A method and apparatus for detecting foreign objects in wireless charging

Abstract

This application provides a foreign object detection method for a wireless charging system. The method determines a first frequency and a second frequency based on the actual resonant frequency of the resonant network. It then determines the voltage difference between the resonant network voltage and a preset voltage at the first and second frequencies, respectively. Finally, it compares the absolute value of the voltage difference at the two different frequencies with a preset threshold to determine the presence of a foreign object. This application also provides a foreign object detection device. Using the foreign object detection method or device described in this application can improve the accuracy of foreign object detection and reduce false positives.

Description

Technical Field

[0001] This application relates to the field of wireless charging technology, and in particular to a method and apparatus for detecting foreign objects in wireless charging. Background Technology

[0002] Among current wireless charging technologies, magnetic induction coupling and resonant coupling are the most widely used. Both technologies are based on the principle of electromagnetic induction. A high-frequency alternating current in the transmitting coil generates a high-frequency magnetic field, which then transfers energy from the transmitting coil to the receiving coil, achieving wireless charging. A typical wireless charging system consists of a power transmitter connected to the mains power supply and a power receiver connected to the load. There is no electrical contact between the power transmitter and the power receiver; wireless energy transfer occurs through electromagnetic induction.

[0003] There is an air gap between the transmitting coil of the power transmitter and the receiving coil of the power receiver in a wireless charging system. Various foreign objects may enter through this gap. When a metallic foreign object is present, eddy currents will be generated in the metal due to the eddy current effect in a time-varying magnetic field, causing the metal to heat up. This may lead to spontaneous combustion (such as aluminum foil spontaneously combusting when the temperature reaches a certain level) or the burning of other items (such as leaves or pieces of paper on the metal burning due to the heat). It will also reduce the energy transmission efficiency of the wireless charging system. To ensure the safe operation and transmission efficiency of the system, metallic foreign object detection is necessary.

[0004] Current wireless charging systems commonly use the induced voltage method for foreign object detection. The principle of this method is to place the detection circuit in a high-frequency magnetic field and determine whether the magnetic field is distorted by judging whether an abnormality occurs in the induced voltage of the detection circuit, thus determining the presence of a foreign object. However, existing wireless charging detection methods lack sufficient accuracy and are prone to false positives. Summary of the Invention

[0005] This application discloses a method and apparatus for detecting foreign objects in wireless charging, which solves the shortcomings of existing methods and apparatuses for detecting foreign objects, such as insufficient accuracy and susceptibility to misjudgment.

[0006] A first aspect of this application provides a method for foreign object detection in a wireless charging system, the method comprising:

[0007] The first input voltage of the resonant network at a first frequency and the second input voltage at a second frequency are obtained, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network.

[0008] Calculate the first difference voltage, which is the difference between the first preset voltage and the first input voltage, where the first preset voltage is the input voltage of the resonant network at the first frequency when there are no metal foreign objects.

[0009] Calculate the second difference voltage, which is the difference between the second preset voltage and the second input voltage, where the second preset voltage is the input voltage of the resonant network at the second frequency when there are no metal foreign objects.

[0010] Calculate the third differential voltage, which is the absolute value of the voltage difference between the first differential voltage and the second differential voltage;

[0011] The presence of foreign objects is determined based on the third differential voltage.

[0012] The foreign object detection method provided in the first aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0013] According to the first aspect, in a first possible implementation of the first aspect, determining whether a foreign object exists based on the third differential voltage specifically includes:

[0014] Determine whether the third differential voltage is greater than a preset threshold. If it is, then determine that there is a foreign object.

[0015] In a first possible implementation of the first aspect of this application, determining the actual resonant frequency of the resonant network can effectively improve the accuracy of foreign object detection.

[0016] According to the first aspect or the first possible implementation of the first aspect, in the second possible implementation of the first aspect, before determining the first frequency and the second frequency, the method further includes:

[0017] Determining the actual resonant frequency of the resonant network specifically includes:

[0018] Measure the inductance and capacitance values ​​of the resonant network, and calculate the actual resonant frequency of the resonant network based on the inductance and capacitance values; or,

[0019] By sweeping the frequency of the resonant network, the frequency corresponding to the maximum input voltage of the resonant network is measured as the actual resonant frequency of the resonant network.

[0020] According to the first aspect or the first to second possible implementations of the first aspect, in the third possible implementation of the first aspect, the first frequency is selected in the frequency range [(f-Δf), f], the second frequency is selected in the frequency range [f, (f+Δf)], where f is the actual resonant frequency of the resonant network, and the value range of Δf is [0.01f, 0.5f].

[0021] According to the first aspect or the first to third possible implementations of the first aspect, in the fourth possible implementation of the first aspect, the resonant network includes N detection coils, where N is an integer greater than or equal to 1.

[0022] In the fourth possible implementation of the first aspect of this application, multiple detection coils can increase the coverage area for foreign object detection.

[0023] According to the first aspect or the first to fourth possible implementations of the first aspect, in the fifth possible implementation of the first aspect, any one of the N detection coils includes a switch, an inductive element and a capacitive element, wherein the switch is connected in series with the inductive element and the capacitive element is connected in parallel with the inductive element.

[0024] A second aspect of this application provides a method for detecting foreign objects while wireless charging, the method comprising:

[0025] Obtain the first input impedance of the resonant network at a first frequency and the second input impedance at a second frequency, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network.

[0026] Calculate the first differential impedance, which is the difference between the first input impedance and the first preset impedance, where the first preset impedance is the input impedance of the resonant network at the first frequency when there are no metallic foreign objects.

[0027] Calculate the second differential impedance, which is the difference between the second input impedance and the second preset impedance, where the second preset impedance is the input impedance of the resonant network at the second frequency when there are no metallic foreign objects.

[0028] Calculate the third differential impedance, which is the absolute value of the impedance difference between the first differential impedance and the second differential impedance;

[0029] The presence of foreign matter is determined based on the third differential impedance.

[0030] The foreign object detection method provided in the second aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0031] According to the second aspect, in a first possible implementation of the second aspect, determining the presence of a foreign object based on the third differential impedance specifically includes:

[0032] Determine whether the third differential impedance is greater than a preset threshold. If it is, then it is determined that there is a foreign object.

[0033] In the first possible implementation of the second aspect of this application, determining the actual resonant frequency of the resonant network can effectively improve the accuracy of foreign object detection.

[0034] According to the second aspect or the first possible implementation of the second aspect, in the second possible implementation of the second aspect, before determining the first frequency and the second frequency, the method further includes:

[0035] Determining the actual resonant frequency of the resonant network specifically includes:

[0036] Measure the inductance and capacitance values ​​of the resonant network, and calculate the actual resonant frequency of the resonant network based on the inductance and capacitance values; or,

[0037] By sweeping the frequency of the resonant network, the frequency corresponding to the maximum input voltage of the resonant network is measured as the actual resonant frequency of the resonant network.

[0038] According to the second aspect or the first to second possible implementations of the second aspect, in the third possible implementation of the second aspect, the first frequency is selected in the frequency range [(f-Δf), f], the second frequency is selected in the frequency range [f, (f+Δf)], where f is the actual resonant frequency of the resonant network, and the value range of Δf is [0.01f, 0.5f].

[0039] According to the second aspect or the first to third possible implementations of the second aspect, in the fourth possible implementation of the second aspect, the resonant network includes N detection coils, where N is an integer greater than or equal to 1.

[0040] In the fourth possible implementation of the second aspect of this application, multiple detection coils can increase the coverage area for foreign object detection.

[0041] According to the second aspect or the first to fourth possible implementations of the second aspect, in the fifth possible implementation of the second aspect, any one of the N detection coils includes a switch, an inductive element and a capacitive element, wherein the switch is connected in series with the inductive element and the capacitive element is connected in parallel with the inductive element.

[0042] A third aspect of this application provides a wireless charging foreign object detection device, the device comprising an AC power source, a resonant network, a measurement circuit, and a controller, wherein:

[0043] The communication source is used to provide communication incentives;

[0044] The resonant network is used to detect whether there are foreign objects between the wireless charging transmitter and receiver;

[0045] The measurement circuit is used to measure the input voltage of the resonant network;

[0046] The controller is used to determine a first frequency and a second frequency, wherein the first frequency is less than the actual resonant frequency of the resonant network, and the second frequency is greater than the actual resonant frequency of the resonant network.

[0047] Determine the first input voltage of the resonant network at the first frequency and the second input voltage at the second frequency;

[0048] Calculate the first difference voltage, which is the difference between the first preset voltage and the first input voltage, where the first preset voltage is the input voltage of the resonant network at the first frequency when there are no metal foreign objects.

[0049] Calculate the second difference voltage, which is the difference between the second preset voltage and the second input voltage, where the second preset voltage is the input voltage of the resonant network at the second frequency when there are no metal foreign objects.

[0050] Calculate the third differential voltage, which is the absolute value of the voltage difference between the first differential voltage and the second differential voltage.

[0051] Determine if the third differential voltage is greater than a preset threshold. If it is, then determine that there is a foreign object.

[0052] The foreign object detection device provided in the third aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0053] According to the third aspect, in a first possible implementation of the third aspect, the AC source includes a constant AC source. The constant AC source in the first possible implementation of the third aspect of this application can improve the stability of the foreign object detection device.

[0054] According to the third aspect or the first possible implementation of the third aspect, in the second possible implementation of the third aspect, the resonant network includes N detection coils, where N is an integer greater than or equal to 1.

[0055] In the second possible implementation of the third aspect of this application, multiple detection coils can increase the coverage area for foreign object detection.

[0056] According to the third aspect or the first or second possible implementation of the third aspect, in the third possible implementation of the third aspect, each of the N detection coils includes a switch, an inductor and a capacitor, the switch is connected in series with the inductor and the capacitor is connected in parallel with the inductor.

[0057] According to the third aspect or the first to third possible implementations of the third aspect, in the fourth possible implementation of the third aspect, the measuring circuit is further configured to:

[0058] Measure the input impedance of the resonant network.

[0059] According to the third aspect or the first to fourth possible implementations of the third aspect, in the fifth possible implementation of the third aspect, the controller is further configured to:

[0060] A first frequency and a second frequency are determined, wherein the first frequency is less than the actual resonant frequency of the resonant network, and the second frequency is greater than the actual resonant frequency of the resonant network.

