Wireless Power Transfer

Abstract

The power transmitter 101 provides power to the power receiver 105 via a power transmission signal generated by a drive signal provided to the power transmitting coil 103. A first controller 209 of the power transmitter 101 controls parameters of the drive signal according to a first mode, the first mode including executing a power control loop to control the power transmission signal in response to a power control error message received from the power receiver 105. A second controller 211 controls parameters of the drive signal according to a second mode, the second mode including setting parameters of the drive signal in response to at least one power transmission signal set point received from the power receiver 105. A circuit 213 selects between a first operating mode and a second operating mode in response to a power transmission control mode request received from the power receiver 105, and a timing circuit 215 modifies timing parameters for a communication time interval between these two operating modes.

Description

[Technical field]

[0001] The present invention relates to wireless power transfer, particularly but not exclusively to wireless power transfer for high power kitchen appliances. [Background technology]

[0002] Most electronic products today require dedicated electrical contacts to receive power from an external source. However, this is often impractical, requiring the user to physically insert a connector or otherwise establish physical electrical contact. Power requirements also typically vary widely, and since most devices now have their own dedicated power source, a typical user will have many different power sources, each dedicated to a specific device. Using an internal battery could potentially eliminate the need for a wired connection to a power source during use, but this is only a partial solution, as the battery still needs to be charged (or replaced). Using a battery can also significantly increase the weight, and potentially the 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 transmitting inductor in a transmitter to a receiving coil in an individual device.

[0004] Power transfer via magnetic induction is a well-known concept and is often applied to transformers with tight coupling between the primary transmitting inductor / coil and the secondary receiving coil. By separating the primary transmitting coil and the secondary receiving coil into 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 establishing wires or physical electrical connections. In fact, this may allow for external charging or powering of a device by simply placing the device next to or on top of the transmitting coil. For example, a transmitting device may have a horizontal surface on which the device can simply be placed for powering.

[0006] Moreover, such wireless power transmission configurations may be advantageously designed to allow the 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 that is compliant with the Qi specification to be used with a power receiving device that is also compliant with the Qi specification, without both devices having to be from the same manufacturer and without both devices having to be designed specifically for each other. The Qi standard further includes features to allow the operation to be tailored to a specific power receiving device (e.g., depending on the specific power drain).

[0007] The Qi specification has been developed by the Wireless Power Consortium and further information can be found, for example, on their website (http: / / www.wirelesspowerconsortium.com / index.html), where, among other things, the laid down specification documents can be found.

[0008] Building on the success of the Qi standard, the Wireless Power Consortium is also developing the Ki Cordless Kitchen standard for higher power applications, specifically kitchen appliances, which extends Qi to enable power transfer above 2 kW while enabling economical and flexible operation.

[0009] Cordless kitchen appliances are powered by wirelessly transmitting power from a transmitting coil to a receiving coil. The transmitting coil is driven by an inverter capable of delivering 0-2500W of power to a resonant circuit including the transmitting coil. Before the inverter is activated, a communication channel is established between the transmitter and receiver. Once communication is established and identification of the two devices has been performed, the transmitter can begin transmitting power to the receiver.

[0010] A wide variety of transmitters and receivers are assumed. For example, coil sizes, inductions, and loads may vary widely. Additionally, the placement of the receiver relative to the transmitter may vary, which may result in substantial changes in coupling between the power transmission coils. Thus, system parameters and conditions for power transfer may vary widely.

[0011] Furthermore, operating conditions, especially power transfer levels, can vary widely. For example, a powered device may have several operating modes. For example, an air fryer device may experience load steps of 50 to 1200 W by switching the heating element on and off, which occurs repeatedly during operation to maintain a constant temperature.

[0012] Devices may also present non-linear loads, for example a powered device may have a motor (e.g. a food processor) instead of a resistive component, which can result in a completely different system response and has significant implications for the design of the control system.

[0013] To tailor operation to various characteristics and parameters, such wireless power transfer systems typically implement a power control loop that steers the system to an appropriate operating point. In such a power control loop, the receiver periodically and frequently (maximum interval of 250 ms for Qi) transmits a power error message that instructs the transmitter to increase or decrease the power level of the generated power transfer signal. The power error message may be generated by the receiver based on a comparison of the received power with a desired received power. The transmitter may dynamically increase or decrease power upon request, allowing the receiver to control operation to the desired operating point.

[0014] However, while such power control approaches tend to provide good performance in many cases, they are not optimal in all situations. They tend to be complex operations requiring high signaling rates. Furthermore, they tend to provide suboptimal dynamic performance in some cases, and the dynamic design is often a trade-off between noise performance and transient response.

[0015] In particular, many envisioned Ki appliances, such as heating appliances (e.g., kettles), are envisioned as very low-cost appliances, and to achieve such low cost it is desirable to keep the required functionality to a minimum as much as possible. However, conventional power control loop approaches tend to be relatively complex, requiring communication capabilities to support relatively high data rates, as well as appropriate measurement and processing capabilities to measure operating conditions and generate appropriate power error messages. This increases the cost of the device, which can hinder the development of very low-cost devices.

[0016] Communication between the transmitter and receiver in a wireless power transfer system is important for efficient operation of the system. To support efficient wireless power transfer, wireless power transfer systems, such as systems based on Qi and Ki, utilize substantial communication between the transmitter and receiver. Initially, Qi only supported communication from the receiver to the transmitter using load modulation of the power transmission signal. However, the evolution of the standard introduced bidirectional communication, and many functions are supported by the communication exchange between the receiver and transmitter. In many systems, communication from the transmitter to the receiver is performed by modulating the power transmission signal. Examples of wireless power transfer systems utilizing communication between the receiver and transmitter are disclosed in US2018 / 323647A1, WO2021 / 048019A1, and US2018 / 323648A1.

[0017] However, this tends to be less suitable for high power levels, and so the Ki et al. system uses a communication function that is not dependent on the power transmission signal and does not use the power transmission signal as a carrier wave modulated by data. In particular, communication between the transmitter and receiver may be achieved by a short-range communication system, for example, specifically by using communication technology based on NFC (Near Field Communication).

[0018] The use of dedicated communication capabilities can often provide improved performance, for example, providing faster communication with more reliable communication and less impact on ongoing power transfer.

[0019] The receiver may, in many embodiments, include an NFC communication capability that provides communication capabilities similar to an NFC contactless smart card. An NFC contactless smart card is typically a small device for contactless communication using electromagnetic coupling between a tuned antenna in a reader and a resonant circuit in a receiver. In many cases, the smart card is a passive device that is powered by a signal induced in the resonant circuit. Similarly, the receiver's NFC communication capability may potentially be powered (e.g., at power up) by an NFC carrier.

[0020] However, while the use of dedicated communication capabilities such as NFC may provide advantageous performance and operation in many cases, it may not be optimal in all cases.

[0021] Wireless power transmission systems may generate electromagnetic interference, and to achieve electromagnetic compatibility with other devices, it is necessary that this electromagnetic interference is not excessive. Electromagnetic interference caused by the power transmission signal may not only interfere with other electric devices, but also with the power transmission device itself. In particular, electromagnetic interference caused by the power transmission signal may interfere with communication functions (e.g., communication functions provided by NFC communication functions).

[0022] Typically, power transmitters are subject to strict electromagnetic interference restrictions, often limited by frequency masks that indicate acceptable electromagnetic interference levels depending on frequency. However, meeting such electromagnetic interference requirements can be very difficult, and electromagnetic interference can occur, especially when the power transmission signal is not at the same level continuously. For example, repeatedly switching off the power transmission signal tends to increase substantial harmonic content, which in many cases may not meet electromagnetic compatibility requirements. Summary of the Invention

[0023] Therefore, it would be advantageous to improve the operation of power transfer systems, in particular to increase flexibility, reduce cost, reduce complexity, improve power transfer system operation, improve fit, improve dynamic performance, improve compatibility, backward compatibility, reduce signaling requirements, reduce receiver measurement requirements, improve communication performance, reduce electromagnetic interference, improve electromagnetic compatibility, support for lower cost devices, and / or improve performance.

[0024] SUMMARY OF THE DISCLOSURE Accordingly, the Invention seeks to preferably mitigate, reduce or eliminate one or more of the above mentioned disadvantages singly or in any combination.

[0025] 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 including a transmitting coil for generating the power transmission signal, a driver for generating a drive signal for the transmitting coil for generating the power transmission signal, the driver generating the drive signal using a power transmission time interval during which the power transmission signal transmits power to the power receiver and a communication time interval during which a power of the power transmission signal is reduced relative to the power transmission time interval, a receiver for receiving messages from the power receiver during the communication time interval, a first controller for controlling parameters of the drive signal according to a first operating mode, the first operating mode including executing a power control loop to control power characteristics of the power transmission signal in response to power control error messages received from the power receiver, the maximum duration between power control error messages being 300 milliseconds or less, and a first controller for controlling parameters of the drive signal according to a second operating mode. the second controller controlling a power transmission control mode of the power transmitter, the second mode of operation including setting a parameter of the drive signal in response to at least one power transmission signal set point received from the power receiver, the power transmission signal set point indicating a target power characteristic of the power transmission signal, the maximum duration between the power transmission signal set points being one second or more, and the second mode of operation including not executing a power control loop that controls the drive signal in response to a power control error message received from the power receiver; circuitry that selects between the first and second operating modes in response to a power transmission control mode request received from the power receiver; and a timing circuit that modifies a timing parameter for a communication time interval depending on whether the power transmitter is operating in the first or second operating mode, the timing parameter being a parameter selected from the group consisting of a duration of the communication time interval and a frequency of the communication time interval.

[0026] The present invention may provide improved performance in many embodiments and may provide an overall improved power transfer operation in many systems and embodiments. This may, among other things, enable a transmitter to dynamically support both relatively high complexity receivers that require precise power delivery and low complexity receivers that do not require tightly controlled or highly accurate power delivery. This approach may enable support of very low complexity receivers, thereby enabling development and production of low cost devices. This approach may, among other things, enable support of very low cost heating devices, such as kettles, pans, or similar kitchen appliances. For example, low cost heating devices may be effectively supported without the need to include dedicated electrical load signal measurements or complex reporting mechanisms. For example, a heating device may be supported without any measurements at all, or may, for example, use only simple temperature measurements to switch heating on or off depending on the current heating temperature.

[0027] In many embodiments, this approach may provide improved support for different types of receivers and loads. In particular, in many embodiments, the first operating mode may be well suited for powering non-linear loads, such as some motors, while the second operating mode may provide highly advantageous performance for linear loads, while providing low complexity and / or low cost.

[0028] The present invention may provide improved communication in many embodiments, and in particular may provide improved communication between a power transmitter and a power receiver using communication channels that do not support power transmission signals as a carrier. The present invention may provide improved power transmission in many embodiments.

[0029] The present invention may, in many embodiments, provide improved adaptation to different communication requirements / priorities in different modes. In many embodiments, electromagnetic interference may be reduced as a result. For example, when the power level is high, the transmitter may operate in a second operating mode in which the timing circuitry adapts timing parameters such that electromagnetic interference is lower. In many embodiments, the timing circuitry may control the timing parameters such that harmonics of the recurring communication time intervals are reduced.

[0030] This approach often achieves improved performance by improving the trade-off between interference mitigation / prevention and other adverse effects.

[0031] In some embodiments, the power transmitter (eg, specifically the driver) may be configured to not generate a drive signal and / or a power transmission signal during the communication time interval.

[0032] The maximum duration between power transmission signal set points that is 1 second or greater may be the longest possible duration between power transmission signal set points received from the power receiver. The duration between power transmission signal set points received from the power receiver may exceed 1 second, and thus the power receiver may be configured to transmit power transmission signal set points with durations between power transmission signal set points that are greater than 1 second, and often 2 seconds, 5 seconds, 10 seconds, or 1 minute.

[0033] The maximum duration between power control error messages, which is 300 ms or less, may be the longest possible duration between power control error messages received from the receiver. The duration between power control error messages received from the receiver may not exceed 300 ms, and thus the receiver may be configured to transmit power control error messages with a duration between power control error messages not exceeding 300 ms.

