Wireless power transfer system

Abstract

A power transmitter (101) wirelessly provides power to a power receiver (105) via a power transfer signal generated by a power transfer coil (103). During the power transmission, the driver (201) generates a power transmission signal to employ a repeating time frame comprising a power transmission time interval and a communication time interval in which the power transmission signal is turned off. The communication driver (209) generates a communication drive signal for the communication coil (207) to generate a communication carrier signal. Communication between the power transmitter and the power receiver is by modulation of a communication carrier signal during a communication time interval. A communication driver (205) generates a communication carrier signal to be present during repeating time frames other than in a timing gap that does not exceed 50% of the duration of the power transfer time interval. The set of timing gaps includes a predetermined pattern of a plurality of timing gaps. A power receiver extracts power from the communication carrier signal and synchronizes operation based on a timing gap.

Description

Technical Field

[0001] The present invention relates to the operation of a wireless power transfer system. Background Art

[0002] Most electrical products today require a dedicated electrical contact to be powered from an external power source. However, this is often impractical and requires the user to physically insert a connector or otherwise establish a physical electrical contact. Typically, the power requirements also vary significantly, and most current devices are provided with their own dedicated power source, resulting in the typical user having a large number of different power sources, each dedicated to a specific device. Although the use of an internal battery can avoid the need for a wired connection to a power source during use, this only provides a partial solution as the battery will need to be recharged (or replaced). The use of a battery can also significantly increase the weight of the device as well as the potential cost and size.

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

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

[0005] Such an arrangement allows for wireless power transfer to a device without requiring any wired or physical electrical connection. In fact, it can simply allow the device to be placed near or on top of the transmitter coil for external recharging or power supply. For example, the power transmitter device can be arranged with a horizontal surface on which the device can simply be placed for power supply.

[0006] Furthermore, such a wireless power transfer arrangement can be advantageously designed such that the power transmitter device can be used with a range of power receiver devices. Specifically, a wireless power transfer method called the Qi specification has been defined and is currently being further developed. This method allows a power transmitter device that meets the Qi specification to be used with a power receiver device that also meets the Qi specification, without these devices having to be from the same manufacturer or having to be dedicated to each other. The Qi standard also includes provisions for allowing the operation of a certain function adapted to a specific power receiver device (e.g., depending on a specific power consumption).

[0007] The Qi specification was developed by the Wireless Power Consortium and more information can be found, for example, on its website:

[0008] http: / / www.wirelesspowerconsortium.com / index.html, where, specifically, the defined specification documents can be found.

[0009] The Wireless Power Consortium has continued to develop the Ki specification (also known as the cordless kitchen specification) based on the Qi specification, which is designed to provide safe, reliable, and efficient wireless power transfer to kitchen appliances. Ki supports much higher power levels of up to 2.5KW.

[0010] In many systems, such as specifically the Qi system, communication from the power receiver to the power transmitter can use load modulation, where the load of the power transfer signal varies according to the data to be sent. However, such load modulation may be difficult to detect whether the power transfer loading of the power transfer signal changes simultaneously. Similarly, communication from the power transmitter to the power receiver can be achieved by modulating the power transfer signal (e.g., amplitude or frequency modulation), but interference to such modulation may be caused by parameter changes of the power transfer signal due to, for example, varying loads.

[0011] Therefore, in some systems, the use of a completely independent communication method has been proposed. Specifically, the Ki wireless power transfer system can use the Near Field Communication (NFC) standard to establish a two-way communication link. The communication is during the power transfer phase that is executed within a short time interval to avoid or reduce interference between power transfer and communication. The power receiver is arranged to detect the NFC carrier to perform communication during the short time interval.

[0012] During the power transfer operation, the power receiver extracts power for the load from the power transfer signal. In many cases, the extraction of power is also used to power functions such as the processing unit, user interface, etc. of the power receiver itself. However, such a method requires additional functions and may not be optimal in all scenarios.

[0013] Therefore, improved operation of the wireless power transfer system would be beneficial. In particular, methods that allow increased flexibility, reduced cost, reduced complexity, improved communication, additional functions, and / or improved performance would be beneficial. Summary of the Invention

[0014] Accordingly, the present invention seeks to preferably attenuate, mitigate, or eliminate one or more of the above disadvantages, either singly or in any combination.

[0015] According to one aspect of the present invention, there is provided a power transmitter for wirelessly providing power to a power receiver via an inductive power transfer signal. The power transmitter includes: a power transfer coil arranged to generate the power transfer signal; a power transfer driver arranged to generate a power transfer drive signal for the power transfer coil, the power transfer driver being arranged to generate the power transfer drive signal during a power transfer phase to employ a repeating time frame including at least a power transfer time interval and a communication time interval, the power transfer driver being arranged to generate the power transfer drive signal during the power transfer time interval and not to generate the power transfer drive signal during the communication time interval; a communication coil arranged to generate a communication carrier signal, a communication driver arranged to generate a communication drive signal for the communication coil to generate the communication carrier signal; a communication unit arranged to communicate with the power receiver using modulation of the communication carrier signal during the communication time interval; wherein, the communication driver is arranged to generate the communication drive signal, the communication drive signal being present during the communication time interval and the power transfer time interval except during a set of fixed time slots during which no communication drive signal is generated, the total combined duration of the set of fixed time slots not exceeding 50% of the duration of the power transfer time interval; wherein, the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

[0016] The present invention can provide improved performance in many embodiments and can provide overall improved power transfer operation in many systems and embodiments. For example, in many embodiments, improved operation and communication can be achieved. The method can allow for efficient and low-complexity synchronization between the power transmitter and the power receiver. In many scenarios, the method can allow for an improved secondary power path from the power transmitter to the power receiver, which provides improved low power level transmission. In many embodiments, the method can allow for a reduction in the complexity of the power receiver and, in many cases, can eliminate the need for the power receiver to include a function for extracting power from the power transfer signal of the internal power receiver circuit.

[0017] The method can allow for increased power extraction from the communication carrier signal while still allowing for effective synchronization and communication.

[0018] In many embodiments, the method can also allow for more continuous power extraction from the communication carrier signal, thereby reducing variations, such as reducing the ripple caused by power extraction. This can further improve load modulation as it can be a more stable communication carrier signal.

[0019] In many embodiments, a set of timing gaps using a predetermined pattern including multiple timing gaps can allow for improved operation and / or facilitate implementation and / or operation. In particular, in many scenarios, it can allow for more accurate detection of the timing gaps and thus can improve synchronous operation, thereby enhancing performance.

[0020] In many embodiments, the duration of the communication time interval does not exceed 5%, 10%, or 20% of the duration of the time frame. In many embodiments, the duration of the power transmission time interval is not less than 70%, 80%, or 90% of the duration of the repeating time frame. In many embodiments, the combined / total duration of the timing gaps may not exceed 1%, 2%, 5%, or 10% of the duration of the power transmission time interval and / or the duration of the repeating time frame.

[0021] Modulation of the communication carrier signal during the communication time interval can be performed by load modulation of the carrier from the power receiver to the power transmitter and / or by amplitude modulation from the power transmitter to the power receiver. The communication can be NFC communication.

[0022] The timing gap can also be referred to as a synchronization time interval, a timing time interval, or a synchronization gap.

[0023] The power transmitter can include a synchronizer for synchronizing the timing of the set of timing gaps with the repeating time interval. Each time interval can have a fixed / predetermined / constant time offset to the repeating time frame (e.g., to its start and / or end). The power transmitter can include a synchronizer for synchronizing the timing of the set of timing gaps with at least one of the timing of the power transmission time interval and the communication time interval.

[0024] The power transmission driver can be arranged to generate the power transmission drive signal and thus the power transmission signal to have a non-zero amplitude during the power transmission time interval and a zero amplitude during the communication time interval.

