Power transmission device and method

Abstract

A power transmission device, which may be a power transmitter 101 or a power receiver 103 for transmitting power via a power transmission signal, includes a power coil 103, 107 for transmitting power with a complementary power transmission coil 107, 103, which is another device for power transmission operation. A first communicator 205, 305 communicates data with the complementary power transmission device using modulation of the power transmission signal. A second communicator 207, 307 communicates power transmission control data via a second communication channel having a communication data rate at least ten times higher than that of the power transmission signal. A presence detector 209, 309 determines whether a complementary power transmission device is present near the power transmission coil 103, 107 in response to the first data, and a power transmission controller 201, 301 limits wireless power transmission from the power transmitter 101 to the power receiver 103 in response to detecting the absence of the complementary power transmission device.

Description

[Technical field]

[0001] The present invention relates to a wireless power transmission apparatus and method, in particular for Wireless Power Consortium wireless power transmission systems, such as, but not limited to, Qi type power transmission systems. [Background technology]

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

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

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

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

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

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

[0008] Further developments aim to introduce a range of new applications and features. For example, the Wireless Power Consortium is developing a standard based on extending the principles of Qi to apply to a variety of kitchen applications and appliances, including heaters, kettles, blenders, pans, etc. In particular, these developments support much higher power levels for power transmission and are known as the Cordless Kitchen standard.

[0009] The Qi standard supports communication from a power receiver to a power transmitter, thereby allowing the power receiver to provide information that may enable the power transmitter to adapt to a particular power receiver. The current standard defines a unidirectional communication link from the power receiver to the power transmitter, where the power receiver communicates by performing load modulation of a power transmission signal that transmits power. Specifically, the load of the power transmission signal by the power receiver is varied to provide modulation of the power signal. The resulting change in electrical characteristics (e.g., a variation in current draw) can be detected and decoded (demodulated) by the power transmitter.

[0010] Thus, at the physical layer, the communication channel from the power receiver to the power transmitter uses the power transmission signal as a data carrier. The power receiver modulates the load, which is detected by changes in amplitude and / or phase of the transmitter coil current or voltage. The data is formatted in bytes and packets.

[0011] Further information can be found in Chapter 6 of Part 1 of the Qi Wireless Power Standard (Version 1.0).

[0012] Initially, Qi utilized only a unidirectional communication link, but a bidirectional communication link has been introduced to allow for greater control and flexibility of power transfer operations. Communication from the power transmitter to the power receiver may be accomplished by modulating the power transfer signal using, for example, amplitude, frequency or phase modulation.

[0013] However, it has been found that communication using power transmission signals is not always optimal. In particular, the communication capacity and possible data rates for communication using the power transmission signal as a carrier wave tend to be quite limited, often limited to a few hundred bits per second. The suitability of the power transmission signal for communication tends to deteriorate significantly with increasing power levels.

[0014] Numerous wireless power transmission systems for higher power levels have been proposed. For example, the Wireless Power Consortium is developing standards based on extending the principles of Qi to apply to various kitchen applications and appliances, including heaters, kettles, blenders, pans, etc. Notably, these developments support much higher power levels for power transmission and are known as the Cordless Kitchen standards.

[0015] Most of these higher power level power transmission systems propose to use a separate communications system that is independent of the power transmission signal and therefore does not specifically use the power transmission signal as a carrier for the communications link.

[0016] Such separate communication systems can typically provide significantly higher data rates and often more reliable communications, which in most practical applications can enable improved and more reliable power transfer.

[0017] However, while the use of a separate communication system can provide many advantages, the inventors have realized that it can also result in less than optimal operation in some scenarios, and in particular in some scenarios can result in potential error conditions when a power receiver is moved, removed or replaced. Summary of the Invention [Problem to be solved by the invention]

[0018] Thus, improved power transfer approaches would be advantageous, particularly approaches that allow for increased flexibility, reduced cost, reduced complexity, improved user experience, additional or improved features or services, more reliable operation, improved error detection, and / or improved performance. [Means for solving the problem]

[0019] Accordingly, the Invention seeks to preferably mitigate, reduce or eliminate one or more of the above mentioned disadvantages singly or in any combination.

[0020] According to one aspect of the present invention, there is provided a power transmission device for wirelessly transmitting power from a power transmitter to a power receiver, the power transmission device being one of the power transmitter and the power receiver, the power transmission device comprising: a power transmission coil for transmitting power via a power transmission signal and a complementary power transmission coil of a complementary power transmission device, the complementary power transmission device being the other of the power transmitter and the power receiver; a first communication device for communicating first data with the complementary power transmission device via a first communication channel using modulation of the power transmission signal during power transmission; a second communication device that communicates power transmission control data with the complementary power transmission device via a second communication channel independent of a power transmission signal, the second communication channel having a communication data rate that is at least ten times the communication data rate of the first communication channel; a presence detector that determines whether the complementary power transmission device is present in the vicinity of the power transmission coil in response to the first data during power transmission; and a power transmission controller configured to limit wireless power transmission from the power transmitter to the power receiver in response to detecting the absence of the complementary power transmission device.

[0021] The present invention can provide improved performance and / or operation in many wireless power transfer systems, including efficient control of power transfer operations, as well as mitigating or reducing the risk of undesirable or undetected error scenarios that may occur, for example, when a power receiver is removed.

[0022] The presence detector may be configured to determine whether a complementary power transmission device is present in the vicinity of the power transmission coil in response to the first data, and in particular may be configured to determine that a power receiver that was present during initialization of the power transmission is no longer present.

[0023] The first and / or second communication channel may be a bidirectional or unidirectional communication channel. The communication channel may be a communication link. The communication data rate may specifically be a maximum communication data rate or may be the communication capacity of the communication link. The communication data rate may be an average communication rate. For example, if the communication channel implements a time slotted operation, the communication data rate may be a communication data rate averaged over all time slots (including time slots in which no data is communicated).

[0024] Proximity need not be a specific or well-defined proximity, i.e., it typically does not correspond to a specific, well-defined, predetermined distance. Rather, the power transfer device and the complementary power transfer device may be considered to be in proximity if the first data meets a certain proximity criterion. The proximity criterion may be met for smaller distances between the power transfer device and the complementary power transfer device and not met for larger distances (thresholds are not necessarily specified or known). In many embodiments and scenarios, the devices are considered to be in proximity when they are at a distance less than the communication range of the first communication link.

[0025] The operations, specifically communication and presence detection, of the first data and the power transmission control data may be performed during a power transmission phase. The power transmission phase is specifically a phase in which a power transmission signal is generated to transmit power from the power transmitter to the power receiver. The power transmission phase may also be a phase in which a power control error message is transmitted from the power receiver to the power transmitter. The power transmitter and the power receiver may implement a power control loop for power transmission during the power transmission phase. The power control loop may adapt a level of the power transmission signal depending on the power control error message.

[0026] According to an optional feature of the invention, the communication data rate of the first communication channel is less than or equal to 500 bits / second.

