Wireless Power Transmission

Abstract

The power transmitter 101 supplies power to the power receiver 105 via an inductive power transmission signal that is also used by the power receiver 105 for communication by load modulation. The power receiver 105 comprises a transmitter 509 configured to transmit symbols according to a first or second communication mode, the first mode modulating data symbols by a chip sequence from a set of sequences and the second communication mode not modulating. The power receiver 105 can transmit data symbols requesting a power transmission signal variation using a chip sequence from the set. The detector 515 can detect whether a variation has occurred, and if so, the selector 513 selects the first communication mode, otherwise the second communication mode. This approach allows for the selection of the appropriate communication mode without requiring data to be transmitted from the power transmitter. This approach can provide improved backward compatibility.

Description

[Technical field]

[0001] The present invention relates to wireless power transfer, and in particular, but not exclusively, to power transfer for systems such as the Qi wireless power transfer standard. [Background technology]

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

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

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

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

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

[0007] The Qi standard has been developed by the Wireless Power Consortium, information about which can be found, for example, on its website http: / / www.wirelesspowerconsortium.com / index.html, in particular the defined specifications.

[0008] To support efficient wireless power transmission, wireless power transmission systems, such as Qi-based systems, utilize substantial communication between the power transmitter and the power receiver. Initially, Qi only supported communication from the power receiver to the power transmitter using load modulation of the power transmission signal. Thus, early Qi devices only supported one-way communication from the power receiver to the power transmitter.

[0009] However, the development of standards has introduced bidirectional communication, and many functions are supported by communication exchanges between the power receiver and the power transmitter. In many systems, communication from the power transmitter to the power receiver is achieved by modulating the power transmission signal.

[0010] Some systems have proposed using separate, dedicated communication capabilities, such as, for example, Bluetooth or NFC (near field communication) based communication. However, while such approaches tend to provide efficient operation in many scenarios, they are also associated with several drawbacks, including the need for dedicated, complex communication circuitry and potentially low confidence that the power transmitter is communicating with the power receiver that is actually being powered. Also, backward compatibility with, for example, Qi-based devices, can be problematic for newer devices based on separate communication.

[0011] However, communicating using load modulation of a power transmission signal that transmits power to a power receiver tends to have several associated drawbacks. For example, load modulation tends to introduce some electrical noise, including both noise into the device's signal and radiated electromagnetic noise. Load modulation can increase electromagnetic interference to other devices, and maintaining sufficient or optimal electromagnetic compatibility has proven difficult.

[0012] It has also been found in practice that load modulation can introduce undesirable spurious oscillations into the drive and power transfer signals. Another drawback is that load modulation of the power transfer signal can result in acoustic noise. Such noise can result from the effect of the variations on the electromagnetic fields caused by the load modulation on the mechanical elements, which in particular can cause the mechanical elements to move and vibrate, potentially generating acoustic noise.

[0013] In some cases, for example, the load modulation communication used in early versions of the Qi standard may not be completely reliable and may in some cases result in some bit errors. For example, high levels of noise may result in bit errors and / or may require an increase in modulation depth which may result in increased electrical or acoustic noise resulting from the load modulation.

[0014] While it may be desirable in some ways to change to a different communication approach, maintaining backward compatibility or reducing the amount of change required to existing designs and approaches is a major challenge that often makes this a difficult prospect.

[0015] A particular problem with continuing to develop a technology standard or standards is that it can result in a system where many different devices conforming to different versions of the standard are deployed simultaneously. It is typically required that such different devices must be able to operate together. For example, the development of the Qi standard will result in many deployed power transmitters and power receivers conforming to different versions of the standard, all of which will require interacting with one another. A particular difficult problem relates to communication where it is required / desired that devices of different versions can communicate efficiently and reliably. Indeed, it is also required that new devices supporting full bidirectional communication can efficiently interact with legacy devices developed to support only unidirectional communication. Also, not only are devices required to work with each other, but it is desirable that more complex devices can efficiently and reliably adapt their operation to select the optimal operation and communication supported by the complementary device. Thus, the challenge faced by the devices when a power transfer is initiated between two devices is to interact to establish an optimal interworking based on the specific capabilities of the devices. Such adaptation is difficult, especially when one of the devices is only capable of unidirectional communication, thereby preventing negotiation protocols and algorithms from being utilized.

[0016] Therefore, improved approaches would be advantageous, particularly approaches that allow for increased flexibility, reduced cost, reduced complexity, improved power transfer operation, increased reliability, reduced communication errors, improved backward compatibility, improved electromagnetic compatibility, reduced electrical and / or acoustic noise, improved communications, improved backward compatibility, facilitated and / or improved adaptation to different capabilities and features of different devices, and / or improved performance. Summary of the Invention [Problem to be solved by the invention]

[0017] Accordingly, the Invention seeks to preferably mitigate, reduce or eliminate one or more of the above mentioned disadvantages singly or in any combination. [Means for solving the problem]

[0018] According to one aspect of the invention, there is provided a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the power receiver comprising an input circuit including a receive coil configured to extract power from the power transmission signal, and a transmitter configured to transmit a set of data symbols to the power transmitter by load modulating the power transmission signal, wherein each data symbol of the data sequence is modulated by a sequence of modulation load values ​​corresponding to a chip sequence of a first set of chip sequences, and the chip sequences of the first chip sequence are linked to different data symbol values, The method includes: a transmitter, the set of data symbols including a requirement for a given variation in the power transmission signal; a detector configured to monitor the power transmission signal to detect the given variation in the power transmission signal; and a selector configured to select a first communication mode as the selected communication mode if the given variation is detected and to select a second communication mode as the selected communication mode if the given variation is not detected, the first communication mode including each data symbol being modulated by a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences and the second communication mode not including any data symbol being modulated by a sequence of modulation load values ​​corresponding to any chip sequence of the first set of chip sequences; and the transmitter is configured to transmit the data symbols to the power transmitter during a power transmission phase using the selected communication mode.

[0019] The present invention may in many embodiments enable improved performance, and in particular may in many embodiments enable improved communication between a power receiver and a power transmitter, which may in many embodiments enable improved power transfer.

[0020] This approach can allow for improved communication and, in many embodiments, can allow for improved tradeoffs between different parameters and operating characteristics. This approach can allow, for example, a reduced modulation depth to be used while still allowing reliable communication. This approach can reduce electrical noise and / or electromagnetic interference, allowing for improved electromagnetic compatibility. This approach can often reduce or prevent acoustic noise.

[0021] This approach can enable improved tradeoffs between various parameters, including computational resource requirements, data detection accuracy, bit error rate, data rate, etc., in many scenarios.

[0022] This approach can allow for advantageous backward compatibility in many systems and, in many embodiments, can allow for easy deployment into existing systems. This approach can allow for improved interworking and accommodation to different device capabilities. This approach can allow for improved interworking with legacy devices, for example, thereby facilitating the introduction of enhanced features.

[0023] This approach can enable improved operation and adaptation in many scenarios without requiring or relying on data communication from the power transmitter to the power receiver, or even the existence of a communication channel from the power transmitter to the power receiver.

[0024] This approach can allow for relatively easy modification of existing approaches, such as those used by the Qi standard. In particular, this approach can allow for enhanced communications in systems such as Qi standard systems that include devices that operate according to the Qi standard's Baseline Power Profile (BPP), which does not include any communications from the power transmitter to the power receiver.

[0025] A chip sequence may be a sequence / pattern of modulation load values. Each of these modulation load values ​​may be constant within a chip duration. Chip sequences for different data symbols have different sequences / patterns of modulation load values.

[0026] In many embodiments, the length of the chip sequence is greater than or equal to 15 chips and less than or equal to 256 chips.

[0027] The set of data symbols may include one or more data symbols. The data symbols may be bits in some embodiments. The selection of the first and / or second communication modes may take into account other parameters. For example, the first communication mode may be selected from a plurality of possible communication modes if a given variation is detected. Similarly, the second communication mode may be selected from a different plurality of possible communication modes if a given variation is not detected. The selection from the possible communication modes may be responsive to other parameters than the variation of the power transmission signal.

[0028] The given variation can be a predetermined variation in many embodiments.

[0029] According to an optional feature of the invention, the second communication mode includes each data symbol being modulated by a sequence of modulation load values ​​corresponding to a chip sequence from the second set of chip sequences.

[0030] This may provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios.

[0031] According to an optional feature of the invention, chip sequences in the second set of chip sequences are linked to different data symbol values, each chip sequence in the first set of chip sequences having a first length and each chip sequence in the second set of chip sequences having a second length different from the first length.

[0032] This may provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios.

[0033] This approach can enable efficient selection and adaptation of appropriate communication modes and modulation approaches.

[0034] The second length is shorter than the first length, and may often be 2, 4, 8, 16, 32, or 64 or more times shorter.

[0035] In accordance with an optional feature of the invention, the given variation is a variation in at least one of a power level of the power transmission signal and a frequency of the power transmission signal.

[0036] This can provide improved performance and / or operation in many scenarios.

[0037] In accordance with an optional feature of the invention, the set of data symbols includes at least one power level change request for the power transmission signal.

[0038] This can provide improved performance and / or operation in many scenarios and / or facilitate implementation and / or deployment. It can reduce the complexity and / or modifications required to implement chip sequence based communication in many implementations. It can also typically allow easier and / or more accurate determination of whether a given variation is present.

[0039] In accordance with an optional feature of the invention, the set of data symbols includes at least one power control loop error message.

[0040] This can provide improved performance and / or operation in many scenarios and / or facilitate implementation and / or deployment. It can reduce the complexity and / or modifications required to implement the approach in many embodiments. It can also typically allow for easier and / or more accurate determination of whether a given variation is present.

[0041] According to an optional feature of the invention, the transmitter is configured to transmit a further set of data symbols using a second communication mode, the further set of data symbols requiring a different variation of the power transmission signal, the different variation being a different variation from the given variation, and the detector is configured to detect the given variation depending on whether the variation of the power transmission signal more closely matches the different variation or whether the variation of the power transmission signal more closely matches a combination of the different variation and the given variation.

[0042] This can provide improved performance and / or operation in many scenarios and / or facilitate implementation and / or deployment. The different variation can specifically be a variation opposite to the given variation.

[0043] According to an optional feature of the invention, the transmitter is configured to transmit a set of data symbols during the power transfer phase.

[0044] This can provide improved performance and / or operation in many scenarios and embodiments.

[0045] According to an optional feature of the invention, the request for the expected variation of the power transfer signal is a request for termination of power transfer, and the selector is configured to select the first communication mode for a subsequent power transfer phase when an end of the power transfer phase is detected.

[0046] This can provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios, which can often provide efficient and / or easy detection of variations while typically utilizing existing operations and messages.

[0047] According to an optional feature of the invention, the transmitter is configured to transmit a set of data symbols in response to detecting a detected power transmission signal from the power transmitter, and the expected fluctuations are fluctuations in the detected power transmission signal.

[0048] This may provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios. The detection power transfer signal may specifically be a ping signal.

[0049] According to an optional feature of the invention, the power receiver further includes the transmitter transmitting a test set of data symbols using a first communication mode with a first value for the communication parameter, the test set of data symbols including a request for a second given variation of the power transmission signal, and the selector configured to set the communication parameter to the first value if the variation of the power transmission signal matches the second given variation and to set the communication parameter to a different value if they do not match.

