Wireless power transmission

Abstract

To provide a power transmitter that supports a changing power level in a wireless power transmission system and a method of operating the same.SOLUTION: A wireless power transmitter comprises a transmitter coil 103 to which a drive signal generated by a driver 201 is applied to generate a power transfer signal. A power loop controller 209 implements a power control loop for controlling the drive signal to adjust a power level of the power transfer signal in response to a power control error message received by a power receiver. A mode storage device 213 stores a plurality of power level modes for the power receiver. Each power level mode is associated with a reference power level for the power transfer signal. A mode circuit 211 adapts the drive signal to set the power level of the power transfer signal to a first reference value in response to reception of a mode request message by the receiver 207. The first reference value corresponds to the reference power level of the first power level mode indicated by the mode request message.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the operation of wireless power transfer systems, and in particular, but not exclusively, to techniques for supporting varying power levels in wireless power transfer systems such as Qi. [Background technology]

[0002] Most current electrical products require dedicated electrical contacts to receive power from an external power source. However, this tends to be impractical, requiring the user to physically insert a connector or otherwise establish physical electrical contact. Power requirements also typically vary widely, and currently most devices are provided with dedicated power sources, resulting in a typical user having numerous different power sources, each dedicated to a specific device. However, while the use of an internal battery can avoid the need for a wired connection to a power source during use, this only provides a partial solution, as the battery requires recharging (or replacement). Additionally, using a battery can substantially increase the weight and potential cost and size of the device.

[0003] To provide a significantly improved user experience, it has been proposed to use wireless power sources in which power is inductively transferred from a transmitter coil in a power transmitter to a receiver coil in an individual device.

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

[0005] Such a configuration allows for wireless power transmission to a device without the need for a wired or physical electrical connection. Indeed, a device can simply be placed adjacent to or on top of the transmitter coil for external recharging or powering. For example, the power transmitter can be configured to have a horizontal surface onto which a device can simply be placed to receive power.

[0006] Furthermore, such wireless power transmission configurations can be advantageously designed so that the power transmitter can be used with a range of power receiving devices. In particular, a wireless power transmission approach known as the Qi standard has been defined and is currently being further developed. This approach allows power transmitter devices that meet the Qi standard to be used with power receiver devices that meet the Qi standard, without the need for them to be from the same manufacturer or proprietary to each other. The Qi standard also includes several features that allow operation to be tailored to specific power receiving devices (e.g., depending on a specific power drain).

[0007] The Qi standard is developed by the Wireless Power Consortium and more detailed information can be found, for example, on their website (http: / / www.wirelesspowerconsortium.com / index.html), in particular the specifications that define it.

[0008] Qi was originally defined as low-power wireless power transmission in version 1.0, which was in effect limited to lower power levels below 5 W. This was extended to higher power levels in subsequent versions, with version 1.2, for example, providing compliance testing addressed for power levels up to 15 W.

[0009] To control and adapt power transfer, wireless power transfer systems typically implement a power control loop, in which the power receiver transmitting power continuously transmits a power error control message to the power transmitter, which responds by increasing or decreasing its power level accordingly. Such a power control loop typically provides an efficient way for the power receiver to control the level of power transmitted from the power transmitter. However, the precise design of such a power control loop is difficult and involves many trade-offs that inherently result in suboptimal performance. For example, it is desirable for the power control loop to respond quickly to changes in required power, while at the same time, it is desirable for the loop to be stable and robust to noise.

[0010] Therefore, improved approaches for wireless power transfer would be advantageous, particularly approaches that enable increased flexibility, reduced cost, reduced complexity, improved support for large power ranges, improved transient power performance, improved adaptability, backward compatibility, improved power transfer operation, and / or improved performance. Summary of the Invention [Problem to be solved by the invention]

[0011] 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]

[0012] According to one aspect of the present invention, there is provided a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, the power transmitter having: a receiver for receiving messages from the power receiver; an output circuit having a transmitter coil for generating the power transmission signal in response to a drive signal applied to the output circuit; a driver circuit for generating the drive signal; a power loop controller implementing a power control loop for controlling the drive signal to adjust a power level of the power transmission signal, the power control loop being configured to make changes to the power level of the power transmission signal in response to a power control error message received from the power receiver; a mode storage device configured to store a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level of the power transmission signal; and a mode circuit configured to adapt the drive signal to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to the reference power level of a first power level mode of the plurality of power level modes indicated in the mode request message.

[0013] The present invention can provide improved performance and / or improved power transfer in many scenarios. In many embodiments, it can enable improved and more efficient power transfer across a range of power levels. This approach can support, enable, improve, or facilitate particularly high-power wireless power transfer in many embodiments.

[0014] In many embodiments, improved switching between different power levels may be achieved, and in particular, transient performance may be improved. This approach may enable a system to take advantage of the benefits offered by an accurate power control loop while mitigating some of the drawbacks of such a loop. In particular, stable and reliable power control operation may be combined with fast transient performance.

[0015] The use of specific power level modes and messaging from the power receiver may, among other things, allow power control loop performance and constraints to be overridden at specific times to provide fast transient performance.

[0016] The reference power level for the power level mode can be represented, for example, by any parameter of the drive signal or transmitter coil signal that affects the power level of the power transmission signal, specifically the amount of power transmitted to the power receiver. The reference power level can specifically be the current, voltage, frequency, power, duty cycle, and / or active duration (burst mode) of the drive signal and / or the current, voltage, frequency, power, duty cycle, and / or active duration (burst mode) of the transmitter coil signal. In many embodiments, the reference power level may be indicated by the coil current of the transmitter current.

[0017] The reference power level for the power level mode may be a reference power level parameter that affects and / or reflects the power level of the power transmission signal.

[0018] Similarly, the first reference value can be represented by any parameter of, for example, the drive signal or transmitter coil signal, that affects the power level of the power transmission signal, specifically the amount of power transmitted to the power receiver. Specifically, the first reference value can be the current, voltage, frequency, power, duty cycle, and / or active duration (burst mode) of the drive signal, and / or the current, voltage, frequency, power, duty cycle, and / or active duration (burst mode) of the transmitter coil signal. In many embodiments, the first reference value can be represented by the coil current of the transmitter current. The first reference value can be for the same parameter as the reference power level of the power level mode indicated in the mode request message, or for a different parameter (in which case the mode circuitry can convert between parameters).

[0019] The power loop controller may be configured to control the drive signal by adapting its parameters that affect the power level of the power transmission signal, such as the current, voltage, frequency, power, duty cycle and / or active duration (burst mode) of the drive signal.

[0020] The parameters that affect the power level of the power transmission signal may specifically have a one-to-one monotonic relationship with the power level of the power transmission signal (at least within the operating range).

[0021] A receiver for receiving a message from a power receiver may also be called a message receiver (for receiving a message from a power receiver).

[0022] In accordance with an optional feature of the invention, a period of time for adapting the drive signal to set the power level of the power transmission signal to the first reference value is less than a time constant of the power control loop.

[0023] This approach may allow for faster adaptation of power transfer operation to changes in power transfer behavior.

[0024] According to an optional feature of the invention, the mode storage device is configured to store a plurality of parameters for at least one power level mode, the plurality of parameters including at least one reference power level representing a power level of the power transmission signal and at least one parameter value for at least one of the drive signal and the transmitter coil signal, the at least one parameter value being a value for at least one of the drive signal and the transmitter coil signal for a power level of the power transmission signal indicated by the reference power level.

