Enhanced communications for wireless power transfer

Abstract

A wireless power transmitter is capable of receiving a result of characterizing a signal transmitted by a wireless power receiver, calculating at least two parameters of a model characterizing an in-band communication channel based on the received result of characterizing a signal transmitted by the wireless power receiver, calculating a plurality of equalization filter taps from the at least two parameters, and applying the calculated equalization filter to a subsequent signal received by the wireless power transmitter via the in-band communication channel. The first parameter can correspond to a time constant of the channel and the second parameter can correspond to a damping value of the communication channel. The wireless power transmitter is capable of transmitting a request to a wireless power receiver to transmit a characterization signal over the in-band communication channel, wherein the characterization signal transmitted by the wireless power receiver is transmitted in response to the transmitted request.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 230,190, filed on August 6, 2021, entitled “ENHANCED COMMUNICATIONS FOR WIRELESS POWER TRANSFER,” U.S. Patent Application No. 17 / 814,099, filed on July 21, 2022, entitled “ENHANCED COMMUNICATIONS FOR WIRELESS POWER TRANSFER,” and PCT Application PCT / US22 / 38871, filed on July 29, 2022, entitled “ENHANCED COMMUNICATIONS FOR WIRELESS POWER TRANSFER,” each of which is incorporated herein by reference in its entirety for all purposes. Background Art

[0003] Wireless power transfer (WPT) systems, including inductive power transfer (IPT) systems, may rely on "in-band" communication, where the transmitted power is used to establish a communication channel between a power transmitting device (i.e., a power transmitter (PTx)) and a power receiving device (i.e., a power receiver (PRx)). Various arrangements are possible, including various implementations, where the power transmitter (PTx) may modulate certain electrical characteristics (such as voltage, frequency, etc.) of the delivered power to convey encoded information to the power receiver (PRx), which is capable of detecting the changes in electrical characteristics (i.e., modulation) imposed by the PTx. Similarly, the power receiver (PRx) may modulate certain electrical characteristics (such as voltage, frequency, etc.) of the received power to convey encoded information to the power transmitter (PTx), which is also capable of detecting the changes in electrical characteristics (i.e., modulation) imposed by the PRx. In some applications, the physical construction and configuration of the device and the electrical operating conditions may impose bandwidth limitations on the communication channel that are lower than the desired communication bandwidth. Summary of the invention

[0004] It would therefore be advantageous to provide wireless power transfer devices and techniques that can adapt to various physical configurations and electrical operating conditions to enhance the available bandwidth of a communication channel.

[0005] A method performed by one or more processing elements of a wireless power transmitter may include receiving a result of a characterization signal sent by a wireless power receiver, calculating at least two parameters of a model characterizing an in-band communication channel based on the received result of the characterization signal sent by the wireless power receiver, calculating a plurality of equalization filter taps from the at least two parameters, and applying the calculated equalization filter to a subsequent signal received by the wireless power transmitter via the in-band communication channel. A first parameter may correspond to a time constant of the channel, and a second parameter may correspond to a damping value of the communication channel. Calculating the second parameter may include determining whether the wireless power transmission system is underdamped. Determining whether the wireless power transmission system is underdamped may include calculating an overshoot caused by the characterization signal sent by the wireless power receiver. If the wireless power transmission system is not underdamped, the second parameter may be set to 1. The characterization signal may be a step signal. The method may also include sending a request to the wireless power receiver to send a characterization signal via the in-band communication channel, wherein the characterization signal sent by the wireless power receiver is transmitted in response to the sent request.

[0006] A wireless power transmitter may include: an inverter that receives a DC input voltage and generates an AC output voltage, a wireless power transmitter coil that receives the AC output voltage from the inverter and delivers power to a wireless power receiver through magnetic coupling, a controller and communication circuit that controls the inverter and provides in-band communication with the wireless power receiver via the wireless power transmitter coil. The controller and communication circuit may be configured to receive a result of a characterization signal sent by the wireless power receiver, calculate at least two parameters of a model that characterizes an in-band communication channel based on the received result of the characterization signal sent by the wireless power receiver, calculate multiple equalization filter taps from the at least two parameters, and apply the calculated equalization filter taps to subsequent signals received by the wireless power transmitter via the in-band communication channel. The first parameter may correspond to a time constant of the channel, and the second parameter may correspond to a damping value of the communication channel. The controller and communication circuit may also be configured to calculate the second parameter in part by determining whether the wireless power transmission system is underdamped. The controller and communication circuit may also be configured to determine whether the wireless power transmission system is underdamped by calculating an overshoot caused by the characterization signal sent by the wireless power receiver. The controller and communication circuit may also be configured to set the second parameter to 1 if the wireless power transmission system is not underdamped. The characterization signal may be a step signal. The controller and communication circuit may also be configured to send a request to the wireless power receiver to send a characterization signal via the in-band communication channel, and wherein the characterization signal sent by the wireless power receiver is transmitted in response to the sent request.

[0007] The wireless power receiver may include a wireless power receiver coil that receives power from a wireless power transmitter via magnetic coupling, a rectifier that receives an AC voltage from the wireless power receiver coil and generates a DC output voltage to power a load, a controller and communication circuit that controls the rectifier and provides in-band communication with the wireless power transmitter via the wireless power receiver coil, wherein the controller and communication circuit may be configured to send a characterization signal to the wireless power transmitter. The controller and communication circuit may provide in-band communication with the wireless power transmitter via load modulation. The load modulation may result in amplitude shift keying of the received power. The control and communication circuit may be configured to send the characterization signal to the wireless power transmitter in response to a request received from the wireless power transmitter. The request received from the wireless power transmitter may be a frequency shift keyed signal. The characterization signal may be a step signal.

