Power Calibration Method
The calibration method addresses the challenges of accurate power measurement in wireless power supply devices by compensating for phase shifts and harmonic distortions, ensuring precise and compliant power measurements.
Patent Information
- Application Number
- JP2024547139
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-11
- Filing Date
- 2023-02-13
- Publication Date
- 2025-03-18
AI Technical Summary
Accurate power measurements in wireless power supply devices are challenging due to high signal frequencies, significant harmonic distortion, and phase shifts between voltage and current measurements, leading to errors in power calculations.
A calibration method for power measurement in wireless power supply applications that involves providing an alternating electrical signal through a wireless power supply coil, performing voltage and current measurements, calculating power values, and introducing compensatory changes to account for phase shifts between voltage and current measurements.
The method effectively compensates for phase shifts and harmonic distortions, ensuring accurate power measurements that conform to specifications, thereby improving the reliability and precision of wireless power supply systems.
Smart Images
Figure 2025507334000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates generally to the field of wireless power, and more particularly to testing of wireless power devices. Even more particularly, the present invention relates to a method for calibrating a power measurement function of a wireless power device. [Background technology]
[0002] As is well known, power measurements at high operating frequencies are difficult for two reasons: first, the fundamental difference between voltage and current measurements results in a phase shift between these two quantities that varies with frequency, and second, the harmonic content of the signal contributes significantly to the observed power value and cannot be ignored or predicted.
[0003] Since power is the product of voltage and current, a user needs measurements of both to get information about power. The power of a periodic signal can be written as P = avg(p(t)) = avg(v(t) i(t)) Here, the averaging must be performed over a period significantly greater than T=1 / f, which is the fundamental frequency of the signal.
[0004] For a pure sinusoidal signal, the equation can be simplified to: P = V I cos(φ) where V and I are the effective values of the voltage and current, and φ is the phase shift between the voltage and current.
[0005] Taking into account the harmonic content can be done by taking a Fourier transform of the input signal (dividing the periodic time series into the sum of all frequencies) and determining the phase shift of each frequency.
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[0006] A related area where power metering is becoming increasingly popular (from safety and energy efficiency perspectives) is wireless power, which is becoming increasingly popular for wireless battery charging in mobile devices such as handheld terminals, tablet computers, laptop computers, cameras, audio players, electric toothbrushes, wireless headsets, smart watches, and a variety of other consumer and home appliances.
[0007] The Wireless Power Consortium has developed a wireless power standard known as Qi. Other known wireless power initiatives include the Alliance for Wireless Power and the Power Matters Alliance. The wireless power standard known as Qi by the Wireless Power Consortium is referred to throughout this specification without limitation as the currently preferred embodiment of wireless power that applies to the present invention. However, the present invention may generally be applied to other wireless power standards or initiatives, including but not limited to those mentioned above.
[0008] The operation of Qi-compliant devices is based on magnetic induction between planar coils. Two types of devices are involved: those that provide wireless power (called base stations or power sources), i.e. wireless power sources, and those that consume wireless power (called mobile devices or power receivers), i.e. wireless power receivers. Power is provided by the base station to the mobile devices. For this purpose, the base station comprises a subsystem (power source) with a primary coil, and the mobile devices comprise a subsystem (power receiver) with a secondary coil. In operation, the primary and secondary coils are two halves of a coreless resonant transformer. A base station typically comprises a flat surface on which a user can place one or more mobile devices, allowing wireless battery charging and operating power for the mobile devices placed on the base station.
[0009] 1, which shows a wireless power supply 120 for wirelessly supplying power to a mobile device 110 (or power receiving product), i.e., a wireless power receiving device. The mobile device 110 can be, for example, a mobile terminal (e.g., a smartphone) 110a, a tablet computer 110b (e.g., a surfpad), a laptop computer 110c, a smart watch 110d, a camera, an audio player, a rechargeable toothbrush, a wireless headset, or any other type of consumer product or appliance.
[0010] Wireless power is illustrated herein as conforming to the Qi standard from the Wireless Power Consortium, and thus the wireless power supply device 120 is a base station or power supply product in Qi terminology, however, the present invention is generally applicable to other wireless power standards or approaches as discussed above.
