Wireless power transmitter and its operating method

Abstract

The transmitter 101 includes a driver 201 that generates a power transfer signal during a power transfer time interval and a drive signal for the transmitting coil to generate an electromagnetic test signal during a measurement time interval. The set of balanced detection coils 207, 209 includes two detection coils, and signals induced in the two detection coils by the electromagnetic field generated by the transmitting coil cancel each other. The estimation circuit 205 determines a position / coupling coefficient estimate for the receiver 105 in response to signals from the set of multiple balanced detection coils 207, 209 during at least one measurement time interval.

Description

Technical Field

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

Background Art

[0002] Most electrical products today require a dedicated electrical contact to receive power from an external power source. However, this is often impractical and requires the user to physically insert a connector or otherwise establish physical electrical contact. Usually, the power requirements also vary greatly, and currently, most devices have their own dedicated power sources, so the average user owns a number of different power sources specific to each device. Using a built-in battery may eliminate the need for a wired connection to a power source during use, but this is only a partial solution since the battery needs to be charged (or replaced). The use of a battery can also significantly increase the weight of the device, and in some cases, the cost and size.

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

[0004] Power transmission by magnetic induction is a well-known concept and is often applied to a transformer having a tight coupling between a primary power transmission inductor / coil and a secondary power receiving coil. By separating the primary power transmission coil and the secondary power receiving coil into 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 a device without requiring the establishment of wires or physical electrical connections. In fact, this can enable external charging or power supply to a device simply by placing the device next to or on top of the power transmission coil. For example, the power transmission device may have a horizontal surface on which a device can be simply placed for power supply.

[0006] Furthermore, such wireless power transmission configurations can be advantageously designed so that the transmitting device can be used with a variety of receiving devices. In particular, a wireless power transmission method called the Qi specification has been defined and is currently under further development. This method allows a Qi-compliant transmitting device to be used with a Qi-compliant receiving device, and the two devices do not need to be from the same manufacturer or specifically designed for each other. The Qi standard further includes features to enable operation adaptation to specific receiving devices (for example, depending on the specific power output).

[0007] The Qi specification was developed by the Wireless Power Consortium, and details can be found, for example, on their website (http: / / www.wirelesspowerconsortium.com / index.html), where you can find the documentation of the defined specifications.

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

[0009] A potential problem with wireless power transmission is that its performance can be highly dependent on specific conditions. In particular, power transmission performance, including efficiency, achievable power levels, and adaptive response time, tends to depend heavily on how the transmitting and receiving coils are positioned relative to each other. Generally, more efficient and reliable power transmission tends to be achieved when the coils are aligned and close to each other.

[0010] Typically, power transmission performance depends on the coupling factor (or coefficient), with higher coupling factors resulting in higher power transmission efficiency.

[0011] By designing the devices such that the placement of the receiving device relative to the transmitting device is strictly restricted, for example by restricting the receiving device to one specific location, the two can be placed closer together, and the coupling coefficient can be increased. However, this is generally undesirable as it limits the practicality of the system. For example, in the case of kitchen appliances where the transmitter is mounted on the worktop, it is preferable that the system adjusts accordingly, with the user simply placing the appliance roughly near the transmitter coil. Furthermore, it is preferable that the power transmission function be implemented without requiring mechanical or physical guiding mechanisms to restrain the receiving device, for example, that the transmitter can be mounted using a perfectly flat worktop surface.

[0012] In reality, the spatial relationship between the transmitter and receiver, and the resulting coupling coefficients, can vary considerably. Often, it would be desirable to identify such varying characteristics and, for example, adjust power transmission or provide user feedback. In particular, it would be desirable to determine the relative position of the receiver and / or the coupling coefficients between the coils.

[0013] Several methods have been proposed to achieve this. One such method involves incorporating multiple transmission coils across an active surface, with the transmitter sequentially switching between the coils until it is determined which coil provides the best power transmission. The determined coil is then used for power transmission.

[0014] However, such methods are suboptimal and tend not to yield ideal performance. The location of the power receiver tends to be very rough, and the adjustment of power transmission operations tends to be limited. [Overview of the Initiative] [Problems that the invention aims to solve]

[0015] Therefore, improved operation for power transmission is advantageous, and in particular, techniques that enable increased flexibility, reduced costs, reduced complexity, improved estimation of receiver location and / or coupling coefficients, backward compatibility, improved suitability for higher power level transmissions, and / or improved performance would be beneficial.

[0016] Therefore, the present invention aims to suitably 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 receiver via an inductive power transmission signal, the power transmitter comprising: a power transmitting coil; a driver that generates a drive signal for the power transmitting coil, the driver generating a drive signal for the power transmitting coil to generate a power transmission signal during at least one power transmission time interval of an iterative time frame, and the driver generating a drive signal for the power transmitting coil to generate an electromagnetic test signal during at least one measurement time interval of an iterative time frame; a set of multiple balanced detection coils coupled in series, each set of balanced detection coils comprising two detection coils, the signals induced in the two detection coils by the electromagnetic field generated by the power transmitting coil cancel each other out; and an estimation circuit that, during at least one measurement time interval, in response to signals from the set of multiple balanced detection coils, estimates the coupling coefficient of the electromagnetic coupling between the power transmitting coil and the receiver coil of the receiver.

[0018] In many embodiments and cases, the present invention can improve the estimation of the coupling coefficient of electromagnetic coupling between a transmitting coil and a receiving coil of a power receiver. In many embodiments, the present invention can enable improvements in power transmission, and in particular, improve the adaptation of power transmission to changing operating conditions.

[0019] The measurement time interval of the repetitive time frame may be timed to coincide with / synchronize with the zero crossing of the amplitude of the power transmission signal and / or the zero crossing of the fluctuating (e.g., AC) supply voltage to the driver's output stage.

[0020] The estimation of coupling coefficients may also be done by estimating the change in coupling coefficients.

[0021] 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. The duration of the measurement time interval may be 5 milliseconds, 10 milliseconds, or 50 milliseconds or less in many scenarios.

[0022] The detection coils are balanced in that the signals induced in the two detection coils by the electromagnetic field generated by the transmission coil cancel each other out. The coupled voltage across the two balanced detection coils is lower than the maximum voltage of each of the two balanced detection coils. Compensation may be at least partial cancellation of the two signals.

[0023] An electromagnetic test signal may also be called a test electromagnetic field, and these terms can be considered synonymous. A set of balanced detection coils can be connected in series. When detection coils / windings are connected in series, the currents flowing through them may be identical. Signals from multiple sets of balanced detection coils during at least one measurement time interval may be signals induced by / resulting from / caused by the electromagnetic test signal.

[0024] In some embodiments, the frequency of the drive signal during the measurement time interval is 50% or more higher than the frequency of the drive signal during the power transmission time interval.

[0025] This can improve and / or facilitate the measurement / determination of signals indicating unbalance in the sensing coil in many embodiments. In particular, the influence of loads added by the receiver load can be reduced. With reduced load influence, position estimation can become more accurate in many embodiments.

[0026] In some embodiments, the frequency of the drive signal during the measurement time interval is 100%, and in some cases more than 200%, higher than the frequency of the drive signal during the power transmission time interval.

[0027] In some embodiments, the voltage amplitude of the drive signal during the measurement time interval is 50% or less of the voltage amplitude of the drive signal during the power transmission time interval.

[0028] In some embodiments, the voltage amplitude of the drive signal during the measurement time interval is 25% or 10% or less of the voltage amplitude of the drive signal during the power transmission time interval.

[0029] In some embodiments, the voltage amplitude of the drive signal is substantially constant during the measurement time interval.

[0030] This can provide improved and / or facilitated receiver position estimation in many embodiments.

[0031] Each balanced detection coil set may include two detection coils, and the two detection coils may be configured such that signals induced in the two detection coils by an electromagnetic field (particularly, the electromagnetic field generated by the power transmission coil) offset / compensate / at least partially cancel each other out in the signal from the set of balanced detection coils.

[0032] The signal from the set of balanced detection coils may specifically be a composite signal of the induced signals from the detection coils in the set of detection coils. The signal may be the composite / sum voltage of the voltages induced in each detection coil (or may include such voltage contributions). The imbalance between the signals induced in the two detection coils of a given detection coil set may be indicated by the voltage (specifically the voltage amplitude) and / or phase of the signal.

[0033] The estimation circuit is configured to obtain an estimate of the coupling coefficient of the electromagnetic coupling between the power transmission coil and the power receiving coil of the receiver in response to signals from a plurality of sets of balanced detection coils during at least one measurement time interval.

[0034] Thereby, particularly the operation of power transmission is improved and the power transmission can be adjusted to changing conditions.

[0035] According to an optional feature of the present invention, the coupling coefficient estimation is relative coupling coefficient estimation.

[0036] This can offer particularly advantageous performance in many embodiments and cases. Relative coupling coefficient estimation can show changes in coupling coefficients.

[0037] According to an optional feature of the present invention, the estimation circuit obtains a coupling coefficient estimate as a coupling coefficient that decreases with increasing amplitude of at least one set of a set of multiple balanced detection coils.

[0038] This can offer particularly advantageous performance in many embodiments and cases.

[0039] According to an optional feature of the present invention, the estimation circuit obtains coupling coefficient estimation as a coupling coefficient that decreases with increasing amplitude difference between at least two sets of a plurality of balanced detection coil sets.

[0040] This can offer particularly advantageous performance in many embodiments and cases.

[0041] According to an optional feature of the present invention, the power transmitter includes an adapter that adjusts power loop parameters in response to coupling coefficient estimation, wherein the power loop parameters are loop parameters of a power control loop that adjusts the power level of a power transmission signal in response to a power control message received from a power receiver.

[0042] This can offer particularly advantageous performance in many embodiments and cases. This may lead to improved power transmission and better adaptation of operation to changing conditions.

[0043] According to an optional feature of the present invention, the power loop parameter is at least one of the loop time constant, the frequency response of the loop filter, and the loop gain.

[0044] This may offer particularly advantageous performance in many embodiments and cases, and in many embodiments in particular, it may improve and / or facilitate the adaptation of power transmission operations.

[0045] According to an optional feature of the present invention, the estimation circuit obtains an estimate of the receiver's position in response to signals from a set of multiple balanced detection coils during at least one measurement time interval.

[0046] This method can improve the estimation of the location of a receiver in wireless power transmission in many embodiments and cases. The present invention enables improvements in power transmission in many embodiments, and in particular can improve the adaptation of power transmission to changing operating conditions.

[0047] According to an optional feature of the present invention, the power transmitter further comprises a user interface that provides a user output that provides a display of the positional deviation of the power receiver in response to the position estimation meeting the requirements.

[0048] This can provide improved and / or simplified operation in many embodiments. This allows users to prevent undesirable situations where efficient power transmission is impossible.

[0049] Specifically, this requirement may include the requirement that the difference / distance between the estimated location and the nominal or preferred location exceeds a threshold.

[0050] The display may include an indication of the direction of movement of the receiver in order to reduce positional errors.

[0051] In some embodiments, the transmitter may further include a user interface that provides a user output that indicates the location of the receiver in response to a location estimation.

[0052] In some embodiments, the transmitter may include a communicator for communicating a position estimation to the receiver. The receiver may include a user interface that provides a user output indicating the receiver's position in response to the position estimation.

