Capacitive modulation in a wireless power receiver

Abstract

This disclosure provides systems, methods and apparatuses for adaptive capacitive modulation. A Power Receiver can support power reception at a variety of power levels, such as 5 watts (5W), 15W, or 25W, among other examples. The Power Receiver can select, from among a plurality of modulators having different capacitance levels, which modulator to use for communication with the Power Transmitter. In some aspects, selection of a modulator is based on an estimated induction coupling factor (Kest) and power level. In instances where coupling is high, a first modulator (e.g., having 4.7 nano-farads (nF) capacitance) is used for low power levels (e.g., 5W) and a second modulator (e.g., having 10 nF to 22 nF) is used for high power levels (e.g., 25 W). The Power Receiver can select the modulator capacitance such that the Power Transmitter avoids capacitive region operation and has sufficient amplitude shift keying (ASK) depth for effective communication.

Description

CAPACITIVE MODULATION IN A WIRELESS POWER RECEIVERCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This Patent Application claims benefit of priority to India Provisional Patent Application No. 202411057394, filed July 29, 2024, entitled “MULTIPLE MODULATORS FOR ADAPTIVE CAPACITANCE IN A WIRELESS POWER RECEIVER,” the contents of which are incorporated by reference herein.TECHNICAL FIELD

[0002] This disclosure relates generally to wireless power and some aspects relate to the use of adaptive capacitive modulation in a Power Receiver to support communication at various power levels and inductive coupling.DESCRIPTION OF RELATED TECHNOLOGY

[0003] A wireless power system includes a Power Transmitter (PTx) and a Power Receiver (PRx). The Power Transmitter can transfer energy to the Power Receiver using a magnetic resonance technique or a magnetic induction technique. In the magnetic resonance technique, a first power transfer coil (sometimes referred to as a primary coil) of the Power Transmitter generates a magnetic field that vibrates in a resonant frequency to transfer energy to a second power transfer coil (sometimes referred to as a secondary coil) of a Power Receiver designed to have the same resonant frequency. In the magnetic induction technique, the Power Transmitter transfers electrical energy using a phenomenon in which power is transferred from a first power transfer coil (sometimes referred to as a primary coil) of the Power Transmitter and a second power transfer coil (sometimes referred to as a secondary coil) of the Power Receiver using electromagnetic induction. The primary coil produces an electromagnetic field for power transfer (such as during a power transfer phase). The electromagnetic field induces a voltage in the secondary coil of the Power Receiver when the secondary coil is present in the electromagnetic field. The Power Receiver can provide the received power to a load or an energy storage unit (such as a battery). Example loads might include a motor, processor(s), a heating element, kitchen appliances, or electronics, among other examples.

[0004] Wireless power technologies continue to evolve as manufacturers and consumers develop new capabilities. Consumers continue to adopt wireless power technology for new applications and deployment scenarios. Some advances in wireless power technology enable a wireless power system to increase the amount of power that can be transferred from a PowerTransmitter to a Power Receiver. To support higher power, voltage, and frequency levels, it is desirable to implement an effective communication system between the Power Receiver and the Power Transmitter.BRIEF SUMMARY

[0005] The systems, methods, and apparatuses of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of this disclosure can be implemented as a Power Receiver of a wireless power system. The Power Receiver includes a power transfer coil for receiving wireless power from a Power Transmitter. The Power Receiver includes one or more modulators coupled to the power transfer coil and enabling capacitive modulation. The Power Receiver includes a controller to select a communication capacitance from among different capacitance levels of the one or more modulators, and communicate with the Power Transmitter using a modulator of the one or more modulators having a capacitance level that corresponds to the selected communication capacitance.

[0007] Another innovative aspect of this disclosure can be implemented as a Power Receiver for receiving wireless power from a Power Transmitter. The Power Receiver includes a power transfer coil, a plurality of modulators enabling capacitive modulation of varied capacitance, and a controller. The controller is configured to communicate with the Power Transmitter using a selected modulator, from among the plurality of modulators, based on a capacitance- related criterion.

[0008] Another innovative aspect of this disclosure can be implemented as a Power Transmitter that includes a power transfer coil to transmit wireless power to a Power Receiver. The Power Transmitter includes a communication unit to receive a first communication from the Power Receiver, and communicate a modulation status packet to a Power Transmitter, where the modulation status packet indicates an amplitude shift keying (ASK) depth, phase angle, or both, of at least the first communication.

[0009] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] Like reference numbers and designations in the various drawings indicate like elements. Note that the relative dimensions of the figures may not be drawn to scale.

[0011] FIG. 1 is a block diagram of an example wireless power system.

[0012] FIG. 2 shows example power profiles of a wireless power system.

[0013] FIG. 3 shows a state diagram of a wireless power system.

[0014] FIG. 4 shows a general diagram of example wireless power transfer system that illustrates how alignment of power transfer coils can impact inductive coupling.

[0015] FIG. 5 shows a simplified diagram of the Power Transmitter and Power Receiver having variable capacitance tank circuits.

[0016] FIG. 6 shows an example Power Receiver with multiple modulators.

[0017] FIG. 7 shows another diagram of an example Power Receiver with multiple modulators.

[0018] FIG. 8 shows a message flow diagram with example operations for selecting communication capacitance.

[0019] FIG. 9 shows a table of example communication capacitances for various power levels and coupling k factors.

[0020] FIG. 10 shows a flow diagram with example operations of a Power Receiver.

[0021] FIG. 11 shows a message flow diagram in which a Power Transmitter communicates a modulation status packet to a Power Receiver to enable adaptive capacitance modulation.

[0022] FIG. 12 shows an example message timing diagram of PRx and PTx communication.

[0023] FIG. 13 shows an example modulation status packet.

[0024] FIG. 14A is an impedance analysis plot using a baseline power profile with various communication capacitance.

[0025] FIG. 14B is a more detailed diagram of a portion of FIG. 14A.

[0026] FIG. 15A shows an example plot of an MPP high coupling condition with and without communication capacitance.

[0027] FIG. 15B is a more detailed diagram of a portion of FIG. 15 A.

[0028] FIG. 16A shows an example plot of an impedance analysis for a low coupling condition.

[0029] FIG. 16B is a more detailed diagram of a portion of FIG. 16 A.

[0030] FIG. 17A shows a plot of MPP load variation at high coupling with a 10 nano-Farad (nF) communication capacitance.

[0031] FIG. 17B is a more detailed diagram of a portion of FIG. 17 A.

[0032] FIG. 18A shows a plot of MPP condition 4.7 nF communication capacitance at 5W to reduce the loss of zero voltage switching (ZVS) risk.

[0033] FIG. 18B is a more detailed diagram of a portion of FIG. 18A.

[0034] FIG. 19A shows a plot of load variation at low coupling (lOnF communication capacitance).

[0035] FIG. 19B is a more detailed diagram of a portion of FIG. 19A.

[0036] FIG. 20A shows a time domain analysis with communication capacitance (4.7-47 nF), 25W, and high coupling.

[0037] FIG. 20B shows a frequency domain analysis related to FIG. 20A.

[0038] FIG. 21A shows a time domain analysis with communication capacitance (4.7-47 nF), 5W, and high coupling.

[0039] FIG. 21B shows a frequency domain analysis related to FIG. 21 A.

[0040] FIG. 22 illustrates a block diagram of an example apparatus for use in a wireless power system.DETAILED DESCRIPTION

[0041] The following description is directed to certain implementations for the purpose of describing innovative aspects of this disclosure. A person of ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in any means, apparatus, system, or method for transmitting or receiving wireless power. Although the concepts and examples described in this document are based on wireless power transfer using example power profiles for magnetic induction, the concepts can apply to other types of deployments including other power profiles, communication protocols, or even other wireless power techniques.

[0042] As described previously, a wireless power system includes a Power Transmitter (PTx) and a Power Receiver (PRx). A Power Transmitter also may be referred to as a wireless power transmission apparatus. A Power Receiver also may be referred to as a wireless power reception apparatus. A Power Receiver includes a secondary coil configured to wirelessly receive power via inductive coupling with a primary coil of the Power Transmitter. A wireless power standard can support different power levels (such as 5 Watts (5W), 15W, 25W, etc.) using different power profiles. A power profile refers generally to a protocol and standard operation for a power transfer mode. As such, a power profile is based on the level of compatibility between a Power Transmitter and a Power Receiver. A first power profile(referred to as a baseline power profile (BPP)) can support up to 5W of wireless power transfer using an operating frequency in the range of 110 kilohertz (kHz) to 205 kHz (typically a Power Transmitter using BPP operates at 128 kHz). A second power profile (referred to as extended power profile (EPP)) introduces additional capabilities, such as extended protocol messages for improved coordination between the Power Transmitter and the Power Receiver, as well as higher power levels (such as up to 1 W). A third power profile (referred to as magnetic power profile (MPP) mode) can operate at higher frequencies (such as 360 kHz) and can support higher power levels (such as 15W, 25W, etc.). For MPP, the Power Receiver and the Power Transmitter both typically have magnetic rings to improve the stable alignment of the two devices. MPP mode currently supports up to 15W and may continue to increase as the MPP mode is further developed.

