Operation Phases in a Wireless Power Transfer (WPT) System

Abstract

The present disclosure provides a system, method, and apparatus for managing phase transitions in a wireless power transfer (WPT) system. For example, the transition between a connection phase and a power transfer phase can be adjusted in relation to a change in a protection switch (one or more switches) of a power receiver. The protection switch can separate or couple a secondary coil of the power receiver to a power receiving circuit (such as a load or a rectifier). A first position of the protection switch can open a circuit including the secondary coil and the power receiving circuit. A second position of the protection switch can close the circuit such that the secondary coil can receive wireless power and supply the wireless power to a load during a power transfer phase. The present disclosure also describes a method by which the WPT system can temporarily pause wireless power transfer while remaining in the power transfer phase.

Description

Technical Field

[0001] The present disclosure generally relates to wireless power, and more specifically, in some implementations, to the operating phases in a wireless power transmission system.

Background Art

[0002] Techniques have been developed to enable wireless transmission of power from a power transmitter to a power receiver. Examples of power receivers can include, among other examples, several types of mobile devices, small electronic devices, computers, tablets, gadgets, appliances (such as cordless blenders, kettles, mixers, etc.), and several types of large electronic devices. Wireless power transmission may sometimes be referred to as non-contact power transmission or contactless power transmission. Wireless power can be transmitted using inductive coupling or resonant coupling between a primary coil of the power transmitter and a secondary coil of the power receiver. For example, the power transmitter can include a primary coil that generates a magnetic field. The magnetic field can induce an electromotive force in the secondary coil of the power receiver when the secondary coil is placed in proximity to the primary coil. In this configuration, the magnetic field can transmit power wirelessly to the secondary coil.

[0003] A wireless power transmission system can operate in different operating phases such as an idle phase, a configuration phase, a connection phase, and a power transmission phase. As different types of power receivers and power transmitters are developed, they can implement features that go beyond conventional wireless power transmission. The power receivers and power transmitters need to adjust the transitions between various operations based on the newly developed features.

Summary of the Invention

Means for Solving the Problems

[0004] The systems, methods, and apparatuses of the present disclosure each have several innovative aspects, and only one of which alone bears the desirable attributes disclosed herein.

[0005] One innovative aspect of the subject matter described in this disclosure can be implemented as a power receiver (PRx) of a wireless power transfer (WPT) system. The PRx can include a secondary coil configured to receive wireless power from a power transmitter (PTx) during at least a portion of an operating power transfer phase. The PRx can include a protection switch disposed between the secondary coil and a load associated with the PRx, and the protection switch is typically in a first position configured to open a circuit including the secondary coil prior to the power transfer phase. The PRx can include a wireless communication unit and a PRx controller. The PRx controller can be configured to determine that the PTx is in an operating connection phase with the PRx. The PRx controller can be configured to generate a switch signal configured to change the protection switch to a second position during the connection phase, and the second position is configured to close a circuit including the secondary coil. The PRx controller can be configured to cause the wireless communication unit to communicate a request for power for the PTx to transmit wireless power after the protection switch has been changed to the second position. The PRx controller can be configured to transition from the connection phase to the power transfer phase.

[0006] Another innovative aspect of the subject matter described in this disclosure can be implemented as the PTx of a WPT system. The PTx can include an inverter configured to generate a wireless power signal. The PTx can include a primary coil operably coupled to the inverter and configured to transmit the wireless power signal with the transmission of wireless power to the secondary coil of the PRx. The PTx may include a wireless communication interface configured to communicate with the wireless communication unit of the PRx. The PTx can include a PTx controller. The PTx controller can be configured to determine that the PRx is in the connection phase of operation with the PTx and, via the wireless communication interface, receive a power request for the PTx to transmit wireless power. The power request can indicate that the PRx has changed a protection switch to close a circuit including the secondary coil and the load of the PRx. The PTx controller can be configured to cause the inverter to generate a wireless power signal for transmitting wireless power in response to the power request. The PTx controller can be configured to transition from the connection phase of operation to the power transmission phase.

[0007] Another innovative aspect of the subject matter described in this disclosure can be implemented as the PRx of a WPT system. The PRx can include a secondary coil operably coupled to a load associated with an on-cycle and an off-cycle, the secondary coil being configured to receive wireless power from the PTx during at least a portion of the power transmission phase of operation. The PRx can include a wireless communication unit and a PRx controller. The PRx controller can be configured to cause the wireless communication unit to communicate with the PTx to enter a power transmission phase in which the PTx can transmit wireless power. The PRx controller can be configured to cause the wireless communication unit to communicate a non-zero power request associated with causing the PTx to transmit wireless power with the on-cycle of the load. The PRx controller can be configured to cause the wireless communication unit to communicate a zero power request message associated with pausing the transmission of wireless power with the off-cycle of the load to the PTx while remaining in the power transmission phase.

[0008] Another innovative aspect of the subject matter described in this disclosure can be implemented as the PTx of a WPT system. The PTx can include an inverter configured to generate a wireless power signal. The PTx can include a primary coil operably coupled to the inverter and configured to transmit the wireless power signal with the transmission of wireless power to the PRx of the operation during at least a portion of the power transmission phase. The PTx can include a wireless communication interface configured to receive a power request from the PRx. The PTx can include a PTx controller. The PTx controller can be configured to communicate with the PRx through the wireless communication interface to enter the power transmission phase. The PTx controller can be configured to cause the inverter to generate a wireless power signal for transmitting wireless power for the load of the PRx during the power transmission phase when the power request is a non-zero power request. The PTx controller can be configured to pause the generation of the wireless power signal for transmitting wireless power for the load during the power transmission phase when the power request is a zero power request.

[0009] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method for the PRx in a WPT system. The method can include determining that the PTx is in an operation connection phase with the PRx. The method can include changing a protection switch of the PRx from a first position to a second position during the connection phase, the protection switch being disposed between a secondary coil of the PRx and a load associated with the PRx, the first position being configured to normally open a circuit including the secondary coil before the power transmission phase of the operation, and the second position being configured to close the circuit. The method can include communicating a power request to the PTx after the protection switch is changed to the second position. The method can include transitioning from the connection phase to the power transmission phase and receiving wireless power from the PTx during at least a portion of the power transmission phase.

[0010] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method of PRx in a WPT system. The method can include coupling a secondary coil of the PRx to a load associated with an on-cycle and an off-cycle, where the secondary coil is configured to receive wireless power from a power transmitter (PTx) during at least a portion of the power transmission phase of operation. The method can include communicating with the PTx to cause the PTx to enter a power transmission phase in which it can transmit wireless power to the PRx. The method can include communicating a non-zero power request to the PTX in association with an on-cycle of the load, where the non-zero power request is associated with causing the PTx to transmit wireless power. The method can include communicating a zero power request message to the PTX in association with an off-cycle of the load, where the zero power request is associated with causing the PTx to pause transmission of wireless power while remaining in the power transmission phase.

[0011] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method of PTx in a WPT system. The method can include determining that the PRx is in a connection phase of operation with the PTx, at least partially based on communication with the PRx. The method can include receiving a power request from the PRx, where the power request is associated with requesting transmission of wireless power from the PTx to the PRx, and the power request represents an indication that the PRx has changed a protection switch to close a circuit including the secondary coil of the PRx. The method can include causing an inverter to generate a wireless power signal for transmitting wireless power in response to the power request. The method can include transitioning from a connection phase of operation to a power transmission phase and transmitting the wireless power signal to transmit wireless power to the secondary coil of the PRx.

[0012] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method of the PTx in a WPT system. The method can include communicating with the PRx to enter a power transmission phase of operation. The method can include receiving a power request from the PRx, where the power request is for controlling the transmission of wireless power for the load of the PRx during at least a portion of the power transmission phase. The method can include, when the power request is a non-zero power request, causing an inverter of the PTx to generate a wireless power signal for transmitting wireless power for the load in the power transmission phase. The method can include, when the power request is a zero power request, including pausing the generation of the wireless power signal for the load at the inverter while remaining in the power transmission phase.

[0013] 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

[0014]

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[0015] Note that the relative dimensions of the following figures may not be drawn to scale. Similar reference numerals and signs in the various drawings indicate similar elements.

DETAILED DESCRIPTION OF THE INVENTION

[0016] A wireless power transfer (WPT) system can include a power transmitter (sometimes referred to as a "wireless power transmission device", "power transmitter", or "PTx") and a power receiver (sometimes referred to as a "wireless power reception device", "power receiver", or "PRx"). The power transmitter can include one or more primary coils that transmit wireless energy (as a wireless power signal that generates a magnetic field) to one or more corresponding secondary coils of the power receiver. The primary coil refers to the wireless energy source of the power transmitter (such as inductive or magnetic resonance energy that generates a magnetic field). The secondary coil disposed in the power receiver can receive wireless energy via the magnetic field. Wireless power transfer refers to the transmission and reception of wireless energy. The wireless energy can be used to power a load or other component associated with the power receiver. Thus, the wireless energy can be called wireless power.

[0017] The WPT system operates in different phases such as an idle phase, a configuration phase, a connection phase, and a power transfer phase. For example, the power transmitter typically starts in the idle phase after being turned on. Turning on the power transmitter refers to supplying power to a controller, a communication unit, a driver, or other components of the power transmitter except for the primary coil. The primary coil is energized only in the power transfer phase after communication between the power receiver and the power transmitter. When new features are introduced into the design of the power transmitter, the transition between some phases may become unclear. For example, the new feature can include a protection switch in a circuit including the secondary coil. The first position of the protection switch can prevent the secondary coil from inducing a voltage from the magnetic field. The second position of the protection switch can enable the secondary coil to receive an induced voltage from the magnetic field. The present disclosure includes an explanation of several types of protection switches. It is necessary to manage the transition between several operating phases in cooperation with the position of the protection switch. Similarly, the transition between operating phases can depend on other new features such as a foreign object detection sequence, a start switch controlled by a user, a load switch associated with the load, the availability of a wired power source, or a specific type of load, among other examples.

[0018] The present disclosure provides a system, method, and apparatus for managing phase transitions in a WPT system. In some implementations, the transition between the connection phase and the power transmission phase (or vice versa) can be adjusted in relation to a change in a protection switch of the power receiver. The present disclosure describes how communication can be configured to adjust the phase transition associated with the protection switch. Examples of the present disclosure can be used in various types of control architectures, including those where the power receiver implements a variable load and a load controller communicates power commands to directly control wireless power transmission, as well as those where the power receiver has a simple load such as a heater load with a single power setting and depends on the control loop of the power transmitter. The present disclosure also describes a method by which wireless power transmission can be temporarily paused while the WPT system remains in the power transmission phase. Such techniques can be useful for devices including loads having on and off cycles. In some implementations, the power receiver can control wireless power transmission for the load without the need to transition from the power transmission phase. For example, a "zero power message" or a "non-zero power message" can be used to disable or enable wireless power transmission, respectively, during the power transmission phase.

[0019] In some implementations, the power receiver can include an energy harvester configured to collect bias power from an out-of-band wireless communication signal. The present disclosure describes how wireless communication signals can be transmitted by the power transmitter during various operating phases so that the power receiver can collect bias power. Bias power can be used to operate one or more components of the power receiver, such as a wireless communication unit, a controller, or a protection switch, among other examples. Since bias power may be required to operate the power receiver while wireless power transmission is disabled, the present disclosure describes several examples in which the wireless communication signal (for bias power) can be adjusted in various operating phases or states of wireless power transmission.

[0020] Certain implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. A power receiver can adjust the protection features of a protection switch with the timing of wireless power transmission. A power transmitter can rely on the communications or protocols described herein to ensure that wireless power transmission is possible at an appropriate time, such as when the protection switch is in a second position. Using phase shift techniques in this disclosure, a power receiver can implement a protection switch for protecting components of a power transmitter while also assisting in the use of wireless power transmission when the wireless power is needed by a load.

[0021] The following description relates to particular implementations for the purpose of illustrating innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented with any means, apparatus, system, or method for wireless power transmission.

[0022] FIG. 1 shows a diagram of an exemplary wireless power transmission system 100. The wireless power transmission system can include a power transmitter 102 and a power receiver 104. The power transmitter 102 includes a primary coil 110. The primary coil 110 can be associated with a power signal generator (not shown). For example, the power signal generator can include an inductor or other component that generates a wireless power signal applied to the primary coil 110. The primary coil 110 can be a wire coil that transmits the wireless power signal as wireless power (sometimes referred to as wireless energy). The primary coil 110 can transmit wireless energy using induction or a magnetic resonance field. Using the wireless power signal, the primary coil 110 can generate a primary magnetic field during wireless power transmission. The power transmitter 102 can also include a power transmitter controller (PTx controller, not shown) that controls components of the power transmitter 102 including those that generate the wireless power signal. For example, the PTx controller can determine an operating point (such as voltage or current) and control the power signal generator to generate a wireless power signal according to the operating point. When the primary coil 110 transmits wireless power 115, the primary coil generates a magnetic field that induces a voltage in the secondary coil 120 of the power receiver 104.

[0023] The power receiver 104 can include a secondary coil 120 configured to receive the wireless power 115. When the secondary coil 120 is aligned with the primary coil 110, the secondary coil 120 can generate an induced voltage based on the wireless power 115 received from the primary coil 110. In some implementations, a capacitor (not shown) can be in series between the secondary coil 120 and a power receiving circuit (not shown). In some implementations, the power receiving circuit can include a rectifier (if present) or other components for conditioning the wireless power and supplying the wireless power for use by a load (not shown). In some implementations, the power receiving circuit can exclude the rectifier and supply the wireless power directly to the load. In some implementations, the load can be integrated into the device including the power receiver 104. In some implementations, the power receiver 104 can supply the wireless power to an external load associated with the power receiver 104. The power receiver 104 can include an electrical reception controller (PRx controller, not shown) configured to control the wireless power transmission operating state with a corresponding PTx controller of the power transmitter 102. The power receiver 104 can also include, among other examples, a wireless communication unit, an energy harvester, as further described herein.

[0024] As described herein, the wireless power signal 115 can be used to wirelessly transmit power using the electromotive force of the secondary coil 120. When the secondary coil 120 is connected to other components (such as a power receiving circuit or a load) associated with the power receiver 118, the electromotive force can generate a voltage and a current in the secondary coil 120. However, there may be times when the power receiver 118 is not ready to use the power, or when the power may damage other components of the power receiver 118. To prevent damage to other components or to disable unintentional wireless power transmission, the power receiver 104 can include one or more switches (not shown) configured to open the circuit including the secondary coil 120. Opening the circuit can also be referred to as disconnecting or separating the secondary coil 120 from the power receiving circuit. Thus, even if a magnetic field is induced in the vicinity of the secondary coil 120, the secondary coil 120 does not conduct current because it is disconnected from the power receiving circuit and the load. One or more switches can prevent an induced voltage from flowing through the power receiving circuit via the secondary coil 120. The present disclosure includes several options for the placement, structure, and operation of the switches.

