Power state transitions in a wireless power system based on combinations of status indicators

Abstract

This disclosure provides systems, methods and apparatuses for a Power Receiver to communicate status information to a Power Transmitter. A Power Receiver and a Power Transmitter may support using combinations of existing status indicators in the Power Receiver Status field of a message to provide a more tailored response to fault conditions in the Power Receiver. In some aspects, the Power Transmitter and Power receiver can use a combination of existing indicators in a Power Receiver Status field to indicate that the Power Receiver is not able to enter a Power State to receive power from the Power Transmitter. This disclosure describes operations of the Power Transmitter to coordinate with the Power Receiver to enter a power saving mode or to enter the power saving mode in the event of a fault or condition preventing the Power Receiver from receiving or using power from a Power Transmitter.

Description

POWER STATE TRANSITIONS IN A WIRELESS POWER SYSTEM BASED ON COMBINATIONS OF STATUS INDICATORSTECHNICAL FIELD

[0001] This disclosure relates generally to wireless power transmission and more specifically to communication between a power transmitter and a power receiver.DESCRIPTION OF RELATED TECHNOLOGY

[0002] A wireless power system may include a Power Transmitter and a Power Receiver. For example, the Power Transmitter may be installed on or included in a countertop or other flat surface. The Power Receiver may be included in a cordless appliance, such as a blender, a kettle, an air fryer, a mixer, or a toaster, among other examples. The Power Transmitter may include a primary coil that produces an electromagnetic field that may induce a voltage in a secondary coil of the Power Receiver w hen the secondary coil is placed in proximity to the primary coil. In this configuration, the electromagnetic field may wirelessly transfer power to the secondary coil. The power may be transferred using inductive coupling or resonant coupling between the primary coil and the secondary coil. The Power Receiver may provide the received pow er to operate the cordless appliance.SUMMARY

[0003] 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.

[0004] In one aspect, a method performed by a Power Transmitter in a wireless power system includes receiving, from a Power Receiver (PRx) in the wireless power system, a communication message including a status field indicating status of the Power Receiver, the status field including a plurality of indicators of the status of the Power Receiver; and controlling a state transition based on a first indicator of the status field that indicates whether the Power Receiver can receive power from the Power Transmitter and a second indicator of the status field that indicates w hether a communication error has occurred.

[0005] In one aspect, a method performed by a Power Receiver in a wireless power system includes determining, by the Pow er Receiver, a current operating condition of the Power Receiver; setting, based on the current operating condition of the Power Receiver, a firstindicator of a status field of a communication message and a second indicator of the status field of the communication message, wherein the first indicator indicates whether the Power Receiver can receive power from a Power Transmitter and the second indicator indicates whether a communication error has occurred; providing the communication message to the Power Transmitter of the wireless power system; and receiving, from the Power Transmitter, a message requesting transition to a power saving mode when the first indicator indicates that the Power Receiver cannot receive power from the Power Transmitter and the second indicator indicates that a communication error has not occurred.

[0006] 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 DRAWINGS

[0007] Figure 1 shows a block diagram of an example wireless power system that includes an example Power Transmitter and an example Power Receiver.

[0008] Figure 2 shows a message flow diagram of an example wireless power transmission process.

[0009] Figure 3 shows a block diagram conceptually illustrating an example Power Transmitter.

[0010] Figure 4 shows a block diagram conceptually illustrating an example Power Receiver.

[0011] Figure 5 shows a block diagram conceptually illustrating an example power negotiation and control.

[0012] Figure 6 shows a block diagram conceptually illustrating a communication protocol.

[0013] Figure 7A is a conceptual diagram illustrating an example message encapsulation technique for a Power Receiver to indicate status.

[0014] Figure 7B is a conceptual diagram illustrating an example Power Receiver Status field for a Power Receiver to indicate status.

[0015] Figures 8A-8D are flowcharts showing example operations for interpreting Power Receiver Status indicators by a Power Transmitter.

[0016] Figures 9A-9C are flowcharts showing example operations for setting Power Receiver Status indicators by a Power Receiver.

[0017] Figure 10 is a timing diagram illustrating a first example of state transitions in a wireless power system.

[0018] Figure 11 is a timing diagram illustrating a second example of state transitions in a wireless power system.

[0019] Figure 12 is a timing diagram illustrating a third example of state transitions in a wireless power system.

[0020] Figure 13 is a timing diagram illustrating a fourth example of state transitions in a wireless power system.

[0021] Figure 14 show s a block diagram of an example apparatus for use in w ireless pow er system.

[0022] Note that the relative dimensions of the figures may not be drawn to scale.DETAILED DESCRIPTION

[0023] 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.

[0024] A wireless power system may include a Power Transmitter (sometimes also referred to as a PTx or a wireless power transmission apparatus) integrated with or otherwise disposed on a surface. The wireless power system also may include a Power Receiver (sometimes also referred to as a PRx or a wireless power reception apparatus). The Power Transmitter may include a primary coil configured to wirelessly transmit power via a magnetic field to a secondary coil in the Power Receiver. In some implementations, the Power Transmitter may include a primary coil that is embedded or manufactured in a surface on which a wireless power reception apparatus can be placed. The wireless power reception apparatus can be an appliance (cordless or coded) that may include a Power Receiver for wirelessly receiving power. A secondary coil of the Power Receiver may obtain wireless energy from the magnetic field and provide it to a power receiving circuit. The power receiving circuit may convert the energy and utilize it to charge or power a load. A Power Receiver may be included or integrated with a cordless appliance having a variable load (such as a blender, heating element, a fan, among other examples). In some implementations, the Pow er Receiver may be included or integrated with a cordless appliance having a fixed load).

[0025] During a power transfer phase, the Power Receiver may periodically communicate power control communication to the Power Transmitter via a communication channel. Power control communications may indicate presence of the Power Receiver or status of the Power Receiver, among other examples. Power control communications may include a power request, a null communication (to indicate presence without feedback), or Power Receiver feedback. The Power Transmitter and the Power Receiver may communicate via Near Field Communication (NFC), Bluetooth™, or other communications techniques.

[0026] This disclosure provides systems, methods and apparatuses for a Power Receiver to communicate status information to a Power Transmitter. In existing systems, a Power Receiver can communicate status information via a Power Receiver Status field of a communication message to the Power Transmitter. The Power Receiver Status field includes bits, that when set, indicate different aspects of the status of the Power Receiver. However, there are a limited number of bits in the Power Receiver Status field. For example, for efficiency purposes, in an existing system, limited individual bits may be used to communicate status, with each bit associated with a different aspect of the Power Receiver Status.

[0027] Due to the limited number of bits in the status field, many different fault scenanos are typically combined into a single bit. Thus, a technical problem with existing systems is that the combining of different operating difficulties results in ambiguity as to the actual fault experienced by the Power Receiver. As a result, the Power Transmitter might assume the worst case when responding to the fault and take remedial actions that may not in fact be necessary. For example, a fault due to a communication error may need reinitialization in order to mitigate or remediate the fault. Other faults due to overtemperature, overcurrent or overvoltage may not need a full reinitialization in order to mitigate the fault. Ho ever, because of the ambiguity in fault determination that results from the limited number of available bits in the Power Receiver Status field of existing systems, the Power Transmitter may assume the worst case, which in some cases means a complete reinitialization regardless of whether such reinitialization is necessary' to remediate the fault or not. Thus, unnecessary time may be taken to remediate a fault, resulting in a poor user experience.

[0028] Further, the Power Transmitter may need to hold power resources in reserve for the Power Receiver because the limited information available to the Power Transmitter does not allow' the Pow'er Transmitter to determine with any degree of certainty w hether or not the Pow er Receiver needs power resources from the Pow er Transmitter. As a result, power resources of the Power Transmitter may be wasted by being held in reserve for a Power Receiver that may not be able to make use of the power resources. These unused power resources are thusunavailable other Power Transmitters that share a common input power cable as in the case of a multi-transmitter hob. As a result. Power Receivers that could be serviced by the other transmitters are not serviced.

[0029] Particular aspects of the subject matter described in this disclosure can be implemented in a practical application, such as a Power Transmitter and / or a Power Receiver to realize one or more technical solutions to the problems discussed above, leading to potential advantages over existing systems. A Power Receiver and a Power Transmitter may support using combinations of existing status indicators in the Power Receiver Status field of a message to provide a more tailored response to fault conditions in the Power Receiver.

[0030] For example, the Power Transmitter and Power receiver can use a combination of existing indicators in a Power Receiver Status field to indicate that the Power Receiver is not able to enter a Power State to receive power from the Power Transmitter. For example, a fault in the Power Receiver may be preventing entry into the power state, or the Power Receiver may be receiving power from an alternative source (e g., power from a main). In such a case, the Power Transmitter can send a request to the Power Receiver asking the Power Receiver if the system can enter a power saving mode. For example, the Power Transmitter can send a message to the Power Receiver requesting a transition to a standby state. If the Power Receiver responds with a “Yes” to the request, or does not respond, the Power Transmitter can transition to a standby state, thereby releasing negotiated power resources reserved for the Power Receiver. If the Power Receiver responds with a “No” to the request, the Power Transmitter can wait and issue the query again. In this case, the Power Transmitter avoids reinitializing the connection with the Power Receiver that would occur in existing systems and waits for the Power Receiver to either resolve the issue causing the Power Receiver to be unable to enter or remain in the power state (e.g., overtemperature, overvoltage, overcurrent etc.) or to indicate that the Power Receiver will enter a power saving mode (e.g., transition to a standby state). Thus, user experience is improved by better fault handling and error recovery procedures enabled by the disclosed communication techniques.

[0031] While the examples in this disclosure are based on wireless power used in kitchen systems, the techniques are applicable to other types of systems. For example, the techniques may be used with wireless power systems associated with home appliances, electronic devices, fans, space heaters, speaker systems, air compressors, garden equipment, or components of an electric vehicle, among other examples.

