Calibration for delta power loss foreign object detection

Abstract

This disclosure provides systems, methods and apparatuses for calibration of a delta power loss (Ploss) foreign object detection (FOD) technique. The disclosed techniques include a calibration protocol that enables a power transmitter and a power receiver to coordinate the measurement and reporting of calibration values for the delta (Ploss) FOD technique.

Description

CALIBRATION FOR DELTA POWER LOSS FOREIGN OBJECT DETECTIONCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This Patent Application claims benefit of priority to India Provisional Patent Application No. 202411061354, filed August 13, 2024, and India Provisional Patent Application No. 202411046847, filed lune 18, 2024, the contents of which are incorporated by reference herein.TECHNICAL FIELD

[0002] This disclosure relates generally to wireless power and some aspects relate to a procedure and protocol messages for foreign object detection based on delta power loss (Pioss).DESCRIPTION OF RELATED TECHNOLOGY

[0003] A wireless power system includes a power transmitter (PTx) and a power receiver (PRx). The power transmitter can transfer energy to the power receiver using a magnetic resonance technique or a magnetic induction technique. In the magnetic resonance technique, a first power transfer coil (sometimes referred to as a primary coil) of the power transmitter generates a magnetic field that vibrates in a resonant frequency to transfer energy to a second power transfer coil (sometimes referred to as a secondary coil) of a power receiver designed to have the same resonant frequency. In the magnetic induction technique, the power transmitter transfers electrical energy using a phenomenon in which power is transferred from a first power transfer coil (sometimes referred to as a primary coil) of the power transmitter and a second power transfer coil (sometimes referred to as a secondary coil) of the power receiver using electromagnetic induction. The primary coil produces an electromagnetic field for power transfer (such as during a power transfer phase). The electromagnetic field induces a voltage in the secondary coil of the power receiver when the secondary coil is present in the electromagnetic field. The power receiver can provide the received power to a load or an energy storage unit (such as a battery). Example loads might include a motor, processor(s), a heating element, kitchen appliances, or electronics, among other examples.

[0004] Wireless power technologies continue to evolve as manufacturers and consumers develop new capabilities. Consumers continue to adopt wireless power technology for new applications and deployment scenarios. For example, newer wireless power transfer techniques are being developed to support improved magnetic coupling. Some advances in wireless power technology enable a wireless power system to increase the amount of power that can be transferred from a power transmitter to a power receiver.BRIEF SUMMARY

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

[0006] One aspect of this disclosure can be implemented as a method of a power transmitter (PTx) for wireless power transfer. The method includes the power transmitter receiving, from a power receiver, a request for a wireless power transfer mode above a power threshold (e.g., high power mode above 15 watts (W)). The method includes the power transmitter implementing a calibration protocol to obtain calibration values for a delta power loss (Pioss) foreign object detection (FOD) technique. The method includes the power transmitter using the calibration values with the delta PiossFOD technique during a power transfer phase of the wireless power transfer mode.

[0007] Another aspect of this disclosure can be implemented as a method of a power receiver (PRx) for wireless power transfer. The method includes the power receiver transmitting, to a power transmitter, a request for a wireless power transfer mode above a power threshold (e.g., high power mode above 15 watts (W)). The method includes the power receiver implementing a calibration protocol to provide, to the power transmitter, calibration values for a delta power loss (Pioss) foreign object detection (FOD) technique.

[0008] Another aspect of this disclosure can be implemented as an apparatus that includes a power transfer coil, a communication unit, and a controller. The apparatus is configured to implement any one of the above-mentioned methods.

[0009] Details of one or more implementations 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, the drawings, and the claims.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] Like reference numbers and designations in the various drawings indicate like elements. Note that the relative dimensions of the figures may not be drawn to scale.

[0011] FIG. 1 is a block diagram illustrating an example wireless power system.

[0012] FIG. 2 is a block diagram illustrating further details of the example wireless power system shown in FIG. 1.

[0013] FIG. 3 shows an example state diagram of a wireless power system.

[0014] FIG. 4 shows an example message flow diagram between a power transmitter and a power receiver.

[0015] FIG. 5 shows another example message flow diagram between a power transmitter and a power receiver.

[0016] FIG. 6 shows another example message flow diagram between a power transmitter and a power receiver.

[0017] FIG. 7 A shows another example message flow diagram between a power transmitter and a power receiver.

[0018] FIG. 7B shows another example message flow diagram between a power transmitter and a power receiver.

[0019] FIG. 8A shows another example message flow diagram between a power transmitter and a power receiver.

[0020] FIG. 8B shows another example message flow diagram between a power transmitter and a power receiver.

[0021] FIG. 9 shows an example flow diagram demonstrating the communication protocol of the delta PLOSS foreign object detection (FOD).

[0022] FIG. 10 shows an example flow diagram of the delta PLOSScalibration process between a power transmitter and a power receiver.

[0023] FIG. 11 shows an example magnetic power profile (MPP) calibration packet (MPPCLB).

[0024] FIG. 12 illustrates an example calibration mode (CLBMODE) data packet.

[0025] FIG. 13 illustrates an example calibration report (CLBPloss) data packet .

[0026] FIG. 14 illustrates a block diagram of an example apparatus for use in a wireless power system.DETAILED DESCRIPTION

[0027] The following description is directed to certain implementations for the purpose of describing innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in any means, apparatus, system, or method for transmitting or receiving wireless power. Although the concepts and examples described in this document are based on wireless power transfer using example power profiles for magnetic induction, the concepts can apply to other types of deploymentsincluding other power profiles, communication protocols, or even other wireless power techniques.

[0028] As described previously, a wireless power system includes a power transmitter (PTx) and a power receiver (PRx). A power transmitter also may be referred to as a wireless power transmission apparatus. A power receiver also may be referred to as a wireless power reception apparatus. A power receiver includes a secondary coil configured to wirelessly receive power via inductive coupling with a primary coil of the power transmitter. A wireless power standard can support different power levels (such as 5 Watts (5W), 15W, 25W, etc.) using different power profiles. A power profile refers generally to a protocol and standard operation for a power transfer mode. As such, a power profile is based on the level of compatibility between a power transmitter and a power receiver. A first power profile (referred to as a baseline power profile (BPP)) can support up to 5W of wireless power transfer using an operating frequency in the range of 102 kilohertz (kHz) to 205 kHz (typically a power transmitter using BPP operates at 128 kHz). A second power profile (referred to as an extended power profile (EPP)) introduces additional capabilities, such as extended protocol messages for improved coordination between the power transmitter and the power receiver, as well as higher power levels (such as up to 15W). A third power profile (referred to as a magnetic power profile (MPP) mode) can operate at higher frequencies (such as 360 kHz) and can support higher power levels (such as 15W, 25W, etc.). For MPP, the power receiver and the power transmitter both typically have magnetic rings to improve the stable alignment of the two devices. MPP mode currently supports up to 15W and may continue to increase as the MPP mode is further developed.

[0029] One of the challenges in high power transfer (e.g., 25W) is foreign object detection (FOD). Legacy techniques, such as MPP power loss accounting (MPLA), may be inaccurate for high power modes (beyond 15W). For FOD in power transfer modes beyond 15W, a Mated Q technique can be used to verify the absence of foreign objects (FO) as a power receiver approaches the interface surface. For example, the Mated Q technique may be performed during a pre-power transfer phase of operation of the wireless power transmission system. Typically, following the Mated Q technique (e.g., during power transfer), a power transmitter employs a calibration on an FOD-free surface and the delta power loss (PLOSS) method to detect the introduction of FOs during power transfer. Delta power loss (PLOSS) (sometimes denoted as APLOSS) is an FOD technique that utilizes a calibration value and periodic measurements to track variations in power loss estimates throughout power transfer. This FOD technique can identify unauthorized foreign object (FO) insertion while transferring power.

[0030] Delta PLOSS (APLOSS) POD operates similarly to MPLA by quantifying the power loss from the transmitting unit (PTx) to the receiving unit (PRx). However, unlike MPLA, which estimates and calculates loss at the coil level, APLOSS performs calculations at both the inverter and rectifier ends. In a perfectly functioning system, MPLA would result in a APLOSS value of zero in the absence of any FO. Because some amount of power loss is inevitable, such as due to measurement inaccuracies, manufacturing discrepancies, environmental temperature changes, system reliability, and modeling errors at varying power levels, etc., APLOSS is expected to be close to zero rather than exactly zero. The presence of an FO notably exacerbates APLOSS, such that when an FO is present, the APLOSS is above a threshold value. By ensuring that the transmitting (TX) and receiving (RX) units are calibrated to an FO-free state, the system can negate baseline errors and focus on detecting variations in power loss.