[0025] The power receiver 104 can be associated with a device (among other examples, such as cordless countertop appliances), and can be intended to operate on a wireless power transmission surface configured with one or more primary coils (for example, on a kitchen countertop, on a stove, or on a hob). FIG. 1 shows some examples 140 of devices that can be used with the power transmitter 102. For example, the device can be a kettle 155, a pot 165, or a blender 175. Other types of devices that can include a power receiver can include, among other examples, slow cookers, rice cookers, coffee machines, toasters, broilers, griddles, electric pans, and any type of device configured to heat liquids or food.

[0026] The power transmitter 102 can be included in kitchen appliances such as a cooking counter or a hob. For example, in some implementations, the hob can include several positions for placing an object. At least one of the positions can include a power transmitter 102 that assists in wireless power transmission to a device including the power receiver 104. In some implementations, the power transmitter 102 can be integrated into a hob that is essentially portable. For example, a portable hob can include a battery or be capable of an external power source for powering the power transmitter 102 and can be suitable for camping.

[0027] The power transmitter 102 and the power receiver 104 can implement a control architecture for managing the transmission of wireless power. The control architecture can define how power requirements are communicated and how the operating point of the power transmitter is controlled. In some implementations, the control architecture can be based on static power control (referred to as "control type 1 architecture" or "type 1"). In some implementations, the control architecture can be based on dynamic power control (referred to as "control type 0 architecture" or "type 0"). Devices implementing a control type 1 architecture may have a fixed load, may not include a measurement circuit, may typically not use auxiliary data transmission, and may require only minimal functionality to keep manufacturing costs down. The control type 1 architecture can be used depending on the control loop of the power transmitter 102 without feedback from the power receiver 104. Devices implementing a control type 0 architecture can have a static or dynamic load and can implement a controller for generating a power request message while power is being transmitted, as well as a measurement circuit for properly controlling that load. The present disclosure includes examples of both type 0 and type 1 control architectures as they relate to transitions between various operating phases.

[0028] Figure 2 shows a block diagram of an exemplary power transmitter 102. The power transmitter 102 can include a power supply 112, a power signal generator 106, and a primary coil 110. The power signal generator 106 is shown as a half-bridge circuit that converts DC power from the power supply 112 into an AC signal applied to the primary coil 110. Although not shown in FIG. 2, the power supply 112 can include a conversion unit that converts an AC main power supply into the DC power of the power supply 112. Further, the power signal generator 106 can be any type of power conversion circuit that can supply an AC signal to the primary coil 110. For example, the power signal generator 106 can include, as shown in FIG. 2, a half-bridge circuit having parallel capacitors. Alternatively, the power signal generator 106 can include a full-bridge circuit. The power signal generator 106 is sometimes referred to as an inverter.

[0029] The power transmitter 102 can also include a wireless communication interface 114 and a communication coil 116. The wireless communication interface 114 can be configured to transmit and receive communication signals via the communication coil 116 (which can be, among other examples, a coil or a loop antenna). The wireless communication interface 114 can implement short-range wireless frequency communication (such as, among other examples, Bluetooth™ or near-field communication (NFC)). The wireless communication interface 114 can include logic for controlling one or more switches and other components that cause the transmission and reception of wireless communication signals via the communication coil 116. The wireless communication interface 114 can be configured to communicate with a power receiver (not shown) using wireless communication signals.

[0030] In some implementations, the wireless communication interface 114 can communicate with the power receiver by transmitting a wireless communication signal and detecting a change in the wireless communication signal representing the communication of information. The wireless communication interface 114 can assist the NFC Type 2 Tag specification or the NFC Type 4A Tag specification as defined by the NFC specification. During the power transmission phase other than the communication carrier, the power signal is further active. Due to the frequency range used for the power signal, the product of the intermodulation of the two signals becomes interference that interferes with reliable NFC communication. To avoid this undesirable effect, the power signal can be periodically switched off at short time intervals. This time interval can be referred to as a communication time slot. Typically, the communication time slot can occur in relation to a zero-crossing event associated with the AC cycle of the AC main power supply or wall outlet.

[0031] The power transmitter 102 also includes a PTX controller 108. The PTx controller 108 can control the operation of the power signal generator 105. Further, the PTx controller 108 can manage the state of the power transmitter 102 when WPT transitions between various operating phases. The PTx controller 108 can communicate (such as transmit or receive communication) with the power receiver using the wireless communication interface 114. In some implementations, the PTx controller 108 can be implemented in an integrated circuit (IC). The PTx controller 108 can be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), or any other suitable electronic device. In some implementations, the wireless communication interface 114 and the PTx controller 108 can be implemented in a common unit.

[0032] The PTx controller 108 can detect the presence or proximity of a power receiver. In some implementations, the presence or proximity of the power receiver can be detected based on a change in load in response to a periodic low-power signal generated by the power signal generator 106 and the primary coil 110. In some implementations, the presence or proximity of the power receiver can occur during a periodic ping process of the wireless communication interface 114 of the power transmitter 102. Alternatively or additionally, the power transmitter 102 can detect the presence or proximity of the power receiver 118 based on communication via a wireless communication signal associated with the wireless communication interface 114. For example, the power transmitter 102 can cause the wireless communication interface 114 to transmit communication or polling signals periodically or continuously. In some implementations, the wireless communication signal (transmitted by the wireless communication interface 114) can include a small amount of power (sometimes referred to as communication bias power or bias power) for powering one or more components of the power receiver.

[0033] The PTx controller 108 can control the characteristics of the wireless power supplied by the power transmitter 102 to the power receiver. After detecting the power receiver 118, the PTx controller 108 can receive information from the power receiver (via the wireless communication interface 114). For example, the PTx controller 108 can receive information as part of a handshake communication with the power receiver. Handshake communication (sometimes referred to as digital handshake) refers to one-to-one communication between the power receiver and the power transmitter 102. During the handshake communication, the power transmitter 102 may transmit a first communication signal, and the power receiver can respond to the first communication signal by transmitting information (such as power rating, manufacturer, model, or receiver parameters when operating with a standard transmitter, among other examples). The PTx controller 108 can use the information received from the power receiver to determine at least one operation control parameter (such as frequency, duty cycle, voltage, etc.) for the wireless power supplied to the power receiver. To configure the wireless power, the PTx controller 108 can modify the frequency, duty cycle, voltage, or any other appropriate characteristic of the power signal generator 106 during the power transmission phase (shown as "A" and "B").

[0034] FIG. 3 shows a block diagram of an exemplary power receiver 300 having a protection switch. The exemplary power receiver 300 can be an example of the power receiver 104 described with reference to FIG. 1. The power receiver 300 may include a load 130, or the load 130 can be an external component connected to the power receiver 300. The exemplary rectifier 126 shown in FIG. 3 is a full-bridge rectifier configured to convert received power from an AC signal to DC power used by the load 130. In some implementations, the power receiver 300 may not include the rectifier 126. Other types of rectifiers or power conversion units can be used in various implementations. Further, the power receiver 300 shows an optional capacitor 326 coupled between two legs of the rectifier 126. In some implementations, the power receiver 300 may not include the optional capacitor 326. FIG. 3 also shows a capacitor 162 that can be coupled to one or more legs of the secondary coil 120. The exemplary power receiver 300 includes a protection switch (referred to as switch 350, also called "S1"). The switch 350 can be connected in series between one leg of the secondary coil 120 and the rectifier 126. The switch 350 can be connected before or after the capacitor 162 when the capacitor 162 is present on its leg. The switch 350 is one type of protection switch described in the present disclosure.

[0035] The power receiver 300 includes a communication coil 134, a wireless communication unit 132, and a PRx controller 128. The wireless communication unit 132 may be configured to receive a communication signal from a power transmitter. The wireless communication unit 132 may include a modulation / demodulation circuit for wireless communication via the communication coil 134 (which may be a coil or loop antenna among other examples). Thus, the PRx controller 128 can wirelessly communicate with the power transmitter via the wireless communication unit 132. In some implementations, the wireless communication unit 132 may be configured to communicate using NFC or Bluetooth technology. The wireless communication unit 132 may also include or be coupled to an energy harvester 332 that can collect energy from the wireless communication signal and supply the collected energy as bias power 330 to operate the PRx controller 128. The bias power 220 can be made sufficient to power the wireless communication unit 132 but less than the amount required to power the load 130. The energy harvester 332 can be configured to supply the collected energy as bias power 330 to power the wireless communication unit 132, the PRx controller 128, or both. For example, the communication signal received by the communication coil 134 can supply enough energy to generate the bias power 330 for startup and initial operation of the wireless communication unit 132 and the PRx controller 128 prior to the power transmission phase via the secondary coil 120. In some implementations, the bias power 330 can also be used to operate the switch 350. The PRx controller 128 can be initially powered by the bias power 330, but the PRx controller 128 can also be powered later using power from the wireless power circuit during the wireless power transmission phase. For simplicity, FIG. 3 omits the circuit or components that connect the PRx controller 128 to obtain power from the wireless power circuit during the wireless power transmission phase.

[0036] The PRx controller 128 can sense the state of the load 130 using the sense signal 331. In some implementations, the sense signal 331 can be directly related to the load 130. Alternatively or additionally, the sense signal 331 can indicate the state of optional components such as a startup switch (not shown) or a load switch (not shown). The startup switch can be based on a user interface such as a button, a touch screen, or any component that can indicate a user's request to activate the load 130. The load switch (not shown) can include a temperature switch, an overvoltage / overcurrent protection switch, a motor lock, or any type of load sensing switch that controls whether the load 130 is active. The PRx controller 128 can control the switch 350 using the switch signal 351. According to aspects of the present disclosure, the PRx controller 128 can operate the switch signal 351 based on a WPT protocol that defines transitions between various operating phases of the WPT system. For example, the PRx controller 128 can cause the switch 350 to connect the secondary coil 120 to the rectifier 126 (or the load 130) during the transition from the connection phase to the power transfer phase. Alternatively or additionally, the PRx controller 128 can cause the switch 350 to disconnect the secondary coil 120 from the rectifier 126 (or the load 130) during the transition from the power transfer phase to the connection phase. In some implementations, the switch 350 can be normally open (NO) such that the secondary coil 120 is disconnected from the rectifier 126 until the switch 350 is closed. In some implementations, the switch 350 can be closed using bias power obtained from the wireless communication unit 132 or from a battery (not shown) included in the power receiver 300.

[0037] The wireless communication unit 132 may assist the specification of NFC Type 2 Tag or NFC Type 4A Tag as defined by the NFC specification. In some implementation forms, the wireless communication unit is configured to communicate with the power transmitter by storing information in a passive tag (such as NFC Type 2 Tag) that can be read by the wireless communication interface of the power transmitter. Alternatively, the wireless communication unit may be configured to communicate with the power transmitter by transmitting the information of the wireless communication signal to the wireless communication interface of the power transmitter (for example, using NFC Type 4A Tag).

[0038] The power receiver 300 shown in FIG. 3 may be an example of one type of power receiver 300. For example, the power receiver 300 includes a rectifier 126 and the load 130 may be suitable for a device including one or more motors or any load operating with DC power. Since the power receiver 300 includes a rectifier 126, the power receiver 300 can implement the type 0 control architecture described herein. Other types of power receivers may not have a motor and may not require a rectifier 126. For example, the load 130 may be a resistive load (such as a heating element) or any load that can operate with AC power.

[0039] FIG. 4 shows a block diagram of another exemplary power receiver 400 having a protection switch. The exemplary power receiver 400 can be another example of the power receiver 104 described with reference to FIG. 1. The components of the power receiver 400 can include components having the same numbers as those of the power receiver 300 described with reference to FIG. 3. However, since the power receiver 400 is configured such that the load 430 operates using the AC signal obtained by the secondary coil 120, it may not include a rectifier. In this example, the load 430 may be referred to as a power receiving circuit configured to utilize the power obtained by the secondary coil 120. The protection switch (switch 450) can be connected in series between the secondary coil 120 and the load 430 so as to prevent the load 430 from being damaged by an unexpected voltage induced in the secondary coil 120 when the load 430 is not operating. The switch 450 is a type of protection switch described in the present disclosure. Similar to the power receiver 300 described with reference to FIG. 3, the PRx controller 128 can be configured to manage the switch 450 based on a WPT protocol that defines transitions between various operating phases of the WPT system. Since the power receiver 300 does not include a rectifier, the power receiver 300 can implement the type 1 control architecture described herein.

[0040] FIG. 5 shows a block diagram of an exemplary power receiver 500 having a protection switch with a plurality of switches. The components of the power receiver 500 can include components having the same numbers as those of the power receiver 300 described with reference to FIG. 3. Instead of a single series switch (such as the switch 350 described with reference to FIG. 3), the power receiver 500 can include a first switch 551 and a second switch 552 connected in series between the legs of the secondary coil 120 and the rectifier 126. The first switch 551 (referred to as "S1") can be connected in series to the first leg of the secondary coil 120. The second switch 552 (referred to as "S2") can be connected in series to the second leg of the secondary coil 120. The first switch 551 and the second switch 552 can also be collectively referred to as a protection switch. Similar to the power receiver 300 described with reference to FIG. 3, the PRx controller 128 can be configured to manage the switch 550 based on a WPT protocol that defines transitions between various operating phases of the WPT system. Since the power receiver 500 includes the rectifier 126, the power receiver 500 can implement the type 0 control architecture described herein.

[0041] The protection switches (e.g., switches 350, 450, 551, and 552 described with reference to FIGS. 3, 4, and 5, respectively) are examples of different types of protection switches implemented in a power receiver. Other types of protection switches can be used with the techniques of the present disclosure. For example, the protection switch can include a shunt switch configured to short-circuit the ends of the secondary coil to prevent or reduce the induced voltage of the secondary coil from reaching the power receiving circuit. In this example, the first position of the shunt switch can normally be closed (to short-circuit the secondary coil), and the second position can open the shunt switch to allow power to flow from the secondary coil to the power receiving circuit.

[0042] Figure 6 shows a diagram 600 of the states of various exemplary operating phases of a WPT system. The state diagram 600 shows the operating phases in which the WPT system can operate. When the power receiver is placed within the interface plane of the power transmitter, the two initiate communication for the purpose of configuring and controlling power transmission. There can be four operating phases associated with the WPT system, an idle phase 610 (sometimes also called the ping phase), a configuration phase 620, a connection phase 630, and a power transmission phase 640. Technical specifications can define how the power transmitter and the power receiver can transition between operating phases. For example, the WPT system typically begins in the idle phase 610 and can transition from the idle phase 610 to the configuration phase 620. From the configuration phase 620, the WPT system can transition to the connection phase 630. From the connection phase 630, the WPT system can transition to the power transmission phase 640. Further, the WPT system can transition back to the idle phase 610 from any of the other phases (configuration phase 620, connection phase 630, or power transmission phase 640), such as when the power receiver is removed from the interface plane. Each of the operating phases is briefly described herein for reference.

[0043] In the idle phase 610 (ping phase), the power transmitter attempts to establish communication with the power receiver. The power receiver may only be placed within the interface plane or may not be present during this operating phase. The power transmitter can attempt to communicate or detect the presence of the power receiver. For example, the power transmitter can use analog pings, out-of-band communication (such as NFC), digital pings, or any combination thereof to determine if a compatible power receiver is present. When the WPT system determines that the power receiver is present (e.g., by verifying NFC communication), the WPT system can transition to the configuration phase 620.