[0011] The wireless power feeder 120 includes a wireless power feeder 122 having a wireless power feed coil 124, and is controlled by a power controller 126. Correspondingly, the mobile device 110 includes a wireless power receiver 112 having a wireless power receiving coil 114. Each of the coils 114, 124 is an inductor having a resistive element. In operation, the wireless power feeder 120 wirelessly feeds power to the mobile device 110 by magnetic induction 118 via the wireless power feed coil 124 and the wireless power receiving coil 114.
[0012] The power received by the wireless receiving coil 114 drives a load 116 in the mobile device 110. Typically, the load 116 may be a rechargeable battery, such as a lithium-ion battery, and thus the wireless power supply 120 serves as a wireless charger for the mobile device 110. In other scenarios, the load 116 is an electronic circuit in the mobile device, and the wireless power supply 120 serves as a wireless power source for the mobile device 110.
[0013] Throughout this specification, wireless charging is used as an example of wireless power transfer, i.e., as one species within a family, without limitation.
[0014] In wireless power applications, it is necessary to know the amount of power output by a power source (in the form of electromagnetic radiation) or absorbed by a powered device (in the form of electromagnetic radiation). In the field of wireless power, accurate power measurement is essential. Apart from the safety aspect regarding foreign object detection, accurate power measurement is also required to measure and determine the efficiency of wireless power systems. In programs such as Energy Star, a reliable evaluation of device performance is a source of competitive advantage for products that offer wireless power. Such a need may exist for various stakeholders, such as developers, manufacturers or suppliers of mobile devices, developers, manufacturers or suppliers of wireless power devices, testing or compliance organizations in the field of wireless power, and testing or compliance organizations in the field of consumer product safety.
[0015] Accurate power measurement in a wireless power system presents several challenges compared to commonly available AC power meters. The signal frequency is 1000 times higher, 100 kHz versus 100 Hz. In addition, the harmonic distortion is much higher, as it is a square wave versus a sine wave. Furthermore, the nature of wireless power systems means that the ratio of active power to apparent power is low (or there is a significant amount of reactive power, since what is being charged is a far from ideal resistive load).
[0016] A common problem in power measurements is that the circuits used to measure voltages have different characteristics than the circuits used to measure currents. The so-called transfer function between the real voltage and its measurement has a different dynamic behavior than the transfer function between the real current and its measurement. So, by the time the values are multiplied, the signals already have an (unequal) phase shift, which introduces errors into the power measurement.
[0017] As you get more harmonic content, the problem becomes more complex (square waves vs. sine waves) and you have more complex loads (inductive or capacitive loads vs. resistive loads). The harmonic content obviously changes because the phase shift caused by the signal changes with frequency. With more harmonic content, there are more frequencies to consider, and each frequency introduces a phase shift.
[0018] The effect of complex loading can be clearly seen when considering the small phase error of a resistive load (φ = 0°) with a highly inductive load (φ = 85°).
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[0019] As can be seen above, at a phase shift of 85 degrees, a change of 1 degree affects the power values by a factor of over 100. This is visualized in Figure 2 which includes a graph 210 which represents a half period of the function y = cos(x). At x degrees close to 0, graph 210 has a flat slope as seen at 220, but at x degrees close to 90, the slope of graph 210 is much steeper as seen at 230.
[0020] The complexity becomes apparent when you consider that wireless power applications require measuring the power flowing into and out of an inductor (power coil). Signals are typically very sensitive to phase errors (the closer to 90 degrees the more sensitive they are to errors). Losses in the power coil itself need to be compensated for. o The power dissipated in the coil itself must be subtracted from the source coil measurement. o The power dissipated in the coil must be added to the receiving coil measurement. o Power coil losses are a complex function and require knowledge of the signal frequency (apart from the current through the coil), harmonic content, coil impedance (as a function of frequency) and temperature. If the voltage is a square wave (typically with an H-bridge inverter), the current will be a triangle wave. This also means that the harmonic content of the voltage will be different to the harmonic content of the current. The present inventors have recognized that there is a need for improvement in these areas. Summary of the Invention
[0021] It is therefore an object of the present invention to provide an improvement in power measurement in wireless power transfer devices, and to obviate or mitigate one or more of the problems identified above.