[0031] This disclosure provides systems, methods, and apparatuses for calibrating a delta PLOSS FOD technique. The disclosed techniques include a calibration protocol that enables a power transmitter and a power receiver to coordinate the measurement and reporting of calibration values and multiple data points (also referred to as test modes, or modes). In some aspects, the calibration protocol enables measurement of calibration protocols during a low power state to establish baseline values that can improve delta Ploss FOD during a power transfer phase. For example, the calibration values can be measured during a low power state and before transitioning to a higher power state (e.g., > 15 watts). In some implementations, when the calibration values are greater than a threshold, the wireless power system (e.g., the power transmitter or the power receiver) can revert to legacy FOD techniques.

[0032] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. A power transmitter and a power receiver can implement a defined calibration protocol (e.g., messages, timing, and procedure) to efficiently calibrate a delta PLOSS FOD technique. By obtaining calibration values before transitioning to a high power transfer state, the wireless power system can perform the delta Ploss FOD technique with greater accuracy after transitioning to the high power state. The techniques of this disclosure enable the power transmitter and the power receiver to coordinate timing and process for obtaining the calibration values, thereby avoiding ambiguity as to when calibration values are measured.

[0033] Some examples of this disclosure refer to a power transmitter and a power receiver. Typically, a power transmitter operates in a power transmission mode to provide power to a power receiver. Similarly, a power receiver typically operates in a power reception mode to receive power from a power transmitter. However, in some implementations, a device can alternatively receive (in the power reception mode) or transmit (in the power transmissionmode). For example, the device can be referred to as a “power transceiver,” a “wireless transmitter / receiver device,” a “power transmitter / receiver,” or other terms to refer to the fact that the device is capable of operating in the power reception mode or the power transmission mode at various times. The device can operate as a power receiver when in vicinity of the power transmitter, and can operate as a power transmitter when in vicinity of a different power receiver. Thus, a same device (such as a smart phone or accessory) can be a power receiver to receive power from an external charger and can also be a power transmitter to provide power to another phone or accessory. Any of the features attributed to a “power transmitter” or a “power receiver” in this disclosure can be implemented by device (e.g., power transceiver) that operates in power transmission / reception modes.

[0034] FIG. 1 is a block diagram illustrating an example wireless power system 100 that includes a power transmitter and a power receiver 104. The power transmitter 102 includes a power transfer coil 110. The power transfer coil 110 is capable of transmitting wireless power 114 by generating a magnetic field that induces a voltage in a power transfer coil 120 of the power receiver 104. The power receiver 104 includes a power transfer coil 120 designed to receive the wireless power 114. The components of the power transmitter 102 and the power receiver 104 are described in further detail below with reference to FIG. 2.

[0035] The techniques of this disclosure provide a calibration protocol for a delta power loss (PLOSS) foreign object detection (FOD) technique. In some aspects, the calibration protocol may be performed during startup or initialization of the system, for example, during a power ramp period or when power is below a threshold amount (e.g., less than 15 W). In some other aspects, the calibration protocol may be performed during power transfer. A linear formula may be used (e.g., derived) to compare power loss from packet to packet to see if the power loss has changed from a reference power loss determined during the initial calibration. PLOSS is calculated as the difference between power transmitted (e.g., at the inverter of the power transmitter) and power received (e.g., at the rectifier of the power receiver). In some aspects, this difference may be defined by the formula:PLOSS=PINV ~ PRECTEquation 1

[0036] PLOSS may be adjusted to PLOSS_COMPENSATED by removing the power loss at attributable to the PTx coil (e.g., power transfer coil 110). The adjustment removes changes in the contributions of loss on the PTx side, for example, power loss due to use of CTX tuningcapacitors. In the formula below, Rcircuit.tx includes the equivalent series resistance (ESR) of the selected CTX capacitors, and may also include ESR due to any switches.Equation 2

[0037] During calibration of PLOSS, the system can determine and store a loss profile of the PTx / PRx versus V2RECT and I2RECT. The loss profile can represent a relationship between PTx / PRx, V2RECT. and I2RECT. In some aspects, this relationship may be modeled as a three- dimensional linear plane. Calibration may be performed by collecting data points with various VRECT and IRECT during the initial power transfer phase. In some aspects, the initial power transfer phase may include power transfer at or below 15W. In some aspects, a delay is introduced when sampling a location in order to ensure that the data is stable. This delay may slow down ramp up which can in turn may increase charge time. It is therefore desirable to collect fewer data points. In some implementations, three data points may be used and can provide enough margin to predict the rest of the plane.

[0038] In some aspects, the three data points may be selected as follows: Three equally spaced points across the VRECT target range are selected: one point at VRECT-MIN, PRECT-MAX; one point at VRECT-NOM, PRECT-NOM; and one point at VRECT-MAX, P ECT-MIN- In some aspects, the selected three points of PRECT and VRECT are used to calculate a and / ? coefficients used in the equations below. The system may take multiple samples at each location. The multiple samples may be used to filter out system noise. In some implementations, twenty- five samples at each location may be taken. Once a point is taken, the validity may be verified by confirming that the MPP power loss accounting (MPLA) power fail output (PFO) threshold is within a predetermined or configurable upper and lower boundary. In some aspects, a calibrated PLOSS_COMPENSATED, referred to as PLOSS_COMPENSATED_CAL, may be determined according to the equation:Equation 3

[0039] PLOSS may be evaluated on receipt of a report packet, and if the threshold is exceeded, the system can revert to 15W operation mode. In some aspects, PLOSS may be determined according to Equation 4:Equation 4

[0040] In some implementations, the values of a and P of Equations 3 and 4 may be derived based on a series of summations as follows.Equation 6

[0041] The unknowns a and P in equations 5 and 6 can be determined as follows:Equation 8

[0042] In some aspects, the system may check to determine that the values for of a and determined in accordance with Equations 7 and 8 are valid before using them for calculating PLOSS-

[0043] In accordance with aspects of this disclosure, the power transmitter (or the power receiver) can initiate the calibration protocol based on entering a high power mode (such as >15W). For example, the calibration protocol can be performed before confirming the high power mode. The calibration protocol can include a sequence of messages, as shown in Figs. 4-13.

[0044] In some implementations, calibration may be initiated by the PTx or PRx via a command transmitted to the PRx or PTx, respectively. In some implementations, the command is an MPP calibration start command (e.g., “MPPCLB_START”). In some implementations, the PRx or the PTx can use the same command with a different field loadedto stop (e.g., exit) the calibration. For example, a first value (e.g., “OxFF”) can indicate a request / command to enter the calibration and a second value (e.g., “0x00”) can indicate a request / command to exit the calibration. Alternatively, a separate message (e.g., “MPPCLB_STOP”) can indicate a request or command to exit the calibration.

[0045] Another type of message (e.g., a calibration mode (“CLBMODE”) message) may be used to initialize the calibration mode before the calibration measurements. A PTx or a PRx (e.g., power transmitter 102 or power receiver 104, respectively) can transmit the CLBMODE message. In some implementations, the CLBMODE indicates parameters for various measurement points, such as a measurement point at VRECT-MIN, PRECT-MAX; a point at VRECT- NOM, PRECT-NOM; and a measurement point at VRECT-MAX, PRECT-MIN- When the CLBMODE indicates parameters for measurement points, other test points can be used. In some implementations, the quantity of test points is greater than three. In some implementations, the power transmitter 102 can dynamically select the quantity of test points based on a variety of factors, such as a Q factor, results of a Mated Q test or MPLA procedure, or the like. Alternatively, the power receiver 104 can indicate the test points to be used for calibration measurements.

[0046] In some implementations, the PRx or PTx can check the calibration capabilities of the other before calibration initialization. For example, the PTx and / or the PRx can communicate capability information and / or version number indicative of whether the PTX or PRX supports the calibration protocol described in this disclosure.

[0047] In some implementations, a measurement report packet can also include the estimated received power along with PRECT, IRECT and VRECT values. The measurement report packet may be referred to as a calibration PLOSS ("CLBPloss") packet or may be referred to by any other name to refer to a packet that includes calibration measurement results.

