A power transfer apparatus and method therefor

Abstract

is arranged to receive first data from the complementary power transfer apparatus. The first data is modulated onto the power transfer signal in accordance with a first modulation scheme where each data symbol is represented by a sequence of time intervals each having a constant modulation level dependent on a data symbol value for the data symbol. A transmitter

Description

[Technical Field]

[0001] This invention relates to a wireless power transfer device and method thereof, and more specifically, but not exclusively, to a wireless power transfer device for Wireless Power Consortium (WPC) wireless power transfer systems (such as Qi-type power transfer systems). [Previous Technology]

[0002] Most electrical products today require dedicated electrical contacts to be powered from an external power source. However, this is often impractical and requires the user to physically insert a connector or otherwise establish physical electrical contact. Power requirements also vary significantly, and most devices currently have their own dedicated power supplies, resulting in a large number of different power supplies for the average user, each dedicated to a specific device. While the use of an internal battery pack can avoid the need for a wired connection to a power source during use, this only provides a partial solution because the battery pack needs to be recharged (or replaced). The use of a battery pack can also substantially increase the weight and potential cost and size of the device.

[0003] To provide a significantly improved user experience, it has been suggested to use a wireless power supply in which power is inductively transferred from a transmitter inductor in a power transmitter device to a receiver coil in an individual device.

[0004] The concept of power transmission via magnetic induction is well-known 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] This configuration allows wireless power transfer to the device without requiring any wires or physical electrical connections. In practice, it can simply allow the device to be placed adjacent to or on top of the transmitter coil for recharging or external power supply. For example, the power transmitter device can be configured with a horizontal surface on which the device can be easily placed for power supply.

[0006] Furthermore, such wireless power transfer configurations can be advantageously designed to allow power transmitter devices to be used with a variety of power receiver devices. Specifically, a wireless power transfer method known as the Qi specification has been defined and is currently under further development. This method allows Qi-compliant power transmitter devices to be used with Qi-compliant power receiver devices, without requiring them to be from the same manufacturer or to be specifically designed for each other. The Qi standard further includes features that allow adaptation to the operation of a particular power receiver device (e.g., depending on specific power consumption).

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

[0008] Further developments aim to introduce a range of new applications and features. For example, the Wireless Power Consortium is developing a standard based on the extended Qi principle for application to a range of kitchen applications and appliances, including heaters, kettles, blenders, and frying pans. These developments particularly support higher power levels for power transfer and are known as the Cordless Kitchen standard.

[0009] The Qi standard supports communication from a power receiver to a power transmitter, enabling the power receiver to provide information that allows the power transmitter to adapt to a specific power receiver. The current standard defines a unidirectional communication link from the power receiver to the power transmitter, where the power receiver communicates by load modulation of a power transfer signal that performs the transfer of power. Specifically, the load of the power receiver's power transfer signal is changed to provide modulation of the power signal. The resulting changes in electrical characteristics (e.g., changes in current draw) can be detected and decoded (demodulated) by the power transmitter.

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

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

[0012] Initially, Qi used only a one-way communication link, but a two-way communication link has been introduced to allow for more advanced control and flexibility in power transfer operations. Communication from the power transmitter to the power receiver can be achieved, for example, by modulating the power transfer signal using amplitude, frequency, or phase modulation.

[0013] Communication provision in a wireless power transfer system includes power transfer parameter negotiation, wireless power transfer control, power transmitter and / or power receiver authentication, power transmitter firmware updates, or other auxiliary data transmission. Communication performance is important for the operation of the power transfer system.

[0014] For example, for the safety of the power receiver, it is important to provide feedback control messages to the power transmitter in precise timing to ensure the stability of the control loop. This communication link is simplex from the power receiver to the power transmitter and is typically implemented as load modulation of the power transfer signal performed on the power receiver side.

[0015] Other communications require a communication channel from the wireless power transmitter to the wireless power receiver (e.g., for credential transmission during authentication). Typically, this channel is implemented as a frequency modulation of a power transfer signal.

[0016] In many systems, power transfer signals are used to communicate in both directions, and therefore power transfer signals are used to support two communication links.

[0017] To provide effective communication, in such cases, power transfer systems generally utilize time-division multiplexing, where communication directions / channels are multiplexed and divided by time. Specifically, a repeating time frame is generally divided into two (or more) time intervals, where only one communication channel is enabled in each time interval.

[0018] In many cases, such half-duplex communication can provide efficient and / or reliable communication. However, this method also has some drawbacks, including:

[0019] The bandwidth of the two channels has been reduced.

[0020] Response time and communication delays may increase. Because communication must be performed in a dedicated time slot defined by the half-duplex protocol, it is not possible to initiate communication at any desired time.

[0021] The increased burden may stem from the fractionalization of larger packets. Since power transfer control must have precise timing, the maximum effective load to be transferred can be constrained by the time between two consecutive control messages.

[0022] Error correction may occur, for example, due to insufficient large packets. The receiving side may not be able to indicate whether large packets are erroneous before communication handover.

[0023] Therefore, improved power transfer methods will be advantageous, and specifically, increased flexibility, reduced costs, reduced complexity, improved communication performance, reduced communication latency, increased data rates, reliable communication, more reliable operation, improved error detection, and / or improved performance will be advantageous. [Summary of the Invention]

[0024] Therefore, the present invention seeks to mitigate, reduce or eliminate one or more of the disadvantages mentioned above, either alone or in any combination.

[0025] According to one aspect of the present invention, a power transfer device is provided for wireless power transfer from a power transmitter to a power receiver, the power transfer device being one of the power transmitter and the power receiver, the power transfer device comprising: a power transfer coil configured to exchange power with a complementary power transfer coil of a complementary power transfer device via a power transfer signal, the complementary power transfer device being the other of the power transmitter and the power receiver; and a receiver configured to receive first data from the complementary power transfer device, the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data... The data symbol is represented by a sequence of time intervals, each of which has a constant modulation level depending on the value of one of the data symbols, the time interval sequence being synchronized to the power transfer signal; a transmitter configured to transmit second data to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme, the duration of a symbol of the data symbol in the second modulation scheme being a divisor of the duration of at least one of the time intervals in the time interval sequence; and a synchronizer configured to synchronize the transmitter to transmit the second data aligned with the first data by synchronizing the transmission of the second data to the power transfer signal.

[0026] In many wireless power transfer systems, the present invention can allow for improved performance and / or operation. Improved communication performance can be achieved in many applications and scenarios. In many applications, reduced communication latency, increased data rates, and / or more flexible communication can be achieved in one or both communication directions. In many cases, such improvements can be achieved while maintaining acceptable communication reliability, and specifically, such operation can be allowed while maintaining an acceptable error rate.

[0027] This method can reduce the impact of interference between communications in different directions, while allowing these communications to use power transfer signals as communication carriers simultaneously.

[0028] In many embodiments and contexts, the method can reduce delays in power control operations, authentication, negotiation, etc., for example by allowing faster message transmission, thereby enabling improved overall power transfer operations.

[0029] Operation can be performed during a power transfer phase, and specifically, the first data and the second data communicate simultaneously. Specifically, the power transfer phase may be a phase in which a power transfer signal is generated to transfer power from the power transmitter to the power receiver. The power transfer phase may be a phase in which a power control error message is transmitted from the power receiver to the power transmitter. During the power transfer phase, the power transmitter and the power receiver may implement a power control loop for transferring power. The power control loop may adjust a level of the power transfer signal in response to the power control error message.

