a second type of foreign object detection result from the wireless power transmitter, when the foreign object detection result indicates that a foreign object is present or likely to be present, change one or more wireless power transmission parameters, limit wireless power transmission, or stop the wireless power transmission, and when the foreign object detection result indicates that a foreign object is not present or likely to be not present, continue the wireless power transmission and perform the recalibration of the first type of foreign object detection. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 A block diagram of a wireless power transmission system is shown in accordance with some embodiments.

[0009] Figure 2 An example of a wireless power transmission method is shown in accordance with some embodiments.

[0010] Figure 3 An example of a plot of power transmission versus time is shown.

[0011] Figure 3A And Figure 3B An example of a plot of power transmission versus time is shown.

[0012] Figure 4An example of a recalibration request sent from a wireless power receiver to a wireless power transmitter is shown in accordance with some embodiments.

[0013] Figure 5 An example of codes indicating various levels of FOPP sent from a wireless power receiver to a wireless power transmitter (PTX) and subsequent actions of the wireless power transmitter are shown in a diagram in accordance with some embodiments.

[0014] Figure 6 An example of a recalibration request sent from a wireless power transmitter to a wireless power receiver is shown in accordance with some embodiments.

[0015] Figure 7 An example of codes indicating various levels of FOPP sent from a wireless power transmitter to a wireless power receiver (PRX) and subsequent actions of the wireless power receiver are shown in a diagram in accordance with some embodiments. DETAILED DESCRIPTION

[0016] Certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, manufacturers can refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." Also, the term "couple" or "coupled" means to be directly or indirectly connected physically or electrically, such that a power supply can flow from one to the other. The term "substantially" does not by itself mean "exactly" or "perfectly," but rather means "to a degree of approximation." The following description is presented to enable any person skilled in the art to make and use the application. Descriptions of specific devices and applications are provided only as examples. The present application is not limited to the specific devices described, but rather, the intent is to cover all modifications, equivalents, and alternatives falling within the scope of the present application as defined by the appended claims.

[0017] The following description is presented to enable any person skilled in the art to make and use the application. Descriptions of specific devices and applications are provided only as examples. The present application is not limited to the specific devices described, but rather, the intent is to cover all modifications, equivalents, and alternatives falling within the scope of the present application as defined by the appended claims.

[0018] Wireless power systems can provide a convenient way to provide power from a first device (e.g., a wireless power transmitter) to a second device (e.g., a wireless power receiver). In many implementations, the wirelessly provided power can be used to power and / or charge a battery in an electronic device.

[0019] Wireless power transmission can be degraded due to the presence of foreign objects in the field generated by a wireless power transmitter. Conductive objects, such as metal objects, may absorb electricity due to the induction of eddy currents within the conductive object. The presence of such an object can significantly reduce the efficiency of wireless power transmission. If a metallic object is present, the efficiency may be drastically reduced (e.g., from 90% to 40%). Furthermore, the temperature of the object may rise significantly due to the absorbed electricity, which is undesirable. This heating can be caused by foreign objects (e.g., paperclips, coins, etc.) inadvertently located within the field generated by the wireless power transmitter. Foreign object detection (FOD) techniques have been developed to detect the presence of foreign objects. It may be desirable to perform FOD before initiating wireless power transmission, during power transmission, or before switching from one power level to another. If a foreign object is detected, wireless power transmission may be halted.

[0020] Some wireless power systems can operate in two or more wireless power transmission modes, which can correspond to different levels of wireless power transmission. For example, a wireless power system 100 having a transmitter 1 and a receiver 11 (such as...) Figure 1 The wireless power system shown can operate in a low-power mode. According to some embodiments, the power transmitted in low-power mode may be 5 watts or less. In some cases, this mode may be referred to as a "basic power performance" mode, although other names may be used. If supported, the wireless power system 100 can operate in one or more high-power modes. For example, a high-power mode may be a wireless power transmission mode in which power levels exceeding 5 watts can occur. In some cases, a high-power mode may switch the power level from 5 watts to 15 watts or even higher. Such one or more modes may be referred to as "extended power performance" or other names may be used. It is understood that with increased power transmission levels, higher levels of power loss and foreign object heat generation may occur. Therefore, it may be beneficial to perform foreign object detection (FOD) before entering high-power mode.

