Coupling coefficients in wireless power systems

Abstract

This disclosure provides systems, methods, and apparatus that enable a transmitter in a wireless power system to determine the coupling coefficient k (k-factor). The k-factor represents the amount of magnetic field coupling between the primary coil of the transmitter and the secondary coil of the receiver. The k-factor affects the effectiveness of power transmission at various operating frequencies. In some embodiments, the transmitter can determine the k-factor before power negotiation so that the transmitter can negotiate negotiated power level limits, partly based on consideration of potential operating frequencies and the k-factor. In some embodiments, a k-factor measurement protocol enables the transmitter to adjust the k-factor evaluation before or during a power supply state.

Description

Technical Field

[0001] The present disclosure generally relates to wireless power supply, and some aspects relate to managing wireless power transmission based on the coupling of electromagnetic fields in a wireless power system.

Background Art

[0002] A wireless power system includes a power transmitter (PTx, sometimes called a wireless power transmitting device) and a power receiver (PRx, sometimes called a wireless power receiving device). The power transmitter includes a primary coil that generates an electromagnetic field during the power supply state. When a secondary coil is placed in the electromagnetic field of the primary coil, a voltage is induced in the secondary coil of the power receiver. The induced voltage can generate power for a load or for use by a rectifier that supplies power to the load. Thus, the power transmitter can wirelessly transmit power to the power receiver using inductive coupling between the primary coil and the secondary coil. An electrical product can operate a load (such as, in particular, a motor, a heating element, an electronic device, or a power storage device, etc.) using the power from the power receiver. The power transmitter can control the operating frequency, operating voltage, or other parameters in the power transmitter to control how much wireless power is supplied to the power receiver. Power negotiation and power control messages between the power receiver and the power transmitter can control some aspects of the wireless power system.

[0003] As described, the primary coil of the power transmitter generates an electromagnetic field and the secondary coil of the power receiver captures the magnetic field. The primary coil and the secondary coil form a loosely coupled transformer. The amount of magnetic flux linkage between the power transmitter and the power receiver depends on the magnetic coupling between the primary coil and the secondary coil. The coupling coefficient k (also called the k-factor) is a value indicating how much electromagnetic field is induced from the primary coil to the secondary coil. The coupling coefficient k can depend on the electrical characteristics of the coils, their relative sizes, the distance between the coils, the alignment of the coils, and the presence of other metals in the electromagnetic field.

Summary of the Invention

[0004] Each of the systems, methods, and apparatuses disclosed herein has several inventive embodiments, and no single embodiment alone embodies the desirable attributes disclosed herein.

[0005] In one embodiment, a method performed by a transmitter includes the step of determining a first coupling coefficient k(k-factor) based on a first instance of k-factor evaluation before the power supply state of the wireless power system, where the first k-factor represents the amount of magnetic coupling between the primary coil of the transmitter and the secondary coil of the receiver. The method includes the step of negotiating a negotiated power level limit based at least in part on the first k-factor before the power supply state. The method includes the step of controlling the transmission of wireless power from the transmitter to the receiver based on the negotiated power level limit during the power supply state.

[0006] In one embodiment, a method performed by a receiver includes the step of receiving one or more pulses via the receiver's secondary coil as part of an evaluation of the coupling coefficient k (k-factor), prior to the power supply state of the wireless power system, where the k-factor represents the amount of magnetic field coupling between the transmitter's primary coil and the receiver's secondary coil. The method includes the step of communicating a measurement report message to the transmitter, where the measurement report message includes one or more measurements of one or more pulses in the receiver's secondary coil.

[0007] Details of one or more implementations of the subject matter described herein are given in the accompanying drawings and the following description. Other features, embodiments, and advantages will become apparent from the specification, drawings, and claims. [Brief explanation of the drawing]

[0008] Similar reference numerals and symbols in various drawings indicate the same elements. Note that relative dimensions in drawings may not be drawn to scale.

[0009] [Figure 1] An exemplary wireless power system including a transmitter and receiver is shown.

[0010] [Figure 2] This shows the electromagnetic coupling between the primary and secondary coils.

[0011] [Figure 3] This shows how the coupling coefficient k (k-factor) affects wireless power transmission at various operating frequencies.

[0012] [Figure 4] The present disclosure shows a state diagram of an instance of a wireless power system and a coupling coefficient k (k-factor) that can be evaluated.

[0013] [Figure 5] The following are illustrative operations of a power transmitter according to several aspects of this disclosure.

[0014] [Figure 6] The following are illustrative operations of a power receiver according to several aspects of this disclosure.

[0015] [Figure 7] This diagram shows the timing and related operations of a wireless power system under various conditions.

[0016] [Figure 8A] The following are exemplary k-factor evaluations prior to power negotiation operations, according to several aspects of this disclosure.

[0017] [Figure 8B] The following are exemplary k-factor evaluations prior to the power supply state, according to several aspects of this disclosure.

[0018] [Figure 8C] The following are some embodiments of this disclosure that illustrate another exemplary k-factor evaluation during a power supply state.

[0019] [Figure 9] The present disclosure provides several embodiments of exemplary k-factor evaluation using receiver measurement.

[0020] [Figure 10] A diagram showing timing considerations for k-factor evaluation according to some aspects of the present disclosure.

[0021] [Figure 11] Exemplary operations for k-factor evaluation using transmitter estimation according to some aspects of the present disclosure are shown.

[0022] [Figure 12] Operations in the power supply state of a wireless power system are shown.

[0023] [Figure 13] A communication timing protocol for k-factor evaluation using measurements during the power supply state of a wireless power system is shown.

[0024] [Figure 14] An exemplary transmitter is shown.

[0025] [Figure 15] An exemplary receiver is shown.

[0026] [Figure 16] A block diagram of an exemplary device for use in a wireless power system is shown.

Mode for Carrying Out the Invention

[0027] The following description is directed to specific implementations for the purpose of illustrating inventive aspects of the present disclosure. However, those skilled in the art will immediately recognize that the teachings of this specification can be applied in many different ways. The described implementations can be implemented in any means, device, system, or method for transmitting or receiving wireless power.

[0028] A wireless power system includes a power transmitter (PTx, sometimes called a wireless power transmitting device) and a power receiver (PRx, sometimes called a wireless power receiving device). The transmitter includes a primary coil that generates an electromagnetic field to induce a voltage in the secondary coil of the receiver from the electromagnetic field of the primary coil. The amount of magnetic flux linkage between the transmitter and receiver depends on the magnetic coupling between the primary and secondary coils. The coupling coefficient k (also called the k-factor) is a value that indicates the amount of magnetic field coupling between the primary and secondary coils. The k-factor indicates how much electromagnetic field can be induced from the primary coil to the secondary coil at various operating frequencies during power transmission. The k-factor can depend on the electrical properties of the coils, their relative sizes, the distance between the coils, the alignment of the coils, and the presence of other metals in the electromagnetic field. The quality factor (Q-factor) is another value in a wireless power system. The Q-factor can depend on the thermal or electrical properties of the coils (capacitance, inductance, resistance, etc.). Both the k-factor and the Q-factor can affect the effectiveness of wireless power transmission. This disclosure relates to a protocol for determining the k-factor, but some concepts may also be applicable to Q-factor evaluation.

[0029] This disclosure provides systems, methods, and apparatus that enable a transmitter to determine and use a k-factor during power negotiation and power control operations. In some embodiments, the transmitter may determine the k-factor before power negotiation so that the transmitter can negotiate a negotiated power level limit, partly based on consideration of the potential operating frequency and the k-factor. For example, a low k-factor may result in a lossy or inefficient system. Conversely, a high k-factor may indicate an over-coupled system in which the transmitter cannot meet the rated power of the receiver. By determining the k-factor before power negotiation, the transmitter can determine whether it can meet the requested power. In some implementations, the negotiated power level limit may be limited based on the k-factor. In some implementations, the transmitter may decide based on the k-factor whether to proceed with power transmission or to suppress entering a power supply state.

[0030] In some embodiments, the transmitter and receiver may participate in k-factor evaluation according to a protocol. This disclosure includes several exemplary protocols for managing k-factor evaluation. For example, the k-factor evaluation may include a test signal (such as one or more pulses) during the k-factor measurement period, allowing the receiver to measure the test signal. The receiver may communicate one or more measurements to the transmitter to help the transmitter calculate the k-factor.

[0031] In some embodiments, the first k-factor evaluation may be performed during the discovery or connection state prior to power negotiation. Additionally or alternatively, the second k-factor evaluation may be performed during the connection state before the transition to the power supply state. Furthermore, in some implementations, the k-factor protocol may initiate k-factor evaluation from time to time during the power supply state. When the k-factor changes, the transmitter can determine whether it can still meet the negotiated power level limits. In some implementations, the transmitter may terminate the power supply state when the k-factor changes in such a way that the transmitter can no longer meet the negotiated power level limits, or when the change in the k-factor indicates a fault or foreign object detection in the receiver.