[0032] Figure 1 shows a block diagram of an example wireless power system 100 that includes an example Power Transmitter 102 and an example Power Receiver 118. A PowerTransmiter (sometimes referred to as “PTx”) is a functional unit that converts electric power to magnetic power. In this disclosure, Power Transmiter 102 includes the PTx as well as a communication system and other electrical components. A Power Receiver (sometimes also referred to as “PRx”) is a part of a wireless power transfer system that converts magnetic power to electric power or heat. In this disclosure, Power Receiver 118 includes the PRx as well as a communication system and other electrical components. The Power Transmiter 102 and the Power Receiver 118 may be separated by an interface space 190. In Figure 1. dashed lines represent communications to distinguish from solid lines that represent electrical circuit lines. The Power Transmiter 102 includes a primary coil 104. The primary coil 104 may be a wire coil which transmits wireless power (which also may be referred to as wireless energy). The primary coil 104 may transmit wireless energy using inductive or magnetic resonant field. The primary coil 104 may be associated with a power transmiter circuit 110. The power transmiter circuit 110 may include components such as a pulse width modulator or voltage controlled oscillator 142, an inverter 144, and a series capacitor 146. The series capacitor 146 and the primary coil 104 are sometimes also referred to as a “tank circuit 147”. The power transmiter circuit 110 may also include other components (not shown) for impedance matching. Power Transmiter 102 also may include one or more sensors 152, such as a voltage sensor and a current sensor (not shown).

[0033] Some or all of the power transmitter circuit 110 may be embodied as an integrated circuit (IC) that implements features of this disclosure for controlling and transmiting wireless power to one or more Power Receivers. The power controller 108 may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC) or any other suitable electronic device.

[0034] Power source 112 may provide power to the po er transmiter circuit 110 in the Power Transmiter 102. Power source 1 12 may convert alternating current (AC) power to direct current (DC) power. For example, power source 112 may include a converter that receives an AC power from an external power supply and converts the AC power to a DC power used by the power transmitter circuit 110.

[0035] The power controller 108 is connected to a first communication interface 114. In some aspects, the first communication interface 1 14 may be an interface that utilizes wireless communications techniques to communicate with other wireless communication interfaces (e.g., second communication interface 132). The first communication interface 114 is connected to a first communication coil 116. In some implementations, the first communication interface 114 and the first communication coil 116 may be collectively referredto as the first communication unit 124. In some implementations, the first communication unit 124 may support Near-Field Communication (NFC). NFC is a technology by which data transfer occurs on a carrier frequency of 13.56 Megahertz (MHz). The first communication unit 124 also may support any suitable communication protocol.

[0036] Power Receiver 118 may include a secondary' coil 120, a series capacitor 122, a series switch 123. a rectifier 126, an appliance controller 136, a second communication interface 132, a sensor 162, a load 130, and a memory (not shown). The series capacitor 122 and the secondary coil 120 are sometimes also referred to as an '‘tank circuit 121”. In some aspects, second communication interface 132 may be an interface that communicates using wireless communication techniques. In some implementations, the Power Receiver 118 also may include a user interface (not shown) or other means for obtaining a load setting 164 indicating a desired operation of the load. In some implementations, the load setting 164 may be stored in a memory' (not shown) of Power Receiver 118. In some implementations, load 130 may also include a drive (not shown) for controlling at least one parameter such as temperature, speed, or torque of the load. In some implementations, the rectifier 126 may be omitted. Although shown as different components, some components may be packaged or implemented in the same hardware. For example, in some implementations, the appliance controller 136 and a pow er reception controller (not shown) may be implemented as a single controller. The appliance controller 136, 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.

[0037] An interface space 190 may demark a space between the Pow er Transmitter 102 and the Power Receiver 118. For example, the interface space may include a surface of the Power Transmitter 102 on which the Power Receiver 118 may be placed. A distance between the primary' coil 104 and the secondary coil 120 may include a thickness of a surface in the interface space 190. During wireless power transfer, the primary coil 104 may induce a magnetic field (referred to as the primary' magnetic field) through the interface space 190 and into an operative environment in which the secondary coil 120 is placed. Thus, the “operative environment” is defined by the primary magnetic field in the system, where the primary magnetic field of a primary coil 104 is detectably present and can detectably interact with the secondary' coil 120.

[0038] The power controller 108 may detect the presence or proximity of a Power Receiver 118. This detection may happen during a periodic pinging process of the first communication interface 114 in Power Transmitter 102. During the pinging process, the first communicationinterface 114 also may supply power (via the first communication coil 116) to the second communication interface 132 (via the second communication coil 134) when the Power Receiver 118 is in proximity. The second communication interface 132 may '‘wake up’’ and power-up the appliance controller 136 and may send a reply signal back to the first communication interface 114. Prior to power transfer, a handshaking process may take place during which the power controller 108 may receive data configuration related to the power rating of the receiver, among other information.

[0039] Different cordless appliances have different load types, different load states, and different power requirements or may require power at a particular voltage and frequency. For example, a cordless blender may include a variable motor load that has multiple user-selectable load states to control motor speed. Depending on the load state, the cordless blender may require different levels of power to operate. In another example, a cordless kettle may include a resistive load that has different load states to control temperature. In yet another example, an air fiy er may be a compound load device and may operate a heater, a fan, or both, at various periods of operation. Each type of load (such as the motor, the resistive load, the heater, the fan, or any combination thereof) may require different amounts of power to operate based on a current load state or load state. Furthermore, cordless appliances may exhibit different levels of voltage gains from a primary coil to a receiver coil at different primary coil excitation frequencies (such as a wireless power transfer frequency) depending on their load type or load state. For example, to achieve a desired load voltage, a cordless blender may operate best at a first operating frequency for a first load state, such as a low motor speed setting. However, as the load state changes, the cordless blender may not achieve the same load voltage when operated at the first operating frequency. For example, the first operating frequency may facilitate a first voltage gain when the cordless blender is set to a first load state (such as a low- speed setting), but the first operating frequency may provide a lower voltage gain when the cordless blender is set to a second setting (such as a higher-speed setting). The load setting 164 may indicate a current load state or a required power needed for the load to operate in the load state.

[0040] The power controller 108 may control characteristics of wireless power that that the Power Transmitter 102 provides to the Power Receiver 118. After detecting the Power Receiver 118, the power controller 108 may receive configuration data from a Power Receiver 118. For example, the power controller 108 may receive the configuration data during a hand shaking process with the Power Receiver 118. The power controller 108 may use the configuration data to determine at least one operating parameter (such as frequency, duty cycle,voltage, etc.) for wireless power generated by the power transmitter circuit 110. The operating parameter may be adjusted based on feedback information from the Power Receiver 118 during the transfer of wireless power in response to a change in the load state or power requirement of load 130. Thus, the power controller 108 may provide wireless power that enables relatively efficient operation of the Power Receiver 118. For example, the transmission controller may configure the wireless power to enable the Power Receiver to operate at peak efficiency for a particular load state, load voltage and operating K-factor.

[0041] The Power Transmitter 102 and the Power Receiver 118 may implement a control architecture for managing the transfer of wireless power. The control architecture may define how power requirements are communicated and how an operating point of the power transmitter is controlled. In some implementations, the control architecture may be based on static power control (referred to as '‘control type 1 architecture” or ‘'type 1”). In some implementations, the control architecture may be based on dynamic power control (referred to as “control ty pe 0 architecture” or “type 0”). An appliance that implements the control ty pe 1 architecture may have a fixed load, might not include measurement circuits, typically may not employ auxiliary data transfer, and may require only minimal functionality so as to contain manufacturing costs. The control type 1 architecture may rely on a control loop of the Power Transmitter 102 without feedback from the Power Receiver 118. An appliance that implements the control type 0 architecture may have a static or dynamic load and may implement a controller to generate a power request message during power transfer as well as measurement circuits for proper control of its load. This disclosure includes examples of both ty pe 0 and ty pe 1 control architectures as they relate to transitions between various operating phases.

[0042] In some implementations, the first communication interface 114 may communicate with a Power Receiver by transmitting a wireless communication signal and detecting changes in the wireless communication signal that represent communication of information. The first communication interface 114 may support NFC Type 2 Tag specifications or NFC Type 4A Tag specifications, as specified by an NFC specification. During a power transfer phase, the communications carrier and the power signal may both be active. Due to the frequency range used for the power signal, the inter-modulation products of the two signals result in interferences disturbing the reliable NFC communication. In order to avoid this unwanted effect, the power signal may be periodically switched-off for short time intervals. The time intervals may be referred to as communication time slots. Typically, the communication time slots may occur in relation to a zero-cross event associated with an AC cycle of an AC mains power or wall plug.

[0043] The second communication interface 132 may support NFC Type 2 Tag specifications or NFC Type 4A Tag specifications, as specified by an NFC specification. In some implementations, the wireless communication unit is configured to communicate with the power transmitter by storing information in a passive tag (such as an NFC Type 2 Tag) that can be read by a wireless communication interface of a Power Transmitter. Alternatively, wireless communication unit may be configured to communicate with the Power Transmitter by transmitting information (such as using an NFC Type 4A Tag) in a wireless communication signal to the wireless communication interface of the power transmitter.

[0044] Figure 2 shows a message flow7diagram 200 of an example wireless power transmission process. Referring to Figure 2, a Power Transmitter 102 detects that a Power Receiver 118 is located in a charging area in a standby mode (operation 205). There may be various methods for detecting the Power Receiver 118 by the Power Transmitter 102, and not limited to a specific method in the present disclosure. As an example, the Power Transmitter 102 may detect that the Power Receiver 118 is located in a charging area by periodically emitting analog ping of a specific frequency, and based on detection current for this, resonance shift or capacitance change. As another example, the Power Transmitter 102 may periodically transmit a detection signal and the Power Receiver 118 may transmit a response signal (for example, a control error packet or a signal strength packet). The Pow er Transmitter 102 may detect that the Power Receiver 118 is located in the charging area based on receiving the response signal within a predetermined time period following the detection signal. As yet another example, the Power Receiver 118 may transmit a searching signal or an advertisement signal to the Powder Transmitter 102. The searching signal or the advertisement signal may traditionally be transmitted using short range radio frequency communication (such as NFC or Bluetooth™). The Power Transmitter 102 may detect the Power Receiver 118 based on reception of the searching signal or the advertisement signal.

[0045] In some implementations, as a preparation step for a wireless power transmission, the Pow er Transmitter 102 may optionally transmit an information request signal to the Power Receiver (operation 210). The information request signal may be a signal for requesting an ID and requesting power information of the Power Receiver 118. As an example, the information request signal may be transmitted in the form of data packet message. As another example, the information request signal may be transmitted in a form of digital ping according to a predefined standard between the Power Transmitter 102 and the Power Receiver 118. In response to the information request signal, the Power Receiver 118 may optionally transmit the ID and configuration information to the Power Transmitter 102 (operation 220). For example,the configuration information may include a requested amount of power or a maximum amount of power that is provided for the Power Receiver 118. In some implementations, the configuration information may include a rated power value associated with the load or an operation of the load. In some implementations, the configuration information also may include a time parameter. For example, the time parameter may indicate an expected time for the Power Receiver to complete the operation based on the rated power value. In some implementations, the information request signal and the ID and configuration information may be communicated using out-of-band communication (separate from the wireless power signal) such as NFC or Bluetooth.

