Wireless power transmission

Abstract

The power transmitter 101 comprises a driver 201 generating a drive signal for an output resonant circuit comprising a transmitter coil 103 generating a power transmission signal. A resonance detector 307 determines a coupled resonant frequency of the output resonant circuit, the coupled resonant frequency being a resonant frequency of an output resonant circuit of the transmitter coil 103 coupled to a receiver coil 107 that is part of a power transmission input resonant circuit of the power receiver 105. The input resonant circuit has a quality factor of 10 or greater. An estimation circuit 309 determines a coupling coefficient estimate for coupling between the transmitter coil 103 and the receiver coil 107 in response to the uncoupled resonant frequency and a first effective resonant frequency of the output resonant circuit. An adapter 311 sets an operating parameter in response to the coupling coefficient estimate.

Description

Technical Field

[0001] The present invention relates to a wireless power transmission system, and more particularly, although not exclusively, to the operation of a power transmitter that provides inductive power transmission to high-power devices such as kitchen appliances.

Background Art

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

[0003] To provide a significantly improved user experience, it has been proposed to use a wireless power source where power is inductively transmitted from a transmitter inductor within a power transmission device to a receiver coil within an individual device.

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

[0005] Such a configuration enables wireless power transmission to the device without the need for wired or physical electrical connections. In fact, to recharge or supply power from an external source, the device can simply be placed adjacent to or on top of the transmitter coil. For example, the power transmitter can be configured to have a horizontal surface on which the device can simply be placed to supply power.

[0006] Furthermore, such wireless power transmission configurations can be advantageously designed so that the power transmitter can be used with a range of power receivers. In particular, a wireless power transmission approach known as the Qi standard has been defined and is currently under further development. This approach allows power transmitters that meet the Qi standard to be used with power receivers that meet the Qi standard, without having to be from the same manufacturer or dedicated to each other. The Qi standard further includes several features that allow for adaptation of operation to specific power receivers (e.g., depending on a particular power drain).

[0007] The Qi standard is developed by the Wireless Power Consortium, and information about it can be found, for example, on their website http: / / www.wirelesspowerconsortium.com / index.html, where you can find the defined standard document.

[0008] The Wireless Power Consortium has been developing the Ki standard (also known as the Cordless Kitchen standard), based on the Qi standard, with the aim of providing safe, reliable, and efficient wireless power transmission to kitchen appliances. Ki supports much higher power levels, up to 2.2 kW.

[0009] EP2940415A1 discloses an approach for foreign object detection that uses a dedicated detection resonant circuit.

[0010] A potential problem with wireless power transmission is that power transmission performance can be highly dependent on specific conditions. In particular, power transmission performance in terms of efficiency, achievable power levels, and adaptive response time tends to depend heavily on how the transmitter and receiver coils are positioned relative to each other. Generally, more efficient and reliable power transmission tends to be achieved by aligning the coils and bringing them closer together.

[0011] Typically, power transmission performance depends on the coupling ratio or coupling coefficient, with higher coupling coefficients resulting in more efficient power transmission.

[0012] Closer alignment and higher coupling coefficients can be achieved by designing the device such that the positioning of the power receiver relative to the power transmitter is strictly constrained, for example, by restricting the power receiver to one specific location. However, this is generally undesirable as it limits the practicality of the system. For example, in the case of kitchen appliances where the power transmitter is mounted on a countertop, it is preferable that the user simply places the appliance approximately near the power transmitter coil, and the system adapts accordingly. Furthermore, it is preferable that the power transmission function be implemented without requiring mechanical or physical guide structures to restrain the power receiver, for example, that the power transmitter be mounted using a perfectly flat countertop surface.

[0013] To account for the possibility of significant changes in operating conditions, power transmission may be initiated using an initial operating point that provides acceptable performance under worst-case conditions. During power transmission, the control loop can adapt the operating point to a more optimal one. Specifically, power transmission may be initiated at a low power level and gradually increased during power transmission. [Overview of the project] [Problems that the invention aims to solve]

[0014] However, such approaches tend to be suboptimal and do not provide ideal performance. They tend to introduce delays before optimal performance is achieved. In many scenarios and situations, this approach may fail to reach the optimal operating point, for example, because the control loop settles on a local extremum rather than proceeding to global optimization.

[0015] Therefore, improved operation for power transmission systems is advantageous, in particular, approaches that enable increased flexibility, reduced cost, reduced complexity, improved coupling coefficient estimation, backward compatibility, improved suitability for higher power level transmission, improved initialization of power transmission, improved adaptation to specific operating conditions, and / or improved performance.

[0016] Therefore, the present invention preferably seeks to mitigate, reduce, or eliminate one or more of the above-mentioned drawbacks, either individually or in any combination. [Means for solving the problem]

[0017] According to one aspect of the present invention, a power transmitter is provided for wirelessly supplying power to a power receiver via an inductive power transmission signal, the power transmitter comprising: an output resonant circuit including a transmitter coil and at least one capacitor; a driver configured to generate a drive signal for the output resonant circuit to generate an inductive power transmission signal; a resonant detector configured to determine a first coupled resonant frequency of the output resonant circuit during a resonant measurement time interval, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit when the transmitter coil is coupled to a receiver coil of a power transmission input resonant circuit of the power receiver, the power transmission input resonant circuit having a quality factor of 10 or more during the resonant measurement time interval; an estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil in accordance with the uncoupled resonant frequency of the output resonant circuit and the first coupled resonant frequency; and an adapter for setting operating parameters in accordance with the estimated coupling coefficient.

[0018] The present invention can provide improved power transmission in many embodiments. In many embodiments, it can provide improved initial performance and / or faster adaptation and convergence to a preferred operating point. In many embodiments, this approach can provide improved adaptation of power transmission to changing operating conditions. This approach can typically provide advantageous power transmission operation and performance while enabling low-complexity implementations. This approach can enable improved adaptation of typically important parameters of power transmission, thereby enabling improved power transmission and enabling efficient and / or reliable and / or accurate determination of coupling coefficients.

[0019] A particular advantage of this approach is that, in many embodiments, certain estimation processes or calculations can be performed entirely on the power transmitter, without necessarily being performed on the power receiver. This can reduce costs in many scenarios. It can also facilitate implementation and / or provide improved backward compatibility.

[0020] The estimated coupling coefficient can be an estimate of the change in coupling coefficient.

[0021] The uncoupled resonant frequency of a resonant circuit can be the resonant frequency when there is no inductive coupling from the resonant circuit to an inductor that is not part of the resonant circuit. For an output resonant circuit, the uncoupled resonant frequency would be the resonant frequency when the transmitter coil is not coupled to the receiver coil (and typically not coupled to any other inductor).

[0022] The first coupled resonant frequency may be the resonant frequency of the output resonant circuit when the output resonant circuit is coupled to the receiver coil 107 and when the power receiver is in the power transmission position for power transmission.

[0023] In some embodiments, the power transmission input resonant circuit has a quality factor of 20, 50, 100, or even 500 or more during the resonance measurement time interval.

[0024] According to an optional feature of the present invention, the resonance detector controls the driver to generate a drive signal whose frequency changes during a resonance measurement time interval, and determines a first coupled resonance frequency according to at least one of the voltage of the drive signal, the current of the drive signal, and the phase difference between the voltage of the drive signal and the current of the drive signal.

