Foreign matter detection method in power transmission process of wireless charging system and power transmitter
By briefly interrupting the power signal in the wireless charging system and sampling the resonant waveform, integrating and averaging operations, the misjudgment problem caused by noise interference is solved, and the accuracy of foreign object detection is improved.
Patent Information
- Application Number
- CN202410012322.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-03
- Publication Date
- 2025-07-04
AI Technical Summary
Existing wireless charging systems are susceptible to noise interference or value deviation when detecting foreign objects, resulting in misjudgment.
By briefly interrupting the power signal, sampling the resonant waveform of the resonant circuit, performing integral and average operations, obtaining the integral average value and resonant frequency, and determining whether foreign objects are approaching based on these values.
It improves the accuracy of foreign object detection and reduces the impact of noise interference and value deviation on judgment.
Smart Images
Figure CN120262718A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present application relate to a wireless charging system, and particularly to a detection method for detecting whether a foreign object approaches a power transmitter in the wireless power transmission process and a power transmitter. Background Art
[0002] In a wireless charging system, a power transmitter (or TX) transfers electrical energy to a power receiver (or RX) placed on or near the power transmitter through electromagnetic waves to charge or supply power to the power receiver. During this process, the coils of the power transmitter and the power receiver have the same or similar resonant frequencies, enabling them to effectively couple, and even if there is a certain distance between them or there are non-metallic objects, energy can be effectively transmitted.
[0003] If a metal object is placed near the power transmitter and the receiver while the power transmitter is supplying power to the power receiver, the power transmitter, the power receiver, and the metal object may be damaged due to the heat generated by the metal object.
[0004] Existing wireless charging systems determine whether there is a foreign object (Foreign Object, FO), such as a metal foreign object, based on the Q factor (Q-Factor). The Q factor is a characteristic parameter of the resonant circuit of the power transmitter. When there is a metal foreign object, the value of the Q factor is different from the value of the Q factor when there is no metal foreign object. Therefore, it is possible to determine whether there is a metal foreign object based on the Q factor. Figure 1A And Figure 1B respectively show the resonant waveforms of the resonant circuit of the power transmitter in the case of no metal foreign object and in the case of having a metal foreign object. As Figure 1A And Figure 1B shown, in the case of having a metal foreign object, the signal amplitude in the resonant waveform will rapidly decrease, and the value of the corresponding Q factor will also be less than the value of the Q factor when there is no metal foreign object.
[0005] The existing method for calculating the Q factor is to calculate the value of the Q factor by grabbing the signal peaks V1 and V2 corresponding to two time points and matching the frequency of the obtained signal. However, once the signal peak V1 or V2 is interfered by noise or has a deviation in value, the calculated value of the Q factor will be distorted, resulting in an easy problem of misjudging whether there is a metal foreign object. Summary of the Invention
[0006] The embodiments of the present application provide a detection method and a power transmitter, which can effectively improve the accuracy of judging whether a foreign object approaches the power transmitter during the power transmission process of the wireless charging system. The technical solutions are as follows:
[0007] According to one aspect of the embodiments of the present application, a detection method is provided for detecting whether a foreign object approaches a power transmitter in a wireless charging system during power transmission. The method includes: using a control circuit to briefly interrupt the power signal transmitted to supply power to a power receiver in the wireless charging system; using a signal sampling circuit to sample the signal generated by the resonant circuit of the power transmitter during the brief interruption of the power signal transmission; using the control circuit to obtain a resonant waveform based on the sampling values sampled by the signal sampling circuit for the signal; using the control circuit to perform an integration operation on the resonant waveform and perform an averaging operation on the integration result to obtain an integration average value; obtaining a resonant frequency of the resonant waveform; and determining whether the foreign object exists based on the integration average value and the resonant frequency.
[0008] According to another aspect of the embodiments of the present application, a power transmitter in a wireless charging system is provided. The power transmitter includes: a control circuit for briefly interrupting the power signal transmitted to supply power to a power receiver in the wireless charging system; a signal sampling circuit connected to the control circuit for sampling the signal generated by the resonant circuit of the power transmitter during the brief interruption of the power signal transmission; wherein the control circuit is further configured to: obtain a resonant waveform based on the sampling values sampled by the signal sampling circuit for the signal; perform an integration operation on the resonant waveform and perform an averaging operation on the integration result to obtain an integration average value; obtain a resonant frequency of the resonant waveform; and determine whether a foreign object approaches the power transmitter based on the integration average value and the resonant frequency.