[0061] Determine the first input impedance of the resonant network at the first frequency and the second input impedance at the second frequency;

[0062] Calculate the first differential impedance, which is the difference between the first input impedance and the first preset impedance, where the first preset impedance is the input impedance of the resonant network at the first frequency when there are no metallic foreign objects.

[0063] Calculate the second differential impedance, which is the difference between the second input impedance and the second preset impedance, where the second preset impedance is the input impedance of the resonant network at the second frequency when there are no metallic foreign objects.

[0064] Calculate the third differential impedance, which is the absolute value of the impedance difference between the first differential impedance and the second differential impedance;

[0065] Determine if the third differential impedance is greater than a preset threshold. If it is, then it is determined that there is a foreign object.

[0066] According to the third aspect or the first to fifth possible implementations of the third aspect, in the sixth possible implementation of the third aspect, the foreign object detection device further includes an alarm, the alarm being used for:

[0067] An alarm is triggered when the controller detects the presence of a foreign object, or the switch controlling the operation of the wireless charging system is turned off when the controller detects the presence of a foreign object.

[0068] The alarm in the sixth possible implementation of the third aspect of this application can effectively improve the user experience of the foreign object detection device.

[0069] A fourth aspect of this application provides a wireless charging transmitting system, the wireless charging transmitting system including a wireless charging foreign object detection device and a wireless charging transmitting device provided in the third aspect, the wireless charging foreign object detection device being used to detect whether there is a foreign object in the wireless charging transmitting system.

[0070] The wireless charging transmitter system provided in the fourth aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0071] A fifth aspect of this application provides a wireless charging receiving system, the wireless charging receiving system including a wireless charging foreign object detection device and a wireless charging receiving device provided in the third aspect, the wireless charging foreign object detection device being used to detect whether there is a foreign object in the wireless charging receiving system.

[0072] The wireless charging receiving system provided in the fifth aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0073] A sixth aspect of this application provides a wireless charging system, the wireless charging system including a wireless charging foreign object detection device and a wireless charging device provided in the third aspect, the wireless charging foreign object detection device being used to detect whether there is a foreign object in the wireless charging system.

[0074] The wireless charging system provided in the sixth aspect of this application can improve the accuracy of foreign object detection and reduce false positives.

[0075] Using the foreign object detection method, apparatus, or system described in this application, the influence of changes in the induced voltage of the resonant network caused by changes in the magnetic field of the transmitting coil, such as changes in the output power, output voltage, and output current of the transmitting coil, on the foreign object detection process can be eliminated, thereby improving the accuracy of foreign object detection and reducing false positives. Attached Figure Description

[0076] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0077] Figure 1 A schematic diagram illustrating the relationship between impedance and frequency of a detection circuit provided in an embodiment of this application;

[0078] Figure 2 A comparison of voltage characteristic curves of a detection circuit for detecting whether an interference-induced voltage is superimposed in the absence of metallic foreign objects, provided in an embodiment of this application;

[0079] Figure 3 A schematic diagram of a wireless charging system provided in an embodiment of this application;

[0080] Figure 4 This is a schematic diagram of a wireless charging system structure provided in an embodiment of this application;

[0081] Figure 5 This is a schematic diagram of a foreign object detection device provided in an embodiment of this application;

[0082] Figure 6 A schematic diagram of a parallel resonant network provided in an embodiment of this application;

[0083] Figure 7 A comparison diagram of the input impedance characteristic curves of a resonant network with and without metallic foreign objects is provided for embodiments of this application.

[0084] Figure 8 This is a schematic flowchart of a foreign object detection method provided in an embodiment of this application;

[0085] Figure 9 This is a schematic diagram of another foreign object detection method provided in an embodiment of this application. Detailed Implementation

[0086] This application pertains to wireless charging scenarios. Wireless charging, also known as Wireless Power Transfer (WPT), refers to a technology that uses a transmitting device to convert electrical energy into other forms of relay energy (such as electromagnetic field energy, light energy, and microwave energy), transmits it over a distance, and then uses a receiving device to convert the relay energy back into electrical energy. The commercialization of wireless charging technology has progressed rapidly. Wireless charging technology for consumer electronics, such as smart terminals and electric toothbrushes, is already quite mature. Besides consumer electronics, the electric vehicle sector is also vigorously developing wireless charging technology. As wireless charging technology gradually transitions from the laboratory to market applications, one of the key issues that needs to be addressed is the foreign object detection problem.

[0087] Among current wireless charging technologies, magnetic induction coupling and resonant coupling are the most widely used. Both technologies are based on the principle of electromagnetic induction. A high-frequency alternating current in the transmitting coil generates a high-frequency magnetic field, which then transfers energy from the transmitting coil to the receiving coil, achieving wireless charging. A typical wireless charging system consists of a power transmitter connected to the mains power supply and a power receiver connected to the load. There is no electrical contact between the power transmitter and the power receiver; wireless energy transfer occurs through electromagnetic induction.

[0088] There is an air gap between the transmitting coil of the power transmitter and the receiving coil of the power receiver in a wireless charging system, and various foreign objects may enter through this gap. When a metallic foreign object is present, due to the eddy current effect of the metal in a time-varying magnetic field, induced eddy currents will form inside the metal, causing it to heat up. This may lead to spontaneous combustion (like aluminum foil spontaneously combusting when heated to a certain temperature) or the burning of other items (such as leaves or pieces of paper on it). Simultaneously, because some energy is consumed by the metallic foreign object, it also reduces the energy transmission efficiency of the wireless charging system.

[0089] In high-power wireless charging scenarios, such as wireless charging systems for electric vehicles, the high power level of these systems increases the risk of overheating due to foreign objects. Therefore, to ensure the safe operation and transmission efficiency of the system, it is necessary to accurately detect metallic foreign objects and prevent disasters.

[0090] Commonly used foreign object detection methods include main power coil detection, auxiliary foreign object detection coil, infrared imaging, temperature detection, acoustic wave detection, and magnetoresistive detection.

[0091] One method for detecting metallic foreign objects using a parallel resonant network works on the principle that the detection circuit operates at the resonant frequency and a constant current source is injected into the parallel resonant network. When there are no metallic foreign objects in the wireless charging system, the resonant frequency is ωr. When there are metallic foreign objects, due to the electromagnetic induction effect, the inductance of the detection circuit will decrease and the resonant frequency will increase. Because the parallel resonant network has a high quality factor, the impedance curve drops rapidly after the resonant frequency, resulting in a small impedance change and low detection accuracy. To improve detection accuracy, a detection point ω3dB, which is 3dB lower than ωr, is used before the resonant frequency. The impedance characteristics of the detection circuit are characterized by the voltage across the resonant circuit. When there is no metal foreign object, the voltage Ueq1 corresponding to the equivalent impedance Zeq1 of the detection circuit at the ω3dB frequency is measured in advance and stored in memory. When detecting metal foreign objects, the voltage Ueq2 corresponding to the equivalent impedance Zeq2 of the detection circuit at the ω3dB frequency is measured. The values ​​of the two voltages Ueq1 and Ueq2 are compared, i.e., ΔU(3dB) = Ueq1 - Ueq2. If the value of ΔU(3dB) exceeds the set threshold, it is considered that there is a foreign object. The schematic diagram of the impedance-frequency relationship of the detection circuit is shown below. Figure 1 As shown, the solid line represents the case with metallic foreign objects, the dashed line represents the case without metallic foreign objects, the horizontal axis represents frequency, and the vertical axis represents impedance.

[0092] The drawback of this approach is that when the wireless charging system is operating, the magnetic field of the transmitting coil also acts on the detection circuit, inducing a voltage in the detection circuit. For example... Figure 2 The diagram shows a comparison of voltage characteristic curves with and without superimposed interference induced voltage in the absence of metallic foreign objects. The interference induced voltage can be the induced voltage of the transmitting coil. Changes in the circuit parameters of the transmitting coil, such as its output power, output voltage, and output current, will cause an induced voltage ΔUg. The curve of the voltage Ueq corresponding to the equivalent impedance of the parallel resonant network as a function of frequency is shown as a dashed line. The curve of the induced voltage ΔUg of the detection circuit and the voltage Ueq corresponding to the equivalent impedance of the parallel resonant network of the detection circuit as a function of frequency is also shown as a dashed line. At a certain frequency point, for example, at a frequency of ω3dB, if the value of ΔUg when Ueq+ΔUg is detected exceeds a set threshold, it will be mistakenly identified as the presence of a foreign object, resulting in a false judgment. Changes in the circuit parameters of the transmitting coil will also cause voltage changes in the detection circuit. Therefore, the cause of voltage changes in the detection circuit could be either a change in the circuit impedance of the detection circuit due to metallic foreign objects, or interference from the magnetic field of the transmitting coil on the detection circuit. Therefore, existing methods for detecting metallic foreign objects do not eliminate changes caused by other factors, such as changes in the output power, output voltage, and output current of the transmitting coil, which cause changes in the induced voltage of the detection circuit. This detection scheme is prone to misjudgment under complex operating conditions.

[0093] Based on the principle of the inductive voltage method, this application proposes a wireless charging foreign object detection method, device, and system to solve the problems existing in the inductive voltage method for detecting foreign objects in the prior art.

[0094] To make the objectives, technical solutions, and advantages of this application clearer, the application will now be described in further detail with reference to the accompanying drawings.

[0095] Electric vehicles are a type of new energy vehicle. Wireless charging systems are a convenient, fully automatic technology that is compatible with autonomous driving functions. Figure 3 This is a schematic diagram of a wireless charging system provided in an embodiment of this application. The wireless charging system includes an electric vehicle 100 and a wireless charging station 101. The electric vehicle 100 may include a wireless charging receiver 1000, and the wireless charging station 101 may include a wireless charging transmitter 1010. Currently, the wireless charging system charges the electric vehicle through the joint operation of the wireless charging receiver 1000 in the electric vehicle 100 and the wireless charging transmitter 1010 in the wireless charging station 101 to perform contactless charging. The wireless charging transmitter 1010 in the wireless charging station 101 sends AC power to the wireless charging receiver 1000 in the electric vehicle 100, and the wireless charging receiver 1000 in the electric vehicle 100 receives the power transmitted from the wireless charging transmitter 1010 in the wireless charging station 101 and stores it in the electric vehicle's battery, thus completing the charging of the electric vehicle.

