Power transmitter and method of operating the same

Abstract

A power transmitter (101) for wirelessly providing power to a power receiver (105), comprising: a retriever (209) that retrieves calibration data, including a set of calibration parameters for each of a plurality of spatial positions of a calibrated receiver relative to a calibration transmitter. A test generator (207) generates a test drive signal for a transmitter coil (103) to generate an electromagnetic test signal, and a test processor (213) determines a set of test parameters in response to the test drive signal. A position estimator (207) estimates a position of the power receiver relative to the power transmitter in response to a comparison of the test parameters for the plurality of spatial positions with calibration parameters. The parameters include a power loss measure, a resonant frequency measure, and a coupling measure. The method and specific parameters provide substantially improved position estimation.

Description

Technical Field

[0001] The present invention relates to the operation of wireless power transfer systems and, in particular, but not exclusively, to the estimation of the relative positions of wireless power receivers in wireless power transfer systems, such as Qi wireless power transfer systems. Background Art

[0002] Most current electrical products require dedicated electrical contacts in order to be powered from an external power source. However, this is often unrealistic and requires the user to physically plug in a connector or otherwise establish physical electrical contact. Typically, power requirements also vary significantly, and most current devices are provided with their own dedicated power source, resulting in a typical user having a large number of different power sources, each dedicated to a specific device. Although the use of internal batteries can avoid the need for wired connection to a power source during use, this only provides a partial solution because the battery will need to be recharged (or replaced). The use of batteries may also significantly increase the weight of the device and potential cost and size.

[0003] In order to provide a significantly improved user experience, the use of wireless power has been proposed, wherein power is inductively transferred from a transmitter coil in a power transmitter device to a receiver coil in an individual device.

[0004] Power transfer via magnetic induction is a well-known concept, mainly applied in transformers with tight coupling between the primary transmitter inductor / coil and the secondary receiver coil. By separating the primary transmitter coil and the secondary receiver coil between the two devices, wireless power transfer between these devices becomes possible based on the principle of loosely coupled transformers.

[0005] Such an arrangement allows wireless power transfer to the device without requiring any wired or physical electrical connection to be made. In fact, it can simply allow the device to be placed near or on top of the transmitter coil for external recharging or powering. For example, the power transmitter device can be arranged with a horizontal surface on which the device can simply be placed for powering.

[0006] In addition, such a wireless power transmission arrangement can be advantageously designed to enable a power transmitter device to be used with a range of power receiver devices. Specifically, a wireless power transmission method known as the Qi specification has been defined and is currently being further developed. This method allows a power transmitter device that meets the Qi specification to be used with a power receiver device that also meets the Qi specification without the devices having to be from the same manufacturer or having to be dedicated to each other. The Qi standard also includes a function for allowing operation to be adapted to a specific power receiver device (e.g., depending on a specific power consumption).

[0007] The Qi specification was developed by the Wireless Power Consortium and more information can be found, for example, on their website: http: / / www.wirelesspowerconsortium.com / index.html , where, in particular, the defined specification document can be found.

[0008] In power transmission systems (such as Qi), the electromagnetic fields generated to transmit the required power level to the power receiver are often very large. In many cases, the presence of such strong fields has an impact on the surroundings. For example, a potential problem with wireless power transmission is that power may be unintentionally transmitted to, for example, metal objects that happen to be near the power transmitter. US 2011 / 196544 A1 describes a calibrated parasitic metal detection system that solves this problem.

[0009] In wireless power transfer systems, it is important to achieve high efficiency of power transfer. A highly efficient wireless power transfer system achieves a high coupling factor (κ) between the transmitter and receiver coils, and it is desirable for the coupling factor κ to be as close to 1 as possible. In order to achieve a high coupling factor, the receiver coil needs to be placed very close to the transmitter coil, and the coils should preferably be precisely aligned. US 2016 / 248280 A1 describes an inductive transfer system with improved tolerance to variations in the alignment of the inductive coils.

[0010] Proper or perfect alignment may also provide other advantages. For example, if the alignment is optimal, the operating parameters may be closer to the nominal or expected operating point, and this may facilitate some operations, such as communication or detection of the presence of a metal object, for example.

[0011] However, for most practical systems, there is no guarantee that the alignment will be optimal. For most currently envisioned applications, the user will have the freedom to position the power receiver device on the power transmitter device (e.g., when placing a mobile phone on a wireless charger). As a result, the coils cannot be guaranteed to be, and in practice are often not, perfectly aligned, and this can lead to poor coupling, which results in, for example, longer charging times, power waste, heating of friendly metal in the receiver, and other inconveniences for the user.

[0012] It is generally not practical to restrict the placement of the power transmitter and power receiver so that perfect alignment is ensured. However, if the misalignment is known, various methods may be used, for example, to compensate for such misalignment or provide feedback that allows the alignment to be improved.

[0013] Hence, an improved method for determining the position of a power receiver relative to a power transmitter would be advantageous, and in particular a method allowing increased flexibility, reduced cost, reduced complexity, improved position estimation, improved communication, improved accuracy, improved adaptability, backward compatibility, improved power transfer operation and / or improved performance would be advantageous. Summary of the invention

[0014] Accordingly, the Invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

[0015] According to aspects of the present invention, there is provided a power transmitter for wirelessly providing power to a power receiver via an electromagnetic power transfer signal; the power transmitter comprising: at least one transmitter coil for generating the power transfer signal during power transfer; a retriever for retrieving calibration data, the calibration data comprising a set of calibration parameters for each of a plurality of spatial positions of a calibration receiver relative to a calibration transmitter, the calibration parameters comprising the following for each of the plurality of spatial positions: a calibration power loss measure for the calibration power receiver at the spatial position, an indication of a calibration resonant frequency measure of a resonant circuit of the calibration power transmitter for the calibration power receiver at the spatial position, an indication of the calibration power loss measure for the calibration power receiver at the spatial position a calibration coupling measure of the coupling between a calibration transmitter and the calibration receiver at the spatial position; a test generator for generating a test drive signal for the transmitter coil to generate an electromagnetic test signal; a test processor for determining a set of test parameters in response to the test drive signal, the test parameters including: a test power loss measure indicative of power extracted from the electromagnetic test signal, a test resonant frequency measure for a resonant circuit including the transmitter coil, a test coupling measure indicative of coupling between the power transmitter and the power receiver; and a position estimator for estimating the position of the power receiver relative to the power transmitter in response to a comparison of the test parameters for the plurality of spatial positions with the calibration parameters.

[0016] The present invention may provide an improved and / or facilitated position estimate of the relative position of a power receiver. The method may generate a position estimate indicating a misalignment or displacement of a receiver coil relative to the transmitter coil. In many embodiments, the method may provide accurate detection, including estimates of three-dimensional or two-dimensional misalignments. The method may be particularly effective in many practical wireless power transfer systems including different types of power transmitters and power receivers.

[0017] The position estimate may, for example, be used to generate user feedback and / or may, for example, be used to compensate other operations for the misalignment.

[0018] The position estimate may specifically indicate a position of the coil of the power receiver relative to the transmitter coil.

[0019] The test power loss metric, the test resonant frequency metric, and the test coupling metric may provide different relationships to the position of the power receiver relative to the power transmitter in that the function between the position and the metric is different for different metrics. In that the combination provides additional information about the position beyond that provided by only one of the metrics, the mutual relationship between the test power loss metric, the test resonant frequency metric, and the test coupling metric may provide an additional indication of the position of the power receiver relative to the power transmitter. The different relationships may, for example, allow for different degrees of facilitation and / or improved position estimation for misalignment, for example, one metric may be more suitable for relatively small misalignments, while another metric may be more suitable for relatively large misalignments.

[0020] The position estimation may generate a position estimate that reflects a degree of misalignment between the power transmitter and the power receiver.

[0021] The comparison caused by the position estimator may, for example, include generating a cost metric for each of the plurality of spatial positions using a cost function that is a monotonically increasing function of a difference between the test power loss metric and the calibration power loss metric, a monotonically increasing function of a difference between the test resonant frequency metric and the calibration resonant frequency metric, and / or a monotonically increasing function of a difference between the test coupling metric and the calibration coupling metric. In such an example, the position estimator may determine the spatial position in response to the cost metrics for the plurality of spatial positions, such as, for example, setting the position estimate based on the spatial position having the lowest cost value.