[0021] Foreign object detection can be performed in a variety of ways, such as by measuring power loss, Q-factor, or resonant frequency. Measurements can be performed without a foreign object to determine baseline values for the parameters. Such techniques can be considered to be “calibration” or “re-calibration”. To perform foreign object detection in practice, the same parameters (e.g., power loss, Q-factor, or resonant frequency) can be measured, and a difference between the measured parameter and the parameter measured during calibration (e.g., in the absence of a foreign object) can be determined to be outside of an acceptable range if a foreign object is present or the likelihood of a foreign object being present is high. For calibration to be valid, FOD measurements can be performed at the same operating power set point as the calibration was performed. Thus, when there is a request to change the power level, a FOD re-calibration can be performed. However, the inventors have realized that if a foreign object is present during the re-calibration, the foreign object can be “calibrated out”, which can result in subsequent foreign object detection being ineffective.

[0022] In some embodiments, prior to performing a FOD re-calibration, a second type of FOD can be used to check for the absence of a foreign object. For example, if a power loss method is used as the primary method of FOD, a different type of FOD (e.g., using Q-factor or resonant frequency measurements) can be performed to verify that there is no FO when recalibrating the power loss FOD technique.

[0023] Before describing methods of performing wireless power transmission, more details of a wireless power transmission system 100 and foreign object detection are now briefly described.

[0024] Figure 1 A block diagram of a wireless power system 100 including a wireless power transmitter 1 and a wireless power receiver 11 is shown. The wireless power transmitter 1 includes a drive circuit 7, which can include an inverter 3 and a matching network 6. The inverter 3 can drive a transmit coil 10 and be impedance matched to the transmit coil through the matching network 6.

[0025] According to some embodiments, the wireless power transmitter 1 can further include a regulated voltage source 2 (e.g., a voltage regulator) for providing a regulated DC voltage to the inverter 3. The regulated voltage source 2 generates a regulated DC output voltage in response to a control stimulus from a controller 5. In some embodiments, the drive circuit 7 can be a class-D or class-E amplifier that converts a DC voltage at the input of the inverter 3 to an AC output voltage to drive the transmit coil 10. Generating the AC output voltage can enable wireless power transmission through electromagnetic induction.

[0026] The controller 5 can also control the signal generator 9 to drive the inverter 3 with a signal having a selected wireless power transmission frequency. As an example, the inverter 3 can be switched at a frequency between 100-205 kHz to transmit power to a wireless power receiver designed to receive wireless power according to the low power Qi receiver of the Qi specification, and can be switched at a frequency between 80-300 kHz to transmit power to a mid-frequency power Qi receiver. The inverter 3 can be switched at a higher frequency, for example, a frequency greater than 1 MHz, or within the ISM band at 6.765-6.795 MHz, to transmit power to a receiver designed to receive wireless power using MR technology. However, these frequencies are provided by way of example only, as wireless power can be transmitted at a variety of suitable frequencies according to any suitable specification. The controller 5 can be an analog circuit or a digital circuit. The controller 5 can be programmable, and can instruct the signal generator 9 to generate a signal at a desired transmission frequency based on stored program instructions, such that the inverter 3 is switched at the desired transmission frequency. The matching network 6 can include one or more impedance matching networks, and facilitates wireless power transmission by presenting an appropriate impedance to the inverter 3. The matching network can include one or more capacitive or inductive components, or any suitable combination of capacitive and inductive components. Since the transmit coil 10 can have an inductive impedance, in some embodiments the matching network 6 can include one or more capacitive components that, when combined with the impedance(s) of the transmit coil 10, present an impedance to the output of the inverter 3 that is suitable for driving the transmit coil 10. For example, the matching network can rotate the input impedance of the transmit coil 10 to approximately match the output impedance of the inverter 3, thereby reducing power reflection from the transmit coil 10. In some embodiments, the resonant frequency of the matching network 6 and the transmit coil 10 can be adjusted (e.g., by variable and / or switched capacitors) during wireless power transmission, and can be set to equal or approximately equal the switching frequency of the inverter 3.

[0027] The transmit coil 10 and receive coil 12 can be implemented by any suitable type of conductor. The conductor can be a wire, including a solid, single core wire or a litz wire. In some cases, the coils can be formed from a patterned conductor, such as a patterned conductor of a printed circuit board or an integrated circuit.

[0028] According to Ampere's law, the alternating current driven in the transmitting coil 10 generates an oscillating magnetic field. According to Faraday's law, this oscillating magnetic field induces an alternating current in the receiver coil 12 of the nearby wireless power receiver 11, generating a voltage across it. The AC voltage induced in the receiver coil 12 is supplied via a matching network 13 to a rectifier 14 that generates an unregulated DC voltage. The rectifier 14 can be a synchronous rectifier, or it can be implemented using diodes and one or more capacitors. The unregulated DC voltage can be regulated using a DC / DC converter 15, the output of which can be filtered and supplied to the load as the output voltage Vout. In some alternative embodiments, the DC / DC converter 15 can be replaced by a linear regulator or a battery charger, or omitted entirely.