[0009] The technical solutions provided by the embodiments of the present application may include the following beneficial effects:
[0010] In the detection method and the power transmitter of the embodiments of the present application, during the power transmission process of the wireless charging system, the power signal transmitted by the power transmitter to supply power to the power receiver is briefly interrupted, and during the brief interruption of the power signal transmission, the attenuated resonant waveform generated by the resonant circuit of the power transmitter is sampled. An integration operation is performed on the sampled resonant waveform to obtain an integration average value and the resonant frequency of the resonant waveform is obtained by estimation. Then, based on the integration average value and the resonant frequency, it is determined whether a foreign object approaches the power transmitter during the power transmission of the power transmitter. Different from the traditional method of calculating the Q factor value of the resonant waveform, the present application can improve the problem that the accuracy of the Q factor value is affected by noise interference or value deviation in the existing method, thus misjudging whether a foreign object approaches the power transmitter. Therefore, the present application can effectively improve the accuracy of determining whether a foreign object approaches the power transmitter during the power transmission process.
[0011] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit this application. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0013] Figure 1A Schematic diagram showing the resonance waveform of the resonance circuit of the power transmitter in the absence of metallic foreign objects.
[0014] Figure 1B Schematic diagram showing the resonance waveform of the resonance circuit of the power transmitter in the presence of metallic foreign objects.
[0015] Figure 2 Schematic block diagram showing the power transmitter according to an embodiment of this application.
[0016] Figure 3A Schematic diagram showing an example of obtaining the integral average value according to an embodiment of this application.
[0017] Figure 3B Schematic diagram showing another example of obtaining the integral average value according to an embodiment of this application.
[0018] Figure 3C Schematic diagram showing an example of obtaining the resonance frequency according to an embodiment of this application.
[0019] Figure 4A Schematic diagram showing the resonance waveform measured when no foreign object is detected during the power transmission process according to an embodiment of this application.
[0020] Figure 4B Schematic diagram showing the resonance waveform measured when a foreign object is detected during the power transmission process according to an embodiment of this application.
[0021] Figure 5 Comparison diagram showing the resonance waveforms with and without foreign objects according to an embodiment of this application.
[0022] Figure 6 Flowchart showing a detection method according to an embodiment of this application.
[0023] DESCRIPTION OF THE REFERENCE NUMERALS:
[0024] 20 Power transmitter
[0025] 21 Converter
[0026] 22 Inverter
[0027] 24 Resonant Circuit
[0028] 26 Signal Sampling Circuit
[0029] 28 Control Circuit
[0030] 29 Signal Shaper
[0031] C p Capacitor
[0032] L p Inductor
[0033] L Peak Curve
[0034] L_INT Curve
[0035] Q_COMP Resonant Waveform
[0036] Q_COMP_UH Waveform
[0037] t Time
[0038] t1 First Time Point
[0039] t2 Second Time Point
[0040] T_period Resonant Frequency
[0041] V Voltage
[0042] V1 First Signal Peak
[0043] V2 Second Signal Peak
[0044] V in Input Voltage
[0045] V R Reference Voltage
[0046] V sw Inverter Output Waveform
[0047] Steps S10 - S60 Specific Embodiments
[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application belong to the scope of protection of the present application.
[0049] A wireless charging system generally includes a power transmitter (or TX) and one or more power receivers (or RX). The power transmitter can be used to wirelessly transmit power to the power receiver to supply power or charge the power receiver. The inventive concept provided in this application is mainly used to detect whether a foreign object (FO) approaches the wireless charging system during the process of the power transmitter transmitting power to the power receiver. For example, whether a foreign object is placed on or near the power transmitter. The foreign object referred to in this application means an object such as a metal or a metal-containing object, a composite material, a mixture, and an alloy, etc., whose electromagnetic wave for wireless transmission will be affected by it, or it can also be a coil-type foreign object having a coil. If a foreign object is detected, the power transmitter can stop transmitting power to the power receiver.
[0050] Regarding the resonant waveform generated by the resonant circuit of the power transmitter, different from the traditional way of calculating the value of the Q factor (Q-Factor) of this resonant waveform, in the embodiments of this application, an integral operation and an averaging operation are performed on this resonant waveform to obtain an integral average value, and the resonant frequency of this resonant waveform is obtained by estimation. Then, based on this integral average value and this resonant frequency, it is determined whether a foreign object approaches the power transmitter during the power transmission process. This way of this application can improve the problem that the existing way affects the accuracy of the value of the Q factor due to noise interference or value deviation, and thus misjudges whether a foreign object approaches the power transmitter.
[0051] Specifically, the embodiments of this application provide a foreign object detection method, and the method includes: briefly interrupting the power signal transmitted for supplying power to the power receiver in the wireless charging system; during the brief interruption of the transmission of this power signal, sampling the signal generated by the resonant circuit of this power transmitter; based on the sampling value obtained by the signal sampling circuit sampling this signal, obtaining a resonant waveform; performing an integral operation on this resonant waveform and performing an averaging operation on the integral result to obtain an integral average value; obtaining a resonant frequency of this resonant waveform; and based on this integral average value and this resonant frequency, determining whether a foreign object approaches the power transmitter.
