Wireless power transfer system

Abstract

The power transmitter (101) wirelessly provides power to the power receiver (105) via the power transfer signal. During the power transfer, the driver (201) generates a power transfer signal to employ a repeating time frame comprising a power transfer time interval and a communication time interval in which the power transfer 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 a power transmitter and a power receiver is achieved by modulating a communication carrier signal during a communication time interval. A determiner (211) determines a power extraction indication indicating a power extraction characteristic for extracting power from the communication carrier signal by the power receiver during at least a portion of the communication time interval, and a level controller (213) controls a level of the communication drive signal during the communication time interval in accordance with the power extraction indication.

Description

Technical Field

[0001] This invention relates to the operation of a wireless power transmission system. Background Technology

[0002] Most modern electrical products require dedicated electrical contacts to be powered from an external power source. However, this is often impractical and requires the user to physically insert connectors or otherwise establish physical electrical contact. Power requirements also typically vary significantly, and most devices are currently supplied with their own dedicated power supplies, resulting in a large number of different power sources for the average user, each dedicated to a specific device. While using 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 will require charging (or replacement). Using a battery can also significantly increase the weight of the device, as well as potential cost and size.

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

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

[0005] This arrangement allows for wireless power transfer to the device without requiring any wired or physical electrical connections. In practice, it can simply allow the device to be placed adjacent to or on top of the transmitter coil for external charging or power supply. For example, the power transmitter device can be arranged on a horizontal surface, and the device can simply be placed on that surface to be powered.

[0006] Furthermore, this wireless power transfer arrangement can be advantageously designed so that power transmitter devices can be used with a range of power receiver devices. Specifically, a wireless power transfer method known as the Qi specification has been defined and is currently under further development. This method allows power transmitter devices that meet the Qi specification to be used with power receiver devices that also meet the Qi specification, without them having to come from the same manufacturer or be specific to each other. The Qi standard also includes features that allow operation adapted to specific power receiver devices (e.g., depending on specific power consumption).

[0007] The Qi specification was developed by the Wireless Power Consortium, and more information can be found, for example, on their website: http: / / www.wirelesspowerconsortium.com / index.html, where the specification document specifically defines the specifications.

[0008] The Wireless Power Consortium (WPC) developed the Ki specification (also known as the Wireless Power Kitchen specification) based on the Qi specification, which aims to provide safe, reliable, and efficient wireless power transmission to kitchen appliances. Ki supports much higher power levels, up to 2.5 kW.

[0009] In many systems, such as the Qi system, communication from a power receiver to a power transmitter can use load modulation, where the load of the power transmission signal varies depending on the data to be transmitted. However, such load modulation can make it difficult to detect whether the power transmission load of the power transmission signal changes simultaneously. Similarly, communication from a power transmitter to a power receiver can be achieved by modulating the power transmission signal (e.g., amplitude or frequency modulation); however, interference with such modulation can be caused by changes in the parameters of the power transmission signal, such as those due to a varying load.

[0010] Therefore, in some systems, a completely separate communication method has been proposed. Specifically, the Ki wireless power transfer system can establish a bidirectional communication link using near-field communication (NFC) or standard protocols. Communication is performed in short time intervals during the power transfer phase to avoid or reduce interference between power transfer and communication. The power receiver is positioned to detect the NFC carrier to perform communication during these short time intervals.

[0011] During power transfer operations, the power receiver extracts power from the load using the power transfer signal. In many cases, power extraction is also used to power functions of the power receiver itself, such as processing units, user interfaces, etc. However, in many cases, the power receiver may also extract power from the NFC communication carrier to power internal circuitry, etc., in certain scenarios and at certain time intervals. This can be done, for example, during operation prior to the power transfer phase when the power transfer signal is unavailable. This can increase the complexity of the power extraction circuitry at the power receiver and may lead to unintended interference between extraction functions, which could affect other functions and operations, such as communication performance, in particular.

[0012] Therefore, improved operation for wireless power transfer systems would be advantageous, specifically, methods that allow for increased flexibility, reduced cost, reduced complexity, improved communication, additional functionality, lower power receiver circuit complexity, lower power receiver circuit cost, reduced interference between power extraction and communication, increased bandwidth / data rate, and / or improved performance. Summary of the Invention

[0013] Therefore, the present invention attempts to mitigate, reduce or eliminate one or more of the above-mentioned disadvantages, preferably alone or in any combination.

[0014] According to one aspect of the invention, a power transmitter is provided for wirelessly providing power to a power receiver via an electromagnetic power transmission signal. The power transmitter includes: a power transmission coil arranged to generate a power transmission signal; a power transmission driver arranged to generate a power transmission drive signal for the power transmission coil, the power transmission driver being arranged to generate the power transmission drive signal during a power transmission phase to employ a repetitive time frame including at least a power transmission time interval and a communication time interval, the power transmission driver being arranged to generate the power transmission drive signal during the power transmission time interval and not generate the power transmission 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 communicator arranged to communicate with the power receiver using load modulation of the communication carrier signal; a determiner arranged to determine a power extraction indication indicating a power extraction characteristic during at least a portion of the communication time interval by which the power receiver extracts power from the communication carrier signal; and a level controller arranged to control the level of the communication drive signal during the communication time interval according to the power extraction indication.

[0015] This invention can provide improved performance in many embodiments and scenarios, and can provide overall improved power transmission operation in many systems and embodiments. For example, in many embodiments, improved operation and communication can be achieved. The method can allow efficient extraction of power from both the power transmission signal and the communication carrier signal, while reducing or mitigating the impact of this power extraction on communication performance. In many scenarios, improved communication performance can be achieved, such as improved reliability, reduced error rate, increased bandwidth, increased data rate, reduced latency, etc.

[0016] In many scenarios, this method can allow for an improved secondary power path from the power transmitter to the power receiver, providing improved low-power level transmission. In many embodiments, this method can allow for reduced complexity in the power receiver. In many scenarios, it can allow for the efficient combination of different power extraction options using low-complexity and low-cost circuitry, such as combining power paths using rectifiers without the need for switches or the need to perform switching operations.

[0017] 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 one or more power transmission time intervals is not less than 70%, 80%, or 90% of the duration of the repeating time frame.

[0018] Modulation of the communication carrier signal during the communication time interval can be achieved through load modulation of the carrier from the power receiver to the power transmitter and / or amplitude modulation from the power transmitter to the power receiver. The communication can be NFC communication.

[0019] A power transfer driver can be arranged to generate a power transfer drive signal, and thus a power transfer signal, having a non-zero amplitude during the power transfer time interval and a zero amplitude during the communication time interval.

[0020] A communication carrier signal can also be simply referred to as a communication carrier. A communication carrier signal can be an electromagnetic field / signal generated by a communication coil.

[0021] According to an optional feature of the invention, the determiner is arranged to set a first level for a communication drive signal during an initialization phase prior to the power transfer phase, the first level being set based on at least one message received from the power receiver; and the determiner is arranged to determine a power extraction indication based on the first level.

[0022] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. It can allow for facilitating and / or improving the setting of the level of the communication drive signal during the communication time interval, and therefore the setting of the level of the communication carrier signal.

[0023] According to an optional feature of the invention, the determiner is arranged to set the level of the communication drive signal to be lower during the power transmission phase than during the initialization phase.