[0027] This can provide particularly advantageous performance in many embodiments and scenarios, and in many embodiments can allow for power transmission of higher power levels and / or can allow for relatively low frequencies of the power transmission signal.

[0028] According to an optional feature of the invention, the communication data rate of the first communication channel is less than or equal to 100 bits / second.

[0029] This can provide particularly advantageous performance in many embodiments and scenarios, and in many embodiments can allow for higher power levels of the power transmission and / or can allow for relatively lower frequencies of the power transmission signal.

[0030] According to an optional feature of the invention, first data is received from a complementary power transmission device, and the presence detector is configured to determine an absence of the complementary power transmission device in response to detecting that the first data satisfying a criterion is not received.

[0031] This can provide a particularly efficient and advantageous operation in many embodiments, which can typically provide low-complexity yet reliable detection of the presence or absence of a power receiver within a suitable power transmission area for a power transmitter.

[0032] The criterion may in particular be that a given data pattern is received within a given time interval. The data pattern may be a static, possibly pre-determined, or a dynamic data pattern.

[0033] According to an optional feature of the invention, the first data includes an identification indication for the complementary power transmission device, and the proximity detector is configured to detect the absence of the complementary power transmission device in response to the received identification indication not meeting a criterion.

[0034] This can provide a particularly efficient and advantageous operation in many embodiments. The criterion can specifically be that a given identifying data pattern is received within a given time interval. The data pattern may be a static, possibly predetermined, or a dynamic data pattern.

[0035] According to an optional feature of the invention, the first communicator is configured to transmit a query message to the complementary power transmission device, and the proximity detector is configured to detect the absence of the complementary power transmission device in response to the absence of first data including a valid response to the query message being received.

[0036] This can provide a particularly efficient and advantageous operation in many embodiments.

[0037] According to an optional feature of the invention, the first data includes control data for power transfer.

[0038] This can provide a particularly efficient and advantageous operation in many embodiments, and in particular can provide improved control data communication.

[0039] According to an optional feature of the invention, the power transmission device further includes a power controller configured to communicate control data for power transmission with the complementary power transmission device, the power controller being configured to communicate some control data with the complementary power transmission device via a first communication channel and other control data with the complementary power transmission device via a second communication channel.

[0040] This can provide particularly efficient and advantageous operation in many embodiments, and in particular can provide improved control data communication. This approach can provide both high data rate and low latency control data communication, for example, by taking advantage of the different characteristics of the different communication links. The control data for power transmission with the complementary power transmission device can include control data that affects dynamic characteristics of the power transmission, such as characteristics of the power transmission signal. The characteristics can be the level, duration, amplitude, strength and / or frequency of the power transmission signal.

[0041] According to an optional feature of the invention, the power transmission signal employs a repetitive time frame including at least a power transmission time interval and a reduced power time interval in which a power level of the power transmission signal is reduced relative to the power transmission time interval, and the first communicator (205, 305) is configured to communicate first data during the reduced power time interval.

[0042] This can provide a particularly efficient and advantageous operation in many embodiments.The power transfer signal can employ a repeating time frame during the power transfer phase.

[0043] According to an optional feature of the invention, the power transfer signal has a fixed non-zero amplitude during a number of subsequent reduced power time intervals.

[0044] This can provide a particularly efficient and advantageous operation in many embodiments.

[0045] According to an optional feature of the invention, the frequency of the power transfer signal is higher during the reduced power time intervals than during the power transfer time intervals.

[0046] This can provide a particularly efficient and advantageous operation in many embodiments.

[0047] According to an optional feature of the invention, the power transfer device is a power receiver and the complementary power transfer device is a power transmitter.

[0048] According to an optional feature of the invention, the power transfer device is a power transmitter and the complementary power transfer device is a power receiver.

[0049] According to an optional feature of the invention, a method of operating a power transmission device for wireless power transmission from a power transmitter to a power receiver, the power transmission device being one of the power transmitter and the power receiver, the method comprising the steps of: a power transmission coil transmitting power via a power transmission signal with a complementary power transmission coil of a complementary power transmission device, the complementary power transmission device being the other of the power transmitter and the power receiver; communicating first data with the complementary power transmission device via a first communication channel using modulation of the power transmission signal during power transmission; communicating power transmission control data between the complementary power transmission device and the complementary power transmission device via a second communication channel independent of the power transmission signal during power transmission, the communication data rate of the second communication channel being at least ten times the communication data rate of the first communication channel; determining whether the complementary power transmission device is present in the vicinity of the power transmission coil during power transmission in response to the first data; and limiting wireless power transmission from the power transmitter to the power receiver in response to detection of absence of the complementary power transmission device.

[0050] According to one aspect of the present invention, there is provided a power transmission system for wirelessly transmitting power from a power transmitter to a power receiver, the power transmitter having a power transmission coil for generating a power transmission signal for transmitting power to the power receiver, a first transmitter communication device for communicating first data with the power receiver via a first communication channel using modulation of the power transmission signal during power transmission, and a second transmitter communication device for communicating power transmission control data with a complementary power transmission device via a second communication channel independent of the power transmission signal during power transmission, wherein a communication data rate of the second communication channel is ten or more times the communication data rate of the first communication channel; The power receiver has a power receiver coil for receiving power via a power transmission signal, a first receiver communicator for communicating first data with the power transmitter via the first communication channel during power transmission, and a second receiver communicator for communicating power transmission control data with the power transmitter via the second communication channel during power transmission, and at least one of the power transmitter and the power receiver further has a presence detector for determining whether a complementary power transmission device is present in the vicinity of the power transmission coil in response to the first data during power transmission, the complementary power transmission device being the other of the at least one of the power transmitter and the power receiver, and a power transmission controller configured to limit wireless power transmission from the power transmitter to the power receiver in response to detecting the absence of the complementary power transmission device.

[0051] These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0052] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Figure 1] 1 illustrates example elements of a power transfer system according to some embodiments of the present invention. [Diagram 2] FIG. 1 illustrates an example of elements of a power transmitter according to some embodiments of the present invention. [Diagram 3] 1 illustrates example elements of a power receiver according to some embodiments of the present invention. [Figure 4] 1 illustrates example elements of an apparatus according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] The following description focuses on embodiments of the invention applicable to wireless power transfer systems utilizing the power transfer approach as known from the Qi standard, 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.

[0054] 1 illustrates an example of a power transfer system according to some embodiments of the present invention. The power transfer system includes a power transmitter 101 including (or coupled to) a transmitter coil / inductor 103. The system further includes a power receiver 105 including (or coupled to) a receiver coil / inductor 107.