[0029] According to some embodiments, the wireless power receiver 11 may include a memory 17 and control logic 16. The control logic 16 may include dedicated circuitry (such as dedicated circuitry formed by logic gates and buffers, and other circuit components), one or more field-programmable gate arrays, a microcontroller, a microprocessor, or a combination thereof. The memory may include at least one of volatile and non-volatile types of memory. The control logic 16 may communicate with the memory 17 and may further communicate with at least one of a rectifier and a DC / DC converter or a linear regulator or a battery charger.

[0030] In some embodiments, the wireless power transmitter 1 may include communication circuitry (e.g., within or connected to the controller 5) for communicating with the wireless power receiver 11. This communication may be in-band or out-of-band. Similarly, the wireless power receiver 11 may include communication circuitry (e.g., within or connected to the control logic 16) for communicating with the wireless power transmitter 1. According to some embodiments, the wireless power receiver 11 may send information to the wireless power transmitter 1 indicating the power required at the wireless power receiver 11, or requesting a change in the power level provided by the wireless power transmitter 1. In response, the wireless power transmitter 1 may increase or decrease its power output accordingly. The wireless power transmitter 1 may control the transmitted power by changing the voltage drive level applied to the transmitting coil 10, and / or the frequency of the oscillating voltage applied to the transmitting coil 10. Any suitable power control technology may be used.

[0031] like Figure 1 As shown, if a conductive foreign object 20 enters the field generated by the transmitting coil 10 of the wireless power transmitter 1, the wireless power transmission efficiency may decrease and / or the conductive foreign object 20 may experience significant heating. Examples of conductive foreign objects 20 include coins, paperclips, and keys.

[0032] According to some embodiments, a method referred to as "power loss balancing" or "loss balancing" can be used to assess whether a foreign object is present or the likelihood of a foreign object being present. In power loss balancing, the power loss associated with the wireless power transmitter 1 and the wireless power receiver 11 is measured during a calibration step in the absence of a foreign object. Assessing the presence of a foreign object can include measuring the power loss and determining whether the power loss is outside of an acceptable range. During power transfer, the amount of power transmitted by the wireless power transmitter can be determined, and the amount of power received by the wireless power receiver can be determined (e.g., measured). The amount of power received by the receiver 11 can be communicated to the wireless power transmitter. The difference between the amount of power transmitted (based on the power applied to the transmitter coil and transmitter losses) and the actual power received (based on the power delivered to the load and receiver losses) is due at least in part to power loss associated with one or more foreign objects.

[0033] In some implementations, if the power loss associated with a foreign object exceeds a threshold amount, the wireless power transfer will be interrupted, whereby the foreign object 20 can be removed. Depending on the operating mode, certain standards (e.g., the Qi standard) can have multiple threshold amounts. For example, in a low power operating mode, the wireless power transfer can be interrupted if the power loss associated with a foreign object exceeds 350 milliwatts. In a high power operating mode, the wireless power transfer can be interrupted if the power loss associated with a foreign object exceeds 750 milliwatts. It should be understood that other threshold amounts can be used in the Qi standard or other standards, and the present disclosure is not limited to these example values.

[0034] In some implementations, foreign object detection can be performed using alternative types of foreign object detection. For example, foreign object detection can be performed by measuring the quality factor Q associated with the transmit coil 10. For example, the wireless power transmitter 1 can excite a resonance in the transmit coil 10 and then allow the stored energy to decay. The observed decay rate depends on the Q of the transmit coil and the parameters of the circuit in which it exists, and can also be affected by any foreign objects 20 that interact with the electromagnetic field generated by the transmit coil 10. Another example of a foreign object detection technique involves measuring the resonant frequency of the wireless power transmitter. A resonant frequency that is outside of an allowed range can indicate the presence of a foreign object. Examples of foreign object detection methods are described in further detail in U.S. Patent Application 15 / 957,704, filed April 19, 2018, entitled “Detecting Foreign Objects in a Wireless Power Transfer System,” the entirety of which is incorporated by reference herein.