[0052] Specifically, the embodiments of this application also provide a power transmitter, which includes: a control circuit for briefly interrupting the power signal transmitted for supplying power to the power receiver in the wireless charging system; a signal sampling circuit connected to the control circuit for sampling the signal generated by the resonant circuit of this power transmitter during the brief interruption of the transmission of this power signal; wherein, the control circuit is further configured to: based on the sampling value obtained by the signal sampling circuit sampling this signal, obtain a resonant waveform; perform an integral operation on this resonant waveform and perform an averaging operation on the integral result to obtain an integral average value; obtain a resonant frequency of this resonant waveform; and based on this integral average value and this resonant frequency, determine whether a foreign object approaches this power transmitter.
[0053] Figure 2 A schematic block diagram showing a power transmitter 20 according to an embodiment of the present application. The power transmitter 20 includes a converter 21, an inverter 22, a resonant circuit 24, a signal sampling circuit 26, and a control circuit 28, and optionally includes a signal shaper or a voltage divider 29. The converter 21, the inverter 22, and the resonant circuit 24 are well-known to those skilled in the art, so a detailed description of these components is not necessary. The acquisition of the damped resonant waveform generated by the resonant circuit 24 can be performed at any node of the loop of the resonant circuit 24, not limited to Figure 2 the node shown between the capacitor C p and the inductor L p . The resonant waveform collected by the signal sampling circuit 26 can be stored in a buffer (not shown) for later processing. The control circuit 28 processes the data of the stored resonant waveform to obtain the integral average value and the resonant frequency. Based on the obtained integral average value and resonant frequency, the control circuit 28 can determine whether there is a foreign object approaching the power transmitter 20.
[0054] The converter 21 can perform appropriate voltage conversion on the DC input voltage V in . The voltage or current output to a load (not shown, such as a power receiver) can mainly depend on the transformation performed by the converter 21. The converter 21 can be a buck converter, which can output an appropriate DC voltage to the inverter 22.
[0055] The inverter 22 is used to convert the DC input voltage V in into an inverter output waveform (V sw ) for driving the oscillation of the resonant circuit 24. For example, the inverter 22 can be a DC-to-AC full bridge inverter with four transistors (not shown), and the inverter 22 can also be implemented as a half-bridge inverter. The control circuit 28 can generate the inverter output waveform (V sw ) by controlling the switching of the transistors (not shown) in the inverter 22, or can control the inverter 22 to disconnect the inverter 22 from the power supply, leaving only the loop of the resonant circuit 24.
[0056] The resonant circuit 24 includes a capacitor C p and an inductor L p connected in series., but not limited thereto. A resonant circuit 24 composed of two capacitors and an inductor, or other types of resonant circuits, may also be adopted. In the wireless charging system, inductive coupling generated between the inductor L of the resonant circuit 24 in the power transmitter 20 p and an inductor (not shown) in the power receiver is used to transmit power from the power transmitter 20 to the power receiver.
[0057] During the power transmission process in which the power transmitter 20 transmits power to the power receiver, the inverter 22 continuously generates an inverter output waveform (V sw ), and the signal waveform output by the resonant circuit 24 will be a signal waveform with a consistent peak voltage. The power transmitter 20 transmits an electromagnetic wave with this signal waveform to the power receiver to supply power or charge the power receiver. If the inverter 22 is briefly disconnected from the power supply for a short period of time at this time (i.e., during the brief interruption of the power signal transmission), the supply of energy stops during this period. Then, for the signal waveform measured for the resonant circuit 24 during this brief interruption of the power signal transmission, the voltage amplitude will gradually decrease, forming a decaying resonant waveform.
[0058] If a foreign object approaches the power transmitter 20 during the power transmission process, then the attenuation amplitude of the resonant waveform measured for the resonant circuit 24 during the brief interruption of the power signal transmission will increase, and the voltage amplitude of the resonant waveform will rapidly decrease. Therefore, it is possible to determine whether a foreign object approaches during the power transmission process by detecting the attenuation amplitude of the resonant waveform during the interruption of the power signal transmission. If a coil-like foreign object approaches the power transmitter 20 during the power transmission process, perhaps the signal amplitude of the resonant waveform does not change much, but the frequency of the resonant waveform measured during the brief interruption of the power signal transmission may change. Therefore, it is also possible to determine whether a coil-like foreign object approaches by detecting the frequency of the resonant waveform.