[0050] This can provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios. This approach can allow efficient adaptation of communication parameters without requiring communication from the power transmitter to the power receiver.

[0051] In some embodiments, the communication parameter is at least one of a chip sequence length and a load modulation depth.

[0052] This may provide improved performance and / or operation and / or ease of implementation and / or deployment in many scenarios.

[0053] According to another aspect of the invention, there is provided a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, the power transmitter comprising: an output circuit including a transmitter coil configured to generate a power transmission signal in response to a drive signal applied to the output circuit; a driver configured to generate the drive signal; a load detector for detecting load variations in the power transmission signal; a detector for detecting validly received data symbols in response to a correlation between a chip sequence of a set of chip sequences and a load variation in the power transmission signal exceeding a threshold, the chip sequences of the set of chip sequences being linked to different data symbol values; an adapter configured to apply variations to the power transmission signal in response to the detection of validly received data symbols; and a selector configured to select a first communication mode as the selected communication mode in response to the detection of a validly received data symbol and to select a second communication mode as the selected communication mode otherwise, The first communication mode includes each data symbol being received according to a correlation between a set of chip sequences and a load variation of the power transmission signal, and the second communication mode does not include each data symbol being received according to a correlation between a set of chip sequences and a load variation of the power transmission signal. The selector includes a load modulation receiver configured to determine a load modulation data symbol received from the power receiver according to the selected communication mode.

[0054] According to another aspect of the invention, there is provided a method of operating a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the method comprising the steps of: an input circuit including a receiver coil for extracting power from the power transmission signal; transmitting a set of data symbols to the power transmitter by load modulating the power transmission signal, wherein each data symbol of the data sequence is modulated by a sequence of modulation load values ​​corresponding to a chip sequence of a first set of chip sequences, the chip sequences of the first set of chip sequences being linked to different data symbol values, the set of data symbols including a request for a given variation of the power transmission signal; monitoring the power transmission signal to detect a given variation of the power transmission signal; selecting a first communication mode as the selected communication mode if the given variation is detected, and selecting a second communication mode as the selected communication mode if the given variation is not detected, the first communication mode including each data symbol being modulated by a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences; The second communication mode includes a step of not including modulating the data symbols with a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences, and a step of transmitting the data symbols to the power transmitter during the power transfer phase using the selected communication mode.

[0055] According to another aspect of the invention, there is provided a method of operating a power transmitter for wirelessly supplying power to a power receiver via an electromagnetic power transmission signal, the method comprising the steps of: a transmitter coil generating a power transmission signal in response to a drive signal applied to the transmitter coil; generating the drive signal; detecting a load variation in the power transmission signal; detecting validly received data symbols in response to a correlation between a chip sequence of a set of chip sequences and a load variation in the power transmission signal exceeding a threshold, where the chip sequences of the set of chip sequences are linked to different data symbol values; applying a variation to the power transmission signal in response to the detection of the validly received data symbols; selecting a first communication mode as a selected communication mode in response to the detection of the validly received data symbols, and otherwise selecting a second communication mode as the selected communication mode, where the first communication mode includes each data symbol being received in response to a correlation between the set of chip sequences and a load variation in the power transmission signal and the second communication mode does not include each data symbol being received in response to a correlation between the set of chip sequences and a load variation in the power transmission signal; and determining load modulated data symbols received from the power receiver in accordance with the selected communication mode.

[0056] It will be understood that the comments provided with respect to the first aspect apply mutatis mutandis to the other aspects.

[0057] These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0058] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Figure 1] FIG. 1 illustrates an example of elements of a power transfer system according to some embodiments of the present invention. [Diagram 2]2 illustrates an example of elements of a power transmitter according to some embodiments of the present invention. [Diagram 3] FIG. 2 illustrates an example of a half-bridge inverter for a power transmitter. [Figure 4] FIG. 1 illustrates an example of a full bridge inverter for a power transmitter. [Diagram 5] FIG. 2 illustrates an example of elements of a power receiver according to some embodiments of the present invention. [Figure 6] FIG. 13 is a diagram showing an example of a chip sequence. [Figure 7] 1 illustrates an example communication exchange according to some embodiments of the present invention. [Figure 8] 1 illustrates an example communication exchange according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] The following description focuses on embodiments of the invention applicable to high power wireless power transfer systems utilizing the power transfer approach as known from the Qi specification, however, it will be understood that the invention is not limited to this application and may be applied to many other wireless power transfer systems.

[0060] 1 illustrates an example of a power transfer system according to some embodiments of the present invention. The power transfer system includes a power transmitter 101 including (or coupled to) a transmitter coil / inductor 103. The system further includes a power receiver 105 including (or coupled to) a receiver coil / inductor 107.

[0061] The system provides an inductive electromagnetic power transmission signal capable of inductively transmitting power from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal, which is propagated as a magnetic flux by a transmitter coil or inductor 103. The power transmission signal can typically have a frequency between about 20 kHz and about 500 kHz, and in many practical systems can be about 120-150 kHz. The transmitter coil 103 and the receiver coil 107 are loosely coupled, and thus the receiver coil 107 picks up (at least a portion of) the power transmission signal from the power transmitter 101. Thus, power is transmitted from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the receiver coil 107. The term power transmission signal is primarily used to refer to the induction signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the receiving coil 107, but it will be understood that equivalently it can also be considered and used to refer to an electrical signal supplied to the transmitter coil 103 or picked up by the receiving coil 107.

[0062] In an embodiment, power receiver 105 is specifically a power receiver that receives power via receiver coil 107. However, in other embodiments, power receiver 105 may include a metallic element, such as a metallic heating element, where the power transmission signal directly induces eddy currents that result in direct heating of the element.

[0063] The operation of the power transmitter 101 and the power receiver 105 will be described below with particular reference to an embodiment generally in accordance with the Qi standard (except for any modifications or extensions described (or entailed) herein). Many wireless power transfer systems utilize resonant power transfer, where the transmitter coil 103 is part of a resonant circuit, and typically the receiver coil 107 is also part of the resonant circuit. In many embodiments, the resonant circuit may be a series resonant circuit, such that the transmitter coil 103 and the receiver coil 107 may be coupled in series with corresponding resonant capacitors. The use of a resonant circuit tends to provide more efficient power transfer. Typically, wireless power transfer systems use a power control loop to steer the system towards a suitable operating point. This power control loop varies the amount of power transmitted from the power transmitter to the power receiver. The received power (or voltage or current) can be measured and, depending on the set power value, an error signal can be generated. The power receiver feeds this error signal to the power control function of the power transmitter, which reduces this static error, ideally to zero.

[0064] FIG. 2 shows elements of the power transmitter 101 of FIG. 1 in more detail.

[0065] The power transmitter 101 includes a driver 201 capable of generating a drive signal that is provided to a power transmitter coil 103, which in return generates an electromagnetic power transmission signal, thereby providing power transmission to a power receiver 105. The transmitter coil 103 is part of an output resonant circuit that includes the transmitter coil 103 and a capacitor 203. In this example, the output resonant circuit is a series resonant circuit, although it will be appreciated that in other embodiments the output resonant circuit can be a parallel resonant circuit. It will be appreciated that any suitable resonant circuit can be used, including those that use multiple inductors and / or capacitors.

[0066] The driver 201 generates the current and voltage that are supplied to the output resonant circuit and thus to the transmitter coil 103. The driver 201 is a drive circuit, typically in the form of an inverter, that generates an AC signal from a DC voltage. The output of the driver 201 is typically a switched bridge that generates the drive signal by appropriate switching of the switches of the switched bridge. Figure 3 shows a half-bridge switched bridge / inverter. Switches S1 and S2 are controlled so that they are never closed at the same time. Alternately, S1 is closed while S2 is open and S2 is closed while S1 is open. The switches are opened and closed at a desired frequency, thereby generating an AC signal at the output. Typically, the output of the inverter is connected to the transmitter inductor via a resonant capacitor. Figure 4 shows a full-bridge switched bridge / inverter. Switches S1 and S2 are controlled so that they are never closed at the same time. Switches S3 and S4 are controlled so that they are never closed at the same time. Alternately, switches S1 and S4 are closed while S2 and S3 are open, and switches S2 and S3 are closed while S1 and S4 are open, thereby producing a square wave signal at the output. The switches are opened and closed at the desired frequency.

[0067] The power transmitter 101 further includes a power transmitter controller 205 configured to control the operation of the power transmitter 101 according to a desired operating principle. In particular, the power transmitter 101 may include many of the functions necessary to perform power control according to the Qi standard.

[0068] The power transmitter controller 205 is particularly configured to control the generation of the drive signal by the driver 201 and is in particular able to control the power level of the drive signal and thus the level of the generated power transmission signal. The power transmitter controller 205 comprises a power loop controller that controls the power level of the power transmission signal in response to power control messages received from the power receiver 105 during the power transfer phase.

[0069] FIG. 5 illustrates some example elements of the power receiver 105. In this example, the receiver coil 107 is coupled to the power receiver controller 501 via a capacitor 503 that forms an input resonant circuit with the receiver coil 107. Thus, the power transfer may be a resonant power transfer between the resonant circuits. In other embodiments, only one or neither of the power receiver and power transmitter may utilize a resonant circuit for power transfer.

[0070] The power receiver controller 501 couples the receiver coil 107 to the load 505 via a switch 507. The power receiver controller 501 includes a power control path that converts the power extracted by the receiver coil 107 to a supply suitable for the load 505. In some embodiments, the power receiver controller 501 can provide a direct power path that simply connects the input resonant circuit to the switch 507 or the load 505, i.e., the power path of the power receiver controller 501 can be implemented simply by two wires. In other embodiments, the power path can include, for example, a rectifier and possibly a smoothing capacitor to provide a DC voltage. In still other embodiments, the power path can include more complex functions such as, for example, a voltage control circuit, an impedance matching circuit, a current control circuit, etc. Similarly, it will be appreciated that the switch 507 may only be present in some embodiments, and in some embodiments the load 505 can be permanently coupled to the input resonant circuit.

[0071] Additionally, the power receiver controller 501 may include various power receiver controller functions required to perform power transfer, particularly functions required to perform power transfer according to the Qi standard.

[0072] The power receiver 105 is configured to transmit data to the power transmitter 101. Such data may include, among other things, a power control loop error message used to implement a feedback power loop for controlling the power level of the power transmission signal during power transmission, as known to those skilled in the art. The power receiver is capable, in many embodiments, of transmitting a variety of different messages that serve different purposes, as known to those skilled in the art. For example, a variety of different messages, such as those specified in the Qi standard, may be transmitted. A message may include one or more data bits / symbols.

[0073] The power receiver is configured to transmit a message to the power transmitter using load modulation.

[0074] As is well known to those skilled in the art, for load modulation, changes in the load of the power transmission signal can be introduced by the power receiver, where the changes depend on the data values ​​to be transmitted, and these changes can be detected by the power transmitter to decode the data from the power receiver.

[0075] Load modulation can be used as a method for the power receiver to communicate control messages or other data to the power transmitter, for example according to the Qi wireless power standard.

[0076] Typically, there are two main ways to perform load modulation: either directly modifying the resistive load / power extraction of the input circuit, and / or detuning the resonance of the input circuit, for example by modifying the reactive load of the input circuit (typically by switching a capacitor in / out in line with the data to be transmitted). A similar approach can be used by the power receiver to load modulate the power transmission signal.