[0043] In addition to different power levels and operating frequencies, each power profile is associated with a communication protocol, referred to as a baseline protocol for BPP, an extended protocol for EPP, and a magnetic protocol for MPP. Some protocol messages are common among the various protocols, while EPP and MPP are associated with changes to the baseline protocol. In some implementations, the Power Transmitter and the Power Receiver operate using the baseline protocol (for BPP) until they detect that both devices support another protocol (such as either the extended protocol (for EPP) or magnetic protocol (for MPP)).

[0044] The Power Transmitter and Power Receiver typically communicate using in-band modulation of the wireless power signal. The Power Transmitter uses frequency shift keying (FSK) modulation on the transmitted wireless power signal for communications from the Power Transmitter to the Power Receiver. The Power Receiver uses amplitude shift keying (ASK) modulation on the received wireless power signal for communications from the Power Receiver to the Power Transmitter. ASK is a modulation technique used to transmit information by varying the amplitude of the carrier signal. This approach involves changing the amplitude of the electromagnetic waves (e.g., by a load current modulator or a capacitive modulator) to encode binary data, which can be used for control and monitoring purposes within the wireless power transfer system.

[0045] Capacitive modulation is a technique used in electronic circuits where the capacitance of a capacitor is varied (e.g., switched on and off) to encode information onto a carrier signal. The modulation of capacitance affects the impedance of the circuit, thus altering the frequency or phase angle of the carrier signal in a manner that represents the information being communicated. Zero Voltage Switching (ZVS) is a technique in power electronics that minimizes switching losses and electromagnetic interference (EMI) byensuring that the switching device transitions on or off when the voltage across it is zero. This approach, achieved using resonant components like inductors and capacitors, is essential for designing efficient power conversion circuits such as DC-DC converters, inverters, and resonant converters. ZVS reduces switching losses, decreases EMI, and enhances overall efficiency, making it widely used in switch-mode power supplies (SMPS), resonant converters, and inverters, thereby significantly improving the performance and reliability of modern power electronic systems.

[0046] This disclosure provides systems, methods, and apparatuses for adaptive capacitive modulation. A Power Receiver can support power reception at a variety of power levels, such as 5 watts (5W), 15W, or 25W, among other examples. The Power Receiver can adapt the communication capacitance based on various factors, such as the power level, operating frequency (e.g., 128khz or 360khz), phase change / angle, rectified voltage, etc. In some aspects, the Power Receiver can select (e.g., from among a plurality of modulators having different capacitance levels) a capacitive modulator to use for communication with the Power Transmitter. Additional technical features may become apparent to those skilled in the art from the subsequent figures, descriptions, and claims. In this disclosure, selection of a modulator can refer to selecting a capacitive modulator having a particular capacitance. For brevity, examples of this disclosure refer selection of a modulator from among multiple available modulators having different capacitance levels. However, the techniques can also apply to implementations in which a single modulator can operate a selected one of multiple modulator capacitance levels.

[0047] In some aspects, selection of a modulator is based on an estimated induction coupling factor (Kest) and power level. In instances where coupling is high, a first modulator (e.g., having 4.7 nano-farads (nF) capacitance) is used for low power levels (e.g., 5W), and a second modulator (e.g., having 10 nF to 22 nF) is used for high power levels (e.g., 25 W). The Power Receiver can select the modulator capacitance such that the Power Transmitter avoids capacitive region operation and has sufficient amplitude shift keying (ASK) depth for effective communication.

[0048] In some aspects, a Power Receiver includes a power transfer coil, a plurality of modulators enabling capacitive modulation of varied capacitance, and a controller configured to communicate with the Power Transmitter using a selected modulator from among the plurality of modulators based on a capacitance-related criterion. The capacitance-related criterion may be based on factors such as the power profile presently in use by the Power Receiver, received power, rectified voltage, operating frequency of the wireless power, coupling factor (Kest), amplitude shift keying (ASK) depth, phase angle, or any combinationthereof. In some implementations, a capacitance level of capacitive modulation may be changed based on the rectified voltage being over one or more thresholds, such as to maintain communication after an overvoltage condition.

[0049] In some aspects, the Power Receiver includes at least a first modulator having a first capacitance and a second modulator having a second capacitance. The controller is configured to receive a message from the Power Transmitter, such as a KEST packet indicating an estimated inductive coupling factor (Kest), and select the modulator based on the Kest. The controller may also receive a modulation status packet from the Power Transmitter, indicating ASK depth, phase angle, or both, and subsequently change to a different modulator based on the information in the modulation status packet.

[0050] The controller is further configured to select the modulator based on a combination of Kest and at least one of the power profile, load requirement, or measurement of received power. When the Kest is below a k factor threshold, the controller selects a default modulator; when Kest is above this threshold, it selects a modulator based on power level. For example, the controller can activate modulation capacitor control when Kest is above the k factor threshold. The modulation capacitor control can take into consideration such factors as the load requirements and power levels. For example, the controller may select a first modulator with approximately 4.7 nano-farad (nF) capacitance when Kest is above the k factor threshold, and the load requirement is 5 Watts. It may select a second modulator with capacitance ranging from 10 nF to 22 nF when Kest is above the k factor threshold, and the load requirement is 25 Watts or higher. The modulation capacitor control can also select the modulator capacitance based on measurements or empirical data that describe what modulation capacitance will produce an ASK depth of at least 300 mV, a phase angle greater than 20 degrees, or both, at the Power Transmitter.

[0051] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The communication from Power Receiver to Power Transmitter can ensure good readability of communicated bits while also using good system dynamics, such as ZVS, on the Power Transmitter.

[0052] A non-exhausted list of innovative aspects of this disclosure includes any one or more of the following aspects:• The Power Receiver can have multiple modulators and switch them according to the loading condition for a better ASK depth.• The Power Receiver can decide the communication capacitance according to k factor and received power to avoid capacitive region operation.• The Power Transmitter can communicate to reduce the communication capacitance when there is a possibility of ZVS risk (current phase angle less than 20 degree).• The Power Transmitter can demand a high value of communication capacitance if the ASK depth is low.• The Power Receiver can change the value of the communication capacitance based on a change command received from the Power Transmitter.• The Power Receiver can change (e.g., decrease) the communication capacitance based on overvoltage condition, such as when a rectified voltage (Vrect) exceeds a predetermined value by a threshold percentage, or when the Vrect exceeds an operating point Vrect value by a threshold.

[0053] FIG. 1 is a block diagram of an example wireless power system 100. The example wireless power system 100 includes a Power Transmitter 110 and a Power Receiver 130. The Power Transmitter 110 includes a power transfer coil 116 (sometimes referred to as a primary coil) and a PTx controller 120. The power transfer coil 116 may be associated with a Power Transmitter circuit 114 (sometimes also referred to as a power signal generator, or a driver circuit, or a driver). The power transfer coil 116 may be a wire coil which transmits wireless power (which also may be referred to as wireless energy). The power transfer coil 116 may transmit wireless energy using an inductive or a resonant magnetic field. The Power Transmitter circuit 114 may include components (not shown) to prepare the wireless power. For example, the Power Transmitter circuit 114 may include one or more switches, drivers, series capacitors, rectifiers, inverters, or other components. In some implementations, the Power Transmitter circuit 114 includes an inverter and a PTx resonant tank circuit (which can be referred to as a “tank circuit” for brevity). The PTx controller 120 may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC) or any other suitable electronic device.