[0048] FIG. 2 is a block diagram illustrating further details of the example wireless power system 100 shown in FIG. 1. The example wireless power system 100 includes the power transmitter 102 and an apparatus 240. Apparatus 240 can include the power receiver 104. The power transmitter 102 includes a power transfer coil 110 and a PTx controller 208. In some implementations, the power transfer coil 110 can also be referred to as a primary coil. The power transfer coil 110 is coupled to a power transmitter circuit 204 (sometimes also referred to as a power signal generator, a driver circuit, a driver, or a PTx tank circuit). The power transfer coil 110 may be a wire coil which transmits wireless power (which also may be referred to as wireless energy). The power transfer coil 110 may transmit wireless energy using an inductive or a resonant magnetic field. The power transmitter circuit 204 mayinclude components (not shown) to prepare the wireless power. For example, the power transmitter circuit 204 may include one or more switches, drivers, series capacitors, rectifiers, inverters, or other components. In some implementations, the power transmitter circuit 204 includes an inverter and a PTx resonant tank circuit (which can be referred to as a “tank circuit” for brevity). The PTx controller 208 may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC) or any other suitable electronic device.

[0049] A power supply 202 provides power to the power transmitter unit 206. In some implementations, the power supply 202 may convert alternating current (AC) power to direct current (DC) power. For example, the power supply 202 may include a converter that receives AC power from an external power supply and converts the AC power to DC power used by the power transmitter circuit 204. Alternatively, or additionally, a component (such as an inverter) of the power transmitter circuit 204 may convert the DC power to the AC power. The power supply 202 may be integrated as part of the power transmitter 102 or may be external to the power transmitter 102. In some implementations, the power transmitter 102 causes the power supply 202 to regulate the DC output voltage of the power supply 202. For example, the PTx controller 208 can set the DC voltage of the power supply 202 based on information (such as a value indicating a requested power) received from the power receiver 104. The power transmitter 102 can receive power configuration information from the power receiver 104 and use the information to set one or more parameters (such as the DC voltage, current, or power output of the power supply 202). In some implementations, the power transmitter 102 includes a DC-DC converter (not shown) between the power supply 202 and the power transmitter circuit 204 to control the variable DC output voltage.

[0050] The PTx controller 208 may be connected to a PTx communication interface 210. The PTx communication interface 210 can be coupled to the power transmitter circuit 204 or the power transmitter circuit 204. In some implementations, the PTx communication unit 210 may support short-range radio frequency communication, such as Near-Field Communication (NFC) or Bluetooth (BT). NFC is a technology by which data transfer occurs on a carrier frequency of 13.56 Megahertz (MHz). The PTx communication unit 210 also may support any suitable communication protocol. The PTx communication unit 210 may contain modulation and demodulation circuits to wirelessly communicate via frequency, amplitude, current, or voltage modulation of a wireless power signal. For example, the PTx communication unit 210 can communicate using frequency shift keying (FSK) modulation applied to a signal sent to the power receiver 104. Additionally, the communication interface210 can have an ASK demodulator for communications received from the power receiver 104 via load modulation of the wireless power signal 114.

[0051] In the example of FIG. 2, the example apparatus 240 includes the power receiver 104 and other components (such as a converter 222, an energy storage unit 224, a load 242, a load controller 244, and / or a user interface 246). The power receiver 104 includes a power transfer coil 120 (referred to as a “secondary coil” to distinguish from the primary coil of a power transmitter), a PRx tank circuit 216 (or “tank circuit”), a bridge circuit 220, a PRx controller 226, and a PRx communication interface 228. The converter 222 can operate as a buck or boost converter to alter the voltage of electricity being supplied to the energy storage unit 224 (when the power receiver 104 is being operated in a power reception mode) or being drawn from the energy storage unit 224 (when the power receiver 104 is being operated in a power transmission mode).

[0052] In some implementations, the apparatus 240 also includes a load controller 244 and a user interface 246 (such as a button, switch, touchpad, indicator, touch screen, or wireless local area network interface). The bridge circuit 220 can be a rectifier. In some implementations, the bridge circuit 220 is capable of operating as a rectifier or an inverter, and may be implemented as an active bridge. The PRx tank circuit 216 can include a capacitor or other components to enable the power transfer coil 120 to receive the wireless power 114 during the power state. Although not shown, a capacitor can be used before the bridge circuit 220 and a load capacitance can be used after the bridge circuit 220 to match impedance and to filter a high frequency component of the rectifier voltage. In accordance with aspects of this disclosure, the PRx tank circuit 216 includes a capacitance component that can alter the capacitance of the PRx tank circuit 216 depending on different power levels, power transmission or reception modes, or power profile, among other examples.

[0053] Although shown as different components, some components may be packaged or implemented in the same hardware. For example, in some implementations, the PRx controller 226 and the load controller 244 may be implemented as a single controller. The PRx controller 226, the load controller 244, the PRx communication interface 228, or any combination thereof, may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC) or any other suitable electronic device. The communication interface 228 may also be referred to as a second communication unit. The PRx communication unit 228 might also include a power harvester (not shown) that can harvest energy from the communication signals and provide harvested bias power to the PRx controller 226 or the load controller 244.

[0054] The PTx controller 208 may detect the presence or proximity of a power receiver 104. This detection may happen during a periodic pinging process of the communication interface 210. The PRx communication interface 228 can send a reply signal back to the PTx communication interface 210 to confirm that it is a power receiver. Prior to power transfer, a handshaking process may take place during which the PTx controller 208 may receive identification and configuration data, among other information, from the power receiver 104. The PTx controller 208 may control characteristics of wireless power it provides to the power receiver 104 based on the configuration data.

[0055] A PRx controller 226 may be operationally coupled to the bridge circuit 220 and the PRx communication interface 228. The PRx communication interface 228 may contain modulation and demodulation circuits to communicate via the power transfer coil 120 (such as before, after, or part of the PRx tank circuit 216). The PRx communication interface 228 may use load modulation to communicate via an in-band communication link (not shown) that includes the power transfer coil 120. For example, the PRx communication unit can communicate using amplitude shift keying (ASK) modulation applied to a load modulation circuit of the PRx tank circuit 216.

[0056] A load controller 244 may be operationally coupled to the load 242 and the PRx controller 226 (or to the PRx communication interface 228, coupling not shown in Fig. 2). The load controller 244 may detect changes to load states. The load controller 244 also may determine a load voltage reference and / or a power requirement of the load. The load controller 244 also may send load voltage references, load current, load power requirement and any other suitable information to the PRx controller 226 or the communication interface 228 for communication to the power transmitter 102. During a power state, the PRx controller 226 may additionally determine and provide feedback information via one or more feedback messages indicating one or more of a measured load voltage, load current, load power requirement, and power available to the load 242. In some feedback messages, the feedback information may include a reference voltage indicating a required voltage for the load 242. In some feedback messages, the feedback information may indicate an error in the output voltage of the load 242. In some feedback messages, the feedback information may include the required power for the load. Although the PRx controller 226 and load controller 244 are shown separately, they may be included in the same component of the power receiver 104.

[0057] In some implementations, the power receiver 104 may be an appliance and may be equipped with safety features, such as a disconnect switch 214, that may be operated in conjunction with the operating states of the power receiver 104 or apparatus 240. For example, the disconnect switch 214 might be maintained in an open position to prevent theflow of current to the load 242 when the power receiver 104 is in a pre-power state (such as a ping phase, a configuration phase, and / or a negotiation phase). Before transitioning to the power state (also referred to as a power transfer phase), the PRx controller 226 might cause the disconnect switch 214 to move to a closed position to enable the flow of current to the load 242. In an emergency condition (such as excessive voltage or current), the PRx controller 226 might open the disconnect switch 214 to prevent damage to the load 242 or other components of the power receiver 104 or the apparatus 240. After the disconnect switch 214 is closed, the PRx controller 226 can communicate a message to the PTx controller 208 to cause the wireless power system to transition to the power state. Alternatively, or additionally, the PRx controller 226 can communicate a power request to begin the transmission of the wireless power 114. Although the disconnect switch 214 is illustrated near the power transfer coil 120, in some implementations, the disconnect switch 214 is located closer to the load 242 and can be referred to as a load disconnect switch.