[0034] In many embodiments, the transmitter is configured not to receive and / or ignore received power control error messages during the second mode of operation. In many embodiments, the transmitter is configured to perform power transmission without requiring a power control error message during the second mode of operation.

[0035] The drive signal may use power transfer time intervals and communication time intervals during both the first and second operating modes.

[0036] According to an optional feature of the invention, the driver uses repeating time frames for the power transfer signal, with each repeating time frame including at least one power transfer time interval and at least some of the repeating time frames including at least one communication time interval.

[0037] This may improve and / or facilitate operation in many embodiments, and in many embodiments, may facilitate cooperation between the communications functions of the transmitter and the receiver.

[0038] According to an optional feature of the invention, the timing circuit allocates a greater proportion of the recurring time frame to the at least one communication time interval in the first mode of operation than in the second mode of operation.

[0039] This may improve and / or facilitate operation in many embodiments, which may improve compliance with communication requirements and characteristics during the first and second modes of operation while potentially reducing electromagnetic interference during the second mode of operation.

[0040] According to an optional feature of the invention, the timing circuit includes communication time intervals in all of the recurring time frames during the first mode of operation, and includes communication time intervals in only a subset of the recurring time frames during the second mode of operation.

[0041] This may improve and / or facilitate operation in many embodiments, in particular, it may make the control and adaptation of communication resources available to the transmitter and receiver in different operating modes less complex, more practical, and / or more robust.

[0042] According to an optional feature of the invention, the timing circuit is configured to set the duration of the communication time interval higher in the first mode of operation than in the second mode of operation.

[0043] This may improve and / or facilitate operation in many embodiments, in particular, it may make the control and adaptation of communication resources available to the power transmitter and power receiver in different operating modes less complex, more practical, and / or more robust. According to an optional feature of the invention, the timing circuit is configured to set a higher duty cycle of the communication time interval in the first mode of operation than in the second mode of operation.

[0044] This may improve and / or facilitate operation in many embodiments, in particular, it may make the control and adaptation of communication resources available to the power transmitter and power receiver in different operating modes less complex, more practical, and / or more robust.

[0045] According to an optional feature of the invention, the timing circuit is configured to set a higher frequency of the communication time intervals in the first mode of operation than in the second mode of operation.

[0046] This may improve and / or facilitate operation in many embodiments, in particular, it may make the control and adaptation of communication resources available to the transmitter and receiver in different operating modes less complex, more practical, and / or more robust.

[0047] According to an optional feature of the invention, the driver is powered by a fluctuating power signal, and the transmitter aligns a central instant of the communication time interval with a power minimum of the fluctuating power signal.

[0048] This may provide improved performance and / or operation in many embodiments, in particular reducing the impact of interruptions on the power transmission signal and / or reducing electromagnetic interference (including, in particular, electromagnetic interference resulting from or adversely affected by the presence of communication time intervals).

[0049] According to an optional feature of the invention, in a first operating mode, the transmitter terminates power transmission when it is detected that a power control error message has not been received for a duration exceeding a first threshold, and in a second operating mode, the transmitter does not cease power transmission when a power transmission signal set point has not been received for a duration exceeding a second threshold, the second threshold being at least twice the first threshold.

[0050] In many embodiments, the first threshold may be less than or equal to 300 ms, 500 ms, 1 sec, 5 sec, etc. In many embodiments, the second threshold may be greater than or equal to 1 sec, 5 sec, 30 sec, 1 min, 10 min, etc.

[0051] According to an optional feature of the invention, the power control error message indicates a desired relative change in a power characteristic of the power transmission signal, and the set point message indicates a desired absolute value of the target power characteristic.

[0052] This may provide advantageous operation in many embodiments, and in particular may allow for efficient, low complexity operation in both modes of operation in many embodiments.

[0053] In some embodiments, the duration between power control error messages is less than or equal to 300 milliseconds, and the maximum duration between power transmission signal setpoints is greater than or equal to 10 seconds.

[0054] These operating modes may have substantially different temporal characteristics. The maximum duration between power transmission signal setpoints may be a duration during which power transmission is guaranteed to be maintained without receiving a new power transmission signal setpoint. The transmitter may be configured to operate in the second operating mode without receiving a new power transmission signal setpoint for a duration of 10 seconds or more.

[0055] In many embodiments, the maximum duration between power transmission signal setpoints is 30 seconds, 1 minute, or even 5 minutes or more.

[0056] In some embodiments, the time constant of the power control loop and the time constant for varying a parameter of the drive signal in response to at least one power transmission signal setpoint differ by at least a factor of 2, 5, or even 10.

[0057] These operating modes may have substantially different temporal characteristics, which may result in improved performance in many embodiments.

[0058] In some embodiments, the second controller implements a drive signal control loop that includes an estimator for generating a power level indication of the power transmission signal, a comparator for generating an error signal in response to comparing the power level indication to a reference power determined from at least one power transmission signal set point, and an adapter for adapting parameters of the drive signal in response to the error signal.

[0059] This may result in suitable operation and / or performance and / or implementation in many embodiments.

[0060] In many embodiments, the time constant of the drive signal control loop is less than or equal to half the update rate of at least one power transfer signal set point.

[0061] In many embodiments, the duration between received power transmission signal setting of at least one power transmission signal setting is 5 seconds or more.

[0062] In some embodiments, during the second mode of operation, parameters of the drive signal are changed only in response to receiving at least one power transmission signal setpoint.

[0063] This can result in improved performance in many embodiments.

[0064] In many embodiments, the parameter of the drive signal is at least one of a current, a voltage, a phase, a duty cycle, and a frequency.

[0065] In some embodiments, the at least one power transmission signal setpoint indicates a target power level for the power transmission signal.

[0066] This may provide particularly advantageous performance in many embodiments and cases, often allowing for low complexity yet highly reliable operation.

[0067] In many embodiments, the at least one power transmission signal setting value indicates at least one of a target power level of the power transmission signal, a target current level of the drive signal, a target voltage level of the drive signal, a target phase of the drive signal, a target duty cycle of the power transmission signal, and a target frequency of the power transmission signal.

[0068] According to an optional feature of the invention, at least one power transmission signal setpoint is linked to a valid time interval, and the second controller sets a parameter of the drive signal to a nominal value at the end of the valid time interval.

[0069] According to an optional feature of the present invention, there is provided a wireless power transfer system including the above-described power transmitter and a power receiver, the power receiver including a coil for extracting power from a power transmission signal, a power circuit for supplying the extracted power from the power transmission signal to a load, and a transmitter for transmitting at least one power transmission signal setting value to the power transmitter during a communication time interval.

[0070] In some embodiments, the receiver transmits at least one power transmission signal setting that indicates a predetermined target power characteristic of the power transmission signal.

[0071] According to an optional feature of the invention, the power receiver transmits at least one power transmission signal setting value as indicative of a target power characteristic of the power transmission signal, independent of measurements of the electrical signal provided to the load.

[0072] In some embodiments, the power receiver is configured to transmit a power transmission signal setpoint in response to a measurement of the electrical signal provided to the load.

[0073] In many embodiments, the receiver operates in multiple loading modes, and when the receiver switches loading modes, it sends new power transmission signal settings to the transmitter.

[0074] According to an optional feature of the invention, the receiver operates in multiple load modes, and the receiver does not send new power transmission signal settings to the transmitter unless the receiver switches load modes.

[0075] A power receiver for wirelessly receiving power from a power receiver via an inductive power transmission signal may be provided, the power receiver comprising: a receiver coil for extracting power from the power transmission signal, a power circuit coupled to the receiving coil for providing power from the receiving coil to a load, and a transmitter for transmitting a message to the power transmitter, the transmitter transmitting a power transmission control mode request to the power transmitter, the power transmission control mode request indicating a request for the power transmitter to control a parameter of a drive signal according to a first operating mode or a second operating mode, the first operating mode including executing a power control loop for controlling power characteristics of the power transmission signal in response to a power control error message received from the power receiver, and the second operating mode including setting a parameter of the drive signal in response to at least one power transmission signal set value received from the power receiver, the power transmission signal set value indicating a target power characteristic of the power transmission signal.

[0076] In many embodiments, the transmitter also transmits a power transmission signal setting to the transmitter.

[0077] According to one aspect of the invention, there is provided a method of operating a power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, the power transmitter including a transmitting coil for generating the power transmission signal, the method including: generating a drive signal for the transmitting coil for generating the power transmission signal, the drive signal being generated using a power transmission time interval during which the power transmission signal transmits power to the power receiver and a communication time interval during which a power of the power transmission signal is reduced relative to the power transmission time interval; receiving a message from the power receiver during the communication time interval; and controlling a parameter of the drive signal according to a first operating mode, the first operating mode including executing a power control loop to control a power characteristic of the power transmission signal in response to a power control error message received from the power receiver, the maximum duration between power control error messages being less than or equal to 300 milliseconds; and controlling the drive signal according to a second operating mode. controlling a parameter of the drive signal in response to at least one power transmission signal set point received from the power receiver, the power transmission signal set point indicating a target power characteristic of the power transmission signal, the maximum duration between the power transmission signal set points being one second or more, and the second operating mode including not executing a power control loop that controls the drive signal in response to a power control error message received from the power receiver; selecting between the first operating mode and the second operating mode in response to a power transmission control mode request received from the power receiver; and modifying a timing parameter for a communication time interval depending on whether the power transmitter is operating in the first operating mode or the second operating mode, the timing parameter being a parameter selected from the group consisting of a duration of the communication time interval and a frequency of the communication time interval.

[0078] A method of operation of a power receiver wirelessly receiving power from a power receiver via an inductive power transmission signal may be provided, the power receiver comprising a receiver coil for extracting power from the power transmission signal, a power circuit coupled to the receiving coil for providing power from the receiving coil to a load, and a transmitter for transmitting a message to the power transmitter, the method including transmitting, by the transmitter, a power transmission control mode request to the power transmitter, the power transmission control mode request indicating a request for the power transmitter to control a parameter of a drive signal according to a first operating mode or a second operating mode, the first operating mode including executing a power control loop for controlling power characteristics of the power transmission signal in response to a power control error message received from the power receiver, and the second operating mode including setting a parameter of the drive signal in response to at least one power transmission signal set value received from the power receiver, the power transmission signal set value indicating a target power characteristic of the power transmission signal.

[0079] These and other aspects, features and advantages of the invention will be elucidated and elucidated with reference to the embodiment(s) described hereinafter. [Brief description of the drawings]

[0080] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: [Figure 1] FIG. 1 illustrates example elements of a power transfer system according to some embodiments of the present invention. [Diagram 2] FIG. 2 illustrates example elements of a transmitter according to some embodiments of the present invention. [Diagram 3] FIG. 3 illustrates example elements of a receiver according to some embodiments of the present invention. [Figure 4] FIG. 4 illustrates example elements of a power transfer path according to some embodiments of the present invention. [Diagram 5] FIG. 5 illustrates example elements of a power transmission path according to some embodiments of the present invention. [Figure 6] FIG. 6 illustrates example elements of a power transfer path according to some embodiments of the present invention. [Figure 7]FIG. 7 illustrates example elements of a power transfer path according to some embodiments of the present invention. [Figure 8] FIG. 8 shows an example of a repeating time frame of a power transmission signal. [Figure 9] FIG. 9 shows an example of a half-bridge inverter for a transmitter. [Figure 10] FIG. 10 shows an example of a full-bridge inverter for a transmitter. [Figure 11] FIG. 11 illustrates an example of a power transmission signal according to some embodiments of the present invention. [Figure 12] FIG. 12 illustrates example communication time intervals, foreign object detection time intervals, and drive signals for a transmitter according to some embodiments of the present invention. [Figure 13] FIG. 13 illustrates an example of electromagnetic interference and interference requirements for a power transmitter according to some embodiments of the present invention. [Figure 14] FIG. 14 illustrates an example of electromagnetic interference and interference requirements for a transmitter according to some embodiments of the present invention. [Figure 15] FIG. 15 illustrates example communication time intervals, foreign object detection time intervals, and drive signals for a transmitter according to some embodiments of the present invention. [Figure 16] FIG. 16 illustrates an example of electromagnetic interference and interference requirements for a transmitter according to some embodiments of the present invention. [Figure 17] FIG. 17 illustrates example communication time intervals, foreign object detection time intervals, and drive signals for a transmitter according to some embodiments of the present invention. [Figure 18] FIG. 18 illustrates an example of electromagnetic interference and interference requirements for a power transmitter according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0081] The following description focuses on embodiments of the invention that are applicable to wireless power transfer systems that utilize power transfer techniques as known from the Qi specification, however, it will be appreciated that the invention is not limited to this application and may be applied to many other wireless power transfer systems.