[0022] According to an optional feature of the invention, the position estimator is arranged to: determine a vertical distance measurement indicating the distance between the transmitter coil and the receiver coil of the power receiver in a direction perpendicular to a contact surface for receiving the power receiver; and determine the position of the power receiver in response to a comparison of the vertical distance measurement with a plurality of spatial positions of a calibration receiver.

[0023] In many embodiments and situations this may provide improved performance. For example, in many practical applications where placement of the power receiver is more restricted in one direction than in other directions, it may provide improved performance.

[0024] The position estimator may take into account the vertical distance measure, for example by using this in the comparison, or may constrain the spatial positions considered, for example by only considering spatial positions that match the vertical distance measure.

[0025] According to an optional feature of the invention, the power transmitter comprises: a communicator for receiving a message from the power receiver; wherein the communicator is arranged to receive a power receiver distance indicator indicating a distance from the receiver coil to an outer surface of the power receiver; and wherein the position estimator is arranged to determine the vertical distance measurement in response to the power receiver distance indicator.

[0026] This may provide a particularly advantageous approach and may in particular provide an efficient way for the power transmitter to adapt to many different power receivers, thereby improving compatibility.

[0027] According to an optional feature of the present invention, the power transmitter comprises: a communicator for receiving a message from the power receiver; wherein the communicator is arranged to receive a power receiver identification indication from the power receiver, and the retriever is arranged to retrieve calibration data matching the power receiver identification indication.

[0028] This may be advantageous in many applications and may allow for a system in which the position estimate may be adapted for different power receivers.The method may allow for a wireless transmission system with efficient interworking between many different types of power receivers and power transmitters.

[0029] The power receiver identification indication may be a device-specific power receiver identification indication or may be, for example, a type-specific power receiver identification indication.

[0030] According to an optional feature of the invention, the retriever is arranged to retrieve the calibration data from the remote source by sending a calibration data request message to the remote source, the calibration data request message comprising an identification indication corresponding to the power receiver identification indication.

[0031] This may provide advantageous performance in many embodiments and may provide an efficient and flexible method for enabling a wireless power transfer system to support many different power receivers and power transmitters.

[0032] According to an optional feature of the invention, the power transmitter further comprises: a communicator for receiving data from the power receiver; wherein the retriever is arranged to receive the calibration data from the power receiver.

[0033] This may provide advantageous performance in many embodiments and may provide an efficient and flexible method for enabling a wireless power transfer system to support many different power receivers and power transmitters.

[0034] According to an optional feature of the invention, at least some of the calibration parameters are provided for calibrating the power receiver with a disconnected load.

[0035] This may in many embodiments provide an improved and generally more accurate position estimate.The determination of the test parameter may accordingly be performed with the power receiver having the load disconnected.

[0036] According to an optional feature of the invention, the calibration data is provided for a reference power transmitter.

[0037] This may provide in many embodiments efficient operation for wireless power transfer systems including many different types of power transmitters.

[0038] According to an optional feature of the invention, the position estimator is arranged to modify at least one of at least one calibration parameter and a test parameter in response to a difference between a property of the power transmitter and a property of the reference power transmitter.

[0039] In many cases this may provide improved position estimates and may enable or facilitate efficient operation of wireless power transfer systems including many different types of power transmitters.

[0040] According to an optional feature of the invention, the test generator is arranged to generate a plurality of different test signals, and the calibration data comprises a plurality of calibration parameters for the different test signals for one spatial location.

[0041] In many situations and applications this may provide an improved position estimate.The position estimator may be arranged to estimate the position of the power receiver in response to a comparison of the test parameters with a plurality of calibration parameters for different test signals.

[0042] According to an optional feature of the invention, the power transmitter comprises a plurality of transmitter coils including the transmitter coil, and the test generator is arranged to generate the test signal for the plurality of transmitter coils.

[0043] In many situations and applications, this can provide an improved position estimate.

[0044] According to an optional feature of the invention, the test generator is arranged to generate a sequence of test signal groups comprising different test signals for different ones of the plurality of transmitter coils, and the calibration data comprises a plurality of calibration parameters for the different test signal groups for one spatial location.

[0045] In many situations and applications this may provide an improved position estimate.The position estimator may be arranged to estimate the position of the power receiver in response to a comparison of the test parameters for different test signal sets with a plurality of calibration parameters.

[0046] According to an optional feature of the invention, at least two of the groups of test signals comprise test signals for different sub-groups of the transmitter coils.

[0047] In many situations and applications, this can provide an improved position estimate.

[0048] According to an optional feature of the invention, the position estimator is arranged to estimate at least two dimensions for the position of the power receiver.

[0049] According to aspects of the invention, there is provided a method of operating a power transmitter that wirelessly provides power to a power receiver via an electromagnetic power transfer signal generated by a transmitter coil; the method comprising: retrieving calibration data, the calibration data comprising a set of calibration parameters for each of a plurality of spatial positions of a calibration receiver relative to a calibration transmitter, the calibration parameters comprising, for each of the plurality of spatial positions: a calibration power loss measure for the calibration power receiver at the spatial position, a calibration resonant frequency measure of a resonant circuit of the calibration power transmitter indicative of the calibration power receiver at the spatial position, a calibration coupling metric indicative of coupling between the calibration transmitter and the calibration receiver at the spatial location; generating a test drive signal for the transmitter coil to generate an electromagnetic test signal; determining a set of test parameters in response to the test drive signal, the test parameters comprising: a test power loss metric indicative of power extracted from the electromagnetic test signal, a test resonant frequency metric for a resonant circuit including the transmitter coil, a test coupling metric indicative of coupling between the power transmitter and the power receiver; and estimating a position of the power receiver relative to the power transmitter in response to a comparison of the test parameters for the plurality of spatial locations with the calibration parameters.

[0050] These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0052] Figure 1 illustrates examples of elements of a power delivery system according to some embodiments of the present invention;

[0053] Figure 2 illustrates examples of elements of a power transmitter according to some embodiments of the present invention;

[0054] Figure 3 illustrates examples of elements of a power receiver according to some embodiments of the present invention;

[0055] Figure 4 illustrates an example of components of an output stage of a power transmitter;

[0056] Figure 5 Some examples of alignment between transmitter coil and receiver coil are illustrated;

[0057] Figure 6 illustrates examples of elements of a power receiver according to some embodiments of the present invention;

[0058] Figure 7 Some examples of alignment between transmitter coil and receiver coil are illustrated;

[0059] Figure 8 Some examples of alignment between a receiver coil and a plurality of transmitter coils are illustrated;

[0060] Fig. 9 illustrates an example of elements of a method of determining calibration parameters according to some embodiments of the present invention;

[0061] Fig.10 An example of elements of a method of estimating a relative position of a power receiver according to some embodiments of the invention is illustrated. DETAILED DESCRIPTION

[0062] The following description focuses on embodiments of the invention applicable to wireless power transfer systems utilizing power transfer methods such as known from the Qi specification. However, it will be appreciated that the invention should not be limited to this application but may be applied to many other wireless power transfer systems.

[0063] Figure 1An example of a wireless power transmission system according to some embodiments of the present invention is illustrated. The power transmission system includes a power transmitter 101, which includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105, which includes (or is coupled to) a receiver coil / inductor 107.

[0064] The system provides an electromagnetic power transfer signal that can inductively transfer power from the power transmitter 101 to the power receiver 105. In particular, the power transmitter 101 generates an electromagnetic signal that is propagated as magnetic flux by the transmitter coil or inductor 130. The power transfer signal can correspond to an electromagnetic power transfer component representing the energy transfer from the power transmitter to the power receiver, and can be considered to correspond to a component of the generated electromagnetic field that transfers power from the power transmitter to the power receiver. For example, if there is no loading of the receiver coil 107, no power will be extracted by the power receiver from the generated electromagnetic field (except for losses). In such a situation, the driving of the transmitter coil 103 can generate an electromagnetic field of potentially high field strength, but the power level of the power transfer signal will be zero (except for losses). In some cases where a foreign object is present, the power transfer signal can be considered to include a component corresponding to the power transfer to the foreign object, and thus the power transfer signal can be considered to correspond to power extracted from the electromagnetic field generated by the power transmitter.

