Operating phases in wireless power transfer (WPT) system

Abstract

This disclosure provides systems, methods, and devices for managing phase transitions for a wireless power transfer (WPT) system. For example, transitions between a connection phase and a power transfer phase may be coordinated in connection with changing the protection switch (s) in the power receiver. The protection switch may decouple or couple a secondary coil of the power receiver from a power receiving circuit, such as a load or rectifier. The first position of the protection switch may open a circuit including the secondary coil and the power receiving circuit. The second position of the protection switch may close the circuit such that the secondary coil may receive the wireless power and provide the wireless power to the load during the power transfer phase. The disclosure also describes how the WPT system may temporarily suspend wireless power transfer while remaining in the power transfer phase.

Description

Technical Field

[0001] The present disclosure relates generally to wireless power and, in some implementations, specifically to operating stages in a wireless power transfer system. Background Art

[0002] Technology has been developed to enable power to be wirelessly transmitted from a power transmitter to a power receiver. Examples of power receivers may include some types of mobile devices, small electronic devices, computers, tablets, gadgets, appliances (such as cordless blenders, kettles or mixers) and some types of larger electronic devices, as well as other examples. Wireless power transmission may be referred to as contactless power transmission or contactless power transmission. Wireless power may be transmitted using inductive coupling or resonant coupling between the primary coil of the power transmitter and the secondary coil of the power receiver. For example, a power transmitter may include a primary coil that generates a magnetic field. When the secondary coil is placed near the primary coil, the magnetic field may induce an electromotive force in the secondary coil of the power receiver. In this configuration, the magnetic field may wirelessly transmit power to the secondary coil.

[0003] The wireless power transmission system can operate in different operation 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 extend beyond traditional wireless power transmission. There is a need for power receivers and power transmitters to coordinate transitions between various operations based on the newly developed features. Summary of the invention

[0004] The systems, methods and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

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

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

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

[0008] Another innovative aspect of the subject matter described in the present disclosure can be implemented as a PTx of a WPT system. The PTx may include an inverter configured to generate a wireless power signal. The PTx may include a primary coil operatively coupled to the inverter and configured to transmit a wireless power signal in association with the transmission of wireless power to the PRx during at least a portion of the power transmission phase of operation. The PTx may include a wireless communication interface configured to receive a power request from the PRx. The PTx may include a PTx controller. The PTx controller may be configured to enable the wireless communication interface to communicate with the PRx to enter the power transmission phase. The PTx controller may be configured to enable the inverter to generate a wireless power signal for the transmission of 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 may be configured to enable the inverter to suspend the generation of a wireless power signal for the transmission of 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 the present disclosure can be implemented as a method for PRx in a WPT system. The method may include determining that the PTx is in a connection phase of operation with the PRx. The method may 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, wherein the first position is configured to normally disconnect a circuit including the secondary coil before a power transfer phase of operation, wherein the second position is configured to close the circuit. The method may include transmitting a power request to the PTx after the protection switch is changed to the second position. The method may include transitioning from the connection phase to the power transfer phase, and receiving wireless power from the PTx during at least a portion of the power transfer phase.

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

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

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

[0013] The 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, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of an example wireless power transfer system is shown.

[0015] Figure 2 A block diagram of an example power transmitter is shown.

[0016] Figure 3 A block diagram of an example power receiver with a protection switch is shown.

[0017] Figure 4 A block diagram of another example power receiver with a protection switch is shown.

[0018] Figure 5 A block diagram of an example power receiver having a protection switch including a plurality of switches is shown.

[0019] Figure 6 A state diagram showing various example operating phases of a WPT system.

[0020] Figure 7 A flow chart illustrating an example process for a power receiver according to some implementations is shown.

[0021] Figure 8 A flow chart illustrating an example process for a power transmitter according to some implementations is shown.

[0022] Fig. 9 A timing diagram showing an example transition from a connection phase to a power transfer phase in a WPT system using a Type 0 control architecture.

[0023] Fig.10 A timing diagram of a WPT protocol with time constraints is shown in which it is defined.

[0024] Fig.11 A timing diagram showing an example transition from a power transfer phase to a connection phase in a WPT system using a Type 0 control architecture.

[0025] Fig.12 A timing diagram showing an example transition from a connection phase to a power transfer phase in a WPT system using a Type 1 control architecture.

[0026] Fig.13 A timing diagram showing an example transition from a power transfer phase to a connection phase in a WPT system using a type 1 control architecture.

[0027] Fig.14 A flow chart illustrating an example process for a power receiver to control wireless power transfer during a power transfer phase according to some implementations.

[0028] Fig.15 A flow chart illustrating an example process of a power transmitter controlling wireless power transfer during a power transfer phase according to some implementations.

[0029] Fig.16 A timing diagram is shown in which zero power requests and non-zero power requests are used during the power transfer phase.

[0030] Fig.17 A timing diagram is shown in which a low power operating point can be used while remaining in the power transfer phase.

[0031] Fig.18 A block diagram of an example device for use in a wireless power transfer system is shown.

[0032] Note that the relative sizes of the following figures may not be drawn to scale. Like reference numerals and names in the various drawings indicate like elements. DETAILED DESCRIPTION

[0033] A wireless power transfer (WPT) system may include a power transmitter (sometimes referred to as a "wireless power transfer device", "power transmitter" or "PTx") and a power receiver (sometimes referred to as a "wireless power receiving device", "power receiver" or "PRx"). The power transmitter may include one or more primary coils that transfer wireless energy (as a wireless power signal) to one or more corresponding secondary coils in the power receiver. The primary coil refers to a wireless energy source in the power transmitter (such as inductive or magnetic resonance energy that produces a magnetic field). The secondary coil located in the power receiver can receive wireless energy via a magnetic field. Wireless power transfer refers to the transmission and reception of wireless energy. Wireless energy can be used to power a load or other components associated with the power receiver; therefore, wireless energy can be referred to as wireless power.

[0034] The WPT system operates in different phases, such as an idle phase, a configuration phase, a connection phase, and a power transmission phase. For example, the power transmitter usually starts in an idle phase after being turned on. Turning on the power transmitter refers to powering the controller, the communication unit, the driver, or other components of the power transmitter other than the primary coil. The primary coil is only done in the power transmission phase after the communication between the power receiver and the power transmitter is powered on. Since new features have been introduced into the power transmitter design, the transitions between some phases may be unclear. For example, the new features may include a protection switch in a circuit including a secondary coil. The first position of the protection switch can prevent the secondary coil from inducing a voltage from a magnetic field. The second position of the protection switch can enable the secondary coil to receive an induced voltage from a magnetic field. The present disclosure includes descriptions of several types of protection switches. There is a need to manage the transitions between some operating phases in coordination with the position of the protection switch. Similarly, the transitions between operating phases may depend on other new features, such as a foreign object detection sequence, an activation switch controlled by a user, a load switch associated with a load, the availability of a wired power source, or certain types of loads, and other examples.

[0035] The present disclosure provides systems, methods, and devices for managing phase transitions of WPT systems. In some implementations, the transition between the connection phase and the power transmission phase (or vice versa) can be coordinated with changing the protection switch in the power receiver. The present disclosure describes how communications can be constructed to coordinate phase transitions associated with the protection switch. Examples of the present disclosure can be used with various types of control architectures, including those in which the power receiver implements a variable load and the load controller transmits power commands to directly control the wireless power transmission, and those in which the power receiver has a simple load (like a heater load with a single power setting) and relies on the control loop of the power transmitter. The present disclosure also describes how the WPT system can temporarily suspend wireless power transmission while remaining in the power transmission phase. Such techniques may be useful for appliances including loads with an on-cycle and an off-cycle. In some implementations, the power receiver can control wireless power transmission for the load without switching out of 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.

[0036] In some implementations, the power receiver may include an energy harvester configured to harvest bias power from an out-of-band wireless communication signal. The present disclosure describes how wireless communication signals may be transmitted by a power transmitter during various operating stages so that the power receiver may harvest bias power. The bias power may 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. Because the bias power may be necessary to operate the power receiver during periods when wireless power transmission is disabled, the present disclosure describes several examples in which wireless communication signals (for bias power) may be coordinated in various operating stages or states of wireless power transmission.

[0037] Particular implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages. A power receiver may coordinate the protection features of a protection switch with the timing of a wireless power transfer. A power transmitter may rely on the communications or protocols described herein to reliably implement wireless power transfer at appropriate times, such as when the protection switch is in a second position. Using the phase conversion techniques in this disclosure, a power receiver may implement a protection switch to protect components of a power transmitter while also supporting the use of wireless power transfer when a load requires wireless power.

[0038] For the purpose of describing the innovative aspects of the present disclosure, the following description is directed to certain implementations. However, one of ordinary skill in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The described implementations can be implemented in any component, device, system, or method for wireless power transmission.

[0039] Figure 1A schematic diagram of an example wireless power transmission system 100 is shown. The wireless power transmission system may include a power transmitter 102 and a power receiver 104. The power transmitter 102 includes a primary coil 110. The primary coil 110 may be associated with a power signal generator (not shown). For example, the power signal generator may include an inductor or other component that generates a wireless power signal applied to the primary coil 110. The primary coil 110 may be a coil that transmits a wireless power signal as wireless power (which may also be referred to as wireless energy). The primary coil 110 may transmit wireless energy using an inductive or magnetic resonance field. Using the wireless power signal, the primary coil 110 may generate a primary magnetic field during wireless power transmission. The power transmitter 102 may also include a power transmitter controller (PTx controller, not shown) that controls components of the power transmitter 102, including those components that generate wireless power signals. For example, the PTx controller may 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 , it generates a magnetic field that induces a voltage in the secondary coil 120 of the power receiver 104 .

[0040] The power receiver 104 may include a secondary coil 120 configured to receive wireless power 115. When the secondary coil 120 is aligned with the primary coil 110, the secondary coil 120 may generate an induced voltage based on the wireless power 115 received from the primary coil 110. In some implementations, a capacitor (not shown) may be connected in series between the secondary coil 120 and the power receiving circuit (not shown). In some implementations, the power receiving circuit may include a rectifier (if present) or other components to regulate the wireless power and provide wireless power for use by a load (not shown). In some implementations, the power receiving circuit may not include a rectifier and directly provide wireless power to the load. In some implementations, the load may be integrated in an appliance including the power receiver 104. In some implementations, the power receiver 104 may provide wireless power to an external load associated with the power receiver 104. The power receiver 104 may include a power receiver controller (PRx controller, not shown) configured to control the wireless power transmission operation state using a corresponding PTx controller of the power transmitter 102. The power receiver 104 may also include a wireless communication unit, an energy harvester, and other examples, as further described herein.

[0041] As described herein, the wireless power signal 115 may be used to wirelessly transmit power using the electromotive force in the secondary coil 120. When the secondary coil 120 is connected to other components associated with the power receiver 118, such as a power receiving circuit or a load, the electromotive force may generate a voltage and a current in the secondary coil 120. However, there may be times during which the power receiver 118 may not be ready to use the power or the power may otherwise damage other components of the power receiver 118. In order to prevent damage to other components or disable the transmission of unintended wireless power, the power receiver 104 may include one or more switches (not shown) configured to disconnect the circuit including the secondary coil 120. Disconnecting the circuit may also be referred to as disconnecting or decoupling the secondary coil 120 from the power receiving circuit. Therefore, even if a magnetic field is induced near the secondary coil 120, the secondary coil 120 will not conduct current because the secondary coil 120 is disconnected from the power receiving circuit or the load. One or more switches may prevent the induced voltage from flowing through the secondary coil 120 to the power receiving circuit. The present disclosure includes several options for the placement, structure, and operation of the switch.

[0042] The power receiver 104 may be associated with an appliance, such as a cordless kitchen appliance, among other examples, which may be intended to operate on a wireless power transfer surface, such as a kitchen countertop, stove, or shelf, configured with one or more primary coils. Figure 1 Some examples 140 of appliances that may be used with the power transmitter 102 are shown. For example, the appliance may be a kettle 155, a pot 165, or a blender 175. Other types of appliances that may include a power receiver may include a slow cooker, a rice cooker, a coffee maker, a toaster, a grill, a frying pan, a rice cooker, any type of appliance configured to heat liquids or food, and other examples.

[0043] The power transmitter 102 may be included in a kitchen appliance such as a cooktop or a shelf. For example, in some implementations, the shelf may include several locations for placing objects. At least one of the locations may include a power transmitter 102 that supports wireless power transfer to an appliance including a power receiver 104. In some implementations, the power transmitter 102 may be integrated into a shelf that is portable in nature. For example, a portable shelf may include a battery or be able to use an external power source to power the power transmitter 102 and may be suitable for camping.

[0044] The power transmitter 102 and the power receiver 104 may implement a control architecture for managing wireless power transmission. The control architecture may define how power requirements are communicated and how the operating point of the power transmitter is controlled. In some implementations, the control architecture may be based on static power control (referred to as a "control type 1 architecture" or "type 1"). In some implementations, the control architecture may be based on dynamic power control (referred to as a "control type 0 architecture" or "type 0"). An appliance implementing a control type 1 architecture may have a fixed load, may not include measurement circuits, may not typically employ auxiliary data transmission, and may require only minimal functionality in order to suppress manufacturing costs. The control type 1 architecture may use a control loop that relies on the power transmitter 102 without feedback from the power receiver 104. An appliance implementing a control type 0 architecture may have a static or dynamic load, and may implement a controller to generate a power request message during power transmission, as well as implement a measurement circuit for properly controlling its load. The present disclosure includes examples of both type 0 and type 1 control architectures because they involve transitions between various operating phases.