[0025] This can provide improved performance in many embodiments. For example, the power transmitter can store both the reference power level in the form of the power extracted by the power receiver. Additionally, the power transmitter can store signal parameter values ​​of the drive signal or transmitter coil signal that result in a corresponding power level of the power transmission signal. For example, the frequency of the drive signal that produces a desired power level can be stored. It will be understood that this can be considered equivalent to a mode storage device that stores multiple reference power levels for a given power level mode, or that the stored reference power level for a given power level mode may comprise multiple elements.

[0026] In accordance with an optional feature of the invention, the power transmitter further comprises a detection circuit that detects a power transmission anomaly in response to a comparison of a current power level of the power transmission signal with a reference power level for a current power level mode of the plurality of power level modes.

[0027] This approach may allow for improved operation, and in particular may allow anomalies such as fault conditions to be detected, thereby allowing the system to respond to such conditions.

[0028] In some embodiments, the detection circuitry is configured to alter a parameter of the power transfer in response to detecting a power transfer anomaly.

[0029] This can provide improved performance in many embodiments, allowing the system to compensate for anomalies such as potential faults. Specifically, the detection circuit can reduce the maximum power limit of the power transfer signal and / or terminate an ongoing power transfer.

[0030] According to an optional feature of the invention, the mode circuitry is configured to determine, during an initialization phase in which the power receiver transitions through at least some of the power level modes, reference power levels for at least some of the plurality of power level modes in association with at least one of the parameter values ​​of the drive signal and the parameter values ​​of the power transmission signal characteristics, and the mode storage device is configured to store the reference power levels for at least some of the power level modes.

[0031] This may provide particularly efficient operation in many embodiments and scenarios, for example, allowing the power transmitter to adapt to different power receivers without requiring pre-stored information.

[0032] The parameter values ​​of the drive signal and / or transmitter coil signal may be measured parameters or may be parameters set by the power transmitter during operation in the initialization phase. For example, the parameter values ​​may be the frequency, current, voltage, duty cycle, and power of the drive signal and / or transmitter coil signal during operation in the power level mode during the initialization phase.

[0033] The measurements of the drive signal characteristics and the measurements of the power transfer signal characteristics may be measurements that allow a suitable parameter to be determined that can be used to indicate a reference power level, such as a transmitter coil current.

[0034] In accordance with an optional feature of the invention, the initialization phase precedes the power transfer phase.

[0035] This can provide improved performance in many embodiments.

[0036] According to an optional feature of the invention, the receiver is configured to receive a power receiver setting message from the power receiver, the power receiver setting message including power receiver setting parameters, and the mode circuit is configured to determine a reference power level for at least one of the plurality of power level modes in response to the power receiver setting characteristics. This can provide improved operation in many embodiments. In many embodiments and scenarios, it can enable the power transmitter to estimate an appropriate reference power level for a particular power receiver with sufficient accuracy. This approach can enable the power transmitter to adapt to a particular power receiver.

[0037] In accordance with an optional feature of the invention, the power receiver configuration parameters include at least one of a power receiver ID, a power receiver type ID, a power receiver coil characteristic, a power receiver coil dimension characteristic, and a power receiver coil inductance characteristic.

[0038] These parameters can provide particularly advantageous adaptations in many embodiments.

[0039] In accordance with an optional feature of the invention, the mode circuitry is configured to determine a coupling coefficient between the power transmitter coil and a power receiver coil of the power receiver based on the power receiver setting parameters, and to determine a reference power level for at least one power level mode based on the coupling coefficient.

[0040] This can provide particularly advantageous operation and / or performance in many embodiments and scenarios.

[0041] According to an optional feature of the invention, mode circuitry is configured to determine a power transfer function between at least one of a parameter of the drive signal and a parameter of the transmitter coil signal and an output power of the power receiver based on the power receiver setting parameters, and to determine a reference power level for the at least one power level mode based on the power transfer function.

[0042] This can provide particularly advantageous operation and / or performance in many embodiments and scenarios.

[0043] According to an optional feature of the invention, the mode storage device is configured to store sets of power level modes for different power receivers, and the mode circuit is configured to select between the sets of power level modes in response to an ID indication received from the power receiver, which can provide improved operation in many embodiments.

[0044] In accordance with an optional feature of the invention, the mode request message includes a timing indicator, and the mode circuitry is configured to adapt a timing for setting a power level of the power transmission signal in response to the timing indicator.

[0045] This can provide particularly advantageous operation and / or performance in many embodiments and scenarios. The timing indicator can indicate one or more changes in power level mode by the power receiver.

[0046] In accordance with an optional feature of the invention, the mode request message is received during the power transfer phase.

[0047] This can provide particularly advantageous operation and / or performance in many embodiments and scenarios.

[0048] According to another aspect of the present invention, there is provided a method of operating a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, the power transmitter having an output circuit including a transmitter coil for generating a power transmission signal in response to a drive signal applied to the output circuit, the method comprising the steps of receiving a message from the power receiver, generating the drive signal, and operating a power control loop that controls the drive signal to adjust a power level of the power transmission signal, the power control loop being configured to make changes to the power level of the power transmission signal in response to a power control error message received from the power receiver; storing in a mode storage device a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level for the power transmission signal; and adapting the drive signal to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to a reference power level for a first power level mode of a plurality of power level modes indicated in the mode request message.

[0049] According to another aspect of the present invention, there is provided a wireless power transfer system including a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transfer signal, the power transmitter having: a receiver for receiving messages from the power receiver; an output circuit including a transmitter coil for generating the power transfer signal in response to a drive signal applied to the output circuit; a drive circuit for generating the drive signal; a power loop controller for controlling the drive signal to adjust a power level of the power transfer signal, the power control loop being configured to make changes to the power level of the power transfer signal in response to a power control error message received from the power receiver; a mode memory configured to store a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level for the power transfer signal; and a mode circuit configured to adapt the drive signal to set the power level of the power transfer signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to a reference power level for a first power level mode of a plurality of power level modes indicated in the mode request message.

[0050] 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]

[0051] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Figure 1] 1A and 1B illustrate examples of elements of a power transfer system according to some embodiments of the present invention. [Figure 2] FIG. 1 illustrates an example of elements of a power transmitter according to some embodiments of the present invention. [Figure 3] 1 illustrates an example of elements of an output stage of a power transmitter. [Figure 4] FIG. 2 illustrates an example of elements of an output stage of a power transmitter. [Figure 5]FIG. 1 illustrates an example of elements of a power receiver according to some embodiments of the present invention. [Figure 6] FIG. 2 is a diagram illustrating an example of a power control loop of the power transfer system of FIG. 1. [Figure 7] 2 is a diagram showing an example of power load fluctuations in the power transmission system of FIG. 1; [Figure 8] FIG. 2 is a diagram showing an example of a model of a power transmission path in the power transmission system of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0052] The following description focuses on embodiments of the invention applicable to wireless power transfer systems that utilize a power transfer approach such as that known from the Qi 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.

[0053] 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.

[0054] The system provides an electromagnetic power transfer signal capable of inductively transferring 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 (typically part of an output circuit in the form of a resonant or tank circuit). The power transfer signal may correspond to an electromagnetic power transfer component representing the transfer of energy from the power transmitter to the power receiver, and may be considered to correspond to the 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 transfer signal (apart from losses) would be zero. In some situations where a foreign object is present, the power transfer signal can be considered to include a component corresponding to power transfer to the foreign object, and therefore the power transfer signal can be considered to correspond to power extracted from the electromagnetic field generated by the power transmitter.