[0032] Certain implementations of the subject matter described herein may be implemented to achieve one or more of the following potential benefits: The k-factor protocol allows transmitters and receivers to adjust k-factor evaluations between different states of a wireless power system. The k-factor protocol may include a predetermined number of k-factor evaluations based on state transitions or protocol messages. Alternatively or additionally, the transmitter can control when and how k-factor evaluations are performed based on communication messages. Thus, the disclosure provides some flexibility for managing k-factor evaluations while also improving the ability to negotiate negotiated power level limits. Furthermore, the k-factor can improve the operation and efficiency of the transmitter by enabling power control based on the measured k-factor.

[0033] Figure 1 shows an exemplary wireless power system 100 including a transmitter 102 and a receiver 118. In Figure 1, dashed lines represent communications and are distinguished from solid lines that represent electrical circuit lines.

[0034] The transmitter 102 includes a primary coil 104 and a transmitter (PTx) controller 108. The primary coil 104 may be associated with a transmitter circuit 106 (sometimes called a power signal generator or driver circuit). The primary coil 104 may be a wire coil that transmits radio power (also called radio energy). The primary coil 104 may transmit radio energy using an inductive field or a magnetic resonance field. The transmitter circuit 106 may include components (not shown) for preparing the radio power. For example, the transmitter circuit 106 may include one or more switches, drivers, series capacitors, rectifiers, inverters, or other components. In some implementations, the transmitter circuit 106, the PTx controller 108, and other components (not shown) may be collectively referred to as a transmitter unit 110. Part or all of the transmitter unit 110 may be embodied as an integrated circuit (IC) that implements features of the present disclosure for controlling one or more radio power receiving devices and transmitting radio power to them. The PTx controller 108 can be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), or any other suitable electronic device.

[0035] Power supply 112 supplies power to the transmitter unit 110. In some implementations, power supply 112 may convert alternating current (AC) power to direct current (DC) power. For example, power supply 112 may include a converter that receives AC power from an external power source and converts the AC power to DC power used by the transmitter circuit 106. Alternatively or additionally, components of the transmitter circuit 106 (such as an inverter) may convert DC power to AC power. Power supply 112 may be integrated as part of the transmitter 102 or may be located outside of the transmitter 102.

[0036] In some implementations, the transmitter 102 causes the power supply 112 to adjust the DC output voltage of the power supply 112. For example, the PTx controller 108 can set the DC voltage of the power supply 112 based on information received from the receiver 118 (such as a value indicating the requested power). The transmitter 102 can receive power configuration information from the receiver 118 and use that information to set parameters (such as the DC output voltage of the power supply 112). The transmitter 102 can receive power configuration information during various operating states, such as discovery state or power supply state. In some implementations, the transmitter 102 includes a DC-DC converter (not shown) between the power supply 112 and the transmitter circuit 106 to control the variable DC output voltage.

[0037] The PTx controller 108 is connected to a first communication interface 114. The first communication interface 114 is connected to a first communication coil 116. In some implementations, the first communication interface 114 and the first communication coil 116 may be collectively referred to as the first communication unit 122. In some implementations, the first communication unit 122 may support Near-Field Communication (NFC). NFC is a technology in which data is transmitted at a carrier frequency of 13.56 megahertz (MHz). In some implementations, the first communication unit 122 may support Bluetooth® (BT) communication. The first communication unit 122 may also support any suitable communication protocol. The first communication unit 122 may include modulation and demodulation circuits for wireless communication via the first communication coil 116. Alternatively, or additionally, the TX controller 108 may use frequency modulation to communicate via an in-band communication link (not shown) including a primary coil 104.

[0038] The power receiver 118 may include a secondary coil 120, a rectifier 124, a power receiver (PRx) controller 126, a second communication interface 130, a load controller 134, a load 128, and memory (not shown). In some implementations, the load 128 may include a drive (not shown) for controlling at least one parameter of the load, such as charging current, speed, or torque. In some implementations, the rectifier 124 may be omitted, for example, when the voltage induced in the secondary coil 120 can directly power the load 128. In some implementations, a series switch (not shown) may be included in series with the secondary coil 120 or in series between the rectifier 124 and the load 128. Although not shown, a load capacitance can be used after the rectifier 124 to reduce the rate of increase in load voltage that occurs when the load 128 suddenly decreases power consumption. Although shown as different components, some components may be packaged or implemented in the same hardware. For example, in some embodiments, the PRx controller 126 and the load controller 134 may be implemented as a single controller. The PRx controller 126, the load controller 134, or any combination thereof may be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), or any other suitable electronic device.

[0039] The PTx controller 108 may detect the presence or proximity of the receiver 118. This detection may occur during a periodic ping process of the first communication interface 114. During the ping process, the first communication interface 114 may also supply power to the second communication interface 130 when the receiver 118 is in proximity to the transmitter 102. The second communication interface 130 may "wake up" the PRx controller 126 to power it on and send a response signal back to the first communication interface 114. A handshake process may occur before power transmission, during which the PTx controller 108 may receive configuration data related to the receiver's power rating, among other information. Based on the configuration data, the PTx controller 108 may control the characteristics of the radio power supplied to the receiver 118.

[0040] The PRx controller 126 can be operably coupled to a rectifier 124 and a second communication interface 130. The second communication interface 130 may include modulation and demodulation circuits for wireless communication via a second communication coil 132. Thus, the PRx controller 126 can wirelessly communicate feedback information to the PTx controller 108 via the second communication interface 130 to the first communication interface 114 using NFC communication. Alternatively, or additionally, the PRx controller 126 may use load modulation to communicate via an in-band communication link (not shown) including a secondary coil 120.

[0041] The load controller 134 may be operably coupled to the load 128 and the second communication interface 130. The load controller 134 may detect changes in load conditions, such as changes in charging current in a battery charging application. The load controller 134 may also determine a load voltage reference. The load controller 134 may also load the voltage reference, load current, and any other appropriate information into the PRx controller 126 or the second communication interface 130 for communication to the transmitter 102. The PRx controller 126 may further determine and provide feedback information indicating the measured load voltage available to the load 128. In some feedback messages, the feedback information may include a reference voltage indicating the voltage required for the load 128. In some feedback messages, the feedback information may indicate an error in the output voltage of the load 128. In some feedback messages, the feedback information may include the power required for the load. Although the PRx controller 126 and the load controller 134 are shown separately, they may be included in the same component of the receiver 118.

[0042] The transmitter 102 controls the operating point of the transmitter circuit 106 using a control loop and a control algorithm. For example, when the PTx controller 108 receives a control error value from the receiver 118, the PTx controller 108 can use the control error value to calculate a reference current (Ireference). The PTx controller 108 also uses a sensor (not shown) to obtain a measured current (Imeasured), which is the current in the transmitter circuit 106. The PTx controller 108 uses Ireference, Imeasured, and the control algorithm to calculate the operating point of the transmitter circuit 106. The operating point can be voltage (also called operating voltage), current (also called operating current), duty cycle, phase shift, or other parameters that control how the transmitter circuit 106 drives the radio power signal to the primary coil 104.

[0043] Figure 2 shows the electromagnetic coupling 200 between the primary coil 104 and the secondary coil 120. The transmitter generates a time-varying magnetic field by driving an alternating current through its primary coil 104. The receiver captures this magnetic field using its secondary coil 120. The primary coil 104 and the secondary coil 120 constitute a loosely coupled transformer. The amount of magnetic flux linkage between the transmitter and receiver depends on the magnetic coupling coefficient k between the two coils, defined as (Equation 1):

number

[0044] The coupling coefficient k in wireless power systems is typically considerably lower than that of conventional core-based transformers, which typically have a k value close to 1 (meaning both coils capture almost all of the magnetic field lines). The best magnetic coupling typically occurs when the two coils are similar in size, properly aligned, and close to each other (e.g., at a distance well smaller than their diameters). The coupling coefficient decreases as the displacement of the coils increases and as the difference in coil sizes increases. The coupling coefficient also decreases as the distance and / or angle between the coils increases. The presence of metal, ferrite, or other magnetically active materials near the coils also affects the coupling coefficient.