[0022] Generally speaking, the present invention is a calibration method for power measurement in wireless power applications (end-user products, test tools, etc.) The method can be used to compensate for the (often unknown) phase shift caused by an independent measurement circuit in power measurement applications.
[0023] In view of the above, one aspect of the present invention is a method for calibrating a power measurement function of a wireless power device. The method includes providing an AC electrical signal through a wireless power coil to drive the wireless power coil at an operating point. The method further includes performing voltage and current measurements on the AC electrical signal or a resulting current signal in the wireless power device, and generating a series of voltage values and a series of current values from the voltage and current measurements. The method further includes calculating a power value from the generated series of voltage values and series of current values, and evaluating whether the calculated power value meets the specification. If not, the method introduces a compensatory change into one of the generated series of voltage values and series of current values to account for a phase shift between the voltage and current measurements at the operating point, and stores the compensatory change for the wireless power device. The power measurement function of the wireless power device can then use the stored compensatory change to generate wireless power measurements at the operating point that comply with the specification.
[0024] Other aspects, objects, features and advantages of the disclosed embodiments will become apparent from the following detailed disclosure, the appended dependent claims, and the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless expressly defined otherwise in this specification.
[0025] All references to a / an / the "element, apparatus, component, means, step, etc." shall be broadly interpreted as meaning at least one example of the element, apparatus, component, means, step, etc. The steps of methods disclosed herein do not have to be performed in the exact order disclosed, unless expressly stated otherwise. [Brief description of the drawings]
[0026] The objects, features and advantages of the embodiments of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a schematic block diagram of a wireless power supply device for wirelessly supplying power to a wireless power receiving device. [Diagram 2] FIG. 2 is a schematic diagram of a cosine function. [Diagram 3] FIG. 3 is a schematic circuit diagram showing a measurement device that can be used to measure current and voltage for the purposes of calculating power. [Figure 4] FIG. 4 illustrates current, voltage and power signals in analog and time-discrete form. [Diagram 5] FIG. 5 is a block diagram showing a first embodiment of a wireless power device having a power measurement function. [Figure 6] FIG. 6 is a flow chart diagram of a first embodiment of a power calibration method operable for the wireless power device of FIG. [Figure 7] FIG. 7 is a block diagram illustrating a second embodiment of a wireless power device having power measurement capability that operates with a calibrated wireless power receiver. [Figure 8] FIG. 8 is a flow chart diagram illustrating a second embodiment of a power calibration method operable for the wireless power device of FIG. [Figure 9] FIG. 9 is a block diagram illustrating a third embodiment of a wireless power device with power measurement capability, which is a wireless power receiver and operates in conjunction with a calibrated wireless power transmitter. [Figure 10] FIG. 10 is a flow chart diagram illustrating a third embodiment of a power calibration method operable for the wireless power device of FIG. [Figure 11] FIG. 11 is a flow chart diagram of a method for calibrating the power measurement functionality of a wireless power device generally in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be embodied in many different forms and should not be construed as being limited to the embodiments described herein, but rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. The terms used in the detailed description of the specific embodiments illustrated in the accompanying drawings are not intended to limit the present invention. In the drawings, like numbers refer to like elements. Elements illustrated as hatched boxes are generally considered to be optional in the particular drawing in which they appear.
[0028] Introduction and Framework of the Invention As mentioned above, the present invention relates to calibration for power measurement in wireless power applications (end user products, test tools, etc.). The calibration can be used to compensate for phase shifts caused by independent measurement circuits in power measurement applications. The method assumes that an accurate loss estimation of the power coil is possible.
[0029] In the following description of the invention and its embodiments, certain actions (or functions) are described. For example, V RMS and I RMS Calibration of the LVDS includes any procedure for reducing errors in voltage and current measurements of a general purpose measurement device. In addition, compensation for phase shifts can be achieved by, for example, - The effective value does not change, - the calculated power values approach the desired values, The trick is to add an artificial delay to the time series of current measurements, such as:
[0030] Furthermore, the change in operating point can be any combination of changes in operating frequency, load resistance, coil current, coil voltage, harmonic content, temperature, and the like.