[0058] FIG. 3 shows an example state diagram 300 of a wireless power system. The state diagram 300 illustrates operating states in which the wireless power system 100 of FIGs. 1 and 2 may operate. When a power receiver (e.g., power receiver 104) is placed within an operating volume on the interface surface of a power transmitter (e.g., power transmitter 102), the two start to communicate to configure settings for the wireless power transfer. In the example state diagram 300 shown in FIG. 3, there are four operating states: a ping phase 302 (sometimes referred to as a ping state), a configuration phase 304 (sometimes referred to as an identification phase), a negotiation phase 306, and a power transfer phase 308 (sometimes referred to as a power transfer state). The ping phase 302, the configuration phase 304, and the negotiation phase 306 can collectively be referred to as pre-power states. A technical specification may define how the power transmitter and power receiver can transition between the operating states. For example, the wireless power system typically begins in the ping phase 302 until the power transmitter detects a power receiver, moving it to the configuration phase 304. In the configuration phase 304, the power transmitter establishes communication and receives the identification information of the power receiver and its static configuration data. In the negotiation phase 306, the power transmitter and power receiver exchange information to agree and adjust parameters related to wireless power transfer. In the power transfer phase 308, the power transmitter transmits wireless power to the power receiver. The power receiver may occasionally or periodically communicate status or feedback control messages to the power transmitter during the power transfer phase 308. The system can move to a reinitialization state (not shown) as needed to reinitialize or return to the ping phase 302when communication, powering, or other activities are no longer taking place. Each of the operating states are briefly described herein for reference.

[0059] In the ping phase 302, the power transmitter attempts to establish communications with a power receiver. The power receiver may be placed on the interface surface or may not be present during this operating state. The power transmitter may attempt to communicate or detect the presence of the power receiver. For example, the power transmitter may use an analog ping, out-of-band communication (such as NFC), a digital ping, impedance change detection, or any combination thereof, to determine that a compatible power receiver is present. In some implementations, the power transmitter transmits different types of ping signals to detect different types of power receivers. For example, the power transmitter can transmit a first type of digital ping using 128 kHz for BPP or EPP and a second type of digital ping using 360 kHz for MPP. The power transmitter might alternate between the first type and second type of digital ping. Alternatively, the power transmitter can initially transmit the first type of digital ping and then transmit the second type of digital ping after receiving a first ping response from the power receiver in response to the first type of digital ping. Once the wireless power system determines that a power receiver is present (such as by confirming NFC communication, receiving a ping response, or other communication from the power receiver in response to a digital ping), the wireless power system may transition to the configuration phase 304.

[0060] In the configuration phase 304, the power receiver may establish communication with the power transmitter and send identification information (e.g., an identification packet) to the power transmitter. In some implementations, the power transmitter may retrieve static configuration information from the power receiver via the NFC communication. In some implementations, the power transmitter can also transmit an identification packet to the power receiver. The power transmitter and the power receiver may use the identification information to verify that they both use compatible versions of a technical specification or protocol for wireless power transfer. The power transmitter and the power receiver may communicate basic settings or communicate regarding their respective capabilities. From the configuration phase 304, the wireless power system may transition to the negotiation phase 306.

[0061] In the negotiation phase 306, the power transmitter and the power receiver may exchange further communications (such as capabilities and / or configuration messages) to negotiate the parameters that govern the power transfer phase 308. For example, a power negotiation can occur during the negotiation phase 306. As one example, the wireless power receiver may have multiple operating modes with respect to power transfer. For instance, the power receiver may be capable of operating in a low power transfer mode, a normal powertransfer mode, and a high power transfer mode. The power transfer mode to be used may be determined as part of the negotiation phase. After negotiating the parameters, the power transmitter may be prepared to transfer wireless power and the power receiver may be prepared to receive the wireless power. The power transmitter may wait for a request or command from the power receiver before transitioning to the power transfer phase 308.

[0062] In the power transfer phase 308, the power transmitter generates a wireless power signal to transfer power to the power receiver via inductive or resonant coupling. The power transmitter generates the wireless power using a frequency, a voltage, and other operating points associated with the amount of power negotiated during the negotiation phase 306.

[0063] From the power transfer phase 308, the power transmitter and the power receiver may transition back to the negotiation phase 306 until a next power transfer operation is performed. Alternatively, the wireless power system might transition to the ping phase 302. In some implementations, if the power transmitter determines that the power receiver is moved, that the power receiver is no longer present in an operating environment of the power transmitter, or that a foreign object has been introduced to the operating environment, the power transmitter might transition to a reinitialization state (not shown) or any of the other prepower states.

[0064] Various FOD techniques can be implemented in the pre-power phases or power transfer phase 308. For example, a deltaFOD technique can be used during the power transfer phase 308 to detect the introduction of a foreign object. In accordance with aspects of this disclosure, a calibration protocol can be implemented during a low power mode of the power transfer phase 308 to improve the accuracy and functionality of the deltaFOD technique. For example, the calibration protocol can yield calibration values that are used with the deltaFOD technique in a high power mode of the power transfer phase 308.

[0065] FIG. 4 shows a message flow diagram 400 between a power transmitter 102 and a power receiver 104. The power transmitter 102 may perform an open air Q test for FOD 402 to verify the absence of foreign objects.

[0066] When operating at a power profile, such as a low or nominal power mode (e.g., less than 15W), the power transmitter 102 may detect the presence or proximity of a power receiver 104 during a first periodic pinging process 404. Prior to power transfer, a handshaking process may take place during which the power transmitter 102 may exchange identification and configuration information message(s) 406, among other information, with the power receiver 104. Additionally, the power transmitter may perform MPLA for FOD 408 to verify the absence of foreign objects during power transfer. MPLA FOD is typically usedfor power transmission lower than 15 watts (W). The power transmitter 102 may also receive, from the power receiver 104, a change power mode message 410, requesting a change to a wireless power transfer mode above a power threshold (e.g., high power mode above 15W).

[0067] In some implementations, before operating at a second power profile, such as high power mode (e.g., > 15W), the power transmitter 102 may perform a Mated Q test for FOD 412 to verify the absence of foreign objects. The mated Q test is typically performed prior to power transfer in high power mode. In this second power profile, the power transmitter 102 may also detect the presence or proximity of a power receiver 104 during a second periodic pinging process 414. The digital ping at the second power profile of a high power mode is typically at a greater frequency than at a first power profile. Typically, the first power profile exchanges a digital ping of 128 kHz while the second power profile exchanges a digital ping of 360 kHz as shown in FIG. 4. Also prior to power transfer, a handshaking process may take place during which the power transmitter 102 may exchange identification and configuration information 416, among other information, with the power receiver 104.

[0068] The system may implement a calibration delta PLOSS FOD 418 as described herein. The power transmitter 102 or the power receiver 104 may initiate the calibration delta PLOSSFOD 418. Details of the calibration process are further described with reference to FIG. 1 and FIG. 5 through FIG. 10.

[0069] The power transmitter 102 may then transfer power 422 to the power receiver 104 at a power profile selected based on the identification and configuration information 416 (or 406) exchanged during the handshaking process. The power transfer system may then implement delta PLOSS FOD 424. The flow proceeds to decision block 426 where the results of delta PLOSS FOD 424 indicate whether or not the power transmitter 102 detects a FO. In the case the power transmitter 102 does not detect a FO, the power transmitter 102 may continue to transfer power 422. If the power transmitter 102 does detect a FO, the flow proceeds to block 420, and the power transmitter 102 stops / reduces power transfer to the power receiver 104.

[0070] FIG. 5 shows a message flow diagram 500 between a power transmitter 102 and a power receiver 104. FIG. 5 is similar to FIG. 4 except that instead of implementing a calibration protocol for a delta PLOSS FOD values, the power receiver 104 sends stored PLOSS calibration values or PLOSS coefficients 517 to the power transmitter 102. The power transmitter 102 uses the stored PLOSS calibration values or PLOSS coefficients 517 to find the delta PLOSS FOD 424. Based on the delta PLOSS FOD 424, at decision block 426, the power transmitter 102 determines whether an FO is detected. As in FIG. 4, if a FO is not detected,the power transmitter 102 continues to transfer power 422. Otherwise, if a FO is detected, the power transmitter 102 stops or reduces power transfer 420 to the power receiver 104.