[0024] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. In many scenarios, this can allow for reduced or disabled power extraction from the communication carrier signal during communication time intervals, resulting in improved communication.

[0025] According to an optional feature of the invention, the determiner is arranged to measure the power of the communication drive signal during at least a portion of the communication time interval, and to determine a power extraction indication based on the measured power of the communication drive signal.

[0026] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. It can allow for facilitating and / or improving the setting of the communication drive signal level during communication time intervals. It can allow for low complexity in both the power transmitter and the power receiver. This method can provide advantageous performance without requiring any dedicated functionality at the power receiver to support the setting of the communication drive signal level.

[0027] In some embodiments, the determiner is arranged to measure power by measuring the input power to the output circuitry of the communication driver.

[0028] According to an optional feature of the invention, the level controller is arranged to constrain the power level of the communication drive signal to be below a maximum value of a threshold when the measured power of the communication drive signal is below that threshold.

[0029] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals. In many scenarios, this can allow for reducing or disabling power extraction from the communication carrier signal during communication time intervals, resulting in improved communication.

[0030] The threshold can be a threshold higher than the power level corresponding to the power extracted from the communication carrier signal through load modulation.

[0031] According to an optional feature of the invention, the threshold exceeds the power level extracted by the power receiver through load modulation.

[0032] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0033] According to an optional feature of the invention, the communicator is arranged to receive a power extraction characteristic indication from a power receiver, the power extraction characteristic indication indicating the characteristics of power extraction performed by the power receiver from a communication carrier signal; and the determiner is arranged to determine a power extraction indication based on the power extraction characteristic indication.

[0034] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0035] According to an optional feature of the invention, the power extraction characteristic indicator indicates the measured power extracted by the power receiver from the communication carrier signal during at least a portion of the communication time interval.

[0036] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0037] In some embodiments, the extracted power indication is an indication of the measured amount of power extracted from the communication carrier signal by a power receiver during at least a portion of the communication time interval.

[0038] In some embodiments, the level controller is arranged to reduce the power level of the communication drive signal to a value that indicates the amount of power extracted by the power receiver is below a threshold.

[0039] According to an optional feature of the invention, the power extraction characteristic indicator indicates the level of the communication carrier signal at which the amount of power extracted by the power receiver from the communication carrier signal is lower than a given threshold during at least a portion of the communication time interval.

[0040] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0041] The threshold can be a predetermined threshold, and specifically it can correspond to essentially no power being extracted from the communication carrier signal.

[0042] According to an optional feature of the invention, the power extraction characteristic indicator indicates the power extraction circuit characteristics of the power receiver.

[0043] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0044] According to an optional feature of the invention, the communicator is arranged to receive a voltage indication from a power receiver, the determiner is arranged to determine a power extraction indication based on the voltage indication, and the voltage indication indicates at least one voltage from the group consisting of: an induced voltage from a power transmission signal; an induced voltage from a communication carrier signal; and a capacitor voltage of a smoothing capacitor for a power supply circuit of the power receiver, the power supply circuit being arranged to be powered by power extracted from the power transmission signal or by power extracted from the communication carrier signal.

[0045] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0046] According to an optional feature of the invention, the level controller is arranged to constrain the level of the communication drive signal to below a threshold depending on the power extraction indication.

[0047] In many embodiments, this can allow for improved operation and / or facilitated implementation and / or operation. This can allow for facilitating and / or improving the setting of the level of the communication drive signal during communication time intervals.

[0048] The threshold can be a monotonically increasing function of the power extraction indicator.

[0049] According to one aspect of the invention, a power receiver is provided for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the power transmission signal employing a repeating time frame comprising 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 comprises: a first power extraction circuit arranged to extract power from the power transmission signal during the power transmission time interval of the power transmission phase; a communication coil for receiving a received communication carrier signal present during the communication time interval; a second power extraction circuit arranged to extract power from the communication carrier signal during at least a power transmission initialization phase; a power source for generating power for the power receiver, the power source being arranged to combine the power extracted from the first power extraction circuit and the power extracted from the second power extraction circuit; and a communicator arranged to communicate with the power transmitter using modulation of the communication carrier signal during the communication time interval; and wherein the communicator is arranged to transmit a power extraction characteristic indication to the power transmitter, the power extraction characteristic indication indicating the characteristics of power extraction performed by the second power extraction circuit.

[0050] According to one aspect of the invention, an operational method is provided for a power transmitter to wirelessly provide power to a power receiver via an electromagnetic power transmission signal, the method comprising: generating the power transmission signal using a power transmission coil; generating a power transmission drive signal for the power transmission coil, which includes generating the power transmission drive signal during a power transmission phase to employ a repetitive time frame comprising at least a power transmission time interval and a communication time interval, the power transmission drive signal being generated during the power transmission time interval and not being generated during the communication time interval; generating a communication carrier signal using a communication coil; generating a communication drive signal for the communication coil to generate the communication carrier signal; communicating with the power receiver using load modulation of the communication carrier signal; determining a power extraction indication indicating a power extraction characteristic by which the power receiver extracts power from the communication carrier signal during at least a portion of the communication time interval; and controlling the level of the communication drive signal during the communication time interval according to the power extraction indication.

[0051] According to one aspect of the present invention, an operational method is provided for a power receiver to wirelessly receive power from a power transmitter via an electromagnetic power transmission signal, the power transmission signal employing a repeating time frame comprising 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 method comprising: a first power extraction circuit extracting power from the power transmission signal during the power transmission time interval of a power transmission phase; a communication coil receiving a received communication carrier signal present during the communication time interval; a second power extraction circuit extracting power from the communication carrier signal during at least a power transmission initialization phase; a power supply generating power for the power receiver, the power supply combining the power extracted from the first power extraction circuit and the power extracted from the second power extraction circuit; a communicator communicating with the power transmitter during the communication time interval using modulation of the communication carrier signal; and wherein the communicator transmits a power extraction characteristic indication to the power transmitter, the power extraction characteristic indication indicating the power extraction characteristics of the second power extraction circuit.

[0052] A wireless power transmission system may be provided, including a power transmitter and a power receiver as described above.

[0053] These and other aspects, features and advantages of the invention will be apparent from the embodiments described below and will be set forth with reference to one or more embodiments described below. Attached Figure Description

[0054] Embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein... Figure 1 Examples of elements of a power transmission system according to some embodiments of the present invention are illustrated; Figure 2 Examples of elements of a power transmitter according to some embodiments of the present invention are illustrated; Figure 3 Examples of elements of a power receiver according to some embodiments of the present invention are illustrated; Figure 4 An example of a time frame of a wireless power transmission system according to some embodiments of the present invention is illustrated; Figure 5 The illustration shows an example of a power transmission signal and a communication carrier signal in a wireless power transmission system; Figure 6 Examples of some elements of a power receiver according to some embodiments of the present invention are illustrated; Figure 7 The illustration shows an example of voltage in a wireless power receiver; and Figure 8 The illustration shows an example of voltage in a wireless power receiver. Detailed Implementation

[0055] The following description focuses on embodiments of the invention applicable to wireless power transmission systems utilizing power transmission methods known from the Ki specification. However, it should be understood that the invention is not limited to this application, but can be applied to many other wireless power transmission systems.

[0056] Figure 1 An example of a power delivery system according to some embodiments of the present invention is illustrated. The power delivery system includes a power transmitter 101, which includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105, which includes (or is coupled to) a receiver coil / inductor 107.