[0096] In one possible implementation, the electric vehicle 100 includes a hybrid electric vehicle or a pure electric vehicle; the wireless charging station 101 includes a fixed wireless charging station, a fixed wireless charging parking space, a wireless charging road, etc. The wireless charging transmitter 1010 can be installed on the ground or buried underground. Figure 3 The diagram shows the wireless charging transmitter 1010 buried underground, which can wirelessly charge an electric vehicle 100 located above it. The wireless charging receiver 1000 can be integrated into the bottom of the electric vehicle 100 or other parts of the vehicle. When the electric vehicle 100 enters the wireless charging range of the transmitter 1010, it can be charged wirelessly. The wireless charging transmitter 1010 can be integrated or discrete. Integrated means the control circuit and transmitting coil are integrated together, while discrete means the transmitting coil and control circuit are separate. The power receiving antenna and rectifier circuit of the receiver 1000 can be integrated or discrete; in the discrete case, the rectifier module is usually placed inside the vehicle.

[0097] Optionally, contactless charging can be achieved through wireless energy transfer between the wireless charging receiver 1000 and the wireless charging transmitter 1010 via electric or magnetic field coupling. Specifically, this can be achieved through electric field induction, magnetic induction, magnetic resonance, or wireless radiation, and this application does not impose any specific limitations on this. In one possible implementation, the electric vehicle 100 and the wireless charging station 101 can also charge bidirectionally. When both the electric vehicle 100 and the wireless charging station 101 include the wireless charging receiver 1000 and the wireless charging transmitter 1010, the wireless charging station 101 can charge the electric vehicle 100 through a power supply, and the electric vehicle 100 can also discharge to the power supply.

[0098] Figure 4 A schematic diagram of a wireless charging system is shown, which consists of a transmitter 201 and a receiver 202. Figure 4 (Left) shows a schematic diagram of a wireless charging transmitter 201 in a wireless charging station. The wireless charging transmitter 201 includes: a power supply 2017, a transmission conversion module 2011 connected to the power supply 2017, a power transmission antenna 2012, a transmission control module 2013 connected to both the transmission conversion module 2011 and the power transmission antenna 2012, a transmission communication module 2014 connected to the transmission control module 2013, an authentication management module 2015 connected to the transmission communication module 2014, and a storage module 2016 connected to the authentication management module.

[0099] The transmitter conversion module 2011 can be connected to the power supply 2017 to obtain energy from the power supply and convert the AC or DC power supply to high-frequency AC power. When the power supply is AC input, the transmitter conversion module consists of a power factor correction unit and an inverter unit. The power factor correction unit can convert 220V power frequency AC power into DC power; when the power supply is DC input, the transmitter conversion module consists of an inverter unit. The power factor correction unit can ensure that the phase of the input current of the wireless charging system is consistent with the phase of the grid voltage, reduce the system harmonic content, improve the power factor value, thereby reducing the pollution of the power grid by the wireless charging system and improving the transmission efficiency and reliability. The power factor correction unit can also increase or decrease the output voltage of the power factor correction unit according to the needs of the downstream stage to meet the required voltage requirements. The inverter unit can convert the voltage output by the power factor correction unit into a high-frequency AC voltage and apply it to the power transmitting antenna. The high-frequency AC voltage can greatly improve the transmission efficiency and transmission distance. It should be noted that the power supply can be a power supply inside the wireless charging transmitter system or an external power supply connected to the wireless charging transmitter system. This application does not impose specific limitations on this.

[0100] The 2012 power transmitting antenna, in the inductive coupling energy transmission mode, uses the principle of electromagnetic induction to transmit alternating current to the receiving antenna in the form of an alternating magnetic field. In the resonant coupling energy transmission mode, a network composed mainly of inductors and capacitors converts high-frequency alternating current into resonant alternating current, and transmits the resonant alternating current to the receiving coil in the form of an alternating magnetic field.

[0101] The transmission control module 2013 is used to control the voltage, current and frequency conversion parameters of the transmission conversion module 2011 circuit according to the actual wireless charging transmission power requirements, and to control the voltage and current output of the high-frequency AC power in the power transmitting antenna 2012. According to different operating conditions, namely different coupling coefficients of the transmitting coil and the receiving coil, and different power requirements of the receiving end, the transmission control module can effectively adjust the electrical parameters of the transmitting coil to cope with different operating conditions.

[0102] The transmitting communication module 2014 is used for wireless communication between the wireless charging transmitter and the wireless charging receiver. The communicated content includes power control information, fault protection information, power on / off information, and interactive authentication information. On one hand, the wireless charging transmitter can receive electric vehicle attribute information, charging requests, power control information, and interactive authentication information sent by the wireless charging receiver. On the other hand, the wireless charging transmitter can also send wireless charging transmission control information, interactive authentication information, and wireless charging history data to the wireless charging receiver. Specifically, the aforementioned wireless communication methods can include, but are not limited to, any one or more combinations of Bluetooth, Wi-Fi, Zigbee, Radio Frequency Identification (RFID), Long Range (Lora) wireless technology, and Near Field Communication (NFC). Furthermore, this transmitting communication module can also communicate with the smart terminal of the electric vehicle's owner, enabling remote authentication and user information transmission through the communication function.

[0103] The Authentication Management Module 2015 is used for the interaction authentication and permission management between the wireless charging transmitter and the electric vehicle in the wireless charging system. The processor in this module can process the interaction authentication and permission management information and control the transmitter to enable the wireless charging function to the receiver that has passed the authentication and permission.

[0104] The storage module 2016 is used to store charging process data, interactive authentication data (e.g., interactive authentication information), and permission management data (e.g., permission management information) of the wireless charging transmitter. The interactive authentication data and permission management data can be factory-set or user-defined, and this application embodiment does not impose specific restrictions on them.

[0105] Figure 4 (Right) A schematic diagram of a wireless charging receiver 202 in an electric vehicle is shown. The wireless charging receiver 202 includes: a power receiving antenna 2021, a receiving control module 2023 connected to the power receiving antenna, a receiving conversion module 2022 connected to the receiving control module, and a receiving communication module 2024. Optionally, the receiving conversion module can also be connected to an energy storage module 2026 via a connection to an energy storage management module 2025. The energy storage management module 2025 can use the energy received by the power receiving antenna 2021 to charge the energy storage module, which is then used for the vehicle drive unit 2027 of the electric vehicle. It should be noted that the energy storage management module and the energy storage module can be located inside or outside the wireless charging receiver; this embodiment does not impose specific limitations on this.

[0106] The power receiving antenna 2021, based on the principle of electromagnetic induction, is used to receive energy from an alternating magnetic field and output alternating current in either inductively coupled or resonantly coupled energy transmission modes.

[0107] The receiver control module 2023 is used to control the voltage, current and frequency conversion parameters of the receiver conversion module according to the actual wireless charging power requirements.

[0108] The receiver conversion module 2022 is used to convert the high-frequency current or voltage received by the power receiving antenna into the DC voltage or DC current required for charging the energy storage module. The receiver conversion module typically consists of a rectifier unit and a DC-DC converter unit; the rectifier unit converts the high-frequency current and voltage or high-frequency resonant current and voltage received by the power receiving antenna into DC voltage and DC current, while the DC-DC converter unit provides a stable DC voltage to the subsequent charging circuit, enabling constant-mode charging.

[0109] The receiving communication module 2024 is used for wireless communication between the wireless charging transmitter and the wireless charging receiver. This includes power control information, fault protection information, power on / off information, and interactive authentication information. On one hand, the wireless charging receiver can send the electric vehicle's attribute information, charging requests, power control information, and interactive authentication information to the wireless charging transmitter; on the other hand, the wireless charging receiver can also receive transmission control information, interactive authentication information, and wireless charging history data sent by the wireless charging transmitter. Specifically, the aforementioned wireless communication methods can include, but are not limited to, any one or more combinations of Bluetooth, Wi-Fi, Zigbee, Radio Frequency Identification (RFID), Long Range (Lora) wireless technology, and Near Field Communication (NFC). Furthermore, this receiving communication module can also communicate with the smart terminal of the electric vehicle's owner. The owner can use the communication function to achieve remote authentication and user information transmission, and control the vehicle and the transmitter for wireless charging interaction through the smart terminal.

[0110] If there are foreign objects in the wireless charging system, the transmission efficiency of the wireless charging system will decrease because the foreign objects will have an eddy current effect in the magnetic field formed by the transmitting coil.

[0111] To accurately and efficiently detect foreign objects in the wireless charging system, Embodiment 1 of this application provides a foreign object detection device, such as... Figure 5 The diagram shown is a schematic representation of the foreign object detection device provided in this application embodiment. The device includes an AC source 301, a resonant network 302, a measurement circuit 303, and a controller 304, used to detect the presence of foreign objects in the wireless charging system. Foreign objects include metallic and non-metallic foreign objects. This foreign object detection device can be applied to wireless charging scenarios for electric vehicles, as well as other wireless charging scenarios, such as wireless charging scenarios for drones or other electronic devices. The wireless charging foreign object detection device can be part of a wireless charging transmitter, i.e., integrated into or connected to and communicating with the wireless charging transmitter; alternatively, it can be part of a wireless charging receiver, i.e., integrated into or connected to and communicating with the wireless charging receiver; or it can be independent.

[0112] The AC source 301 can be a constant current source, capable of outputting a constant AC current with an arbitrarily set frequency, providing AC excitation for the resonant network 302. A constant AC current means that the current does not change with the load. In one possible implementation, the frequency setting range of the constant AC current is 10kHz-10MHz. A constant AC source can improve the stability of the foreign object detection device.

[0113] The resonant network 302 is used to detect the presence of foreign objects between the wireless charging transmitter and receiver. For example, it can be a parallel resonant network circuit. The resonant network 302 includes N equivalent detection coils, where N is an integer greater than or equal to 1. Each of the N detection coils includes a switch, an inductor, and a capacitor; the switch and inductor are connected in series, and the capacitor and inductor are connected in parallel.