[0031] First, FIG. 3 shows an example of a typical measurement device 300 that can be used to measure current and voltage for the purpose of calculating power. The configuration of the measurement device 300 is practically conventional. Thus, those skilled in the art will readily recognize that the measurement device 300 includes a current measurement circuit 320 and a voltage measurement circuit 340, both of which are powered by a voltage source 310 via elements 312 and 314. The current measurement circuit 320 includes circuit elements 322-338 and outputs a current signal 339. The voltage measurement circuit 340 includes circuit elements 342-346 and outputs a voltage signal 349. Those skilled in the art will readily recognize that other configurations are possible for implementing electronic circuits that measure current and voltage for the purpose of calculating power.
[0032] The current signal 339 and the voltage signal 349 are sampled by an analog-to-digital converter (ADC) which converts the actual (analog) voltages into numbers that can be digitally processed.
[0033] The ADC operates at a sampling frequency of f sample A measurement sample is taken at , which means that two consecutive samples are spaced apart in time by T sample =1 / f sampleThis means that the continuous-time signal v(t) is a discrete time series v(n), where n is the instantaneous value taken at time t. This time series is sample This results in a representation of a digital signal with a value every second. Figure 4 shows an example where the continuous lines show the continuous time signals v(t), i(t), p(t) and the stem plots show the discrete time series of these signals v(n), i(n), and p(n). In this example, a 100 kHz signal and a 1 MHz sampling frequency are used. The phase shift between the voltage signal 410 and the current signal 420 is 60 degrees, which can be seen by taking the average value of the power signal 430 and comparing it to the following function:
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[0034] The mean value of a continuous time signal, averaged over 500μs, is 7.4995W. Using the same averaging window, the mean value of a discrete time series signal is 7.4948W, which is obtained by simply taking the mean value of a 500μs long time series.
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[0035] In accordance with the present invention, one or the other of the time series is adjusted to compensate for the phase shift experienced by the signal in a particular measurement device.
[0036] For example, the current time series (see stem plot (420) in FIG. 4) can be modified with an artificial phase shift such that the original time series is defined as: t = k T sample For each i(n)=i(t), t = k T sample For each i(n)=i(t+ε) is converted to
[0037] The value of i(t+ε) is obtained by linear interpolation between samples i(t0) and i(t1).
[0038] By adjusting the value of ε, the calculated power values can be adjusted without affecting the effective current results.
[0039] General invention concept Please refer to Fig. 11. As shown in Fig. 11, a method 1100 for calibrating a power measurement function of a wireless power device is provided. Other non-limiting embodiments of a wireless power device 510, 710, 940 and its power measurement function 516, 716, 946 are described below with reference to Figs. 5, 7 and 9, and respective embodiments of the method 1100 are shown in Figs. 6, 8 and 10.
[0040] The method 1100 includes providing 1110 an alternating electrical signal through a wireless power coil to drive the wireless power coil at an operating point. Examples of such wireless power coils are shown at 520, 720, and 920 in FIGS. 5, 7, and 9.
[0041] The method 1100 further includes performing 1120 voltage and current measurements within the wireless power device on the alternating electrical signal or the resulting current signal.
[0042] Next, the method 1100 generates a series of voltage values and a series of current values from the voltage and current measurements, and calculates 1140 a power value from the generated series of voltage values and series of current values.
[0043] Next, the method 1100 evaluates (1150) whether the calculated power value meets specifications. This may include comparing the calculated power value to an expected power value, and the calculated power value is deemed to meet specifications if it does not deviate from the expected power value by more than a margin of error or is within an acceptable range of accuracy. The expected power value may follow requirements set forth in a wireless power standard, such as Qi. In some embodiments (such as those described below with respect to FIGS. 7 and 8), the expected power value follows a received power value determined by a calibrated wireless power receiver cooperating with the wireless power device.
[0044] If the calculated power values do not meet the specifications evaluated in step 1150, a compensatory change (see value ε above) is introduced 1160 into either the generated series of voltage values and series of current values to account for the phase shift between the voltage and current measurements at the operating point. The compensatory change is stored 1170 for the wireless power device. This enables a power measurement function (e.g., 516, 716, 946) of the wireless power device (e.g., 510, 710, 940) to generate specification-compliant wireless power measurements at the operating point by using the stored compensatory change to compensate for the phase shift.