[0053] According to an optional feature of the present invention, the power transmitter further comprises an adapter that adjusts the operating parameters of power transmission in response to position estimation.

[0054] This can offer particularly advantageous performance in many embodiments, and in particular, it can improve receiver position estimation and power transmission in many embodiments and cases.

[0055] This can provide particularly advantageous performance in many embodiments and cases. The operating parameters may be, for example, the maximum power level of the power transmission signal and / or the current power level of the power transmission signal.

[0056] In some embodiments, the adapter adjusts power loop parameters in response to position estimation, where power loop parameters are loop parameters of a power control loop that adjust the power level of the power transmission signal in response to power control messages received from the receiver.

[0057] According to an optional feature of the present invention, the adapter adjusts power loop parameters in response to position estimation, and the power loop parameters are loop parameters of a power control loop that adjust the power level of a power transmission signal in response to a power control message received from a power receiver.

[0058] This can offer particularly advantageous performance in many embodiments. This may lead to improved power transmission and better adaptation of operation to changing conditions.

[0059] According to an optional feature of the present invention, the estimation circuit detects a change in position for a receiver if the signal satisfies a criterion, the criterion includes the requirement that the number of signals from a set of balanced detection coils is less than a threshold number, where the number of signals is at least 2, and the imbalance between signals induced in two detection coils of the set of balanced detection coils exceeds a second threshold.

[0060] This may offer particularly advantageous performance in many embodiments and cases, and in particular, it may improve position estimation in many embodiments. This may improve the fit to current conditions and operating scenarios. In many embodiments, the number of thresholds may be at least 3, and in many embodiments, the number of thresholds may be equal to the number of sets of balanced detection coils.

[0061] According to an optional feature of the present invention, the transmitter further comprises a compensator that compensates for the imbalance between signals induced in two detection coils when no foreign object is present, for the signals of at least one set of balanced detection coils, and the estimator obtains a position estimate in response to the amount of compensation for at least one set of balanced detection coils.

[0062] This may offer particularly advantageous performance in many embodiments and cases, and in particular, it may improve position estimation in many embodiments. This may facilitate position estimation and simplify the determination of unbalanced displays.

[0063] In many embodiments, the transmitter may include a foreign object detector coupled to a set of multiple balanced detection coils, which performs foreign object detection during a measurement time interval, wherein the foreign object detector detects foreign objects in response to the characteristics of signals from the set of multiple balanced detection coils that satisfy a foreign object detection criterion. The signals may be from the compensated set of multiple balanced detection coils.

[0064] The foreign object detection criteria may include a first requirement that a signal from at least one of a set of multiple balanced detection coils indicates that the imbalance between signals induced in two detection coils of at least one set of multiple balanced detection coils exceeds a first threshold.

[0065] The foreign object detection criteria may include a second requirement that the number of signals from a set of multiple balanced detection coils is less than a threshold number, indicating that the signal imbalance induced in two detection coils of a set of balanced detection coils exceeds a second threshold, and the threshold number may be at least 2.

[0066] According to an optional feature of the present invention, the compensator determines the static and dynamic components of the compensation, the static component being independent of the presence of the receiver, the dynamic component being dependent on the presence of the receiver, and the estimator determining the position estimate in response to the dynamic component.

[0067] According to another aspect of the present invention, a method is provided for operating a power transmitter that wirelessly supplies power to a receiver via an inductive power transmission signal, the method comprising a power transmitting coil and a set of a plurality of balanced detection coils coupled in series, each set of balanced detection coils comprising two detection coils, wherein the signals induced in the two detection coils by the electromagnetic field generated by the power transmitting coil cancel each other out, the method comprising a driver generating a drive signal for the power transmitting coil, the driver generating a drive signal for the power transmitting coil to generate a power transmission signal during at least one power transmission time interval of an iterative time frame, and generating a drive signal for the power transmitting coil to generate an electromagnetic test signal during at least one measurement time interval of an iterative time frame, and during at least one measurement time interval, determining an estimation of the coupling coefficient of electromagnetic coupling between the power transmitting coil and the receiver coil of the receiver in response to signals from the plurality of balanced detection coils.

[0068] The above and other aspects, features, and advantages of the present invention will be described and made apparent with reference to the embodiments described below. [Brief explanation of the drawing]

[0069] Hereinafter, embodiments of the present invention, which are merely examples, will be described with reference to the following drawings. [Figure 1] Figure 1 shows an example of elements of a power transmission system according to a part of the present invention. [Figure 2] Figure 2 shows an example of elements of a power transmission according to a part of the present invention. [Figure 3] Figure 3 shows an example of a half-bridge inverter for a power transmission. [Figure 4] Figure 4 shows an example of a full-bridge inverter for a power transmission. [Figure 5] Figure 5 shows an example of a time frame for the wireless power transmission system in Figure 1. [Figure 6] Figure 6 shows an example of a detection coil for a power transmitter according to some embodiments of the present invention. [Figure 7] Figure 7 shows an example of an electromagnetic field and detection coil for a power transmitter according to some embodiments of the present invention. [Figure 8] Figure 8 shows an example of a drive signal for a power transmitter according to some embodiments of the present invention. [Figure 9] Figure 9 shows an example of a drive signal for a power transmitter according to some embodiments of the present invention. [Figure 10] Figure 10 shows an example of elements of a power transmission according to a part of the present invention. [Figure 11] Figure 11 shows an example of a detection coil for a power transmitter according to some embodiments of the present invention. [Figure 12] Figure 12 shows an example of a detection coil for a power transmitter according to some embodiments of the present invention. [Figure 13] Figure 13 shows an example of an electromagnetic field and detection coil for a power transmitter according to some embodiments of the present invention. [Figure 14]Figure 14 shows an example of an electromagnetic field and detection coil for a power transmitter according to some embodiments of the present invention. [Figure 15] Figure 15 shows an example of an electromagnetic field and detection coil for a power transmitter according to some embodiments of the present invention. [Figure 16] Figure 16 shows an example of an electromagnetic field and detection coil for a power transmitter according to some embodiments of the present invention. [Figure 17] Figure 17 shows an example of the coupling coefficient and loop gain of a power transmission system as a function of the displacement between the transmitting and receiving coils. [Modes for carrying out the invention]

[0070] The following description focuses on embodiments of the present invention applicable to wireless power transmission systems utilizing power transmission techniques such as those known from the Qi or Ki specifications. However, it will be understood that the present invention is not limited to this application and can be applied to many other wireless power transmission systems.

[0071] Figure 1 shows an example of a power transmission system according to some embodiments of the present invention. The power transmission system comprises a transmitter 101 including (or coupled to) a transmitting coil / inductor 103. The system further comprises a receiver 105 including (or coupled to) a receiving coil / inductor 107.

[0072] The system supplies an electromagnetic power transmission signal that can inductively transmit power from the transmitter 101 to the receiver 105. Specifically, the transmitter 101 generates an electromagnetic signal that is propagated as magnetic flux by a coil or inductor 103. The power transmission signal can typically have a frequency of about 20 kHz to about 500 kHz, and in the case of a Qi-enabled system, it can often be in the range of 95 kHz to 205 kHz, or in the case of a Ki-enabled system, for example, it can typically be in the range of 20 kHz to 80 kHz. Since the transmitting coil 103 and the receiving coil 107 are loosely coupled, the receiving coil 107 picks up the power transmission signal (at least a portion of it) from the transmitter 101. Thus, power is transmitted from the transmitter 101 to the receiver 105 via wireless inductive coupling from the transmitting coil 103 to the receiving coil 107. The term "power transmission signal" is primarily used to refer to the inductive signal / magnetic field between the transmitting coil 103 and the receiving coil 107 (magnetic flux signal), but it can also be considered and sometimes used to refer to any electrical signal supplied to the transmitting coil 103 or picked up by the receiving coil 107.

[0073] In this example, the power receiver 105 is specifically a power receiver that receives power via a power receiving coil 107. However, in other embodiments, the power receiver 105 may include a metal element, such as a metal heating element, in which case the power transmission signal directly induces eddy currents, and thus directly heats the metal element.

[0074] The system is configured to transmit substantial power levels, and specifically, in many embodiments, the transmitter can support power levels of 500mW, 1W, 5W, 50W, 100W, or more than 500W. For example, with respect to Qi-enabled applications, power transmission can typically be in the 1-5W power range for low-power applications (basic power profile), up to 15W for Qi specification version 1.2, up to 100W for high-power applications such as power tools, laptops, drones, and robots, and higher than 100W, and potentially even higher than 2000W, for very high-power applications such as Qi kitchen applications.

[0075] The operation of the transmitter 101 and receiver 105 will be described below, with specific reference to embodiments that generally conform to the Qi or Ki specifications (excluding any modifications or enhancements described herein or resulting therefrom), or embodiments suitable for high-power kitchen specifications developed by the Wireless Power Consortium. In particular, the transmitter 101 and receiver 105 conform to or substantially correspond to elements of Qi specification version 1.0, 1.1, or 1.2 (excluding any modifications or enhancements described herein or resulting therefrom).

[0076] In many wireless power transmission systems, the operating conditions for power transmission can change dynamically, for example, depending on the spatial arrangement of the transmitting coil 103 and the receiving coil 107. In many systems, it is desirable to be able to measure the characteristics of the electromagnetic conditions and adjust the operation accordingly.

[0077] As will be explained in more detail below, the system in Figure 2 employs a measurement technique that utilizes time-division multiplexing during the power transmission phase. In particular, the measurement and power transmission under current conditions can be performed, for example, at multiple separate time intervals, thereby significantly reducing interference between them (especially the influence of power transmission on the measurement and estimation of associated operating parameters).

[0078] The system shown in Figure 1 will be described in more detail below. In this example, the electromagnetic power transmission signal and the electromagnetic test signal used for measurement are generated by the same coil. Also, the signals / fields may be referred to by different terms; that is, the electromagnetic signal / field generated during the power transmission time interval may be called the power transmission signal, and the electromagnetic signal / field generated during the measurement time interval may be called the electromagnetic test signal, or simply the test signal.

[0079] Figure 2 shows the elements of the power transmission 101 in Figure 1 in more detail.

[0080] The power transmitter 101 includes a driver 201 capable of generating a drive signal supplied to the power transmission coil 103, which in turn generates an electromagnetic power transmission signal to provide power transmission to the power receiver 105. The power transmission signal is supplied during the power transmission time interval of the power transmission phase.

[0081] The driver 201 generates the current and voltage supplied to the transmission inductor 103. The driver 201 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 201 is typically a switchbridge, which generates the drive signal through the proper switching of the switches in the switchbridge. Figure 3 shows a half-bridge switchbridge / inverter. Switches S1 and S2 are controlled so that they are never closed simultaneously. Alternately, S1 closes while S2 is open, and S2 closes 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 transmission inductor via a resonant capacitor. Figure 4 shows a full-bridge switchbridge / inverter. Switches S1 and S2 are controlled so that they are never closed simultaneously. Switches S3 and S4 are controlled so that they are never closed simultaneously. Alternately, switches S1 and S4 close while S2 and S3 are open, and S2 and S3 close while S1 and S4 are open, thereby generating a square wave signal at the output. The switch is opened and closed at the desired frequency.