[0114] In one possible implementation, the resonant network 302 is a resonant network composed of N inductor elements (L1…Ln) and capacitor element C1. Each of the N inductor elements L1, L2…Ln, when connected to the circuit, forms a resonant circuit that can be considered as an equivalent detection coil, i.e., there are a total of N detection coils. Each of these N detection coils includes a switch, an inductor element, and a capacitor element. Multiple detection coils can increase the coverage area for foreign object detection. The term "equivalent" in "equivalent detection coil" refers to the equivalent total inductance, which may be the result of multiple inductor coils connected in series or parallel. The inductor elements L1, L2…Ln in the equivalent detection coil are connected in parallel with the capacitor element C1 to form a parallel resonant network. The inductor elements L1, L2…Ln are connected in series with the switching switches S1, S2…Sn. Each equivalent coil refers to the coil composed of each equivalent inductor and capacitor C1. In one possible implementation, during foreign object detection, the closed and closed switches S1, S2…Sn are switched alternately to detect foreign objects in the areas covered by the coils of the connected parallel resonant network, including the inductive elements L1, L2…Ln. For example, as... Figure 6 The diagram shows a parallel resonant network. When switch S1 is closed, the coil of inductor L1 and capacitor C1 are connected in parallel to form a parallel resonant network. When resonance occurs, the following equation is satisfied: ω is the resonant angular frequency, and the relationship between the resonant angular frequency ω and the resonant frequency f is ω = 2πf. L is the inductance of inductor L1, and C is the capacitance of capacitor C1. At this time, a constant AC source Is (i.e., AC source 301) provides current excitation, allowing for the detection of metallic foreign objects within the area enclosed by L1 and C1. C1 can be considered as the equivalent resonant capacitance of the resonant network.

[0115] It is understandable that there are multiple ways to design the structure of the metal foreign object detection coil (resonant network 302). Before designing the hardware circuit, finite element simulation of the magnetic field can be performed. By changing the shape, size, connection method, and inductance of different small coils, magnetic field simulation of foreign object detection can be performed on various metals of different sizes and materials to determine the scheme with better detection accuracy as the coil design method. Each equivalent coil of the resonant network can be used as a detection coil. Therefore, the resonant network 302 can be regarded as a detection coil network composed of multiple detection coils. The resonant network uses multiple detection coils to cover a larger detectable area. It is understood that there can also be only one detection coil. The specific number and area of ​​detection coils can be designed according to the actual working conditions, and this application does not impose any restrictions.

[0116] In one possible implementation, after simulation and analysis, the actual resonant frequency of the resonant network 302 is determined to be f = 300kHz, the equivalent inductance of the detection coil connected to the circuit is 100uH, the equivalent capacitance is 2.82nF, and the detection coil is a parallel resonant network. Based on the impedance characteristics of the parallel resonant network, the impedance characteristic curve of the input impedance Z1 of the resonant network without any metal foreign objects can be plotted, and the impedance characteristic expression of the input impedance Z1 of the resonant network is given by equation (1).

[0117]

[0118] ω is the resonant angular frequency, and the relationship between the resonant angular frequency ω and the resonant frequency f is ω=2πf. L is the inductance of the detection coil formed by the closed switch in the resonant network, C is the capacitance of capacitor C1, and π is pi.

[0119] According to the characteristics of parallel resonant networks, the impedance of the parallel resonant network is at its maximum value at the resonant frequency f = 300kHz.

[0120] When there is a metallic foreign object, the change in inductance ΔL caused by electromagnetic induction in the foreign object detection coil is usually only about 2%. The impedance characteristic expression of the input impedance Z2 of the resonant network when there is a metallic foreign object is Equation (2).

[0121]

[0122] When a metallic foreign object is present, the smaller the change in inductance caused by the foreign object, the more difficult it is to detect. Therefore, to ensure the detection of sufficiently small metal objects, a detection method can be studied using an inductance change ΔL of 1%, i.e., the inductance becomes 99%L. Figure 7 The figure shows a comparison of the impedance characteristic curves of the input impedance Z1 and Z2 of the resonant network with and without metallic foreign objects.

[0123] Depend on Figure 7It can be seen that within the resonant frequency range f = 300kHz (below the resonant frequency without metal foreign objects), the input impedance Z1 of the resonant network without metal foreign objects is larger than that with metal foreign objects (Z2). Near the resonant frequency point fw of the resonant network with metal foreign objects, the input impedances of the resonant networks with and without metal foreign objects can be considered approximately the same. Above the frequency point fw, the input impedance of the resonant network with metal foreign objects is larger than that without. Furthermore, the further away from the designed resonant frequency f of the resonant network without metal foreign objects, the smaller the impedance difference between the cases with and without metal foreign objects at the same frequency. Therefore, to improve detection accuracy, it is best to select the detection point within a certain offset range. From the impedance characteristic curve, it can be seen that when the frequency offset exceeds 10% of the resonant frequency, the difference in input impedance between the cases with and without metal foreign objects is very small, resulting in low detection accuracy. Therefore, it is assumed that the frequency offset range Δf is 10% of the resonant frequency.

[0124] The measurement circuit 303 is used to measure the input voltage of the resonant network. The measurement process includes voltage sampling, filtering, and amplification. The output of the measurement circuit is a voltage proportional to the input voltage of the resonant network. The measurement circuit can be a common voltage measurement circuit or voltage measurement device.

[0125] The controller 304 is used to process the voltage signal U1 measured by the measuring circuit and the initial voltage signal U2 stored in the controller when there is no metal foreign object, and to perform corresponding calculations. The controller determines whether there is a metal foreign object by comparing the calculation result with the preset threshold. If the result is greater than the threshold, it is determined that there is a metal foreign object. If the result is not greater than the threshold, it is determined that there is no metal foreign object.

[0126] The controller 304 may include a filtering unit, a calculation unit, an amplification unit, and a comparison unit. The filtering unit filters out the excitation frequency components of the AC source 301; the calculation unit calculates the voltage signal; the amplification unit amplifies the calculated output signal to a size easily distinguishable; and the comparison unit compares the output of the preceding stage with a set threshold, outputting different signals based on the comparison result, such as high-level and low-level signals. It is understood that the internal structure of the controller is not limited; any device, module, or unit capable of processing voltage signals and comparing the numerical relationship between U1 and U2 is considered part of the controller described in this application. The controller 304 may also include a memory for storing the initial voltage signal U2 when there are no metallic foreign objects. The controller 304 may also include a control unit for determining frequency test points f1 and f2 and sending signals containing frequency test points f1 and f2 to the AC source 301 to control the frequency of the AC power output by the AC source.

[0127] In one possible implementation, the controller 304 acquires the output voltage signal U1 of the resonant network 302 and the initial voltage signal U2 pre-stored in the controller when there are no metal foreign objects. Using U1 and U2 as signal sources, and with U1 and U2 being equal in magnitude, the signals are processed through a series of filtering, amplification, and addition operations. When the difference between U1 and U2 is zero, the controller 304 outputs signal A, indicating the absence of foreign objects in the wireless charging system. When the voltages U1 and U2 are unequal, the difference between U1 and U2 is not zero, and the controller 304 outputs signal B, indicating the presence of foreign objects in the wireless charging system. Signals A and B can be digital signals with significantly identifiable differences or analog signals with significantly identifiable differences that can be recognized by other parts of the system. For example, signal A may be low or zero, and signal B may be high. Optionally, the system may also include a switch to control the operation of the wireless charging system, which shuts off the normal operation of the wireless charging system by recognizing signal B to prevent accidents. It may also include an alarm, which is activated when the controller 304 detects the presence of a foreign object. The alarm performs different physical actions based on different signals to alert the user to the intrusion. When no foreign object is present, signal A is recognized by the alarm, and the alarm does not react. When a foreign object is present, signal B is recognized by the alarm, and the alarm reacts physically, such as flashing the LED light or emitting a buzzer, thus alerting the user to the presence of a metallic foreign object.

[0128] In another possible implementation, controller 304 is used to determine the actual resonant frequency f of the resonant network; determine frequency test points f1 and f2, where f1 is less than the actual resonant frequency f and f2 is greater than the actual resonant frequency f; optionally, f1 and f2 can both be less than or greater than the actual resonant frequency f; and determine the input voltage U of resonant network 302 at frequency f1. 2f1 and the input voltage U at frequency f2 2f2 Calculate the differential voltage ΔU1, where ΔU1 is the preset voltage U. 1f1 The input voltage U of the resonant network 302 at frequency f1 2f1 The difference, i.e., ΔU1=U 1f1 -U 2f1 Preset voltage U 1f1 Given the resonant network 302 without any metallic foreign objects, calculate the input voltage at frequency f1; calculate the difference voltage ΔU2, where ΔU2 is the preset voltage U. 1f2 The input voltage U of the resonant network 302 at frequency f2 2f2 The difference, i.e., ΔU2=U 1f2 -U 2f2 Preset voltage U 1f2Let f2 be the input voltage of the resonant network at frequency f2 when there are no metal foreign objects; calculate the total difference voltage ΔU, which is the absolute value of the voltage difference between difference voltage ΔU1 and difference voltage ΔU2, i.e., ΔU=|ΔU1-ΔU2|; determine whether ΔU is greater than a preset threshold. If it is greater, it is determined that there is a foreign object; if it is not greater, it is determined that there is no foreign object.

[0129] In another possible implementation, controller 304 determines the actual resonant frequency f of the resonant network; determines frequency test points f1 and f2, where f1 is less than the actual resonant frequency f and f2 is greater than the actual resonant frequency f. Optionally, both f1 and f2 can be less than or greater than the actual resonant frequency f. It also determines the input impedance L of the resonant network 302 at frequency f1. 2f1 and the input impedance L at frequency f2 2f2 Calculate the differential impedance ΔL1, where ΔL1 is the preset impedance L. 1f1 The input impedance L of the resonant network 302 at frequency f1 2f1 The difference, i.e., ΔL1=L 1f1 -L 2f1 Preset impedance L 1f1 The input impedance of the resonant network 302 at frequency f1 is given when there are no metallic foreign objects; the differential impedance ΔL2 is calculated, where ΔL2 is the preset impedance L. 1f2 The input impedance L of the resonant network 302 at frequency f2 2f2 The difference, i.e., ΔL2=L 1f2 -L 2f2 Preset impedance L 1f2 Let f2 be the input impedance of the resonant network at frequency f2 when there are no metal foreign objects; calculate the total differential impedance ΔL, which is the absolute value of the impedance difference between differential impedance ΔL1 and differential impedance ΔL2, i.e., ΔL=|ΔL1-ΔL2|; determine whether ΔL is greater than a preset threshold. If it is greater, it is determined that there is a foreign object; if it is not greater, it is determined that there is no foreign object.