[0045] Optionally, but preferably, the steps of method 1100 are repeated for multiple operating points, as shown at 1180 in FIG.
[0046] The operating point is typically defined by one or a combination of two or more of the following parameters: Fundamental frequency of AC electrical signals Harmonic components of AC electrical signals Load resistance Nominal effective current value of AC electrical signal Nominal effective voltage value of AC electrical signal · Operating temperature
[0047] To make the calibration reliable, the method 1100 typically includes an implementation step of independently evaluating the ability of the power measurement functionality (e.g., 516, 716, 946) of the wireless power device (e.g., 510, 710, 940) to determine effective voltage and current values with a specified accuracy (see 612-614 in FIG. 6, 812-814 in FIG. 8, 1012-1014 in FIG. 10), and, if necessary, calibrating the power measurement functionality of the wireless power device (see 618 in FIG. 6, 818 in FIG. 8, 1018 in FIG. 10).
[0048] Preferably, in step 1130 of method 1100, the series of voltage values is a time series generated by sampling voltage measurements obtained by voltage measurement circuit 340 (FIG. 3) of the wireless power device at a sampling rate. Correspondingly, the series of current values is a time series generated by sampling current measurements obtained by current measurement circuit 320 of the wireless power device at a sampling rate.
[0049] The compensatory modification conveniently takes the form of an artificial delay added to these time series. Thus, the compensatory modification is introduced in step 1160 of method 1100 (and corresponding to step 630 of FIG. 6, step 830 of FIG. 8, and step 1030 of FIG. 10) by applying an artificial delay ε to one of the time series of current or voltage values, with respect to the original time series i(n)=i(t) or v(n)=v(t), with a delay t=k·T sample is compensated for every T sample is the inverse of the sampling rate and an artificial delay ε is applied to obtain the compensated time series i(n) = i(t + ε) or v(n) = v(t + ε).
[0050] More specifically, an artificial delay ε is preferably applied to one of the time series of current or voltage values such that its effective value does not change and the power value calculated from the compensated time series and the other time series of current or voltage values complies with or is closer to the specification.
[0051] Exemplary embodiments 5 and 6 show a first example of a wireless power device 510 having a power measurement function 516 that can be calibrated using a first embodiment 600 of a method 1100 in accordance with the present invention described above.
[0052] The wireless power device 510 of Fig. 5 is a test tool for wireless power transfer (abbreviated as WPT). More specifically, it is designed for testing an end-user's wireless power receiver such as the mobile device 110 (e.g., 110a to 110d) of Fig. 1 described above. The wireless power device 510 includes a wireless power feeder having a wireless power feed coil 520 and driven by a generator 512 with an H-bridge inverter. The wireless power feed coil 520 is provided within the wireless power feeder 510, electrically coupled to the wireless power feeder 510, or associated with the wireless power feeder 510 (e.g., by inductive forwarding).
[0053] During a typical test, the wireless power device 510 operates at different operating points in the presence of a wireless power receiver for the purpose of testing the wireless power receiver for compliance with a standard applicable to wireless power transmission, such as Qi, etc. To this end, the wireless power device 510 further comprises one or more sensors, such as a temperature sensor, for measuring parameters of the test environment.
[0054] The operating point may relate to, for example, the frequency, shape, direction and / or magnitude of the electric field generated by the wireless power coil 520, the surface temperature measured by one or more sensors, or any combination thereof or derivatives thereof.
[0055] The wireless power device 510 further comprises a measurement function operatively coupled to the wireless power coil 520 and configured to measure or determine various measurement data including the voltage and current of the electrical signals flowing through the wireless power coil 520. As will be appreciated by those skilled in the art, these electrical signals are not only affected by the drive signals provided by the power generating device 512, but also by electromagnetic (or inductive) interactions with the wireless power receiving device as may be present during normal testing. Thus, the measurement function comprises circuitry 514 for voltage and current measurements, which may be implemented, for example, as the measurement device 300 described above with reference to FIG.