[0045] Figure 2 1 shows a block diagram of an example power transmitter 102. The power transmitter 102 may include a power source 112, a power signal generator 106, and a primary coil 110. The power signal generator 106 is illustrated as having a half-bridge circuit to convert the DC power from the power source 112 into an AC signal applied to the primary coil 110. Figure 2 Although not shown in the figure, the power supply 112 may include a conversion unit that converts the AC mains power into the DC power of the power supply 112. In addition, the power signal generator 106 may be any type of power conversion circuit that can provide an AC signal to the primary coil 110. For example, the power signal generator 106 may include a Figure 2 . Alternatively, the power signal generator 106 may include a full-bridge circuit. The power signal generator 106 may also be referred to as an inverter.

[0046] The power transmitter 102 may also include a wireless communication interface 114 and a communication coil 116. The wireless communication interface 114 may be configured to send or receive communication signals via the communication coil 116 (which may be a coil or a loop antenna, among other examples). The wireless communication interface 114 may implement short-range radio frequency communications (such as Bluetooth TM or near field communication (NFC), among other examples). The wireless communication interface 114 may include logic for controlling one or more switches and other components that enable transmission and reception of wireless communication signals via the communication coil 116. The wireless communication interface 114 may be configured to communicate with a power receiver (not shown) using wireless communication signals.

[0047] In some implementations, the wireless communication interface 114 can communicate with the power receiver by transmitting a wireless communication signal and detecting changes in the wireless communication signal that represent the transfer of information. The wireless communication interface 114 can support the NFC type 2 tag specification or the NFC type 4A tag specification as specified by the NFC specification. During the power transfer phase, in addition to the communication carrier, the power signal is also active. Due to the frequency range used for the power signal, the intermodulation products of the two signals cause interference that hinders reliable NFC communication. In order to avoid this unwanted effect, the power signal can be periodically cut off in a short time interval. The time interval can be referred to as a communication slot. Typically, the communication slot can occur in association with a zero-crossing event, which is associated with an AC cycle of a wall plug or AC mains power.

[0048] The power transmitter 102 also includes a PTX controller 108. The PTx controller 108 can control the operation of the power signal generator 105. In addition, when the WPT is converted between various operating stages, the PTx controller 108 can manage the state of the power transmitter 102. The PTx controller 108 can communicate with the power receiver (such as transmit or receive communication) 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.

[0049] The PTx controller 108 can detect the presence or proximity of a power receiver. In some implementations, the presence or proximity of a power receiver can be detected based on a load change 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 a power receiver may occur during a periodic inspection process of the wireless communication interface 114 in the power transmitter 102. Alternatively or additionally, the power transmitter 102 can detect the presence or proximity of a 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 periodically or continuously transmit a communication or polling signal. In some implementations, the wireless communication signal (transmitted by the wireless communication interface 114) may include a small amount of power (which may be referred to as communication bias power or bias power) to power one or more components of the power receiver.

[0050] The PTx controller 108 may control the characteristics of the wireless power provided by the power transmitter 102 to the power receiver. After detecting the power receiver 118, the PTx controller 108 may receive information from the power receiver (via the wireless communication interface 114). For example, the PTx controller 108 may receive the information as part of a handshake communication with the power receiver. Handshake communication (sometimes referred to as digital handshake) refers to a 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 may respond to the first communication signal by transmitting information such as the rated power, manufacturer, model, or parameters of the receiver when operating on a standard transmitter, among other examples. The PTx controller 108 may use the information it receives from the power receiver to determine at least one operational control parameter (such as frequency, duty cycle, voltage, etc.) of the wireless power it provides to the power receiver. To configure the wireless power, the PTx controller 108 may modify (shown as "A" and "B") the frequency, duty cycle, voltage, or any other suitable characteristic of the power signal generator 106 during the power transfer phase.

[0051] Figure 3 A block diagram of an example power receiver 300 with a protection switch is shown. The example power receiver 300 may be a reference Figure 1 An example of a power receiver 104 is described. The power receiver 300 may include the load 130 , or the load 130 may be an external component connected to the power receiver 300 . Figure 3 The example rectifier 126 illustrated in the figure is a full-bridge rectifier that is configured to convert the received power from the AC signal into 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 may be used in various implementations. In addition, the power receiver 300 illustrates an optional capacitor 326 coupled between the two branches of the rectifier 126. In some implementations, the power receiver 300 may not include the optional capacitor 326. Figure 3 Also shown is a capacitor 162 that can be coupled to one or more branches of the secondary coil 120. The example power receiver 300 includes a protection switch (referred to as switch 350, also labeled "S1"). The switch 350 can be connected in series between one branch of the secondary coil 120 and the rectifier 126. When the capacitor 162 is present on the branch, the switch 350 can be connected before or after the capacitor 162. The switch 350 is a type of protection switch described in the present disclosure.

[0052] 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 modulation and demodulation circuits to wirelessly communicate via the communication coil 134 (which may be a coil or a loop antenna, among other examples). Thus, the PRx controller 128 may 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 may harvest energy from the wireless communication signal and provide the harvested energy as bias power 330 to operate the PRx controller 128. The bias power 220 may be sufficient to power the wireless communication unit 132, but less than the amount required to power the load 130. The energy harvester 332 may be configured to provide the harvested 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 may provide sufficient energy to generate bias power 330 for starting and initially operating the wireless communication unit 132 and the PRx controller 128 prior to a power transfer phase via the secondary coil 120. In some implementations, the bias power 330 may also be used to operate the switch 350. Although the PRx controller 128 may initially be powered by the bias power 330, the PRx controller 128 may also be subsequently powered using power from the wireless power circuit during the wireless power transfer phase. For simplicity, Figure 3 Circuits or components that interface with the PRx controller 128 to obtain power from the wireless power circuit during the wireless power transfer phase are omitted.

[0053] The PRx controller 128 may use the sensing signal 331 to sense the state of the load 130. In some implementations, the sensing signal 331 may be directly related to the load 130. Alternatively or additionally, the sensing signal 331 may indicate the state of an optional component, such as an activation switch (not shown) or a load switch (not shown). The activation switch may be based on a user interface, such as a button, a touch screen, or any component that may indicate a user request to activate the load 130. The load switch (not shown) may include a temperature switch, an overvoltage / overcurrent protection switch, a motor lock, or any type of load-sensitive switch that controls whether the load 130 is active. The PRx controller 128 may use a switch signal 351 to control the switch 350. According to aspects of the present disclosure, the PRx controller 128 may operate the switch signal 351 based on a WPT protocol that defines transitions between various operating phases of a WPT system. For example, the PRx controller 128 may cause the switch 350 to connect the secondary coil 120 to the rectifier 126 (or the load 130) according to a transition from a connection phase to a power transmission phase. Alternatively or additionally, the PRx controller 128 may cause the switch 350 to disconnect the secondary coil 120 from the rectifier 126 (or the load 130) according to the transition from the power transmission phase to the connection phase. In some implementations, the switch 350 may be normally open (NO) so that the secondary coil 120 is disconnected from the rectifier 126 until the switch 350 is closed. In some implementations, the switch 350 may be closed using bias power obtained from the wireless communication unit 132 or from power from a battery (not shown) included in the power receiver 300.

[0054] The wireless communication unit 132 may support the NFC Type 2 tag specification or the NFC Type 4A tag specification as specified by the NFC specification. In some implementations, the wireless communication unit is configured to communicate with the power transmitter by storing information in a passive tag (such as an NFC Type 2 tag) that can be read by the wireless communication interface of the power transmitter. Alternatively, the wireless communication unit may be configured to communicate with the power transmitter by transmitting information in a wireless communication signal (such as using an NFC Type 4A tag) to the wireless communication interface of the power transmitter.

[0055] Figure 3The power receiver 300 shown in FIG. 1 may be an example of a type of power receiver 300. For example, the power receiver 300 includes a rectifier 126 and may be suitable for an appliance in which the load 130 includes one or more motors or any load that operates with DC power. Because the power receiver 300 includes the rectifier 126, the power receiver 300 may implement a type 0 control architecture as 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.

[0056] Figure 4 FIG. 4 is a block diagram of another example power receiver 400 with a protection switch. The example power receiver 400 may be a reference Figure 1 Another example of a power receiver 104 is described in detail below. The components of the power receiver 400 may include the same Figure 3 The power receiver 300 described has similarly numbered components. However, the power receiver 400 may not include a rectifier because the load 430 is configured to operate using the AC signal obtained by the secondary coil 120. In this example, the load 430 can be referred to as a power receiving circuit that is configured to utilize the power obtained by the secondary coil 120. A protection switch (switch 450) can be connected in series between the secondary coil 120 and the load 430 to prevent the load 430 from being damaged by an unexpected voltage induced in the secondary coil 120 when the load 430 is not operated. Switch 450 is a type of protection switch described in the present disclosure. Similar to reference Figure 3 In the power receiver 300 described, the PRx controller 128 can be configured to manage the switch 450 based on the WPT protocol, which defines the transitions between various operating phases of the WPT system. Because the power receiver 300 does not include a rectifier, the power receiver 300 can implement a type 1 control architecture as described herein.

[0057] Figure 5 A block diagram of an example power receiver 500 having a protection switch including a plurality of switches is shown. Components of the power receiver 500 may include the same Figure 3 The power receiver 300 depicted has similarly numbered components. Instead of a single series switch (such as that shown in FIG. Figure 3350 described above), the power receiver 500 may include first and second switches 551 and 552 connected in series between the branches of the secondary coil 120 and the rectifier 126. The first switch 551 (labeled as "S1") can be connected in series to the first branch of the secondary coil 120. The second switch 552 (labeled as "S2") can be connected in series to the second branch of the secondary coil 120. The first and second switches 551 and 552 can also be collectively referred to as protection switches. Similar to reference Figure 3 1. As described in the power receiver 300, the PRx controller 128 may be configured to manage the switch 550 based on a WPT protocol that defines transitions between various operating phases of the WPT system. Because the power receiver 500 includes the rectifier 126, the power receiver 500 may implement a type 0 control architecture as described herein.

[0058] Protection switch (such as reference Figure 3 , 4 5) are examples of different types of protection switches implemented in a power receiver. Other types of protection switches may be used with the techniques of the present disclosure. For example, the protection switch may include a shunt switch configured to short-circuit the ends of the secondary coil to prevent or reduce the induced voltage in the secondary coil from reaching the power receiving circuit. In this example, the first position of the shunt switch may be closed (to short-circuit the secondary coil) under normal conditions, and the second position may open the shunt switch to allow power to cross from the secondary coil to the power receiving circuit.

[0059] Figure 6 A state diagram 600 of various example operation phases of a WPT system is shown. The state diagram 600 illustrates the operation phases in which the WPT system can operate. When the power receiver is placed within the interface surface of the power transmitter, the two begin to communicate for the purpose of configuring and controlling power transmission. There may be four operation phases associated with the WPT system: an idle phase 610 (sometimes also referred to as a verification phase), a configuration phase 620, a connection phase 630, and a power transmission phase 640. The technical specification may define how the power transmitter and the power receiver may be switched between operation phases. For example, a WPT system typically starts in an idle phase 610 and may be switched from the idle phase 610 to the configuration phase 620. From the configuration phase 620, the WPT system may be switched to the connection phase 630. From the connection phase 630, the WPT system may be switched to the power transmission phase 640. In addition, the WPT system may be switched 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 surface. Each of the operating stages is briefly described herein for reference.

[0060] In the idle phase 610 (check phase), the power transmitter attempts to establish communication with the power receiver. The power receiver may be placed only on the interface surface, or may not exist during this operation phase. The power transmitter may attempt to communicate or detect the presence of the power receiver. For example, the power transmitter may use analog checking, out-of-band communication (such as NFC), digital checking, or any combination thereof to determine that a compatible power receiver exists. Once the WPT system determines that the power receiver exists (such as by confirming NFC communication), the WPT system may transition to the configuration phase 620.

[0061] 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 retrieve static configuration information from the power receiver via NFC communication. The power transmitter and the power receiver can use this information to verify that they both use compatible versions 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.

[0062] In the connection phase 630, the power transmitter and the power receiver may exchange further communications to negotiate parameters governing the power transfer phase. After the parameters are negotiated, the power transmitter may be ready to transmit wireless power, and the power receiver may be ready to receive wireless power. However, the power transmitter may wait for a request or command from the power receiver before switching to the power transfer phase 640. For example, this may be useful when a cordless appliance (such as a blender, toaster, mixer, or microwave oven, among other examples) is configured to wait for user interaction. The user may initiate the power transfer phase 640 through a user interface of the power receiver (such as an activation switch), which in turn communicates with the power transmitter to switch to the power transfer phase 640.

[0063] During the power transfer phase 640, the power transmitter may transfer wireless power to the power receiver. Typically, the power transmitter will periodically perform a foreign object detection assessment during the power transfer phase 640. In some embodiments, the power transmitter may perform a foreign object detection assessment to ensure that no foreign objects are present before transitioning from the connection phase 630 to the power transfer phase 640. The power transmitter may also perform periodic foreign object detection assessments during the power transfer phase 640. The idle phase 610, the configuration phase 620, and the connection phase 630 may be collectively referred to as the pre-power phase 602, and the power transfer phase 640 may be referred to as the during-power phase 604.