[0077] Correspondingly, in the power transmitter, a detection approach such as that known for the Qi standard system can be used to detect load variations. For example, a direct measurement of the power level or current amplitude of the drive signal can be used as an indicator of the load and therefore the load modulation variations introduced by the power receiver, as known to those skilled in the art.

[0078] The power receiver 105 comprises a data transmitter 509 configured to transmit data to the power transmitter 101 by load modulating the power transmission signal. For example, the data transmitter 509 can be configured to switch in / out a communication capacitor that is placed in parallel with the power receiver controller 501 or the resonant capacitor 503 and can thereby vary the resonant frequency and the loading of the power transmission signal.

[0079] The data transmitter 509 can be coupled to the power receiver controller 501 and can be configured to receive data from the power receiver controller 501 for transmission to the power transmitter.

[0080] For example, the data transmitter 509 may receive power error control data from the power receiver controller 501 and transmit corresponding power error control messages to the power transmitter 101 using load modulation. In operation, the system is typically configured to control the drive signal such that the power transmission signal achieves appropriate operating parameters / characteristics and the power transmission operates at an appropriate operating point. To do so, the power transmitter is configured to control parameters of the drive signal using a power control loop in which the power characteristics of the power transmission signal / drive signal are controlled in response to power control error messages received from the power receiver.

[0081] At regular, typically frequent intervals, the power receiver transmits a power control error message to the power transmitter. In some embodiments, a direct power set point change message (rather than a relative error message) can be transmitted indicating the desired absolute power level. The power receiver 105 includes functionality to support such a power control loop, for example, the power receiver controller 501 can continuously monitor the power or voltage of the load signal supplied to the load and detect whether this is above or below a desired value. At regular intervals, it can generate a power control error message requesting that the power level of the power transmission signal be increased or decreased, and can transmit this power control error message to the power transmitter. Such error control messages, as well as other messages, can be transmitted by load modulation.

[0082] The data transmitter 509 is configured to transmit data to the power transmitter using different modes corresponding to different load modulation transmission modes.

[0083] In the first communication mode, the data transmitter 509 is configured to transmit data symbols by load modulating the power transmission signal with a sequence of modulated load values ​​corresponding to the chip sequences. The chip sequences are selected from a first set of chip sequences, and in this example, the data transmitter 509 is coupled to a chip sequence storage unit 511 in which the first set of chip sequences is stored. Typically, the set of chip sequences includes a chip sequence for each possible data symbol value. For example, in the case where binary communication is used, the first set of chip sequences may include only two chip sequences. It will be appreciated that the chip sequence storage unit 511 may store the chip sequences in any suitable form and need not store a complete sequence for each possible data symbol. For example, one or more chip sequences may be represented by a relationship with another chip sequence. For example, in the case of binary communication, the chip sequence storage unit 511 may store only a single chip sequence corresponding to one of the binary data values. The chip sequence for the other binary data value may be represented by the same stored bit sequence, which may be given as the inverse of the stored bit sequence. Thus, in many cases the first set of chip sequences will utilise complementary inverse chip sequences for pairs of data symbols and therefore typically only half of the chip sequences used will be explicitly stored in chip sequence store 511, with the remaining chip sequences being automatically and implicitly stored as their inverses.

[0084] The chip sequences in the first set are typically the same length.

[0085] Load modulation can provide advantageous operation in many systems and applications, and tends to provide reliable, low-complexity operation suitable for power transmission systems in which a power transmission signal is generated for the purpose of transmitting power. Reusing the power transmission signal as a communications carrier typically reduces complexity and requires less circuitry, thereby reducing cost. The Qi standard was originally implemented using unidirectional communication from the power receiver to the power transmitter by using load modulation with a modulation symbol shape that allows easy distinction between binary data values.

[0086] However, load modulation, as used, for example, in the Qi system, may also have some associated drawbacks, which may relate, for example, to issues such as electromagnetic compatibility, communication quality (bit error rate), and audible noise.

[0087] Load modulation generates additional components in the electromagnetic spectrum and can cause additional electromagnetic interference and electrical noise. It has also been found that in many cases the changes in the electromagnetic field caused by load modulation can cause mechanical forces and movements that result in audible noise. It has also been found that strong load modulation can disrupt the energy balance in wireless power systems and result in spurious oscillations in the communication carrier spectrum. When spurious oscillations are present, wireless power transmitters are often unable to properly demodulate the signal and therefore must interrupt the power supply to maintain safe operation.

[0088] This problem tends to get worse for higher power transmission levels. Indeed, as the power level of the power transmission signal increases, the load change due to the load modulation is typically required to increase as well. Typically, the load modulation is required to be a suitable percentage of the power level of the power transmission signal, i.e., the maximum power level. For example, the load modulation caused by the load modulation may be required to have a magnitude of, for example, about 1% or more of the typical load of the power receiver (i.e., the load change of the receiver coil caused by the load modulation would be required to be 1% or more of the total load of the receiver coil 107). Qi was originally introduced for low power applications, less than about 5W. At such low power levels, the impact of the drawbacks of load modulation are relatively manageable or not very significant. However, the maximum power level of Qi has now been increased to a maximum of 15W, and work is underway to further increase this to a maximum level of 45W. However, at such power levels, the drawbacks mentioned above tend to become more pronounced, and these may pose a significant obstacle to further development of the Qi standard.

[0089] The systems of Figures 1, 2 and 5, according to a first communication mode, can utilize an approach that can address one or more of the problems associated with load modulation in many situations. In the first communication mode, load modulation is used, where each symbol is represented by a chip sequence including multiple chips, typically by a sequence including 15 to 127 chips. Thus, rather than simply varying the load according to each symbol or bit, the data transmitter 509 is configured to transmit a given symbol (typically a bit) through a series of load changes and variations, where the changes and variations are different for each symbol. Specifically, a chip sequence can be defined for each symbol, and when transmitting a given symbol, the data transmitter 509 can read the chip sequence for that particular symbol and proceed to load modulate the power transmission signal according to the chip sequence for that symbol.

[0090] When the power transmitter can support the first communication mode, the power transmitter can detect load modulation by considering the entire sequence, specifically, the power transmitter can attempt to determine the received symbol as the symbol for which the detected load variation pattern most closely matches the chip sequence pattern of that symbol.

[0091] Such an approach in particular allows the modulation depth, i.e. the magnitude of the load fluctuations, to be significantly reduced, which can, for example, reduce electromagnetic noise and interference, reduce acoustic noise, and reduce spurious vibrations. It can also result in many embodiments in an improved signal-to-noise ratio, resulting in, for example, significantly improved and more reliable communications, often with a lower bit error rate. Thus, an overall improved power transfer can be achieved.

[0092] In many embodiments, binary communication may be used, where only two data symbol values ​​are possible (corresponding to a "0" or a "1" bit value). In such cases, one bit value may be represented by a given chip sequence, and the other bit value may be associated with the inverse bit sequence, i.e., the bit sequence resulting from changing each chip value to its opposite value. Thus, the two bit sequences are typically complementary, one resulting from multiplying the other by -1 (chip values ​​are represented by +1 and -1).

[0093] A particular advantage in such a case is that demodulation is particularly easy since a single correlation can be used to distinguish between bit values, since the magnitude of the correlation is the same for the chip sequence, but the sign of the correlation value is opposite.

[0094] The following description focuses on such binary communications, although it will be understood that the invention is not limited to only binary communications.

[0095] The data transmitter 509 can then be configured to receive, typically from the power receiver controller 501, data symbols to be transmitted to the power transmitter, determine a corresponding chip sequence and proceed to load modulate the power transmission signal with this chip sequence. Typically, the data symbols are binary, but in some cases higher order modulation symbols may be used (i.e., having more than two possible values). In some cases, such higher order data symbols may correspond to combinations of the received data bits. For example, two bits can be combined into a single quaternary data symbol. Such combinations may be possible both when those data bits are related and, for example, when they are completely independent.

[0096] In this example, the data transmitter 509 is particularly coupled to a chip sequence store 511 in which different chip sequences for respective data symbols are stored. The chip sequence store 511 may store a set of reference chip sequences, each reference chip sequence being linked to a particular data symbol value. In response to receiving a data symbol for transmission, the load data transmitter 509 may proceed to retrieve a corresponding chip sequence from the chip sequence store 511. Thus, the data transmitter 509 may particularly retrieve from the chip store 511 a chip sequence from a first set of chip sequences used in a first communication mode.

[0097] FIG. 6 shows some examples of two possible chip sequences. Each chip sequence includes a series of chips, each chip having a certain modulation load level selected from a set of modulation levels. Typically, the set of modulation levels is two, corresponding to a binary chip sequence in which the modulation load level can switch between two possible levels. Thus, the symbol time is divided into a number of chip intervals, the modulation load level of each chip interval is selected from a predetermined set of modulation load levels, and the modulation load level sequence of chips is different for each chip sequence. Typically, each sequence includes at least 10 chips, and often includes significantly more chips. In many embodiments, each chip sequence can have a length of 2N −1, where N is an integer typically equal to or greater than 4.

[0098] A longer chip sequence may provide improved noise suppression, etc., but may also result in a reduced data rate since the symbol time will increase for a given chip rate. Increasing the chip sequence length also increases the complexity and resource demands, especially at the receiver where correlation with a longer sequence may inherently require a large number of calculations. A typical suitable value is N=5, which is a chip length of 31 chips.

[0099] Each of the stored chip sequences is assigned to one symbol. Thus, each possible data symbol value that may need to be transmitted to the power transmitter can have a linked / associated chip sequence. For example, if only two data symbols are possible, i.e., if binary communication is implemented, the set of chip sequences can include only two chip sequences. In this case, the chip sequences can be inverses of each other as mentioned above, specifically, one can result from the multiplication of the other by -1.

[0100] The first set of chip sequences may include more than one chip sequence for a given data symbol, i.e., multiple sequences may be linked to the same data symbol (e.g., chip sequences having different lengths). Typically, however, each chip sequence is linked to one data symbol, and one data symbol is linked to only one chip sequence in the first set of chip sequences.

[0101] It will be appreciated that such a binary approach, in which two inverse chip sequences are used, is equivalent to considering two possible binary values ​​as being modulated by the same chip sequence, but with data symbols having opposite data values ​​(e.g., +1 and -1).

[0102] When the power receiver wishes to transmit a data symbol, its value is fed from the power receiver controller 501 to the data transmitter 509 and then the corresponding chip sequence is read from the chip sequence store 511. In the binary case, this chip sequence can be generated by multiplying the symbol value with a common stored chip sequence.

[0103] The determined chip sequence is then provided to a data transmitter 509 configured to control a switchable load for the input circuit to modulate the appropriate chip sequence on the power transmission signal. In this example, the data transmitter 509 can be configured to switch in and out (on / off) a modulating load according to the chips of the chip sequence, i.e., the load can be changed according to the modulating load value of the chip sequence. Typically, the data transmitter 509 can be configured to switch in / out, for example, a communication capacitor arranged in parallel with the power receiver controller 501 or the resonant capacitor 503, thereby changing the resonant frequency and the load of the power transmission signal.