[0059] The signal sampling circuit 26 can sample the signal (e.g., voltage signal) generated by the resonant circuit 24 of the power transmitter 20 during the short interruption transmission period of the power signal to obtain a sampling value. The above-mentioned resonant waveform is composed of these sampling values. A signal sampling circuit well-known to those skilled in the art can be used to implement the above-mentioned signal sampling. In order to detect whether there is a foreign object approaching the power transmitter during the power transmission process, the time point for the signal sampling circuit 26 to perform sampling can be during the short interruption transmission period of the power signal. During the power transmission process, the transmission of the power signal can be periodically interrupted briefly, and the signal sampling circuit 26 can collect the signal generated by the resonant circuit 24 during these short interruption transmission periods. During the power transmission process, the transmission of the power signal can also be interrupted on-demand to collect the resonant waveform. The signal sampling operation performed by the signal acquisition circuit 26 can be carried out during a period of time (which can be called the signal acquisition period) within the interruption transmission period of the power signal.
[0060] The control circuit 28 can obtain the resonant waveform based on the sampling value obtained by the signal sampling circuit 26 for sampling the signal. The data sampled by the signal sampling circuit 26 can be first stored in a buffer (not shown), and then the control circuit 28 reads the data from the buffer (not shown) to obtain the resonant waveform. The control circuit 28 can analyze the resonant waveform to obtain an integral average value and a resonant frequency corresponding to the resonant waveform. Then, the control circuit 28 determines whether there is a foreign object approaching the power transmitter 20 based on this integral average value and resonant frequency.
[0061] The control circuit 28 can analyze only the waveform of the upper half cycle or the lower half cycle of the resonant waveform to obtain the integral average value and the resonant frequency. Or, the signal sampling circuit 26 can sample only the resonant waveform of the upper half cycle or the lower half cycle and output the resonant waveform of the upper half cycle or the lower half cycle to the control circuit 28 for subsequent analysis.
[0062] Optionally, the power transmitter 20 can further include a signal shaper or a voltage divider 29 for proportionally reducing the signal generated by the resonant circuit 24. The specific structure of the signal shaper 29 is well-known to those skilled in the art. If the amplitude of the signal (e.g., voltage signal) generated by the resonant circuit 24 (e.g., 100V) is too large, the signal generated by the resonant circuit 24 can be appropriately adjusted by the signal shaper 29, and then the signal sampling circuit 26 samples the adjusted signal. In this way, the requirements for the signal processing capabilities of the signal sampling circuit 26 and the control circuit 28 can be effectively reduced.
[0063] The control circuit 28 can be an integrated circuit, which may include control logic and processing logic. The control logic can be used to control the operation of the inverter 22 and other electronic components of the power transmitter 20, and can also be used to control the entire charging process to the power receiver. The arithmetic logic can be used to perform necessary processing or operations on the acquired data, and the result obtained by the arithmetic logic operation can be fed back to the control logic so that the control logic can adjust the power supply process.
[0064] The control circuit 28 can also include signal processing logic, which can perform a certain degree of processing on the received signal, such as noise reduction, filtering, shaping, etc. on the signal. The signal sampling circuit 26 can also be integrated into the control circuit 28 to form a part of the signal processing logic, simplifying the overall circuit layout of the power transmitter 20. Of course, the control logic, arithmetic logic, and / or signal processing logic can constitute a generalized control circuit 28, but these logics are distributed in different electronic components.
[0065] During power transmission, the transmission of the power signal can be periodically interrupted briefly at regular intervals, and whether there is a foreign object approaching can be detected during this brief power interruption. If a foreign object approaching the power transmitter 20 is detected during the brief power interruption, the power transmitter 20 can stop supplying power to the power receiver. Specifically, during power transmission, the resonant circuit 24 is fed with the inverter output waveform (Vsw), and during the brief interruption of the power signal transmission, the feeding of the inverter output waveform (Vsw) is stopped. In detail, the control circuit 28 controls the inverter 22 to make the inverter 22 continuously output the inverter output beam (Vsw), but during the brief interruption of the power signal transmission, the control circuit 28 disconnects the inverter 22 from the power supply briefly. Further, the signal sampling circuit 26 samples the signal generated by the resonant circuit 24 during the brief interruption of the power signal transmission, that is, the signal sampling operation performed by the signal sampling circuit 26 is carried out after the inverter 22 is disconnected from the power supply. Further, the control circuit 28 obtains the resonant waveform based on the sampling value sampled during the brief interruption of the power signal transmission, that is, the resonant waveform obtained at this time is a decaying resonant waveform. Therefore, the control circuit 28 can detect whether there is a foreign object approaching the power transmitter 20 by analyzing the decaying resonant waveform during the brief interruption of the power signal transmission.