[0064] In some implementations, the transition from the connection phase to the power transfer phase and from the power transfer phase to the connection phase may be a challenge due to the hardware and safety procedures involved. For example, a cordless appliance may have a protection switch that should be turned to the second position before entering the power transfer phase. If the power transmitter is to start wireless power transfer when the protection switch is still in the first position, the magnetic field from the power transmitter may cause dangerous conditions or high voltages in the appliance. In addition, the power transmitter (or power receiver) may experience a fault condition or damage. In some implementations, the power transmitter may need to perform a foreign object detection (FOD) assessment before switching to the power transfer phase. The technology disclosed herein may define a protocol to be followed during the transition from connection mode to power transfer mode (and vice versa).

[0065] The present disclosure provides systems, methods, and devices for managing phase transitions of a wireless power transfer (WPT) system. For example, the transition between the connection phase and the power transfer phase can be coordinated with respect to changing a protection switch (one or more switches) in a power receiver. The protection switch can decouple or couple the secondary coil of the power receiver with a power receiving circuit (such as a load or a rectifier). The first position of the protection switch can disconnect the circuit including the secondary coil and the power receiving circuit. The second position of the protection switch can close the circuit so that the secondary coil can receive wireless power and provide wireless power to the load during the power transfer phase. The present disclosure also describes how the WPT system can temporarily suspend wireless power transfer while remaining in the power transfer phase.

[0066] Figure 7 700 for a power receiver according to some implementations. The operations of process 700 may be implemented by a power receiver as described herein. For example, the operations of process 700 may be implemented by reference to Figure 1 , 3 , 4 or 5 described in any of the power receivers 104, 300, 400 or 500. For simplicity, the operation is described as being performed by the device. In box 710, the device may determine that the PTx is in a connection phase of operation with the PRx. In box 720, during the connection phase, the device may change the protection switch of the PRx from a first position to a second position, the protection switch being arranged between the secondary coil of the PRx and the load associated with the PRx, wherein the first position is configured to normally disconnect the circuit including the secondary coil before the power transfer phase of the operation, wherein the second position is configured to close the circuit. In box 730, after the protection switch is changed to the second position, the device may transmit a power request to the PTx. In box 740, the device may transition from the connection phase to the power transfer phase. In box 750, the device may receive wireless power from the PTx during at least a portion of the power transfer phase.

[0067] Figure 8 800 according to some implementations. The operations of process 800 may be implemented by a power transmitter as described herein. For example, the operations of process 800 may be implemented by the power transmitters described in the respective embodiments of the present invention. Figure 1 and Figure 2 The device may be implemented in any of the power transmitters 102 described herein. For simplicity, the operations are described as being performed by the device. In box 810, the device may determine, based at least in part on communication with PRx, that PRx is in a connection phase of operation with PTx. In box 820, the device may receive a power request from PRx, the power request being associated with a request to transfer wireless power from PTx to PRx, wherein the power request indicates an indication that PRx has changed a protection switch to close a circuit including a secondary coil of PRx. In box 830, in response to the power request, the device may cause the inverter to generate a wireless power signal for the transmission of wireless power. In box 840, the device may transition from the connection phase to the power transfer phase of operation. In box 850, the device may transmit a wireless power signal to transfer wireless power to the secondary coil of PRx.

[0068] Fig. 9 A timing diagram 900 is shown of an example transition from a connection phase 960 to a 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 (labeled as PRx 902) and a PTx controller (labeled as PTx 904). The PRx 902 and the PTx 904 may implement a type 0 control architecture, which means that the PRx 902 may use control messages to control wireless power transfer. For example, in a type 0 control architecture, the PRx 902 may control voltage, frequency, power, activation, deactivation, or other settings associated with wireless power transfer. As described with reference to FIG. Figure 6 As described, PRx 902 and PTx 904 can follow a state diagram of various operation stages. The timeline of PRx 902 and PTx 904 assumes that the WPT system has been converted (shown at line 920) to the connection stage 960. For the sake of brevity, the stage operation 910 (such as the idle stage and the configuration stage) occurring before the connection stage 960 is omitted. At time 925, PRx 902 can determine that the activation switch associated with the load has been turned on. For example, the activation switch can include a user input indicating that the load is expected to be activated. Examples of activation switches can include buttons, flip switches, knobs or touch screens (and associated processors) and other examples. Some appliances may not include an activation switch, and PRx 902 may assume that the load is always ready to receive wireless power.

[0069] At time 930, PRx 902 may transmit a phase transition request message. For example, PRx 902 may transmit a "NEXT / pow" command (requesting PTx 904 to transition to the power transfer phase as the next operating phase). PTx 904 may respond to the phase transition request message (shown at time 940) with a confirmation message. After receiving the confirmation message, PRx 902 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 secondary coil of PRx from conducting energy. For example, the first position may disconnect or decouple the secondary coil from a power receiving circuit (such as a rectifier or a load). The first position may disconnect a circuit including the secondary coil. In the second position, the protection switch may enable the secondary coil to conduct energy, such as an induced voltage from a magnetic field generated by PRx.

[0070] After the protection switch has changed to the second position (such as after the switch signal at time 950 follows the time at which the protection switch changes to the second position), the PRx 902 may transmit a power request (sometimes also referred to as a power request message) to the PTx 904 at time 955. In some implementations, the power request may be included in the control message. The PTx 904 may receive the power request and enable a power signal generator (such as an inverter) of the PTx to transmit wireless power 115. If the PTx 904 has not changed at the time of the phase transition request (at time 930) or the power request (at time 955), it may also transition (shown at time 970) to the power transmission phase 980. Although the definition of when the power transmission phase 980 begins may vary, in some implementations, the transmission of wireless power 115 may occur only after the power request at time 955. The power request may implicitly indicate that the PRx 902 has changed the protection switch to the second position. In some implementations, the WPT specification may define the timing for the PRx 902 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 the PRx 902 has coupled the secondary coil to the load in accordance with the WPT specification. Thus, wireless power 115 occurs only after the PTx 904 has confirmed (explicitly or implicitly) that the PRx 902 has configured the power receiving circuit including the secondary coil and the rectifier or load to consume wireless power.

[0071] 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 the grid (such as a DC operated PRx), the power signal generator may be enabled after a small delay after receiving the power request control message 955. Because the PTx 904 may wait for the power request, the WPT system may avoid overvoltage faults in the PTx or open circuits in transmitting wireless power to the PTx in accordance with the present disclosure.

[0072] Fig. 9 Also shown is an example timing of FOD evaluation 935 during the connection phase 960. Some power transmitters perform frequent FOD evaluations during the connection phase, while some other power transmitters perform FOD evaluations just before entering the power transfer phase. In some implementations, it may be required to perform FOD evaluation 935 before transitioning from the connection phase to the power transfer phase. FOD evaluation 935 may occur in response to a phase transition request (at time 930) and before confirmation (at time 940).

[0073] For FOD assessment, PTx 904 can scan for foreign objects using various techniques, such as active or passive excitation of foreign object detection coils to observe impedance differences indicating the presence of foreign objects. When no foreign object flag (FO) is detected, PTx 904 can reset (or clear) FO, and when FO is detected, the FO flag can be set. A power transmitter that scans FO only before power transmission can set the FO flag to an initial value to indicate that the FOD assessment has not yet been performed. After receiving a phase transition request (at time 930), PTx 904 can check the status of the FO flag. If the FO flag is cleared / reset, and in the absence of other constraints, PTx 904 can send a confirmation to PRx 902 (at time 940). If the FO flag is set, PTx 904 can perform FOD assessment 935. If FO is detected, PTx 904 can prompt a user action, transmit a fault condition, or otherwise disable the transition to the power transmission phase. For example, PTx 904 can transmit a negative confirmation (NAK) to PRx 902. Alternatively, if FO is not detected by FOD evaluation 935 , and in the absence of other constraints, PTx 904 may deliver an acknowledgement (ACK) to PRx 902 .

[0074] Fig. 9Also illustrated is how out-of-band communication (labeled as NFC 906) can be related to the timing of operation of PRx 902 and PTx 904. For example, the NFC 906 timeline reflects the time when PTx 904 can communicate with PRx 902. In some instances, PTx 904 can transmit wireless communication signals according to the NFC 906 timeline, and PRx 902 can harvest energy (bias power) from the wireless communication signals. The NFC 906 timeline shows communication signals 992, 994, 996, 998, and 999. For example, communication signals 992 and 994 can appear during the connection phase 960 to provide bias power to PRx 902. The communication signals can be stopped during the FOD evaluation 935 so that the communication signals do not interfere with the FOD evaluation 935. In addition, the NFC 906 timeline illustrates communication signals 996, 998, and 999 that appear during the communication time slots of the power transfer phase. The communication time slots may occur in relation to zero crossing events associated with the AC cycle of the wireless power 115. Even during instances 996, 998, and 999, the main power from the PTx 904 to the PRx 902 may be stopped to enable interference-free communication between the PTx 904 and the PRx 902.

[0075] Note that the communication signal 994 may extend beyond the connection phase 960 and into the power transfer phase 980. This allows the communication signal 994 to provide bias power to the PRx 902 until the wireless power 115 begins at time 975. After the wireless power 115 is transferred from the PTx 904 to the PRx 902, the PRx 902 may utilize the wireless power 115 (instead of or in addition to the bias power) to power the PRx controller.

[0076] Fig.10 A timing diagram 1000 is shown in which a WPT protocol is defined with time constraints. Fig.10 Example operation phases, communication and timing in Fig. 9 Those described with like reference numerals in FIG. Fig.10The time limit that can be implemented as a part of WPT protocol is illustrated, which includes phase transition request, confirmation message or power request at time 925, 940 and 955 respectively. For example, the confirmation message of time 940 can be received in a limited time (labeled as T1 1010) after the phase transition request message of 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 message. If PRx 902 does not receive the confirmation message in T1 1010, a timeout error may occur. In such an example, PRx 902 can wait for a predetermined time, and then send a new phase transition request (not shown). Alternatively or additionally, PRx 902 can present a timeout error indication via a user interface associated with PRx 902. PRx 902 may be required to send a power request (at time 955) within a limited time (labeled as T2 1020) after the confirmation (at time 940). In some implementations, the value of T2 1020 may be 100 ms. T2 1020 may be the second maximum time allowed between the confirmation message and the control message. If PTx 904 does not receive a power request within T2 1020, PTx 904 may present a timeout error indication via a user interface associated with PTx 904.

[0077] Fig.11 A timing diagram 1100 is shown of an example transition from a power transfer phase 1110 to a connection phase 1180 in a WPT system using a type 0 control architecture. The PRx 902 and PTx 904 may be in a state following any process (such as referring to Fig. 9 or the WPT protocol described in 10) of the power transmission phase 1110. Fig. 9 Similarly, PRx 902 and PTx 904 can implement a type 0 control architecture. PTx 904 can transmit wireless power 115 to power a load associated with PRx 902. At some point in time, the job associated with the load can be completed. At time 1120, PRx 902 can detect a condition associated with the end operation of the load. The condition can include an activation switch being disconnected (such as by user input or by processor programming). Alternatively, the condition can include a load switch associated with the load changing to a state associated with the end operation of the load. For example, the load switch can include a temperature switch (such as a bimetallic switch) that disconnects when the load has reached 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).

[0078] After detecting the condition (at time 1120), the PRx 902 may communicate a phase transition request at time 1130. For example, the phase transition request may be a "NEXT / con" command (requesting the PTx 904 to transition to the connection phase as the next operating phase). In some implementations, the PTx 904 may not reject the phase transition request requesting to transition out of the power transfer phase. After receiving the phase transition request, the PTx 904 may stop the transmission of the wireless power 115 and may send an acknowledgement (ACK) message (shown at time 1140). The PTx 904 may also transition (shown at time 1150) to the connection phase 1180. The ACK message (at time 1140) may inform the PRx 902 that the PTx 904 has or is about to stop the transmission of the wireless power 115. Stopping the transmission of the wireless power 115 may include the PTx 904 causing a power signal generator (such as an inverter of the PTx 904) and a primary coil of the PTx 904 to stop generating a magnetic field associated with the wireless power 115. In some implementations, the PTx 904 may not reject a phase transition request requesting a transition out of the power transfer phase. However, if the PRx 902 does not receive an ACK message, the PRx 902 may pass a new phase transfer request (NEXT / con) to attempt a protocol-compliant transition to the connection phase.

[0079] After receiving the ACK (at 1140), the PRx 902 may disable the secondary coil (shown at time 1160). For example, the PRx 902 may remove the switch signal that keeps the protection switch closed. Alternatively, the PRx 902 may send a switch signal configured to cause the protection switch to disconnect the circuit including the secondary coil. In some implementations, the PRx 902 may wait for a period of time after the ACK before disabling the secondary coil. In some implementations, the PRx 902 may include a voltage sensor configured to measure the voltage on the secondary coil. The PRx 902 may wait to disconnect the circuit including the secondary coil until the PRx 902 has confirmed that the voltage is below a threshold (indicating that the PTx 904 has stopped the transmission of the wireless power 115). Therefore, the time 1160 associated with disabling the secondary coil may vary, but ideally follows the ACK (at 1140) indicating that the wireless power 115 has been or is about to be stopped. Using this technique, the PRx 902 can ensure that the protection switch is not inadvertently changed prematurely to the first position, in which the secondary coil is disabled before the wireless power 115 has stopped. If the protection switch is changed before the wireless power 115 has stopped, components of the PRx 902 may be damaged by high current or high voltage or unintentional power transfer. In the event that the PRx 902 does not receive an ACK from the PTx 904 after attempting multiple phase transition requests (NEXT / con), the PRx 902 may continue to disable the secondary coil.