[0044] In the configuration phase 620, the power receiver can send basic identification and configuration data to the power transmitter. For example, the power transmitter can obtain static configuration information from the power receiver via NFC communication. The power transmitter and the power receiver can use this information to verify that both use a compatible version of the technical specifications or protocols for wireless power transmission. The power transmitter and the power receiver can communicate basic settings or communicate about their respective capabilities. From the configuration phase 620, the WPT system can transition to the connection phase 630.

[0045] In the connection phase 630, the power transmitter and the power receiver can exchange further communication to negotiate the parameters that manage the power transmission phase. After negotiating the parameters, the power transmitter is ready to transmit wireless power and the power receiver is ready to receive wireless power. However, the power transmitter may wait for a request or command from the power receiver before transitioning to the power transmission phase 640. This can be useful, for example, when a cordless device (such as a blender, toaster, mixer, or microwave, among other examples) is configured to be used during interaction with the user. The user can start the power transmission phase 640 via the user interface of the power receiver (such as a start switch), which communicates with the power transmitter to transition to the power transmission phase 640.

[0046] During the power transmission phase 640, the power transmitter can transmit wireless power to the power receiver. Usually, the power transmitter periodically performs a foreign object detection evaluation during the power transmission phase 640. In some cases, the power transmitter can perform a foreign object detection evaluation to ensure the absence of foreign objects before transitioning from the connection phase 630 to the power transmission phase 640. The power transmitter can also perform periodic foreign object detection evaluations during the power transmission phase 640. The idle phase 610, the configuration phase 620, and the connection phase 630 can be collectively referred to as the pre-power phase 602, and the power transmission phase 640 can be referred to as the power continuation phase 604.

[0047] In some implementations, the transition from the connection phase to the power transmission phase and the reverse transition can pose challenges due to related hardware and safety procedures. For example, a cordless device can have a protection switch that should be rotated to a second position before entering the power transmission phase. If the power transmitter starts wireless power transmission while the protection switch is still in the first position, the magnetic field from the power transmitter can cause a dangerous condition or high voltage in the device. Additionally, the power transmitter (or power receiver) can potentially experience a fault condition or damage. In some implementations, the power transmitter may need to perform a foreign object detection (FOD) evaluation before transitioning to the power transmission phase. The techniques of the present disclosure can define the protocol to be followed while transitioning from the connection mode to the power transmission mode and vice versa.

[0048] The present disclosure provides a system, method, and apparatus for managing phase transitions of a wireless power transfer (WPT) system. For example, the transition between a connection phase and a power transfer phase can be adjusted in relation to a change in a protection switch (one or more switches) of a power receiver. The protection switch can separate or couple a secondary coil of the power receiver to a power receiving circuit (such as a load or a rectifier). A first position of the protection switch can open a circuit including the secondary coil and the power receiving circuit. A second position of the protection switch can close the circuit such that the secondary coil can receive wireless power and supply the wireless power to a load during a power transfer phase. The present disclosure also describes a method by which the WPT system can temporarily pause wireless power transfer while remaining in a power transfer phase.

[0049] FIG. 7 shows a diagram of a flowchart of an exemplary process 700 of a power receiver according to some implementations. The operations of process 700 can be performed by a power receiver as described herein. For example, the operations of process 700 can be performed by any of power receivers 104, 300, 400, or 500 described with reference to FIGS. 1, 3, 4, or 5, respectively. For brevity, the operations are described as being performed by a device. At block 710, the device can determine that the PTx is in an operational connection phase with the PRx. At block 720, during the connection phase, the device can change a protection switch of the PRx from a first position to a second position, the protection switch being disposed between a secondary coil of the PRx and a load associated with the PRx, the first position being configured to normally open a circuit including the secondary coil prior to an operational power transfer phase, and the second position being configured to close the circuit. At block 730, after the protection switch has been changed to the second position, the device can communicate a power request to the PTx. At block 740, the device can transition from the connection phase to a power transfer phase. At block 750, during at least a portion of the power transfer phase, the device can receive wireless power from the PTx.

[0050] FIG. 8 shows a flowchart of an exemplary process 800 of a power transmitter according to some implementations. The operations of process 800 can be performed by the power transmitter described herein. For example, the operations of process 800 can be performed by any of the power transmitters 102 described with reference to FIGS. 1 and 2, respectively. For brevity, the operations are described as being performed by the device. At block 810, the device may determine that the PRx is in the operational connection phase with the PTx, at least in part based on communication with the PRx. At block 820, the device may receive a power request from the PRx. The power request is associated with a request for wireless power transmission from the PTx to the PRx, and the power request represents an indication that the PRx has changed a protection switch to close a circuit including the secondary coil of the PRx. At block 830, the device may cause an inverter to generate a wireless power signal for transmitting wireless power in response to the power request. At block 840, the device may transition from the operational connection phase to the power transmission phase. At block 850, the device may transmit the wireless power signal to transmit wireless power to the secondary coil of the PRx.

[0051] Figure 9 shows a timing diagram 900 of an exemplary transition from connection phase 960 to power transfer phase 980 in a WPT system using a type 0 control architecture. The timing diagram 900 is used to describe the operation of a PRx controller (referred to as PRx902) and a PTx controller (referred to as PTx904). PRx902 and PTx904 may implement a type 0 control architecture. This means that PRx902 can control wireless power transfer using control messages. For example, in a type 0 control architecture, PRx902 can control voltage, frequency, power, start, stop, or other settings associated with wireless power transfer. PRx902 and PTx904 can follow the state diagrams of various operation phases as described with reference to FIG. 6. Assume that the timeline of PRx902 and PTx904 is such that the WPT system has already transitioned to connection phase 960 (shown by line 920). Phase operations 910 (such as idle phase and configuration phase) that occur before connection phase 960 are omitted for brevity. At time 925, PRx902 may determine that an activation switch associated with the load has been turned on. For example, the activation switch can include user input indicating a desire to activate the load. Examples of activation switches can include, among other examples, buttons, flip switches, knobs, or touchscreens (and associated processors). Some devices may not include an activation switch, and PRx902 can assume that the load is always ready to receive wireless power.

[0052] At time 930, PRx902 may communicate a phase transition request message. For example, PRx902 may communicate a "NEXT / pow" command (requesting PTx904 to transition to the power transmission phase as the next operation phase). PTx904 may respond to the phase transition request message with an acknowledgment message (shown at time 940). After receiving the acknowledgment message, PRx902 may send a switch signal (shown at time 950) to change the protection switch from the first position to the second position. In the first position, which may be the default or "normal" position, the protection switch may disable the conduction of energy by the secondary coil of the PRx. For example, in the first position, the secondary coil can be disconnected or separated from the power receiving circuit (such as a rectifier or load). The first position can open the circuit including the secondary coil. In the second position, the protection switch may enable the conduction of energy such as the induced voltage from the magnetic field generated by the PRx by the secondary coil.

[0053] After the protection switch changes to the second position (e.g., after the time when the protection switch changes to the second position after the switch signal at time 950), PRx902 may communicate a power request (sometimes also called a power request message) to PTx904 at time 955. In some implementations, the power request may be included in a control message. PTx904 can receive the power request and enable the PTx power signal generator (such as an inverter) to transmit wireless power 115. PTx904 can also transition to the power transmission phase 980 (shown at time 970) if it has not been changed in the phase shift request (at time 930) or the power request (at time 955). The specification of when the power transmission phase 980 starts can vary, but in some implementations, the transmission of wireless power 115 can occur only after the power request at time 955. The power request can implicitly indicate that PRx902 has changed the protection switch to the second position. In some implementations, the WPT specification can define the timing of PRx902 to couple the secondary coil to the load during the connection phase 960 and before the power request (at time 955) such that the power request explicitly or implicitly indicates that PRx902 has coupled the secondary coil to the load in accordance with the WPT specification. Thus, wireless power 115 occurs only after PTx904 has (explicitly or implicitly) confirmed that PRx902 has configured a power receiving circuit including either the secondary coil and a rectifier or the load to consume the wireless power.

[0054] In some implementations, the power signal generator is enabled at or after the first natural zero crossing of the AC main power or AC cycle following the power request (shown at time 975). For systems operating off-grid (such as DC operating PRx), the power signal generator can be enabled after a slight delay after the power request control message 955 is received. Since PTx904 can wait for the power request, according to the present disclosure, the WPT system can avoid overvoltage faults at the PTx or avoid transmitting wireless power into an open circuit of the PTx.

[0055] FIG. 9 also shows an exemplary timing of the FOD evaluation 935 during the connection phase 960. Some power transmitters perform frequent FOD evaluations during the connection phase, while some others perform the FOD evaluation just before entering the power transmission phase. In some implementations, the FOD evaluation 935 may need to be performed before transitioning from the connection phase to the power transmission phase. The FOD evaluation 935 may occur before the acknowledgement response (at time 940) in response to the phase transition request (at time 930).

[0056] For FOD evaluation, the PTx 904 can scan for foreign objects using various techniques such as active or passive excitation of the foreign object detection coil to observe the impedance difference indicating the presence of a foreign object. The PTx 904 can reset (or clear) the foreign object flag (FO) when no FO is detected and can set the FO flag when an FO is detected. A power transmitter that only scans for FO before power transmission can set the FO flag set as an initial value to indicate that no FOD evaluation has been performed. After receiving the phase transition request (at time 930), the PTx 904 can check the status of the FO flag. If the FO flag is cleared / reset and there are no other constraints, the PTx 904 can send an acknowledgement response (at time 940) to the PRx 902. If the FO flag is set, the PTx 904 can perform the FOD evaluation 935. When an FO is detected, the PTx 904 can prompt the user's action, send a fault condition, or disable the transition to the power transmission phase. For example, the PTx 904 can communicate a negative acknowledgement response (NAK) to the PRx 902. Alternatively, if no FO is detected by the FOD evaluation 935 and there are no other constraints, the PTx 904 can communicate an acknowledgement response (ACK) to the PRx 902.

[0057] FIG. 9 also illustrates how out-of-band communication (referred to as NFC906) may be related to the timing of the operation of PRx902 and PTx904. For example, the NFC906 timeline reflects the time during which PTx904 can communicate with PRx902. In some cases, PTx904 communicates a wireless communication signal according to the timeline of NFC906, and PRx902 may collect energy (bias power) from the wireless communication signal. The NFC906 timeline shows communication signals 992, 994, 996, 998, and 999. For example, communication signals 992 and 994 can occur during connection phase 960 and can supply bias power to PRx902. The communication signals can stop during FOD evaluation 935 so that the communication signals do not interfere with FOD evaluation 935. Further, NFC906 shows, in a timeline, communication signals 996, 998, and 999 that occur during communication time slots of the power transmission phase. The communication time slots can occur in relation to zero-crossing events associated with the AC cycle of wireless power 115. Even during instances 996, 998, and 999, the main power supply from PTx904 to PRx902 can be stopped to enable interference-free communication between PTx904 and PRx902.

[0058] Note that communication signal 994 can extend beyond connection phase 960 into power transmission phase 980. This is because communication signal 994 can supply bias power to PRx902 until wireless power 115 starts at time 975. After wireless power 115 is transmitted from PTx904 to PRx902, PRx902 can use wireless power 115 (instead of or in addition to bias power) to power the PRx controller.

[0059] FIG. 10 shows FIG. 1000 of the timing defined by the WPT protocol within a limited time. The exemplary operation phases, communications, and timings of FIG. 10 are the same as those described with similar reference numerals in FIG. 9. FIG. 10 shows the limited time that can be implemented as part of the WPT protocol including phase transition requests, confirmation response messages, or power requests at times 925, 940, and 955 respectively. For example, the confirmation response message at time 940 can be received within a limited time (referred to as T1 1010) following the phase transition request message at time 930. In some implementations, the value of T1 1010 can be 100 milliseconds (ms). T1 1010 can be the first maximum time allowed between the phase transition request message and the confirmation response message. If PRx902 does not receive the confirmation response message within T1 1010, a timeout error can occur. In such a case, PRx902 can wait for a predetermined time and then send a new phase transition request (not shown). Alternatively or additionally, PRx902 can present a timeout error display via the user interface associated with PRx902. PRx902 can be required to send a power request (at time 955) within a limited time (labeled T2 1020) following the confirmation response (at time 940). In some implementations, the value of T2 1020 can be 100 ms. T2 1020 can be the second maximum time allowed between the confirmation response message and the control message. If PTx904 does not receive the power request within T2 1020, PTx904 can present a timeout error indication via the user interface associated with PTx904.

[0060] Figure 11 shows a diagram 1100 of an exemplary transition timing from power transmission phase 1110 to connection phase 1180 in a WPT system using a type 0 control architecture. PRx902 and PTx904 can be in the power transmission phase 1110 according to any procedure such as the WPT protocol described with reference to FIG. 9 or FIG. 10. Similar to FIG. 9, PRx902 and PTx904 can implement a type 0 control architecture. PTx904 can transmit wireless power 115 to supply power to the load associated with PRx902. At some point, a job associated with the load can be completed. As shown at time 1120, PRx902 can detect a state associated with the end of the operation of the load. The state can include, for example, that the activation switch is off (either by user input or programmatically by a processor). Alternatively, the state can include that a load switch associated with the load changes to a state associated with the end of the operation of the load. For example, the load switch can also include a temperature switch (such as a bimetal switch) that turns off when the load reaches a target temperature. Alternatively, the load switch can also be any switch that disconnects the load from the wireless power receiving circuit (secondary coil or rectifier).

[0061] After detecting the state (at time 1120), PRx902 may communicate a phase transition request at time 1130. For example, the phase transition request may be a "NEXT / con" command (requesting PTx904 to transition to the connection phase as the next operation phase). In some implementations, PTx904 may not reject a phase transition request that requests a transition from the power transmission phase. After receiving the phase transition request, PTx904 may stop transmitting the wireless power 115 and may send an acknowledgment (ACK) message (shown at time 1140). PTx904 may also be able to transition to the connection phase 1180 (shown at time 1150). The ACK message (at time 1140) may notify PRx902 whether PTx904 has the transmission of the wireless power 115 or will stop it shortly. Stopping the transmission of the wireless power 115 may include PTx904 stopping generating the magnetic field associated with the wireless power 115 in a power signal generator (such as an inverter of PTx904) and the primary coil of PTx904. In some implementations, PTx904 may not reject a phase transition request that requests a transition from the power transmission phase. However, if PRx902 does not receive the ACK message, PRx902 may communicate a new phase transmission request (NEXT / con) and attempt a protocol-compliant transition to the connection phase.