[0054] A power source 112 provides power to the power transmitter unit 118. In some implementations, the power source 112 may convert alternating current (AC) power to direct current (DC) power. For example, the power source 112 may include a converter that receives an AC power from an external power supply and converts the AC power to a DC power used by the Power Transmitter circuit 114. Alternatively, or additionally, a component (such as an inverter) of the Power Transmitter circuit 114 may convert the DC power to the AC power. The power source 112 may be integrated as part of the Power Transmitter 110 or may beexternal to the Power Transmitter 110. In some implementations, the Power Transmitter 110 causes the power source 112 to regulate the DC output voltage of the power source 112. For example, the PTx controller 120 can set DC voltage of the power source 112 based on information (such as a value indicating a requested power) received from the Power Receiver 130. The Power Transmitter 110 can receive power configuration information from the Power Receiver 130 and use the information to set a parameter (such as the DC output voltage of the power source 112). In some implementations, the Power Transmitter 110 includes a DC-DC converter (not shown) between the power source 112 and the Power Transmitter circuit 114 to control the variable DC output voltage.

[0055] The PTx controller 120 is connected to a communication interface 122. The communication interface 122 is connected to the PTx tank circuit. The communication interface 122 may contain modulation and demodulation circuits to communicate via frequency, amplitude, current, or voltage modulation of a wireless power signal. For example, the communication interface 122 can have an FSK modulator for communications sent to the Power Receiver 130. And the communication interface 122 can have an ASK demodulator for communications received from the Power Receiver 130.

[0056] FIG. 1 shows an example wireless power system 100, including an example apparatus 150 that includes a Power Receiver 130 and other components (such as a converter 142, an energy storage unit 144, a load 152, a load controller 154, and / or a user interface 156). The Power Receiver 130 includes a power transfer coil 132 (sometimes referred to as a “secondary coil” to distinguish from the primary coil of a Power Transmitter), a PRx tank circuit 136 (or “tank circuit”), a rectifier 140, a PRx controller 146, and a PRx communication interface 148. The converter 142 can operate as a buck or boost converter to alter the voltage of electricity being supplied to the energy storage unit 144 (when the Power Receiver 130 is being operated in a power reception mode) or being drawn from the energy storage unit 144 (when the Power Receiver 130 is being operated in a power transmission mode). In some implementations, the apparatus 150 also includes a load controller 154 and a user interface 156 (such as a button, switch, touchpad, indicator, touch screen, or wireless local area network interface). In some implementations, the rectifier 140 is capable of operating as a rectifier or an inverter, and may be implemented as an active bridge. The PRx tank circuit 136 can include a capacitor or other components to enable the secondary power transfer coil 132 to receive the wireless power 158 during the power state. Although not shown, a small capacitor can be used before the rectifier 140, and a load capacitance can be used after the rectifier 140 to match impedance and to filter a high frequency component of the rectifier voltage. In accordance with aspects of this disclosure, the PRx tank circuit 136 includes a capacitancecomponent that can alter the capacitance of the PRx tank circuit 136 depending on different power levels, power transmission or reception modes, or power profile, among other examples.

[0057] Although shown as different components, some components may be packaged or implemented in the same hardware. For example, in some implementations, the PRx controller 146 and the load controller 154 may be implemented as a single controller. The PRx controller 146, the load controller 154, the PRx communication interface 148, or any combination thereof, may be implemented as a microcontroller, dedicated processor, integrated circuit, application specific integrated circuit (ASIC), or any other suitable electronic device. The PRx communication interface 148 can also be referred to as a second communication unit. The second communication unit might also include a power harvester (not shown) that can harvest energy from the communication signals and provide harvested bias power to the PRx controller 146 or the load controller 154.

[0058] The PTx controller 120 may detect the presence or proximity of a Power Receiver 130. This detection may happen during a periodic pinging process of the communication interface 122. The PRx communication interface 148 can send a reply signal back to the communication interface 122 to confirm that it is a Power Receiver. Prior to power transfer, a handshaking process may take place during which the PTx controller 120 may receive identification and configuration data, among other information, from the Power Receiver 130. The PTx controller 120 may control characteristics of wireless power it provides to the Power Receiver 130 based on the configuration data.

[0059] A PRx controller 146 may be operationally coupled to the rectifier 140 and the PRx communication interface 148. The PRx communication interface 148 may contain modulation and demodulation circuits to communicate via the power transfer coil 132 (such as before, after, or part of the PRx tank circuit 136). The PRx communication interface 148 may use load modulation to communicate via an in-band communication link (not shown) that includes the power transfer coil 132. In accordance with this disclosure, the PRx communication interface 148 (also referred to as a communication unit) can have multiple modulators 160. Each modulator can have a different capacitance. Thus, the PRx controller 146 can select one of the modulators 160 based on a modulation capacitance that is appropriate based on capacitance-related considerations described in this disclosure.

[0060] A load controller 154 may be operationally coupled to the load 152 and the PRx controller 146 (or to the communication interface PRx communication interfaces 148, coupling not shown in FIG. 1). The load controller 154 may detect changes to loadstates. The load controller 154 also may determine a load voltage reference and / or a power requirement of the load. The load controller 154 also may send load voltage references, load current, load power requirement, and any other suitable information to the PRx controller 146 or the PRx communication interface 148 for communication to the Power Transmitter 110. During a power state, the PRx controller 146 may additionally determine and provide one or more feedback information indicating a measured load voltage, load current, load power requirement, and power available to the load 152. In some feedback messages, the feedback information may include a reference voltage indicating a required voltage for the load 152. In some feedback messages, the feedback information may indicate an error in the output voltage of the load 152. In some feedback messages, the feedback information may include the required power for the load. Although the PRx controller 146 and load controller 154 are shown separately, they may be included in the same component of the Power Receiver 130.

[0061] Some appliances are equipped with safety features, such as a disconnect switch 134, that are operated in conjunction with the operating states. For example, the disconnect switch 134 might be maintained in an open position to prevent the flow of current to the load 152 when the Power Receiver 130 is in the pre-power states (such as a standby state, a discovery state, or a connected state). Before transitioning to the power state, the PRx controller 146 might cause the disconnect switch 134 to move to a closed position to enable the flow of current to the load 152. In an emergency condition (such as excessive voltage or current), the PRx controller 146 might open the disconnect switch 134 to prevent damage to the load 152 or other components of the Power Receiver 130 or the apparatus 150. After the disconnect switch 134 is closed, the PRx controller 146 can communicate a message to the PTx controller 120 to cause the wireless power system to transition to the power state. Alternatively, or additionally, the PRx controller 146 can communicate a power request to begin the transmission of the wireless power 158. Although the disconnect switch 134 is illustrated near the power transfer coil 132, in some implementations, the disconnect switch 134 is located closer to the load 152 and can be referred to as a load disconnect switch.

[0062] FIG. 2 shows example power profiles 200 of a wireless power system. The example power profiles 200 include a baseline power profile (BPP) 202, an extended power profile (EPP) 204, and a magnetic power profile (MPP) 206. Other power profiles may be developed in the future to support higher power (such as 50W) or different operating frequencies. Each power profile is associated with a protocol, supported power levels, and design features. Table 1 summarizes some example differences.Table 1.

[0063] A technical specification defines the communications physical layer, message format, and order of communications for each protocol. For example, the magnetic protocol is based on a communications physical layer that uses in-band modulation via a power signal. For the magnetic protocol communications physical layer, the Power Transmitter uses FSK modulation for PTx communications and the Power Receiver uses ASK modulation for PRx communications.

[0064] According to a current version of the technical specification for MPP, the Power Transmitter and the Power Receiver both can include a permanent magnetic ring for physical alignment of the devices. In some implementations, a Power Transmitter can have a movable primary coil with or without a permanent magnetic ring. For example, the technical specification for MPP might evolve such that the permanent magnetic ring is optional for some types of Power Transmitters, such as a moving coil PTx.

[0065] FIG. 3 shows a state diagram 300 of a wireless power system. The state diagram 300 illustrates the operating states in which the wireless power system may operate. When a Power Receiver is placed within an operating volume on the interface surface of a Power Transmitter, the two start to communicate to configure settings for the wireless power transfer. There are four operating states shown in FIG. 3: a ping phase 302 (sometimes also referred to as a ping state), a configuration phase 304 (sometimes referred to as an identification phase), a negotiation phase 306, and a power transfer phase 308 (sometimes referred to as a power transfer state). The ping phase 302, the configuration phase 304, and the negotiation phase 306 can collectively be referred to as pre-power states. A technical specification may define how the Power Transmitter and Power Receiver can transition between the operating states. For example, the wireless power system typically begins in the ping phase 302 until the Power Transmitter detects a Power Receiver, moving it to the configuration phase 304. In the configuration phase 304, the Power Transmitter establishescommunication and receives the identification information of the Power Receiver and its static configuration data. In the negotiation phase 306, the Power Transmitter and Power Receiver exchange information to agree and adjust parameters related to wireless power transfer. In the power transfer phase 308, the Power Transmitter transmits wireless power to the Power Receiver. The Power Receiver may occasionally or periodically communicate status or feedback control messages to the Power Transmitter during the power transfer phase 308. The system can move to a reinitialization state (not shown) as needed to reinitialize or return to the ping phase 302 when communication, powering, or other activities are no longer taking place. Each of the operating states are briefly described herein for reference.