[0057] 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 is propagated as a magnetic flux by 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 the component of the generated electromagnetic field that transfers power from the power transmitter to the power receiver. For example, if there is no load on the receiving coil 107, the power receiver will not extract power from the generated electromagnetic field (except for losses). In this case, the driving of the transmitter coil 103 can generate a potentially high-intensity electromagnetic field, but the power level of the power transfer signal will be zero (except for losses). In some cases where an external target is present, the power transfer signal can be considered to include a component corresponding to the power transfer to the external target, and therefore the power transfer signal can be considered to correspond to the power being extracted from the electromagnetic field generated by the power transmitter.

[0058] The power transmission signal can typically have a frequency between about 20 kHz and about 500 kHz, and for Ki-compatible systems, it is typically in the range of 20 kHz to 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 a portion) of the power transmission signal from the power transmitter 101. Therefore, power is transmitted from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the power receiving coil 107. The term power transmission signal is primarily used to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107; however, it should be understood that, equivalently, 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.

[0059] In this 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, in which case the power transmission signal directly induces eddy currents, resulting in direct heating of the element. Therefore, the power receiver can provide a load to the power transmission signal by including an inductive power extraction element, which may specifically be a power extraction coil or an electrical (e.g., heating) element in which current is induced by the power transmission signal.

[0060] The system is configured to transmit high power levels, and specifically, the power transmitter can support power levels exceeding 50W, 100W, 500W, or 1kW. For example, for Ki-type applications, power transmission may typically exceed 100W, and for very high-power applications, it may be as high as 2500W or more.

[0061] In the following description, the operation of power transmitter 101 and power receiver 105 will be generally based on specifications developed by the Wireless Power Consortium (except for the modifications and enhancements described herein (or which occur accordingly)). Specifically, power transmitter 101 and power receiver 105 may conform to or be substantially compatible with Ki standard elements.

[0062] Many wireless power transmission systems, and specifically high-power systems such as Ki, utilize resonant power transmission, in which 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 receiver coil 107 can be coupled in series with corresponding resonant capacitors. The use of resonant circuits tends to provide more efficient power transmission.

[0063] More in detail, Figure 2 The diagram shows Figure 1 The components of the power transmitter 101 and Figure 3 The diagram shows Figure 1 The power receiver 105 is a component.

[0064] The power transmitter 101 includes a driver 201 that can generate a drive signal fed to a transmitter coil 103, which in turn generates an electromagnetic power transfer signal that provides power transfer to a power receiver 105. The power transfer signal is provided (at least) during the power transfer time interval of the power transfer phase.

[0065] The driver 201 may typically include an output circuit in the form of an inverter, as is well known to those skilled in the art, and is typically formed by driving a full bridge or a half bridge.

[0066] The power transmitter 101 also includes a power transmitter controller 203, which is arranged to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 may include many functions required to perform power control according to the Ki specification.

[0067] The power transmitter controller 203 is specifically arranged to control the generation of a drive signal by the driver 201, and it can specifically control the power level of the drive signal, and correspondingly control the level of the generated power transmission signal. The power transmitter controller 203 includes a power loop controller that controls the power level of the power transmission signal in response to a power control message received from the power receiver 105 during a power control phase.

[0068] In order to receive data and messages from the power receiver 105, the power transmitter 101 includes a first communicator 205, which is arranged to receive data and messages from the power receiver 105 and to transmit data and messages to the power receiver 105 (as those skilled in the art will understand, a data message may provide one or more bits of information).

[0069] In this method, communication is performed by modulating a communication carrier signal generated by a 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, which is fed to the first communication coil 207 to generate a communication carrier signal. The communication driver 209 can typically be arranged to generate a communication drive signal / communication carrier signal with a frequency substantially different from the power transmission drive signal / power transmission signal. In many embodiments, the frequency of the communication carrier signal can be no less than 10, 100, or 500 times the frequency of the power transmission signal. In many embodiments, the frequency of the communication drive signal / communication carrier signal can have a frequency no less than 500 kHz, 1 MHz, or 10 MHz. Specifically, for an NFC implementation, the communication carrier signal frequency can be 13.56 MHz.

[0070] The first communicator 205 is coupled to the communication driver 209 and is arranged to control the communication driver 209 to modulate the communication drive signal / communication carrier signal in order to transmit data to the power receiver (in the following reference to the communication drive signal, an implicit reference to the communication carrier signal is also suitably included).

[0071] In this specific example, the modulation is amplitude modulation of the communication drive signal, and specifically uses binary communication utilizing amplitude shift keying (ASK). However, it should be understood that in other embodiments, modulation may use other methods, such as phase or frequency modulation of the communication drive signal.

[0072] In some embodiments, the first communicator 205 may receive data to be transmitted to the power receiver, for example, from the power transmitter controller 203, and in response generate a control modulation signal fed to the communication driver 209. The control modulation signal may be, for example, a binary signal matching the data to be transmitted, and the communication driver 209 may be arranged to generate a communication drive signal with a corresponding amplitude variation.

[0073] For communication from a power receiver to a power transmitter, the modulation of the communication drive signal can be load modulation. The power receiver can be arranged to modulate the power transmission signal by changing the load of the power transmission signal generated by the transmitter coil 103 according to the data to be transmitted. The first communicator 205 can be arranged to sense changes in the voltage and / or current of the transmitter coil 103 and demodulate the load modulation based on these. Those skilled in the art will appreciate the principles of load modulation, and therefore will not describe them in further detail.

[0074] In many embodiments, communication may be based on near-field communication, NFC, or other specifications, and the power receiver may specifically include NFC functionality. In many embodiments, the first communicator 205, communication driver 209, and first communication coil 207 may (at least) implement the functionality of an NFC reader. Therefore, in many embodiments, the communication drive signal / communication carrier signal is a constant level (except for modulation) 13.56 MHz signal.

[0075] The following description will focus on an example where communication between a power transmitter and a 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 via amplitude shift keying (ASK), and the modulation of the NFC carrier in the direction from the power receiver to the power transmitter is via load modulation.

[0076] exist Figures 1 to 3 In this system, communication is performed during the power transmission phase within a communication time interval. Specifically, the transmitter controller 203 can be arranged to synchronize the first communicator 205 such that communication operations (typically both receiving and transmitting data) are performed during the communication time interval of the power transmission phase (and typically only during the communication time interval of the power transmission phase), i.e., within the time interval allocated for communication.

[0077] This can significantly improve communication performance.

[0078] As will be described in more detail below, the method utilizes a time-division approach during the power transmission phase, where operations such as external target detection and communication, as well as power transmission, can be performed, for example, at different time intervals, thereby allowing interference between them (specifically, the impact of power transmission on external target detection / communication) to be significantly reduced.

[0079] Specifically, for a wireless power transmission system, the power transmission signal undergoes repeated time frames comprising at least one power transmission time interval and one communication time interval.

[0080] The power transmitter can be configured to turn off the power transmission signal during the communication time interval, and in some embodiments, the power receiver can be configured to disconnect the load during the reduced power time interval.

[0081] The power transmitter (and typically the power receiver) can then be configured to perform one or more operations (functions, processes, procedures) during the communication interval; that is, the execution of one or more operations of the power transmitter can be synchronized to occur during the communication interval. For example, it can typically synchronize external target detection performance and communication that occur during the communication interval. In this way, it is possible to reduce and often minimize the impact of power transmission and the power transmission signal on a given operation (particularly external target detection and communication).