[0104] Thus, in this example, each symbol (typically bit) time interval is divided into multiple (e.g., 31) chip intervals, the modulation load is constant within each chip interval, and the modulation load varies (changes or does not change) between chip intervals according to a different pattern for each data symbol.

[0105] In order to receive the load modulation according to the first communication mode, the power transmitter must have the necessary functionality to support chip sequence based communication. Figure 2 is an example of a power transmitter capable of receiving data from the power receiver 105 of Figure 5 transmitted according to the first communication mode.

[0106] The power transmitter 101 of FIG. 2 comprises a load detector 209 configured to detect load variations of the power transmission signal, and in particular can determine a load variation sequence of the power transmission signal and / or the drive signal. The load variation sequence can thus correspond to a received chip sequence when data is being transmitted. For example, the load value (e.g., current and / or power) of the drive signal can be measured and sampled at time intervals corresponding to chip intervals during the time when a message is (expected to be) received from the power receiver. In some cases, the value can be normalized and quantized, e.g., if a binary chip sequence is used, the load detector can generate a binary sequence representing, for example, high and low load. The received chip sequence of the load modulation is thus generated from the sampling of the signal of the output circuit.

[0107] The load detector 209 is coupled to the load modulation receiver 207 to which it provides the received load variation (corresponding to the chip sequence of the modulated load value). The load modulation receiver stores a set of reference chip sequences that correspond specifically to the chip sequences stored and used by the power receiver. Thus, the load modulation receiver 207 stores chip sequences of a first set of chip sequences, and the power receiver and the power transmitter store local replicas of the chip sequences linked with the data symbols. The power transmitter 101 comprises a local representation of the chip sequences used by the power receiver. The power receiver and the power transmitter store the corresponding links between the reference chip sequences and the data symbols.

[0108] In this example, the load modulation receiver 207 may only store a single data symbol chip sequence, i.e., the data symbol chip sequence used to modulate the binary data symbols (so the single stored data symbol chip sequence is equal to the chip sequence representing one binary data value and the inverse (typically sign-reversed) chip sequence represents the other binary data value).

[0109] The load modulation receiver 207 is configured to determine the load modulation data symbols received from the power receiver according to the correlation between the stored data symbol chip sequences (of the first set of chip sequences) and the load variations of the power transmission signal. Specifically, in some embodiments, the load modulation receiver 207 can correlate the determined load variation sequence provided by the load detector 209 with all the stored data symbol chip sequences of the first set of chip sequences to determine a correlation value for each. In cases such as the described binary case where some sequences are inverse to each other, only one correlation can be performed, and the sign of the correlation value reflects the correlation with the two possible chip sequences.

[0110] Thus, the load modulation receiver 207 may correlate the receiver load variation sequence with the reference chip sequence(s) to determine a correlation value indicating how closely they match.

[0111] The load modulation receiver 207 can then determine the data symbol as the data symbol linked to the chip sequence whose associated correlation value is high enough to exceed a given threshold. The threshold can be an adaptive threshold in many embodiments, for example the threshold can be set depending on the correlation value with other symbols. As a specific example, the threshold is set as the value of the next highest correlation value (e.g. a minimum threshold is applied), so that the data symbol is selected as the data symbol with the highest correlation value (e.g. exceeding the minimum threshold).

[0112] Thus, when operating in the first communication mode, the power receiver can transmit data to the power transmitter using load modulation with a relatively long chip sequence per data symbol, and a power transmitter with suitable capabilities can be configured to receive this communication. This approach can provide significantly improved communication and operation in many embodiments. In particular, significantly improved communication performance and reliability, in particular the symbol signal to noise ratio, can be significantly increased. This can allow the modulation depth, specifically the modulation load variation relative to the power transmission signal level / power transmission level, to be significantly reduced. In fact, in many cases the modulation depth can be reduced by a factor of 10, 100 or more. This can reduce and mitigate many of the drawbacks of using load modulation, for example reducing electromagnetic interference, reducing electrical noise, reducing mechanical noise, and preventing or mitigating spurious vibrations.

[0113] For example, using chip rates corresponding to the bit rates used in Qi (up to 2 kBps communication rates), the improvement in the signal-to-noise ratio can be increased by an amount corresponding to the sequence length. For example, using a bit length of 63 or 127 can increase the symbol energy-to-noise ratio by a corresponding amount while maintaining the same bit error rate, allowing the modulation depth to be reduced by a factor of 63 or 127, respectively.

[0114] A drawback of such an approach is that the effective communication rate may be reduced. For example, using sequence lengths of 63 or 127 may reduce the effective baud rate to 30.7 or 15.7 bps, respectively. To address this, the chip time interval duration may be reduced. This reduction is an appropriate trade-off between the desired communication rate and bit error performance and may be selected for a particular application and implementation. Increasing the chip rate results in a corresponding, potentially significant, increase in the required bandwidth and frequency spectrum of the load modulation. However, it is a particular advantage of the current approach that communications in wireless power transfer systems are typically not bandwidth limited or sensitive to the bandwidth of the communications, and thus such additional bandwidth may typically be available without impacting other functions or performance.

[0115] In many embodiments, the system can be configured to synchronize the load modulation communication with the power transmission signal / drive signal.

[0116] In many embodiments, the data transmitter 509 can be configured to specifically synchronize the load modulation of the first chip sequence to the power transmission signal. The power transmission signal typically has an operating frequency in the range of 10 kHz to 500 kHz, and for Qi, is often around 100 kHz. The data transmitter 509 can synchronize the chip time interval to be synchronized to the oscillation and period of the power transmission signal. For example, in many embodiments, the data transmitter 509 can use a chip duration / time interval that is a multiple of the power transmission signal period. Thus, each chip can have a duration that is a multiple of the period of the power transmission signal, i.e., the duration of the chip interval can be N*T, where N is an integer and T is the duration of the period of the power transmission signal / drive signal.

[0117] In many embodiments, the data transmitter 509 not only synchronizes the duration of the chip interval to the duration of the period of the power transmission signal, but also aligns the start and / or stop timing of the chips to the timing of the power transmission signal. In particular, the transition times between chips can be synchronized to occur at the zero crossings of the power transmission signal or, for example, at a fixed offset relative to the zero crossings of the power transmission signal. It will be appreciated that the synchronization can be based on the timing of the signal induced in the receiver coil 107 by the power transmission signal.

[0118] Similarly, the data transmitter 509 can be configured to generate a receive chip sequence from samples of the load of the power transmission signal (possibly after matched filtering is applied).

[0119] The load detector 209 can sample signals in the output circuit that correspond to the power transmission signal, specifically the current and / or power of the drive signal, the relative phase between the current and voltage of the drive signal, the current through the transmitter coil 103, etc. The load modulation receiver 207 can then generate chip sequences to correspond to the load values ​​at these sampling times, and can proceed to determine correlation values ​​by correlating the received chip sequences in the form of sampled modulated load values ​​with a reference value.

[0120] It will be appreciated that in some approaches, the correlation can be based on hard decision values, i.e., a direct comparison of hard-decision received chip values ​​with chip values ​​can be used. In some embodiments, the decision can be based on, for example, soft decision modulation load / chip values. For example, in the case of a binary transmission approach, the reference chip sequence may be a binary sequence with only two possible values. However, the received chip sequence can be represented by soft decision values, such as values ​​that directly indicate the measured modulation load value.

[0121] In many embodiments, the load detector 209 is configured to synchronize its sampling to the power transfer signal, and specifically this can be achieved by synchronizing it to the drive signal.

[0122] In many embodiments, the synchronization may be sampling, such that one sample is taken every chip (possibly after matched filtering). In particular, if the chip rate is equal to N times the period of the power transmission signal, the sampling can be synchronized once every N times. Thus, in many embodiments, the synchronization can be such that the sampling rate is equal to the chip frequency of the load modulation.

[0123] In some embodiments, sampling can be a two-stage process in which several samples are generated at a higher frequency and then decimated to a given sample rate. For example, for a chip duration of 10 times the period of the power transmission signal, the sampler can take one sample per period. The averaging filter can then sum the last 10 samples, i.e. it can be a square window FIR filter that sums the 10 most recent samples (with equal weights). The output of the sampling is then the sampled output of this filter, specifically the output every 10 periods, consistent with the filter being the sum of the 10 periods within a single chip. Thus, sampling at synchronized instants can be effectively achieved by appropriately synchronized decimation at the output of the filter.

[0124] In other embodiments, only a single sampling of the analog signal of the output circuit is performed per chip. In such a situation, the timing of the sampling can be synchronized to occur at the center of the symbol duration for each sample.

[0125] Thus, in many embodiments, the operating frequency of the drive signals and the power transmission signals may be an integer multiple of the sampling rate of the sampling of the signals of the output circuit and / or an integer multiple of the chip frequency of the load modulation. The multiples may be the same, in particular 1. Indeed, in many embodiments, the integer multiples are advantageously relatively low to allow for efficient communication and higher data rates. In many embodiments, the integers advantageously do not exceed 1, 3, 5, 10 or 20.

[0126] Synchronizing the load modulation to the power transmission signal, in many practical implementations, allows for a reduction in the amount of sampling that the power transmitter must perform, and therefore allows for an increase in the chip rate and / or bit rate. In the extreme case where the chip frequency is the same as the power transmission signal frequency, the power receiver can vary the load according to the chip sequence every cycle of the power transmission signal. Alternatively, the power receiver can vary the load according to the chip sequence every N cycles of the power signal, reducing the chip frequency by a factor of N.

[0127] Synchronous modulation facilitates modulation detection at the power transmitter by allowing it to apply synchronous sampling techniques and correlating the detected signal with its post-step modulation sequence. This approach can be significantly easier to implement while typically achieving efficient communication.

[0128] The length of the chip sequence can be selected to suit the particular preferences and requirements of an individual embodiment, and can be selected to provide a suitable compromise between communication reliability and performance (e.g., bit rate), data rate, bandwidth, modulation depth, associated drawbacks, etc. In most embodiments, lengths of 8 chips or more and / or 128 chips or less provide suitable and advantageous performance, particularly for wireless power transfer systems such as the Qi system.

[0129] In many embodiments, the first set of chip sequences may include only two chip sequences, in such an example, each symbol may be represented by one or the other chip sequence depending on the symbol value, and thus each symbol may be a binary symbol (bit) and the communication may be a binary communication.

[0130] In some embodiments, the first set of chip sequences can include more than two chip sequences, allowing more than two different symbol values. For example, in some embodiments, the first set of chip sequences can include three chip sequences, allowing, for example, three different symbol values ​​for each symbol communicated by the chip sequences. In other embodiments, more sequences can be included, allowing each chip sequence / data symbol to represent more data values, thereby increasing the effective bit rate. Such an approach is particularly suitable for longer chip sequences, where a larger difference in correlation values ​​between chip sequences is feasible.

[0131] For example, for a chip length of 31 bits, 2147483648 different sequences are possible, and the system can select two of these sequences that have high autocorrelation and low cross-correlation. Typically, these sequences can be selected as the sequence with the highest autocorrelation and the binary inverse chip sequence with the lowest cross-correlation (normalized cross-correlation is -1 using the binary values ​​of -1 and 1). These two sequences can then be used for binary communication that allows high reliability, since the correlation performed by the load modulation receiver 207 produces significantly different correlation values ​​for the two possible chip sequences being received.