[0130] It is understood that, optionally, there can be M frequency test points, where M is an even number greater than or equal to 2. In one possible implementation, the frequencies of 0.5M frequency points are less than the actual resonant frequency of the resonant network, and the frequencies of 0.5M frequency points are greater than the actual resonant frequency of the resonant network. The differential voltage or differential impedance of the resonant network 302 at each frequency point is determined according to the method in the above embodiment, and the total differential impedance is determined. The total differential impedance is the maximum value of the absolute value of the differential impedance at each frequency point.

[0131] Embodiment 2 of this application provides a foreign object detection method, such as... Figure 8The diagram shows the flow chart of this foreign object detection method. The core flow of this method is as follows:

[0132] S401: Determine the actual resonant frequency f of the resonant network. In the absence of metallic foreign objects, calculate the actual resonant frequency of the resonant network 302 based on the measured inductance value of each equivalent coil, or, sweep the frequency near the design value of the resonant frequency of the resonant network 302 to determine the actual resonant frequency f of the resonant network 302.

[0133] In the theoretical design of the resonant network 302, the resonant frequency is determined. However, due to the inherent accuracy range of the resonant network components, some errors may exist between the design and actual values. Therefore, during circuit debugging before actual foreign object detection, it is necessary to first measure the inductance and capacitance values ​​of each equivalent coil and calculate the resonant frequency of the resonant network corresponding to each equivalent coil when there are no metal foreign objects. Alternatively, the resonant frequency can be detected by frequency sweeping. Frequency sweeping refers to changing the excitation frequency of the constant current AC source within a certain range, while measuring the input voltage on the resonant network. The frequency of the constant current AC source corresponding to the maximum input voltage on the resonant network is the resonant frequency of the resonant network. Because the deviation between the design and actual values ​​is usually not large, frequency sweeping can typically be performed near the design value of the resonant frequency. For example, if the design value of the resonant frequency is f... d =300kHz. A frequency sweep is performed in the vicinity of the design resonant frequency, such as the frequency range [280kHz, 320kHz]. The frequency corresponding to the maximum voltage on the resonant network is determined as the initial resonant frequency without any metallic foreign objects. Since the detection method for each equivalent coil is the same, the above process uses one coil as an example. It can be understood that the actual resonant frequencies of the remaining coils can be determined using a similar method.

[0134] S402: Determine the frequency test points. Since the impedance characteristic curves corresponding to different resonant frequencies exhibit different rates of descent on either side of the resonant frequency, a frequency test point can be determined on each side of the resonant frequency f of the resonant network 302. In one possible implementation, on both sides of the actual resonant frequency f of the resonant network 302, using (f-Δf) and (f+Δf) as boundaries respectively, a frequency point f1 is selected within the interval [(f-Δf), f], and a frequency point f2 is selected within the interval [f, (f+Δf)]. f1 and f2 are used as the frequency test points for detecting metallic foreign objects. The relationship between the frequency test points f1 and f2 and the resonant frequency f is: f1 is less than the actual resonant frequency f of the resonant network, and f2 is greater than the actual resonant frequency f of the resonant network. Optionally, both f1 and f2 can be less than or greater than the actual resonant frequency f of the resonant network. The selection criterion for the value of Δf depends on the impedance characteristic curve. The principle is that the impedance difference between the presence and absence of foreign objects at the same frequency is relatively significant. In one possible implementation, the range of Δf is [0.01f, 0.5f]. For example, the impedance difference between the presence and absence of foreign objects is usually larger within a range of 0.1f to the left and right of the actual resonant frequency f of the resonant network 302. Beyond this range, the difference becomes smaller. In this case, Δf = 0.1f is selected. That is, on both sides of the actual resonant frequency f of the resonant network 302, with (f-0.1f) and (f+0.1f) as boundaries, a frequency point f1 is selected in the interval [(f-0.1f), f], and a frequency point f2 is selected in the interval [f, (f+0.1f)]. f1 and f2 are used as frequency test points for metal foreign object detection. For example, when the actual value of the resonant frequency f = 300kHz is obtained by frequency sweep, Δf = 0.1f = 30kHz is calculated. On both sides of the actual resonant frequency f = 300kHz of the resonant network 302, with f-Δf = f-0.1f = 270kHz and f+Δf = f+0.1f = 330kHz as boundaries, a frequency point f1 = 290kHz is selected in the interval [270kHz, 300kHz], and a frequency point f2 = 314kHz is selected in the interval [300kHz, 330kHz]. 290kHz and 314kHz are used as frequency test points for detecting metal foreign objects.

[0135] S403: Determine the input voltage U of the resonant network at frequency point f1 when there are no metallic foreign objects. 1f1 and the input voltage U at frequency point f2 1f2 , will U 1f1 As the preset voltage at frequency point f1, U 1f2The preset voltage is used at frequency point f2. In the absence of metallic foreign objects, a constant current source sends a current excitation at frequency f1, and the measuring circuit detects the input voltage U of the resonant network 302. 1f1 And the frequency f1 and the input voltage U 1f1 The data is saved to the memory of controller 304. In the absence of metallic foreign objects, a constant current source sends a current excitation at frequency f2, and the measuring circuit detects the input voltage U of the resonant network 302. 1f2 and put frequency f2 and U 1f2 The data is saved to the memory of controller 304. For example, in the absence of metallic foreign objects, a constant current source sends a current excitation at a frequency of f1 = 290kHz, and the measuring circuit detects the input voltage U of the resonant network 302. 1f1 And the frequency f1 = 290kHz and the input voltage U 1f1 The data is saved to the memory of controller 304. In the absence of metallic foreign objects, the constant current source sends a current excitation at a frequency of f2 = 314 kHz, and the measuring circuit detects the input voltage U of the resonant network 302. 1f2 And set the frequency f2 = 314kHz and U 1f2 Saved to the memory of controller 304.

[0136] S404: Determine the input voltage U of the resonant network 302 at frequency point f1 during metal foreign object detection. 2f1 and the input voltage U at frequency point f2 2f2 During metal foreign object detection, a constant current source sends a current excitation at a frequency of f1, and the measuring circuit 303 detects the input voltage U of the resonant network 302. 2f1 And the frequency f1 and the input voltage U 2f1 The data is saved to the memory of controller 304. During metal foreign object detection, a constant current source sends a current excitation at a frequency of f2, and measurement circuit 303 detects the input voltage U of resonant network 302. 2f2 and put frequency f2 and U 2f2 The data is saved to the memory of the controller 304. For example, during metal foreign object detection, the constant current source sends a current excitation with a frequency of f1 = 290kHz, and the measurement circuit 303 detects the input voltage U of the resonant network 302. 2f1 And the frequency f1 = 290kHz and the input voltage U 2f1 The data is saved to the memory of controller 304. During metal foreign object detection, the constant current source sends a current excitation with a frequency of f2 = 314kHz, and the measurement circuit 303 detects the input voltage U of the resonant network 302. 2f2 And set the frequency f2 = 314kHz and U 2f2 Saved to the memory of controller 304.

[0137] S405: Calculate the preset voltage U of the resonant network 302 at frequency point f1. 1f1 and input voltage U 2f1 The difference ΔU1 is the voltage difference at frequency point f1. In controller 304, the input voltage U of the resonant network is compared when there are no metal foreign objects and the current excitation frequency of the constant current source is f1. 1f1 The input voltage U of the resonant network when detecting metallic foreign objects and the current excitation frequency of the constant current source is f1. 2f1 The difference ΔU1, ΔU1=U 1f1 -U 2f1 When no metal foreign object is detected, it can be understood that, theoretically, U... 1f1 =U 2f1 ΔU1=U 1f1 -U 2f1 =0. However, since system parameters cannot be exactly the same, in practice, when judging U... 1f1 and U 2f1 When the difference is less than a certain threshold, i.e., ΔU1 = U 1f1 -U 2f1 <U set1 Therefore, it can be assumed that no foreign object exists during metal foreign object detection. For example, when f1 = 290 kHz, during metal foreign object detection, ΔU1 = U 1f1 -U 2f1 When no metal foreign object is detected, U 1f1 with U 2f1 If the difference is less than a certain threshold, ΔU1=U 1f1 -U 2f1 <U set1 When a metallic foreign object is detected, U 1f1 with U 2f1 If the difference is greater than a certain threshold, ΔU1=U 1f1 -U 2f1 >U set1 Optionally, ΔU1 can also be used to calculate the input voltage U of the resonant network 302 at frequency point f1. 2f1 and preset voltage U 1f1 The difference, i.e., ΔU1=U 2f1 -U 1f1 .

[0138] S406: Calculate the preset voltage U of the resonant network 302 at frequency point f2. 1f2 and input voltage U 2f2 The difference ΔU2 is the voltage difference at frequency point f2. In controller 304, the input voltage U of the resonant network is compared when there are no metal foreign objects and the current excitation frequency of the constant current source is f2. 1f2The input voltage U of the resonant network when detecting metallic foreign objects and the current excitation frequency of the constant current source is f2. 2f2 The difference ΔU2, ΔU2=U 1f2 -U 2f2 When no metal foreign object is detected, it can be understood that, theoretically, U... 1f2 =U 2f2 ΔU2=U 1f2 -U 2f2 =0. However, since system parameters cannot be exactly the same, in practice, when judging U... 1f2 and U 2f2 When the difference is less than a certain threshold, i.e., ΔU2 = U 1f2 -U 2f2 <U set2 Therefore, it can be assumed that no foreign object exists during metal foreign object detection. For example, when f1 = 290 kHz, during metal foreign object detection, ΔU2 = U 1f2 -U 2f2 When no metal foreign object is detected, U 1f2 with U 2f2 If the difference is less than a certain threshold, ΔU2=U 1f2 -U 2f2 <U set2 When a metallic foreign object is detected, U 1f2 with U 2f2 If the difference is greater than a certain threshold, ΔU2=U 1f2 -U 2f2 >U set2 Optionally, ΔU2 can also be used to calculate the input voltage U of the resonant network 302 at frequency point f2. 2f2 and preset voltage U 1f2 The difference, i.e., ΔU2=U 2f2 -U 1f2 .

[0139] S407: Calculate the absolute value ΔU of the voltage difference between the voltage difference at frequency point f1 and the voltage difference at frequency point f2, where ΔU is the total voltage difference. In controller 304, the total voltage difference is obtained by calculating the absolute value of the voltage difference between the voltage difference at frequency point f1 and the voltage difference at frequency point f2, i.e., ΔU=|ΔU1-ΔU2|.