[0065] The power transfer signal may typically have a frequency between about 20 kHz and about 500 kHz, and is often used for Qi compatible systems typically in the range from 95 kHz to 205 kHz (or for example for high power kitchen applications, the frequency may typically be in the range between 20 kHz and 80 kHz, for example). The transmitter coil 103 is loosely coupled with the power receiving coil 107, and therefore, the power receiving coil 107 picks up (at least part of) the power transfer signal from the power transmitter 101. Thus, power is transferred from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the receiving coil 107. The term power transfer signal is primarily used to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107, but it will be appreciated that, by equivalents, it may also be considered and used as a reference to an electrical signal provided to the transmitter coil 103 or picked up by the power receiving coil 107.

[0066] In this example, the power receiver 105 is specifically a power receiver that receives power via a receiver coil 107. However, in other embodiments, the power receiver 105 may include a metallic element, such as a metallic heating element, in which case the power transmission signal directly induces eddy currents, resulting in direct heating of the element.

[0067] The system is arranged to transfer substantial power levels, and in particular the power transmitter may in many embodiments support power levels in excess of 500 mW, 1 W, 5 W, 50 W, 100 W or 500 W. For example, for Qi corresponding applications, the power transfer may be typically in the 1-5 W power range for low power applications (basic power profile), up to 15 W for Qi specification version 1.2, in the range up to 100 W for higher power applications (such as power tools, laptops, drones, robots etc.), and in excess of 100 W and reaching over 1000 W for very high power applications (such as e.g. kitchen applications).

[0068] Hereinafter, the operation of the power transmitter 101 and the power receiver 105 will be described with specific reference to an embodiment generally in accordance with the Qi specification (except for the modifications and enhancements described herein (or corresponding thereto)) or an embodiment adapted for the higher power kitchen specification developed by the Wireless Power Alliance. Specifically, the power transmitter 101 and the power receiver 105 may comply with or be substantially compatible with elements of Qi specification versions 1.0, 1.1, or 1.2 (except for the modifications and enhancements described herein (or corresponding thereto).

[0069] In order to have a wireless power transfer system such as Figure 1 For optimal performance in a wireless power transfer system (e.g., a wireless power transfer system), it is desirable that the power transfer coils 103, 107 of the power transmitter 101 and the power receiver 105 are closely aligned so that they share the maximum amount of magnetic flux. Therefore, it is desirable that the coils 103, 107 are geometrically aligned so as to maximize the coupling factor (κ) between the transmitter coil and the receiver coil. In practical applications, the alignment between the power transmitter and the power receiver is variable, and therefore a perfect or even known alignment is not possible.

[0070] However, as will be described below, Figure 1 The system includes functionality for estimating the displacement between the transmitter coil 103 and the receiver coil 107, and in particular estimating the position of the receiver coil 107 relative to the transmitter coil 103. Knowing this displacement can be used in many different ways to provide improved performance. For example, it can be used to determine suitable parameters for power transfer (e.g., maximum power level), provide user feedback, compensate for detection operations, including, for example, detection of load communication or the presence of metal objects, etc.

[0071] The estimation of the displacement / alignment / relative position is based on comparing a plurality of test parameter values ​​with corresponding calibration or reference parameter values ​​for a typically relatively large number of possible displacements of the power receiver. In the method, the power transmitter 101 is arranged to perform a test to generate a plurality of test parameters and then compare this with calibration data retrieved for the receiver, wherein the calibration data comprises calibration values ​​for different misalignments / displacements.

[0072] Figure 2 The components of the power transmitter 101 are shown, and Figure 3 More detailed illustration Figure 1 Elements of the power receiver 105.

[0073] The power transmitter 101 comprises a driver 201 which may generate a drive signal fed to the transmitter coil 103 which in turn generates an electromagnetic field and hence an electromagnetic power transfer signal which provides a power transfer to the power receiver 105. The power transfer signal is provided (at least) during a power transfer phase.

[0074] The driver 201 may typically include an output circuit in the form of an inverter, typically formed by driving a full bridge or a half bridge, as will be known to the skilled person. Figure 4 An example of a typical output stage of a power transmitter is illustrated in which the inverter is formed by four FETs coupled in a bridge configuration, and in which the transmitter coil 103 (LTx) is also coupled to a capacitor (CTx) to form a resonant output circuit. The power transmitter 101 also includes a power transmitter controller 203, which is arranged to control the operation of the power transmitter 101 according to the desired operating principle. In particular, the power transmitter 101 may include many functions required to perform power control according to the Qi specification.

[0075] The power transmitter controller 203 is particularly arranged to control the generation of the drive signal by the driver 201, and it may in particular control the power level of the drive signal, and thus the level of the generated power transfer signal / electromagnetic field. The power transmitter controller 203 comprises a power loop controller which controls the power level of the power transfer signal in response to power control messages received from the power receiver 105 during the power control phase.

[0076] In order to receive data and messages from the power receiver 105, the power transmitter 101 includes a first communicator 205, which is arranged to receive data and messages from the power receiver 105 (as the skilled person will appreciate, the data message may provide one or more bits of information). In this example, the power receiver 105 is arranged to load modulate the power transfer signal generated by the transmitter coil 103, and the first communicator 205 is arranged to sense changes in the voltage and / or current of the transmitter coil 103 and demodulate the load modulation based on these. The skilled person will be aware of the principles of load modulation as used, for example, in the Qi wireless power transfer system, and therefore these will not be described in further detail.

[0077] In many embodiments, the first communicator 205 is further arranged to send data to the power receiver 105 and may in particular be arranged to modulate the power transfer signal using frequency, amplitude, or phase modulation.

[0078] In some embodiments, communication may be performed using a separate communication channel, which may be implemented using a separate communication coil or indeed using the transmitter coil 103. For example, in some embodiments near field communication may be implemented or a high frequency carrier (e.g. having a carrier frequency of 13.56 MHz) may be superimposed on the power transfer signal.

[0079] The power transmitter 101 further comprises a position estimator 207, which is arranged to estimate the position of the power receiver relative to the power transmitter, i.e. it may in particular estimate the misalignment between the power transmitter 101 and the power receiver 105. In many embodiments, the position estimator may in particular estimate the position of the receiver coil 107 relative to the transmitter coil 103 (which may be considered to be equivalent to determining the relative position of the power receiver relative to the power transmitter). The position of the power receiver / receiver coil relative to the power transmitter / transmitter coil will be referred to as the relative position or (mis)alignment of the power receiver in the following.

[0080] In some embodiments, the relative position of the power receiver may be determined as a three-dimensional relative position. However, in most practical applications, the degrees of freedom for positioning the power receiver are substantially limited to two dimensions. This may typically be the case where a power receiver device is placed on a power transmitter device for powering, since in such cases the power transmitter device typically has a horizontal surface on which the surface of the power receiver device is placed, resulting in typically the same vertical displacement but different horizontal displacements / misalignments. As an example, Figure 5The alignment of the receiver coil profile 503 relative to the transmitter coil profile 501 is illustrated for perfect alignment, misalignment of the x-axis, and misalignment of the y-axis, respectively. The misalignment will typically be dynamic and depend on how the user places the power receiver on the power transmitter. Every time the user places the power receiver device, it is not guaranteed to be perfectly aligned. Large misalignments cause poor coupling, which results in longer charging times, power waste, heating of friendly metals in the power receiver, and other inconveniences for the user.

[0081] In many embodiments, the position estimator 207 is arranged to estimate this horizontal misalignment, and it may in particular detect not only the distance or magnitude of any misalignment, but also the direction of the misalignment. Thus, in many embodiments, the position estimator 207 is arranged to estimate the two-dimensional relative position of the power receiver.

[0082] The position estimate is based on comparing the measured test parameters with the retrieved calibration data, which includes calibration parameters corresponding to the test parameters. The calibration parameters are provided for a range of different relative positions, and typically for a range of different three-dimensional positions (even for estimated positions in two dimensions as will be described later). The calibration data is typically generated during the manufacturing and / or design phase, and can, for example, be provided for reference receivers and reference transmitters from a central store, including calibration data for many different power transmitter and power receiver combinations.

[0083] The calibration and test parameters include at least a power loss measure, a resonant frequency measure and a coupling measure. The position estimation thus includes a multivariate comparison between the test parameter values ​​and the calibration parameter values ​​for a range of different position offsets. Furthermore, the parameters provide a particularly advantageous selection to provide a good indication of different relative positions. Different parameters tend to have different correlations on different misalignments, and they therefore combine synergistically to provide additional information indicative of misalignment.