[0062] After receiving the ACK (at 1140), PRx902 may disable the secondary coil (shown at time 1160). For example, PRx902 can remove the switch signal that had kept the protection switch closed. Alternatively, PRx902 can send a switch signal configured to open the circuit including the secondary coil to the protection switch. In some implementations, PRx902 may wait for a period after the ACK before disabling the secondary coil. In some implementations, PRx902 can include a voltage sensor configured to measure the voltage of the secondary coil. PRx902 can wait to open the circuit including the secondary coil until PRx902 confirms that the voltage is below a threshold (indicating that PTx904 has stopped transmitting wireless power 115). Thus, the time 1160 associated with disabling the secondary coil can be diverse, but ideally follows the ACK (at 1140) indicating that wireless power 115 has stopped or will soon stop. Using this technique, PRx902 can ensure that the protection switch does not inadvertently and prematurely change to a first position where the secondary coil is disabled before wireless power 115 stops. If the protection switch is changed before wireless power 115 stops, the components of PRx902 may be damaged by high current or high voltage or unintended power transmission. In a situation where PRx902 does not receive an ACK from PTx904 after attempting multiple phase transition requests (NEXT / con), PRx902 can proceed to disable the secondary coil.

[0063] FIG. 11 also illustrates how out-of-band communication (referred to as NFC906) can be related to the timing of the operation of PRx902 and PTx904 during the transition from power transmission phase 1110 to connection phase 1180. The timeline of NFC906 shows communication signals 1112, 1114, and 1116 that occur during communication time slots in power transmission phase 1110. The communication time slots can occur in relation to zero-crossing events associated with the AC cycle of the wireless power 115. Note that communication signal 1122 can start when the transmission of wireless power 115 stops (at time 1140). This is to enable communication signal 1122 to supply bias power to PRx902. In some implementations, communication signal 1122 can start during power transmission phase 1110 (after the transmission of wireless power 115) before PTx904 transitions to connection phase 1180 (at time 1150). This is because the wireless power 115 ends at a natural zero-crossing instance associated with the AC main power or AC cycle, and the transition to the connection phase (at time 1150) can occur later.

[0064] The examples of FIGS. 9 - 11 can be related to a WPT system implementing a type 0 control architecture. However, some WPT systems can implement a type 1 control architecture. FIGS. 12 - 13 show how such a system can adjust the timing of various phase transitions.

[0065] FIG. 12 shows a timing diagram 1200 of an exemplary transition from a connection phase 1280 to a power transmission phase 1290 in a WPT system using a type 1 control architecture. The timing diagram 1200 is used to describe the operations of a PRx controller (referred to as PRx 1202) and a PTx controller (referred to as PTx 1204). In FIG. 11, PRx 1202 and PTx 1204 may implement a type 1 control architecture. This means that PRx 1202 may have limited control over wireless power transmission. For example, in a type 1 control architecture, PRx 1202 can use a passive tag (such as an NFC Type 2 Tag) to communicate limited information to PTx 1204 and can rely on PTx 1204 to use its internal power control loop to control wireless power transmission. PRx 1202 and PTx 1204 can follow the state diagrams of various operational phases as described with reference to FIG. 6. Assume that the timeline of PRx 1202 and PTx 1204 is such that the WPT system has already transitioned to the connection phase 1280 (shown at time 1220). Phase operations 1210 (such as an idle phase and a configuration phase) that occur before the connection phase 1280 are omitted for brevity. These phase operations 1210 can include communication of an NFC data exchange format (NDEF) 1215. In some implementations, the communication between PRx 1202 and PTx 1204 can be based on a limited communication where the wireless communication interface of PTx 1204 "reads" information from the wireless communication unit of PRx 1202. For example, the wireless communication unit can be a passive tag (e.g., an NFC Type 2 Tag) that stores information readable by the wireless communication interface of PTx 1204.

[0066] At time 1240, PRx1202 may determine that the activation switch associated with the load has been turned on. For example, the activation switch can include user input indicating a desire to activate the load. Some devices may not include an activation switch, and PRx1202 can assume that the load is always ready to receive wireless power. PRx1202 can communicate a power request (at time 1250) only after the secondary coil has been enabled (shown at time 1230). The secondary coil can be enabled by PRx1202 sending a switch signal to change the protection switch from a first position to a second position. In the first position, the protection switch can open the circuit including the secondary coil. In the second position, the protection switch can close the circuit including the secondary coil. The exact timing for enabling the secondary coil can vary based on the type of device and the preference of the manufacturer. In some implementations, PRx1202 can change the protection switch to the second position as soon as PRx1202 enters the connection phase 1280. Alternatively, PRx1202 can change the protection switch to the second position after the activation switch has been turned on.

[0067] After receiving a power request (at time 1250), PTx1204 may initiate transmission of wireless power 115 (shown as starting at time 1260). For example, PTx1204 can cause a power signal generator (such as an inverter) to generate a wireless power signal for transmission by the primary coil of PTx1204. In some implementations, the power signal generator is enabled following the power request (time 1250) at the first natural zero crossing of the AC main power or AC cycle (shown at time 1260) or thereafter. PRx1202 may need to close a protection switch (at time 1230) before communicating the power request (at time 1250). Since PTx1204 can wait for the power request, according to the present disclosure, the WPT system can avoid overvoltage faults at PRx1202 and can prevent transmission of wireless power 115 to an open circuit of PRx1202. In some implementations, the WPT specification can define the timing of PRx1202 to couple the secondary coil to the load during connection phase 1280 and before the power request (at time 1250) such that the power request implicitly indicates that PRx1202 has coupled the secondary coil to the load in accordance with the WPT specification.

[0068] As described with reference to FIG. 9, PTx1204 can perform a foreign object detection (FOD) evaluation 1225 (similar to FOD evaluation 935 in FIG. 9) during connection phase 1280. The timing of FOD evaluation 1225 can be diverse since it may not be triggered by communication from PRx1202. However, in some implementations, the WPT specification can require PTx1204 to perform FOD evaluation 1225 before transitioning from the connection phase to the power transfer phase or before transmission of wireless power 115. If a foreign object is detected, PTx1204 can prompt user action, transmit a fault condition, or prevent the transition to the power transfer phase.

[0069] FIG. 12 also illustrates how out-of-band communication (referred to as NFC1206) can be related to the timing of the operation of PRx1202 and PTx1204. For example, the timeline of NFC1206 reflects the time during which PTx1204 can transmit wireless communication signals 1212, 1214, 1222, 1226, and 1228 to communicate with PRx1202 or to assist in bias power harvesting of PRx1202. For example, communication signals 1212 and 1214 can occur during connection phase 1280 to supply bias power to PRx1202. The communication signals can stop during FOD evaluation 1225 so that the communication signals do not interfere with FOD evaluation 1225. Further, the timeline of NFC1206 indicates communication signals 1222, 1226, and 1228 that occur during communication time slots of power transfer phase 1290 during which the main power supply from PRx to PTx can be temporarily stopped. The communication time slots can occur in relation to zero-crossing events associated with the AC cycle of wireless power 115.

[0070] As described with reference to FIG. 9, communication signal 1214 can extend from connection phase 1280 into power transfer phase 1290. This is because communication signal 1214 can supply bias power to PRx1202 until wireless power 115 starts at time 1260. After wireless power 115 is transmitted from PTx1204 to PRx1202, PRx1202 can use wireless power 115 (instead of or in addition to bias power) to supply power to the PRx controller.

[0071] Figure 13 shows a diagram 1300 of an exemplary timing of the transition from a power transmission phase to a connection phase in a WPT system using a type 1 control architecture. PRx1202 and PTx1204 can be in the power transmission phase 1310 according to any procedure such as the WPT protocol described with reference to FIG. 12. Similar to FIG. 12, PRx1202 and PTx1204 can implement a type 1 control architecture. PTx1204 can transmit wireless power 115 to supply power to the load associated with PRx1202. At some point, the job associated with the load can be completed. As shown at time 1320, PRx1202 can detect a state associated with the end of the operation of the load. The state can include, among other examples, that the activation switch is off, or that the load switch associated with the load changes to a state associated with the end of the operation of the load.

[0072] After detecting the state (at time 1320), PRx1202 can communicate a zero power or power off request at time 1330. For example, PRx1202 can modify the information of the passive tag so that PTx1204 receives a zero power or power off request by reading the passive tag. After receiving the zero power or power off request (at time 1330), PTx1204 can stop transmitting wireless power 115 (shown at time 1340). PTx1204 can also transition to the connection phase 1380 (shown at time 1370). Stopping the transmission of wireless power 115 can include PTx1204 stopping generating the magnetic field associated with wireless power 115 in the power signal generator (such as the inverter of PTx1204) and the primary coil of PTx1204.

[0073] PRx1202 can also disable the secondary coil (shown at time 1360). For example, PRx1202 can remove the switch signal that had kept the protection switch closed. Alternatively, PRx1202 can send a switch signal configured to open the circuit including the secondary coil to the protection switch. In some implementations, PRx1202 can wait for a period following a zero power or power off request so as to allow the time when PTx1204 stops transmitting the wireless power 115. Thus, the time 1360 associated with disabling the secondary coil can be diverse as long as it follows the zero power or power off request (at 1330).

[0074] FIG. 12 also illustrates how out-of-band communication (referred to as NFC1206) can be related to the timing of the operations of PRx1202 and PTx1204 during the transition from the power transmission phase 1310 to the connection phase 1380. The timeline of NFC1206 shows the communication signals 1312 and 1314 that occur during the communication time slots in the power transmission phase 1310. The communication time slots can occur in relation to the zero-crossing events associated with the AC cycles of the wireless power 115. Note that the communication signal 1316 can start when the transmission of the wireless power 115 stops (at time 1340). This is to enable the communication signal 1316 to supply bias power to PRx1202. In some implementations, the communication signal 1316 can start during the power transmission phase 1310 (after the transmission of the wireless power 115) before PTx1204 transitions to the connection phase 1380 (at time 1150). This is because the wireless power 115 ends at a natural zero-crossing instance associated with the AC main power or AC cycle, and the transition to the connection phase 1380 can occur later.

[0075] The above description explains the transition between the connection phase and the power transfer phase. In other words, the description describes the timing associated with wireless power transfer related to the protection switch. There may be some implementations where it is desirable to remain in the power transfer phase while temporarily pausing the transmission of wireless power. For example, some devices have loads associated with on-cycles and off-cycles. The transition between the connection phase and the power transfer phase may be less efficient than temporarily pausing the transmission of wireless power to assist with the off-cycle of the load. An example of a device with such a load may be an ice maker. The ice maker may have a motor that performs a series of on-cycles and off-cycles. An example of a device with such a load may be a blender with a pulse sequence. There is a need for PRx to manage the periodic transmission of wireless power during the power transfer phase. The present disclosure also describes a method by which a WPT system can temporarily pause wireless power transmission while remaining in the power transfer phase. These techniques may include the use of one or more zero-power requirements and non-zero power requirements.

[0076] FIG. 14 shows an exemplary process 1400 flowchart diagram of a power receiver for controlling wireless power supply during power transmission phases, according to some implementations. The operations of process 1400 can be performed by a power receiver as described herein. For example, the operations of process 1400 can be performed by any of the power receivers 104, 300, 400, or 500 described with reference to FIGS. 1, 3, 4, or 5, respectively. For simplicity, the operations are described as being performed by the device. In block 1410, the device may couple the secondary coil of the PRx to a load associated with an on-cycle and an off-cycle, and the secondary coil is configured to receive wireless power from the PTx during at least a portion of the power transmission phase of operation. In block 1420, the device may communicate with the PTx to enter a power transmission phase in which the PTx can transmit wireless power to the PRx. In block 1430, the device can communicate a non-zero power request to the PTX associated with the on-cycle of the load, and the non-zero power request is associated with causing the PTx to transmit wireless power. In block 1440, the device can communicate a zero power request message to the PTX associated with the off-cycle of the load, and the zero power request is associated with causing the PTx to pause transmission of wireless power while remaining in the power transmission phase.

[0077] FIG. 15 shows a flowchart of an exemplary process 1500 of a power transmitter for controlling wireless power supply during power transmission phases according to some implementations. The operations of process 1500 can be implemented by the power transmitter described herein. For example, the operations of process 1500 can be implemented by any of the power transmitters 102 described with reference to FIGS. 1 and 2, respectively. For simplicity, the operations are described as being performed by the device. At block 1510, the device can communicate with the PRx to enter the power transmission phase of the operation. At block 1520, the device may receive a power request from the PRx, and the power request is for controlling the transmission of wireless power for the load of the PRx during at least a portion of the power transmission phase. At block 1530, when the power request is a non-zero power request, the device can cause the inverter of the PTx to generate a wireless power signal for transmitting wireless power for the load in the power transmission phase. At block 1540, when the power request is a zero power request, the device can pause the generation of the wireless power signal for the load at the inverter while remaining in the power transmission phase.

[0078] FIG. 16 shows a timing diagram 1600 in which zero power requests and non-zero power requests are used during a power transmission phase 1620. The timing diagram 1600 is used to describe the operations of a PRx controller (referred to as PRx 1602) and a PTx controller (referred to as PTx 1604). In FIG. 16, PRx 1602 and PTx 1604 can implement either a type 0 control architecture or a type 1 control architecture. PRx 1602 and PTx 1604 can follow the diagrams of the states of various operation phases as described with reference to FIG. 6. The timelines of PRx 1602 and PTx 1604 assume that the WPT system has already transitioned to the power transmission phase 1620 (shown by line 1607). The phase operations 1605 (such as the idle phase, configuration phase, and connection phase, etc.) that occur before the power transmission phase 1620 are omitted for simplicity.

[0079] Timing diagram 1600 begins when the load associated with PRx1602 is in on - cycle 1651. During on - cycle 1651, the load may consume wireless power 115 for the operation of the load (e.g., among other examples, an ice maker or a blender motor). However, the load can have an off - cycle 1652, during which time the load does not require wireless power. It is desirable to stop transmitting wireless power during off - cycle 1652 to protect PRx1602 or the load from damage, conserve energy, and extend the life of electronic components. However, also, since the next on - cycle 1653 occurs immediately after off - cycle 1652, it may be desirable to remain in the power transmission phase 1620. Thus, in some aspects, the present disclosure provides techniques for temporarily pausing the transmission of wireless power during an off - cycle associated with the load of PRx1602.

[0080] PRx1602 can communicate a zero - power request (shown at time 1630) to PTx1604 to stop the transmission of wireless power 115. The zero - power request can be communicated by modifying the information of the passive tag or by transmitting a communication signal including the zero - power request from PRx1602. In an implementation where PRx1602 has a protection switch, PRx1602 can keep the protection switch enabled so that the circuit including the secondary coil remains closed during the power transmission phase. After receiving the zero - power request from PRx1602, PTx1604 can stop the transmission of wireless power 115 (shown at time 1640). For example, PTx1604 can turn off a power signal generator (such as an inverter).

[0081] When the off-cycle 1652 ends, PRx 1602 communicates a non-zero power request (at time 1660) and causes PTx 1604 to resume transmitting wireless power 115. After receiving the non-zero power request (at time 1660) from PRx 1602, PTx 1604 may resume transmitting wireless power 115 (shown at time 1670). For example, PTx 1604 can turn on a power signal generator (such as an inverter).

[0082] Note that zero power requests and non-zero power requests may be referred to by other terms. Further, as further described with reference to FIG. 17, a "zero" power request may indicate a nominal non-zero power setting, but for clarity, is referred to herein as a zero power request. In some implementations, PRx 1602 can communicate a series of zero power requests and non-zero power requests corresponding to the start of the load off-cycle and on-cycle, respectively. Further, the zero power requests and non-zero power requests can be communicated according to a pre-configured duty cycle or setting associated with the load so that the user does not need to continuously press or release an activation switch.