[0008] A method performed by one or more processing elements of a wireless power transmitter may include: receiving results of a characterization signal sent by a wireless power receiver; calculating at least two parameters of a model characterizing an in-band communication channel based on a subset of the received results of the characterization signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the channel and a second parameter corresponds to a damping value of the communication channel; calculating a plurality of equalization filter taps from the at least two parameters; and applying the calculated equalization filter to a subsequent signal received by the wireless power transmitter via the in-band communication channel. The subset of the received results may correspond to samples having values ​​within a predetermined window of the characterization signal. The predetermined window may be defined by a first threshold and a second threshold. The first threshold may be 10% and the second threshold may be 90%. The characterization signal may be a step signal. The characterization signal may be a known characteristic of a communication protocol used by the in-band communication channel. The known characteristic may include a stop bit at the end of a data packet. The method may also include sending a request to the wireless power receiver to send the characterization signal via the in-band communication channel, wherein the characterization signal sent by the wireless power receiver is transmitted in response to the sent request.

[0009] A wireless power transmitter may include: an inverter that receives a DC input voltage and generates an AC output voltage; a wireless power transmitter coil that receives the AC output voltage from the inverter and delivers power to a wireless power receiver through magnetic coupling; a controller and communication circuit that controls the inverter and provides in-band communication with the wireless power receiver via the wireless power transmitter coil, wherein the controller and communication circuit: receive results of a characterization signal sent by the wireless power receiver; calculate at least two parameters of a model that characterizes an in-band communication channel based on a subset of the received results of the characterization signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the channel and a second parameter corresponds to a damping value of the communication channel; calculate a plurality of equalization filter taps from the at least two parameters; and apply the calculated equalization filter taps to a subsequent signal received by the wireless power transmitter via the in-band communication channel. The subset of the received results may correspond to samples having values ​​within a predetermined window of the characterization signal. The predetermined window may be defined by a first threshold and a second threshold. The first threshold may be 10%, and the second threshold may be 90%. The characterizing signal may be a step signal. The characterizing signal may be a known characteristic of the communication protocol used by the in-band communication channel. The known characteristic may include a stop bit at the end of the data packet.

[0010] A method performed by one or more processing elements of a wireless power transmitter may include: receiving the result of a characterization signal sent by the wireless power receiver, wherein the characterization signal is a known characteristic of a communication protocol used by the in-band communication channel; calculating at least two parameters of a model characterizing the in-band communication channel based on a subset of the received result of the characterization signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the channel and a second parameter corresponds to a damping value of the communication channel; calculating a plurality of equalization filter taps from the at least two parameters; and applying the calculated equalization filter to subsequent signals received by the wireless power transmitter via the in-band communication channel. The known characteristic includes a stop bit at the end of a data packet.

[0011] A wireless power transmitter may include: an inverter that receives a DC input voltage and generates an AC output voltage; a wireless power transmitter coil that receives the AC output voltage from the inverter and delivers power to a wireless power receiver through magnetic coupling; a controller and communication circuit that controls the inverter and provides in-band communication with the wireless power receiver via the wireless power transmitter coil, wherein the controller and communication circuit: receive a result of a characterization signal sent by the wireless power receiver, wherein the characterization signal is a known characteristic of a communication protocol used by the in-band communication channel; calculate at least two parameters of a model that characterizes the in-band communication channel based on the received result of the characterization signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the channel and a second parameter corresponds to a damping value of the communication channel; calculate a plurality of equalization filter taps from the at least two parameters; and apply the calculated equalization filter taps to subsequent signals received by the wireless power transmitter via the in-band communication channel. The known characteristic may include a stop bit at the end of a data packet. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A block diagram of a wireless power transfer system is illustrated.

[0013] Figure 2 A simplified schematic diagram of a wireless power transfer system is illustrated.

[0014] Figure 3 A flow chart of a first portion of an inductive power transfer communication channel equalization technique including an exemplary characterization waveform is illustrated.

[0015] Figure 4 A flow chart of a second portion of an inductive power transfer communication equalization technique including an exemplary resulting equalization filter is illustrated.

[0016] Figure 5 A more detailed flow chart of an inductive power transfer communication channel equalization technique is illustrated.

[0017] Figure 6 Messaging associated with a wireless power transfer system is illustrated.

[0018] Figure 7 Messaging associated with training and equalization for high speed communications in a wireless power transfer system is illustrated.

[0019] Figure 8 The training and equalization techniques are illustrated with associated messaging in a wireless power transfer system with high-speed communications.

[0020] Fig. 9Channel estimation and equalization processes for high-speed communication in a wireless power transfer system are illustrated.

[0021] Fig.10 A modified channel estimation and equalization process is illustrated in which samples below a first threshold or above a second threshold are discarded to improve the accuracy of the calculated coefficients.

[0022] Fig.11 A modified channel estimation and equalization process is illustrated in which known characteristics of the data stream are used as characterizing signals. DETAILED DESCRIPTION

[0023] In the following description, for the purpose of explanation, many specific details are set forth in order to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings in the drawings of the present disclosure represent structures and devices in block diagram form for simplicity. For the sake of clarity, not all features of actual implementations are described in the present disclosure. In addition, the language used in the present disclosure is selected for readability and instructional purposes and has not been selected to describe or limit the disclosed subject matter. Instead, the attached claims are intended for this purpose.

[0024] Various embodiments of the disclosed concepts are illustrated by way of example, and are not limited to individual drawings, in which similar reference numerals indicate similar elements. For simplicity and clear illustration, reference numerals are repeated in different drawings to indicate corresponding or similar elements, where appropriate. In addition, many specific details are shown in order to provide a full understanding of the specific implementation described herein. In other cases, methods, procedures, and components are not described in detail to avoid blurring the related functions described. Mentioning "one", "a kind of" or "another" embodiment in this disclosure is not necessarily the same or different embodiments, and this means at least one. A given drawing may be used to illustrate more than one embodiment or more than one type of features of the present disclosure, and all elements in the drawings may not be required for a given embodiment or type. When provided in a given drawing, the reference numeral refers to the same element throughout several drawings, but it may not be repeated in each drawing. Unless otherwise specified, the drawings are not drawn to scale, and the proportions of certain components may be enlarged to better illustrate the details and features of the present disclosure.