[0030] According to the first modulation scheme, each data symbol can be represented by a constant modulation level mode, wherein different data symbols have different modes. In some embodiments, according to the second modulation scheme, each data symbol can be represented by a constant modulation level mode, wherein different data symbols have different modes.

[0031] A constant modulation level can be a constant frequency for frequency modulation, a constant phase for phase modulation, a constant amplitude for amplitude modulation, a constant load for load modulation, etc. The time interval sequence may include two or more time intervals and is used for at least one data symbol, and typically, for all data symbols, the modulation level of at least two of these time intervals in the time interval sequence may be different. A time interval having a constant modulation level may mean that a parameter of the power transfer signal depends on whether the data symbol is constant / unchanging but varies / modulates during the time interval.

[0032] Modulation schemes can include, for example, frequency modulation schemes, phase modulation schemes, amplitude modulation schemes, load modulation schemes, etc.

[0033] The duration of the data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence, which is equivalent to the duration of at least one time interval of the time interval sequence being an integer multiple of the duration of the data symbol in the second modulation scheme. The divisor / multiple may be a multiple of one. The duration of the data symbol in the second modulation scheme may be equal to the duration of at least one time interval of the time interval sequence.

[0034] The transmitter can be configured to transmit second data to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme having a symbol duration, such that a duration of the time interval of the time interval sequence is an integer multiple of the symbol duration;

[0035] The transmitter may be configured to transmit second data to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme, wherein the duration of such time intervals is an integer multiple of the duration of one of the data symbols of the second modulation scheme.

[0036] The synchronizer can be configured to synchronize the transmitter to transmit the second data aligned with the time interval sequence of the first data by synchronizing the transmission of the second data to the power transfer signal.

[0037] According to an optional feature of the invention, the duration of the time interval is at least twice the duration of the data symbol of the second modulation scheme.

[0038] This can provide improved performance and operation in many scenarios and applications. In many scenarios, it allows for low-complexity operation and facilitates and / or improves communication. In many embodiments, the method can facilitate asymmetric communication, which is particularly advantageous in many wireless power transfer systems.

[0039] According to an optional feature of the invention, the duration of the time interval is at least eight times the duration of the data symbol of the second modulation scheme.

[0040] This can provide improved performance and operation in many scenarios and applications. In many scenarios, it allows for low-complexity operation and facilitates and / or improves communication. In many embodiments, the method can facilitate asymmetric communication, which is particularly advantageous in many wireless power transfer systems.

[0041] According to one optional feature of the present invention, the first modulation scheme employs biphase modulation.

[0042] This allows for operation that is particularly advantageous and / or facilitates operation in many applications. Specifically, it facilitates methods for reducing interference between communications in opposite directions in many applications. Each time interval of the time interval sequence may correspond to one interval of the biphase modulation. Each time interval sequence may contain two intervals.

[0043] In some embodiments, the first modulation scheme may employ Manchester code.

[0044] According to an optional feature of the invention, an average modulation level of the transmission of the second data during a symbol duration of the transmission of the first data is independent of the data value of the second data.

[0045] This can provide improved communication and wireless power transfer operations in many applications and scenarios. Specifically, it allows for improved communication by reducing interference between communications in two directions. In many scenarios, this method can reduce interference from the transmission of the second data to the reception of the first data.

[0046] According to an optional feature of the invention, the transmitter is configured to transmit a plurality of dummy symbols to align the data size of the second data to the symbol duration of the first data.

[0047] This can provide improved performance in many embodiments and applications.

[0048] In many embodiments, the transmitter is configured to transmit several dummy symbols to align one of the second data packets (size) to the time intervals.

[0049] According to an optional feature of the invention, the transmitter is configured to continuously transmit second data unless the first data meets a non-response criterion.

[0050] This can provide improved communication in many embodiments and allow higher throughput in many applications, where data is continuously transmitted and action is taken only in the event of an error or undesirable condition.

[0051] The non-response criteria may include, for example, considering that the expected response message was not received.

[0052] According to an optional feature of the invention, the transmitter is configured to retransmit second data in response to the first data meeting the non-response criterion.

[0053] According to one optional feature of the present invention, the power transfer device is the power receiver, the first modulation scheme uses frequency modulation, and the second modulation scheme uses load modulation.

[0054] In many scenarios, this may allow for particularly advantageous operation and / or performance and / or implementation.

[0055] According to one optional feature of the present invention, the power transfer device is the power transmitter, the first modulation scheme uses load modulation, and the second modulation scheme uses frequency modulation.

[0056] In many scenarios, this may allow for particularly advantageous operation and / or performance and / or implementation.

[0057] According to an optional feature of the invention, the synchronizer is configured to synchronize the transmitter in response to an amplitude change in one of the power transfer signals.

[0058] According to an optional feature of the invention, the synchronizer is configured to synchronize the transmitter in response to the cycle of the power transfer signal.

[0059] According to another aspect of the present invention, a power transfer system comprising a power receiver and a power transmitter is provided for performing a wireless power transfer from the power receiver to the power receiver, the power transmitter comprising: a first power transfer coil configured to transfer power to a second power transfer coil of the power receiver via a power transfer signal; a first receiver configured to receive first data from the power receiver, the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, each of the time intervals having a constant modulation level depending on the value of one of the data symbols, the time interval sequence being synchronized to the power transfer signal; and a first transmitter configured to transmit second data to the power receiver by modulating the power transfer signal according to a second modulation scheme. The power receiver includes: a power receiver wherein the duration of a symbol of the data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence; and a first synchronizer configured to synchronize the transmitter to transmit the second data aligned with the first data by synchronizing the transmission of the second data to the power transfer signal; and the power receiver comprising: a second power transfer coil configured to receive power from the first power transfer coil of the power transmitter via the power transfer signal; a second transmitter configured to transmit the first data to the power transmitter according to the second modulation scheme; a second receiver configured to receive the second data from the power transmitter according to the second modulation scheme; and a second synchronizer configured to synchronize the second transmitter to transmit the first data with time intervals of the time interval sequence aligned with the power transfer signal.

[0060] According to another aspect of the present invention, a method of operating a power transfer device for wireless power transfer from a power transmitter to a power receiver is provided, the power transfer device being one of the power transmitter and the power receiver, the power transfer device comprising: a power transfer coil configured to exchange power with a complementary power transfer coil of a complementary power transfer device via a power transfer signal, the complementary power transfer device being the other of the power transmitter and the power receiver; the method comprising: receiving first data from the complementary power transfer device, the first data being modulated according to a first modulation scheme. On the power transfer signal, each data symbol is represented by a sequence of time intervals, each time interval having a constant modulation level depending on the value of one of the data symbols, the time interval sequence being synchronized to the power transfer signal; second data is transmitted to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme, the duration of a symbol of the data symbol in the second modulation scheme being a divisor of the duration of at least one time interval of the time interval sequence; and the transmission of the second data to be aligned with the first data is synchronized by synchronizing the transmission of the second data to the power transfer signal.