[0055] The power transmission signal may typically have a frequency between about 20 kHz and about 500 kHz, and for Qi-compatible systems, is typically in the range of 95 kHz to 205 kHz (or for high-power kitchen applications, for example, the frequency may typically be in the range of 20 kHz to 80 kHz). The transmitter coil 103 and the receiving coil 107 are loosely coupled, and thus the receiving 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 receiving coil 107. The term power transmission signal is primarily used to refer to the inductive signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107.

[0056] 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 may 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.

[0057] The system is configured to transmit substantial power levels, and specifically, in many embodiments, the power transmitter can support power levels of 500 mW, 1 W, 5 W, 50 W, 100 W, or greater than 500 W. For example, for Qi-enabled applications, power transmission can typically range from 1 to 5 W for low-power applications (baseline power profile), up to 15 W for Qi standard version 1.2, up to 100 W for high-power applications such as power tools, laptops, drones, robots, and the like, and in the range of greater than 100 W and greater than 1000 W for very high-power applications, such as those supported by the Cordless Kitchen standard being developed by the Wireless Power Consortium.

[0058] The operation of power transmitter 101 and power receiver 105 will be described below with particular reference to embodiments that generally conform to the Qi standard (except for modifications and extensions (or resulting from) described herein) or are suitable for high-power kitchen specifications being developed by the Wireless Power Transfer Consortium. In particular, power transmitter 101 and power receiver 105 conform to or are substantially compatible with elements of Qi standard version 1.0, 1.1, or 1.2, or are suitable for higher power cordless kitchen standards (except for modifications and extensions (or resulting from) described herein).

[0059] FIG. 2 shows elements of the power transmitter 101 of FIG. 1 in more detail.

[0060] The power transmitter 101 includes a driver 201 capable of generating a drive signal, which is provided to an output circuit, which in this example is a resonant circuit formed by a transmitter coil 103 and a transmitter capacitor 203. The transmitter coil 103 is driven by the drive signal, which generates an electromagnetic field. Thus, an electromagnetic power transfer signal is generated that provides power transfer to the power receiver 105. The power transfer signal is provided during (at least) a power transfer phase.

[0061] Driver 201 is a drive circuit, typically in the form of an inverter, that generates an AC signal from a DC voltage. The output of driver 201 is typically a switch bridge that generates a drive signal by appropriate switching of the switches of the switch bridge. Figure 3 shows a half-bridge switch bridge / inverter. Switches S1 and S2 are controlled so that they are never closed simultaneously. Alternately, 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 4 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. Alternately, 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.

[0062] In some implementations, S1 and S3 may be open and S2 and S4 may be closed during part of the cycle, and vice versa during another part of the cycle. This is known as phase control. This approach produces a square wave with a zero level in between. The drive circuitry is implemented using discrete electronics and the output circuitry is formed by solid-state switches such as transistors, although it will be appreciated that other implementations are possible, including, for example, using integrated or mechanical switches to form the output circuitry.

[0063] The drive circuitry can be implemented as an integrated circuit, such as, for example, an application specific integrated circuit (ASIC). In some embodiments, the circuitry may be implemented as a programmed processing unit, such as firmware or software running on a suitable processor, such as, for example, a central processing unit, a digital signal processing unit, or a microcontroller. In such embodiments, it will be understood that the processing unit may include on-board or external memory, clock driver circuits, interface circuits, user interface circuits, etc. Such circuits may further be implemented as part of the processing unit, as an integrated circuit, and / or as discrete electronic circuits.

[0064] Thus, the driver 201 generates a drive signal for the output resonant circuit and, therefore, for the transmitter coil 103. The drive signal causes current to flow through the transmitter coil, thereby generating an electromagnetic power transfer signal. The drive signal typically has a (substantially) constant voltage amplitude for a given power transfer configuration. In an example, this constant voltage amplitude is achieved by setting a constant rail voltage for the driver's output circuit; i.e., the rail voltage V for the bridge in FIGS. 3 and 4 is constant for a given power transfer configuration. Switching by the bridge transistors switches the output voltage between 0 and V for a half bridge and between V and −V for a full bridge, respectively. Thus, in an example, the power transmitter can set the rail voltage to be constant for any given power transfer configuration, but (possibly) to vary between power transfer configurations.

[0065] The power transmitter 101 further includes a power transmitter controller 205 configured to control operation of the power transmitter 101 according to desired operating principles. In particular, the power transmitter 101 can include many of the functions required to perform power control according to the Qi standard, including interacting with a power receiver, providing a user interface, etc., as appropriate for the particular application and standard.

[0066] The power transmitter 101 further comprises a first communicator 207 configured to receive data and messages from the power receiver 105 (as will be appreciated by those skilled in the art, data messages can provide one or more bits of information). In an example, the power receiver 105 is configured to load modulate the power transmission signal generated by the transmitter coil 103, and the first communicator 207 is configured to sense variations in the voltage and / or current of the transmitter coil 103 and demodulate the load modulation based thereon. Those skilled in the art will know the principles of load modulation, e.g., as used in Qi wireless power transfer systems, and therefore these will not be described in further detail.

[0067] The first communicator 207 may further be arranged to transmit data to the power receiver, for example by specifically modulating the drive signal and thus the power transmission signal using frequency, amplitude and / or phase modulation.

[0068] It will be understood that other approaches for communicating data between the power transmitter 101 and the power receiver 105 may be used in other embodiments. For example, in some embodiments, communication may be performed using a separate communication coil, or a separate communication channel that may actually be achieved using the transmitter coil 103. For example, in some embodiments, near field communication may be implemented, or a high frequency carrier (e.g., having a carrier frequency of 13.56 MHz) may be superimposed on the power transmission signal.

[0069] FIG. 5 shows some exemplary elements of the power receiver 105. The receiver coil 107 is coupled to a power receiver controller 501, which couples the receiver coil 107 to a load 503. In many embodiments, the receiver coil 107 is part of a power receiver input circuit that also includes a capacitor to form a resonant circuit with the receiver coil 107. The power receiver controller 501 includes a power control path that converts the power extracted by the receiver coil 107 into a power source suitable for the load. Additionally, the power receiver controller 501 can include various power receiver controller functions required to perform power transfer, particularly functions required to perform power transfer according to the Qi standard.

[0070] The power receiver 105 further comprises a second communicator 505 configured to receive data transmitted from the power transmitter 101. In an embodiment, the second communicator 505 is configured to suitably demodulate amplitude, frequency and / or phase modulation of the power transmission signal to obtain the data transmitted from the power transmitter.

[0071] The second communicator 505 is further configured to transmit data to the power transmitter 101 by varying the load on the receiver coil 107 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.

[0072] As previously mentioned, in other embodiments, other communication methods may be used, for example, a separate dedicated short-range communication approach such as NFC may be used.

[0073] The power transmitter and power receiver further include functionality for implementing a power control loop to dynamically adapt the power level of the power transmission signal during the power transmission phase. The power receiver can continuously monitor the received power level and compare it to a desired power level. A power control error message can then be transmitted, and the power transmitter can increase or decrease the power level by modifying the characteristics of the drive signal.