[0055] The system provides wireless inductive power transmission from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates a wireless inductive power transmission signal (also called a power transmission signal or an inductive power transmission signal) that is propagated as a magnetic flux by a transmitter coil or inductor 103. The power transmission signal may typically have a frequency between about 20 kHz and about 500 kHz, and for Qi-compatible systems is typically in the range of 95 kHz to 205 kHz (or for example, for high-power kitchen applications, the frequency may typically be in the range of 20 kHz to 80 kHz). The transmitter coil 103 and the receiver coil 107 are loosely coupled, and thus the receiver coil 107 picks up (at least a portion of) the power transmission signal from the power transmitter 101. Thus, power is transmitted from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the receiver coil 107. It will be understood that the term power transmission signal is used primarily to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the receiver coil 107, but may also be considered and used to refer to an electrical signal provided to the transmitter coil 103 or picked up by the receiver coil 107.

[0056] In the example, power receiver 105 is specifically a power receiver that receives power via receiver coil 107. However, in other embodiments, power receiver 105 may include a metallic element, such as a metallic heating element, where the power transmission signal induces eddy currents that result in heating of the element.

[0057] The system may be configured to transmit substantial power levels, and specifically in many embodiments the power transmitter may support power levels of 500 mW, 1 W, 5 W, 50 W, 100 W or greater than 500 W. For example, in Qi-enabled applications, power transmission may typically range from 1-5 W power for low power applications, to greater than 100 W and even greater than 1000 W for high power applications supported by the Cordless Kitchen standard being developed by the Wireless Power Consortium.

[0058] In the following, the operation of the power transmitter 101 and the power receiver 105 will be described with particular reference to embodiments that comply with the Qi standard (except for the modifications and extensions described (or resulting from) in this specification) or are suitable for the higher power Cordless Kitchen standard.

[0059] The system of FIG. 1 utilizes bidirectional communication to support power transfer operations. The bidirectional communication is used to configure, establish, and control the power transfer and may include the exchange of various control data. In particular, the communication channel between the wireless power transmitter and the wireless power receiver is considered essential to establish a feedback loop from the wireless power receiver to the wireless power transmitter, which is essential for the stability of the power system.

[0060] As an example, the current Qi standard limits the amount of power for wireless power transmission to 15 watts. Such a power amount may be considered a low-power wireless power system. This system uses power transmitter modulation as the means of communication between the power transmitter and the power receiver. This is also known as an in-band communication channel.

[0061] However, such communication is not ideal for all systems and tends to be suboptimal, especially for higher power levels. Specifically, for applications with higher transmission power levels, the modulation of the power transmission signal becomes an additional source of losses, and also increases the absolute power level of losses. These losses cause heat dissipation, for example, in the power electronics of the wireless power system or in materials within the operating range of the wireless power system.

[0062] It is also desirable to have a high communication data rate between the power transmitter and the power receiver to provide efficient control of the power transmission. However, this is typically very difficult to achieve using the power transmission signal as a carrier signal, and especially for higher power applications such as kitchen applications the achievable data rates are typically too low to support the desired functionality. In particular, at operating frequencies of the power transmission signal on the order of 20-300 kHz, the channel bandwidth is often not sufficient for more complex operations, such as for authentication of the power receiver.

[0063] Therefore, higher power level systems, such as those conforming to the Cordless Kitchen standard, tend to replace the in-band communication using the power transmission signal with an out-of-band communication channel realized by a separate, usually dedicated, short-range communication system that is unrelated to the power transmission signal and does not use the power transmission signal as a carrier for communication. This is often a short-range communication system, such as, for example, Bluetooth or an NFC communication system.

[0064] However, the inventors have recognized that there may be certain drawbacks associated with such an approach, and that these may be effectively addressed by the system of FIG. 1, which implements two communication channels between the power transmitter and the power receiver, with a particularly low data rate communication link established using the power transmission signal as a carrier, and a higher data rate communication link established using a separate communication system. The inventors have recognized that, in particular, proximity detection may be performed based on the low data rate communication channel using the power transmission signal, thereby enabling more reliable and robust operation, which may in particular reduce the risk of strong magnetic fields being generated when the power receiver is not present (or when the wrong power receiver is present).

[0065] Specifically, wireless power transmission in a system occurs when the power receiver coil is close to the wireless power transmitter coil and these coils have a sufficient coupling coefficient to transfer energy with high efficiency. This proximity region is usually specified as a combination of the misalignment between the wireless power receiver coil and the transmitter coil and the maximum vertical distance between them. This volume is considered as the wireless power operating region / volume of the wireless power system.

[0066] The inventors have recognized that in the case of wireless power transmission using an established out-of-band communication channel, the communication link typically has a range that differs from the wireless power operating region / volume, which can cause problems that are essentially avoided by traditional in-band communication approaches.

[0067] In the system of Figure 1, a dual parallel communication system is implemented with one communication link / channel being an out-of-band communication link independent of the power transmission signal and the other communication link / channel being an in-band communication link using the power transmission signal as a carrier for modulation with data. The in-band communication link is implemented at a low data rate and the out-of-band communication link is implemented at a high data rate. The data rate of the out-of-band communication link is more than 10 times higher than the in-band communication link.

[0068] The out-of-band communication link is used for communication of control data, which may in particular be control data supporting the power transfer signal, such as power control messages, etc. Thus, power transfer operations may be based on an exchange of a significant amount of data / information.

[0069] The in-band communication link is used to provide proximity detection for the system to detect whether the power transmitter and power receiver are in actual proximity / remain in proximity. Thus, the in-band communication link can be used to detect when the power receiver and / or power transmitter have been moved out of proximity with each other, and in response, the system can proceed to, for example, terminate power transmission.

[0070] This approach reflects the inventors' realization that it is important to detect when a wireless power receiver is located within a wireless power operating area / volume. As soon as the wireless power receiver leaves the wireless power operating volume, the wireless power transmission should be interrupted (e.g., stopped or reduced to a low level) to ensure that the large magnetic field from the wireless power transmitter does not have any negative effects on other devices (e.g., it can cause undesirable heating in metal objects, or potentially damage other electrical equipment, especially if a different power receiver is brought close to the power transmitter).

[0071] To address this issue, the system may include proximity / presence detection techniques that attempt to establish a clear one-to-one relationship between wireless power receivers and wireless power transmitters of power transmission. Proximity / presence detection, in this context, may be considered as the ability of a wireless power transmitter to detect / estimate the presence or absence of an associated wireless power receiver within the operating volume.

[0072] In systems such as Qi, where communication is based on modulation of the power transmission signal, this is inherently possible since removing the power receiver from the power operation results in a breakdown in communication leading to the termination of power transmission.

[0073] However, in the case of wireless power transmission with an established out-of-band communication link, where the range of the communication link is larger than the corresponding wireless power operating volume, the power transmission may continue since valid control data may still be exchanged. The system of FIG. 1 can handle such a scenario since it includes a presence / proximity detection function to determine that the (suitable) power receiver is located within the appropriate wireless power operating volume for the power transmitter. Furthermore, this presence / proximity detection is based on supplementing the out-of-band communication link with an in-band communication link that is specifically used to perform presence detection. Specifically, the control data may be communicated at a high data rate using an out-of-band communication link that has a high data rate to effectively support the power transmission, and the in-band communication link may complement this by communicating presence data that is used to perform presence detection. Specifically, if the communication of the correct presence data is successful, it may be determined that the power transmitter and power receiver are nearby, and if the communication of the presence data is not successful, it may be determined that they are not nearby enough to be detected. The presence data may typically be any data suitable for detecting the presence of a power receiver in the vicinity of a power transmitter (or vice versa).