[0035] Figure 2An example of a wireless power transfer method is shown in accordance with some embodiments. The method can begin at step SI after wireless power transfer between a wireless power transmitter and a wireless power receiver has begun. During operation, the wireless power receiver can decide to change the power level requested from the wireless power transmitter. The decision can be made by the control logic 16 of the wireless power receiver when the load increases or the spatial position of the wireless power receiver relative to the wireless power transmitter increases (e.g., misalignment between the transmitter and receiver can cause the wireless power receiver to request more power). However, the wireless power receiver can decide to change the power level requested from the wireless power transmitter for any of a variety of reasons, and the techniques described herein are not limited in this respect. In some embodiments, the wireless power receiver can request the wireless power transmitter to transition from a low power mode to a high power mode. Alternatively, the wireless power receiver can request the wireless power transmitter to transition from a high power mode to a low power mode.

[0036] In step S2, the wireless power receiver can send a FOD recalibration request to the wireless power transmitter. As described above, system parameters can vary at different power levels, such that recalibration of the FOD technique can be needed when a change in power level is desired. For example, the wireless power transmitter can operate in a half-bridge configuration when delivering up to 5W of power, and in a full-bridge configuration when delivering higher power levels (e.g., 10-30W). As another example, the wireless power receiver can operate at a 5V rectifier output when delivering 5W or less of load power, and can operate at a higher voltage (e.g., 10-20V) when delivering higher load power (e.g., 10-30W). In some embodiments, the recalibration request is sent in response to an electromagnetic parameter (e.g., voltage, current, or power received from the wireless power transmitter) at the wireless power receiver being requested to change by a threshold amount (e.g., at least 10% or 50%) or an amount greater than the threshold amount. When a change in system configuration or operating power parameters (e.g., output voltage, current, or power (electromagnetic parameters)) occurs, FOD recalibration is performed to achieve better loss balancing, and thus more accurate calculation of foreign object related losses. In some embodiments, the threshold amount for requesting recalibration can be variable, and can depend on the size of the electromagnetic parameter. For example, if the wireless power transmission is already being performed at a high power level, the threshold amount can be set lower so that recalibration is performed more frequently. However, if the value of the electromagnetic parameter (e.g., operating power) is lower, the threshold amount can be set higher so that recalibration is not performed as frequently. Additionally, an authentication process can be performed between the wireless power transmitter and the wireless power receiver to verify that the wireless power receiver is capable of operating at the requested power level (e.g., verify that the wireless power receiver can handle higher power levels) before the modified power level is provided to the wireless power receiver.

[0037] The inventors have realized that if a foreign object is present in the electromagnetic field generated by the wireless power transmitter during recalibration, but does not exceed the threshold amount of the selected foreign object detection method, the foreign object can be "calibrated out." That is, the recalibration can improperly recalibrate the wireless power transmitter under the assumption that no foreign object is present (when in fact a foreign object is present). This improper recalibration can result in the foreign object detection method failing to detect the foreign object.

[0038] Figure 3 An example of a plot of power transfer versus time is shown, which illustrates the foregoing problem. Subsequent FOD recalibrations at points A, B, and C have progressively increasing transmit power levels, resulting in the FO-related power loss being "calibrated out," and ultimately resulting in excessive power consumption in the FO.

[0039] In some embodiments, this can be avoided by performing a second type of foreign object detection in step S3 prior to performing the requested recalibration of the first type of foreign object detection. This can help to ensure that there is no foreign object present when the recalibration is performed. The second type of foreign object detection can measure at least one parameter different from the parameter measured by the first type of foreign object detection (e.g. power loss, Q-factor or resonance frequency). For example, if the requested recalibration is a foreign object detection of the power loss method, a different (second) type of foreign object detection can be performed prior to that recalibration, e.g. a foreign object detection measuring the Q-factor and / or the resonance frequency. If the second type of foreign object detection measures the Q-factor and / or the resonance frequency, the wireless power transmitter can measure the system Q-factor and / or the self-resonance frequency, which are the Q-factor and the resonance frequency of the transmit coil of the wireless power transmitter in the presence of the wireless power receiver. In some embodiments, the second type of foreign object detection can be performed within a predetermined time interval after the recalibration request is sent.

[0040] In step S4, based on the result of the second type of foreign object detection, further actions can be taken. For example, if the second type of foreign object detection detects that there is no foreign object or it is likely that there is no foreign object, the wireless power transmitter and the wireless power receiver can proceed with performing the requested recalibration for the first type of foreign object detection. The transmission of power can proceed with modifications.