[0025] The communication driver can be arranged to generate the communication drive signal and thus the communication carrier signal to have a non-zero amplitude, except during the timing gap. The communication driver can be arranged to generate the communication drive signal and thus the communication carrier signal to have an amplitude variation less than 10% of the average amplitude outside the timing gap. The communication driver can be arranged to generate the communication drive signal to have a zero amplitude during the timing gap.

[0026] According to an optional feature of the present invention, the communication driver is arranged to generate the communication drive signal such that at least a first timing gap in the set of timing gaps has a fixed time offset to the timing of the power transmission time interval.

[0027] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0028] In some embodiments, the communication driver may be arranged to generate the communication drive signal such that at least a first timing gap in the set of timing gaps has a fixed time offset with respect to the timing of a communication time interval.

[0029] In some embodiments, the communication driver may be arranged to generate the communication drive signal such that at least a first timing gap in the set of timing gaps has a fixed time offset with respect to the timing of a repeating time frame.

[0030] According to an optional feature of the present invention, the set of timing gaps is included in a power transfer time interval.

[0031] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0032] According to an optional feature of the present invention, the predetermined pattern is a pattern of a plurality of timing gaps having the same duration and the same time difference between consecutive timing gaps of the same repeating time frame.

[0033] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0034] According to an optional feature of the present invention, the predetermined pattern is selected from a plurality of predetermined patterns.

[0035] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0036] According to an optional feature of the present invention, the power transfer driver is arranged to be powered by a time-varying power supply signal, and the communication driver is arranged to synchronize the timing of the set of timing gaps with the varying power supply signal.

[0037] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0038] The time-varying power supply signal may be generated from a mains power supply, for example directly or by rectification of an AC mains signal. The repeating time frame may be synchronized with the time-varying power supply signal / mains power supply. The power transfer driver may be arranged to generate a time-varying drive signal during the power transfer time interval, and the communication driver may be arranged to synchronize the timing of the set of timing gaps with the time-varying drive signal.

[0039] According to an optional feature of the present invention, the communication driver is arranged to synchronize the end of a timing gap in the set of timing gaps with the end of the power transfer time interval.

[0040] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation.

[0041] According to an optional feature of the present invention, the power transmitter is arranged to exchange configuration messages with the power receiver, the configuration messages including an indication of the nature of at least one of the plurality of timed slots.

[0042] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation. The configuration message may be an NDEF message for NFC communication.

[0043] According to an optional feature of the present invention, the total combined duration of the timed slots does not exceed 5% of the duration of the power transfer time interval.

[0044] According to an aspect of the present invention, there is provided a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transfer signal, the power transfer signal employing a repeating time frame including at least a power transfer time interval and a communication time interval, the power transfer signal being present during the power transfer time interval and absent during the communication time interval, the power receiver comprising: an inductive power extraction element arranged to extract power from the power transfer signal during the power transfer time interval of a power transfer phase; a communication coil for receiving a received communication carrier signal, the communication carrier signal being present during the communication time interval and the power transfer time interval except during a set of timed slots, and no communication carrier signal being present during the set of timed slots, the total combined duration of the set of timed slots not exceeding 50% of the duration of the power transfer time interval; a communication unit arranged to communicate with the power transmitter using modulation of the communication carrier signal during the communication time interval; a synchronizer arranged to synchronize the operation of the power receiver with the timing of the set of timed slots; wherein the set of timed slots includes a predetermined pattern of a plurality of timed slots.

[0045] In many embodiments, this may allow for improved operation and / or facilitate implementation and / or operation. In many scenarios, it may allow for providing a power receiver with lower complexity and / or lower cost. In many scenarios, the method may reduce or even avoid the requirements for circuitry for extracting power from the power transfer signal for internal power receiver functions.

[0046] According to an aspect of the present invention, there is provided a wireless power transfer system including the power transmitter and the power receiver as described above.

[0047] According to an aspect of the present invention, there is provided a method of operating a power transmitter that wirelessly provides power to a power receiver via an inductive power transfer signal. The method includes: a power transfer coil generating the power transfer signal; generating a power transfer drive signal for the power transfer coil, the drive signal being generated during a power transfer phase to employ a repeating time frame that includes at least a power transfer time interval and a communication time interval, the power transfer drive signal being generated to be present during the power transfer time interval but not present during the communication time interval; a communication coil generating a communication carrier signal; generating a communication drive signal for the communication coil to generate the communication carrier signal; communicating with the power receiver using modulation of the communication carrier signal during the communication time interval; wherein, the communication drive signal is generated to be present during the communication time interval and the power transfer time interval except during a set of fixed time slots during which no communication drive signal is generated, and the total combined duration of the set of fixed time slots does not exceed 50% of the duration of the power transfer time interval; wherein, the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

[0048] According to an aspect of the present invention, there is provided a method of operating a power receiver that wirelessly receives power from a power transmitter via an electromagnetic power transfer signal. The power transfer signal employs a repeating time frame that includes at least a power transfer time interval and a communication time interval, the power transfer signal being present during the power transfer time interval and not present during the communication time interval. The power receiver includes: extracting power from the power transfer signal during the power transfer time interval of a power transfer phase; a communication coil receiving a received communication carrier signal, the communication carrier signal being present during the communication time interval and the power transfer time interval except during a set of fixed time slots during which no communication carrier signal is present, and the total combined duration of the set of fixed time slots does not exceed 50% of the duration of the power transfer time interval; communicating with the power transmitter using modulation of the communication carrier signal during the communication time interval; and synchronizing the operation of the power receiver with the timing of the set of fixed time slots; wherein, the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

[0049] These and other aspects, features, and advantages of the present invention will be apparent from and will be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Embodiments of the present invention will be described by way of example only with reference to the drawings, wherein

[0051] Figure 1 Illustrates an example of elements of a power transfer system according to some embodiments of the present invention;

[0052] Figure 2 Illustrates an example of elements of a power transmitter according to some embodiments of the present invention;

[0053] Figure 3 Illustrates an example of elements of a power receiver according to some embodiments of the present invention;

[0054] Figure 4 Illustrates an example of a time frame of a wireless power transfer system according to some embodiments of the present invention;

[0055] Figure 5 Illustrates examples of a power transfer signal and a communication carrier signal in a wireless power transfer system;

[0056] Figure 6 Illustrates examples of a power transfer signal and a communication carrier signal in a wireless power transfer system according to some embodiments of the present invention;

[0057] Figure 7 Illustrates an example of elements of a power transfer path for wireless power transfer operation; and

[0058] Figure 8 Illustrates examples of a power transfer signal and a communication carrier signal in a wireless power transfer system according to some embodiments of the present invention. Detailed Description

[0059] The following description focuses on embodiments of the present invention applicable to a wireless power transfer system that utilizes a power transfer method such as that known from the Qi standard. However, it should be understood that the present invention is not limited to this application, but can be applied to many other wireless power transfer systems.

[0060] Figure 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, and the power transmitter 101 includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105, and the power receiver 105 includes (or is coupled to) a receiver coil / inductor 107.

[0061] The system provides an electromagnetic power transfer signal that can inductively transfer power from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal that propagates as a magnetic flux through the transmitter coil or inductor 103. The power transfer signal can correspond to an electromagnetic power transfer component representing the energy transfer from the power transmitter to the power receiver and can be considered to correspond to a component of the generated electromagnetic field that transfers power from the power transmitter to the power receiver. For example, if there is no loading of the receiving coil 107, the power receiver will not extract power from the generated electromagnetic field (except for losses). In such a scenario, driving the transmitter coil 103 can generate an electromagnetic field with potentially high field strength, but the power level of the power transfer signal will be zero (except for losses). In some cases where there is a foreign object, it can be considered that the power transfer signal includes a component corresponding to power transfer to the foreign object and, thus, the power transfer signal can be considered to correspond to the power extracted from the electromagnetic field generated by the power transmitter.