[0061] According to another aspect of the present invention, a method of operating a power transfer system comprising a power receiver and a power transmitter is provided for performing a wireless power transfer from the power receiver, the power transmitter comprising a first power transfer coil configured to transfer power to a second power transfer coil of the power receiver via a power transfer signal, and the power receiver comprising the second power transfer coil configured to receive power from the first power transfer coil of the power transmitter via the power transfer signal; the method comprising the power transmitter performing the following steps: receiving first data from the power receiver, the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, the respective time intervals being... The system has a constant modulation level depending on the value of one of the data symbols, the time interval sequence is synchronized to the power transfer signal; second data is transmitted to the power receiver by modulating the power transfer signal according to a second modulation scheme, the duration of a symbol of the data symbol in the second modulation scheme being a divisor of the duration of at least one time interval of the time interval sequence; and the transmission of the second data to be aligned with the first data is synchronized by synchronizing the transmission of the second data to the power transfer signal; and the power receiver performs the following steps: transmitting the first data to the power transmitter according to the second modulation scheme; receiving the second data from the power transmitter according to the second modulation scheme; and synchronizing the transmission of the first data to be aligned with the time intervals of the time interval sequence by synchronizing the transmission of the second data to the power transfer signal.

[0062] These and other aspects, features and advantages of the present invention will be explained and will be apparent from the following description of one or more embodiments.

Implementation Method

[0064] The following description focuses on embodiments of the invention applicable to wireless power transfer systems using power transfer methods (such as those known from the Qi or Ki specifications). However, it will be understood that the invention is not limited to this application, but can be applied to many other wireless power transfer systems.

[0065] FIG1 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, which includes (or is coupled to) a transmitter coil / inductor 103. The system further includes a power receiver 105, which includes (or is coupled to) a receiver coil / inductor 107.

[0066] The system provides wireless inductive power transfer from power transmitter 101 to power receiver 105. Specifically, power transmitter 101 generates a wireless inductive power transfer signal (also referred to as a power transfer signal or inductive power transfer signal), which is propagated as a magnetic flux by transmitter coil or inductor 103. The power transfer signal can generally have a frequency between about 20 kHz and about 500 kHz, and is generally in the range of 95 kHz to 205 kHz for Qi-compatible systems. For high-power applications, such as Ki specifications for high-power kitchen applications, the frequency can be, for example, generally in the range of 20 kHz to 80 kHz. Transmitter coil 103 and receiver coil 107 are loosely coupled, and therefore receiver coil 107 picks up (at least part) of the power transfer signal from power transmitter 101. Thus, power is transferred from power transmitter 101 to power receiver 105 via wireless inductive coupling from transmitter coil 103 to receiver coil 107. The term "electrical transfer signal" is primarily used to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the receiver coil 107. However, it should be understood that, by equivalence, it can also be regarded as and used as a reference for the electrical signal provided to the transmitter coil 103 or picked up by the receiver coil 107.

[0067] In this example, the power receiver 105 is specifically a power receiver that receives power via a receiver coil 107. However, in other embodiments, the power receiver 105 may include a metallic element, such as a metallic heating element, in which case the power transfer signal induces eddy currents, resulting in direct heating of the element.

[0068] The system is configured to transfer substantial power levels, and specifically, the power transmitter in many embodiments can support power levels exceeding 500 mW, 1 W, 5 W, 50 W, 100 W, or 500 W. For example, for Qi-compliant applications, power transfer can generally be in the 1 to 5 W power range for low-power applications, and exceed 100 W and up to 2000 W for high-power applications, such as those supported by the Ki specification developed by the Wireless Power Consortium.

[0069] In the following description, the operation of the power transmitter 101 and the power receiver 105 will be specifically described with reference to embodiments according to the Qi specification (except for modifications and enhancements to the description herein (or therein)).

[0070] The system in Figure 1 utilizes bidirectional communication to support power transfer operations. Bidirectional communication is used to configure, establish, and control power transfer, and may include the exchange of a range of control data. Specifically, the communication channel between the wireless power receiver and the wireless power transmitter is considered critical to establishing a feedback loop from the wireless power receiver to the wireless power transmitter, which is extremely important for power system stability.

[0071] In many systems, communication between a power transmitter and a power receiver can advantageously be achieved using a power transfer signal as a communication carrier. The communication transmitter of the power transmitter or power receiver can modulate the power transfer signal in response to data transmission, and the complementary power receiver can demodulate the power transfer signal to retrieve data. Communication using a power transfer signal is also known as intra-band communication.

[0072] Many systems (such as Qi, in particular) use power transfer signals for two-way communication, and therefore use the same communication carrier to transmit data in opposite directions. Thus, a particular case in such systems is that a single power transfer signal for transferring power between devices is also used as a communication carrier for multiple communication links in opposite directions.

[0073] To support such multiple communications, systems such as Qi use a time-division multiplexing approach, in which communication in two directions is performed at different time intervals, so that communication is performed in only one direction at a time. Specifically, a repeating time frame can be used for power transfer signals, wherein the time frame includes different time intervals for communication from the power transmitter to the power receiver (hereinafter also referred to as the forward direction or forward communication) and for communication from the power receiver to the power transmitter (hereinafter also referred to as the reverse direction or reverse communication).

[0074] Such methods can achieve independence between communications in different directions. This is particularly difficult to achieve in wireless power transfer systems using power transfer signals as carriers for multiple communications. Specifically, using different modulation schemes and techniques is generally insufficient to separate communications.

[0075] Specifically, Qi uses frequency modulation for forward communication and load modulation for reverse communication. Load modulation can be considered an example of amplitude modulation where the receiver detects changes in the amplitude of the power transfer signal caused by load modulation / change. However, the amplitude of the power transfer signal generally depends on its frequency, and in many systems, frequency changes are used to adjust the power level of the power transfer signal. Therefore, frequency modulation directly causes amplitude changes. Furthermore, frequency modulation changes are generally detected by a frequency demodulator, which can also have some sensitivity to (especially rapid) amplitude changes of the carrier wave (i.e., the power transfer signal). Therefore, crosstalk is often particularly difficult to resolve in wireless power transfer systems, leading most such systems to use time-division multiplexing methods to isolate communication with each other.

[0076] However, such methods also have drawbacks. These methods substantially reduce available communication capacity, and specifically, if only one communication is performed, the effective data rate is often substantially reduced compared to the maximum available in both directions. Furthermore, substantial communication delays can arise from the inability to perform communication until the time interval allocated to the communication channel. This also reduces communication reliability and performance. For example, shorter data symbols (and therefore lower symbol energy) may be required, or less error correction may be needed. This can directly lead to a lower data rate.

[0077] Reduced communication performance will affect the overall performance of the wireless power transfer system. Reduced communication capacity may reduce potential functions (e.g., there may not be enough time to perform the communication required for some functions) and / or reduce the performance of some implemented functions (such as reducing the response time or accuracy of power control loops).

[0078] In fact, in order to provide effective control over power transfer, a high communication data rate between the power transmitter and the power receiver is also desirable.

[0079] The following describes a method that allows for improved performance in many situations and for many applications. This method can specifically allow, facilitate, or improve simultaneous communication in two directions. This method generally allows for reduced interference between communications, such that the detection / demodulation of communication in one direction is less affected by communication in the other direction. In some cases, the detection / demodulation of communication in the other direction can also be less sensitive, and thus in many embodiments, overall cross-interference in both directions can be reduced, thereby allowing or improving simultaneous communication in two opposite directions.

[0080] In this method, the first modulation scheme (which may be a forward modulation scheme or a reverse modulation scheme) is a modulation scheme in which each data symbol value is represented by a sequence of time intervals and each time interval has a constant modulation level depending on the data symbol value. In the first modulation scheme, each data symbol may be represented by a sequential modulation level pattern, wherein different data symbols have different patterns. The modulation level of each time interval may be selected from a set of modulation levels. In some applications, the patterns of all possible data symbols may contain different modulation levels. In other applications, for all time intervals, one or more data symbols may contain different modulation levels, and potentially, one or more data symbols may have the same constant modulation level. In some applications, all time intervals of at least one data symbol may have different modulation levels. In some applications, the time intervals of each data symbol of all data symbols may have different modulation levels.