[0083] FIG. 16 also illustrates how out-of-band communication (referred to as NFC1606) is used during the period between zero power requests and non-zero power requests. The timeline of NFC1606 shows communication signals 1612 and 1616 that occur during communication time slots in the power transmission phase 1620. The communication time slots can occur in relation to zero-crossing events associated with the AC cycle of the wireless power 115. Further, PTx1604 can transmit communication signal 1614 during the period between a zero power request (at time 1630) and a non-zero power request (at time 1660). This is to enable the communication signal 1614 to supply bias power to PRx1602. It should be recalled that in some implementations, the bias power can be used to operate a protection switch that closes the circuit of the secondary coil. Thus, FIG. 16 provides a technique in which the protection switch can remain in the second position even when wireless power 115 is not being transmitted during the off-cycle 1652.

[0084] FIG. 17 shows a timing diagram 1700 in which a low-power operating point can be used while remaining in the power transmission phase. The features of FIG. 17 have the same meaning as described with reference to FIG. 16, including PRx1602, PTx1604, NFC1606, phase operation 1605, line 1607, power transmission phase 1620, on-cycle 1651, off-cycle 1652, on-cycle 1653, zero power requirement (at time 1630), non-zero power requirement (at time 1660), pausing the transmission of wireless power 115 at time 1640, and resuming the transmission of wireless power 115 at time 1670. What is important in FIG. 17 is that when PTx1604 pauses the transmission of wireless power 115 for use by the load, PTx1604 may not completely stop the wireless power transmission. Rather, PTx1604 can transmit wireless power 1715 at a low-power operating point 1755. The low-power operating point can be a non-critical operating point (UOP) or a secure communication operating point (SCOP). The wireless power 1715 at the low-power operating point 1755 is lower than that required by the load but may be sufficient to power the PRx controller or other components of PRx1602. Specifically, in some implementations, the wireless power 1715 at the low-power operating point 1755 may be sufficient to keep the protection switch actuated to close the circuit including the secondary coil of PRx1602. In some implementations, it should be recalled that the protection switch operates by wireless power during the power transmission phase. Thus, FIG. 17 provides a technique in which the protection switch can remain in a second position during off-cycle 1652 while also benefiting from zero-power and non-zero-power requirements to define the off-cycle 1652 of the load. NFC1606 can be used for communications 1712, 1714, 1716, 1718, and 1722 that typically occur during the communication time slots of power transmission phase 1620. For example, the communication time slot can be an instance when PRx1602 can communicate a zero-power requirement, a non-zero-power requirement, or any type of control message associated with the transmission of wireless power 115.

[0085] FIG. 18 shows a block diagram of an exemplary apparatus 1800 for use in a wireless power transfer system. In some implementations, apparatus 1800 can be a power receiver, such as any of the power receivers described herein. In some implementations, apparatus 1800 can be a power transmitter, such as any of the power transmitters described herein. Apparatus 1800 can include a processor 1802 (including, in some cases, multiple processors, multiple cores, multiple nodes, or implementing multi-threading, etc.). Apparatus 1800 can also include a memory 1806. Memory 1806 can be system memory or any one or more of the possible realizations of the computer-readable media described herein. Apparatus 1800 can also include a bus 1811 (e.g., PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.). In some implementations, controller 1862 can be distributed internally to processor 1802, memory 1806, and bus 1811. Controller 1862 can perform some or all of the operations described herein. Apparatus 1800 can include other components not shown in FIG. 18. For example, if apparatus 1800 is a power receiver, the apparatus can have one or more switches (protection switches) in a circuit including a power transfer coil 1866.

[0086] Memory 1806 can include computer instructions executable by processor 1802 to implement the functions of the implementation forms described with reference to FIGS. 1-17. Any one of these functions can be implemented partially (or entirely) in hardware or by processor 1802. For example, the function can be implemented in an application-specific integrated circuit, logic implemented in processor 1802, a peripheral device, or a coprocessor on a card. Further, the implementation can include fewer or additional components not shown in FIG. 18. Processor 1802, memory 1806, and controller 1862 can be coupled to bus 1811. Although shown as being coupled to bus 1811, memory 1806 can be coupled to processor 1802.

[0087] The operations shown in FIGS. 1-18 and described herein are examples intended to assist in the understanding of the exemplary implementation forms and should not be used to limit potential implementation forms or the scope of the claims. Some implementation forms can include additional operations, fewer operations, operations in parallel or in a different order, and some operations can be performed differently.

[0088] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the exact forms disclosed. Changes and modifications may be made in light of the above disclosure or obtained from practice of the aspects. Although the aspects of the present disclosure have been described with respect to various examples, any combination of aspects from any example is also within the scope of the present disclosure. The examples of the present disclosure are provided for educational purposes. Alternatively, or in addition to the other examples described herein, the examples can include any combination of the following implementation form options (specified as clauses for reference).

[0089] Clause 1. A power receiver (PRx) of a wireless power transfer (WPT) system, the PRx comprising: a secondary coil configured to receive wireless power from a power transmitter (PTx) during at least a part of an operating power transfer phase; a protection switch disposed between the secondary coil and a load associated with the PRx, the protection switch being normally in a first position configured to open a circuit including the secondary coil prior to the power transfer phase; a wireless communication unit; and a PRx controller configured to determine that the PTx is in an operating connection phase with the PRx and generate a switch signal during the connection phase to change the protection switch to a second position, the second position being configured to close the circuit including the secondary coil, and after the protection switch is changed to the second position, cause the wireless communication unit to communicate a power request for the PTx to transmit wireless power and configured to transition from the connection phase to the power transfer phase.

[0090] Clause 2. The PRx according to Clause 1, wherein when the protection switch is in the second position, the secondary coil can receive wireless power during the power transfer phase and supply the wireless power to the load.

[0091] Clause 3. The PRx according to any one of Clauses 1 to 2, wherein the wireless communication unit is configured to communicate with the PTx by storing information in a passive tag readable by the wireless communication interface of the PTx, and the PRx controller is configured to communicate a power request by modifying the information of the passive tag to include a power-on indication in the wireless communication unit.

[0092] Clause 4. The PRx according to any one of Clauses 1 to 2, wherein the wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx, and the PRx controller is configured to cause the wireless communication unit to transmit a power request of a control message to the PTx.

[0093] Clause 5. The PRx controller is further configured to cause the wireless communication unit to transmit a phase transition request message associated with requesting PTx to transition to the power transmission phase during the connection phase, receive a confirmation response message from PTx in response to the phase transition request message via the wireless communication unit, and, after receiving the confirmation response message, further cause the wireless communication unit to transmit a request for power of the control message, the PRx described in Clause 4.

[0094] Clause 6. The PRx controller is further configured to detect whether an activation switch associated with the load is turned on and refrain from causing the wireless communication unit to transmit a phase transition request message until after the activation switch is turned on, the PRx described in Clause 5.

[0095] Clause 7. The phase transition request message, the confirmation response message, and the control message are associated with a WPT specification that defines the time when the protection switch changes from the first position to the second position such that the protection switch changes to the second position before the control message, the PRx described in any one of Clauses 5 to 6.

[0096] Clause 8. The WPT specification defines a first maximum time allowed between the phase transition request message and the confirmation response message and a second maximum time allowed between the confirmation response message and the control message, the PRx described in Clause 7.

[0097] Clause 9. The PRx controller is further configured to determine that an activation switch associated with the load is turned on and, after the activation switch is turned on and the protection switch is in the second position, cause PTx to transition to the power transmission phase, the PRx described in any one of Clauses 1 to 8.

[0098] Clause 10. An energy harvester integrated with or operably coupled to a wireless communication unit, the energy harvester configured to collect bias power from a communication signal received by a communication coil associated with the wireless communication unit and supply the bias power to a PRx controller at least during a connection phase to supply the PRx controller with bias power, the PRx according to any one of Clauses 1 to 9, further comprising such an energy harvester.

[0099] Clause 11. The PRx according to Clause 10, wherein the PRx controller is powered by bias power during a connection phase and at least partially powered by wireless power during a power transmission phase.

[0100] Clause 12. The PRx according to any one of Clauses 10 to 11, wherein the switch signal is generated using at least initially bias power.

[0101] Clause 13. The PRx controller according to any one of Clauses 1 to 12, configured to detect a state associated with the end of operation of a load, the state including a load switch that disconnects the load or a startup switch that is off, and based on the state, to transition the PTx and PRx from a power transmission phase to a connection phase, and further configured to change a protection switch to a first position with the transition from the power transmission phase to the connection phase.

[0102] Clause 14. The wireless communication unit is configured to communicate with the PTx by storing information in a passive tag readable by the wireless communication interface of the PTx, and the PRx controller is configured to modify the information of the passive tag to indicate zero power or a power-off request to transition the PTx to a connection phase and, after modifying the information of the passive tag, to change the protection switch to a first position, the PRx according to Clause 13.

[0103] Clause 15. The wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx. The PRx controller causes the wireless communication unit to transmit a second phase transition request message associated with requesting the PTx to transition to the connection phase. The PRx described in Clause 13, which, via the wireless communication unit, receives a second confirmation response message from the PTx in response to the second phase transition request message, the second confirmation response message indicating that the PTx has or will transition to the connection phase, and is configured to change the protection switch to the first position after receiving the second confirmation response message.

[0104] Clause 16. The PRx according to any one of Clauses 1 to 15, wherein the PRx controller further configures the wireless communication unit to communicate a zero power request message associated with pausing the transmission of wireless power to the load while remaining in the power transmission phase, and to communicate a non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time.

[0105] Clause 17. The PRx according to Clause 16, further including an energy harvester integrated with or operably coupled to the wireless communication unit, the energy harvester configured to collect bias power during the period between the zero power request message and the non-zero power request message from the communication signal received by the communication coil associated with the wireless communication unit in the power transmission phase.

[0106] Clause 18. The zero power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe turn-on operating point (SCOP) that is lower than that required by the load but sufficient to power the PRx controller or other components of the PRx.

[0107] Clause 19. The PRx according to any one of Clauses 16 to 18, wherein the load operates in an on-cycle and an off-cycle, the duration of the period is associated with the off-cycle, and the duration extends over one or more alternating current (AC) power cycles.

[0108] Clause 20. A power receiver (PRx) of a wireless power transfer (WPT) system, the PRx comprising a secondary coil operably coupled to a load associated with an on-cycle and an off-cycle, the secondary coil configured to receive wireless power from a power transmitter (PTx) during at least a portion of a power transfer phase of operation, a wireless communication unit, and a PRx controller configured to cause the wireless communication unit to communicate with the PTx to enter a power transfer phase in which the PTx can transmit wireless power, cause the wireless communication unit to communicate a non-zero power request associated with causing the PTx to transmit wireless power in association with an on-cycle of the load, and cause the wireless communication unit to communicate a zero power request message associated with causing the PTx to suspend transmission of wireless power in association with an off-cycle of the load while remaining in the power transfer phase.

[0109] Clause 21. The PRx according to Clause 20, wherein the load is associated with a series of on-cycles and off-cycles, and the PRx controller is configured to manage transmission of wireless power using a non-zero power request and a zero power request respectively associated with the on-cycle and the off-cycle.

[0110] Clause 22. The PRx according to any one of Clauses 20 to 21, further comprising an energy harvester integrated with or operably coupled to the wireless communication unit, the energy harvester configured to collect bias power from a communication signal received by a communication coil associated with the wireless communication unit in a power transfer phase during a period associated with the off-cycle.

[0111] Clause 23. The zero-power request message is associated with requesting transmission of radio power at a non-critical operating point (UOP) or a safe bypass operating point (SCOP) that is lower than that requested by the load but sufficient to power the PRx controller or other components of the PRx, and is the PRx described in any one of Clauses 20 to 22.

[0112] Clause 24. A power transmitter (PTx) of a wireless power transmission (WPT) system, the PTx comprising: an inverter configured to generate a wireless power signal; a primary coil operably coupled to the inverter and configured to transmit the wireless power signal with the transmission of wireless power to a secondary coil of a power receiver (PRx); a wireless communication interface configured to communicate with a wireless communication unit of the PRx; and a PTx controller configured to determine that the PRx is in an operation connection phase, receive, via the wireless communication interface, a power request for the PTx to transmit wireless power, the power request indicating an indication that the PRx has changed a protection switch to close a circuit including the secondary coil of the PRx, and cause the inverter to generate a wireless power signal for transmitting wireless power in response to the power request, and configured to transition from the operation connection phase to a power transmission phase.

[0113] Clause 25. The WPT specification defines the timing for the PRx to couple the secondary coil to the load during the connection phase and before the wireless power of the power request, such that the power request implicitly indicates that the PRx has coupled the secondary coil to the load in accordance with the WPT specification, for the PTx described in Clause 24.

[0114] Clause 26. The protection switch is arranged between the secondary coil and the load of the PRx. The protection switch is normally in a first position configured to open the circuit including the secondary coil. The PTx controller is configured to determine that the PRx changes the protection switch to a second position at least partially based on the power request for wireless power. The second position of the protection switch is configured to close the circuit including the secondary coil. The PTx according to any one of Clauses 24 to 25.

[0115] Clause 27. The PTx controller is further configured to perform a foreign object detection (FOD) evaluation during a connection phase before causing the inverter to generate a wireless power signal. The PTx according to any one of Clauses 24 to 26.

[0116] Clause 28. The wireless communication interface is configured to communicate with the wireless communication unit of the PRx by reading information of the passive tag of the wireless communication unit. The PTx controller is configured to receive a power request via an indication of power-on of the information. The PTx according to any one of Clauses 24 to 27.

[0117] Clause 29. The wireless communication interface is configured to receive a transmission from the wireless communication unit of the PRx. The PTx controller is configured to receive a power request via a control message in the transmission. The PTx according to any one of Clauses 24 to 26.

[0118] Clause 30. The PTx controller receives, during a connection phase, a phase transition request message from the PRX via the wireless communication interface. The phase transition request message is associated with a request to cause the PTx to transition to a power transmission phase. The wireless communication interface is further configured to transmit a confirmation response message to the PRx in response to the phase transition request message, and to receive a control message after transmitting the confirmation response message. The PTx according to Clause 29.

[0119] Clause 31. The PTx described in Clause 30 is configured such that the PTx controller performs an FOD evaluation after the phase transition request message and before the confirmation response message.

[0120] Clause 32. The PTx described in any one of Clauses 30 to 31, where the phase transition request message, the confirmation response message, and the control message are associated with the WPT specification that defines the timing for PRx to close the circuit including the secondary coil so that the circuit is closed before the control message.

[0121] Clause 33. The PTx described in Clause 32, where the WPT specification defines a first maximum time allowed between the phase transition request message and the confirmation response message and a second maximum time allowed between the confirmation response message and the control message.

[0122] Clause 34. The PTx described in any one of Clauses 32 to 33, where the WPT specification requires PRx to couple the secondary coil to the load via a protection switch before the power request.