[0062] The power transfer signal can typically have a frequency between approximately 20 kHz and approximately 500 kHz and, for a Ki - compatible system, typically in the range between 20 kHz and 80 kHz. The transmitter coil 103 and the power receiving coil 107 are loosely coupled, and thus, the power receiving coil 107 picks up (at least part of) the power transfer signal from the power transmitter 101. Thus, power is transferred from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the power receiving coil 107. The term power transfer signal is mainly used to refer to the inductive signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107, but it should be understood that, by equivalence, it can also be considered and used as a reference to the electrical signal provided to the transmitter coil 103 or picked up by the power receiving coil 107.

[0063] In this example, the power receiver 105 is specifically a power receiver that receives power via the receiver coil 107. However, in other embodiments, the power receiver 105 can include a metal element, such as a metal heating element, in which case the power transfer signal directly induces eddy currents, resulting in direct heating of the element. Thus, the power receiver can provide a load to the power transfer signal by including an inductive power extraction element, which can specifically be a power extraction coil or an electrical (e.g., heating) element, where a current is induced by the power transfer signal.

[0064] The system is arranged to transfer substantial power levels, and in particular, the power transmitter can support power levels in excess of 50 W, 100 W, 500 W, or 1 kW. For example, for Ki-type applications, power transfer can often exceed 100 W, and for very high power applications, power transfer can be as high as in excess of 2500 W.

[0065] Hereinafter, the operation of the power transmitter 101 and the power receiver 105 will be described specifically with reference to embodiments that generally conform to the specifications developed by the Wireless Power Consortium (except for the modifications and enhancements described herein (or corresponding thereto)). In particular, the power transmitter 101 and the power receiver 105 can follow the elements of the Ki standard or be substantially compatible with the elements of the Ki standard.

[0066] Many wireless power transfer systems (and especially high power systems such as Ki) utilize resonant power transfer, where the transmitter coil 103 is part of a resonant circuit and typically the receiver coil 107 is also part of a resonant circuit. In many embodiments, the resonant circuit can be a series resonant circuit, and thus the transmitter coil 103 and the receiver coil 107 can be serially coupled with corresponding resonant capacitors. The use of resonant circuits tends to provide more efficient power transfer.

[0067] Figure 2 More specifically illustrated Figure 1 the elements of the power transmitter 101, and Figure 3 More specifically illustrated Figure 1 the elements of the power receiver 105.

[0068] The power transmitter 101 includes a driver 201 that can generate a drive signal that is fed to the transmitter coil 103, which in turn generates an electromagnetic power transfer signal that provides power transfer to the power receiver 105. The power transfer signal is provided during at least the power transfer time interval of the power transfer phase.

[0069] The driver 201 can generally include an output circuit in the form of an inverter, which is typically formed by driving a full bridge or a half bridge, as will be known to those skilled in the art.

[0070] The power transmitter 101 also includes a power transmitter controller 203 that is arranged to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 can include many of the functions required to perform power control according to the Qi specification.

[0071] The power transmitter controller 203 is specifically arranged to control the generation of the drive signal by the driver 201, and it can specifically control the power level of the drive signal, and thus control the level of the generated power transfer signal. The power transmitter controller 203 includes a power loop controller that controls the power level of the power transfer signal in response to a power control message received from the power receiver 105 during a power control phase.

[0072] To receive data and messages from the power receiver 105, the power transmitter 101 includes a first communicator 205 that is arranged to receive data and messages from the power receiver 105 and send data and messages to the power receiver 105 (as will be understood by those skilled in the art, data messages can provide information of one or more bits).

[0073] In this method, communication is performed by modulating a communication carrier signal generated by the first communication coil 207. The power transmitter specifically includes a communication driver 209 coupled to the first communication coil 207. The communication driver 209 is arranged to generate a communication drive signal that is fed to the first communication coil 207 to generate a communication carrier signal. The communication driver 209 can generally be arranged to generate the communication drive signal / communication carrier signal to have a frequency substantially different from that of the power transfer drive signal / power transfer signal. In many embodiments, the frequency of the communication carrier signal can be not less than 10, 100, or 500 times higher than the frequency of the power transfer signal. In many embodiments, the frequency of the communication drive signal / communication carrier signal can have a frequency of not less than 500 kHz, 1 MHz, or 10 MHz. Specifically, for NFC implementations, the communication carrier signal frequency can be 13.56 MHz.

[0074] The first communicator 205 is coupled to the communication driver 209 and is arranged to control the communication driver to modulate the communication drive signal / communication carrier signal in order to send data to the power receiver (in due course, in the following references to the communication drive signal, an implicit reference to the communication carrier signal is also included).

[0075] In a specific example, the modulation is amplitude modulation of the communication drive signal, and specifically binary communication using amplitude shift keying (ASK) is used. However, it should be understood that in other embodiments, other methods of modulation can be used, such as phase or frequency modulation of the communication drive signal.

[0076] In some embodiments, the first communicator 205 may receive, for example, data to be sent to the power receiver from the power transmitter controller 203, and in response generate a control modulation signal that is fed to the communication driver 209. The control modulation signal may be, for example, a binary signal that matches the data to be sent, and the communication driver 209 may be arranged to generate a communication drive signal with corresponding amplitude variations.

[0077] For communication from the power receiver to the power transmitter, the modulation of the communication drive signal may be load modulation. The power receiver may be arranged to modulate the power transfer signal by changing the loading of the power transfer signal generated by the transmitter coil 103 according to the data to be sent. The first communicator 205 may be arranged to sense changes in the voltage and / or current of the transmitter coil 103 and demodulate the load modulation based thereon. Those skilled in the art will be aware of the principles of load modulation and will therefore not be described in more detail.

[0078] In many embodiments, the communication may be in accordance with the Near Field Communication (NFC) standard, and the power receiver may specifically include NFC functionality. In many embodiments, the first communicator 205, the communication driver 209, and the first communication coil 207 may (at least) implement the functionality of an NFC reader. Thus, in many embodiments, the communication drive signal / communication carrier signal is a 13.56 MHz signal at a constant level (except for modulation).

[0079] The following description will focus on an example where the communication between the power transmitter and the power receiver is via NFC communication, and specifically where the modulation of the NFC carrier in the direction from the power transmitter to the power receiver is by amplitude shift keying (ASK), and the modulation of the NFC carrier in the direction from the power receiver to the power transmitter is by load modulation.

[0080] In Figure 1-3 's system, the communication is during a power transfer phase that is executed at communication time intervals. Specifically, the transmitter controller 203 may include / implement a synchronizer 206 that is arranged to synchronize the first communicator 205 such that communication operations (generally both receiving and sending data) are performed during the communication time intervals of the power transfer phase (and generally only during the communication time intervals of the power transfer phase), i.e., during the time intervals allocated for communication.

[0081] This can significantly improve communication performance.

[0082] As will be described in more detail below, the method utilizes a time-division method during the power transfer phase, where operations such as foreign object detection and communication as well as power transfer can be performed, for example, in different time intervals, thereby allowing a significant reduction in interference between these operations (in particular, the impact of power transfer on foreign object detection / communication).

[0083] Specifically, for a wireless power transfer system, the power transfer signal undergoes a repetitive time frame including at least one power transfer time interval and one communication time interval.

[0084] The power transmitter can be arranged to turn off the power transfer signal during the communication time interval, and in some embodiments, the power receiver can be arranged to disconnect the load during a reduced power time interval.