[0066] In the ping phase 302, the Power Transmitter tries to establish communication with a Power Receiver. The Power Receiver may be just placed on the interface surface or may not be present during this operating state. The Power Transmitter may attempt to communicate or detect the presence of the Power Receiver. For example, the Power Transmitter may use an analog ping, out-of-band communication (such as near field communication (NFC)), a digital ping, impedance change detection, or any combination thereof, to determine that a compatible Power Receiver is present. In some implementations, the Power Transmitter transmits different types of ping signals to detect different types of Power Receivers. For example, the Power Transmitter can transmit a first type of digital ping using 128 kHz for BPP or EPP and a second type of digital ping using 360 kHz for MPP. The Power Transmitter might alternate between the first type and second type of digital ping. Alternatively, the Power Transmitter can initially transmit the first type of digital ping and then transmit the second type of digital ping after receiving a first ping response from the Power Receiver in response to the first type of digital ping. Once the wireless power system determines that a Power Receiver is present (such as by confirming NFC communication or receiving a ping response or other communication from the Power Receiver in response to a digital ping), the wireless power system may transition to the configuration phase 304.

[0067] In the configuration phase 304, the Power Receiver may establish communication with the Power Transmitter and send identification information (such as an identification packet) to the Power Transmitter. In some implementations, the Power Transmitter may retrieve static configuration information from the Power Receiver via the NFC communication. In some implementations, the Power Transmitter can also transmit an identification packet to the Power Receiver. The Power Transmitter and the Power Receiver may use the identification information to verify that they both use compatible versions of a technical specification or protocol for wireless power transfer. The Power Transmitter and Power Receiver may communicate basic settings or communicate regarding their respectivecapabilities. From the configuration phase 304, the wireless power system may transition to the negotiation phase 306.

[0068] In the negotiation phase 306, the Power Transmitter and the Power Receiver may exchange further communications (such as capabilities and / or configuration messages 350) to negotiate the parameters that govern the power transfer phase 308. For example, a power negotiation can occur during the negotiation phase 306. After negotiating the parameters, the Power Transmitter may be prepared to transfer wireless power, and the Power Receiver may be prepared to receive the wireless power. The Power Transmitter may wait for a request or command from the Power Receiver before transitioning to the power transfer phase 308.

[0069] In the power transfer phase 308, the Power Transmitter generates a wireless power signal to transfer power to the Power Receiver via inductive or resonant coupling. The Power Transmitter generates the wireless power using a frequency, a voltage, and other operating points associated with the amount of power negotiated during the negotiation phase 306.

[0070] From the power transfer phase 308, the Power Transmitter and the Power Receiver may transition back to the negotiation phase 306 until a next power transfer operation is needed. Alternatively, the wireless power system might transition to the ping phase 302. In some implementations, if the Power Transmitter determines that the Power Receiver is moved, that the Power Receiver is no longer present in an operating environment of the Power Transmitter, or that a foreign object has been introduced to the operating environment, the Power Transmitter might transition to a reinitialization state (not shown) or any of the other pre-power states.

[0071] In accordance with aspects of this disclosure (shown at block 350), a Power Receiver can select communication capacitance based on estimated inductive coupling factor (Kest) and power level. K estimation is a process to determine the Kest. Typically, K estimation is done during the configuration / ping phase. The Power Transmitter calculates the Kest and provides the Kest value to the Power Receiver. Based on the Kest value and power requirement, the Power Receiver can select a power profile (such as those in FIG. 3). During the negotiation phase 306, the Power Receiver may select a default modulation capacitance (such as 22 nF). During the negotiation phase 306 or the power transfer phase 308, the Power Receiver can select a different communication capacitance, as needed, based on changes in the Kest, the power level, or both.

[0072] In some aspects, the Power Receiver can use modulation capacitance control during the power transfer phase 308. Shown at block 352, the Power Receiver can select communication capacitance based on modulation status (e.g., ASK depth and phase angle).The Power Transmitter can provide the modulation status in a modulation status packet. When the Power Receiver processes the modulation status packet, the Power Receiver can select a different modulator if needed to adjust the modulation capacitance.

[0073] FIG. 4 shows a general diagram 400 of example wireless power transfer system that illustrates how alignment of power transfer coils can impact inductive coupling. The wireless power transfer system includes a Power Transmitter 110 and a Power Receiver 130. The Power Transmitter 110 includes a power transfer coil 116. The power transfer coil 116 is capable of transmitting wireless power 158 by generating a magnetic field that induces a voltage in a power transfer coil 132 of the Power Receiver 130. The Power Receiver 130 includes a power transfer coil 132 designed to receive the wireless power 114. The components of the Power Transmitter 110 and the Power Receiver 130 are described in further detail with reference to FIG. 5.

[0074] Alignment of the power transfer coil 132 and the power transfer coil 116 can vary along an X or Y axis (shown at arrows 492) in a plane 498 that is parallel to an interface surface of the Power Transmitter 110. In some implementations, alignment can vary in three directions (such as X, Y, and Z axis). The alignment can impact power transfer efficiency during a power transfer phase. The Kcstis an estimate of the inductive coupling between the power transfer coil 132 and the power transfer coil 116 based on their alignment and power transfer efficiency.

[0075] FIG. 5 shows a simplified diagram of the Power Transmitter and Power Receiver having variable capacitance tank circuits. FIG. 5 omits (for brevity) some elements of the Power Transmitter and the Power Receiver shown in FIG. 1. The Power Transmitter and Power Receiver can include the elements described in FIG. 1. For brevity, the power source and inverter (Power Transmitter circuit 114) are collectively shown as an input voltage 502 on the Power Transmitter side. On the Power Receiver side, the diagram 500 focuses on the capacitance elements, while other elements (such as a bridge circuit, converter, etc.) are collectively shown as a load 152.

[0076] FIG. 5 is provided to illustrate the capacitance levels of various capacitors in a traditional design of the Power Transmitter and the Power Receiver. Table 2 further lists these capacitance levels for reference.Table 2. Traditional capacitance levels

[0077] Initially the Power Transmitter and the Power Receiver may presume a BPP mode. In the BPP mode, the Stl 520 and St2 522 are closed (so that the PTX tank circuit has a total capacitance of 491 nF). In the BPP mode, the Sri 540 is open (so that the PRx tank circuit has a total capacitance of 174 nF).

[0078] After communicating capability information and determining coupling, the Power Transmitter and the Power Receiver can change to the MPP mode. In the MPP mode, when there is a high degree of coupling, the Stl 520 is closed making the PTx tank circuit capacitance 101 nF. In the MPP mode, when there is a low degree of coupling, the Stl 520 is open making the PTx tank circuit capacitance 68 nF. In a traditional implementation, for MPP, the Power Receiver closes Sri 540 making the PRx tank circuit capacitance 710 nF, regardless of the degree of coupling.

[0079] FIG. 5 shows that the capacitance of the Power Receiver tank circuit and the Power Transmitter tank circuit can require adjustment due to the coupling, frequency, or power level. In a legacy design, the Power Transmitter and the Power Receiver might only have one modulator each. In accordance with this disclosure, the Power Receiver can implement multiple modulators, where each modulator has a different nominal capacitance.

[0080] FIG. 6 shows a diagram 600a of an example Power Receiver 130 with multiple modulators. The Power Receiver 130 includes the power transfer coil 132 coupled to a PRx tank circuit 136 and a rectifier 140. In the example of FIG. 6, the Power Receiver 130 operates as a traditional Power Receiver such that the rectifier 140 provides a rectified voltage (Vrect) to the converter 142. The converter 142 supplies a DC voltage to the load 152. In some implementations, an apparatus also includes a dump load 610 (either as part of the load 152 or the Power Receiver 130). The dump load 610 can consume a small amount of current (such as 50 milliamps (mA)), referred to as ballast current, during times when the load 230 load is under a “no load” or a very light load condition. The dump load 610 can ensure that a minimum current is drawn. For example, when the load 152 (or energy storage unit 144) is disconnected or drawing less than 50 mA, the dump load 610 can draw ballast current to round the total equivalent DC current up to 50 mA. When the load 152 (or energy storage unit 144) is connected and drawing more than 50 mA, ballast current is not effective or has negligibleimpact. For a Power Receiver that also supports a wireless power transmission mode, the dump load 610 might be disabled or disconnected.