[0025] Figure 1A simplified block diagram of a wireless power transmission system 100 is illustrated. The wireless power transmission system includes a power transmitter (PTx) 110 that wirelessly transmits power to a power receiver (PRx) 120, such as via an inductive coupling 130. The power transmitter 110 can receive input power, which is converted by an inverter 114 into an AC voltage having specific voltage and frequency characteristics. The inverter 114 can be controlled by a controller / communication module 116, which operates as further described below. In various embodiments, the inverter controller and the communication module can be implemented in a common system (such as a system based on a microprocessor, a microcontroller, etc.). In other embodiments, the inverter controller can be implemented by a separate controller module and a communication module with a communication device therebetween. The inverter 114 can be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and can be implemented using any suitable semiconductor switching device technology (e.g., MOSFET, IGBT, etc. manufactured using silicon, silicon carbide, or gallium nitride devices).

[0026] The inverter 114 can deliver the generated AC voltage to the transmitter coil 112. In addition to allowing magnetic coupling to the wireless coil of the receiver, Figure 1 The illustrated transmitter coil block 112 may include tuning circuits (such as additional inductors and capacitors) that facilitate operation of the transmitter under different conditions (such as different degrees of magnetic coupling to the receiver, different operating frequencies, etc.). The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil can be formed as a winding of wire around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless transmitter coil may also include a magnetically permeable material (e.g., ferrite) core that is configured to affect the flux pattern of the coil in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a variety of transmitter coil arrangements suitable for a given application.

[0027] The PTx controller / communication module 116 may monitor the transmitter coil and use information derived therefrom to control the inverter 114 to suit a given situation. For example, the controller / communication module may be configured to operate the inverter 114 at a given frequency or output voltage depending on the particular application. In some embodiments, the controller / communication module may be configured to receive information from the PRx device and control the inverter 114 accordingly. This information may be received via the power transmission coil (i.e., in-band communication) or may be received via a separate communication channel (not shown, i.e., out-of-band communication). For in-band communication, the controller / communication module 116 may detect and decode signals (such as voltage, frequency, or load changes) applied by the PRx on the magnetic link to receive information, and may command the inverter to modulate the delivered power by manipulating various parameters of the generated voltage (such as voltage, frequency, etc.) to transmit information to the PRx. In some embodiments, the controller / communication module may be configured to employ frequency shift keying (FSK) communication to convey data to the PRx, in which the frequency of the inverter signal is modulated. The controller / communication module 116 may be configured to detect amplitude shift keying (ASK) communications or load modulation based communications from the PRx. In either case, the controller / communication module 126 may be configured to vary the current drawn on the receiver side to manipulate the waveform seen on the Tx coil, thereby delivering information from the PRx to the PTx. For out-of-band communications, additional modules may be provided that allow communication between the PTx and PRx, such as WiFi, Bluetooth, or other radio links, or any other suitable communication channel.

[0028] As described above, the controller / communication module 116 can be a single module, for example, disposed on a single integrated circuit, or can be constructed from multiple modules / devices disposed on different integrated circuits or a combination of integrated circuits and discrete circuits having analog components and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuits.

[0029] The PTx device 110 may optionally include other systems and components, such as a separate communication module 118. In some embodiments, the communication module 118 may communicate with a corresponding module tag in the PRx via a power transfer coil. In other embodiments, the communication module 118 may communicate with a corresponding module using a separate physical channel 138.

[0030] As mentioned above, the wireless power transfer system also includes a wireless power receiver (PRx) 120. The wireless power receiver may include a receiver coil 122 that may be magnetically coupled 130 to the transmitter coil 112. As discussed above, the transmitter coil 112, Figure 1The illustrated receiver coil block 122 may include tuning circuits (such as additional inductors and capacitors) that facilitate operation of the transmitter under different conditions (such as different degrees of magnetic coupling to the receiver, different operating frequencies, etc.). The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil can be formed as a wire winding around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless receiver coil may also include a magnetically permeable material (e.g., ferrite) core that is configured to affect the flux pattern of the coil in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a variety of receiver coil arrangements suitable for a given application.

[0031] The receiver coil 122 outputs an AC voltage induced therein by magnetic induction via the transmitter coil 112. The output AC voltage may be provided to a rectifier 124, which provides a DC output power to one or more loads associated with the PRx device. The rectifier 124 may be controlled by a controller / communication module 126, which operates as further described below. In various embodiments, the rectifier controller and the communication module may be implemented in a common system (such as a system based on a microprocessor, a microcontroller, etc.). In other embodiments, the rectifier controller may be implemented by a separate controller module and a communication module with a communication device therebetween. The rectifier 124 may be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc. manufactured using silicon, silicon carbide, or gallium nitride devices).

[0032] The PRx controller / communication module 126 may monitor the receiver coil and use the information derived therefrom to control the rectifier 124 to suit a given situation. For example, the controller / communication module may be configured to cause the rectifier 124 to provide a given output voltage depending on the particular application. In some embodiments, the controller / communication module may be configured to transmit information to the PTx device to effectively control the power delivered to the receiver. This information may be transmitted via the power transmission coil (i.e., in-band communication) or may be transmitted via a separate communication channel (not shown, i.e., out-of-band communication). For in-band communication, the controller / communication module 126 may, for example, modulate the load current or other electrical parameters of the received power to transmit the information to the PTx. In some embodiments, the controller / communication module 126 may be configured to detect and decode signals (such as voltage, frequency, or load changes) imposed on the magnetic link by the PTx to receive information from the PTx. In some embodiments, the controller / communication module 126 may be configured to receive frequency shift keying (FSK) communications in which the frequency of the inverter signal has been modulated to convey data to the PRx. The controller / communication module 126 may be configured to generate amplitude shift keying (ASK) communications or load modulation based communications from the PRx. In either case, the controller / communication module 126 may be configured to vary the current drawn on the receiver side to manipulate the waveform seen on the Tx coil, thereby delivering information from the PRx to the PTx. For out-of-band communications, additional modules may be provided that allow communication between the PTx and PRx, such as WiFi, Bluetooth, or other radio links, or any other suitable communication channel.