[0081] The modulation level can be a value of a parameter that is modulated / changed depending on the data symbol. For example, for FM, the modulation level can be frequency modulation; for LM, the modulation level can be the load of the power transfer signal; for PM (phase modulation), the modulation level can be the phase of the power transfer signal; and for AM (amplitude modulation), the modulation level can be the amplitude of the power transfer signal.

[0082] Therefore, a data symbol can be represented by a sequence of time intervals. For each time interval, the modulation level is set to a constant value, which depends on the data symbol. In many applications, the modulation levels for each time interval of at least two of the possible data symbols may be different.

[0083] The method will be described in further detail with reference to FIG2, which shows the components of the power transmitter 101, and FIG3 shows the components of the power receiver 105 of FIG1 in more detail.

[0084] Figure 2 illustrates in more detail an example of the components of the power transmitter 101 of Figure 1. The transmitter coil 103 is coupled to a driver 201, which generates a drive signal for the transmitter coil 103. The driver 201 generates current and voltage signals fed to the transmitter inductor 103. The driver 201 is generally a drive circuit in the form of a inverter that generates an AC signal from a DC voltage. The output of the driver 201 is generally a switched bridge that generates the drive signal by appropriate switching of the switches of the switched bridge.

[0085] The driver 201 is coupled to a power transmitter controller 203, which is configured to control the operation of the power transmitter 101. The power transmitter controller 203 may be configured to control the operation of the power transmitter 101 to perform desired and required functions associated with the system's power transfer protocol, and in this example, may be specifically configured to control the power transmitter 101 to operate according to the Qi specification. For example, the power transmitter controller 203 may include functions for detecting power receivers, initiating power transfer, supporting power transfer, and terminating power transfer.

[0086] In an example, the power transmitter 101 further includes a first transmitter 205 configured to use a power transfer signal as a communication carrier to transmit data to the power receiver 105. The first transmitter 205 may be configured to use a modulation scheme to modulate the data onto the power transfer signal. For example, the first transmitter 205 may control a driver to change the frequency, amplitude, and / or phase of the drive signal in response to the data to be transmitted. Thus, the power transmitter controller 203 may use, for example, frequency, amplitude, and / or phase modulation to transmit data to the power receiver 105. The first transmitter 205 may be specifically configured to convey a message to the power receiver by frequency modulation of the power transfer signal according to the Qi specification. Thus, the first transmitter 205 is configured to use a communication link in the positive frequency band to transmit data to the power receiver 105.

[0087] The power transmitter 101 further includes a first receiver 207 configured to receive data from the power receiver 105. The first receiver 207 can generally be configured to receive messages from the power receiver 105 via a load modulation power transfer signal, as known to those skilled in the art, for example, from the Qi power transfer specification.

[0088] As illustrated in the exemplary diagram of Figure 3, the receiver coil 107 of the power receiver 105 is coupled to a power receiver controller 301, which couples the receiver coil 107 to a load 303. The power receiver controller 301 includes a power control path that converts the power extracted by the receiver coil 107 into a suitable supply for the load 303. Furthermore, the power receiver controller 301 may include various power receiver controller functions required to perform power transfer, and specifically includes functions required to perform power transfer according to the Qi specification.

[0089] The power receiver 105 further includes a second transmitter 305 configured to use a power transfer signal as a carrier to communicate with the first transmitter 205. Thus, the first receiver 207 and the second transmitter 305 establish an intra-band communication link.

[0090] In a specific example, the second transmitter 305 is configured to modulate the power transfer signal by load modulation, and the first receiver 207 is configured to decode the load modulation to recover the transmitted data. It should be understood that techniques and methods for load modulation (and demodulation) are known to those skilled in the art and are not further described herein for the sake of brevity.

[0091] The power receiver 105 further includes a second receiver 307 configured to receive data transmitted from the first transmitter 205, and therefore configured to demodulate the modulation of the power transfer signal performed by the first transmitter 205, in order to demodulate the data transmitted by the first transmitter 205. In a specific example, the second receiver 307 includes an FM demodulator configured to demodulate the FM modulation of the first transmitter 205.

[0092] Therefore, the power receiver and power transmitter establish two communication channels in the forward and reverse directions, respectively, thereby allowing bidirectional communication. Communication in the forward direction is performed according to one modulation scheme (hereinafter referred to as the forward modulation scheme), and communication in the reverse direction is performed according to another modulation scheme (hereinafter referred to as the reverse modulation scheme). The modulation schemes in the two directions are generally selected to be different; that is, the forward and reverse modulation schemes are generally different and use different types of modulation. In many embodiments, the two modulation schemes may employ different modulation formats, and specifically, different selections from the group of frequency modulation, load modulation, phase modulation, and amplitude modulation may be used (however, other modulation formats may be used in some applications). In a specific example, the forward modulation scheme uses frequency modulation (FM), while the reverse modulation scheme uses load modulation (LM).

[0093] Two communication links could potentially cause cross-interference because they both use power transfer signals as communication carriers. However, the system employs simultaneous communication in both directions, rather than time-division multiplexing between communications. This simultaneous communication is supported by interference mitigation methods, as will be explained below.

[0094] In many embodiments, the set of modulation levels may include only two modulation levels; that is, the modulation of the power transfer signal may be set to one of two different modulation levels for each time interval. In such instances, the data symbols may therefore be represented by a sequence and pattern of binary modulation levels. Furthermore, in many embodiments, the data symbols may be binary symbols, and therefore the modulation according to the first modulation scheme may be selected between two different sequences / patterns of modulation levels.

[0095] As a specific example, the first modulation scheme may employ biphase or Manchester code. In this case, each data symbol may be transmitted as one of two sequences, each of which is divided into two time intervals. Specifically, for one bit value, the sequence may contain two time intervals (also called half-bits) with the same constant modulation level, and for the other bit value, the sequence may contain two time intervals (half-bits) with different constant modulation levels. Thus, in this case, one bit value is represented by no change in the modulation parameter value, and the other bit value is represented by a change in the modulation parameter value. Figure 4 illustrates such an example. As another example, in some embodiments, the modulation levels may be selected differently in the two time intervals.

[0096] Therefore, the first modulation scheme uses a method in which the duration of a data symbol is divided into time intervals, wherein the modulation level is constant for each time interval, and wherein the modulation level is different for at least one or more time intervals for different data symbols. In many applications, the time intervals have a constant duration, that is, all time intervals may have the same duration.

[0097] The second modulation scheme employs a modulation scheme in which the symbol duration of the data symbols in the second modulation scheme is a divisor of the duration of at least one time interval (and generally all time intervals) of the time interval sequence. Therefore, the duration of one of these time intervals (and generally, all of these time intervals) is a multiple of the duration of the data symbols in the second modulation scheme. The divisor / multiple can be any integer (including one), that is, specifically, the symbol duration of the second modulation scheme can be the same as the duration of a plurality of time intervals.

[0098] Therefore, during a single time interval of transmitting one constant modulation level according to the first modulation scheme, one or more full symbols can be transmitted according to the second modulation scheme.