[0082] The power transmitter 101 further comprises a power transmitter controller 203 configured to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 may include a number of functions necessary to perform power control according to the Qi or Ki specification.

[0083] The power transmitter controller 203 is configured to control the generation of drive signals by the driver 201, and specifically to control the power level of the drive signals, and therefore the level of the power transmission signals generated. The power transmitter controller 203 includes a power loop controller that controls the power level of the power transmission signals in response to power control messages received from the receiver 105 during the power control phase.

[0084] The system in Figure 1 uses a method to measure the characteristics of the electromagnetic field, particularly its spatial variations, and to estimate the position of the receiver relative to the transmitter, and / or the coupling coefficient between the transmitting and receiving coils. Because this method can be tuned to reflect current conditions, it can provide improved operation in many embodiments. In many embodiments, this can be achieved while keeping complexity and / or resource requirements low.

[0085] In this example, the driver 201 and the transmission coil 103 are configured to generate both an electromagnetic power transmission signal for transmitting power to a receiver and an electromagnetic test signal for performing measurements (e.g., used for estimating position and / or coupling coefficients). The transmitter may use 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 one measurement time interval. An example of such a repeating time frame is shown in Figure 5, where the power transmission time interval is denoted by PT and the measurement time interval is denoted by D (the time interval may also be called the detection time interval). In this example, each time frame FRM includes only one measurement time interval and one power transfer time interval, and these (and 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 also be included in the time frame, or multiple measurement time intervals and / or power transmission time intervals may be included in each time frame. Furthermore, in some embodiments, the durations of different time intervals (and the time frame itself) may change dynamically.

[0086] Thus, in this method, measurement and power transmission are separated in the time domain, thereby reducing mutual interference between power transmission and measurement / estimation. Consequently, variability and uncertainty caused by variations in the operating conditions of power transmission can be removed from measurement and estimation, providing a more reliable and accurate estimation process.

[0087] Therefore, in the power transmission phase, the transmitter is configured to perform power transmission during power transmission time intervals in a time frame. Specifically, during these time intervals, the transmitter 101 and receiver 105 may operate a power control loop. The power control loop may be based on communication within the power transmission time intervals, or on communication outside the power transmission time intervals, for example, within dedicated communication time intervals. For example, each measurement time interval may be separated by a plurality of alternating power transmission time intervals and communication time intervals. Therefore, the level of power transmitted may be dynamically changed. In the measurement time intervals of the power transmission phase time frame, at least one parameter of the drive signal, and therefore at least one parameter of the electromagnetic test signal, is typically set to a predetermined value, or, for example, a value determined during adjustment operations performed prior to the measurement time interval. Therefore, the parameter may be set to a predetermined value in the measurement time interval (i.e., a value determined before the measurement time interval, and often a value determined before the power transmission phase). In contrast, during the power transmission time intervals, the parameter may not be constrained to this predetermined value.

[0088] For example, during a power transmission time interval, the system may operate a power control loop that allows it to change the power level of the power transmission signal in response to power control messages from the receiver. The power control loop can control / modify at least one of the current, voltage, and frequency of the drive signal / power transmission signal. In contrast, the parameters modified by the power control loop during a power transmission time interval may be set to predetermined values ​​of current, voltage, and / or frequency determined before the power transmission phase during the measurement time interval.

[0089] In many embodiments, a constant (usually lower) amplitude (usually voltage) of the drive signal is set during the measurement time interval. In addition or alternatively, a predetermined frequency may be set for the drive signal during the measurement time interval, which is usually significantly higher than that of the drive signal during the power transmission time interval.

[0090] As a result, the power transmission signal, which is the electromagnetic signal generated during the power transmission time interval, typically has significantly different characteristics from the electromagnetic test signal, which is the electromagnetic signal generated during the measurement time interval. The electromagnetic signal or field generated during the power transmission time interval is called the power transmission signal, while the electromagnetic signal or field generated during the measurement time interval is called the electromagnetic test signal, or simply the test signal. However, in the system in Figure 2, it will be understood that the electromagnetic signal is generated from the same coil in both the power transmission time interval and the measurement time interval, and that the same driver, etc., is used in both the power transmission time interval and the measurement time interval. In fact, in many embodiments, the reference to the test signal may be considered equivalent to the power transmission signal in the measurement time interval.

[0091] The power transmitter 101 includes an estimator 205 configured to perform measurements and estimate position and / or coupling coefficients based on measurements of the generated electromagnetic field. The determined coupling coefficients may be relative coupling coefficients or changes in coupling coefficients.

[0092] Therefore, during the interval in which measurements are performed, i.e., during the measurement time interval, the estimator 205 evaluates the state of the electromagnetic field to obtain measurements that can be used for estimation. During the measurement time interval, the transmitter 101 generates an electromagnetic test signal, and the estimation is based on an evaluation of the characteristics and properties of the electromagnetic field.

[0093] In this system, measurement / estimation is based on detecting signals in a set of balanced detection coils induced by an electromagnetic test signal. The set of balanced detection coils includes at least two detection coils 207, 209 configured to offset each other in the negative direction in the presence of a uniform magnetic field and an electromagnetic field generated by the transmission coil 103, for example, specifically in the presence of an electromagnetic test signal. Specifically, the transmitter includes a set of balanced detection coils, each set of balanced detection coils including a first detection coil 207 and a second detection coil 209 coupled such that the electromagnetic fields generated by the transmission coils cancel each other out (at least partially). The set of balanced detection coils is also called induced balance.

[0094] The following explanation will first focus on the operation of a single inductive balance, i.e., the operation of a single set of balanced detection coils, such as shown in Figure 6. For a set of balanced detection coils, the electromagnetic field generated by the transmission coil 103 induces a signal in the first detection coil 207 and a signal in the second detection coil 209. However, since the induced voltages have opposite polarities, the voltage (amplitude) of the series coupling of detection coils 207 and 209 due to the electromagnetic field generated by the transmission coil 103 is lower than at least the maximum of the individual detection coils 207 and 209 due to the electromagnetic field generated by the transmission coil 103, typically neither of them. Therefore, the first detection coil 207 and the second detection coil 209 are coupled such that the induced voltages from the electromagnetic field generated by the transmission coil 103 at least partially cancel each other out.

[0095] The detection coils are configured to correspond to at least two windings, each generating an opposing signal when an electromagnetic test signal is present between the two coils. Thus, the opposing signals may at least partially cancel each other out, and therefore the levels of the measurement induction signals across the series connection of detection coils 207, 209 are reduced, and in some cases substantially canceled out. This significantly increases the magnetic field strength available for measurement. In fact, in many embodiments and cases, the resulting induced voltage can (ideally) be attributed solely to the difference in magnetic flux between the windings. Such differences or asymmetries between windings may also be due, for example, to the asymmetric placement of the receivers relative to each detection coil, or to the presence of foreign matter.

[0096] An example of a detection coil configuration is shown in Figure 6. In this example, the first detection coil 207 is formed as the first winding L1, and the second detection coil 209 is formed as the second winding L2, which is (inversely) connected in series. Therefore, the coupled voltages of the two windings are offset from each other with respect to a uniform electromagnetic field. In this example, the detection coils 207, 209 / windings L1, L2 are arranged opposite each other and symmetrically with respect to a center point. Furthermore, these detection coils are formed in a plane, and the transmission coil 103 is also formed in the same plane (or at least in a substantially parallel plane). In this example, the detection coils 207, 209 are formed inside the transmission coil 103. Furthermore, the detection coils 207, 209 have substantially the same external shape and are formed to cover substantially the same area.

[0097] As a result, the magnetic fluxes passing through the two detection coils 207 and 209 are substantially the same but in opposite directions. Consequently, the induced voltages in the two detection coils 207 and 209 are substantially the same but have opposite phases / polarities, and the coupling voltage of the two series-coupled detection coils 207 and 209 cancels out, becoming substantially zero.

[0098] Therefore, the detection coils 207 and 209 are configured such that, in the presence of a uniform field and / or the absence of other objects and the presence of an electromagnetic field generated by the transmission coil 103, the inductive signals / voltages cancel each other out at least partially, ideally resulting in a coupling voltage of zero.

[0099] In the configurations shown in Figures 2 and 6, the induction signal of the first of the two detection coils has a voltage opposite to that of the induction signal of the second of the two detection coils. The induction signals of the two detection coils have opposite phases with respect to a uniform magnetic field. The induction signals in the two detection coils have opposite phases. The two detection coils are coupled in series and in opposite phases so that the induction signals have opposite polarity. These characteristics exist for a uniform field and a distortion-free field generated by the transmission coil 103.

[0100] In the presence of metallic foreign matter, the electromagnetic field is distorted, potentially leading to asymmetry between the fields of the two detection coils 207 and 209. This can be true when the metallic foreign matter is located near the transmission coil 103, but it can also be true when there is a receiver with a metallic component that is asymmetrical to the detection coils 207 and 209 (typically because the receiver's position is asymmetrical with respect to the detection coils 207 and 209). Therefore, in such cases, asymmetry will exist in the magnetic fields of the two detection coils 207 and 209.

[0101] Typically, in the case of a metallic object, the generated electromagnetic test signal induces eddy currents, and as a result, the metallic object generates an electromagnetic field such that the combined electromagnetic field is distorted with respect to the electromagnetic field of the generated electromagnetic test signal. The generated asymmetric electromagnetic field induces different signals in the first detection coil 207 and the second detection coil 209, as shown in Figure 7. In the case where the receiver is symmetric with respect to the detection coils 207, 209 and no foreign objects are present, the magnetic flux through the two detection coils 207, 209 is symmetric, and the combined voltage is substantially zero. However, if the receiver does not provide symmetric distortion, or if foreign objects are present, a difference will occur in the induced signals. This difference in the induced signals of the two detection coils 207, 209 can be used to estimate the position and / or coupling coefficient of the receiver. It can also be used to detect the presence of foreign objects.

[0102] In the system shown in Figure 2, the combined voltage of the pair of detection coils 207 and 209 may be measured directly and used to perform the measurement. In some embodiments, more complex techniques can be used, for example, the detection coils may be coupled in series with a transformer so that the current flowing through the detection coils 207 and 209 also flows through the primary winding of the transformer. Thus, the detection coils 207 and 209 and the primary winding may be part of a series circuit through which the current induced in the detection coils 207 and 209 flows. In that case, the secondary winding may be coupled to the estimator 205, and for example, the current flowing through the secondary winding can be measured and used as a measure of the imbalance between the induced signals in the two detection coils 207 and 209.

[0103] The imbalance indicated by the signal from the inductive balance, specifically the output voltage, can be used as an indicator of the position of the transmitter controller, the coupling coefficient (and specifically the change in the coupling coefficient) between the transmitting coil 103 and the receiving coil 107, and / or to indicate the presence of foreign matter. For example, if the signal from a set of balanced detection coils meets a certain criterion, e.g., the absolute value exceeds a detection threshold, this can be considered to indicate the possible presence of foreign matter. Thus, in some embodiments, the use of balanced detection coils may enable the estimator 205 to perform foreign matter detection. As another example, the presence of a signal indicating imbalance can be used as an indicator of an asymmetrical arrangement of the receiver, or as an indicator of the coupling coefficient (particularly the change in the coupling coefficient).