[0074] In particular, the power transmitter comprises a power loop controller 209 configured to control the power level of the power transmission signal by adjusting parameters / characteristics of the drive signal. The power loop controller 209 can adjust parameters such as current, voltage, frequency, duty cycle, active duration (burst mode) of the drive signal, which results in a change in the power level of the power transmission signal.

[0075] The power loop controller 209 can be implemented as an integrated circuit, such as, for example, an application specific integrated circuit (ASIC). In some embodiments, the power loop controller 209 may be implemented as a programmed processing unit, such as firmware or software running on a suitable processor, such as, for example, a central processing unit, a digital signal processing unit, or a microcontroller. In such embodiments, it will be understood that the processing unit may include on-board or external memory, clock driving circuits, interface circuits, user interface circuits, etc. Such circuitry may further be implemented as part of the processing unit, as an integrated circuit, and / or as discrete electronic circuitry.

[0076] In some embodiments, the power loop controller 209 may be implemented partially or completely as a discrete electronic circuit. In different embodiments, the power loop controller can be implemented as an analog electronic circuit, a digital electronic circuit, or a mixed analog circuit.

[0077] It will be appreciated that different parameters may be used to represent the power level of the power transmission signal in different embodiments. For example, in many embodiments, the power level of the power transmission signal may be represented by a characteristic or parameter of the transmitter coil signal, such as, specifically, the current, voltage, frequency, duty cycle, and / or power of the signal in the transmitter coil 103. In many embodiments, the power level of the power transmission signal may be given or represented by the coil current for the transmitter coil 103. In many embodiments, a power control loop may control the power level of the power transmission signal by, specifically, controlling the level of the coil current through the transmitter coil 103.

[0078] In some embodiments, the power level of the power transmission signal may be represented by characteristics or parameters of the drive signal, such as, in particular, the current, voltage, frequency, duty cycle, active duration and / or power of the drive signal.

[0079] For example, increasing the current or duty cycle of the drive signal directly affects the signal in the transmitter coil 103 and thus the generated power transfer signal, thereby increasing the power level of the power transfer signal.

[0080] Indeed, the power level of the power transmission signal may depend on several parameters, and in various embodiments, any such parameters may be used to represent and / or control the power level of the power transmission signal. It will also be understood that different parameters may be used to represent the power level of the power transmission signal. For example, the power receiver and the power transmitter may use different parameters to represent the power level of the power transmission signal (e.g., the power transmitter may use the current in the transmitter coil 103, and the power receiver may use the extracted power level). In such embodiments, for example, a conversion between different parameters and representations may be used, or data related to one parameter may be adapted by making a relative change to another parameter.

[0081] It will also be understood that the parameter controlled and adapted by the power control loop may be modified directly or indirectly by changing another parameter. For example, the power control loop may control the coil current for the transmitter coil 103, and may do so by varying the frequency of the drive signal, for example, to vary the coil current to a desired value.

[0082] FIG. 6 illustrates an example of the functional aspects of an exemplary power control loop that may be employed in the system of FIG.

[0083] The loop is particularly concerned with the coil current I txc The coil current I can be considered as a loop output or loop variable. txc corresponds to the power level of the power transmission signal. Specifically, the magnetic flux and field strength generated by the transmitter coil 103 is directly determined by the coil current, and therefore the signal induced in the receiver coil 107 is directly determined by the transmitter coil current.

[0084] Thus, the loop includes a power path from the transmitter coil current to the power level extracted by the power receiver 105. This path includes the generation of the electromagnetic flux of the power transmission signal, the induction of the signal in the power receiver coil, the power receiver power path, etc. The extracted power (e.g., delivered to the load 503) is compared by the power receiver 105 with a desired (current) reference power level PWR REF. Based on the comparison power control error indicator, ERR is generated and transmitted to the power transmitter 101 in a power control error message.

[0085] The power transmitter 101 controls the coil current I txc The power level of the power transmission signal, specifically the coil current I txcThe change in is relative, so the control loop can increase or decrease the power level from the current level depending on the power control error indicator / message. The relative change in power level / coil current corresponds to including an integral function 603 in the power control loop.

[0086] Furthermore, the power loop controller 209 and the power transmitter implement a specific power modification circuit 605 for varying the power level in response to the power control error indicator. For example, the power control error message may request that the power level be increased by a given relative amount, e.g., 2%. In response, the power modification circuit 605 modulates the coil current I txc You may decide that the cost should be increased by 2% and proceed to implement this change.

[0087] In many embodiments, the power level can be adapted by modifying the characteristics / parameters of the drive signal. Thus, the power modifying circuit 605 may include circuitry for modifying the parameters of the drive signal, which in turn may adjust the power level, in particular the coil current I txc This produces the desired change in

[0088] Specifically, in many embodiments, the output circuit of the power transmitter and the input circuit of the power receiver include resonant circuits, and the power transmission signal and the coil current I txc The power level of the coil current I is controlled by varying the drive frequency of the drive signal to approach or move away from the resonant frequency. Thus, by varying the frequency to approach the resonant frequency, the coil current I txc It is possible to increase the number of employees.

[0089] Other parameters of the drive signal that may alternatively or additionally be modified include the current, voltage, power, duty cycle, or duration of the drive signal, increasing any of which will increase or decreasing the power level of the power transmission signal.

[0090] In some embodiments, the power modifying circuit 605 adjusts the drive signal parameters and the power transmission signal level (coil current I txc For example, if a request to increase the power level by 2% is received, the power modification circuit 605 can directly modify the drive signal frequency or current by a certain amount. Such a direct correspondence can be based, for example, on a look-up table generated during a manufacturing or calibration process.

[0091] In many embodiments, the power modifying circuit 605 may include an inner loop that controls drive signal parameters to effect a desired change in the power level of the power transmission signal, such as adjusting the coil current I in response to a received error power control message. txc An internal circuit may be implemented to change the reference value for I. Then, the inner loop calculates the actual coil current I. txc For example, the drive signal frequency can be adjusted until ≡(t) ...

[0092] It will also be appreciated that in many embodiments the power levels may be effective or real power levels, however in other embodiments the power levels considered may be complex, reactive or apparent power levels.

[0093] A power control loop provides a highly effective and reliable approach for a power receiver to control power transmission operation. For example, it allows the power receiver to continuously adapt the transmitted power level to maintain a desired speed for a load in the form of a motor, for example.

[0094] The system of FIG. 1 further includes additional functionality for controlling the operation of the power control loop in specific circumstances, thereby providing improved operation in many scenarios.

[0095] Specifically, in the system, the power receiver can have multiple power level modes associated with the power transmission. Specifically, the power receiver can be associated with a set / multiple power level modes, each linked to a reference power level for the power transmission signal. The power receiver can be configured to operate in different discrete modes, each having a given power level requirement from the power transmission signal. For example, a power receiver in the form of a blender can have, say, five different motor speed settings and therefore be associated with five different operating modes, each of which extracts a different amount of power from the power transmission signal.

[0096] The power transmitter 101 includes a mode circuit 211 coupled to a power loop controller 209 and a mode memory 213. The mode memory 213 may be configured to store data for different power level modes. Specifically, the mode memory 213 is configured to store a set of power level modes for the power receiver, with each power level mode associated with a reference power level for the power transmission signal.