[0041] If the second type of foreign object detection detects that there is a foreign object or it is likely that there is a foreign object, the wireless power transmitter can take one or more other actions to mitigate the effects of the foreign object. For example, in some embodiments, the wireless power transmitter can immediately stop the wireless power transmission. In some embodiments, the wireless power transmitter can not stop the wireless power transmission and can report the result of the second type of foreign object detection to the wireless power receiver. The wireless power receiver can then take action based on the result of the second type of foreign object detection. For example, in some embodiments, the wireless power receiver can continue to request the original power level, can send a new set of FOD calibration parameters to the wireless power transmitter, can reduce its output power, or can instruct the wireless power transmitter to stop the wireless power transmission.

[0042] Figure 3AAn example of a plot of power transfer versus time is shown. A first type of FOD (e.g., power loss balancing) can be performed before power transfer (BPT). When no foreign object is detected, power increases to point "A". The first type of FOD can be performed during power transfer (DPT), which detects an acceptable level of power loss, as shown by the dashed line. The wireless power transmitter can then receive a request from the wireless power receiver to increase the level of power transfer to point "B", which can be a transition from a low power mode to a high power mode. The wireless power transmitter can send a recalibration request for the first type of FOD. The second type of FOD is then performed before recalibration. In this example, power transfer is stopped in time interval "FOD OPI" (foreign object detection performed on power interruption). During time interval FOD OPI, the second type of FOD is performed. For example, a FOD that includes measuring the Q-factor can be performed. In this example, the second type of FOD does not detect a foreign object in the first power interruption, so recalibration is performed and power transfer is allowed to increase to point "B". If a foreign object is detected in a subsequent power interruption by performing the Q-factor method, recalibration is not allowed and power is not allowed to increase to point "C", so power transfer can effectively end based on the results of the second type of FOD method.

[0043] Figure 3B Another example is shown in which the results of the second type of FOD method meet the requirements for increasing the transmitted power from point "A" to point "B" and point "C".

[0044] Examples of the format of the recalibration request are shown in Figure 4 and Figure 5 Figure 4 An example of a recalibration request sent from the wireless power receiver to the wireless power transmitter (e.g., in step S2) is shown according to some embodiments. The B1 and B2 bytes can be different from the previous implementation that includes an estimated received power value. The mode field in the B0 byte can be set to 011. As Figure 4 ​As shown, the B1 byte can include two fields: a Min FO Slot Rep field and a Max FO Slot-time Sustainable field. The Min FO Slot Rep field indicates a minimum FO slot repetition time, which is the minimum time between subsequent FO detection slots. In some embodiments, the minimum FO slot repetition time can be between 0.5s - 4s, inclusive. However, the techniques described herein are not limited in this regard as the FO slot repetition time can have any suitable value. An FO slot is a slot in which regular FOD is performed. The Max FO Slot-time Sustainable field indicates the maximum length of an FO slot, which in some embodiments can be between 10ps - 320ps, inclusive. However, the techniques described herein are not limited in this regard as the Max FO Slot-time Sustainable field can have any suitable value. The B2 byte can include a FO Presence Probability field, which can indicate the likelihood of FO presence. In some embodiments, this likelihood can have a value between 0 (indicating zero likelihood of FO presence) and 1 (indicating 100% likelihood of FO presence), which can be expressed in any form, e.g., binary form. In some embodiments, the FO Presence Probability field can be four bits in length. In some embodiments, the wireless power receiver can measure the FO Presence Probability using a different technique than the one used by the wireless power transmitter, e.g., based on measuring the temperature in one or more locations of the wireless power receiver. For example, uniform heating can indicate heating due to environmental factors, e.g., the wireless power receiver being in sunlight or otherwise in an elevated temperature location. However, a change in temperature across different locations of the wireless power receiver can indicate localized heating due to a foreign object. Temperature sensors at different locations (e.g., different sides) of the wireless power receiver can measure the temperature, and if there is a sufficiently large difference (e.g., between the screen side of the mobile device and the back of the mobile device), the wireless power receiver can determine that there is a high FO Presence Probability. When the wireless power transmitter is notified of a high FO Presence Probability, it can take various measures, e.g., stop or limit wireless power transmission. In some embodiments, when the wireless power receiver notifies the wireless power transmitter of a high Foreign object Presence Probability (FOPP), the wireless power transmitter can adjust its FOD threshold amount for any FOD technique.