[0066] In some embodiments, the control circuit 28 obtains the integral average value and the resonance frequency based on a scaled-down version of the resonance waveform. For example, the signal generated by the resonance circuit 24 can be scaled down via the signal shaper 29 and then sampled by the signal sampling circuit 26; alternatively, the signal sampling circuit 26 can scale down the sampled signal; or, the control circuit 28 can scale down the sampling signal received from the sampling circuit 26.
[0067] In some embodiments, the control circuit 28 obtains the integral average value and the resonance frequency based on the waveform of the upper half or the lower half of the resonance waveform. Specifically, the control circuit 28 analyzes the entire completed waveform of the resonance waveform, or can also only analyze the waveform of the upper half or the lower half of the resonance waveform to obtain the integral average value and the resonance frequency. This analysis of partial waveforms can reduce the required amount of computation and improve the detection speed.
[0068] In some embodiments, the control circuit 28 obtains the integral average value and the resonance frequency based on the resonance waveform in a signal acquisition interval during the interruption of the power signal transmission. Specifically, the control circuit 28 can analyze only the resonance waveform during a period (referred to as the signal acquisition period) within the interruption period of the corresponding power signal to obtain the integral average value and the resonance frequency, so as to reduce the amount of computation.
[0069] In some embodiments, please refer to Figure 3A , the resonance waveform is represented by Q_COMP. During the short interruption period T_interrupt of the power signal, the control circuit 28 can obtain the integral average value by calculating the area between the peak curve L formed by the first signal peak V1 at the first time point t1 and the second signal peak V2 at the second time point t2 in the corresponding resonance waveform and the reference voltage V R . Specifically, the control circuit 28 obtains a first signal peak V1 at the first time point t1 in the resonance waveform; obtains a second signal peak V2 at the second time point t2 in the resonance waveform; obtains the peak curve L based on the first signal peak V1 and the second signal peak V2; and based on the peak curve L and the reference voltage V R , performs an integration operation, and averages the obtained integration result based on the difference between the first time point t1 and the second time point t2 to obtain the integral average value. Among them, the peak curve L can be a curve fitted by the first signal peak V1, the second signal peak V2, and all the signal peaks between the first time point t1 and the second time point t2. After obtaining the peak curve L, the integration result obtained by integrating the peak curve L can be obtained from the area between the peak curve L and the reference voltage V Rcharacterized by the area therebetween. That is, the control circuit 28 obtains the area of the region between the peak curve L and the reference voltage V R therebetween. After obtaining this integration result, the control circuit 28 performs averaging based on time (that is, divides this integration result by the difference between the first time point t1 and the second time point t2), so as to obtain the integration average value.
[0070] In some other embodiments, please refer to Figure 3B , the resonant waveform is represented by Q_COMP. During the short interruption transmission period T_interrupt of the power signal, the control circuit 28 can obtain the integration average value by calculating the area between all the signal waveforms between the first time point t1 and the second time point t2 in the resonant waveform and the reference voltage V R therebetween. Specifically, the control circuit 28 obtains the first time point t1 corresponding to a first signal peak V1 in the resonant waveform; obtains the second time point t2 corresponding to a second signal peak V2 in the resonant waveform; performs an integration operation on all the signal waveforms between the first time point t1 and the second time point t2, and averages the obtained integration result based on the difference between the first time point t1 and the second time point t2, so as to obtain the integration average value. Among them, the control circuit 28 performs an integration operation on each signal waveform between the first time point t1 and the second time point t2 individually, obtains the area of the region between each signal waveform and the reference voltage V R therebetween, and sums up the areas of each region to obtain the integration result. This integration result is characterized by the sum of the areas between all the signal waveforms between the first time point t1 and the second time point t2 and the reference voltage V R therebetween. After obtaining this integration result, the control circuit 28 performs averaging based on time (that is, divides this integration result by the difference between the first time point t1 and the second time point t2), so as to obtain the integration average value.
[0071] The above integration average value can represent the change rate of the voltage peak (or the envelope of the voltage signal) in the resonant waveform, can characterize the attenuation situation of this resonant waveform, and thus is suitable for judging whether there is a foreign object approaching the power transmitter 20. Moreover, using the integration average value can avoid the situation that the signal peaks V1 and V2 affect the judgment accuracy due to noise interference or value deviation.
[0072] In some embodiments, please refer to Figure 3C, during the short interruption T_interrupt of the power signal transmission, the control circuit 28 can obtain the resonant frequency T_period by calculating the average time occupied by each signal waveform between the first time point t1 and the second time point t2 in the resonant waveform. Specifically, the control circuit 28 obtains the first time point t1 corresponding to a first signal peak V1; obtains the second time point t2 corresponding to a second signal peak V2; sums up and averages the time occupied by each signal waveform between the first time point t1 and the second time point t2, and converts the obtained result into a frequency to obtain the resonant frequency. For example, assuming that the periods of the signal waveforms between the first time point t1 and the second time point t2 are T1, T2, …, T9 respectively, then the average period T_avg of these 9 signal waveforms can be obtained as (T1 + T2 + … + T9) / 9. Since the frequency is the reciprocal of the period, the resonant frequency can be obtained as 1 / T_avg.