[0097] Mode circuit 211 can be implemented as an integrated circuit, such as, for example, an application specific integrated circuit (ASIC). In some embodiments, mode circuit 211 may be implemented as a programmed processing unit, such as firmware or software running on a suitable processor, such as, for example, a central processing unit, a digital signal processing unit, or a microcontroller. In such embodiments, it will be understood that the processing unit may include on-board or external memory, clock driving circuits, interface circuits, user interface circuits, etc. Such circuitry may further be implemented as part of the processing unit, as an integrated circuit, and / or as discrete electronic circuitry.

[0098] In some embodiments, the mode circuitry 211 may be implemented partially or completely as a discrete electronic circuit. In different embodiments, the power loop controller can be implemented as an analog electronic circuit, a digital electronic circuit, or a mixed analog circuit.

[0099] The power level mode may be represented by different parameters in different embodiments, and any suitable parameter capable of indicating a power level may be used. For example, the reference power level may be represented by a value indicative of the actual load provided by the power receiver to the load 503. In other embodiments, the reference power level may be represented by a nominal power extracted from the power receiver for nominal operating conditions, such as no object being present and the power transmitter and power receiver having a nominal position relative to each other. In still other embodiments, the reference power level may be represented by a value of a loop variable controlled, such as a reference coil current value for a given mode. In still other embodiments, the reference power level may be represented by a value of a parameter of the power transmitter controlled to provide a desired power level. In many embodiments, the reference power level may be represented by a value of a characteristic of the drive signal, such as the current, voltage, frequency, duty cycle, active duration (burst mode), etc. All of these parameters may reflect the power level in various embodiments, and changes in the values ​​of such parameters may affect the power level of the power transmission signal. It will also be understood that in some embodiments, a combination of parameters may be used (e.g., using different parameters for different power level modes).

[0100] In the system, the power receiver can operate in a distinct set of power level modes, and the mode storage device can store a reference power level for each mode.

[0101] In the system, the power receiver may switch to a different mode and, in this regard, may send a message to the power transmitter to notify it of the mode change. The power receiver may specifically send a mode request message that may indicate the power level mode to which the power receiver is switching (or wishes to switch). It will be understood that any form of indication may be used. For example, the power level modes may be associated with individual IDs, and the mode request message may include the ID of the power level mode to which the power receiver wishes to switch.

[0102] When receiver 207 receives the mode request message, it forwards the ID to mode circuit 211, which accesses mode storage device 213 to obtain a reference power level for the power level mode specified by the ID. Mode circuit 211 is configured to adapt the drive signal to set the power level of the power transmission signal to this reference value, i.e., can adapt the drive signal to result in a power transmission signal having a value corresponding to the obtained reference value.

[0103] The reference value can be represented by any suitable value, and specifically, the coil current I txc It will be appreciated that the power level of the power transmission signal may be represented by any value or parameter that affects the power level of the power transmission signal, such as the drive signal current, voltage, frequency, duty cycle, or active duration (burst mode). The values ​​may be adapted directly or indirectly, for example, by adapting the drive signal current, voltage, frequency, duty cycle, or active duration (burst mode). Indeed, the values ​​of these parameters may, in some embodiments, be considered to be reference values ​​that are themselves set by mode circuitry 211 and that affect the power level of the power transmission signal.

[0104] The first reference value depends on the reference power level for the indicated power level mode. Thus, upon receiving a mode request message, mode circuit 211 can obtain the reference power level for the power level mode indicated in the mode request message. From this reference power level, a reference value for a given parameter related to the power level of the power transmission signal can then be determined (the power level of the power transmission signal depends on the value of the parameter for which the first reference value is determined). The first reference value may be determined specifically for a loop parameter, which is a parameter that represents a signal value at a point in the loop. Then, mode circuit 211 can set the parameter of the drive signal so that the parameter is at the first reference value.

[0105] In many embodiments, this can be done directly. For example, in many embodiments, reference values ​​may be determined directly for drive signal parameters such as drive signal current, voltage, frequency, duty cycle, active duration (burst mode), etc. The mode circuit 211 may then proceed to directly set the drive signal to the reference values. For example, the power receiver may transition to a particular power level mode and send a mode request message indicating this mode. The mode circuit 211 may directly determine that a reference power level corresponding to a given value of drive signal frequency has been stored for this mode and may immediately change the drive signal frequency to this value without considering the current value (or any other value) of the frequency. For example, assuming the power transfer resonant circuit is tuned to, say, 100 kHz, a mode request message indicating mode 1 may, say, cause the mode circuit 211 to set the drive signal frequency to 150 kHz; a mode request message indicating mode 2 may, say, cause the mode circuit 211 to set the drive signal frequency to 160 kHz; and a mode request message indicating mode 3 may, say, cause the mode circuit 211 to set the drive signal frequency to 170 kHz.

[0106] In some embodiments, the reference value may be determined for a parameter other than the drive signal parameter itself. For example, it may be specifically the coil current I txc In such a case, the mode circuit 211 can adapt the parameters of the drive signal to produce the desired parameter value for the transmitter coil signal. This can, in some embodiments, be, for example, the frequency of the drive signal and the coil current I txc This can be achieved by the mode circuit 211 using a direct relationship or function between the adapted characteristics of the drive signal and the parameters of the transmitter coil signal, such as a direct relationship between the coil current I and the drive signal. This relationship can be stored, for example, in a look-up table. However, in many embodiments, it is difficult to determine such a relationship, and the power transmitter may implement a fast inner loop, for example. For example, the coil current I txc can be measured and compared to a desired first reference value, and the frequency of the drive signal can be determined by the coil current I txc can be quickly changed / adapted to yield a desired value of

[0107] In many embodiments, the stored reference power level may be directly represented by the first reference value, i.e., the mode circuit 211 may directly obtain the reference power level of the requested power level mode and use it as the reference value, i.e., may directly set the reference parameter to this value. For example, in many embodiments, the mode storage device 213 may directly store frequencies for each of the power level modes, and when a mode request message is received, it may directly extract the stored frequency value and set the drive signal to this frequency. In other embodiments, some conversion may be required, which may be achieved, for example, using a lookup table into which data may be entered during a calibration phase.

[0108] In embodiments, the mode storage device may store multiple parameters for each power level mode, such as both drive signal parameters and extracted power values. Thus, in such cases, the reference power level may include multiple components, or equivalently, the mode storage device may store multiple reference power levels for each power level mode. In such embodiments, the mode circuit 211 may use the appropriate parameter value, or may use multiple parameter values. For example, if the mode request message indicates that the power receiver should switch to a power level mode that extracts, for example, 500 W, the mode circuit 211 may identify the power level mode that corresponds to the extracted power of 500 W and retrieve the drive frequency stored for this power level mode.

[0109] This approach can provide a system that can adapt very quickly to different operating modes. The mode request message can be sent during the power transfer phase, thus providing a means for quickly changing the power transfer operating point. Typically, power adaptation is achieved using power loop control, which, while adapted to provide efficient operation, is typically relatively slow to provide reliable performance. The described operation provides a means to override the power control loop, specifically, the power control loop can be dynamically changed / reinitialized to a new operating point consistent with the new power level mode during the power transfer phase.

[0110] Thus, the mode circuit 211 can be configured to adapt the drive signal by changing the power control loop variables in response to receiving a mode request message.

[0111] Mode circuit 211 is configured to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message. The power level of the power transmission signal is a state variable of the power control loop, and therefore mode circuit 211 is configured to set the state variable of the power control loop to a reference value in response to receiving a mode request message, the reference value depending on the mode request message, and specifically depending on the power level mode indicated in the mode request message.