[0099] Figure 5 illustrates an example of the method. Figure 5 illustrates the transmission of a single data symbol according to a first modulation scheme, wherein this is transmitted by a sequence of k time intervals TI, wherein the modulation level of each time interval is constant (e.g., constant frequency or load). For each time interval, n data symbols are transmitted in the other direction using a second modulation scheme, wherein n is an integer greater than or equal to one.

[0100] The symbol rate of the second modulation scheme is higher than that of the first modulation scheme. For each time interval, the number of data symbols transmitted under the second modulation scheme is equal to one (that is, the symbol duration of the second modulation scheme is equal to the duration of the time interval), and the data rate of the second modulation scheme will be up to a multiple of the data rate of the first modulation scheme corresponding to the number of time intervals in the sequence of data symbols represented according to the first modulation scheme.

[0101] In the system, communication in both directions (i.e., according to the two modulation schemes) is further synchronized, such that data transmitted according to the second modulation scheme is synchronized with data transmitted according to the first modulation scheme, and specifically, the duration of data symbols can be aligned with the time interval of the sequence. Therefore, specifically, the start and / or end time of the symbols transmitted according to the modulation scheme can be aligned with the start and / or end time of the time interval of the data transmitted according to the first modulation scheme.

[0102] Furthermore, the transmission can be aligned with the power transfer signal. For example, the start / end time of the data symbols and / or time intervals can be aligned with the zero crossover, peak, transition, or specific point / phase of the power transfer signal cycle. Therefore, transmissions in both directions can be aligned with and synchronized with the power transfer signal. Moreover, the alignment and synchronization of transmissions in both directions, and specifically, the alignment between the data symbols of the second modulation scheme and the time intervals of the first modulation scheme, can be achieved by synchronizing the two transmissions with the power transfer signal. This method provides accurate and low-complexity synchronization.

[0103] Specifically, in many embodiments, communication enables the power receiver and power transmitter to communicate synchronously with and thus with the power signal. Full-duplex communication with variable data / Bauer rate can be applied, and the system can align bit communication (including multi-bit sequences) in one communication channel with a stable and constant modulation level in a complementary channel. This method facilitates and typically enables or allows effective full-duplex communication.

[0104] In this method, the slower rate transmission (according to the first modulation scheme) can be synchronized such that the modulation state remains constant during the transmission of one or more entire data symbols transmitted at a faster rate (according to the second modulation scheme). In many embodiments, a transmitter operating according to the first modulation scheme can transmit several bits or groups of bits at a constant modulation level of a transmitter transmitting according to the second modulation scheme.

[0105] Synchronized and aligned communication can substantially reduce cross-interference and, in many embodiments, can allow and improve simultaneous communication in opposite directions using power transfer signals as a common communication carrier. Specifically, it is possible to achieve transmission according to a second modulation scheme while providing interference-free or reduced interference for transmission according to a first modulation scheme. In many embodiments, specifically, improved communication can be achieved where it is feasible to receive transmissions according to the second modulation scheme with improved reliability. For example, a reduced error rate for a given symbol energy can typically be achieved by reducing interference.

[0106] This method allows for improved communication, and specifically, in many embodiments, enables full-duplex simultaneous communication in both directions between the power transmitter and the power receiver. Specifically, the performance of higher data rate communications can typically be substantially improved by reducing interference. This is particularly attractive in many cases because higher data rates tend to be more sensitive to interference (as they typically have reduced symbol energy). This method is particularly suitable for situations where communication requirements are typically asymmetric wireless power transfer. For example, in many embodiments, a substantially higher data rate in one direction can be provided than in the other, while allowing higher data rate communication to still achieve low error rates and reliable performance.

[0107] Hereinafter, a specific example will be described with respect to a method in which a high data rate communication system is transmitted from a power transmitter to a power receiver, namely, wherein a first transmitter 205 transmits data according to a second modulation scheme, and a second transmitter transmits data according to the first modulation scheme. In the example, the second modulation scheme is an FM modulation scheme, and therefore the power transmitter / first transmitter 205 is configured to FM modulate the power transfer signal.

[0108] The first transmitter 205 may be specifically configured to transmit data symbols, such as binary data symbols using Frequency Shift Keying (FSK), wherein each data symbol value (a bit for a binary modulation scheme) is represented by a power transfer signal set to a specific frequency, which is unique to the data symbol. The first transmitter 205 may be configured to transmit FSK symbols at high data rates (such as, specifically, data rates from 0.1 kbps to 100 kbps).

[0109] In this example, the second transmitter 305 is configured to transmit data according to a first modulation scheme, which in this case may use load modulation, and specifically, may use biphase / Manchester encoding. In this example, the first modulation scheme may use load modulation, and therefore the power receiver / second transmitter 305 is configured to load modulate the power transfer signal. Load modulation is such that each data symbol is represented by a pattern / sequence of a set of load levels, wherein the load level is constant in each time interval. In many embodiments, the load modulation may be a binary combination, and therefore the second transmitter 305 may select between two sequences / patterns of constant load level depending on the bit value being transmitted. In many embodiments, the pattern / sequence may be a pattern / sequence of binary load levels. For each time interval, a pattern / sequence corresponding to the data symbol or bit to be transmitted may be selected from one of the two load levels.

[0110] The data (symbol) rate of load modulation is lower than that of FM modulation. The first transmitter 305 can be configured to transmit load-modulated symbols at a lower data rate (such as, specifically, a data rate of, for example, 1 kbp to 200 kbp).

[0111] The power transmitter includes a first synchronizer 209 configured to synchronize the first transmitter 205 to transmit data in alignment with and synchronously with the power transfer signal. For example, the transmission may be synchronized such that the start and / or end times of the symbols coincide with the zero crossover of the power transfer signal or the minimum value of the periodic amplitude variation of the power transfer signal.

[0112] Similarly, the power receiver includes a second synchronizer 309 configured to synchronize the second transmitter 305 to transmit data in alignment with and synchronously with the power transfer signal. For example, the transmission may be synchronized such that the start and / or end times of the symbols coincide with the zero crossover of the power transfer signal or the minimum value of the periodic amplitude variation of the power transfer signal.

[0113] In some embodiments, the first synchronizer 209 and / or the second synchronizer 309 may be configured to synchronize individual data transmissions to the timing of a cycle of power transfer signals. The frequency of the power transfer signals is generally in the range of 20 kHz to 500 kHz. The first synchronizer 209 and / or the second synchronizer 309 may be synchronized to these cycles such that, for example, each symbol begins at a zero crossover or peak of the cycle.

[0114] In many embodiments, data symbols may have a duration of several (and possibly many) cycles. The synchronizer may be further configured to synchronize data transmission in response to the timing of data received by the receiver of the device. Therefore, the synchronizer can adjust the transmission of data according to the second modulation scheme in response to the timing of data received according to the second modulation scheme. Specifically, the synchronizer may be able to detect modulation level changes in the received data and align the data symbols to be aligned transmitted by the transmitter with the modulation level change. Specifically, the synchronizer may detect the modulation level change and then adjust the transmission such that the start of the new symbol coincides with the zero crossover of the power transfer signal closest to such modulation level change.

[0115] For example, the first synchronizer 209 may be configured to detect changes in load level caused by load modulation of the second transmitter 305. Based on such load level changes, the timing of the time interval can be determined. For example, if the time interval is determined to have a duration corresponding to, for example, 10 cycles of the power transfer signal, the first synchronizer 209 may operate the phase-locked loop based on an error signal reflecting the difference between the timing of the predicted time interval transition and the detected level change. Furthermore, the predicted timing of the time interval transition / modulation level change and / or the timing of the measured modulation level change can be synchronized with the zero-crossing time of the power transfer signal (specifically, quantized as the zero-crossing time of the power transfer signal).