[0085] Then, the power transmitter (and generally the power receiver) can be arranged for one or more operations (functions, processes, procedures) to be performed during the communication time interval, i.e., it can synchronize the execution of one or more operations of the power transmitter to occur during the communication interval. For example, it can generally synchronize the execution of foreign object detection and communication to occur during the communication time interval. In this way, it can be achieved that the impact of power transfer and the power transfer signal on a given operation (in particular, foreign object detection and communication) can be reduced and generally minimized.

[0086] Figure 3 Some exemplary elements of the power receiver 105 are illustrated.

[0087] The receiver coil 107 is coupled to the power receiver controller 301, and the power receiver controller 301 couples the receiver coil 107 to the load 303 via a switch 305 (i.e., it is a switchable load 305). The power receiver controller 301 includes a power control path that converts the power extracted by the receiver coil 107 into a suitable power supply for the load 303. In addition, the power receiver controller 301 can include various power receiver controller functions required to perform power transfer, and in particular, functions required to perform power transfer according to the Qi specification.

[0088] To support communication from the power receiver 105 to the power transmitter 101, the power receiver 105 includes a second communicator 307 and a second communication coil 309. The second communication coil 309 is arranged to be coupled to the first communication coil 207, and thus a communication carrier signal induces a current (at least emf) in the second communication coil 309.

[0089] The second communicator 307 is coupled to the second communication coil 309 and is arranged to determine an amplitude change of the inductive signal and demodulate the amplitude modulation of the communication carrier signal. Thus, the second communicator 307 is arranged to decode data transmitted from the power transmitter by amplitude modulation of the communication carrier signal. It should be understood that in other embodiments, the second communicator 307 may be arranged to decode data modulated onto the communication carrier signal using other modulation formats such as frequency or phase modulation.

[0090] The second communicator 307 is also arranged to perform load modulation on the communication carrier signal in order to transmit data from the power receiver to the power transmitter. Specifically, the second communicator 307 may include a load (such as a capacitor) that can be switched between being coupled to the second communication coil 309 and not being coupled to the second communication coil 309 depending on the data to be transmitted. These load modulations can then be detected by the first communicator 205 of the power transmitter.

[0091] In a specific example, the second communication coil 309 and the second communicator 307 may provide NFC - compatible communication operation. Specifically, the second communication coil 309 may be arranged to provide a function corresponding to an NFC tag and decode data that has been ASK - modulated onto the communication carrier signal according to the NFC specification.

[0092] Thus, the second communicator 307 is arranged to transmit data to the power transmitter by changing the loading of the receiver coil 107 in response to data to be sent to the power transmitter 101. Then, as will be known to those skilled in the art, the power transmitter 101 detects and demodulates the load change.

[0093] In this example, the second communicator 307 is also arranged to demodulate the amplitude, frequency, and / or phase modulation of the communication carrier signal in order to retrieve data transmitted from the power transmitter.

[0094] The system applies a repetitive time frame during the power transfer phase, where the time frame includes at least one power transfer time interval and at least one communication time interval. An example of such a repetitive time frame is illustrated in Figure 4 where the power transfer time interval is indicated by PT and the communication time interval is indicated by C. In this example, each time frame FRM includes only one communication time interval and one power transfer time interval. However, it should be understood that in other embodiments, other time intervals may also be included in the time frame, or multiple communication time intervals and / or power transfer time intervals may be included in each time frame.

[0095] The power transfer driver 201 is controlled by the power transmitter controller 205 to generate a drive signal only during a power transfer time interval and not during a communication time interval. Thus, the driver generates a drive signal during the power transfer time interval and thus generates a power transfer signal, while the drive signal and thus the power transfer signal are turned off during the communication time interval.

[0096] During the power transfer phase, the power transmitter is thus arranged to perform power transfer during the power transfer time intervals of the time frame of the power transfer phase. Specifically, during these time intervals, the power transmitter and the power receiver can operate a power control loop (the power control loop can be based on communication within a communication time interval corresponding to a repeating time interval). Thus, the level of the power being transferred can vary dynamically.

[0097] However, during the communication time intervals of the time frame of the power transfer phase, the power drive signal is turned off, and thus no power transfer signal is generated during the communication time interval.

[0098] Communication between the power transmitter and the power receiver is during the power transfer phase in the communication time intervals and is typically only performed in the communication time intervals. Communication via the first communication coil 207 and the second communication coil 309 is only performed in the communication time intervals, and specifically, modulation of the communication carrier signal only occurs in the communication time intervals.

[0099] In this system, the first communicator 205 is thus arranged to send data only during the communication time intervals and thus to modulate (e.g., amplitude) the communication carrier signal only during the communication time intervals. Similarly, it typically only seeks to demodulate data during the communication time intervals.

[0100] Similarly, the second communicator 307 is arranged to communicate only during the communication time intervals when in the power transfer phase. In this system, the second communicator 307 is thus arranged to send data only during the communication time intervals and thus to perform load modulation on the communication carrier signal only during the communication time intervals. Similarly, it typically only seeks to demodulate data during the communication time intervals.

[0101] Thus, during the power transfer phase, the first communicator 205 and the second communicator 307 are arranged to communicate only during the communication time intervals. Such an approach can provide highly advantageous performance and has in particular been found to provide significantly improved communication performance. Specifically, this method reduces interference from the power transfer signal to communication operations, thus providing more reliable and robust communication with reduced bit errors.

[0102] In Figure 5An example of how communication can be performed in communication time intervals of a repeating time frame is shown. Figure 5 A power transfer signal 501 generated during a power transfer time interval PT and a modulated communication carrier signal 503 generated during a communication time interval C are shown. Figure 5 A time division between power transfer and communication is implemented, where each operation is performed in a dedicated time interval.

[0103] However, in Figure 1-4 the method of the system of, a more flexible and overlapping method is applied. In fact, in this method, the power transmitter is arranged to generate a communication carrier signal that exists during the power transfer time interval, and thus, when the power transfer signal is generated during the power transfer time interval, it coexists. However, the communication carrier signal is not generated to be continuously present, but one or more fixed time gaps are inserted in the time frames in which the communication drive signal and the communication carrier signal are not generated. Thus, relatively short gaps are typically inserted into the generation of the communication carrier signal. Further, in this method, the modulation of the communication carrier signal is controlled differently from the generation of the communication carrier signal, and specifically, the modulation is controlled to occur only during the communication time interval. Thus, the communication drive signal and the communication carrier signal generated during the power transfer time interval are unmodulated.

[0104] Figure 6 An example of a method that can be used by the system of Figure 1-4 is illustrated. In this example, the power transfer signal 601 is as for Figure 5 , but the communication carrier signal 603 is generated throughout the repeating time frame (except for the short fixed time gaps in each time frame in which the communication carrier signal 603 is turned off).

[0105] This method can be particularly used to provide a second low-level power transfer path from the power transmitter to the power receiver. Specifically, the power receiver includes a power extractor 311, which is arranged to extract power from the communication carrier signal when the communication carrier signal is present. In a specific example, the power extractor 311 can extract power from an NFC carrier signal accordingly.

[0106] Thus, power can be provided from the power transmitter to the power receiver via communication carrier signal / NFC carrier power harvesting. This can provide power to low power levels, as well as low voltage electronics such as NFC hardware or user interfaces, for example.

[0107] The power extractor 311 can be relatively simple, and an example of a power extraction circuit / power path is illustrated in Figure 7 .

[0108] Figure 7The circuit diagram of the components illustrating an example of the power path of the power extractor 311 is shown. In this example, the second communication coil 309 is referred to by the name LRX, and when this is subjected to a communication carrier signal, a corresponding AC voltage / current is induced in the coil. The second communication coil 309 is coupled to a series capacitor CRX, which together form an input resonant circuit that is also coupled to a rectifier bridge B1. A smoothing capacitor C1 is coupled to the output of the bridge. Thus, a DC voltage is generated across the capacitor C1. The amplitude of the ripple on the DC voltage will depend on the size of the smoothing capacitor and the load RL supplied by the power extractor 311. The use of the input resonant circuit formed by LRX and CRX provides a more efficient power transfer coupling. The inclusion of CRX causes the circuit to resonate at the communication carrier frequency, and thus power harvesting mainly operates at the communication frequency.