[0081] Returning to the PRx tank circuit 136, FIG. 6 shows capacitance levels of the capacitors (Crxl 530 and Crx2 532) are based on a traditional design in which the Crxl 530 is 174 nF, and the Crx2 532 is 536 nF. The Crxl 530 is always connected such that the minimum capacitance of the PRx tank circuit 136 (in this design) is 174 nF). During a digital ping initially in BPP mode, the switch Sri 540 is open so that the capacitance is only 174 nF (based on the Crxl 530). When the Power Transmitter (not shown) and the Power Receiver both support MPP mode, the PRx controller (now shown) can cause the Sri 540 to close such that the total capacitance of the PRx tank circuit 136 is 710 nF.

[0082] FIG. 6 also shows the Power Receiver 130 includes multiple modulators 160, such as a first modulator 612, a second modulator 614, and a third modulator 616. Although referred to as separate modulators for brevity, it should be understood that some implementations include a single communication unit with separate modulation circuits, or even a single modulator with variable capacitance. The terms “modulator” and “modulation circuit” can be used interchangeably in this disclosure.

[0083] As described in this disclosure, the Power Receiver 130 may select a particular modulator (or configuration of a single capacitive modulator) to implement a different communication capacitance. In some implementations, the Power Receiver 130 may select the communication capacitance based on a capacitance-related criterion.

[0084] FIG. 7 shows another diagram 700 of an example Power Receiver with multiple modulators. The Power Receiver includes the power transfer coil 132 coupled to a PRx tank circuit 136 and the rectifier 140. The PRx tank circuit 136 is coupled to a first modulator 612 with a first modulation capacitance 702, a second modulator 614 with a second modulation capacitance 704, and a third modulator 616 with a third modulation capacitance 706.

[0085] The Power Receiver may have multiple modulators and switch them according to the loading condition for a better ASK depth. In some implementations, the PRx can decide the communication unit capacitance according to k factor and received power in order to avoid capacitive region operation. The Power Receiver performs k factor estimation as per MPP protocol. During the configuration phase or the negotiation phase, depending on the Kestvalues, the Power Receiver selects the modulation capacitance. If Kest is low (e.g., below 0.81), the modulation capacitor may operate with one capacitor value (e.g., 22 nF). If Kest is high (e.g., above 0.81), the Power Receiver activates modulation capacitor control. When Kest is high, the modulation capacitor controller selects a lower modulation capacitance (e.g., 4.7nF) during light load (5W), and the modulation capacitor controller selects higher modulation capacitance (lOnF to 22 nF) during high load (25 W).

[0086] In some implementations, the Power Transmitter can communicate a modulation status packet or other message to cause the Power Receiver to reduce the communication capacitance when there is a possibility of ZVS risk (e.g., the phase angle is less than 20 degrees). The Power Transmitter may demand a high value of communication capacitance if the ASK depth is low. The Power Receiver may change the value of the communication capacitance when a change command comes from the Power Transmitter. The Power Transmitter may measure the ASK depth and phase angle during the power transfer phase.

[0087] Although examples of this disclosure refer to k factor, received power, rectified voltage, ASK depth, etc., as examples of capacitance-related criterion for selecting communication capacitance, other example capacitance-related criterion are possible. For example, the Power Receiver might select a different communication capacitance based on detection of an overvoltage condition. During the ASK modulation, the Power Receiver can monitor the Vrect rectifier voltage. When the Power Receiver detects that the Vrect is over a certain predetermined value (or over the operating point target Vrect) by a threshold amount (e.g., 10%, 15%, 20% or other higher values), then the Power Receiver might adjust the communication capacitance by selecting a different capacitance value or modulator. For example, during the overvoltage condition, the Power Receiver can select a lower value for the communication capacitance than currently being used. As an illustrative example, if the Power Receiver is using a 33nF capacitor before detecting the overvoltage condition, then the Power Receiver can change a lower value (e.g., 15nF) capacitor after detecting the overvoltage condition. After adjusting the capacitor, the Power Receiver continues the ASK modulation using the newly selected capacitor value and continues to monitor the Vrect rectifier voltage. The Power Receiver can detect the overvoltage condition by any variety of criteria, such as when Vrect exceeds certain predetermined value by a threshold amount / percentage, when Vrect exceeds a current operating point Vrect value by a threshold amount / percentage, any other overvoltage criterion, or a combination of criteria.

[0088] FIG. 8 shows a message flow diagram 800 with example operations for selecting communication capacitance. The Power Transmitter 110 and the Power Receiver 130 participate in a procedure (shown as arrow 802) to estimate the coupling factor. In MPP, the calculation of the estimated inductive coupling factor takes place in Power Transmitter 110. The Power Receiver 130 provides information, such as rectified voltage, power profile, and scaling factors. The Power Transmitter 110 transmits low power while measuring the inputvoltage. Based on the measured input voltage and the rectified voltage (as reported by the Power Receiver 130), the Power Transmitter 110 calculates the Kest.

[0089] Shown at arrow 804, the Power Transmitter 110 communicates the Kest to the Power Receiver 130 (such as via a KEST packet). At block 808, the Power Receiver 130 selects communication capacitance based, at least in part, on the Kest. In the power transfer phase, the Power Transmitter 110 transmits wireless power 810 to the Power Receiver 130. The Power Receiver 130 can adjust communication capacitance based on the Kest and the received power (block 812).

[0090] Variations of these operations are possible. Below is an example variation with further detail:1. Kest is performed as per the MPP protocol; This Kest is performed during the configuration / ping phase. The Kest is used for the right MPP profile activation.2. If Kest is low, the Power Receiver 130 selects a default modulation capacitance (e.g., 22 nF or 33 nF). If Kest is high, the Power Receiver 130 activates modulation capacitor control. Prior to any changes based on activation of the modulation capacitor control, the Power Receiver uses the default modulation capacitance (e.g., 22 nF). Modulation capacitor control is active during the power transfer phase.3. Kest is high: Modulation capacitor control to select lower modulation cap (4.7 nF), during light load (5W) requirement of the Power Receiver.4. Kest is high: Modulation capacitor control to select higher modulation cap (lOnF to 22 nF) during high load (25W) requirement of the Power Receiver.

[0091] FIG. 9 shows table 900 of example communication capacitances for various power levels and coupling k factors. The examples are provided only for illustrative purposes and other values of communication capacitance could be used. At BPP / EPP power level (128 kHz), any coupling k factor and a first load power (e.g., 5W) has a corresponding communication capacitance is 47 nF. At MPP power level (360 kHz), a low coupling k factor and a first load power has a corresponding communication capacitance of 4.7-47 nF, and a low coupling k factor and a second load power (e.g., 25W) has a corresponding communication capacitance of 4.7-22 nF. At MPP a high coupling k factor and a first load power has a corresponding communication capacitance of 4.7-10 nF, and a high coupling k factor and second load power has a corresponding communication capacitance of 10-22 nF.

[0092] FIG. 10 shows a flow diagram 1000 with example operations of a Power Receiver. At block 1005, the Power Receiver obtains k factor estimation based on k factor estimation procedure according to the MPP protocol. At decision block 1010, the system determines ifthe k factor is less than the coupling factor threshold. If it is (e.g., low coupling), the flow proceeds to block 1030, and the Power Receiver uses a default modulation capacitance (e.g., 22 nF). If the k factor is not less than the coupling factor threshold (e.g., high coupling), the flow may continue to block 1012 and optionally activate modulation capacitance control.

[0093] At decision block 1015, the system determines if the load requirement is less than the load threshold. If the load requirement is less than the load threshold (e.g., load requirement 5W), the flow proceeds to block 1020, and the Power Receiver uses a first modulation capacitance (e.g., 4.7 nF). If the load requirement is not less than the load threshold (e.g., load requirement 25W), the flow proceeds to block 1025, and the Power Receiver uses a second modulation capacitance (e.g., 10-22 nF).