[0082] Figure 3 Some exemplary components of the power receiver 105 are illustrated.

[0083] Receiver coil 107 is coupled to power receiver controller 301, which couples receiver coil 107 to load 303 via switch 305 (i.e., it is a switchable load 305). Power receiver controller 301 includes a first power extraction circuit arranged to extract power from the power transmission signal during a power transmission time interval in the power transmission phase. The first power extraction circuit may specifically extract power for load 303 during the power transmission phase, but will also typically extract power for functions of the power receiver itself, such as control functions and power actually for the power receiver controller 301 itself, as well as power for functions such as communication.

[0084] The power receiver controller 301 may specifically include a power control path that converts the power extracted by the receiver coil 107 into a suitable power supply for the load 303. Furthermore, the power receiver controller 301 may include various power receiver controller functions required to perform power transfer, and specifically functions required to perform power transfer according to the Qi specification.

[0085] To support communication from power receiver 105 to power transmitter 101, 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 current (at least one eMF) is induced in the second communication coil 309 by the communication carrier signal.

[0086] The second communicator 307 is coupled to the second communication coil 309 and is arranged to determine amplitude changes in the induced signal and demodulate the amplitude modulation of the communication carrier signal. Therefore, the second communicator 307 is arranged to decode data transmitted from the power transmitter via 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.

[0087] 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 and not 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.

[0088] In a specific example, the second communication coil 309 and the second communicator 307 can provide NFC-compatible communication operations. Specifically, the second communication coil 309 can be arranged to provide functions corresponding to an NFC tag and to decode data that has been modulated onto a communication carrier signal according to the NFC specification.

[0089] Therefore, the second communicator 307 is arranged to transmit data to the power transmitter by changing the load of the receiver coil 107 in response to data to be transmitted to the power transmitter 101. As known to those skilled in the art, the load change is then detected and demodulated by the power transmitter 101.

[0090] In this example, the second communicator 307 is further configured to demodulate the amplitude, frequency, and / or phase modulation of the communication carrier signal in order to acquire data transmitted from the power transmitter.

[0091] The system applies repeated time frames during the power transmission phase, wherein the time frame includes at least one power transmission time interval and at least one communication time interval. Figure 4The diagram illustrates an example of such repeating time frames, where the power transmission 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 transmission time interval. However, it should be understood that in other embodiments, other time intervals may also be included in the time frames, or multiple communication time intervals and / or multiple power transmission time intervals may be included in each time frame.

[0092] The power transmission driver 201 is controlled by the power transmitter controller 203 to generate a drive signal only during the power transmission time interval and not during the communication time interval. Therefore, the driver generates a drive signal and thus a power transmission signal during the power transmission time interval, and turns off the drive signal and thus the power transmission signal during the communication time interval.

[0093] During the power transmission phase, the power transmitter is thus arranged to perform power transmission during the power transmission time intervals of the time frame of the power transmission phase. Specifically, during these time intervals, the power transmitter and power receiver can operate a power control loop (which can be based on communication within a communication time interval corresponding to the repetition time interval). Therefore, the level of the transmitted power can be dynamically changed.

[0094] However, during the communication time interval of the time frame in the power transmission phase, the power drive signal is turned off, and therefore no power transmission signal is generated during the communication time interval.

[0095] Communication between the power transmitter and the power receiver is performed during the power transmission phase within a communication time interval, and typically only during the communication time interval. Communication via the first communication coil 207 and the second communication coil 309 is performed only during the communication time interval, and specifically, modulation of the communication carrier signal occurs only during the communication time interval.

[0096] In this system, the first communicator 205 is therefore arranged to transmit only data during the communication time interval, and thus modulates the communication carrier signal only (e.g., amplitude). Similarly, it typically seeks to demodulate data only during the communication time interval.

[0097] Similarly, the second communicator 307 is arranged to communicate only during the communication time interval when it is in the power transmission phase. In this system, the second communicator 307 is therefore arranged to transmit only data during the communication time interval and thus only perform load modulation on the communication carrier signal. Likewise, it typically seeks to demodulate data only during the communication time interval.

[0098] Therefore, during the power transmission phase, the first communicator 205 and the second communicator 307 are arranged to communicate only during the communication time interval. This approach provides highly advantageous performance and has specifically been found to offer significantly improved communication performance. Specifically, this method reduces interference from the power transmission signal on communication operation, thereby providing more reliable and robust communication with reduced bit errors.

[0099] Figure 5 The diagram illustrates an example of how communication can be performed within a communication time interval of repeating time frames, showing a power transmission signal 501 generated during a power transmission time interval PT and a modulated communication carrier signal 503 generated during a communication time interval C. Figure 5 Time division between power transmission and communication is implemented, where each operation is performed in a dedicated time interval.

[0100] The power receiver also includes a second power extraction circuit 311 arranged to extract power from the communication carrier signal. The signal induced in the second communication coil 309 can be rectified and smoothed, for example, to generate a DC signal that can supply power to, for example, the control functions of the power receiver. The second power extraction circuit 311 can be arranged to extract power during the power transfer initialization phase, and therefore can extract power from the communication carrier signal before power transfer is initialized and, in many cases, before the power transfer signal is generated. Specifically, the second power extraction circuit 311 can extract power from the communication carrier signal during the connection phase of Ki power transfer initialization.

[0101] The power receiver includes a power supply circuit 313 coupled to a power receiver controller 301 / first power extraction circuit and a power extraction circuit 311. The power supply circuit 313 can receive extracted power from the first and second power extraction circuits 311, 313, and further combine such power signals to generate a power supply (signal) for the power receiver. The power supply can be provided to some (but sometimes not all) of the power receiver's circuitry, such as for control and / or communication functions.

[0102] This combination can be, for example, a time-based combination, where power is sometimes generated from a communication carrier signal, i.e., from power extracted by the second power extraction circuit 311, and at other times from a power transmission signal, i.e., from power extracted by the first power extraction circuit.

[0103] In many embodiments, the first power extraction circuit, the second power extraction circuit 311, and the power supply circuit 313 can advantageously be very low-complexity circuits, thereby allowing for a low-cost and low-complexity power receiver implementation. Specifically, Figure 6An example of a low-complexity implementation is illustrated, in which the first power extraction circuit and the second power extraction circuit 311 are coupled together via a set of diodes 601, 603 (such that the power signals generated by the first power extraction circuit and the second power extraction circuit 311 are coupled to the anodes of diodes 601, 603 and the cathodes are coupled together). The connected cathodes are coupled to capacitor 605, which smooths the output voltage of the power supply circuit 313. (It should be understood that the diodes and, in effect, the capacitor can be considered equivalently as part of the first power extraction circuit and / or the second power extraction circuit 311).

[0104] However, such a method may lead to conflicts with other functions, and specifically with time-frame-based power transfer and communication, and specifically with discontinuous power transfer signals and / or communication carrier signals. Specifically, in the previously described slotted communication method, both the communication carrier signal and the power transfer signal are applied discontinuously, resulting in a bias power supply transition between power extraction from the communication carrier signal by the second power extraction circuit 311 (also known as communication carrier-powered mode) and power extraction from the power transfer signal by the first power extraction circuit (also known as power carrier-powered mode). When the bias power supply transitions from power carrier-powered mode to communication carrier-powered mode, the load on the communication carrier signal changes. Specifically, in Figure 6 In the example, if the output voltage of the second power extraction circuit 311 is higher than the DC voltage on the capacitor 605 (assuming there is no voltage drop across the diode), the current from the second power extraction circuit 311 is used to charge the capacitor and provide power to, for example, control electronics.