[0080] Fig.11 Also illustrated is how out-of-band communications (labeled NFC 906) may be related to the timing of operations of the PRx 902 and PTx 904 during the transition from the power transfer phase 1110 to the connection phase 1180. The NFC 906 timeline illustrates communication signals 1112, 1114, and 1116 occurring during communication time slots in the power transfer phase 1110. The communication time slots may occur in relation to zero crossing events associated with the AC cycle of the wireless power 115. Note that the communication signal 1122 may begin when the wireless power 115 transmission stops (at time 1140). This allows the communication signal 1122 to provide bias power for the PRx 902. In some implementations, the communication signal 1122 may begin during the power transfer phase 1110 (after the wireless power 115 transmission) before the PTx 904 transitions (at time 1150) to the connection phase 1180. This is because the wireless power 115 may end at a natural zero crossing associated with the AC mains power or AC cycle, while the transition to the connection phase (at time 1150) may occur later.

[0081] Fig. 9The example in –11 may be related to a WPT system implementing a type 0 control architecture. However, some WPT systems may implement a type 1 control architecture. Fig.12 –13 illustrates how such a system can coordinate the timing of the various phase transitions.

[0082] Fig.12 A timing diagram 1200 is shown of an example transition from a connection phase 1280 to a power transfer phase 1290 in a WPT system using a type 1 control architecture. The timing diagram 1200 is used to describe the operation of a PRx controller (labeled as PRx 1202) and a PTx controller (labeled as PTx 1204). Fig.11 In the embodiment of the present invention, the PRx 1202 and the PTx 1204 may implement a type 1 control architecture, which means that the PRx 1202 may have limited control over the wireless power transfer. For example, in a type 1 control architecture, the PRx 1202 may use a passive tag (such as an NFC type 2 tag) to pass limited information to the PTx 1204 and may rely on the PTx 1204 to control the wireless power transfer using the internal power control loop of the PTx 1204. Figure 6 As described, the PRx 1202 and PTx 1204 may follow a state diagram of various operational phases. The timeline for the PRx 1202 and PTx 1204 assumes that the WPT system has transitioned (shown at time 1220) to the connection phase 1280. For the sake of brevity, phase operations 1210 (such as the idle phase and the configuration phase) that occur before the connection phase 1280 are omitted. Those phase operations 1210 may include NFC data exchange format (NDEF) 1215 communications. In some implementations, the communication between the PRx 1202 and the PTx 1204 may be based on limited communication, where the wireless communication interface of the PTx 1204 "reads" information from the wireless communication unit of the PRx 1202. For example, the wireless communication unit may be a passive tag (such as an NFC Type 2 tag) that stores information that can be read by the wireless communication interface of the PTx 1204.

[0083] At time 1240, PRx 1202 may determine that an activation switch associated with the load has been turned on. For example, the activation switch may include a user input indicating the expectation of activating the load. Some appliances may not include an activation switch, and PRx 1202 may assume that the load is always ready to receive wireless power. PRx 1202 may transmit a power request (at time 1250) only after the secondary coil has been enabled (shown at time 1230). The secondary coil may be enabled by PRx 1202 sending a switch signal to change the protection switch from a first position to a second position. In the first position, the protection switch may disconnect a circuit including the secondary coil. In the second position, the protection switch may close a circuit including the secondary coil. The exact time for enabling the secondary coil may vary based on the type of appliance and the manufacturer's preferences. In some implementations, once PRx 1202 enters the connection phase 1280, PRx 1202 may change the protection switch to the second position. Alternatively, PRx 1202 may change the protection switch to the second position after the activation switch is turned on.

[0084] After receiving the power request (at time 1250), the PTx 1204 may begin transmitting the wireless power 115 (shown as starting at time 1260). For example, the PTx 1204 may cause a power signal generator (such as an inverter) to generate a wireless power signal for transmission through the primary coil of the PTx 1204. 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 (shown at time 1260) after the power request (at time 1250). Because the PRx 1202 may require the protection switch to be closed (at time 1230) before delivering the power request (at time 1250), the PTx 1204 may wait for the power request, and according to the present disclosure, the WPT system may avoid overvoltage faults in the PRx 1202 and may avoid transmitting the wireless power 115 to an open circuit in the PRx 1202. In some implementations, the WPT specification may define the timing for PRx 1202 to couple the secondary coil to the load during the connection phase 1280 and before the power request (at time 1250) such that the power request implicitly indicates that PRx 1202 has coupled the secondary coil to the load in accordance with the WPT specification.

[0085] As reference Fig. 9 As described, PTx 1204 may perform FOD evaluation 1225 during connection phase 1280 (similar to Fig. 91225). The timing of the FOD evaluation 1225 may vary, as it may not be triggered by communication from the PRx 1202. However, in some implementations, the WPT specification may require the PTx 1204 to perform the FOD evaluation 1225 prior to transitioning from the connection phase to the power transfer phase or prior to transmission of wireless power 115. If FO is detected, the PTx 1204 may prompt a user action, communicate a fault condition, or otherwise disable the transition to the power transfer phase.

[0086] Fig.12 Also illustrated is how out-of-band communications (labeled NFC 1206) may be related to the timing of the operations of the PRx 1202 and PTx 1204. For example, the NFC 1206 timeline reflects the times at which the PTx 1204 may transmit wireless communication signals 1212, 1214, 1222, 1226, and 1228 to communicate with the PRx 1202 or to support bias power acquisition of the PRx 1202. For example, the communication signals 1212 and 1214 may occur during the connection phase 1280 to provide bias power to the PRx 1202. The communication signals may be stopped during the FOD evaluation 1225 so that the communication signals do not interfere with the FOD evaluation 1225. In addition, the NFC 1206 timeline illustrates the communication signals 1222, 1226, and 1228 occurring during the communication time slots in the power transfer phase 1290, during which the main power from the PRx to the PTx may be temporarily stopped. The communication time slots may occur in relation to zero-crossing events associated with the AC cycle of the wireless power 115 .

[0087] As reference Fig. 9 As depicted, the communication signal 1214 may extend beyond the connection phase 1280 and into the power transfer phase 1290. This allows the communication signal 1214 to provide bias power to the PRx 1202 until the wireless power 115 begins at time 1260. After the wireless power 115 is transferred from the PTx 1204 to the PRx 1202, the PRx 1202 may utilize the wireless power 115 (instead of or in addition to the bias power) to power the PRx controller.

[0088] Fig.13 A timing diagram 1300 is shown for an example transition from the power transfer phase to the connection phase in a WPT system using a type 1 control architecture. PRx 1202 and PTx 1204 may follow any process (such as reference Fig.12 The WPT protocol described in the specification is in the power transmission phase 1310. Fig.12Similarly, PRx 1202 and PTx 1204 can implement a type 1 control architecture. PTx 1204 can transmit wireless power 115 to power a load associated with PRx 1202. At a certain point in time, the operation associated with the load can be completed. At time 1320, PRx 1202 can detect a condition associated with the end of operation of the load. The condition can include an activation switch being opened or a load switch associated with the load changing to a state associated with the end of operation of the load, as well as other examples.

[0089] After detecting the condition (at time 1320), the PRx 1202 may communicate a zero power or power off request at time 1330. For example, the PRx 1202 may modify information in the passive tag so that the PTx 1204 receives the zero power or power off request by reading the passive tag. After receiving the zero power or power off request (at time 1330), the PTx 1204 may stop (shown at time 1340) the transmission of the wireless power 115. The PTx 1204 may also transition (shown at time 1370) to the connection phase 1380. Stopping the transmission of the wireless power 115 may include the PTx 1204 causing a power signal generator (such as an inverter of the PTx 1204) and a primary coil of the PTx 1204 to stop generating a magnetic field associated with the wireless power 115.

[0090] PRx 1202 may also disable the secondary coil (shown at time 1360). For example, PRx 1202 may remove the switch signal that keeps the protection switch closed. Alternatively, PRx 1202 may send a switch signal configured to cause the protection switch to open a circuit including the secondary coil. In some implementations, PRx 1202 may wait for a period of time after the zero power or power off request to allow PTx 1204 time to stop transmitting wireless power 115. Thus, the time 1360 associated with disabling the secondary coil may vary, as long as it follows the zero power or power off request (at 1330).

[0091] Fig.12Also illustrated is how out-of-band communications (labeled NFC 1206) may be related to the timing of the operations of the PRx 1202 and PTx 1204 during the transition from the power transfer phase 1310 to the connection phase 1380. The NFC 1206 timeline illustrates communication signals 1312 and 1314 occurring during communication time slots in the power transfer phase 1310. The communication time slots may occur in relation to zero crossing events associated with the AC cycle of the wireless power 115. Note that the communication signal 1316 may begin when the wireless power 115 transmission stops (at time 1340). This allows the communication signal 1316 to provide bias power for the PRx 1202. In some implementations, the communication signal 1316 may begin during the power transfer phase 1310 (after the wireless power 115 transmission) before the PTx 1204 transitions (at time 1150) to the connection phase 1380. This is because the wireless power 115 may end at a natural zero crossing associated with the AC mains power or AC cycle, while the transition to the connection phase 1380 may occur later.

[0092] The foregoing description describes the transition between the connection phase and the power transfer phase. In other words, the description describes the timing of wireless power transfer associated with the protection switch. There may be some implementations in which it is desired to stay in the power transfer phase while temporarily suspending the transmission of wireless power. For example, some appliances have loads associated with an on-cycle and an off-cycle. The transition between the connection phase and the power transfer phase may not be as efficient as temporarily suspending the transmission of wireless power to support the off-cycle of the load. An example of an appliance with such a load may be an ice crusher. The ice crusher may have a motor that implements a series of on-cycles and off-cycles. An example of an appliance with such a load may be a blender with a pulse train. There is a need for PRx to manage the periodic transmission of wireless power during the power transfer phase. The present disclosure also describes how a WPT system can temporarily suspend wireless power transfer while remaining in the power transfer phase. The technology may include using one or more zero power requests and non-zero power requests.

[0093] Fig.14 1400 is a flowchart of an example process 1400 for controlling a power receiver for wireless power transfer during a power transfer phase according to some implementations. The operations of process 1400 may be implemented by a power receiver as described herein. For example, the operations of process 1400 may be implemented by reference to Figure 1 , 3, 4 or 5 described in any of the power receivers 104, 300, 400 or 500. For simplicity, the operation is described as being performed by the device. In box 1410, the device can couple the secondary coil of PRx to a load associated with an on period and an off period, and the secondary coil is configured to receive wireless power from PTx during at least a portion of the power transmission phase of the operation. In box 1420, the device can communicate with PTx to enter a power transmission phase in which PTx can transmit wireless power to PRx. In box 1430, the device can transmit a non-zero power request to PTX in association with the on period of the load, and the non-zero power request is associated with causing PTx to transmit wireless power. In box 1440, the device can transmit a zero power request message to PTX in association with the off period of the load, and the zero power request is associated with causing PTx to suspend the transmission of wireless power while remaining in the power transmission phase.

[0094] Fig.15 1 is a flow chart showing an example process 1500 of a power transmitter controlling wireless power transfer during a power transfer phase according to some implementations. The operations of process 1500 may be implemented by a power transmitter as described herein. For example, the operations of process 1500 may be implemented by the power transmitters described in the respective embodiments. Figure 1 and Figure 2 The invention can be implemented in any of the power transmitters 102 described herein. For simplicity, the operations are described as being performed by the device. In box 1510, the device can communicate with PRx to enter a power transfer phase of operation. In box 1520, the device can receive a power request from PRx, which is used to control wireless power transfer to the load of PRx during at least a portion of the power transfer phase. In box 1530, when the power request is a non-zero power request, the device can cause the inverter of PTx to generate a wireless power signal for the transmission of wireless power to the load during the power transfer phase. In box 1540, when the power request is a zero power request, the device can cause the inverter to suspend the generation of the wireless power signal to the load while remaining in the power transfer phase.

[0095] Fig.16 A timing diagram 1600 is shown in which a zero power request and a non-zero power request are used during a power transfer phase 1620. The timing diagram 1600 is used to describe the operation of a PRx controller (labeled PRx 1602) and a PTx controller (labeled PTx 1604). Fig.16 In the embodiment, PRx 1602 and PTx 1604 can implement a type 0 control architecture or a type 1 control architecture. Figure 6As described, PRx 1602 and PTx 1604 may follow a state diagram of various operational phases. The timeline of PRx 1602 and PTx 1604 assumes that the WPT system has transitioned (shown at line 1607) to the power transfer phase 1620. For the sake of brevity, phase operations 1605 (such as the idle phase, configuration phase, and connection phase) occurring before the power transfer phase 1620 are omitted.

[0096] The timing diagram 1600 begins at a time when a load associated with the PRx 1602 is in an on-period 1651. During the on-period 1651, the load may be consuming wireless power 115 for operation of the load (such as a motor of a blender or ice crusher, among other examples). However, the load may have an off-period 1652 during which the load does not require wireless power. It is desirable to stop the transmission of wireless power during the off-period 1652 to protect damage to the PRx 1602 or the load, conserve energy, and extend the life of electronic components. However, since the next on-period 1653 will occur shortly after the off-period 1652, it may also be desirable to remain in the power transmission phase 1620. Therefore, in some aspects, the present disclosure provides techniques for temporarily suspending the transmission of wireless power during an off-period associated with the load of the PRx 1602.