[0025] This can provide a particularly advantageous approach, resulting in a very effective and practical determination of the coupling coefficient and, thus, an improved setting of the operating parameters.

[0026] According to an optional feature of the present invention, the resonance detector controls the driver to perform a frequency sweep of the drive signal from a high frequency to a low frequency, and determines the first coupled resonance frequency as the first detected frequency at which the resonance criterion of the drive signal is satisfied.

[0027] This can provide an improved detection of the coupled resonance frequency for the output resonance circuit in many embodiments, and thus an improved coupling coefficient estimation and an improved setting of the operating parameters leading to improved power transmission.

[0028] According to an optional feature of the present invention, the resonance measurement time interval is during the initialization of the power transmission operation, and the operating parameters are initial operating parameters for the power transmission operation.

[0029] This approach can enable an improvement in the initialization of power transmission. This approach can enable a faster and / or more reliable convergence towards a preferred operating point for power transmission.

[0030] According to an optional feature of the present invention, the driver is configured to generate a drive signal during the power transmission phase according to an iterative time frame comprising at least one power transmission time interval and at least one measurement time interval, wherein the resonant measurement time interval is included in the measurement time interval.

[0031] This approach could enable improved adaptation to changing operating conditions during power transmission, particularly in relation to the movement of the power receiver relative to the power transmitter.

[0032] In many embodiments, the duration of the measurement time interval is 5%, 10%, or 20% or less of the duration of the time frame. In many embodiments, the duration of the measurement time interval is 70%, 80%, or 90% or more of the time frame. In many scenarios, the duration of the measurement time interval does not exceed 5 milliseconds, 10 milliseconds, or 50 milliseconds.

[0033] According to an optional feature of the present invention, the operating parameter is a parameter that controls the power level of the power transmission signal.

[0034] This can provide particularly advantageous operation in many embodiments.

[0035] The parameters that control the power level of a power transmission signal may specifically be parameters of the drive signal, such as the frequency, duty cycle, phase, current, and / or voltage of the drive signal.

[0036] According to an optional feature of the present invention, the operating parameter is a power loop parameter, which is a loop parameter of a power control loop configured to adapt the power level of a power transmission signal in response to a power control message received from a power receiver.

[0037] This can offer particularly advantageous operation in many embodiments. It can allow the control response for power transmission to dynamically adapt and / or optimize to the current state. This approach can enable faster control operation while ensuring control loop stability in many scenarios.

[0038] The loop parameters may specifically be the loop gain and / or loop delay.

[0039] According to an optional feature of the present invention, the estimation circuit is further configured to determine an estimated coupling coefficient value according to the uncoupled resonant frequency of the power transmission input resonant circuit.

[0040] This could enable improved estimation of coupling coefficients in many scenarios. It can also facilitate the determination of coupling coefficient estimates.

[0041] The uncoupled resonant frequency of a power transmission input resonant circuit would be the resonant frequency of the power transmission input resonant circuit when the receiver coil is not coupled to the transmitter coil (and typically not coupled to any other inductor).

[0042] According to an optional feature of the present invention, the resonant detector is further configured to determine a second coupled resonant frequency of the output resonant circuit during a resonant measurement time interval, the second operating resonant frequency being a different resonant frequency of the output resonant circuit in the presence of a power receiver, and the estimation circuit is further configured to determine an estimated coupling coefficient value according to the second operating resonant frequency.

[0043] In many embodiments, this can provide particularly advantageous and / or enhanced operation and / or performance.

[0044] According to an optional feature of the present invention, the estimation circuit is configured to determine the coupling coefficient estimates according to at least one of the following equations:

number

[0045] Here, f p f is the uncoupled resonant frequency of the resonant output circuit, s is the uncoupled resonant frequency of the power transmission input resonant circuit, Fres1 is the first coupled resonant frequency, Fres2 is the second coupled resonant frequency, and k is the coupling coefficient.

[0046] In many embodiments, this can provide particularly advantageous and / or enhanced operation and / or performance.

[0047] According to another aspect of the present invention, a wireless power transmission system is provided which includes a power transmitter and a power receiver, wherein the power transmitter is configured to wirelessly supply power to the power receiver via an inductive power transmission signal, and the power transmitter is An output resonant circuit comprising a transmitter coil and at least one capacitor; a driver configured to generate a drive signal for the output resonant circuit to generate an inductive power transmission signal; and a resonant detector configured to determine a first coupled resonant frequency of the output resonant circuit during a resonant measurement time interval, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit when the transmitter coil is coupled to a receiver coil of a power transmission input resonant circuit of the power receiver, the power transmission input resonant circuit comprising a resonant detector having a quality factor of 10 or more during the resonant measurement time interval; an estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil in accordance with the uncoupled resonant frequency of the output resonant circuit and the first coupled resonant frequency; and an adapter for setting operating parameters in accordance with the estimated coupling coefficient, wherein the power receiver comprises a power transmission input resonant circuit comprising a receiver coil 107 and at least one capacitor for extracting power from the power transmitter, the power transmission input resonant circuit having a quality factor of 10 or more during the resonant measurement time interval.

[0048] According to an optional feature of the present invention, the power receiver further includes a circuit for switching from a power transmission mode in which the quality factor is not restricted to 10 or more during the resonant measurement time interval to a measurement mode, wherein the quality factor is 10 or more when the power receiver is operating in measurement mode.

[0049] In many embodiments, this can provide particularly advantageous and / or enhanced operation and / or performance.

[0050] According to an optional feature of the present invention, the power receiver further includes a circuit for short-circuiting the power transmission input resonant circuit during the resonant measurement time interval.

[0051] In many embodiments, this can provide particularly advantageous and / or enhanced operation and / or performance.

[0052] According to another aspect of the present invention, a method is provided for operating a power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, the power transmitter having an output resonant circuit including a transmitter coil and at least one capacitor, the method comprising: generating a drive signal for the output resonant circuit to generate an inductive power transmission signal; determining a first coupled resonant frequency of the output resonant circuit during a resonant measurement time interval, the first coupled resonant frequency being the resonant frequency of the output resonant circuit when the transmitter coil 103 is coupled to the receiver coil 107 of the power transmission input resonant circuit of the power receiver, the power transmission input resonant circuit having a quality factor of 10 or more during the resonant measurement time interval; determining an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil in accordance with the uncoupled resonant frequency of the output resonant circuit and the first coupled resonant frequency; and setting operating parameters in accordance with the estimated coupling coefficient. [Brief explanation of the drawing]

[0053] Embodiments of the present invention will be described with reference to the drawings, merely as examples. [Figure 1] A figure showing examples of elements of a power transmission system according to several embodiments of the present invention. [Figure 2] Figure 1 shows an example of an equivalent circuit of a power transmission system. [Figure 3] A figure showing examples of elements of a power transmitter according to several embodiments of the present invention. [Figure 4] A diagram showing an example of a half-bridge inverter for a power transmitter. [Figure 5] A diagram showing an example of a full-bridge inverter for a power transmitter. [Figure 6] A figure showing an example of elements of a power receiver according to several embodiments of the present invention. [Figure 7] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 8] Figure 3 shows an example of the coupled resonant frequency of the output resonant circuit of the power transmitter as a function of the coupling coefficient. [Figure 9] Figure 3 shows an example of the coupled resonant frequency of the output resonant circuit of the power transmitter as a function of the coupling coefficient. [Figure 10] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 11] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 12] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 13] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 14] Figure 3 shows an example of the response of the output resonant circuit of the power transmitter. [Figure 15] Figure 1 shows an example of a time frame for a wireless power transmission system. [Modes for carrying out the invention]

[0054] The following description focuses on embodiments of the present invention applicable to wireless power transmission systems utilizing power transmission approaches such as those known from the Qi or Ki standards. However, it will be understood that the present invention is not limited to this application and may be applied to many other wireless power transmission systems.