[0094] FIG. 11 shows a message flow diagram 1100 in which a Power Transmitter communicates a modulation status packet to a Power Receiver to enable adaptive capacitance modulation. The operations shown in FIG. 11 can be performed during the power transfer phase. At block 1103, the Power Transmitter 110 measures the ASK depth and current phase angle associated with a previous communication 1102 from the Power Receiver 130 to the Power Transmitter 110. Shown at arrow 1104, the Power Transmitter 110 can send an attention (ATN) packet to the Power Receiver 130 requesting to communicate. The Power Receiver 130 can respond with a data stream response (DSR) / poll packet 1105 granting permission for the Power Transmitter 110 to communicate. The Power Transmitter 110 communicates a modulation status packet (shown as MOD status packet 1106).

[0095] At block 1107, the Power Receiver 130 processes the modulation status packet to determine if changes are needed to the modulation capacitance. For example, if the modulation status packet indicates the ASK depth is too low (e.g., below 300 mV), the Power Receiver 130 can select a modulator having a higher capacitance. In another example, if the modulation status packet indicates a phase angle less than 20 degrees, the Power Receiver 130 can select a modulator having a lower capacitance. In some implementations, if the modulation status packet indicates low phase angle and low ASK depth, the Power Receiver 130 adjusts to a lower capacitance because priority is given to correcting the low phase angle. In some implementations, the Power Receiver 130 prioritizes low phase angle (rather than low ASK depth) as the capacitance-related criterion for adjusting the modulation capacitance. In some implementations, overvoltage mitigation is an example capacitance-related criterion for adjusting the modulation capacitance.

[0096] Shown at arrow 1108, the Power Receiver 130 communicates an acknowledgement (ACK)Zconfirmation to the Power Transmitter 110 within a maximum time (referred to as(response). In cases, the Power Receiver 130 might not respond to the MOD status packet in time. Shown at block 1109, after N attempts (such as 3) of the Power Transmitter 110 sending a MOD status packet without getting an acknowledgement, the Power Transmitter 110 stops power transmission.

[0097] Variations of these operations are possible. Below is an example variation with further detail:1. PTx measures the ASK depth & communication phase angle during the power transfer phase.2. PTx updates the modulation status packet - MOD status packet.3. PTx sends ATN to PRx (PTx requests to communicate. PRx follows the attention handling as described in a communications protocol specification).4. PRx grants this permission by sending a DSR / poll data packet, enabling the PTx to send its MOD Status packet.5. PTx send the MOD Status packet to PRx.6. PRx controller makes changes to modulation capacitance, and provides the ACK / Confirmation to the PTx, within the max time (tresponse).7. After three failed attempts for communication with PRx with MOD Status, PTx should stop the power.

[0098] FIG. 12 shows an example timing diagram of PRx and PTx communication. At block 1204, the Power Receiver sends an extended control error (XCE) packet. At block 1206, the Power Transmitter communicates an ATN message. At block 1208, the Power Receiver sends a DSR / POLL packet. At block 1210, the Power Transmitter communicates a MOD status packet.

[0099] In some implementations, The Power Receiver is expected to send the ACK 1216 within a maximum time (tresponse 1212), as illustrated in a first example 1202a. In a second example 1202b, the Power Receiver either does not send the ACK 1216 or sends it too late (such as beyond a time out limit (ttimeout 1214). The second example 1202b is an example of a failed attempt to send a MOD status packet and receive ACK.

[0100] FIG. 13 shows an example modulation status packet 1300. The modulation status packet 1300 can indicate an ASK depth 1302 and / or a phase angle 1304. Example values for the fields containing the ASK depth 1302 and the phase angle 1304 are provided below. The following values are provided for illustrative purposes and any variety of packet format, fields, or values can be used to convey modulation status.• Bo -ASK deptho FF - for ASK depth is OK (Depth greater than 300 mV) o FE - for ASK depth is NAK (Depth lesser than 300 mV)• Bi -Phase angle (between current and voltage) o FF - for Phase angle >20 deg (Voltage phase signal should lead higher than 20 deg from the current signal phase) o FE - for Phase angle <20 deg

[0101] Having described the operations and examples in FIG. 1 through FIG. 13, the next several figures provide more background and reasoning for implementing adaptive capacitive modulation. In FIG. 14A through FIG. 20B various impedance analysis plots are shown. The goal of the communication system is to achieve a phase angle of greater than 20 degrees to prevent the Power Transmitter tank circuit from operating in a capacitive region. When the phase angle is greater than 20 degrees, the Power Transmitter tank circuit operates in the inductive region which is desirable for wireless power transfer.

[0102] FIG. 14A shows an impedance analysis plot 1400a for a wireless power system using a baseline power profile with various communication capacitances. FIG. 14B is a more detailed plot 1400b of a portion 1410 of FIG. 14A. At 128 kHz and 5W, the system is primarily inductive in nature (see at arrow 1412 the phase angle is well above 20 degrees). The communication capacitor can be selected to achieve the necessary voltage dip without compromising ZVS. Values up to 47 nF demonstrate no risk of the system impedance shifting to the capacitive region.

[0103] FIG. 15A shows an example plot 1500a of an MPP high coupling condition with and without communication capacitance. FIG. 15B is a more detailed plot 1500b of a portion 1510 of FIG. 15 A. At 360 kHz and 25W, the system is inductive in the absence of communication capacitors (shown at arrow 1514). However, a high-value communication capacitor can shift the system impedance to become capacitive (shown at arrow 1512), posing a risk of losing ZVS. The use of a 47 nF capacitor indicates that the system impedance is nearing a capacitive state (with the impedance curve phase angle approaching negative). Thus, the system impedance imposes an upper limit on the communication capacitor value, while the ASK modulation depth sets a lower limit.

[0104] FIG. 16A shows an example plot 1600a of an impedance analysis for a low coupling condition in an MPP 360 kHz operation. FIG. 16B is a more detailed plot 1600b of a portion 1610 of FIG. 16 A. The plots demonstrate that there is no risk to ZVS under low coupling conditions when using a communication capacitor with a value between 4.7 nF and 22 nF (see at arrow 1612, phase angle is at or above 20 degrees).

[0105] FIG. 17A shows a plot 1700a of MPP load variation at high coupling with a lOnF communication capacitance in an MPP 360 kHz operation. FIG. 17B is a more detailed plot 1700b of a portion 1710 of FIG. 17A. Under high coupling conditions and a 5W load, using a lOnF communication capacitor poses a risk of losing ZVS for the Power Transmitter (see low phase angle below 20 degrees at arrow 1712). Therefore, a lOnF capacitor is unsuitable for this operating condition.

[0106] FIG. 18A shows a plot 1800a of MPP condition using 4.7 nF communication capacitance at 5W to reduce the loss of ZVS risk. FIG. 18B is a more detailed plot 1800b of a portion 1810 of FIG. 18 A. The plots show applying a lower value capacitance such as 4.7 nF can avoid the ZVS risk at 5W (see arrow 1812 showing phase angle above 20 degrees for 4.7 nF modulation capacitor while arrow 1814 shows phase angle below 20 degrees for 10 nF modulation capacitor).

[0107] FIG. 19A shows a plot 1900a of load variation at low coupling (lOnF communication capacitance) in MPP. FIG. 19B is a more detailed plot 1900b of a portion of FIG. 19A. The plots show there is no ZVS risk at low coupling condition with lOnF communication capacitance value (see arrow 1912 where phase angle is above 20 degrees).

[0108] Having described the phase angle and capacitance / inductance considerations in FIG. 14A through FIG. 19B, the next several figures show another consideration for adaptive capacitive modulation. FIG. 20 A through FIG. 2 IB include time domain and frequency domain plots explaining ASK depth as a factor when selecting modulation capacitance. The goal of the communication system is to achieve a sufficient ASK depth (e.g., 300 mv) for the Power Transmitter to successfully sense the ASK modulated bit transitions from LOW to HIGH state. When the ASK depth is below a threshold amount, the Power Transmitter might not detect the bit. Thus, the Power Receiver may use a modulation capacitance that increases ASK depth when it is below the threshold. Meanwhile, too much capacitance might cause the Power Transmitter to operate in the capacitive region which is poor for wireless power transfer. Therefore, the Power Transmitter might select a lowest modulation capacitance that satisfies the minimum ASK depth without causing the phase angle to fall below a phase threshold (such as 20 degrees).

[0109] FIG. 20A shows a time domain analysis 2000a of a 25W wireless power system with high coupling and showing the impact of different communication capacitance (4.7-47 nF). FIG. 20B shows a frequency domain analysis 2000b related to FIG. 20A. The selection of different modulation capacitances can result in varying ASK depth 2002. For example, the modulation capacitance of 4.7 nF has a very small ASK depth. Although 4.7 nF modulationcapacitance is preferable to ensure ZVS, it may be necessary to use a 10 nF if the Power Transmitter reports that the ASK depth is too low to successfully demodulate the communication.