[0123] Clause 35. The PTx described in any one of Clauses 24 to 34, where the wireless communication interface is configured to transmit a communication signal to the wireless communication unit of PRx at least during the connection phase, and the communication signal can be used by PRx to collect bias power to operate the PRx controller of PRx.

[0124] Clause 36. The PTx described in any one of Clauses 24 to 35, where the wireless communication interface is configured to receive a zero power or power off request from the information of the passive tag of the wireless communication unit of PRx, and the PTx controller is configured to stop generating a wireless power signal to the inverter in response to the zero power or power off request and transition to the connection phase.

[0125] Clause 37. After the PTx controller stops generating the wireless power signal for the inverter, the wireless communication interface is further configured to cause the PRx wireless communication unit of the PRx to transmit a communication signal, where the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx, as described in Clause 36 of the PTx.

[0126] Clause 38. The wireless communication interface is configured to receive a second phase transition request message associated with requesting the PTx to transition to the connection phase. The PTx controller causes the inverter to stop generating the wireless power signal, transition to the connection phase, and cause the wireless communication interface to transmit a second acknowledgment response message to the PRx in response to the second phase transition request message, where the second acknowledgment response message is configured to indicate that the PTx has or will transition to the connection phase, as described in any one of Clauses 24 to 35 of the PTx.

[0127] Clause 39. During the power transmission phase, the wireless communication interface is configured to receive a zero power request message associated with pausing the transmission of wireless power for the load while remaining in the power transmission phase. The PTx controller causes the inverter to stop generating the wireless power signal to transmit wireless power for the load in response to receiving zero power, and is configured to remain in the power transmission phase, as described in any one of Clauses 24 to 38 of the PTx.

[0128] Clause 40. During the power transmission phase, the wireless communication interface is configured to subsequently receive a non-zero power request message associated with resuming the transmission of wireless power for the load. The PTx controller is configured to cause the inverter to resume generating the wireless power signal to transmit wireless power for the load in response to receiving the non-zero power request, as described in Clause 39 of the PTx.

[0129] Clause 41. The PTx controller is further configured to cause the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx after stopping generating the wireless power signal for the inverter, the communication signal being usable by the PRx to collect bias power to operate the PRx controller in the power transmission phase during the period between the zero power request message and the non-zero power request message, the PTx as described in Clause 40.

[0130] Clause 42. The zero power request message is associated with requiring the transmission of wireless power at a non-critical operating point (UOP) or a safe turn-off operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx. The PTx controller, in response to receiving the zero power request, causes the inverter to generate a low power signal for the transmission of wireless power for the PRx controller at the UOP or SCOP, and the primary coil is configured to transmit the low power signal in association with the transmission of wireless power for the PRx controller, the PTx as described in any one of Clauses 39 to 40.

[0131] Clause 43. A power transmitter (PTx) of a wireless power transmission (WPT) system, the PTx including an inverter configured to generate a wireless power signal, a primary coil operably coupled to the inverter and configured to transmit the wireless power signal in association with the transmission of wireless power to a power receiver (PRx) during at least a portion of the power transmission phase of operation, a wireless communication interface configured to receive a power request from the PRx, and a PTx controller configured to communicate with the PRx via the wireless communication interface to enter the power transmission phase, and, if the power request is a non-zero power request, cause the inverter to generate a wireless power signal for transmitting wireless power to the load of the PRx in the power transmission phase, and, if the power request is a zero power request, cause the inverter to pause generating the wireless power signal for transmitting wireless power to the load in the power transmission phase.

[0132] Clause 44. The load of PRx is associated with a series of on - cycles and off - cycles, and the wireless communication interface is configured to receive a corresponding series of non - zero power requests and zero power requests respectively associated with the on - cycles and off - cycles, and the PTx controller is configured to control the inverter based at least in part on the series of non - zero power requests and zero power requests, the PTx described in Clause 43.

[0133] Clause 45. The PTx controller is further configured to cause the wireless communication interface to transmit a communication signal to the wireless communication unit of PRx during the period between the zero power request message and the non - zero power request message, and the communication signal is available for the PRx to collect bias power to operate the PRx controller of PRx during the power transmission phase during the period between the zero power request message and the non - zero power request message, the PTx described in any one of Clauses 43 to 44.

[0134] Clause 46. The zero power request message is associated with requiring the transmission of wireless power at a non - critical operating point (UOP) or a safe turn - off operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of PRx, and the PTx controller, in response to receiving the zero power request, causes the inverter to generate a low - power signal for the transmission of wireless power for the PRx controller at the UOP or SCOP, and the primary coil is configured to transmit the low - power signal along with the transmission of wireless power for the PRx controller, the PTx described in any one of Clauses 43 to 45.

[0135] Clause 47. A method for a power receiver (PRx) in a wireless power transfer (WPT) system, the method comprising: determining that a power transmitter (PTx) is in an operational connection phase with the PRx; during the connection phase, changing a protection switch of the PRx from a first position to a second position, the protection switch being disposed between a secondary coil of the PRx and a load associated with the PRx, the first position being configured to normally open a circuit including the secondary coil prior to an operational power transfer phase, and the second position being configured to close the circuit; communicating a power request to the PTx after the protection switch has been changed to the second position; transitioning from the connection phase to a power transfer phase; and receiving wireless power from the PTx during at least a portion of the power transfer phase.

[0136] Clause 48. Communicating the power request includes modifying information of a passive tag of a wireless communication unit of the PRx to include a power-on indication, the passive tag being readable by a wireless communication interface of the PTx, the method of clause 47.

[0137] Clause 49. Communicating the power request includes transmitting, via a wireless communication unit of the PRx, a power request as a control message to the PTx, the method of clause 47.

[0138] Clause 50. The method of clause 49 further includes transmitting a phase transition request message associated with requesting the PTx to transition to the power transfer phase during the connection phase; receiving an acknowledgement response message from the PTx in response to the phase transition request message; and transmitting a power request as a control message after receiving the acknowledgement response message.

[0139] Clause 51. The method of clause 50 further includes detecting whether an activation switch associated with the load has been turned on, and withholding transmitting the phase transition request message until after the activation switch has been turned on.

[0140] Clause 52. The phase transition request message, the confirmation response message, and the control message are associated with the WPT specification that defines the time when the protection switch changes from the first position to the second position such that the protection switch changes to the second position before the control message, and are in accordance with the method described in any one of Clauses 50 to 51.

[0141] Clause 53. The WPT specification defines the first maximum time allowed between the phase transition request message and the confirmation response message, and the second maximum time allowed between the confirmation response message and the control message, and is in accordance with the method described in Clause 52.

[0142] Clause 54. Further includes determining that the activation switch associated with the load is turned on, and causing the PTx to transition to the power transmission phase via communication with the PTx after the activation switch is turned on and the protection switch is in the second position, and is in accordance with the method described in any one of Clauses 47 to 53.

[0143] Clause 55. Using an energy harvester integrated with or operably coupled to the wireless communication unit to collect bias power from the communication signal received by the communication coil associated with the wireless communication unit of the PRx, and using the bias power to supply power to the PRx controller of the PRX at least during the connection phase, and is in accordance with the method described in any one of Clauses 47 to 54.

[0144] Clause 56. Further includes using bias power to supply power to the PRx controller during the connection phase, and using wireless power to supply power to the PRx controller during at least a part of the power transmission phase, and is in accordance with the method described in Clause 55.

[0145] Clause 57. Changing the protection switch of the PRx from the first position to the second position includes at least initially generating a switch signal for controlling the protection switch using bias power, and is in accordance with the method described in any one of Clauses 55 to 56.

[0146] Clause 58. Detecting a state associated with the end of the operation of a load, the state including a load switch that disconnects the load or a startup switch that is off, detecting, based on the state, shifting PTx and PRx from a power transmission phase to a connection phase, and changing a protection switch to a first position in connection with the shift from the power transmission phase to the connection phase, the method according to any one of Clauses 47 to 57, further comprising.

[0147] Clause 59. Determining to shift from a power transmission phase to a connection phase, modifying information of a passive tag of a wireless communication unit of PRx to indicate a zero power or power-off request for shifting PTx to the connection phase, the passive tag being readable by a wireless communication interface of PTx, modifying, and after modifying the information of the passive tag, changing a protection switch to a first position, the method according to Clause 58, further comprising.

[0148] Clause 60. Determining to shift from a power transmission phase to a connection phase, transmitting a second phase shift request message associated with requesting PTx to shift to the connection phase, receiving a second confirmation response message from PTx in response to the second phase shift request message, the second confirmation response message indicating that PTx has or will shift to the connection phase, receiving, and after receiving the second confirmation response message, changing a protection switch to a first position, the method according to Clause 58.

[0149] Clause 61. Communicating a zero power request message associated with suspending wireless power transmission for a load while remaining in the power transmission phase, and then communicating a non-zero power request message associated with resuming wireless power transmission to the load after a certain period, the method according to any one of Clauses 47 to 60, further comprising.

[0150] Clause 62. The method according to clause 61, further comprising collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit of PRx in a power transmission phase during a period between a zero power request message and a non-zero power request message.

[0151] Clause 63. A method of a power receiver (PRx) in a wireless power transfer (WPT) system, the method comprising coupling a secondary coil of the PRx to a load associated with an on-cycle and an off-cycle, the secondary coil being configured to receive wireless power from a power transmitter (PTx) during at least a portion of an active power transmission phase; communicating with the PTx to enter a power transmission phase in which the PTx can transmit wireless power to the PRx; communicating a non-zero power request to the PTX associated with the on-cycle of the load, the non-zero power request being associated with causing the PTx to transmit wireless power; and communicating a zero power request message to the PTX associated with the off-cycle of the load, the zero power request being associated with causing the PTx to pause wireless power transmission while remaining in the power transmission phase.

[0152] Clause 64. The method according to clause 63, further comprising controlling wireless power transmission using non-zero power requests and zero power requests respectively associated with the on-cycle and the off-cycle, wherein the load is associated with a series of on-cycles and off-cycles.

[0153] Clause 65. The method according to any one of clauses 63 to 64, further comprising collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit of PRx in a power transmission phase during a period associated with the off-cycle.

[0154] Clause 66. The zero power request message is associated with requesting transmission of radio power at a non-critical operating point (UOP) or a safe bypass operating point (SCOP) that is lower than that requested by the load but sufficient to supply power to the PRx controller or other components of the PRx, and is the method according to any one of Clauses 63 to 65.

[0155] Clause 67. A method of a power transmitter (PTx) in a wireless power transmission (WPT) system, the method comprising: determining, at least in part based on communication with the power receiver (PRx), that the PRx is in an operating connection phase with the PTx; receiving a power request from the PRx, the power request being associated with requesting transmission of radio power from the PTx to the PRx, and the power request indicating that the PRx has changed a protection switch to close a circuit including the secondary coil of the PRx; generating, by an inverter, a radio power signal for transmitting radio power in response to the power request; transitioning from the operating connection phase to a power transmission phase; and transmitting the radio power signal to the secondary coil of the PRx.

[0156] Clause 68. The WPT specification defines the timing at which the PRx couples the secondary coil to the load during the connection phase and before the power request for radio power, such that the power request implicitly indicates that the PRx has coupled the secondary coil to the load in accordance with the WPT specification, and is the method according to Clause 67.

[0157] Clause 69. The protection switch is disposed between the secondary coil and the load of the PRx, the protection switch is normally in a first position configured to open the circuit including the secondary coil, and the method further comprises determining, at least in part based on a power request for radio power, that the PRx has changed the protection switch to a second position, the second position of the protection switch being configured to close the circuit including the secondary coil, and is the method according to any one of Clauses 67 to 68.

[0158] The method according to any one of clauses 67 to 69, further comprising causing the inverter to perform a foreign object detection (FOD) evaluation during a connection phase before generating a wireless power signal.

[0159] Receiving a power request includes reading information of a passive tag of the wireless communication unit of the PRx and receiving the power request via a power-on indication of the information, according to the method of any one of clauses 67 to 70.

[0160] Receiving a power request includes receiving the power request via a control message in a transmission from the wireless communication unit of the PRx, according to the method of any one of clauses 67 to 69.

[0161] Receiving a phase transition request message from the PRX, the phase transition request message being associated with requesting the PTx to transition to a power transmission phase, receiving, transmitting an acknowledgment response message to the PRX in response to the phase transition request message, and receiving a control message after transmitting the acknowledgment response message, according to the method of clause 72.

[0162] The method according to clause 73, further comprising performing an FOD evaluation after the phase transition request message and before the acknowledgment response message.

[0163] The phase transition request message, the acknowledgment response message, and the control message are associated with a WPT specification that determines the timing for the PRx to close a circuit including a secondary coil so that the circuit is closed before the control message, according to any one of clauses 73 to 74.

[0164] The WPT specification determines a first maximum time allowed between the phase transition request message and the acknowledgment response message and a second maximum time allowed between the acknowledgment response message and the control message, according to the method of clause 75.

[0165] Clause 77. The WPT specification requires the method described in any one of Clauses 75 to 76, which requires the secondary coil to be coupled to the load via a protection switch before power is required, for PRx.

[0166] Clause 78. Transmitting a communication signal from the wireless communication interface of PTx to the wireless communication unit of PRx during at least the connection phase, where the communication signal is usable by PRx to collect bias power to operate the PRx controller of PRx, the method described in any one of Clauses 67 to 77 further including transmitting.

[0167] Clause 79. Receiving a zero power or power off request from the information of the passive tag of the wireless communication unit of PRx, in response to the zero power or power off request, stopping the inverter from generating a wireless power signal, and transitioning to the connection phase, the method described in any one of Clauses 67 to 78 further including these steps.

[0168] Clause 80. After stopping the inverter from generating a wireless power signal, transmitting a communication signal from the wireless communication interface of PTx to the wireless communication unit of PRx, where the communication signal is usable by PRx to collect bias power to operate the PRx controller of PRx, the method described in Clause 79 further including transmitting.

[0169] Clause 81. Receiving a second phase transition request message associated with requesting PTx to transition to the connection phase, stopping the inverter from generating a wireless power signal, transitioning to the connection phase, and in response to the second phase transition request message, transmitting a second confirmation response message to PRx, where the second confirmation response message indicates whether PTx has or will transition to the connection phase, the method described in any one of Clauses 67 to 78 further including transmitting.

[0170] Clause 82. Further comprising receiving a zero power request message associated with suspending wireless power transmission for a load while remaining in a power transmission phase, stopping the inverter from generating a wireless power signal to transmit wireless power for the load in response to receiving zero power, and remaining in the power transmission phase, the method according to any one of Clauses 67 to 81.

[0171] Clause 83. Further comprising receiving a non-zero power request message associated with resuming wireless power transmission for the load, and in response to receiving the non-zero power request, resuming the inverter from generating a wireless power signal to transmit wireless power for the load, the method according to Clause 82.

[0172] Clause 84. After stopping the inverter from generating a wireless power signal, causing the wireless communication interface of the PTx to transmit a communication signal to the wireless communication unit of the PRx, the communication signal being usable by the PRx to collect bias power to operate the PRx controller in the power transmission phase during the period between the zero power request message and the non-zero power request message, the method according to Clause 83.