[0046] Based on the ID and configuration information, the Power Transmitter 102 configures parameters (referred to as an operating point) for power transmission and performs a wireless power transmission to the Power Receiver 118 (operation 230). For example, the Power Transmitter may create a power transmission contract based on the ID and the configuration information and may control the wireless power transmission according to the power transmission contract. The process, performed by the Power Transmitter 102. from the start to the end of the wireless power transmission to the Power Receiver may be called a (wireless) power transfer phase 235. In some implementations, the Power Receiver 1 18 may provide the received wireless power to an external load such as a heating element, motor, or battery, among other examples. In some implementations, an operation of the Power Receiver 118 may be based on the external load and a user-configurable setting. For example, the operation may include boiling water, toasting bread, or cooking food. In other examples, the operation may be based on charging a battery or other energy storage device to a desired level.

[0047] The Power Transmitter 102 may monitor the parameters for power transmission (operation 245) and may abort the wireless power transmission (operation 250) when any one of the parameters exceeds a stated limit. Alternatively, the wireless power transmission process of operation 230 may be ended by a request of the Power Receiver 118. For example, the Pow er Receiver 118 may transmit a signal for requesting termination of the wireless power transmission to the Power Transmitter 102, when the operation of the Power Receiver 118 is complete.

[0048] During the pow er transfer phase 235, the Power Receiver 118 periodically transmits powder control communications to the Power Transmitter 102 (shown at operations 240-1, 240- 2, 240-3, and 240-4). Examples of a pow er control communication may include a control error packet (CEP), a power request message, or a status message, among other examples. This isperformed for controlling an amount of power which is transmitted from the Power Transmitter 102 to the Power Receiver 118, that is, to perform a power control.

[0049] In some aspects, the Power Transmitter 102 monitors a status field of the power control communications and checks for an indicator indicating communication errors (operation 245). If the indicator is persistent for a threshold time, the Power Transmitter 102 will stop transmitting power (operation 250) to the Power Receiver 118 and move to reinitialization state.

[0050] Figure 3 shows a block diagram conceptually illustrating an example Power Transmitter 300. The Power Transmitter 300 may be an example of the Powder Transmitter 102 described with reference to Figures 1 and 2, respectively. The Power Transmitter 300 may include a power source 302, which is shown as an AC power source. However, the power source 302 may be a DC power source or any other suitable source power. The power source 302 may be connected to a rectifier 304 (which also may be referred to bridge rectifier, or other related terms). The rectifier 304 which may be connected to a capacitor 306. The rectifier 304 may provide DC power to a first switch 316 and a second switch 318. The first switch 316 and second switch 318 together form an inverter 311 that generates an AC voltage from the DC power. The first switch 316 and the second switch 318 may be metal-oxi de-semiconductor field-effect transistors (MOSFETs) or Insulated Gate bipolar Transistors (IGBTs), among other examples. A first pulse width modulator (PWM) driver 312 may be connected to the first switch 316, and a second PWM driver 314 may be connected to the second switch 318. The power controller 108 may be connected to the first PWM driver 312 and the second PWM driver 314. The powder controller 108 may control the PWM drivers 312 and 314 to cause wireless power transmission according to a desired operating duty cycle, or operating frequency, among other examples. The Power Transmitter 300 may include other components (such as capacitors 320) in the path betw een the power source 302 and a primary coil 322. The rectifier 304, capacitor 306, switches 316 and 318, and capacitors 320 may be collectively referred to as the power transmitter (PTx) circuit 350. The pow er controller 108 controls one or more components of the PTx circuit 350 to manage the transmission of wireless power.

[0051] The power controller 108 may exchange communications with a Power Receiver via a communication unit. The communication unit may include a communication interface 326, a communication controller (not shown) or other component connected to a communication coil 328. In some implementations, the communication interface 326 and the communication coil 328 are configured to communicate using an NFC communicationprotocol. In some implementations, the communication interface 326 and the power controller 108 may be collocated in a common processor or chip.

[0052] The power controller 108 may detect the Power Receiver in proximity to the primary coil 322 and conduct a handshaking process during which the power controller 108 receives information from the Power Receiver. The power controller 108 may receive the information via the communication interface 326. In some implementations, the information may include one or more reference control parameters such as operating frequencies of the Power Receiver at different reference coupling factors (K-factors), load voltages and load powers of the Power Receiver. In some implementations, the information may indicate a load type and a load state for a variable load associated with the Power Receiver. Load state represents the combined state of load voltage and corresponding load power of the appliance. The power controller 108 may utilize this information to provide wireless power having characteristics that enable the Power Receiver to operate. For example, the power controller 108 may determine an operating parameter and provide wireless power by controlling the first and second PWM drivers (312 and 314. respectively) based on the operating parameter. The PWM drivers (312 and 314, respectively) may operate the first switch 316 and the second switch 318. The first switch 316 and second switch 318 may energize the primary coil 322 in a manner that transmits wireless power according to the operating parameter to a secondary7coil of the Power Receiver.

[0053] The Power Transmitter 300 may include a measurement unit 308. The measurement unit 308 may measure one or more characteristics (such as voltage, current, or both) through the PTx circuit 350. In some implementations, the measurement circuit may be connected to the rectifier (such as either on the power source 302 side as shown in Figure 3 or on the wireless power transmission circuit side). In some implementations, the measurement unit 308 may be configured to measure a voltage and current through the rectifier 304 or the inverter 311.

[0054] Figure 4 shows a block diagram conceptually illustrating an example Powder Receiver 400. The Power Receiver 400 may be an example of the Power Receiver 118 described with reference to Figures 1, 2 and 3. The Power Receiver 400 includes a secondary coil 402. The secondary coil 402 may be connected to a rectifier 404 and a capacitor 406. In some implementations, the secondary coil 402 is connected to the rectifier 404 via a series capacitor (not shown), a series switch (not shown), or other electrical components. The rectifier 404 may be electrically coupled to the load 408 or an energy storage device (not shown, such as a battery) through a series switch (not shown). In some implementations, the rectifier 404, the capacitor 406, or both, may be absent in the Power Receiver, depending on the kind of load408 (such as heating elements). The Power Receiver 400 also may include a communication interface 426, which may include a second communication coil 428. The communication interface 426 may be connected to a receiver (RX) controller 424.

[0055] The receiver controller 424 may receive various information and determine a control error value, a power request value or other feedback to communicate to a Power Transmitter via the communication interface 426. In Figure 4, dotted lines represent control or information lines to distinguish from solid lines that represent electrical circuit lines. The control or information lines may include electrical connections to or from a receiver controller 424 and other components of the Power Receiver 400. In some implementations, the receiver controller 424 may receive information indicating load settings, power requirements or power estimates from a load controller (not shown) connected to the load 408. The receiver controller 424 also may receive voltage information from a voltage sensor 414 that is connected to the rectifier 404. The voltage information may indicate a voltage available to the load 408.

[0056] The RX controller 424 also may communicate with a Power Transmitter via the communication interface 426. In some implementations, the RX controller 424 may obtain configuration data from a memory (not shown). The configuration data may be transmitted by the communication interface 426 to the Power Transmitter. The RX controller 424 also may obtain information indicating load states and / or power estimates from a load controller (not shown) or user interface (not shown). At various times before, during, or after the transfer of wireless power, the communication interface 426 may transmit, to the Power Transmitter, the aforementioned configuration data, voltage measurement information, coupling information, power request information, load voltage information, the load state, among other examples. The load setting may be a user-selectable setting, such as a temperature setting, cooking time, or motor speed setting, among other examples. In some implementations, the configuration data may include a rated power value and a time parameter associated with an operation of the load 408. For example, the time parameter may indicate an expected time to boil water, toast bread, or cook food based on the load setting. In some instances, the RX controller 424 may transmit some or all of the configuration data to the transmission controller during a handshaking process, as descnbed herein. In some instances, the RX controller 424 may transmit feedback information to a Power Transmitter. The feedback information may include one or more of a load state, a reference voltage, a power estimate or request for the load, the coupling factor information, the load voltage information, a fault state (when detected by the example Power Receiver 400), or any combination thereof.

[0057] A PTx controller (not shown) of the Power Transmitter may modify the wireless power being transmitted to the Power Receiver 400 based on the feedback information. The communication interface 426 may be configured to communicate messages to the Power Transmitter during predetermined communication slots. For example, the communication slots may be determined based on a synchronization unit (not shown), clock, or other device. For example, communication slots may occur at times when there is no switching in the Power Transmitter and may be determined when the coil sensed voltage (at the secondary coil 402) is zero.

[0058] Figure 5 shows an example system state diagram 500 with example power negotiation operations. The system state diagram 500 consists of five main states: standby state 510, discovery state 520, connected state 530, power state 540, and reinit state 550. The Power Transmitter enters the standby state 510 when the user connects it to the mains. In the standby state 510, the Power Transmitter looks for the presence of a valid receiver. The Power Transmitter remains in the standby state 510 waiting for an event that causes transition to the discovery’ state 520. Examples of such events include user interaction with the Power Transmitter or detection of a Power Receiver. For example, if the Power Transmitter detects placement of a Power Receiver, the Power Transmitter transitions to the discovery state 520.

[0059] In discovery’ state 520, the Power Transmitter performs object classification and obtains configuration information about a detected device. For example, the Power Transmitter can perform Near Field Communications (NFC) object classification and NFC activation to read a static configuration via NFC Data Exchange Format (NDEF). If an NFC-A device is found, the Power Transmitter reads the NDEF record to determine if the NFC-A device is a Power Receiver and to retrieve static configuration information.

[0060] After successful discovery of a Power Receiver during the discovery state 520, the Power Transmitter transitions to the connected state 530. In this state, the Power Transmitter and Power Receiver exchange information to negotiate parameters related to wireless power transfer or wireless charging.

