Wireless Power Transmission

Abstract

The power transmitter 101 wirelessly supplies power to the power receiver 105 via a power transmission signal generated by the power transmission coil 103. The power receiver 105 includes a receiving coil 107 that extracts power from the power transmission signal during a power transmission phase, and communicators 307, 309 that communicate with the power transmitter 101. The power transmitter 101 transmits a message to the power receiver 105 that includes a frequency indicator indicating the frequency of the envelope of the power transmission signal. The controller 307 adapts power transmission operation in response to the frequency indicator. For example, timing parameters of communications, foreign object detection tests, or measurements can be adjusted to reflect the envelope frequency. In some cases, operation of a load can be adjusted in response to the envelope frequency.

Description

[Technical Field]

[0001] The present invention relates to the operation of wireless power transmission from a power transmitter to a power receiver, and particularly, but not exclusively, to transmitting power wirelessly to high power devices such as kitchen appliances. [Background technology]

[0002] Most electronic products today require dedicated electrical contacts to be powered from an external source. However, this tends to be impractical, requiring the user to physically insert a connector or establish physical electrical contact. Power requirements also typically vary widely, and most devices now have their own dedicated power sources, meaning the typical user owns many different power sources, each dedicated to a specific device. While using an internal battery could eliminate the need for a wired connection to a power source during use, this is only a partial solution, as the battery will need to be recharged (or replaced). Using a battery can significantly increase the weight of the device, as well as its cost and size.

[0003] To significantly improve the user experience, it has been proposed to use wireless power sources in which power is inductively transferred from a transmitting inductor in a power transmitting device to a receiving coil in an individual device.

[0004] Power transfer via magnetic induction is a well-known concept and is primarily applied to transformers with tight coupling between the primary transmitter inductor / coil and the secondary receiver coil. Separating the primary transmitter coil and secondary receiver coil between the two devices allows wireless power transfer between them based on the principle of a loosely coupled transformer.

[0005] Such a configuration allows for wireless power transfer to the device without the need for wires or physical electrical connections. In fact, the device can be externally charged or powered simply by being configured next to or above the transmitter coil. For example, the power transmission device can be configured on a horizontal surface where the device can be powered simply by being configured.

[0006] Moreover, such wireless power transmission configurations may be advantageously designed to allow a power transmitting device to be used with a variety of power receiving devices. In particular, a wireless power transmission approach known as the Qi specification has been defined and is currently being further developed. This approach allows a power transmitting device compliant with the Qi specification to be used with a power receiving device that is also compliant with the Qi specification, without the devices needing to be from the same manufacturer or proprietary to each other. The Qi standard further includes several features that allow it to adapt its operation to a particular power receiving device (e.g., depending on a particular power consumption).

[0007] The Wireless Power Consortium has been developing the Ki specification (also known as the Cordless Kitchen standard), which builds on the Qi standard and aims to provide safe, reliable and efficient wireless power transfer to kitchen appliances. Ki supports very high power levels up to 2.5KW.

[0008] Many systems, particularly Qi systems, may use load modulation in communication from a power receiver to a power transmitter. In load modulation, the load of the power transmission signal varies depending on the data being transmitted. However, it may be difficult to detect such load modulation if the power transmission load of the power transmission signal is also fluctuating at the same time. Similarly, communication from a power transmitter to a power receiver may be achieved by modulating the power transmission signal (e.g., amplitude modulation or frequency modulation), but interference with such modulation may occur due to fluctuations in the parameters of the power transmission signal, for example, due to load fluctuations.

[0009] Some systems have proposed using a completely independent communication approach. Specifically, the Ki wireless power transfer system can establish a bidirectional communication link using the Near Field Communication (NFC) standard. Communication is performed at short time intervals during the power transfer phase to avoid or reduce interference between power transfer and communication. The power receiver is configured to detect the NFC carrier to perform communication during the short time intervals.

[0010] During power transfer operation, the power receiver extracts power for the load from the power transfer signal. Often, the extracted power is also used to power the power receiver's own functions, such as a processing unit, a user interface, etc. However, such an approach requires additional functionality and may not be optimal in all scenarios.

[0011] Power transfer devices are desirable for use in a variety of conditions, operating scenarios, and geographies, but traditional power transfer devices are not optimal in all scenarios and may provide suboptimal performance in some situations.

[0012] Therefore, improved approaches to wireless power transfer systems would be advantageous, particularly approaches that allow for increased flexibility, reduced cost, reduced complexity, improved communication, additional functionality, improved adaptation to various operational scenarios, improved operation in different geographic regions and different operational conditions, and / or improved performance. Summary of the Invention [Problem to be solved by the invention]

[0013] Accordingly, the Invention seeks to preferably mitigate, reduce or eliminate one or more of the above mentioned disadvantages singly or in any combination. [Means for solving the problem]

[0014] According to one aspect of the present invention, there is provided a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the power receiver comprising: an input circuit including a receiver coil configured to extract power from the power transmission signal during a power transmission phase; a communicator configured to communicate with the power transmitter, the communicator configured to receive a message from the power transmitter, the message including a frequency indicator indicating a frequency of an envelope of the power transmission signal; and a controller configured to adapt power transmission operation in response to the frequency indicator.

[0015] The present invention allows for improved performance and / or operation and / or implementation in many embodiments, which allows for improved overall power transfer operation in many systems and embodiments.

[0016] This approach, in many embodiments, can provide improved operation and, in many applications, can enable improved adaptation of the power receiver (including the load) to specific operating conditions. In some cases, it can prevent malfunctions or potentially destructive operation. In many applications, it can improve operation. In many applications, this approach allows the power receiver to provide indicators to other functions or users that reflect the characteristics of viable operation.

[0017] The inventors have recognized that envelope variations of power transmission signals may occur, and that these frequencies may vary depending on the scenario and / or geography. For example, envelope variations may be due to changes in power supply signals / voltages, which may vary from region to region because power grids / infrastructure / mains power sources use different frequencies in different regions. Furthermore, the inventors have recognized that frequency variations of such envelope variations may affect performance (and even cause failure or damage). Furthermore, the inventors have recognized that improved performance may be achieved by adapting the power transmitter and power receiver to communicate a frequency indicator, and by the power receiver adapting its power transmission operation in response to such frequency indicator.

[0018] This approach, in many embodiments, reduces the sensitivity of the power transmission signal envelope to different frequencies, i.e., the effects caused by the power transmitter being powered by AC power signals of different frequencies, for example.

[0019] In particular, this approach improves performance in many scenarios and can be adapted to situations where the power transmission signal generated by the power transmitter depends on a power supply voltage that may vary in frequency. For example, it can improve performance in systems where the power transmitter may be powered by a 50 Hz power supply or a 60 Hz power supply.

[0020] The power transfer drive signal / power transfer signal may be generated to have a periodically time-varying envelope, and the frequency indicator may indicate the period / frequency of this periodic variation. The periodic variation may be substantially sinusoidal (or rectified sinusoidal) in shape (e.g., for at least a portion of a cycle). Such a sinusoidal signal may be interrupted by non-power transfer time intervals near the minimum / zero crossings of the signal. The frequency indicator may indicate the frequency / duration between such non-power transfer time intervals.

[0021] The power transmission signal may employ a repeating time frame including a power transmission interval during which the power transmission signal is generated and a non-power transmission interval during which the power transmission signal is not generated. The power transmission time interval may include at least 50%, 60%, 70%, 80%, or 90% of the repeating time frame. The repeating time frame may be synchronized with the variation of the envelope, and a frequency indicator may indicate the (recurrence) frequency of the repeating time frame.