[0110] The time domain analysis 2000a was conducted to determine the ASK depth with different communication capacitor values. As indicated in the frequency domain analysis 2000b for high coupling conditions and a 25W load, the smallest communication capacitor results in the smallest ASK depth 2012. Larger capacitor values, such as lOnF or 22 nF, can be used to achieve better ASK depth. Meanwhile, a larger capacitor, such as 47 nF, poses a threat to ZVS operation (shown at arrow 2010). For ZVS operation, the zero crossing of the tank current needs to lag behind the zero crossing of the inverter voltage (shown at arrow 2008). The inclusion of a communication capacitor reduces this phase lag.

[0111] FIG.21A shows a time domain analysis 2100a with communication capacitance (4.7- 47 nF), 5W, and high coupling. FIG. 21B shows a frequency domain analysis 2100b related to FIG. 21A. The time domain analysis 2100a shows the ASK depth with different communication capacitor values. The frequency domain analysis 2100b indicates that, under light load conditions, a communication capacitor as small as lOnF can threaten ZVS on the Power Transmitter side. Therefore, switching to a high capacitor value should be restricted under light load conditions.

[0112] FIG. 22 illustrates a block diagram of an example apparatus for use in a wireless power system. In some implementations, the apparatus 2200 may be a Power Receiver. The apparatus 2200 can include a processor 2202 (possibly including multiple processors, multiple cores, multiple nodes, or implementing multi-threading, etc.). The apparatus 2200 also can include a memory 2204. The memory 2204 may be system memory or any one or more of the possible realizations of computer-readable media described herein. The apparatus 2200 also can include a bus 2206 (such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus,® AHB, AXI, etc.).

[0113] The apparatus 2200 may include one or more controllers 2208 (such as a PTx controller). In some implementations, the controller 2208 can be distributed within the processor 2202, the memory 2204, and the bus 2206. The controller 2208 may perform some or all of the operations described herein. For example, the controller 2208 may implement the processes described with reference to any one of FIG. 1 through FIG. 12, or any combination thereof.

[0114] The memory 2204 can include computer instructions executable by the processor 2202 to implement the functionality of the implementations described herein. Any one ofthese functionalities may be partially (or entirely) implemented in hardware or on the processor 2202. For example, the functionality may be implemented with an application specific integrated circuit, in logic implemented in the processor 2202, in a co-processor on a peripheral device or card, etc. Further, realizations may include fewer or additional components not illustrated in FIG. 22. The processor 2202, the memory 2204, and the controller 2208 may be coupled to the bus 2206. Although illustrated as being coupled to the bus 2206, the memory 2204 may be coupled to the processor 2202 or the controller 2208.

[0115] The apparatus 2200 also includes a multiple modulators 2210. The multiple modulators 2210 are selectively used by the controller 2208 (which also may be referred to as a control unit, PRx controller, or similar terms. In some implementations, the multiple modulators 2210 are part of a communication unit (not shown). The controller 2208 can use the multiple modulators 2210 to implement adaptive capacitive communication as described in this disclosure.

[0116] FIG. 1 through FIG. 22 and the operations described herein are examples meant to aid in understanding example implementations and should not be used to limit the potential implementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently.

[0117] This disclosure addresses some shortcomings with legacy communication implementations in a wireless power system. A single capacitive modulation circuit across the power range 5W to 25 W may have demodulation issues. The single modulation capacitance may not be capable of communicating effectively across the power range. There are two aspects for the good communication system: PTx readability of the communicated bits, and good system dynamics for ZVS on PTx. Operating conditions can impact ASK demodulation as shown in table 3. Table 3 shows the impact of some vactors, such as (i) High Coupling (ii) 360 kHz (iii) PTx in ZVS operation (>20 deg. phase angle difference) (iv) 5W to 25W power range.Table 3.

[0118] In accordance with an aspect of this disclosure, a potential implementation can use two or more capacitive modulation circuits. A high power (25W) system may use Cl-2 (~10 nF or 22 nF) as the preferred modulation circuit. A low power (5W) system to use C3-4 (~4.7 nF) as the preferred modulation circuit. Generally, a system design guideline is to make Cl- 2 greater than C3-4, in high coupling & 360 kHz.

[0119] In some aspects, the Power Receiver chooses appropriate modulation capacitor based on received power, the rectified voltage, the Kest, the phase change / angle, the operating frequency, or any combination thereof.

[0120] In some aspects the Power Transmitter communicates issues related to modulation depth and ZVS to Power Receiver.

[0121] Some examples of this disclosure refer to a Power Transmitter and a Power Receiver. Typically, a Power Transmitter operates in a power transmission mode to provide power to a Power Receiver. Similarly, a Power Receiver typically operates in a power reception mode to receive power from a Power Transmitter. In some implementations, a device can alternatively receive (in the power reception mode) or transmit (in the power transmission mode). For example, the device can be referred to as a “Power Transceiver,” a “wireless transmitter / receiver device,” a “Power Transmitter / Receiver,” or other terms to refer to the fact that the device is capable of operating in the power reception mode or the power transmission mode at various times. The device can operate as a Power Receiver when in vicinity of the Power Transmitter, and can operate as a Power Transmitter when in vicinity of a different Power Receiver. Thus, a same device (such as a smart phone or accessory) can be a Power Receiver to receive power from an external charger and can also be a Power Transmitter to provide power to another phone or accessory. Other terms for a Power Transceiver might include a “power trans-receiver,” a wireless power transmit and receive unit (WPTRU), or Power Transmit-Receiver (PTRx), among other examples. A Power Transceiver can be any device that is capable of alternatively operating as a Power Receiverand a Power Transmitter. Any of the features attributed to a “Power Transmitter” or a “Power Receiver” in this disclosure can be implemented by device (e.g., Power Transceiver) that operates in power transmission / reception modes.

[0122] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. While the aspects of the disclosure have been described in terms of various examples, any combination of aspects from any of the examples is also within the scope of the disclosure. The examples in this disclosure are provided for pedagogical purposes. Alternatively, or in addition to the other examples described herein, examples include any combination of the described implementation options (enumerated as clauses for clarity).

[0123] Clause 1: A Power Receiver of a wireless power system, the Power Receiver comprising: a power transfer coil for receiving wireless power from a Power Transmitter; a plurality of modulators enabling capacitive modulation of varied capacitance; and a controller configured to communicate with the Power Transmitter using a selected modulator, from among the plurality of modulators, based on a capacitance-related criterion.

[0124] Clause 2: The Power Receiver of clause 1, wherein the capacitance-related criterion is based on at least one of: a power profile presently in use by the Power Receiver, received power, rectified voltage, an operating frequency of the wireless power, a coupling factor (Kest), an amplitude shift keying (ASK) depth, a phase angle, or any combination thereof

[0125] Clause 3: The Power Receiver of clause 1 or 2, wherein the plurality of modulators includes at least a first modulator having a first capacitance and a second modulator having a second capacitance.

[0126] Clause 4: The Power Receiver of any one of clauses 1 to 3, wherein the controller is configured to: receive, from the Power Transmitter, a message (e.g., a KEST packet) indicating an estimated inductive coupling factor (Kest); select the selected modulator based, at least in part, on the Kest.

[0127] Clause 5: The Power Receiver of clause 4, wherein the controller is configured to select the selected modulator based on a combination of the Kest and at least one of a power profile, a load requirement, or a measurement of received power.

[0128] Clause 6: The Power Receiver of clause 4 or 5, wherein the controller is configured to: select a first modulator of the plurality of modulators when the Kest is below a k factorthreshold; select a second modulator of the plurality of modulators when the Kest is above the k factor threshold.

[0129] Clause 7: The Power Receiver of any one of clauses 4 to 6, wherein the controller is configured to: activate modulation capacitor control when the Kest is above a k factor threshold; and select the selected modulator based on the modulation capacitor control, wherein the modulation capacitor control causes the controller to select a first capacitor when the load requirement is below a power threshold, and select a second capacitor when the load requirement is above the power threshold.

[0130] Clause 8: The Power Receiver of any one of clauses 4 to 7, wherein the controller is configured to: select a first modulator having approximately 4.7 nano-farad (nF) capacitance when the Kest is above a k factor threshold and a load requirement is 5 Watts, select a second modulator having capacitance in a range from 10 nF to 22 nF when the Kestis above the k factor threshold and the load requirement is 25 Watts or higher.