[0116] Such a method can provide highly accurate timing of data symbols transmitted by the first transmitter 205, so that they are closely aligned with the time intervals in the transmission in the other direction.

[0117] It should be understood that in some embodiments, the second synchronizer 309 may apply an equivalent method that, based on the timing of the modulation level changes and power transfer signal cycles in the transmission from the first transmitter 205, can adjust the timing of load modulation so that the data symbols and frequency changes are aligned.

[0118] Synchronization of the power transfer signals of two transmissions allows the transmissions to be aligned and synchronized with each other. In some embodiments, synchronization at the two ends may be performed solely by synchronizing to the power transfer signals, without taking into account the specific symbol timing properties of the other communication link (in the opposite direction).

[0119] In some embodiments, one or two synchronizers may be configured to synchronize the timing of data transmission of the corresponding device / apparatus to the amplitude variation in the power transfer signal, and specifically, the amplitude variation in the power transfer signal.

[0120] Amplitude variations can specifically be caused by variations in the amplitude of the supplied power / voltage. For example, in many embodiments, the voltage supply to the driver / reverse 201 is generated directly from the mains power supply voltage without any voltage regulation or smoothing (but may have some rectification), and thus can practically be supplied typically by a sinusoidal or rectified sinusoidal voltage. Generally, this has a relatively low frequency of 50 Hz or 60 Hz (or twice that if rectification is applied), and the driver generates a higher frequency drive signal from this supply voltage. The amplitude / power level of this higher frequency drive signal therefore varies with the supply voltage signal.

[0121] For example, driver 201 is generally a drive circuit in the form of a inverter that generates an AC signal from a DC voltage. The output of driver 201 is generally a switching bridge that generates a drive signal by appropriate switching of the switches of the switching bridge. Figure 6 shows a half-bridge switching bridge / inverter. Control switches S1 and S2 are such that they are never closed at the same time. Alternatively, when S2 is open, S1 is closed, and when S1 is open, S2 is closed. The switches open and close at the desired frequency, thereby generating an AC signal at the output. Generally, the output of the inverter is connected to the transmitter inductor via a resonant capacitor. Figure 7 shows a full-bridge switching bridge / inverter. Control switches S1 and S2 are such that they are never closed at the same time. Control switches S3 and S4 are such that they are never closed at the same time. Alternatively, when S2 and S3 are open, switches S1 and S4 are closed, and then when S1 and S4 are open, S2 and S3 are closed, thereby generating a square wave signal at the output. Open and close the relationship at the desired frequency.

[0122] The power transmitter is generally driven by a mains power AC signal (essentially a sine wave as shown in the first line Umains of Figure 8). The mains power voltage Umains can be rectified by an AC / DC converter to generate a voltage Udc_abs. A large storage capacitor for smoothing this rectified mains power voltage is generally not used in such applications because it would increase the total mains power harmonic distortion and potentially be costly. Therefore, a varying DC voltage is generated by the AC / DC converter, and this voltage can be used to supply the driver. This results in the output voltage of the inverter corresponding to Uac_HF. The resonant circuit of the transmitter coil 103 generally results in a smoothed portion, thereby generating a power transfer signal, as reflected by the signal Usc_Tx in Figure 8.

[0123] Therefore, in many wireless power transfer systems, power transfer signals with periodic amplitude variations are generated. In such cases, data transmission can be synchronized to the changes in the power / amplitude level, and specifically, can be synchronized to occur around its minimum value, generally corresponding to a zero crossover of the supply voltage to the driver. In other instances, synchronization can, for example, be aligned with the maximum value of the power transfer signal.

[0124] As an example, the first synchronizer 209 may be configured to determine the minimum amplitude of the power transfer signal. Specifically, the first synchronizer 209 may apply an amplitude detector to the current passing through the transmitter coil 103. In many embodiments, the first synchronizer 209 may directly evaluate the timing of the signal in the transmitter coil 103 (or even use, for example, a measuring coil to evaluate the timing of the electromagnetic field), rather than evaluating the supply voltage of the driver's inverter, to reflect any delay or timing offset between the power transfer signal and these signals. However, in some embodiments, the first synchronizer 209 may indeed be synchronized based on the driver's signal.

[0125] The first synchronizer 209 may be configured to control the first transmitter 205 such that the symbol time is aligned with the power transfer signal. For example, the start and stop times may be aligned to coincide with the minimum (or maximum) value of the power transfer signal.

[0126] In a similar manner, the second synchronizer 309 can detect the amplitude change of the sensed power transfer signal and determine the timing of the minimum (or, for example, maximum) value. Then, the second transmitter 305 can be controlled to align the transmitted data symbols with the power transfer signal. For example, not only the start and end times of the data symbols, but also the start and end times of the time interval can be aligned with the minimum value of the amplitude change.

[0127] In such methods, the synchronization of the power transmitter transmission and the power receiver transmission to the power transfer signal can cause these transmissions to be aligned with each other without further consideration of other parameters (such as specific data timing), that is, it is not necessarily necessary to consider the timing data from the received data.

[0128] As a specific example, the first transmitter 205 may be configured to transmit a single data symbol / bit for each cycle of the power transfer signal (i.e., for each interval between two minimum values, thus corresponding to half the cycle of the input main power supply signal). The second transmitter 305 may be configured to transmit a constant modulation level of a modulation level sequence / pattern for each cycle of the power transfer signal (i.e., for each interval between two minimum values, thus corresponding to half the cycle of the input main power supply signal). Therefore, the duration of the symbol transmitted according to the second modulation scheme is equal to the cycle of the power transfer signal, and the duration of the single time interval transmitted according to the first modulation scheme is equal to the cycle of the power transfer signal, and therefore the duration of the data symbol of the second modulation scheme is equal to the length of the sequence / pattern multiplied by the cycle of the power transfer signal.

[0129] Furthermore, in this example, the timing of the data symbols transmitted by the first modulation scheme is aligned with the timing of the data symbols transmitted by the second modulation scheme, and there are indeed individual time intervals. Therefore, the method can allow alignment as previously described, wherein the entire data symbol of the first modulation scheme is transmitted during a time period with constant modulation accuracy according to the transmission in the other direction of the second modulation scheme.

[0130] In many embodiments, the duration of these time intervals is at least equal to the symbol duration of the data symbols of the second modulation scheme. In fact, in many embodiments, each data symbol according to the first modulation scheme can be represented by a sequence of two constant modulation levels / time intervals. Therefore, the symbol rate transmitted by the second modulation scheme can be twice that of the first modulation scheme, and the communication link can provide very different bandwidth / capacity.

[0131] In practice, in many embodiments, the asymmetry can be substantially large, and in many embodiments, the duration of such time intervals is at least two or even eight times the symbol duration of the data symbols of the second modulation scheme. (Assuming a binary data symbol scenario), such a method can allow more data to be transmitted in one direction, specifically, the entire byte, during the time it takes to transmit a single bit in the other direction. Therefore, highly asymmetric communication can be supported.

[0132] Figure 9 illustrates an example in which a first modulation scheme is used for communication from the power receiver to the power transmitter (i.e., via the second transmitter 305), and a second modulation scheme is used for communication from the power transmitter (i.e., via the first transmitter 205).