[0132] The particular sequences and patterns used may depend on the preferences and requirements of the individual implementation. Typically, the sequences are selected to provide good correlation properties, specifically, the set of chip sequences is selected to consist of sequences with high autocorrelation and low cross-correlation values. In many embodiments, the chip sequences may be selected as maximum length sequences. For example, in many embodiments, the chip sequences may be selected as maximum length sequences generated from a polynomial, the order of the polynomial being selected by the power receiver according to the desired / selected modulation depth and the desired communication rate. In particular, pseudo-noise sequences developed for and used in direct sequence spread spectrum communication and code division multiple access systems tend to be well suited to the described approach.

[0133] As mentioned above, the set of sequences may include mirror image or inverted chip sequences, i.e., for a given binary chip sequence, the set of chip sequences may also include chip sequences in which all chips have complementary values. For example, if the load values ​​are represented by 1 and -1, the set of chip sequences may also include, for each chip sequence, a chip sequence resulting from multiplication by -1 (equivalent to a swap between 0 and 1 for all chips for chip sequences represented by values ​​of 1 and 0). Indeed, in some embodiments, the set of chip sequences may include only a chip sequence and its inverted chip sequence. It will be appreciated that in such embodiments, only a single representation needs to be stored to represent the pair of chip sequence and inverted chip sequence.

[0134] Such an approach is particularly suitable for many applications and can provide good performance and low complexity. For example, a single correlation between the received chip sequence and a reference chip sequence can provide correlation values ​​for both the reference chip sequence and the inverse chip sequence. Indeed, in the absence of noise, the correlation value for one of the reference chip sequences is +1, and the correlation value for the inverse reference chip sequence is -1. Thus, a single correlation value applicable to two symbol values / sequences can be determined and can be directly used to select between the two symbols.

[0135] It will be appreciated that the approach of using an inverted reference chip sequence can be considered equivalent to multiplying the binary data symbols with a single reference chip sequence (using values ​​of 1 and -1 to represent binary values).

[0136] As a specific example, the system may adopt the following approach when operating in the first communication mode: 1. The power receiver significantly reduces the depth of load modulation, resulting in no spurious vibration and reduced electrical and acoustic noise. 2. The power receiver encodes the individual bits as a direct (e.g., pseudorandom) chip sequence that has a steep autocorrelation function. 3. The power receiver operates the load (typically by changing the load or detuning a resonant circuit) in synchronization with the power transmission signal (e.g., a transition every power signal cycle or a transition every multiple power signal cycles). 4. The power transmitter measures the load change, for example, by measuring the power transmitter coil voltage or coil current at a sampling time synchronized to the power transmission signal (e.g., one sample per power signal cycle, multiple samples per power signal cycle, or one sample per multiple power signal cycles). 5. The power transmitter decodes the data by correlating the digitized samples with the chip sequence by which the data was modulated. 6. The chip sequence and the number of power signal cycles per symbol may be known in advance by the power receiver and the power transmitter.

[0137] An advantage of the described approach is that it provides improved backward compatibility in many scenarios and requires relatively little modification to many power transfer systems. For example, the Qi power transfer system already uses load modulation and would require relatively little modification to support the above-described approach.

[0138] However, a difficult problem is that while the described first communication mode can provide superior performance, it requires that both the power receiver and the power transmitter be able to support the communication approach. However, in many systems, there may be a large amount of legacy devices, potentially both power transmitters and power receivers, that may not be able to support advanced communication approaches such as the first communication mode. For example, many Qi power transmitters are deployed according to earlier versions of the standard that do not include such chip sequence-based communication, and therefore the power receiver may not be able to use a communication mode based on such communication to communicate with the power transmitter. Similarly, a power transmitter that can receive load modulation messages based on chip sequence modulation may be required to communicate with a legacy power receiver that is not able to use chip sequence communication.

[0139] To address such issues, the power transmitter and / or the power receiver may comprise functionality for communicating with other types of devices, such as legacy devices, etc. Thus, in addition to the functionality for communicating according to a first communication mode, the power transmitter and / or the power receiver may further comprise functionality for communicating according to a second communication mode, in particular a legacy communication mode.

[0140] However, even if such a second legacy communication mode exists, thereby enabling a power transmitter and / or power receiver capable of chip sequence communication to communicate with legacy devices that do not have this capability, there are significant challenges in how to adapt the operation of the devices in individual scenarios, which can be particularly difficult in systems such as Qi, where some legacy devices can potentially only communicate in one direction.

[0141] For example, in the Baseline Power Profile (BAP) of the Qi standard, only communication is performed from the wireless power receiver to the wireless power transmitter. This would make it rather difficult to adapt the communication. In fact, considering such a unidirectional nature of the communication, it is not possible to have the wireless power transmitter and the wireless power receiver negotiate to determine which communication format to use, as is typically feasible with the availability of bidirectional communication used in the Extended Power Profile (EPP) of the Qi standard. However, in order to efficiently introduce more advanced and better performing chip sequence modulation approaches, it is also required that the device can interact with complementary devices that do not have this capability, and in particular, it is desirable for Qi devices to interact with complementary devices that meet the BPP of the Qi standard.

[0142] The power receiver of FIG. 5 is configured to support chip sequence-based communication while providing functionality for adapting the communication mode depending on the capabilities of the power transmitter with which it interacts. This can enable the adaptation in many embodiments without requiring explicit communication from the power transmitter, specifically without a communication channel being established from the power transmitter to the power receiver. This approach can enable chip sequence-based communication to be introduced into a Qi system, for example, while supporting and enabling interaction and interoperation with legacy devices, particularly legacy devices compatible with BPP. While the following description focuses on such an implementation, it will be understood that this approach or concept is not limited to this particular scenario.

[0143] In this approach, in addition to being able to communicate according to a first communication mode, the data transmitter 509 is also able to communicate according to a second communication mode, which in contrast to the first communication mode does not use chip sequences from the first set of chip sequences to modulate data symbols onto the power transmission signal.

[0144] Thus, the second communication mode may use a different approach and may not use chip sequences linked to possible data symbols according to the first communication mode. Rather, a second communication mode is used that load modulates data symbols onto a power transmission signal using a different approach / standard. The second communication mode may specifically be a mode that is backward compatible and supported by legacy equipment that does not support the first communication mode. Thus, the second communication mode may specifically be a legacy communication mode.

[0145] In a specific example, the second communication mode may be a communication mode according to the BPP of the Qi standard. Thus, the second communication mode may include a data transmitter 509 that transmits binary data symbols to the power transmitter by load modulating data bits onto a power transmission signal using bi-phase encoding as defined by the Qi standard. Thus, each data symbol can be transmitted in the second communication mode using differential Manchester encoding (DM).

[0146] Thus, unlike the second communication mode and the first communication mode, this approach can enable a dynamic and automatic approach for the power receiver to adapt to the capabilities of the power transmitter and whether it can support chip sequence communication using the first communication mode. If not, the power receiver continues to use the second communication mode, e.g., a legacy communication mode.

[0147] The second communication mode may also use chip sequence-based communication in some embodiments, but uses a different chip sequence than that used in the first communication mode. However, in many embodiments, the second communication mode may not be chip sequence-based communication, i.e., in some embodiments, the second communication mode may employ non-chip sequence-based communication. For example, in many embodiments, two binary data symbols may be linked to two modulation load values ​​in the second communication mode. For example, for one binary value, the modulation capacitor is connected to the receiver coil 107, and for the other binary value, the modulation capacitor is disconnected. Thus, the modulation load is constant throughout the data symbol time, and no modulation load change occurs during each data symbol or within the symbol duration. Thus, in such a scenario, the power receiver may accommodate a power transmitter that does not support any chip sequence-based communication but only supports conventional load modulation. However, if the power transmitter supports chip sequence-based communication, the power receiver may adapt to use this modulation approach.

[0148] In some embodiments, the second communication mode does not support communication from the power transmitter to the power receiver, but only supports communication from the power receiver to the power transmitter.

[0149] The power receiver is configured to select between using a first communication mode and a second communication mode. Specifically, for a power transfer operation, the power receiver selects whether to use the first communication mode or the second communication mode. Typically, this selection may be made once per power transfer operation, but it will be understood that in some embodiments, this selection may be made more than once per power transfer, or, for example, the same selection may be used for several power transfer operations.

[0150] To select between the first and second communication modes, the power receiver 105 comprises a selector 513 configured to select between the communication modes and to control the data transmitter 509 to communicate data symbols using the selected communication mode. For example, the selector 513 can select the first or second communication mode as part of an initialization of the power transfer operation or, for example, at the beginning of a power transfer phase, and the selected communication mode is used during the remainder of the power transfer operation.

[0151] The selection of the communication mode can be based on an approach in which the power receiver first transmits a set of one or more data symbols to the power transmitter, the transmitted set of data symbols including a request for the power transmitter to apply a variation to the power transmission signal.

[0152] The variation of the power transmission signal to be applied by the power transmission can be, for example, a variation of the frequency, phase or level of the power transmission signal, which can be imposed by applying a corresponding variation to the drive signal. The variation can be a relative or absolute variation.

[0153] Thus, the power receiver can transmit a set of data symbols requesting the power transmitter to apply a given / expected variation to the power transmission signal. For example, a power up or power down request can be transmitted to the power transmitter, with the corresponding given variation corresponding to an increase or decrease, respectively, in the power level of the power transmission signal.

[0154] The set of data symbols, hereinafter also referred to as request data symbols or bits for brevity, are transmitted using load modulation, and each data symbol is transmitted by load modulation using a chip sequence selected from a first set of chip sequences. Specifically, the request data symbols can be transmitted using a first communication mode.

[0155] The power receiver 105 further comprises a detector 515 coupled to the power receiver controller 501 and the selector 513. The detector 515 is configured to monitor the power transmission signal to detect whether an expected variation in the electromagnetic signal occurs.

[0156] For example, the power receiver controller 501 can provide information of the power level of the power transmission signal to the detector 515. For example, the power receiver controller 501 can continuously monitor the power supplied to the load to support a power control loop. The measured power level of the load corresponds to the power transmission signal power level, and the power receiver controller 501 can provide the measured power level to the detector 515. The detector 515 can further recognize a given variation expected in response to the requested data symbol, for example, by receiving a copy of the requested data symbol, or by an expected variation, which is often a predetermined variation that can be stored in the detector 515. The detector 515 can then be configured to compare the measured power level with the expected variation to detect whether the power transmission signal varies as expected if the data symbol request is responded to by the power transmitter.

[0157] The detector 515 may then provide the results of the detection operation to the selector 513, and in particular may indicate whether the expected variation was detected.

[0158] Detector 515 may apply any suitable matching criteria depending on the details of a particular embodiment. For example, in some embodiments, it may be detected whether the power level is increased (or decreased), e.g., by a given amount and / or for a given time. In other embodiments, it may be detected, for example, whether the power level corresponds to a pattern reflecting expected fluctuations.

[0159] The detector 515 is coupled to the selector 513 and provides information on whether the expected variation is detected. The selector 513 is configured to select between the first and second communication modes depending on whether the expected variation is detected. Specifically, if it is determined that the expected variation is detected, the selector 513 may select the first communication mode, and if the expected variation is not detected, the selector 513 may select the second communication mode. The selector 513 may then control the data transmitter 509 to use the selected communication mode, for example, typically during the remainder of the power transfer phase. Then, following the selection of the communication mode, the power receiver, specifically the data transmitter 509, proceeds to transmit data symbols to the power transmitter while using the selected communication mode.