[0055] Figure 1 shows an example of a power transmission system according to several embodiments of the present invention. The power transmission system includes a power transmitter 101 including (or coupled to) a transmitter coil / inductor 103. The system further includes a power receiver 105 including (or coupled to) a receiver coil / inductor 107.

[0056] The system provides an inductive electromagnetic power transmission signal that can inductively transmit power from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal, which is propagated as magnetic flux by a transmitter coil or inductor 103. The power transmission signal can typically have a frequency between approximately 20 kHz and approximately 500 kHz, in the case of a Qi-compatible system, a frequency in the range of 95 kHz to 205 kHz, and in the case of a Ki-compatible system, a frequency in the range of 20 kHz to 80 kHz. The transmitter coil 103 and the receiving coil 107 are loosely coupled, and therefore the receiving coil 107 picks up (at least a portion of) the power transmission signal from the power transmitter 101. Thus, power is transmitted from the power transmitter 101 to the power receiver 105 via radio inductive coupling from the transmitter coil 103 to the receiving coil 107. The term "power transmission signal" is primarily used to refer to the inductive signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the receiving coil 107, but it will be understood that, as an equivalent, it may also be considered and used to refer to the electrical signal supplied to the transmitter coil 103 or extracted by the receiving coil 107.

[0057] In this embodiment, the power receiver 105 is specifically a power receiver that receives power via a receiver coil 107. However, in other embodiments, the power receiver 105 may include a metallic element, such as a metal heating element, in which case the power transmission signal directly induces eddy currents that result in direct heating of the element.

[0058] The system is configured to transmit substantial power levels, and specifically in many embodiments, the power transmitter can support power levels of 500mW, 1W, 5W, 50W, 100W, or more than 500W. For example, in a Qi-enabled application, power transmission can typically range from 1 to 5W for low-power applications (basic power profile), up to 15W for Qi standard version 1.2, up to 100W for high-power applications such as power tools, laptops, drones, robots, etc., and over 100W or even over 2000W for very high-power applications such as kitchen applications.

[0059] The operation of the power transmitter 101 and power receiver 105 will be described below with particular reference to embodiments suitable for higher-power kitchen specifications, which generally conform to the Qi or Ki standards (except for modifications and extensions described herein or that are necessarily required thereto) or are being developed by the Wireless Power Consortium. In particular, the power transmitter 101 and power receiver 105 may conform to or be substantially compatible with elements of Qi standard version 1.0, 1.1, or 1.2 (except for modifications and extensions described herein or that result therefrom).

[0060] Many wireless power transmission systems, particularly high-power systems such as Ki, utilize resonant power transmission in which the transmitter coil 103 is part of a resonant circuit, and typically the receiver coil 107 is also part of a resonant circuit. In many embodiments, the resonant circuit can be a series resonant circuit, and therefore the transmitter coil 103 and receiver coil 107 can be coupled in series with a corresponding resonant capacitor. The use of a resonant circuit tends to provide more efficient power transmission.

[0061] In most power transmission systems, a communication channel is established between the power transmitter 101 and the power receiver 105 before power transmission begins. Once communication is established and identification of the two devices is achieved, the power transmitter 101 can begin transmitting power to the power receiver 105.

[0062] Figure 2 shows an example of an electrical equivalent diagram of the power transmission function of a power transmitter 101 and a power receiver 105. Various power transmitters and power receivers can exist in a given system, and they can have significantly different characteristics and parameters. For example, coil size, inductance, and load can vary considerably. Therefore, system parameters can actually vary considerably between different devices, mechanical configurations, positioning, etc., as specifically shown in Figure 2. In particular, the placement of the power receiver, and thus the relative positions of the receiving coil 107 and the transmitter coil 103, can substantially affect the coupling between the coils, i.e., the primary (transmitter) inductor Lp and the secondary (transmitter) inductor Ls, and thus can significantly alter the system behavior.

[0063] Furthermore, power receivers can have several different modes of operation, in which, for example, several loads may be switched on or off in different modes. For example, if the power receiver is an air flyer device, heating elements may be switched on and off. This may cause very large load steps, for example, from 50 to 1200W, or vice versa. Moreover, such load switching may be repeated during the operation of the device to maintain a constant temperature.

[0064] The system may also include nonlinear loads instead of resistive elements, and the power receiver may drive a motor, such as the motor in a food processor. This results in a completely different system response, which has a significant impact, especially on the control system design.

[0065] Typically, wireless power transmission systems use a power control loop to guide the system towards the appropriate operating point. This power control loop varies the amount of power transmitted from the power transmitter to the power receiver. The received power (or voltage or current) can be measured, and an error signal can be generated based on the set power value. The device sends this error signal to the power control function of the power transmitter, reducing this static error to ideally zero.

[0066] However, the system's performance and operation vary greatly depending on the combination and arrangement of existing power transmitters and receivers, and therefore the appropriate operating point also varies considerably. This includes the state during power transmission startup / initialization, and consequently, the optimal initial operating point also varies significantly.

[0067] One of the main parameters affecting operation is the coupling coefficient. Furthermore, the coupling coefficient tends to depend on the positioning of the power receiver relative to the power transmitter (specifically, the power receiver coil 107 relative to the power transmitter coil 103), and therefore depends on specific operating conditions. In contrast, most of the other parameters in Figure 2 tend to be known and tend to be relatively constant for a particular combination of power transmitter and receiver coils 107. Thus, typically, almost all relevant system parameters will be known, except for the coupling coefficient. The coupling coefficient, in particular, depends on several parameters, including the size / shape of the coils and the distance between the power transmitter and power receiver.

[0068] The system in Figure 1 includes a function for estimating the coupling coefficient and adapting the operating parameters accordingly. Specifically, in many embodiments, parameters of the control loop, such as the open-loop transfer function and / or loop gain, may be adapted to optimize and control closed-loop performance. As another example, a preferred (typically early) operating point, such as the power level, may be adapted according to the coupling coefficient. Measurement and adaptation may be performed before power transmission in some embodiments, or alternatively or additionally, after power transmission.

[0069] As an illustrative example, once a power receiver is placed on a power transmitter, communication can be established between them. This allows the power transmitter to begin transmitting power, but first, a suitable operating point must be established. One option is to select a very safe and reliable operating point that can be guaranteed to work in worst-case scenarios, and then gradually adapt the operating point during power transmission. However, such an approach tends to be slow and inefficient, and in fact, in many scenarios, it may be impossible to gradually adapt to the optimal operating point (for example, the system may stick to a local maximum rather than progressing to a global maximum).

[0070] Therefore, it may be preferable to determine a desired operating point and begin operation at or near this desired operating point. The desired operating point can be estimated using all known system parameters. These may include (or consist of) primary and secondary inductances, primary and secondary resonances, load resistance, power and voltage, and coupling coefficients, for example. With all these parameters known, the transfer function of the power path can be calculated and the initial operating point can be determined. However, while most parameters can be known by the power transmitter, for example, based on communication of power receiver parameters from the power receiver, the coupling coefficients depend on the arrangement / mismatch of the equipment and therefore cannot be known in advance.