[0045] Figure 5An example of a chart showing codes indicating various levels of FOPP sent from a wireless power receiver to a wireless power transmitter and subsequent actions by the wireless power transmitter (PTX) is shown in accordance with some embodiments. In some embodiments, even codes can be assigned to optional (recommended) actions and odd codes can be assigned to mandatory requests. For example, binary code 0000 or 0001 can indicate that no FO is sensed and can allow a transition to a higher power level. The wireless power receiver can periodically send a message (e.g., packet) to the wireless power transmitter including information indicating the amount of power received by the wireless power transmitter. In response to a low FOPP, as indicated by binary code 0000 or 0001, the repetition rate of such messages can be set to a lowest frequency. Binary code 0011 or 0010 can indicate that FO is unlikely, but the information indicating the amount of power received by the wireless transmitter can have an increased variance. The wireless power transmitter can average such power information over time to reduce the impact of noise. In response to a slightly elevated FOPP, as indicated by binary code 0011 or 0010, the wireless power transmitter can reduce the time period over which the average power information is taken in order to respond more quickly. In general, the wireless power transmitter can only stop wireless power transmission after a number of out-of-range FOD measurements reaches a certain value (e.g., 3-5 times). This number can be reduced (e.g., to 2-3 times) when the likelihood of FO is high (e.g., when the binary code is 0011 or 0010). Binary code 0100 or 0101 can indicate that there is a higher likelihood of FO being present. The wireless power transmitter can look at its current FOPP estimate. Binary code 0110 or 0111 can indicate that there is no FO, but the uncertainty of FO being present is high. For example, the PTX can set its FOPP value to a higher value in response to a high FOPP value received from the wireless power receiver. When the PRX indicates a high FOPP, the PTX can reconsider the FOD threshold amount and make the FOD threshold amount easier to be exceeded. Binary code 1000 or 1001 can indicate that FO is present, but the uncertainty of FO being present is high. The PTX can reconsider the FOD threshold amount. Binary code 1010 or 1011 can indicate that the wireless power receiver is operating at high power in a hot environment and thus needs extra care. If a low Q factor is measured during wireless power transmission, the wireless power transmitter can increase its FOPP estimate value. Binary code 1100 or 1101 can indicate that the wireless power receiver is operating at the highest power in a hot environment and thus needs extra care. If the Q factor is low, the wireless power transmitter can stop wireless power transmission. Binary code 1110 or 1111 can indicate that the foreign object likelihood is at the highest level.If the Q factor is low, the wireless power transmitter can stop wireless power transmission.

[0046] In some embodiments, the wireless power transmitter can send a request for recalibration to the wireless power receiver. Figure 6 An example of a request for recalibration sent from a wireless power transmitter to a wireless power receiver is shown in accordance with some embodiments. Byte B0 can include a request for recalibration. Byte Bl can include a likelihood of FO presence, which can have the same format as discussed above based on Figure 4 the techniques described herein. Based on the likelihood of FO presence, the wireless power receiver can take various actions, one of which can include sending a request for recalibration to the wireless power transmitter (e.g., in step S2).

[0047] Figure 7Code indicating various levels of FOPP sent from a wireless power transmitter to a wireless power receiver (PRX) and subsequent actions by the wireless power receiver are shown according to some embodiments. Certain FOPP codes can be used for a request for non-re-calibration, while other FOPP codes can be used as a request for re-calibration. In some embodiments, even codes can be assigned to optional (recommended) actions, and odd codes can be assigned to mandatory requests. Binary code 0000 or 0001 can indicate that no FO is perceived. Binary code 0010 or 0011 can indicate that there is a low likelihood of FO, but the FO loss estimate has increased variability (e.g., as a result of multiple measurements). In response, the wireless power receiver can send information about the amount of power received to the wireless power transmitter more frequently. Binary code 0100 or 0101 can indicate that there is a high likelihood of FO, and can cause the wireless power receiver to send information about the amount of power received more frequently than in the case of a lower level FOPP. Binary code 0110 or 0111 can indicate that there is no FO, but there is a high uncertainty of FO. The wireless power receiver can reduce the requested power level and send information about the amount of power received as soon as possible. Binary code 1000 or 1001 can indicate that there is a FO, but there is a high uncertainty of FO. In response, for 1000, the wireless power receiver can request re-calibration. For 1001, a re-calibration at a high power point can be requested. For 1010, there is an indication that there can be a FO, and a request for re-calibration at both a low power point and a high power point. For 1011, there is an indication that there can be a FO, and a request for re-calibration at least at three power points. For 1100, there is an indication that there is a high likelihood of FO, and a request for re-calibration at least at four power points. For 1101, there is an indication that there is a high likelihood of FO, and a suggestion to stop. For 1110, there is an indication that there is a near certainty of FO, and a need to reduce power and perform re-calibration. For 1111, there is an indication that wireless power transmission is now being stopped.