[0084] The position estimator 207 is coupled to a retriever 209, which is arranged to retrieve calibration data from an external or internal source. Thus, the retriever retrieves data providing a set of calibration parameters for each of a plurality of spatial positions of the calibration receiver relative to the calibration transmitter. For example, the calibration data may be stored in a local storage and extracted and fed to the position estimator 207.

[0085] The power transmitter 101 further comprises a test generator 211 which is arranged to generate a test drive signal for the transmitter coil 103 which results in the generation of a test electromagnetic signal. In the example, the test generator 211 is coupled to the power transmitter controller 203 and is arranged to control this to control the driver 201 to generate the electromagnetic test signal. In other embodiments, the test generator 211 may, for example, directly control the driver 201 or may, for example, itself comprise a driver for generating a drive signal which may then be fed to the transmitter coil 103.

[0086] The power transmitter 101 also includes a test processor 213 for determining a set of test parameter values ​​in response to the test drive signal. The test processor 213 can specifically measure or determine the influence of the power receiver on the generated electromagnetic test signal. The influence can be measured directly or indirectly. For example, the power level, frequency variation, response to the frequency sweep, etc. of the drive signal can be determined and the test parameters can be generated based on these values. In some cases, information from the power receiver can also be used to provide data that allows the test parameters to be determined. The test processor 213 specifically generates a test power loss metric, a test resonant frequency metric, and a test coupling metric.

[0087] The resulting test parameters are then fed to the position estimator 207 where they are used to estimate the relative position of the power receiver by comparing them with the corresponding parameter values ​​in the calibration data.

[0088] Figure 3 Some exemplary elements of the power receiver 105 are illustrated.

[0089] The receiver coil 107 is coupled to a power receiver controller 301, which couples the receiver coil 107 to a load 303 (i.e., it is a switchable load 305) via a switch 305. The power receiver controller 301 includes a power control path that converts the power extracted by the receiver coil 107 into a suitable supply for the load. In addition, the power receiver controller 301 may include various power receiver controller functions required to perform power transfer, and specifically the functions required to perform power transfer in accordance with the Qi specification.

[0090] To support communication from the power receiver 105 to the power transmitter 101 , the power receiver 105 includes a second communicator 307 .

[0091] The second communicator 307 is arranged to send data to the power transmitter by varying the load of the receiver coil 107 in response to the data to be sent to the power transmitter 101. The load variation is then detected and demodulated by the power transmitter 101, as will be known to those skilled in the art.

[0092] In an example, the second communicator 307 is furthermore arranged to demodulate the amplitude, frequency and / or phase modulation of the power transfer signal in order to retrieve the data sent from the power transmitter.

[0093] Figure 5 A circuit schematic diagram of elements of an example of a power path of a power receiver 105 is illustrated. In this example, the power receiver 105 comprises a receiver coil 107 referred to by the name LRX. In this example, the receiver coil 107 is part of a resonant circuit and the power receiver 105 therefore also comprises a resonant capacitor CRX. The receiver coil 107 is subjected to an electromagnetic signal / field and, therefore, an AC voltage / current is induced in the coil. The resonant circuit is coupled to a rectifier bridge having a smoothing capacitor C1, which is coupled to the output of the bridge. Thus, a DC voltage is generated across the capacitor C1. The magnitude of the ripple on the DC voltage will depend on the size of the smoothing capacitor and on the load.

[0094] The bridge B1 and the smoothing capacitor C1 are coupled to a load 303 indicated by reference numeral RL via a switch 305 illustrated by switch S1. The switch 305 can therefore be used to connect or disconnect the load from the power path, and therefore the load is a switchable load 305. It will be appreciated that although the switch S1 is shown as a conventional switch, it may of course be implemented by any suitable device (including typically by a MOSFET). It will also be appreciated that the load 303 is illustrated as a simple passive port, but it may of course be any suitable load. For example, the load 303 may be a battery to be charged, a mobile phone or another communication or computing device, a simple passive load, etc. In practice, the load 303 is not necessarily an external load or a dedicated internal load, but may, for example, include elements of the power receiver 105 itself. Therefore, in Figure 3 and Figure 4 The load 303 illustrated in can be considered to represent any load / electromagnetic signal of the receiver coil 107 that can be disconnected by the switch 305 / S1 , and it is therefore also referred to as a switchable load 305 .

[0095] The power receiver 105 further comprises a test controller 309, which is arranged to support the power transmitter when performing position estimation. The test controller 309 is coupled to the second communicator 307 and is arranged to provide information to the second communicator 307 for transmission to the power transmitter 101. For example, the test controller 309 may control the second communicator 307 to send information identifying the power receiver itself (e.g., providing device identification or device type identification). The test controller 309 may also be arranged to control the switch 305 so that the switchable load 305 may be disconnected during the time when the test generator 211 generates the test signal.

[0096] The position estimation is based on a multivariate analysis taking into account at least three different parameters.The position estimator 207 is arranged to determine the position based on comparing calibration and test values ​​for at least the power loss measure, the resonant frequency measure and the coupling measure.

[0097] The power loss measure will be referred to as PM pl x,y,z and may be a value indicative of the power extracted by the power receiver 105 from the electromagnetic signal generated by the transmitter coil 103. The power loss measure may specifically reflect the resistive power dissipated in the transmitter and in friendly metal of the receiver exposed to the magnetic field of the transmitter.

[0098] In many embodiments, the power loss measure may be determined for a predetermined and fixed load of the power receiver, and may in particular be determined for a disconnected power receiver's load 303 (and for minimizing the loading of the power receiver on the power transfer signal). Thus, in many embodiments, the power loss measure may reflect the amount of magnetic flux from the transmitter coil 103 that is exposed to the receiver and friendly metal in the environment. Since this will depend on the relative position of the power receiver with respect to the power transmitter, the power loss measure will provide useful information about the position of the power receiver. Furthermore, a non-uniform distribution of friendly metal in the power receiver provides a power loss measure PM for the same coil misalignment distance. pl x,y,z changes and thus provide additional information such as in the direction of misalignment.

[0099] For example, a power loss measure may be determined in response to a measurement reflecting the value of power loss of the electromagnetic test signal when this is generated. For example, the power of the test drive signal during a test situation in which the power receiver has disconnected its load may be measured and used as a power loss measure.

[0100] In other embodiments, a more indirect measure may be used as a power loss measure. For example, in most embodiments, the transmitter coil 103 is part of an output resonant circuit and power loss from an electromagnetic signal will tend to have an effect corresponding to a resistive load of the resonant circuit. Therefore, the damping of the resonant circuit will increase for increasing power loss, and in some embodiments, a power loss measure may be generated as a measure that reflects such damping. For example, the power loss measure may be generated as a Q factor value or the like.

[0101] The resonant frequency measure will also be referred to as PM rf x,y,zand may indicate the resonant frequency of the (output) resonant circuit comprising the transmitter coil 103. As is well known in the art of wireless power transmission, a transmitting coil is often coupled with at least one capacitor to form an (n output) resonant circuit. Similarly, a receiver coil is often coupled with at least one capacitor to form an (n input) resonant circuit. In most practical situations, the use of such a resonant circuit has been found to provide substantially improved power transfer.

[0102] In the absence of any power receiver (or other conductive element), the output resonant circuit will have a given resonant frequency that is typically determined only by the capacitance and inductance of the components of the output resonant circuit. However, in the presence of a power receiver, the induced current in the power receiver will result in a change in the resonant frequency of the output resonant circuit. Furthermore, the effect will depend on the level of influence of the power receiver, and therefore the relative position of this. Therefore, a resonant frequency measure that reflects the resonant frequency can provide information indicative of the relative position of the power receiver.

[0103] The resonant frequency measure may be measured, for example, by a test generator 211 generating a frequency swept signal and a test processor 213 measuring the response of the output resonant circuit and identifying, for example, a maximum value for current drawing.

[0104] The coupling factor measure will also be referred to as PM κ x,y,z and indicates the coupling between the power transmitter and the power receiver (and hence the transmitter coil 103 and the receiver coil 107). Thus, the coupling factor measure will indicate the electromagnetic coupling between the coils and will reflect the amount of flux passing through the two coils. Thus, the coupling factor measure will depend on the relative position of the power receiver and will therefore provide information about this.