[0033] As described above, the controller / communication module 126 can be a single module, for example, disposed on a single integrated circuit, or can be constructed from multiple modules / devices disposed on different integrated circuits or a combination of integrated circuits and discrete circuits having analog and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuits. The PRx device 120 may optionally include other systems and components, such as a communication ("communication") module 128. In some embodiments, the communication module 128 can communicate with a corresponding module in the PTx via a power transfer coil. In other embodiments, the communication module 128 can communicate with a corresponding module or tag using a separate physical channel 138.

[0034] Many variations and enhancements of the wireless power transmission system 100 described above are possible, and the following teachings apply to any of such variations and enhancements.

[0035] Figure 2A simplified schematic diagram of an inductive wireless power transmission system 100 is illustrated. The wireless power transmission system 100 includes a power receiver 120, an inductive link 130, and a wireless power transmitter 110, as described above. The inductive link 130 is not a separate device, but includes components that are part of the wireless power receiver 120 (e.g., a power receiver winding LRx and a tuning capacitor CRx) or as part of the wireless power transmitter 110 (e.g., a power transmitter winding LTx and a tuning capacitor CTx). The corresponding power transmitter and receiver windings may be magnetically coupled, for example, by being placed in physical proximity, thereby allowing power delivery and providing a communication channel between the power transmitter 110 and the power receiver 120. In some embodiments, power transmission may be unidirectional from a transmitter to a receiver, but bidirectional power transmission may also be allowed, where power may flow from a "receiver" to a "transmitter" (if appropriate in a particular context). In either case, communication may be bidirectional between the wireless power transmitter 110 and the wireless power receiver 120.

[0036] In one embodiment, the wireless power transmitter 110 may modulate one or more electrical characteristics (e.g., frequency) of the delivered power to communicate the encoded information to the wireless power receiver 120 using frequency shift keying (FSK) or other communication techniques. These frequency (or other parameter) changes may be reflected across the inductive link 130, and the power receiver 120 may include circuitry for detecting and decoding these frequency (or other electrical parameter) changes. Similarly, the wireless power receiver 120 may modulate the load applied (and therefore draw power) from the inductive link to communicate the encoded information to the power transmitter 110. In the simplified schematic diagram shown, the load modulation may be provided by a circuit represented by a switching current source 226. By switching an additional load in parallel with the normal load of the receiver device on the DC side of the rectifier 124, the power drawn from the inductive power link may be increased or decreased. Thus, the current amplitude changes may be reflected across the inductive link 130 and may be detected and decoded by circuitry in the wireless power transmitter 110 (e.g., by a demodulation block 133).

[0037] The physical construction of the wireless power transmitter 110 and the wireless power receiver 120, their configuration (e.g., relative positioning, alignment, and separation), and electrical operating conditions (e.g., the amount of power being transmitted, electrical noise or interference, etc.) may all affect the bandwidth of the above-mentioned communication channel. In some cases, the frequency response from the wireless power receiver 120 to the wireless power transmitter 110 may cause the symbols transmitted in time to spread to other symbols, thereby causing inter-symbol interference (ISI) and degrading the communication quality. These limitations may be caused by various physical limitations, but in general, the communication channel may be regarded as a filter with a frequency response that may distort the transmitted symbols. However, in some applications, the power transmitter may derive and apply a filter that is the inverse of the channel frequency response to allow for higher communication bandwidth. However, in some applications, the transmitter may derive and apply a filter that is the inverse of this slow frequency response to allow for higher communication bandwidth. This technique is a form of equalization.

[0038] Equalization can be achieved by causing or inviting the PRx device to transmit a predetermined characterization signal that can be received and analyzed by the PTx device. The characterization signal can initially be received by the signal front end 131, which can apply various conditioning and analysis to the received signal. PTx can employ computational techniques based on a communication channel model that can characterize the channel according to two parameters: τ, corresponding to the time constant of the channel, and ζ, corresponding to the damping factor of the channel. These parameters relate to the physical and electrical characteristics of a given channel. Once τ and ζ are determined, they can be used to determine the filter taps of the filter that the PTx device can apply to the received signal to overcome the bandwidth limitations of the channel, thereby allowing higher data rate communications. These filter taps define the filters that can be applied to the communication channel by the equalization block 132 of the PTx device. Now let's look at the filter taps with respect to FIG. 1 . Figures 3 to 5 This technique is described in more detail.

[0039] Figure 3 A high-level flow chart depicting the first part of the channel estimation technique introduced above is illustrated. Beginning at box 201, the PRx device 120 may send a step response signal 201a. The transmitter may use this step signal 201a to characterize the channel. As an alternative to the step signal, other signals with known, agreed and / or predetermined characteristics may be used in place of the step function, such as an impulse function (i.e., δ(t)), a predefined chirp signal, etc. This characterization signal may be sent in response to an invitation from the PTx device 110 to send such a signal or otherwise indicate that it is ready to receive such a signal. In such cases, the PTx device or PRx device may initiate a high-speed communication initiation process including a channel estimation technique. Various messaging and communication techniques that can be used to establish a high-speed communication channel are described in more detail below. In some cases, the PRx device may be configured to send a characterization signal as part of its own startup and negotiation process.