[0105] This can be achieved through, for example Figure 7 Two examples of behavior during the communication time interval are illustrated. In the first example, the capacitor voltage V DC The voltage V was initially lower than the signal from the second power extraction circuit 311. NFC_pot Therefore, diode 601 is turned on and capacitor 605 is charged until it reaches the voltage of the signal from the second power extraction circuit 311. Accordingly, the load NFC LD is initially high and decreases until a constant level corresponds to the load where diode 601 is in the non-conducting mode (typically corresponding to the load provided by the second power extraction circuit 311 itself).

[0106] In the second example, the voltage V across capacitor 605 DC The voltage was initially higher than the signal from the second power extraction circuit 311. However, as power was extracted from the power supply circuit 313, the capacitor voltage decreased until it reached the voltage V of the extracted power signal. NFCFurthermore, diode 601 is turned off to allow charging of capacitor 605, thereby generating a constant capacitor voltage. The corresponding load of the communication carrier signal is therefore initially at a low level, but increases when diode 601 begins to conduct.

[0107] Therefore, the operation causes a change in the load of the communication carrier signal, which is not due to load modulation of the second communicator 307. This load change may be detrimental to load-modulated communication with the power transmitter.

[0108] Even if load variations are limited to, for example, the initial interval of the communication time slot, they can still have a significant impact on operation. In fact, to achieve high power delivery efficiency, the duration of the communication time slot should be minimized, and a practical value for the time slot duration could be, for example, 1.5 ms with a 10 ms repetition rate, synchronized with the zero-crossing of the 50 Hz power supply (8.66 ms repetition rate for a 60 Hz power supply connection). As mentioned above, transients initiated by the bias power supply can impose parasitic carrier load modulation and reduce the effective time available for communication within the time slot, thereby reducing valuable payload. In fact, the NFC specification assumes that the NFC carrier is stable and unmodulated for a short period before the first symbol transition. Therefore, it is highly desirable to reduce or remove load variations in the communication carrier signal (by any means other than load modulation) for as many communication time slots as possible, and ideally throughout the entire duration of the communication time slot.

[0109] Another problem is that the load of load 303 may frequently change during the communication interval, and when the second power extraction circuit 311 is coupled to load 605 (e.g., disconnected via diode 601), these will generally directly affect the load of the communication carrier signal and thus interfere with load modulation and communication with the power transmitter.

[0110] One possible way to mitigate such problems is for the power receiver to actively control a switch to disable any power extraction from the communication carrier signal during the communication time interval or, in fact, throughout the entire power transmission phase. For example, the switch could disconnect the second power extraction circuit 311 from the power supply circuit 313. However, implementing this functionality would require additional power receiver circuitry, increasing the complexity and cost of the power receiver. In many cases, the complexity and cost of the power receiver are critical, and therefore, increasing complexity and adding circuitry to the power receiver is undesirable. Furthermore, including, for example, a switch between the second power extraction circuit 311 and the power supply circuit 313 would result in additional power loss and switching delay.

[0111] Figure 2 power transmitter and Figure 3Power receivers can provide different approaches that may be advantageous in many scenarios.

[0112] The power transmitter specifically includes a determiner 211, which is arranged to determine a power extraction indication that indicates the power extraction characteristics by which the power receiver extracts power from the communication carrier during at least a portion of the communication time interval. As will be described in more detail later, the power extraction characteristics may be the load of the measured communication carrier signal, the field strength / communication carrier signal level at which no power is extracted, power extraction circuit characteristics, etc.

[0113] The power transmitter also includes a level controller 213, which is arranged to control the level of a communication drive signal during a communication time interval according to a power extraction indication, and thus control the level of a communication carrier signal. In many embodiments, the level controller 213 is arranged to constrain the communication drive signal to be below / not exceeding a given threshold, wherein the threshold is determined from the power extraction indication.

[0114] In many embodiments, level controller 213 is arranged to set the level of the communication drive signal, and thus the level of the communication carrier signal, such that the communication carrier has a magnetic field strength that causes the induced signal, and the signal extracted by the second power extraction circuit 311 has a value that causes the corresponding diode 601 to de-conduct. Therefore, in many embodiments, level controller 213 can be arranged to set the level of the communication drive signal such that no power is extracted from the communication carrier signal during the communication time interval.

[0115] Figure 8 The illustration shows an example (corresponding to) Figure 6 and 7 (Scene), where the extracted power signal voltage V NFC The voltage is lower than the capacitor voltage V throughout the entire duration of the communication time interval. DC Therefore, the load on the communication carrier is isolated from the load of the generated power supply signal, and thus is generally substantially constant throughout the communication time interval, except for load variations caused by load modulation. Therefore, improved communication can be achieved, and specifically, communication can be performed throughout the entire duration of the communication time interval, thereby allowing for increased communication bandwidth and data rates.

[0116] In some embodiments, the determiner 211 may be arranged to measure the power of the communication drive signal during the communication time interval and determine a power extraction indication based on the measurement.

[0117] Determiner 211 may include the function of measuring the power of the communication drive signal. For example, for a constant voltage amplitude, the power of the communication drive signal can be determined by measuring the current of the communication drive signal, and thus the current through the first communication coil 207. For example, the RMS current can be measured during the communication time interval and used as a direct measure of the load on the communication carrier signal. In the case where the only load on the communication carrier signal is the modulation load through the power receiver, the corresponding current and power level of the communication drive signal will be very low. However, if power is extracted from the second power extraction circuit 311 during the communication time interval, the current and power level of the communication drive signal will increase by an amount corresponding to the extracted power (and any additional losses). Therefore, the measurement of the power of the communication drive signal can directly provide an indication of the power extraction operation at the power receiver, and specifically an indication of whether the second power extraction circuit 311 extracts power.

[0118] In some embodiments, the determiner 211 may be arranged, for example, to determine the power by measuring the input power to the output circuit of the communication driver. For example, it may measure the input power to an inverter that generates the communication drive signal and drives the second communication coil 207. In other embodiments, the signal of the output circuit, such as current, may be measured directly.

[0119] The level controller 213 can then adjust the level of the communication drive signal based on the measured power level. For example, in some embodiments, the determiner 211 may be arranged to perform a measurement for a fixed / predetermined amplitude / level of the communication drive signal, and can then further determine a new level of the communication drive signal as a function of the measured power, and in some embodiments, a new level of the communication drive signal as a predetermined function. This function may typically be a monotonically decreasing function of the measured power level, and thus the level of the communication drive signal may be set to a lower value for an increase in the measured power level.

[0120] In many embodiments, level controller 213 and determiner 211 can be arranged to form a loop in which the level of the communication drive signal is repeatedly adjusted based on measurements. For example, if the measured power level is higher than a given threshold, level controller 213 can further decrease the level of the communication drive signal by a given step size. If the measured power level is lower than the threshold, level controller 213 can instead increase the level by a given step size. Thus, the signal level of the communication drive signal can be dynamically adjusted to maintain the extracted power from the communication drive signal, and therefore the communication carrier signal, at no more than a given threshold.