[0173] Clause 85. The zero power request message is associated with requesting wireless power transmission at a non-critical operating point (UOP) or a safe turn-off operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx. The method further comprises, in response to receiving the zero power request, causing the inverter to generate a low power signal for wireless power transmission for the PRx controller at the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in association with wireless power transmission for the PRx controller, the method according to any one of Clauses 82 to 83.

[0174] Article 86. A method of a power transmitter (PTx) in a wireless power transfer (WPT) system, the method comprising: communicating with a power receiver (PRx) to enter an active power transfer phase; receiving a power request from the PRx, the power request being for controlling the transmission of wireless power to the load of the PRx during at least a portion of the power transfer phase; generating, in the power transfer phase, a wireless power signal for transmitting wireless power to the load to the inverter of the PTx when the power request is a non-zero power request; and pausing the generation of the wireless power signal for the load to the inverter while remaining in the power transfer phase when the power request is a zero power request.

[0175] Article 87. The method of Article 86, further comprising: receiving a series of non-zero power requests and zero power requests respectively associated with a series of on-cycles and off-cycles of the load of the PRx; and controlling the inverter at least partially based on the series of non-zero power requests and zero power requests.

[0176] Article 88. The method according to any one of Articles 86 to 87, further comprising causing the wireless communication interface of the PTx to transmit a communication signal to the wireless communication unit of the PRx during a period between a zero power request message and a non-zero power request message, the communication signal being usable by the PRx to collect bias power for operating the PRx controller of the PRx in the power transfer phase during the period between the zero power request message and the non-zero power request message.

[0177] Clause 89. The zero power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe bypass operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx. The method further includes, in response to receiving a zero power request, causing the inverter to generate a low power signal for the transmission of wireless power for the PRx controller at the UOP or SCOP, and transmitting the low power signal in association with the transmission of wireless power for the PRx controller, the method according to any one of clauses 86 to 88.

[0178] The figures, operations, and components described herein are examples intended to assist in the understanding of exemplary implementations and should not be used to limit potential implementations or the scope of the claims. Some implementations can include additional operations, fewer operations, operations in parallel or in a different order, and some operations can be performed differently.

[0179] As used herein, the phrase "at least one of" or "one or more of" a list of articles refers to any combination of those articles including a single member. 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, b, and c.

[0180] The various exemplary components, logics, logical blocks, modules, circuits, operations, and algorithm processes described in connection with the implementations disclosed herein can be implemented as electronic hardware, firmware, software, or any combination of hardware, firmware, or software, including the structures disclosed herein and their structural equivalents. The interchangeability of hardware, firmware, and software has been generally described in terms of functionality and is illustrated in the various exemplary components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the design constraints imposed on the particular application and the overall system.

[0181] The hardware and data processing devices used to implement the various exemplary components, logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented or executed using a general-purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device (PLD), discrete gates or transistor logic, discrete hardware components, or any arbitrary combination of these designed to perform the functions described herein. A general-purpose processor can be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. In some implementations, certain processes, operations, and methods can be executed by circuitry specific to a given function.

[0182] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, the various functions of the components disclosed herein, or the various blocks or steps of the methods, operations, processes, or algorithms 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 instructions 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 can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can 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.

[0183] Various changes to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Accordingly, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with the disclosure, principles, and novel features disclosed herein.

[0184] Furthermore, the various features described herein in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation can also be implemented separately in multiple implementations or in any suitable sub-combination. Thus, features may be described above as acting in a particular combination and may even initially be claimed as such, but one or more features from the claimed combination can, in some cases, be deleted from that combination, and the claimed combination can be directed to a partial combination or a variation of a partial combination.

[0185] Similarly, operations are shown in the drawings in a particular order, but this should not be understood as requiring that such operations be performed in the particular order shown or in a sequential order, or that all of the operations shown be performed, to achieve a desirable result. Further, the drawings can schematically show one or more exemplary processes in the form of a flowchart or a flow diagram. However, other operations not shown can be incorporated into the exemplary processes schematically shown. For example, one or more additional operations can be performed before, after, simultaneously with, or in between any of the operations shown. Depending on the circumstances, multitasking and parallel processing may be advantageous. Additionally, the separation of the 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 into a single software product or packaged into multiple software products.

Claims

1. A power receiver (PRx) of a wireless power transfer (WPT) system, wherein the PRx comprises: A secondary coil configured to receive wireless power from a power transmitter (PTx) during at least a part of an active power transfer phase; A protection switch disposed between the secondary coil and a load associated with the PRx, the protection switch being normally in a first position configured to open a circuit including the secondary coil prior to the power transfer phase; and A wireless communication unit; and The PRx controller, wherein It determines that the PTx is in an active connection phase with the PRx, Generates a switch signal configured to change the protection switch to a second position during the connection phase, the second position being configured to close the circuit including the secondary coil, After the protection switch is changed to the second position, causes the wireless communication unit to communicate a request for power to the PTx for transmitting the wireless power, A PRx controller configured to transition from the connection phase to the power transfer phase, comprising a PRx.

2. The PRx according to claim 1, wherein when the protection switch is in the second position, the secondary coil can receive the wireless power and supply the wireless power to the load during the power transfer phase.

3. The wireless communication unit is configured to communicate with the PTx by storing information in a passive tag readable by the wireless communication interface of the PTx, The PRx controller is configured to communicate the power request by modifying the information of the passive tag to include a power-on indication to the wireless communication unit, according to any one of claims 1 to 2. The described PRx.

4. The wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx, The PRx controller is configured to cause the wireless communication unit to transmit the power request of the control message to the PTx, according to any one of claims 1 to 2. The described PRx.

5. The PRx controller is during the connection phase, Causing the wireless communication unit to transmit a phase transition request message associated with requesting the PTx to transition to the power transmission phase, Receiving, via the wireless communication unit, an acknowledgment message from the PTx in response to the phase transition request message, The PRx according to claim 4, further configured to cause the wireless communication unit to transmit the power request of the control message after receiving the acknowledgment message.

6. The PRx controller, Detecting whether an activation switch associated with the load is turned on, The PRx according to claim 5, further configured to refrain from causing the wireless communication unit to transmit the phase transition request message until after the activation switch is turned on.

7. The phase transition request message, the acknowledgment message, and the control message are associated with a WPT specification that defines a time when the protection switch changes from the first position to the second position such that the protection switch is changed to the second position before the control message. The PRx according to any one of claims 5 to 6.

8. The WPT specification, Defining a first maximum time allowed between the phase transition request message and the acknowledgment message, The PRx according to claim 7, defining a second maximum time allowed between the acknowledgment message and the control message.

9. The PRx controller, Determining that an activation switch associated with the load has been turned on, The PRx according to any one of claims 1 to 8, further configured to cause the PTx to transition to the power transmission phase after the activation switch is turned on and the protection switch is in the second position.

10. An energy harvester integrated with or operably coupled to the wireless communication unit, the energy harvester, Collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit, The PRx according to any one of claims 1 to 9, further comprising an energy harvester configured to supply the bias power to the PRx controller at least during the connection phase to supply power to the PRx controller.

11. The PRx controller is powered by the bias power during the connection phase and at least partially powered by the wireless power during the power transmission phase, the PRx according to claim 10.

12. The switch signal is generated using at least initially the bias power, the PRx according to any one of claims 10 to 11.

13. The PRx controller, detects a state associated with the end of operation of the load, the state including a load switch that disconnects the load or a startup switch that is off, based on the state, shifts the PTx and the PRx from the power transmission phase to the connection phase, is further configured to change the protection switch to the first position with the transition from the power transmission phase to the connection phase, the PRx according to any one of claims 1 to 12.

14. The wireless communication unit is configured to communicate with the PTx by storing information in a passive tag readable by the wireless communication interface of the PTx, The PRx controller, shifts the PTx to the connection phase by modifying the information of the passive tag to indicate zero power or a power-off request, is configured to change the protection switch to the first position after modifying the information of the passive tag, the PRx according to claim 13.

15. The wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx, The PRx controller, causes the wireless communication unit to transmit a second phase transition request message associated with requesting the PTx to transition to the connection phase, receives, via the wireless communication unit, a second confirmation response message from the PTx in response to the second phase transition request message, the second confirmation response message indicating that the PTx has or will transition to the connection phase, is configured to change the protection switch to the first position after receiving the second confirmation response message, the PRx according to claim 13.

16. The PRx controller, Cause the wireless communication unit to communicate a zero-power request message associated with the suspension of wireless power transmission to the load while remaining in the power transmission phase. The PRx according to any one of claims 1 to 15, further configured to cause the wireless communication unit to communicate a non-zero power request message associated with resuming the transmission of the wireless power to the load after a period of time. **Claim 17** An energy harvester integrated with or operably coupled to the wireless communication unit, configured to collect bias power during the period between the zero-power request message and the non-zero power request message from a communication signal received by a communication coil associated with the wireless communication unit in the power transmission phase. The PRx according to claim 16 further comprises the energy harvester. **Claim 18** The zero-power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe current transfer operating point (SCOP) that is lower than that required by the load but sufficient to supply power to the PRx controller or other components of the PRx. The PRx according to claim 16. **Claim 19** The PRx according to any one of claims 16 to 18, wherein the load operates in on-cycles and off-cycles, the duration of the period is associated with the off-cycle, and the duration extends over one or more alternating current (AC) power cycles. **Claim 20** A power receiver (PRx) of a wireless power transmission (WPT) system, wherein the PRx comprises: A secondary coil operably coupled to a load associated with on-cycles and off-cycles, configured to receive wireless power from a power transmitter (PTx) during at least a part of an operating power transmission phase. A wireless communication unit, and A PRx controller, wherein Cause the wireless communication unit to communicate with the PTx to cause the PTx to enter the power transmission phase in which the wireless power can be transmitted. Cause the wireless communication unit to communicate a non-zero power request associated with causing the PTx to transmit the wireless power along with the on-cycle of the load. A PRx comprising a PRx controller configured to communicate to the wireless communication unit a zero-power request message associated with pausing the transmission of the wireless power to the PTx in accordance with the off-cycle of the load while remaining in the power transmission phase.

21. The PRx according to claim 20, wherein the load is associated with a series of on-cycles and off-cycles, and the PRx controller is configured to manage the transmission of the wireless power using non-zero power requests and zero-power requests respectively associated with the on-cycles and off-cycles.

22. The PRx according to any one of claims 20 to 21, further comprising an energy harvester integrated with or operably coupled to the wireless communication unit, the energy harvester being configured to collect bias power from a communication signal received by a communication coil associated with the wireless communication unit in the power transmission phase during a period associated with the off-cycle.

23. The PRx according to any one of claims 20 to 22, wherein the zero-power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe current transfer operating point (SCOP) that is lower than that required by the load but sufficient to power the PRx controller or other components of the PRx.

24. A power transmitter (PTx) of a wireless power transmission (WPT) system, the PTx comprising an inverter configured to generate a wireless power signal, a primary coil operably coupled to the inverter and configured to transmit the wireless power signal in association with the transmission of the wireless power to a secondary coil of a power receiver (PRx), a wireless communication interface configured to communicate with a wireless communication unit of the PRx, and a PTx controller, wherein the PTx controller determines that the PRx is in an operation connection phase with the PTx, receives, via the wireless communication interface, a request for power for the PTx to transmit the wireless power, the request for power indicating that the PRx has changed a protection switch for closing a circuit including the secondary coil of the PRx. Cause the inverter to generate the wireless power signal for transmitting the wireless power in response to the power request. A PTx comprising a PTx controller configured to transition from the connection phase to the power transmission phase of operation. **Claim 25** The WPT specification defines the timing at which the PRx couples the secondary coil to the load during the connection phase and before the power request for the wireless power, such that the power request implicitly indicates that the PRx has coupled the secondary coil to the load according to the WPT specification. The PTx according to claim 24. **Claim 26** The protection switch is disposed between the secondary coil and the load of the PRx. The protection switch is normally in a first position configured to open the circuit including the secondary coil. The PTx controller is configured to determine that the PRx has changed the protection switch to a second position at least partially based on the power request for wireless power. The second position of the protection switch is configured to close the circuit including the secondary coil. The PTx according to any one of claims 24 to 25. **Claim 27** The PTx controller is further configured to perform a foreign object detection (FOD) evaluation during the connection phase before causing the inverter to generate the wireless power signal. The PTx according to any one of claims 24 to 26. **Claim 28** The wireless communication interface is configured to communicate with the wireless communication unit of the PRx by reading information of the passive tag of the wireless communication unit. The PTx controller is configured to receive the power request via the power-on indication of the information. The PTx according to any one of claims 24 to 27. **Claim 29** The wireless communication interface is configured to receive transmissions from the wireless communication unit of the PRx. The PTx controller is configured to receive the power request via a control message in the transmission. The PTx according to any one of claims 24 to 26. **Claim 30** The PTx controller during the connection phase Receiving, from the PRx, a phase transition request message via the wireless communication interface, the phase transition request message being associated with a request for the PTx to transition to the power transmission phase, Causing the wireless communication interface to transmit an acknowledgement response message to the PRx in response to the phase transition request message, The PTx according to claim 29, further configured to receive the control message after transmitting the acknowledgement response message.

31. The PTx according to claim 30, wherein the PTx controller is configured to perform an FOD evaluation after the phase transition request message and before the acknowledgement response message.

32. The phase transition request message, the acknowledgement response message, and the control message are associated with a WPT specification that determines a timing for the PRx to close the circuit including the secondary coil so that the circuit is closed before the control message, according to any one of claims 30 to 31.

33. The WPT specification is A first maximum time allowed between the phase transition request message and the acknowledgement response message, and A second maximum time allowed between the acknowledgement response message and the control message, according to claim 32.

34. The WPT specification requests the PRx to couple the secondary coil to the load via the protection switch before the power request, according to any one of claims 32 to 33.

35. The wireless communication interface is configured to transmit a communication signal to the wireless communication unit of the PRx at least during the connection phase, the communication signal being usable by the PRx to collect bias power to operate the PRx controller of the PRx, according to any one of claims 24 to 34.

36. The wireless communication interface is configured to receive a zero power or power off request from information of a passive tag of the wireless communication unit of the PRx, The PTx controller is Stopping generating the wireless power signal to the inverter in response to the zero power or power off request, and Configured to transition to the connection phase, according to any one of claims 24 to 35.

37. The PTx controller is further configured to cause the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx after stopping generating the wireless power signal to the inverter, the communication signal being usable by the PRx to collect bias power to operate the PRx controller of the PRx. The PTx according to claim 36.

38. The wireless communication interface is configured to receive a second phase transition request message associated with requesting the PTx to transition to the connection phase, The PTx controller, causes the inverter to stop generating the wireless power signal, transitions to the connection phase, and causes the wireless communication interface to transmit a second confirmation response message to the PRx in response to the second phase transition request message, the second confirmation response message being configured to indicate that the PTx has or will transition to the connection phase. The PTx according to any one of claims 24 to 35.