[0105] The determination of the coupling factor measure may be different in different embodiments. For example, in some embodiments, the test generator 211 may generate a test drive signal that results in an electromagnetic test signal. The power receiver may then measure the induced voltage and send that measurement back to the power transmitter, which may determine the coupling factor measure from this (it may even use the reported induced voltage directly as the coupling factor measure).

[0106] As another example, the test generator 211 may gradually increase the level of the test drive signal until the power receiver detects that the induced voltage reaches a given threshold. It may then send a message to the power transmitter indicating that this has occurred and the test processor 213 may then determine the coupling factor measure in response to the level of the test drive signal when this occurs (or indeed use the level directly as the coupling factor measure).

[0107] As another example, coupling can be measured by a transmitter applying a known voltage to the transmitter coil and a power receiver reporting the voltage induced in the receiving coil. The ratio of the two provides a coupling measure. Thus, the coupling measure can be determined by the ratio of the voltage on the receiving coil 107 and the voltage of the transmitter coil 103.

[0108] Three specific parameters provide a particularly efficient and advantageous set of parameters that can significantly improve position estimation in many practical situations and applications. They provide a particularly efficient synergy in information. In particular, different parameters can have different correlations on the relative position / misalignment resulting in a combination of parameters, and the joint consideration of these, which leads to more accurate position estimation in many applications. For example, the coupling factor measure will tend to have a substantially linear relationship with increasing misalignment, while the power loss measure will tend to have a substantially quadratic relationship. Different measures provide different relationships and therefore the mutual relationship between them provides additional information. Moreover, different relationships and correlations may lead to different measures, thereby providing particularly useful information for different amplitudes of displacement, thereby allowing more accurate position estimation over a larger range.

[0109] Although the three parameters described above provide particularly efficient and high performance position estimates in many cases, it will be appreciated that the method is not limited to use of only these parameters, but additional parameters may be considered in many embodiments.

[0110] The calibration data may include a set of calibration parameters for each of a plurality of spatial positions of the calibration receiver relative to the calibration transmitter, wherein each set includes at least one calibration power loss metric, one calibration resonant frequency metric, and one calibration coupling metric. For example, the calibration data may include a three-dimensional array, each dimension corresponding to a spatial dimension (x, y, and z) and the array elements being a set of calibration parameters for the alignment between the transmitter coil and the receiver coil corresponding to the set of spatial dimensions. Thus, each set of calibration parameters may include a metric corresponding to a metric generated by the power transmitter during the test operation.

[0111] The calibration data may typically be predetermined calibration data and may be generated, for example, during a manufacturing or design phase. In particular, during a design (including prototyping) or manufacturing phase, a manufacturer may utilize a power transmitter using a plurality of predetermined or defined test signals and perform measurements using power receivers positioned at potentially a large number of relative positions. For each position and each test signal, the resulting parameters may be measured using the same method that would be used by the power transmitter in the field. The resulting measurements may be stored as a calibration parameter set. For example, as previously mentioned, a three-dimensional array may be generated using relative position coordinates forming three dimensions and determined parameters for corresponding positions stored as array elements.

[0112] The resulting calibration may then be stored, for example, in the power transmitter (eg, the retriever 209 may include storage for storing calibration data). However, in many embodiments, the data may be stored centrally for later retrieval by the power transmitter, as will be described in more detail later.

[0113] In different embodiments, different methods will be used by the position estimator 207 to estimate the relative position. In some embodiments, a simple comparison can be used, wherein the position estimator 207 evaluates a cost function for all positions where the calibration data includes a parameter set. The cost function can indicate the difference between the test parameters determined by the test processor 213 and the calibration test parameters for a particular position. For example, a cost function that monotonically increases for each difference between the test parameter measurement and the corresponding calibration parameter measurement can be used. The position estimator 207 can use the cost function to determine the cost value for each position. The estimated relative position can then be determined as the position of the group of parameters that results in the lowest cost value.

[0114] In other embodiments, more complex processes may be used. For example, in some embodiments, machine learning methods may be used to find matching parameter groups and associated positions. Such machine learning methods may, for example, be based on a learning process performed during the design or manufacturing phase.

[0115] The machine learning algorithm using supervised learning consists of building a training set in examples corresponding to the described calibration data. In supervised learning, the learning algorithm is fed with various measured test parameters, such as power loss, coupling factor, and resonant frequency, and the corresponding x, y misalignment values ​​are used as outputs. Once the training is complete, we have a set of measured parameters and a corresponding set of outputs in the form of x, y, and z values ​​for each output parameter, performing a polynomial curve fit such as y1=a11*X1+a12*X1*X1+…+a21*X2+q22*X2*X2+....a31*X3+a32*X3*X3.....

[0116] Where y1 = x misalignment, aij = fitting coefficient and Xi = characteristic, such as power loss.

[0117] Based on this fitting curve in the calibration phase, during in-field operation, the characteristic values ​​X1 = power loss, X2 = coupling factor and X3 = resonance frequency are measured.

[0118] Using the above curve fitting equations for y1 (x displacement) and y2 (y displacement), the measured eigenvalues ​​are fed into the equations to retrieve the misalignment information.

[0119] As mentioned previously, the array may reflect three spatial dimensions, and indeed in many embodiments the relative position may be determined as a three-dimensional relative position. However, in many practical applications the positioning freedom of the power receiver is substantially limited to two dimensions.

[0120] Thus in many embodiments, the distance between the transmitter coil 103 and the receiver coil 107 may include a distance in one direction over which the user has little control and influence and a distance in a two-dimensional plane over which the user has some freedom in positioning. The former will be referred to as the separation distance between the transmitter coil 103 and the receiver coil 107, and the second will be referred to as the misalignment of the transmitter coil 103 and the receiver coil 107 in the following. The direction in which the user has little freedom (i.e., the direction of the separation distance) will typically be perpendicular to the contact surface for receiving the power receiver. Furthermore, since arranging the coils to be parallel to the contact surface tends to result in the highest coupling factor, this direction will typically be perpendicular to the plane of the transmitter coil 103 and, in fact, the plane of the receiver coil 107.

[0121] The situation can be illustrated by an example of a cross section showing an arrangement of a power transmitter and a power receiver. Figure 7 Fig. 1. The power receiver is positioned with the lower surface placed on the upper surface of the power transmitter. Figure 7 An interface 701 between the two surfaces is shown. The transmitter coil 103 and the receiver coil 107 will typically be included within the device and will therefore be offset relative to the external surface and will therefore be at a distance from the surface 701. In the example, d tx Indicates the distance between the interface surface 701 and the transmitter coil 103. rx is the distance between the interface surface 701 and the receiver coil 107. The total separation distance between the receiver coil 107 and the transmitter coil 103 is d tx-rx =d rx +d tx + any interfacial surface thickness. We refer to this as the "z" parameter.

[0122] In many cases, the separation distance between the transmitter coil 103 and the receiver coil 107 may be predictable. For example, the distance between the coils and the corresponding contact or interface surface will be known for a particular device. In practice, it is possible that these distances may vary a bit (e.g., a phone cover on a smartphone may increase the distance between the coils and the corresponding contact or interface surface). rx value and therefore d tx-rx values, in small amounts). However, this can usually introduce only small and acceptable inaccuracies.

[0123] The total separation distance can affect the coupling factor. This value can also be affected by the misalignment between the transmitter coil 103 and the receiver coil 107 and is determined by the term d misRefers to. mis Represented by "x" and "y" parameters, ie, by values ​​in the plane of the contact surface.

[0124] Expect to make tx-rx and d mis is minimized to achieve a high coupling factor. Alternatively or additionally, it is desirable to compensate these values. tx-rx tend to be fixed (by construction), d mis Varies depending on the user and usage. For example, for laptops and mobile ecosystems, free placement of power receiver devices is important for consumer convenience. In such a situation, the user may take advantage of a large misalignment distance d mis The receiver coils are placed such that the coupling factor may become below a required threshold resulting in very inefficient power transfer, or such that it substantially affects some operations of the power transfer system (eg, communications).