[0061] A brief description of power negotiation follows. The Power Receiver may communicate a Requested Power negotiation value to the Power Transmitter. The Requested Power negotiation value may be based on the power rating of the load. The Power Receiver and the Power Transmitter may negotiate a Guaranteed Power based on the Requested Power negotiation value and the available power of the Power Transmitter. The Power Transmitter may accept the Requested Power negotiation value as the Guaranteed Power or reject it. For example, the Power Transmitter may accept the Requested Power negotiation value as theGuaranteed Power if the available power is more than a sum of the Requested Power negotiation value and an estimated power transmission loss (PTx-loss). Alternatively, there may be cases when the Power Transmitter cannot accept the Requested Power negotiation value. For example, the Power Transmitter may determine that the available power is less than the sum of the Requested Power negotiation value and the estimated PTx-loss. The Power Transmitter may communicate a message to the Power Receiver indicating that the Power Transmitter rejects the Requested Power negotiation value. In some implementations, the Power Receiver may communicate a subsequent Requested Power negotiation value and wait for an acceptance or rejection of the Requested Power negotiation value as the Guaranteed Power. In some implementations, the Power Transmitter may calculate an alternative power negotiation value that the Power Transmitter can satisfy based on the Available Power. The Power Transmitter may communicate the alternative power negotiation value (sometimes referred to as a suggested power negotiation value) to the Power Receiver. The Power Receiver may respond with an acknowledgement if the Power Receiver accepts the alternative power negotiation value as the Guaranteed value.

[0062] Once the Guaranteed Power has been negotiated, the Power Transmitter may reserve a Negotiated Power (based on a sum of the Guaranteed Power and the estimated PTx- loss) out of the Available Power, thereby reducing the power for other Power Transmitters that share the total source power. Each Power Transmitter may perform similar power negotiation (and reservations of Negotiated Power) with their respective Power Receivers using the Available Power remaining after reservations from other Power Transmitters. Because the Negotiated Power accounts for the estimated PTx-loss, the total power usage by multiple Power Transmitters will not exceed the Maximum Power of the power source.

[0063] From the connected state 530, the Power Receiver can request the Power Transmitter to move to the power state 540, the standby state 510, or the reinit (reinitialize) state 550. In the power state 540, the Power Transmitter may perform Foreign Object Detection (FOD) operations, then applies the power signal to transmit wireless power to the Power Receiver, repeating this cycle for the duration of the power state 540. Communication or FOD is performed during slots in the power signal. Some examples of communication in the power state 540 may be relevant to power control. For example, during the power state 540, the Power Receiver may communicate a Power Request (P-request) message (sometimes referred to as “Requested Power’ or CTRL / rpl) to cause the Power Transmitter to adjust the power level of the wireless power transfer to the Power Receiver. The Requested Power during power transfer phase may not exceed the Guaranteed Power previously negotiated between the PowerTransmitter and the Power Receiver. Communication or FOD may result in moving to a different state.

[0064] In the reinit state 550, the Power Transmitter stops communication and power delivery to the Power Receiver, and the system reinitializes. During this reinitialization, the Power Transmitter suspends communication and power transfer for a reinit timeout period (e.g., 500ms) before moving to the discovery state 520. The reinit timeout period can be used by the Power Receiver for completing a reset.

[0065] Examples of conditions which may cause a system to transition to the reinit state 550 include:• The Power Transmitter or Power Receiver detects a communication error.• The Power Receiver is removed.• The Power Receiver disconnects from a load on the Power Receiver during power transfer.

[0066] Figure 6 shows a block diagram 600 conceptually illustrating a communication protocol. A Power Transmitter 102 may communicate with a Power Receiver 118. The communication protocol may include a message 620 from the Power Transmitter 102 to the Power Receiver 118 or a message 610 from the Power Receiver 118 to the Pow er Transmitter 102, or both. This disclosure includes several enhancements to the communication protocol to support various features of a wireless power system. In some implementations, the communication protocol is implemented using NFC communication units at the Power Transmitter 102 and the Power Receiver 118. In some implementations, communications between the Power Transmitter 102 and the Power Receiver 118 can be accomplished via READx and WRITEx commands. The Power Transmitter 102 can issue a READx command to retrieve a message frame from the Power Receiver 118. The Power Transmitter 102 can issue a WRITEx command to send a message frame to the Pow er Receiver 118.

[0067] Figure 7A is a conceptual diagram illustrating an example message encapsulation technique 700 for a Power Receiver to indicate status. In some aspects, a communication message frame 708 provided to the Power Transmitter by the Power Receiver in response to a READx command can include one or more messages 706. A message 706 can include a corresponding payload 704. Additionally, the message frame 708 from the Power Receiver to a Power Transmitter includes a status field 710 (such as PRx status) that is provided prior to the one or more messages 706.

[0068] Figure 7B is a conceptual diagram illustrating an example Power Receiver Status field for a Power Receiver to indicate status. The status field 720 of Figure 7B may be an implementation of status field 710 of Figure 7A.

[0069] The status field 720 may include one or more indicators. In some implementations, the status field 720 is one byte with various bits allocated to a status value or indicator. In some examples, status indicators 722 of status field 720 may include one or more of the following indicators / values for the Power Receiver:• PSTP: power stop request (request by Power Receiver during power transfer indicating that the Power Transmitter should stop transferring power.• COMM ERR: communication error detected.• LD_CNCTD: status indicating whether power receiver load connected or disconnected.

[0070] The example PRx status indicators are provided for pedagogical purposes and not intended as an exhaustive or exclusive list. Furthermore, some implementations may omit or include various ones of the example PRx status indicators described herein. In some aspects, a no power bit (NPB) can be used instead of the PSTP (power stop) bit to indicate that the receiver cannot receive power from the transmitter.

[0071] Figure 8A is a flowchart 800 showing example operations for interpreting Power Receiver Status indicators by a Power Transmitter. A Power Transmitter can receive a communication message from a Power Receiver (block 802). The communication message can include a status field indicating the status of the Power Receiver. The status field can include multiple indicators of the status of the Power Receiver. For example, the status field can include the indicators described above with respect to Figures 7 A and 7B.

[0072] After receiving the message, the Power Transmitter can control a state transition based on a first indicator of the status field that indicates whether the Power Receiver can receive power from the Power Transmitter and a second indicator of the status field that indicates whether a communication error has occurred (block 804).

[0073] Figure 8B is a flowchart 820 showing example operations for interpreting Power Receiver Status indicators by a Power Transmitter while the Power Transmitter is in a connected state. A Power Transmitter can receive a communication message from a Power Receiver (block 824). The communication message can include a status field indicating the status of the Power Receiver. The status field can include multiple indicators of the status of the Power Receiver. In the example shown in Figure 8B, a first indicator indicates that thePower Receiver is not to receive power from the Power Transmitter. A second indicator can indicate that there is no communication error between the Power Transmitter and the Power Receiver.

[0074] The indicator that the Power Receive is not to receive power from the Power Transmitter can indicate that the Power Receiver is unable to transition from the connected state to the power state. The Power Receiver may indicate that the Power Receiver should not receive power from the Power Transmitter for various reasons. For example, a fault in the Power Receiver may prevent the Power Receiver from accepting or being able to use power transmitted by the Power Transmitter. As another example, the Power Receiver may be a hybrid apparatus that is able to receive power from a wired source (e.g.. a main) or can receive power from a wireless source (e.g., the Power Transmitter). When the Power Receiver is receiving power from a wired source, the Power Receiver can indicate that the Power Receiver is not to receive power from the Power Transmitter because it is already receiving power from a different source, e.g., the wired source.

[0075] After receiving the message from the Power Receiver indicating that the Power Transmitter should not transmit power to the Power Receiver, the Power Transmitter can send a message to the Power Receiver requesting a transition to a power save mode (block 826). In some implementations conforming to the Ki Cordless Kitchen Wireless Power Specification, the Power Transmitter can send a "NEXT / stb" message (indicating a request for a state transition and indicating the next state requested is the standby state) to the Power Receiver to request that the Power Receiver agree to a transition to the standby state. The sender of a “NEXT” message requests the recipient to move to another state or trigger an action. The recipient of a NEXT message will ty pically acknowledge the request (positive or negative) by responding with a response (“RESP”) message. For example, the Power Receiver might agree that the Power Transmitter (and the Power Receiver) transition to the standby state. Alternatively, the Power Receiver might indicate that the Power Receiver does not agree to the transition to the standby state, in which case the Power Transmitter and the Power Receiver will remain in the connected state.

[0076] The Power Transmitter can check to determine if the Power Transmitter receives a response to the message requesting transition to a power save mode (decision block 828). For example, the Power Transmitter may request that the Power Receiver transition to a standby state. If the Power Transmitter does not receive a response to the request (“NO” branch of block 828). the Power Transmitter can enter the standby state (block 832).

[0077] If the Power Transmitter receives a response to the request (‘‘YES” branch of block 828). the Power Transmitter can determine if the Power Receiver's response to the message indicates the Power Receiver agrees to the transition to the power save mode (block 830). If the Power Receiver indicates agrees to the transition to the power save mode (“YES” branch of block 830), the Power Transmitter enters a standby state (block 832). When entering standbystate, the Power Transmitter releases any power reserved for the receiver thereby increasing the power that can be drawn by other transmitters sharing the same source.

[0078] If the Power Receiver’s response to the request indicates that the Power Receiver does not agree to the transition to the power save mode (“NO” branch of block 830), the Power Transmitter can wait a predetermined time (block 834) and return to block 826 to repeat the request to transition to the power save mode. As an example, the Power Receiver may be experiencing a transient or temporary fault condition such as an overtemperature, overvoltage, overcurrent or other such transient event. The Power Receiver may desire to wait for the transient fault to clear, after which it can request that the Power Transmitter reenter the power state. As another example, the Power Receiver may be waiting for user input. After receiving the user input, the Power Receiver can request that the Power Transmitter enter the power state. In this case of waiting for user input, if the waiting time is longer than a threshold, the Power Receiver may send a response (received by the Pow er Transmitter at block 828) indicating that the Power Receiver agrees for the transmitter to move to the standby state at block 832.

[0079] Because the Power Transmitter and Pow er Receiver remain in the connected state during the process of repeating the request to transition to the power save mode, communications between the Pow er Transmitter and Pow er Receiver can continue, and should the fault be cleared, the Power Transmitter and Power Receiver can resume power transmission and reception without having to enter a reinitialization state, thereby saving time and resources.