[0048] As noted above, the wireless power transmitter or receiver can be controlled using a controller 5 or control logic 16, which can be implemented by any suitable type of circuitry. For example, the controller 5 or control logic 16 can be implemented using hardware or a combination of hardware and software. When implemented using software, suitable software code can be executed on any suitable processor (e.g., a microprocessor) or set of processors. The one or more controllers can be implemented in a number of ways, such as with dedicated hardware or with a general purpose hardware (e.g., one or more processors) programmed with microcode or software to perform the functions described above.

[0049] To this end, it should be understood that one implementation of the embodiments described herein includes at least one computer-readable storage medium (e.g., RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD), etc.) encoding a computer program (i.e., a plurality of executable instructions) that, when executed in one or more processors, performs the functions described above for one or more embodiments. Additionally, it should be understood that the term "computer-readable storage medium" as used herein includes any type of computer- readable storage media including non-transitory storage media. Furthermore, to the extent that the term "program" or "computer program" is used herein, it should be understood that it is a non- limiting term (for example and without limitation) to refer to any type of computer code (e.g., software or computer application software, firmware, microcode, or any other form of computer instruction) that can be executed on one or more processors to implement the functions described herein.

[0050] Although the present application has been described in terms of the preferred embodiments, it is to be understood that the application is not to be limited to the details of the above-described embodiments but can be modified within the scope and spirit of the application. Accordingly, any and all modifications, variations or equivalent arrangements which do not depart from the spirit or scope of the application should be considered to be within the scope of the application.

Claims

1. A method of operating a wireless power transmitter, characterized by, comprising: receiving, from a wireless power receiver, a request for a first type of foreign object detection to perform a recalibration in response to the wireless power receiver attempting to change an electromagnetic parameter provided by a wireless power transmitter; in response to receiving the request, performing a second type of foreign object detection to produce a foreign object detection result before the recalibration of the first type of foreign object detection is performed, wherein the second type of foreign object detection is an alternative type of foreign object detection performed after receiving the request and before the recalibration of the first type of foreign object detection is performed; when the foreign object detection result of the second type of foreign object detection indicates that a foreign object is present or likely to be present, not performing the recalibration of the first type of foreign object detection and stopping or limiting wireless power transmission, and / or communicating the foreign object detection result of the second type of foreign object detection to the wireless power receiver; and when the foreign object detection result of the second type of foreign object detection indicates that a foreign object is not present or likely to be not present, performing the recalibration of the first type of foreign object detection and continuing the wireless power transmission; wherein the wireless power receiver sends the request to attempt to change from a low power mode of the wireless power transmission to a high power mode of the wireless power transmission, or from a high power mode of the wireless power transmission to a low power mode of the wireless power transmission; wherein the first type of foreign object detection and the second type of foreign object detection measure different parameters.

2. The method of claim 1, wherein, The first type of foreign object detection measures power loss.

3. The method of claim 2, wherein, The second type of foreign object detection measures Q-factor and / or system self-resonant frequency.

4. The method of claim 1, wherein, The request is sent in response to the wireless power receiver attempting to change the electromagnetic parameter by an amount greater than or equal to a threshold amount.

5. The method of claim 4, wherein, The electromagnetic parameter comprises a voltage, a current, or a power level provided to the wireless power receiver by an electromagnetic field emitted by the wireless power transmitter.

6. The method of claim 4, wherein, The threshold amount is dynamically changeable according to a magnitude of the voltage, the current, or the power level provided to the wireless power receiver by the electromagnetic field emitted by the wireless power transmitter.

7. The method of claim 4, wherein, The threshold amount is at least 10%.

8. The method of claim 4, wherein, The threshold amount is at least 50%.

9. The method of claim 1, wherein, When the foreign object detection result of the second type of foreign object detection indicates that a foreign object is not present or likely to be not present, the method further comprises communicating the foreign object detection result of the second type of foreign object detection to the wireless power receiver.

10. A wireless power transmitter, comprising: comprising: circuitry configured to: receive, from a wireless power receiver, a request for a first type of foreign object detection to perform a recalibration in response to the wireless power receiver attempting to change an electromagnetic parameter provided by a wireless power transmitter; in response to receiving the request, perform a second type of foreign object detection to produce a foreign object detection result before the recalibration of the first type of foreign object detection is performed, wherein the second type of foreign object detection is an alternative type of foreign object detection performed after receiving the request and before the recalibration of the first type of foreign object detection is performed; when the foreign object detection result of the second type of foreign object detection indicates presence or possible presence of a foreign object, not performing the recalibration of the first type of foreign object detection, and stopping or limiting wireless power transmission, and / or communicating the foreign object detection result of the second type of foreign object detection to the wireless power receiver; and when the foreign object detection result of the second type of foreign object detection indicates absence or possible absence of a foreign object, performing the recalibration of the first type of foreign object detection and continuing the wireless power transmission; wherein the wireless power receiver sends the request to attempt to change from a low power mode of the wireless power transmission to a high power mode of the wireless power transmission, or from a high power mode of the wireless power transmission to a low power mode of the wireless power transmission; wherein the first type of foreign object detection and the second type of foreign object detection measure different parameters.