[0073] Please refer to Figure 4A (No foreign object), during the power transmission process in which the power transmitter 20 transmits power to the power receiver, the inverter 22 continuously generates an inverter output waveform (V sw ). During the short interruption of the power signal transmission, the inverter 22 is disconnected from the power supply and no longer outputs (V sw ). The original obtained resonant waveform Q_COMP can be integrated by taking only the upper half of its waveform to obtain a waveform Q_COMP_UH as shown Figure 4A below. Of course, it is also possible to take only the lower half of the waveform for integration. In addition, it is also possible to sample or obtain signals only during a short period of time (i.e., the signal acquisition period) during the interruption of the power signal transmission. The real-time result of the integration operation is shown as the curve L_INT Figure 4A below. Although real-time integration is not necessary, the real-time integration result can also be used to achieve real-time judgment of whether there is a foreign object approaching. Please also refer to Figure 4A (No foreign object) and Figure 4B (With foreign object). When a foreign object is detected during the power transmission process, the attenuation amplitude of its resonant waveform will also become larger, and the slope change of the real-time integration average value will also become larger.
[0074] In terms of obtaining the resonant frequency, the resonant waveform Q_COMP (represented by a dotted line) can be signal-processed to obtain a corresponding resonant frequency acquisition waveform L_PERIOD. The period change of this resonant frequency acquisition waveform L_PERIOD is basically the same as the period change of the resonant waveform Q_COMP, and the frequency calculated from this resonant frequency acquisition waveform L_PERIOD can be used to characterize the resonant frequency of the resonant waveform Q_COMP.
[0075] The control circuit 28 of the power transmitter 20 determines whether there is a foreign object approaching the power transmitter 20 during the power transmission based on the integral average value and the resonance frequency, for example, whether there is a foreign object placed on or near the power transmitter 20. Specifically, the control circuit 28 can compare the integral average value with at least one first threshold and compare the resonance frequency with at least one second threshold to determine whether the object exists during the power transmission. The first threshold and the second threshold can be determined respectively based on the integral average value and the resonance frequency of the resonance waveform without a foreign object and when there is a power receiver (RX) during the power transmission process, and these thresholds can also be set based on empirical values obtained through experiments. For example, if during the short interruption period T_interrupt of the power signal transmission, the integral average value calculated for the measured resonance waveform falls within the first threshold range (which may at least include the first threshold), it can be determined that there is a foreign object approaching the power transmitter 20 during the power transmission process. If during the short interruption period T_interrupt of the power signal transmission, the estimated resonance frequency of the measured resonance waveform does not fall within the second threshold range (which may at least include the second threshold), that is, the resonance frequency does not change significantly, it can be determined that the object approaching the power transmitter 20 during the power transmission process is a foreign object; and if the estimated resonance frequency of the measured resonance waveform falls within the second threshold range, that is, the resonance frequency changes significantly, it can be determined that the object approaching the power transmitter 20 during the power transmission process may be a foreign object of a coil type.
[0076] Therefore, the power transmitter 20 according to the embodiment of the present application can detect whether there is a foreign object and / or a foreign object of a coil type approaching during the power transmission process, and if there is a foreign object, it can stop the ongoing power supply.
[0077] As Figure 5 shown, when a foreign object (for example, a coin) approaches the power transmitter 20, the attenuation amplitude of the resonance waveform will increase significantly, and its attenuation amplitude is significantly greater than the attenuation amplitude of the resonance waveform when there is no foreign object approaching.
[0078] Figure 6 Displays a flowchart of an object detection method according to an embodiment of the present application. Please refer to Figure 2 and Figure 6 , the foreign object detection method according to the embodiment of the present application includes the following steps:
[0079] Step S10: Temporarily interrupt the power signal transmitted to the power receiver in the wireless charging system. During the power transmission, the power signal transmission can be periodically interrupted briefly at regular intervals, and it is detected whether there is a foreign object approaching during this short power interruption period. During the power transmission process in which the power transmitter 20 transmits power to the power receiver, the inverter 22 continuously generates an inverter output waveform (V sw)。In this step, the control circuit 28 can control the inverter 22 to be briefly disconnected from the power source for a short period of time (i.e., during the brief interruption of the power signal transmission) to detect whether there is a foreign object approaching the power transmitter 20.