[0080] Figure 8C is a flowchart 840 showing example operations for interpreting Power Receiver Status indicators by a Power Transmitter while the Power Transmitter is in a power state. A Power Transmitter can receive a communication message from a Power Receiver (block 844). The communication message can include a status field indicating the status of the Power Receiver. The status field can include multiple indicators of the status of the Power Receiver. In the example shown in FIG. 8C, a first indicator indicates that the Power Receiver no longer w ants to receive powder from the Powder Transmitter. A second indicator can indicate that there is no communication error between the Power Transmitter and the Power Receiver. The indicator that the Power Receive is not to receive power from the Power Transmitter canindicate that the Power Receiver is experiencing a fault or other condition that prevents Power Receiver operation.

[0081] After receiving the message from the Power Receiver indicating that the Power Transmitter should not transmit power to the Power Receiver, the Power Transmitter can stop power transmission to the Power Receiver and enter a connected state (block 846). In some aspects, the Power Transmitter stops power transmission to the Power Receiver with 20ms of receiving the communication message.

[0082] The Power Transmitter can send a message to the Power Receiver requesting transition to a power save mode (block 848). In some implementations conforming to the Ki Cordless Kitchen Wireless Power Specification, the Power Transmitter can send a “NEXT / stb” message to the Power Receiver to request transition to a standby state.

[0083] The Power Transmitter can check to determine if the Power Transmitter receives a response to the message requesting transition to the power save mode (decision block 850). For example, the Power Transmitter may request transition to a standby state. If the Power Transmitter does not receive a response to the request (“NO” branch of block 850), the Power Transmitter can enter the standby state (block 854). The Power Transmitter also releases the power reserved for the receiver to a common pool that can be used by other transmitters, for example, transmitters that share a common source.

[0084] If the Power Transmitter receives a response to the request (“YES” branch of block 850). the Power Transmitter can determine if the Power Receiver’s response to the request indicates the Power Receiver agrees to the transition to the power save mode (block 852). If the Power Receiver indicates agrees to the transition to the power save mode (“YES” branch of block 852), the Power Transmitter enters a standby state (block 854).

[0085] If the Power Receiver’s response to the request indicates that the Power Receiver does not agree to the transition to the power save mode (“NO” branch of block 852), the Power Transmitter can wait a predetermined time (block 856) and return to block 826 to repeat the request to transition to the power save mode. As an example, the Power Receiver may be experiencing a transient or temporary fault condition such as an overtemperature, overv oltage, overcurrent or other such transient event. The Power Receiver may desire to wait for the transient fault to clear, after which it can request that the Power Transmitter reenter the power state. As another example, the Power Receiver may be waiting for user action to clear the fault. After receiving the user input, the Power Receiver can request that the Power Transmitter enter the power state.

[0086] Because the Power Transmitter and Power Receiver remain in the connected state during the process of repeating the request to transition to the power save mode, communications between the Power Transmitter and Power Receiver can continue, and should the fault be cleared, the Power Transmitter and Power Receiver can resume power transmission and reception without having to enter a reinitialization state, thereby saving time and resources.

[0087] Figure 8D is a flowchart 860 showing example operations for interpreting Power Receiver Status indicators by a Power Transmitter when the Power Receiver is experiencing communications errors. In some implementations, the Power Transmitter and the Power Receiver can be in either the connected state or the power state. A Power Transmitter can receive a communication message from a Power Receiver (block 862). The communication message can include a status field indicating the status of the Power Receiver. The status field can include multiple indicators of the status of the Power Receiver. In the example shown in FIG. 8D, a first indicator indicates that the Power Receiver no longer wants to receive power from the Power Transmitter. The second indicator can indicate that there is a communication error between the Power Transmitter and the Power Receiver.

[0088] In this example, the Power Receiver uses the first indicator and the second indicator to indicate that the Power Receiver is experiencing persistent communication errors. The Power Transmitter can enter a reinitialization state (block 864). Entering the reinitialization state can be advantageous, because it can free power resources associated with the Power Receiver experiencing persistent communication errors so that the power resource can be made available for use by other Power Receivers. In some aspects, the Power Receiver may detect a persistent communication error based on a number of unsuccessful communication attempts exceeding a predetermined or configurable threshold. As an example, the Power Receiver may detect a persistent communication error after five unsuccessful communication attempts. In some aspects, the Power Receiver may detect a persistent communication error when the Power Receiver cannot make a successful communication attempt after a predetermined or configurable threshold amount of time. For example, the Power Receiver may detect a persistent communication error after 100 ms elapses without a successful communication attempt. In some aspects, the Power Transmitter monitors the status field of a communication message from the Power Receiver and checks the status field for the second indicator indicating communication errors. If the error is persistent for a threshold time, the Power Transmitter will stop power to the receiver (if in power state) and move the entire system to reinitialization state. The Power Transmitter can do this without waiting for the Power Receiver to set the first indicator indicating to stop power.

[0089] Figure 9A is a flowchart 900 showing example operations for setting Power Receiver Status indicators by a Power Receiver. The Power Receiver can determine a current operating condition of the Power Receiver (block 902). For example, the Power Receiver can determine if any faults exist in the operation of the Power Receiver. In the case that the Power Receiver is a hybrid receiver that can receive power via wireless power transfer or via a wired source (e.g., a main).

[0090] The Power Receiver can set, based on the current operating condition of the Power Receiver, a first indicator of a status field of a communication message and a second indicator of the status field of the communication message, where the first indicator indicates whether the Power Receiver can receive power from a Power Transmitter and the second indicator indicates whether a communication error has occurred (block 904).

[0091] The Power Receiver can provide the communication message to a Power Transmitter (block 906).

[0092] The Power Receiver may receive, from the Power Transmitter, a message requesting transition to a power saving mode in the case that the Power Receiver has set the first indicator to indicate that the Power Receiver cannot receive power from the Power Transmitter and the second indicator to indicate that a communication error has not occurred (block 908).

[0093] Figure 9B is a flowchart 920 showing example operations for setting Power Receiver Status indicators by a Power Receiver while the Power Receiver is in a connected state or a power state. The Power Receiver can detect that a condition exists in the operation of the Power Receiver that prevents power transfer to the Power Receiver from the Power Transmitter (block 922). For example, a fault in the operation of the Power Receiver may prevent power transfer. The Power Receiver may be a hybrid receiver that can receive power via wireless power transfer or via a wired source (e.g., a main). When receiving power via the wired source, the Power Receiver may prevent power wireless transfer from the Power Transmitter.

[0094] The Power Receiver can send a communications message to the Power Transmitter with a status field having indicators set to indicate that a condition exists that prevents power transfer to the Power Receiver (block 924). For example, the Power Receiver can set a first indicator of the status field of the communication message and a second indicator of the status field of the communication message, where the first indicator indicates whether the Power Receiver can receive power from a Power Transmitter and the second indicator indicates whether a communication error has occurred.

[0095] The Power Receiver can determine a current state of the Power Receiver (block 926). If the Power Receiver is in a connected state (“CONNECTED” branch of block 926), the Power Receiver can wait for the condition to be cleared.

[0096] If the condition has not cleared, the Power Receiver may receive a message requesting transition to a power saving mode from the Power Transmitter. For example, the Power Transmitter may send a “NEXT / stb” message to the Power Receiver in implementations conforming to the Ki Cordless Kitchen Wireless Power Specification. In some aspects, the Power Receiver itself can send a message to transition to power saving mode (not shown in flow chart).

[0097] The Power Transmitter may send a message to the Power Receiver requesting transition to a power saving mode in the case that the Power Receiver has set the first indicator to indicate that the Power Receiver cannot receive power from the Power Transmitter and the second indicator to indicate that a communication error has not occurred. The Power Receiver can check to see if such a request has been received from the Power Transmitter (block 932). If the Power Receiver has received a message requesting transition to a power saving mode (“YES” branch of block 932). the Power Receiver can respond to the request to transition to the power saving mode (block 940). If the response at block 940 indicates that the Power Receiver agrees to the transition to power saving mode (“YES” branch of block 942), the Power Receiver can enter the power saving mode (block 944). For example, the Power Receiver can enter a standby state. If the response at block 940 indicates that the Power Receiver does not agree to the transition to the power saving mode (“NO” branch of block 942), the method returns to block 924 to send a subsequent message to the Power Transmitter with the first indicator set to indicate that the Power Receiver cannot receive power from the Power Transmitter and the second indicator to indicate that a communication error has not occurred.

[0098] If the Power Receiver has not received a request to transition to the power saving mode (“NO” branch of block 932), the Power Receiver can return to block 924 to send a subsequent message to the Pow er Transmitter. As mentioned earlier, in some cases (not shown in flow chart), the Power Receiver itself can send a message requesting for transition to Power Saving mode.

[0099] If the Power Receiver is in a power state (“POWER” branch of block 926), the Powder receiver can wait for a T1 period of time (block 934). In some implementations, T1 may be in a range from 5ms - 30ms. for example, 20ms.

[0100] The Power Receiver can then enter a connected state (block 936) as the Power Transmitter stops the power transfer within T1 period.

[0101] In some aspects, the power receiver opens an electrical connection between the Power Receiver and a load of the Power Receiver (e.g., a battery). For example, the Power Receiver may wait for up to a T2 period of time (block 937) and can open a safety relay (block 938) at the end of the T2 period of time. The Power Receiver may open the safety relay within the T2 period of time once the power transfer from the Power Transmitter has stopped. In some implementations, T2 can be in a range from 25ms - 60ms, for example, 40ms.

[0102] The Power Transmitter may send a message to the Power Receiver requesting transition to a power saving mode. The Power Receiver can check to see if such a request has been received from the Power Transmitter (block 939). If the Power Receiver has received a message requesting transition to a power saving mode ("YES" branch of block 939), the Power Receiver can respond to the request to enter a power saving mode (block 940). If the Power Receiver has not received a message requesting transition to a power saving mode (“NO” branch of block 939), the method returns to block 924 to send a subsequent message to the Power Transmitter. In some cases (not show n in flow' chart), the Pow er Receiver itself can send a message requesting for transition to Power Saving mode.

[0103] If the response at block 940 indicates that the Power Receiver agrees to the transition to the power saving mode (“YES” branch of block 942), the Power Receiver can enter the power saving mode (block 944). For example, the Power Receiver can enter a standby state. If the response at block 940 indicates that the Power Receiver does not agree to the transition to a power saving mode (“NO” branch of block 942). the method returns to block 924 to send a subsequent message to the Power Transmitter.