[0056] As part of the testing functionality of the wireless power device 510 , there is a power calculation function 516 for calculating power from voltage and current measurements provided by the circuitry 514 .
[0057] The wireless power device 510 may be implemented, for example, by or based on a CATS II Mobile Device Tester, commercially available from Strandreundsgatan 30, SE 211 28, Malmö, Sweden. The wireless power device 510 may be compliant with the test power device described, for example, in Chapter 4 of the "Qi Wireless Power System," Power Class 0 Specification, Part 3: Conformance Testing, Version 1.2.4, February 2018, or a compatible subsequent version of this specification.
[0058] Unlike normal testing, when performing the calibration method 600 of Figure 6, the wireless power device 510 operates in the absence of a wireless power receiver. This method will now be described.
[0059] The purpose of the method 600 is to generate compensation data (e.g., value ε) for the compensatory changes referenced in steps 1160 and 1170, as described above for the method 1100 of FIG. 11. The method 600 of FIG. 6 begins with introductory steps 610-618 to ensure reliable calibration. As described above, these steps involve an independent evaluation of the ability of the power measurement function (power calculation function 516) of the wireless power device 510 to determine effective voltage and current values to a predetermined accuracy, and calibrating the power measurement function of the wireless power device if necessary. When the calibration method 600 of FIG. 6 is performed, the wireless power device 510 is operated in isolation (without the presence of a wireless power receiver), so the effective voltage and current values should ideally be zero (0), and any deviation from zero (0) beyond a specified accuracy requires calibration in step 618 using some external equipment with a verified calibration capability.
[0060] After these installation steps, a check is made in step 622 to ensure that there is no conductive or magnetically permeable material that is not part of the powered product (wireless power device 510) in the vicinity of the wireless power coil 520. This step may involve manual (visual) inspection by a human test operator or automated inspection, for example using digital image capture and analysis.
[0061] In steps 624-630 of method 600, the main functions of the inventive calibration method 1100, i.e., steps 1110-1160 described above, are performed by operating the wireless power device 510 at one operating point. The determined compensatory change (value ε) is stored in step 632, as described for step 1170 of the inventive calibration method 1100. Storage of the determined compensatory change may involve any storage means available within or otherwise associated with the wireless power device 510. Non-limiting examples are computer readable internal memory such as ROM, RAM, SRAM, DRAM, FLASH, DDR or SDRAM, or secondary storage such as a solid-state drive or hard drive, or remote (e.g., cloud-based) storage accessible by local or wide area communication means such as wireless communication such as Bluetooth, WiFi, W-CDMA, GSM, UTRAN, HSPA, LTE, LTE Advanced or 5G, or wired communication such as simple electrical wiring, USB or serial communication such as Ethernet.
[0062] This enables the power measurement function (power calculation function 516) of the wireless power device 510 to generate wireless power measurement results at operating points that are consistent with the relevant specifications during subsequent operation of the wireless power device 510 for normal testing (i.e., in the presence of a wireless power receiving device) by applying the stored compensatory changes when the power calculation function 516 calculates any power measurement results.
[0063] The procedure of steps 624 - 630 is then repeated for other operating points, as shown at 634 - 638 , and respective compensatory changes are stored at 632 for each operating point of the wireless power device 510 .
[0064] The method 600 ends at 644 once all operating points have been visited.
[0065] In summary, in a first example / embodiment of FIGS. 5 and 6 , all steps of method 600 are performed by a wireless power device 510, a wireless power transfer coil 520 is provided in or electrically coupled to or associated with the wireless power device, voltage and current measurements are performed on an AC electrical signal provided through the wireless power transfer coil 520 in the absence of a wireless receiving coil, and evaluating whether the calculated power value meets specifications includes evaluating whether it is within a specified error range from zero power.
[0066] Figures 7 and 8 show a second example of a wireless power device 710 having a power measurement function 716 that can be calibrated using a second embodiment 800 of the method 1100 according to the present invention described above. The main difference with respect to the first example 510 / first embodiment 600 in Figures 5 and 6 is that the wireless power device 710 is operated together with a calibrated wireless power receiving device 740.