[0080] Step S20: During the brief interruption of the power signal transmission, sample the signal (e.g., voltage signal) generated by the resonant circuit of the power transmitter. Specifically, the control circuit 28 can control the inverter 22 to continuously generate an inverter output waveform (Vsw) to charge the power receiver, and then during the brief interruption of the power signal transmission, disconnect the inverter 22 from the power source, and the signal sampling circuit 26 samples the signal generated by the resonant circuit 24 at this time.
[0081] Step S30: Based on the sampled values obtained by sampling, obtain a resonant waveform. The sampled values sampled by the signal sampling circuit 26 during the brief interruption of the power signal transmission can be transmitted to the control circuit 28, or these sampled values are stored in a buffer (not shown), and then the control circuit 28 reads the stored sampled values from the buffer (not shown) to obtain a resonant waveform, which is a decaying resonant waveform.
[0082] Step S40: Perform an integration operation on the resonant waveform and perform an averaging operation on the integration result to obtain an integration average value. In one embodiment, refer to Figure 3A , during the brief interruption of the power signal transmission, the control circuit 28 can obtain the integration result by calculating the area between the peak curve L formed by the first signal peak V1 at the first time point t1 and the second signal peak V2 at the second time point t2 in the corresponding resonant waveform and the reference voltage V R , and perform an averaging operation on the integration result based on time to obtain the integration average value. In another embodiment, refer to Figure 3B , during the brief interruption of the power signal transmission, the control circuit 28 can obtain the integration result by calculating the area between all the signal waveforms between the first time point t1 and the second time point t2 in the resonant waveform and the reference voltage V R , and perform an averaging operation on the integration result based on time to obtain the integration average value.
[0083] Step S50: Obtain a resonant frequency of the resonant waveform. Please refer to Figure 3C , during the brief interruption of the power signal transmission, the control circuit 28 can obtain the resonant frequency by calculating the average time occupied by each signal waveform between the first time point t1 and the second time point t2 in the resonant waveform.
[0084] Step S60: Determine whether there is a foreign object approaching the power transmitter 20 based on the integral average value and the resonance frequency. The control circuit 28 can compare the integral average value with at least one first threshold and compare the resonance frequency with at least one second threshold to determine whether there is a foreign object approaching the power transmitter 20 during the power transmission process. For example, it can be determined whether there is a foreign object during the power transmission process based on whether the integral average value falls within the first threshold range. Or, by determining whether the resonance frequency falls within the second threshold range, it can be determined whether the object approaching the power transmitter 20 during the power transmission process is a coil-like foreign object.
[0085] In the foreign object detection method and the power transmitter according to the embodiments of the present application, during the power transmission process of the wireless charging system, the power signal transmitted by the power transmitter to supply power to the power receiver is briefly interrupted, and during the brief interruption of the power signal transmission, the attenuated resonance waveform generated by the resonance circuit of the power transmitter is sampled. The sampled resonance waveform is subjected to integral operation to obtain an integral average value and the resonance frequency of the resonance waveform is obtained by estimation. Then, based on the integral average value and the resonance frequency, it is determined whether there is a foreign object approaching the power transmitter during the power transmission of the power transmitter. Different from the traditional method of calculating the Q factor value of the resonance waveform, the present application can improve the accuracy of the Q factor value affected by noise interference or value deviation in the existing method, thus solving the problem of misjudging whether there is a foreign object approaching the power transmitter. Therefore, the present application can effectively improve the accuracy of determining whether there is a foreign object approaching the power transmitter during the power transmission process.
[0086] Although the present disclosure has been disclosed above with preferred embodiments, it is not intended to limit the present disclosure. Those skilled in the art in the technical field to which the present disclosure belongs can make various changes and modifications without departing from the concept and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to what is defined by the claims.
Claims
1. A foreign object detection method for detecting whether a foreign object approaches a power transmitter in a wireless power charging system during power transmission. The method includes: Using a control circuit to briefly interrupt the power signal transmitted to supply power to a power receiver in the wireless power charging system; Using a signal sampling circuit to sample the signal generated by the resonant circuit of the power transmitter during the brief interruption of the power signal transmission; Using the control circuit to obtain a resonant waveform based on the sampling values sampled by the signal sampling circuit for the signal; Using the control circuit to perform an integration operation on the resonant waveform and perform an averaging operation on the integration result to obtain an integration average value; Obtaining a resonant frequency of the resonant waveform; And Judging the existence of the foreign object based on the integration average value and the resonant frequency.
2. The foreign object detection method according to claim 1, wherein the step of obtaining the integration average value includes: Obtaining a first signal peak value at a first time point in the resonant waveform; Obtaining a second signal peak value at a second time point in the resonant waveform; Obtaining a peak curve based on the first signal peak value and the second signal peak value; And Performing an integration operation based on the peak curve and a reference voltage, and averaging the obtained integration result based on the difference between the first time point and the second time point to obtain the integration average value.