[0022] The non-power transmission time intervals can be used for communication (one-way or two-way) between the power transmitter and the power receiver.

[0023] The envelope of a vibration signal is a smooth curve that outlines its extreme values, and the envelope of a power transmitter drive signal / power transmission signal / induced signal is a smooth curve that outlines the extreme values ​​of the fluctuations that occur at the power transmission signal frequency / switch frequency. The frequency of the power transmission signal envelope can typically be greater than 1 kHz. The frequency of the power transmission signal envelope is typically less than 200 Hz.

[0024] In accordance with an optional feature of the invention, the communicator is configured to receive the frequency indication during a power transfer initiation phase prior to the power transfer phase.

[0025] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transfer operation and user experience. In many scenarios, the power receiver can adapt to a particular envelope frequency before the power transfer phase begins, for example, by setting the power transfer operating parameters or mode before initiating power transfer. This can improve operation, for example, preventing the power transfer phase from beginning with unacceptable performance.

[0026] In many embodiments, the communicator is configured to receive a frequency indication prior to the power transfer phase.

[0027] According to an optional feature of the invention, the controller is configured to terminate the power transfer initiation in response to the frequency indicator meeting a criterion.

[0028] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transfer operation and user experience. The criteria can, for example, consider whether the frequency indicator indicates an acceptable envelope frequency and, if not, terminate the initiation of power transfer. The criteria can specifically comprise a requirement that the frequency indicator indicate an envelope frequency that is not part of a set or range of acceptable frequencies. This set can, in some embodiments, include only a single frequency. For example, if the frequency indicator is a one-bit indicator of a 50 Hz or 60 Hz envelope frequency and the power receiver can only operate at a 50 Hz envelope frequency, the criteria can comprise a requirement that the frequency indicator indicate a 60 Hz envelope frequency.

[0029] In accordance with an optional feature of the invention, the power receiver further includes a user interface, and the controller is configured to control the user interface to generate a user alert.

[0030] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transfer operation and user experience, for example by notifying the user of anticipated changes in operating parameters or operation.

[0031] In accordance with an optional feature of the invention, the controller is configured to adapt timing characteristics of the power transfer operation in response to the frequency index.

[0032] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transfer operation and user experience. The power receiver can be configured to synchronize one or more operations to a particular envelope frequency, thereby improving performance.

[0033] According to an optional feature of the invention, the controller is configured to set initial timing characteristics of the power transfer phase in response to the frequency index.

[0034] This allows for particularly advantageous operation and adaptation in many embodiments. This approach improves initial performance when entering the power transfer phase. For example, timing loops controlling operations such as communications and foreign object detection can be initialized at a timing frequency corresponding to the envelope frequency indicated by the frequency index, and can adapt within a narrow bandwidth around the indicated envelope frequency.

[0035] In accordance with an optional feature of the present invention, the power transfer operation is a communication operation.

[0036] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transmission operation and user experience. Adapting communications to the envelope frequency typically improves and provides more reliable communications between the power receiver and power transmitter.

[0037] In many embodiments, the controller can be configured to adapt the timing of communications, such as the timing of transmission of messages to the power transmitter, in response to the frequency index.

[0038] In accordance with an optional feature of the invention, the controller is configured to control at least one of the initiation, duration and repetition interval of the measurement operation.

[0039] This allows for particularly advantageous operation and adaptation in many embodiments: this approach improves the adaptation of measurement operation in many scenarios, leading to improved measurement and typically improved operation.

[0040] In accordance with an optional feature of the invention, the frequency index is a one-bit index.

[0041] This allows for particularly advantageous operation and adaptation in many embodiments, and in particular allows for improved operation while maintaining very low communication overhead.

[0042] According to one aspect of the present invention, there is provided a power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, the power transmitter comprising: a power transmission coil configured to generate the power transmission signal; a power transmission driver configured to generate a power transmission drive signal for the power transmission coil to generate the power transmission signal during a power transmission phase; a communicator configured to communicate with the power receiver; and a controller configured to control the communicator to send a message to the power receiver including a frequency indicator indicating the frequency of an envelope of the power transmission signal during the power transmission phase.

[0043] In accordance with an optional feature of the invention, the power transmitter further includes a power supply input for receiving an AC supply power, and the frequency indicator indicates a frequency of the AC supply power.

[0044] This allows for particularly advantageous operation and adaptation in many embodiments, typically improving power transmission operation and user experience. The AC supply power may be supplied power from a power grid / mains supply, in particular powering a power transmitter.

[0045] According to an optional feature of the invention, the controller is configured to measure a frequency of the AC supply power and to determine a frequency indicator in response to the measured frequency of the AC supply power.

[0046] This allows for particularly advantageous operation and adaptation in many embodiments, in particular providing a more flexible power transmitter that can dynamically adapt to different operating scenarios, typically improving power transfer operation and user experience.

[0047] According to one aspect of the present invention, there is provided a method of operating a power receiver that wirelessly receives power from a power transmitter via an electromagnetic power transmission signal, the method comprising the steps of: an input circuit including a receiver coil extracting power from the power transmission signal during a power transmission phase; communicating with the power transmitter to receive a message from the power transmitter including a frequency indicator indicating a frequency of an envelope of the power transmission signal; and adapting power transmission operation in response to the frequency indicator.

[0048] According to one aspect of the present invention, there is provided a method of operating a power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, the method comprising the steps of: generating a power transmission drive signal for a power transmission coil to generate the power transmission signal in a power transmission phase; and communicating with the power receiver to send a message to the power receiver, the message including a frequency indicator indicating a frequency of an envelope of the power transmission signal during the power transmission phase.

[0049] These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0050] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Figure 1] 1 illustrates example elements of a power transfer system according to some embodiments of the present invention. [Figure 2] 2 illustrates example elements of a power transmitter according to some embodiments of the present invention. [Figure 3] 2 illustrates example elements of a power receiver according to some embodiments of the present invention. [Figure 4] 1A and 1B illustrate example time frames for a wireless power transfer system according to some embodiments of the present invention. [Figure 5] FIG. 1 illustrates an example of a half-bridge inverter for a power transmitter. [Figure 6]FIG. 1 illustrates an example of a full-bridge inverter for a power transmitter. [Figure 7] FIG. 10 is a diagram showing an example of envelope fluctuation of a power transmission signal for wireless power transmission operation. DETAILED DESCRIPTION OF THE INVENTION

[0051] The following description focuses on embodiments of the invention applicable to wireless power transfer systems utilizing the power transfer approach as known from the Ki standard, however, it will be understood that the invention is not limited to this application and may be applied to many other wireless power transfer systems.

[0052] 1 illustrates an example of a power transfer system according to some embodiments of the present invention. The power transfer system includes a power transmitter 101 including (or coupled to) a transmitter coil / inductor 103. The system further includes a power receiver 105 including (or coupled to) a receiver coil / inductor 107.