[0140] S408: Compare ΔU with a pre-set threshold and determine whether a metallic foreign object exists based on the comparison result. Theoretically, when no metallic foreign object exists, ΔU = |ΔU1 - ΔU2| = 0. When a metallic foreign object exists, its presence will distort the induced magnetic field. For example, a metallic foreign object will also induce an electromotive force in a time-varying magnetic field. This electromotive force will generate a closed-loop current, i.e., eddy current, inside the metallic foreign object, which can generate a magnetic field. Non-metallic foreign objects, such as biological foreign objects, can also distort the time-varying magnetic field. Therefore, the embodiments of this application can also be used in other non-metallic foreign object detection application scenarios. In one possible implementation, the eddy current magnetic field generated by the metallic foreign object will generate an induced electromotive force on the resonant network 302, i.e., a foreign object induced voltage is superimposed on the input voltage of the resonant network 302, such as... Figure 1 As shown, from Figure 1 It can be seen that the impedance of the resonant circuit differs depending on whether a metallic foreign object is present on either side of the resonant frequency ω1 near the resonant frequency ωr. At frequencies less than ω1, the impedance of the detection circuit with a metallic foreign object is greater than that without; at frequencies greater than ω1, the impedance of the resonant circuit with a metallic foreign object is less than that without. This difference in impedance affects the voltage. However, the direction and magnitude of the difference between the foreign object-induced voltage and the input voltage of the resonant network 302 are different at different frequencies; that is, ΔU1 and ΔU2 are not equal, and ΔU = |ΔU1 - ΔU2| ≠ 0. It is understandable that in practical applications, due to the existence of errors, ΔU may not be zero even when no metallic foreign object is present. Therefore, to increase detection accuracy, a threshold U can be preset according to the specific working conditions and error range requirements. set In controller 304, the total differential voltage ΔU is compared with a preset threshold. When ΔU is greater than the preset threshold range, i.e., ΔU = |ΔU1 - ΔU2| > U... set The presence of a foreign object is considered; when ΔU is less than a pre-set threshold range, i.e., ΔU = |ΔU1 - ΔU2| < U set If the reading is negative, it is considered that there is no metallic foreign object. It is understood that, compared to measuring the voltage difference at a single frequency, the method in this application embodiment of measuring the voltage difference at two frequencies can effectively improve detection accuracy and avoid false measurements.

[0141] from Figure 1As can be seen, under the two different conditions of no metal foreign object and with metal foreign object, the impedance characteristic curve of the resonant network has different values ​​on both sides of the resonant frequency. However, the induced voltage generated by the common interference signal can be considered to be approximately equal at different frequencies. Therefore, the above method can effectively eliminate the common interference signal that occurs under different complex working conditions, such as the change of the magnetic field of the transmitting coil and the different coupling coefficients caused by the different relative positions between the transmitting coil and the receiving coil. This improves the accuracy of metal foreign object detection, reduces false judgments, and achieves the goal of high-precision metal foreign object detection.

[0142] For example, when detecting metallic foreign objects, there is interference caused by changes in the magnetic field of the transmitting coil. When there are no metallic foreign objects and the constant current source's excitation frequency is f1, the input voltage of the resonant network is U. 1f1 The change in the magnetic field of the transmitting coil generates an interference voltage Ui1 when the current excitation frequency of the constant current source is f1. Therefore, during the detection of metallic foreign objects, when the constant current source sends a current excitation at a frequency of f1, the input voltage of the resonant network 302 detected by the measuring circuit 303 should be Ui1. 2f1 +Ui1. The input voltage of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f2 is U. 1f2 The change in the magnetic field of the transmitting coil generates an interference voltage Ui2 when the current excitation frequency of the constant current source is f2. Therefore, during the detection of metallic foreign objects, when the constant current source sends a current excitation at a frequency of f2, the input voltage of the resonant network 302 detected by the measuring circuit 303 should be Ui2. 2f2 +Ui2. In controller 304, compare the input voltage U of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f1. 1f1 When interference occurs due to changes in the magnetic field of the transmitting coil, the input voltage U of the resonant network for detecting metallic foreign objects at the current excitation frequency f1 of the constant current source is... 2f1 The difference between +Ui1 and ΔU1, ΔU1=U 1f1 -(U 2f1 +Ui1). Compare the input voltage U of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f2. 1f2 When interference occurs due to changes in the magnetic field of the transmitting coil, the input voltage U of the resonant network for detecting metallic foreign objects at the current excitation frequency f2 of the constant current source is... 2f2 The difference between +Ui2 and ΔU2, ΔU2=U 1f2 -(U 2f2 +Ui2). In controller 304, the total voltage difference ΔU = |ΔU1 - ΔU2| between frequencies f1 and f2 is calculated. However, the induced voltage caused by the change in the magnetic field of the transmitting coil is equal at different frequencies, i.e., Ui1 = Ui2, as shown below. Figure 2The diagram shows the frequency variation of the input voltage of the resonant network superimposed with the interference-induced voltage. In the diagram, Ueq represents the input voltage of the resonant network, and Ueq+ΔU represents the input voltage of the resonant network superimposed with the interference-induced voltage. Therefore, when there is no metallic foreign object, theoretically, the total difference voltage ΔU = |ΔU1 - ΔU2| = 0. It can be understood that in reality, the total difference voltage ΔU will be less than a threshold, and there will be no false positives. When a foreign object is present, the total difference voltage is the same as when there is no induced voltage interference and a foreign object is present; the threshold setting can also be the same, and similarly, no false positives will occur.

[0143] Embodiment 3 of this application provides another method for foreign object detection. The difference from Embodiment 2 is that in Embodiment 3, the measuring circuit detects the impedance of the resonant network. When the excitation of the resonant network is an alternating current source, the relationship between the voltage and impedance of the resonant network is U = I*Z. Detecting the voltage is the most direct method. After detecting the impedance of the resonant network, the voltage of the resonant network can also be calculated based on the measured impedance and the current data of the current source. There are many methods for impedance detection, such as impedance detection circuits or impedance detection devices, which are not limited here. Figure 9 The flowchart shown is for this method of detecting metallic foreign objects. The core process of this method is as follows:

[0144] S501: Determine the actual resonant frequency f of the resonant network. In the absence of metallic foreign objects, calculate the actual resonant frequency of the resonant network 302 based on the measured inductance value of each equivalent coil, or, sweep the frequency near the design value of the resonant frequency of the resonant network 302 to determine the actual resonant frequency f of the resonant network 302.

[0145] In the theoretical design of the resonant network 302, the resonant frequency is determined. However, due to the inherent precision of the resonant network components, some errors may occur between the design and actual values. Therefore, during circuit debugging before actual foreign object detection, it is necessary to first measure the inductance and capacitance values ​​of each equivalent coil and calculate the resonant frequency of the resonant network corresponding to each equivalent coil when there are no metal foreign objects. Alternatively, the resonant frequency can be detected by frequency sweeping. Frequency sweeping refers to changing the excitation frequency of the constant current AC source within a certain range, while measuring the input voltage on the resonant network. The frequency of the constant current AC source corresponding to the maximum input voltage on the resonant network is the resonant frequency of the resonant network. Because the deviation between the design and actual values ​​is usually not large, frequency sweeping can typically be performed near the design value of the resonant frequency. For example, if the design value of the resonant frequency is f... d=300kHz. A frequency sweep is performed in the vicinity of the design resonant frequency, such as the frequency range [280kHz, 320kHz]. The frequency corresponding to the maximum voltage on the resonant network is determined as the initial resonant frequency without any metallic foreign objects. Since the detection method for each equivalent coil is the same, the above process uses one coil as an example. It can be understood that the actual resonant frequencies of the remaining coils can be determined using a similar method.

[0146] S502: Determine the frequency test points. Since the impedance characteristic curves corresponding to different resonant frequencies exhibit different rates of descent on either side of the resonant frequency point, a frequency test point can be determined on both sides of the resonant frequency f of the resonant network 302. In one possible implementation, on both sides of the actual resonant frequency f of the resonant network 302, using (f-Δf) and (f+Δf) as boundaries respectively, a frequency point f1 is selected within the interval [(f-Δf), f], and a frequency point f2 is selected within the interval [f, (f+Δf)]. f1 and f2 are used as the frequency test points for detecting metallic foreign objects. The relationship between the frequency test points f1 and f2 and the resonant frequency f is: f1 is less than the actual resonant frequency f of the resonant network, and f2 is greater than the actual resonant frequency f of the resonant network. Optionally, both f1 and f2 can be less than the actual resonant frequency f of the resonant network, or both can be greater than the actual resonant frequency f of the resonant network. The selection criterion for the value of Δf depends on the impedance characteristic curve. The principle is that the impedance difference between the presence and absence of foreign objects at the same frequency is relatively significant. In one possible implementation, the range of Δf is [0.01f, 0.5f]. For example, the impedance difference between the presence and absence of foreign objects is usually larger within a range of 0.1f to the left and right of the actual resonant frequency f of the resonant network 302. Beyond this range, the difference becomes smaller. In this case, Δf = 0.1f is selected. That is, on both sides of the actual resonant frequency f of the resonant network 302, with (f-0.1f) and (f+0.1f) as boundaries, a frequency point f1 is selected in the interval [(f-0.1f), f], and a frequency point f2 is selected in the interval [f, (f+0.1f)]. f1 and f2 are used as frequency test points for metal foreign object detection. For example, when the actual value of the resonant frequency f = 300kHz is obtained by frequency sweep, Δf = 0.1f = 30kHz is calculated. On both sides of the actual resonant frequency f = 300kHz of the resonant network 302, with f-Δf = f-0.1f = 270kHz and f+Δf = f+0.1f = 330kHz as boundaries, a frequency point f1 = 285kHz is selected in the interval [270kHz, 300kHz], and a frequency point f2 = 320kHz is selected in the interval [300kHz, 330kHz]. 285kHz and 320kHz are used as frequency test points for metal foreign object detection.