[0071] Therefore, in this example, the power transmitter can proceed to measure / estimate the coupling coefficient. This can be done, for example, by determining one or more resonant frequencies of the power transmitter resonant circuit when loaded by the power receiver. The power receiver may enter a high-Q mode during such measurement, and the resonant frequency can be determined by the power transmitter by frequency sweep of the signal driving the transmitter coil 103. Based on the resonant frequency, the coupling coefficient can be calculated based on the self-propelled resonant frequencies of the power receiver resonant frequency and the power transmitter resonant frequency.

[0072] Then, using these coupling coefficients, the complete transfer function can be calculated, and the initial operating point and required operating parameters, such as the initial power level and / or loop gain, can be determined. By setting the operating parameters to the calculated values, it becomes possible to reach the initial operating point from the start of power transmission, resulting in the appropriate power / current being supplied to the power receiver.

[0073] In fact, by measuring the coupling coefficients of the power transmission system before power is transmitted, a better estimate of the system response can be made. This can lead to a better selection of the initial operating point (power signal frequency, duty cycle, loop gain, etc.). This can allow the desired power level to be reached much faster. Furthermore, such an approach can reduce the risk of overvoltage or overcurrent conditions occurring.

[0074] Furthermore, measuring the coupling coefficient during power transmission and adapting the operating parameters based on such measurements can provide improved performance and typically offer more precise optimization and adaptation.

[0075] Figure 3 shows the elements of the power transmitter 101 in Figure 1 in more detail.

[0076] The power transmitter 101 includes a driver 301 capable of generating a drive signal supplied to the power transmitter coil 103, which in turn generates an electromagnetic power transmission signal, thereby providing power transmission to the power receiver 105. The transmitter coil 103 is part of an output resonant circuit, which includes the transmitter coil 103 and the capacitor 303. In this example, the output resonant circuit is a series resonant circuit, but it will be understood that in other embodiments, the output resonant circuit may be a parallel resonant circuit. It will be understood that any suitable resonant circuit, including one containing multiple inductors and / or capacitors, may be used.

[0077] The driver 301 generates the current and voltage supplied to the output resonant circuit and, therefore, to the transmitter coil 103. The driver 301 is typically a drive circuit in the form of an inverter that generates an AC signal from a DC voltage. The output of the driver 301 is usually a switch bridge that generates the drive signal by the proper switching of the switches of the switch bridge. Figure 4 shows a half-bridge switch bridge / inverter. Switches S1 and S2 are controlled so that they are never closed at the same time. Alternately, S1 is closed while S2 is open, and S2 is closed while S1 is open. The switches are opened and closed at a desired frequency, thereby generating an AC signal at the output. Typically, the output of the inverter is connected to the transmitter inductor via a resonant capacitor. Figure 5 shows a full-bridge switch bridge / inverter. Switches S1 and S2 are controlled so that they are never closed at the same time. Switches S3 and S4 are controlled so that they are never closed at the same time. The switches S1 and S4 are closed alternately while S2 and S3 are open, and the switches S2 and S3 are closed while S1 and S4 are open, thereby generating a square wave signal at the output. The switches are opened and closed at the desired frequency.

[0078] The power transmitter 101 further comprises a power transmitter controller 305 configured to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 may include many functions necessary to perform power control according to the Qi or Ki standard.

[0079] The power transmitter controller 305 is configured to control the generation of drive signals by the driver 301, and in particular can control the power level of the drive signals, and therefore the level of the generated power transmission signals. The power transmitter controller 305 includes a power loop controller that controls the power level of the power transmission signals in response to power control messages received from the power receiver 105 during the power transmission phase.

[0080] The power transmitter controller 305 may further include functions for communicating with the power receiver 105. For example, the power transmitter controller 305 may be configured to transmit data to the power receiver 105 by modulating the power transmission signal and to receive data from the power receiver 105 by detecting load modulation of the power transmission signal. In other embodiments, it will be understood that other means of communication may be used, such as implementing a separate communication function like NFC communication.

[0081] The use of a resonant circuit including the transmitter coil 103 is well known to provide more efficient power transmission in many scenarios. Furthermore, a power receiver that similarly uses a resonant circuit, i.e., when the receiver coil 107 is part of the resonant circuit, can result in resonant power transmission that offers numerous advantages, including highly efficient power transmission and ease of control of power transmission, for example, by controlling the frequency of the drive signal.

[0082] Figure 6 shows some exemplary elements of the power receiver 105.

[0083] The receiver coil 107 is coupled to the power receiver controller 601 via a capacitor 603 that forms an input resonant circuit together with the receiver coil 107. Therefore, power transmission can be resonant power transmission between resonant circuits.

[0084] The power receiver controller 601 couples the power receiver coil 107 to the load 605, particularly via a switch 607 capable of short-circuiting the load 605. The power receiver controller 601 includes a power control path that converts the power extracted by the receiver coil 107 into a suitable supply for the load 605. In some embodiments, the power receiver controller 601 can provide a direct power path that simply connects the input resonant circuit to the switch 607 or the load 605, i.e., the power path of the power transmitter controller 303 can be implemented by simply two wires. In other embodiments, the power path may include, for example, a rectifier and, optionally, a smoothing capacitor to supply a DC voltage. In yet another embodiment, the power path may include more complex functions such as, for example, a voltage control circuit, an impedance matching circuit, or a current control circuit. Similarly, it will be understood that the switch 607 may be present only in some embodiments, and in some embodiments the load 605 may be permanently coupled to the input resonant circuit.

[0085] Furthermore, the power receiver controller 601 may include various power receiver controller functions required to perform power transmission, in particular functions required to perform power transmission in accordance with the Qi or Ki standard.

[0086] The power receiver controller 601 may further include functions for communicating with the power transmitter 101. For example, it may be configured to decode and demodulate data modulated on the power transmission signal, and to transmit data to the power transmitter 101 by load modulating the power transmission signal. In some embodiments, separate communication functions such as NFC communication functions may be employed.

[0087] During operation, the system is configured to control the drive signal so that the power transmission signal achieves appropriate operating parameters / characteristics and power transmission operates at the appropriate operating point. To do this, the power transmitter is configured to control the parameters of the drive signal using a power control loop in which the power characteristics of the power transmission signal / drive signal are controlled in response to power control error messages received from the power receiver.

[0088] At regular, typically frequent intervals, the power receiver sends a power control error message to the power transmitter. The power receiver 105 is equipped with functions to support such a power control loop; for example, the power receiver controller 601 can continuously monitor the power or voltage of the load signal supplied to the load and detect whether it is above or below a desired value. It can generate a power control error message at regular intervals requesting that the power level of the power transmission signal be increased or decreased, and it can send this power control error message to the power transmitter.

[0089] Upon receiving a power control error message from the power receiver, the transmitting controller 305 may determine how the drive signal parameters should be modified to increase or decrease the power level of the power transmission signal as required. It can then control and adapt the drive signal parameters accordingly.

[0090] Therefore, a power control loop is used in the power receiver to control the power characteristics of the power transmission signal to bring about a desired operating point. Thus, the operation of power transmission is controlled by the power control loop, and its effective operation is crucial to the system's performance. Therefore, initializing or adapting the power control loop to the operating conditions is important for optimal performance.