[0133] In such examples, the frequency of the power transfer signal may be approximately 128 kHz. The first transmitter 205 may include a frequency modulator that modulates each bit using 8 cycles (16 kbp on a 128 kHz carrier). A single byte may require 11 bits when including start bits, stop bits, and same bits. In an example, the second transmitter 305 may employ biphase modulation, resulting in a minimum duration / time interval of half a bit (half the bit duration required to transmit one bit) for a constant modulation level. The first transmitter 205 may transmit the entire byte (including extra bits) for each load-modulated half-bit (time interval), such that for each load-modulated bit transmitted in the reverse direction, two entire FM byte groups are transmitted in the forward direction. This may specifically result in a 727 bp bit rate for a load-modulated channel (16 kbp FSK channel / 11 bits per byte / 2 byte groups per bit).

[0134] Figure 10 illustrates another example. In this case, the first transmitter 205 transmits three bits per load modulation half-bit / time interval, such that each load modulation bit transmits six FM bits, resulting in a bit rate of at least 2.6 kbp for the load modulation channel (16 kbp FSK channel / 6 bits per byte).

[0135] Figure 11 illustrates an example in which the power transmitter, the first transmitter 205, and the forward communication link employ a first modulation scheme, while the power receiver, the second transmitter 305, and the reverse communication link employ a second modulation scheme. Therefore, in this example, the reverse communication link, which can still use load modulation, can thus have a higher data rate than the forward communication link, which can still use frequency modulation.

[0136] Furthermore, in an example, the load modulation system is modulated using direct sequence spread spectrum modulation, wherein the load modulation bits are represented by a direct sequence of a suitable number of chips. In an example, the power transfer signal may have a frequency of approximately 128 kHz. The power receiver / second transmitter 305 may use the direct sequence to manipulate loads with low magnitudes, wherein in a specific example, the sequence has a length of 35 chips. The power transmitter / first transmitter 205 may employ a frequency modulator that utilizes biphase modulation, resulting in a minimum constant modulation level of half a bit / symbol, i.e., where each data symbol is represented by a pattern / sequence of two modulation levels. The second transmitter 305 / load modulator may transmit the entire direct sequence per FM half bit, thereby making the bit rate of the forward FM communication link half the bit rate of the reverse communication link.

[0137] This method can provide substantially improved communication and can in particular reduce interference from slower communication links to faster communication links.

[0138] Furthermore, in some embodiments, during the symbol duration of transmission in the slower communication link (according to the first modulation scheme), the modulation level of transmission in the faster communication link can be selected such that the average modulation level of transmission in the faster communication link (according to the second modulation scheme) is independent of the data value of the second data. In fact, in many embodiments, the average modulation level over at least one time interval of the time interval sequence is independent of the data value.

[0139] For example, in the examples of Figures 9 and 10, biphase modulation can be used for FM modulation, where, for example, "0" is represented by half a bit of frequency f1 followed by half a bit of frequency f2, and "1" is represented by half a bit of frequency f2 followed by half a bit of frequency f1. In this case, the power transfer signal has the same duration as frequencies f1 and f2, regardless of the transmitted bits. Therefore, the average effect / interference of FM transmission on amplitude variation will be the same, and the impact on the transmitted data can be reduced when averaged over the entire symbol duration.

[0140] Therefore, in such methods, interference from faster communication links to slower communication links can also be reduced / mitigated.

[0141] In some embodiments, one or both of the transmitters 205, 305 may be configured to transmit several (one or more) dummy symbols to align the data size of the faster communication link data to the data symbols of the slower communication link. The data size may be, for example, the data packet size, the data block, or, for example, a byte.

[0142] For example, the number of symbols that can be transmitted during the symbol time of the slower communication link (according to the second modulation scheme) can correspond to the number of faster / shorter data symbols that can be transmitted per time interval multiplied by the number of time intervals in the sequence / pattern. If this number is not aligned with the size of a given data block or packet, a dummy symbol (which can have any value and can be simply ignored by the receiving device) is transmitted to align the data size (block / packet) with the data symbols of the slower communication link.

[0143] For example, in Figure 10, preferably, a dummy bit is transmitted after b10 (instead of transmitting b0) to align the beginning of the new byte with the new LM symbol.

[0144] In some embodiments, a transmitter using a higher data rate can be configured to continuously transmit data unless the data on a slower data rate communication link meets the non-acknowledgment criteria. A non-acknowledgment may be the omission of an expected acknowledgment or, for example, a direct non-acknowledgment message.

[0145] Therefore, in some cases, for example, the first transmitter 205 can be configured to continuously transmit data on a faster communication link. This transmission can continue uninterrupted as long as the received data is acknowledged using a slower communication link. Thus, the faster communication link can utilize maximum bandwidth / transmission volume without introducing pauses or delays due to waiting for or checking acknowledgments. This can be achieved through full-duplex simultaneous communication, where acknowledgment feedback can be implemented without interrupting rapid data transmission.

[0146] If a non-acknowledgment is received (or the expected acknowledgment is not received), the transmitter may terminate the fast data transfer and may continue to perform a retransmission.

[0147] Therefore, while allowing for fast and efficient feedback / acknowledgment / retransmission, it is possible to simultaneously achieve very fast communication using the full capacity of a fast link.

[0148] As a specific example, one of the transmitters may use a faster communication link to transmit an uninterrupted byte stream with embedded bit or byte error detection, while the other transmitter uses a slower communication link to indicate that a byte or several bytes have been successfully received. This allows for the transmission of burst packets over the communication medium and reduces the number of retransmissions by isolating errors.

[0149] A beneficial example of using very long data packets (bundle transfer) in wireless power systems is when authentication credentials are transmitted from a power transmitter to a power receiver via a frequency modulation channel.

[0150] To reduce the time required to transmit authentication credentials, it is highly advantageous to provide an uninterrupted byte stream in a faster link (generally, an FM forward link). However, in the event of errors that are not detected and corrected in a timely manner, the credentials must be completely retransmitted, doubling the authentication time.

[0151] In this case, the load modulation channel is used to let the power transmitter know whether the last byte (or several bytes) has been received without error.

[0152] This invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. Optionally, this invention can be implemented at least partially as computer software running on one or more data processing and / or digital signal processors. The elements and components of embodiments of this invention can be implemented physically, functionally, and logically in any suitable manner. In practice, functionality can be implemented in a single unit, in a plurality of units, or as part of other functional units. Therefore, this invention can be implemented in a single unit or can be physically and functionally distributed among different units, circuits, and processors.

[0153] While the invention has been described with reference to some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is limited only by the appended claims. Additionally, while features may appear to be described in connection with specific embodiments, those skilled in the art will recognize that various features of the described embodiments can be combined according to the invention. In the claims, the terminology includes, but does not exclude, the presence of other elements or steps.