[0040] In block 202, a signal r(t) / 202a or other characterizing signal corresponding to the step response may be received by the PTx device 110. As shown, the system may be in one of two operating conditions, depending on the nature of the channel. In operating condition 1, the system is "underdamped," and the received step response 202a has an overshoot. In operating condition 2, the system is "critically damped" or "overdamped," and the received step response 202a has no overshoot. In operating condition 1 (i.e., the underdamped case), the parameters τ and ζ may be derived (e.g., by the PTx device) from the normalized function f using the illustrated equations nrm Calculation, the following reference Figure 5 In operating condition 2 - critically damped or overdamped condition - τ can be calculated using the same formula as in operating condition 1, and ζ can be assumed to be 1, which corresponds to critical damping but is sufficiently accurate even in the overdamped case. Figure 5 As described in the description of the invention, the approximate formulas for τ and ζ are sufficiently computationally tractable so that they can be implemented using one or more processing elements (such as a digital signal processor or microcontroller integrated circuit) that may be part of the PTx controller / communication circuit 116, thereby making them particularly suitable for various consumer electronic applications. In some applications, the one or more processing elements may also or alternatively include an FPGA, ASIC, or other type of processor or appropriately configured circuit.

[0041] Now turn to Figure 4 , the equalization technique continues to block 304, where the PTx device may take the estimated τ and ζ parameters and calculate the equalizer taps, i.e., the taps of the discrete time filter g(n). More specifically, in operating condition 1—the underdamped case—the frequency domain representation of the equalizer G(ω) may be obtained from τ and ζ using Figure 4 Given in and referred to below Figure 5 The time domain filter taps g(n) may then be calculated by applying an inverse discrete Fourier transform (or other suitable transform) to this frequency domain representation. Alternatively, a suitable infinite impulse response (IIR) filter may be calculated and applied. In operating condition 2—critically damped or overdamped conditions—ζ may be assigned a value of 1, and the time domain filter taps g(n) may be calculated using the formula discussed in more detail in FIG. 1 . Figure 4 Given in and referred to below Figure 5 In either case, the resulting equalization filter g(n) may be applied to subsequent signals received by the PTx device from the PRx device to compensate for the filtering effects of the communication channel.

[0042] Box 306 illustrates an exemplary equalizer tap sequence 306 for an operating condition 1 (underdamped) configuration. As can be seen, there is a large positive tap value, followed by a smaller but still relatively large negative tap, followed by several non-zero but relatively smaller tap values. Box 307 illustrates an exemplary equalizer tap sequence 307 for an operating condition 2 (critically damped or overdamped) configuration. As can be seen, there is a large positive tap value, followed by a smaller but still relatively large negative tap, followed by a zero tap value. These respective filter tap configurations can be found in all underdamped or critical / overdamped systems—with different values ​​depending on the exact physical characteristics and configuration and electrical operating conditions.

[0043] Figure 5 The above reference is described in more detail. Figure 3 and Figure 4 An expanded block diagram / flow chart of the described technology. Beginning at block 401, PRx 120 and PTx 110 may agree to negotiate a high-speed communication link. Prior to this point, all communications between PRx 120 and PTx 110 may be conducted according to a predefined protocol, which may be an industry standard protocol, such as the Qi protocol published by the Wireless Power Consortium (WPC). In block 411, after PRx and PTx agree to negotiate a high-speed communication exchange, PTx 110 may transmit to PRx 120 a request for PRx 120 to send a step response (or other signal to be used to characterize the communication channel). In some embodiments, this request may be transmitted using a frequency shift keying (FSK) technique, in which PTx 110 modulates the frequency of the transmitted power in a manner that can be detected and decoded by appropriate circuitry in PRx 120. Other modulation schemes may also be appropriately used in a given application. In block 421, PRx 120 may receive and decode the request. In response thereto, in block 422, PRx 120 may silence the channel for a predetermined time period corresponding to the number of switching cycles of the converter driving the transmit coil (i.e., the switching frequency of the system). In some embodiments, this switching frequency may be in the hundreds of kilohertz, for example, 100kHz to 120kHz, 128kHz, 326kHz, or 360kHz. In some embodiments, this switching frequency may be in the megahertz range, for example, 1MHz-2MHz. In other embodiments, any suitable switching frequency may be used, such as in the gigahertz range. The number of cycles for which the channel is silenced may be M, where M is greater than the value N1. The number of cycles M may be on the order of tens of cycles (e.g., 20 cycles), which may correspond to a time period of tens of microseconds (or greater).

[0044] During an interval corresponding to N1 (greater than M), as indicated in block 412, PTx 110 may sample the channel, thereby deriving a signal f(n), which may be represented by IQ decomposition as:

[0045]

[0046] PTx may also be configured (block 413) to calculate a value f(0) according to the following formula:

[0047]

[0048] Where N1 is the total number of samples on the PTx side at the start of the silent period, and the function value is the corresponding sample. The value f(0) may correspond to an average initial condition and may be used for normalization, as described in more detail below.

[0049] After the M cycles are completed, in box 423, PRx 120 may send a step response (or other characterizing signal). At the same time (box 414), PTx 110 may sample f(n), i.e., the received step response (or other characterizing signal) for a number of cycles N2 that is much greater than N1. For example, N2 may be about hundreds of cycles (e.g., 200 cycles) corresponding to a time period of hundreds of microseconds (or greater). In the illustrated example, N2 is an order of magnitude greater than N1, but other values ​​may be used as long as N2 is sufficiently greater than N1. Then (box 415), PTx 110 may calculate f(∞) according to the formula, where N1 is the total number of samples on the PTx side at the end of the silent period:

[0050]

[0051] Then, moving to block 416, PTx 110 may calculate a normalized response f using each measured response value f(n) and the calculated f(0) and f(∞) according to the following equation: nrm (n):

[0052]

[0053] Once the normalization function is calculated, PTx can calculate τ (block 417) according to the following formula:

[0054]

[0055] Where ΔT is the sampling time. In addition, PTx can calculate the overshoot value OS (block 418) according to the following formula:

[0056] OS=-max(min(f nrm (n),-0.5))

[0057] The overshoot value can be 0.5 and f nrm Therefore, the overshoot value will end up being between 0 and 0.5.