[0160] 2 is a power transmitter that can support a first communication mode, and that can further support a second communication mode and thus can communicate with the power receiver 105, specifically, can receive data from the power receiver according to both a chip sequence-based communication approach that uses a first set of chip sequences and a legacy communication that does not use these sequences.

[0161] Thus, the load modulation receiver 207 can operate in (at least) two different communication modes, one of which uses chip sequence modulation and the other of which typically uses legacy communication approaches.

[0162] The power transmitter 101 further comprises a sequence modulation detector 211 configured to detect whether any valid data symbols are received on the transmission signal by load modulation using a sequence from the first set of chip sequences. The sequence modulation detector 211 is coupled to the load detector 209 and receives information of the power transmission signal load variation therefrom.

[0163] The sequence modulation detector 211 is configured to detect whether a valid data symbol is received depending on a correlation between one, a plurality, typically all, of the first set of chip sequences and the load variation of the power transmission signal. Specifically, if it is detected that the correlation exceeds a given threshold, the corresponding data symbol can be considered to be received.

[0164] It will be appreciated that in many embodiments, the sequence modulation detector 211 and the load modulation receiver 207 can share functionality, and in particular, the sequence modulation detector 211 can be implemented by appropriate elements of the load modulation receiver 207, specifically by functionality of the load modulation receiver 207 that is also used to receive data according to the first communication mode. Indeed, although not required, the detection of the sequence modulation detector 211 can in many embodiments directly correspond to the load modulation receiver 207 attempting to receive data symbols from the power receiver according to the first communication mode. Indeed, in many embodiments, the detection and sequence modulation detector 211 may be inherent and implicit (embedded) functionality of the load modulation receiver 207, and in particular, the implementation of the load modulation receiver 207 may essentially be an implementation of the sequence modulation detector 211 if some data symbols received according to the first communication mode result in a change to the power transmission signal.

[0165] The sequence modulation detector 211 is coupled to an adapter 213 configured to apply a variation to the power transmission signal in response to detection of a validly received data symbol. The adapter 213 can be specifically configured to control the power receiver controller 501 to control the driver 201 to modify the power receiver in response to the received data symbol. Specifically, the received data symbol can be a requested data symbol as described above, and the adapter 213 can be configured to control the power receiver controller 501 and the driver 201 to apply a variation to the power transmission signal as requested by the requested data symbol.

[0166] For example, in some embodiments, the detected data symbol can be a power change request, such as a power control error message, among other things. The power transmitter can adapt the power level of the power transmission signal to reflect the power change request / control error. Thus, the adapter 213 can be part of a power modification circuit, and in particular a power control loop function, in some embodiments.

[0167] The power transmitter further comprises a power transmitter communication selector 215 configured to select between the first and second communication modes and to control the load modulation receiver 207 to use the selected communication mode.

[0168] Then, when in the first communication mode, the load modulation receiver 207 receives load modulated data symbols by correlating load variations of the power transmission signal with sequences of the first set of chip sequences and determining received data symbols according to the correlation.

[0169] However, when in the second communication mode, the load modulation receiver 207 does not correlate with the first set of chip sequences and attempts to receive data according to a different communication mode (which may be specifically a legacy communication mode). In a particular example, the load modulation receiver 207 receives data symbols modulated according to the original communication approach of the Qi standard.

[0170] The selection of the communication mode depends on whether a data symbol is detected by the sequence modulation detector 211. Specifically, the power transmitter communication selector 215 is configured to select the second communication mode as a default. Specifically, when not engaging in power transmission, for example as part of terminating the power transmission, the power transmitter communication selector 215 can set the communication mode to the second communication mode. Thus, the power transmitter can be configured to transmit according to the legacy communication mode. However, if the detection indicates that a detection of a data symbol modulated by a sequence of the first set of chip sequences has been received, the power transmitter communication selector 215 can switch the load modulation receiver 207 to use the first communication mode.

[0171] It will be appreciated that in some embodiments, the power transmitter 101, and specifically the load modulation receiver 207, can be configured to operate simultaneously in the first communication mode and the second communication mode when receiving data from the power receiver.

[0172] Thus, both the power receiver 105 of FIG. 5 and the power transmitter 101 of FIG. 1 are capable of communicating using chip sequence communication according to a first communication mode. Furthermore, the power transmitter 101 and the power receiver 105 can adapt the communication to use a second communication mode. The power receiver 105 can transmit data symbols using a first set of chip sequences, and if an expected change in the power transmission signal is detected following this, the power receiver 105 selects the first communication mode and proceeds with this communication mode. Similarly, the power transmitter 101 is configured to switch to the first communication mode in response to receiving data symbols using the first set of chip sequences, further introducing the expected variation into the power transmission signal.

[0173] In this manner, the power receiver 105 and the power transmitter 101 are configured to interoperate to establish that the first communication mode is a viable communication mode and to switch to using this communication mode.

[0174] Thus, the power receiver 105 and the power transmitter 101 of FIG. 5 and FIG. 2 are each configured to interoperate to adopt a more advanced first communication mode, thereby enabling the advantages provided thereby. Furthermore, the power receiver 105 and the power transmitter 101 are both (typically) capable of communicating separately according to a legacy communication mode. For example, if the power transmitter 101 is used with a legacy power receiver (rather than the power receiver of FIG. 5), the power transmitter is configured to receive data from this power receiver, and thus can support power transmission operations by the legacy power receiver. Similarly, the power receiver 105 can interact with and transmit data to the legacy power transmitter, and proceed to set up a legacy power transmission operation with it.

[0175] Furthermore, the device can automatically adapt and select a suitable communication mode. In a situation where both the power transmitter and the power receiver can communicate using a first communication mode, they can both adapt to select and use this communication. If not, the second communication mode is selected. For example, the power transmitter and the power receiver can be configured to initialize a power transmission operation using the second communication mode, and then switch to the first communication mode if a request data symbol is successfully received resulting in an expected power transmission signal fluctuation. Thus, the device can automatically adapt to use a suitable communication mode, specifically, automatically switch to use a preferred first communication mode when feasible. Furthermore, this can be achieved without the need for any data transmission or communication channel from the power transmitter to the power receiver.

[0176] This approach can therefore overcome the limitation of not having a communication channel from the wireless power transmitter to the wireless power receiver, and further allows the introduction of a chip sequence based communication scheme in a backward compatible manner, based on the power receiver sending a set of data packets / symbols modulated with the chip sequence to the power transmitter and detecting whether the latter exhibits the expected / predetermined behavior.

[0177] The power receiver can, in particular, in many embodiments, mix chip sequence modulated data packets with backward compatible data packets, i.e., can, in particular, mix data symbols transmitted according to the first communication mode with symbols transmitted according to the second communication mode. The data packets can be transmitted to meet all timing and content requirements of the appropriate standard, in particular legacy standards that may be used by some devices of the system. For example, they can meet the requirements of the legacy or original Qi standard. A legacy power transmitter does not detect chip sequence modulated data packets, rather, they are considered as noise on the channel and therefore, they are ignored by the power transmitter. However, this power transmitter receives data messages transmitted using legacy modulation. Thus, the legacy power transmitter reacts as if only data packets using the legacy communication mode were transmitted. In contrast, a chip sequence modulatable power transmitter can also detect data packets modulated with chip sequences and respond to them by modifying the power transmission signal. These changes to the power transmission signal can be detected by the power receiver and can be distinguished from changes that would occur if only legacy data packets were received. In this way, this approach allows the power receiver to determine whether the power transmitter is a chip sequence modulation capable power transmitter or whether the power transmitter is a legacy power transmitter that does not support this.

[0178] This approach can provide a backwards compatible approach that facilitates migration from using legacy communication approaches to using chip sequence based communication in many scenarios without requiring any communication channel from the power transmitter to the power receiver.

[0179] As mentioned above, the request data symbol may in many embodiments include at least one request for a change in the power level of the power transmission signal. In response to receiving this request, the power transmitter 101 may proceed to change the power level as requested. As known to those skilled in the art, this change may be, for example, by changing the power level (current and / or voltage) or frequency of the drive signal (in case of resonant coupling, this also changes the power level of the power transmission signal), thereby increasing the effective electromagnetic field strength / power transfer.

[0180] In many embodiments, the request data symbol is transmitted as part of the power transfer phase. For example, the power receiver can proceed to standardized steps for initializing power transfer using only the second communication mode, i.e., specifically, in many embodiments, the legacy communication mode. Indeed, power transfer can be initiated using the second communication mode, and at some point (typically shortly after initiating power transfer), the power receiver can transmit a request data symbol using the first communication mode. The request data symbol can request a change in power level, and if the power receiver detects these changes, communication can potentially be switched to the first communication mode for all data transfers.

[0181] In many embodiments, the request data symbol may specifically include / have / be configured with one or more power control loop error messages. Thus, the power receiver may transmit power control loop error messages to the power transmitter during the power transfer phase to support the power control loop. The power receiver may, for example, start transmitting these error messages (which may specifically be power up or power down requests) using the second communication mode. However, at some point, the power receiver may switch to transmitting one, several or all of these error messages using the first communication mode. If this still results in the power level of the power transfer signal being controlled and adapted according to the error messages, the power receiver may switch permanently (during the power transfer) to the first communication mode. If not, it may return to the second communication mode for future error control messages.

[0182] As a particular example, the power receiver can proceed to a power transfer phase using conventional / legacy communication (second communication mode) and then start to test whether the power transmitter supports chip sequence-based communication (first communication mode). Figure 7 can show such an example. In Figure 7, white background characters indicate communication according to the second communication mode, and black background characters indicate communication according to the first communication mode.

[0183] In such an example, the wireless power receiver can transmit a conventional control error data packet (CE / 0) containing a zero value and a chip sequence control error data packet (CE / x) containing a non-zero value. The legacy wireless power transmitter only receives the conventional data packet and therefore keeps the transmitted power at a constant level. However, the enhanced power transmitter supporting chip sequence communication can also receive the chip sequence data packet and therefore increases the power level (due to the non-zero value). Thus, the wireless power receiver can distinguish between the legacy wireless power transmitter and the new wireless power transmitter according to the change in the power level of the power transmission signal.

[0184] Thus, in some embodiments, such as the above example, the power receiver can be configured to transmit the request data symbols according to both the first and second communication modes, i.e., the first set of data symbols can be transmitted according to the first communication mode and the second set of data symbols can be transmitted according to the second communication mode. The two data sets can be such that the variation of the power transmission signal when only the data symbols of the second set (transmitted according to the second communication mode) are received is different from the variation that results when both data sets are received. Thus, the power receiver can determine whether the measured variation of the power transmission signal matches the variation resulting from both data sets being received, and if so, switch to the first communication mode. Alternatively, if the variation of the power transmission signal more closely matches that of only the request of the second set of data symbols, the power receiver can switch to using only the second communication mode.

[0185] In many embodiments, the two data sets transmitted according to the first and second communication modes may each require different modifications / variations, and the selector 513 may be configured to select between the different communication modes depending on whether the detected modifications / variations match more closely with the combined modifications / variations resulting from both data sets, or more closely with the modifications / variations resulting from only the second set of data symbols, i.e. more closely with the modifications / variations resulting from only the requested data symbols transmitted using the second communication mode.