[0091] In the described system, the power transmitter has the function of estimating the coupling coefficient and adapting the operation of the power transmission system, specifically the power control loop, based on the coupling coefficient.

[0092] The power transmitter is specifically configured to determine the coupling coefficient to the power receiver in response to the detection / measurement of one or more resonant frequencies of the output resonant circuit (and / or equivalently, the drive signal) when coupled to the receiver coil 107 and the input resonant circuit. It can then adapt the operation of the power transmission system accordingly.

[0093] The power transmitter 101 includes a resonant detector 307 configured to determine the coupled resonant frequency of the output resonant circuit during a resonant measurement time interval, the coupled resonant frequency being the resonant frequency of the output resonant circuit in the presence of a power receiver, i.e., when the transmitter coil 103 is coupled to the receiver coil 107 of the power receiver. Thus, the coupled resonant frequency reflects the effective resonant frequency of the output resonant circuit when the transmitter coil 103 is coupled to the receiver coil 107. Due to the coupling of the two coils, the effective inductance of the transmitter coil 103 is different from the self-inductance of the transmitter coil 103 when it is not coupled to either receiver coil 107. Similarly, the effective inductance of the receiver coil 107 is different from the self-inductance of the receiver coil 107 when it is not coupled to either transmitter coil 103. As a result, in the absence of coupling, the effective resonance is different from the self-resonance. Furthermore, due to the coupling of the two coils, and therefore the two resonant circuits, the drive signal effectively experiences two (different) resonant frequencies; that is, due to the coupling, the output resonant circuit effectively has two resonant frequencies, which are different from the self (uncoupled) resonant frequency of the output resonant circuit.

[0094] The effective resonant frequency or coupled resonant frequency of the output resonant circuit differs from the self-resonant frequency of the output resonant circuit when not coupled to another inductor, and the difference depends on the coupling. Therefore, detecting the coupled resonant frequency or operating resonant frequency of the output resonant circuit can provide information about the coupling to the receiver coil 107, which can be used in the power transmitter 101 to estimate the coupling coefficient.

[0095] The resonant detector 307 is coupled to an estimation circuit 309 configured to determine an estimated coupling coefficient for the coupling between the transmitter coil 103 and the receiver coil 107, based at least on the coupled and uncoupled resonant frequencies of the resonant output circuit. The uncoupled frequency of the output resonant circuit is the resonant frequency of the output resonant circuit when it is not coupled to the inductor, specifically the receiver coil 107. The uncoupled resonant frequency is also called the self-resonant frequency of the output resonant circuit.

[0096] Therefore, the estimation circuit 309 is configured to estimate the coupling coefficient based on the effect of the coupling between the transmitter coil 103 and the receiver coil 107 on the resonant frequency of the output resonant circuit.

[0097] The estimation circuit 309 is coupled to an adapter 311 configured to set operating parameters according to the coupling coefficient estimates. In some embodiments, this setting may be relative or absolute. The adapter 311 can perform relative setting of operating parameters by, for example, increasing or decreasing the parameter value by a given amount, for example, increasing or decreasing the power level from the current value.

[0098] In some embodiments, the adapter 311 may be configured to set parameter values ​​for a power transmission signal that control the power level of the power transmission signal, specifically by adapting or setting operating values ​​for power transmission signal parameters. Such parameter values ​​may include frequency (which affects the power level of the resonant power transmission system), phase of the power transmission signal, amplitude (current and / or voltage), or duty cycle.

[0099] For example, with a high coupling coefficient, power transmission between coils is efficient, and therefore a high power level can be set. On the other hand, with a low coupling coefficient, power transmission is less efficient, and therefore a lower level should be set.

[0100] Therefore, by estimating the coupling coefficient, it is possible to determine an appropriate power level, and when initiating power transmission operation, this can be initialized to that power level set to the desired value by appropriately setting the operating parameters of the power transmission signal.

[0101] The appropriate power level can be determined, for example, using a lookup table (LUT) generated during manufacturing. For example, based on measurements performed on different power receivers having different characteristics (e.g., coil dimensions, power receiver inductance values, etc.), the appropriate power level for different coupling coefficients can be determined and stored in the LUT. During operation, when initializing a new power transmission with a new power receiver, the power receiver can transmit relevant parameter values ​​to the power transmitter, which can further estimate the coupling coefficients. The resulting values ​​can be used to perform a table lookup in the LUT, and the power transmission can be initialized with the corresponding power level. The LUT can, in particular, output appropriate values ​​for the frequency, duty cycle, and / or amplitude of the drive signal. The adapter 311 can then provide this information, for example, to the power transmitter controller 305, which can control the driver 301 to generate a drive signal with these characteristics. Thus, the system can start a power transmission with the appropriate parameters, and then adaptation can be performed by the power control loop.

[0102] In some embodiments, the adapter 311 may, alternatively or additionally, adapt power control loop parameters of the power control loop to control the power level of the power transmission signal based on power control messages received from the power receiver (105).

[0103] The open-loop performance of a power control loop is highly dependent on the coupling coefficient, and therefore the closed-loop performance is similar. In fact, in many scenarios, the closed loop may only be stable for a certain number of coupling coefficient values. Typically, the loop gain is substantially proportional to the coupling coefficient, and if the coupling coefficient changes significantly, the gain will also change. Variations in the loop gain directly affect the closed-loop time (and frequency) response, including the loop's stability. Adapter 311 may be configured to modify the loop gain to compensate for variations in the coupling coefficient so that the overall gain can reach a desired level. This can provide optimized performance with a faster operating loop, as there is no need to set the loop gain to guarantee stability in the worst-case scenario.

[0104] In some embodiments, more complex adaptations of the loop may be made, such as tuning the delay or (open-loop) frequency response. This can provide more flexible adaptations, which may allow for more precise customization of performance. For example, the filter response may be adapted to prevent any potential self-oscillation and instability.

[0105] Regarding the power level of a power transmission signal, the parameters can be determined, for example, by measurement and experimentation during design / manufacturing, and the appropriate parameters are stored in the LUT. In fact, the same LUT can store parameters for both the control loop and power level settings.

[0106] It will be understood that the applicable operating parameters are not limited to power level parameters or loop parameters, and other parameters, such as foreign object detection parameters or communication parameters, may be set alternatively or additionally in some embodiments.

[0107] In different embodiments, the estimator 309 may use a different approach to determine the coupling coefficients. As shown in the example in Figure 7, the response of the output resonant circuit when coupled to the input resonant circuit includes two resonances. Figure 7 shows an example of the response to typical system parameters (amplitude and phase of the primary current with respect to the amplitude of a constant voltage of the drive signal), and as clearly shown, the response includes two resonance peaks.

[0108] Figure 8 shows an example of how the resonant frequency of a coupled output resonant circuit changes for different coupling coefficients k. For example, the uncoupled resonant frequencies of both the output and input resonant circuits are 0.3 × 10⁻⁶. 5 This is the normalized frequency. As can be seen, when coupled, it yields a first resonant frequency above the uncoupled frequency and a second resonant frequency below the uncoupled frequency. Also, as is clear, there is a strong dependence of the resonant frequency on the coupling coefficient, and the difference increases as the coupling coefficient increases.