[0121] This method can be configured to constrain the power level of the communication drive signal such that it is lower than the measured power of the communication drive signal being below a threshold (maximum value). The power level is specifically set / reduced to a level where the measured communication drive signal is below a given value / threshold.

[0122] In many embodiments, the threshold can be set such that it is higher than the power level corresponding to load modulation, and specifically to the power extracted by the modulated load of the power receiver. The threshold can also be set to include a component corresponding to the load of the metal on the communication carrier, where current can be induced by the communication carrier signal. For example, the threshold can be adjusted to reflect power losses that the communication carrier signal may induce and thus cause in the metal portions of the power transmitter and power receiver themselves. The threshold can be set, for example, during the initialization phase, where measurements can be performed to measure both the effects of load modulation and, optionally, the power losses of any metal, but the power receiver is arranged not to extract any power. For example, during a short interval during the initialization process, the power transmitter and power receiver can enter a test mode, where the power receiver modulates the communication carrier signal while the second power extraction circuit 311 is turned off, and the power transmitter measures the resulting power level of the communication drive signal. The threshold can then be set based on this power level, for example, to a level that is, say, 20%–50% higher.

[0123] Therefore, the threshold is typically set to exceed the power level extracted by the power receiver through load modulation, and thus the level of the communication drive signal can be set to allow load modulation but prevent any significant power extraction by the second power extraction circuit 311. Typically, the power level of load modulation (and nearby metal) is much lower than the usual power extraction level, and therefore this approach can provide significantly improved operation and a more stable communication carrier signal for load modulation.

[0124] It should be understood that in some embodiments, power can be measured over the entire communication time interval, and an average value can be determined, for example. In other embodiments, power can be measured only for a portion of the communication time interval, such as, for example, during the initial portion of the communication time interval, where power is more likely to be extracted from the communication carrier signal, for example.

[0125] In some embodiments, the initialization of the power transfer phase includes an initialization phase in which the level of the communication carrier signal is determined. During the initialization phase, a power transfer signal is typically not generated, and the power receiver extracts power from the communication carrier signal. Specifically, for a Ki wireless power transfer system, the power transmitter and power receiver may enter a connection phase, where the power transmitter and power receiver communicate to prepare for transitioning to a power state. Specifically, power negotiation is performed, and other parameters may be shared between the transmitter and receiver. During this phase, the user can typically use the power receiver's user interface to select settings or power on the device.

[0126] During the initialization phase, and specifically during the connection phase, the determiner 211 may be arranged to determine the level of the communication drive signal, and thus the level of the communication carrier signal. This initialization phase level is determined based on communication with the power receiver, and specifically may be determined by the power transmitter transmitting at least one level indication to the power transmitter and the power transmitter adjusting the level accordingly.

[0127] For example, in some implementations, the power receiver may transmit a level request message during the connection / initialization phase, and the power transmitter may accordingly set the level of the communication drive signal. For instance, the power receiver may simply transmit its identifier (e.g., a type identifier), and the power transmitter may extract a suitable communication drive signal level stored for a given (type) power receiver. The suitable level may be determined, for example, during the manufacturing or design phase through experimentation and measurement, and then stored in the power transmitter during production.

[0128] In many embodiments, the power transmitter and power receiver can be arranged to establish a control loop during the connection / initialization phase, which adjusts the level of the communication drive signal / communication carrier signal to an appropriate level. For example, the power receiver can repeatedly compare the current power extraction parameters, such as the voltage across capacitor 605 (the only power extraction in this phase is typically from the communication carrier signal via a second power extraction circuit 311), with a reference level, and based on this, transmit requests to increase or decrease the level of the communication carrier signal. The power transmitter can increase or decrease the level of the communication drive signal by a given step size in response to each request. The loop can then adjust the signal level of the communication drive signal / communication carrier signal to an appropriate level to provide the desired power extraction parameters, such as the desired voltage across capacitor 605.

[0129] Therefore, during the connection / initialization phase, the level of the communication drive signal is set to a level suitable for the current power receiver and power transmission arrangement. This level can then be used as a power extraction indication (or this can be derived from it), based on which the level during the power transmission phase is set. For example, the level determined during the connection / initialization phase can be considered a reference level for the communication drive signal, and the level during the power transmission phase can be set as a function of it. For example, in some embodiments, the level of the communication drive signal during the communication time interval of the power transmission phase can be set to the same as the reference level.

[0130] In many embodiments, the level during the communication time interval can be set to different levels and can be determined by a non-unity function applied to the reference level. In some embodiments, it is feasible to set the level during the communication time interval to be higher than the reference level, but in most embodiments, it can be set to a lower level. Therefore, the level of the communication drive signal is typically set lower during the communication time interval in the power transfer phase than in the initialization phase.

[0131] This reflects the fact that the level during the connection / initialization phase is typically determined to provide appropriate power extraction from the communication carrier signal, while it is generally desirable that the level of the communication drive signal during the communication time interval be set as high as possible without causing power extraction. Determining the level during the communication time interval based on a reference level during the connection / initialization phase provides an efficient method for determining appropriate trade-offs, while allowing for relatively low complexity and resource requirements. In many embodiments, the level of the communication drive signal can simply be set to not exceed a predetermined fraction of the reference level determined during the connection / initialization phase, such as, for example, 30%, 50%, or 70% of the reference level.

[0132] Therefore, as a specific example, in some embodiments, the power transmitter can select an arbitrarily lower power level for the NFC carrier (communication carrier signal) compared to the level of the NFC carrier (communication carrier signal) applied during the connection phase. Additionally, the power transmitter can verify that the power level is suitable for communication by measuring the load on the NFC carrier during the communication time slot and estimating whether the power extraction is reflected in that load. The setting can be determined by estimating the power transmitted to the power receiver during the connection phase (when NFC power is inevitably used to power the power receiver) and by power measurements during the communication time interval. This power measurement can be performed, for example, on the DC power supply side or in the NFC inverter that generates the communication drive signal.

[0133] In the previous example, the determination of the power extraction indication was primarily based on the operation at the power transmitter (including measurements performed at the power transmitter), which is used to set the level of the communication drive signal during the communication time interval.

[0134] However, in many embodiments, the power receiver is arranged to transmit a power extraction characteristic indication to the power transmitter, wherein the power extraction characteristic indication indicates the characteristics of power extraction performed by the second power extraction circuit. For example, the power receiver may perform an operation or measurement to determine the characteristics / parameters of power extracted from the communication carrier signal. The second communicator 307 may be arranged to transmit a message with its indication to the power transmitter, which may then determine the levels of the power extraction indication and the communication drive signal based on the received power extraction characteristic indication.

[0135] In many embodiments, a power receiver is arranged to measure the power extracted from a communication carrier signal and generate a power extraction characteristic indication to reflect the measured value. This value may be measured specifically during the communication time interval, or during at least a portion of the communication time interval.

[0136] For example, the power receiver controller 301 can be arranged to measure the current through the diode 601 connected to the second power extraction circuit 311 and use it as an example of a power extraction characteristic indication, or it can actually directly measure the power from the output of the second power extraction circuit 311 and transmit it to the power transmitter as a power extraction characteristic indication.