[0082] 1 illustrates an example of a power transfer system according to some embodiments of the present invention. The power transfer system comprises a transmitter 101 including (or coupled to) a transmitting coil / inductor 103. The system further comprises a receiver 105 including (or coupled to) a receiving coil / inductor 107.

[0083] The system provides an electromagnetic power transmission signal that may inductively transmit power from the transmitter 101 to the receiver 105. Specifically, the transmitter 101 generates an electromagnetic signal that is propagated as a magnetic flux by a coil or inductor 103. The power transmission signal may correspond to an electromagnetic force transmission component that represents the energy transfer from the transmitter to the receiver, and may be considered to correspond to a component of the generated electromagnetic field that transfers power from the transmitter to the receiver. For example, if there is no load on the receiver coil 107, the receiver does not extract power (except for losses) from the generated electromagnetic field. In such a case, the power level of the power transmission signal will be zero (except for losses), although the driving of the transmitter coil 103 may generate an electromagnetic field that may be of high strength in some cases. In some situations where a foreign object is present, the power transmission signal may be considered to include a component that corresponds to the power transfer to the foreign object, and thus the power transmission signal may be considered to correspond to the power extracted from the electromagnetic field generated by the transmitter.

[0084] The power transmission signal may typically have a frequency of about 20 kHz to about 500 kHz, and often for Qi-enabled systems may typically be 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). Since the transmitting coil 103 and the receiving coil 107 are loosely coupled, the receiving coil 107 picks up (at least a portion of) the power transmission signal from the transmitter 101. Thus, power is transmitted from the transmitter 101 to the receiver 105 via wireless inductive coupling from the transmitting coil 103 to the receiving coil 107. The term power transmission signal is primarily used to refer to the inductive signal / magnetic field between the transmitting coil 103 and the receiving coil 107 (magnetic flux signal), but may also be considered and may be used to refer to an electrical signal provided to the transmitting coil 103 or picked up by the receiving coil 107.

[0085] The receiver 105 in this example is specifically a receiver that receives power via a receiving coil 107. However, in other embodiments, the receiver 105 may include a metallic element, such as a metallic heating element, in which case the power transmission signal directly induces eddy currents, thus directly heating the metallic element.

[0086] The system is configured to transmit significant power levels, and specifically, in many embodiments the 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 may typically be in the power range of 1-5 W for low power applications (basic power profile), up to 15 W for Qi specification version 1.2, up to 100 W for high power applications such as power tools, laptops, drones, and robots, and potentially greater than 100 W and up to greater than 1000 W for very high power applications such as kitchen applications.

[0087] The operation of the transmitter 101 and receiver 105 is described below with specific reference to embodiments that generally conform to the Qi specification (except for modifications and enhancements described (or resulting) herein) or are suitable for the High Power Kitchen specification being developed by the Wireless Power Consortium. In particular, the transmitter 101 and receiver 105 may conform to or substantially correspond to elements of the Qi specification version 1.0, 1.1 or 1.2, or the Ki Cordless Kitchen specification (except for modifications and enhancements described (or resulting) herein).

[0088] FIG. 2 illustrates an example of a power transmitter according to some embodiments of the present invention.

[0089] The transmitter 101 includes a driver 201 capable of generating a drive signal that is provided to the transmitting coil 103, which in turn generates an electromagnetic power transfer signal that provides for the transfer of power to the receiver 105. The power transfer signal is provided during a power transfer phase.

[0090] In this example, the sending coil 103 is part of a tank circuit. In a specific example, the tank circuit is formed by the sending coil 103 and the sending capacitor 203 coupled in parallel to form a parallel resonant / tank circuit. It will be appreciated that in many other embodiments, the sending coil 103 may be part of a series resonant / tank circuit.

[0091] As is well known to those skilled in the art, the driver 201 may include an output circuit in the form of an inverter, typically formed by driving a full or half bridge.

[0092] The transmitter 101 further comprises a transmitter controller 205 configured to control the operation of the transmitter 101 according to a desired operating principle.

[0093] To receive data and messages from the receiver 105, the transmitter 101 comprises a first communicator 207 configured to receive data and messages from the receiver 105 (as will be appreciated by those skilled in the art, a data message may provide one or more information bits). In this embodiment, the receiver 105 is configured to load modulate the power transmission signal generated by the transmitting coil 103, and the first communicator 207 is configured to sense variations in the voltage and / or current of the transmitting coil 103 and demodulate the power transmission signal based thereon. Those skilled in the art will be aware of the principles of load modulation, e.g., those used in Qi wireless power transfer systems, and therefore these will not be described in further detail.

[0094] As will be familiar to those skilled in the art, in many embodiments the first communicator 207 may also be configured to transmit data to the receiver 105, for example, by modulating the power transmission signal.

[0095] In the specifically described exemplary embodiment, the communication is performed using another communication channel, which may be realized using another communication coil, or using the transmitting coil 103. For example, near field communication (NFC) may be implemented, or a high frequency carrier wave (e.g., a carrier wave having a frequency of 13.56 MHz) may be superimposed on the power transmission signal. In many embodiments, the first communicator 207 may be an NFC or RFID card reader.

[0096] It will be appreciated that these are merely examples and that any means or functionality for communicating messages / data between the transmitter and receiver (in either direction) may be used.

[0097] FIG. 3 illustrates some example elements of the receiver 105.

[0098] The receiver coil 107 is coupled to a receiver controller 301, which couples the receiver coil 107 to a load 303 (i.e., a switchable load 305) via a switch 305. The receiver controller 301 includes a power control path that converts the power extracted by the receiver coil 107 into a supply suitable for the load 303. Additionally, the receiver controller 301 may include various receiver controller functions necessary to perform a power transfer, in particular functions necessary to perform a power transfer according to the Qi specification.

[0099] In many, but not all, embodiments, the receive coil 107 may be part of a tank / resonant circuit and may be coupled in parallel or series with a capacitor. Thus, in many embodiments, the power transfer may be a resonant power transfer between resonant circuits.

[0100] To support communication from the receiver 105 to the transmitter 101, the receiver 105 includes a second communicator 307. The second communicator 307 may specifically be a load modulator configured to vary the load of the receiving coil 107 in response to data to be transmitted to the transmitter 101. As known to those skilled in the art, the load variation is then detected and demodulated by the transmitter 101. As known to those skilled in the art, the second communicator 307 may further be configured to receive data from the transmitter 101, for example by demodulating the modulation of the power transmission signal.

[0101] In many embodiments, the second communicator 307 is configured to communicate without using a power transmission signal and may in particular be for a separate communication system, for example an NFC communication unit.

[0102] Specifically, the first communicator 207 and the second communicator 307 may be matching / complementary communication functions configured to communicate with each other.

[0103] The system is configured to control the drive signal such that the power transmission signal achieves the proper operating parameters / characteristics and the power transmission operates at the proper operating point. In practice, the system is configured to operate in a number of different modes that use different approaches to control the drive signal and the power transmission signal. Furthermore, the operating mode can be selected by the receiver, which can send a message that controls the transmitter to operate in the selected mode.

[0104] The transmitter 101 comprises a first controller 209 coupled to the first communicator 207 and the driver 201 (and possibly other functionality such as the transmit controller 205). The first controller 209 is configured to control parameters of the drive signal according to a first mode of operation, in which the system and the transmitter execute a power control loop that controls the power characteristics of the power transmission signal in response to a power control error message received from the receiver.

[0105] At regular, and typically frequent, intervals, the receiver transmits a power control error message to the transmitter. As an example, the receiver 105 may include functionality to support a power control loop, which may include, for example, the receiver controller 301 continuously monitoring the power or voltage of the load signal supplied to the load and detecting whether it is higher or lower than a desired value. The receiver may generate a power control error message at regular intervals requesting that the power level of the power transmission signal be increased or decreased, and transmit this power control error message to the transmitter (using the communication channel formed by the first and second communicators 209, 307).

[0106] Upon receiving the power control error message from the power receiver, the message is forwarded to the first controller 209, which can determine how to modify the drive signal parameters to increase or decrease the power level of the power transmission signal according to the request. If the power transmission is operating in the first mode, the first controller 209 can control and adapt the drive signal parameters accordingly.

[0107] In this first operating mode, therefore, a power control loop is used which controls the power characteristics of the power transmission signal so as to obtain a desired operating point at the receiver.

[0108] A power control loop operating in the first mode of operation may, in some embodiments, be a power control loop in accordance with the requirements and specifications of the Qi or Ki kitchen appliance specifications.

[0109] The transmitter 101 of Fig. 2 can also operate in a second mode of operation. The transmitter 101 comprises a second controller 211 connected to the first communicator 207 and the driver 201 (and possibly other functions such as the transmit controller 205). The second controller 211 is configured to control parameters of the drive signal according to the second mode of operation. In this second mode of operation, the second controller 211 is configured to set parameters of the drive signal according to a power transmission signal set value received from the receiver, the set value indicating a target power characteristic of the power transmission signal.

[0110] The set point may, for example, indicate a fixed absolute power level of the power transmission signal. Indeed, the power control error message typically indicates a requested relative change, while the set point typically indicates a requested absolute value of the target power characteristic of the power transmission signal. The second controller 211 may then control the drive signal according to this requested fixed absolute power level, for example setting the voltage, current or frequency such that a power transmission signal having a desired power level is generated. The second controller 211 may then be configured to maintain this constant level.

[0111] The receiver 101 may, for example, transmit a setpoint only at the beginning of power operation, and the transmitter may then continue to maintain this constant power level throughout the power transfer. Thus, in this case, no power control is performed in the second operating mode, and the fixed power level requested by the receiver is maintained.

[0112] Such an approach may be very suitable for some receivers and appliances, in particular low-complexity devices may be implemented without the need to implement power control loop feedback (e.g. a kettle typically only requires approximate power to be induced to the heating element, not a precise or dynamically adapted specific power level).

[0113] Thus, in the second mode of operation, the power control loop is disabled and no adaptation of the drive signal in response to a power control loop error message received from the receiver may be performed. In the second mode of operation, the transmitter may be configured not to use a power control loop that includes the receiver. In the second mode of operation, the power control loop used in the first mode of operation may be disabled and not affect the drive signal.

[0114] The power levels that can be provided in the two operating modes may be the same in many embodiments, or in fact more power may be provided in the second operating mode than in the first operating mode. In many embodiments, the maximum (allowable) power level in the second operating mode is at least as high as the maximum (allowable) power level in the first operating mode. The maximum power level may be limited by many factors, such as the supplied power, component characteristics, safety limits, etc. These factors are independent of the operating mode, and the operating mode may not change the maximum power level that can be provided / extracted by the receiver.

[0115] For each embodiment, different parameters of the drive signal may be adjusted (by the first controller 209 and the second controller 211), and the set value may indicate different characteristics of the power transmission signal. In the following description, we focus on an example where the set value indicates the requested or desired power level of the power transmission signal, and the drive signal parameter to be adjusted is the actual power of the drive signal. In most cases, the power losses (e.g., in the resonant circuit and the transmitting coil 103) are relatively low, and the power level of the power transmission signal can be considered / assumed to be the same as the power level of the drive signal. In other cases, the system may include considering differences between the drive signal parameters and the power transmission signal characteristics when determining the drive signal parameter value. For example, the second controller 211 may compensate by setting the power level of the drive signal higher than that required by the set value, taking into account losses occurring in the output circuit. For example, it may be set 10% higher, or a dedicated function (e.g., implemented as a look-up table populated by a calibration process) may be used to convert the set value to an appropriate target value of the drive signal parameter / power level.