[0104] In wireless power transmission systems, the presence of an object (typically a conductive element that extracts power from a power transmission signal and is not part of the transmitter 101 or receiver 105, i.e., an element that is unintended, undesirable, and / or interfering with respect to power transmission) can be highly inconvenient during power transmission. Such an undesirable object is referred to in the art as a foreign object.

[0105] Foreign objects can not only reduce efficiency by adding power loss to the operation, but can also degrade the quality of the power transmission operation itself (for example, by interfering with power transmission efficiency or by extracting power that is not directly controlled (e.g., by the power transmission loop)). Furthermore, the induction of current within the foreign object (specifically, eddy currents within the metal parts of the foreign object) can often lead to heating of the foreign object, which is highly undesirable.

[0106] In the example shown in the figure, the two detection coils 207 and 209 are positioned on opposite sides of each other and are located in the same magnetic plane as the transmission coil 103. When such an inductive equilibrium is exposed to a symmetric detection electromagnetic field generated by the transmission coil 103, the voltages at the terminals of the detection coils 207 and 209 are ideally and theoretically substantially zero.

[0107] In this method, a signal is induced in each detection coil, and in the case of a uniform magnetic field (as is usually the case when no foreign objects are present), the balanced detection coils substantially cancel each other out. The outputs of detection coils 207 and 209 are coupled to the estimator 205. Thus, signals are induced in detection coils 207 and 209 (by the electromagnetic field generated by the transmission coil), and the generated (difference) induced signal that crosses the outputs of the balanced detection coils 207 and 209 is supplied to the estimator 205. The resulting signal is then evaluated by the estimator 205. Therefore, the signal evaluated by the estimator 205 represents the signals induced in detection coils 207 and 209, specifically the canceled-out difference / sum induced signal.

[0108] As shown in Figure 7, placing a metal piece on one side of the inductive equilibrium makes the density of the detected electromagnetic test signal / field asymmetric, and a voltage can be measured at the terminal of the inductive equilibrium. The estimator 205 may be configured to detect foreign objects in response to the characteristics of the induced signal from the inductive equilibrium that satisfy the foreign object detection criteria. Thus, a particular advantage of using inductive equilibrium is that it can provide highly advantageous foreign object detection in many embodiments.

[0109] Similarly, as shown in Figure 7, if the receiver is positioned such that its metal components are shifted laterally to the inductive equilibrium, the density of the detected electromagnetic test signal / field will also become asymmetrical, and a voltage may be measured at the terminals of the inductive equilibrium. The estimator 205 may be configured to estimate the position and coupling coefficient (which may be relative coupling coefficient) based on the imbalance. Thus, a particular advantage of using the inductive equilibrium is that in many embodiments it can provide a very favorable position and / or coupling detection estimation. In many embodiments, the estimator 205 can use information about the characteristics of the receiver provided by the receiver, such as the diameter of the surface in contact with the transmitter, to calculate the absolute positional shift.

[0110] As described above, the transmitter can be configured to control the drive signal so that it exhibits different parameters during the measurement time interval and the power transmission time interval. This can be used, in particular, to reduce the effect and influence of the load on the electromagnetic test signal by the receiver.

[0111] For example, it has been proposed to disconnect the load on a power receiver during short measurement time intervals using a power receiver equipped with an actively opening switch. However, this solution is not ideal for higher power levels, such as kW, because the disconnection switch would result in additional losses and increased costs. In some high-power applications, such as when the load is an inductively heated metal element in which eddy currents are directly induced within it by the power transmission signal to cause heating, it is simply impossible to implement such switching.

[0112] This can be addressed by matching the parameters of the drive signal during the measurement time interval to the power transmission time interval, and this can be used to mitigate the influence of the receiver load on the measurement.

[0113] In many embodiments, the driver 201 is configured to increase the frequency of the drive signal during the measurement time interval compared to the frequency during the power transmission time interval, specifically, to set the drive signal frequency to be 50% or more higher than the frequency of the drive signal during the power transmission time interval. Thus, the driver 201 can generate an electromagnetic test signal having a significantly higher frequency than the power transmission signal.

[0114] In many cases, significantly increasing the frequency can improve measurement, estimation, and detection, and reduce the impact of the receiver load. For example, both the transmitter and receiver may have resonant circuits formed for power transmission, for example, the transmitting coil 103 and the receiving coil 107 may both have (for example, f resIt may be part of a resonant circuit (with a resonant frequency of 25 kHz). If the driving frequency is increased during the measurement time interval (for example to 50 kHz), the transmitter resonant circuit will operate in inductive mode, and the current in the transmitting coil 103 will decrease. Furthermore, the system will no longer be tuned, so the current in the receiving coil will also decrease. This will further decrease the current in the transmitter. The overall effect corresponds to the effect resulting from a partially disconnected load.

[0115] In many embodiments, the driver 201 may be configured to reduce the voltage of the drive signal during the measurement time interval with respect to the power transmission time interval, specifically, the voltage amplitude of the drive signal during the measurement time interval may be set to be 50% (or often 25%, and possibly 10%) or less of the voltage amplitude of the drive signal during the power transmission time interval.

[0116] A reduced voltage can generate a weaker electromagnetic test signal, resulting in a lower electromagnetic field during the measurement time interval than during the power transmission time interval. This, in many cases, can improve estimations based on measurements within the measurement time interval. In some embodiments, a voltage drop can be advantageous because it can lead to the disconnection of the receiver load. For example, if the voltage drops to a certain level, the receiver, which includes a rectifier and battery, may not receive enough induced voltage to conduct the rectifier, thus being powered by the battery. This can effectively disconnect the load from the electromagnetic test signal, potentially improving measurement performance.

[0117] In many embodiments, the driver 201 may be configured to keep the voltage amplitude of the drive signal constant during the measurement time interval. As a result, a more uniform electromagnetic test signal may be generated, which may improve measurements based on the balanced detection coils 207, 209, and consequently, foreign object detection. For example, if the voltage amplitude fluctuates over time, the test signal, and therefore the unbalanced signal from the unbalanced type, will fluctuate, and the estimation accuracy will decrease unless this fluctuation can be compensated for or taken into account.

[0118] In many embodiments, the driver 201 may be configured to generate a drive signal having a constant voltage amplitude at least 50% lower and a frequency at least 50% higher than the drive signal during the power transmission time interval during the measurement time interval.

[0119] As an example, during the power transmission time interval, the drive signal is generated at a first operating frequency close to the resonant frequencies of both the transmitter and receiver in order to transmit wireless power with high efficiency.

[0120] During the measurement time interval, the first operating frequency of the drive signal is moved away from the resonant frequencies of both the transmitter and receiver and changed to a second, higher operating frequency. This second, higher operating frequency of the drive signal can be fixed at a predetermined value that is at least 1.5 times higher than the first operating frequency, i.e., the frequency of the power transmission signal.

[0121] Furthermore, the drive signal voltage Uinv is changed to a constant second amplitude (e.g., provided by a different voltage source) that is lower than during the power transmission time interval.

[0122] By using a second drive signal with a higher operating frequency and a second drive signal with a lower constant voltage amplitude, the current flowing through the transmission coil 103 is greatly reduced and kept constant. Furthermore, since the driver current lags behind the driver signal voltage, the inverter at the output of the driver 201 operates in a zero-voltage switching scenario, thus greatly reducing switching noise.

[0123] An example of the drive signal amplitude in such a scenario is shown in Figure 8. In the figure, operation during the power transmission time interval is shown as Mode 1, and operation during the measurement time interval is shown as Mode 2. In this example, the voltage amplitude remains constant during the power transmission time interval, for example, because the inverter is supplied from a constant voltage source.

[0124] Figure 9 shows a corresponding example where the voltage amplitude changes during a power transmission time interval. This can be achieved, for example, by supplying the inverter with a rectified (but not smoothed) AC voltage. The supply voltage during the measurement time interval, which can be synchronized with the zero crossing of the AC signal, is supplied via an alternative power source that provides a substantially constant voltage. An example of a circuit that can generate such a drive signal is shown in Figure 10. In this circuit, the output inverter circuits (M1, M2, Cp1, Cp2) are driven by a rectified AC mains voltage, except when the rectified voltage is less than a given voltage (48V in this example) across a smoothing capacitor C3 supplied by a second supply circuit (second Udc). During this time, the inverter circuits are supplied from the smoothing capacitor C3 through D5, resulting in a substantially constant supply voltage and a constant voltage amplitude for the drive signal.

[0125] In such an example, the transmission coil 103 generates an electromagnetic test signal corresponding to a substantially constant electromagnetic field for measurement during the measurement time interval, where the electromagnetic test signal has a predetermined higher second operating frequency. The amplitude of the estimated electromagnetic field / electromagnetic test signal is determined primarily by the second lower output voltage of the driver 201. In this case, the undisconnected load of the receiver is effectively detuned from the transmitter, thus reducing its influence on the electromagnetic field / electromagnetic test signal.

[0126] In the specific system described above, the power transmitter includes multiple inductive balances, i.e., multiple balance-type sensing coil sets, and the estimation of position / coupling coefficients and foreign object detection can be performed based on output signals from two or more of these balance-type sensing coil sets.

[0127] For example, as shown in Figure 11, the transmitter may be constructed to include three balanced sensing coil sets, each set containing two wedge-shaped coils. In this example, the estimator 205 can measure the output signals from each of the three balanced sensing coil pairs and use these to perform position estimation, coupling coefficient compensation, and / or foreign object detection. The exact criteria used will depend on the priorities and requirements of the individual embodiment.

[0128] In many embodiments, as is indeed the case in the example in Figure 11, the balanced detection coil is located within the transmission coil 103. This can typically improve performance and, in particular, provide a uniform electromagnetic test signal / field for different coils.

[0129] Using multiple inductive equilibria improves performance in many embodiments and provides additional information, particularly regarding magnetic field inhomogeneities. Specifically, it may provide an index of the spatial characteristics of the inhomogeneities. This can be used to generate an estimate of the position of an object causing the inhomogeneity, and in particular, to generate an estimate of the receiver's position, as the receiver is often the source of the inhomogeneity (especially in the absence of foreign objects). Similarly, signals from multiple inductive equilibria can be used to generate an estimate of the (e.g., relative) coupling coefficient between the transmitter and receiver. This (e.g., relative) coupling coefficient estimate may be generated by first generating a receiver position estimate and then converting this into a coupling coefficient estimate. In many embodiments, the coupling coefficient estimate is a relative coupling coefficient estimate. In other embodiments, the (relative) coupling coefficient estimate may be generated independently of the explicit intermediate position estimate that is generated.

[0130] Therefore, in the transmitter of Figure 2, the estimator 215 is configured to obtain a position estimate of the receiver in response to signals from a set of multiple balanced sensing coils during at least one measurement time interval. In some embodiments, the estimator may be configured to obtain an estimate of the (typically relative) coupling coefficients of the receiver in response to signals from a set of multiple balanced sensing coils during at least one measurement time interval. The (typically relative) coupling coefficient estimate may be generated without generating a position estimate.