[0045] Figure 3 shows how the k-factor affects wireless power transmission at various operating frequencies. Both the transmitter and receiver exhibit resonant behavior. These resonances occur at frequencies fp and fs when they occur individually and therefore without interaction between them (k=0). When the receiver is placed on top of the transmitter, both elements couple, and the resonant frequencies fp and fs repel each other. The resulting system transfer function may have one or two peaks depending on the coupling and receiver quality (Q-factor). Resonance is influenced by the coupling and Q-factor, and the system transfer function has a single peak that occurs at low coupling. Regardless of the number of peaks, the resonance can be shifted from fp and fs. Figure 3 shows graph 300 for examples of different k-factors. The horizontal axis (relative operating frequency 304) shows the operating frequency divided by the primary resonance fp. The vertical axis shows the transfer function 302, which is the voltage across the load divided by the voltage of the transmitter's power supply.

[0046] Examining Graph 300, the first curve 306 shows the transfer function for a coupling coefficient k of k=0.5. The second curve 308 shows the transfer function for a coupling coefficient k of k=0.4. For the first curve 306, it is clear that two distinct peaks appear in the transfer function. The separation between the two peaks may increase as the coupling coefficient k increases. The appearance of the two peaks in the transfer function, and the complex behavior of their positions with respect to frequency, indicates that the coupling coefficient k and load impedance typically have a substantial impact on the power transmission efficiency of the system.

[0047] Experimental test results show that low and high k-factors can affect system performance in different ways. In some cases, a high k-factor may result in the transmitter being unable to meet load demands. For example, a flattened peak in the power transmission curve may mean that the operating frequency cannot be selected to meet the required power. Conversely, a low k-factor (as shown in curve 308) may result in a single large peak that may exceed the transmitter's power capacity. Therefore, some aspects of this disclosure enable the transmitter to determine the k-factor before power negotiation so that the transmitter can determine whether it has enough available power to meet the receiver's power requirements and operate within a k-factor power transfer function.

[0048] Figure 4 shows a state diagram 400 of an instance of a wireless power system and a coupling coefficient k (k-factor) evaluation possible according to an aspect of the present disclosure. The state diagram 400 shows the operating states in which the wireless power system can operate. When a receiver is placed within the interface surface of a transmitter, the receiver and transmitter begin communicating for the purpose of configuring and controlling power transmission. There may be four operating states associated with the wireless power system: a standby state 402 (sometimes called a ping state), a discovered state 404 (sometimes called a configured state), a connected state 406, and a powered state 408 (sometimes called a power transmission state). The technical specification may define how the transmitter and receiver can transition between operating states. For example, a wireless power system typically starts in a standby state 402 until the transmitter discovers the receiver, and then proceeds to a discovered state 404. In the discovered state 404, the transmitter establishes communication and receives the receiver's identification and static configuration data. In connection state 406 and power supply state 408, the transmitter and receiver exchange information to agree on and adjust parameters related to wireless power transmission. The system may, if necessary, move to a reinitialization state (not shown) and reinitialize, or return to a standby state, when communication, power supply, or other activities are no longer taking place. Each of the operating states is briefly described herein for reference.

[0049] In standby state 402, the transmitter attempts to establish communication with the receiver. The receiver may simply be located on the interface surface or may not be present during this operating state. The transmitter may attempt to communicate or detect the presence of the receiver. For example, the transmitter may determine that a suitable receiver is present using analog ping, out-of-band communication (such as NFC), digital ping, or any combination thereof. Once the wireless power system determines that a receiver is present (for example, by confirming NFC communication), the wireless power system may transition to discovery state 404.

[0050] In discovery state 404, the receiver may transmit basic identification and configuration data to the transmitter. For example, the transmitter may retrieve static configuration information from the receiver via NFC communication. The transmitter and receiver may use this information to verify that they are both using compatible versions of the technical specifications or protocols for wireless power transmission. The transmitter and receiver may communicate basic settings or their respective capabilities. From discovery state 404, the wireless power system may transition to connected state 406.

[0051] In connection state 406, the transmitter and receiver may exchange further communications to negotiate parameters governing the power supply state. For example, power negotiation 410 may occur during connection state 406. After negotiating the parameters, the transmitter prepares to transmit wireless power and the receiver prepares to receive wireless power. However, the transmitter may wait for a request or command from the receiver before transitioning to power supply state 408. This may be useful, for example, when cordless electrical appliances (among other examples, blenders, toasters, mixers, or microwave ovens) are configured to be used while withholding user interaction. The user may initiate power supply state 408 by the receiver's user interface (e.g., a power switch), and the receiver also communicates with the transmitter to transition to power supply state 408.

[0052] In the power supply state 408, the transmitter can transmit radio power to the receiver. Typically, the transmitter periodically performs a foreign object detection (FOD) evaluation during the power supply state 408. In some embodiments, the transmitter may perform an FOD evaluation to ensure that no foreign objects are present before transitioning from the connected state 406 to the power supply state 408. The transmitter may also perform a periodic FOD evaluation during the power supply state 408. The standby state 402, the discovered state 404, and the connected state 406 may be collectively referred to as the pre-power supply state, while the power supply state 408 may be referred to as the power supply state.

[0053] According to aspects of this disclosure, a power transmitter may perform one or more k-factor evaluations. For example, a power transmitter may perform a first k-factor evaluation 412 as part of a state transition from a discovered state 404 to a connected state 406. The first k-factor evaluation 412 may be included at the end of the discovered state 404 or at the beginning of the connected state 406. A power transmitter may perform a second k-factor evaluation 414 as part of a transition from a connected state 406 to a powered state 408 (for example, at the end of the connected state 406 or at the beginning of the powered state 408). Additionally or alternatively, a power transmitter may perform one or more further k-factor evaluations 416 during the powered state 408.

[0054] This disclosure includes several examples of k-factor evaluation. For example, k-factor evaluation may be based on measurements taken by the receiver and communicated to the transmitter during the k-factor measurement period. The transmitter may calculate the k-factor based on the measurements. Alternatively, or additionally, k-factor evaluation may include estimations of electromagnetic coupling based on configuration data or other communications from the receiver, without explicit measurements for k-factor evaluation.

[0055] Figure 5 shows exemplary operation 500 of a transmitter according to several aspects of the present disclosure. For example, operation 500 may be performed by transmitter 102 or transmitter 1400, which are described with reference to other figures of the present disclosure. In block 502, the transmitter determines a first coupling coefficient k(k factor) based on a first instance of k factor evaluation before the power supply state of the radio power system, where the first k factor represents the amount of magnetic coupling between the primary coil of the transmitter and the secondary coil of the receiver. In block 504, the receiver includes the step of negotiating a negotiated power level limit based at least in part on the first k factor before the power supply state. In block 506, the receiver controls the transmission of radio power from the transmitter to the receiver based on the negotiated power level limit during the power supply state.

[0056] Figure 6 shows exemplary operation 600 of a receiver according to several aspects of the present disclosure. For example, operation 600 may be performed by receiver 118 or receiver 1500, which are described with reference to other figures of the present disclosure. In block 602, the receiver receives one or more pulses via the receiver's secondary coil as part of an evaluation of the coupling coefficient k (k-factor) prior to the supply state of the wireless power system, where the k-factor represents the amount of magnetic coupling between the primary coil of the transmitter and the secondary coil of the receiver. In block 604, the receiver communicates a measurement report message to the transmitter, which includes one or more measurements of one or more pulses in the receiver's secondary coil.

[0057] Figure 7 shows the timing diagram 700 and associated operations in various states of the wireless power system. The timing diagram 700 is used to illustrate the operations of the receiver (PRx) 118 and the transmitter (PTx) 102. Although described as the operations of the receiver 118 and the transmitter 102, it is clear that the operations can be performed by the PTx controller 108 and the PRx controller 126, respectively. The receiver 118 and the transmitter 102 may follow state diagrams for various operating states, as described with reference to Figure 4. In Figure 7, some operations in the standby and discovery states 404 are omitted for brevity. During the standby state, the user may place an electrical product having a receiver in the interface space of the transmitter. The transmitter discovers the receiver and communicates with it to obtain identification and configuration information (not shown).

[0058] When the receiver 118 has completed the identification and configuration phase, it communicates a state transition request (NEXT / con) 702. The "NEXT" message is a type of communication message that indicates a request to transition to another state. The "NEXT" message also indicates the requested state, such as NEXT / con for a transition request to a connected state, or NEXT / pow for a transition request to a power supply state. The transmitter 102 may respond to the state transition request (NEXT / con) 702 with a response message ("RESP / ok") 704. The "RESP" message can indicate OK ("ok"), NG ("nok"), undefined ("nd"), or busy ("bsy"). In some implementations, the "RESP" message is a response that can indicate an acknowledgment ("ack"), a negation ("nak"), or an undefined ("nd"). In the example in Figure 7, the response (RESP / ok) 704 is either "ok" or "ack," indicating agreement to transition to connection state 406.