[0104] In some implementations, the Powder Receiver can determine, at any point in the method illustrated in Figure 9B, if the condition still exists that prevents the Power Receiver from receiving power from the Po er Transmitter For example, an overtemperature, overvoltage, overcurrent, or other potentially transient condition may no longer be present. As another example, a hybrid Power Receiver may be removed from a wired power source, thereby allowing wireless pow er transfer to take place. If the condition preventing wireless power transfer has been cleared, the Power Receiver can request that the Power Transmitter and Power Receiver enter the power state.

[0105] Figure 9C is a flowchart 960 showing example operations for setting Power Receiver Status indicators by a Power Receiver when the Power Receiver is experiencing persistent communications errors. In some implementations, the operations illustrated in Figure 9C may be performed when the Power Receiver is in the connected state or the powerstate. The Power receiver can detect that there is a persistent communications error in the Power Receiver (block 962).

[0106] The Power Receiver can send a communications message to the Power Transmitter with a status field having indicators set to indicate that a condition exists that prevents power transfer to the Power Receiver, and that the Power Receiver is experiencing persistent communications error (block 964). For example, the Power Receiver can set a first indicator of the status field of the communication message to indicate that the Power Receiver is not to receive power from the Power Transmitter and set the second indicator of the status field to indicate that the Power Receiver is experiencing persistent communication errors. The two indicators can cause the Power Transmitter to enter a reinitialization state upon receipt of a message having a status field with the two indicators set. As mentioned earlier, in some cases, the Power Transmitter can monitor the communication error status indicator and if the indicator is set for more than a threshold time, then without waiting for the Power Receiver to set the first indicator indicating that the Power Receiver cannot receive power, it can stop the power (if in power state) and cause the system to enter the Reinitialization state.

[0107] Figures 10-13 are timing diagrams illustrating various state transitions that may occur during the operation of a wireless power transmission system including a Power Transmitter (e.g., Power Transmitter 102, 300) and a Power Receiver (e.g., Power Receiver 118, 400). In the examples shown in Figures 10-13, the x axis 1010 represents time. The example timing diagrams of Figures 10-13 are discussed in the context of the Ki Cordless Kitchen Wireless Power Specification. However, the techniques described herein may be readily applied to other wireless power transfer specifications.

[0108] Figure 10 is a timing 1000 diagram illustrating a first example of state transitions in a wireless power system. The timing diagram 1000 shown in FIG. 10 illustrates example state transitions in a wireless power system that occur in the absence of faults in the Power Receiver that may prevent the Power Receiver from being able to enter the power state. In the example of Figure 10, the timing diagram 1000 starts with the discover state (also referred to as the ‘"discovery phase") at time To. The discover state runs from To to Ti. While the Power Receiver and Power Transmitter are in the discovery state, a user may place an appliance (e.g.. the Power Receiver) in proximity to the Power Transmitter. The Power Transmitter detects that an object has been placed in proximity to the Power Transmitter and attempts to use NFC techniques to read NDEF data from the object. As discussed above, the NDEF data can identify the object (e.g., the appliance) as a Power Receiver eligible to receive Power from the Power Transmitter.

[0109] After the Power Transmitter recognizes the Power Receiver, the Power Transmitter and Power receiver transition to the connected state (also referred to as a “connected phase”). The connected state runs from Ti to T2. While in the connected state, the Power Transmitter and Power Receiver negotiate various power transmission parameters, including guaranteed power. The Power Transmitter and Power Receiver may exchange message as part of the power negotiation process. In the example shown in Figure 10, there are no faults occurring in the Power Receiver, thus the PSTP and COMM ERR bits are not set in the Power Receiver Status field. During the connected state, the user may turn on the appliance. The Power Receiver can send a “NEXT / pow” message to the Power Transmitter instructing the Power Transmitter to transition to the power state (also referred to as the power phase). Additionally, the Power Transmitter can obtain the Power Receiver Status. Again, no faults have occurred, so the PSTP and COMM ERR bits of the status field remain cleared. .

[0110] The power state runs from T2 onward. During the power state, power is transferred wirelessly from the Power Transmitter to the Power Receiver. Power may be managed during the power state using “ctrl” messages.

[0111] Figure 11 is a timing diagram 1100 illustrating a second example of state transitions in a wireless power system. The timing diagram 1100 shown in Figure 11 illustrates example state transitions in a wireless power system that occur when a fault in the Power Receiver prevents the Power Receiver from being able to enter the power state from the connected state. In the example of Figure 11, the timing diagram 1100 starts at time To with the Power Transmitter (and the Power Receiver) being in the standby state (also referred to as the “standby phase”). The standby state runs from To to Ti. In some cases, The Power Receiver may be absent on the interface surface and the system may enter the discovery phase when the Power Receiver is placed on the interface surface as shown in Figure 11.

[0112] The discover}' state runs from Ti to T2. The Power Transmitter detects that an object has been placed in proximity to the Power Transmitter and attempts to use NFC techniques to read NDEF data from the object. As discussed above, the NDEF data can identity' the object (e.g., the appliance) as a Power Receiver eligible to receive Power from the Power Transmitter.

[0113] After the Power Transmitter recognizes the Power Receiver, the Power Transmitter and Power receiver transition to the connected state (also referred to as a “connected phase”). The connected state runs from T2 to Ts. At the beginning of the connected state i.e., close to T2, the Power Transmitter and Power Receiver do a negotiation and the Power Transmitter reserves a negotiated power from the AC mains for the Power Receiver. This is not shown in Figure 11. In the example shown in Figure 1 1, a fault or change in status occurs at T3. As aresult of the fault, the Power Receiver indicates that a power stop is required, that is, the Power Transmitter should not start transmitting a power signal to the Power Receiver. The Power Receiver sets the PSTP bit to 1 to indicate the power stop request and clears the COMM ERR bit to indicate that there is no communication error. At time T4, the Power Transmitter receives a message from the Power Receiver where the Power Receiver status field of the message has the PSTP bit set. At time Ts, the Power Transmitter sends a “NEXT / stb” message to the Power Receiver requesting if the Power Transmitter can enter a standby state. The Power Receiver receives the NEXT / stb message, and at time Te acknowledges the message, indicating that the Power Receiver agrees to transit to the standby state. At time T7, the Power Transmitter receives the acknowledgment, and transitions to the standby state. The Power Transmitter can release the negotiated power reserved for the Power Receiver. Although not shown in Figure 11, if the operating state was power state as against the connected state shown in Figure 1 1, when the Power Receiver senses a fault, it can initiate a power stop by setting the PSTP bit in the status. This can cause the Power Transmitter to stop transmitting power to the Power Receiver and move to the connected state. After this movement to the connected state, the Power Transmitter and Power Receiver protocol follows the one from time Ts to Ts in Figure 11. In other words, the Power Transmitter can issue Next / stb to request the receiver if it can move to connected state and if the Power Receiver accepts the same it will acknowledge the request at Te and the system moves to standby by T7.

[0114] Figure 12 is a timing diagram 1200 illustrating a third example of state transitions in a wireless power system. The timing diagram 1200 shown in FIG. 12 illustrates example state transitions in a wireless power system that occur when a fault in the Power Receiver prevents the Power Receiver from being able to transition the power state. In the example of FIG. 12, when notified of the fault, the Power Transmitter issues a request that the Power Receiver enter a power saving mode. In this example, the Power Receiver respondsc'No:’ to the request.

[0115] In the example of Figure 12, the timing diagram 1200 starts at time To with the Power Transmitter being in the standby state. The standby state runs from To to Ti.

[0116] The discovery state runs from Ti to T2 when a user places an appliance (e.g.. the Power Receiver) in proximity to the Power Transmitter. The Power Transmitter detects that an object has been placed in proximity to the Powder Transmitter and attempts to use NFC techniques to read NDEF data from the object. As discussed above, the NDEF data can identify the object (e.g., the appliance) as a Power Receiver eligible to receive Power from the Power Transmitter.

[0117] After the Power Transmitter recognizes the Power Receiver, the Power Transmitter and Power receiver transition to the connected state (also referred to as a “connected phase”). The connected state runs from T2 to Ts. At the beginning of the connected state i.e., close to T2, the Power Transmitter and Power Receiver do a negotiation and the Power Transmitter reserves a negotiated power from the AC mains for the Power Receiver. This is not shown in Figure 12. In the example shown in Figure 12, a fault occurs at Ts. As a result of the fault, the Power Receiver indicates that a power stop is required. The Power Receiver sets the PSTP bit to 1 to indicate the power stop request, and clears the COMM_ERR bit to indicate that there is no communication error. At time T4, the Power Transmitter receives a message from the Power Receiver where the Pow er Receiver status field of the message has the PSTP bit set. At time Ts, the Power Transmitter sends a “NEXT / stb” message to the Power Receiver indicating that the Power Receiver should enter a standby state. In this example, the Power Receiver receives the NEXT / stb message, and at time Te replies to the message, indicating that the Powder Receiver will not transition to the standby state (NOK or “NOT OKAY” message). At time T7, the Power Transmitter receives the NOK message from the Power Transmitter, and waits for action from the Power Receiver. For example, the Power Transmitter may wait for the Power Receiver to clear a transient fault, be unplugged from a wired source, or for a user action on the Power Receiver. The Pow er Transmitter can periodically repeat the NEXT / stb message, and if a NOK message is received from the Power Receiver, the Power Transmitter can continue to wait for action on the Power Receiver. If the Power Transmitter receives an ACK or fails to receive a response, the Power Transmitter can enter the standby state. Although not shown in Figure 12, if the operating state w as the pow er state as against connected state shown in Figure 12, when the Pow er Receiver senses a fault, it can initiate a power stop by setting the PSTP bit in the status. This will make the Power Transmitter stop power to the receiver and move to connected phase. Post this movement to connected phase, the Power Transmitter and Power Receiver protocol follows the one from time Ts to Ts in Figure 12. i.e., the Power Transmitter can issue a Next / stb command to request the Power Receiver to transition to the connected state. If the Po er Receiver rejects the request, it can reject the request at T6. For example, the Power Receiver can send a “not ok” (NOK) at Te. In some cases, if the Power Transmitter has waited for a threshold time with the Power Receiver rejecting the request to transition to standby mode, The Pow er Transmitter can voluntarily enter standby mode without having to wait for the Power Receiver’s permission.