[0097] PRx 1602 may communicate a zero power request (shown at time 1630) to cause PTx 1604 to stop the transmission of wireless power 115. The zero power request may be communicated by modifying information in a passive tag or by transmitting a communication signal including the zero power request from PRx 1602. In an implementation where PRx 1602 has a protection switch, PRx 1602 may 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 PRx 1602, PTx 1604 may stop the transmission of wireless power 115 (shown at time 1640). For example, PTx 1604 may cause a power signal generator (such as an inverter) to shut down.

[0098] As the disconnection period 1652 ends, the PRx 1602 may communicate a non-zero power request (at time 1660) to cause the PTx 1604 to resume transmission of the wireless power 115. After receiving the non-zero power request (at time 1660) from the PRx 1602, the PTx 1604 may resume transmission of the wireless power 115 (shown at time 1670). For example, the PTx 1604 may turn on a power signal generator (such as an inverter).

[0099] Note that zero power requests and non-zero power requests may be referred to by other terms. Fig.17As further described, a "zero" power request may indicate a nominal non-zero power setting, but for clarity, it is referred to herein as a zero power request. In some implementations, the PRx 1602 may communicate a series of zero power requests and non-zero power requests corresponding to the beginning of an off-period and an on-period of the load, respectively. In addition, the zero power request and the non-zero power request may 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 the activation switch.

[0100] Fig.16 Also illustrated is how out-of-band communication (labeled NFC 1606) is used during the time period between the zero power request and the non-zero power request. The NFC 1606 timeline illustrates communication signals 1612 and 1616 occurring during the communication time slot in the power transfer phase 1620. The communication time slot may occur in association with a zero crossing event associated with the AC cycle of the wireless power 115. In addition, the PTx 1604 may transmit a communication signal 1614 during the time period between the zero power request (at time 1630) and the non-zero power request (at time 1660). This allows the communication signal 1614 to provide bias power to the PRx 1602. Recall that in some implementations, the bias power may be used to operate a protection switch of the circuit that closes the secondary coil. Thus, Fig.16 Techniques are provided in which the protection switch may remain in the second position even if wireless power 115 is not being transmitted during the disconnect period 1652 .

[0101] Fig.17 A timing diagram 1700 is shown in which a low power operating point may be used while remaining in the power transfer phase. Fig.17 The characteristics of Fig.16 The same meanings as described, including PRx 1602, PTx 1604, NFC 1606, phase operation 1605, line 1607, power transmission phase 1620, on-period 1651, off-period 1652, on-period 1653, zero power request (at time 1630), non-zero power request (at time 1660), pausing the transmission of wireless power 115 at time 1640, and resuming the transmission of wireless power 115 at time 1670. Fig.17Importantly, when PTx 1604 suspends the transmission of wireless power 115 for use by the load, PTx 1604 may not completely stop wireless power transmission. Instead, PTx 1604 may transmit wireless power 1715 at a low power operating point 1755. The low power operating point may be an uncritical operating point (UOP) or a safe communications operating point (SCOP). The wireless power 1715 at the low power operating point 1755 may be an amount of power less than that required by the load, but sufficient to power the PRx controller or other components of PRx 1602. Specifically, in some implementations, the wireless power 1715 at the low power operating point 1755 may be sufficient to keep the protection switch activated to close the circuit including the secondary coil of PRx 1602. Recall that in some implementations, the protection switch is operated by the wireless power during the power transmission phase. Therefore, Fig.17 Techniques are provided in which the protection switch can be maintained in the second position during the disconnection period 1652 while also benefiting from zero power and non-zero power requests to define the disconnection period 1652 of the load. The NFC 1606 can be used for communications 1712, 1714, 1716, 1718, and 1722 that would normally occur during a communication slot in the power transfer phase 1620. For example, a communication slot can be an instance in which the PRx 1602 can communicate a zero power request, a non-zero power request, or any type of control message associated with the transmission of wireless power 115.

[0102] Fig.18 A block diagram of an example device 1800 for use in a wireless power transfer system is shown. In some implementations, device 1800 may be a power receiver, such as any of the power receivers described herein. In some implementations, device 1800 may be a power transmitter, such as any of the power transmitters described herein. Device 1800 may include a processor 1802 (which may include multiple processors, multiple cores, multiple nodes, or implement multithreading, etc.). Device 1800 may also include memory 1806. Memory 1806 may be system memory or any one or more of the possible implementations of computer-readable media described herein. Device 1800 may also include a bus 1811 (such as PCI, ISA, PCI-Express, AHB, AXI, etc.). In some implementations, the controller(s) 1862 may be distributed within the processor 1802, the memory 1806, and the bus 1811. The controller(s) 1862 may perform some or all of the operations described herein. The device 1800 may include Fig.18 For example, if the device 1800 is a power receiver, the device may have one or more switches (protection switches) in the circuit including the power transmission coil 1866.

[0103] Memory 1806 may include computer instructions executable by processor 1802 to implement reference Figure 1-17 The functionality of the implementation described herein. Any of these functionalities may be implemented partially (or entirely) in hardware or on the processor 1802. For example, the functionality may be implemented in a dedicated integrated circuit, in logic implemented in the processor 1802, in a coprocessor on a peripheral device or card, etc. In addition, the implementation may include Fig.18 The processor 1802, memory 1806, and controller(s) 1862 may be coupled to the bus 1811. Although illustrated as being coupled to the bus 1811, the memory 1806 may be coupled to the processor 1802.

[0104] Figure 1-18 The operations described herein are examples intended to aid in understanding example implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some different operations.

[0105] The foregoing disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit the aspects to the precise forms disclosed. Modifications and variations may be made based on the above disclosure, or modifications and variations may be obtained from the practice of the aspects. Although aspects of the present disclosure have been described based on various examples, any combination of aspects from any of the examples in the examples is also within the scope of the present disclosure. The examples in the present disclosure are provided for teaching purposes. Alternatively, or in addition to other examples described herein, the examples include any combination of the following implementation options (identified as clauses for reference).

[0106] Clause 1. A power receiver (PRx) of a wireless power transmission (WPT) system, the PRx comprising: a secondary coil, the secondary coil being configured to receive wireless power from a power transmitter (PTx) during at least a portion of a power transmission phase of operation; a protection switch, the protection switch being disposed between the secondary coil and a load associated with the PRx, wherein the protection switch is normally in a first position, the first position being configured to disconnect a circuit including the secondary coil before the power transmission phase; and a wireless communication unit; and a PRx controller, the PRx controller being configured to: determine that the PTx is in a connection phase of operation with the PRx, during the connection phase, generate a switch signal, the switch signal being configured to cause the protection switch to change to a second position, wherein the second position is configured to close the circuit including the secondary coil, after the protection switch is changed to the second position, cause the wireless communication unit to transmit a power request for the PTx to transmit the wireless power; and transition from the connection phase to the power transmission phase.

[0107] Clause 2. The PRx of clause 1, wherein the protection switch in the second position enables the secondary coil to receive the wireless power and provide the wireless power to the load during the power transfer phase.

[0108] Clause 3. A PRx according to any one of clauses 1-2, wherein the wireless communication unit is configured to communicate with the PTx by storing information in a passive tag, the passive tag being readable by the wireless communication interface of the PTx, and wherein the PRx controller is configured to cause the wireless communication unit to transmit the power request by modifying the information in the passive tag to include a power-on indication.

[0109] Clause 4. A PRx according to any one of clauses 1-2, wherein the wireless communication unit is configured to communicate with the PTx by transmitting information to a wireless communication interface of the PTx, and wherein the PRx controller is configured to cause the wireless communication unit to transmit the power request to the PTx in a control message.

[0110] Clause 5. A PRx according to Clause 4, wherein the PRx controller is further configured to: during the connection phase: cause the wireless communication unit to transmit a phase transition request message associated with requesting the PTx to transition to the power transmission phase, receive a confirmation message from the PTx via the wireless communication unit in response to the phase transition request message, and cause the wireless communication unit to transmit the power request in the control message after receiving the confirmation message.

[0111] Clause 6. The PRx of clause 5, wherein the PRx controller is further configured to detect whether an activation switch associated with the load has been turned on, and to prohibit the wireless communication unit from transmitting the phase transition request message until after the activation switch has been turned on.

[0112] Clause 7. A PRx according to any one of clauses 5-6, wherein the phase transition request message, the confirmation message and the control message are associated with a WPT specification, and the WPT specification defines when the protection switch changes from the first position to the second position, so that the protection switch changes to the second position before the control message.

[0113] Clause 8. The PRx of clause 7, wherein the WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and a second maximum time allowed between the confirmation message and the control message.

[0114] Clause 9. A PRx according to any one of clauses 1-8, wherein the PRx controller is further configured to: determine that an activation switch associated with the load has been turned on, and after the activation switch has been turned on and the protection switch is in the second position, cause the PTx to transition to the power transmission stage.

[0115] Clause 10. The PRx according to any one of clauses 1-9 further includes: an energy harvester, which is integrated with or operatively coupled to the wireless communication unit, and the energy harvester is configured to: harvest bias power from a communication signal received by a communication coil associated with the wireless communication unit, and provide the bias power to the PRx controller at least during the connection phase to power the PRx controller.

[0116] Clause 11. The PRx of Clause 10, wherein the PRx controller is powered by the bias power during the connection phase and is at least partially powered by the wireless power during the power transfer phase.

[0117] Clause 12. The PRx of any of clauses 10-11, wherein the switching signal is at least initially generated using the bias power.

[0118] Clause 13. A PRx according to any one of clauses 1-12, wherein the PRx controller is further configured to: detect a condition associated with the termination operation of the load, wherein the condition includes a load switch disconnecting the load or an activation switch being turned off, and based on the condition, cause the PTx and the PRx to transition from the power transmission phase to the connection phase, and cause the protection switch to change to the first position in association with the transition from the power transmission phase to the connection phase.

[0119] Clause 14. A PRx according to clause 13, wherein the wireless communication unit is configured to communicate with the PTx by storing information in a passive tag, and the passive tag can be read by the wireless communication interface of the PTx; and wherein the PRx controller is configured to: cause the PTx to transition to the connection stage by modifying the information in the passive tag to indicate a zero power or power-off request, and after modifying the information in the passive tag, cause the protection switch to change to the first position.

[0120] Clause 15. A PRx according to Clause 13, wherein the wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx; and wherein the PRx controller is configured to: cause the wireless communication unit to transmit a second phase transition request message associated with requesting the PTx to transition to the connection phase, receive a second confirmation message from the PTx via the wireless communication unit in response to the second phase transition request message, the second confirmation message indicating that the PTx has or will transition to the connection phase, and after receiving the second confirmation message, cause the protection switch to change to the first position.

[0121] Clause 16. A PRx according to any one of clauses 1-15, wherein the PRx controller is further configured to: cause the wireless communication unit to transmit a zero power request message, the zero power request message being associated with suspending the transmission of wireless power to the load while remaining in the power transmission stage, and causing the wireless communication unit to transmit a non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time.

[0122] Clause 17. The PRx according to Clause 16 further includes: an energy harvester, which is integrated with or operatively coupled to the wireless communication unit, and the energy harvester is configured to harvest bias power from the communication signal received by the communication coil associated with the wireless communication unit during the power transfer phase during a time period between the zero power request message and the non-zero power request message.

[0123] Clause 18. A PRx according to Clause 16, wherein the zero power request message is associated with a request for transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), wherein the wireless power is lower than the power required by the load but sufficient to power the PRx controller or other components of the PRx.

[0124] Clause 19. A PRx as described in any of clauses 16-18, wherein the load operates with an on-cycle and an off-cycle, wherein the duration of the time period is associated with the off-cycle, and wherein the duration spans one or more alternating current (AC) power cycles.

[0125] Clause 20. A power receiver (PRx) of a wireless power transfer (WPT) system, the PRx comprising: a secondary coil operatively coupled to a load associated with an on-period and an off-period, the secondary coil being 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, the PRx controller being configured to: cause the wireless communication unit to communicate with the PTx to enter the power transfer phase in which the PTx is capable of transmitting the wireless power, cause the wireless communication unit to transmit a non-zero power request associated with causing the PTx to transmit the wireless power in association with the on-period of the load, and cause the wireless communication unit to transmit a zero power request message associated with causing the PTx to suspend the transmission of the wireless power in association with the off-period of the load while remaining in the power transfer phase.

[0126] Clause 21. A PRx according to clause 20, wherein the load is associated with a series of on-cycles and off-cycles, and wherein the PRx controller is configured to manage the transmission of the wireless power using non-zero power requests and zero power requests associated with the on-cycles and off-cycles, respectively.

[0127] Clause 22. The PRx according to any one of clauses 20-21 further comprises: an energy harvester, which is integrated with or operatively coupled to the wireless communication unit, and the energy harvester is configured to harvest bias power from a communication signal received by a communication coil associated with the wireless communication unit during the power transmission phase during a time period associated with the disconnection period.

[0128] Clause 23. A PRx according to any of clauses 20-22, wherein the zero power request message is associated with a request for the transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power the PRx controller or other components of the PRx.

[0129] 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 operatively coupled to the inverter and configured to transmit the wireless power signal in association 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 a connection phase of operation with the PTx, receive a power request for the PTx to transmit the wireless power via the wireless communication interface, wherein the power request indicates that the PRx has changed the protection switch to close an indication of a circuit including the secondary coil of the PRx, and in response to the power request, cause the inverter to generate the wireless power signal for the transmission of the wireless power; and transition from the connection phase to a power transmission phase of operation.