[0059] At time 706, the receiver 118 detects that the start switch associated with the load has been turned on. For example, the start switch may include user input indicating a request to start the load. Examples of a start switch include, among others, a button, a flip switch, a knob, or a touchscreen (and associated processor). Some devices may not include a start switch, and the receiver 118 may assume that the load is always ready to receive wireless power. The receiver 118 may participate in power negotiations 708 with the transmitter 102 based on the power requirements of the load. Power negotiations 708 may include one or more power negotiation messages, such as a first power negotiation message 710 from the receiver 118 to the transmitter 102 and a second power negotiation message 712 from the transmitter 102 to the receiver 118.

[0060] Following the power negotiation 708, the receiver 118 sends a state transition request (NEXT / pow) 714 requesting a state transition to the power supply state 408. In some implementations, the transmitter 102 may perform one or more actions with respect to the FOD evaluation 716 before agreeing to the transition to the power supply state 408. In some implementations, the FOD evaluation 716 may need to be performed before the transition from the connected state 406 to the power supply state 408. For the FOD evaluation, the transmitter 102 may scan for foreign objects using various techniques, such as active or passive excitation of a foreign object detection coil, to observe impedance differences indicating the presence of foreign objects. Assuming no foreign objects are detected during the FOD evaluation 716, the transmitter 102 responds with a response (RESP / ok) 718.

[0061] After receiving a response (RESP / ok) 718 in response to a state transition request (NEXT / pow) 714, the receiver 118 can activate the enablement switch 720, allowing the receiver's switch to couple the secondary coil to the receiving circuit (such as a rectifier or load). In the first position (which may be the default or "normal" position), the switch may disable the receiver's secondary coil from conducting energy. For example, the first position may disconnect or uncouple the secondary coil from the power receiving circuit. The first position may open the circuit containing the secondary coil. In the second position, the switch may allow the secondary coil to conduct energy, such as an induced voltage from a magnetic field. After the switch has changed to the second position, the receiver 118 may communicate a power request message 722 (a control message indicating the requested power, such as "CTRL" or "CTRL / rqp") to the transmitter 102.

[0062] Transmitter 102 receives power request message 722 and can enable its power signal generator (such as an inverter) to begin transmitting a wireless power signal 726. In some implementations, the power signal generator is enabled at or after the AC mains power or the first natural zero crossing of the AC cycle (indicated at time 724) following the power request message 722. For systems operating off-grid (such as DC operating PRx), the power signal generator may be enabled a short delay after the power request message 722 is received.

[0063] Figure 7 also shows the activity of communication channel 730 in relation to the timing of the operation of receiver 118 and transmitter 102. Communication channel 730 may be out-of-band communication (such as NFC) using separate antennas and signals. Although communication channel 730 is isolated from the primary and secondary coils, communication through 730 may affect several operations, such as FOD evaluation 716. In some embodiments, the communication signal may be stopped during FOD evaluation 716 to prevent interference. Furthermore, the communication timeline of communication channel 730 shows communications 736, 738, and 740 occurring during communication time slots in the power supply state 408. Communication time slots may occur in relation to zero-crossing events associated with the AC cycle of the radio power signal 726.

[0064] While the operation 700 in Figure 7 served as the background for the explanation, several examples of k-factor evaluation can be described with reference to Figures 8A to 11. There are three exemplary times (positions in various operating states) in which k-factor evaluation may be performed. For example, k-factor evaluation may be performed during the connection state 406 before power negotiation 708 or as part of a state transition. k-factor evaluation may be performed in relation to FOD evaluation 716 before the state transition to the power supply state 408. One or more k-factor evaluations may be performed during 408. Figures 8A to 11 provide further details about these various k-factor evaluations, their potential uses, and related protocols. For example, k-factor evaluation before power negotiation 708 can enable the transmitter to more accurately calculate power capacity and negotiated power level limits. k-factor evaluation before power supply state 408 can enable the transmitter to more accurately calculate the operating point of the radio power signal. The k-factor evaluation during the power supply state 408 allows the transmitter to detect a change in the power transfer function and potentially necessitates the termination of the power supply state 408 to renegotiate the negotiated power level limits.

[0065] Figure 8A shows an exemplary k-factor evaluation 800a prior to power negotiation operation in several aspects of the present disclosure. The messages and operations in Figure 8A include similar messages and operations (with the same reference numbers) as those described with reference to Figure 7. In Figure 8A, the first k-factor evaluation 806 occurs as part of a state transition from discovery state 404 to connected state 406 (for example, at the end of discovery state 404 or the beginning of connected state 406).

[0066] In some implementations, the first k-factor evaluation 806 is initiated by the transmitter 102 following a state transition request (NEXT / con) 702. For example, in the response (RESP / ok) 804, the transmitter 102 may include an indicator to inform the receiver 118 that the transmitter 102 is initiating the first k-factor evaluation 806 as part of a state transition. The procedure for the first k-factor evaluation 806 may include one or more actions and messages, as will be further illustrated with reference to Figure 9.

[0067] The transmitter 102 determines the k-factor by determining a first k-factor evaluation 806, and can use this k-factor in its own process for power negotiation 808. For example, the transmitter 102 may calculate the available power of the transmitter (the power available for the transmitter to transmit to the receiver) based on a power transfer function that takes the k-factor into account. Power negotiation 808 may result in a negotiated power level limit that can be satisfied based on the power transfer function associated with the k-factor.

[0068] In some cases, the transmitter 102 may determine its maximum power transmission capacity under existing k-factor conditions and set a negotiated power level limit accordingly. In some cases, if the k-factor is too high (above a first threshold), the transmitter 102 may determine that it cannot set an operating frequency that will supply the requested negotiated power to the receiver 118. An over-coupled system (high k-factor) may experience a decrease in voltage gain under rated PRx load conditions. Thus, the transmitter may rate higher power, but due to the lower voltage gain, the receiver may not receive the voltage necessary to meet the rated power of the load. In such cases, the transmitter 102 may reject the requested negotiated power and propose a different negotiated power level limit, or the transmitter 102 may notify the receiver 118 that it cannot meet the rated power of the receiver 118.

[0069] In some examples, if the k factor is too low (below the second threshold), the transmitter 102 may determine that the operating frequency required to supply the requested power would cause the transmitter 102 to exceed its available power or PTx rated power, and may reject the requested negotiated power. In some implementations, the transmitter 102 may also notify the receiver 118 that the k factor is low (indicating a low alignment of the primary and secondary coils), and the receiver 118 may prompt the user to correct the alignment by repositioning the receiver 118.

[0070] Figure 8B shows an exemplary k-factor evaluation 800b prior to a power supply state according to several embodiments of this disclosure. The messages and actions in Figure 8B include similar messages and actions (having the same reference numbers) as those described with reference to Figures 7 and 8A. Figure 8B illustrates a second k-factor evaluation 820 performed prior to a state transition to a power supply state 408. In some embodiments, the second k-factor evaluation 820 may be added to the first k-factor evaluation 806. Alternatively, the first k-factor evaluation 806 may be omitted in some implementations. The second k-factor evaluation 820 may be useful to the transmitter 102 in determining a power transfer function (such as curves 306 or 308 described with reference to Figure 3) that assists the transmitter 102 in setting the operating frequency to meet the required power. The procedure for the second k-factor evaluation 820 may include one or more actions and messages, as further described with reference to Figure 9. In some implementations, the response (RESP / ok) 816 (as a response to the state transition request (NEXT / pow) 714) may include an indicator to notify the receiver 118 that the transmitter 102 will begin the second k-factor evaluation 820 before transitioning to the power supply state 408. Figure 8B shows the second k-factor evaluation 820 occurring after the FOD evaluation 716, but the timing of the second k-factor evaluation 820 may be at other points in the connection state 406, such as before the FOD evaluation 716 or after the power request message 722. For example, the second k-factor evaluation (shown as the second k-factor evaluation 824) may be performed before the FOD evaluation 716, as shown in Figure 8C.

[0071] Figure 8C shows another exemplary k-factor evaluation 800c during a power supply state according to several aspects of the present disclosure. The messages and actions in Figure 8C include similar messages and actions (having the same reference numerals) as those described with reference to Figures 7, 8A, and 8B. In Figure 8C, one or more k-factor evaluations 822 may occur during the power supply state 408. The procedure for one or more k-factor evaluations 822 may include one or more actions and messages, as will be further described with reference to Figures 12 and 13. One or more k-factor evaluations 822 may result in an updated k-factor due to a change in alignment or electromagnetic coupling between the primary and secondary coils.

[0072] In some implementations, one or more k-factor evaluations 822 can be added to the first k-factor evaluation 806, the second k-factor evaluation 824, or both. Alternatively, the first k-factor evaluation 806, the second k-factor evaluation 824, or both may be omitted in some implementations. One or more k-factor evaluations 822 may be useful to the transmitter 102 in determining a power transfer function (such as curves 306 or 308 as described with reference to Figure 3) that assists the transmitter 102 in setting the operating frequency to meet the required power.