3. The foreign object detection method according to claim 2, wherein the integration result is characterized by the area between the peak curve and the reference voltage.
4. The foreign object detection method according to claim 1, wherein the step of obtaining the integration average value includes: Obtaining a first time point corresponding to a first signal peak value; Obtaining a second time point corresponding to a second signal peak value; Performing an integration operation on all signal waveforms between the first time point and the second time point, and averaging the obtained integration result based on the difference between the first time point and the second time point to obtain the integration average value.
5. The foreign object detection method according to claim 4, wherein the integration result is characterized by the sum of the areas between all signal waveforms between the first time point and the second time point and a reference voltage.
6. The foreign object detection method according to claim 1, wherein the step of obtaining the resonant frequency includes: Obtaining a first time point corresponding to a first signal peak value; Obtaining a second time point corresponding to a second signal peak value; And Adding up and averaging the time occupied by each signal waveform between the first time point and the second time point, and converting the obtained result into a frequency to obtain the resonant frequency.
7. The foreign object detection method according to claim 1, wherein the step of judging the existence of the foreign object includes: Comparing the integration average value with at least one first threshold value and comparing the resonant frequency with at least one second threshold value to judge the existence of the foreign object.
8. The foreign object detection method according to claim 1, wherein the control circuit obtains the integration average value and the resonant frequency based on a scaled-down version of the resonant waveform.
9. The foreign object detection method according to claim 1, wherein the control circuit obtains the integral average value and the resonance frequency based on the waveform of the upper half cycle or the lower half cycle of the resonance waveform.
10. The foreign object detection method according to claim 1, wherein the control circuit obtains the integral average value and the resonance frequency based on the resonance waveform in a signal acquisition interval during a short interruption of the power signal transmitted to the power receiver in the wireless charging system.
11. A power transmitter in a wireless charging system, the power transmitter comprising: A control circuit for briefly interrupting the power signal transmitted to the power receiver in the wireless charging system; A signal sampling circuit connected to the control circuit for sampling the signal generated by the resonance circuit of the power transmitter during the short interruption of the power signal; Wherein the control circuit is further configured to: Obtain a resonance waveform based on the sampling values sampled by the signal sampling circuit for the signal; Perform an integration operation on the resonance waveform and perform an averaging operation on the integration result to obtain an integral average value; Obtain a resonance frequency of the resonance waveform; and Judge whether there is a foreign object approaching the power transmitter based on the integral average value and the resonance frequency.
12. The power transmitter according to claim 11, wherein the control circuit is configured to: Obtain a first signal peak value at a first time point in the resonance waveform; Obtain a second signal peak value at a second time point in the resonance waveform; Obtain a peak curve based on the first signal peak value and the second signal peak value; And Based on the peak curve and a reference voltage, perform an integration operation, and based on the difference between the first time point and the second time point, average the obtained integration result to obtain the integral average value.
13. The power transmitter according to claim 12, wherein the integration result is characterized by the area between the peak curve and the reference voltage.
14. The power transmitter according to claim 11, wherein the control circuit is configured to: Obtain a first time point corresponding to a first signal peak value; Obtain a second time point corresponding to a second signal peak value; Perform an integration operation on all the signal waveforms between the first time point and the second time point, and based on the difference between the first time point and the second time point, average the obtained integration result to obtain the integral average value.
15. The power transmitter according to claim 14, wherein the integration result is characterized by the sum of the areas between all the signal waveforms between the first time point and the second time point and a reference voltage.
16. The power transmitter according to claim 11, wherein the control circuit is configured to: Obtain a first time point corresponding to a first signal peak value; Obtain a second time point corresponding to a second signal peak value; and Sum up and average the time occupied by each signal waveform between the first time point and the second time point, and convert the obtained result into a frequency to obtain the resonance frequency.
17. The power transmitter according to claim 11, wherein the control circuit is configured to: Compare the integral average value with at least one first threshold value, and compare the resonant frequency with at least one second threshold value to determine whether there is a foreign object approaching the power transmitter.
18. The power transmitter according to claim 11, wherein the control circuit obtains the integral average value and the resonant frequency based on a scaled-down version of the resonant waveform.
19. The power transmitter according to claim 11, wherein the control circuit obtains the integral average value and the resonant frequency based on the waveform of the upper half cycle or the lower half cycle of the resonant waveform.
20. The power transmitter according to claim 11, wherein the control circuit obtains the integral average value and the resonant frequency based on the resonant waveform in a signal acquisition interval during a short interruption of the power signal transmission.