[0116] The transmitter further comprises a selection circuit 213 configured to switch the transmitter between a first and a second mode of operation. In this example, the selection circuit 213 is configured to select between the first and second modes by controlling either the first controller 209 or the second controller 211 to be active, and to provide a control signal to the driver to adjust a parameter of the drive signal. In other embodiments, other approaches may be used, such as, for example, selecting between the outputs of the two controllers 209, 211 and coupling only the appropriate output to the driver 201, controlling the driver 201 to only respond to signals from the appropriate controller, etc.

[0117] The selection circuit 213 is coupled to the first communicator 207. The receiver is configured to transmit a power transfer control mode request to the transmitter, the power transfer control mode request indicating a mode of operation requested by the transmitter. In this example, the power transfer control mode request may indicate a request to the transmitter to operate in a first mode of operation or a second mode of operation (it will be understood that in other embodiments more than two modes of operation are possible).

[0118] The selection circuit 213 is configured to select an operation mode indicated by the power transmission control mode request, specifically, the selection of the first or second operation mode to be used for power transmission to the power receiver is performed according to the power transmission control mode request. Thus, in this approach, the power receiver transmits a power transmission control mode request that controls the power transmission signal control operation of the power transmitter.

[0119] This approach potentially allows the transmitter to operate with a variety of different receivers, including more complex receivers and power transfer operations that require precisely controlled power transfer and can support a full power control loop. In addition, it may also support simple receivers that require only approximate power transfer and are less susceptible to power fluctuations. This could potentially support very low-cost receivers, for example, without sacrificing the potential performance that may be offered to more demanding high-end receivers. This approach can provide improved performance that can be tailored efficiently and with low complexity to the specific requirements and priorities of individual power transfer operations and receivers.

[0120] Also, the advantage of this approach is that the power transfer can be adapted to various loads. For example, the first operating mode may be very suitable for both linear and nonlinear loads, e.g. motors, while the second operating mode may be best suited for linear or substantially linear loads. Thus, the second operating mode may be selected and used for linear loads with low complexity operation, e.g. resistive loads. However, even if the nonlinear load is not critical in terms of the required power delivery accuracy, it may be advantageous to select the first operating mode due to the improved compensation of the nonlinearity.

[0121] As a concrete example to illustrate this approach, a cordless kitchen appliance may be powered by wirelessly transmitting power from a transmitting coil 103 to a receiver, where the transmitting coil 103 is driven by a driver / inverter capable of sending 0-2500 W of power to a resonant circuit including the transmitting coil 103. Before the inverter is activated, a communication channel is established between the transmitter and the receiver. Once communication is established and identification of the two devices has been performed, the transmitter can begin transmitting power to the receiver. An equivalent circuit of the power transfer operation is shown in Figure 4.

[0122] A wide variety of transmitters and receivers are possible. For example, coil sizes, inductions, and loads can vary widely. Thus, the system parameters as represented by the equivalent components in Figure 4 vary with specific devices and mechanical structures. Also, the placement of the receiver changes the coupling between the coils (Lp and Ls), which in turn changes the system behavior.

[0123] Additionally, the device may have multiple modes of operation, e.g., several loads may be switched on or off, e.g., a heating element may be turned on and off, resulting in a load step of, e.g., 50W to 1200W.

[0124] Conventional systems have tended to use a power control loop to ensure that the correct operating point is reached. This control loop varies the amount of power sent to the receiver. The received power (or voltage or current) may be measured by the receiver and compared to a reference value to generate an error indication. The receiver may send this error indication to a control system in the transmitter, which may adjust the drive signal to minimize the static error. The error indication is sent as a power control error message. Such control loops have some response time, and internal delays and low pass filtering prevent the loop from reaching the correct operating point immediately.

[0125] The transmitter described with reference to FIG. 2 may be configured to operate with a conventional receiver using such a power control loop during a first mode of operation.

[0126] However, depending on the instrument and application, the speed at which the correct operating point is reached may be very important. Additionally, in some instruments, reaching a specific exact power level may not be as important, and it may be sufficient that the power level provided is within an appropriate range, which may sometimes vary widely.

[0127] For such devices and applications, control of the power transmission signal power may be based on the receiver transmitting a power transmission signal set point that indicates a target power characteristic of the power transmission signal, and the transmitter simply controls the drive signal to provide this power characteristic without implementing the normal full power control loop implemented in the first mode of operation. Thus, in such devices and applications, the transmitter may instead operate in the second mode of operation.

[0128] The receiver can send a power transfer control mode request to the transmitter prior to power transfer to select the preferred control. For example, if the device requires a fast control loop, the received power can be measured in the device and an appropriate power control error message can be sent to the transmitter. If power changes are infrequent and an approximate power delivery is required, the power transfer control can instead be based on the receiver sending a setpoint to the transmitter.

[0129] This approach may offer an opportunity to reduce the cost of the device, since no expensive power measurement and control means are required, making it possible to manufacture very simple devices without including internal measurement circuitry.

[0130] In some embodiments, the operation in the second operation mode may be a substantially static operation. Specifically, the second controller 211 may be configured to change the drive signal parameters only when a power transmission signal setpoint is received from the power receiver. Thus, after receiving the setpoint, the power transmitter may set the drive signal parameters to a fixed value and provide an operating point according to the setpoint until a new setpoint is received.

[0131] In this example, the setpoint may embody a predetermined target power characteristic of the power transmission signal. For example, a power receiver may be designed for a given power level. For example, a heating element of a kettle may be designed for, say, 2 kW of inductive power. Such a power receiver may be configured to transmit a setpoint corresponding to a predetermined power level, and may not include any measurements of current conditions or other considerations. Instead, a less complex approach may be implemented in which, each time such a power receiver initiates a power transmission, the power receiver transmits a setpoint requesting the power transmitter to control its operation to provide the requested power. That is, in this example, each time the kettle initiates a power transmission, it transmits a setpoint requesting a continuous, constant provision of a fixed power of 2 kW. The power transmitter then sets the drive signal parameters to provide a power transmission signal of such power level, typically by controlling the drive signal parameters to be at a 2 kW (or slightly higher) drive signal power level.

[0132] In many static embodiments, the receiver may transmit a setpoint that indicates a target power characteristic that is independent of measurements of the electrical signal provided to the load. Thus, the receiver may generate the setpoint without any consideration or measurement of the electrical load signal, and in fact, in many embodiments, may be completely independent of current conditions or measurements. In such embodiments, the receiver controller 301 may store one or more appropriate setpoints that may be retrieved and transmitted to the transmitter during initialization of the power transfer.

[0133] Figure 5 shows an example of power transfer and control paths that may be present in such an embodiment. Such an approach may be well suited to low complexity kettles, as discussed above, which may simply send a setpoint with a given power request as part of the power transfer setup, and the transmitter will then pursue this power level throughout operation. In many embodiments, the setpoint may simply request that the maximum possible power level be provided.

[0134] In this example, the receiver itself does not contain any measurement electronics, it just transmits a power setpoint signal. This can result in a cheaper device than one that includes measurement circuitry. There can be small steady-state errors in the actual power the device receives, but for heating appliances this is not usually a problem. With such an approach, the effects of changes in system parameters (e.g., changes due to moving the receiver) may not be recognized.

[0135] In some embodiments, the receiver may be configured to operate in multiple load modes. Each load mode may be associated with a different set of parameters of the load signal provided to the load. For example, each load mode may be associated with a different power supplied to the load, a different combination of voltage and current supplied to the load, etc. For example, a kettle may be configured to operate in a high power mode, operate in a low power mode, or be shut off.

[0136] Each of these modes may be associated with a different set point, such as a different target / demand / request power, for the power transmission signal. In such an embodiment, the receiver may transmit a new set point each time the receiver switches to a new loading mode. For example, the receiver controller 301 may store the appropriate set point for each loading mode and, upon switching to a new loading mode, retrieve and transmit the corresponding set point to the transmitter. The transmitter may then adapt to the new set point. Indeed, in many embodiments, a change in the loading signal provided to the load is accomplished via transmission of a new set point and adaptation by the transmitter.

[0137] In many embodiments, the receiver may be configured not to send new power transmission signal settings to the transmitter unless it switches loading modes, for example, the receiver may send new settings each time it switches to a new loading mode, but if the system is operating in the same loading mode, no additional settings are sent.

[0138] The system can thus provide simple static operation and power transfer signal control while at the same time allowing different load modes to be supported with different characteristics.

[0139] In some embodiments, the receiver does not perform measurements of electrical parameters of the load signal supplied to the load, but may adjust its operation in response to measurements of other modalities such as motion, vibration, or temperature.

[0140] For example, as shown in Figure 6, the kettle of Figure 5 may in some embodiments include a thermometer 601 that measures the temperature of the liquid in the kettle. The thermometer 601 is coupled to measurement circuitry 603 that converts the measurement signal into an appropriate data representation that is provided to the receiver controller 301.

[0141] In such cases, the receiver controller 301 may be configured to determine that a new setpoint should be transmitted in response to a measurement of a non-electrical characteristic that meets a criterion. For example, if motion is detected, the receiver controller 301 may transmit a setpoint that switches the power transmission signal to a lower power level such that the risk of unintended induction in other elements is reduced.

[0142] This approach may be combined with a receiver operating in multiple different load modes. For example, if the measurements meet the criteria, the receiver may switch to another load mode and a new setpoint may be sent. As a specific example, a kettle may include a thermometer that measures the temperature of the liquid to be heated. When a new power transfer operation is initiated, the receiver may switch to a maximum load mode and a setpoint indication requesting maximum power may be sent to the transmitter, resulting in a maximum power level of power transfer (e.g., 2 kW). If the thermometer indicates that the boiling point has been reached, the receiver may switch to a low power mode, e.g., a power level of 50 W. When the temperature falls below a predetermined level, e.g., 90° C., the receiver may return to full power and a setpoint requesting maximum power may be sent to the transmitter. In this way, the liquid may achieve heating to a desired temperature while allowing for a very low complexity operation.

[0143] The above approach can be used to support heating devices with especially simple control means. For example, it is desirable to be able to produce a Ki heating device (e.g., a kettle) as a low-cost device to compete with other heating devices (e.g., cheap corded kettles, etc.). To keep the cost very low, it is important to minimize the requirements and features that need to be included. This approach may result in a very low-complexity control mechanism that does not require many features, in particular reducing the measurement and reporting requirements. The latter may be very important, since it may be possible to produce a receiver using, for example, only NFC communication rather than the more expensive Bluetooth communication. Moreover, this support can be provided without sacrificing support for more complex and expensive devices that require precise power control.

[0144] In this approach, such low-cost heating appliances need only communicate a simple, static power request to the transmitter, which processes this and generates a power transmission signal with appropriate characteristics by the transmitter appropriately setting drive signal parameters, for example, using a fast inner drive signal control loop.

[0145] In such a case, the receiver / heating device may simply receive power and perform no other control actions. However, many embodiments may include a low-cost temperature measurement that measures the temperature and simply checks if the measurement reaches a given temperature. When the temperature reaches this level, a new setpoint may be sent, for example, which may correspond to a power off command (the new setpoint is zero output), or may correspond to a low power value, for example.

[0146] Indeed, in many embodiments the power level is fixed (or communicated once, e.g., during initial setup of the device) and the set point may be communicated as a simple binary value, e.g., a set point indication of 1 may result in a power transmission signal having a power level of, e.g., 2000 W, and a set point indication of 0 may result in a power transmission signal having a power level of, e.g., 50 W (or e.g., 0 W).

[0147] In some embodiments, a more dynamic approach may be employed in which the receiver is configured to transmit a power transmission signal setpoint in response to a measurement of the electrical signal provided to the load. The receiver controller 301 may specifically determine an appropriate value for the target power characteristic of the power transmission signal in response to the measurement of the electrical load signal. Thus, in some embodiments, the receiver controller 301 may be configured to transmit a new setpoint indication when the measurement is detected to meet a criterion. Alternatively or additionally, the setpoint, e.g., a requested power level, may be determined based on the measurement.