[0073] In some implementations, if the k-factor changes (for example, if the updated k-factor during the power supply state 408 is different from the first k-factor used in the power negotiation 808), the transmitter may determine, based on the updated k-factor, whether it can still meet the negotiated power level limit. If the change between the first k-factor and the updated k-factor results in the transmitter 102 being unable to meet the negotiated power level limit, the transmitter 102 may exit the power supply state 408 and return to the discovered state 404, or return to the connected state 406.

[0074] Figure 9 shows an exemplary k-factor evaluation 910 using receiver measurements according to several aspects of this disclosure. Timing diagram 900 shows the operation of receiver 118, transmitter 102, and activity on communication channel 730. The exemplary k-factor evaluation 910 may be an example of a first k-factor evaluation 806, a second k-factor evaluation 820, or a second k-factor evaluation 824, as described with reference to Figures 8A, 8B, and 8C. For context and brevity, the exemplary k-factor evaluation 910 is shown in the position of the second k-factor evaluation 820 in Figure 8B.

[0075] In response to a state transition request message 912 (such as a "NEXT" message) from the receiver 118, the transmitter 102 may communicate a RESP / ok message 914. The state transition request message 912 may be "NEXT / con" (such as a state transition request (NEXT / con) 702) or "NEXT / pow" (such as a state transition request (NEXT / pow) 714). For brevity, the state transition request message 912 is referred to as a "NEXT / x" message. In scenarios where the state transition request message 912 is a "NEXT / pow" message, the transmitter 102 may perform the FOD evaluation 716 before (or after) the k-factor evaluation 910.

[0076] The RESP / ok message 914 may include an instruction that the k-factor evaluation 910 will be performed before the state transition. For example, the RESP / ok message 914 may include a hold indicator, flag, or other value to prevent the receiver 118 from immediately taking the next step of the state transition. For example, a hold indicator may prevent the receiver 118 from activating the enable switch in the secondary coil. In some implementations, the hold indicator may be included in the PTx state field of the RESP / ok message 914.

[0077] The k-factor evaluation 910 may be initiated by a k-factor measurement request message 916 from the transmitter 102 to the receiver 118. For example, the k-factor measurement request message 916 may be "MEAS" and may optionally include instructions to measure one or more parameters. The receiver 118 may respond with an acknowledgment 918 (e.g., "RESP / ok") to confirm receipt of the k-factor measurement request message 916.

[0078] During the k-factor measurement period 932, the transmitter 102 transmits one or more pulses 920 for k-factor measurement. In block 922, the receiver 118 measures parameters (among other examples, voltage, current, frequency, etc.) in the secondary coil. For example, the parameters may represent the amount of induced voltage or some reference metric indicating the amount of electromagnetic coupling between the secondary and primary coils, based on one or more pulses 920.

[0079] After the k-factor measurement period 932, the receiver 118 communicates a measurement report 924 to the transmitter 102 to indicate the measured value. The transmitter 102 may respond with a RESP / ok message 926 to acknowledge receipt of the measurement report 924. In block 928, the transmitter 102 can calculate the k-factor based on the measured value in the measurement report 924 and the corresponding measured value taken by the transmitter 102 during the k-factor measurement period 932.

[0080] Following the k-factor evaluation 910, the receiver 118 can proceed to the next action 930, such as a state transition to the requested next state. In an example where the k-factor evaluation 910 takes place after the FOD evaluation 716 and before the state transition to the power supply state, the next action 930 may include operating the switch and communicating a CTRL / rqp message.

[0081] Figure 9 also shows the activity of the communication channel 730 in relation to the k-factor evaluation 910. In some implementations, the receiver 118 and transmitter 102 may temporarily suspend communication during the k-factor measurement period 932 to prevent interference or inaccurate measurements that may occur as a result of the communication.

[0082] Figure 10 shows timing considerations 1000 for k-factor evaluation according to several aspects of this disclosure. An exemplary k-factor evaluation includes the same operations and messages as the k-factor evaluation 910 described with reference to Figure 9. However, the technical specification may define time limits (e.g., maximum duration) for specific operations. For example, the first period (T1) 1010 may be the maximum time allowed between a state transition request message 912 ("NEXT / x") and the next action 930 (e.g., switch activation or a "CTRL / rqp" message). For example, T1 1010 may be a maximum of 100 milliseconds (ms). Transmitter 102 may communicate a k-factor measurement request message 916 to initiate an instance of k-factor evaluation during T1 1010 following the state transition request message 912.

[0083] The transmitter 102 and receiver 118 may be required to complete the k-factor evaluation within a maximum period (T2) 1012 during the first period (T1). For example, T2 1012 could be a maximum of 50 ms between the k-factor measurement request message 916 and the RESP / ok message 926 that completes the k-factor evaluation. In some implementations, the k-factor measurement period may have a maximum period (T3), such as 10 ms.

[0084] Figure 11 shows exemplary operation 1100 for a k-factor evaluation 1110 using transmitter estimation, according to several aspects of this disclosure. The k-factor evaluation 1110 does not have to include measured values ​​or protocol messages. Instead, the transmitter 102 may estimate the k-factor based on data available to the transmitter (shown as block 1112). For example, the transmitter 102 may estimate the k-factor using calculations based on NFC data exchange format (NDEF) parameters and the initial ("start") load resistance or power value of the receiver 118. In some implementations, the transmitter 102 may acquire this data during communication in the discovered or connected state. Although shown following the FOD evaluation 716, the k-factor evaluation 1110 can be performed at any point in the discovered or connected state, including concurrently with other operations such as the FOD evaluation 716.

[0085] Figure 12 shows the operation 1200 in a power supply state 408 of a wireless power system. During power supply state 408, the transmitter applies a power signal 1204 for the duration of Tpower that follows the slot of Tslot, and then turns on the power signal 1204 for another duration of Tpower. This is repeated as long as the transmitter remains in power supply state 408. During a slot, the transmitter or receiver can perform communication 1206 or FOD evaluation 1202. According to some aspects of this disclosure, one or more slots may be used for communication related to k-factor measurement 1208 and k-factor evaluation. There is no particular order or sequence in which slots can include FOD evaluation 1202, communication 1206, or k-factor measurement 1208. However, as illustrated with reference to Figure 13, a communication protocol may allow scheduling of k-factor measurement 1208 in a particular slot.

[0086] Figure 13 shows a communication timing protocol 1318 for k-factor evaluation using measurements during the power supply state of a wireless power system. The top of Figure 13 shows the power signal 1204 occurring for iterative instances of Tpower within the power supply state 408. Slots are indicated by dashed lines (e.g., slot 1302) and typically occur in relation to zero-crossing events of the AC signal corresponding to the power signal 1204. Figure 13 provides examples of how slots may be used for communication, FOD evaluation, or k-factor measurement.

[0087] Every other slot typically alternates between read ("R") and write ("W") slots. In the read slots (such as read slot 1304), the transmitter 102 receives data from the receiver 118. For example, the transmitter 102 can read an NFC tag or other communication containing data from the receiver 118. The read slots may be used by the receiver 118 to communicate power control messages to the transmitter 102. In the write slots, the transmitter 102 can communicate data to the receiver 118, such as writing data to an NFC tag.

[0088] Some of the read slots may be repurposed for FOD evaluation or k-factor measurement. For example, in write slot 1306, transmitter 102 may indicate that the next write slot 1308 will be used for FOD evaluation. To avoid communication interfering with the FOD evaluation, write slot 1308 may refrain from communication during its Tslot. Similarly, k-factor measurement may be requested during a write slot to allow for accurate measurement without communication interference. In write slot 1310, transmitter 102 may communicate a k-factor measurement request message to receiver 118 to indicate that the next write slot 1312 is a k-factor measurement period. During the Tslot of slot 1312, receiver 118 and transmitter 102 may suppress communication. In some implementations, transmitter 102 may transmit at least one pulse during write slot 1312, and receiver 118 may measure a parameter (such as induced voltage) associated with at least one pulse. During the subsequent reading slot 1314, the receiver 118 communicates a measurement report 1316 to indicate the measured values ​​of the parameters.

[0089] Figure 14 shows an exemplary power transmitter 1400. Power transmitter 1400 may be an example of power transmitter 102 as described in this specification. Power transmitter 1400 may include a power supply 112, a power signal generator 106, and a primary coil 104. The power signal generator 106 is shown with a half-bridge circuit for converting DC power from power supply 112 into an AC signal applied to the primary coil 104. Although not shown in Figure 14, power supply 112 may include a converter that converts an AC mains power supply into DC power for power supply 112. Furthermore, power signal generator 106 may be any type of power conversion circuit that can provide an AC signal to the primary coil 104. For example, power signal generator 106 may include a half-bridge circuit with parallel capacitors. Alternatively, power signal generator 106 may include a full-bridge circuit. Power signal generator 106 is also called an inverter.