[0109] Figure 9 corresponds to Figure 8, but the normalized average uncoupled resonant frequency of the output resonant circuit is 0.268 × 10⁻⁶. 5 Therefore, the normalized mean uncoupled resonant frequency of the input resonant circuit is still 0.3 × 10⁻⁶. 5 An example is shown. As you can see, this results in a slightly different coupling resonance frequency.

[0110] In some embodiments, dependency measurements, as shown in Figures 8 and 9, may be performed during manufacturing and design for the relevant power transmitter and receiver coil 107 combinations. The results may be stored in a LUT included in the power transmitter (or, for example, stored centrally and read out when setting up a new power transmission). Following the determination of the coupling resonant frequency, a table lookup may be performed by the estimator 309 to derive the estimated coupling coefficients.

[0111] In some embodiments, the resonant detector 307 can be configured to detect the coupled resonant frequency during the resonant measurement time interval by varying the frequency of the drive signal, specifically by performing a frequency sweep over a frequency range that can correspond to the frequency interval in which the coupled resonant frequency is expected to exist, or where the coupling coefficient can be considered sufficiently high to provide acceptable power transmission. The resonant detector 307 can then monitor the drive signal and, for example, detect extreme values ​​of current or voltage amplitude. For example, in the case of a series resonant circuit, the resonant detector 307 can control the driver 301 to vary the frequency with a constant voltage amplitude over a certain range. The current amplitude can then be measured for different frequencies to determine the coupled resonant frequency at which the maximum current amplitude is measured. As another example, the resonant detector 307 can detect when the phase difference between the current and voltage of the drive signal is zero (or close to zero), i.e., when the load by the output resonant circuit is purely resistive. If the coupled resonant frequency is not detected within the frequency interval, this indicates that the coupling coefficient is not within a suitable interval for power transmission, and power transmission may be terminated.

[0112] In some embodiments, the frequency sweep of the drive signal may be from higher frequencies to lower frequencies, and the coupled resonant frequency can be determined as the first frequency detected in which a resonance criterion (e.g., an extremum of the signal's current or voltage amplitude or a zero phase difference between voltage and current) is satisfied. Thus, instead of detecting a global extremum, for example, a first local extremum may be detected.

[0113] Such an approach may allow for the detection of two maximum coupling resonance frequencies. The inventors recognized that the greatest variation in coupling resonance frequency with respect to a changing coupling coefficient occurs for the highest coupling resonance frequency, and therefore this can be typically advantageous, especially when only one coupling resonance frequency is used.

[0114] In some embodiments, both coupling resonance frequencies may be detected and used to determine the coupling coefficient estimate. For example, two separate LUTs may be provided for the low coupling resonance frequency and the high coupling resonance frequency, and the coupling coefficient estimate may be determined as the average of the two table lookup results.

[0115] In other embodiments, other approaches may be used to determine the coupled resonant frequency of the output resonant circuit. For example, in some embodiments, a successive approximation approach can be used. Such an approach would be very advantageous and useful when determining the resonant frequency based on frequency intervals. This approach may enable fast detection of one or more resonant frequencies.

[0116] In some embodiments, the power receiver can communicate system parameters to the power transmitter, such as the uncoupled resonant frequency and / or receiver coil inductance, which can then be used to determine the coupling coefficient from the coupled resonant frequency. For example, the LUT may also depend on these power receiver coefficients, or different LUTs may be provided to different power receivers (in fact, in some embodiments, the LUT may be provided by the power receiver).

[0117] In some embodiments, the determination of the coupling coefficients can be based on an analytical formula. Specifically, the estimation circuit 309 may be configured to determine the coupling coefficient estimates according to at least one of the following equations:

number

number

[0118] Here, f p f is the uncoupled resonant frequency of the resonant output circuit, sis the uncoupled resonant frequency of the power transmission input resonant circuit, Fres1 is the highest coupled operating resonant frequency, Fres2 is the lowest coupled resonant frequency, and k is the coupling coefficient.

[0119] These equations are applied to a coupled resonant circuit and can be used (directly or indirectly) by the resonant detector 307.

[0120] In some embodiments, only one of these equations is used, and in fact, the coupling coefficient estimate may be based on only one of the coupling resonant frequencies. For example, as described, the highest coupling resonant frequency may be determined by detecting the first peak in a sweep from high to low frequencies. Based on the first equation above, the coupling coefficient estimate can be calculated using this highest coupling resonant frequency, with known values ​​for the uncoupled resonant frequencies of the input and output resonant circuits, respectively.

[0121] Using the same approach, the coupling coefficients can be determined based on the lowest coupling resonance frequency.

[0122] In some embodiments, both the highest and lowest coupling resonance frequencies can be measured, and both formulas can be used. For example, two coupling coefficient values ​​can be calculated using the first and second formulas and their respective measured coupling resonance frequencies, and a coupling coefficient estimate can be generated as the average of these. In other embodiments, the coupling coefficient estimate can be calculated to yield the smallest error between the above formulas and the measured values.

[0123] In some embodiments, both coupled resonant frequencies and both equations can be used, but the uncoupled resonant frequency of the input resonant circuit is not used. Instead, this variable can be estimated using the above equations and the two coupled resonant frequencies. Thus, in such an approach, more complex estimations and calculations can be used to avoid the need for specific characteristics of the input resonant circuit to be known by the power transmitter. Such an approach may be particularly useful in implementations in existing systems where some power receivers may not be able to communicate this information.

[0124] The approach described is based on estimating the coupling coefficient by considering the change in resonant frequency caused by the coupling of the output resonant circuit to the input resonant circuit. This change depends not only on the coupling coefficient but also on the quality factor Q of the input resonant circuit. This is evident from Figures 10-14, which show how the two coupled resonant frequencies change for different coupling coefficients (in each graph, k = [0.1, 0.2, ..., 0, 9]), but also how the change depends on the Q value (this can be seen by comparing the different graphs, each showing graphs for Q = 1000, 10, 3, 1, 0.1).

[0125] In this approach, the quality factor of the input resonant circuit is 10 or greater during the resonance measurement time interval, and may typically be higher. This ensures that the detection of the coupled resonant frequency is reliable and reasonably accurate, and therefore, the coupling coefficient estimation is also reliable and accurate. Thus, it can ensure that the adaptation of the operating point is reliable and enables efficient operation.

[0126] In some embodiments, a high Q during the resonant measurement time interval can be ensured by a power receiver designed such that the Q value of the input resonant circuit is always greater than 10, i.e., the input resonant circuit always has a quality factor greater than 10. However, this is typically in contrast to the desire to supply adequate power to the load.

[0127] For example, in the case of a Ki system, a load on the input resonant circuit with a typical power value results in a Q factor that is typically less than 5, often less than 2.

[0128] Therefore, in many embodiments, the power receiver may be configured to switch operating modes from a low-quality coefficient mode for at least a certain period outside the resonant measurement time interval to a high-quality coefficient mode having a Q value of at least 10 during the resonant measurement time interval. This can enable efficient power transmission and efficient coupling coefficient estimation. Thus, the power receiver may be configured to switch from a power transmission mode in which the quality coefficient is not constrained to be greater than 10 and may actually be substantially less than 10 to enable efficient power transmission to a measurement mode during the resonant measurement time interval in which the quality coefficient is 10 or greater.