[0148] An example of such an approach is shown in FIG. 7, where the voltage of the signal provided to the load is measured and used to control the set point transmission.

[0149] In this example, the receiver controller 301 measures the load voltage (e.g., motor voltage) U_Rx and evaluates whether it meets a criterion. Specifically, in many embodiments, the receiver controller 301 can compare the load signal voltage U_Rx to a desired reference level U_Rx_set. If the difference exceeds a given level, the receiver controller 301 can proceed to generate and transmit a new set point indication. For example, if the measured voltage is too low, a higher power level of the power transmission signal can be requested, and if the measured voltage is too high, a lower power level of the power transmission signal can be requested.

[0150] In many embodiments, the second controller 211 may be configured to control the drive parameters by implementing a control loop in the transmitter that uses the received setpoint as a reference or target value, i.e., a target value for a characteristic of the loop is determined based on the setpoint, and the loop is run such that an error signal between this and the current loop parameters is minimized.

[0151] 5 through 7 show examples where the second controller 211 implements such an inner transmitter drive signal control loop.

[0152] In these examples, the drive signal control loop is based on power measurements. The target power level of the control loop is determined as a function of the received set point indication and the power characteristics of the power transmission signal. In many embodiments, the power reference Pset may simply be set to the power level requested for the power transmission signal. An estimator determines the power level indication Pmeas of the power transmission signal. In the examples of Figures 5 to 7, this is based on a power estimate of the drive signal, specifically by measuring the current and voltage of the drive signal generated by the driver 201 and deriving an averaged / low-pass filtered power estimate from the multiplication of these measurements.

[0153] A comparator may then compare the estimated drive signal power Pmeas with a power reference Pset to generate an error signal Perr representing a power level error indication indicative of the difference between the two. The error signal Perr is filtered by a low pass filter PID1 that includes at least one integral. The resulting signal Dcon is the error signal that is provided to an adapter that is configured to modify the power level of the drive signal, in this example by modifying the duty cycle of the drive signal using pulse width modulation (PWM) of the output of driver 201.

[0154] Thus, in some embodiments, the second mode of operation may include the transmitter implementing a local feedback control loop to control the drive signal, and thus the power transmission signal, allowing for accurate and rapid adaptation to a particular set point while potentially reducing the complexity and cost of the receiver.

[0155] In such embodiments, the adaptive performance and operation of the inner transmitter drive signal control loop is typically much faster than any changes or fluctuations that may result from a set point update. In many embodiments, the time constant of the drive signal control loop is less than or equal to half the set point update rate, often ¼, 1 / 10, or 1 / 100. In many applications, the time it takes for the drive signal control loop to adapt to a new set point can be considered substantially instantaneous compared to the timing of operations associated with the new set point.

[0156] Thus, the above approach may enable a single power transmitter to operate in multiple different power transmission signal control modes under the control of the power receiver.

[0157] Typically, the power control loop in the first operating mode is very quick to adapt to variations, while the set point approach in the second operating mode tends to be much slower. In fact, these two approaches are typically used in receivers that require accurate and fast power control, and in receivers that are less susceptible to power variations and inaccuracies and that only undergo slow and infrequent changes (e.g., when changing load modes).

[0158] In practice, in most applications, the time between power control error messages is 300 ms or less (e.g., for Qi or Ki enabled systems, a power control error message must be sent at least every 250 ms), and the maximum time between power transmission signal setpoints is 10 seconds or more, or even 50 or 100 seconds or more. In fact, in many embodiments, the setpoints do not need to be updated, and the maximum time between setpoints may in principle be infinite.

[0159] In contrast, the maximum time between power transmission signal setpoints is 1 second or more, and the transmitter is configured to operate in the second mode of operation for 1 second or more without receiving a power transmission signal setpoint. The transmitter when operating in the second mode of operation is configured to continue power transmission for 1 second or more, typically 5, 10, 60 seconds or more, and indeed indefinitely. Thus, when in the second mode of operation, power transmission continues based on the last received power transmission signal setpoint even if no further power transmission signal setpoints are received for 5, 10, 60 second, and indeed often indefinite intervals.

[0160] In many embodiments, the transmitter may be configured to terminate power transmission when operating in a first mode of operation and detecting that a power control error message has not been received for a time period longer than a first threshold. This first threshold may be 250-300 ms in many applications (e.g., Qi or Ki systems) where a power control error message must be transmitted at least every 250 ms. In some embodiments, a higher threshold may be selected to account for potentially some failed transmissions. In many embodiments, the first threshold may be 250 ms, 300 ms, 500 ms, 1 second, or more.

[0161] In contrast, in the second mode of operation, the transmitter is configured not to terminate power transmission even if no power transmission signal setting is received for a time period longer than a second threshold. The second threshold is at least twice the first threshold, and often at least 10 or 100 times the first threshold. In many embodiments, the transmitter is configured not to terminate power transmission even if no power transmission signal setting is received after the first power transmission signal setting, i.e., even if only one power transmission signal setting is received. Thus, in many embodiments, repeated transmission and reception of power transmission signal setting values ​​is not required in the second mode of operation. Rather, in many embodiments, only an initial power transmission signal setting is required, and the transmitter maintains the corresponding power level until a new power transmission signal setting is received, or, if no further power transmission signal setting values ​​are received, until power transmission operation is terminated or the system switches to the first mode of operation.

[0162] In many embodiments, no power control error message is received in the second mode of operation. In many embodiments, the transmitter may be configured to continue power transmission operations when in the second mode of operation even if no data is received from the transmitter requesting a change in power level. In many embodiments, the second threshold may be 1 second, 10 seconds, 60 seconds, 10 minutes, or more.

[0163] In many embodiments, the time constant of the power control loop and the time constant for changing the drive signal parameters in response to a new set point differ by a factor of at least 2, and often by a factor of at least 5, 10, 20, or 100. In most embodiments, the power control loop is fast responding while the set point approach is substantially static.

[0164] Indeed, in many embodiments, the interval between receipt of transmitted setpoints is 5 seconds, 10 seconds, or even 60 seconds or more.

[0165] It should be understood that different parameters of the drive signal may be controlled in different embodiments, for example, as described above, the first controller 209 and the second controller 211 may directly control the power level of the drive signal, for example using the drive signal control loop described above.

[0166] In some embodiments, the adaptation may be performed by adapting either the current and / or the voltage of the drive signal. For example, a fixed supply voltage may be provided to the driver 201 and the drive signal may have a corresponding fixed voltage amplitude. In such an embodiment, the adaptation may be performed by adapting the current of the drive signal.

[0167] In some embodiments, adapting the power transfer signal power can be done by adapting the duty cycle of the drive signal, for example, increasing the duty cycle typically increases the average power level and decreasing the duty cycle typically decreases the average power level.

[0168] In some embodiments, the adaptation can be done by adapting the frequency of the drive signal: for example, for a resonant output circuit, changing the frequency closer to the resonant frequency will result in higher power transfer levels, and changing the frequency away from the resonant frequency will result in lower power levels.

[0169] In some embodiments, the adaptation can be done by adapting the phase of the drive signal, for example phase shift modulation may be applied to a full bridge inverter.

[0170] In many embodiments, the set point may indicate a target power level of the power transmission signal. Alternatively or additionally, the set point may directly indicate other possible parameters that may indicate a power characteristic of the power transmission signal, such as a target duty cycle of the power transmission signal or a target frequency of the power transmission signal. Indeed, in some embodiments, the set point may directly indicate a parameter or characteristic of the drive signal, such as a target current level or a target voltage level of the drive signal.

[0171] The operation of a wireless power transfer system is based on communication between a power transmitter and a power receiver, and in particular, the power control loop is based on frequent transmission of messages (power control error messages) from the power receiver to the power transmitter. The reliability and efficiency of the communication between the power transmitter and the power receiver are very important and have a significant impact on the overall performance of the wireless power transfer. In many practical systems, suitable performance is achieved by using communication based on the NFC specification as described above.

[0172] Thus, in many embodiments, the system uses NFC as a medium for communication between the wireless power transmitter and receiver. The advantage of NFC is that it provides a one-to-one physical relationship between the power and communication coils due to the very short range nature of the communication channel, and there is very low risk of communication between the transmitter and the receiver that is not being powered by the transmitter. Furthermore, by incorporating an NFC carrier, it can be used to power the communication electronics of the wireless receiver without activating the transmitter.

[0173] However, a problem with communications in wireless power transfer systems, including systems using NFC, is that the communications can be susceptible to interference from the power signal. Although the frequency of the communication carrier can be significantly different from the operating frequencies of the drive signal and power transfer signal (e.g., 13.56 MHz versus 20-80 kHz), the power level of the power transfer signal in Ki et al.'s system can be very high, typically several orders of magnitude higher than the power of the communication carrier. Thus, substantial mutual interference can occur, affecting communication performance and, therefore, the performance of the overall power transfer.

[0174] Many systems, notably Ki et al.'s, solve this problem by separating power transfer and (NFC) communication in time, in particular using a time division approach where a repeating time frame is divided into at least one power transfer interval and one communication time interval. In such a case, power transfer is only performed outside the communication time interval, and interference from power transfer to communication can be avoided.

[0175] 1 and 2, the driver 201 is configured to generate drive signals for separating the communication and power transfer into multiple separate communication time intervals, specifically multiple communication time intervals and multiple power transfer time intervals. In the following example embodiment, in the first operating mode, and optionally also in the second operating mode, the driver 201 uses repeating time frames for the drive signals and the power transfer signals during the power transfer phase.

[0176] The recurring time frame includes at least one power transmission time interval and one communication time interval. An example of such a recurring time frame is shown in FIG. 8. The power transmission time interval is denoted by PT and the communication time interval is denoted by C. In this example, each time frame FRM consists of only one communication time interval C and one power transmission time interval PT, both of which (and the time frame itself) have substantially the same duration in each frame. However, it will be understood that in other embodiments, other time intervals (e.g., foreign object detection intervals) may also be included in the recurring time frame, or multiple communication time intervals and / or power transmission time intervals may be included in each time frame. Furthermore, in some embodiments, the durations of the different time intervals (and the time frame itself) may change dynamically, as described below.

[0177] In this example, the power transfer is performed within the power transfer time interval. The driver is configured to generate a drive signal, and thus a power transfer signal, during the power transfer time interval, specifically a drive signal having a non-zero amplitude / power is generated during the power transfer time interval. However, a reduced power level is used during the communication time interval, specifically no power transfer signal is generated in many embodiments. In general, this is achieved by the driver 201 not generating a drive signal during the communication time interval (or equivalently, the drive signal is controlled to have zero or near-zero amplitude / power (e.g., specifically the drive signal is generated to have an amplitude below an amplitude threshold of 0, 1, 2, 3, 5, or 10V, and / or the drive signal is generated to have a power below a power threshold of 1, 2, 3, 5, 10W, or below, for example, 1, 2, 3, 5, or 10% of the maximum power of the power transfer)).

[0178] By separating communication and power transfer in time, specifically by using repetitive time frames, the mutual interference from power transfer to communication operations can be significantly reduced (possibly even reduced to zero). Thus, the interference caused by power transfer signals to communication can be significantly reduced, even reduced to practically zero. This significantly improves communication performance and reliability, resulting in improved and more reliable power transfer operations.

[0179] Thus, in the power transfer phase, the transmitter is configured to perform power transfer during power transfer time intervals of the time frame. Specifically, during these time intervals, during the first operating mode, the transmitter 101 and the receiver 105 may run a power control loop. The power control loop may be based on communication within the power transfer time interval or may be based on communication outside the power transfer time interval, e.g., within a dedicated communication time interval. Thus, the level of transmitted power may be dynamically changed. Within the communication time interval, the power transfer signal may be substantially turned off, while a power control error message may be communicated to control the power loop operation during the power transfer time interval.