[0090] The transmitter 1400 may also include a wireless communication interface 114 and a communication coil 116. The wireless communication interface 114 may be configured to transmit or receive communication signals via the communication coil 116 (which may, in other examples, be a coil or a loop antenna). The wireless communication interface 114 may implement short-range radio frequency communication (such as Bluetooth® or Near-Field Communication (NFC)). The wireless communication interface 114 may include logic for controlling one or more switches and other components that cause the transmission and reception of wireless communication signals via the communication coil 116. The wireless communication interface 114 may be configured to communicate with a receiver (not shown) using wireless communication signals.

[0091] In some implementations, the wireless communication interface 114 may communicate with the receiver by transmitting wireless communication signals and detecting changes in the wireless communication signals that represent the communication of information. The wireless communication interface 114 may support the NFC Type 2 tag specification or the NFC Type 4A tag specification, as specified by the NFC specification. During the power supply state, in addition to the communication carrier, the power signal is also active. Due to the frequency range used for the power signal, the intermodulation product of the two signals results in interference that disrupts reliable NFC communication. To avoid this undesirable effect, the power signal may be periodically switched off for short time intervals. These time intervals are sometimes called communication time slots. Typically, communication time slots may occur in relation to zero-crossing events associated with the AC mains power or the AC cycle of a wall outlet.

[0092] The transmitter 1400 also includes a PTx controller 108. The PTx controller 108 may be configured to implement any of the k-factor evaluations described herein, including k-factor measurement, power negotiation, and control of messages and operations for k-factor-based power control. The PTx controller 108 may control the operation of the power signal generator 105. Furthermore, the PTx controller 108 may manage the state of the transmitter 1400 as transitions between various operating states. The PTx controller 108 may communicate with the receiver (such as transmitting or receiving communications) using a wireless communication interface 114. In some implementations, the PTx controller 108 may be implemented in an integrated circuit (IC). The PTx controller 108 may be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), or any other suitable electronic device. In some implementations, the wireless communication interface 114 and the PTx controller 108 may be implemented in a common unit.

[0093] The PTx controller 108 may detect the presence or proximity of a receiver. In some implementations, the presence or proximity of a receiver may be detected based on load changes in response to periodic low-power signals generated by the power signal generator 106 and the primary coil 104. In some implementations, the presence or proximity of a receiver may occur during a periodic ping process of the radio communication interface 114 in the transmitter 1400. Alternatively or additionally, the transmitter 1400 may detect the presence or proximity of a receiver 118 based on communication via radio communication signals associated with the radio communication interface 114. For example, the transmitter 1400 may cause the radio communication interface 114 to periodically or continuously transmit communication or polling signals. In some implementations, the radio communication signals (transmitted by the radio communication interface 114) may include a small amount of power (which may be called communication bias power or bias power) to power one or more components of the receiver.

[0094] The PTx controller 108 can control the characteristics of the radio power that the transmitter 1400 provides to the receiver. After detecting the receiver 118, the PTx controller 108 may receive information from the receiver (via the radio communication interface 114). For example, the PTx controller 108 may receive information as part of a handshake communication with the receiver. Handshake communication (sometimes called a digital handshake) refers to one-to-one communication between the receiver and the transmitter 1400. During the handshake communication, the transmitter 1400 may transmit a first communication signal, and the receiver may respond to the first communication signal by transmitting information (for example, power rating, manufacturer, model, or receiver parameters when operating with a standard transmitter). The PTx controller 108 may use the information received from the receiver to determine at least one operating control parameter (such as frequency, duty cycle, voltage) for the radio power provided to the receiver. To configure wireless power, the PTx controller 108 may modify the frequency, duty cycle, voltage, or any other appropriate characteristics of the power signal generator 106 during the power supply state (indicated as "A" and "B").

[0095] Figure 15 shows an exemplary power receiver 1500. The exemplary power receiver 1500 may be an example of a power receiver 118 described with reference to any of the figures in this specification. The power receiver 1500 may include a load 128, or the load 128 may be an external component connected to the power receiver 1500. The exemplary rectifier 124 shown in Figure 15 is a full-bridge rectifier configured to convert received power from an AC signal into DC power used by the load 128. In some implementations, the power receiver 1400 may not include a rectifier 126. Other types of rectifiers or power conversion units may be used in various implementations. Furthermore, the power receiver 1400 shows an optional capacitor 1504 coupled between the two legs of the rectifier 124. In some implementations, the power receiver 1500 may not include the optional capacitor 1504. Figure 15 also shows a capacitor 1502 which may be coupled to one or more legs of the secondary coil 120. An exemplary power receiver 1500 includes a switch 1506. In Figure 15, the switch 1506 is shown connected in series between one leg of the secondary coil 120 and the rectifier 124. A switch 1406 may be connected before or after the capacitor 1502 when the capacitor 1502 is present at its leg. Although 1506 is shown connected in series, other configurations are possible. For example, instead of a single series switch (such as the switch 1506 shown in Figure 15), the power receiver 1500 may include first and second switches (not shown) connected in series between both legs of the secondary coil 120 and the rectifier 124. The first switch (not shown) may be connected in series with the first leg of the secondary coil 120. The second switch (not shown) may be connected in series with the second leg of the secondary coil 120. The first and second switches may be collectively referred to as a switch. Other types of switches may be used in conjunction with the techniques of this disclosure. For example, the switch may include a shunt switch that can be connected in parallel with the legs of the secondary coil 120. This causes the shunt switch to short-circuit the ends of the secondary coil 120 during the k-factor measurement period.

[0096] The receiver 1500 includes a second communication coil 132, a second communication interface 130, and a PRx controller 126, as described with reference to Figure 1. The second communication coil 132 may be configured to receive communication signals from the transmitter. The second communication interface 130 may include modulation and demodulation circuits for wireless communication via the second communication coil 132 (which may, among other examples, be a coil or a loop antenna). Thus, the PRx controller 126 can wirelessly communicate with the transmitter via the second communication interface 130. In some implementations, the second communication coil 132 may be configured to communicate using NFC or Bluetooth technology.

[0097] The PRx controller 126 can detect the state of the load 128 using a sensing signal 1410. In some implementations, the sensing signal 1410 may be directly related to the load 128. Alternatively, or additionally, the sensing signal 1410 may indicate the state of an optional component, such as an activation switch (not shown) or a load switch (not shown). The activation switch may be based on a user interface, such as a button, a touchscreen, or any component that can indicate a user request to activate the load 128. The load switch (not shown) may include a temperature switch, an overvoltage / overcurrent protection switch, a motor lock, or any type of load-sensitive switch that controls whether the load 128 is active. The PRx controller 126 can control the switch 1406 using a switch signal (SI). According to aspects of this disclosure, the PRx controller 126 may operate the switch signal SI based on a protocol for obtaining k-factor measurements in various states of the wireless power system. For example, the PRx controller 126 may cause the switch 1406 to disconnect the secondary coil 120 from the rectifier 126 (or load 128) during the k-factor measurement period.

[0098] The second communication interface 130 may support the NFC Type 2 tag specification or the NFC Type 4A tag specification, as specified by the NFC specification. In some implementations, the wireless communication unit is configured to communicate with the transmitter by storing information in a passive tag (such as an NFC Type 2 tag) that can be read by the transmitter's wireless communication interface. Alternatively, the wireless communication unit may be configured to communicate with the transmitter by transmitting information in a wireless communication signal (such as using an NFC Type 4A tag) to the transmitter's wireless communication interface.

[0099] The power receiver 1400 shown in Figure 15 may be an example of one type of power receiver 1400. For example, the power receiver 1400 may include a rectifier 126 and be suitable for electrical products that include a load 128 which is one or more motors or any load operated by DC power. Since the power receiver 1400 includes a rectifier 126, the power receiver 1400 may implement a type O control architecture. Other types of power receivers may not have motors and may not require a rectifier 126. For example, the load 128 may be a resistive load (such as a heating element) or any load that can be operated by AC power.

[0100] Figure 16 shows a block diagram of exemplary equipment for use in a wireless power system. In some implementations, equipment 1500 may be a wireless power transmitter (such as transmitter 102) as described in this specification. Equipment 1500 may include a processor 1502 (which may include multiple processors, multiple cores, multiple nodes, or implement multithreading). Equipment 1500 may also include memory 1504. Memory 1504 may be system memory or any one or more of the possible realizations of computer-readable media as described in this specification. Equipment 1500 may also include a bus 1506 (such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB®, AXI, etc.).