[0130] A PTx according to clause 24, wherein a WPT specification defines the timing of the PRx coupling the secondary coil to the load during the connection phase and before the power request for wireless 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.

[0131] Clause 26. A PTx according to any one of clauses 24-25, wherein the protection switch is disposed between the secondary coil and the load of the PRx, and wherein the protection switch is normally in a first position, the first position being configured to disconnect the circuit including the secondary coil; and wherein the PTx controller is configured to determine, at least in part based on the power request for wireless power, that the PRx has caused the protection switch to change to a second position, wherein the second position of the protection switch is configured to close the circuit including the secondary coil.

[0132] Clause 27. The PTx of any of clauses 24-26, wherein 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.

[0133] Clause 28. A PTx according to any one of clauses 24-27, wherein the wireless communication interface is configured to communicate with the wireless communication unit of the PRx by reading information in a passive tag of the wireless communication unit, and wherein the PTx controller is configured to receive the power request via a power-on indication in the information.

[0134] Clause 29. The PTx of any of clauses 24-26, wherein the wireless communication interface is configured to receive a transmission from the wireless communication unit of the PRx, and wherein the PTx controller is configured to receive the power request via a control message in the transmission.

[0135] Clause 30. A PTx according to Clause 29, wherein the PTx controller is further configured to: during the connection phase, receive a phase transition request message from the PRX 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, in response to the phase transition request message, cause the wireless communication interface to transmit a confirmation message to the PRx, and receive the control message after transmitting the confirmation message.

[0136] Clause 31. The PTx of clause 30, wherein the PTx controller is configured to perform a FOD evaluation after the phase transition request message and before the confirmation message.

[0137] Clause 32. A PTx according to any one of clauses 30-31, wherein the phase transition request message, the confirmation message and the control message are associated with a WPT specification, and the WPT specification defines the timing of the PRx closing the circuit including the secondary coil so that the circuit is closed before the control message.

[0138] Clause 33. PTx according to clause 32, wherein the WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and a second maximum time allowed between the confirmation message and the control message.

[0139] Clause 34. The PTx of any of clauses 32-33, wherein the WPT specification requires the PRx to couple the secondary coil to the load via the protection switch prior to the power request.

[0140] Clause 35. A PTx according to any one of clauses 24-34, wherein 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, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx.

[0141] Clause 36. A PTx according to any one of clauses 24-35, wherein the wireless communication interface is configured to receive a zero power or power-off request from information in a passive tag of the wireless communication unit of the PRx; and wherein the PTx controller is configured to: in response to the zero power or power-off request, cause the inverter to stop generating the wireless power signal and switch to the connection stage.

[0142] Clause 37. The PTx according to clause 36, wherein 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 causing the inverter to stop generating the wireless power signal, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx.

[0143] Clause 38. A PTx according to any one of clauses 24-35, wherein the wireless communication interface is configured to receive a second phase transition request message associated with a request for the PTx to transition to the connection phase; and wherein the PTx controller is configured to: cause the inverter to stop generating the wireless power signal and transition to the connection phase, and in response to the second phase transition request message, cause the wireless communication interface to transmit a second confirmation message to the PRx, wherein the second confirmation message indicates that the PTx has or is about to transition to the connection phase.

[0144] Clause 39. A PTx according to any one of clauses 24-38, wherein, during the power transfer phase, the wireless communication interface is configured to receive a zero power request message associated with suspending the transmission of wireless power to the load while remaining in the power transfer phase; and wherein the PTx controller is configured to: in response to receiving the zero power, cause the inverter to stop generating the wireless power signal for the transmission of the wireless power to the load, and remain in the power transfer phase.

[0145] Clause 40. A PTx according to clause 39, wherein, 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 to the load; and wherein, in response to receiving the non-zero power request, the PTx controller is configured to cause the inverter to resume generating the wireless power signal for the transmission of the wireless power to the load.

[0146] Clause 41. A PTx according to clause 40, wherein 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 causing the inverter to stop generating the wireless power signal, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx during the power transfer phase during a time period between the zero power request message and the non-zero power request message.

[0147] Clause 42. A PTx according to any one of clauses 39-40, wherein the zero power request message is associated with a request for transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx, and wherein the PTx controller is configured to: in response to receiving the zero power request, cause the inverter to generate a low power signal for the transmission of the wireless power to the PRx controller at the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in association with the transmission of the wireless power to the PRx controller.

[0148] Clause 43. 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 operatively 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 a power transmission phase of operation; a wireless communication interface configured to receive a power request from the PRx; and a PTx controller configured to: cause the wireless communication interface to communicate with the PRx to enter the power transmission phase, when the power request is a non-zero power request, cause the inverter to generate the wireless power signal for the transmission of the wireless power to the load of the PRx during the power transmission phase, and when the power request is a zero power request, cause the inverter to suspend generation of the wireless power signal for the transmission of the wireless power to the load during the power transmission phase.

[0149] Clause 44. A PTx according to clause 43, wherein the load of the PRx is associated with a series of on-cycles and off-cycles, wherein the wireless communication interface is configured to receive a corresponding series of non-zero power requests and zero power requests associated with the on-cycles and off-cycles, respectively, and wherein 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.

[0150] Clause 45. A PTx according to any one of clauses 43-44, wherein the PTx controller is further configured to enable the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx during a time period between a zero power request message and a non-zero power request message, and wherein the communication signal can be used by the PRx to collect bias power during the power transfer phase to operate the PRx controller of the PRx during the time period between the zero power request message and the non-zero power request message.

[0151] Clause 46. A PTx according to any one of clauses 43-45, wherein the zero power request message is associated with a request for transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx, and wherein the PTx controller is configured to: in response to receiving the zero power request, cause the inverter to generate a low power signal for the transmission of the wireless power to the PRx controller at the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in association with the transmission of the wireless power to the PRx controller.

[0152] 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 a connection phase of operation 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, wherein the first position is configured to normally disconnect a circuit including the secondary coil before a power transfer phase of operation, wherein the second position is configured to close the circuit; after the protection switch is changed to the second position, transmitting a power request to the PTx; transitioning from the connection phase to the power transfer phase; and receiving wireless power from the PTx during at least a portion of the power transfer phase.

[0153] Clause 48. The method of clause 47, wherein communicating the power request comprises modifying information in a passive tag of the wireless communication unit of the PRx to include a power-on indication, and wherein the passive tag is readable by the wireless communication interface of the PTx.

[0154] Clause 49. The method of Clause 47, wherein communicating the power request comprises transmitting the power request in a control message to the PTx via a wireless communication unit of the PRx.

[0155] Clause 50. The method according to Clause 49 further includes, during the connection phase: transmitting a phase transition request message associated with requesting the PTx to transition to the power transmission phase; receiving a confirmation message from the PTx in response to the phase transition request message; and after receiving the confirmation message, transmitting the power request in the control message.

[0156] Clause 51. The method of clause 50, further comprising: detecting whether an activation switch associated with the load has been turned on; and prohibiting transmission of the phase transition request message until after the activation switch has been turned on.

[0157] Clause 52. A method according to any one of clauses 50-51, wherein the phase transition request message, the confirmation message and the control message are associated with a WPT specification, and the WPT specification defines when the protection switch changes from the first position to the second position, so that the protection switch changes to the second position before the control message.

[0158] Clause 53. A method according to clause 52, wherein the WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and a second maximum time allowed between the confirmation message and the control message.

[0159] Clause 54. The method according to any one of clauses 47-53 further includes: determining that an activation switch associated with the load has been turned on; and after the activation switch has been turned on and the protection switch is in the second position, switching the PTx to the power transmission stage via communication with the PTx.

[0160] Clause 55. The method according to any one of clauses 47-54 further includes: using an energy harvester to harvest bias power from a communication signal received by a communication coil associated with a wireless communication unit of the PRx, the energy harvester being integrated with or operatively coupled to the wireless communication unit; and using the bias power to power the PRx controller of the PRX at least during the connection phase.

[0161] Clause 56. The method of clause 55, further comprising: using the bias power to power the PRx controller during the connection phase; and using the wireless power to power the PRx controller during at least a portion of the power transfer phase.

[0162] Clause 57. The method of any of clauses 55-56, wherein causing the protection switch of the PRx to change from the first position to the second position comprises: using the bias power to at least initially generate a switching signal to control the protection switch.

[0163] Clause 58. The method according to any one of clauses 47-57 further includes: detecting a condition associated with the termination operation of the load, wherein the condition includes the load switch disconnecting the load or the activation switch being turned off, and based on the condition, causing the PTx and the PRx to switch from the power transmission stage to the connection stage; and causing the protection switch to change to the first position in association with the transition from the power transmission stage to the connection stage.

[0164] Clause 59. The method according to Clause 58 further includes: determining the transition from the power transfer phase to the connection phase; modifying the information in the passive tag of the wireless communication unit of the PRx to indicate zero power or a power-off request so that the PTx transitions to the connection phase, wherein the passive tag can be read by the wireless communication interface of the PTx; and after modifying the information in the passive tag, changing the protection switch to the first position.

[0165] Clause 60. According to the method described in Clause 58, determining to switch from the power transmission phase to the connection phase; transmitting a second phase transition request message associated with requesting the PTx to switch to the connection phase; in response to the second phase transition request message, receiving a second confirmation message from the PTx, the second confirmation message indicating that the PTx has or will switch to the connection phase, and after receiving the second confirmation message, changing the protection switch to the first position.

[0166] Clause 61. The method according to any one of clauses 47-60 further includes: transmitting a zero power request message associated with suspending the transmission of wireless power to the load while maintaining the power transmission stage; and subsequently transmitting a non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time.

[0167] Clause 62. The method of clause 61 further comprising: collecting bias power from a communication signal received by a communication coil associated with a wireless communication unit of the PRx during the power transfer phase during a time period between the zero power request message and the non-zero power request message.

[0168] Clause 63. A method for 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 a power transfer phase of operation; communicating with the PTx to enter a power transfer phase in which the PTx is capable of transferring wireless power to the PRx; transmitting a non-zero power request to the PTX in association with the on-cycle of the load, the non-zero power request being associated with causing the PTx to transfer the wireless power; and transmitting a zero power request message to the PTX in association with the off-cycle of the load, the zero power request being associated with causing the PTx to suspend the transmission of the wireless power while remaining in the power transfer phase.

[0169] Clause 64. A method according to clause 63, wherein 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 non-zero power requests and zero power requests associated with the on-cycles and the off-cycles, respectively.

[0170] Clause 65. The method of any one of clauses 63-64, further comprising: collecting bias power from a communication signal received by a communication coil associated with a wireless communication unit of the PRx during the power transmission phase during a time period associated with the disconnection period.

[0171] Clause 66. A method according to any one of clauses 63-65, wherein the zero power request message is associated with a request for the transmission of wireless power at a uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx.

[0172] Clause 67. A method for a power transmitter (PTx) in a wireless power transmission (WPT) system, the method comprising: determining, at least in part based on communication with a power receiver (PRx), that the PRx is in a connection phase of operation with the PTx; receiving a power request from the PRx, the power request being associated with a request for transmission of wireless power from the PTx to the PRx, wherein the power request indicates an indication that the PRx has changed the protection switch to close a circuit including a secondary coil of the PRx; in response to the power request, causing an inverter to generate a wireless power signal for the transmission of the wireless power; transitioning from the connection phase to a power transmission phase of operation; and transmitting the wireless power signal to transmit the wireless power to the secondary coil of the PRx.

[0173] Clause 68. A method according to clause 67, wherein a WPT specification defines the timing of the PRx coupling the secondary coil to the load during the connection phase and before the power request for wireless 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.

[0174] Clause 69. A method according to any one of clauses 67-68, wherein the protection switch is arranged between the secondary coil and the load of the PRx, and wherein the protection switch is normally in a first position, the first position being configured to disconnect the circuit including the secondary coil, the method further comprising: determining, at least in part based on the power request for the wireless power, that the PRx has caused the protection switch to change to a second position, wherein the second position of the protection switch is configured to close the circuit including the secondary coil.

[0175] Clause 70. The method of any of clauses 67-69, further comprising: performing a foreign object detection (FOD) assessment during the connection phase before causing the inverter to generate the wireless power signal.

[0176] Clause 71. The method of any of clauses 67-70, wherein receiving the power request comprises: reading information in a passive tag of a wireless communication unit of the PRx; and receiving the power request via a power-on indication in the information.

[0177] Clause 72. The method of any of clauses 67-69, wherein receiving the power request comprises receiving the power request via a control message in a transmission from a wireless communication unit of the PRx.

[0178] Clause 73. The method according to Clause 72 further includes: receiving a phase transition request message from the PRX, the phase transition request message being associated with requesting the PTx to transition to the power transmission phase, transmitting a confirmation message to the PRx in response to the phase transition request message, and receiving the control message after transmitting the confirmation message.

[0179] Clause 74. The method according to Clause 73 also includes performing a FOD evaluation after the phase transition request message and before the confirmation message.

[0180] Clause 75. A method according to any one of clauses 73-74, wherein the phase transition request message, the confirmation message and the control message are associated with a WPT specification, and the WPT specification defines the timing of the PRx closing the circuit including the secondary coil so that the circuit is closed before the control message.

[0181] Clause 76. A method according to clause 75, wherein the WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and a second maximum time allowed between the confirmation message and the control message.