[0131] As an example, in the configuration shown in Figure 11, three inductive equilibria are used to provide an indicator of the source of non-uniformity. For example, if object 1101 (which could in principle be a small receiver) is located within the detection coil L1, the L1-L2 inductive equilibria will generate a large signal, while the other inductive equilibria L3-L4 and L5-L6 may generate a low signal because the electromagnetic field passing through the corresponding detection coils is substantially uniform. Therefore, it can be estimated that the position of object 1101 is closest to L1 (in this specific example, within L1). The distinction between whether object 1101 is closer to L1 or L2 can typically be determined by comparing the phase of the inductive equilibria signal with the drive signal that generates the electromagnetic test signal (because the two detection coils induce signals that are out of phase with each other).

[0132] In many embodiments, as shown in Figure 2, the outputs of all inductive balanced / balanced sensing coil sets are supplied to an estimator 205, which can measure signals from all inductive balanced coils. The estimator 205 may determine the voltage and / or current of each balanced sensing coil set during the measurement time interval; for example, typically the voltage of each balanced sensing coil set is determined and can be used to estimate the position / coupling coefficient.

[0133] In many embodiments, the transmitter in Figure 2 includes a compensator 211. The compensator 211 is configured to compensate for imbalances between signals induced in two sensing coils when no foreign objects are present and, optionally, when the receiver is in its nominal or recommended position, for signals from one or more, typically all, sets of balanced sensing coils. In some embodiments, the compensation may include static compensation, for example, compensation for differences in the geometric characteristics of different sensing coils within the same balanced sensing coil set. The static compensation may be compensation for imbalances independent of the presence of the receiver, specifically, compensation for imbalances when the receiver is not present.

[0134] In many embodiments, the compensator 211 may be configured to perform dynamic compensation that depends on the presence of a power receiver, and specifically on the location of the power receiver. In dynamic compensation, the compensation value may be adjusted during operation, for example, when a particular event occurs. Typically, dynamic compensation can determine a composite compensation value that includes compensation for static imbalances that arise from asymmetry in the transmitter and also exist even when no receiver is present.

[0135] Dynamic compensation can be performed during operation and power transmission, and compensation can be sought that includes both static and dynamic compensation components. The static compensation component may be a compensation component for unbalance when there is no receiver, or when the receiver meets nominal requirements, such as having certain predetermined characteristics and / or being located in a predetermined position (typically a favorable and / or central position relative to the transmitting coil). The dynamic compensation component may be a compensation component that changes with changing operating conditions, and is therefore a component that can change during operation. In particular, it may change with the position of the receiver.

[0136] In many embodiments, the dynamic compensation component can be determined by a dynamic compensation process that involves determining a composite compensation for the current conditions and then subtracting a static compensation component (e.g., determined before power transmission).

[0137] In practice, detection coils 207 and 209 can be generated to be as identical as possible and designed to cancel each other's inductive signals as much as possible. However, in practice, it has been found that even when no foreign objects are present and no receiver is present (or a symmetrical receiver is present), there tends to be some asymmetry and differences in the parameters of detection coils 207 and 209, and possibly in the electromagnetic environment. Furthermore, asymmetry and imbalance can often result in a combined voltage across detection coils 207 and 209 that is as magnitude as the voltage caused by the misalignment of the receiver or any foreign object to be detected. Therefore, even with balanced inductive / detection coils, detection performance may be difficult or unideal in some embodiments.

[0138] The compensator 211 may be configured to compensate the signal by measuring a value during a measurement time interval, under the assumption that no foreign object is present; that is, the signal resulting from the test signal can be obtained when it is assumed that no foreign object is present. This may be indicated, for example, by the absence of foreign object detection by appropriate foreign object detection, or it may be considered to be the case when a specific user input is provided indicating the absence of foreign object. For example, the user may press a button to initialize the calibration / compensation measurement. In some cases, a compensation measurement may be performed when a new receiver is detected and the user who has placed the new receiver on the transmitter indicates that no foreign object is present.

[0139] In many embodiments, static compensation can be performed when no foreign objects or receivers are present, and the resulting compensation value can be stored as a static compensation component. This can then be used, for example, during dynamic compensation to determine the dynamic compensation component.

[0140] Based on measurements of imbalance (reflecting the signals from a set of balanced detection coils in the absence of foreign objects), compensation values ​​can be determined and applied to each signal. Generally, the compensation value may be the inverse of the measured imbalance, such as (at least partially) offsetting the imbalance. For example, the voltage or current amplitude of the output signal from a set of balanced detection coils in the absence of foreign objects may be measured. Subsequently, this measured amplitude can be subtracted from the measured amplitude of the signal from the set of balanced detection coils to generate a compensated signal amplitude. These compensated signal amplitudes can then be used to evaluate the foreign object detection criterion instead of the measured amplitude of the signal.

[0141] Specifically, the compensator 211 can generate a compensation value that offsets the signal value from a set of balanced detection coils measured when no foreign matter is present (assuming this is the case), (having the opposite phase / polarity to the signal value).

[0142] In some embodiments, compensation may be a single value, such as a compensation current or compensation voltage amplitude, but rather a compensation signal having the same amplitude as the measured signal but in opposite phase (thus canceling out the unbalanced signal). For example, the compensation signal may be generated to have the same frequency as the measured signal (thus having the same frequency as the electromagnetic test signal). The phase and / or amplitude may be set to values ​​that provide the desired compensation.

[0143] In many embodiments, compensation improves estimation and foreign object detection. Indeed, even if the detection coils 207, 209 are perfectly balanced and / or perfectly characterized during the manufacturing process, the electromagnetic field, and therefore the inductive signal, also depends on the specific environment, and in particular tends to vary depending on, for example, the powered equipment used and its precise location. Therefore, performance can be significantly improved if the compensation can be dynamically adapted, specifically calibrated to the current electromagnetic environment. This compensation can be useful in mitigating or reducing imbalances between the detection coils and / or in the environment surrounding them. This can often improve performance, specifically by providing more accurate estimation and foreign object detection.

[0144] This compensation can, in many embodiments, compensate for imbalances caused by features other than foreign objects, thus providing significantly more accurate foreign object detection. However, compensation can also be used to generate location / coupling coefficient estimates. In many embodiments, such estimates can also be generated using compensation values, specifically dynamic compensation values, that are applied to (at least partially) offset the imbalance signal when no foreign object is present. Thus, compensation not only improves foreign object detection, but also facilitates, and in some cases improves, location / coupling coefficient estimation (including coupling coefficient change estimation).

[0145] A particular advantage of such methods is that, in many cases and in certain embodiments, characteristics can be individually tuned for different operations. Generally, foreign object detection is performed frequently and with rapid reaction times so that the presence of foreign objects can be detected very quickly. Also, foreign object detection is usually based on small unbalanced signals.

[0146] In many embodiments and cases, compensation can be performed at a lower frequency and a slower update rate / response time. Thus, the characteristics can be different for each operation and optimized for the specific operation. In practice, since changes in compensation are usually caused by changes in the position of the receiver, the estimation of position and coupling coefficients can usually have similar characteristics to those required for compensation.

[0147] As an example, the configuration in Figure 12 can be considered for a system in which foreign object detection is based on measuring the voltage amplitude Ufod from multiple balanced detection coil sets, each containing two detection coils (L1, L2), (L3, L4), and (L5, L6).

[0148] In this example, before initiating power transmission, static calibration of the foreign object detection system can be performed to compensate for / remove any inherent offsets from the voltages Ufod(L1-L2), Ufod(L3-L4), and Ufod(L5-L6). These offset voltages may be due to a non-uniform detection H field. In this example, the windings of the transmission coil 103 are not mounted perfectly symmetrically on the winding. In this example, the inductive equilibrium L3-L4 and L5-L6 capture more or less the same uniform detection H field. However, the magnetic field captured by the inductive equilibrium L1-L2 is not uniform due to the local wiring layout of the transmission coil 103 below coil L2. Under these conditions, active calibration can be applied by compensating the voltage Ufod(L1-L2) of the inductive equilibrium L1-L2 with a signal Ucomp(L1-L2) that has the correct amplitude and phase for the voltage U_Tx.

[0149] This initial compensation can be performed in the absence of a receiver, and can therefore be used to determine the asymmetry of the transmitter itself and reflect the static compensation component.

[0150] Figure 13 illustrates another cause of offset voltage in the presence of a power receiver. If the power receiver / power receiving device 1301 is positioned misaligned on the active region of the power transmitter, the detected H field from the power transmission coil 103 is expected to become even more distorted and non-uniform. This is particularly pronounced if the device contains metal components.

[0151] In this example, active offset calibration can also be performed. Due to the size of the device 1301 relative to the size of the active region, the distribution of the detected H field from the transmitting coil 103 may be non-uniform over a wide area, possibly even across the entire region. As a result, all three inductive equilibria are affected, and an offset signal is generated. In this situation, three independent compensation voltages Ucomp(L1-L2), Ucomp(L3-L4), and Ucomp(L5-L6) can be determined and applied to the three inductive equilibria, respectively. Here, each compensation voltage has the correct amplitude and phase for the voltage-induced offset unbalanced signal.

[0152] This second compensation, performed in the presence of the receiver, can be carried out during operation, specifically during the measurement time interval. The resulting compensation value can be applied to the signal from the inductive equilibrium when performing foreign object detection. However, the compensation value can also be used to generate position estimates and / or coupling coefficient estimates. By subtracting the static compensation value obtained during testing without the receiver from the measured compensation value, a dynamic compensation component can be generated that more accurately (strictly) reflects the effect of the asymmetrical placement of the receiver. Estimates can then be generated based on these dynamic compensation components from the inductive equilibrium.

[0153] In the example in Figure 14, after active calibration / compensation is performed and compensation is applied, the foreign object FO is placed on the active region. Due to the position of the foreign object on the active region, the detection H field from the transmission coil 103 is expected to be non-uniform near the inductive equilibria L1-L2 and L5-L6. As a result, detection voltages appear at the terminals of both of these inductive equilibria, indicating the presence of the foreign object. However, it is unlikely that the foreign object will cause a disbalance in the third inductive equilibria L3-L4. The estimator 205 can determine that a foreign object has been detected. Thus, as illustrated, a system with three inductive equilibria can detect a foreign object even when a misaligned device is placed on the active region.

[0154] In the example shown in Figure 15, although no foreign object is present, the device 1301 has been moved from its original position in the active region. This movement alters the distribution of the detection H field (i.e., the test magnetic field) of the power transmission coil 103 across the entire detection region. As a result, the signal from the inductive equilibrium changes significantly, potentially reducing the accuracy of foreign object detection.

[0155] When compensation is performed after movement, the compensation values ​​change significantly from the previous values ​​to compensate for the new asymmetry. Applying the new compensation values ​​allows for accurate foreign object detection again. Furthermore, the modified compensation values ​​can be used to update the position and / or coupling coefficient estimates.

[0156] The compensator 211 may be configured to update / adjust / calibrate compensation at different times and under different circumstances, depending on the priorities and requirements of individual embodiments. In many embodiments, the compensator 211 may be configured to initiate compensation adjustment when it is detected that a new receiving device has been placed on the transmitter. This allows the compensation to be aligned not only with static characteristics but also, for example, with the position of the receiving device on the transmitter. Furthermore, in many embodiments, new dynamic compensation may be performed at regular intervals, typically relatively frequently. In some embodiments, new compensation may be performed when a change in signal value is detected, but the foreign object detection algorithm determines that no foreign object is present (e.g., all inductive equilibrium shows a large change).