[0147] S503: Determine the input impedance L of the resonant network at frequency point f1 when there are no metallic foreign objects. 1f1 and the input impedance L at frequency point f2 1f2 , L 1f1 As the preset impedance at frequency point f1, L 1f2 As the preset impedance at frequency point f2. In the absence of metallic foreign objects, a constant current source sends a current excitation at frequency f1, and the measuring circuit detects the input impedance L of the resonant network 302. 1f1 And the frequency f1 and input impedance L 1f1 The data is saved to the memory of controller 304. In the absence of metallic foreign objects, a constant current source sends a current excitation at frequency f2, and the measuring circuit detects the input impedance L of the resonant network 302. 1f2 and frequency f2 and L 1f2 The data is saved to the memory of controller 304. For example, in the absence of metallic foreign objects, a constant current source sends a current excitation at a frequency of f1 = 285 kHz, and the measuring circuit detects the input impedance L of the resonant network 302. 1f1 And set the frequency f1 = 285kHz and the input impedance L 1f1 The data is saved to the memory of controller 304. In the absence of metallic foreign objects, a constant current source sends a current excitation at a frequency of f2 = 320kHz, and the measuring circuit detects the input impedance L of the resonant network 302. 1f2 And set the frequency f2 = 320kHz and L 1f2 Saved to the memory of controller 304.

[0148] S504: Determine the input impedance L of the resonant network 302 at frequency point f1 when performing metal foreign object detection. 2f1 and the input impedance L at frequency point f2 2f2 During the detection of metallic foreign objects, a constant current source sends a current excitation at a frequency of f1, and the measuring circuit 303 detects the input impedance L of the resonant network 302. 2f1 And the frequency f1 and input impedance L 2f1 The data is saved to the memory of controller 304. During metal foreign object detection, a constant current source sends a current excitation at frequency f2, and measurement circuit 303 detects the input impedance L of resonant network 302. 2f2 and frequency f2 and L 2f2 The data is saved to the memory of controller 304. For example, during metal foreign object detection, a constant current source sends a current excitation at a frequency of f1 = 285kHz, and measurement circuit 303 detects the input impedance L of resonant network 302. 2f1 And set the frequency f1 = 285kHz and the input impedance L 2f1The data is saved to the memory of controller 304. During metal foreign object detection, a constant current source sends a current excitation with a frequency of f2 = 320kHz, and measurement circuit 303 detects the input impedance L of resonant network 302. 2f2 And set the frequency f2 = 320kHz and L 2f2 Saved to the memory of controller 304.

[0149] S505: Calculate the preset impedance L of the resonant network 302 at frequency point f1. 1f1 and input impedance L 2f1 The difference ΔL1 is the impedance difference at frequency point f1. In controller 304, the input impedance L of the resonant network is compared when there are no metallic foreign objects and the current excitation frequency of the constant current source is f1. 1f1 The input impedance L of the resonant network when detecting metallic foreign objects and the constant current source is excited at frequency f1. 2f1 The difference ΔL1, ΔL1=L 1f1 -L 2f1 When no metal foreign object is detected, it can be understood that, theoretically, L... 1f1 =L 2f1 ΔL1=L 1f1 -L 2f1 =0. However, since system parameters cannot be exactly the same, in practice, when judging L... 1f1 and L 2f1 When the difference is less than a certain threshold, i.e., ΔL1 = L 1f1 -L 2f1 <L set1 Therefore, it can be assumed that no foreign object exists during metal foreign object detection. For example, when f1 = 285 kHz, ΔL1 = L when performing metal foreign object detection. 1f1 -L 2f1 When no metal foreign object is detected, L 1f1 With L 2f1 If the difference is less than a certain threshold, ΔL1=L 1f1 -L 2f1 <L set1 When a metallic foreign object is detected, L 1f1 With L 2f1 If the difference is greater than a certain threshold, ΔL1=L 1f1 -L 2f1 >L set1 Optionally, ΔL1 can also be used to calculate the input impedance L of the resonant network 302 at frequency point f1. 2f1 and preset impedance L 1f1 The difference, i.e., ΔL1=L 2f1 -L 1f1 .

[0150] S506: Calculate the preset impedance L of the resonant network 302 at frequency point f2. 1f2 and input impedance L 2f2 The difference ΔL2 is the impedance difference at frequency point f2. In controller 304, the input impedance L of the resonant network is compared when there are no metallic foreign objects and the current excitation frequency of the constant current source is f2. 1f2 The input impedance L of the resonant network when detecting metallic foreign objects and the constant current source is excited at frequency f2. 2f2 The difference ΔL2, ΔL2=L 1f2 -L 2f2 When no metal foreign object is detected, it can be understood that, theoretically, L... 1f2 =L 2f2 ΔL2=L 1f2 -L 2f2 =0. However, since system parameters cannot be exactly the same, in practice, when judging L... 1f2 and L 2f2 When the difference is less than a certain threshold, i.e., ΔL2 = L 1f2 -K 2f2 <L set2 Therefore, it can be assumed that no foreign object exists during metal foreign object detection. For example, when f1 = 285 kHz, ΔL2 = L during metal foreign object detection. 1f2 -L 2f2 When no metal foreign object is detected, L 1f2 and L 2f2 If the difference is less than a certain threshold, ΔL2 = L 1f2 -L 2f2 <L set2 When a metallic foreign object is detected, L 1f2 and L 2f2 If the difference is greater than a certain threshold, ΔL2=L 1f2 -L 2f2 >L set2 Optionally, ΔL2 can also be used to calculate the input impedance L of the resonant network 302 at frequency point f2. 2f2 and preset impedance L 1f2 The difference, i.e., ΔL1=L 2f2 -L 1f2 .

[0151] S507: Calculate the absolute value ΔL of the impedance difference between the differential impedance at frequency point f1 and the differential impedance at frequency point f2, where ΔL is the total differential impedance. In controller 304, the total differential impedance is obtained by calculating the absolute value of the impedance difference between the differential impedance at frequency point f1 and the differential impedance at frequency point f2, i.e., ΔL=|ΔL1-ΔL2|.

[0152] S508: Compare ΔL with a pre-set threshold and determine whether a metallic foreign object exists based on the comparison result. Theoretically, when no metallic foreign object exists, ΔL = |ΔL1 - ΔL2| = 0. When a metallic foreign object exists, its presence distorts the induced magnetic field. For example, a metallic foreign object in a time-varying magnetic field will induce an electromotive force (EMF), which will generate a closed-loop current, i.e., eddy current, inside the metallic foreign object. Eddy currents can generate a magnetic field. Non-metallic foreign objects, such as biological foreign objects, can also distort the time-varying magnetic field. Therefore, this embodiment can also be used for other non-metallic foreign object detection applications. In one possible implementation, the eddy current magnetic field generated by the metallic foreign object will induce an EMF on the resonant network 302. The induced EMF, in turn, will affect the input impedance, i.e., the foreign object induced impedance will be superimposed on the input impedance of the resonant network 302. Figure 1 As shown, from Figure 1 It can be seen that the impedance of the resonant circuit differs depending on whether a metallic foreign object is present on either side of the resonant frequency ω1 near the resonant frequency ωr. At frequencies less than ω1, the impedance of the detection circuit with a metallic foreign object is greater than that without; at frequencies greater than ω1, the impedance of the resonant circuit with a metallic foreign object is less than that without. However, the direction and magnitude of the difference between the foreign object induced voltage and the input voltage of the resonant network 302 are different at different frequencies, which also leads to different input impedances of the resonant network at different frequencies, i.e., ΔL1 and ΔL2 are not equal, ΔL=|ΔL1-ΔL2|≠0. It is understandable that in practical applications, due to the existence of errors, ΔL may not be zero even when there is no metallic foreign object. Therefore, to increase detection accuracy, a threshold L can be preset according to the specific working conditions and error range requirements. set In controller 304, the total differential impedance ΔL is compared with a preset threshold. When ΔL is greater than the preset threshold range, i.e., ΔL = |ΔL1 - ΔL2| > L, the impedance is determined. set The presence of a foreign object is considered; when ΔL is less than a pre-set threshold range, i.e., ΔL = |ΔL1 - ΔL2| < L set If the impedance difference is measured at two frequencies, it is considered that there is no metallic foreign object. It is understood that the method of measuring the impedance difference at one frequency, as described in this application embodiment, can effectively improve detection accuracy and avoid false measurements.

[0153] from Figure 1As can be seen, under the two different conditions of no metal foreign object and with metal foreign object, the impedance characteristic curve of the resonant network has different differences on both sides of the resonant frequency. However, the induced voltage generated by the common interference signal can be considered to be approximately equal at different frequencies, and the change in impedance caused by the induced voltage is also the same. Therefore, the above method can effectively eliminate the common interference signal that occurs under different complex working conditions, such as the change of the magnetic field of the transmitting coil, the different coupling coefficient caused by the different relative positions between the transmitting coil and the receiving coil, etc., thereby improving the accuracy of metal foreign object detection, reducing false judgments, and achieving the goal of high-precision metal foreign object detection.

[0154] For example, interference caused by changes in the magnetic field of the transmitting coil during metal foreign object detection, and the input impedance of the resonant network when there is no metal foreign object and the current excitation frequency of the constant current source is f1, is L. 1f1 The change in the magnetic field of the transmitting coil generates an interference impedance Li1 when the current excitation frequency of the constant current source is f1. Therefore, during the detection of metallic foreign objects, when the constant current source transmits current excitation at a frequency of f1, the input impedance of the resonant network 302 detected by the measuring circuit 303 should be L. 2f1 +Li1. The input impedance of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f2 is L. 1f2 The change in the magnetic field of the transmitting coil generates an interference impedance Li2 when the current excitation frequency of the constant current source is f2. Therefore, during the detection of metallic foreign objects, when the constant current source transmits current excitation at a frequency of f2, the input impedance of the resonant network 302 detected by the measuring circuit 303 should be L. 2f2 +Li2. In controller 304, compare the input impedance L of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f1. 1f1 When interference occurs due to changes in the magnetic field of the transmitting coil, the input impedance L of the resonant network for detecting metallic foreign objects at the current excitation frequency f1 of the constant current source is... 2f1 +Li1 difference ΔL1, ΔL1=L 1f1 -(L 2f1 +Li1). Compare the input impedance L of the resonant network when there are no metallic foreign objects and the current excitation frequency of the constant current source is f2. 1f2 When interference occurs due to changes in the magnetic field of the transmitting coil, the input impedance L of the resonant network for detecting metallic foreign objects at the current excitation frequency f2 of the constant current source is... 2f2 The difference between +Li2 and ΔL2, ΔL2=L 1f2 -(L 2f2+Li2). In controller 304, the total differential impedance ΔL = |ΔL1 - ΔL2| at frequencies f1 and f2 is calculated. Since the induced voltage caused by the change in the magnetic field of the transmitting coil is approximately equal at different frequencies, the change in impedance caused by the induced voltage is also the same, i.e., Li1 = Li2. Therefore, when there is no metallic foreign object, theoretically, the total differential impedance ΔL = |ΔL1 - ΔL2| = 0. It can be understood that in reality, the total differential impedance ΔL will be less than a threshold, and there will be no false positives. When a foreign object is present, the total differential impedance is the same as when there is no induced impedance interference and a foreign object is present; the threshold setting can also be the same, and there will still be no false positives.