[0131] Clause 9: The Power Receiver of any one of clauses 1 to 8, wherein the controller is configured to: receive a modulation status packet from the Power Transmitter, wherein the modulation status packet indicates an amplitude shift keying (ASK) depth, phase angle, or both; and change to a different selected modulator, from among the plurality of modulators, based on the modulation status packet.

[0132] Clause 10: The Power Receiver of clause 9, wherein the controller is configured to select the selected modulator based on which modulator has a capacitance that will produce an ASK depth of at least 300 mV at the Power Transmitter.

[0133] Clause 11: The Power Receiver of clause 9 or 10, wherein the controller is configured to select the selected modulator based on which modulator has a capacitance that will result in a phase angle greater than 20 degrees at the Power Transmitter.

[0134] Clause 12: The Power Receiver of any one of clauses 1 to 11, further comprising: a communication unit that implements the plurality of modulators as multiple modulation circuits that can be individually selected and activated by the controller.

[0135] Clause 13: A Power Transmitter, comprising: a power transfer coil to transmit wireless power to a Power Receiver; a communication unit to: receive a first communication from the Power Receiver; and communicate a modulation status packet to a Power Transmitter, wherein the modulation status packet indicates an amplitude shift keying (ASK) depth, phase angle, or both, of at least the first communication.

[0136] Clause 14: The Power Transmitter of clause 13, further comprising: a controller configured to cause the power transfer coil to cease transmission of the wireless power whenthe communication unit does not receive a response from the Power Receiver in response to N consecutive modulation status packets.

[0137] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this specification belongs. The terms “first,” “second,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The use of terms “including,” “comprising” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “connected” and “coupled” are not restricted to physical or mechanical connections or couplings and can include electrical connections or couplings, whether direct or indirect. Furthermore, terms “circuit” and “circuitry” and “control unit” may include either a single component or a plurality of components, which are either active and / or passive and are connected or otherwise coupled together to provide the described function. In addition, the term operationally coupled as used herein includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software based communication, or combinations thereof.

[0138] Some or all of the foregoing or the following implementations can be jointly combined or formed to be a new or another one implementation. The foregoing or the following techniques can be used to solve at least (but not limited to) the issue(s) or scenario(s) mentioned in this disclosure. Any two or more than two of the foregoing or the following paragraphs, (sub)-bullets, points, actions, or claims described in each method / technique / implementation may be combined logically, reasonably, and properly to form a specific method. Any sentence, paragraph, (sub)-bullet, point, action, or claim described in each of the foregoing or the following technique(s) / implementation(s) / concept(s) may be implemented independently and separately to form a specific method. Dependency, such as “based on,” “more specifically,” “where” or etc., in technique(s) / implementation(s) / concept(s) mentioned in this disclosure is just one possible implementation which would not restrict the specific method.

[0139] Certain techniques are described in this disclosure as including logic or a number of components or modules. Modules can be software modules (e.g. , code, or machine-readable instructions stored on non- transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC),a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g. , as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0140] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general -purpose processors or one or more special-purpose processors.

[0141] As used herein, the terms “component” and “module” are intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software. As used herein, the phrase “based on” is intended to be broadly construed to mean “based at least in part on.”

[0142] As used herein, a phrase referring to a list of items separated by “or” refers to any combination of those items, including single members. For example, “a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

[0143] In this disclosure, an expression of “X / Y” may include meaning of any of the following: “X or Y” or “X and Y” or “X and / or Y." An expression of “(A) B” or “B (A)” may include concept of “only B.” An expression of “(A) B” or “B (A)” may include the concept of “A+B” or “B+A.”

[0144] Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.

[0145] The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed in this specification and the structural equivalents thereof. The interchangeability of hardware, firmware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes describedabove. Whether such functionality is implemented in hardware, firmware or software depends upon the particular application and design constraints imposed on the overall system.

[0146] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process or algorithm disclosed herein can be implemented as one or more modules of one or more computer programs. Such computer programs can include non- transitory processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by, or to control the operation of, a data processing apparatus including the components of the devices described herein. By way of example, and not limitation, such storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0147] Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0148] Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0149] The drawings may schematically depict one or more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing maybe advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. Tn some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

Claims

CLAIMSWhat is claimed is:

1. A Power Receiver of a wireless power system, the Power Receiver comprising: a power transfer coil for receiving wireless power from a Power Transmitter; one or more modulators coupled to the power transfer coil and enabling capacitive modulation; and a controller to: select a communication capacitance from among different capacitance levels of the one or more modulators, and communicate with the Power Transmitter using a modulator of the one or more modulators having a capacitance level that corresponds to the selected communication capacitance.

2. The Power Receiver of claim 1, wherein the controller: selects a first capacitance level as the communication capacitance when the Power Receiver activates a first power profile for a first power level and a first operating frequency of 128 kilohertz (khz); or selects a second capacitance level as the communication capacitance when the Power Receiver activates a second power profile for a second power level higher than the first power level and a second operating frequency of 360 khz.

3. The Power Receiver of claim 1 or 2, wherein the controller selects the communication capacitance based on at least one of: a power profile presently in use by the Power Receiver, received power, rectified voltage, an operating frequency of the wireless power, a coupling factor (Kest), an amplitude shift keying (ASK) depth, a phase angle, an overvoltage condition at the Power Receiver, or any combination thereof.

4. The Power Receiver of any one of claims 1 to 3, wherein the one or more modulators includes at leasta first modulator having a first capacitance level, and a second modulator having a second capacitance level.

5. The Power Receiver of any one of claims 1 to 4, wherein the controller is configured to: receive, from the Power Transmitter, a message (KEST packet) indicating an estimated inductive coupling factor (Kest); and select the communication capacitance based, at least in part, on the Kes(.

6. The Power Receiver of claim 5, wherein the controller performs at least one operation to: select a first capacitance level for the communication capacitance when the Kestis below a k factor threshold; select a second capacitance level for the communication capacitance when the Kest is above the k factor threshold; or activate modulation capacitor control when the Kest is above the k factor threshold, wherein the modulation capacitor control causes the controller to select a first capacitor when a load requirement is below a power threshold, and select a second capacitor when the load requirement is above the power threshold.

7. The Power Receiver of claim 5 or 6, wherein the controller is configured to: communicate using a first modulator having approximately 4.7 nano-farad (nF) capacitance when the Kest is above a k factor threshold and a load requirement is 5 Watts. communicate using a second modulator having capacitance in a range from 10 nF to 22 nF when the Kest is above the k factor threshold and the load requirement is 25 Watts or higher.

8. The Power Receiver of any one of claims 1 to 7, wherein the controller is configured to: receive a modulation status packet from the Power Transmitter, wherein the modulation status packet indicates an amplitude shift keying (ASK) depth, phase angle, or both; and change to a different selected communication capacitance based on the modulation status packet.

9. The Power Receiver of claim 8, wherein the controller is configured to select the communication capacitance based on which capacitance level will produce an ASK depth of at least 300 mV at the Power Transmitter.

10. The Power Receiver of claim 8 or 9, wherein the controller is configured to select the communication capacitance that will result in a phase angle greater than 20 degrees at the Power Transmitter.

11. The Power Receiver of any one of claims 1 to 10, further comprising: a communication unit that implements the one or more modulators as multiple modulation circuits that can be individually selected and activated by the controller.

12. The Power Receiver of any one of claims 1 to 11, wherein the one or more modulators include multiple capacitive modulators, each capacitive modulator having a different capacitance level; and wherein the controller selecting the communication capacitance includes the controller selecting a particular capacitive modulator from among the multiple capacitive modulators based on the particular capacitive modulator having a capacitance level that matches the selected communication capacitance.

13. A Power Transmitter, comprising: a power transfer coil to transmit wireless power to a Power Receiver; a communication unit to: receive a first communication from the Power Receiver; and communicate a modulation status packet to a Power Transmitter, wherein the modulation status packet indicates an amplitude shift keying (ASK) depth, phase angle, or both, of at least the first communication.

14. The Power Transmitter of claim 13, further comprising: a controller to: calculate the ASK depth, phase angle, or both; and generate the modulation status packet to cause the Power Receiver to adjust a communication capacitance of an ASK modulator of the Power Receiver.

15. The Power Transmitter of claim 13 or 14, further comprising: a controller to cause the power transfer coil to cease transmission of the wireless power when the communication unit does not receive a response from the Power Receiver in response to N consecutive modulation status packets.

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