[0157] The estimator 205 may use different estimation methods depending on the embodiment. The estimation of position and / or coupling coefficients is based on the imbalance indicated by the signal from the inductive equilibrium. In some embodiments, the signal is measured directly and used directly. For example, the estimator 205 may include a measurement circuit that measures the signal from the inductive equilibrium during a measurement time interval and uses these to estimate the position. This method may be used, for example, in embodiments where (dynamic) compensation is not used, or it may be used, for example, to determine the relative position / coupling coefficients with respect to those when (latest) compensation / calibration has been performed.

[0158] In other embodiments, signals from disequilibrium and inductive equilibrium are represented by compensated values ​​determined during compensation / calibration. The compensated values ​​can be considered to correspond to the measured values ​​of the signal from inductive equilibrium at the time of compensation determination (and when no foreign object is present), and the dynamic compensated component can be considered to correspond to the disequilibrium component, which is likely to be due to the presence and position of the receiver. Using compensated signals without directly measuring the signals simplifies processing and operation, and in particular, it may facilitate the use of the inductive equilibrium set for both position / coupling coefficient estimation and, for example, foreign object detection.

[0159] In the following, the term "measured signal" is used to refer to the signal from the inductive equilibrium used to estimate the position / coupling coefficients. Depending on the embodiment, it will be understood that the measured signal may correspond to the compensation signal, the dynamic compensation component of the compensation signal, or the signal measured directly from the inductive equilibrium (currently being measured).

[0160] In most embodiments, as illustrated, the unbalance of a given inductive equilibrium tends to increase with increasing receiver offset from the center position. Therefore, the amplitude of the unbalance can be an indicator of how far the receiver is from this center position. The amplitude may also depend on the distance in a direction perpendicular to the principal direction of the inductive equilibrium, and thus may decrease with offset in this direction. The phase of the measured signal may indicate the direction of the offset, as the direction of the offset affects which sensing coil receives the greatest inductive signal. The phase can be determined by comparing the phase of the measured signal with the phase of the test signal, and the phase difference indicates the direction in which the receiver is offset.

[0161] Therefore, in some embodiments, the position estimation along the axis of an induced equilibrium can be determined based on the amplitude and phase of the estimated signal from that induced equilibrium. By repeating this for all induced equilibrium, a position representation along the axis of each induced equilibrium can be obtained. By combining these position estimations, the position estimation of the receiver can be determined. For example, the position estimation can be generated as the position where the projection on each induced equilibrium axis yields the least squares sum error.

[0162] In many embodiments, the position estimate is not obtained individually for each induced equilibrium, but rather a combined, congruent estimate is generated. For example, as described above, the amplitude of the measurement signal may depend not only on the offset along the axis of the induced equilibrium but also on the orthogonal direction. However, the position offset in this direction can have a significant impact on the imbalance of other induced equilibria, and these measurement signals may be used to compensate for the first measurement signal for the orthogonal position offset. For example, the measurement signal can be normalized based on the signal amplitude of other measurement signals before obtaining the position estimate along the axis of the induced equilibrium.

[0163] In many embodiments, position estimation may be based on prior characterization (e.g., during manufacturing). For example, during manufacturing, measurement signals of a given transmitter and receiver combination may be measured at many different locations. The results may be stored in the transmitter's memory as an N-input LUT (lookup table), where N is the number of inductive equilibria. During operation, the measurement signals may be used to perform a table lookup, and the entry closest to the measurement signal value (e.g., represented by amplitude and phase) is retrieved. This retrieved location may be used as a position estimate.

[0164] In such embodiments, LUTs can be generated for various different receivers or types of receivers. All of these LUTs are stored in the transmitter's memory, and the appropriate LUT can be selected, for example, based on data received from the receiver indicating the type of receiver (i.e., indicating the LUT that best reflects the currently supported receivers).

[0165] In many embodiments, information regarding the characteristics of the receiver is stored in the receiver's memory and can be sent to the transmitter, for example, during initial setup or setting changes. This information may include, for example, the diameter of the receiver coil, the resonant frequency, and the load impedance. The transmitter may use this information when determining the position / coupling coefficient. For example, it may be used to select a LUT containing data generated for receivers with similar characteristics.

[0166] In some embodiments, position estimation may be based on considering a known distance in the direction perpendicular to the coil (z-direction). Often, the z-distance may be unknown or variable, but in some embodiments, this distance may be constant and / or known (e.g., stored during manufacturing). In some embodiments, the z-distance may be determined or learned during operation. If the z-direction is known, it can be taken into account when determining the position and / or coupling coefficients. This eliminates unknown parameters / variables, allowing, for example, absolute values ​​to be determined.

[0167] In many embodiments, the position estimation may be relative, and may be used, for example, to indicate how far the receiver has moved from its previous position. In fact, in many embodiments, one of the distances is likely to be unknown, in particular the Z-distance in the direction perpendicular to the plane of the planar transmitting and receiving coils. For example, the distance between the receiving and transmitting coils, and the inductive equilibrium, are usually unknown because they may differ from receiver to receiver, or they may be unknown characteristics of the transmitter at the time of design. For example, if the transmitter is implemented as part of a kitchen counter, the thickness of the counter may be unknown.

[0168] Since the characteristics of the measured signal may depend on the z-distance, determining the absolute position can be difficult or uncertain. However, in such systems, this method can often be used to determine the relative position, particularly the change in position.

[0169] Such techniques can be combined with, for example, compensation. For instance, compensation / calibration can be performed at a given point in time during operation to offset the imbalance measured by the inductive equilibrium. Then, the signal from the inductive equilibrium can be measured, and the position change can be determined in relation to the current signal. That is, the compensated current signal can be used as the measured signal to determine the position change relative to the compensated signal.

[0170] In some embodiments, the transmitter and / or receiver may include a user interface 215 which can be configured to provide a user output indicating that the receiver is misaligned. The misalignment may be determined depending on whether the position estimate meets the requirements. For example, if the position estimate indicates that the receiver is too far from a preferred position, a user warning or display may be generated. The preferred position may specifically correspond to a position where the signals from the inductive balance are unbalanced. In many embodiments, the preferred position may be the center position relative to the transmitting coil and / or the position where the coupling coefficient (or change in coupling coefficient) between the transmitting and receiving coils is maximum. In examples where the user interface is provided to (and possibly "too") the receiver, the transmitter may include a communicator capable of transmitting an index of the position estimate to the receiver, which can process this and provide an appropriate user output.

[0171] In some embodiments, the requirements may include relative considerations, for example, that a user position shift indicator is generated in response to the detection of a change in the position of the receiver. Thus, in some embodiments, if the position estimate indicates that the receiver has moved (or been moved), a user position shift indicator or warning may be generated.

[0172] For example, if the requirements are met, a light or, for example, a warning / sound may be emitted to indicate that a misalignment has been detected.

[0173] In some embodiments, the user interface may be configured to provide a user output that provides a display of the receiver's position, which is determined in response to a position estimation. The position display may be a display of a relative position, such as a display of the position relative to a preferred position or a nominal position.

[0174] In some embodiments, the position indicator may be provided as an indication of how the receiver should be moved toward a preferred position. For example, the display may show an arrow indicating the direction in which the receiver should be moved toward the preferred position. The distance to the preferred position may be given, for example, by directly indicating the distance from the current position estimate to the preferred position, or indirectly by, for example, adjusting the size of the arrow according to the distance.

[0175] As an example, Figure 16 shows a case where the receiver 1301 is misaligned relative to the transmission coil, and the misalignment is so large that it is highly likely that efficient power transmission will not be possible. In this example, the receiver is too far from the active region to be "out of range," and the recalibration procedure may not be initiated. However, while inductive balance L1-L2 is affected by the device, inductive balance L3-L4 and L5-L6 are also affected, though to a much smaller degree.

[0176] In this example, the estimator 205 can still be used to estimate the position of the receiver, which can be used to detect whether the device is approaching the active area of ​​the transmitter, and even from which direction it is approaching. This information can be used to guide the receiver to its central position by means such as a display or audio.

[0177] In some embodiments, the transmitter may be configured to generate a position change indicator in response to the detection of a change in the position estimation. Different position / change movement indicators may be used depending on the embodiment. In some embodiments, as described above, it may be used to generate a user indicator, such as an audible alarm, that indicates to the user that the receiving device has moved and should probably be returned (by the user) to the optimal position for charging.

[0178] In other embodiments, the movement indicator may be used to adjust the operating parameters of the power transmission, such as the maximum power transmission level. For example, if movement is detected, the power level may be limited to the minimum power immediately after detection. Thereafter, the power level may be gradually increased for the new operating condition, while ensuring that the power transmission is reliable and safe (for example, by ensuring that no foreign objects are detected over a long period of time).

[0179] In some embodiments, the moving indicator may be used to indicate changes in the power control loop. For example, the loop gain, loop filter response, or loop time constant may be adjusted. For instance, during normal operation, slowly adjusting the loop gain while ensuring loop stability may optimize the loop performance for the current operating scenario. If the receiver moves suddenly, the change in coupling coefficients can significantly alter the loop operation, potentially destabilizing the current loop parameters. Therefore, when the moving indicator is generated, the power controller 203 can change the loop gain to a predetermined safe value that ensures the stability of all coupling coefficients. The system can then begin adjusting the loop (specifically the loop gain) again to provide a faster loop response, for example, while ensuring stability for the current conditions.

[0180] In many embodiments, the transmitter may include an adapter 213 configured to adjust the operating parameters of power transmission in response to position and / or coupling estimates. For example, if the position estimate indicates that the receiver is too far from the center position, or if the position estimate indicates movement as described above, the maximum power level of the power transmission signal may be reduced or power transmission may be stopped entirely.

[0181] In some embodiments, the adapter 209 may be configured to adjust power transmission in response to position estimation, and the adjustment may be power transmission operating parameters such as power level, frequency, duty cycle, and duration of power transmission time interval.

[0182] For example, if the position estimation indicates that the receiver has moved, this may change the operating conditions. In this case, the estimator 205 may reduce the power level to ensure safe and reliable operation, and in specific cases, may even terminate power transmission. The receiver can then transition to an operating mode in which full power transmission is gradually achieved by the system gradually adapting to the new operating conditions (for example, a slow power control operation may be used, or a complete reinitialization of power transmission may occur if the ongoing power transmission was stopped).

[0183] In many embodiments, the estimator 205 may be configured to detect a change in the position of the receiver if the measurement signals satisfy a criterion that includes the requirement that the number of measurement signals indicating an imbalance exceeding a second threshold is lower than a threshold number of at least two.

[0184] If an inductive equilibrium system, particularly one with three inductive equilibria as illustrated, is properly calibrated before this displacement, then as a result, the equilibrium state of all three inductive equilibria is affected, and a detection voltage is generated for all three inductive equilibria. In this case, the first requirement for foreign object detection is met, and an initial indication that a foreign object may be present is triggered. However, the second requirement that all three inductive equilibria do not show a large unbalance / detection signal is not met. In this case, the first indication is ignored, and the estimator 205 does not generate a foreign object detection. This helps to avoid false detection of foreign objects.