[0053] The system provides an electromagnetic power transmission signal capable of inductively transmitting power from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal, which is propagated as magnetic flux by a transmitter coil or inductor 103. The power transmission signal can be considered to correspond to an electromagnetic power transmission component representing the transfer of energy from the power transmitter to the power receiver, and to correspond to a component of the generated electromagnetic field that transfers power from the power transmitter to the power receiver. For example, if there is no load on the receiver coil 107, no power is extracted by the power receiver from the generated electromagnetic field (apart from losses). In such a scenario, driving the transmitter coil 103 can generate an electromagnetic field of potentially high field strength, but the power level of the power transmission signal (apart from losses) will be zero. In some situations where a foreign object is present, the power transmission signal can be considered to include a component corresponding to the transfer of power to the foreign object, and therefore the power transmission signal can be considered to correspond to power extracted from the electromagnetic field generated by the power transmitter.

[0054] The power transmission signal may typically have a frequency between about 20 kHz and about 500 kHz, and for Ki-compatible systems, may typically have a frequency in the range of 20 kHz to 80 kHz. The transmitter coil 103 and power receiver coil 107 are loosely coupled, and thus the power receiver coil 107 picks up (at least a portion of) the power transmission signal from the power transmitter 101. Thus, power is transmitted from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the power receiver coil 107. While the term power transmission signal is primarily used to refer to the induction signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiver coil 107, it will be understood that, equivalently, it may also be considered and used to refer to an electrical signal supplied to the transmitter coil 103 or picked up by the power receiver coil 107.

[0055] In an embodiment, power receiver 105 is specifically a power receiver that receives power via receiver coil 107. However, in other embodiments, power receiver 105 can include a metallic element, such as a metallic heating element, where the power transmission signal directly induces eddy currents that result in direct heating of the element. Consequently, the power receiver can load the power transmission signal by including an inductive power extraction element, specifically a power extraction coil or an electrical (e.g., heating) element in which a current is induced by the power transmission signal.

[0056] The system is configured to transmit significant power levels; specifically, the power transmitter can support power levels of 50 W, 100 W, 500 W, or even greater than 1 kW. For example, for Ki-type applications, power transmission is often greater than 100 W, and can even exceed 2500 W for very high power applications.

[0057] The operation of power transmitter 101 and power receiver 105 is described below with particular reference to embodiments that generally conform to the standard being developed by the Wireless Power Consortium (except for modifications and enhancements described (or resulting from) therein). In particular, power transmitter 101 and power receiver 105 conform to or are substantially compatible with elements of the Ki standard.

[0058] Many wireless power transfer systems, particularly high-power systems such as Ki, use resonant power transfer in which the transmitter coil 103 is part of a resonant circuit, and typically the receiver coil 107 is also part of the resonant circuit. In many embodiments, the resonant circuit is a series resonant circuit, such that the transmitter coil 103 and receiver coil 107 can be coupled in series with corresponding resonant capacitors. The use of a resonant circuit tends to provide more efficient power transfer.

[0059] FIG. 2 illustrates elements of the power transmitter 101, and FIG. 3 shows elements of the power receiver 105 of FIG. 1 in more detail.

[0060] The power transmitter 101 has a driver 201 operable to generate a drive signal that is supplied to a transmitter coil 103, which in turn generates an electromagnetic power transfer signal by which power is transferred to a power receiver 105. The power transfer signal is provided (at least) during a power transfer time interval of a power transfer phase.

[0061] The driver 201 may comprise an output circuit in the form of an inverter, typically formed by driving a full or half bridge, as is well known to those skilled in the art.

[0062] The power transmitter 101 further includes a power transmitter controller 203 configured to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 may include many of the functions necessary to perform power control according to the Qi or Ki standards.

[0063] The power transmitter controller 203 is particularly configured to control the generation of the drive signal by the driver 201 and is particularly able to control the power level of the drive signal and therefore the level of the generated power transmission signal. The power transmitter controller 203 comprises a power loop controller that controls the power level of the power transmission signal in response to power control messages received from the power receiver 105 during a power control phase.

[0064] To receive data and messages from the power receiver 105, the power transmitter 101 comprises a first communicator 205 configured to receive data and messages from the power receiver 105 and to transmit data and messages to the power receiver 105 (as will be appreciated by those skilled in the art, a data message may provide one or more bits of information).

[0065] In this approach, communication is performed by modulating a communication carrier signal generated by the first communication coil 207. The power transmitter specifically includes a communication driver 209 coupled to the first communication coil 207. The communication driver 209 is configured to generate a communication drive signal that is supplied to the first communication coil 207 to generate the communication carrier signal. The communication driver 209 can typically be configured to generate a communication drive signal / communication carrier signal having a frequency significantly different from that of the power transmission drive signal / power transmission signal. In many embodiments, the frequency of the communication carrier signal can be 10 times or more, 100 times or more, or 500 times or more the frequency of the power transmission signal. In many embodiments, the frequency of the communication drive signal / communication carrier signal is no less than 500 kHz, 1 MHz, or 10 MHz. In particular, for NFC implementations, the communication carrier signal frequency is 13.56 MHz.

[0066] The first communicator 205 is coupled to the communication driver 209 and configured to control it to modulate a communication drive signal / communication carrier signal to transmit data to the power receiver (references to the communication drive signal below also include implicit references to the communication carrier signal, where appropriate).

[0067] The modulation is illustratively amplitude modulation of the communication drive signal, specifically binary communication using Amplitude Shift Keying (ASK), although it will be appreciated that other approaches may be used in other embodiments, such as phase modulation or frequency modulation of the communication drive signal.

[0068] In some embodiments, the first communicator 205 can receive, for example, data to be transmitted to the power receiver from the power transmitter controller 203 and, in response, generate a control modulation signal that is provided to the communication driver 209. The control modulation signal can be, for example, a binary signal that corresponds to the data to be transmitted, and the communication driver 209 can be configured to generate the communication drive signal to have a corresponding amplitude variation.

[0069] In communication from the power receiver to the power transmitter, the modulation of the communication drive signal can be load modulation. The power receiver can be configured to modulate the power transmission signal by varying the load of the power transmission signal generated by the transmit coil 103 according to the data to be transmitted. The first communicator 205 can be configured to sense variations in the voltage and / or current of the transmit coil 103 and demodulate the load modulation based thereon.

[0070] In many embodiments, the communication may conform to Near Field Communication (NFC) standards, and the power receiver may specifically include NFC functionality. In many embodiments, the first communicator 205, the communication driver 209, and the first communication coil 207 may implement (at least) the functionality of an NFC reader. Thus, in many embodiments, the communication drive signal / communication carrier signal is a 13.56 MHz signal at a constant level (excluding modulation).

[0071] In the following description, we will focus on an example in which the communication between the power transmitter and the power receiver is NFC communication, and more specifically, the modulation of the NFC carrier in the direction from the power transmitter to the power receiver is amplitude shift keying (ASK), and the modulation of the NFC carrier in the direction from the power receiver to the power transmitter is load modulation.

[0072] 1-3, communication occurs during a power transfer phase that takes place during a communication time interval. Specifically, the transmitter controller 203 may have / implement a synchronizer configured to synchronize the first communicator 205 such that communication operations (typically both data reception and transmission) occur within (typically only during) the communication time interval of the power transfer phase, i.e., the time interval allocated for communication.

[0073] This significantly improves communication performance, and in particular reduces interference from power transmission signals to communication signals.

[0074] This approach, in some embodiments, utilizes a time-sharing approach in the power transfer phase, where operations such as foreign object detection and communication are performed in different time intervals from the main power transfer, thereby allowing for significantly reduced interference between them (particularly the impact of power transfer on foreign object detection / communication).