[0125] In many embodiments, the position estimator 207 may be arranged to determine a separation distance, i.e. it may determine a vertical distance measure indicating the distance between the transmitter coil 103 and the receiver coil 107 in a direction perpendicular to the contact surface for receiving the power receiver transmitter coil 103 .

[0126] In a typical embodiment, the power transmitter 101 has locally stored a signal reflecting the distance d from the transmitter coil 103 to the contact surface. tx The distance typically depends only on the physical design of the power transmitter device and will therefore be known at the design stage and may be stored in the power transmitter device during the manufacturing stage.

[0127] In some embodiments, the distance d from the contact surface of the receiver to the receiver coil 107 is rx It may be known by the power transmitter or may be estimated or replaced by a typical or nominal value.For example, if the power transmitter is only intended for use with a specific power receiver, the power receiver separation distance may be known.

[0128] However, in most embodiments, the power receiver separation distance will not be known by the power transmitter. However, in many such embodiments, the power transmitter may be arranged to receive a message from the power receiver that includes a power receiver distance indicator indicating the distance from the receiver coil to the outer surface of the power receiver. For example, the power receiver may have stored the power receiver separation distance d rx The local value of d is obtained by the power receiver, and during the initialization phase, when the power receiver first detects, the power receiver can send information about d to the power transmitter. rx information.

[0129] The position estimator 207 may then proceed to determine the total separation distance between the receiver coil 107 and the transmitter coil 103 as d tx-rx =d rx +d tx (In the example, it is assumed that the contact surfaces are in direct contact, so the interface distance does not need to be considered).

[0130] The position estimator 207 may then proceed to respond to the separation distance / vertical distance measure d tx-rx The position of the power receiver is determined by comparison with the spatial position of the calibration receiver in the calibration data.

[0131] For example, in some embodiments, the cost function may be generated to also take into account the difference between the determined separation distance and the corresponding distance of the array entry. In particular, the more the z-value of the position for a given set of calibration parameters differs from the determined separation distance, the higher the cost function (i.e., the cost function is a monotonically increasing function of the difference between the separation distance and the distance reflected by the z-value).

[0132] In some embodiments, the position estimator 207 may simply ignore all calibration parameter sets corresponding to z-direction distances that differ from the separation distance by more than a given threshold. Thus, in some embodiments, the position estimator 207 may be arranged to select a subset of the stored calibration parameter sets whose spatial positions satisfy the criteria with respect to the determined separation distance, and estimate the relative position based on this subset only.

[0133] In many cases, considering the separation distance as an "input" (constraint parameter) to the position estimate rather than as a result thereof can provide a more accurate position estimate.

[0134] The above description has focused on an example where the calibration data only includes data for a particular power receiver. However, in many embodiments, the power transmitter will be designed to operate with many different types of power receivers having significantly different characteristics. In some systems, the differences may be small enough to still allow a reasonable position estimate based on average or nominal calibration data.

[0135] However, in many embodiments, calibration data will be generated for multiple power receivers and in particular may be generated for multiple different types of power receivers. In such embodiments, the power receiver may send a message to the power transmitter, which includes a power receiver identification indication, and the retriever 209 may be arranged to retrieve calibration data matching the power receiver identification indication and use this for position estimation.

[0136] In many embodiments, the power receiver identification indication may include an identification of an individual device, and it may uniquely identify the power receiver device. For example, this may be the case if the user is arranged to perform a process of generating calibration data (e.g., by being instructed to position the power receiver at different misalignments and proceeding to perform the test). The resulting data may be stored locally in the power transmitter and retrieved whenever a particular power receiver is positioned for being powered.

[0137] In many embodiments, the power receiver identification indication may be a type identification of the power receiver. Thus, the device may not be uniquely identified, but the retriever 209 will be arranged to retrieve calibration data for a specific type of power receiver. This will allow the calibration data to be reused for many different types of devices and will generally avoid the necessity for the user to perform a calibration process. For example, when a new power receiver device is placed on the market (e.g., a new smartphone), the manufacturer may perform a calibration test to generate calibration data. The results may be stored in a suitable form and provided to the power transmitter via a suitable distribution method.

[0138] In some embodiments, a combination of device-specific and type-specific data may be used. For example, a user may perform a calibration procedure for one or more of his personal devices that are often used with the power transmitter. The resulting calibration data may be stored locally and used whenever the power transmitter is used with one of these devices. However, if the power transmitter is used with a different power receiver device, the type-specific calibration data may instead be retrieved and used in the position estimate.

[0139] In different embodiments, the retriever 209 may be arranged to retrieve calibration data from different sources.

[0140] In some embodiments, the retriever 209 may include a local storage storing the calibration data, and the retriever 209 may be arranged to retrieve the appropriate data therefrom. Such an approach may be suitable for embodiments in which the user generates the calibration data or in which the power transmitter may assume that the power receiver is limited to a typically very small number of devices with known characteristics.

[0141] However, in many systems, the power transmitter is required to be able to interoperate with a large number of different devices of different types and with different characteristics. In fact, in many systems, since the power transmitter is required to also interoperate with future devices, the range of potential power receiver devices that need to be supported may not be known.

[0142] Thus, in some embodiments, one or more central sources may include calibration data for multiple power receivers. For example, a standards (or other responsible) body may operate a central deposit to which manufacturers of power receivers provide calibration data each time they place a new device on the market.

[0143] In some embodiments, the retriever 209 may be arranged to retrieve calibration data from a remote server, such as a central server operated by a third party. The retriever 209 may, for example, generate a calibration data request message including an identification indication corresponding to the power receiver identification indication in response to receiving a power receiver identification indication from the power receiver. In many embodiments, the power receiver identification indication may, for example, simply be a power receiver type identification and this may be used directly in the calibration data request message. However, in other embodiments, the indication may be modified, for example, a device-specific power receiver identification indication may be converted to a type-specific identification.

[0144] In this way, the power transmitter can be arranged to retrieve calibration data for any (authorized) power receiver, and can also be arranged to retrieve the latest and specific calibration data for the exact power receiver currently supported. The retriever 209 can, for example, include an interface for coupling the power transmitter to the Internet and it can be connected to the central server via the Internet.

[0145] In some embodiments, the power transmitter may be arranged to receive calibration data from the power receiver. For example, during manufacture of the power receiver, the manufacturer may perform a calibration process and store the resulting calibration data in a local memory of the power receiver. When power transfer is initialized with the power transmitter, the power receiver may send the calibration data to the power transmitter, which may then proceed to use this for position estimation.

[0146] In some embodiments, the power receiver may not store the relevant calibration data itself, but may instead be arranged to contact a central server to retrieve the appropriate data. The power receiver may then send this to the power transmitter. In many applications, such an approach may be practical, as power receiver devices tend to be relatively complex and have communication capabilities (e.g., smartphones), while power transmitters tend to be of relatively low complexity and may not have communication capabilities.

[0147] The above description has focused on the situation where calibration data is provided for a specific power transmitter. This is suitable, for example, for embodiments in which the calibration data is stored locally in the power transmitter. However, in embodiments in which the calibration data is retrieved from, for example, a remote source or a power receiver, the calibration data may be available for a range of power transmitters to support a plurality of different power transmitters. In such embodiments, the power transmitter may retrieve calibration data not only for a specific power receiver but for a specific power transmitter / power receiver combination. Therefore, in many embodiments, the retrieval of the calibration data may also include the identification of the power transmitter. For example, in addition to the identification of the power receiver, the calibration data request message may also include the identification of the power transmitter.

[0148] In many embodiments, calibration data may be provided for a reference transmitter rather than for a specific transmitter. For example, the calibration data may be determined for a nominal reference transmitter during the manufacturing phase of the power receiver. The resulting data may then be stored, for example, in a central server or in the power receiver itself.

[0149] Thus, in such an embodiment, the power transmitter may receive calibration data that is not specific to the individual power transmitter but rather relates to a reference transmitter. However, in the event that the power transmitter has properties close enough to the reference power transmitter, these may be used directly.

[0150] In other embodiments, the position estimator may be arranged to modify the calibration data to reflect differences between a reference power transmitter and an actual power transmitter. Thus, one or more of the calibration parameters (or equivalently one or more of the test parameters) may be modified to reflect differences between the properties of the power transmitter and the properties of the reference power transmitter.