[0109] The bridge B1 and the smoothing capacitor C1 are coupled to the load RL via a switch S1, which can be used to turn on and off power extraction / harvesting. It should be understood that in many embodiments, the power extractor 311 can be directly and permanently coupled to the load RL without the presence of a switch.

[0110] Figure 7 Also shown is a load modulation capacitor C2, which can be connected in parallel with or disconnected from the second communication coil 309 based on the switching of a switch S2. The second communicator 307 can control the switch S2 during communication time intervals to provide the desired load modulation.

[0111] Thus, the power extractor 311 can be implemented with low-complexity and low-cost circuitry.

[0112] Power extraction is supported by an extended duration of the communication carrier signal and is thus generated and produced even during the power transfer time intervals. In fact, in many embodiments, the fixed time gaps during which no communication carrier signal is generated can be very short and substantially insignificant, thereby allowing power extraction to be performed almost constantly. This can provide a significantly increased extracted power. For example, for NFC implementations, the extracted power can typically be as high as about 200 mW, while using a method such as Figure 5 (where the communication time interval for each 10 msec time frame is typically about 1.5 msec) would allow only 30 mW to be extracted. Additionally, a more stable output voltage with significantly reduced ripple can be achieved because the smoothing capacitor only needs to support the power during short fixed time gaps rather than most of the time frame. Generally, this can allow much smaller capacitors to be used, which can significantly reduce cost and improve reliability because capacitors not only tend to be relatively expensive but also tend to be less reliable and more error-prone than most electronic components.

[0113] The ability to extract increased power from a communication carrier signal can be significant in many scenarios and can allow for significant design flexibility. For example, many electronic circuits including low-performance processing circuitry (e.g., including a microcontroller) can be designed to have a power consumption of less than 200 mW, while it is generally very difficult or impossible to design such a circuit with a power consumption of less than 30 mW. In many practical applications, the increased power level can significantly reduce complexity and cost. In fact, if more power than a given method can extract from the communication carrier signal is required, additional power supplies need to be implemented to draw power from a high-voltage power transmission system (i.e., from a power transmission signal). For example, this can be a capacitive power supply requiring high-voltage capacitors or a specific type of buck converter suitable for high-voltage input. This generally requires components that are more expensive and bulkier than those required for a method such as the method described for the power extractor 311.

[0114] The method can also allow for improved load modulation by reducing ripple. In Figure 7 the example, expanding the communication carrier signal results in the voltage on C1 having less ripple. Thus, the load modulation introduced by C2 will be for a more constant situation with less variation, resulting in improved load-modulated communication. In particular, as other variations decrease, the variation caused by C2 is more easily detected by the power transmitter.

[0115] Thus, the method for many practical applications allows for significantly reduced complexity and cost. For example, a power receiving device including a heating element as a load can be directly powered by a power transmission signal that induces a current directly in the heating element. In fact, in such an example, the method described can, in many cases, allow the control and support circuitry and the user interface to be implemented and fully powered by the communication carrier signal and specifically by the NFC carrier. Thus, in some cases, the method can allow for the design of a power receiving device that does not include electronic circuitry powered by the power transmission signal. Thus, complex high-voltage power extraction circuitry can be completely avoided. This would generally be impossible if, for example, only 30 mW of power supply were available.

[0116] However, instead of generating a continuous power transmission signal throughout the time frame, one or more fixed time gaps are applied in the time frame during which no communication drive signal and communication carrier signal are generated (hereinafter these will be referred to simply as fixed time gaps for brevity). In Figure 6 the example, a short fixed time gap 605 is introduced at the end of each power transmission time interval and immediately before the start of the communication time interval.

[0117] These timing gaps are used to provide timing information from the power transmitter to the power receiver. Specifically, the timing gaps can be introduced to start and / or stop at specific and / or predetermined moments within each time frame.

[0118] Thus, Figure 3 the power receiver includes a synchronizer 313 to synchronize the operation of the power receiver to the timing of the (one or more) timing gaps. The synchronizer 313 can specifically adapt the time of the local time base in response to the timing of the (one or more) timing gaps and can time the operation of the power receiver according to the local time base.

[0119] Operations that can be synchronized to the timing of the timing gaps can include any suitable time operations of the power receiver. In particular, the synchronizer 313 can synchronize the timing of the locally applied repeating time frames, i.e., it can synchronize the timing to the application and operation of the functions of the repeating time frames. The synchronizer 313 can specifically synchronize the operations of the communication time intervals and the power transfer time intervals to the timing gaps. As a specific example, the modulation and / or demodulation of the communication carrier signal by the second communicator 307 can be synchronized to / based on the timing of the timing gaps.

[0120] Thus, the timing gaps of the communication carrier signal allow the power transmitter and the power receiver to operate in close alignment and synchronization, and in particular allow the operation of the power receiver to be aligned and synchronized with the repeating time frames employed by the power transfer signal, which is generated by the power transfer driver.

[0121] Generally, all repeating time frames are the same and have the same time intervals, where these time intervals have the same duration and order in each time frame.

[0122] In many embodiments, the repeating time frame can have a duration between 5 and 25 msecs, and specifically, in many embodiments, it can be 10 ms or 20 ms (for a 50 Hz mains-powered power transmitter) or 8.3 ms or 16.7 ms (for a 60 Hz mains-powered power transmitter).

[0123] The duration of the power transfer time interval is generally not less than 60% or 80% of the repeating time frame. In many embodiments, the duration of the power transfer time interval can be in the range of 3 - 20 msec, and specifically between 5 - 9.5 msec. In many embodiments, the duration of the power transfer time interval can be in the range of 7 - 9 msec, and specifically can be approximately 8.5 msec.

[0124] The duration of the communication time interval is typically substantially less than the power transfer time interval and can typically be no more than 20% or 30% of the duration of the power transfer time interval. The duration of the communication time interval can typically be in the range of 1 - 2 milliseconds.

[0125] The duration of the fixed time slots can depend on the specific preferences and requirements of individual embodiments. However, the communication carrier signal is generated to substantially extend into the power transfer time interval, and specifically, the total combined duration of the set of fixed time slots does not exceed 50% of the duration of the power transfer time interval. Thus, the communication carrier signal is generated within at least 50% of the power transfer time interval. In many embodiments, the combined duration of the fixed time slots is significantly smaller, and in fact, in many embodiments, the combined total duration of the set of fixed time slots does not exceed 20%, 10%, 5%, 2%, or even 1% of the duration of the power transfer time interval and / or the repetition time frame.

[0126] Thus, the duration of the fixed time slots remains relatively short, allowing for extraction of increased power levels. At the same time, the fixed time slots can remain long enough to be detectable by the synchronizer 313 to allow for accurate timing determination. In many embodiments, each fixed time slot can be no less than 0.1%, 0.5%, 1%, 2%, or 5% of the duration of the timing frame. In many embodiments, the duration of the fixed time slots can be in the range from 0.1 msec to 5 msec, and specifically in the range from 0.2 msec to 1 msec.

[0127] Thus, in an example, the particular generation of the communication drive signal and the communication carrier signal enables the signal to provide multiple features in addition to the primary purpose of the communication for which it is provided. In particular, the method can advantageously generate a communication carrier signal that not only provides a means / carrier for communication but also allows for an effective low-level power transfer path and provides timing / synchronization information from the power transmitter to the power receiver.

[0128] Thus, efficient operation can be achieved, which can not only provide highly advantageous performance but also, for example, reduce the complexity and cost of the circuitry required at the power receiver.