[0074] The described approach therefore implements wireless power receiver proximity detection during wireless power transmission, specifically during the power transmission phase. This approach can, for example, enable the power transmitter to detect the proximity of the power receiver and terminate the power transmission if it is detected that the power receiver has left the wireless power operation volume. For example, if the proximity detection fails during the power transmission phase, the system can terminate the power transmission. The presence / proximity detection can be based on a system that utilizes the power transmission signal as a communication carrier for modulation with presence data. This can in particular tightly couple the presence / proximity detection and the power transmission operation, resulting in a more robust operation. When the power receiver detection is no longer present, the power transmission / power transmission phase can be terminated to avoid undesirable operation scenarios occurring, in particular undesirable strong electromagnetic fields that are generated when this is not required as part of an effective power transmission.

[0075] This approach is explained in further detail with reference to FIG. 2, which illustrates elements of the power transmitter 101, and FIG. 3, which illustrates elements of the power receiver 105 of FIG. 1 in more detail.

[0076] Figure 2 shows example elements of the power transmitter 101 of Figure 1 in more detail. The transmitter coil 103 is coupled to a driver 201 which generates a drive signal for the transmitter coil 103. The driver 201 generates current and voltage signals that are supplied to the transmitter inductor 103. The driver 201 is a drive circuit, typically in the form of an inverter that generates an AC signal from a DC voltage. The output of the driver 201 is typically a switch bridge which generates the drive signal by appropriate switching of the switches of the switch bridge.

[0077] The driver 201 is coupled to a power transmitter controller 203 configured to control the operation of the power transmitter 101. The power transmitter controller 203 is configured to control the operation of the power transmitter 101 to perform necessary and desired functions associated with a power transmission protocol of the system, and in this example, may be specifically configured to control the power transmitter 101 to operate in accordance with the Cordless Kitchen standard. For example, the power transmitter controller 203 may include functionality for initiating power transmission, supporting power transmission, terminating power transmission, and detecting a power receiver.

[0078] In an embodiment, the power transmitter 101 further comprises a first transmitter communicator 205 configured to communicate with the power receiver 105. The first transmitter communicator 205 is configured to communicate with the power receiver 105 using the power transmission signal as a communication carrier, i.e., can modulate data onto the power transmission signal. The first transmitter communicator 205 is configured to communicate with the power receiver 105 using an in-band communication link.

[0079] The power transmitter communicator 205 may typically be configured to receive messages from the power receiver 105, with the power receiver 105 load modulating the power transmission signal, as known to those skilled in the art, for example from the Qi power transmission standard. The power transmitter communicator 205 may communicate messages to the power receiver, for example, by modulating the power transmission signal, as known to those skilled in the art. For example, the first transmitter communicator 205 may control the driver to vary the frequency, amplitude and / or phase of the drive signal according to the data to be transmitted. Thus, the power transmitter controller 203 may transmit data to the power receiver 105, for example, using frequency, amplitude and / or phase modulation. It will be appreciated that while in many embodiments the first transmitter communicator 205 may support bidirectional communication, in some embodiments the communication may be only one-way.

[0080] The power transmitter 101 further comprises a second transmitter communicator 207 configured to communicate with the power receiver 105 independent of the power transmission signal. The second transmitter communicator 207 is configured to communicate with the power receiver 105 using a communication link that uses a different communication carrier than the power transmission signal. Thus, the second transmitter communicator 207 is independent of the power transmission signal and establishes an out-of-band communication link where data communicated over this link is not modulated onto the power transmission signal.

[0081] The exact communication approach and communication carrier used may vary in different embodiments and can depend on the preferences and requirements of the particular application. The out-of-band communication link is typically implemented by a short-range communication system having a range significantly greater than the range of the power transmission and significantly exceeding the wireless power transmission operating volume.

[0082] In many embodiments, the out-of-band communication link may be implemented by a standardized short-range communication system, such as a Bluetooth or NFC communication system. Such communication systems may provide an efficient out-of-band communication link offering high data rates, reliable communication and typically low-cost implementation. This may enable, among other things, efficient exchange of control data for power transmission. In many embodiments, the second transmitter communicator 207 may support bidirectional communication, although it will be appreciated that in some embodiments communication may be only unidirectional.

[0083] 3, the receiver coil 107 of the power receiver 105 is coupled to a power receiver controller 301 that couples the receiver coil 107 to a load 303. The power 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 power receiver controller 301 can include various power receiver controller functions required to perform a power transfer, in particular functions required to perform a power transfer in accordance with the Cordless Kitchen standard.

[0084] The power receiver 105 further comprises a first receiver communicator 305 configured to communicate with the first transmitter communicator 205 using the power transmission signal as a carrier. Thus, the first transmitter communicator 205 and the first receiver communicator 305 establish an in-band communication link.

[0085] In-band communication links typically have very low data rates, making the system particularly suitable for the high power levels of wireless power transmission, e.g., over 100 W. These high levels make communication using the power transmission signal as a communication carrier very challenging, and data rates must be kept relatively low to ensure reliable communication and minimize impact on the power transmission.

[0086] In most embodiments, the communication data rate for communication over the in-band communication link is 1000 bits / second or less, 500 bits / second or less, or 100 bits / second or less, which is typically suitable for high power transmission and provides a reliable communication link.

[0087] However, in most embodiments, it is not sufficient to enable optimized power transfer control. For example, it is desired that the control data be communicated at a higher data rate. For example, the power control data can be communicated as a power control loop error message that can indicate an absolute error (discrepancy between expected power / current level at the receiver) or a relative error (report only if the receiver needs more or less power).

[0088] To support this higher data rate communication, the power receiver 105 further comprises a second receiver transceiver 307 that establishes an out-of-band communication link with the second transmitter transceiver 207. Thus, the secondary resonant circuit 205 may be complementary to the first transmitter transceiver 205.

[0089] Thus, the power transmitter 101 and the power receiver 105 can simultaneously establish two communication links during a power transfer operation, each of which may be unidirectional (in either direction) or bidirectional.

[0090] The two communication links typically have very different characteristics. Specifically, the communication data rate of the out-of-band communication link is more than 10 times the communication data rate of the in-band communication link. Thus, the communication rate of the out-of-band communication link is much greater than the communication rate of the in-band communication link. However, the communications may also differ in other parameters such as communication reliability and error rate.

[0091] Moreover, typically, the ranges of the two communication links are different, or at least are not known to be identical. In most embodiments, the out-of-band communication link has a (much) longer range than the in-band communication link. Furthermore, due to the fact that the in-band communication link utilizes a power transmission signal as a communication carrier, the range of the in-band communication link is inherently coupled with the range of the power transmission, as opposed to the out-of-band communication link.