[0186] In many embodiments, the first set of request data symbols transmitted according to the first communication mode can request an opposite change to that requested by the second set of request data symbols transmitted according to the second communication mode. For example, the second set of request data symbols can consist of a power down request and the first set of request data symbols can consist of a power up request. The combined effect of these requests is a constant power level, but the effect of only the second set of request data symbols is a continuous decrease in the power level. The power receiver can then simply detect whether the power level remains substantially the same (in which case the first communication mode is selected) or whether it decreases (in which case the second communication mode is selected). After selection, normal power control loop operation can be resumed or initialized and a control error message is transmitted using the selected communication mode.

[0187] In some embodiments, the power receiver may be configured to alternate between sequences of one or more conventional power control error messages and sequences of one or more chip-sequence modulated power control error messages.

[0188] For example, in some embodiments, such as a Qi system, the power receiver may initially control power to a desired level using conventional control error data packets (e.g., Qi CE data packets) containing positive values ​​(requesting an increase in power level), and then alternate with conventional modulated control error data packets containing negative values ​​(requesting power down) and chip-sequence modulated control error data packets containing positive values ​​(requesting power up). If the power level drops, the wireless power transmitter may be considered a legacy power transmitter, and if it remains close to the desired level, the power transmitter may be considered a chip-sequence capable power transmitter.

[0189] It will be appreciated that in many embodiments more complex variations may be used, for example a specific desired power level variation pattern, with detection being made responsive to correlation of this pattern with the detected power level variation.

[0190] In some embodiments, the request data symbol transmitted using the first communication mode can be a request for termination of power transmission, specifically, it can be a request that the power transmission be terminated. If the power transmitter proceeds to terminate the power transmission, the power receiver can assume that the power transmitter is not a legacy power transmitter, and a new power transmission can be initiated based on the communication according to the first communication mode. Thus, the selector 513 can select the first communication mode if an end of the power transmission is detected, and can continue to use the second communication mode otherwise.

[0191] For example, a power receiver can use legacy communication to proceed to the power transmission phase. When it wants to test whether a power transmitter supports chip sequence communication, the power receiver can send chip sequence modulated End Power Transfer (EPT) data packets (mixed with conventional data packets) to the power transmitter. A legacy power transmitter will not detect these EPT data packets and therefore continue power transmission. However, a properly equipped power transmitter will resume power transmission as requested, indicating to the wireless power receiver that it can switch to chip sequence communication when resuming power transmission.

[0192] In some embodiments, the power receiver and the power transmitter can be configured to adapt a communication parameter for the first communication mode, which can specifically be a chip sequence length, and the following description focuses on this example, however, it will be appreciated that in other embodiments, other communication parameters such as data rate, modulation depth, etc. can be adapted.

[0193] In some embodiments, the first communication mode can be initialized using default operating parameters, specifically using a default chip sequence length. After setup, the data transmitter 509 can transmit some request data symbols using different communication parameters, specifically transmitting some request data symbols using different chip sequence lengths. The selector 513 can then detect whether the subsequent variations match the requirements of these request data symbols, or whether they match variations that occur when the request data symbols transmitted using the changed communication parameters have not been received. In the former case, the selector 513 can proceed to change the communication parameters to the new values, and if not, can proceed to use the previous values ​​for the communication parameters.

[0194] As a particular example, such an approach can be used to determine or adapt the modulation depth. When communicating in a first communication mode, the power receiver can start using a different modulation depth. If the power transmitter can still receive data symbols (of a power up or power down request), the power receiver will see the power level change in response to the request, and the power receiver knows it can proceed using the new modulation depth. However, if the power transmitter can no longer reliably receive data symbols (e.g., if there are too many bit errors), the power receiver will not see the power level deviate from the expected variation, and can revert to the previous modulation depth.

[0195] As another example, this approach can be used to change or adapt the chip sequence length.

[0196] For example, when communicating in the first communication mode, the power receiver can be configured to select different chip sequence lengths depending on conditions, e.g., noise, attenuation, etc. It can be configured, for example, to switch between shorter and longer chip sequences.

[0197] For example, if the power receiver when using a shorter chip sequence sees that the power level does not change as expected from the data symbols (power up / power down) transmitted to the power transmitter, the power transmitter can expect not to receive those data symbols reliably. In particular, this may be due to bit errors caused by a signal-to-noise ratio that is too low. If it is known that the power transmitter can use a different sequence length, the power transmitter can switch directly to a longer sequence. However, it may try to switch to a shorter sequence when working with a longer chip sequence. It can do so, for example, using the following approach: a) The power receiver can start with a mix of data symbols transmitted using short and long chip sequences, with data symbols using long chip sequences requiring the power level to remain constant and data symbols using short chip sequences requiring the power level to be increased or decreased. When it is observed that the power levels change predictably (increasing or decreasing), it can continue to use only the short chip sequences. b) The power receiver can stop using the long chip sequence and start using the short chip sequence for the data symbols it uses to request a power level change. If no power level change is observed, it is assumed that the power transmitter is now unable to reliably receive the short chip sequence and therefore the power receiver reverts to using the long sequence. On the other hand, if the power level is observed to change as expected, it continues to use the short chip sequence.

[0198] As another example, when communicating in a first communication mode, the power receiver may start by using a chip sequence having a length that can be received by any power transmitter that supports the first communication mode. However, some power transmitters may also be capable of using longer chip sequences, and therefore the power receiver may attempt to increase the chip sequence length to increase the signal-to-noise ratio and thereby provide more reliable communication. Different approaches that the power receiver may utilize in such cases include the following: a) The power receiver can start with a mix of data symbols transmitted using short and long chip sequences, with data symbols using short chip sequences requiring the power level to remain constant and data symbols using long chip sequences requiring the power level to be increased or decreased. When it is observed that the power levels change predictably (increasing or decreasing), it can continue to use only the long chip sequences. b) The power receiver can stop using the short chip sequence and start using the long chip sequence for the data symbols it uses to request a power level change. If no change in power level is observed, the power transmitter is deemed unable to receive the long chip sequence and reverts to using the short sequence. On the other hand, if the power level is observed to change as expected, it continues to use the long chip sequence.

[0199] In the sequence length adapting example above, the power receiver can assist the power transmitter by informing it that it will start using chip sequences with different lengths, for example, by intermixing data symbols of short and long chip sequences, or by informing the power transmitter whether it will start using chip sequences of other lengths exclusively (for data symbols that require a power level change). As part of this messaging, it can indicate the period of time that it will use chip sequences of other lengths before returning to chip sequences of the current length. This can enable the power transmitter to optimize its communication decoding.

[0200] In either case, the power receiver can assist the power transmitter by informing it that it will begin using short chip sequences and whether it will do so by intermixing short and long chip sequence data symbols or by exclusively using short chip sequences (for data symbols that require a power level change). As part of this warning, the period of time during which the short chip sequences will be used can be indicated. This can enable the power transmitter to optimize its communication decoding.

[0201] In the above example, this approach is applied after power transfer initialization and during the power transfer phase, however, in some embodiments, this approach can be applied before the power transfer phase.

[0202] Specifically, in some embodiments, the data transmitter 509 can be configured to transmit the request data symbol in response to a detection power transmission signal generated by the power transmitter. This detection power transmission signal can be an electromagnetic detection signal generated by the power transmitter before the power transmission phase. The detection power transmission signal can be specifically an electromagnetic detection signal generated to indicate the presence of the power transmitter to the power receiver and to enable the power transmitter to detect the presence of the power receiver.

[0203] The detected power transfer signal is generated by the transmitter coil 103 and can also transfer power from the power transmitter to the power receiver (albeit usually at a very small value). Thus, the detected power transfer signal is also a power transfer signal.

[0204] The detection power transmission signal may in particular be a ping signal. The detection power transmission signal may in particular be a ping signal according to the Qi standard, in particular according to the Qi standard version 1.0 and later.

[0205] Thus, in such an example, the power receiver can transmit a request data symbol on the detect power transmission ping signal, and the power transmitter can respond by applying a corresponding change to the power transmission signal if it is able to receive the request data symbol. If the power receiver detects the corresponding expected variation, the power receiver can proceed to initiate a power transmission phase using the first communication mode, otherwise the power receiver can use the second communication mode.

[0206] As a particular example, the power receiver can transmit a special test chip sequence in response to detecting the detection power transmission signal. This chip sequence can be a chip sequence of the first set of chip sequences. Legacy power transmitters would ignore this chip sequence, but a first communication mode compatible transmitter can detect this chip sequence and proceed to, for example, apply a predetermined variation to the detection power transmission signal. The power receiver can then monitor for this predetermined variation and select between the first and second communication modes depending on whether it is detected.

[0207] As a specific example of a Qi system, the power receiver may transmit a test chip sequence to the power transmitter before responding to a digital ping from the wireless power transmitter with a conventional SIG data packet. A legacy wireless power transmitter would see this as noise and wait for the conventional SIG data packet. It would then proceed with the power transmission setup using the legacy approach. However, a first communication mode capable wireless power transmitter may be configured to provide a signature / variation on the digital Ping signal to indicate that it has detected the test chip sequence. A simple signature / variation may be a change (e.g., a step) in the operating frequency or power level of the digital Ping signal. Once the wireless power receiver detects the signature / variation, it may proceed with the chip sequence data packet (first communication mode), potentially not using conventional data packet communication at all.

[0208] FIG. 8 is an example in which communication in the second communication mode is shown against a white background, and communication in the first communication mode is shown against a black background.

[0209] FIG. 8 shows an example where the power transmitter is a legacy power transmitter (top half) and an example where the power transmitter supports chip sequence communication (bottom half). In the former case, the wireless power transmitter does not detect the test chip sequence and the wireless power receiver proceeds to use the legacy communication method. In the latter case, the wireless power transmitter detects the test chip sequence and introduces a signature variation in the digital Ping signal. The wireless power receiver recognizes this signature variation and proceeds to use only chip sequence-based communication.

[0210] In some embodiments, the second communication mode can be a low bandwidth communication mode. Typically, each data symbol can be modulated by a data symbol shape having a bandwidth (e.g., a 3 dB bandwidth) not exceeding N·1 / T, where N is an integer less than or equal to 4 and T is the data symbol time. In many embodiments, the bandwidth will not exceed 2 / T.

[0211] The chip sequence length for the first set of chip sequences is typically relatively long, typically comprising, for example, 16 or more chips. The bandwidth of the data symbols modulated according to the first communication mode is typically significantly greater than the bandwidth of the data symbols modulated according to the first communication mode.

[0212] In some embodiments, each data symbol may be modulated by a chip sequence having a bandwidth (e.g., a 3 dB bandwidth) of N·1 / T or greater, where N is an integer greater than or equal to 8 and T is the data symbol period (T may also be considered as the chip sequence length). In many embodiments, the bandwidth may be 16 / T or greater.

[0213] In many embodiments, each chip sequence of the first set of chip sequences can include 4, 8, or 16 or more load modulation level changes. In contrast, the second communication mode can include in many embodiments one or less load modulation levels per data symbol, or in some embodiments two load modulation levels. The second communication mode can include up to one load modulation level change for a data symbol.

[0214] In many embodiments, the second communication mode can use, among other things, bi-phase encoding. In many embodiments, each data symbol can be transmitted in the second communication mode using Differential Manchester Encoding (DM). Each data symbol can be linked to a specific DM encoding sequence.