[0129] The method can be particularly advantageous for embodiments in which the communication carrier signal is an NFC carrier. In such an embodiment, the power transmitter can implement the NFC reader function. In such a method, NFC is the master device and controls the communication with the power receiver that listens and responds as necessary. Thus, the power receiver is unaware of the timing of the communication. However, the described approach can advantageously and efficiently provide a timing synchronization method.

[0130] Another advantage of the continuous supply function powered by the power extracted from the NFC carrier is that such power can be very consistent, regardless of the power delivered to the main load through inductive power transfer. For example, the Ki power receiver covers a wide range of power levels. For example, depending on how the blender is used, the blender may require between 25 W and 1.5 kW, and thus the main power supply needs to be able to operate within this large input range to always provide sufficient power to the low-voltage circuit. This is particularly important at very low powers using phase cut / discontinuous mode and power is transferred only during part of the mains cycle.

[0131] In many embodiments, the power driver 201 may be powered by a time-varying power supply signal. In particular, the supply voltage to the output stage may be generated from an AC voltage, such as specifically from an AC mains voltage. In some embodiments, the AC voltage may be directly used as the supply voltage for the output circuit (e.g., inverter) of the power driver 201. In many embodiments, the supply voltage may alternatively be generated as a rectified mains voltage. Thus, in many embodiments, the (absolute) supply voltage varies as a (possibly rectified) sine wave with a given period. As a result, the generated power transfer drive signal has a (sine wave) time-varying amplitude, as also Figure 5 and 6 shown. The amplitude has a minimum value (usually a zero value) corresponding to the zero crossing of the input supply voltage and specifically corresponding to the zero crossing of the mains. Thus, the power transfer drive signal / power transfer signal is generated with a period having half the period of the AC mains signal.

[0132] In such embodiments, the repeating time frame and accordingly the power transfer time interval and the communication time interval can be synchronized with the varying power supply signal and thus with the timing of the amplitude variation of the power transfer drive signal. In particular, the communication time interval can be arranged to be at (including) the minimum value of the amplitude (corresponding to the zero crossing of the mains signal).

[0133] Similarly, the communication driver 209 is arranged to generate a communication drive signal and thus generate a communication carrier signal such that the timing gap is also synchronized with the varying power supply signal.

[0134] Thus, in many embodiments, the repeating time frame, the power transfer time interval, the communication time interval, and the timing gap (especially in the power transmitter) are synchronized with the time-varying power supply signal and in particular with the mains power supply.

[0135] In different embodiments, the timing gap can be arranged at different positions in the time frame.

[0136] In many embodiments, a timing gap may be included to indicate the transition from the power transfer time interval to the communication time interval. For example, inFigure 6 In the example of, the fixed time gap is located at the end of the power transfer time interval and thus when the communication time interval is about to start. Such a fixed time gap can facilitate the synchronization of the repeated time frames at the receiver and, in particular, can allow for a low-complexity adaptation of the timing of operations related to the communication time interval and the power transfer time interval. In particular, it can allow for an improved and / or simplified adaptation of the timing of communication operations. The synchronizer 313 can, for example, simply detect the fixed time gap and switch to communication time interval operation when the end of the fixed time gap is detected. Specifically, modulation and demodulation can be performed immediately after the end of the fixed time gap is detected.

[0137] In some embodiments, the power transmitter can alternatively or additionally add a fixed time gap at the start of the power transfer time interval. For example, just before the power transfer driver 201 that generates the power transfer drive signal turns on the power transfer signal, the communication driver 209 can be controlled to insert a gap in the generated communication carrier signal such that this ends when the power transfer signal is turned on. Such a gap can be used, for example, by the synchronizer 313 of the power receiver for, e.g., turning on a load, terminating any modulation of the communication carrier signal, stopping the demodulation of the communication carrier signal, etc.

[0138] As another example of an operation or process that can be synchronized by the timing of such a fixed time gap is, for example, measuring the true RMS power by measuring the power during a complete repeated time frame that can correspond to the mains cycle and calculating the RMS power based on the measured values. To perform such a measurement, it is important to measure the entire mains period and thus the measurement should start exactly at the start of the mains period and end exactly at the end. In some embodiments, the period can be represented by the interval between two fixed time gaps.

[0139] In some embodiments, the fixed time gap can, for example, alternatively or additionally be located at other times in the repeated time frame and specifically within the power transfer time interval. For example, a fixed time gap can be inserted at the maximum amplitude level of the power transfer signal, thereby allowing for an accurate measurement of this level at the power receiver simply by timing the measurement of the fixed time gap. Such a measurement can, for example, be used as an indication of the power transfer (e.g., to a heating element or a motor).

[0140] In many embodiments, one or more of the fixed time gaps are included in the power transfer time interval and, in fact, in many embodiments, the fixed time gap is introduced only during the power transfer time interval. In many embodiments, no fixed time gap is included in the communication time interval.

[0141] Such methods can typically provide improved performance as the impact of the timing gap can be reduced. For example, it can avoid communication being interrupted by communication carrier signals that are not available for modulation. In many scenarios, it can also allow for lower complexity on the power receiver side and facilitate the synchronizer 313 (e.g., allowing functions to be triggered simply by detecting the start or end of the timing gap, as in the previously provided examples).

[0142] However, it should be understood that in some embodiments, one, more, or all of the timing gaps can be outside the power transfer time interval and can actually be during the communication time interval. For example, a timing gap can be provided at the start of the communication time interval instead of positioning the timing gap at the end of the power transfer time interval. For example, the start of the timing gap can occur while the power transfer signal is turned off, and the end of the timing gap can occur, for example, after a fixed duration of the timing gap. In such a case, the synchronizer 313 can control the modulation / demodulation to start at the end of the timing gap.

[0143] Each repetition time frame can include only a single timing gap. This can, for example, allow for lower complexity operation and / or minimize the interruption to the communication carrier signal.

[0144] However, in this method, the timing gap can include a setting pattern of multiple timing gaps. The pattern of the timing gap can specifically be a predetermined pattern. The pattern can be given / characterized by the duration of the timing gap and the delay / time offset between the timing gaps.

[0145] In many embodiments, the duration of each timing gap can be the same, but it should be understood that in some embodiments, the timing gaps can have different durations. Similarly, the time offset between adjacent timing gaps can typically be the same, but can be different in some embodiments.

[0146] In some embodiments, the predetermined pattern can be a set of timing gaps where the time offset / delay / duration between consecutive timing gaps with the same duration and the same repetition time frame is the same. Figure 7 An example of such a method is illustrated, where a pattern consisting of four short equally spaced timing gaps with the same duration is used.

[0147] The use of such patterns can improve operation in many cases. It can generally provide improved detection of the fixed time slots, thereby allowing for more accurate synchronization. In fact, using a pattern instead of a single fixed time slot can provide the advantage of improved detectability. In many embodiments, there may be multiple mechanisms capable of generating gaps in the NFC carrier, such as communication errors, transitions between connection modes and power modes, foreign object detection (FOD) measurements, etc. In some embodiments, this may make it difficult for the power receiver to properly distinguish the fixed time slots from other gaps that may be caused by other factors (such as those indicated above). It is almost impossible or even impossible to achieve more accurate and reliable detection and thus synchronization from the patterns in which other events occur.

[0148] In some embodiments, the pattern can be a pattern selected from a plurality of predetermined patterns. This can, for example, allow for the identification of the power transmitter and can allow for coexistence between different power transmitters.

[0149] For example, the power transmitter arrangement may include a plurality of transmitter coils positioned relatively close to each other. For example, the working surface may have a plurality of power transfer locations that can be used by the power receiving device. However, this may result in the generation of multiple communication carrier signals very close to each other. In some embodiment cases, different fixed time slot patterns can be used for different transmitter coils. This can reduce interference and allow for improved synchronization and can thus provide improved interoperability between different transmitter coils / power transmitters arranged close to each other.