[0151] For example, if it is known that a reference power transmitter has a given physical design with a certain distance from the transmitter coil to the contact surface that is substantially greater than the corresponding distance from the transmitter coil to the contact surface for the power transmitter 101, then the calibration data for the reference transmitter may be modified by, for example, increasing the recorded coupling factor by a given ratio.

[0152] As another example, if a reference power transmitter is known to include a given amount of friendly metal that causes some power loss in the friendly metal itself, then the power loss calibration parameters may be adapted based on the known differences in friendly metal for the current power transmitter.

[0153] In many embodiments, the test generator 211 may be arranged to generate a plurality of different test signals, and the test parameters may be generated for the different signals. Similarly, the calibration data may include a plurality of calibration parameters for the different test signals for each spatial location.

[0154] In some embodiments, the same test parameters / calibration parameters may be determined for different test signals. For example, coupling factors may be generated for low signal levels and high signal levels or for different frequencies.

[0155] Thus, the position estimator 207 may consider multiple power loss metrics, multiple resonant frequency metrics, and / or multiple coupling metrics for each position and test.

[0156] In some embodiments, the power transmitter may include multiple transmitter coils, and the test generator 211 may be arranged to generate test signals for the multiple transmitter coils. In such a case, the responses of the different transmitter coils 103 may provide additional information that may be very useful for estimating the position. Figure 8 An example of a planar arrangement of multiple transmitter coils is shown in FIG. Figure 8 Different positions of the power receiver 105 are also illustrated.

[0157] For example, in some embodiments, the same test signal may be applied to all transmitter coils, and the resulting parameter value may be estimated, for example, based on the detected power of the drive signal, the induced voltage reported by the power receiver, etc., as previously described.

[0158] In other embodiments, at least some of the test parameter values ​​may be generated for individual subsets of transmitter coils, for example by measuring individual power levels for the individual subsets. This may provide additional information, for example, the power loss measure will be higher for a subset of transmitter coils proximal to the power receiver than for transmitter coils further away from the power receiver. Such spatial variations will be reflected in the corresponding calibration parameters, as these may be generated by performing the same test for different locations of the calibration power receiver.

[0159] In some embodiments, the power transmitter may also perform tests in which different test signals are applied to different transmitter coils, including not providing any drive signal to one or more transmitter coils. In some embodiments, the test generator 211 may generate a sequence of test signal groups, wherein different groups include different test signals for different transmitter coils. The test generator 211 may apply the test signal groups sequentially so that a series of test parameter measurements are generated. For example, a constant frequency signal may be applied to some transmitter coils, while a frequency sweep may be applied to other transmitter coils. Calibration data may be generated by performing the same tests during the calibration phase, and thus additional information may be generated and used for position estimation.

[0160] In some embodiments, at least some of the groups include test signals for different subsets of transmitter coils. Thus, in some cases, only subsets of transmitter coils may be driven to generate electromagnetic test signals with the subsets changing between groups. Thus, the spatial characteristics of the electromagnetic test signals may be sequentially changed by changing the effective topology of the test arrangement. For example, the test generator 211 may sequentially drive only one transmitter coil until all transmitter coils have been driven once. For each transmitter coil, a subset of test parameter measurements (power loss measurement, resonant frequency measurement, coupling factor measurement) may be generated, and a combined set of test parameter values ​​may be generated by combining all subsets. The resulting combined test parameter set may then be compared with the corresponding calibration parameter set generated during the calibration phase.

[0161] It will be appreciated that the estimated position can be used for many different purposes and in many different applications, and the particular use will depend on the preferences and requirements of individual embodiments. For example, in some embodiments it can be used to provide accurate user feedback that can be used to improve positioning. In other embodiments, if the position of the power receiver is detected such that there may potentially be a space where such an object is close to the transmitter coil, it can, for example, be used to prevent a potentially risky situation where the power transfer signal may induce a current in a metal object but reduce the maximum power level. In other embodiments, the position / misalignment estimate can be used to compensate for other operations by the power receiver, such as, for example, communication and detection of load modulation in particular.

[0162] In the following, certain more detailed examples of the operation of a wireless transmission system according to the previously described principles will be described. Fig. 9 and Fig.10 The example is also reflected in Fig. 9 shows a flow chart for the calibration phase, Fig.10 A flow chart for the testing phase through a power transmitter is shown.

[0163] In an example, a factory calibration step, typically done in a factory, considers a receiver (with a disconnected load) and a known transmitter, such as a reference transmitter as described in a wireless power transfer specification document.

[0164] Various coil drive topologies for power transmitters, such as coil activation, power transmitter coil drive current, voltage and operating frequency, and separation distance d tx-rx , we set various d mis The (x,y) misalignment values ​​are used to measure various parameters of interest for wireless power transfer systems. The parameters of interest include power loss metrics, frequency resonance metrics, and coupling metrics.

[0165] For each coil topology, perform power transmitter coil activation, power transmitter coil drive current, voltage, operating frequency and d tx-rx and d mis The parameters of interest mentioned above are set, measured, and recorded. These sets of values ​​provide a fingerprint of the wireless transmission system for a given coil topology, i.e., coil activation, coil drive current, voltage, operating frequency, and tx-rx and d mis Setup. Once calibration is complete, a database of calibration data is created, and this is then loaded onto the internal memory of the corresponding power receiver and power transmitter.

[0166] Next, based on the database information and the current positioning of the power receiver on the power transmitter, the power transmitter applies a set of input stimuli, such as power transmitter coil current, voltage, and operating frequency, and performs multiple measurements and records various parameters of interest for each setting. The set of measurements is compared with the corresponding input parameters (i.e., d tx-rx , coil topology, power transmitter drive current, voltage, and operating frequency). The d mis The values ​​(ie, x and y misalignments) are calculated using, for example, well-known machine learning. The algorithm may be run on an embedded processor on the power transmitter.

[0167] In the case of multiple power transmitter coils setup as shown, another measurement dimension is added. We can activate only one of the power transmitter coils or we can activate multiple coils. Thus, if there are N coils, then we can have a coil activation scenario of N C r combination.

[0168] For each drive power transmitter coil activation and x, y, z distance measurement, we can set various coil currents, voltages, and frequencies by changing the duty cycle and clock frequency of the inverter in the driver.

[0169] For each of these coil activation topologies and drive current, voltage, frequency settings, we can then perform measurements of the parameters of interest and build a three-dimensional matrix with values ​​corresponding to the scenario.

[0170] Fig. 9 Measurement flow chart for an N-coil power transmitter and a single coil power receiver is shown for various x, y and z distances, coil currents, voltages and frequencies, and coil activation scenarios.

[0171] The input sweep parameters for the characterization are:

[0172] 1. Coil activation topology (combination of coils to be activated)

[0173] 2. Input frequency

[0174] 3. Input voltage

[0175] 4. Coil current

[0176] 5. "X", "Y" and "Z" distances

[0177] The creation of a measurement database forms the first step in the determination of the estimated misalignment of the power transmitter and power receiver coils in the field. Once the measurement database is created for a known power transmitter and power receiver pair, the database information is stored on each corresponding power transmitter and power receiver during manufacturing in the factory, or can be downloaded, for example from a remote server, to the power transmitter and power receiver once configured in the field.

[0178] In the field, when the power receiver is placed on the power transmitter for the first time, the power receiver and the power transmitter establish communication and recognize each other. After the recognition step, the power transmitter requests a d rx The power transmitter sets the coil topology, sets the coil current drive current, voltage and operating frequency. The power transmitter then performs various measurements and calculates various parameters of interest, such as PM pl x,y,z 、PM rf x,y,z 、PM κ x,y,z wait.

[0179] The power transmitter can then set different coil topologies or different drive currents, voltages and frequencies and repeat the measurements and record them.

[0180] Using this set of multiple measurements, a search algorithm is executed in the measurement results database to find the "x,y" entry that is closest to the measured value for the parameter of interest measured and recorded in the factory calibration for various input parameters such as coil activation topology, drive current, voltage and operating frequency.

[0181] The closest matching "x,y" values ​​of the parameter of interest in the database and measurement data matching are determined, for example, using well-known machine learning algorithms.

[0182] Extract the estimated value of "x,y" from the measurement result database.

[0183] Fig.10An example of a flow chart for estimating, by a power transmitter, misalignment of power transmitter and power receiver coils is shown.