[0058] Moving to block 419, PTx may determine whether the overshoot value is greater than 1%. If not, the system may be considered critically damped (operating condition 2), and PTx may calculate the filter tap g(n) for the frequency domain representation of the equalizer G(ω) using the formula (block 420):

[0059]

[0060] G(ω) can be inversely transformed to generate g(n), as described above with reference to Figure 4 described.

[0061] Alternatively, if the overshoot is greater than 1%, the system may be considered underdamped (operating condition 2), meaning that ζ is less than 1 and may be calculated from the overshoot (block 421) according to:

[0062]

[0063] Then, in block 422, the frequency domain representation of the equalizer G(ω) may be calculated by: G(ω)=e jω -2acos(w0)+a 2 e -jω in:

[0064]

[0065] G(ω) can be inversely transformed to generate g(n), as described above with reference to Figure 4 described.

[0066] Now go to Figure 6 , illustrates a communication process 500 that can be used to initiate communication between a wireless power transmitter (PTx) and a wireless power receiver (PRx). The process can start at a slow data rate (e.g., 2kbps). Initially, in box 1, PRx can transmit a plurality of messages 501 that are digital connectivity detection (ping) / identification / communication. In response, in box 2, PRx can transmit a request for an identification message 502a to PTx. These and other messages from PRx can be transmitted via amplitude shift keying (ASK) of the received power signal, as described above with reference to Figure 1 to Figure 2 In response, PTx may transmit an identification message 502b. These and other messages from PTx may be transmitted via frequency shift keying (FSK) of the received power signal, as described above with reference to Figure 1 to Figure 2 Furthermore, for these and all other messages described herein, even if shown as a single message, each message may include multiple packets, depending on the exact protocol and implementation.

[0067] In box 3, PRx may transmit a request (message 503a) for the capabilities of the PTx device (e.g., power transfer capabilities, such as maximum power transfer rate, power transfer frequency, etc.). In response, PTx may transmit a message 503b indicating such capabilities. In box 4, PRx may transmit a request (message 503a) for the communication capabilities of the PTx device (e.g., the ability to communicate in-band at various frequencies, data rates, etc.). In response, PTx may transmit a message 503b indicating its communication capabilities. In some applications, these two sets of capability messages may be combined into a single group. After the estimation phase, in box 4, PRx may transmit a message 514a applying the new configuration (e.g., higher data rate). PTx may reply with a confirmation message 514b. Finally, in box 5, PRx may transmit a message 505a indicating the end of the negotiation phase, which may be confirmed by a message 505b from the PTx device.

[0068] After this exchange, PRx and PTx can transfer power and then enter the Figure 7 Starting in block 1, when power transfer may be in progress, PRx may transmit a message 511a requesting to enter a training phase, during which the communication channel may be as described above with reference to Figures 3 to 5 The PTx may acknowledge the request via an ACK message 511b. Then, in block 2, the training phase may begin with PRx transmitting training parameters, such as an indication for channel equalization and a desired high speed data rate (e.g., 20 kbps), which may be accepted / approved by PTx. PTx may transmit an ACK message 512b confirming these parameters. Then, block 3 may include a channel estimation phase 513, which may be described above with reference to Figures 3 to 5 Described and referenced below Figures 8 to 9 5. The power transmission may be resumed / continued at a higher communication rate as confirmed by message 515 in block 5.

[0069] Figure 8 The channel estimation stage 513 is illustrated in more detail. In general, the channel estimation is as described above with reference to Figures 3 to 5 As described above. Figure 8As described, the training phase may be initiated by PRx transmitting a start training message 512a to PTx, which may be confirmed by PTx with an ACK message 512b. This may mark a transition to a high speed (e.g., 20kpbs) communication scheme, and may include one or more channel estimation steps 513a, 513b during the direct equalization training cycle. As shown, each of these channel estimation blocks may include the PRx device silencing / quieting the channel, sending a step (or other characterizing signal), and delaying to allow PTx to perform its processing. More specifically, PTx may search for a step signal (or other characterizing signal) substantially simultaneously with the above-described actions of PRx, and upon receiving such a signal, process the received signal to derive channel estimation parameters, as described above with reference to Figures 3 to 5 Based on these channel estimation parameters, appropriate filters for channel equalization may be calculated (513c) as described above. Then, via messaging 514a and 514b, the new channel configuration may be applied and power transmission may be resumed (515).

[0070] Fig. 9 A simplified timing diagram of channel estimation attempts 513a, 513b is illustrated. The channel estimation process may include one or more of these attempts. This process is generally consistent with that described above and provides exemplary timing intervals, but other time periods may be appropriate, depending on the frequency of communication, the switching frequency of the power converter, etc. Starting in box 601, PRx may silence / quiet the communication channel for a specific time period, for example, 15ms. Then, in box 602, PRx may send a step signal (or other characterization signal). This may again take a time period of (for example) 15ms. After this, in box 603, there may be a delay period again, for example, 15ms, before another channel estimation attempt or channel estimation phase is completed.

[0071] Substantially simultaneously with the above operations, the PTx may operate in acquisition mode for a period of time sufficient to capture a step or other characterizing function (e.g., 40 ms) (block 605), with buffers on either side (block 604) to account for slight timing differences between the PTx and PRx devices. Subsequently, in block 605, the PTx may perform the required processing to characterize the channel and calculate the filter taps, which may be a relatively short period of time, e.g., 5 ms. As described above, all of these time periods are merely exemplary, and other suitable time periods may be appropriately employed.