[0180] However, while such a time separation between communication and power transmission may provide many important advantages, it may also have some associated disadvantages. For example, repeated interruptions may generate audible noise in many situations (e.g., caused by mechanical effects of surrounding objects in response to changes in the generated magnetic field). Also, switching on and off the drive and power transmission signals may generate amplitude harmonics, which may generate electrical and electromagnetic noise. For example, interrupting the power signal may generate electromagnetic interference (e.g., 50 Hz harmonics) in the mains. The longer the power interruption due to the communication time interval, the larger the filters required to adequately suppress the noise. Also, longer communication time intervals may result in power being switched on and off for higher power levels, which may result in increased mains-related noise and more electromagnetic interference.

[0181] Furthermore, since there is no power transmission signal during the communication time interval, power must be provided for a shorter period of time, which results in a higher power level during the power transmission time interval. Furthermore, since power transmission may be intermittent, many applications require the receiver to have some form of energy storage (e.g., a capacitor) to maintain power supply during the communication time interval. Since many approaches require power transmission to be stopped for communication, communication may be limited to short data messages to minimize the interruption of power transmission. This drawback tends to become more significant as power transmission levels increase, and tends to be very significant in applications such as Ki, which may be used to transmit very high power levels.

[0182] 2 includes a timing circuit 215 configured to control the timing of the communication time interval, and in particular, the timing circuit 215 is configured to vary timing parameters of the communication time interval between a first mode of operation and a second mode of operation. Thus, the selection circuit 213 can vary the timing characteristics of the communication time interval depending on whether the transmitter is operating in the first mode of operation or the second mode of operation.

[0183] In particular, the timing circuit 215 may be configured to allocate a higher (usually significantly higher) percentage of time to the communication time intervals during the first mode of operation than during the second mode of operation. Thus, the system may distinguish between different modes of operation by dynamically adapting the communication capabilities. The transmitter of FIG. 2 may provide improved performance by adapting the communication performance, in particular by adapting the time division into (at least) the power transfer time intervals and the communication time intervals to obtain (at least) the power transfer time intervals and the communication time intervals that are best suited for the different communication performances for each mode of operation. This may enable, for example, improved power transfer, reduced operational complexity, reduced electromagnetic interference, and improved electromagnetic compatibility.

[0184] Indeed, in some embodiments, the receiver may be configured to select an operating mode based on acceptable electromagnetic interference. For example, the receiver may select to operate in a first operating mode and switch to a second operating mode if excessive electromagnetic interference results. As a specific example, this approach may allow the receiver to use full power control for lower power levels when electromagnetic interference is relatively low. However, if electromagnetic interference increases with increasing power transfer levels, the receiver may accordingly switch to the second operating mode for higher power levels, thereby reducing electromagnetic interference for a given power level.

[0185] The power transfer system may be configured to provide less communication capacity in the second mode of operation than in the first mode of operation. The reduced communication capacity in the second mode of operation may be achieved by implementing the second mode of operation such that communication between the receiver and the transmitter is reduced in the second mode of operation than in the first mode of operation. In particular, the second mode of operation does not require frequent power control error messages to support a dynamic power control loop, and in fact, in many embodiments, may be implemented without power feedback except for an initial power transfer signal set point. Thus, the system may dynamically and flexibly adapt tradeoffs between, for example, power transfer efficiency, flexibility, accuracy, and electromagnetic interference, versus complexity and electromagnetic compatibility.

[0186] Thus, the timing circuit 215 may be configured to reduce communication capacity for the second mode of operation, and the second mode of operation may be configured to use less communication to support power transfer.

[0187] In particular, during the second operating mode (e.g., when static control is used), less data and fewer messages need to be sent from the receiver to the transmitter, and the timing circuit 215 can be adapted to use shorter or fewer communication time intervals.

[0188] In many embodiments, the drive signals and power transmission signals are driven to use a repeating time frame that includes power transmission time intervals (where power is transmitted and typically a power control loop is performed) and low power time intervals (where power is reduced compared to the power transmission time intervals). These low power time intervals may typically be used as communication time intervals where at least some communication can occur (no or little interference from power transmission). In some embodiments, the low power time intervals may also be used for foreign object detection, and indeed in some embodiments, the low power time intervals may be used to perform communication and foreign object detection simultaneously.

[0189] In many embodiments, the driver 201 may be powered by a varying power supply signal, typically a varying power supply voltage. The drive signal may typically be generated to have an amplitude that follows the varying power supply signal, and in particular the varying power supply voltage.

[0190] For example, the output of the driver 201 is typically a switched bridge, which generates a drive signal by appropriate switching of the switches of the switched bridge. FIG. 9 shows a half-bridge switched bridge / inverter. Switches S1 and S2 are controlled to never close at the same time. 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 output of the inverter is connected to a transmitting inductor via a resonant capacitor. FIG. 10 shows a full-bridge switched bridge / inverter. Switches S1 and S2 are controlled to never close at the same time. Switches S3 and S4 are controlled to never close at the same time. Alternately, switches S1 and S4 are closed while S2 and S3 are open, and 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. In such a driver, the supply voltage may be a varying supply voltage, and the drive signal may be generated to have an amplitude equal to the supply voltage except for a small voltage drop across the switch elements.

[0191] For example, in many embodiments, the supply voltage for the driver 201 (specifically the output inverter such as the output inverters of Figures 9 and 10) may be generated from a rectified (and possibly partially smoothed) AC mains voltage. The unsmoothed and rectified voltage, i.e. the input mains voltage and therefore the drive signal voltage, reaches a minimum zero volts at a time corresponding to the zero crossing of the mains voltage. For a partially smoothed and rectified mains voltage, the minimum voltage / power may occur later than the zero crossing and may be higher than zero volts.

[0192] In such an embodiment, the low power / foreign object detection / communication time interval may be synchronized to a minimum of the (absolute) power signal / voltage. Timing circuit 215 may be configured to synchronize the communication time interval such that the time point of the minimum of the varying power signal falls within the low power time interval, typically such that the communication time interval is centered at the time point of the minimum.

[0193] In many embodiments, the timing of the low power / communication time interval is such that the time interval is centered around a minimum in the varying power supply signal, and thus typically around a minimum in the power transmission signal. In many embodiments, the timing circuit 215 may be configured to control the timing of the communication time interval such that the zero level of the input power supply voltage (often a zero crossing of the input power supply voltage) is substantially centered around the communication time interval.

[0194] For example, if the driver 201 receives a 50 Hz rectified mains voltage, the zero crossings of the mains, and therefore the rectified mains voltage and power minima, occur at 10 ms intervals, and each repeating time frame may be set to have a 10 ms duration. An example of the resulting drive signal / power transfer signal is shown in Figure 11, which shows the drive signal / power transfer signal during power transfer time interval PT and communication time interval C.

[0195] In many embodiments, a repetitive time frame may be used in both the first and second operating modes, and further, the communication time interval may be centered around a power / amplitude minimum of the power source power. Using such a repetitive time frame allows communication and power transfer to be separated in the time domain, resulting in a significantly reduced (possibly zero) mutual interference from power transfer to communication. Thus, the interference caused by the power transfer signal to communication can be greatly reduced, even reduced to practically zero. This significantly improves communication performance and reliability, resulting in improved and more reliable power transfer operation.

[0196] Thus, in the power transfer phase, the transmitter is configured to perform power transfer during a power transfer time interval of the time frame. Specifically, during the first operating mode, the transmitter 101 and the receiver 105 may perform a power control loop during the power transfer time interval based on the communication performed during the communication time interval. Thus, the level of the transmitted power may be dynamically changed. Within the communication time interval, the power transfer signal may be substantially turned off, but a power control error message may be communicated to control the power loop operation during the power transfer time interval.

[0197] However, while such a time separation between communication and power transmission can provide many important advantages, it can also have some associated disadvantages, for example, as noted above, in many situations repeated interruptions can cause audible noise, and the on / off switching of drive and power transmission signals can cause amplitude harmonics, electrical and electromagnetic noise, and interference and electromagnetic noise (50 Hz harmonics).

[0198] Furthermore, the absence of a power transmission signal during the communication time interval requires that power be provided for a shorter period of time, which in turn requires a higher power level during the power transmission time interval. Also, because power transmission may be intermittent, many applications require the receiver to have some kind of energy storage. A short communication time interval may severely limit communication, which may affect the performance of the power transmission.

[0199] FIG. 12 shows an example where a repetitive time frame may be used that includes alternating communication time intervals (T_slot_com) and foreign object detection time intervals (T_slot_fod) separated by a power transmission signal. The repetitive time frame has a duration equal to the time period of the source power, and the communication time intervals and foreign object detection time intervals are centered on the zero crossings / minimums of the source power. FIG. 12 further shows an example of the drive signal current (Imains) when the time slot durations of the communication time intervals and foreign object detection time intervals are 1.2 ms and the power transmission is 2.2 kW.

[0200] Figure 13 shows the possible harmonics compared to the permissible limits according to IEC 61000-3-2: Limits for harmonic current emissions. As can be seen, the current drawn and the presence of low power time intervals result in harmonics close to the IEC 61000-3-2 limits. It is preferable that the amplitude of these harmonics is small.

[0201] Also, the magnitude of the harmonics depends on the power level and as the power level increases the limits are no longer met. For example, Figure 14 shows a corresponding example where the power level is increased to 3 kW.

[0202] In some embodiments, the timing circuit 215 may be configured to reduce the duration of the communication time interval (and often other low power time intervals, such as foreign object detection time intervals) during the second mode of operation as compared to the first mode of operation. For example, FIG. 15 shows an example corresponding to FIG. 12, but with the transmitter in the second mode of operation, in which the low power time interval is reduced to 0.6 ms. FIG. 16 shows the harmonic response to a 3 kW power transmission corresponding to FIG. 14. In comparison, it can be seen that the level of harmonics is significantly reduced, and indeed the reduction in time slot duration brings the harmonics into compliance with the IEC limits.

[0203] In some embodiments, the receiver may be configured to operate in a first mode of operation for low power levels. However, if the receiver determines that a power transfer above a given level is required, the receiver may send a request to the transmitter to switch to a second mode of operation and transmit a power transfer signal set point indicating the desired power transfer level. The transmitter may then switch to the second mode of operation, set the power level to the requested amount, and reduce the duration of the communication time interval (e.g., from 1.2 ms to 0.6 ms in this example). Such an approach may allow, for example, to increase power transfer while still ensuring that electromagnetic interference is kept below a required level.

[0204] In some embodiments, therefore, timing circuit 215 is configured to set the duration of the communication time interval higher in the first mode of operation than in the second mode of operation. A shorter duration in the second mode may reduce harmonics, electromagnetic interference, etc., but may not allow for frequent transmission of power control error messages. In contrast, a longer communication time interval in the first mode of operation may allow for more information and longer messages, which may be used to support a power control loop, and in particular may be set sufficient to allow frequent communication of power control error messages.

[0205] In some embodiments, the timing circuit 215 may be configured to change the frequency of the communication time intervals between different operating modes. The timing circuit 215 may change the duration between communication time intervals depending on whether the transmitter is operating in a first or second operating mode. Thus, in many embodiments, the timing circuit 215 is configured to set the frequency of the communication time intervals higher in the first operating mode than in the second operating mode.

[0206] As an example, the timing circuit 215 may be configured to maintain the duration of each communication time interval at a constant duration. For example, the duration of the communication time interval may be configured to be long enough to transmit a complete message from the receiver to the transmitter (or vice versa). If messages may have different lengths, the duration of the communication time interval may be set, for example, to a minimum value that ensures that the longest message can be transmitted. As a specific example, the duration of the communication time interval may be set to a fixed value, for example, fixed at 1.2 milliseconds for both the first and second operating modes.

[0207] However, the duration between communication time intervals, and therefore the frequency of the communication time intervals, may be set to be (possibly significantly) different in the two modes. For example, in a first operating mode, the communication time intervals may be synchronized with the variations in the mains power, and a communication time interval may be included each time the mains power reaches a power minimum (typically corresponding to a zero crossing of the mains). For a mains frequency of 50 Hz, the frequency of the communication time intervals may be 100 Hz, corresponding to a new communication time interval occurring every 10 milliseconds.