[0185] In some embodiments, the compensator 211 is configured to initiate compensation adjustments in response to the fulfillment of a second requirement of the foreign object detection criterion. Thus, if an imbalance is detected by an inductive equilibrium exceeding a threshold number, and often if an imbalance is detected for all inductive equilibrium, the compensator 211 can initiate new compensation adjustments. Specifically, new values ​​of signals from different inductive equilibrium (e.g., amplitude and phase of voltage and / or current) can be measured and used as new compensation signals thereafter.

[0186] As mentioned above, the imbalance affecting all inductive equilibrium is likely due to a change in the receiver's position, rather than the presence of foreign objects. Therefore, adjusting the compensation may improve foreign object detection by aligning with a new position that allows for more accurate measurement of imbalances that may be caused by foreign objects.

[0187] Therefore, in this method, the foreign object detection criterion includes an evaluation of the number of measurement signals that show unbalance above a threshold. This evaluation can be performed, for example, by comparing the signal amplitude to the threshold, and whether the amplitude exceeds the threshold can be tested. The requirements may depend on which set of balanced detection coils are being evaluated, and therefore may differ from set to set.

[0188] The number of inductive equilibria where the unbalance exceeds a threshold can be determined, and the foreign object detection criterion requires that this number be at least the threshold number, i.e., that at least the same number of inductive equilibria as the threshold number indicate an unbalance exceeding the threshold. Only in this case is foreign object detection considered to exist; otherwise, no foreign object is considered to exist, and instead, the receiver is considered to have moved. In many embodiments, foreign object detection is considered to have occurred only if the number of unbalances is below the threshold; otherwise, the receiver is considered to have moved.

[0189] In many embodiments, the number of thresholds may be 3 or more, and / or the number of thresholds may be equal to the number of sets of balanced detection coils among the multiple sets of balanced detection coils.

[0190] For example, in the examples shown in Figures 11 to 16, the power transmitter has three inductive balances, and the requirement is to use a threshold number of 3. As a result, for example, a change in position is detected when all measurement signals show a sufficiently high level of unbalance.

[0191] This method can provide improved performance in many embodiments and cases, and can provide accurate indication that the receiver has been moved.

[0192] In many embodiments, particularly efficient operation can be achieved by making the threshold number equal to the number of sets of balanced detection coils. This can provide more reliable position change detection in some embodiments. This allows the position change indication to be limited to only being activated when an object large enough to affect all inductive equilibria is present and moving, for example, a small device may be considered a foreign object.

[0193] Similarly, using a threshold number of 3 compared to using a threshold number of 2 may offer some specific advantages. Specifically, it is possible, or likely, for a foreign object to be positioned to cause imbalance in two balanced sensing coil sets (for example, if it is positioned across the regions of two sensing coils in different balanced sensing coil sets), while it is far less likely that a foreign object could be positioned to strongly affect three balanced sensing coil sets. In fact, this would usually require the foreign object to span three different sensing coils, which is very unlikely (and in some cases even impossible) in many applications, given the need for a receiver to perform power transmission.

[0194] This method can provide particularly efficient and reliable detection of receiver movement. In embodiments, this method can also provide improved foreign object detection. For example, foreign object detection may depend on at least one of the inductive equilibria exhibiting a disequilibrium above a given level, and if this is detected, it may be assumed that a foreign object causing the disequilibrium is present. However, if all measurement signals are detected to be showing a sufficiently high level of disequilibrium, this detection may be invalidated because it is far more likely to be due to the movement of a (relatively large) receiver rather than a small foreign object (in fact, in many cases, it may be impossible for a foreign object to exist that is large enough to affect all the inductive equilibria due to the size of the receiver).

[0195] Therefore, in some embodiments, the foreign object detection criteria include not only the requirement that the unbalance must exceed a threshold, but also the requirement that not all induced equilibria show unbalance. In many embodiments, the mere fact that one of the measured signals shows a (sufficiently) high level of unbalance is not considered sufficient to indicate that a foreign object has been detected. In addition, a second requirement must be met, which involves considering multiple detection signals (or at least some of them) together.

[0196] In some embodiments, the transmitter may be configured to distinguish between unbalance due to a change in the receiver's position (and therefore coupling coefficient) and unbalance due to the presence of foreign matter, depending on the amplitude of the measured / detected signal. In the above system, the inductive equilibrium may indicate unbalance due to a change in the movement / position of the device or due to foreign matter. In the former case, a large amplitude change is usually detected (and is usually detected in at least two inductive equilibria), while in the latter case, the amplitude change is usually much smaller because the foreign matter is small compared to the receiver (or usually only one or two inductive equilibria are affected). Therefore, in many embodiments, the position estimation and / or coupling coefficient (change) estimation also depend on the size of the detected unbalance. Specifically, in many embodiments, a change in position and / or coupling coefficient may be detected (only) if the measured signal indicates an unbalance exceeding a given threshold. Otherwise, it may be considered that the unbalance is likely due to foreign matter.

[0197] In some embodiments, the transmitter may include a receiver configured to receive data from the receiver. In such embodiments, the receiver may be configured to transmit physical characteristic data to the transmitter, which indicates one or more physical characteristics of the receiver, specifically physical characteristics relating to its extent. For example, the physical characteristic data may indicate the size, length, dimensions, etc., of the receiver. Thus, the physical characteristic data may indicate characteristics relating to the spatial extent of the receiver. In some embodiments, the physical characteristic data may instead or additionally indicate the spatial extent, or, for example, the amount of conductive material (metal) that is part of the receiver.

[0198] In such embodiments, physical characteristic data can be supplied to an estimator 205 which may be configured to adjust position estimation / coupling coefficient (change) estimation in accordance with the physical characteristic data. For example, a function may be executed to determine the position along the inductive equilibrium axis in accordance with the measured signal, depending on the physical dimensions. As another example, the selection of a LUT, which includes position estimation for various combinations of multiple measured signal characteristics, may be done in accordance with the received data.

[0199] The estimator 205 can estimate an estimate of the coupling coefficient (change) of the electromagnetic coupling between the transmitting coil 103 and the receiving coil 107 in response to signals from the inductive equilibrium during the measurement time interval, typically in response to the measurement signal. In many embodiments, the estimator 205 may be configured to obtain a relative coupling coefficient estimate rather than an absolute coupling coefficient estimate. Specifically, the estimator 205 may be configured to monitor the measurement signal to detect changes in the coupling coefficient and, if there are changes, estimate the magnitude (and direction) of those changes.

[0200] The coupling coefficients depend on the relative position of the receiving coil 107 with respect to the transmitting coil 103. In many embodiments, the estimator 205 may be configured to first determine the position of the receiving coil relative to the transmitter, and then determine the corresponding coupling coefficients from the determined position. For example, a measurement signal may be used to perform a table lookup that provides a relative position estimate. This relative position estimate can then be used as a lookup to a second lookup table that provides a coupling coefficient estimate. In other embodiments, the coupling coefficients may be generated directly without explicitly determining the position estimate as an explicit value. In such embodiments, the coupling coefficients may be determined directly by the estimator 205, and the position estimate may not be determined (but can be considered an intrinsic and implicit part of the coupling coefficient estimate generation). For example, the first lookup table may directly output the coupling coefficient estimate rather than the position estimate used for the second lookup table.

[0201] The estimator 205 may provide the adapter 213 with a display of the coupling coefficient estimate, and the adapter 213 may be configured to adjust the parameters of the power transmission operation in response to the coupling coefficient estimate. Specifically, the adapter 213 may be configured to adjust the power loop parameters in response to the coupling coefficient estimate, where the power loop parameters are the loop parameters of a power control loop that adjusts the power level of the power transmission signal in response to power control messages received from a receiver. Specifically, the power loop parameters may be the loop time constant, the frequency response of the loop filter, and / or the loop gain.

[0202] The performance of a power control loop depends heavily on the coupling coefficient. Generally, the loop stability (frequency domain) and settling time (time domain) of a closed-loop system are determined by the loop gain and associated phase margin. In general, for control loops, loop parameters such as loop gain and loop filter characteristics are crucial to loop performance and are usually tightly controlled or, in practice, substantially constant in many control loops to achieve not only the desired performance but also the fundamental stability of the feedback loop. However, in the case of power control loops in wireless power transmission systems, loop parameters, particularly loop gain, depend heavily on the coupling coefficient. Furthermore, the coupling coefficient can usually vary considerably, and without sufficient care, there is a high risk of undesirable loop performance, or in some cases, instability. The above method allows for the dynamic estimation of the coupling coefficient, and the loop operation can be adjusted accordingly. For example, the loop gain can be adjusted to compensate for gain fluctuations caused by variations in the coupling coefficient. As another example, 360° feedback that causes oscillation or instability can be avoided by modifying the loop filter or loop delay to alter the phase feedback operation.

[0203] As an example, Figure 17 shows the changes in the coupling coefficient (called the K-factor 1701) and loop gain 1703 for various displacements 1705 of the receiving coil 107 and the transmitting coil 103. As can be seen from the figure, a key parameter affecting the loop gain is the K-factor between the receiving coil 107 and the transmitting coil 103. The K-factor is determined by the size of the coils, the Z-distance between the coils, and the displacement of the coils in the plane. By being able to estimate the K-factor, the transmitter can support the receiver over a wider area and with a wider range of displacements while maintaining closed-loop stability.

[0204] Figure 17 shows the functions of the K factor and loop gain with respect to a given Z-distance displacement. As the receiving coil 107 moves away from the center of the transmitting coil 103, the K factor decreases to zero, and at a certain displacement, the K factor changes sign. On the other hand, the system loop gain initially increases as the receiver moves away from the center. This is due to the resonant behavior of the transmitter resonant tank formed by the transmitting coil 103 and one or more capacitors. However, at a certain displacement, power transmission becomes impossible due to the loss of coupling, and the loop gain decreases to zero. This behavior clearly demonstrates that knowing the K factor can be of great help in maintaining closed-loop stability.

[0205] Therefore, knowing the coupling coefficients helps keep the control loop optimized for loop stability, overshoot, and maintaining the desired settling time.

[0206] Regarding position estimation, coupling coefficient estimation is typically relative, and changes in coupling coefficients can be estimated and detected using loop parameters adjusted according to the relative estimation, for example by applying relative changes to the gain. In fact, in many cases the distance in the z direction is unknown, and the coupling coefficients may depend on this distance. This hinders the acquisition of absolute estimates of coupling coefficients, but it may be possible to detect relative changes.

[0207] The specific method for estimating coupling coefficients may vary from embodiment to embodiment. In many embodiments, measurements are taken during manufacturing, and the measurement results are stored in various LUTs in the transmitter for different receivers. The transmitter uses the measurement signals for its table lookup to identify the optimal LUT (the LUT that best matches the receiver) and retrieve the coupling coefficient estimates.

[0208] In some embodiments, the estimator 205 may be configured to obtain a coupling coefficient estimate as a coupling coefficient that decreases with increasing amplitude of at least one set of multiple balanced detection coil sets. This may reflect the fact that, as shown in Figure 17, the coupling coefficient tends to decrease as the displacement increases, the unbalance increases as the displacement increases, and therefore the amplitude of the measured signal tends to increase for at least one inductive equilibrium.