[0118] Figure 13 is atiming diagram 1300 illustrating a fourth example of state transitions in a wireless power system. The timing diagram 1300 shown in FIG. 13 illustrates examplestate transitions in a wireless power system in which the Power Receiver detects persistent communications errors. The x axis 1310 is not necessarily the same time scale as x axis 1010.

[0119] In the example of Figure 13 the timing diagram 1300 starts at time To with the PowerTransmitter and the Power Receiver being in the standby state. The standby state runs from To to Ti.

[0120] The discovery state runs from Ti to T2 when a user places an appliance (e.g., the Power Receiver) in proximity to the Power Transmitter. The Power Transmitter detects that an object has been placed in proximity to the Power Transmitter and attempts to use NFC techniques to read NDEF data from the object. As discussed above, the NDEF data can identify the object (e.g., the appliance) as a Power Receiver eligible to receive Power from the Power Transmitter.

[0121] After the Power Transmitter recognizes the Power Receiver, at time T2 the Power Transmitter and Power receiver transition to the connected state (also referred to as a “connected phase’'). The Power Transmitter and Power Receiver do a Power Negotiation at the beginning of connected phase i.e., close to T2 (not shown in Figure 13). In the example shown in Figure 13, the Power Receiver detects that there are persistent communications errors. As a result of the communications errors, the Power Receiver indicates that a power stop is required. The Power Receiver sets the PSTP bit to 1 to indicate the power stop request, and also sets the COMM_ERR bit to indicate that there are persistent communications errors. At time T4, the Power Transmitter receives a message from the Power Receiver where the Power Receiver status field of the message has the PSTP bit set and the COMM_ERR bit set. In some aspects, the Power Transmitter waits for 20ms and at time T5, the Power Transmitter transitions to the reinitialization state. Following reinitialization procedures that run from time Tx to T(x+1), the Power Transmitter can transition to the discovery state. The Power Receiver is also reinitialized and moves to discovery state as well. In some aspects, while doing Reinitialization the Power Transmitter releases the power reserved for the Power Receiver.

[0122] Figure 14 shows a block diagram of an example apparatus for use in wireless power system. In some implementations, the apparatus 1400 may be a Power Transmitter (such as the Power Transmitter 102) described herein. In some implementations, the apparatus 1400 may be an example of any one of the Power Transmitters 102 or 300, or any one of the power controllers 108 described with reference to any of the Figures 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 1406. Memory 1406 may be system memory or any one or more of the possible realizationsof computer-readable media described herein. The apparatus 1400 also can include a bus 1411 (such as PCI. ISA, PCI-Express. HyperTransport®, InfiniBand®. NuBus,® AHB, AXI, etc.).

[0123] The apparatus 1400 may include one or more controller(s) 1462 configured to manage multiple primary or secondary coils (such as a coil array 1464). In some implementations, the controller(s) 1462 can be distributed within processor 1402, the memory 1406, and the bus 1411. The controller(s) 1462 may perform some or all of the operations described herein. For example, the controller(s) 1462 may be a transmission controller, such as any of the transmission controllers described herein.

[0124] The memory 1406 can include computer instructions executable by the processor 1402 to implement the functionality or techniques of the implementations described with reference to Figures 1-7. 8A-8C, 9A, 9B, and 10-12. 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 co-processor on a peripheral device or card, etc. Further, realizations may include fewer or additional components not illustrated in Figure 14. The processor 1402. the memory 1406. and the controller(s) 1462 may be coupled to the bus 1411. Although illustrated as being coupled to the bus 1411, the memory 1406 may be coupled to the processor 1402.

[0125] Figures 1-14 and the operations described herein are examples meant to aid in understanding example implementations and should not be used to limit the potential implementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently.

[0126] The discussion above has been presented in the context of a Power Receiver Status field having a first indicator and a second indicator that can be combined as an indicator that a Power Receiver can receive power from a Power Transmitter. However, the techniques may be readily adapted to a separate bit that serves as an indicator that a Power Receiver can receive power from a Power Transmitter. For example, a "‘power reception enable" bit in the Power Receiver Status may be used instead of the PSTP and COMM ERR bits. Further, the techniques described herein can be applied using other combinations of bits of the Power Receiver Status field.

[0127] Additionally, the discussion above has been presented in the context of wireless power systems in wireless kitchen environments. However, the techniques disclosed herein can be readily applied to other environments. For example, the techniques discussed hereincan be applied to light electric vehicles (EVs) that generally include vehicles having less than five kWh batteries and less than lOkW engine power. Examples of such vehicles include micromobility vehicles such as electric bicycles and electric kick-scooters, electric powered two or three wheelers (ePTW) such as e-mopeds, e-scooters, and e-rickshaws; MicroEVs such as electric microcars, low-speed electric vehicles, neighborhood EVs (NEVs), electric quadricycles: electric transporters such a e-forklifts, e-golfcarts with less than 120V batteries.

[0128] Other environments include automated guided vehicles (AGVs), commercial drones, yard appliances such as electric lawn mowers, and larger household appliances such as vacuum cleaners.

[0129] 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 descnbed herein, examples include any combination of the following implementation options (enumerated as clauses for clarity).CLAUSES

[0130] Clause 1. A method of a Power Transmitter (PTx) in a wireless po er system, including: receiving, from a Power Receiver (PRx) in the wireless power system, a communication message including a status field indicating status of the Power Receiver, the status field including a plurality of indicators of the status of the Power Receiver; and controlling a state transition based on a first indicator of the status field that indicates whether the Power Receiver can receive power from the Power Transmitter and a second indicator of the status field that indicates whether a communication error has occurred.

[0131] Clause 2. The method of clause 1, further including: providing, to the Power Receiver by the Pow er Transmitter, a first message requesting transition to a standby state when the first indicator has a first value that indicates that the Power Receiver cannot receive power from the Power Transmitter, the second indicator has a second value that indicates that a communication error has not occurred, and a current state of the Power Transmitter is a connected state.

[0132] Clause 3. The method of clause 2, further including: receiving a response to the first message from the Power Receiver; and transitioning, by the Pow er Transmitter, from theconnected state to the standby state when the response indicates that the Power Receiver agrees to the transition to the standby state.

[0133] Clause 4. The method of clause 2, further including: transitioning, by the Power Transmitter, from the connected state to the standby state when the Power Transmitter fails to receive a response to the first message from the Power Receiver.

[0134] Clause 5. The method of clause 2, further including: receiving a response to the first message from the Power Receiver; and when the response to the first message from the Power Receiver indicates that the Power Receiver does not agree to the transition to the standby state, the Power Transmitter performs operations including: waiting for a predetermined time period, and providing, to the Power Receiver by the Power Transmitter, a second message requesting transition to the standby state.

[0135] Clause 6. The method of clause 1, further including: when the first indicator has a first value that indicates that the Power Receiver cannot receive power from the Power Transmitter, the second indicator has a second value that indicates that a communication error has not occurred, and a current state of the Power Transmitter is a power state, the Power Transmitter performs operations including: ending power transfer to the Power Receiver by the Power Transmitter, transitioning, by the Power Transmitter, from the power state to a connected state; and providing, to the Power Receiver, a first message requesting transition to a standby state.

[0136] Clause 7. The method of clause 6, further including: receiving a response to the first message from the Power Receiver; and transitioning, by the Power Transmitter, from the connected state to the standby state when the response indicates that the Power Receiver agrees to the transition to the standby state.

[0137] Clause 8. The method of clause 6, further including: transitioning, by the Power Transmitter, from the power state to the standby state when the Power Transmitter fails to receive a response to the first message from the Power Receiver.

[0138] Clause 9. The method of clause 6, further including: receiving a response to the first message from the Power Receiver; and when the response to the first message indicates that the Power Receiver does not agree to the transition to the standby state, the Power Transmitter performs operations including: waiting for a predetermined time period, and providing, to the Power Receiver, a second message requesting transition to the standby state.

[0139] Clause 10. The method of any of clauses 1-9. further including: transitioning, by the Power Transmitter, to a reinitialization state when the first indicator has a first value thatindicates that the Power Receiver cannot receive power from the Power Transmitter, and the second indicator has a second value that indicates that the communication error has occurred.

[0140] Clause 11. A method of a Power Receiver in a wireless power system, including: determining, by the Power Receiver, a current operating condition of the Power Receiver; setting, based on the current operating condition of the Power Receiver, a first indicator of a status field of a communication message and a second indicator of the status field of the communication message, where the first indicator indicates whether the Power Receiver can receive power from a Power Transmitter and the second indicator indicates whether a communication error has occurred; providing the communication message to the Power Transmitter of the wireless power system; and receiving, from the Power Transmitter, a message requesting transition to a standby state when the first indicator has a first value that indicates that the Power Receiver cannot receive power from the Power Transmitter and the second indicator has a second value that indicates that a communication error has not occurred.

[0141] Clause 12. The method of clause 11, where a current state of the Power Receiver includes a connected state, where the current operating condition of the Power Receiver includes a fault condition preventing the Power Receiver from transitioning from the connected state to a power state, and where setting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field includes: setting the first indicator to the first value that indicates that the Power Receiver cannot receive power from the Power Transmitter and setting the second indicator to the second value that indicates that a communication error has not occurred.

[0142] Clause 13. The method of clause 12, further including: continuing to set the first indicator of the status field in one or more first subsequent communications messages sent to the Power Transmitter to the first value that indicates that the Power Receiver cannot receive power from the Power Transmitter while the current operating condition includes the fault condition, where setting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field of the communication message includes setting the first indicator of the status field in one or more second subsequent communications messages sent to the Power Transmitter to a third value that indicates that the Power Receiver can receive power from the Power Transmitter when the current operating condition indicates the fault condition has been cleared.

[0143] Clause 14. The method of clause 11, where the Power Receiver is capable of receiving power via a wired source and via wireless power transmission from the Power Transmitter, where a current state of the Power Receiver includes a connected state, wheresetting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field includes: setting the first indicator to the first value that indicates that the Power Receiver cannot receive power from the Power Transmitter and setting the second indicator to the second value that indicates that a communication error has not occurred when the Power Receiver is receiving power via the wired source.