[0072] Fig.10 A modified channel estimation and equalization process is illustrated in which samples below a first threshold or above a second threshold are discarded to improve the accuracy of the calculated coefficients. More specifically, Fig.10Graph 700 illustrates samples corresponding to a received characterization signal (curve 741), a first curve 743 employing all such samples to calculate channel estimation parameters (e.g., τ (time constant parameter) and ζ (damping parameter), as described above), and a second curve 746 in which certain samples are discarded to improve the accuracy of the calculated channel estimation parameters. In some cases, the physical and electrical properties of the channel may cause the received characterization signal 741 to exhibit an undershoot 742. In such cases, using all received samples according to the techniques described above may result in the calculation of channel estimation parameters corresponding to the first curve 743 that may not match the actual characterization signal as closely as desired. For example, as illustrated, curve 743 begins to rise earlier, stops rising later, and generally has a smaller slope / larger radius of curvature than the received characterization samples corresponding to curve 741.

[0073] To overcome this potential inaccuracy, certain samples may be excluded from the calculation of the channel estimation parameters. For example, in the case of a step function characterizing a signal, samples having values ​​less than a first threshold TH1% (744) and samples having values ​​greater than a threshold TH2% (745) may be discarded or otherwise excluded from the channel estimation parameter calculation. The first threshold TH1% may be a relatively small fraction or percentage of the full scale value of the step function, such as 10%, although other values ​​such as 1%, 2%, 5%, 15%, 20%, etc. may also be used. The second threshold TH2% may be a relatively large fraction or percentage of the full scale value of the step function, such as 90%, although other values ​​such as 99%, 98%, 95%, 85%, 80%, etc. may also be used. Discarding such samples may also be described as using only samples having amplitude values ​​corresponding to a center window characterizing the signal (e.g., between TH1% and TH2%). Doing so may produce channel estimation parameters corresponding to a calculated curve 746 that more closely tracks the received samples 741.

[0074] In at least some applications, channel estimation using only a selected subset of characterization signal samples as described above can have various advantages. First, as described above, the accuracy of the calculated channel estimation parameters can be improved, such as in situations with undershoot (as illustrated) or other characterization signal anomalies, particularly near extremes of characterization signal values. An additional advantage of such techniques is that the accuracy with which the timing of the characterization signal needs to be determined is reduced. Additionally, memory usage and / or computation time can be reduced by using a smaller number of samples. Finally, relative to Fig.10 The sample subset technique described is compatible with all channel estimation techniques described herein and can be adapted to work with a variety of characterization signal types.

[0075] In the channel estimation and equalization techniques described above, channel estimation is based on reception of a predetermined characterizing signal transmitted by a device (eg, a wireless power receiver). However, in some applications, known characteristics of the data stream may be used as such a predetermined characterizing signal. Fig.11 A modified channel estimation and equalization process is illustrated in which known characteristics of a data stream are used as characterizing signals. More specifically, Fig.11 A data stream 800 is illustrated which includes two data packets 851 and 852. Fig.11 In the upper portion of FIG. 8 , data packets 851 and 852 are represented as digital bits (i.e., 1s and 0s), and in FIG. Fig.11 In the lower portion of FIG. 8 , data packets 851 and 852 are represented as simple amplitude shift keying waveforms. Fig.11 As depicted, the digital 1 corresponds to a high amplitude, while the digital 0 corresponds to a low amplitude. However, other encoding techniques may also be used. As an example, however, Manchester encoding may also be used, where transitions in the waveform are used to represent digital values. In any case, the amplitude used for encoding may be any suitable voltage, current, etc. As in the examples described above, in some embodiments, the amplitude of the load current may be modulated by the wireless power receiver to provide the desired ASK waveform.

[0076] Returning to the data stream 800 and the constituent packets 851, 852, the specification of the communication protocol used by the data stream 800 can be advantageously used as a characterization signal for channel estimation according to the above-mentioned techniques. For example, the communication protocol may specify that each packet 851, 852 is followed by a silent period 853, 854. The communication protocol may also specify that each packet will start with a start sequence, followed by a payload, followed by one or more stop bits. Other packet components and definitions are possible, such as parity bits or other redundant data for error detection and recovery. For the purposes of discussion herein, the packet and protocol definition examples are relatively simple for ease of understanding, but in actual implementations, any desired packet structure may be used, which is consistent with the packet structure defined by the Qi wireless power transmission standard published by the Wireless Power Alliance.

[0077] In the illustrated example, each packet 851, 852 begins with a start sequence 851a, 851b, which is Fig.11, but can be any desired value. In each packet 851, 852, the start bit can be followed by an 8-bit payload 851b, 852b, which can be different from one packet to the next. After each payload is a stop bit 851c, which is always 1, although other ends of packet markers or patterns can be used. The combination of a predetermined stop bit and a subsequent silent period in each packet can be used as a characterization signal for the above-mentioned channel estimation technique. In other words, the step-down from the high amplitude of 1 bit to the silent period after each packet can be used as a step characterization signal as described above. However, this specific characteristic is not the only characteristic that can be used as a characterization signal, but any known property of the data stream can be used as a characterization signal, although using certain known properties rather than other properties may be preferred because they can provide better channel characterization.

[0078] In at least some applications, channel estimation using known characteristics of data streams as described above may have various advantages. First, the use of known characteristics may eliminate the need for separate predetermined exchanges to facilitate the transmission and reception of characterization signals. This may also reduce the time required to perform channel estimation. In addition, the channel characterization signal is always available, and if the conditions change, the channel characterization signal may be used at any time to update the channel estimate and the equalization parameters derived therefrom. Various features and embodiments of enhanced communication in wireless power transmission systems are described above. Such an arrangement may be used in a variety of applications, but may be particularly advantageous when used in conjunction with a portable electronic device that uses wireless charging and a corresponding wireless charging device. In addition, although many specific features and various embodiments have been described, it should be understood that unless otherwise stated as mutually exclusive, various features and embodiments may be combined into various arrangements in specific embodiments. Therefore, the various embodiments described above are provided only by way of example and should not be interpreted as limiting the scope of the present disclosure. Various modifications and changes may be made to the principles and embodiments of this document without departing from the scope of the present disclosure and without departing from the scope of the claims.