39. During the power transmission phase, the wireless communication interface is configured to receive a zero power request message associated with pausing the transmission of the wireless power for the load while remaining in the power transmission phase, The PTx controller, causes the inverter to stop generating the wireless power signal for transmitting the wireless power for the load in response to receiving the zero power, and is configured to remain in the power transmission phase. The PTx according to any one of claims 24 to 38.

40. During the power transmission phase, the wireless communication interface is configured to subsequently receive a non-zero power request message associated with resuming the transmission of the wireless power for the load, The PTx controller is configured to cause the inverter to resume generating the wireless power signal for transmitting the wireless power for the load in response to receiving the non-zero power request. The PTx according to claim 39.

41. After the PTx controller stops the inverter from generating the wireless power signal, the PTx controller is further configured to cause the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx, where the communication signal is for collecting bias power to operate the PRx controller of the PRx in the power transmission phase during the period between the zero power request message and the non-zero power request message, and is usable by the PRx. The PTx according to claim 40.

42. The zero power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe commutation operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx. The PTx controller In response to receiving the zero power request, the PTx controller causes the inverter to generate a low power signal for the transmission of the wireless power for the PRx controller at the UOP or SCOP, and the primary coil is configured to transmit the low power signal along with the transmission of the wireless power for the PRx controller. The PTx according to any one of claims 39 to 40.

43. A power transmitter (PTx) of a wireless power transmission (WPT) system, where the PTx An inverter configured to generate a wireless power signal. A primary coil operably coupled to the inverter and configured to transmit the wireless power signal along with the transmission of wireless power to a power receiver (PRx) during at least a part of the power transmission phase of operation. A wireless communication interface configured to receive a power request from the PRx, and A PTx controller, where The PTx controller communicates with the PRx through the wireless communication interface to enter the power transmission phase. When the power request is a non-zero power request, during the power transmission phase, the PTx controller causes the inverter to generate the wireless power signal for transmitting the wireless power to the load of the PRx. When the power request is a zero power request, during the power transmission phase, the PTx controller is configured to pause the generation of the wireless power signal for transmitting the wireless power to the load. The PTx includes the PTx controller.

44. the load of the PRx is associated with a series of on-cycles and off-cycles, the wireless communication interface is configured to receive a corresponding series of non-zero power requests and zero power requests respectively associated with the on-cycles and off-cycles, the PTx controller is configured to control the inverter at least partially based on the series of non-zero power requests and zero power requests, the PTx according to claim 43.

45. the PTx controller is further configured to cause the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx during a period between a zero power request message and a non-zero power request message, the communication signal is usable by the PRx to collect bias power to operate the PRx controller of the PRx in the power transmission phase during the period between the zero power request message and the non-zero power request message, the PTx according to any one of claims 43 to 44.

46. the zero power request message is associated with requiring transmission of wireless power at a non-critical operating point (UOP) or a safe turn-off operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx, the PTx controller, in response to receiving the zero power request, causes the inverter to generate a low power signal for the transmission of the wireless power for the PRx controller at the UOP or SCOP, and the primary coil is configured to transmit the low power signal along with the transmission of the wireless power for the PRx controller, the PTx according to any one of claims 43 to 45.

47. A method of a power receiver (PRx) in a wireless power transfer (WPT) system, the method comprising: determining that a power transmitter (PTx) is in an operation connection phase with the PRx, During the connection phase, changing the protection switch of the PRx from a first position to a second position, the protection switch being disposed between the secondary coil of the PRx and a load associated with the PRx, the first position being configured to normally open a circuit including the secondary coil prior to the power transmission phase of operation, and the second position being configured to close the circuit. After the protection switch is changed to the second position, communicating a power request to the PTx. Transitioning from the connection phase to the power transmission phase, and Receiving wireless power from the PTx during at least a portion of the power transmission phase. A method comprising.

48. Communicating the power request includes modifying information of a passive tag of a wireless communication unit of the PRx to include a power-on indication, the passive tag being readable by a wireless communication interface of the PTx. The method according to claim 47.

49. Communicating the power request includes transmitting the power request to the PTx in a control message via a wireless communication unit of the PRx. The method according to claim 47.

50. During the connection phase, Transmitting a phase transition request message associated with requesting the PTx to transition to the power transmission phase, Receiving an acknowledgment response message from the PTx in response to the phase transition request message, and Further comprising transmitting the power request of the control message after receiving the acknowledgment response message. The method according to claim 49.

51. Detecting whether an activation switch associated with the load has been turned on, and Further comprising refraining from transmitting the phase transition request message until after the activation switch has been turned on. The method according to claim 50.

52. The phase transition request message, the acknowledgment response message, and the control message are associated with a WPT specification that defines a time when the protection switch changes from the first position to the second position such that the protection switch changes to the second position prior to the control message. The method according to any one of claims 50 to 51.

53. The WPT specification is defining a first maximum time allowed between the phase transition request message and the confirmation response message, and defining a second maximum time allowed between the confirmation response message and the control message, the method according to claim 52. **Claim 54** determining that an activation switch associated with the load is turned on, and further comprising, via communication with the PTx, after the activation switch is turned on and the protection switch is in the second position, causing the PTx to transition to the power transmission phase, the method according to any one of claims 47 to 53. **Claim 55** collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit of the PRx using an energy harvester integrated with or operably coupled to the wireless communication unit, and further comprising powering the PRx controller of the PRX using the bias power at least during the connection phase, the method according to any one of claims 47 to 54. **Claim 56** powering the PRx controller using the bias power during the connection phase, and further comprising powering the PRx controller using the wireless power during at least a part of the power transmission phase, the method according to claim 55. **Claim 57** changing the protection switch of the PRx from the first position to the second position comprises at least initially generating a switch signal for controlling the protection switch using the bias power, the method according to any one of claims 55 to 56. **Claim 58** detecting a state associated with the end of operation of the load, the state including a load switch for disconnecting the load or an activation switch that is off, based on the state, causing the PTx and the PRx to transition from the power transmission phase to the connection phase, and further comprising changing the protection switch to the first position with the transition from the power transmission phase to the connection phase, the method according to any one of claims 47 to 57. **Claim 59** determining to transition from the power transmission phase to the connection phase Modifying the information of the passive tag of the wireless communication unit of the PRx to indicate a zero power or power-off request for transitioning the PTx to the connection phase, wherein the passive tag can be read by the wireless communication interface of the PTx, modifying, and After modifying the information of the passive tag, further comprising changing the protection switch to the first position, the method according to claim 58.

60. Determining to transition from the power transmission phase to the connection phase, Transmitting a second phase transition request message associated with requesting the PTx to transition to the connection phase, Receiving a second confirmation response message from the PTx in response to the second phase transition request message, wherein the second confirmation response message indicates that the PTx has or will transition to the connection phase, receiving, and After receiving the second confirmation response message, changing the protection switch to the first position, the method according to claim 58.

61. Communicating a zero power request message associated with suspending the transmission of wireless power for the load while remaining in the power transmission phase, and Thereafter, communicating a non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time, the method according to any one of claims 47 to 60.

62. Further comprising collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit of the PRx in the power transmission phase during the period between the zero power request message and the non-zero power request message, the method according to claim 61.

63. A method of a power receiver (PRx) in a wireless power transfer (WPT) system, the method comprising: Coupling a secondary coil of the PRx to a load associated with on-cycles and off-cycles, the secondary coil being configured to receive wireless power from a power transmitter (PTx) during at least a portion of an active power transmission phase, coupling, Communicating with the PTx for the PTx to enter a power transmission phase in which the PTx can transmit wireless power to the PRx, Communicating a non-zero power request associated with the on-cycle of the load to the PTx, wherein the non-zero power request is associated with communicating and communicating a zero power request message to the PTx in association with the off-cycle of the load, wherein the zero power request is associated with causing the PTx to pause the transmission of the wireless power while remaining in the power transmission phase, a method comprising. **Claim 64** The load is associated with a series of on-cycles and off-cycles, and the method further comprises controlling the transmission of the wireless power using the non-zero power request and the zero power request respectively associated with the on-cycle and the off-cycle. The method according to claim 63. **Claim 65** The method according to any one of claims 63 to 64, further comprising collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit of the PRx in the power transmission phase during a period associated with the off-cycle. **Claim 66** The zero power request message is associated with requesting the transmission of wireless power at a non-critical operating point (UOP) or a safe turn-off operating point (SCOP) that is lower than that required by the load but sufficient to power the PRx controller or other components of the PRx. The method according to any one of claims 63 to 65. **Claim 67** A method of a power transmitter (PTx) in a wireless power transmission (WPT) system, the method comprising: determining, at least in part based on communication with the PRx, that the power receiver (PRx) is in an operation connection phase with the PTx; receiving a power request from the PRx, wherein the power request is associated with requesting transmission of wireless power from the PTx to the PRx, and the power request represents an indication that the PRx has changed the protection switch to close a circuit including the secondary coil of the PRx; causing an inverter to generate a wireless power signal for transmitting the wireless power in response to the power request; transitioning from the operation connection phase to a power transmission phase, and A method comprising transmitting the wireless power signal to transmit the wireless power to the secondary coil of the PRx. **Claim 68** The WPT specification determines the timing at which the PRx couples the secondary coil to the load during the connection phase and before the power requirement of the wireless power, such that the power requirement implicitly indicates that the PRx has coupled the secondary coil to the load in accordance with the WPT specification. The method according to claim 67. **Claim 69** The protection switch is disposed between the secondary coil and the load of the PRx. The protection switch is normally in a first position configured to open the circuit including the secondary coil. The method includes Determining that the PRx changes the protection switch to a second position based at least in part on the power requirement for the wireless power, wherein the second position of the protection switch is configured to close the circuit including the secondary coil. The method according to any one of claims 67 to 68, further comprising. **Claim 70** The method according to any one of claims 67 to 69, further comprising performing a foreign object detection (FOD) evaluation during the connection phase before causing the inverter to generate the wireless power signal. **Claim 71** Receiving the power requirement includes Reading information of a passive tag of the wireless communication unit of the PRx, and Receiving the power requirement via a power-on indication of the information. The method according to any one of claims 67 to 70. **Claim 72** Receiving the power requirement includes Receiving the power requirement via a control message in a transmission from the wireless communication unit of the PRx. The method according to any one of claims 67 to 69. **Claim 73** Receiving a phase transition request message from the PRX, wherein the phase transition request message is associated with requesting the PTx to transition to the power transmission phase. Transmitting an acknowledgement response message to the PRx in response to the phase transition request message, and Receiving the control message after transmitting the acknowledgement response message. The method according to claim 72, further comprising. **Claim 74** The method according to claim 73, further comprising performing an FOD evaluation after the phase transition request message and before the confirmation response message. **Claim 75** The phase transition request message, the confirmation response message, and the control message are associated with a WPT specification that determines a timing for the PRx to close the circuit including the secondary coil so that the circuit is closed before the control message, according to any one of claims 73 to 74. **Claim 76** The WPT specification defines a first maximum time allowed between the phase transition request message and the confirmation response message, and a second maximum time allowed between the confirmation response message and the control message, according to claim 75. **Claim 77** The WPT specification requires the PRx to couple the secondary coil to the load via the protection switch before the power request, according to any one of claims 75 to 76. **Claim 78** Transmitting a communication signal from the wireless communication interface of the PTx to the wireless communication unit of the PRx at least during the connection phase, the communication signal being usable by the PRx to collect bias power to operate the PRx controller of the PRx, further comprising, according to any one of claims 67 to 77. **Claim 79** Receiving a zero power or power off request from information of a passive tag of the wireless communication unit of the PRx, responding to the zero power or power off request by stopping the inverter from generating the wireless power signal, and transitioning to the connection phase, further comprising, according to any one of claims 67 to 78. **Claim 80** After stopping the inverter from generating the wireless power signal, transmitting a communication signal from the wireless communication interface of the PTx to the wireless communication unit of the PRx, the communication signal being usable by the PRx to collect bias power to operate the PRx controller of the PRx, further comprising, according to claim 79. **Claim 81** Receiving a second phase transition request message associated with requesting the PTx to transition to the connection phase causing the inverter to stop generating the wireless power signal; transitioning to the connection phase; and responding to the second phase transition request message by transmitting a second confirmation response message to the PRx, the second confirmation response message indicating that the PTx has or will have a transition to the connection phase, the method according to any one of claims 67 to 78, further comprising transmitting.

82. During the power transmission phase, receiving a zero power request message associated with pausing the transmission of the wireless power for the load while remaining in the power transmission phase; causing the inverter to stop generating the wireless power signal for transmitting the wireless power for the load in response to receiving the zero power; and remaining in the power transmission phase, the method according to any one of claims 67 to 81, further comprising.

83. subsequently, receiving a non-zero power request message associated with resuming the transmission of the wireless power for the load; and responding to receiving the non-zero power request by causing the inverter to resume generating the wireless power signal for transmitting the wireless power for the load, the method according to claim 82, further comprising.

84. after causing the inverter to stop generating the wireless power signal, causing the wireless communication interface of the PTx to transmit a communication signal to the wireless communication unit of the PRx, the communication signal being usable by the PRx to collect bias power to operate the PRx controller in the power transmission phase during the period between the zero power request message and the non-zero power request message, the method according to claim 83, further comprising transmitting.

85. The zero power request message is associated with requesting transmission of wireless power at a non-critical operating point (UOP) or a safe turn-on operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx, the method comprising In response to receiving the zero power request, causing the inverter to generate a low power signal for the transmission of the wireless power for the PRx controller in the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in connection with the transmission of the wireless power for the PRx controller, the method according to any one of claims 82 to 83, further comprising causing.

86. A method of a power transmitter (PTx) in a wireless power transmission (WPT) system, the method comprising: Communicating with a power receiver (PRx) to enter a power transmission phase of operation; Receiving a power request from the PRx, the power request being for controlling the transmission of wireless power to the load of the PRx during at least a portion of the power transmission phase; When the power request is a non-zero power request, in the power transmission phase, causing the inverter of the PTx to generate a wireless power signal for transmitting the wireless power for the load; and When the power request is a zero power request, pausing the generation of the wireless power signal for the load in the inverter while remaining in the power transmission phase.

87. The load of the PRx is associated with a series of on-cycles and off-cycles, and the method further comprises: Receiving a series of non-zero power requests and zero power requests respectively associated with the series of on-cycles and off-cycles; and Controlling the inverter at least partially based on the series of non-zero power requests and zero power requests. The method according to claim 86.

88. Further comprising causing the wireless communication interface of the PTx to transmit a communication signal to the wireless communication unit of the PRx during a period between a zero power request message and a non-zero power request message, The communication signal being usable by the PRx to collect bias power to operate the PRx controller of the PRx in the power transmission phase during the period between the zero power request message and the non-zero power request message. The method according to any one of claims 86 to 87.

89. The zero power request message is associated with requiring transmission of wireless power at a non-critical operating point (UOP) or a safe current diversion operating point (SCOP) that is lower than required by the load but sufficient to power the PRx controller or other components of the PRx, and the method is, in response to receiving the zero power request, causing the inverter to generate a low power signal for the transmission of the wireless power for the PRx controller at the UOP or SCOP, and transmitting the low power signal in association with the transmission of the wireless power for the PRx controller, the method according to any one of claims 86 to 88, further comprising.

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