[0112] The signal adaptation may be independent of the operation of the power control loop, and thus, in response to a mode request message, this approach may override the operation of the power control loop to reinitialize operation for the new power level mode.

[0113] In some embodiments, the mode circuitry 211 can be configured, in response to receiving a mode request message, to change a power control loop state variable to adapt the drive signal to set the power level of the power transmission signal to a first reference value, the first reference value corresponding to a reference power level of a first power level mode of a plurality of power level modes indicated in the mode request message.

[0114] In some embodiments, the mode circuitry 211 may be configured to, in response to receiving a mode request message, adapt the drive signal to set a power level of the power transmission signal to a first reference value, the first reference value corresponding to a reference power level of a first power level mode of a plurality of power level modes indicated in the mode request message, and the adaptation includes modifying a state variable of the power control loop.

[0115] In some embodiments, the mode circuitry 211 may be configured, in response to receiving a mode request message, to adapt the drive signal by modifying a state variable of the power control loop to set the power level of the power transmission signal to a first reference value, the first reference value corresponding to a reference power level of a first power level mode of a plurality of power level modes indicated in the mode request message.

[0116] In some embodiments, the mode circuitry 211 may be configured, in response to receiving a mode request message, to adapt the drive signal by modifying a state variable of the power control loop to set the power level of the power transmission signal to a first reference value, the first reference value corresponding to a reference power level of a first power level mode of a plurality of power level modes indicated in the mode request message.

[0117] The mode circuit 211 may be configured to overwrite or replace the current values ​​of the loop state variables with reference values ​​that depend on the power level mode indicated in the mode request message.

[0118] The adaptation of the drive signal / setting of the power level of the power transmission signal / changing the power level of the power transmission signal may be faster than can be achieved by the power control loop. The time constant / period for adapting / setting the power level of the power transmission signal to a reference value in response to a mode request message may be shorter than the time constant / period of the power control loop. In some embodiments, the setting of the power level may be a step change.

[0119] In many embodiments, the time constant of the power control loop is 250 msec or more, 500 msec or more, or 1 second or more, while the setting of the power level in response to the mode request message can be of a lower duration, specifically less than 100 msec, 250 msec, or 500 msec, respectively.

[0120] In many embodiments, the period for adapting the drive signal to set the power level is less than the time constant of the power control loop, and in many embodiments, may be less than 50% or even 25% of this time constant. This period may be the delay from when the mode request message is received until the power level of the power transmission signal is set to (or reaches) the first reference value. The time constant of the control loop reflects how quickly the loop reacts to changes. The time constant may be the period for a loop variable (e.g., the power level of the power transmission signal) to reach 63.2% of its final (steady-state) value following a step change.

[0121] It will be appreciated that different approaches can be used for the power transmitter to determine and store the power level mode and associated reference levels, as will be described in more detail below.

[0122] In some embodiments, power level modes and reference power levels may be stored for multiple power receivers. Thus, the mode storage device 213 may be configured to store sets of power level modes for different power receivers.

[0123] When initializing a power transfer operation (or indeed at any suitable time), the power receiver can transmit its identification, and the mode circuit 211 / mode storage device 213 can then proceed to retrieve the set of power level modes that match the particular ID.

[0124] In some embodiments, the ID may be a unique device ID. This may be very useful, for example, in embodiments where the stored power level modes and reference power levels are determined by individual initialization with each device. For example, when a new power receiver is detected, the power transmitter may begin an initialization routine that determines the power level modes and reference power levels. The next time a power receiver is detected, the power transmitter may proceed to use the already stored values ​​without performing the initialization process. The power transmitter may then gradually accumulate data for appropriate power receivers, allowing functions for various power receivers to be used with less overhead.

[0125] Alternatively or additionally, the ID may be a type ID indicating, for example, the model, manufacturer, etc. of the power receiver. The power transmitter may, for example, store power level mode data for a variety of devices of different types, and upon receiving the type ID, may select the power level mode data that matches the received ID.

[0126] In some embodiments, the power level mode and reference power level data may be based on an initialization phase performed by the power transmitter and power receiver.

[0127] For example, in some embodiments, initialization of a new power transmission (e.g., only for power receivers with no stored power level mode data) may include first running a process to determine a reference value to use during operation. During this initialization phase, the power receiver goes through different power level modes, and for each power level mode, mode circuit 211 may determine a value representing the power level and store this as the reference power level for that mode.

[0128] For example, a predetermined timing can be applied for the power receiver to step through the power level modes, e.g., operate for 10 seconds in each mode before switching to the next mode. Alternatively, the power receiver can send a message when switching to the next mode, or the power transmitter can send a message requesting that the next mode be applied.

[0129] For each power level mode, the power transmitter may operate a power control loop to reach a steady state, where the power transmitter may adjust a desired parameter, such as the coil current I, used to represent the power transmission signal power level. txc Or a value such as the drive signal frequency can be measured, and this value can be stored as the reference power level for that mode.

[0130] The power receiver can then switch to the next power level mode, for example, at the request of the power transmitter, and the process can be repeated.

[0131] This approach may typically be implemented by having the power receiver step through power level modes in sequence, typically from lower power levels to higher power levels, which may reduce the risk of undesired overvoltage conditions, for example.

[0132] The initialization process may typically be performed as part of the power transfer initialization and therefore may be performed before the power transfer phase.

[0133] As a specific example, an air fryer, a kitchen appliance that uses convection to circulate hot air around food, may cycle the heating element on and off. This typically results in very large load steps, e.g., 50 to 1200 W, which will be repeated throughout the device's operation to maintain a constant temperature. Figure 7 shows a schematic diagram of a power step, PWR, and the resulting temperature change, TEMP.

[0134] In this example, after the device is turned on and power transfer proceeds with power controlled by the power control loop, an operating point is saved (SVE 1 and 2). The operating point reflects the power transfer level of the power transfer signal for the air fryer's current power level mode and can be represented by any suitable parameter values ​​as previously described.

[0135] Values ​​can be stored for both the high power level mode and the low power level mode, thereby providing reference power levels for two different power level modes to the mode storage device 213. The power receiver can then send a mode request message MRQ when changing power level modes, thereby enabling the power transmitter to use the stored values ​​to jump directly to (near) the new operating point by overriding the power control loop.

[0136] Thus, when a power level mode change is about to occur, the power receiver can be notified that a load change is occurring and which mode to transition to. The system, and specifically the power transmitter, will then know which operating point it should jump to. This reduces the risk of transmitting too much or too little power, for example, due to delays in the control loop. This helps prevent damage to equipment or reduces the risk of the power receiver powering down, even in extreme situations.

[0137] Additionally, the stored data can be used for future power transmissions between the power receiver and power transmitter, as the stored values ​​can be stored and retrieved between different power transmission operations. The mode storage device 213 can, among other things, store values ​​for multiple power receivers, and when a power receiver is detected for power transmission, can proceed to use the stored set for this power receiver. If a new power receiver is detected, or if the stored data is deemed invalid, for example, by being too old, the power transmitter and power receiver can proceed to generate and store new / updated data for the power receiver.

[0138] Thus, if a power transmitter / power receiver device combination and a particular power mode is used in the future, the operating point actually used can be reused. The operating values ​​are determined during start-up or initialization by stepping the system through all power level modes, as described above, and the resulting operating points and reference power levels are represented by any suitable parameters, and the values ​​are stored as the reference power levels.