[0182] Clause 77. The method of any of clauses 75-76, wherein the WPT specification requires the PRx to couple the secondary coil to the load via the protection switch prior to the power request.

[0183] Clause 78. The method according to any one of clauses 67-77 further includes: 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, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx.

[0184] Clause 79. The method according to any one of clauses 67-78 further includes: receiving a zero power or power-off request from information in a passive tag of the wireless communication unit of the PRx; causing the inverter to stop generating the wireless power signal in response to the zero power or power-off request; and transitioning to the connection stage.

[0185] Clause 80. The method according to Clause 79 further includes: after causing the inverter to stop 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, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx.

[0186] Clause 81. The method according to any one of clauses 67-78 further includes: 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 in response to the second phase transition request message, transmitting a second confirmation message to the PRx, the second confirmation message indicating that the PTx has or is about to transition to the connection phase.

[0187] Clause 82. The method according to any one of clauses 67-81 further includes, during the power transfer phase: receiving a zero power request message associated with pausing the transmission of wireless power to the load while remaining in the power transfer phase; in response to receiving the zero power, causing the inverter to stop generating the wireless power signal for the transmission of the wireless power to the load; and remaining in the power transfer phase.

[0188] Clause 83. The method according to Clause 82 further includes: subsequently receiving a non-zero power request message associated with resuming the transmission of the wireless power to the load; and in response to receiving the non-zero power request, causing the inverter to resume generating the wireless power signal for the transmission of the wireless power to the load.

[0189] Clause 84. The method according to Clause 83 further includes: 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, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx during the power transmission phase during the time period between the zero power request message and the non-zero power request message.

[0190] Clause 85. A method according to any one of clauses 82-83, wherein the zero power request message is associated with a request for transmission of wireless power at a uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power the PRx controller or other components of the PRx, the method further 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 to the PRx controller at the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in association with the transmission of the wireless power to the PRx controller.

[0191] Clause 86. A method for 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 used to control the transmission of wireless power to a load of the PRx during at least a portion of the power transmission phase; when the power request is a non-zero power request, causing an inverter of the PTx to generate a wireless power signal for the transmission of the wireless power to the load during the power transmission phase; and when the power request is a zero power request, causing the inverter to suspend generation of the wireless power signal to the load while remaining in the power transmission phase.

[0192] Clause 87. A method according to clause 86, wherein 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 associated with the series of on-cycles and off-cycles, respectively; and controlling the inverter at least partially based on the series of non-zero power requests and zero power requests.

[0193] Clause 88. The method according to any one of clauses 86-87 further includes: enabling the wireless communication interface of the PTx to transmit a communication signal to the wireless communication unit of the PRx during a time period between a zero power request message and a non-zero power request message, wherein the communication signal can be used by the PRx to collect bias power during the power transmission phase to operate the PRx controller of the PRx during the time period between the zero power request message and the non-zero power request message.

[0194] Clause 89. A method according to any one of clauses 86-88, wherein the zero power request message is associated with a request for transmission of wireless power at a uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power the PRx controller or other components of the PRx, the method further 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 to the PRx controller at the UOP or SCOP; and transmitting the low power signal in association with the transmission of the wireless power to the PRx controller.

[0195] The drawings, operations, and components described herein are examples intended to aid in understanding example implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some different operations.

[0196] As used herein, a phrase referring to "at least one of" or "one or more of" a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover the following possibilities: only a, only b, only c, 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.

[0197] The various illustrative components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in conjunction with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or a combination of hardware, firmware, or software, including the structures disclosed in this specification and their structural equivalents. The interchangeability of hardware, firmware, and software has been generally described in terms of functionality and illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0198] The hardware and data processing devices for implementing the various illustrative components, logic, logic blocks, modules and circuits described in conjunction with the aspects disclosed herein may be implemented or executed with 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 gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, specific processes, operations and methods may be performed by circuits specific to a given function.

[0199] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of the components disclosed herein or 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 a computer program may include non-transitory processor executable or computer executable instructions encoded on one or more tangible processor-readable or computer-readable storage media, which are used to be executed or control its operation by a data processing device including a component of the device described herein. As an example and not a limitation, such a storage medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store program codes in the form of instructions or data structures. The above combination should also be included in the scope of the storage medium.

[0200] Various modifications to the implementations described in this disclosure may be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Therefore, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and novel features disclosed herein.

[0201] In addition, various features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented separately in multiple implementations or in any suitable subcombination. As such, although features may be described above as functioning in a particular combination, and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and a claimed combination may be directed to a subcombination or variations of a subcombination.

[0202] Similarly, although operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring such operations to be performed in the particular order shown or in a continuous order, or requiring the operations of all descriptions to be performed to achieve the desired result. In addition, the accompanying drawings can schematically depict one or more example processes in the form of a flow chart or a simplified flow chart. However, other operations that are not depicted can be incorporated into the example processes schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously or between any operations in the illustrated operations. In some cases, multitasking and parallel processing can be advantageous. In addition, the separation of the various system components in the implementation described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or encapsulated in multiple software products.

Claims

1. A power receiver (PRx) of a wireless power transmission (WPT) system, the PRx comprising: a 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 protection switch disposed between the secondary coil and a load associated with the PRx, wherein the protection switch is normally in a first position configured to disconnect a circuit including the secondary coil before the power transfer phase; as well as a wireless communication unit; and A PRx controller configured to: determining that the PTx is in a connection phase of operation with the PRx, During the connection phase, generating a switch signal configured to cause the protection switch to change to a second position, wherein the second position is configured to close the circuit including the secondary coil, after the protection switch is changed to the second position, causing the wireless communication unit to transmit a power request for the PTx to transmit the wireless power; as well as A transition is made from the connection phase to the power transfer phase.

2. The PRx according to claim 1, wherein: The protection switch in the second position enables the secondary coil to receive the wireless power and provide the wireless power to the load during the power transfer phase.

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

4. The PRx according to any one of claims 1-2, in, 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 enable the wireless communication unit to transmit the power request to the PTx in a control message.

5. The PRx according to claim 4, wherein: The PRx controller is further configured to, 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 a confirmation message from the PTx via the wireless communication unit in response to the phase transition request message, and The wireless communication unit is caused to transmit the power request in the control message after receiving the confirmation message.

6. The PRx according to claim 5, wherein: The PRx controller is also configured to: detecting whether an activation switch associated with the load has been turned on, and The wireless communication unit is prohibited from transmitting the phase change request message until after the activation switch has been turned on.

7. The PRx according to any one of claims 5-6, wherein The phase transition request message, the confirmation message, and the control message are associated with a WPT specification, which defines when the protection switch changes from the first position to the second position, so that the protection switch changes to the second position before the control message.

8. The PRx according to claim 7, wherein: The WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and A second maximum time allowed between the confirmation message and the control message.

9. The PRx according to any one of claims 1 to 8, wherein The PRx controller is also configured to: determining that an activation switch associated with the load has been turned on, and After the activation switch has been turned on and the protection switch is in the second position, the PTx is switched to the power transmission phase.

10. The PRx according to any one of claims 1-9, further comprising: an energy harvester, the energy harvester being integrated with or operatively coupled to the wireless communication unit, the energy harvester being configured to: collecting bias power from a communication signal received by a communication coil associated with the wireless communication unit, and The bias power is provided to the PRx controller at least during the connection phase to power the PRx controller.

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

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

13. The PRx according to any one of claims 1 to 12, wherein: The PRx controller is also configured to: detecting a condition associated with an end operation of the load, wherein the condition includes a load switch disconnecting the load or an activation switch being turned off, Based on the condition, switching the PTx and the PRx from the power transfer phase to the connection phase, and The protection switch is changed to the first position in association with a transition from the power transfer phase to the connection phase.

14. The PRx according to claim 13, in, The wireless communication unit is configured to communicate with the PTx by storing information in a passive tag, the passive tag being readable by a wireless communication interface of the PTx; and Wherein, the PRx controller is configured to: causing the PTx to transition to the connection phase by modifying the information in the passive tag to indicate a zero power or power off request, and After modifying the information in the passive tag, the protection switch is changed to the first position.

15. The PRx according to claim 13, in, The wireless communication unit is configured to communicate with the PTx by transmitting information to the wireless communication interface of the PTx; as well as Wherein, the PRx controller is configured to: causing the wireless communication unit to transmit a second phase transition request message associated with requesting the PTx to transition to the connection phase, receiving a second confirmation message from the PTx via the wireless communication unit in response to the second phase transition request message, the second confirmation message indicating that the PTx has or will transition to the connection phase, and After receiving the second confirmation message, the protection switch is changed to the first position.

16. The PRx according to any one of claims 1-15, wherein The PRx controller is also configured to: causing the wireless communication unit to transmit a zero power request message associated with suspending transmission of wireless power to the load while remaining in the power transmission phase, and The wireless communication unit is caused to communicate a non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time.

17. The PRx of claim 16, further comprising: an energy harvester integrated with or operatively coupled to the wireless communication unit, the energy harvester being configured to harvest bias power from a communication signal received by a communication coil associated with the wireless communication unit during the power transfer phase during a time period between the zero power request message and the non-zero power request message.

18. The PRx according to claim 16, wherein: The zero power request message is associated with requesting the transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), which is lower than the power required by the load but sufficient to power the PRx controller or other components of the PRx.

19. The PRx according to any one of claims 16-18, wherein The load operates with an on-cycle and an off-cycle, wherein a duration of the time period is associated with the off-cycle, and wherein the duration spans one or more alternating current (AC) power cycles.

20. A power receiver (PRx) of a wireless power transfer (WPT) system, the PRx comprising: a secondary coil operatively coupled 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 a power transfer phase of operation; wireless communication unit; as well as A PRx controller configured to: causing the wireless communication unit to communicate with the PTx to enter the power transmission phase in which the PTx is capable of transmitting the wireless power, causing the wireless communication unit to communicate a non-zero power request associated with causing the PTx to transmit the wireless power in association with the on-period of the load, and The wireless communication unit is caused to transmit a zero power request message associated with causing the PTx to suspend the transmission of the wireless power in association with the disconnection period of the load while maintaining the power transmission stage.

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

22. The PRx of any one of claims 20-21, further comprising: an energy harvester integrated with or operatively coupled to the wireless communication unit, the energy harvester being configured to harvest bias power from a communication signal received by a communication coil associated with the wireless communication unit during the power transfer phase during a time period associated with the disconnection period.

23. The PRx according to any one of claims 20-22, wherein The zero power request message is associated with requesting the transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power 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 operatively coupled to the inverter and configured to transmit the wireless power signal in association 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; as well as A PTx controller, the PTx controller being configured to: determining that the PRx is in a connection phase of operation with the PTx, receiving, via the wireless communication interface, a power request for the PTx to transmit the wireless power, wherein 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 the inverter to generate the wireless power signal for the transmission of the wireless power in response to the power request; and Transition from the connection phase to the power transfer phase of operation.

25. The PTx according to claim 24, wherein: The WPT specification defines the timing of the PRx coupling the secondary coil to the load during the connection phase and before the power request for wireless power, so that the power request implicitly indicates that the PRx has coupled the secondary coil to the load according to the WPT specification.

26. The PTx according to any one of claims 24-25, in, The protection switch is disposed between the secondary coil and the load of the PRx, and wherein the protection switch is normally in a first position configured to disconnect the circuit including the secondary coil; as well as Wherein the PTx controller is configured to determine that the PRx has caused the protection switch to change to a second position based at least in part on the power request for wireless power, wherein the second position of the protection switch is configured to close the circuit including the secondary coil.

27. The PTx according to any one of claims 24-26, wherein: The PTx controller is also configured to: Prior to causing the inverter to generate the wireless power signal, a foreign object detection (FOD) evaluation is performed during the connection phase.

28. The PTx according to any one of claims 24-27, in, a wireless communication interface configured to communicate with the wireless communication unit of the PRx by reading information in a passive tag of the wireless communication unit, and Wherein, the PTx controller is configured to receive the power request via a power-on indication in the information.

29. The PTx according to any one of claims 24-26, in, The wireless communication interface is configured to receive transmissions from the wireless communication unit of the PRx, and Wherein, the PTx controller is configured to receive the power request via a control message in the transmission.

30. The PTx according to claim 29, wherein: The PTx controller is further configured to, during the connection phase: receiving a phase transition request message from the PRX via the wireless communication interface, the phase transition request message being associated with requesting the PTx to transition to the power transmission phase, In response to the phase transition request message, causing the wireless communication interface to transmit a confirmation message to the PRx, and The control message is received after transmitting the confirmation message.

31. The PTx of claim 30, wherein: The PTx controller is configured to perform a FOD evaluation after the phase transition request message and before the confirmation message.

32. The PTx according to any one of claims 30-31, wherein The phase transition request message, the confirmation message, and the control message are associated with WPT specifications, which define the timing for the PRx to close the circuit including the secondary coil so that the circuit is closed before the control message.

33. The PTx according to claim 32, wherein: The WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and A second maximum time allowed between the confirmation message and the control message.

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

35. The PTx according to any one of claims 24-34, in, The wireless communication interface is configured to transmit communication signals to the wireless communication unit of the PRx at least during the connection phase, wherein the communication signals can be used by the PRx to harvest bias power to operate a PRx controller of the PRx.

36. The PTx according to any one of claims 24-35, in, The wireless communication interface is configured to receive a zero power or power down request from information in a passive tag of the wireless communication unit of the PRx; and Wherein, the PTx controller is configured as follows: In response to the zero power or power off request, causing the inverter to stop generating the wireless power signal, and Transition to the connection phase.