11. The wireless power transmitter of claim 10, wherein, The first type of foreign object detection measures power loss.

12. The wireless power transmitter of claim 11, wherein, The second type of foreign object detection measures Q-factor and / or system self-resonant frequency.

13. The wireless power transmitter of claim 10, wherein, The request is sent in response to the wireless power receiver attempting to change the electromagnetic parameter by an amount greater than or equal to a threshold amount.

14. The wireless power transmitter of claim 13, wherein, wherein the electromagnetic parameter comprises a voltage, current, or power level provided to the wireless power receiver by an electromagnetic field transmitted by the wireless power transmitter.

15. The wireless power transmitter of claim 13, wherein, The threshold amount is at least 10%.

16. The wireless power transmitter of claim 13, wherein, The threshold amount is at least 50%.

17. A method of operating a wireless power receiver, the method comprising: comprising: sending, to a wireless power transmitter, a request to perform a recalibration of a first type of foreign object detection when attempting to change an electromagnetic parameter provided by the wireless power transmitter; receiving a second type of foreign object detection result from the wireless power transmitter, wherein the second type of foreign object detection is an alternative type of foreign object detection performed after sending the request and before performing the recalibration of the first type of foreign object detection; when the second type of the foreign object detection result indicates presence or possible presence of a foreign object, not performing the recalibration of the first type of foreign object detection, and changing one or more wireless power transmission parameters to limit wireless power transmission or to stop the wireless power transmission; and when the second type of the foreign object detection result indicates absence of a foreign object or possible absence of a foreign object, continuing the wireless power transmission and performing the recalibration of the first type of foreign object detection; wherein the wireless power receiver sends the request to attempt to change from a low power mode of the wireless power transmission to a high power mode of the wireless power transmission, or from a high power mode of the wireless power transmission to a low power mode of the wireless power transmission; wherein the first type of foreign object detection and the second type of foreign object detection measure different parameters.

18. The method of claim 17, wherein, The first type of foreign object detection measures power loss, and the second type of foreign object detection measures Q-factor and / or system self-resonant frequency.

19. The method of claim 17, wherein, The request includes an indication of a likelihood of presence of a foreign object.

20. The method of claim 19, wherein, The wireless power receiver is configured to determine the likelihood of presence of a foreign object by measuring a temperature change.

21. A wireless power receiver, comprising: comprising: circuitry configured to: send, to a wireless power transmitter, a request to perform a recalibration of a first type of foreign object detection when attempting to change an electromagnetic parameter provided by the wireless power transmitter; receive a second type of foreign object detection result from the wireless power transmitter, wherein the second type of foreign object detection is an alternative type of foreign object detection performed after sending the request and before performing the recalibration of the first type of foreign object detection; when the second type of foreign object detection result indicates that a foreign object is present or likely to be present, not performing the recalibration of the first type of foreign object detection and changing one or more wireless power transmission parameters, limiting wireless power transmission, or stopping the wireless power transmission; and when the second type of foreign object detection result indicates that a foreign object is not present or is not likely to be present, continuing the wireless power transmission and performing the recalibration of the first type of foreign object detection; wherein the wireless power receiver sends the request to attempt to change from a low power mode of the wireless power transmission to a high power mode of the wireless power transmission or from a high power mode of the wireless power transmission to a low power mode of the wireless power transmission; wherein the first type of foreign object detection and the second type of foreign object detection measure different parameters.

22. The wireless power receiver of claim 21, wherein, the first type of foreign object detection measures power loss and the second type of foreign object detection measures Q-factor and / or system self-resonant frequency.

23. The wireless power receiver of claim 21, wherein, the request includes an indication of a likelihood of a foreign object being present.

24. The wireless power receiver of claim 21, wherein, the wireless power receiver is configured to determine the likelihood of the foreign object being present by measuring a temperature change. the wireless power receiver is configured to determine the likelihood of the foreign object being present by measuring a temperature change.

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