[0075] Specifically, for a wireless power transfer system, the power transfer signal may be subject to a repeating time frame that includes at least one power transfer time interval and one communication time interval.

[0076] The power transmitter can be configured to turn off the power transmission signal during the communication time interval, and the power receiver can be configured in some embodiments to disconnect the load during the power reduction time interval.

[0077] The power transmitter (and typically the power receiver) can then arrange for one or more operations (functions, processes, procedures) to be performed during the communication time interval, i.e., the execution of one or more operations of the power transmitter can be synchronized to occur during the communication time interval. For example, foreign object detection and communication can typically be synchronized to occur during the communication time interval. In this way, the impact of power transmission and power transmission signals on predetermined operations, specifically foreign object detection and communication, can be reduced, and in many cases minimized.

[0078] FIG. 3 shows some exemplary elements of the power receiver 105.

[0079] The receiver coil 107 is coupled to a power receiver controller 301, which couples the receiver coil 107 to a load 303 via a switch 305 (i.e., is a switchable load 305). The power receiver controller 301 includes a power control path that converts the power extracted by the receiver coil 107 to a supply suitable for the load 303. Additionally, the power receiver controller 301 may include various power receiver controller functions required to perform power transfer, particularly functions required to perform power transfer according to the Qi or Ki standards. The load (and switch) may be considered part of the power receiver (or, in some applications, may be considered to be external to the power receiver).

[0080] To support communication from the power receiver 105 to the power transmitter 101, the power receiver 105 includes a second communication device 307 and a second communication coil 309. The second communication coil 309 is configured to couple with the first communication coil 207 such that a communication carrier signal induces a current (at least an electromotive force) in the second communication coil 309.

[0081] The second communicator 307 is coupled to the second communication coil 309 and is configured to determine the amplitude change of the induced signal and demodulate the amplitude modulation of the communication carrier signal. In this manner, the second communicator 307 is configured to decode data transmitted from the power transmitter by amplitude modulation of the communication carrier signal. It will be appreciated that in other embodiments, the second communicator 307 can be configured to decode data modulated on the communication carrier signal using other modulation formats, such as frequency modulation or phase modulation.

[0082] The second communicator 307 is further configured to load modulate the communication carrier signal to transmit data from the power receiver to the power transmitter. Specifically, the second communicator 307 may have a load (such as a capacitor) that can be switchably coupled or not coupled to the second communication coil 309 depending on the data to be transmitted. These load modulations are detected by the first communicator 205 of the power transmitter.

[0083] In a specific example, the second communication coil 309 and the second communication device 307 can provide an NFC-compatible communication operation. Specifically, the second communication coil 309 can provide functionality compatible with NFC tags and be configured to decode data ASK-modulated onto a communication carrier signal in accordance with the NFC standard.

[0084] Thus, the second communication coil 309 is configured to transmit data to the power transmitter 101 by varying the load on the second communication coil 309 in response to the data to be transmitted to the power transmitter 101. The load variation is then detected and demodulated by the power transmitter 101, as known to those skilled in the art.

[0085] In an embodiment, the second communicator 307 is further configured to demodulate the amplitude, frequency and / or phase modulation of the communication carrier signal to retrieve the data transmitted from the power transmitter.

[0086] As mentioned above, in a specific example, the system utilizes recurring time frames during the power transfer phase, the time frames including at least one power transfer time interval and at least one communication time interval. An example of such a recurring time frame is shown in FIG. 4, where the power transfer time interval is designated PT and the communication time interval is designated C. In this example, each time frame FRM consists of only one communication time interval and one power transfer time interval. However, it will be understood that in other embodiments, other time intervals can also be included in the time frame, or multiple communication time intervals and / or power transfer time intervals can be included in each time frame.

[0087] The power transfer driver 201 is controlled by the power transmitter controller 205 to generate the drive signal only during the power transfer time intervals and not during the communication time intervals. Thus, the driver generates the drive signal, and therefore the power transfer signal, during the power transfer time intervals, while the drive signal, and therefore the power transfer signal, is turned off during the communication time intervals.

[0088] Thus, in the power transmission phase, the power transmitter is configured to perform power transmission during power transmission time intervals of the time frame of the power transmission phase. In particular, during these time intervals, the power transmitter and the power receiver can operate a power control loop (which can be based on communication within communication time intervals corresponding to the recurrence time intervals). Thus, the level of transmitted power can be dynamically changed.

[0089] However, during the communication time interval of the power transfer phase time frame, the power drive signal is switched off so that no power transfer signal is generated during the communication time interval.

[0090] In addition to communication, the communication carrier signal can provide an auxiliary power supply from the power transmitter to the power receiver. The auxiliary power transmission / path can provide a low power supply that can be used to power internal circuitry such as a user interface or power receiver control functions. This would be particularly suitable for providing reduced power to the power receiver outside of the power transmission phase.

[0091] The communication carrier signal can accordingly be used to provide a second, low-level power transmission path from the power transmitter to the power receiver. To support this, the power receiver includes a power extractor 311 configured to extract power from the communication carrier signal. In a specific example, the power extractor 311 can optionally extract power from an NFC carrier signal. The power extractor 311 is coupled to a load circuit 313 that can be powered by the power extracted from the communication carrier signal by the power extractor 311. The load circuit 313 may typically be control logic / support functions / circuitry of the power receiver and / or may include a user interface for the power receiver. The load circuit 313 may include or be composed of elements of the power receiver controller 201 and / or the second communicator 307, for example.

[0092] Therefore, power can be supplied from the power transmitter to the power receiver via communication carrier signal / NFC carrier power harvesting. This can power low-power level, e.g., low-voltage electronics such as NFC hardware and user interfaces. For example, in the case of an NFC implementation, the extracted power can be up to about 200mW.

[0093] This approach therefore allows for significant reductions in complexity and cost in many practical applications. For example, a power receiving device that includes a heating element as a load can be powered directly by a power transmission signal that directly induces a current in the heating element. Indeed, in such instances, the described approach often allows control and support circuitry and a user interface to be implemented to be powered entirely from a communications carrier signal, specifically an NFC carrier. This approach therefore makes it possible, in some cases, to design a power receiving device that does not include electronic circuitry powered by the power transmission signal. Thus, complex high-voltage power extraction circuitry can be avoided entirely. It is also well suited for powering a power receiver outside of a power transfer phase, such as when power transfer is initiated.

[0094] In many embodiments, the wireless power transmission system and power transmitter can be configured to operate in different phases / modes.

[0095] In many embodiments, the wireless power transmission system, and thus the power transmitter and / or power receiver, can be configured to operate in different phases, particularly a power transmission phase in which a power transmission signal is generated and thus a power transmission operation to supply power to the load 303 occurs. In the power transmission phase, the power transmitter generates a power transmission drive signal and generates a power transmission signal in response. In the power transmission phase, power is supplied / transmitted to the power receiver by the power transmission signal. As described above, the power transmission signal can use a recurring time frame, and the power transmission signal is provided in a power transmission time interval, which can also include a communication time interval and / or a foreign object detection time interval. During the power transmission phase, a communication carrier signal can also be generated when communication occurs in the communication time interval.

[0096] During the power transfer phase, the power transmitter can operate in a power transfer mode in which the power transfer signal is generated by a power transfer driver, which generates a drive signal accordingly. In some embodiments, the power transfer signal / drive signal may be generated continuously during the power transfer phase, while in other scenarios it can be more intermittent, for example, interrupted by communication or foreign object detection intervals. Typically, however, the power transfer signal is generated for at least 70%, 80%, 90%, or 95% of the time during the power transfer phase.