[0092] In this system, this is utilized to provide proximity / presence detection during the power transfer phase.

[0093] As a specific example, the power transmitter 101 includes a transmitter presence detector 209 configured to determine whether a power receiver is present in the vicinity of the transmitter coil 103 based on data communicated via the in-band communication link.

[0094] In some embodiments, the first transmitter communication device 205 may be configured to receive data from the power receiver 105 and may be configured to determine the absence (non-presence) of the power receiver 105 in response to detecting that presence data satisfying a given criterion is not / is not received.

[0095] In many embodiments, the criterion may simply be that a given data pattern is received. For example, the transmitter presence detector 209 may receive data that is compared to a predefined pattern, and if they match (according to predefined matching criteria), it is determined that the power receiver is still present. If no data matching the predefined pattern is received within a given time limit, the transmitter presence detector 209 may determine that the power receiver is no longer within the operating area of ​​the power transmission.

[0096] To support such operation, the power receiver can transmit a desired predetermined pattern at regular intervals, potentially continuously. For example, a continuous feedback system can be created in which the power receiver continuously transmits data and the power transmitter continuously evaluates whether such data is being received successfully. If this communication feedback loop is active, it should mean that the power receiver is close enough to allow reliable communication using the power transmission signal, and therefore the power receiver is considered to be present (i.e., close enough / nearby) within the power transmission operating volume. Thus, this approach can continuously determine whether a power receiver is present in the vicinity of the transmitter coil 103 corresponding to the communication range of the in-band communication link. Since the in-band communication link is based on using the power transmission signal as a communication carrier, the communication range of the in-band communication link is intrinsically linked with the power transmission range, and thus this approach provides a good estimation / detection of whether the power receiver is present within the power transmission operating volume.

[0097] The transmitter presence detector 209 is coupled to the power transmitter controller 203, which is configured to limit the power transmission in response to detecting the absence of a complementary device. The transmitter presence detector 209 can thus continuously transmit the results of the detection process to the power transmitter controller 203 and proceed to limit the power transmission if it indicates that the power receiver is not (likely not) within the operating volume. The limiting may typically be by applying a maximum power level limit to the power transmission signal if the maximum power level is lower than the maximum power level limit of the power transmission (when no limit is applied).

[0098] Typically, the power transmitter controller 203 is configured to terminate power transmission in response to detecting the absence of a power receiver (equivalent to limiting the power transmission or maximum power level limit to zero). Thus, if a power transmission is in progress (the system is operating in a power transmission phase) and the power transmitting device detects the absence of a power receiver, for example, by determining that expected data is not being received on the in-band communication link, the power transmitter controller 203 is notified and proceeds to terminate the power transmission, thereby preventing a strong magnetic signal from being generated in the absence of a power receiver.

[0099] The above description has focused on a scenario in which a power transmitter detects whether a power receiver is present and controls power transmission accordingly. However, it will be appreciated that in other embodiments, the detection function may alternatively or additionally be in the power receiver. Indeed, all comments provided above and below with respect to systems in which the detection function is present in the power transmitter may also be considered to apply to the complementary situation in which the detection function is present in the power receiver (e.g., a reference to a power transmitter detecting whether a power receiver is nearby applies mutatis mutandis to a power receiver detecting whether a power transmitter is nearby).

[0100] Specifically, the power receiver 105 may include a receiver presence detector 309 configured to determine whether the power transmitter 101 is present in the vicinity of the receiver coil 107 based on data communicated via the in-band communication link.

[0101] In some embodiments, the first receiver communication device 305 may be configured to receive data from the power transmitter 101 and may be configured to determine the absence of the power transmitter 101 in response to detecting that presence data meeting a given criterion is not received.

[0102] As described for the complementary scenario, the criterion may simply be that a given data pattern is received. For example, the receiver presence detector 309 can receive data transmitted from the first transmitter communicator 205, for example by AM, FM or PM modulation of the power transmission signal, which can be compared to a given pattern. If they match (according to a given matching criterion), it is determined that the power transmitter 101 is still present, and therefore that reliable power transmission is feasible. If no data within a given threshold that matches the predetermined pattern is received, the receiver presence detector 309 can determine that the power transmitter 101 is no longer present within the operating area of ​​power transmission.

[0103] Also, as described for the complementary scenario, the first transmitter communicator 205 can continuously transmit a predetermined pattern, which the receiver presence detector 309 can continuously monitor. Again, since the communication is based on the power transmission signal being used as a carrier, this is a good indication of whether the power receiver and power transmitter are close enough that the power receiver is considered to be within the power transmission operating volume.

[0104] The receiver presence detector 309 is coupled to the power receiver controller 301 and notifies the power receiver controller 301 when it is detected (by the appropriate data not being received) that the power transmitter is no longer in the vicinity of the receiver coil 107. The power receiver controller 301 can proceed to restrict power transfer operations. This can be performed in different manners depending on the application, but in many embodiments can be accomplished by the power receiver 105 communicating a data request or command to the power transmitter using an out-of-band communication link (which typically has a much wider range than an in-band communication link).

[0105] The power receiver 105 can directly send commands, for example, to terminate power transmission or to limit the power level to a given value. In other embodiments, the power receiver controller 301 can modify the transmission of control data such that this results in a desired change in power transmission. For example, a continuous power down request can be sent. As another example, the power receiver controller 301 can withhold the transmission of messages that are essential to continue the power transmission. For example, if an error control message is not sent, the power transmitter 101 will terminate the power transmission.

[0106] Thus, in general, the described functionality may be considered to apply to a power transmission device (either a power transmitter or a power receiver) for performing power transmission with a complementary power transmission device (the other of the power transmitter and the power receiver). For simplicity, the description focuses on a scenario in which the power transmission device including the detection functionality is a power transmitter and the complementary device is a power receiver, but it will be understood that the comments provided also apply when the detection functionality is in the power receiver and the complementary device is a power transmitter. Indeed, in many embodiments, the detection functionality may be implemented in both the power transmitter and the power receiver.

[0107] The explanations and respective comments thus provided also apply (mutatis mutandis) to the complementary set-up, i.e. by exchanging the characteristics and references of the power receiver and the power transmitter, where appropriate.

[0108] In many embodiments, the data used for presence detection (hereafter referred to as presence data) may specifically be an identification of the complementary device, i.e., the power transmitter 101 or the power receiver 105. The identification may be a predefined ID in some embodiments. For example, at the time of manufacture, each device may be assigned a given data pattern and this data pattern may be transmitted as the presence data. The presence detector may have predefined knowledge of the ID data pattern in some embodiments (e.g., the power transmitter may be designed to work with a specific power receiver), but in most embodiments it will be communicated during the initialization of the power transfer. For example, when the power transfer is initialized, the power receiver may transmit an ID data pattern (signature) to the power transmitter, and the transmitter presence detector 209 may start checking that during the power transfer, it receives a data pattern matching this signature from the power receiver often enough. If, instead, no data pattern or an incorrect data pattern is received, the power transmitter may proceed to terminate the power transfer. Thus, if a power receiver is removed and quickly replaced with another power receiver, this will be detected by the transmitter presence detector 209 and power transmission will terminate, even if the power transmitter was able to receive valid control data from the previous power receiver via the out-of-band communication link.