[0215] In some embodiments, in the second communication mode, each data symbol is modulated by a sequence of modulation load values ​​corresponding to a chip sequence in the second set of chip sequences, and the chip sequences in the second set of chip sequences are linked to different data symbol values. However, the chip sequences in the second set of chip sequences are different from the chip sequences in the first set of chip sequences, in particular, the lengths of the chip sequences in the two sets are typically different, and in many cases, the chip sequences in the second set of chip sequences are shorter than the chip sequences in the first set of chip sequences, typically 2, 4, 8 or 16 times shorter, or even shorter.

[0216] For example, in some embodiments, the first set of chip sequences can include chip sequences having a length of 15, 31, 63, or 127 chips or more, and the second set of chip sequences can include two chip sequences having a length of two chips. For example, the second set of chip sequences can include one chip sequence of two identical load modulation values ​​and one chip sequence of two different load modulation values ​​for binary communication. Thus, one binary data symbol can be represented by a channel data symbol without a load change, and one binary data symbol can be represented by a channel data symbol with one load change or transition. For example, Manchester encoding can be used.

[0217] In some embodiments, the first and second sets of chip sequences have the same length, but the two sets still contain different chip sequences. The two sets may typically have chip sequences that have good autocorrelation properties and good cross-correlation properties not only with other sequences in the same set, but also with sequences in other sets.

[0218] Such an approach would allow for upgrades to existing systems to allow, for example, additional chip sequences to be used.

[0219] For example, a wireless power system using binary chip sequence communication may be deployed, where one chip sequence is defined and two binary values ​​are represented by this chip sequence and an inverse chip sequence. Thus, some legacy devices may be configured to communicate using binary chip sequence communication based on two inverse chip sequences. Such an approach may provide adequate operation in many embodiments. However, it will be recognized that at some points it may be advantageous to extend to use additional chip sequences. For example, it may be advantageous to introduce alternative chip sequence pairs that may be selected for binary communication. This may allow, for example, increased interference performance, since more chip sequences are available for selection. It may allow, for example, different power receivers to be placed in close proximity without the communication causing too much mutual interference, since different sequences may be applied to the different power receivers. Such a scenario may arise, for example, in situations where a power transmitter device comprises multiple coils and the ability to simultaneously power multiple power receivers.

[0220] However, in such cases, some power receivers may be modern power receivers configured to communicate using any of the chip sequences, while other power receivers may be legacy power receivers that only support a second set of sequences that includes the legacy chip sequences. Similarly, some power transmitters may be configured to communicate using any chip sequence, while other power transmitters may be legacy power transmitters that are only capable of communicating using the second set of chip sequences.

[0221] In such a case, the described approach can be used to allow for adaptation such as including additional chip sequences of the same length. A new power transmitter can be introduced using two communication modes, one a legacy mode using the second set of sequences and the other a new mode using a different set of sequences different from the second set but having the same length. The legacy power receiver communicates using the second set of sequences, and such a power receiver can be supported by any power transmitter. The new power receiver can, for example, attempt to communicate with the power transmitter using the first set of chip sequences when it first detects the power transmitter, and this communication requests a change in the power transmission signal. If this change is then detected, the power receiver can proceed to use the first set of chip sequences, otherwise the power receiver can switch to using the second set of chip sequences.

[0222] This configuration can therefore bias the power receiver to use the new chip sequence when possible while still supporting legacy devices.

[0223] A modulated load may be a load component of the load of a power transmission signal / drive signal that is due to / dependent on / varying with load modulation.

[0224] It will be appreciated that for clarity, the above description has described embodiments of the invention with reference to different functional circuits, units and processors. However, it will be apparent that any suitable distribution of functionality between different functional circuits, units or processors may be used without departing from the invention. For example, functionality shown to be performed by separate processors or controllers may be performed by the same processor or controller. Thus, references to specific functional units or circuits should not be regarded as indicative of a strict logical or physical structure or organization, but merely as references to suitable means for providing the described functionality.

[0225] The invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of embodiments of the invention may be physically, functionally and logically implemented in any suitable way. Indeed functionality may be implemented in a single unit, in multiple units or as part of other functional units. Thus, the invention may be implemented in a single unit or may be physically and functionally distributed between different units, circuits and processors.

[0226] Although the present invention has been described in relation to several embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the appended claims. Furthermore, although certain features may appear to be described in relation to a particular embodiment, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0227] Furthermore, although individually recited, a plurality of means, elements, circuits or method steps may be implemented by, for example, a single circuit, unit or processor. Moreover, although individual features may be included in different claims, these may in some cases be advantageously combined and the inclusion in different claims does not imply that the combination of features is not feasible and / or advantageous. Moreover, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate. The inclusion of a feature in a dependent claim of an independent claim does not imply a limitation to this independent claim, but rather indicates that the feature is equally applicable to other independent claims, as appropriate. Moreover, the order of features in the claims does not imply a particular order in which the features must be operated, and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Moreover, a reference to the singular does not exclude a plurality. Thus, references to "a", "an", "first", "second", etc. do not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. 1. A power receiver that wirelessly receives power from a power transmitter via an electromagnetic power transmission signal, comprising: an input circuit having a receiver coil configured to extract power from the power transmission signal; a transmitter configured to transmit a set of data symbols to the power transmitter by load modulating the power transmission signal, where each data symbol of a data sequence is modulated by a sequence of modulation load values ​​corresponding to a chip sequence of a first set of chip sequences, where the chip sequences of the first set of chip sequences are linked to different data symbol values, and the set of data symbols includes a request for a given variation of the power transmission signal; a detector configured to monitor the power transmission signal to detect the given variation in the power transmission signal; a selector configured to select a first communication mode as a selected communication mode if the given variation is detected and to select a second communication mode as a selected communication mode if the given variation is not detected, the first communication mode comprising each data symbol being modulated with a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences and the second communication mode not comprising modulating data symbols with a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences; A power receiver, wherein the transmitter is configured to transmit data symbols to the power transmitter during a power transfer phase using the selected communication mode.

2. 2. The power receiver of claim 1, wherein the second communication mode includes each data symbol being modulated with a sequence of modulation load values ​​corresponding to a chip sequence of a second set of chip sequences, the chip sequences of the second set of chip sequences being linked to different data symbol values.

3. each chip sequence of the first set of chip sequences has a first length, and each chip sequence of the second set of chip sequences has a second length different from the first length; 3. The power receiver of claim 2.

4. 4. The power receiver of claim 1, wherein the given variation is a variation in at least one of a power level of the power transmission signal and a frequency of the power transmission signal.

5. 5. The power receiver of claim 1, wherein the set of data symbols includes at least one power level change request for the power transmission signal.

6. 6. A power receiver as claimed in claim 1, wherein the set of data symbols comprises at least one power control loop error message.

7. 7. The power receiver of claim 1, wherein the transmitter is configured to transmit a further set of data symbols using the second communication mode, the further set of data symbols requiring a different variation of the power transmission signal, the different variation being a different variation from the given variation, and the detector is configured to detect the given variation depending on whether a change in the power transmission signal more closely matches the different variation or whether a change in the power transmission signal more closely matches a combination of the different variation and the given variation.

8. 8. A power receiver according to claim 1, wherein the transmitter is configured to transmit the set of data symbols during a power transfer phase.

9. 9. The power receiver of claim 8, wherein the request for the given variation of the power transmission signal is a request for an end of power transmission, and the selector is configured to select the first communication mode for a subsequent power transmission phase when an end of the power transmission signal is detected.

10. 10. A power receiver as claimed in any one of claims 1 to 9, wherein the transmitter is configured to transmit the set of data symbols in response to detection of a detected power transmission signal from the power transmitter, and the given variation is a variation of the detected power transmission signal.

11. 11. The power receiver of claim 1, wherein the transmitter transmits a test set of data symbols at a first value of a communication parameter using the first communication mode, the test set of data symbols including a requirement for a second given variation of the power transmission signal, and the selector is configured to set the communication parameter to the first value if the variation of the power transmission signal matches the second given variation, and to set the communication parameter to another value if the variation does not match.

12. 1. A power transmitter that wirelessly supplies power to a power receiver via an electromagnetic power transmission signal, comprising: an output circuit having a transmitter coil configured to generate the power transfer signal in response to a drive signal applied to the output circuit; A driver configured to generate the drive signal; a load detector for detecting a load fluctuation of the power transmission signal; a detector for detecting validly received data symbols in response to a correlation exceeding a threshold between a chip sequence of a set of chip sequences and a load variation of the power transmission signal, the chip sequence of the set of chip sequences being linked to different data symbol values; an adapter configured to apply a variation to the power transmission signal in response to detecting the validly received data symbol; a selector configured to select a first communication mode as a selected communication mode in response to detection of the validly received data symbol and to select a second communication mode as a selected communication mode if the validly received data symbol is not detected, the first communication mode including each data symbol being received in response to a correlation between the set of chip sequences and a load variation of the power transmission signal, and the second communication mode not including each data symbol being received in response to a correlation between the set of chip sequences and a load variation of the power transmission signal; a load modulation receiver configured to determine load modulation data symbols received from the power transmission signal in accordance with the selected communication mode; A power transmitter comprising:

13. A wireless power transmission system comprising a power receiver according to any one of claims 1 to 11 and a power transmitter according to claim 12.

14. 1. A method of operating a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, comprising: an input circuit having a receiver coil extracting power from the power transmission signal; Transmitting a set of data symbols to the power transmitter by load modulating the power transmission signal, where each data symbol of a data sequence is modulated by a sequence of modulation load values ​​corresponding to a chip sequence of a first set of chip sequences, where chip sequences of the first set of chip sequences are linked to different data symbol values, and where the set of data symbols includes a requirement for a given variation of the power transmission signal; monitoring the power transmission signal to detect the given variation in the power transmission signal; selecting a first communication mode as a selected communication mode if the given variation is detected and selecting a second communication mode as a selected communication mode if the given variation is not detected, the first communication mode comprising each data symbol being modulated with a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences and the second communication mode not comprising each data symbol being modulated with a sequence of modulation load values ​​corresponding to a chip sequence of the first set of chip sequences; and transmitting data symbols to the power transmitter during a power transfer phase using the selected communication mode.

15. 1. A method of operating a power transmitter that wirelessly provides power to a power receiver via an electromagnetic power transmission signal, comprising: a transmitter coil generating the power transfer signal in response to a drive signal applied to the transmitter coil; generating the drive signal; detecting a load change on the power transmission signal; detecting validly received data symbols in response to a correlation exceeding a threshold between a chip sequence of a first set of chip sequences and a load variation of the power transmission signal, wherein the chip sequences of the first set of chip sequences are linked to different data symbol values; applying a variation to the power transmission signal in response to detecting the validly received data symbol; selecting a first communication mode as a selected communication mode in response to detection of the validly received data symbol, and selecting a second communication mode as a selected communication mode if the validly received data symbol is not detected, the first communication mode including each data symbol being received in response to a correlation between the set of chip sequences and a load variation of the power transmission signal, and the second communication mode not including each data symbol being received in response to a correlation between the set of chip sequences and a load variation of the power transmission signal; and determining load modulated data symbols received from the power transmission signal in accordance with the selected communication mode.

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