[0097] Additionally, the wireless power transfer system can be configured to operate in a standby phase in which a power transfer signal is not generated by the power transmitter and therefore no power transfer signal is present. In the standby phase, the power transmitter operates in a standby mode and the power transfer driver 201 does not generate a power transfer drive signal, so no drive signal is provided to the transmitter coil 103. In the standby mode / phase, no power transfer signal is generated by the transmitter coil 103. In the standby phase / mode, the power transmitter and system attempt to minimize power consumption.

[0098] For example, the system can operate in a standby phase / mode in which the presence of a power receiver is not detected by the power transmitter. During this scenario, no power transmission signal is generated, and no communication carrier signal is generated. The power transmitter monitors the presence of a power receiver. In particular, the power transmitter can generate an electromagnetic detection signal at regular intervals, and if a load on this signal is detected, the power transmitter can assume that a power receiver is potentially present. The electromagnetic detection signal can be a communication carrier signal. Once a power receiver is detected, the power transmitter can transition to the configuration phase.

[0099] During the configuration phase, configuration information / data can be exchanged between the power transmitter and the power receiver. The configuration information / data can provide the other device with information about the characteristics of the power receiver and the power transmitter. Each device can adapt its operating parameters based on the exchanged configuration data. Thus, the configuration phase is used by the power transmitter and the power receiver to exchange specific information about the characteristics of the particular device, thereby adapting operation to the particular pairing of the power transmitter and the power receiver.

[0100] If the configuration phase is not successful, for example, if the power transmitter does not receive an appropriate message from the power receiver or if an explicit termination is received, the power transmitter may return to the standby phase.

[0101] Upon successful completion of configuration and communication, the power transmitter proceeds to the connection phase. During the connection phase, the power transmitter and power receiver have established communication and the devices are adapted to each other, but power transmission has not yet begun. During the connection phase, a communication carrier signal is generated, which may be present continuously during the connection phase. However, no power transmission signal is generated during the connection phase. Foreign object detection may also be performed during the connection phase. Communication may also occur between the power transmitter and the power receiver. The power receiver may often be configured to extract power from the communication carrier signal (e.g., to power internal functions of the power receiver) during the connection phase.

[0102] The connection phase can last for a significant period of time, including several hours or more, in many scenarios. For example, if a kitchen device with a power receiver as described, such as a blender, is configured on a countertop with a wireless power transmitter as described, it can go through a setup phase and then enter the connection phase in an adapted connection mode. The device can then remain in this state for a lengthy period corresponding to the device, e.g., a blender remaining on the countertop ready to be operated but not actually switched on.

[0103] In response to detecting an appropriate event, the power transmitter and power receiver can transition from the connection phase to the power transfer phase. This event is typically detected by the power receiver, which can send a message to the power transmitter to request entry into the power transfer phase. For example, if a user performs an appropriate user action, such as pressing an on button, the power receiver can responsively send a request to the power transmitter to enter the power transfer phase.

[0104] The power transmitter (and power receiver) can then proceed to transition to power transmission.

[0105] When power transmission terminates, the power transmitter and power receiver may return to the idle phase or the connected phase depending on the particular cause of the termination (e.g., if the device is switched off, the power transmitter may return to the connected phase, and if the device is removed, the power transmitter may return to the idle phase).

[0106] The setup phase and connection phase are sometimes collectively referred to as the initialization phase.

[0107] The connected phase and standby phase have in common that no power transmission / power drive signals are generated, and thus are typically pre-power phases. However, they differ in that the communication carrier signal is generated for a longer percentage of time during the connected phase than during the standby phase. Indeed, during the connected phase, the communication carrier signal may be generated continuously during the connected phase in many embodiments, or at least 50%, 60%, 70%, 80%, 90%, or 95% of the time in each embodiment. In contrast, during the standby phase, the communication carrier signal is generated for 1%, 2%, 5%, or 10% of the time in each embodiment. Thus, the communication carrier signal is generated a much higher percentage of the time (at least 5, 10, or 20 times more in each embodiment). These approaches result in much lower power consumption during the standby phase than during the connected phase, while reducing latency and enabling high-data-rate communication during the connected phase. Additionally, the power receiver's functionality can be enhanced by providing a larger auxiliary power supply.

[0108] Power transmitters are often powered from an AC (alternating current) source, particularly from the mains power supply, i.e., the local power net infrastructure in which the power transmitter is used. Thus, the power transmitter may have a power supply input 211 that receives AC supply power (e.g., AC voltage and current). In many embodiments, the input supply power is a mains AC voltage of 110V, 220V, or 240V.

[0109] The power supply input 211 provides power to the overall power transmitter functionality and typically includes functionality for generating a low voltage and power regulated DC supply voltage for powering the electronic functions of the power transmitter. For example, the power supply input 211 may generate a voltage regulated DC power supply (e.g., 3.3V, 5V, 9V, or 12V) that can be used to power the various electronic and processing functions.

[0110] The power supply input 211 is further configured to provide a power supply to the driver 201, and in particular to the inverter output, although rather than providing a constant regulated DC voltage, the power supply to the driver output is often an AC or rectified AC voltage that follows variations in the input power signal.

[0111] The driver 201 generates the current and voltage that is supplied to the output resonant circuit and hence to the transmitter coil 103. The driver 201 is typically a drive circuit in the form of an inverter that generates a relatively high frequency (most often 10 kHz or higher) AC signal from the supply voltage. The higher the switching frequency, the easier the power transfer to the power receiver.

[0112] The output of the driver 201 is typically a switch bridge that generates a drive signal by appropriately switching the switches of the switch bridge. Figure 5 shows a half-bridge switch bridge / inverter. Switches S1 and S2 are controlled so that they are never closed simultaneously. Alternating, S1 is closed while S2 is open, and S2 is closed while S1 is open. The switches are opened and closed at a desired frequency, thereby generating an AC signal at the output. Typically, the inverter output is connected to a transmitter inductor through a resonant capacitor. Figure 6 shows a full-bridge switch bridge / inverter. Switches S1 and S2 are controlled so that they are never closed simultaneously. Switches S3 and S4 are controlled so that they are never closed simultaneously. Alternating, switches S1 and S4 are closed while S2 and S3 are open, and switches S2 and S3 are closed while S1 and S4 are open, thereby generating a square wave signal at the output. The switches are opened and closed at a desired frequency.

[0113] Thus, in contrast to control electronics and processing functions, which are typically provided with a constant, regulated power supply voltage, the supply voltage to driver 201 is typically a varying voltage, specifically a typically rectified AC voltage without further smoothing. As a result, the generated drive signal is typically a signal with relatively high frequency (typically at least 1 kHz) switching of an envelope voltage that itself is a time-varying voltage but at a much lower frequency (typically 200 Hz or less). The power supply voltage is generated by reducing the input power signal to a low voltage (e.g., approximately 40 V) using a power transformer and then rectifying it using a rectifier bridge or the like. The resulting supply signal is a rectified sinusoidal signal, and therefore the drive signal has a periodic envelope corresponding to the rectified sine wave. Thus, the drive signal is generated to have a (typically) periodically varying envelope / amplitude, typically a sinusoidal envelope / amplitude.