[0155] The methods described in Embodiments 2 or 3 above can be applied to the foreign object detection device described in Embodiment 1.

[0156] It is understood that the difference in the differential voltage or differential resistance described in the above embodiments can be either the actual difference in the direction of the voltage or resistance, or a processed difference, such as the absolute value of the actual difference. Specific designs can be tailored to actual needs, and this application does not impose any limitations.

[0157] This application provides a fourth embodiment of a wireless charging transmitter system capable of detecting foreign objects, which includes the foreign object detection device described in embodiment one and... Figure 4 The wireless charging transmitter shown in the diagram uses a foreign object detection device to detect whether there are foreign objects in the wireless charging transmitter system, which will not be described in detail here.

[0158] This application provides a fifth embodiment of a wireless charging receiver system capable of detecting foreign objects, which includes the foreign object detection device described in embodiment one and... Figure 4 The wireless charging receiver shown includes a foreign object detection device used to detect whether there are foreign objects in the wireless charging receiver system, which will not be described in detail here.

[0159] This application provides a sixth embodiment of a wireless charging system capable of detecting foreign objects, which includes the foreign object detection device described in embodiment one and... Figure 4 The wireless charging transmitter and receiver shown are described below. The foreign object detection device is used to detect whether there are foreign objects in the wireless charging system, which will not be described in detail here.

[0160] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software programs, implementation can be entirely or partially in the form of a computer program product. The computer program product includes at least one computer instruction. When the computer program instruction is loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates at least one available medium. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0161] It should be noted that the specific descriptions of each step in the method provided in Embodiments 2 or 3 of this application can be found in the specific descriptions of the corresponding contents in the device embodiment of Embodiment 1 above, and will not be repeated here. Furthermore, the method provided in Embodiments 2 or 3 of this application is used to implement the foreign object detection function of the foreign object detection device in Embodiment 1 above, and therefore can achieve the same effect as the above embodiments.

[0162] Using the foreign object detection method, apparatus, or system described in the embodiments of this application, the influence of changes in the induced voltage of the resonant network caused by changes in the magnetic field of the transmitting coil, such as changes in the output power, output voltage, and output current of the transmitting coil, on the foreign object detection process can be eliminated, thereby improving the accuracy of foreign object detection and reducing false positives.

[0163] Through the above description of the embodiments, those skilled in the art can clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0164] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0165] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of the embodiments of this application, depending on actual needs.

[0166] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0167] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of this application embodiment, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0168] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any way. Although this application has disclosed preferred embodiments above, it is not intended to limit the application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A method for detecting foreign objects during wireless charging, characterized in that, The method includes: Obtain a first input voltage at a first frequency and a second input voltage at a second frequency for the resonant network, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network, or the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is less than the actual resonant frequency of the resonant network, or the first frequency is greater than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network. Calculate the first difference voltage, which is the difference between the first preset voltage and the first input voltage, where the first preset voltage is the input voltage of the resonant network at the first frequency when there are no metal foreign objects. Calculate the second difference voltage, which is the difference between the second preset voltage and the second input voltage, where the second preset voltage is the input voltage of the resonant network at the second frequency when there are no metallic foreign objects. Calculate the third differential voltage, which is the absolute value of the voltage difference between the first differential voltage and the second differential voltage; Determine whether the third differential voltage is greater than a preset threshold. If it is, then determine that there is a foreign object.

2. The method according to claim 1, characterized in that, Before determining the first frequency and the second frequency, the method further includes: Determining the actual resonant frequency of the resonant network specifically includes: Measure the inductance and capacitance values ​​of the resonant network, and calculate the actual resonant frequency of the resonant network based on the inductance and capacitance values; or, By sweeping the frequency of the resonant network, the frequency corresponding to the maximum input voltage of the resonant network is measured as the actual resonant frequency of the resonant network.

3. The method according to claim 1, characterized in that, The first frequency is selected in the frequency range [(f-Δf), f], and the second frequency is selected in the frequency range [f, (f+Δf)], where f is the actual resonant frequency of the resonant network, and the value range of Δf is [0.01f, 0.5f].

4. The method according to any one of claims 1-3, characterized in that, The resonant network includes N detection coils, where N is an integer greater than or equal to 1.

5. The method according to claim 4, characterized in that, Each of the N detection coils includes a switch, an inductor, and a capacitor. The switch is connected in series with the inductor, and the capacitor is connected in parallel with the inductor.

6. A method for detecting foreign objects during wireless charging, characterized in that, The method includes: Obtain a first input impedance of the resonant network at a first frequency and a second input impedance at a second frequency, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network, or the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is less than the actual resonant frequency of the resonant network, or the first frequency is greater than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network. Calculate the first differential impedance, which is the difference between the first input impedance and the first preset impedance, where the first preset impedance is the input impedance of the resonant network at the first frequency when there are no metallic foreign objects. Calculate the second differential impedance, which is the difference between the second input impedance and the second preset impedance, where the second preset impedance is the input impedance of the resonant network at the second frequency when there are no metallic foreign objects. Calculate the third differential impedance, which is the absolute value of the impedance difference between the first differential impedance and the second differential impedance; Determine whether the third differential impedance is greater than a preset threshold. If it is, then it is determined that there is a foreign object.

7. The method according to claim 6, characterized in that, Before determining the first frequency and the second frequency, the method further includes: Determining the actual resonant frequency of the resonant network specifically includes: Measure the inductance and capacitance values ​​of the resonant network, and calculate the actual resonant frequency of the resonant network based on the inductance and capacitance values; or, By sweeping the frequency of the resonant network, the frequency corresponding to the maximum input voltage of the resonant network is measured as the actual resonant frequency of the resonant network.

8. The method according to claim 6, characterized in that, The first frequency is selected in the frequency range [(f-Δf), f], and the second frequency is selected in the frequency range [f, (f+Δf)], where f is the actual resonant frequency of the resonant network, and the value range of Δf is [0.01f, 0.5f].

9. The method according to any one of claims 6-8, characterized in that, The resonant network includes N detection coils, where N is an integer greater than or equal to 1.

10. The method according to claim 9, characterized in that, Each of the N detection coils includes a switch, an inductor, and a capacitor. The switch is connected in series with the inductor, and the capacitor is connected in parallel with the inductor.

11. A wireless charging foreign object detection device, characterized in that, The device includes an AC source, a resonant network, a measurement circuit, and a controller, wherein: The communication source is used to provide communication incentives; The resonant network is used to detect whether there are foreign objects between the wireless charging transmitter and receiver; The measurement circuit is used to measure the input voltage of the resonant network; The controller is used to acquire a first input voltage of the resonant network at a first frequency and a second input voltage at a second frequency, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network, or the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is less than the actual resonant frequency of the resonant network, or the first frequency is greater than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network. Calculate the first difference voltage, which is the difference between the first preset voltage and the first input voltage, where the first preset voltage is the input voltage of the resonant network at the first frequency when there are no metal foreign objects. Calculate the second difference voltage, which is the difference between the second preset voltage and the second input voltage, where the second preset voltage is the input voltage of the resonant network at the second frequency when there are no metallic foreign objects. Calculate the third differential voltage, which is the absolute value of the voltage difference between the first differential voltage and the second differential voltage; Determine whether the third differential voltage is greater than a preset threshold. If it is, then determine that there is a foreign object.

12. The detection device according to claim 11, characterized in that, The AC source includes a constant AC source.

13. The detection device according to claim 11 or 12, characterized in that, The resonant network includes N detection coils, where N is an integer greater than or equal to 1.

14. The detection device according to claim 13, characterized in that, Each of the N detection coils includes a switch, an inductor, and a capacitor. The switch is connected in series with the inductor, and the capacitor is connected in parallel with the inductor.

15. The detection device according to claim 11, characterized in that, The measurement circuit is also used for: Measure the input impedance of the resonant network.

16. The detection device according to claim 11, characterized in that, The controller is also used for: Obtain a first input impedance of the resonant network at a first frequency and a second input impedance at a second frequency, wherein the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network, or the first frequency is less than the actual resonant frequency of the resonant network and the second frequency is less than the actual resonant frequency of the resonant network, or the first frequency is greater than the actual resonant frequency of the resonant network and the second frequency is greater than the actual resonant frequency of the resonant network. Calculate the first differential impedance, which is the difference between the first input impedance and the first preset impedance, where the first preset impedance is the input impedance of the resonant network at the first frequency when there are no metallic foreign objects. Calculate the second differential impedance, which is the difference between the second input impedance and the second preset impedance, where the second preset impedance is the input impedance of the resonant network at the second frequency when there are no metallic foreign objects. Calculate the third differential impedance, which is the absolute value of the impedance difference between the first differential impedance and the second differential impedance; Determine whether the third differential impedance is greater than a preset threshold. If it is, then it is determined that there is a foreign object.

17. A wireless charging transmitter system, characterized in that, The wireless charging transmitting system includes a wireless charging foreign object detection device and a wireless charging transmitting device as described in any one of claims 11-16, wherein the wireless charging foreign object detection device is used to detect whether there is a foreign object in the wireless charging transmitting system.

18. A wireless charging receiver system, characterized in that, The wireless charging receiving system includes a wireless charging foreign object detection device and a wireless charging receiving device as described in any one of claims 11-16, wherein the wireless charging foreign object detection device is used to detect whether there is a foreign object in the wireless charging receiving system.

19. A wireless charging system, characterized in that, The wireless charging system includes a wireless charging foreign object detection device and a wireless charging device as described in any one of claims 11-16, wherein the wireless charging foreign object detection device is used to detect whether there is a foreign object in the wireless charging system.

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