[0101] The device 1500 may include one or more controllers 1508 (such as a TX controller) configured to manage the power transmission circuit 106. In some implementations, the controllers 1508 may be distributed within the processor 1502, memory 1504, and bus 1506. The controllers 1508 may perform some or all of the operations described herein. For example, the controllers 1508 may implement the processes described with reference to any one of Figures 4 to 13, or any combination thereof.

[0102] Memory 1504 may include computer instructions that can be executed by processor 1502 to implement the functions of the implementation described herein. Any one of these functions may be partially (or completely) implemented in hardware or on processor 1502. For example, the function may be implemented by an application-specific IC, within the logic implemented on processor 1502, within a coprocessor on a peripheral device or card, etc. Furthermore, the implementation may include fewer or additional components not shown in Figure 15. Processor 1502, memory 1504, and controller 1508 may be coupled to bus 1506. Although shown as coupled to bus 1506, memory 1504 may be coupled to processor 1502.

[0103] The operations described in Figures 1 to 16 and in this specification are examples intended to help understand exemplary implementations and should not be used to limit potential implementations or the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in different sequences, and several different operations.

[0104] The foregoing disclosure provides examples and explanations, but is not intended to be exhaustive or to limit the embodiments to the exact forms disclosed. Modifications and variations may be made in light of the foregoing disclosure or obtained from the practice of embodiments. While embodiments of this disclosure have been described in relation to various examples, any combination of embodiments from any of the examples is also within the scope of this disclosure. The examples in this disclosure are provided for educational purposes. Alternatively, or in addition to other examples described in this specification, the examples include any combination of the following implementation options (identified as subsections for reference):

[0105] term

[0106] (Section 1) A method performed by a transmitter of a wireless power system, A step of determining a first coupling coefficient k(k-factor) based on a first instance of k-factor evaluation before the power supply state of the wireless power system, wherein the first k-factor represents the amount of magnetic field coupling between the primary coil of the transmitter and the secondary coil of the receiver, Prior to the aforementioned power supply state, the step of negotiating a power level limit negotiated at least in part on the first k factor, The steps include controlling the transmission of the wireless power from the transmitter to the receiver based on the negotiated power level limit during the power supply state, A method that includes this.

[0107] (Section 2) The step of determining the aforementioned first k factor is: The method according to paragraph 1, comprising the step of performing the first instance of the k-factor evaluation before the power negotiation while the wireless power system is in a discovered or connected state.

[0108] (Section 3) The step of negotiating the aforementioned power level limits is: A step of calculating the available power of the transmitter based at least in part on the first k factor, The steps include receiving a message from the power receiver indicating the requested power, The steps include determining the negotiated power level limit based at least in part on the available power and the requested power, The method described in item 1 or 2, including the method described in item 1 or 2.

[0109] (Section 4) The first instance of the k-factor evaluation is, The steps include: acquiring configuration data from the receiver while the wireless power system is in a discovered or connected state; A step of estimating the first k-factor based at least partially on the aforementioned configuration data, The method described in any one of items 1 to 3, including the method described in item 1 to 3.

[0110] (Section 5) The first instance of the k-factor evaluation is, The steps include transmitting one or more pulses via the primary coil during the k-factor measurement period, A step of receiving a measurement report message from the power receiver, wherein the measurement report message includes one or more measurements of the one or more pulses in the secondary coil; A step of calculating the first k factor based at least partially on one or more of the aforementioned measurements, The method described in any one of items 1 to 3, including the method described in item 1 to 3.

[0111] (Section 6) The method according to any one of claims 1 to 5, further comprising the step of determining a second k factor after negotiating the negotiated power level limits and before the state transition to the power supply state.

[0112] (Section 7) The step of determining the aforementioned second k factor is: The method according to paragraph 6, comprising the step of performing a second instance of the k-factor evaluation to measure the second k-factor before or after the foreign object detection (FOD) evaluation that occurs as a precursor to the state transition to the power supply state.

[0113] (Section 8) The method of claim 6 or 7, further comprising the step of suppressing a transition to the power supply state if the second k factor differs from the first k factor, and as a result the magnetic field coupling changes after negotiating the negotiated power level limit.

[0114] (Section 9) For each instance of the k-factor evaluation, the transmitter communicates a k-factor measurement request message to the receiver, wherein the k-factor measurement request message is associated with starting the instance of the k-factor evaluation. The steps include receiving an acknowledgment from the receiver that confirms the k-factor measurement request message, The steps include transmitting one or more pulses through the primary coil during the k-factor measurement period of the k-factor evaluation, A step of receiving a measurement report message from the power receiver, wherein the measurement report message includes one or more measurements of the one or more pulses in the secondary coil, A step of calculating the k-factor based at least partially on one or more of the aforementioned measurements, The method described in any one of items 1 to 8, further including the above.

[0115] (Section 10) The method according to the clause, further comprising the step of suppressing communication during the k-factor measurement period.

[0116] (Section 11) The steps include receiving a state transition request message (NEXT / x) from the aforementioned power receiver, The steps include communicating the k-factor measurement request message to initiate an instance of the k-factor evaluation during a first period (T1) following the state transition request message, The steps include completing the k-factor evaluation within the maximum period (T2) of the first period (T1), The method described in item 9 or 10, further comprising:

[0117] (Section 12) The method according to item 11, wherein the k-factor measurement period has a maximum period (T3) during the maximum period (T2).

[0118] (Section 13) The steps include: determining the k-factor which has been updated during the power supply state; The method according to any one of claims 1 to 12, further comprising the step of verifying whether the transmitter can continue to meet the negotiated power level limits based on the updated k-factor.

[0119] (Section 14) The step of determining the updated k-factor from time to time is performed during the power supply state, The steps include: communicating an instruction during the first transmitter communication time slot that the second transmitter communication time slot is a k-factor measurement period; The steps include transmitting at least one pulse via the primary coil during the second transmitter communication time slot, The steps include receiving a measurement report message indicating a measurement value of at least one pulse in the second transmitter communication time slot during a receiver communication time slot following the second transmitter communication time slot, A step of calculating the updated k-factor based at least partially on the measured value of the at least one pulse, The method described in paragraph 15, including the method described in paragraph 15.

[0120] (Section 15) A step of determining whether the transmitter can meet the negotiated power level limit based on the updated k-factor, The steps include: terminating the power supply state based on the determination that the transmitter is unable to meet the negotiated power level limit as a result of the change between the first k factor and the updated k factor; It further includes, The method according to item 13 or 14, wherein the step of terminating the power supply state includes a step of transitioning to the discovery state or the connection state.

[0121] (Section 16) A primary coil configured to transmit wireless power to a receiver, A controller configured to perform the method described in any one of items 1 to 15, A power transmitter that includes a power transmission.

[0122] (Section 17) A method performed by a receiver of a wireless power system, Steps include: receiving one or more pulses via the secondary coil of the receiver as part of evaluating the coupling coefficient k (k-factor) before the wireless power system is powered; and receiving one or more pulses via the secondary coil of the receiver as part of evaluating the coupling coefficient k (k-factor), where the k-factor represents the amount of magnetic field coupling between the primary coil of the transmitter and the secondary coil of the receiver. A step of communicating a measurement report message to the transmitter, wherein the measurement report message includes one or more measurements of the one or more pulses in the secondary coil of the receiver; A method that includes this.

[0123] (Section 18) A step of receiving a k-factor measurement request message from the transmitter, wherein the k-factor measurement request message relates to initiating the k-factor evaluation. The steps include: communicating an acknowledgment to the transmitter confirming the k-factor measurement request message, The steps include measuring one or more pulses during the k-factor measurement period after the acknowledgment response, The method described in paragraph 17, further including the following.

[0124] (Section 19) The method according to item 18, further comprising the step of suppressing communication during the k-factor measurement period.

[0125] (Section 20) During the aforementioned power supply state, The steps include receiving an instruction during the first transmitter communication time slot that the second transmitter communication time slot is a k-factor measurement period, The steps include measuring at least one pulse received in the secondary coil during the second transmitter communication time slot, The steps include communicating a measurement report message indicating the measured value of at least one pulse during the receiver communication time slot following the second transmitter communication time slot, The method described in any one of items 17 to 19, further including the method described in the other item.

[0126] (Section 21) It is a power receiver, A secondary coil configured to receive wireless power from a transmitter, A controller configured to perform the method described in any one of items 17 to 20, A power receiver that includes a power receiver.

[0127] Another inventive aspect of the subject matter described herein may be implemented as a computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform any one of the above functions.