[0067] The wireless power receiving coil 750 is provided within, electrically coupled to, or associated with the calibrated wireless power receiving device 740. The calibrated wireless power receiving device 740 comprises a load 742 and a circuit 744 for voltage and current measurement coupled to the wireless power receiving coil 740. The circuit 744 may be implemented, for example, as the measurement device 300 described above with reference to FIG. 3. The calibrated wireless power receiving device 740 further comprises a power calculation function 746 for calculating power from the voltage and current measurements provided by the circuit 744.
[0068] The wireless power device 710 of FIG. 7 is a test tool for wireless power transmission. It is or can be the same as the wireless power device 510 of FIG. 5, except that it is designed to perform the calibration method 800 of FIG. 8 in the presence of a calibrated wireless power receiver 740. The calibration method 800 of FIG. 8 is or can be the same as the calibration method 600 of FIG. 6, except for steps 826 and 830, where the compensatory change (value ε) is determined by comparing the calculated power value with the expected power value given by the received power value determined by the power calculation function 746 of the wireless power receiver 740. Thus, unlike step 626 of FIG. 6, the expected power value does not become a zero (0) value.
[0069] In summary, in the second example / embodiment of FIGS. 7 and 8 , the wireless power device is a wireless power source 710, the wireless power source coil 720 is disposed within or electrically coupled to or otherwise associated with the wireless power source 710, all steps of method 800 are performed by the wireless power source 710 (except for providing a received power value from a calibrated wireless power receiver 740), the voltage and current measurements are performed on an AC electrical signal provided through the wireless power source coil 710 in the presence of the wireless power receiver coil 750 of the calibrated wireless power receiver 740, and evaluating whether the calculated power value meets the specifications includes evaluating whether it matches within a predetermined error range the received power value determined by the calibrated wireless power receiver 740.
[0070] 9 and 10 show a third example of a wireless power device 940 having a power measurement function 946 that can be calibrated using the third embodiment 1000 of a method 1100 according to the present invention described above.
[0071] In this third example / embodiment, the roles of the wireless power supply device 910 and the wireless power receiving device 940 are switched compared to the second example / embodiment. Whereas in Figures 7 and 8, the wireless power receiving device 740 was already calibrated so that a compensatory change could be determined for the wireless power supply device 710, Figures 9 and 10 make use of the fact that the wireless power supply device 910 has already been calibrated according to the second example / embodiment of Figures 7 and 8 or according to the first example / embodiment of Figures 5 and 6. Thus, the calibrated wireless power supply device 910 is used for the purpose of being able to determine a compensatory change for the wireless power receiving device 940, which may be, for example, a WPT test tool designed for testing base stations (e.g., wireless Qi chargers).
[0072] 9 and 10, the wireless power device has a wireless receiving coil 950 disposed in or electrically coupled to or associated with the wireless power receiving device 940, a wireless power transfer coil 920 disposed in or electrically coupled to or associated with the wireless power transfer device 910, the power transfer step 1110 of the method 1100 of FIG. 11 is performed by the wireless power transfer device 910, and all other steps of the method 1100 of FIG. 11 are performed by the wireless power receiving device 940, and in response to the AC electrical signal being provided via the wireless power transfer coil 920, voltage and current measurements are made on the resulting AC electrical signal received via the wireless power receiving coil 950 of the wireless power receiving device 940, and evaluating whether the calculated power value meets the specifications includes evaluating whether it falls within a specified error range from the transmit power value determined by the wireless power transfer device 910.
[0073] Although the present invention has been described primarily with reference to certain embodiments, those skilled in the art will readily appreciate that other embodiments than those disclosed above are equally possible within the scope of the present invention as defined by the appended claims.