[0071] FIG. 6 shows a message flow diagram 600 between a power transmitter 102 and a power receiver 104. The flow begins at a first power profile, such as low / nominal power mode (e.g., <15W). FIG. 6 is similar to FIG. 4 except that there is no initial change of power mode before beginning power transfer 614 between the power transmitter 102 and power receiver 104. Sometime during or after this power transfer 614, the power receiver 104 sends a control error packet 616 to the power transmitter 102 requesting a power profile greater than 15W.

[0072] The power receiver 104 may then initiate calibration and delta Pioss FOD 618 based on the control error packet 616 requesting power greater than 15W. The flow proceeds to 418 where the system may implement a calibration protocol for a delta PLOSS FOD and continues the same FOD calibration technique method as described above in FIG. 4.

[0073] FIG. 7A shows a message flow diagram 700 between a power transmitter 102 and a power receiver 104. In some implementations, the power transmitter 102 sends a message 702 to begin the APLOSS calibration phase (e.g., via a MPPCLB_START packet), and the power receiver 104 may return an acknowledgement message 704 to the power transmitter 102. In other implementations, the power receiver 104 sends a message 706 to begin the calibration phase (e.g., via a MPPCLB_START packet), and the power transmitter 102 may return an acknowledgment message 708 to the power receiver 104.

[0074] After beginning the calibration phase via message 706, calibration may be performed for each of one or more modes, where a mode enables measurement of a data point. In some aspects, the modes may refer to different power levels such that each power level (i.e., mode) can be used to measure calibration values of a data point. In some aspects, three data points are used for calibration, corresponding to three power transmission modes: Mode 1, Mode 2, and Mode 3. In some aspects, Mode 1 represents VRECT-MIN, PRECT-MAX, Mode 2 represents VRECT-NOM, PRECT-NOM, and Mode 3 represents VRECT-MAX, PRECT-MIN. In some other aspects, more than three data points may be used for calibration and other modes may correspond to such additional data points.

[0075] The operations shown as part of block 710 (e.g., operations 712a, 714a, 718a, and 719a) may be repeated for each of the one or more test points for which APLOSS calibration measurement is to be performed. To initialize the calibration, the power transmitter 102 may send a message 712a (e.g., a CLBMODE packet). In some implementations, the message 712a indicates the mode / point to be measured (e.g., Mode 1, Mode 2, Mode 3) and / or other information that may be used for obtaining calibration data for the test point. For example,after sending message 706 (e.g., MPPCLB_START packet) to begin the calibration phase, the power transmitter 102 may send a first CLBMODE packet to instruct the power receiver 104 to initialize calibration in preparation for obtaining measurements and generating a calibration report for a mode / point.

[0076] At block 714a, the power receiver 104 may measure the corresponding Vrect, Irect, and Preet at the Vrect and Irect location determined based on the mode. The power receiver may perform multiple samples at the point specified by the mode to obtain calibration measurements. In some aspects, the power receiver 104 may perform twenty-five samples to reduce the impact of system noise on the measurements.

[0077] In some aspects, after obtaining measurements for a mode, the power receiver 104 may transmit to the power transmitter 102 a calibration report data packet 718a (e.g., via a CLBPloss packet) containing the calibration measurements for the mode. For example, the power receiver 104 may send the calibration data report packet 718a in response to receiving the set calibration mode packet 712a from the power transmitter 102 and after performing the measurements of block 714a. In some implementations, the power transmitter 102 may optionally send an acknowledgement 719a to the power receiver 104 acknowledging receipt of the calibration report data packet 718a.

[0078] As noted above, operations 712a, 714a, 718a, and 719a may be performed for each mode. For example, after sending an MPPCLB_START packet, the power transmitter 102 may send three CLBMODE packets to obtain calibration data for Mode 1, Mode 2, and Mode 3. In response, the power receiver 104 may send three CLBPloss packets, one in response to each of the three CLBMODE packets.

[0079] In some implementations, the power receiver 104 may send to the power transmitter 102 an end calibration message 720a to indicate completion of the calibration mode when there are no modes left to calibrate.

[0080] At block 722, the power transmitter 102 calculates PLOSS coefficients based on calibration data points. For example, the power transmitter 102 may fit the measurements to Equation 3 above to determine a and . In some implementations, if the error is greater than a threshold, the power transmitter 102 aborts calibration and falls back to traditional FOD techniques as seen at block 726.

[0081] FIG. 7B shows a message flow diagram 750 between a power transmitter 102 and a power receiver 104. The example shown in FIG. 7B is similar to that shown in FIG. 7A except that in FIG. 7A, the power receiver 104 sends the calibration report data packet 718a in response to receiving the set calibration mode packet 712a, while in FIG. 7B, the powerreceiver 104 sends the calibration report data packet 718a in response to receiving a get request packet 716a. The example shown in FIG. 7B starts with operations 702, 704, 706, and 708 which have been described above with respect to FIG. 7A.

[0082] The operations shown as part of block 710B (e.g., operations 712a, 714a, 716a, and 718a) may be repeated for each of the one or more modes / points for which APLOSS calibration is to be performed. Like the example shown in FIG. 7 A, to initialize the calibration for a mode, the power transmitter 102 may send a message 712a (e.g., a CLBMODE packet) to identify the mode to be calibrated and other information that may be used for obtaining calibration data for the mode.

[0083] At block 714a, the power receiver 104 may measure the corresponding Vrect, Irect, and Preet at the Vrect and Irect location determined based on the mode. The power receiver may perform multiple samples at the Mode to obtain calibration measurements. In some aspects, the power receiver may perform twenty-five samples to reduce the impact of system noise on the measurements.

[0084] The power transmitter may transmit a get request packet 716a to request a calibration report. In response to receiving the get request packet 716a, the power receiver 104 may transmit to the power transmitter 102 a calibration report data packet 718a (e.g., via a CLBPloss packet) containing the calibration measurements for the mode.

[0085] As noted above, operations 712a, 714a, 716a, and 718a may be performed for each mode. For example, after sending a MPPCLB_START packet, the power transmitter 102 may send three CLBMODE packets to obtain calibration data for Mode 1, Mode 2, and Mode 3.

[0086] In some implementations, the power receiver 104 may send the power transmitter 102 an end calibration message 720a to indicate completion of the calibration phase when there are no modes / points left to calibrate.

[0087] Blocks 722 and 726 of FIG. 7B are described above with respect to FIG. 7A.

[0088] FIG. 8A shows a message flow diagram 800 between a power transmitter 102 and a power receiver 104. FIG. 8A is similar to FIGs. 7A and 7B except that the calibration measurements / reports 810 are aggregated across multiple modes rather than a calibration report per mode. The example shown in FIG. 8A starts with operations 702, 704, 706, and 708 which have been described above with respect to FIG. 7A.

[0089] The example shown in FIG. 8A is different from that shown in FIGs. 7A and 7B in that the operations shown as part of block 810 (e.g., operations 712b and 714b) can be consolidated for efficient measurement of multiple modes. In this example, the power transmitter 102 may set the calibration mode via message 712b (e.g., via a CLBMODE packet)with an indicator indicating that multiple modes are to be calibrated. For example, the power transmitter 102 may transmit a single CLBMODE packet that indicates calibration data is to be obtained for multiple modes (e.g., Mode 1, Mode 2, and Mode 3). In response to the CLBMODE packet, the power receiver can initialize the PiOSs calibration for the indicated modes.

[0090] At block 714b, the power receiver 104 measures the Vrect, Irect, and Preet at the Vrect and Irect locations corresponding to the multiple modes. The power receiver may perform multiple samples at each of the points specified by the multiple modes to obtain calibration measurements. In some aspects, the power receiver may perform twenty-five samples to reduce the impact of system noise on the measurements. As an example, the power receiver may obtain samples at the Mode 1 location (Vrect min, Preet max), the Mode 2 location (Vrect nom, Preet nom), and the Mode 3 location (Vrect max, Preet min).

[0091] The power receiver 104 may then transmit to the power transmitter 102 a calibration report data packet 718b. In the example shown in FIG. 8 A, the calibration data report packet 718b may be sent in response to receiving the set calibration mode packet 712B. For example, the power receiver 104 may transmit a CLBPloss packet containing the calibration data obtained at operation 714b. In the example of FIG. 8A, this packet includes aggregated measurements for multiple modes / data points. For example, the data may include data related to PRECT, VRECT, IRECT, mode of capture, and other power receiver voltage and current parameters corresponding to the multiple modes. In some implementations, the power transmitter 102 may optionally send an acknowledgement 719b to the power receiver 104 acknowledging receipt of the calibration report data packet 718b.