[0139] For example, in the case of an air fryer, the heating element may be turned on or off, but the fan always remains on. During appliance startup, only the fan is initially turned on and its operating point is measured and saved (SVE 1). Then, the heating element is turned on and the associated operating point is measured and stored (SVE 2). Then, during operation, when the heating element is to be turned on / off, the power receiver can signal that a load change is about to occur, and a mode request message MRQ for a different power mode is generated and sent to the power transmitter. The power transmitter can then immediately enter the correct operating point without control loop delays. The power receiver may be notified that the power transmitter has switched to the correct power mode by receiving a handshake in the form of a command.

[0140] In some embodiments, the power transmitter may further comprise a detection circuit 215 configured to detect a power transmission anomaly in response to a comparison of a current power level of the drive signal with a reference power level for the current power level mode of the set of power level modes.

[0141] When operating in a particular power level mode, the power control loop may vary the power level of the power transmission signal in response to error control messages from the power receiver. However, these variations are expected to be relatively small. For example, when an air fryer is operating in a 1200 W load mode, the exact power drawn will vary, and the power receiver may control this so that the exact desired power for the current situation is drawn. However, while this power level may vary accordingly, the variation is expected to be limited under normal operating conditions; for example, the power would be expected to range from 1100 W to 1300 W during normal operation.

[0142] Thus, the detection circuit 215 can compare the current power level to a stored reference power level for the power level mode the system is currently operating in. For example, the detection circuit 215 can compare the currently measured coil current I txc can be compared to the coil current stored for the state in which the device is operating.

[0143] If the comparison indicates that the current power level differs too much from the reference power level, for example, if the measured coil current differs from the stored reference coil current value by more than a threshold value, the detection circuit 215 can determine that the current operating point is not one that should be experienced during normal operation and therefore determine that an anomaly has been detected.

[0144] In such a case, the detection circuit 215 can, for example, notify the transmitter controller 205 that an anomaly has been detected. In response, the transmitter controller 205 can proceed to change the parameters of the power transfer. For example, it can be configured to limit the power level below a given value, e.g., the maximum coil current I txc can be set to a level low enough to ensure that no damage occurs. In some embodiments, the maximum power level may be set to zero, and specifically, power transfer may be terminated if an anomaly is detected.

[0145] It will be appreciated that the exact criteria used to detect anomalies based on the comparison will depend on the preferences and requirements of a particular implementation, and many different approaches and criteria are possible. It will also be appreciated that the evaluation can include other considerations, such as converting between different parameters. For example, if the reference power level is stored as a coil current value, but the current power level is set / measured based on the drive signal frequency, the comparison can include converting between the coil current and the drive signal frequency.

[0146] It will also be appreciated that the action taken in response to detecting an anomaly will depend on the preferences and requirements of a particular embodiment. For example, in some embodiments, power transfer may be restricted or terminated. In other embodiments, detecting an anomaly may simply result in the generation of a user alert, such as, for example, switching on a warning light. In yet other embodiments, a message may be sent to a receiver, which may take action in response, such as altering the power supply to a load.

[0147] In some embodiments, the mode request message includes a timing indicator, and the mode circuitry is configured to adapt the timing for setting the level of the drive signal in response to the timing indicator.

[0148] Specifically, the mode request message may include an indication of when the power receiver intends to switch to a new power level mode. For example, the mode request message may indicate that the power receiver intends to switch to a new power level mode immediately, in which case the power transmitter may immediately switch to the new mode by setting the power level of the power transmission signal to a corresponding reference value, e.g., setting the coil current to a stored reference value of the coil current for the new power level mode.

[0149] In other situations, the power receiver may send a mode request message indicating that a power level mode change will occur at some time in the future, for example, 5 seconds. In this case, the power transmitter may delay setting the power level for the indicated time, i.e., 5 seconds to delay setting the power level to override the loop.

[0150] In some embodiments, the timing indicator can indicate multiple power level mode changes. For example, the mode request message can indicate that the power receiver switches between two different modes (e.g., two power level modes of an air fryer) at a given interval (e.g., every 20 seconds), and the power transmitter can proceed to time direct power level settings to correspond to these switches.

[0151] It will be appreciated that in some embodiments, the power transmitter may send a confirmation message to the power receiver that a power level setting has been or will be made, and the power receiver may wait for such a confirmation message before switching between power level modes.

[0152] In some embodiments, the power transmitter may be configured to determine the reference power level based on data received from the power receiver.

[0153] In this example, the mode circuit 211 can receive information from the power receiver that enables it to calculate a reference power level. In particular, the power receiver can provide a receiver configuration message comprising power receiver configuration parameters. The mode circuit 211 can determine a reference power level for at least one power level mode of the set of power level modes based on the power receiver configuration characteristics.

[0154] The power receiver setting parameters may specifically comprise at least one of the following: Power receiver ID; Power receiver type ID; Power receiver coil characteristics; Power receiver coil dimensional characteristics; and Power receiver coil inductance characteristics.

[0155] The power receiver ID or type ID may enable the power transmitter to obtain data describing the characteristics of this power receiver. This data may directly provide, for example, the power level mode and reference power level for a particular receiver, as described above. However, typically, it includes power receiver characteristics that indicate the power receiver's power processing. For example, the ID or type ID may enable the power transmitter to obtain configuration data describing the characteristics (e.g., dimensions or inductance) of the power receiver coil. Thus, the power receiver coil characteristics may be transmitted directly by the power receiver or may be provided indirectly by identifying the power receiver and allowing the power transmitter to obtain the relevant data. This data may be obtained from internal storage in some embodiments, or from an external server in many embodiments. For example, each manufacturer may provide a database accessible (e.g., via the Internet) to appropriately equipped power transmitters.

[0156] In some embodiments, configuration data received from the power receiver can be used to calculate appropriate values ​​for setting parameters of the drive signal or transmitter coil signal when a power level mode change occurs. For example, it can be used to calculate the drive signal frequency, duty cycle, or coil current for different power level modes. The power level mode can be represented, for example, by a load power value indicating the power delivered to the load 503 by the power receiver, and the data received from the power receiver can be used to calculate the corresponding value of the power level parameter to be applied by the mode circuit 211. For example, this data can be used to calculate the coil current required to deliver the indicated power to the load 503.

[0157] This data can be used, for example, to determine the power path from the parameters set in the power transmitter to the load in the power receiver. Figure 8 shows an example model for the power path from the driver 201 voltage to the load 503.

[0158] In this example, the following reference symbols are used: Vin: The voltage of the drive signal from the driver 201. Rp: Internal resistance of the driver and losses in the output circuit. Cp: ​​Capacitor 203 of the power transmitter resonant output circuit. Lp: Transmitter coil 103 Ls: Receiver coil 107 Cs: Capacitor of the power receiver input resonant circuit Rl: Load 503

[0159] One of the key parameters for power transmission in a wireless power transmission system is the coupling coefficient between the power transmitter coil and the power receiver coil, which depends on several factors, including receiver coil characteristics. Therefore, the power receiver configuration data can be used to determine the coupling coefficient between the power transmitter coil and the power receiver coil. The mode circuit 211 can determine one or more reference power levels for at least one power level mode based on the coupling coefficient.