[0114] The generated drive signal, and therefore the power transmission signal, has two frequency characteristics: a fast switching frequency and a slow envelope / amplitude frequency that represents the periodic variation of the envelope / amplitude of the drive signal / power transmission signal. Figure 7 shows an example of such a drive signal / power transmission signal.

[0115] Amplitude variations in the power transmission signal result in corresponding variations in the induced current / voltage in the receiver coil 107. Therefore, the induced power signal also has a corresponding time-varying characteristic, and therefore the transmitted power exhibits periodic time variations.

[0116] In the example of Figure 7, the envelope of the drive signal / power transfer signal follows a rectified sine wave except near the zero crossings / minima where the amplitude of the drive signal / power transfer signal is set to zero. Thus, in this example, a recurring time frame is imposed similar to the example of Figure 4, where the drive signal / power transfer signal is active during power transfer time intervals PT and the signal is off during short communication time intervals C.

[0117] In this approach, the power transmitter is configured to transmit a message providing information of the envelope variation to the power receiver. Specifically, the power transmitter controller 203 is configured to control the first communicator 205 to transmit a message to the power receiver including a frequency indicator indicating the frequency of the envelope of the power transmission signal during the power transmission phase.

[0118] The power receiver is configured to receive this message, and in particular the second communicator 307 is configured to receive this message and provide a frequency indicator to the power receiver controller 301. The power receiver controller 301 can then adapt its operation according to the envelope frequency indicated by the frequency indicator and therefore based on the frequency of the envelope variation of the induced signal.

[0119] In this manner, the power receiver controller 301 is configured to adapt the power transfer operation in response to the frequency indicator. The power transfer operation may be a direct part of the power transfer path or, for example, the operation of a load powered by the power transfer.

[0120] The inventors have recognized that improved operation and power transfer can be achieved by enabling power transfer operation to adapt to specific frequencies of envelope variations. Indeed, the inventors have recognized that envelope variations are not merely insignificant, having only a minor effect on the operation of the power receiver and a negligible effect on the power load, but can be significant in some scenarios and for some devices. The inventors have recognized that in some scenarios, a change in envelope frequency resulting from the power transmitter being powered from a mains network having a different frequency (e.g., changing from 50 Hz to 60 Hz mains) can degrade the performance of the powered device / load or even cause the powered device to fail. The inventors have further recognized that this can be mitigated or overcome by providing means for the power receiver to perform adaptive operation that can adapt to envelope variations, particularly specific envelope frequencies.

[0121] For example, some devices may have very specific frequency input requirements to drive a motor, or mechanisms in between that require a specific power supply frequency to operate. In many conventional approaches, the power receiver supplies the load with power derived directly from the inductive signal with minimal smoothing, and indeed in many high-power implementations, an AC signal (or a rectified AC signal) is supplied directly to the load, exposing the load to full-envelope power fluctuations. Therefore, in many efficient implementations, the load experiences a time-varying supply signal that directly tracks the envelope fluctuations, and such approaches are more efficient, have less complexity (and component count), and consume less component power.

[0122] However, as recognized by the inventors, such an approach may result in undesirable behavior and performance, since some loads are very sensitive to the frequency of the power supply voltage. For example, calculations and measurements of average (or RMS) voltage and / or power at the receiver depend on knowledge of the envelope frequency. Synchronizing the measurement to the AC frequency is fundamental to providing the correct measurement to request the correct amount of power from the transmitter.

[0123] In the described approach, the power transmitter is configured to actively inform the power receiver of a particular envelope frequency of the power transmission signal and thus the frequency of variation of the supply signal supplied to the load, and the power receiver is configured to adapt its power transmission operation in response to this envelope frequency, specifically, to proceed with the power transmission operation only if the envelope frequency matches a frequency that can actually be supported by the power receiver / load.

[0124] The particular power transfer operation adapted and the particular adaptation performed will depend on the particular preferences and requirements of each individual embodiment, particularly the characteristics of the power receiving device and its intended operation. As an example, in some embodiments, power transfer may be performed only if the envelope frequency has an appropriate value. For example, a particular device may be configured to operate only at a frequency of 50 Hz, and therefore power transfer may be performed only if the power transmitter is actually powered from a 50 Hz mains supply, resulting in 50 Hz envelope fluctuations. Other advantageous examples of adapting power transfer operations are described below.

[0125] In many embodiments, transmission of the frequency indicator message occurs before the power transmitter (and power receiver) enters the power transfer phase. In many embodiments, the power transmitter is configured to transmit the frequency indicator message during a power transfer initiation phase prior to the power transfer phase. Prior to the power transfer phase, initialization can occur where parameters for the power transfer operation are established and the power transfer operation is configured / initialized.

[0126] For example, the power transmitter may be configured to transmit a frequency indication message during the negotiation / configuration phase described above.

[0127] During initialization and configuration of the power transfer operation, the power receiver is accordingly provided with information regarding the envelope frequency and can adapt the power transfer operation accordingly.

[0128] In many embodiments, the power receiver can be configured to set operating parameters of the power transfer operation depending on the envelope frequency.

[0129] For example, in some embodiments in which the load includes a motor driven by an induced envelope signal, the motor can be configured to operate in one mode for an envelope frequency of 50 Hz (or 100 Hz for a rectified envelope signal) and in another mode for an envelope frequency of 60 Hz (or 120 Hz for a rectified envelope signal).

[0130] As an example, the rectified envelope signal can be supplied to a motor via a rectifier circuit configured to perform commutation for the motor. Commutation switching is preferably performed to coincide with a minimum value of the rectified envelope power signal (or at a zero crossing in the case of an unrectified envelope power signal). Thus, the commutator circuit can be configured to operate in 50 Hz mode or 60 Hz mode, for example, using a loop (with a small bandwidth around 50 Hz (100 Hz) or 60 Hz (120 Hz), depending on the mode) that locks to the envelope signal.

[0131] In such a case, the power receiver controller 301 can be configured to select an operating mode depending on the received frequency indicator: if the envelope frequency indicates a 50 Hz frequency, the loop used to time the commutation switching is initialized to 50 Hz with a small bandwidth around it (e.g., ±1 Hz), and if the frequency indicator indicates a 60 Hz frequency, the loop used to time the commutation switching is initialized to 60 Hz with a small bandwidth around it (e.g., ±1 Hz).

[0132] In some embodiments, the load may only tolerate one specific envelope frequency for operation. For example, the load may be a motor driven at a fixed commutation frequency. In such cases, the power receiver controller 301 may be configured to proceed with power transfer only if the indicated envelope frequency matches the frequency required by the load. If there is no match, the power receiver controller 301 may instead terminate power transfer initialization, never entering the power transfer phase.

[0133] The message can be a capabilities message that contains data reflecting the capabilities of the power transmitter, such as the version of the technical specification that the power receiver supports, the maximum power level that can be provided, the communication capabilities of the power transmitter, etc. Such information can be used by the power receiver to adapt its operation to be compatible with the particular power transmitter. For example, in the case of a Ki power transmission system, such a message, called a capabilities message, is sent during the configuration phase.

[0134] The frequency indicator can be transmitted as a field in a message, particularly in such a capability message. Thus, some bits can be reserved for the frequency indicator in the message transmitted from the power transmitter to the power receiver. In some embodiments, the message may include only the frequency indicator (and overhead data), but in many embodiments, the frequency indicator can be included in the message along with other data, e.g., other data describing the characteristics / capabilities of the power transmitter.