[0092] The flow proceeds to block 722 to where the power transmitter 102 calculates PLOSS coefficients based on calibration data points. In some implementations, if the error is greater than a threshold, the power transmitter 102 aborts calibration and falls back to traditional FOD techniques as seen at block 726.

[0093] FIG. 8B shows a message flow diagram 850 between a power transmitter 102 and a power receiver 104. FIG. 8B shows a message flow diagram 850 between a power transmitter 102 and a power receiver 104. The example shown in FIG. 8B is similar to that shown in FIG. 8 A except that in FIG. 8 A, the power receiver 104 sends the calibration report data packet 718a in response to receiving the set calibration mode packet 712a, while in FIG. 8B, the power receiver 104 sends the calibration report data packet 718a in response to receiving a get request packet 716a. The example shown in FIG. 8B starts with operations 702, 704, 706, and 708 which have been described above with respect to FIG. 7A. The example continueswith the operations shown in block 810 which have been described above with respect to FIG. 8A.

[0094] In some aspects, power transmitter 102 may send a get request packet 716b to the power receiver 104 to request the calibration data for the multiple nodes. The power receiver 104 may then transmit to the power transmitter 102 a calibration report data packet 718b in response to receipt of the get request packet 716b. For example, the power receiver 104 may transmit a CLBPloss packet containing the calibration data obtained at operation 714b. Like the example of FIG. 8 A, in the example of FIG. 8B, the packet includes aggregated measurements for multiple modes / data points.

[0095] The flow proceeds to block 722 to where the power transmitter 102 calculates PLOSS coefficients based on calibration data points. In some implementations, if the error is greater than a threshold, the power transmitter 102 aborts calibration and falls back to traditional FOD techniques as seen at block 726.

[0096] FIG. 9 shows an example flow diagram 900 illustrating example operations of the communication protocol of the delta PLOSS FOD method. In this example, low and nominal power modes use an MPLA FOD method, and high power modes use the mated Q protocol. Each step of the communication protocol may have a time out limit that the power transmitter and power receiver adhere to. For example, the calibration of delta PLOSS at operation 920 may have a time limit within which the calibration is to be completed. For instance, there may be a time limit with respect to the entrance and exit of the calibration process.

[0097] The flow begins where the power transmitter (such as power transmitter 102) conducts a pre-power FOD 902 in order to verify the absence of foreign objects prior to any power transfer. When a power receiver (such as power receiver 104) is placed on the charging surface, the power transmitter begins PRx detection using the digital ping 904. The power transmitter and power receiver may exchange packets including signal strength (SIG), identification (ID), and extended identification (XID) packets at 128 kHz as well as system characterization such as gain measurement 906. The power receiver then sends a power mode select message requesting a power mode selection 908 to the power transmitter. In some implementations, the power receiver may request one of three different modes, including (1) a low power mode, (2) a nominal mode, or (3) a high power mode. In this example, the power receiver requests a high power mode. In other implementations, the power receiver may request a higher power mode, and the power transmitter may enter the low or nominal power mode and begin power transfer using MPLA based FOD techniques before entering the high- power mode.

[0098] At block 910, the power receiver receives mated Q coefficients and reports as well as optional mated Q results. The flow continues to block 912 where the power receiver prepares for the power mode, and the power transmitter moves up to 360 kHz. The flow then proceeds to confirm the high power mode 914. The power transmitter completes the mated Q FOD technique and reassesses the power mode selection at block 916. Flow proceeds to block 918, where if an FO is detected, the power transmitter moves to low / nominal power mode and performs MPLA during the power transfer.

[0099] If no FO is detected, the power transmitter confirms the high power mode 914 and proceeds to block 920 to begin calibration of delta PLOSS 920. The power transmitter may enter high power mode (such as communication protocol for the high power mode) in which the delta PLOSS calibration is being performed. Additionally, in some implementations, the power transmitter may request delta PLOSS calibration based on the control error request including a request for power greater than 15W. In other words, the power transmitter may request delta PLoss calibration while the power transmitter and power receiver are operating in a low power mode and before transitioning to a high power mode. Alternatively, or additionally, the power transmitter and the power receiver may enter the high power mode in preparation for increasing the power level and perform the delta PLoss calibration before modifying the power level to greater than 15W. The power transmitter may receive the delta PLoss calibration data from the receiver. In some implementations, the power transmitter may perform fitting using the calibration data to calculate a and P (referenced in Equations 3-8 discussed above) coefficients for determining delta PLoss during high power mode power transfer. In some implementations, a and are not calculated. In some implementations a and P are provided by the power receiver as part of calibration data. In some implementations, the power transmitter may skip the step at block 920. Further details on the delta PLOSS calibration performed by some implementations are discussed below with reference to FIG. 10.

[0100] The flow then proceeds to block 922 where the power transmitter transfers power to the power receiver (perhaps based on extended control error (XCE) packets). As noted above, power transfer may occur during and after the delta PLOSS calibration of block 920. After successful delta PLOSS calibration, XCE packets may continue to be received by the power transmitter and may be used to increase the power level of wireless power transfer during the power transfer phase in the higher power mode.

[0101] The flow proceeds to block 924 where the power receiver sends Vrect, Irect, and Preet data to the power transmitter using a DPloss packet. The power transmitter can use the Vrect, Irect, and Preet data to determine whether an FO is present or not. The power receivermay send the Vrect, Irect, and Preet data on a regular basis during the power transfer phase. In some aspects, the Vrect, Irect, and Preet data may be provided via CLBPloss or similar packets.

[0102] In this example, the flow proceeds to block 926 where the power transmitter confirms a FO because the delta PLOSS exceeds a threshold, and the power transmitter limits the power to nominal power. For example, the power transmitter may quantify the power loss from the power transmitter to the power receiver based on APLOSS calculations with respect to the inverter and rectifier ends of the power transfer. As noted above, the presence of an FO notably exacerbates APLOSS, such that when an FO is present, the APLOSS is above a threshold value.

[0103] At this new power mode, the flow proceeds to block 928 where the power transmitter transfers power (perhaps based on XCE packets) in nominal power with MPLA FOD techniques to the power receiver. The flow proceeds to block 930, where if an FO is confirmed in MPLA, the power transmitter stops / reduces the power and continues to do the power transfer at less than or equal to 15W otherwise.

[0104] FIG. 10 shows an example flow diagram 1000 of the delta PLOSS calibration process between a power transmitter and a power receiver. FIG. 10 provides further details of the delta PLOSS calibration performed at block 920 of FIG. 9. Each step of the calibration may have a time out limit that the power transmitter and power receiver adhere to. Additionally, or alternatively, the calibration process as a whole may have a time limit within which the power transmitter 102 and the power receiver 104 are to complete the PLOSS calibration. In some aspects, failure to complete the calibration within the specified time limit may result in the device failing a compliance test.

[0105] The flow begins at block 1004 where the power transmitter communicates to the power receiver using a calibration command (e.g., a MPPCLB_START command). The power receiver may provide an acknowledgement signal at this step. In some implementations, the power receiver communicates to the power transmitter using the calibration command (e.g., the MPPCLB_START command), and the power transmitter may provide an acknowledgement signal at this step. In some aspects, the load may be set to the Mode 1 condition, according to a first voltage condition prior to calibration.

[0106] The flow continues to block 1006, where, in this example, the power transmitter requests Mode 1 calibration (Vrect min, Preet max) and uses the system characterization parameter to decide the power transmitter operating condition via a CLBMODE command. In some implementations, the power receiver may request Mode 1 calibration and use the systemcharacterization parameter to decide the operating condition via CLBMODE command. The power transmitter 102 may set up the Vin (by controlling the duty, phase, or other control parameters) based on system gain characteristics to match the desired Vrect on the power receiver.