[0160] For example, the power transmitter may store multiple reference power levels corresponding to a reference power receiver and a nominal power level mode. However, for each power level mode, different reference power levels may be stored for different coupling coefficients, which are important values ​​in determining the power transmitter parameters related to the extracted power level. The received information can then be used to calculate the coupling coefficient for the current power receiver, and the power transmitter can accordingly obtain the reference power level that matches the current coupling coefficient.

[0161] In some embodiments, mode circuitry 211 can be configured to determine a power transfer function between relevant parameters of the drive signal or transmitter coil signal and the output power from the power receiver to the load. Thus, the power transfer function can reflect the relationship between the parameters set by mode circuitry 211 and the resulting power receiver output power. This power transfer function can then be used to directly calculate a reference value for the desired parameter from the load power from the power receiver.

[0162] The power transfer function is therefore calculated from power receiver setting data transmitted from the power receiver, and determining the power transfer function may specifically include determining a coupling coefficient between the power transmitter coil and the power receiver coil.

[0163] More specifically, the power receiver configuration data can be used to fill in the unknown values ​​Cs, Ls, Rs, and Rl in Figure 8. The power transmitter configuration data can be used to fill in Rp, Cp, and Lp. The coupling coefficient determines the shared flux path between Ls and Lp. This can be estimated / calculated using the dimensions of the coil setup. Depending on the coil diameter and the distance between the two, simulations / measurements can be performed to see the effect on the coupling coefficient. A function / lookup table can then be created to output the coupling coefficient for a specific coil dimension and placement. The coupling coefficient can also be measured by disconnecting the load on one side and supplying a voltage / current to the other side. With the load disconnected, no power is transferred, but a voltage is present, which indicates the magnitude of the mutual inductance relative to the self-inductance. For all models, Kirchhoff's laws can be used to derive the transfer function from input voltage to output current / voltage. Based on these values, the power delivered to the load can be determined (and conversely, the drive signal parameters for a particular load can also be determined).

[0164] It will be understood 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 be performed by the same processor or controller. References to specific functional units or circuits should therefore be seen only as references to suitable means for providing the described functionality, rather than to indicative of a strict logical or physical structure or organization.

[0165] 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.

[0166] 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 "comprises" does not exclude the presence of other elements or steps.

[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 the 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 that category, but rather indicates that the feature is equally applicable to other claim categories, as 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 a method claim does not imply that the steps must be performed in that 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. A parameter or value corresponding to another parameter or value may indicate that one parameter / value is believed / expected to result in the other parameter / value; specifically, a parameter / value corresponding to a power level may mean that the parameter / value is believed / expected to result in a power level. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. 1. A power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, comprising: a receiver for receiving a message from the power receiver; an output circuit having a transmitter coil for generating the power transfer signal in response to a drive signal applied to the output circuit; a drive circuit for generating the drive signal; a power loop controller implementing a power control loop for controlling the drive signal to adjust a power level of the power transmission signal, the power control loop being configured to apply changes to the power level of the power transmission signal in response to a power control error message received from the power receiver; and a mode storage device configured to store a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level for the power transmission signal; a mode circuit configured to adapt the drive signal to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to a reference power level of a first power level mode of the plurality of power level modes indicated in the mode request message; and A power transmitter having

2. 10. The power transmitter of claim 1, further comprising: a detection circuit for detecting a power transmission anomaly in response to a comparison between a current power level of the power transmission signal and a reference power level of a current power level mode of the plurality of power level modes.

3. 3. The power transmitter of claim 1, wherein a period for adapting the drive signal to set the power level of the power transmission signal to the first reference value is less than a time constant of the power control loop.

4. 4. The power transmitter of claim 1, wherein the mode circuit is configured to determine the reference power levels for at least some of the plurality of power level modes in relation to at least one of a parameter value of the drive signal and a parameter value of the power transmission signal characteristic during an initialization phase in which the power receiver passes stepwise through the at least some power level modes, and the mode storage device is configured to store the reference power levels for the at least some power level modes.

5. 5. The power transmitter of claim 4, wherein the mode storage device is configured to store a plurality of parameters for at least one power level mode, the plurality of parameters including at least one reference power level representing a power level of the power transmission signal and at least one parameter value for at least one of the drive signal and the transmitter coil signal, the at least one parameter value being a value of the at least one of the drive signal and the transmitter coil signal for a power level of the power transmission signal indicated by a reference power level.

6. The power transmitter of claim 4 , wherein the initialization phase precedes a power transmission phase.

7. 7. The power transmitter of claim 1, wherein the receiver is configured to receive a power receiver setting message from the power receiver, the power receiver setting message having power receiver setting parameters, and the mode circuit is configured to determine the reference power level for at least one power level mode of the plurality of power level modes in response to the power receiver setting characteristics.

8. The power receiver configuration parameters are: Power receiver ID, Power Receiver Type ID, power receiver coil characteristics, Power receiver coil dimension characteristics, Power receiver coil inductance characteristics, 8. The power transmitter of claim 7, comprising at least one of:

9. 9. The power transmitter of claim 7, wherein the mode circuitry is configured to determine a coupling coefficient between the power transmitter coil and a power receiver coil of the power receiver based on the power receiver setting parameters, and to determine the reference power level for the at least one power level mode based on the coupling coefficient.

10. 10. The power transmitter of claim 7, wherein the mode circuitry is configured to determine a power transfer function between at least one of a parameter of the drive signal and a parameter of a transmitter coil signal and an output power of the power receiver based on the power receiver setting parameters, and to determine the reference voltage level for the at least one power level mode based on the power transfer function.

11. 11. The power transmitter of claim 1, wherein the mode storage device is configured to store sets of power level modes for different power receivers, and the mode circuit is configured to select the set of power level modes in response to an ID indicator received from the power receiver.

12. 12. The power transmitter of claim 1, wherein the mode request message comprises a timing indicator, and the mode circuit is configured to adapt a timing for setting the power level of the power transmission signal in response to the timing indicator.

13. The power transmitter of claim 1 , wherein the mode request message is received during a power transmission phase.

14. 1. A method of operating a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, the power transmitter having an output circuit having a transmitter coil for generating the power transmission signal in response to a drive signal applied to the output circuit, the method comprising: receiving a message from the power receiver; generating the drive signal; operating a power control loop that controls the drive signal to adjust a power level of the power transmission signal, the power control loop being configured to apply changes to the power level of the power transmission signal in response to a power control error message received from the power receiver; storing, in a mode storage device, a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level for the power transmission signal; adapting the drive signal to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to a reference power level for a first power level mode of the plurality of power level modes indicated in the mode request message; A method having the following.

15. 1. A wireless power transfer system having a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transfer signal, the power transmitter comprising: a receiver for receiving a message from the power receiver; an output circuit having a transmitter coil for generating the power transfer signal in response to a drive signal applied to the output circuit; a drive circuit for generating the drive signal; a power loop controller for controlling the drive signal to adjust a power level of the power transmission signal, the power control loop configured to apply changes to the power level of the power transmission signal in response to a power control error message received from the power receiver; and a mode storage device configured to store a plurality of power level modes for the power receiver, each power level mode being associated with a reference power level for the power transmission signal; a mode circuit configured to adapt the drive signal to set the power level of the power transmission signal to a first reference value in response to receiving a mode request message, the first reference value corresponding to a reference power level of a first power level mode of the plurality of power level modes indicated in the mode request message; and A wireless power transmission system comprising:

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