[0135] In many embodiments, the frequency indicator may advantageously be a 1-bit indicator. In many embodiments, a single-bit frequency indicator may be provided that indicates whether the envelope frequency is 50 Hz or 60 Hz (100 Hz or 120 Hz for rectified signals), typically corresponding to whether the power transmitter is powered from a 50 Hz or 60 Hz mains supply / grid / infrastructure.

[0136] Therefore, in many applications and scenarios, this approach can be limited to indicating whether the envelope frequency is one of two possible options, specifically, whether it is a periodic envelope variation of 50 / 100 Hz or 60 / 120 Hz. This provides very efficient operation with little additional communication overhead, since the required data can be limited to a single bit. Therefore, this approach can be adapted to minimize the impact on existing communications (with small communication overhead) by leveraging the recognition that a simple binary frequency indicator is sufficient to cover virtually all practical applications in many systems.

[0137] As mentioned above, the power receiver can be configured to adapt its power transfer operation in response to the frequency indicator in different manners in different embodiments. As mentioned above, the power receiver controller 301 can in many embodiments be configured to terminate an ongoing power transfer operation, or more typically, can proceed with terminating the initialization and prevent the power receiver (and power transmitter) from entering the power transfer phase if a proximity indicator is received as part of the power transfer initialization. In such a case, the power receiver can be configured, for example, to send a message to the power transmitter indicating that initialization should be terminated.

[0138] In many embodiments, the power receiver can be configured to proceed with the power transfer phase, but can also be configured to adapt operating parameters for the power transfer operation. The power receiver can be configured to directly adapt the portion of the power transfer operation that generates the signal to the load, or can be configured to adapt the operation of the load, to adapt to a particular envelope frequency. For example, the power receiver can adapt the operation of a motor to operate in a 50 / 100 Hz mode or a 60 / 120 Hz mode.

[0139] In many embodiments, the power receiver may include a synchronizer configured to adapt timing characteristics of the power transfer operation in response to the frequency index, the timing characteristics typically being a repetition frequency or repetition time interval of the operation used for the particular operation.

[0140] For example, as previously described, synchronizer 315 can be configured to synchronize the timing of commutation switching to the zero crossing / envelope minimum. Synchronizer 315 can control the switching by activating a phase-locked loop that synchronizes to the minimum and controls the switching to coincide with it. Depending on the frequency index, the phase-locked loop can be set to a frequency around 50 / 100 Hz or 60 / 120 Hz.

[0141] In many embodiments, the timing parameters can be initial timing parameters for operation in the power transfer phase. For example, the timing loop can be initiated at a frequency of 50 / 100 Hz or 60 / 120 Hz, and then the loop can be configured to adapt to a particular envelope frequency (e.g., within ±1 Hz) during the power transfer loop to accommodate slight variations in the frequency of the local power grid supply.

[0142] In some embodiments, the synchronizer 315 can be configured to adapt timing characteristics for communication operations, particularly the timing characteristics of sending messages to the power transmitter and / or receiving messages from the power transmitter.

[0143] As mentioned above, communication (both ways) between the power transmitter and power receiver is advantageously carried out in many embodiments during communication time intervals, and these time intervals are advantageously positioned around the minimum times of the power transmission signal envelope, thereby reducing interference of the power transmission signal with the communication and reducing the impact on power transmission efficiency (due to the lower instantaneous power due to the lower level of the envelope).

[0144] The second communicator 307 is configured to transmit messages during communication time intervals (in both directions). For example, a new message can be transmitted at (or shortly after) the start of a new communication time interval (for a communication time interval allocated for transmission from the power receiver to the power transmitter). Similarly, the second communicator can be configured to start detecting and receiving messages at the start of a communication time interval (allocated for transmission from the power transmitter to the power receiver). The synchronizer 315 can be configured to provide the second communicator 307 with information about the start of the communication time interval. For example, similar to the approach described for synchronizing the commutation switching, the synchronizer 315 can operate a timing loop (specifically, a timing phase-locked loop) that synchronizes to the zero crossings / minima of the envelope of the power transmission signal / induction signal. Similarly, the timing loop can be set to operate at 50 Hz or 60 Hz, depending on the envelope frequency indicated by the frequency index.

[0145] The synchronizer 315 can be configured to determine the timing of transmitting a message to the power transmitter as a function of the frequency index, as described above. As a simpler example, the synchronizer 315 can detect a minimum in the envelope of the induced signal and proceed to generate the message transmission times at regular time intervals from the point of this minimum, the time intervals having a duration equal to a period (or half period) of the envelope frequency indicated by the frequency index.

[0146] In some embodiments, the synchronizer 315 can be configured to adapt at least one of the start, duration and repetition interval of the measurement operation depending on the frequency index.

[0147] For example, in many scenarios it may be desirable to measure, for example, the minimum level of an envelope signal, and the described approach can be used to time these measurements by adjusting the time between measurements to match the time period of the envelope signal indicated by the frequency index.

[0148] In some cases, for example, a measurement can be used to determine the time point of a minimum in the envelope signal. The start of a new measurement to detect the next time point of the minimum can be set after a delay of 95% of the envelope signal period indicated by the frequency index. The end of the measurement can be set after a delay of 105% of the envelope signal period indicated by the frequency index. Thus, in this approach, the measurement used to detect the time point of the next minimum can be controlled by synchronizer 315 to cover 10% of the period and be centered on the expected time point of the next minimum.

[0149] In some embodiments, the synchronizer 315 can be configured to adapt the time interval over which measurements are performed. For example, a measurement of the average level of the induced signal envelope can be determined by measuring the signal level at different times over the duration of the envelope signal. The synchronizer 315 can set the period of the measurements accordingly. For example, if the frequency indicator indicates an envelope frequency of 50 Hz, the measurement period can be set to a multiple of 20 ms, and if it indicates 60 Hz, the measurement period can be set to a multiple of 16.7 ms.

[0150] In many embodiments, the power receiver includes a user interface 317. The user interface 317 can provide indications to the user via, for example, a display, lights, audio, etc., and can receive user input from buttons, a keyboard, voice commands, gesture commands, etc. In many embodiments, the user interface 317 can include less complex user indications, such as operator or warning lights, and dedicated buttons or switches for initiating certain functions.

[0151] In some embodiments, the power receiver is configured to generate a user display in response to the frequency indicator. Indeed, in some embodiments, the power receiver may directly display to the user the envelope frequency indicated by the frequency indicator. For example, a small display may simply indicate 50 Hz or 60 Hz.

[0152] In other cases, the power receiver may provide a user alert / warning to indicate to the user if power transfer will not occur, for example, because the envelope frequency does not match the frequency required by the power receiver / load.

[0153] In some cases, a power receiver may operate at different / both envelope frequencies but perform better at one frequency than the other. In such cases, the power receiver may be configured to indicate the performance currently being provided, for example, by indicating that reduced operation / performance is being provided.

[0154] In some cases, the power receiver can be configured to notify the user if it is unable to function at the specified frequency. This information can be provided prior to entering the power transfer phase, and the power receiver can be prevented from actually entering power transfer unless the user provides manual input to override the warning and proceed to the power transfer phase. In this case, the power receiver can proceed to the power transfer phase, but will operate out of specification or with degraded performance.

[0155] As previously mentioned, the power transmitter may include a power supply input 211 that receives AC supply power and provides an AC or rectified AC (varying DC) supply to the driver 201 (particularly the output / inverter of the driver 201). In such a case, the frequency indicator may indicate the frequency of the AC supply power.