37. The PTx according to claim 36, wherein: The PTx controller is also configured to enable the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx after causing the inverter to stop generating the wireless power signal, wherein the communication signal can be used by the PRx to collect bias power to operate the PRx controller of the PRx.

38. The PTx according to any one of claims 24-35, in, The wireless communication interface is configured to receive a second phase transition request message associated with requesting the PTx to transition to the connected phase; and Wherein, the PTx controller is configured as follows: causing the inverter to stop generating the wireless power signal, Transitioning to the connection phase, In response to the second phase transition request message, the wireless communication interface transmits a second confirmation message to the PRx, wherein the second confirmation message indicates that the PTx has transitioned or will transition to the connection phase.

39. The PTx according to any one of claims 24-38, in, During the power transfer phase, the wireless communication interface is configured to receive a zero power request message associated with suspending the transmission of wireless power to the load while remaining in the power transfer phase; and Wherein, the PTx controller is configured as follows: in response to receiving the zero power, causing the inverter to cease generating the wireless power signal for the transmission of the wireless power to the load, and Maintain the power transfer phase.

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

41. The PTx according to claim 40, in, The PTx controller is also configured to enable the wireless communication interface to transmit a communication signal to the wireless communication unit of the PRx after causing the inverter to stop generating the wireless power signal, wherein the communication signal can be used by the PRx to collect bias power during the power transfer phase to operate the PRx controller of the PRx during a time period between the zero power request message and the non-zero power request message.

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

43. 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 operatively coupled to the inverter and configured to transmit the wireless power signal in association with the transfer of wireless power to a power receiver (PRx) during at least a portion of a power transfer phase of operation; a wireless communication interface configured to receive a power request from the PRx; as well as A PTx controller, the PTx controller being configured to: causing the wireless communication interface to communicate with the PRx to enter the power transfer phase, When the power request is a non-zero power request, causing the inverter to generate the wireless power signal for the transmission of the wireless power to the load of the PRx during the power transmission phase, and When the power request is a zero power request, the inverter is caused to suspend generation of the wireless power signal for the transmission of the wireless power to the load in the power transmission phase.

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

45. The PTx according to any one of claims 43-44, in, 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 time period between a zero power request message and a non-zero power request message, and The communication signal can be used by the PRx to collect bias power during the power transfer phase to operate a PRx controller of the PRx during the time period between the zero power request message and the non-zero power request message.

46. ​​The PTx according to any one of claims 43-45, in, The zero power request message is associated with requesting the transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP) that is lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx, and Wherein, the PTx controller is configured as follows: In response to receiving the zero power request, the inverter is caused to generate a low power signal for the transmission of the wireless power to the PRx controller at the UOP or SCOP, wherein the primary coil is configured to transmit the low power signal in association with the transmission of the wireless power to the PRx controller.

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 a connection phase of operation with said PRx; causing a protection switch of the PRx to change 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, wherein the first position is configured to normally open a circuit including the secondary coil prior to a power transfer phase of operation, and wherein the second position is configured to close the circuit; after the protection switch is changed to the second position, transmitting a power request to the PTx; transitioning from the connection phase to the power transfer phase; as well as Wireless power is received from the PTx during at least a portion of the power transfer phase.

48. The method of claim 47, wherein: Transmitting the power request includes modifying information in a passive tag of the wireless communication unit of the PRx to include a power-on indication, and wherein the passive tag is readable by the wireless communication interface of the PTx.

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

50. The method of claim 49, further comprising, during the connection phase: transmitting a phase transition request message associated with requesting the PTx to transition to the power transmission phase; receiving a confirmation message from the PTx in response to the phase transition request message; as well as After receiving the confirmation message, the power request is transmitted in the control message.

51. The method of claim 50, further comprising: detecting whether an activation switch associated with the load has been turned on; as well as Transmission of the phase change request message is prohibited until after the activation switch has been turned on.

52. The method according to any one of claims 50-51, wherein: The phase transition request message, the confirmation message, and the control message are associated with a WPT specification, which defines when the protection switch changes from the first position to the second position, so that the protection switch changes to the second position before the control message.

53. The method of claim 52, wherein: The WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and A second maximum time allowed between the confirmation message and the control message.

54. The method according to any one of claims 47 to 53, further comprising: determining that an activation switch associated with the load has been turned on; as well as After the activation switch has been turned on and the protection switch is in the second position, the PTx is switched to the power transmission stage via communication with the PTx.

55. The method according to any one of claims 47 to 54, further comprising: harvesting bias power from a communication signal received by a communication coil associated with a wireless communication unit of the PRx using an energy harvester, the energy harvester being integrated with or operatively coupled to the wireless communication unit; as well as The bias power is used to power a PRx controller of the PRX at least during the connection phase.

56. The method of claim 55, further comprising: powering the PRx controller using the bias power during the connection phase; as well as The PRx controller is powered using the wireless power during at least a portion of the power transfer phase.

57. The method according to any one of claims 55-56, wherein: Changing the protection switch of the PRx from the first position to the second position comprises: A switching signal is generated at least initially using the bias power to control the protection switch.

58. The method according to any one of claims 47 to 57, further comprising: detecting a condition associated with an end operation of the load, wherein the condition includes a load switch disconnecting the load or an activation switch being turned off, Based on the condition, switching the PTx and the PRx from the power transmission phase to the connection phase; as well as The protection switch is changed to the first position in association with a transition from the power transfer phase to the connection phase.

59. The method of claim 58, further comprising: determining to switch from the power transmission phase to the connection phase; modifying information in a passive tag of the wireless communication unit of the PRx to indicate a zero power or power-off request to cause the PTx to transition to the connection phase, wherein the passive tag can be read by the wireless communication interface of the PTx; as well as After modifying the information in the passive tag, the protection switch is changed to the first position.

60. The method according to claim 58, determining to switch 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 message from the PTx in response to the second phase transition request message, the second confirmation message indicating that the PTx has or will transition to the connection phase, and After receiving the second confirmation message, the protection switch is changed to the first position.

61. The method according to any one of claims 47 to 60, further comprising: communicating a zero power request message associated with suspending transmission of wireless power to the load while remaining in the power transmission phase; as well as A non-zero power request message associated with resuming the transmission of wireless power to the load after a period of time is then communicated.

62. The method of claim 61 further comprising: During a time period between the zero power request message and the non-zero power request message, bias power is collected during the power transfer phase from a communication signal received by a communication coil associated with a wireless communication unit of the PRx.

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 a power transfer phase of operation; communicating with the PTx to enter a power transfer phase wherein the PTx is capable of wirelessly transferring power to the PRx; communicating a non-zero power request to the PTX in association with the on-period of the load, the non-zero power request being associated with causing the PTx to transmit the wireless power; as well as A zero power request message is delivered to the PTX in association with the disconnection period of the load, the zero power request being associated with causing the PTx to suspend the transmission of the wireless power while remaining in the power transmission phase.

64. The method of claim 63, wherein: The load is associated with a series of on-cycles and off-cycles, the method further comprising: The transmission of the wireless power is controlled using a non-zero power request and a zero power request associated with the on-period and the off-period, respectively.

65. The method according to any one of claims 63-64, further comprising: During a time period associated with the off period, bias power is collected during the power transfer phase from a communication signal received by a communication coil associated with the wireless communication unit of the PRx.

66. The method according to any one of claims 63 to 65, wherein: The zero power request message is associated with requesting the transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx.

67. A method of a power transmitter (PTx) in a wireless power transfer (WPT) system, the method comprising: determining, based at least in part on communications with a power receiver (PRx), that the PRx is in a connection phase of operation with the PTx; receiving a power request from the PRx, the power request being associated with requesting a transfer of wireless power from the PTx to the PRx, wherein the power request represents an indication that the PRx has changed the protection switch to close a circuit including a secondary coil of the PRx; causing an inverter to generate a wireless power signal for the transmission of the wireless power in response to the power request; transitioning from said connection phase to a power transfer phase of operation; as well as The wireless power signal is transmitted to transfer the wireless power to the secondary coil of the PRx.

68. The method of claim 67, wherein: The WPT specification defines the timing of the PRx coupling the secondary coil to the load during the connection phase and before the power request for wireless power, so that the power request implicitly indicates that the PRx has coupled the secondary coil to the load according to the WPT specification.

69. The method according to any one of claims 67-68, wherein: The protection switch is disposed between the secondary coil and the load of the PRx, and wherein the protection switch is normally in a first position configured to disconnect the circuit including the secondary coil, the method further comprising: The PRx is determined based at least in part on the power request for the wireless power to have caused the protection switch to change to a second position, wherein the second position of the protection switch is configured to close the circuit including the secondary coil.

70. The method according to any one of claims 67-69, further comprising: Prior to causing the inverter to generate the wireless power signal, a foreign object detection (FOD) evaluation is performed during the connection phase.

71. The method according to any one of claims 67 to 70, wherein: Receiving the power request includes: reading information in a passive tag of a wireless communication unit of the PRx; and The power request is received via a power-on indication in the information.

72. The method according to any one of claims 67 to 69, wherein: Receiving the power request includes: The power request is received via a control message in a transmission from a wireless communication unit of the PRx.

73. The method of claim 72, further comprising: receiving a phase transition request message from the PRX, the phase transition request message being associated with requesting the PTx to transition to the power transmission phase, In response to the phase transition request message, transmitting a confirmation message to the PRx, and The control message is received after transmitting the confirmation message.

74. The method of claim 73 further comprises performing a FOD evaluation after the phase transition request message and before the confirmation message.

75. The method according to any one of claims 73-74, wherein: The phase transition request message, the confirmation message, and the control message are associated with WPT specifications, which define the timing for the PRx to close the circuit including the secondary coil so that the circuit is closed before the control message.

76. The method of claim 75, wherein: The WPT specification defines: a first maximum time allowed between the phase transition request message and the confirmation message, and A second maximum time allowed between the confirmation message and the control message.

77. The method according to any one of claims 75-76, wherein: The WPT specification requires the PRx to couple the secondary coil to the load via the protection switch before the power request.

78. The method of any one of claims 67-77, further comprising: A communication signal is transmitted from the wireless communication interface of the PTx to the wireless communication unit of the PRx at least during the connection phase, wherein the communication signal can be used by the PRx to harvest bias power to operate a PRx controller of the PRx.

79. The method of any one of claims 67-78, further comprising: receiving a zero power or power off request from information in a passive tag of said wireless communication unit of said PRx; In response to the zero power or power off request, causing the inverter to stop generating the wireless power signal; and Transition to the connection phase.

80. The method of claim 79, further comprising: After the inverter stops generating the wireless power signal, a communication signal is transmitted from the wireless communication interface of the PTx to the wireless communication unit of the PRx, wherein the communication signal can be used by the PRx to collect bias power to operate a PRx controller of the PRx.

81. The method of any one of claims 67-78, further comprising: 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; as well as In response to the second phase transition request message, a second confirmation message is transmitted to the PRx, wherein the second confirmation message indicates that the PTx has transitioned or will transition to the connection phase.

82. The method of any one of claims 67-81, further comprising, during the power transfer phase: receiving a zero power request message associated with suspending the transmission of wireless power to the load while remaining in the power transmission phase; In response to receiving the zero power, causing the inverter to stop generating the wireless power signal for the transmission of the wireless power to the load; and Maintain the power transfer phase.

83. The method of claim 82, further comprising: subsequently receiving a non-zero power request message associated with resuming the transmission of the wireless power to the load; as well as In response to receiving the non-zero power request, causing the inverter to resume generating the wireless power signal for the transmission of the wireless power to the load.

84. The method of claim 83, further comprising: After causing the inverter to stop generating the wireless power signal, the wireless communication interface of the PTx transmits a communication signal to the wireless communication unit of the PRx, wherein the communication signal can be used by the PRx to collect bias power during the power transmission phase to operate the PRx controller of the PRx during a time period between the zero power request message and the non-zero power request message.

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

86. A method of a power transmitter (PTx) in a wireless power transfer (WPT) system, the method comprising: Communicates with a power receiver (PRx) to enter the power transfer phase of operation; receiving a power request from the PRx, the power request being used to control the transfer of wireless power to a load of the PRx during at least a portion of the power transfer phase; When the power request is a non-zero power request, causing the inverter of the PTx to generate a wireless power signal for the transmission of the wireless power to the load during the power transmission phase; as well as When the power request is a zero power request, the inverter is caused to suspend generating the wireless power signal for the load while maintaining the power transmission phase.

87. The method of claim 86, wherein: The load of the PRx is associated with a series of on-cycles and off-cycles, the method further comprising: receiving a series of non-zero power requests and zero power requests associated with the series of on-periods and off-periods, respectively; and The inverter is controlled based at least in part on the series of non-zero power requests and the zero power request.

88. The method of any one of claims 86-87, 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 time period between a zero power request message and a non-zero power request message, The communication signal can be used by the PRx to collect bias power to operate a PRx controller of the PRx during the power transfer phase during the time period between the zero power request message and the non-zero power request message.

89. The method according to any one of claims 86 to 88, wherein: The zero power request message is associated with requesting transmission of wireless power at an uncritical operating point (UOP) or a safe commutation operating point (SCOP), the wireless power being lower than the power required by the load but sufficient to power a PRx controller or other components of the PRx, the method further 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 to the PRx controller at the UOP or SCOP; and The low power signal is transmitted in association with the transmission of the wireless power to the PRx controller.

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