[0128] Another inventive aspect of the subject matter described herein may be implemented as a system having means for implementing any one of the functions described above.

[0129] Another inventive aspect of the subject matter described herein may be implemented as a device having one or more processors configured to perform one or more operations from any one of the methods described above.

[0130] When used in this specification, the phrase “at least one of” or “one or more of” the list of items refers to any combination of those items, including a single member. For example, “at least one of a, b, or c” is intended to include the possibilities of a only, b only, c only, a and b combination, a and c combination, b and c combination, and a, b, and c combination.

[0131] The various exemplary components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in relation to the implementations disclosed in this specification may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware, or software, including the structures disclosed in this specification and their structural equivalents. Hardware, firmware, and software compatibility is generally described in terms of functionality and illustrated in the various exemplary components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0132] Hardware and data processing equipment used to implement the various exemplary components, logic, logic blocks, modules, and circuits described in relation to the embodiments disclosed in this specification may be implemented or run using general-purpose single or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices (PLDs), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this specification. A general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors working with a DSP core, or any other such configuration. In some implementations, specific processes, operations, and methods may be performed by circuits specific to a given function.

[0133] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of the components disclosed in this specification, or various blocks or steps of the methods, operations, processes, or algorithms disclosed in this specification, can be implemented as one or more modules of one or more computer programs. Such computer programs may include non-temporary processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for controlling or executing the operation of a data processing device including the components of the device described in this specification. Such storage media may include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other media that can 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.

[0134] Various modifications to the implementations described herein may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Therefore, the claims are not intended to limit the implementations described herein and are considered to encompass the broadest scope consistent with this disclosure, the principles disclosed herein, and the novel features.

[0135] Furthermore, various features described in this specification in the context of separate embodiments may be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may be implemented separately or in any suitable partial combination in multiple implementations. As described above, features are described and may be initially claimed to operate in a particular combination, but in some cases one or more features from the claimed combination may be decoupled from the combination, and the claimed combination may be directed towards a partial combination or a variation of a partial combination.

[0136] Similarly, while actions are shown in a specific order in the diagram, this should not be understood as requiring that such actions be performed in a specific order or sequentially to achieve the desired result, and that all illustrated actions be performed. Furthermore, a diagram may schematically represent one or more exemplary processes in the form of a flowchart or flow chart. However, other actions not illustrated may be incorporated into the schematicly represented exemplary process. For example, one or more additional actions may be performed before, after, concurrently with, or in between any of the illustrated actions. In some situations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the above-described implementation should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems may typically be integrated together in a single software product or packaged in multiple software products.

Claims

1. A method performed by a transmitter of a wireless power system, A step of determining a first coupling coefficient k (k-factor) based on a first instance of k-factor evaluation before the power supply state of the wireless power system, wherein the first k-factor represents the amount of magnetic field coupling between the primary coil of the transmitter and the secondary coil of the receiver, Prior to the aforementioned power supply state, the step of negotiating a power level limit negotiated at least in part on the first k factor, The steps include controlling the transmission of wireless power from the transmitter to the receiver based on the negotiated power level limit during the power supply state, A method that includes this.

2. The step of determining the first k-factor is: The method according to claim 1, further comprising the step of performing the first instance of the k-factor evaluation before power negotiation while the wireless power system is in a discovered state or a connected state.

3. The step of negotiating the aforementioned power level limits is: A step of calculating the available power of the transmitter based at least in part on the first k factor, The steps include receiving a message from the power receiver indicating the requested power, The steps include determining the negotiated power level limit based at least in part on the available power and the requested power, The method according to claim 1, including the method described in claim 1.

4. The first instance of the k-factor evaluation is, The steps include: acquiring configuration data from the receiver while the wireless power system is in a discovered or connected state; A step of estimating the first k-factor based at least partially on the aforementioned configuration data, The method according to claim 1, including the method described in claim 1.

5. The first instance of the k-factor evaluation is, The steps include transmitting one or more pulses via the primary coil during the k-factor measurement period, A step of receiving a measurement report message from the power receiver, wherein the measurement report message includes one or more measurements of the one or more pulses in the secondary coil; A step of calculating the first k-factor based at least partially on one or more of the aforementioned measurements, The method according to claim 1, including the method described in claim 1.

6. The method according to claim 1, further comprising the step of determining a second k factor after negotiating the negotiated power level limit and before the state transition to the power supply state.

7. The step of determining the second k factor is: The method according to claim 6, further comprising the step of performing a second instance of the k-factor evaluation to measure the second k-factor before or after the foreign object detection (FOD) evaluation that occurs as a precursor to the state transition to the power supply state.

8. The method according to claim 6, further comprising the step of suppressing a transition to the power supply state if the second k-factor differs from the first k-factor, and as a result the magnetic field coupling changes after negotiating the negotiated power level limit.

9. For each instance of the k-factor evaluation, the transmitter communicates a k-factor measurement request message to the receiver, wherein the k-factor measurement request message is associated with starting the instance of the k-factor evaluation. The steps include receiving an acknowledgment from the receiver that confirms the k-factor measurement request message, The steps include transmitting one or more pulses via the primary coil during the k-factor measurement period of the k-factor evaluation, A step of receiving a measurement report message from the power receiver, wherein the measurement report message includes one or more measured values ​​of one or more pulses in the secondary coil, A step of calculating the k-factor based at least partially on one or more of the aforementioned measurements, The method according to claim 1, further comprising:

10. The method according to claim 9, further comprising the step of suppressing communication during the k-factor measurement period.

11. The steps include receiving a state transition request message (NEXT / x) from the aforementioned power receiver, The steps include communicating the k-factor measurement request message to initiate an instance of the k-factor evaluation during a first period (T1) following the state transition request message, The steps include completing the k-factor evaluation within the maximum period (T2) of the first period (T1), The method according to claim 9, further comprising:

12. The method according to claim 11, wherein the k-factor measurement period has a maximum period (T3) during the maximum period (T2).

13. The steps include: determining the k-factor which has been updated during the power supply state; A step of verifying whether the transmitter can continue to meet the negotiated power level limit based on the updated k-factor, The method according to claim 1, further comprising:

14. The step of determining the updated k-factor from time to time is performed during the power supply state, The steps include: communicating an instruction during the first transmitter communication time slot that the second transmitter communication time slot is a k-factor measurement period; The steps include transmitting at least one pulse via the primary coil during the second transmitter communication time slot, The steps include receiving a measurement report message indicating the measured value of at least one pulse in the second transmitter communication time slot during the receiver communication time slot following the second transmitter communication time slot, A step of calculating the updated k-factor based at least partially on the measured value of the at least one pulse, The method according to claim 13, including the method described in claim 13.

15. A step of determining whether the transmitter can meet the negotiated power level limit based on the updated k-factor, The steps include: terminating the power supply state based on the determination that the transmitter is unable to meet the negotiated power level limit as a result of the change between the first k factor and the updated k factor; It further includes, The method according to claim 13, wherein the step of terminating the power supply state includes a step of transitioning to a discovery state or a connection state.

16. A primary coil configured to transmit wireless power to a receiver, A controller configured to carry out the method described in any one of claims 1 to 15, A power transmitter that includes a power transmission.

17. A method performed by a receiver of a wireless power system, Steps include: receiving one or more pulses via the secondary coil of the receiver as part of evaluating the coupling coefficient k (k-factor) before the wireless power system is powered; and receiving one or more pulses via the secondary coil of the receiver as part of evaluating the coupling coefficient k (k-factor), where the k-factor represents the amount of magnetic field coupling between the primary coil of the transmitter and the secondary coil of the receiver. A step of communicating a measurement report message to the transmitter, wherein the measurement report message includes one or more measurements of the one or more pulses in the secondary coil of the receiver. A method that includes this.

18. The steps include receiving a k-factor measurement request message from the transmitter, wherein the k-factor measurement request message relates to initiating a k-factor evaluation, The steps include: communicating an acknowledgment to the transmitter confirming the k-factor measurement request message, The steps include measuring one or more pulses during the k-factor measurement period following the acknowledgment response, The method according to claim 17, further comprising:

19. The method according to claim 18, further comprising the step of suppressing communication during the k-factor measurement period.

20. During the aforementioned power supply state, The steps include receiving an instruction during the first transmitter communication time slot that the second transmitter communication time slot is a k-factor measurement period, The steps include measuring at least one pulse received in the secondary coil during the second transmitter communication time slot, The steps include: communicating a measurement report message indicating the measured value of at least one pulse during the receiver communication time slot following the second transmitter communication time slot; The method according to claim 17, further comprising:

21. It is a power receiver, A secondary coil configured to receive wireless power from a transmitter, A controller configured to carry out the method described in any one of claims 17 to 20, A power receiver that includes a power receiver.

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