[0137] The power transmitter can receive a power extraction characteristic indication and, based on this, determine the level of the communication drive signal. For example, the received measurement can be used for measurements performed by the power transmitter, as previously described, for example, to implement a feedback loop that continuously adjusts the level of the communication drive signal until it reaches a level where the received power extraction characteristic indication indicates that no power is being extracted by the second power extraction circuit 311. Specifically, in some embodiments, the level controller 213 can be arranged to reduce the power level of the communication drive signal to a value below a threshold indicated by the extracted power indication, which in many cases can be close to zero (e.g., only exceeding the power level modulated by the load).

[0138] In some embodiments, the power receiver may be arranged to receive a voltage indication from the power receiver in many embodiments, and the determiner 211 may determine the power extraction indication based on this (and thus the level controller 213 may set the level of the communication drive signal accordingly).

[0139] The voltage indication can be, for example, an indication of the voltage induced by a communication carrier signal (in the second communication coil 309). The voltage indication can be an indication of the induced voltage from the communication carrier signal, such as the voltage on the second communication coil 309 or the voltage at the output of the second power extraction circuit 311. For example, in some embodiments, the power receiver can transmit an indication of the voltage generated by the communication carrier signal at the output of the second power extraction circuit 311. For example, the voltage (amplitude) at the anode of diode 601 can be measured and transmitted to the power receiver. The power transmitter can then be arranged to compare it with a desired level and set the level of the communication drive signal accordingly.

[0140] For example, it might be desirable for the power supply circuit 313 to generate a voltage of 12V, and therefore, for the voltage across capacitor 605 to be approximately 12V during the duration of the communication time interval. However, it might be desirable for this to be driven by power extraction from the power transfer signal rather than the communication carrier signal, and therefore the level of the communication drive signal could be set such that the voltage at the output of the second power extraction circuit 311 / at the anode of diode 601 is below that value (with some margin). This setting can be based on the power receiver measuring and reporting this value, and the level controller 213 setting the level accordingly. For example, a predetermined function can be used to determine the relative change in the level of the communication drive signal to the measured value. For example, if the measured voltage exceeds, for example, 10V, the level can be reduced by a factor that increases for the increased voltage. If the measured voltage is less than, for example, 8V, the level of the communication drive signal can be increased by a factor that increases for the decreased voltage. Therefore, the system can seek to set the level of the communication carrier signal so that the induced voltage at the anode of diode 601 is between 8V and 10V to provide a high level that is low enough, however, to prevent power extraction and to keep diode 601 in a non-conducting state throughout the communication time interval.

[0141] In some embodiments, the power receiver may alternatively or additionally provide a voltage indication of the induced voltage from the communication carrier signal, such as the voltage from the output of the first power extraction circuit / at the anode of diode 603. For example, the power receiver may provide such a voltage indication, and the level controller 213 may set the level of the communication drive signal such that the voltage at the output of the second power extraction circuit 311 is less than the measured value. This can be done, for example, by setting the level of the communication drive signal using a predetermined function based solely on the voltage reported at the output of the first power extraction circuit, or in many embodiments by comparing the voltages reported for the communication carrier signal and for the power transfer signal (specifically, the output of the first or second power extraction circuit 311). For example, if the measured voltage of the first power extraction circuit exceeds the measured voltage of the second power extraction circuit 311 by a given amount, the level of the communication drive signal may be increased. If it exceeds by a smaller amount, the level of the communication drive signal may remain unchanged, and if it exceeds by even a smaller amount (or in fact, the voltage of the second power extraction circuit 311 exceeds the voltage of the first power extraction circuit), the level of the communication drive signal may be decreased.

[0142] In some embodiments, a voltage indication of the voltage on a smoothing capacitor (such as specifically capacitor 605) can be reported and used to set the level of the communication drive signal. Specifically, the method described for a voltage indication representing the voltage from the first power extraction circuit can also be used (with appropriate modifications) based on the voltage indication of capacitor 605.

[0143] In some embodiments, the power receiver may be arranged as a transmit power extraction characteristic indicator that indicates the level of the communication carrier signal at which the amount of power extracted by the power receiver from the communication carrier signal is below a given threshold during at least a portion of the communication time interval.

[0144] For example, a power receiver can be configured to transmit an indication of an acceptable / preferred magnetic field strength, such as a specific value in A / m.

[0145] In this configuration, the power transmitter can be arranged to determine the appropriate level of the communication drive signal to provide the desired field strength. For example, the level controller 213 may include predetermined functions, such as stored as a lookup table, that provide the specific level of the communication drive signal for a given field strength indication. Such functions can be determined, for example, by measurements taken during the design and manufacturing phases, and can be based, for example, on assumed nominal conditions (such as the assumed positioning arrangement between the power transmitter and the power receiver).

[0146] This approach allows for low complexity, but still allows for efficient adjustments to operations to provide improved performance in many scenarios.

[0147] In some embodiments, the power receiver may be arranged to transmit a power extraction characteristic indication that indicates the characteristics of the power extraction circuitry of the power receiver. In some embodiments, the power extraction characteristic indication may indicate the characteristics of the circuitry used to extract power from a communication carrier signal (and / or from a power transmission signal). The level of the communication drive signal can then be set according to this indication.

[0148] As an example, a power extraction characteristic indication may indicate that the power receiver has the function of extracting power from a communication carrier signal, and therefore it includes power extraction circuitry arranged to extract power from the communication carrier signal. In this case, the power transmitter may, for example, use any of the methods described above to adjust and set the level of the communication drive signal. Conversely, if a power extraction characteristic indication is received indicating that the power receiver does not include the function of extracting power from the communication carrier signal, or in fact, if no power extraction characteristic indication is received to provide any indication of power extraction circuitry, the power transmitter may instead be arranged to set the communication drive signal to a given predetermined fixed level.

[0149] As another example, the power extraction characteristic indication may indicate that the power receiver includes power extraction circuitry for extracting power from the communication carrier signal, and this may further include whether the power receiver includes a switch for disabling such power extraction circuitry from the communication carrier signal during the power transmission phase. In such a case, if no such switch is included, the power transmitter, as previously described, can be similarly arranged to adjust the level of the communication drive signal, which could otherwise be set to a predetermined level.

[0150] It should be understood that, for clarity, embodiments of the invention have been described above with reference to various functional circuits, units, and processors. However, it will be apparent that any suitable functional distribution among the different functional circuits, units, or processors can be used without departing from the invention. For example, a function shown to be performed by a separate processor or controller may be performed by the same processor or controller. Therefore, references to specific functional units or circuits are to be considered only as references to suitable means for providing the described functions, and not as indications of a strict logical or physical structure or organization.

[0151] This invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The invention can 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 invention can be implemented physically, functionally, and logically in any suitable manner. In practice, functionality can be implemented in a single unit, in multiple units, or as part of other functional units. Therefore, the invention can be implemented in a single unit or can be physically and functionally distributed among different units, circuits, and processors.

[0152] Although the invention has been described in conjunction with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, while features may appear to have been described in conjunction with specific embodiments, those skilled in the art will recognize that various features of the described embodiments can be combined according to the invention. In the claims, the term does not exclude the presence of other elements or steps.

[0153] It should be understood that referencing a preferred value does not imply any limitations beyond the value determined in the external target detection initialization mode; that is, it is preferred because it is determined in the adaptive processing. A reference to a preferred value can replace a reference to, for example, a first value.