[0208] In contrast, when the transmitter is in the second operating mode, the communication time intervals may occur much less frequently. For example, communication time intervals may only be generated, for example, every second or every 10 seconds. Thus, while a complete message may still be transmitted within each communication time interval, the data message rate is much lower. In this case, it may not be possible to support fast adaptation of the power transfer, for example a fast response power control loop. However, since the second operating mode is specifically one in which static operation is used, such fast operation and adaptation is not necessary.

[0209] In many embodiments, the timing circuit 215 may be configured to set a higher duty cycle of the communication time interval during the first mode of operation than during the second mode of operation. The duty cycle may be a ratio of the time in the communication time interval to the total time in the communication time interval and the power transfer time interval. The duty cycle may be a ratio between the duration of the communication time interval and the sum of the duration of the communication time interval and the duration of the power transfer time interval (specifically, adjacent power transfer time intervals).

[0210] Thus, during the first mode of operation, the timing circuit 215 may increase the relative time spent in communication time intervals as compared to the time spent in power transfer time intervals. Such an increase in the duty cycle may be achieved by increasing the duration and / or frequency of the communication time intervals during the first mode of operation as compared to the second mode of operation.

[0211] As noted above, in many embodiments, the transmitter may use repeating time frames for the drive signal and the power transmission signal. In some embodiments, the repeating time frames may be used during a first mode of operation but not during a second mode of operation. For example, during a first mode of operation, the time frames may be repeated every 10 or 20 milliseconds, for example for a 50 Hz power source. Each time frame may be divided into a power transmission time interval and a communication time interval, and the same division may be used for each time frame. In contrast, during a second mode of operation, the timing circuit 215 may be configured to generate the communication time intervals in an ad-hoc or semi-random manner.

[0212] For example, during the second mode of operation, the timing circuit 215 can randomly vary the duration between communication time intervals (typically according to upper and / or lower duration limits). When the timing circuit 215 determines that a new communication time interval is to begin, it can turn off the power transmission signal and generate the communication carrier. When the receiver detects that the power is turned off and / or that the communication carrier is present, it can begin transmitting pending messages to the transmitter, for example, by load modulating the carrier.

[0213] Such ad-hoc and / or (pseudo-)random variation of the duration between communication time intervals may have the advantage, for example, of being able to spread out the electromagnetic interference in frequency. Specifically, instead of concentrating the electromagnetic interference in harmonics of the frequency of the communication time intervals, the variation may cause the electromagnetic interference energy to be more evenly distributed in frequency, resulting in a lower noise density.

[0214] In some embodiments, a repeating time frame may be used when the transmitter is in the second mode of operation, but the repeating time frame may be modified during the second mode of operation as compared to the first mode of operation.

[0215] In many embodiments, the timing circuit 215 may be configured to vary the percentage of the recurring time frames allocated to the communication time interval from embodiment to embodiment, and in particular to reduce that percentage during the second mode of operation.

[0216] Specifically, for repeating time frames having the same period in the first and second modes of operation, the duration of the communication time interval may be shortened. As a specific example corresponding to the above example, timing circuit 215 may shorten the duration of the communication time interval from 1.2 ms to 0.6 ms when switching from the first mode of operation to the second mode of operation while maintaining a fixed duration of the repeating time frame at 10 ms (e.g., as in the examples of Figures 12 and 15, respectively).

[0217] In some embodiments, the timing circuit 215 may be configured to change the frequency of the communication time intervals in the repeating time frame depending on the operating mode. For example, in some embodiments, the timing circuit 215 may be configured to increase the duration between the communication time intervals when switching to the second operating mode. This may be achieved, for example, by changing the duration / repetition frequency of the repeating time frame. For example, the timing circuit 215 may impose the pattern of FIG. 12 during the first operating mode, and then switch to the pattern of FIG. 17 during the second operating mode. In the example of FIG. 17, the duration of the communication time intervals (and foreign object detection time intervals) is maintained at 1.2 ms, but only half of the multiple power supply power minima are associated with the low power time intervals. Thus, the example of FIG. 17 can be considered to correspond to the example of FIG. 12, but with twice the duration of the repeating time frame frames. This may result in reduced interference, specifically harmonics at half the frequency but at a reduced level, as shown in FIG. 18.

[0218] In some embodiments, the timing circuit 215 may be configured to adapt whether a communication time interval is included in a recurring time frame to follow different patterns during the first and second modes of operation. Specifically, during the first mode of operation, the timing circuit 215 may control the transmitter to generate a communication time interval in every recurring time frame. In contrast, when switching to the second mode of operation, the timing circuit 215 may transition to generating a communication time interval in only some of the recurring time frames.

[0219] For example, the transmitter may continue to use recurring time frames having the same duration when in the second mode of operation, but only include a communication time interval in every other time frame (corresponding to the frequency of the communication time intervals being reduced by a factor of two when switching from the first mode of operation to the second mode of operation). In other cases, the timing circuit 215 may be configured to include a communication time interval only in every third, fourth, etc. recurring time frame. In some embodiments, the pattern of recurring time frames that include communication time intervals may be non-periodic, e.g., following a predetermined pattern. In yet other embodiments, the recurring time frames in which communication time intervals are included may be pseudo-random.

[0220] It will be appreciated that different approaches may be used for different embodiments depending on the particular preferences and requirements of the embodiment, and that different approaches may be combined, e.g., timing circuit 215 may be configured to vary both the duration and frequency of communication time intervals between two different modes of operation.

[0221] The above approach may adapt the communications, and in particular the timing characteristics of the communication time interval, to the different operation in the two different modes. In particular, the communication resources available for communications between the transmitter and receiver may be adapted to reflect that these may differ (often significantly) between the two modes. This may be used in particular to reduce electromagnetic interference and to increase electromagnetic compatibility. In particular, interference from harmonics of the communication time interval may be reduced very significantly in many embodiments.

[0222] For clarity, the above description describes embodiments of the invention in terms of different functional circuits, units, and processors. However, it will be appreciated that functionality may be suitably distributed between different functional circuits, units, or processors without detracting from the invention. For example, functionality described as being performed by multiple separate processors or controllers may be performed by the same processor or controller. Thus, references to specific functional units or circuits should not be construed as indicative of a strict logical or physical structure or organization, but rather as references to suitable means for providing the described functionality.

[0223] The invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may 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 the embodiments of the 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 invention may be implemented as a single unit or may be physically and functionally distributed between different units, circuits and processors.

[0224] Although the present invention has been described in relation to several embodiments, the present invention is not limited to the specific forms described in the specification. The scope of the present invention is limited only by the appended claims. Moreover, even if a feature appears to be described in relation to a specific embodiment, a person skilled in the art will recognize that various features of the above-mentioned embodiments can be combined in accordance with the present invention. In the claims, the terms "comprise", "include" and the like do not exclude the presence of other elements or steps.

[0225] It will be understood that the reference to a preferred value does not imply any limitation beyond being a value determined in a foreign object detection initialization mode, i.e., preferred to be determined in a fitting process. Reference to a preferred value may be replaced with a reference to a first value, for example.

[0226] Furthermore, although individually recited, a plurality of means, elements, circuits, or method steps may be implemented by, for example, a single circuit, unit, or processor. Moreover, although individual features are included in different claims, they may be combined as desired, and the inclusion of such features 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 claim category does not necessarily limit the feature to this category, but the feature may be 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 should be acted upon, and in particular the order of individual steps in a method claim does not imply that the steps must be performed in that order. The steps may be performed in any suitable order. Furthermore, the singular does not exclude the plural; thus, the use of "first", "second", etc. does not exclude a plural. Reference signs in the claims are merely exemplary for clarity and do not limit the scope of the claims in any way.

[0227] In general, examples of wireless power transmission apparatus and methods are illustrated by the following embodiments.

[0228] Embodiment A power transmitter (101) for wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, the power transmitter (101) comprising: A power transmission coil (103) that generates the power transmission signal; A driver (201) that generates a drive signal for the power transmission coil (103) to generate the power transmission signal; A receiver (207) for receiving a message from the power receiver (105); a first controller (209) for controlling parameters of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to a power control error message received from the power receiver (105); a second controller (211) for controlling the parameters of the drive signal according to a second operating mode, the second operating mode including setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal; and a circuit (213) that selects between the first operating mode and the second operating mode in response to a power transmission control mode request received from the power receiver (105).

[0229]

[0023] Embodiment 2. The power transmitter of embodiment 1, wherein the power control error message indicates a desired relative change in the power characteristic of the power transmission signal, and the set point message indicates a desired absolute value of the target power characteristic.

[0230]

[0021] Embodiment 3. The power transmitter of embodiment 1 or 2, wherein the duration between the power control error messages is less than or equal to 300 milliseconds, and the maximum duration between the power transmission signal setpoints is greater than or equal to 10 seconds.

[0231] Embodiment 4. A power transmitter according to any one of embodiments 1 to 3, wherein a time constant of the power control loop and a time constant for modifying the parameter of the drive signal in response to the at least one power transmission signal setpoint differ by a factor of at least two.

[0232]

[0023] Embodiment 5. The second controller (211) implements a drive signal control loop, the drive signal control loop comprising: an estimator for generating a power level representation of the power transmission signal; a comparator for generating an error signal in response to a comparison between the power level indication and a reference power determined from the at least one power transmission signal setpoint; 5. The transmitter of any one of embodiments 1 to 4, further comprising: an adapter for adapting the parameters of the drive signal in response to the error signal.

[0233]

[0023] Embodiment 6. The power transmitter of any one of embodiments 1 to 5, wherein in the second mode of operation, the parameters of the drive signal are changed only in response to receiving the at least one power transmission signal setpoint.

[0234]

[0023] Embodiment 7. The power transmitter of any one of embodiments 1 to 6, wherein the at least one power transmission signal setpoint indicates a target power level of the power transmission signal.

[0235] Embodiment 8. A transmitter as described in any one of embodiments 1 to 7, wherein the at least one power transmission signal setting value is linked to a valid time interval, and the second controller (211) sets the parameter of the drive signal to a nominal value at the end of the valid time interval.

[0236] A wireless power transmission system including the power transmitter (101) according to any one of the first to eighth embodiments and the power receiver (105), wherein the power receiver (105) is a coil (107) for extracting power from the power transmission signal; a power circuit (301, 305) for supplying power extracted from the power transmission signal to a load (303); a transmitter (307) for transmitting the at least one power transmission signal setting value to the power transmitter.

[0237] Embodiment 10. The wireless power transfer system according to embodiment 9, wherein the power receiver transmits the at least one power transfer signal setpoint indicative of a predetermined target power characteristic of the power transfer signal.

[0238] Embodiment 11 A wireless power transmission system as described in embodiment 9 or 10, wherein the receiver (105) transmits the at least one power transmission signal setting value as indicative of a target power characteristic of the power transmission signal independent of a measurement of the electrical signal provided to the load (303).

[0239] Embodiment 12. The wireless power transmission system according to embodiment 9, wherein the power receiver (105) transmits the power transmission signal setting value in response to a measurement value of an electrical signal provided to the load (303).

[0240] Embodiment 13. A wireless power transmission system according to any one of embodiments 9 to 12, wherein the receiver (105) operates in multiple load modes, and the receiver (105) does not transmit a new power transmission signal setting value to the transmitter (101) unless the load mode is switched.

[0241] A power receiver (105) for wirelessly receiving power from a power receiver (101) via an inductive power transmission signal, the power receiver (105) comprising: a receiving coil (107) for extracting power from the power transmission signal; a power circuit (301, 305) coupled to the receiving coil (107) and supplying power from the receiving coil to a load (303); a transmitter (307) for transmitting a message to the power transmitter (101), the transmitter (307) transmitting a power transmission control mode request to the power transmitter (101), the power transmission control mode request indicating a request to the power transmitter to control a parameter of the drive signal according to a first operation mode or a second operation mode. the first mode of operation includes executing a power control loop to control a power characteristic of the power transmission signal in response to a power control error message received from the power receiver; The second operating mode includes setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal.