[0144] Clause 15. The method of clause 14, further including: continuing to set the first indicator of the status field in one or more first subsequent communications messages sent to the Power Transmitter to the first value that indicates that the Power Receiver cannot receive power from the Power Transmitter while the Power Receiver is receiving power from via the wired source; and setting the first indicator of the status field in one or more second subsequent communications messages sent to the Pow er Transmitter to a third value that indicates that the Power Receiver can receive power from the Power Transmitter when the Power Receiver is no longer receiving power via the wired source.

[0145] Clause 16. The method of clause 11, where a current state of the Power Receiver includes a power state, where the current operating condition of the Power Receiver includes a fault condition, and where setting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field includes: setting the first indicator to the first value that indicates that the Power Receiver cannot receive power from the Power Transmitter and setting the second indicator to the second value that indicates that a communication error has not occurred.

[0146] Clause 17. The method of clause 16, further including: transitioning from the power state to a connected state after a predetermined first time period has elapsed.

[0147] Clause 18. The method of clause 17, further including: opening an electrical connection from the Power Receiver to a load after a predetermined second time period has elapsed.

[0148] Clause 19. The method of clause 18, where the predetermined first time period includes a first time value within a first range including 5ms - 40ms and the predetermined second time period includes a second time value within a second range including 25ms-60ms.

[0149] Clause 20. The method of any one of clauses 11-19, further including: providing, to the Pow er Transmitter, a response to the message requesting transition to the standby state.

[0150] Clause 21. The method of any one of clauses 11-20, where the current operating condition includes a persistent communication error, where setting, based on the current operating condition of the Pow er Receiver, the first indicator of the status field and the secondindicator of the status field includes: setting the first indicator to a value that indicates that the Power Receiver cannot receive power from the Power Transmitter and setting the second indicator to a value that indicates that a communication error has occurred, where the Power Transmitter is configured to transition to a reinitialization state when the first indicator is set to the first value and the second indicator is set to the second value.

[0151] Clause 22. A Power Transmitter, including: a controller configured to perform any one of the methods of clauses 1-10.

[0152] Clause 23. A Power Receiver, including: a controller configured to perform any one of the methods of clauses 11-21.

[0153] Another innovative aspect of the subject matter described in this disclosure can be implemented as a computer-readable medium having stored therein instructions which, when executed by a processor, causes the processor to perform any one of the above-mentioned methods or features described herein.

[0154] Another innovative aspect of the subject matter described in this disclosure can be implemented as a system having means for implementing any one of the above-mentioned methods or features described herein.

[0155] As used herein, a phrase referring to “at least one of’ or “one or more of’ a list of items refers to any combination of those items, including single members. For example, “at least one of: a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c. and a combination of a and b and c.

[0156] The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementations disclosed 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.

[0157] The hardware and data processing apparatus used to implement the various illustrative components, logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes, operations and methods may be performed by circuitry that is specific to a given function.

[0158] 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.

[0159] 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.

[0160] 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 aclaimed 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.

[0161] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, 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.

Claims

CLAIMSWhat is claimed is:

1. A method of a Power Transmitter (PTx) in a wireless power system, comprising: receiving, from a Power Receiver (PRx) in the wireless power system, a communication message including an indicator that indicates that a communication error has occurred; detecting a persistent communication error based, at least in part, on the indicator; and transitioning to a reinitialization state when the persistent communication error has occurred.

2. The method of claim 1 , wherein the indicator is set to indicate that the communication error has occurred in response to detecting a plurality of unsuccessful communication attempts.

3. The method of claim 2, wherein the plurality’ of unsuccessful communication attempts comprises five unsuccessful communication attempts.

4. The method of claim 1, wherein: detecting the persistent communication error comprises detecting the persistent communication error after a threshold number of communication errors have occurred.

5. The method of claim 1, wherein the indicator comprises a first indicator included in a status field of the communication message, wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, and wherein the method further comprises transitioning to the reinitialization state when the first indicator indicates that the communication error has occurred and the second indicator indicates that the Power Receiver cannot receive power from the Power Transmitter.

6. The method of any of claims 1-4, wherein the indicator comprises a first indicator included in a status field of the communication message, and wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, the method further comprising:providing, to the Power Receiver by the Power Transmitter, a first message requesting transition to a standby state when the first indicator has a first value that indicates that the communication error has not occurred, the second indicator has a second value that indicates that the Power Receiver cannot receive power from the Power Transmitter, and a current state of the Power Transmitter is a connected state.

7. The method of claim 6, further comprising: transitioning, by the Power Transmitter, from the connected state to the standby state when the Power Transmitter receives a response to the first message that indicates that the Power Receiver agrees to the transition to the standby state or when the Power Transmitter fails to receive the response to the first message from the Power Receiver.

8. The method of claim 6, further comprising: receiving a response to the first message from the Power Receiver; and when the response to the first message from the Power Receiver indicates that the Power Receiver does not agree to the transition to the standby state, the Power Transmitter performs operations comprising: waiting for a predetermined time period, and providing, to the Power Receiver by the Power Transmitter, a second message requesting transition to the standby state.

9. The method of any of claims 1-4, wherein the indicator comprises a first indicator included in a status field of the communication message, and wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, the method further comprising: when the first indicator has a first value that indicates that the communication error has not occurred, the second indicator has a second value that indicates that the Power Receiver cannot receive power from the Power Transmitter, and a current state of the Power Transmitter is a power state, the Power Transmitter performs operations comprising: ending power transfer to the Power Receiver by the Power Transmitter, transitioning, by the Power Transmitter, from the power state to a connected state; and providing, to the Power Receiver, a first message requesting transition to a standby state.

10. The method of claim 9, further comprising: transitioning, by the Power Transmitter, from the connected state to the standby state when the Power Transmitter receives a response to the first message from the Power Receiver that indicates that the Power Receiver agrees to the transition to the standby state or when the Power Transmitter fails to receive the response to the first message from the Power Receiver.

11. The method of claim 9, further comprising: when a response to the first message indicates that the Power Receiver does not agree to the transition to the standby state, the Power Transmitter performs operations comprising: waiting for a predetermined time period, and providing, to the Power Receiver, a second message requesting transition to the standby state.

12. A method of a Power Receiver in a wireless power system, comprising: determining, by the Power Receiver, a current operating condition of the Power Receiver; setting, based on the current operating condition of the Power Receiver, an indicator that indicates whether a communication error has occurred; and providing a communication message including the indicator to a Power Transmitter of the wireless power system; wherein the indicator is set to indicate that the communication error has occurred in response to detecting that the current operating condition comprises a persistent communication error.

13. The method of claim 12, wherein the detecting that the current operating condition comprises the persistent communication error comprises detecting a threshold number of unsuccessful communication attempts.

14. The method of any of claims 12 or 13, wherein the indicator comprises a first indicator included in a status field of the communication message, and wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, the method further comprising setting the second indicator to indicatethat the Power Receiver cannot receive power from the Power Transmitter in response to detecting that the current operating condition comprises the persistent communication error.

15. The method of any of claims 12 or 13, wherein the indicator comprises a first indicator included in a status field of the communication message, and wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter. the method further comprising receiving, from the Power Transmitter, a message requesting transition to a standby state when the status field in the message provided to the Power Transmitter comprises the first indicator set to a first value that indicates that the communication error has not occurred and the second indicator set to a second value that indicates that the Power Receiver cannot receive power from the Power Transmitter.

16. The method of claim 12 or 13, wherein a current state of the Power Receiver comprises a connected state, wherein the current operating condition of the Power Receiver comprises a fault condition preventing the Power Receiver from transitioning from the connected state to a power state, wherein the indicator comprises a first indicator, wherein the first indicator is included in a status field of the communication message, wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, and wherein setting, based on the cunent operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field comprises: setting the first indicator to a first value that indicates that the communication error has not occurred and setting the second indicator to a second value that indicates that the Power Receiver cannot receive power from the Power Transmitter .

17. The method of claim 16, further comprising: continuing to set the second indicator of the status field in one or more first subsequent communications messages sent to the Power Transmitter to the second value that indicates that the Power Receiver cannot receive power from the Power Transmitter while the current operating condition comprises the fault condition; and setting the second indicator in one or more second subsequent communications messages sent to the Power Transmitter to a third value that indicates that the Power Receivercan receive power from the Power Transmitter when the current operating condition indicates the fault condition has been cleared.

18. The method of claim 12 or 13, wherein the indicator comprises a first indicator, wherein the first indicator is included in a status field of the communication message, wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, wherein the Power Receiver is capable of receiving power via a wired source and via wireless power transmission from the Power Transmitter, and wherein setting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field comprises: setting the second indicator to indicate that the Power Receiver cannot receive power from the Power Transmitter when the Power Receiver is receiving power via the wired source.

19. The method of claim 18, further comprising: continuing to set the second indicator of the status field in one or more first subsequent communications messages sent to the Power Transmitter to indicate that the Power Receiver cannot receive power from the Power Transmitter while the Power Receiver is receiving power from via the wired source; and setting the second indicator of the status field in one or more second subsequent communications messages sent to the Power Transmitter to indicate that the Power Receiver can receive power from the Power Transmitter when the Power Receiver is no longer receiving power via the wired source.

20. The method of claims 12 or 13, wherein the indicator comprises a first indicator, wherein the first indicator is included in a status field of the communication message, wherein the status field further includes a second indicator that indicates whether the Power Receiver can receive power from the Power Transmitter, wherein a current state of the Power Receiver comprises a power state, wherein the current operating condition of the Power Receiver comprises a fault condition, and wherein setting, based on the current operating condition of the Power Receiver, the first indicator of the status field and the second indicator of the status field comprises: setting the first indicator to indicate that the communication error has not occurred and setting the second indicator to indicate that the Power Receiver cannot receive power from the Power Transmitter.

21. The method of claim 20, further comprising: transitioning from the power state to a connected state after a predetermined first time period has elapsed.

22. The method of claim 21, further comprising: opening an electrical connection from the Power Receiver to a load after a predetermined second time period has elapsed.

23. The method of claim 22, wherein the predetermined first time period comprises a first time value within a first range comprising 5ms - 40ms and the predetermined second time period comprises a second time value within a second range comprising 25ms-60ms.

24. The method of any one of claims 15-23, further comprising: setting the second indicator to a value that indicates that the Power Receiver cannot receive power from the Power Transmitter when the current operating condition comprises the persistent communication error.

25. A Power Transmitter, comprising: a controller configured to perform any one of the methods of claims 1-11.

26. A Power Receiver, comprising: a controller configured to perform any one of the methods of claims 12-24.

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