[0129] This can be achieved, for example, by switch 607. For example, if the power path directly couples switch 607 and load 605 to the input resonant circuit, the switch can normally couple load 605 to the input resonant circuit outside of the resonant measurement time interval. However, during the resonant measurement time interval, switch 607 can disconnect load 605. In the case of an input parallel resonant circuit, switch 607 can disconnect load 605, for example, so that no current is drawn from the input resonant circuit. In contrast, in the case of an input series resonant circuit, switch 607 can disconnect the load by short-circuiting load 605, thereby short-circuiting the power transmission input resonant circuit during the resonant measurement time interval.

[0130] In some embodiments, such changes in the quality factor can occur without the power receiver having any particular function. For example, in some embodiments, the load can essentially provide an essentially short circuit during startup, which can essentially allow a resonant measurement time interval preceding power transmission with a high-Q input resonant circuit. For example, when the load is a motor, it can start up almost like a short circuit. Another example is when a rectifier and a high-power capacitor are present in the power path, which also behaves almost like a short circuit when the capacitor is discharged.

[0131] In many embodiments, a resonant measurement time interval (or at least one resonant measurement time interval) may precede power transmission. Specifically, the determination of coupling coefficient estimates and the setting of operating parameters may be performed during the initialization of the power transmission operation. Thus, before power transmission, the power transmitter can determine appropriate operating parameter values ​​for a particular power receiver and a specific position of the power receiver. Power transmission can then be initiated using these parameter values ​​as initial operating parameter values.

[0132] For example, in many embodiments, this approach can be used to determine the initial loop gain and power level values ​​of the power transmission signal. Thus, the system can begin power transmission with a higher probability of being close to the optimal operating point, eliminating the need for slow and incremental adaptation from a safe operating point for the initial worst-case scenario. Therefore, faster optimization can be achieved, and the risk of failing to reach the best operating point can be reduced.

[0133] Furthermore, during the coupling coefficient estimation before power transmission, the power receiver can enter a measurement mode for detecting the coupling resonant frequency. Specifically, switch 607 can short-circuit the load to provide a high-quality coefficient to the input resonant circuit. When the system enters the power transmission phase, the power receiver can switch to the normal power transmission operating mode, specifically the short circuit can be removed.

[0134] In some embodiments, this approach may be applied alternatively or additionally during the power transmission phase. In such approaches, coupling coefficient estimation may be particularly useful for adapting loop parameters and performance. For example, it may be used to adapt loop parameters so that substantially the same control performance can be achieved for different positions of the power receiver. Thus, improved performance, in particular reduced sensitivity to variations in the position of the power receiver, can be achieved.

[0135] In many embodiments in which this approach is used during the power transmission phase, the system may be configured to operate in a time slot mode in which measurement and coupled resonant frequency detection are performed during a measurement time interval. The resonant measurement time interval may, specifically, be performed during a reduced measurement time interval of an iterative time frame further comprising at least one power transmission time interval in which power is transmitted to a power receiver.

[0136] Therefore, in such embodiments, the system can utilize time division during the power transmission phase. In particular, the detection of the coupled resonant frequency and power transmission can be performed, for example, at separate time intervals, thereby allowing for a substantial reduction in interference between them.

[0137] In this example, the driver 301 and transmitter coil 103 are configured to generate an electromagnetic power transmission signal for the purpose of transmitting power to a power receiver during the power transmission interval. In addition, the drive signal may be used to detect the coupling resonant frequency in order to determine the coupling coefficient estimate during the measurement time interval. The power transmitter may employ a repeating time frame for the drive signal during the power transmission phase, and the time frame includes at least one power transmission time interval and at least one resonant measurement time interval. An example of such a repeating time frame is shown in Figure 15, where the power transmission time interval is denoted by PT and the measurement time interval (this time interval may also be called the detection time interval) is denoted by D. In this example, each time frame FRM includes only one resonant measurement time interval and one power transmission time interval, and these (as well as the time frame itself) have the same duration in each frame. However, it will be understood that in other embodiments, other time intervals (e.g., communication intervals) may be included in the time frame, or that multiple resonance measurement time intervals and / or power transmission time intervals may be included in each time frame. Furthermore, in some embodiments, the duration of each time interval (and in fact the time frame itself) may change dynamically.

[0138] In this approach, measurement, communication, and power transmission are separated in the time domain, thereby reducing mutual interference between power transmission and measurement and coupling coefficient estimation. Therefore, variability and uncertainty arising from variations in operating conditions for power transmission can be isolated from measurement and estimation, resulting in a more reliable and accurate estimation process. Furthermore, it allows a drive signal to be generated (and optimized) for the detection of the coupling resonant frequency. In particular, the resonant detector 307 can perform frequency sweeps and operate in a manner suitable for this detection.

[0139] Furthermore, this allows the power receiver to be specifically adapted to provide improved or optimal characteristics for detection. In particular, in many embodiments, the power receiver can switch from a power operating mode during the power transmission time interval, in which the load is coupled to the input resonant circuit (and therefore the quality coefficient of the input resonant circuit is low), to a measurement mode, for example, by short-circuiting the load with switch 607, thereby ensuring that the quality coefficient of the input resonant circuit is high. Thus, the time-slot approach can enable or facilitate the effective estimation of coupling coefficients during the power transmission phase.

[0140] In some embodiments, the power transmitter may be configured to determine an index or measurement of misalignment of the power receiver relative to the power transmitter (particularly of the power receiver coil 107 relative to the power transmitter coil 103). Specifically, a lower coupling coefficient indicates a larger misalignment. Furthermore, in such embodiments, the power transmitter may be configured to generate a user output indicating the misalignment. Specifically, it can provide a user warning indicating to the user that the power receiver should be repositioned if the coupling coefficient falls below a threshold.

[0141] For clarification, the above description will be understood to have illustrated embodiments of the invention with reference to different functional circuits, units, and processors. However, it will be apparent that any appropriate distribution of functions between different functional circuits, units, or processors can be used without departing from the invention. For example, functions that are shown to be performed by separate processors or controllers may be performed by the same processor or controller. Thus, references to specific functional units or circuits should be considered only as references to appropriate means for providing the described functions, and not as indicating a strict logical or physical structure or organization.

[0142] The present invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The present invention may optionally be implemented at least partially as computer software running on one or more data processors and / or digital signal processors. Elements and components of embodiments of the present invention can be implemented physically, functionally, and logically in any suitable way. In fact, functionality may be implemented in a single unit, in multiple units, or as part of other functional units. Therefore, the present invention may be implemented in a single unit, or it may be physically and functionally distributed among different units, circuits, and processors.

[0143] Although the present invention has been described in relation to several embodiments, it is not intended to be limited to any particular form described herein. Rather, the scope of the present invention is limited only by the appended claims. Furthermore, while certain features may appear to be described in relation to a particular embodiment, those skilled in the art will recognize that various features of the described embodiments can be combined in accordance with the present invention. In the claims, the term “comprising” does not preclude the existence of other elements or steps.

[0144] Furthermore, although listed individually, multiple means, elements, circuits, or method steps may be implemented, for example, by a single circuit, unit, or processor. Additionally, individual features may be included in different claims, but these may be advantageously combined in some cases, and inclusion in different claims does not mean that the combination of features is unfeasible and / or unfavorable. Also, including a feature in one category of claims does not imply limitation to that category, but rather indicates that the feature is equally applicable to other claim categories as needed. Including a feature in a dependent claim of an independent claim does not imply limitation to that independent claim, but rather indicates that the feature is equally applicable to other independent claims where appropriate. Furthermore, the order of features in a claim does not imply a specific order in which the features must operate, and in particular, the order of individual steps in a method claim does not imply that the steps must be performed in that order. Rather, the steps can be performed in any suitable order. Furthermore, singular references do not exclude plurals. Therefore, references such as "a," "an," "first," "second," etc., do not exclude plurals. The reference numerals in the claims are provided merely as clear examples and should not be construed as limiting the scope of the claims in any way.