[0154] Furthermore, although listed separately, multiple devices, elements, circuits, or method steps can be implemented by, for example, a single circuit, unit, or processor. Additionally, although individual features may be included in different claims, these features can be advantageously combined, and inclusion in different claims does not imply that such a combination of features is infeasible and / or disadvantageous. Moreover, including a feature in one claim class does not imply a limitation on that class, but rather indicates that the feature is equally applicable to other claim classes where appropriate. Furthermore, the order of features in a claim does not imply any particular order in which the features must operate, and specifically, the order of steps in a method claim does not imply that the steps must be performed in that order. Rather, the steps can be performed in any suitable order. Furthermore, singular references do not exclude plural. Therefore, references to “a,” “an,” “first,” “second,” etc., do not exclude plural. Reference numerals in the claims are provided as clarifying examples only and should not be construed as limiting the scope of the claims in any way.

Claims

1. A power transmitter (101) for wirelessly providing power to a power receiver (105) via an electromagnetic power transmission signal, the power transmitter (101) comprising: A power transmission coil (103) is arranged to generate the power transmission signal; A power transfer driver (201) is arranged to generate a power transfer drive signal for the power transfer coil (103), the power transfer driver (201) is arranged to generate the power transfer drive signal 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 driver (201) is arranged to generate the power transfer drive signal during the power transfer time interval and not generate the power transfer drive signal during the communication time interval; A communication coil (207) is arranged to generate a communication carrier signal; A communication driver (209) is arranged to generate a communication drive signal for the communication coil to generate the communication carrier signal; A communicator (205) is arranged to communicate with the power receiver (105) using load modulation of the communication carrier signal; Determiner (211) is arranged to determine a power extraction indication that indicates a power extraction characteristic by which the power receiver extracts power from the communication carrier signal during at least a portion of the communication time interval; and A level controller (213) is arranged to control the level of the communication drive signal during the communication time interval according to the power extraction indication.

2. The power transmitter according to claim 1, wherein, The determiner (211) is arranged to set a first level for the communication drive signal during an initialization phase prior to the power transfer phase, the first level being set based on at least one message received from the power receiver; and the determiner (211) is arranged to determine the power extraction indication based on the first level.

3. The power transmitter according to any of the preceding claims, wherein, The determiner (211) is configured to set the level of the communication drive signal to be lower in the power transmission phase than in the initialization phase.

4. The power transmitter according to any of the preceding claims, wherein, The determiner (211) is arranged to measure the power of the communication drive signal during at least a portion of the communication time interval, and to determine the power extraction indication based on the measured power of the communication drive signal.

5. The power transmitter according to any of the preceding claims, wherein, The level controller is configured to constrain the level of the communication drive signal to be below a maximum value of a threshold when the measured power of the communication drive signal is below a threshold value.

6. The power transmitter according to claim 5, wherein, The threshold exceeds the level of power extracted by the power receiver through load modulation.

7. The power transmitter according to any of the preceding claims, wherein, The communicator (205) is arranged to receive a power extraction characteristic indication from the power receiver (105), the power extraction characteristic indication indicating the characteristics of power extraction by the power receiver (105) from the communication carrier signal; and the determiner (211) is arranged to determine the power extraction indication based on the power extraction characteristic indication.

8. The power transmitter according to claim 7, wherein, The power extraction characteristic indicator indicates the measured power extracted by the power receiver from the communication carrier signal during at least a portion of the communication time interval.

9. The power transmitter according to claim 7, wherein, The power extraction characteristic indicator indicates the level of the communication carrier signal at which the amount of power extracted by the power receiver (105) from the communication carrier signal is lower than a given threshold during at least a portion of the communication time interval.

10. The power transmitter according to claim 8, wherein, The power extraction characteristics indicate the power extraction circuit characteristics of the power receiver.

11. The power transmitter according to any of the preceding claims, wherein, The communicator (205) is arranged to receive a voltage indication from the power receiver (105), the determiner (211) is arranged to determine a power extraction indication based on the voltage indication, and the voltage indication indicates at least one voltage from the group consisting of: Induced voltage from the power transmission signal; Induced voltage from the communication carrier signal; as well as The capacitor voltage of the smoothing capacitor used in the power supply circuit of the power receiver (105), the power supply circuit being arranged to be powered by power extracted from the power transmission signal or by power extracted from the communication carrier signal.

12. The power transmitter according to any of the preceding claims, wherein, The level controller is configured to constrain the level of the communication drive signal to below a threshold depending on the power extraction indication.

13. A power receiver (105) for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, said power transmission signal employing a repetitive time frame comprising at least a power transmission time interval and a communication time interval, said power transmission signal being present during said power transmission time interval and absent during said communication time interval, said power receiver (105) comprising: A first power extraction circuit (301) is arranged to extract power from the power transmission signal during the power transmission time interval of the power transmission phase; A communication coil (309) for receiving a received communication carrier signal, which exists during a communication time interval; A second power extraction circuit (311) is arranged to extract power from the communication carrier signal during at least the power transmission initialization phase; A power source (313) for generating power for the power receiver (105), the power source (313) being arranged to combine power extracted from the first power extraction circuit (301) and the second power extraction circuit (311); and A communicator (307) is arranged to communicate with the power transmitter (101) during the communication time interval by modulating the communication carrier signal; and wherein the communicator (307) is arranged to transmit a power extraction characteristic indication to the power transmitter (101), the power extraction characteristic indication indicating the characteristics of power extraction performed by the second power extraction circuit (311).

14. A method of operation for a power transmitter (101) to wirelessly provide power to a power receiver (105) via an electromagnetic power transmission signal, the method comprising: The power transmission coil (103) generates the power transmission signal; Generating a power transmission drive signal for the power transmission coil (103) includes generating the power transmission drive signal during a power transmission phase to employ a repeating time frame that includes at least a power transmission time interval and a communication time interval, wherein the power transmission drive signal is generated during the power transmission time interval and is not generated during the communication time interval; The communication coil (207) generates a communication carrier signal and generates a communication drive signal for the communication coil to generate the communication carrier signal; The power receiver (105) communicates using load modulation of the communication carrier signal; A power extraction indication is determined, the power extraction indication indicating a power extraction characteristic in which the power receiver extracts power from the communication carrier signal during at least a portion of the communication time interval; as well as The level of the communication drive signal is controlled during the communication time interval according to the power extraction indication.

15. An operational method for a power receiver (105) to wirelessly receive power from a power transmitter (101) via an electromagnetic power transmission signal, the power transmission signal employing a repetitive time frame comprising at least a power transmission time interval and a communication time interval, the power transmission signal being present during the power transmission time interval but absent during the communication time interval, the method comprising: The first power extraction circuit (301) extracts power from the power transmission signal during the power transmission time interval of the power transmission phase; The communication coil (309) receives the received communication carrier signal, which exists during the communication time interval; The second power extraction circuit (311) extracts power from the communication carrier signal during at least the power transmission initialization phase; A power source (313) generates power for the power receiver (105), the power source (313) combining the power extracted from the first power extraction circuit (301) and the second power extraction circuit (311); and The communicator (307) communicates with the power transmitter (101) during the communication time interval by modulating the communication carrier signal, and wherein the communicator (307) transmits a power extraction characteristic indication to the power transmitter (101), the power extraction characteristic indication indicating the characteristics of power extraction performed by the second power extraction circuit.

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