Claims
1. A method (1100) for calibrating a power measurement function (516, 716, 946) of a wireless power device (510, 710, 940), comprising: Supplying (1110) an AC electric signal through a wireless power supply coil (520, 720, 920) to drive the wireless power supply coil at an operating point; making (1120) voltage and current measurements on the AC electrical signal or the resulting current signal at the wireless power device; generating 1130 a series of voltage values and a series of current values from the voltage and current measurements; Calculating 1140 a power value from the generated series of voltage values and series of current values; Evaluating (1150) whether the calculated power value meets specifications; If not, introducing 1160 a compensatory change to one of the generated series of voltage values and series of current values to account for a phase shift between the voltage and current measurements at the operating point; storing (1170) the compensatory changes for the wireless power device (510, 710, 940) to enable the power measurement function (516, 716, 946) to generate wireless power measurements at the operating point that are consistent with the specification. The method includes:
2. The method of claim 1 , wherein the steps of the method are repeated (1180) for multiple operating points.
3. The operating point is the fundamental frequency of the AC electrical signal; harmonic components of the AC electrical signal; Load resistance, a nominal effective current value of the AC electrical signal; a nominal effective voltage value of the AC electrical signal; operating temperature, The method according to claim 1 or 2, wherein the method is defined by one or a combination of two or more of the following:
4. Independently evaluating (612-614, 812-814, 1012-1014) the power measurement function (516, 716, 946) of the wireless power device (510, 710, 940) for determining effective voltage and current values with a predetermined accuracy; Optionally, calibrating (618, 818, 1018) the power measurement functionality of the wireless power device (510, 710, 940); The method of claim 1 , further comprising an introducing step.
5. the series of voltage values being a time series generated by sampling the voltage measurements obtained by a voltage measurement circuit (340) of the wireless power device (510, 710, 940) at a sampling rate; the series of current values being a time series generated by sampling the current measurements obtained by a current measurement circuit (320) of the wireless power device (510, 710, 940) at the sampling rate; 5. The method according to any one of claims 1 to 4.
6. The compensatory change is ｓａｍｐｌｅ For each original time series i(n)=i(t) or v(n)=v(t), an artificial delay ε is introduced by applying 1160, 630, 830, 1030 to one of said time series of current or voltage values, T ｓａｍｐｌｅ is the inverse of the sampling rate, and the artificial delay ε is applied to obtain a compensated time series i(n)=i(t+ε) or v(n)=v(t+ε), The method according to claim 5.
7. 7. The method of claim 6, wherein the artificial delay ε is applied to a time series of one of current or voltage values such that its effective value does not change and the power value calculated from the compensated time series and the other time series of current or voltage values meets or is close to the specification.
8. All steps of the method are performed by the wireless power device (510); The wireless power supply coil (520) is provided within a wireless power supply device, electrically coupled to the wireless power supply device, or associated with the wireless power supply device; the voltage measurements and current measurements are performed on the alternating current electrical signal as provided through the wireless power supply coil in the absence of a wireless power receiving coil; evaluating whether the calculated power value meets the specification includes evaluating whether the calculated power value is within a specified error range from zero power.
8. The method according to any one of claims 1 to 7.
9. The wireless power device is a wireless power supply device (710), The wireless power supply coil (720) is provided within the wireless power supply device (710), electrically coupled to the wireless power supply device (710), or associated with the wireless power supply device (710); All steps of the method are performed by the wireless power supply device (710), The voltage and current measurements are performed on the AC electrical signal provided via the wireless power supply coil (710) in the presence of a wireless power receiving coil (750) of a calibrated wireless power receiving device (740); evaluating whether the calculated power value meets the specification includes evaluating whether the calculated power value matches within a predetermined error range a received power value determined by a calibrated wireless power receiving device (740).
8. The method according to any one of claims 1 to 7.
10. The wireless power device is a wireless power receiving device (940) having a wireless power receiving coil (950), the wireless power receiving coil (950) being disposed within the wireless power receiving device (940), electrically coupled to the wireless power receiving device (940), or associated with the wireless power receiving device (940); The wireless power supply coil (920) is provided within the wireless power supply device (910), electrically coupled to the wireless power supply device (910), or associated with the wireless power supply device (910); The power supply step (1110) is performed by the wireless power supply device (910), All other steps of the method are performed by the wireless power receiving device (940); In response to the AC electrical signal being fed via the wireless power feed coil (920), the voltage measurements and the current measurements are performed on a resultant AC electrical signal received via the wireless power receiving coil (950) of the wireless power feeder (940); Evaluating whether the calculated power value satisfies the specification includes evaluating whether the calculated power value falls within a predetermined error range from a transmission power value determined by the wireless power supply device (910).
8. The method according to any one of claims 1 to 7.