[0109] Thus, in many embodiments, detection of the absence of a complementary device, and in particular detection of the absence of a power receiver by the transmitter presence detector 209, is based on detection of failure to receive an identification indication that meets predetermined criteria, such as failure to receive an expected data pattern within a predetermined time period.

[0110] In many embodiments, the ID indication may be a temporary ID, specifically designed only for this particular power transfer operation. For example, during power transfer initialization, the power transmitter may assign and transmit a data signature (pattern) to the power receiver. The power receiver may then proceed to transmit this data signature at regular intervals during the power transfer operation, and the transmitter presence detector 209 will continually monitor for this data signature and terminate the power transfer if it is not received frequently enough.

[0111] It will also be appreciated that in many embodiments, ID may be transmitted in both directions and both devices may monitor to ensure that proper ID indications are received. Thus, in many embodiments, during power transfer, ID data may be communicated bidirectionally using an in-band communication link and continuation of power transfer may be dependent on correct ID data being received at both devices.

[0112] Specifically, before power transmission starts, the power transmitter and the power receiver can exchange TXID and RXID. During power transmission, the power transmitter transmits TXID and the power receiver transmits RXID via an in-band communication link. Then, if the wireless power transmitter identifies an incorrect (unauthorized) wireless power receiver in the wireless power operating volume (incorrect RXID) or does not identify a wireless power receiver in the wireless power operating volume (no RXID), the wireless power transmitter terminates the power transmission. Similarly, if the power receiver identifies an incorrect wireless power transmitter in the operating volume (incorrect TXID), the power receiver can report this to the power transmitter with which the power transmission was initialized, which can then proceed to terminate the power transmission.

[0113] It will be appreciated that different embodiments may use different presence data and ID indications, including, for example, an out-of-band communications link MAC address, a CRC or other data sequence, or the like.

[0114] In some embodiments, the data exchange can use a request and response format, whereby messages performing detection can initiate and control communications. For example, the transmitter presence detector 209 can determine that it is time for a presence test (e.g., at regular intervals) and can initiate the first transmitter communicator 205 to send a query message to the power receiver requesting a response. For example, a simple pattern may be requested that corresponds to a request for the power receiver ID to be transmitted. In response, the power receiver can proceed to transmit a response message.

[0115] In such a case, if the transmitter presence detector 209 receives a valid response (e.g., proper identification) within a given duration, it can determine that the power receiver is still present. However, if an acceptable response message is not received, the transmitter presence detector 209 determines that the absence of a power receiver has been detected and proceeds to control the power transmitter controller 203 to terminate power transmission.

[0116] The advantage of such an approach is that presence sensing needs to be performed only in one device, typically the power transmitter, but presence is only detected if in-band communication between the power transmitter and the power receiver is possible in both directions.

[0117] In many embodiments, the out-of-band communication link may be used to communicate control data for power transfer, as described above, while the in-band communication link is used only to communicate data for presence detection, such as, for example, only identification data. However, in some embodiments, the system may be configured to distribute control data communication over the in-band and out-of-band communication links, such that both communication approaches may be used for communication of control data.

[0118] This can provide certain advantages in many scenarios. In particular, an out-of-band communication link can provide a high maximum data rate and thus may be suitable for supporting control data having a high data rate. However, despite having a high data rate, many out-of-band communication links tend to provide higher communication delays than in-band communication links. Indeed, many embodiments are characterized in that the in-band communication link supports lower data rates than the out-of-band communication link, but also has a significantly lower data rate. Thus, the in-band communication link may be used in some embodiments for particularly delay-sensitive control data, while the out-of-band communication link is used for high data rate control data.

[0119] As an example, a low latency in-band communication link may be utilized for time critical control data that may indicate immediate actions requested by the power receiver, such as adjusting the power to a negotiated level or immediately ceasing power transmission. An out-of-band communication link may be utilized to negotiate exact power levels or absolute power mismatches, provide an interface to the user to control power transmission, or negotiate other auxiliary data not directly related to power transmission.

[0120] In many embodiments, the presence detection may be based on data that is control data communicated over the in-band communication link. For example, if the transmitter presence detector 209 detects that valid power control messages are received over the in-band communication link frequently enough, it may consider that a power receiver is actually present. However, if the transmitter presence detector 209 detects that no power control messages are received, it may consider that the absence of a power receiver is detected.

[0121] In some embodiments, the power transmission signal is subjected to a repeating time frame that includes at least one power transmission time interval and one reduced power time interval. The repeating time frame is applied to the power transmission signal during the power transmission phase.

[0122] The power level of the power transmission signal is reduced during the reduced power time interval relative to the power transmission time interval, and typically the maximum allowed power during the reduced power time interval is at least 5, 10 or 50 times lower than during the power transmission time interval. The reduction in power level can result from actions at the power transmitter and / or the power receiver. For example, in some embodiments, the power transmitter may be configured to turn off the power transmission signal during the reduced power time interval and / or the power receiver may be configured to disconnect the load during the reduced power time interval.

[0123] The power transmitter and / or the power receiver are configured to perform a communication of presence data during the reduced power time interval, the communication of the presence data being an in-band communication using the power transmission signal as a communication carrier, and accordingly, the power level of the power transmission signal is not set to zero during the reduced power time interval but is set to a lower power level value.

[0124] Typically, the power level of the power transmission signal is further set to a constant fixed value during the reduced power time interval. In some embodiments, the power level during the reduced power time interval is set to a fixed, constant, predetermined value, while in some embodiments the power level may be adapted. However, in most embodiments, this adaptation will be very slow and the power level can be considered to be constant during at least some consecutive reduced power time intervals.

[0125] Thus, the power transmission signal is typically set to a fixed non-zero amplitude / power level for a number of subsequent reduced power time intervals, the power level being further reduced compared to the power level that may be applied outside the reduced power time intervals, and in particular the maximum power level may be reduced during the reduced power time intervals compared to the power transmission signal.

[0126] Figure 4 illustrates an example of operation with a repeating time frame. Figure 4 shows the amplitude of the power transfer signal during a reduced power transfer time interval 401 and during a power transfer interval 403, where in example A the power level changes during the power transfer interval and in example B the power level is constant during the power transfer time interval 403.

[0127] In many embodiments, the voltage supply provided to the driver / inverter 201 is generated directly from the mains voltage without voltage regulation or smoothing (possibly with some rectification) and may therefore in practice often be generated by a sinusoidal or rectified sinusoidal supply voltage. Typically this has a relatively low frequency of 50Hz or 60Hz (or twice that if rectification is applied) and the driver generates a higher frequency drive signal from this supply voltage. The amplitude / power level of the higher frequency drive signal varies accordingly with the supply voltage signal, as shown in FIG. 4.