[0150] In many embodiments, the power transmitter and the power receiver can be arranged to adapt the nature of one or more fixed time slots based on the communication exchange between the power transmitter and the power receiver. Specifically, a configuration message having a request or indication of the nature of the fixed time slot can be sent from the power receiver. The configuration message can, for example, include a direct or indirect request for the nature of at least one of the plurality of fixed time slots. Alternatively or additionally, the configuration message can provide information on the configuration of the power receiver. The configuration message can, for example, be part of a negotiation method performed during the initialization of power transfer (such as during the connection phase of the Ki power receiver and the wireless power transfer system). Then, the power transmitter can continue to adapt the nature of the fixed time slot in response to the configuration message. For example, the power receiver can request a specific fixed time slot pattern or fixed time slot duration, and the power transmitter can continue to set the value accordingly.

[0151] In some embodiments, the configuration message may indicate whether the power receiver can support the described operation (e.g., a power receiver capable of supporting the operation may be arranged to send a message indicating that it does have such an ability). The indication may be directly related to the operation or may be more general, such as by indicating the version of the specification compatible with the power receiver. In such a case, if the power receiver indicates that it can support the operation, the power transmitter may be arranged to use only the described operation and, in particular, the timed slots.

[0152] For NFC implementations, the configuration message may specifically be an NDEF (NFC Data Exchange Format) message.

[0153] It should be understood that, for clarity, the above description has described embodiments of the invention with reference to different functional circuits, units, and processors. However, it will be apparent that any suitable distribution of functionality between different functional circuits, units, or processors may be used without departing from the invention. For example, functions illustrated as being performed by separate processors or controllers may be performed by the same processor or controller. Thus, the reference to a particular functional unit or circuit is only considered a reference to a suitable module for providing the described functionality and does not indicate a strict logical or physical structure or organization.

[0154] The present invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The present invention may optionally be implemented at least in part as computer software running on one or more data processors and / or digital signal processors. The elements and components of embodiments of the present invention can be physically, functionally, and logically implemented in any suitable manner. In fact, the functionality can be implemented in a single unit, in multiple units, or as part of other functional units. As such, the present invention can be implemented in a single unit or can be physically and functionally distributed between different units, circuits, and processors.

[0155] Although the invention has been described in connection with some embodiments, it is not intended to limit the invention to the specific forms set forth herein. On the contrary, the scope of the invention is limited only by the appended claims. Additionally, although features may seem to be described in connection with specific embodiments, those skilled in the art will recognize that the various features of the described embodiments can be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0156] It should be understood that the reference to a preferred value does not imply any limitation beyond that which is determined as a value in the foreign object detection initialization mode, i.e., preferably by virtue of its being determined during an adjustment process. The reference to a preferred value may replace the reference to, for example, a first value.

[0157] In addition, although listed individually, multiple modules, elements, circuits or method steps can be implemented by, for example, a single circuit, unit or processor. In addition, although individual features may be included in different claims, these may be advantageously combined, and inclusion in different claims does not mean that the combination of features is not feasible and / or disadvantageous. The inclusion of features in a class of claims does not mean a restriction on the class, but rather indicates that the feature is equally applicable to other claim classes when appropriate. In addition, the order of features in the claims does not mean any specific order in which the features must work, and in particular, the order of individual steps in the method claims does not mean that the steps must be performed in that order. On the contrary, the steps can be performed in any suitable order. In addition, singular references do not exclude multiples. Therefore, references to "one", "one", "first", "second", etc. do not exclude multiples. The figure marks in the claims are provided only to make the examples clear and should not be interpreted as limiting the scope of the claims in any way.

[0158] In general, examples of a power transmitter and an operating method thereof, a power receiver and an operating method thereof, and a wireless power transmitter are indicated by the following embodiments.

[0159] Example:

[0160] Embodiment 1. A power transmitter (101) for wirelessly providing power to a power receiver (105) via an inductive power transfer signal, the power transmitter (101) comprising:

[0161] a power transfer coil (103) arranged to generate said power transfer signal;

[0162] a power transfer driver (201) arranged to generate a power transfer drive signal for the power transfer coil (103), the power transfer driver (201) being arranged to generate the power transfer drive signal during a power transfer phase to adopt a repeating time frame comprising at least a power transfer time interval and a communication time interval, the power transfer driver (201) being arranged to generate the power transfer drive signal during the power transfer time interval and not to generate the power transfer drive signal during the communication time interval;

[0163] a communication coil (207) arranged to generate a communication carrier signal,

[0164] a communication driver (209) arranged to generate a communication drive signal for the communication coil to generate the communication carrier signal;

[0165] A communication unit (205) arranged to communicate with the power receiver (105) during a communication time interval using modulation of the communication carrier signal;

[0166] wherein the communication driver (205) is arranged to generate the communication drive signal, the communication drive signal being present during the communication time interval except during a set of fixed time slots during which no communication drive signal is generated, the total combined duration of the set of fixed time slots not exceeding 50% of the duration of the power transmission time interval.

[0167] Example 2. The power transmitter (101) according to any one of the preceding embodiments, wherein the communication driver (205) is arranged to generate the communication drive signal such that at least a first fixed time slot in the set of fixed time slots has a fixed time offset with respect to the timing of the power transmission time interval.

[0168] Example 3. The power transmitter (101) according to any one of the preceding embodiments, wherein the set of fixed time slots is included in the power transmission time interval.

[0169] Example 4. The power transmitter (101) according to any one of the preceding embodiments, wherein the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

[0170] Example 5. The power transmitter (101) according to Example 4, wherein the predetermined pattern is a pattern of a plurality of fixed time slots having the same duration and the same time difference between consecutive fixed time slots in the same repeating time frame.

[0171] Example 6. The power transmitter (101) according to Example 4 or 5, wherein the predetermined pattern is selected from a plurality of predetermined patterns.

[0172] Example 7. The apparatus according to any one of the preceding embodiments, and the power transmission driver (201) is arranged to be powered by a time-varying power supply signal, and the communication driver (205) is arranged to synchronize the timing of the set of fixed time slots with the varying power supply signal.

[0173] Example 8. The power transmitter (101) according to any one of the preceding embodiments, wherein the communication driver (205) is arranged to synchronize the end of a fixed time slot in the set of fixed time slots with the end of the power transmission time interval.

[0174] Example 9. A power transmitter (101) according to any one of the preceding embodiments, wherein the power transmitter (101) is arranged to exchange configuration messages with the power receiver (105), the configuration messages including an indication of the nature of at least one of the plurality of fixed time slots.

[0175] Example 10. A power transmitter (101) according to any one of the preceding embodiments, wherein the total combined duration of the fixed time slots does not exceed 5% of the duration of the power transfer time interval.

[0176] Example 11. A power receiver (105) for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transfer signal, the power transfer signal employing a repeating time frame including at least a power transfer time interval and a communication time interval, the power transfer signal being present during the power transfer time interval and absent during the communication time interval, the power receiver (105) comprising:

[0177] An inductive power extraction element (107) arranged to extract power from the power transfer signal during the power transfer time interval of the power transfer phase;

[0178] A communication coil (309) for receiving a received communication carrier signal, the communication carrier signal being present during the communication time interval and the power transfer time interval except during a set of fixed time slots, and no communication carrier signal being present during the set of fixed time slots, the total combined duration of the set of fixed time slots not exceeding 50% of the duration of the power transfer time interval;

[0179] A communication unit (307) arranged to communicate with the power transmitter using modulation of the communication carrier signal during the communication time interval;

[0180] A synchronizer (313) arranged to synchronize the operation of the power receiver with the timing of the set of fixed time slots.