[0079] The foregoing describes an exemplary embodiment of a wireless power transmission system capable of transmitting certain information between a PTx and a PRx in the system. The present disclosure contemplates that this information transfer improves the ability of devices to provide wireless power signals to each other in an efficient manner to facilitate battery charging, such as by sharing the power handling capabilities of the devices with each other. Entities implementing the present technology should be careful to ensure compliance with established privacy policies and / or privacy practices to the extent that any sensitive information is used in a particular implementation. In particular, such entities will be expected to implement and consistently apply privacy practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Implementers should inform users where personally identifiable information is expected to be sent in the wireless power transmission system, and allow users to "opt-in" or "opt-out" participation. For example, if a power transmitter is configured to poll for sensitive information from a power receiver, such information may be presented to the user when the user places the device onto the power transmitter.

[0080] Once the data is no longer needed, risks can be minimized by limiting the collection of data and deleting the data. In addition, and when applicable, data de-identification can be used to protect the privacy of users. For example, a device identifier can be partially masked to convey the power characteristics of the device without uniquely identifying the device. De-identification can be facilitated by removing identifiers, controlling the amount or specificity of stored data (e.g., collecting location data at a city level rather than an address level), controlling how data is stored (e.g., aggregating data across users), and / or other methods such as differential privacy when appropriate. Robust encryption can also be used to reduce the possibility of communications between inductively coupled devices being spoofed.

Claims

1. A method performed by one or more processing elements of a wireless power transmitter, the method comprising: receiving a result of a characterization signal sent by the wireless power receiver; calculating at least two parameters of a model characterizing an in-band communication channel based on a subset of the received results of the characterizing signal transmitted by the wireless power receiver, wherein a first parameter corresponds to a time constant of the communication channel and a second parameter corresponds to a damping value of the communication channel; calculating an equalization filter from the at least two parameters; as well as The calculated equalization filter is applied to subsequent signals received by the wireless power transmitter via the in-band communication channel. 2 . The method of claim 1 , wherein the subset of received results corresponds to samples having values ​​within a predetermined window characterizing the signal. The method according to claim 2 , wherein the predetermined window is defined by a first threshold and a second threshold. The method according to claim 3 , wherein the first threshold is 10% and the second threshold is 90%. The method according to claim 1 , wherein the characterization signal is a step signal.

6. The method of claim 1, wherein the characterizing signal is a known characteristic of a communication protocol used by the in-band communication channel.

7. The method of claim 6, wherein the known characteristic comprises a stop bit at the end of a data packet.

8. The method of claim 1, further comprising sending a request to the wireless power receiver to send the characterization signal over the in-band communication channel, wherein the characterization signal sent by the wireless power receiver is transmitted in response to the sent request.

9. A wireless power transmitter, comprising: an inverter that receives a DC input voltage and generates an AC output voltage; a wireless power transmitter coil that receives the AC output voltage from the inverter and delivers power to a wireless power receiver through magnetic coupling; a controller and communication circuitry that controls the inverter and provides in-band communication with the wireless power receiver via the wireless power transmitter coil, wherein the controller and communication circuitry: receiving a result of a characterization signal sent by the wireless power receiver; calculating at least two parameters of a model characterizing an in-band communication channel based on a subset of the received results of the characterizing signal transmitted by the wireless power receiver, wherein a first parameter corresponds to a time constant of the communication channel and a second parameter corresponds to a damping value of the communication channel; calculating an equalization filter from the at least two parameters; as well as The calculated equalization filter is applied to subsequent signals received by the wireless power transmitter via the in-band communication channel. 10 . The wireless power transmitter of claim 9 , wherein the subset of received results corresponds to samples having values ​​within a predetermined window characterizing the signal. The wireless power transmitter of claim 10 , wherein the predetermined window is defined by a first threshold and a second threshold. 12 . The wireless power transmitter of claim 11 , wherein the first threshold is 10% and the second threshold is 90%. The wireless power transmitter of claim 9 , wherein the characterization signal is a step signal.

14. The wireless power transmitter of claim 9, wherein the characterizing signal is a known characteristic of a communication protocol used by the in-band communication channel.

15. The wireless power transmitter of claim 14, wherein the known characteristic comprises a stop bit at the end of a data packet.

16. A method performed by one or more processing elements of a wireless power transmitter, the method comprising: receiving a result of a characterizing signal transmitted by the wireless power receiver, wherein the characterizing signal is a known characteristic of a communication protocol used by an in-band communication channel; calculating at least two parameters of a model characterizing the in-band communication channel based on the received results of the characterizing signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the communication channel and a second parameter corresponds to a damping value of the communication channel; calculating an equalization filter from the at least two parameters; as well as The calculated equalization filter is applied to subsequent signals received by the wireless power transmitter via the in-band communication channel.

17. The method of claim 16, wherein the known characteristic comprises a stop bit at the end of a data packet.

18. A wireless power transmitter, the wireless power transmitter comprising: an inverter that receives a DC input voltage and generates an AC output voltage; a wireless power transmitter coil that receives the AC output voltage from the inverter and delivers power to a wireless power receiver through magnetic coupling; a controller and communication circuitry that controls the inverter and provides in-band communication with the wireless power receiver via the wireless power transmitter coil, wherein the controller and communication circuitry: receiving a result of a characterizing signal transmitted by the wireless power receiver, wherein the characterizing signal is a known characteristic of a communication protocol used by an in-band communication channel; calculating at least two parameters of a model characterizing the in-band communication channel based on the received results of the characterizing signal sent by the wireless power receiver, wherein a first parameter corresponds to a time constant of the communication channel and a second parameter corresponds to a damping value of the communication channel; calculating an equalization filter from the at least two parameters; as well as The calculated equalization filter is applied to subsequent signals received by the wireless power transmitter via the in-band communication channel.

19. The wireless power transmitter of claim 18, wherein the known characteristic comprises a stop bit at the end of a data packet.

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