[0107] The flow proceeds to block 1008 where the power receiver sets Mode 1 and transfers the Preet, Vrect, and Irect to the power transmitter via a CLBPloss packet. In some examples, the power receiver can send this packet after a predefined or configurable time interval, and the power transmitter may acknowledge. For example, in Mode 1 the time interval may be based on a time measure or can be based on N measurements for better data accuracy. In some examples the power transmitter sends a get request command for the CLBPloss packet and provides an acknowledgment signal after receiving the packet. In some implementations, the power receiver sends the Preet, Irect, and Vrect to the power transmitter immediately. In some implementations, the power receiver may accumulate the results for the modes and send all multiple values (e.g., nine values) at once. At block 1010, the power transmitter calculates the Pinv for Mode 1.

[0108] Steps 1006 through 1010 may be repeated at block 1012 for Mode 2 (Vrect nom, Preet nom) and Mode 3 (Vrect max, Preet min). For example, as discussed above, the power transmitter may send a CLBMODE packet once for each mode. In some implementations, the power receiver may indicate after block 1012 that the calibration is over and communicate such to the power transmitter. In some examples, the power receiver may indicate the calibration is over by sending a MPPCLB_STOP packet with a value that indicates calibration is over (e.g., OxFF).

[0109] The flow proceeds to block 1014, where the power transmitter computes the a, p, PLOSS_COMPENSATED, and maximum error. The flow proceeds to block 1016 where if the maximum error is greater than a threshold, the power transmitter aborts calibration and moves to low or nominal power and uses MPLA. If the maximum error is less than a threshold, the power transmitter moves the power transfer to a higher power mode. In this case, the power transmitter may use high power FOD techniques (e.g., delta PLOSS) during the power transfer as described above with respect to blocks 924 and 926 of FIG. 9.

[0110] FIG. 11 illustrates an example of an MPP calibration packet (MPPCLB) 1100. As described above, an MPP power transmitter may send this packet to an MPP power receiver, or vice versa. A "MPPCLB_START" packet may refer to an MPPCLB packet that begins the calibration procedure, while an “MPPCLB_STOP” packet may refer to an MPPCLB packet that stops the calibration procedure. Although described as a common packet format (as“MPPCLB”), the MPPCLB_START and MPPCLB_STOP packets may be separate packet formats.

[0111] In some implementations, the recipient responds ACK if the recipient is ready to start calibration. In some implementations, the recipient responds NACK if the recipient is not ready to start calibration. In some implementations, the recipient responds with an attention (ATN) packet to indicate the pattern is not allowed, such as when the MPPCLB packet is not permitted based on the current operating state. As described above, the roles of power transmitter and power receiver may be reversed, and the power receiver may send the MPPCLB packet to the power transmitter, and the power transmitter may respond.

[0112] FIG. 12 illustrates an example of a calibration mode (CLBMODE) packet 1200. As described above, an MPP power transmitter may send the CLBMODE packet to an MPP power receiver. In some implementations, the power receiver responds ACK if the power receiver is ready to move to mode X (e.g., Mode 1, Mode 2, or Mode 3) measurement. In some implementations, the power receiver responds NAK to indicate either the power receiver is not allowed to move to mode X measurement or the power receiver is not ready to move to mode X measurement. In some implementations, the power receiver responds with an ATN packet to indicate the mode X measurement is not allowed. Within the CLBMODE packet, bits bO to b3 of byte BO are used to indicate the mode measurement.

[0113] As described above, the roles of the power transmitter and power receiver may be reversed with respect to initiating calibration mode. For example, the power receiver may send the CLBMODE packet to the power transmitter, and the power transmitter may respond. In some implementations, the power transmitter responds ACK if the power receiver is ready to perform delta PLOSS calibration for mode X (e.g., Mode 1, Mode 2, or Mode 3). In some implementations, the power transmitter responds NAK to indicate either the power transmitter is not allowed to move to mode X measurement or the power transmitter is not ready to receive mode X calibration data. In some implementations, the power transmitter responds with an ATN packet to indicate the mode X calibration is not supported. Within the CLBMODE packet, bits bO to b3 of byte B0 are used to indicate the mode measurement.

[0114] FIG. 13 illustrates an example of a calibration report data (CLBPloss) packet 1300. As described in the diagrams above, an MPP power receiver may send a CLBPloss packet to an MPP power transmitter. Within the packet, bits bO to b3 of byte B0 are used to indicate the mode measurement. In the example shown in FIG. 13, bit bO of the byte B0 is set to a value of one (1) and bits 1-3 are set to zero (0), indicating Mode 1 measurement. The CLBPloss packet 1300 may include values for PRECT (starting at byte B2), VRECT (starting at byteB4), and 1RECT (starting at byte B6) as shown in the example of FIG. 13. The power transmitter may then respond with an ACK to acknowledge receiving the packet. The power transmitter may respond with a NAK to indicate the mode is not allowed. The power transmitter may also respond ATN to indicate the mode is not allowed.

[0115] FIG. 14 illustrates a block diagram of an example apparatus for use in a wireless power system. In some implementations, the apparatus 1400 may be a wireless power apparatus (such as any of the power transmitter or power receiver described herein. The apparatus 1400 can include a processor 1402 (possibly including multiple processors, multiple cores, multiple nodes, or implementing multi -threading, etc.). The apparatus 1400 also can include a memory 1404. The memory 1404 may be system memory or any one or more of the possible realizations of computer- readable media described herein. The apparatus 1400 also can include a bus 1406 (such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.).

[0116] The apparatus 1400 may include one or more controllers 1408 (such as a PTx and / or PRx controller). In some implementations, the controller 1408 can be distributed within the processor 1402, the memory 1404, and the bus 1406. The controller 1408 may perform some or all of the operations described herein. For example, the controller 1408 may implement the processes, aspects, features, and / or functions described with reference to any one of FIG. 1 through FIG. 13, or any combination thereof.

[0117] The memory 1404 can include computer instructions executable by the processor 1402 to implement the functionality of the implementations, aspects and features described herein. Any one of these functionalities may be partially (or entirely) implemented in hardware or on the processor 1402. For example, the functionality may be implemented with an application specific integrated circuit, in logic implemented in the processor 1402, in a coprocessor on a peripheral device or card, etc. Further, realizations may include fewer or additional components not illustrated in FIG. 14. The processor 1402, the memory 1404, and the controller 1408 may be coupled to the bus 1406. Although illustrated as being coupled to the bus 1406, the memory 1404 may be coupled to the processor 1402 or the controller 1408.

[0118] The apparatus 1400 also includes a protocol feature(s) 1410. The protocol feature(s) 1410 is controlled by the controller 1408. For example, the protocol feature(s) 1410 may be implemented in a power supply (e.g., a power adapter) that is communicatively coupled to the controller 1408 of the power transmitter.

[0119] FIG. 1 through FIG. 14 and the operations described herein are examples meant to aid in understanding example implementations and should not be used to limit the potentialimplementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently.

[0120] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. While the aspects of the disclosure have been described in terms of various examples, any combination of aspects from any of the examples is also within the scope of the disclosure. The examples in this disclosure are provided for pedagogical purposes. Alternatively, or in addition to the other examples described herein, examples include any combination of the described implementation options (enumerated as clauses for clarity).

[0121] Clause 1: A method for wireless power transfer by a power transmitter (PTx), the method comprising: receiving, from a power receiver, a request for a wireless power transfer mode above a power threshold; performing a calibration protocol to obtain one or more calibration values for delta power loss (PLOSS) foreign object detection (FOD); and determining whether a foreign object is present based on the one or more calibration values and the delta PLOSS FOD during a power transfer phase of the wireless power transfer mode.

[0122] Clause 2: The method of clause 1, wherein the performing the calibration protocol includes: communicating, to the power receiver, a command to initiate the performing the calibration protocol.

[0123] Clause 3: The method of clause 1, wherein the performing the calibration protocol includes: receiving, from the power receiver, a message to initiate the performing the calibration protocol.

[0124] Clause 4: The method of any one of claims 2 or 3, wherein the command comprises a calibration initiation command (MPPCLB_START).

[0125] Clause 5: The method of any one of claims 1 to 4, wherein the performing the calibration protocol includes: for each of a plurality of calibration points / modes, communicating, to the power receiver, a calibration mode (CLBMODE) packet indicating a calibration point / mode; and transmitting power for at least a predefined time for the calibration point / mode.

[0126] Clause 6: The method of clause 5, wherein the plurality of calibration points / modes includes at least three calibration points / modes.

[0127] Clause 7: The method of any one of claims 5 or 6, wherein the performing the calibration protocol includes: for each of the plurality of calibration points / modes, receiving, from the power receiver, a measurement report (CLBPloss) including at least one of power, voltage, or current measurements of a rectifier of the power receiver.