[0156] In some cases, the power transmitter can be pre-configured to provide a saved or predetermined frequency indicator (e.g., during design / manufacturing). For example, the power transmitter can include a (semi-)permanent memory in which data reflecting the envelope frequency is stored. For example, during installation of a permanent power transmitter, an installer can set a configuration parameter indicating the power supply frequency (e.g., to reflect whether the power transmitter is connected to a 50 Hz or 60 Hz power grid). The parameter is stored in the (semi-)permanent memory, and during initialization of power transmission, the power transmitter can read the stored value of the envelope frequency and proceed to transmit the corresponding frequency indicator.

[0157] In some embodiments, the power transmitter can be configured to dynamically determine a supply frequency and a corresponding frequency indicator to transmit to the power receiver.

[0158] For example, a power transmitter can be configured, upon power-up, to detect zero crossings of the AC supply power and measure the time between the zero crossings, and then proceed to determine the corresponding supply frequency (or directly use the measured time between the zero crossings as an indicator of the duration and therefore frequency of the power supply frequency). A frequency indicator (e.g., an appropriate bit value indicating a 50 Hz or 60 Hz supply) can then be selected and transmitted to the power receiver, for example, during initialization of the power transmission.

[0159] The previous examples have focused on cases where the frequency indicator indicates one of two frequencies, specifically the feed / envelope frequency, either 50 Hz / 100 Hz or 60 Hz / 120 Hz. This is particularly advantageous in many embodiments, as it allows a single bit to be used to provide information that will nevertheless typically be sufficient for the majority of practical applications.

[0160] However, in other embodiments, the frequency index can represent many more possible frequencies, and can in fact be configured to represent many different frequencies. Specifically, the frequency index can be represented by multiple bits, such as, for example, a 4, 8, or 16-bit data field.

[0161] For example, in some embodiments, the power transmitter can be powered by a DC power source (e.g., when the power transmitter is battery-powered). In such cases, the power transmitter can include an internal power supply unit to provide a fluctuating supply voltage to the driver 201. For example, switching / rectification of the DC power supply can be performed, followed by smoothing to produce near-sinusoidal fluctuations. Such an approach can provide a fluctuating envelope that provides a suitable minimum for, for example, reduced interference communications, allowing for improved foreign object detection during such times.

[0162] In such an embodiment, the supply frequency, and therefore the envelope frequency, is selected by the power transmitter and is not limited by the frequency of the power grid. Thus, a wide range of different frequencies can be selected, for example, different power transmitters or the same power transmitter in different modes can select different frequencies. In this case, the frequency indicator can indicate the specific frequency selected by the power transmitter for a particular application / scenario.

[0163] It will be appreciated that, for clarity, the above description has described embodiments of the invention with reference to different functional circuits, units, and processors. However, it will be apparent that any suitable distribution of functionality between different functional circuits, units, or processors may be used without departing from the invention. For example, functionality shown to be performed by separate processors or controllers may also be performed by the same processor or controller. References to specific functional units or circuits should therefore be seen merely as references to suitable means for providing the described functionality, rather than to indicative of a strict logical or physical structure or organization.

[0164] The present invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The present invention may optionally be implemented at least in part as computer software running on one or more data processors and / or digital signal processors. The elements and components of embodiments of the present invention may be physically, functionally, and logically implemented in any suitable way. Indeed, functionality may be implemented in a single unit, in multiple units, or as part of other functional units. Thus, the present invention may be implemented in a single unit, or may be physically and functionally distributed between different units, circuits, and processors.

[0165] Although the present invention has been described in connection with several embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the appended claims. Furthermore, while certain features may appear to be described in connection with particular embodiments, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0166] It will be understood that the reference to a preferred value does not imply any limitation beyond it being the value determined in the foreign object detection initialization mode, i.e., it is preferably determined in the adaptation process. Reference to a preferred value can be used in place of a reference to, for example, a first value.

[0167] Furthermore, although individually listed, a plurality of means, elements, circuits, or method steps may be implemented by, for example, a single circuit, unit, or processor. Furthermore, although individual features may be included in different claims, these may be advantageously combined in some cases, and their inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. Furthermore, the inclusion of a feature in one category of claims does not imply limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, where appropriate. Furthermore, the order of features in the claims does not imply a particular order in which the features must operate, and in particular the order of individual steps in method claims does not imply that the steps must be performed in this order. Rather, steps may be performed in any suitable order. Furthermore, a reference to the singular does not exclude a plurality; thus, references to "a," "an," "first," "second," etc. do not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.

Claims

1. 1. A power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, comprising: an input circuit including a receiver coil configured to extract power from the power transmission signal during a power transfer phase; a communicator configured to communicate with the power transmitter, the communicator configured to receive a message from the power transmitter, the message including a frequency indicator indicating a frequency of an envelope of the power transmission signal; and a controller configured to adapt power transfer operation in response to the frequency indicator.

2. The power receiver of claim 1 , wherein the communicator is configured to receive the frequency indication during a power transfer initiation phase prior to the power transfer phase.

3. 3. The power receiver of claim 1, wherein the controller is configured to terminate power transfer initiation in response to the frequency indicator meeting a criterion.

4. 4. The power receiver of claim 1, further comprising a user interface, the controller being configured to control the user interface to generate a user alert.

5. 5. A power receiver according to claim 1, wherein the controller is configured to adapt timing characteristics of power transfer operations in response to the frequency indicator.

6. The power receiver of claim 5 , wherein the controller is configured to set initial timing characteristics of the power transfer phase in response to the frequency index.

7. 7. The power receiver of claim 5, wherein the power transfer operation is a communication operation.

8. 8. A power receiver according to claim 1, wherein the controller is configured to adapt at least one of a start, a duration and a repetition interval of a measurement operation.

9. 9. A power receiver according to claim 1, wherein the frequency index is a one-bit index.

10. 1. A power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, comprising: a power transmission coil configured to generate the power transmission signal; a power transfer driver configured to generate a power transfer drive signal for the power transfer coil to generate the power transfer signal during a power transfer phase; a communicator configured to communicate with the power receiver; a controller configured to control the communicator to transmit a message to a power receiver including a frequency indicator indicative of a frequency of an envelope of the power transmission signal during the power transfer phase; A power transmitter having

11. 11. The power transmitter of claim 10, further comprising a power supply input for receiving an AC supply power, and wherein the frequency indicator indicates a frequency of the AC supply power.

12. 12. The power transmitter of claim 11, wherein the controller is configured to measure a frequency of the AC power supply and to determine the frequency indicator in response to the measured frequency of the AC power supply.

13. A wireless power transmission system comprising the power receiver of claim 1 and the power transmitter of claim 10.

14. 1. A method of operating a power receiver that wirelessly receives power from a power transmitter via an electromagnetic power transmission signal, comprising: an input circuit including a receiver coil extracting power from the power transfer signal during a power transfer phase; communicating with the power transmitter to receive a message from the power transmitter including a frequency indicator indicating a frequency of an envelope of the power transmission signal; adapting power transfer operation in response to the frequency indicator; A method having the following.

15. 1. A method of operating a power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, comprising: generating a power transfer drive signal for a power transfer coil to generate the power transfer signal during a power transfer phase; communicating with the power receiver to transmit a message to the power receiver including a frequency indicator indicative of a frequency of an envelope of the power transmission signal during the power transfer phase; A method having the following.

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