[0128] In such cases, the reduced power time intervals can be synchronized to variations in the power / amplitude level, specifically to occur around its minimum value, typically corresponding to a zero crossing of the supply voltage to the driver.

[0129] This can provide improved performance, in particular optimizing power transfer performance by minimizing the impact on power transfer due to the introduction of these reduced power time intervals.

[0130] Note that Figure 4 illustrates the power level during the power transfer time interval and shows that the power level during the reduced power time interval is reduced in comparison. However, as discussed above, the power transfer signal is not turned off and the power level is not set to zero. Rather, it is set to a lower, often predetermined, value.

[0131] The presence data is then communicated during the reduced power time interval, and thus during the time during which the power transmission signal may be set to a constant, predetermined level, ensuring more reliable communication and reducing the impact on the power transmission operation of modulating the power transmission signal, which in turn allows for more reliable and robust operation and presence detection.

[0132] In fact, the reduced power level may reduce communication range as the communication carrier power is correspondingly reduced, thereby ensuring that the power receiver and power transmitter are close enough for safe power transmission if the presence data can be successfully communicated, and in fact the power level during the reduced power time interval may be specifically selected to provide a desired communication range for the presence data.

[0133] This approach reflects the realization that for higher power levels, in-band communication may be unreliable or cause unacceptable power losses. For drivers based on AC mains, the modulation of the power carrier may be performed near the mains zero crossing, where the transmitted power level is sufficiently low. During the power transfer / power transfer phase, the power transmitter can operate in two modes: main mode (high power transfer mode) and low power transfer mode, corresponding to the power transfer time interval and the reduced power time interval, respectively.

[0134] Specifically, the wireless power transmitter may periodically suspend its main power supply for a short interval (reduced power time interval). During this slot, the wireless power transmitter provides lower power to the wireless power receiver. During the low power carrier transmission, the wireless power transmitter and the wireless power receiver may exchange data (e.g., RXID and / or TXID) through modulation of the low power carrier.

[0135] In some embodiments, the power transmitter 101 may be configured to not only change the power level, but also change the frequency during the reduced power time intervals. Specifically, it may be configured to increase the frequency of the power transmission signal to be higher during the reduced power time intervals than during the power transmission time intervals. For example, during power transmission, the frequency of the power transmission signal may be 100 kHz, and during the reduced power time intervals, it may be increased to 150 kHz.

[0136] This higher frequency is less suitable for power transmission, but can enable improved communications. For example, it allows for higher bandwidth and therefore higher communication data rates. This can be particularly important for slotted operation, since communication can only be performed in reduced power time intervals, rather than for the entire duration. Thus, the average communication rate may be significantly lower than the instantaneous data rate during the reduced power time interval, and therefore it is important to try to maximize the instantaneous data rate.

[0137] It will be appreciated that for clarity, the above description has described embodiments of the invention with reference to different functional circuits, units and processors. However, it will be apparent that any suitable distribution of functionality between different functional circuits, units or processors may be used without departing from the invention. For example, functionality shown to be performed by separate processors or controllers may be performed by the same processor or controller. Thus, references to specific functional units or circuits should not be regarded as indicative of a strict logical or physical structure or organization, but merely as references to suitable means for providing the described functionality.

[0138] Not all mains signal slots are used for proximity tracking. A given solution opens the possibility of using only some slots (e.g. every other power slot) to transmit low power and detect proximity, while other slots can be used for foreign object detection or other purposes. The size of the slots in which the mains power is interrupted and the interval between two slots can be static values ​​preprogrammed by the wireless power transmitter, preprogrammed static values ​​in the wireless power receiver, or values ​​negotiated between the wireless power receiver and the wireless power transmitter over the communication channel. A trade-off should be taken into account between the slot size, the slot occurrence frequency and the mains power interruption, with too long an interval between slots increasing the risk, and at the same time, the slot size should be sufficient for at least some communication using the low power carrier. In wireless power systems where AC mains power is transmitted, it makes sense to interrupt the power supply near the zero crossings of the AC mains power in order to reduce power losses. Figure 4 shows the time diagram of alternating mains power and low power supply in both AC mains and DC cases.

[0139] To keep the slot size short, the ID transmission can be split into multiple slots, which increases the system response time but reduces the transmitted power level in the AC mains case and reduces the power gap in the DC case.

[0140] The invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. Elements and components of 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 in a single unit or may be physically and functionally distributed between different units, circuits and processors.

[0141] Although the present invention has been described in relation to several embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the appended claims. Moreover, although certain features may appear to be described in relation to a particular embodiment, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0142] 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 may be included in different claims, these may in some cases be advantageously combined, and their inclusion in different claims does not imply that the combination of features is not feasible and / or advantageous. Moreover, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, where appropriate. Moreover, the order of features in the claims does not imply a particular order in which the features must be operated, and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Moreover, a reference to the singular does not exclude a plurality. Thus, reference to "a", "an", "first", "second", etc. does not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any manner.

[0143] The following is provided:

[0144] A power transmission device for wireless power transmission from a power transmitter (101) to a power receiver (103), the power transmission device being one of a power transmitter and a power receiver, the power transmission device comprising: a power transmission coil (103, 107) for transmitting power to a complementary power transmission coil (107, 103) of a complementary power transmission device via a power transmission signal, the complementary power transmission device being the other of the power transmitter (101) and the power receiver (105); a first communicator (205, 305) for communicating first data with the complementary power transmission device over a first communication channel using modulation of the power transmission signal;

[0145] a second communication device (207, 307) for communicating power transmission control data with the complementary power transmission device via a second communication channel, the communication data rate of the second communication channel being at least 10 times higher than the communication data rate of the first communication channel; The power transmission device includes a presence detector (209, 309) configured to determine whether a complementary power transmission device is present in the vicinity of the power transmission coil (103, 107) in response to the first data, and a power transmission controller (201, 301) configured to limit wireless power transmission from the power transmitter (101) to the power receiver (103) in response to detecting the absence of the complementary power transmission device.

[0146] A method of operating a power transfer apparatus for wireless power transfer from a power transmitter (101) to a power receiver (103), the power transfer apparatus being one of the power transmitter and the power receiver, the method comprising: a step of the power transmission coil (103, 107) transmitting power to a complementary power transmission coil (107, 103) of a complementary power transmission device via a power transmission signal, the complementary power transmission device being the other of the power transmitter (101) and the power receiver (105); communicating first data to a complementary power transmission device over a first communication channel using modulation of the power transmission signal; communicating power transmission control data with the complementary power transmission device via a second communication channel independent of the power transmission signal, the communication data rate of the second communication channel being at least ten times higher than the communication data rate of the first communication channel; The method includes a step of determining whether a complementary power transmission device is present in the vicinity of the power transmission coil (103, 107) in response to the first data, and a step of restricting wireless power transmission from the power transmitter (101) to the power receiver (103) in response to detecting that a complementary power transmission device is not present.