[0209] In some embodiments, the estimator 205 may be configured to obtain coupling coefficient estimates as coupling coefficients that decrease with increasing amplitude differences between at least two sets of a plurality of balanced detection coil sets.

[0210] For example, during manufacturing, measurements may be taken to determine the maximum coupling coefficient for the ideal arrangement of different receivers or types of receivers. For instance, the measurements may determine the coupling coefficient for a centrally located receiver of a specific size. The measured values ​​may be stored in a lookup table (LUT).

[0211] During operation, the estimation circuit 205 can access the LUT and extract the current maximum coupling coefficient of the receiver. Then, based on the difference in the inductive equilibrium unbalance, the offset of the receiver's position from the ideal position can be estimated. A larger amplitude difference between the inductive equilibrium positions results in a larger offset from the receiver's central equilibrium position and a lower coupling coefficient. The decrease from the maximum coupling coefficient provided by the LUT may also be calculated using a function determined during manufacturing, where the decrease increases as the amplitude difference increases. This decrease can then be applied to the maximum coupling coefficient to generate the current estimate of the coupling coefficient.

[0212] More specifically, the estimator 205 may be configured, for example, in some embodiments, to determine the coupling coefficients using the following procedure, depending on the implementation.

[0213] The receiving device is placed on the transmitting area and identified by the transmitting device. The device communicates the diameter of its footprint to the transmitting device. The transmitting device can then access the LUT to obtain the maximum K factor (coupling coefficient) for a given diameter footprint. This is the case when the receiving coil is precisely centered on the power coil. The compensation circuit 211 can then compensate the three output signals of the three inductive balanced coils so that the output signals are adjusted to substantially zero. If the three compensated signals are sufficiently similar (e.g., equal or of the same order), this can be considered to indicate that the K factor provided by the LUT is close to the actual current situation. The control loop can then be adjusted based on the K factor value. However, if the three compensated signals are significantly different, the device is not centered on the power coil. This is likely to indicate that the K factor provided by the LUT is inaccurate, specifically that the value provided by the LUT is higher than the actual value. Thus, the estimation circuit 205 can reduce the coupling coefficient (K coefficient) to reflect the difference between the signals. For example, in some embodiments, a fixed low K-factor value may be provided if the difference between the output signals meets a criterion indicating that the difference is sufficiently large. In other embodiments, a function may be used to reduce the K-factor value, and this function depends on the difference between the output signals from each inductive equilibrium. The transmitter may then set the initial loop gain parameters to reflect the estimated (usually reduced) coupling coefficients so that overshoot at the output can be avoided or reduced.

[0214] In many embodiments, the coupling coefficient estimate may be a relative coupling coefficient estimate, and therefore, if a change is detected in the signal from the inductive equilibrium, that change can be translated into a change in the coupling coefficient estimate. In many embodiments, a change in the signal from the inductive equilibrium, such as an increase in unequilibrium, can be directly considered to reflect a change in the coupling coefficient estimate, such as indicating a decrease in the coupling coefficient. The transmitter can then quickly correct its operation by a certain relative amount, for example, by correcting the power control loop.

[0215] In some embodiments, the transmitter may be configured to change the driver's operating point in response to coupling coefficient estimation, and in particular, in response to detection of relative changes in coupling coefficient estimation, relative changes may be applied to operating parameters such as the voltage or other parameters of the inverter that generates the drive signal.

[0216] In some embodiments, the transmitter may be configured to change the frequency of the drive signal in response to coupling coefficient estimation, and in particular, a relative change in frequency may be applied in response to the detection of a relative change in coupling coefficient estimation.

[0217] A power transmitter can maintain an operating / driving frequency for power transmission such that it falls within a certain frequency interval, where this interval depends on the coupling coefficient estimation.

[0218] As an example, a power transmitter may be configured to supply a constant voltage to the output / load. Generally, a change in the coupling coefficient changes the (power) transmission function. The change in the coupling coefficient estimate can be used to adjust the power transfer parameters to reflect and compensate for such changes in the power transmission function. Specifically, the power transmitter may adjust the duty cycle and / or frequency based on the coupling coefficient estimate.

[0219] The transmitter may be configured to detect, for example, a change in the coupling coefficient estimate (e.g., a sudden step change caused by the sudden movement of the receiver). The transmitter may then be configured to determine the corresponding change to the duty cycle and / or frequency of the drive signal, which may be applied immediately to the drive signal. The system may then continue the power control loop while slowly adjusting the frequency and / or duty cycle. For example, the initial step change may be relatively inaccurate, and the power control loop will then adjust toward the optimal value. However, the initial rapid step change based on the coupling coefficient estimate may significantly improve transition performance, for example, by greatly mitigating overvoltage or undervoltage conditions.

[0220] In many embodiments, the power transmitter may have, for example, a predetermined function or lookup table that has absolute or relative coupling coefficient estimates as inputs and provides absolute or relative duty cycles or frequencies as outputs. The function or lookup table may be determined, for example, during the manufacturing or design phase.

[0221] By adjusting the method and operation based on coupling coefficient estimation, significant performance improvements can be achieved. Wireless power transmission systems and power transmission functions are typically nonlinear, and coupling coefficient estimation can provide additional information about the system's characteristics and gains.

[0222] For clarity, the above description describes embodiments of the invention in relation to different functional circuits, units, and processors. However, it will be understood that functions can be appropriately distributed among different functional circuits, units, or processors without impairing the invention. For example, a function described as being performed by multiple separate processors or controllers may be performed by the same processor or controller. Therefore, references to specific functional units or circuits should be considered not as indicating a strict logical or physical structure or organization, but as references to appropriate means for providing the described function.

[0223] The present invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The present invention may be at least partially implemented 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 practice, the functionality may be implemented as a single unit, multiple units, or as part of other functional units. Thus, the present invention may be implemented as a single unit, or it may be physically and functionally distributed among different multiple units, circuits, and processors.

[0224] Although the present invention has been described in relation to several embodiments, the present invention is not limited to the specific forms described in the specification. The scope of the present invention is limited only by the appended claims. Furthermore, even if a certain feature appears to be described in relation to a particular embodiment, those skilled in the art will recognize that various features of the above embodiments can be combined in accordance with the present invention. In the claims, terms such as "equipment," "includes," etc., do not preclude the presence of other elements or steps.

[0225] Furthermore, even if listed individually, multiple means, elements, circuits, or method steps may be carried out by, for example, a single circuit, unit, or processor. Moreover, even if individual features are included in different claims, they can be suitably combined, and their inclusion in different claims does not mean that the combination of features is impossible and / or unfavorable. Also, the inclusion of a feature in one claim category does not mean that the feature is limited to that category; the feature may be equally applicable to other claim categories as appropriate. The inclusion of a feature in a dependent claim of an independent claim does not imply limitation to that independent claim; the feature may be applicable to other independent claims as appropriate. Furthermore, the order of features in a claim does not indicate a specific order in which the features should act, and in particular, the order of individual steps in a method claim does not mean that the steps must be performed in that order. The steps may be performed in any suitable order. Also, singular expressions do not preclude plural forms; therefore, expressions such as "first," "second," etc., do not preclude plurals. Reference numerals in the claims are merely examples for clarity and do not in any way limit the scope of the claims.

Claims

1. A power transmitter for wirelessly supplying power to a power receiver via an inductive power transmission signal, wherein the power transmitter is Power transmission coil and A driver for generating a drive signal for the power transmission coil, wherein the driver generates the drive signal for the power transmission coil to generate the inductive power transmission signal during at least one power transmission time interval of the iterative time frame, and also generates the drive signal for the power transmission coil to generate an electromagnetic test signal during at least one measurement time interval of the iterative time frame, A set of series-connected balanced detection coils, the set of balanced detection coils comprising two detection coils, wherein the signals induced in the two detection coils by the electromagnetic field generated by the power transmission coil cancel each other out, A power transmitter comprising, during at least one measurement time interval, an estimation circuit that, in response to a signal from the set of balanced detection coils, estimates the coupling coefficient of the electromagnetic coupling between the transmitting coil and the receiving coil of the power receiver.

2. The power transmission according to claim 1, wherein the coupling coefficient estimation is relative coupling coefficient estimation.

3. The power transmitter according to claim 1 or 2, wherein the estimation circuit determines the coupling coefficient estimate as a coupling coefficient that decreases with increasing amplitude of the signal of the set of balanced detection coils.

4. Having at least two sets of the balanced detection coils, The power transmitter according to any one of claims 1 to 3, wherein the estimation circuit determines the coupling coefficient estimate as a coupling coefficient that decreases with increasing amplitude difference between the set of at least two balanced detection coils.

5. The power transmitter according to any one of claims 1 to 4, comprising an adapter that adjusts power loop parameters in response to the coupling coefficient estimation, wherein the power loop parameters are loop parameters of a power control loop that adjusts the power level of the inductive power transmission signal in response to a power control message received from the power receiver.

6. The power transmission according to claim 5, wherein the power loop parameter is at least one of the loop time constant, the frequency response of the loop filter, and the loop gain.

7. The power transmitter according to any one of claims 1 to 6, wherein the estimation circuit determines the position estimation of the power receiver in response to signals from the set of balanced detection coils during the at least one measurement time interval.

8. The power transmitter according to claim 7, further comprising a user interface that provides a user output that indicates the positional deviation of the power receiver in response to the positional estimation meeting the requirements.

9. The power transmitter according to claim 7 or 8, further comprising an adapter that adjusts the operating parameters of inductive power transmission in response to the position estimation.

10. The power transmitter according to claim 9, wherein the adapter adjusts power loop parameters in response to the position estimation, and the power loop parameters are loop parameters of a power control loop that adjusts the power level of the inductive power transmission signal in response to a power control message received from the power receiver.

11. The power transmitter according to any one of claims 7 to 10, wherein the estimation circuit detects a change in position for the power receiver when the signal meets a criterion, the criterion includes the requirement that the number of signals from the set of balanced detection coils is less than a threshold number, where the number of signals is at least 2, indicating that the imbalance between the signals induced in the two detection coils of the set of balanced detection coils exceeds a second threshold.

12. The power transmitter according to any one of claims 7 to 11, further comprising a compensator that compensates for the imbalance between the signals induced in the two detection coils when no foreign matter is present, the set of balanced detection coils for the signal, and the estimation circuit determines the coupling coefficient estimation in response to the amount of compensation of the set of balanced detection coils.

13. The power transmitter according to claim 12, wherein the compensator determines the static and dynamic components of the compensation, the static component is independent of the presence of the power receiver, the dynamic component is dependent on the presence of the power receiver, and the estimation circuit determines the position estimation in response to the dynamic component.

14. 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 is Power transmission coil and A set of balanced detection coils connected in series, the set of balanced detection coils comprising two detection coils, wherein the signals induced in the two detection coils by the electromagnetic field generated by the power transmission coil cancel each other out, The aforementioned method, The driver generates a drive signal for the power transmission coil in order to generate the inductive power transmission signal during at least one power transmission time interval of the iterative time frame and to generate an electromagnetic test signal during at least one measurement time interval of the iterative time frame, A method comprising the step of determining an estimate of the coupling coefficient of the electromagnetic coupling between the transmitting coil and the receiving coil of the receiver of a power receiver in response to a signal from the set of balanced detection coils during at least one measurement time interval.

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