[0184] It will be appreciated that, for the sake of clarity, the above description has described embodiments of the present invention with reference to different functional circuits, units and processors. However, it will be apparent that any suitable distribution of functions between different functional circuits, units or processors may be used without departing from the present invention. For example, functions illustrated as being performed by a separate processor or controller may be performed by the same processor. Therefore, references to specific functional units or circuits are only considered references to suitable devices for providing the described functions, and do not indicate a strict logical or physical structure or organization.

[0185] The present invention can be implemented in any suitable form, including hardware, software, firmware or any combination of these. The present invention can be optionally implemented at least in part as computer software running on one or more data processors and / or digital signal processors. Each element and component of an embodiment of the present invention can be implemented physically, functionally and logically in any suitable manner. In fact, the function can be implemented in a single unit, in multiple units or as a part of other functional units. Like this, the present invention can be realized in a single unit, or can be physically and functionally distributed between different units, circuits and processors.

[0186] Although the present invention has been described in conjunction with some embodiments, it is not intended to limit the present invention to the specific forms set forth herein. On the contrary, the scope of the present invention is limited only by the appended claims. In addition, although it may appear that features have been described in conjunction with specific embodiments, those skilled in the art will recognize that the various features of the described embodiments may be combined according to the present invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0187] It will be appreciated that reference to a preferred value does not imply any limitation other than it being a value determined in the foreign object detection initialisation mode, ie it is preferred by virtue of which it is determined during the adjustment process. Reference to a preferred value may be replaced by reference to, for example, the first value.

[0188] In addition, although listed separately, multiple devices, elements, circuits or method steps can be implemented by, for example, a single circuit, unit or processor. In addition, although individual features may be included in different claims, these features may be advantageously combined, and inclusion in different claims does not mean that the combination of features is not feasible and / or disadvantageous. The inclusion of features in a class of claims does not mean a limitation on the class, but rather indicates that the feature is equally applicable to other claim classes when appropriate. In addition, the order of features in the claims does not mean any specific order in which the features must work, and in particular, the order of the individual steps in the method claims does not mean that the steps must be performed in that order. Instead, the steps can be performed in any suitable order. In addition, singular references do not exclude multiples. Therefore, references to "one", "one", "first", "second", etc. do not exclude multiples. The figure marks in the claims are provided only to make the examples clear and should not be interpreted as limiting the scope of the claims in any way.

Claims

1. A power transmitter (101) for wirelessly providing power to a power receiver (105) via an electromagnetic power transfer signal; the power transmitter (101) comprising: at least one transmitter coil (103) arranged to generate said power transfer signal during power transfer; A retriever (209) arranged to retrieve stored calibration data, the stored calibration data comprising a set of calibration parameters for each of a plurality of spatial positions of a calibration receiver relative to a calibration transmitter, the calibration parameters comprising for each of the plurality of spatial positions: a calibration power loss measure for said calibration receiver at said each spatial location, indicating a calibration resonant frequency measure of a resonant circuit of the calibration power transmitter for the calibration receiver at each of the spatial locations, a calibration coupling metric indicative of coupling between the calibration transmitter and the calibration receiver at each of the spatial locations; a test generator (207) arranged to generate a test drive signal for the transmitter coil (103) to generate an electromagnetic test signal; A test processor (213) is arranged to determine a set of test parameters in response to the test drive signal, the test parameters comprising: a test power loss measure indicative of power extracted from the electromagnetic test signal, a test resonant frequency measurement for a resonant circuit comprising the transmitter coil (103), a test coupling metric indicative of coupling between the power transmitter (101) and the power receiver (105), the test power loss metric, the test resonant frequency metric and the test coupling metric providing different relationships to a position of the power receiver relative to the power transmitter, whereby a mutual relationship between the test power loss metric, the test resonant frequency metric and the test coupling metric provides an additional indication of the position of the power receiver relative to the power transmitter; as well as A position estimator (207) is arranged to estimate the position of the power receiver relative to the power transmitter in response to a comparison of the test parameters with the calibration parameters for the plurality of spatial positions.

2. The power transmitter according to claim 1, wherein: The position estimator (207) is arranged to: determine a vertical distance measurement indicating the distance between the transmitter coil (103) and the receiver coil (107) of the power receiver (105) in a direction perpendicular to a contact surface for receiving the power receiver (105); and determine the position of the power receiver (105) in response to a comparison of the vertical distance measurement with a plurality of spatial positions of a calibration receiver.

3. The power transmitter according to claim 2, further comprising: A communicator (205) for receiving a message from the power receiver (105); wherein the communicator (205) is arranged to receive a power receiver distance indicator indicating a distance from the receiver coil (107) to an outer surface of the power receiver (105); and wherein the position estimator (207) is arranged to determine the vertical distance measurement in response to the power receiver distance indicator.

4. The power transmitter according to any one of claims 1 to 3, further comprising: A communicator (205) arranged to receive a message from the power receiver (105); wherein the communicator is arranged to receive a power receiver identification indication from the power receiver, and the retriever (209) is arranged to retrieve calibration data matching the power receiver identification indication.

5. The power transmitter according to claim 4, wherein: The retriever (209) is arranged to retrieve the calibration data from the remote source by sending a calibration data request message to the remote source, the calibration data request message comprising an identification indication corresponding to the power receiver identification indication.

6. The power transmitter according to any one of claims 1 to 3, further comprising: A communicator (205) is arranged to receive data from the power receiver (105); wherein the retriever (209) is arranged to receive the calibration data from the power receiver (105).

7. The power transmitter according to any one of claims 1 to 3, wherein: At least some of the calibration parameters are provided for calibrating the receiver with the load disconnected.

8. The power transmitter according to any one of claims 1 to 3, wherein: The calibration data is provided for a reference power transmitter.

9. The power transmitter according to claim 8, wherein: The position estimator (207) is arranged to modify at least one of at least one calibration parameter and a test parameter in response to a difference between a property of the power transmitter (105) and a property of the reference power transmitter.

10. The power transmitter according to any one of claims 1 to 3, wherein: The test generator (211) is arranged to generate a plurality of different test signals, and the calibration data comprises a plurality of calibration parameters for the different test signals at a spatial location.

11. The power transmitter according to any one of claims 1 to 3, comprising a plurality of transmitter coils, the plurality of transmitter coils including the transmitter coil (103), and wherein, The test generator (211) is arranged to generate test signals for the plurality of transmitter coils.

12. The power transmitter according to claim 11, the test generator (211) being arranged to generate a sequence of test signal groups comprising different test signals for different transmitter coils of the plurality of transmitter coils, and the calibration data comprising a plurality of calibration parameters for the different test signal groups for a spatial location.

13. The power transmitter according to claim 12, wherein: At least two of the test signal groups include test signals for different subsets of the transmitter coils.

14. The power transmitter according to any one of claims 1 to 3, wherein: The position estimator (207) is arranged to estimate at least two dimensions for the position of the power receiver (105).

15. A method of operating a power transmitter (101) for wirelessly providing power to a power receiver (105) via an electromagnetic power transfer signal generated by a transmitter coil (103): the method comprising: Retrieving stored calibration data, the stored calibration data comprising a set of calibration parameters for each of a plurality of spatial positions of a calibration receiver relative to a calibration transmitter, the calibration parameters comprising, for each of the plurality of spatial positions: a calibration power loss measure for said calibration receiver at said each spatial location, indicating a calibration resonant frequency measure of a resonant circuit of the calibration power transmitter for the calibration receiver at each of the spatial locations, a calibration coupling metric indicative of coupling between the calibration transmitter and the calibration receiver at each of the spatial locations; generating a test drive signal for the transmitter coil 103 to generate an electromagnetic test signal; A set of test parameters is determined in response to the test drive signal, the test parameters comprising: a test power loss measure indicative of power extracted from the electromagnetic test signal, a test resonant frequency measurement for a resonant circuit comprising the transmitter coil (103), a test coupling metric indicative of coupling between the power transmitter (101) and the power receiver (105), the test power loss metric, the test resonant frequency metric and the test coupling metric providing different relationships to a position of the power receiver relative to the power transmitter, whereby a mutual relationship between the test power loss metric, the test resonant frequency metric and the test coupling metric provides an additional indication of the position of the power receiver relative to the power transmitter; and The position of the power receiver relative to the power transmitter is estimated in response to a comparison of the test parameters and the calibration parameters for the plurality of spatial locations.

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