[0147] A power transmission system for wireless power transmission from a power transmitter (101) to a power receiver (103), comprising: The power transmitter (101) a power transmitter coil (103) for generating a power transmission signal for transmitting power to a power receiver (105); a first transmitter communicator (205) for communicating first data with the power receiver (105) over a first communication channel using modulation of the power transmission signal; a second transmitter communicator (207) for communicating power transmission control data with the complementary power transmission device over a second communication channel, the communication data rate of the second communication channel being at least ten times higher than the communication data rate of the first communication channel; The power receiver (103) a power receiver coil (107) for receiving power via a power transmission signal, a first receiver communicator (305) for communicating first data with the power receiver (105) via a first communication channel, and a second receiver communicator (307) for communicating power transmission control data with the power transmitter (101) via a second communication channel; At least one of the power transmitter (101) and the power receiver (103) further comprises: a presence detector (209, 309) for determining whether a complementary power transmission device is present in the vicinity of the power transmission coil (103, 107) in response to the first data, the complementary power transmission device being the other of the at least one of the power transmitter (101) and the power receiver (103), and a power transmission controller (201, 301) configured to limit wireless power transmission from the power transmitter (101) to the power receiver (103) in response to detecting the absence of the complementary power transmission device.

Claims

1. 1. A power transmission device for wireless power transmission from a power transmitter to a power receiver, the power transmission device being one of the power transmitter and the power receiver, the power transmission device comprising: a power transmission coil for transmitting power with a complementary power transmission coil of a complementary power transmission device via a power transmission signal, the complementary power transmission device being the other of the power transmitter and the power receiver; a first communicator for communicating first data with the complementary power transmission device over a first communication channel using modulation of the power transmission signal during power transmission; a second communicator for communicating power transmission control data with the complementary power transmission device during power transmission via a second communication channel independent of the power transmission signal, the communication data rate of the second communication channel being at least ten times higher than the communication data rate of the first communication channel; a presence detector that determines whether the complementary power transfer device is present in the vicinity of the power transfer coil during power transfer in response to the first data; a power transfer controller configured to limit the wireless power transfer from the power transmitter to the power receiver in response to detecting the absence of the complementary power transfer device; having the power transmission signal during power transmission uses a repetitive time frame having at least a power transmission time interval and a reduced power time interval, during the reduced power time interval a power level of the power transmission signal is reduced relative to the power transmission time interval, and the first communicator is configured to communicate the first data during the reduced power time interval; the first communicator and the second communicator are configured to simultaneously establish a communication link for the first communication channel and a communication link for the second communication channel during a power transfer operation. Power transmission device.

2. The power transfer device of claim 1 , wherein the communication data rate of the first communication channel is 500 bits / second or less.

3. The power transfer device of claim 1 , wherein the communication data rate of the first communication channel is 100 bits / second or less.

4. 4. The power transmission device of claim 1, wherein the first data is received from the complementary power transmission device, and the presence detector is configured to determine the absence of the complementary power transmission device in response to detecting that the first data satisfying a criterion is not received.

5. 5. A power transmission device as claimed in any one of claims 1 to 4, wherein the first data includes an identification of the complementary power transmission device, and the presence detector is configured to detect the absence of the complementary power transmission device in response to the identification satisfying a criterion not being received.

6. 6. The power transmission device of claim 1, wherein the first communication device is configured to transmit a query message to the complementary power transmission device, and the presence detector is configured to detect the absence of the complementary power transmission device in response to the first data having a valid response to the query message not being received.

7. The power transfer device according to claim 1 , wherein the first data comprises control data for power transfer.

8. 8. The power transmission device of claim 1, further comprising a power controller configured to communicate control data for power transmission with the complementary power transmission devices, the power controller being configured to communicate some control data with the complementary power transmission devices via the first communication channel and other control data with the complementary power transmission devices via the second communication channel.

9. 9. The power transfer arrangement of claim 1, wherein the power transfer signal has a fixed, non-zero amplitude during a number of consecutive reduced power time intervals.

10. 10. The power transfer arrangement of claim 1, wherein a frequency of the power transfer signal is higher during the reduced power time intervals than during the power transfer time intervals.

11. 11. The power transfer device of claim 1, wherein the power transfer device is the power receiver and the complementary power transfer device is the power transmitter.

12. 11. The power transfer device of claim 1, wherein the power transfer device is the power transmitter and the complementary power transfer device is the power receiver.

13. 1. A power transfer system for wireless power transfer from a power transmitter to a power receiver, comprising: The power transmitter comprises: a power transmitter coil for generating a power transmission signal for transmitting power to the power receiver; a first transmitter communicator for communicating first data with the power receiver over a first communication channel using modulation of the power transmission signal during power transmission; a second transmitter communicator for communicating power transmission control data with the power receiver during power transmission via a second communication channel independent of the power transmission signal, the communication data rate of the second communication channel being at least ten times higher than the communication data rate of the first communication channel; The power receiver includes: a power receiver coil for receiving power via the power transmission signal; a first receiver communicator for communicating the first data with the power transmitter over the first communication channel during power transmission; a second receiver communicator for communicating the power transmission control data with the power transmitter over the second communication channel during power transmission; At least one of the power transmitter and the power receiver further comprises: a presence detector for determining whether a counterpart device of a power transfer operation is present in the vicinity of the power transmitter coil or the power receiver coil during power transfer in response to the first data; a power transfer controller configured to limit the wireless power transfer from the power transmitter to the power receiver in response to detecting the absence of the counterpart device; the power transmission signal during power transmission uses a repetitive time frame having at least a power transmission time interval and a reduced power time interval, during the reduced power time interval a power level of the power transmission signal is reduced relative to the power transmission time interval, and the first transmitter transceiver and the first receiver transceiver are configured to communicate the first data during the reduced power time interval; the first transmitter communicator, the second transmitter communicator, the first receiver communicator, and the second receiver communicator are configured to simultaneously establish a communication link for the first communication channel and a communication link for the second communication channel during a power transfer operation. system.

14. The power transfer device of claim 1, wherein the first data is presence data dedicated to determining whether the complementary power transfer device is present in the vicinity of the power transfer coil.

15. A power transmission device as described in claim 1 or 14, wherein the first communication channel is used only to communicate data for determining whether the complementary power transmission device is present in the vicinity of the power transmission coil.

16. A power transmission device as described in claim 1, 14 or 15, wherein the power transmission control data includes a power control loop error message.

17. The method of claim 1, wherein the first data is presence data dedicated to determining whether the complementary power transfer device is present in the vicinity of the power transfer coil, the power transfer control data includes a power control loop error message; The power transfer apparatus of claim 1 , wherein the presence data and the power control loop error message are both communicated during a power transfer phase.

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