[0242] A method of operating a power transmitter (101) for wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, comprising: A power transmission coil (103) for generating the power transmission signal; The method comprises: generating a drive signal for the power transmitting coil (103) to generate the power transmission signal; receiving a message from the power receiver (105); controlling parameters of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to a power control error message received from the power receiver (105); controlling the parameters of the drive signal according to a second mode of operation, the second mode of operation including setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal; selecting between the first operating mode and the second operating mode in response to a power transfer control mode request received from the power receiver (105).

[0243] A method of operating a power receiver (105) for wirelessly receiving power from a power receiver (101) via an inductive power transmission signal, the power receiver (105) comprising: a receiving coil (107) for extracting power from the power transmission signal; a power circuit (301, 305) coupled to the receiving coil (107) and supplying power from the receiving coil to a load (303); and a transmitter (307) for transmitting a message to the power transmitter (101), the method including transmitting, by the transmitter (307), a power transmission control mode request to the power transmitter (101), the power transmission control mode request indicating a request to the power transmitter to control a parameter of the drive signal according to a first operating mode or a second operating mode; the first mode of operation includes executing a power control loop to control a power characteristic of the power transmission signal in response to a power control error message received from the power receiver; The method, wherein the second operating mode includes setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal.

[0244] A power transmitter (101) for wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, the power transmitter (101) comprising: A power transmission coil (103) that generates the power transmission signal; a driver (201) that generates a drive signal for the power transmitting coil (103) to generate the power transmission signal, the driver (201) generating the drive signal using a power transmission time interval during which the power transmission signal transmits power to the power receiver (105) and a communication time interval during which the power of the power transmission signal is reduced with respect to the power transmission time interval; a receiver (207) for receiving messages from the power receiver (105) during a communication time interval; a first controller (209) for controlling parameters of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to power control error messages received from the power receiver (105), wherein a maximum duration between power control error messages is less than or equal to 300 milliseconds; a second controller (211) for controlling the parameters of the drive signal according to a second operating mode, the second operating mode including setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal, and a maximum duration between power transmission signal set values ​​being equal to or greater than one second; a circuit (213) for selecting between the first operating mode and the second operating mode in response to a power transfer control mode request received from the power receiver (105); and a timing circuit (215) for varying timing parameters for the communication time interval between the first and second modes of operation.

[0245] Embodiment 2: A transmitter as described in embodiment 1, wherein the driver (201) uses repeating time frames for the power transmission signal, each repeating time frame including at least one power transmission time interval, and at least some of the repeating time frames including at least one communication time interval.

[0246]

[0023] Embodiment 3. The transmitter of embodiment 2, wherein the timing circuit (215) allocates a greater percentage of a recurring time frame to the at least one communication time interval in the first mode of operation than in the second mode of operation.

[0247]

[0023] Embodiment 4: A transmitter as described in embodiment 2 or 3, wherein the timing circuit (215) includes a communication time interval in all recurring time frames during the first operating mode, and includes a communication time interval in only a subset of the recurring time frames during the second operating mode.

[0248] Embodiment 5 The power transmitter according to any one of embodiments 1 to 4, wherein the timing circuit (215) sets the duration of the communication time interval longer in the first operation mode than in the second operation mode.

[0249]

[0023] Embodiment 6. The power transmitter according to any one of embodiments 1 to 5, wherein the timing circuit (215) sets a duty cycle of the communication time interval higher in the first operation mode than in the second operation mode.

[0250] Embodiment 7 The power transmitter according to any one of embodiments 1 to 6, wherein the timing circuit (215) sets a frequency of the communication time interval higher in the first operation mode than in the second operation mode.

[0251] Embodiment 8. A transmitter as described in any one of embodiments 1 to 7, wherein the driver (201) is powered by a fluctuating power supply signal, and the transmitter aligns a central point of the communication time interval with a signal minimum of the fluctuating power supply signal.

[0252] Embodiment 9: A power transmitter as described in any one of embodiments 1 to 8, wherein, in the first operating mode, the power transmitter terminates power transmission when it is detected that the power control error message has not been received for a duration exceeding a first threshold, and, in the second operating mode, the power transmitter does not stop power transmission when the power transmission signal setting value has not been received for a duration exceeding a second threshold, the second threshold being at least twice the first threshold.

[0253]

[0023] Embodiment 10. The power transmitter of any one of embodiments 1 to 9, wherein the power control error message indicates a desired relative change in the power characteristic of the power transmission signal and the set point message indicates a desired absolute value of the target power characteristic.

[0254] Embodiment 11. A transmitter as described in any one of embodiments 1 to 10, wherein the at least one power transmission signal set value is linked to a valid time interval, and the second controller (211) sets the parameter of the drive signal to a nominal value at the end of the valid time interval.

[0255] A wireless power transmission system including the power transmitter (101) according to any one of the first to eleventh embodiments and the power receiver (105), wherein the power receiver (105) is a coil (107) for extracting power from the power transmission signal; a power circuit (301, 305) for supplying power extracted from the power transmission signal to a load (303); a transmitter (307) for transmitting at least one power transmission signal setting value to the power transmitter during a communication time interval.

[0256] Embodiment 13. A wireless power transmission system as described in embodiment 10 or 12, wherein the receiver (105) transmits the at least one power transmission signal setting value as indicative of a target power characteristic of the power transmission signal independent of a measurement of the electrical signal provided to the load (303).

[0257] Embodiment 14. A wireless power transmission system as described in embodiment 12 or 13, wherein the receiver (105) operates in multiple load modes, and the receiver (105) does not transmit a new power transmission signal setting value to the transmitter (101) unless the load mode is switched.

[0258] A method of operating a power transmitter (101) for wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, comprising: A power transmission coil (103) for generating the power transmission signal; The method comprises: generating a drive signal for the power transmitting coil (103) for generating the power transmission signal, the drive signal being generated using a power transmission time interval during which the power transmission signal transmits power to the power receiver (105) and a communication time interval during which the power of the power transmission signal is reduced with respect to the power transmission time interval; receiving a message from the power receiver (105) during a communication time interval; controlling parameters of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to power control error messages received from the power receiver (105), wherein a maximum duration between power control error messages is less than or equal to 300 milliseconds; controlling the parameters of the drive signal according to a second operating mode, the second operating mode including setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver (105), the power transmission signal set value indicating a target power characteristic of the power transmission signal, and a maximum duration between power transmission signal set values ​​being equal to or greater than one second; selecting between the first operating mode and the second operating mode in response to a power transfer control mode request received from the power receiver; and changing a timing parameter for the communication time interval between the first mode of operation and the second mode of operation.

Claims

1. 1. 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 for generating a power transmission signal; a driver that generates a drive signal for the power transmitting coil to generate the power transmission signal, the driver generating the drive signal using a power transmission time interval during which the power transmission signal transmits power to the power receiver; A receiver for receiving a message from the power receiver; a first controller for controlling parameters of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to power control error messages received from the power receiver, wherein a maximum duration between power control error messages is less than or equal to 300 milliseconds; a second controller for controlling the parameters of the drive signal according to a second mode of operation, the second mode of operation including setting the parameters of the drive signal in response to at least one power transmission signal set value received from the power receiver, the power transmission signal set value indicating a target power characteristic of the power transmission signal, and a maximum duration between power transmission signal set values ​​being equal to or greater than one second; a circuit for selecting between the first operation mode and the second operation mode in response to a power transmission control mode request received from the power receiver, The driver further generates the drive signal using a communication time interval in which a power of the power transmission signal is reduced relative to the power transmission time interval; The receiver receives a message from the power receiver during a communication time interval; the second mode of operation including not executing a power control loop that controls the drive signal in response to a power control error message received from the power receiver; and a timing circuit for modifying a timing parameter for the communication time interval depending on whether the transmitter is operating in the first mode of operation or the second mode of operation, the timing parameter comprising: the duration of said communication time interval, and a timing circuit for timing the communication time interval, the timing circuit being a parameter selected from the group consisting of: a frequency of the communication time interval.

2. 2. The transmitter of claim 1, wherein the driver uses repetitive time frames for the power transmission signal, each repetitive time frame including at least one power transmission time interval, and at least some of the repetitive time frames including at least one communication time interval.

3. 3. The power transmitter of claim 2, wherein the timing circuit allocates a greater percentage of a recurring time frame to the at least one communication time interval in the first mode of operation than in the second mode of operation.

4. 4. The transmitter of claim 2 or 3, wherein the timing circuit includes a communication time interval in all recurring time frames during the first mode of operation and includes a communication time interval in only a subset of the recurring time frames during the second mode of operation.

5. The power transmitter of claim 1 , wherein the timing circuit sets the duration of the communication time interval longer in the first operating mode than in the second operating mode.

6. The power transmitter of claim 1 , wherein the timing circuit sets a duty cycle of the communication time interval higher in the first operating mode than in the second operating mode.

7. The power transmitter according to claim 1 , wherein the timing circuit sets the frequency of the communication time interval higher in the first operation mode than in the second operation mode.

8. 8. The transmitter of claim 1, wherein the driver is powered by a fluctuating power supply signal, and the transmitter aligns a central point of the communication time interval with a signal minimum of the fluctuating power supply signal.

9. 9. The power transmitter of claim 1, wherein in the first operating mode, the power transmitter terminates power transmission when it detects that the power control error message has not been received for a duration exceeding a first threshold, and in the second operating mode, the power transmitter does not terminate power transmission if the power transmission signal setting value has not been received for a duration exceeding a second threshold, the second threshold being at least twice the first threshold.

10. 10. The power transmitter of claim 1, wherein the power control error message indicates a desired relative change in the power characteristic of the power transmission signal and a setpoint message indicates a desired absolute value of the target power characteristic.

11. 11. The transmitter of claim 1, wherein the at least one power transmission signal setpoint is linked to a valid time interval, and the second controller sets the parameter of the drive signal to a nominal value at the end of the valid time interval.

12. A wireless power transmission system comprising the power transmitter according to any one of claims 1 to 11 and the power receiver, wherein the power receiver is a coil for extracting power from the power transmission signal; a power circuit for supplying power extracted from the power transmission signal to a load; a transmitter for transmitting at least one power transmission signal setting value to the power transmitter during a communication time interval.

13. 13. The wireless power transfer system of claim 12, wherein the receiver transmits the at least one power transmission signal setpoint as indicative of a target power characteristic of the power transmission signal independent of a measurement of the electrical signal provided to the load.

14. 14. The wireless power transmission system according to claim 12 or 13, wherein the power receiver operates in a plurality of load modes, and the power receiver does not transmit a new power transmission signal setting value to the power transmitter unless the load mode is switched.

15. 1. A method of operating a power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, the power transmitter comprising: a power transmission coil for generating a power transmission signal; The method comprises: generating a drive signal for the power transmitting coil to generate the power transmission signal, the drive signal being generated using a power transmission time interval during which the power transmission signal transmits power to the power receiver and a communication time interval during which the power of the power transmission signal is reduced with respect to the power transmission time interval; receiving a message from the power receiver during a communication time interval; controlling a parameter of the drive signal according to a first mode of operation, the first mode of operation including executing a power control loop to control power characteristics of the power transmission signal in response to power control error messages received from the power receiver, wherein a maximum duration between power control error messages is less than or equal to 300 milliseconds; controlling the parameters of the drive signal according to a second mode of operation, the second mode of operation including setting the parameters of the drive signal in response to at least one power transmission signal set point received from the power receiver, the power transmission signal set point indicating a target power characteristic of the power transmission signal, a maximum duration between power transmission signal set points being equal to or greater than one second, and the second mode of operation including not executing a power control loop that controls the drive signal in response to a power control error message received from the power receiver; selecting between the first and second operating modes in response to a power transfer control mode request received from the power receiver; modifying a timing parameter for the communication time interval depending on whether the power transmitter is operating in the first mode of operation or the second mode of operation, the timing parameter comprising: the duration of said communication time interval, and and c) varying a parameter selected from the group consisting of a frequency of the communication time interval.

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