[0181] Example 12. The power receiver further includes a power extractor (311) coupled to the communication coil (309) and arranged to extract a power signal from the communication coil (309) and supply power to the circuitry of the power receiver through the power signal.

[0182] Example 13. A wireless power transfer system comprising a power transmitter according to any one of Examples 1 - 10 and a power receiver according to any one of Examples 11 and 12.

[0183] Embodiment 14. A method for operating a power transmitter (101), the power transmitter wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, the method comprising:

[0184] A power transmission coil (103) generates the power transmission signal;

[0185] Generate a power transmission drive signal for the power transmission coil (103), the drive signal being generated during a power transmission phase to employ a repeating time frame including at least a power transmission time interval and a communication time interval, the power transmission drive signal being generated to be present during the power transmission time interval but absent during the communication time interval;

[0186] A communication coil (207) generates a communication carrier signal;

[0187] Generate a communication drive signal for the communication coil to generate the communication carrier signal;

[0188] Communicate with the power receiver (105) during the communication time interval using modulation of the communication carrier signal;

[0189] Wherein the communication drive signal is generated to be present during the communication time interval and the power transmission time interval except during a set of fixed time slots during which no communication drive signal is generated, and the total combined duration of the set of fixed time slots does not exceed 50% of the duration of the power transmission time interval.

[0190] Embodiment 15. A method for operating a power receiver (105), the power receiver wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, the power transmission signal employing a repeating time frame including at least a power transmission time interval and a communication time interval, the power transmission signal being present during the power transmission time interval and absent during the communication time interval, the power receiver (105) comprising:

[0191] Extract power from the power transmission signal during the power transmission time interval of the power transmission phase;

[0192] A communication coil (309) receives a received communication carrier signal, the communication carrier signal being present during the communication time interval and the power transmission time interval except during a set of fixed time slots during which no communication carrier signal is present, and the total combined duration of the fixed time slots does not exceed 50% of the duration of the power transmission time interval;

[0193] Communicate with the power transmitter using modulation of the communication carrier signal during the communication time interval; and

[0194] Synchronize the operation of the power receiver with the timing of the set of timing gaps.

Claims

1. A power transmitter (101) for wirelessly supplying power to a power receiver (105) via inductive power transfer signals, the power transmitter (101) comprising: A power transfer coil (103) arranged to generate the power transfer signals; A power transfer driver (201) arranged to generate a power transfer drive signal for the power transfer coil (103), the power transfer driver (201) being arranged to generate the power transfer drive signal during a power transfer phase to employ a repetitive time frame including at least a power transfer time interval and a communication time interval, the power transfer driver (201) being arranged to generate the power transfer drive signal during the power transfer time interval and not to generate the power transfer drive signal during the communication time interval; A communication coil (207) arranged to generate a communication carrier signal, A communication driver (209) arranged to generate a communication drive signal for the communication coil to generate the communication carrier signal; A communication unit (205) arranged to communicate with the power receiver (105) during the communication time interval using modulation of the communication carrier signal; Wherein the communication driver (205) is arranged to generate the communication drive signal, the communication drive signal being present during the communication time interval and the power transfer time interval except during a set of fixed time slots during which no communication drive signal is generated, the total combined duration of the set of fixed time slots not exceeding 50% of the duration of the power transfer time interval; wherein the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

2. The power transmitter (101) according to any one of the preceding claims, wherein, The communication driver (205) is arranged to generate the communication drive signal such that at least a first fixed time slot in the set of fixed time slots has a fixed time offset from the timing of the power transfer time interval.

3. The power transmitter (101) according to any one of the preceding claims, wherein, The set of fixed time slots is included in the power transfer time interval.

4. The power transmitter (101) according to claim 1, wherein, The predetermined pattern is a pattern of a plurality of fixed time slots having the same duration and the same time difference between consecutive fixed time slots in the same repetitive time frame.

5. The power transmitter (101) according to claim 1 or 4, wherein, The predetermined pattern is selected from a plurality of predetermined patterns.

6. The apparatus according to any one of the preceding claims, and the power transfer driver (201) is arranged to be powered by a time-varying power supply signal, and the communication driver (205) is arranged to synchronize the timing of the set of fixed time slots with the varying power supply signal.

7. The power transmitter (101) according to any one of the preceding claims, wherein, The communication driver (205) is arranged to synchronize the end of a fixed time slot in the set of fixed time slots with the end of the power transfer time interval.

8. The power transmitter (101) according to any one of the preceding claims, wherein, The power transmitter (101) is arranged to exchange configuration messages with the power receiver (105), the configuration messages including an indication of the nature of at least one fixed time slot of the plurality of fixed time slots.

9. The power transmitter (101) according to any one of the preceding claims, wherein, The total combined duration of the fixed time slots does not exceed 5% of the duration of the power transfer time interval.

10. A power receiver (105) for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, the power transmission signal employing a repeating time frame that at least includes a power transmission time interval and a communication time interval, the power transmission signal being present during the power transmission time interval and absent during the communication time interval, the power receiver (105) comprising: An inductive power extraction element (107) arranged to extract power from the power transmission signal during the power transmission time interval of a power transmission phase; A communication coil (309) for receiving a received communication carrier signal, the communication carrier signal being present during the communication time interval and the power transmission time interval except during a set of fixed time slots during which no communication carrier signal is present, the total combined duration of the set of fixed time slots not exceeding 50% of the duration of the power transmission time interval; A communication unit (307) arranged to communicate with the power transmitter during the communication time interval using modulation of the communication carrier signal; A synchronizer (313) arranged to synchronize the operation of the power receiver with the timing of the set of fixed time slots; wherein the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

11. The power receiver further comprises a power extractor (311) coupled to the communication coil (309) and arranged to extract a power signal from the communication coil (309) and supply power to the circuitry of the power receiver through the power signal.

12. A wireless power transfer system comprising a power transmitter according to any one of claims 1-9 and a power receiver according to any one of claims 10 and 11.

13. An operating method for a power transmitter (101), the power transmitter wirelessly supplying power to a power receiver (105) via an inductive power transmission signal, the method comprising: A power transmission coil (103) generating the power transmission signal; Generating a power transmission drive signal for the power transmission coil (103), the drive signal being generated during a power transmission phase to employ a repeating time frame that at least includes a power transmission time interval and a communication time interval, the power transmission drive signal being generated to be present during the power transmission time interval but absent during the communication time interval; A communication coil (207) generating a communication carrier signal; Generating a communication drive signal for the communication coil to generate the communication carrier signal; Communicating with the power receiver (105) during the communication time interval using modulation of the communication carrier signal; Wherein, the communication drive signal is generated to exist during a communication time interval and the power transmission time interval except during a set of fixed time slots, during which no communication drive signal is generated, and the total combined duration of the set of fixed time slots does not exceed 50% of the duration of the power transmission time interval; wherein, the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

14. An operating method for a power receiver (105), the power receiver wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, the power transmission signal employing a repeating time frame including at least a power transmission time interval and a communication time interval, the power transmission signal existing during the power transmission time interval and not existing during the communication time interval, the power receiver (105) comprising: extracting power from the power transmission signal during the power transmission time interval of the power transmission phase; a communication coil (309) receiving a received communication carrier signal, the communication carrier signal existing during a communication time interval and the power transmission time interval except during a set of fixed time slots, during which no communication carrier signal exists, and the total combined duration of the fixed time slots does not exceed 50% of the duration of the power transmission time interval; communicating with the power transmitter using modulation of the communication carrier signal during the communication time interval; and synchronizing the operation of the power receiver with the timing of the set of fixed time slots; wherein, the set of fixed time slots includes a predetermined pattern of a plurality of fixed time slots.

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