[0154] Furthermore, although individually listed, a plurality of components, elements, circuits, or method steps may be implemented, for example, by a single circuit, unit, or processor. Additionally, although individual features may be included in different claims, there may be advantageous combinations, and including features in different claims does not imply that a combination of features is feasible and / or advantageous. Including a feature in a claim of one class does not imply a limitation on that class, but rather indicates that the feature may be equally applicable to other claims as needed. Furthermore, the order of features in the claims does not imply any specific order in which the features must act, and the order of individual steps in a method claim does not specifically imply that the steps must be performed in this order. More precisely, the steps may be performed in any suitable order. Moreover, singular references do not exclude plural references. Therefore, references to "a," "an," "first," "second," etc., do not exclude plurals. Reference marks in the claims are provided only as illustrative examples and should not be construed in any way as limiting the scope of the claims. [Simplified Explanation of the Diagram]

[0063] Embodiments of the present invention will be described by way of example only with reference to the drawings, wherein [Figure 1] illustrates an example of elements of a power transfer system according to some embodiments of the present invention; [Figure 2] illustrates an example of elements of a power transmitter according to some embodiments of the present invention; [Figure 3] illustrates an example of elements of a power receiver according to some embodiments of the present invention; [Figure 4] illustrates an example of biphase coding; [Figure 5] illustrates an example of a transmission scheme according to some embodiments of the present invention; [Figure 6] illustrates an example of a inverter for a power transmitter according to some embodiments of the present invention; [Figure 7] illustrates an example of an inverter for a power transmitter according to some embodiments of the present invention; [Figure 8] illustrates an example of a signal for a power transmitter according to some embodiments of the present invention; [Figure 9] illustrates an example of a transmission scheme according to some embodiments of the present invention; [Figure 10] illustrates an example of a transmission scheme according to some embodiments of the present invention; and [Figure 11] illustrates an example of a transmission scheme according to some embodiments of the present invention.

Claims

1. A power transfer device for wireless power transfer from a power transmitter (101) to a power receiver (103), the power transfer device being one of the power transmitter (101) and the power receiver (101, 103), the power transfer device comprising: a power transfer coil (103, 107) configured to exchange power with a complementary power transfer coil (107, 103) of a complementary power transfer device via a power transfer signal, the complementary power transfer device being the other of the power transmitter (101) and the power receiver (105); and a receiver (207, 307) configured to receive first data from the complementary power transfer device, the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, each of the time intervals having a constant modulation level depending on the value of one of the data symbols, the time interval sequence being synchronized to the power transfer signal; A transmitter (205, 305) configured to transmit second data to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme, wherein the duration of a symbol of the data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence; and a synchronizer (209, 309) configured to synchronize the transmitter (205, 305) to transmit the second data aligned with the first data by synchronizing the transmission of the second data to the power transfer signal.

2. The power transfer equipment as requested in claim 1, wherein the duration of such time intervals is at least twice the duration of the data symbols of the second modulation scheme.

3. The power transfer device as claimed in any of the preceding claims, wherein the duration of such time intervals is at least eight times the duration of the data symbols of the second modulation scheme.

4. The power transfer equipment as described in any of the aforementioned requests, wherein the first modulation scheme employs two-phase modulation.

5. A power transfer device as claimed in any of the preceding claims, wherein an average modulation level of the transmission of the second data during a symbol duration of the transmission of the first data is independent of the data value of the second data.

6. A power transfer device as claimed in any of the preceding claims, wherein the transmitter (205, 305) is configured to transmit a plurality of dummy symbols to align the size of one of the second data to the duration of one of the symbols of the first data.

7. The power transfer device as requested in any of the foregoing claims, wherein the transmitter (205, 305) is configured to continuously transmit the second data unless the first data meets a non-response criterion.

8. The power transfer device as claimed in claim 7, wherein the transmitter (205, 305) is configured to retransmit the second data in response to the first data meeting the non-response criterion.

9. The power transfer device as claimed in any of the preceding claims, wherein the power transfer device is the power receiver (105), the first modulation scheme uses frequency modulation, and the second modulation scheme uses load modulation.

10. The power transfer device as claimed in any of the preceding claims, wherein the power transfer device is the power transmitter (101), the first modulation scheme uses load modulation, and the second modulation scheme uses frequency modulation.

11. A power transfer device as claimed in any of the preceding claims, wherein the synchronizer (209, 309) is configured to synchronize the transmitter in response to an amplitude change in the power transfer signal.

12. A power transfer device as claimed in any of the preceding claims, wherein the synchronizer (209, 309) is configured to synchronize the transmitter in response to a cycle of the power transfer signal.

13. A power transfer system comprising a power receiver (103) and a power transmitter (101) for performing a wireless power transfer from the power receiver (103), the power transmitter (101) comprising: a first power transfer coil (103) configured to transfer power to a second power transfer coil (107) of the power receiver (103) via a power transfer signal; and a first receiver (205) configured to receive first data from the power receiver (103), the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, each time interval having a constant modulation level depending on a data symbol value of the data symbol, the time interval sequence being synchronized to the power transfer signal; A first transmitter (207) configured to transmit second data to a power receiver (101) by modulating the power transfer signal according to a second modulation scheme, wherein the duration of a symbol of the data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence; and a first synchronizer (209) configured to synchronize the transmitter to transmit the second data aligned with the first data by synchronizing the transmission to the power transfer signal of the second data; and the power receiver (103) comprising: a second power transfer coil (107) configured to receive power from the first power transfer coil (103) of the power transmitter (103) via the power transfer signal; and a second transmitter (305) configured to transmit the first data to the power transmitter (101) according to the second modulation scheme; A second receiver (307) configured to receive second data from the power transmitter (101) according to the second modulation scheme; and a second synchronizer (309) configured to synchronize the second transmitter (305) to transmit the first data at time intervals of the time interval sequence aligned with the power transfer signal.

14. A method of operating a power transfer device for wireless power transfer from a power transmitter (101) to a power receiver (103), the power transfer device being one of the power transmitter (101) and the power receiver (103), the power transfer device comprising: a power transfer coil (103, 107) configured to exchange power with a complementary power transfer coil (107, 103) of a complementary power transfer device via a power transfer signal, the complementary power transfer device being the other of the power transmitter (101) and the power receiver (105); the method comprising: receiving first data from the complementary power transfer device, the first data being modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, each of the time intervals having a constant modulation level depending on a data symbol value of the data symbol, the time interval sequence being synchronized to the power transfer signal; The second data is transmitted to the complementary power transfer device by modulating the power transfer signal according to a second modulation scheme, wherein the duration of a symbol of the data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence; and the transmission of the second data to be aligned with the first data is synchronized by synchronizing the transmission of the second data to the power transfer signal.

15. A method of operating a power transfer system comprising a power receiver (103) and a power transmitter (101), for performing a wireless power transfer from the power receiver (103), the power transmitter comprising a first power transfer coil (103) configured to transfer power to a second power transfer coil (107) of the power receiver (103) via a power transfer signal, and the power receiver comprising the second power transfer coil (107) configured to receive power from the first power transfer coil (107, 103) of the power transmitter (103) via the power transfer signal; the method comprising the power transmitter (101) performing the following steps: The power receiver (103) receives first data modulated onto the power transfer signal according to a first modulation scheme, wherein each data symbol is represented by a time interval sequence, each time interval having a constant modulation level depending on the value of one of the data symbols, the time interval sequence being synchronized to the power transfer signal; the power transfer signal is modulated according to a second modulation scheme to transmit second data to the power receiver (103), wherein the duration of a symbol of a data symbol in the second modulation scheme is a divisor of the duration of at least one time interval of the time interval sequence; and the transmission of the second data to be aligned with the first data is synchronized by synchronizing the transmission of the second data to the power transfer signal; and the power receiver (103) performs the following steps: transmitting the first data to the power transmitter (101) according to the second modulation scheme; The second data is received from the power transmitter (101) according to a second modulation scheme; and the transmission of the first data to be aligned with the time intervals of the time interval sequence is synchronized by synchronizing the transmission of the second data to the power transfer signal.

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