[0128] Clause 8: The method of any one of claims 5 or 6, further comprising: receiving, from the power receiver, an aggregated measurement report that includes at least one of power, voltage, or current measurements of a rectifier of the power receiver for each of the plurality of calibration points / modes.

[0129] Clause 9: The method of any one of claims 7-8, further comprising: communicating a get request packet to the power receiver; and receiving, from the power receiver, the measurement reports or the aggregated measurement report.

[0130] Clause 10: The method of any one of claims 1-9, further comprising: calculating coefficients for a PLOSS -compensated formula based on the calibration values.

[0131] Clause 11: A method for wireless power transfer by a power receiver (PRx), the method comprising: transmitting, to a power transmitter, a request for a wireless power transfer mode above a power threshold; and performing a calibration protocol to provide, to the power transmitter, one or more calibration values for delta power loss (PLOSS) foreign object detection (FOD).

[0132] Clause 12: The method of clause 11, wherein the performing the calibration protocol includes: receiving, from the power transmitter, a command to initiate the performing the calibration protocol.

[0133] Clause 13: The method of clause 11 or 12, wherein the performing the calibration protocol includes: for each of a plurality of calibration points / modes: receiving, from the power transmitter, a calibration mode (CLBMODE) packet indicating an indicator of a calibration point / mode; and measuring at least one of power, voltage, or current of a rectifier of the power receiver during at least part of a predefined time for the calibration point / mode.

[0134] Clause 14: The method of clause 13, for each of the plurality of calibration points / modes: communicating, to the power transmitter, a measurement report (CLBPloss) including a measurement of the at least one of power, voltage, or current of the rectifier of the power receiver.

[0135] Clause 15: The method of clause 13, further comprising: communicating, to the power transmitter, an aggregated measurement report that includes one or more measurements of the at least one of power, voltage, or current of the rectifier for each of the plurality of calibration points / modes.

[0136] Clause 16: The method of clause 14 or 15, further comprising: receiving a get request packet from the power transmitter; and communicating the measurement report or the aggregated measurement report in response to the get request packet.

[0137] Clause 17: An apparatus comprising: a power transfer coil; a communication unit; and a controller, in combination with the communication unit, configured to implement any one of the methods of any one of clauses 1 to 16.

[0138] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this specification belongs. The terms “first,” “second,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The use of terms “including,” “comprising” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “connected” and “coupled” are not restricted to physical or mechanical connections or couplings and can include electrical connections or couplings, whether direct or indirect. Furthermore, terms “circuit” and “circuitry” and “control unit” may include either a single component or a plurality of components, which are either active and / or passive and are connected or otherwise coupled together to provide the described function. In addition, the term operationally coupled as used herein includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software based communication, or combinations thereof.

[0139] Some or all of the foregoing or the following implementations can be jointly combined or formed to be a new or another one implementation. The foregoing or the following techniques can be used to solve at least (but not limited to) the issue(s) or scenario(s) mentioned in this disclosure. Any two or more than two of the foregoing or the following paragraphs, (sub)-bullets, points, actions, or claims described in each method / technique / implementation may be combined logically, reasonably, and properly to form a specific method. Any sentence, paragraph, (sub)-bullet, point, action, or claim described in each of the foregoing or the following technique(s) / implementation(s) / concept(s) may be implemented independently and separately to form a specific method. Dependency, such as “based on,” “more specifically,” “where” or etc., in technique(s) / implementation(s) / concept(s) mentioned in this disclosure is just one possible implementation which would not restrict the specific method.

[0140] Certain techniques are described in this disclosure as including logic or a number of components or modules. Modules can be software modules e.g., code, or machine-readableinstructions stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g. , as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g. , as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0141] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

[0142] As used herein, the terms “component” and “module” are intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software. As used herein, the phrase “based on” is intended to be broadly construed to mean “based at least in part on.”

[0143] As used herein, a phrase referring to a list of items separated by “or” refers to any combination of those items, including single members. For example, “a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

[0144] In this disclosure, an expression of “X / Y” may include meaning of any of the following: “X or Y” or “X and Y” or “X and / or Y." An expression of “(A) B” or “B (A)” may include concept of “only B.” An expression of “(A) B” or “B (A)” may include the concept of “A+B” or “B+A.”

[0145] Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.

[0146] The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed in this specification and the structural equivalents thereof. The interchangeability of hardware, firmware and software has been described generally, 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 upon the particular application and design constraints imposed on the overall system.

[0147] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process or algorithm disclosed herein can be implemented as one or more modules of one or more computer programs. Such computer programs can include non- transitory processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by, or to control the operation of, a data processing apparatus including the components of the devices described herein. By way of example, and not limitation, such storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0148] Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0149] Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0150] The drawings may schematically depict one or more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

Claims

CLAIMSWhat is claimed is:

1. A method for wireless power transfer by a power transmitter (PTx), the method comprising: receiving, from a power receiver, a request for a wireless power transfer mode above a power threshold; receiving, from the power receiver, a message to start a calibration protocol for a delta power loss (PLOSS) foreign object detection (FOD) technique; obtaining, via the calibration protocol with the power receiver, one or more calibration values; and detecting a foreign object during a power transfer phase of the wireless power transfer mode based on the one or more calibration values and the delta PLOSS FOD technique.

2. The method of claim 1, wherein the obtaining the one or more calibration values includes: for each of a plurality of calibration points, transmitting power for at least a predefined time for the calibration point; and receiving, from the power receiver, a measurement report including one or more calibration values, the measurement report including at least one of power, voltage, or current measurements of a rectifier of the power receiver.

3. The method of claim 2, wherein the plurality of calibration points includes at least three calibration points.

4. The method of any one of claim 2 or 3, wherein receiving the measurement report includes receiving, from the power receiver, an aggregated measurement report that includes the one or more calibration values for multiple ones of the plurality of calibration points.

5. The method of any one of claims 1 to 4, further comprising: calculating coefficients for a Ptoss-compensated formula based on multiple calibration values of the one or more calibration values.

6. The method of any one of claims 1 to 5, further comprising: communicating, to the power receiver, capability information indicating that the power transmitter supports the calibration protocol.

7. The method of any one of claims 1 to 6, further comprising:before performing the calibration protocol, perform a Mated Q test for FOD to verify the absence of foreign objects.

8. The method of any one of claims 1 to 7, further comprising: obtaining the one or more calibration values using the calibration protocol during a low power state before below the power threshold; and detecting the foreign object using the one or more calibration values and the delta PLOSS FOD technique during the power transfer phase of the wireless power transfer mode above the power threshold.

9. A method for wireless power transfer by a power receiver (PRx), the method comprising: transmitting, to a power transmitter, a request for a wireless power transfer mode above a power threshold; and communicating, to the power transmitter,, a message to start a calibration protocol for a delta power loss (PLOSS) foreign object detection (FOD) technique; performing the calibration protocol to measure one or more calibration values; providing the one or more calibration values to the power transmitter for delta power loss (PLOSS) foreign object detection (FOD) technique of the power transmitter.

10. The method of claim 9, wherein the providing the one or more calibration values includes: for each of a plurality of calibration points, receiving power for at least a predefined time for the calibration point; and obtaining measurements of at least one of power, voltage, or current of a rectifier of the power receiver during at least part of a predefined time for the calibration point; providing, to the power transmitter, a measurement report including one or more calibration values based on the measurements.

11. The method of claim 10, wherein the plurality of calibration points includes at least three calibration points.

12. The method of any one of claims 9 to 11, further comprising: communicating, to the power transmitter, a request for calibration capability information; and receiving, from the power transmitter,, calibration capability information indicating that the power transmitter supports the calibration protocol.

13. The method of any one of claims 9 to 12, further comprising:performing the calibration protocol during a low power state before below the power threshold, to provide the one or more calibration values for the power transmitter to use with the delta PLOSS FOD technique during the power transfer phase of the wireless power transfer mode above the power threshold.

14. The method of any one of claims 9 to 13, further comprising: ending the calibration protocol before transitioning to the wireless power transfer mode above the power threshold.

15. An apparatus comprising: a power transfer coil; a communication unit; and a controller, in combination with the communication unit, configured to implement any one of the methods of any one of claims 1 to 14.

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