Claims

1. A power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, A transmitter coil and an output resonant circuit having at least one capacitor, A driver configured to generate a drive signal for the output resonant circuit in order to generate the aforementioned inductive power transmission signal, A resonance detector configured to measure the first coupled resonance frequency of the output resonance circuit during a resonance measurement time interval, wherein the first coupled resonance frequency is the resonance frequency of the output resonance circuit in which the transmitter coil is coupled to the receiver coil of the power transmission input resonance circuit of the power receiver. An estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil, depending on the uncoupled resonance frequency and the first coupled resonance frequency of the output resonant circuit, An adapter for setting operating parameters according to the estimated coupling coefficients, It has, A power transmitter in which the operating parameters are power loop parameters, which are loop parameters of a power control loop configured to adapt the power level of the inductive power transmission signal in response to a power control message received from the power receiver.

2. The power transmitter according to claim 1, wherein the resonance detector controls the driver to generate the drive signal having a fluctuating frequency during the resonance measurement time interval, and measures the first coupled resonance frequency according to at least one of the voltage of the drive signal, the current of the drive signal, and the phase difference between the voltage of the drive signal and the current of the drive signal.

3. The power transmitter according to claim 1 or 2, wherein the resonance detector is configured to control the driver to perform a frequency sweep of the drive signal from a high frequency to a low frequency, and to measure the first coupled resonance frequency as the first detected resonance frequency at which a resonance criterion for the drive signal is satisfied.

4. The power transmitter according to any one of claims 1 to 3, wherein the resonance measurement time interval is during the initialization of the power transmission operation, and the operation parameter is the initial operation parameter of the power transmission operation.

5. The power transmitter according to any one of claims 1 to 4, wherein the driver is configured to generate the drive signal during the power transmission phase according to a repeating time frame comprising at least one power transmission time interval and at least one measurement time interval, and the resonant measurement time interval is included in the measurement time interval.

6. The power transmitter according to any one of claims 1 to 5, wherein the operating parameter is a parameter that controls the power level of the inductive power transmission signal.

7. A power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, A transmitter coil and an output resonant circuit having at least one capacitor, A driver configured to generate a drive signal for the output resonant circuit in order to generate the aforementioned inductive power transmission signal, A resonance detector configured to measure the first coupled resonance frequency of the output resonance circuit during a resonance measurement time interval, wherein the first coupled resonance frequency is the resonance frequency of the output resonance circuit in which the transmitter coil is coupled to the receiver coil of the power transmission input resonance circuit of the power receiver. An estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil, depending on the uncoupled resonance frequency and the first coupled resonance frequency of the output resonant circuit, An adapter for setting operating parameters according to the estimated coupling coefficients, It has, A power transmitter wherein the estimation circuit is further configured to determine the estimated coupling coefficient value according to the uncoupled resonant frequency of the power transmission input resonant circuit.

8. The power transmitter according to any one of claims 1 to 7, wherein the resonance detector is further configured to measure a second coupled resonance frequency of the output resonant circuit during the resonance measurement time interval, the second coupled resonance frequency being a different resonance frequency of the output resonant circuit in the presence of the power receiver, and the estimation circuit is further configured to determine the estimated coupling coefficient value according to the second coupled resonance frequency.

9. A power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, A transmitter coil and an output resonant circuit having at least one capacitor, A driver configured to generate a drive signal for the output resonant circuit in order to generate the aforementioned inductive power transmission signal, A resonance detector configured to measure the first coupled resonance frequency of the output resonance circuit during a resonance measurement time interval, wherein the first coupled resonance frequency is the resonance frequency of the output resonance circuit in which the transmitter coil is coupled to the receiver coil of the power transmission input resonance circuit of the power receiver. An estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil, depending on the uncoupled resonance frequency and the first coupled resonance frequency of the output resonant circuit, An adapter for setting operating parameters according to the estimated coupling coefficients, It has, The estimation circuit is configured to determine the estimated coupling coefficient value according to at least one of the following equations: [Math 2] [Math 3] f p f is the non-coupled resonant frequency of the output resonant circuit, s A power transmitter in which is the uncoupled resonant frequency of the power transmission input resonant circuit, Fres1 is the first coupled resonant frequency, Fres2 is the second coupled resonant frequency, and k is the coupling coefficient.

10. A wireless power transmission system comprising a power transmitter and a power receiver, wherein the power transmitter is configured to wirelessly supply power to the power receiver via an inductive power transmission signal. The power transmitter is the power transmitter described in any one of claims 1 to 9. The aforementioned power receiver is A wireless power transmission system having a receiver coil for extracting power from the power transmitter and a power transmission input resonant circuit having at least one capacitor.

11. The wireless power transmission system according to claim 10, wherein the power receiver further includes a circuit for switching from a power transmission mode in which the quality factor of the power transmission input resonant circuit is not restricted to 10 or more to a measurement mode during the resonance measurement time interval, and when the power receiver is operating in the measurement mode, the quality factor is 10 or more.

12. The wireless power transmission system according to claim 10 or 11, wherein the power receiver has a circuit for short-circuiting the power transmission input resonant circuit during the resonance measurement time interval.

13. A method for operating a power transmitter that wirelessly supplies power to a power receiver via an inductive power transmission signal, wherein the power transmitter has an output resonant circuit having a transmitter coil and at least one capacitor, and the method for operating the power transmitter is: The steps include generating a drive signal for the output resonant circuit in order to generate the aforementioned inductive power transmission signal, A step of measuring the first coupled resonant frequency of the output resonant circuit during a resonance measurement time interval, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit in which the transmitter coil is coupled to the receiver coil of the power transmission input resonant circuit of the power receiver. The steps include determining an estimated coupling coefficient for the coupling between the transmitter coil and the receiver coil according to the uncoupled resonant frequency and the first coupled resonant frequency of the output resonant circuit, The steps include setting operating parameters according to the estimated coupling coefficients, It has, An operating method in which the operating parameter is a power loop parameter, which is a loop parameter of a power control loop configured to adapt the power level of the inductive power transmission signal in response to a power control message received from the power receiver.

14. A power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, A transmitter coil and an output resonant circuit having at least one capacitor, A driver configured to generate a drive signal for the output resonant circuit in order to generate the aforementioned inductive power transmission signal, A resonance detector configured to measure the first coupled resonance frequency of the output resonance circuit during a resonance measurement time interval, wherein the first coupled resonance frequency is the resonance frequency of the output resonance circuit in which the transmitter coil is coupled to the receiver coil of the power transmission input resonance circuit of the power receiver. An estimation circuit configured to determine an estimated coupling coefficient of the coupling between the transmitter coil and the receiver coil, depending on the uncoupled resonance frequency and the first coupled resonance frequency of the output resonant circuit, An adapter for setting operating parameters according to the estimated coupling coefficients, It has, A power transmitter in which the aforementioned operating parameters are foreign object detection parameters.

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